WO2023278456A2 - Pyrimidine-compliant peptide nucleic acid compositions and methods of use thereof - Google Patents

Pyrimidine-compliant peptide nucleic acid compositions and methods of use thereof Download PDF

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WO2023278456A2
WO2023278456A2 PCT/US2022/035328 US2022035328W WO2023278456A2 WO 2023278456 A2 WO2023278456 A2 WO 2023278456A2 US 2022035328 W US2022035328 W US 2022035328W WO 2023278456 A2 WO2023278456 A2 WO 2023278456A2
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pna
oligomer
pna oligomer
nucleobase
hydrogen
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PCT/US2022/035328
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WO2023278456A3 (en
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James M. Coull
Mark Fiandaca
Thomas Zengeya
Andrew FRALEY
Derek Sim
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Neubase Therapeutics, Inc.
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Publication of WO2023278456A3 publication Critical patent/WO2023278456A3/en

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
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    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/87—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation
    • C12N15/88—Introduction of foreign genetic material using processes not otherwise provided for, e.g. co-transformation using microencapsulation, e.g. using amphiphile liposome vesicle
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
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    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/11—DNA or RNA fragments; Modified forms thereof; Non-coding nucleic acids having a biological activity
    • C12N15/111—General methods applicable to biologically active non-coding nucleic acids
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/63—Introduction of foreign genetic material using vectors; Vectors; Use of hosts therefor; Regulation of expression
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N2310/00—Structure or type of the nucleic acid
    • C12N2310/10—Type of nucleic acid
    • C12N2310/15—Nucleic acids forming more than 2 strands, e.g. TFOs
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N2310/00—Structure or type of the nucleic acid
    • C12N2310/30—Chemical structure
    • C12N2310/31—Chemical structure of the backbone
    • C12N2310/318—Chemical structure of the backbone where the PO2 is completely replaced, e.g. MMI or formacetal
    • C12N2310/3181—Peptide nucleic acid, PNA
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
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    • C12N2310/00—Structure or type of the nucleic acid
    • C12N2310/30—Chemical structure
    • C12N2310/33—Chemical structure of the base

Definitions

  • Those methods include use of targeted nucleases such as zinc finger nucleases (ZFNs), transcription activator-like effector-based nucleases (TALENs), and the clustered regularly interspaced short palindromic repeat system (CRISPR/Cas9).
  • ZFNs zinc finger nucleases
  • TALENs transcription activator-like effector-based nucleases
  • CRISPR/Cas9 clustered regularly interspaced short palindromic repeat system
  • FIG.1A is an illustration of a generic peptide nucleic acid (PNA) subunit where B represents a nucleobase, and ⁇ , ⁇ , and ⁇ represent optionally substituted positions on the PNA backbone.
  • FIG.1B is an illustration of an example tail-clamp PNA (tcPNA) oligomer bound to a double stranded DNA (dsDNA).
  • FIG.1C illustrates the various components in an illustration of an example tcPNA oligomer bound to a dsDNA.
  • FIGS.2A-2B are illustrations of the Hoogsteen face (HG face) and Watson-Crick face (WC face) of cytosine (C) (FIG.2A) and thymine (T) (FIG.2B), where R indicates a nucleic acid backbone.
  • FIG.3 is an illustration of Hoogsteen (i.e., HG-binding) interactions between nucleobases (e.g., a nucleobase of a PNA subunit) and a canonical nucleobase in a Watson-Crick base pair (e.g., a base pair in double-stranded DNA).
  • the nucleobases shown are pyridin-2- amine (i.e., “M”) HG-binding to the guanine of a G-C base pair (M*G-C), pseudoisocytosine (i.e., “J”) HG-binding to the guanine of a G-C base pair (J*G-C), 2-thiopseudoisocytosine (i.e., “L”) HG-binding to the guanine of a G-C base pair (L*G-C), thymine (i.e., “T”) HG-binding to the adenine of an A-T base pair (T*A-T), pyrimidin-2(1H)-one HG-binding to the cytosine of a C-G base pair (P*C-G), and pyridazin-3(2H)-one HG-binding to the thymine of a T-A base pair (E*T-A).
  • FIG.4 is an illustration of several common (but non-limiting) unprotected nucleobases (identified as “B” in FIG.1) that can be linked to a PNA monomer (or subunit of a polymer/oligomer).
  • FIG.5 is an illustration of various nucleobases used in PNA synthesis.
  • FIGS.6A-6B are illustrations of the complexes formed between tcPNA oligomers and nucleic acids, where “WC” indicates the Watson-Crick binding segment, and “HS” indicates the Hoogsteen-binding segment of the tcPNAs.
  • FIG.6A depicts the complex of Compound No.1 (when X is pyrimidin-2(1H)-one) or Compound No.2 (when X is “GlyGly”) with the nucleic acid sequence SEQ ID NO: 7.
  • FIG.6B depicts the complex of Compound Nos.1 or 2 with the nucleic acid sequence SEQ ID NO: 8.
  • FIGS.7A-7B is an illustration of various side chains that can be linked to a PNA subunit, including the side-chains of amino acids.
  • FIG.8A is an illustration of the PEG2 linker monomer used in some embodiments herein.
  • FIG.8B is an illustration of the PEG2 linker residue as incorporated as a subunit of a PNA oligomer used in some embodiments herein.
  • FIG.8C is an illustration of the PEG3 linker monomer used in some embodiments herein.
  • FIG.8D is an illustration of the PEG3 linker residue as incorporated as a subunit of a PNA oligomer used in some embodiments herein.
  • FIG.9 is an image of 6 HPLC chromatographs; each chromatogram demonstrating the separation obtained by analysis of a crude sample of a different fully-deprotected PNA oligomer.
  • FIG.10 is an image of 6 HPLC chromatographs; each chromatogram demonstrating the separation obtained by analysis of a crude sample of the same 6 PNA oligomers illustrated in FIG.9.
  • each PNA oligomer is a partially protected PNA oligomer comprising two Fmoc protecting groups, one linked to the N-terminal alpha amine group and one linked to the N-terminal epsilon amine group of an N-terminal lysine residue.
  • FIGS.11A-11D are images of isothermal titration calorimetry (ITC) (top) and the corresponding graphical representations (bottom), following complexing tcPNA oligomers (Compounds 1 or 2) with DNA oligonucleotides (SEQ ID NO: 7 or 8).
  • FIG.11A are the results from Compound No.1 + SEQ ID NO: 7
  • FIG.11B are the results from Compound No.1 + SEQ ID NO: 8
  • FIG.11C are the results from Compound No.2 + SEQ ID NO: 7
  • FIG.11D are the results from Compound No: 2 + SEQ ID NO: 8.
  • FIGS.12A-12B are images of electrophoretic separations performed after incubating a DNA amplicon (SEQ ID NO: 13) with different PNA oligomers (Compound Nos.3-6).
  • FIG. 12A is the separation after 0.5 hours of incubation
  • FIG.12B is the separation after 18 hours of incubation.
  • bp] indicates the size (base-pair)
  • lane A1 is a size marker
  • lane B1 is Compound No.5 + amplicon
  • lane C1 is Compound No.6 + amplicon
  • lane D1 is Compound No.3 + amplicon
  • lane E1 is Compound No.4 + amplicon
  • lane F1 is amplicon only.
  • PNAs Peptide nucleic acids
  • PNAs are small polymeric nucleic acid mimics that can bind directly to a target nucleic acid sequence with high affinity and sequence specificity.
  • PNAs can form a number of structures upon interacting with a target nucleic acid, including stable PNA/DNA/PNA triplexes.
  • PNA-based methods involving the formation of triplex structure can require a stretch of purine nucleobases as the target nucleic acid sequence (e.g., target DNA sequence).
  • triplex formation can involve the formation of a complex whereby one polypyrimidine segment of a PNA oligomer binds to a homopurine target nucleic acid sequence by Watson-Crick face binding and another polypyrimidine segment of a PNA oligomer (optionally from the same or a different PNA oligomer) binds to the homopurine target nucleic acid sequence by Hoogsteen face binding.
  • PNA oligomers capable of targeting nucleic acid sequences (including genomic DNA, such as genomic DNA in a living organism) that include one or more pyrimidine nucleobases within the target nucleic acid sequence, and compositions and related methods of use thereof.
  • PNA oligomers e.g., tail clamp PNA oligomers, that can target pyrimidine-containing nucleic acid sequences are sometimes referred to herein as “pyrimidine-compliant” or “pyrimidine-target-compliant.”
  • a pyrimidine-compliant PNA oligomer participates in Hoogsteen binding with a pyrimidine nucleobase in a target nucleic acid sequence (e.g., a target DNA sequence).
  • a pyrimidine-compliant PNA oligomer does not participate in Hoogsteen binding with a pyrimidine nucleobase in a target nucleic acid sequence (e.g., a target DNA sequence).
  • Embodiments of the PNA oligomers disclosed herein can be used in various applications such as diagnostic assays, nucleic acid sequencing (e.g. nanopore sequencing) and antisense applications.
  • the PNA oligomers and methods disclosed herein can exhibit improved ease of administration and relatively low off target effects.
  • peptide nucleic acids PNAs
  • compositions and related methods of use thereof PNAs
  • Hoogsteen face binding or “HF binding,” as used herein, refers to the base pair interactions between cognate nucleobases that occurs on the Hoogsteen face of a target nucleobase (e.g., in a target sequence; e.g. a target DNA sequence).
  • Hoogsteen face binding between cognate nucleobase pairs is distinct from Watson-Crick face binding (or WC face binding) between the same cognate nucleobase pairs; for example, a nucleobase typically engages in simultaneous Hoogsteen face binding with a first PNA subunit nucleobase and Watson-Crick face binding with a second PNA subunit nucleobase, e.g., to form a PNA/DNA/PNA triplex. See, for example, FIGS.2A-2B and FIG.3.
  • a “Hoogsteen face hydrogen bond” is a hydrogen bond between cognate base pairs that occurs on the Hoogsteen face of the target nucleobase (e.g., in a target sequence; e.g. a target DNA sequence).
  • a target nucleic acid sequence e.g., a target DNA sequence or target RNA sequence
  • An HCB PNA subunit comprises an “HCB nucleobase” that exhibits one or more of the following properties: i.
  • the HCB nucleobase participates in Hoogsteen face binding with a target sequence cytosine, wherein said target sequence cytosine also participates in Watson-Crick face binding through at least two canonical Watson-Crick hydrogen bonds with a second PNA subunit comprising a guanine or derivative thereof, e.g., 7-deazaguanine, hypoxanthine or 7- deazahypoxanthine; ii. the HCB nucleobase comprises at least one hydrogen bond acceptor, e.g., a carbonyl oxygen atom and/or one hydrogen bond donor, e.g., an amine hydrogen atom; iii.
  • the HCB nucleobase participates in at least one Hoogsteen hydrogen bond with a target sequence cytosine that is not a canonical cytosine-guanine Watson-Crick hydrogen bond; iv. a carbonyl oxygen atom in the HCB nucleobase participates in a Hoogsteen hydrogen bond with a hydrogen bond donor (e.g., an amine hydrogen atom) in the target sequence cytosine; v.
  • a hydrogen bond donor e.g., an amine hydrogen atom
  • the bond length of a Hoogsteen hydrogen bond between the HCB nucleobase and the target sequence cytosine is between 0.1 ⁇ and 10 ⁇ (e.g., between 1 ⁇ and 5 ⁇ ), e.g., as determined by X-ray crystallography; e.g., the bond length of the hydrogen bond between a nitrogen atom in the HCB nucleobase and the amine hydrogen atom of the target sequence cytosine is between 0.1 ⁇ and 10 ⁇ (e.g., between 1 ⁇ and 5 ⁇ ), e.g., as determined by X-ray crystallography; vi.
  • the bond length of the cytosine hydrogen at N4-PNA subunit hydrogen bond on the Watson-Crick face is between 1 ⁇ and 5 ⁇ ; vii. the bond length of the cytosine N3 nitrogen-PNA subunit hydrogen bond on the Watson- Crick face is between 1 ⁇ and 5 ⁇ ; viii. the bond length of the cytosine carbonyl oxygen at C2-PNA subunit hydrogen bond on the Watson-Crick face is between 0.1 ⁇ and 10 ⁇ (e.g., between 1 ⁇ and 5 ⁇ ); or ix.
  • the gel shift of a complex formed between a PNA oligomer comprising the HCB nucleobase and a target nucleic acid sequence comprising a cognate cytosine is greater than or equal to the gel shift of the target nucleic acid.
  • the HCB nucleobase has one of properties i)-ix). In some embodiments, the HCB nucleobase has two of properties i)-ix). In some embodiments, the HCB nucleobase has three of properties i)-ix). In some embodiments, the HCB nucleobase has four of properties i)-ix). In some embodiments, the HCB nucleobase has five of properties i)-ix).
  • the HCB nucleobase has six of properties i)-ix). In some embodiments, the HCB nucleobase has seven of properties i)-ix). In some embodiments, the HCB nucleobase has eight of properties i)-ix). In some embodiments, the HCB nucleobase has each of properties i)- ix). [0028] In some embodiments, the HCB nucleobase participates in at least one hydrogen bond with a target sequence cytosine that is other than a canonical Watson-Crick cytosine-guanine bond.
  • HCB nucleobase participates in a hydrogen bond with an amine hydrogen atom in the target sequence cytosine that is not involved in Watson-Crick face binding.
  • the HCB PNA subunit comprises pyrimidin-2(1H)-one.
  • the HCB nucleobase is P.
  • An HTB PNA subunit comprises an HTB nucleobase that exhibits one or more of the following properties: i.
  • the HTB nucleobase participates in Hoogsteen face binding with a target sequence thymine or uracil, wherein said target sequence thymine or uracil also participates in Watson- Crick face binding through at least one canonical Watson-Crick hydrogen bond with a second PNA subunit comprising an adenine or derivative thereof, e.g., 7-deazaadenine, 2,6- diaminopurine, or 7-deaza-2,6-diaminopurine; ii. the HTB nucleobase comprises at least one hydrogen bond donor, e.g., an amine hydrogen atom and/or one hydrogen bond acceptor, e.g., a carbonyl oxygen atom; iii.
  • the HTB nucleobase participates in at least one Hoogsteen hydrogen bond with a target sequence thymine (or uracil) that is not a canonical thymine-adenine (or uracil-adenine) Watson- Crick hydrogen bond; iv. a hydrogen atom in the HTB nucleobase participates in a Hoogsteen hydrogen bond with a hydrogen bond acceptor (e.g., a carbonyl oxygen atom) in the target sequence thymine (or uracil); v.
  • a hydrogen bond acceptor e.g., a carbonyl oxygen atom
  • the bond length of a Hoogsteen hydrogen bond between the HTB nucleobase and the target sequence thymine (or uracil) is between 0.1 ⁇ and 10 ⁇ (e.g., between 1 ⁇ and 5 ⁇ ), e.g., as determined by X-ray crystallography; e.g., the bond length of the hydrogen bond between a hydrogen atom in the HTB nucleobase and the carbonyl oxygen atom of the target sequence thymine (or uracil) is between 1 ⁇ and 5 ⁇ , e.g., as determined by X-ray crystallography; vi.
  • the bond length of the thymine (or uracil) carbonyl oxygen at C4-PNA subunit hydrogen bond on the Watson-Crick face is between 1 ⁇ and 5 ⁇ ; vii. the bond length of the thymine (or uracil) hydrogen at N3-PNA subunit hydrogen bond on the Watson-Crick face is between 1 ⁇ and 5 ⁇ ; viii. the bond length of the thymine (or uracil) carbonyl oxygen at C2-PNA subunit hydrogen bond on the Watson-Crick face is between 0.1 ⁇ and 10 ⁇ (e.g., between 1 ⁇ and 5 ⁇ ); or ix.
  • the gel shift of a complex formed between a PNA oligomer comprising the HTB nucleobase and a target nucleic acid sequence comprising a cognate thymine (or uracil) is greater than or equal to the gel shift of the target nucleic acid.
  • the HTB nucleobase has one of properties i)-ix). In some embodiments, the HTB nucleobase has two of properties i)-ix). In some embodiments, the HTB nucleobase has three of properties i)-ix). In some embodiments, the HTB nucleobase has four of properties i)-ix). In some embodiments, the HTB nucleobase has five of properties i)-ix).
  • the HTB nucleobase has six of properties i)-ix). In some embodiments, the HTB nucleobase has seven of properties i)-ix). In some embodiments, the HTB nucleobase has eight of properties i)-ix). In some embodiments, the HTB nucleobase has each of properties i)- ix). [0031] In some embodiments, the HTB nucleobase participates in at least one hydrogen bond with a target sequence thymine (or uracil) that is other than a canonical Watson-Crick thymine- adenine bond (or uracil-adenine bond).
  • a hydrogen atom of the HTB nucleobase participates in a hydrogen bond with a carbonyl oxygen atom in the target sequence thymine (or uracil) that is not involved in Watson-Crick face binding.
  • the HTB PNA subunit comprises pyridazin-3(2H)-one.
  • the HTB nucleobase is E.
  • “Peptide nucleic acid,” “PNA,” or “PNA oligomer” as used herein, refers to a non-natural polymer composition comprising linked nucleobases capable of sequence specifically hybridizing to a nucleic acid.
  • a PNA oligomer is comprised of PNA subunits, each of which comprise a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid.
  • the term “peptide nucleic acid”, “PNA”, or “PNA oligomer” also applies to polymers comprising two or more PNA subunits, phosphono-PNA analogues (pPNAs); trans-4-hydroxy-L-proline nucleic acids (HypNAs); and (1S,2R/1R,2S)-cis- cyclopentyl PNAs (cpPNAs).
  • a “PNA monomer,” (also sometimes referred to as a “PNA synthon”) as used herein, refers to a single discrete building block for PNA synthesis.
  • a PNA monomer comprises a backbone moiety and optionally a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid.
  • a first PNA monomer is activated, for example, by exposure to an activating group (e.g., a carboxyl activating group such as PyBOP or HATU).
  • an activating group e.g., a carboxyl activating group such as PyBOP or HATU
  • PNA monomer is then coupled to a particular reactive moiety (e.g., a free amine terminus (i.e., N-terminus)) on a second deprotected PNA monomer or a PNA oligomer to form a growing PNA oligomer chain.
  • a particular reactive moiety e.g., a free amine terminus (i.e., N-terminus)
  • PNA monomers include Fmoc/Bhoc PNA monomers, Fmoc/t-boc PNA monomers, boc/Z PNA monomers, boc/cbz PNA monomers, and others.
  • a “PNA subunit” as used herein, refers to a subunit within a PNA oligomer.
  • a PNA subunit comprises a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid, e.g., as shown in FIG.1A.
  • a PNA subunit comprises an aminoethylglycine backbone with an amine terminus (i.e., N-terminus) and a carboxyl terminus (i.e., C-terminus), and a nucleobase moiety attached to the backbone through a methylene carbonyl linker.
  • PNA subunits can include Watson-Crick (i.e., WC-binding) PNA subunits which mediate WC-binding to nucleobases in a target nucleic acid sequence, and can include Hoogsteen (i.e., HG-binding) PNA subunits that mediate HG-binding to nucleobases in a target nucleic acid sequence.
  • the nucleobases within a PNA subunit may be naturally occurring or non-naturally occurring.
  • nucleobases examples include adenine, guanine, thymine, cytosine, uracil, pseudoisocytosine, 2-thiopseudoisocytosine, 5- methylcytosine, 5-hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine (or 2,6- diaminopurine), 2-thiouracil, 2-thiothymine, 2-thiocytosine, 5-chlorouracil, 5-bromouracil, 5- iodouracil, 5-chlorocytosine, 5-bromocytosine, 5-iodocytosine, 5-propynyl uracil, 5-propynyl cytosine, 6-azo uracil, 6-azo cytosine, 6-azo thymine, 7-methylguanine, 7-methyladenine, 8- azaguanine, 8-azaadenine, 7-deazaguanine, 7-deazaadenine, 3-
  • a PNA subunit does not comprise a nucleobase (i.e., is abasic).
  • a PNA subunit can be a “Gly-Gly” subunit comprising two glycine residues covalently linked by an amide bond, neither of which comprises a nucleobase i.e., does not comprise a nucleobase moiety (e.g., a Gly-Gly bridge).
  • a “pyrimidine-compliant PNA subunit” or “PC PNA subunit” is a PNA subunit that allows for a pyrimidine nucleobase in a target sequence (e.g., a target nucleic acid sequence).
  • a PC PNA subunit comprises a PNA nucleobase capable of Hoogsteen binding to a pyrimidine nucleobase in a target sequence.
  • a PC PNA subunit can be an HCB PNA subunit or an HTB PNA subunit
  • a PNA nucleobase can be an HCB nucleobase or an HTB nucleobase.
  • a PC PNA subunit accommodates a nucleobase (e.g., a pyrimidine nucleobase) in a target sequence by forming no bonds to the nucleobase (e.g., does not participate in hydrogen binding with the nucleobase in a target sequence).
  • a PC PNA subunit does not comprise a nucleobase (i.e., is abasic).
  • a PC PNA subunit may be a “Gly-Gly” subunit comprising two glycine residues covalently linked by an amide bond, neither of which comprises a nucleobase.
  • a tcPNA comprises: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase; (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (a) a first region of the PNA
  • a tcPNA comprises i) a first region of the PNA oligomer comprising a plurality of PNA subunits that participate in binding to the Hoogsteen face of a target nucleic acid sequence and ii) a second region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target nucleic acid sequence.
  • the first region and second region of PNA subunits are linked by a linker (e.g., a polyethylene glycol linker, e.g., PEG2 depicted in FIG.8B, or PEG3 depicted in FIG.8D).
  • a tcPNA may further comprise iii) a third region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target tail nucleic acid sequence and/or iv) a positively charged region comprising one or more positively charged moieties (e.g., positively charged amino acids such as lysine, ornithine or arginine), which can be present on a terminus of the tcPNA.
  • a tcPNA comprises i), ii) and iii).
  • a tcPNA comprises i), ii), iii), and iv).
  • a tcPNA comprises a PC PNA subunit (e.g., an HCB PNA subunit or an HTB PNA subunit) in the first region of the PNA oligomer.
  • An example of tcPNA is depicted in FIG.1B.
  • “Watson-Crick face binding,” or “WC face binding” as used herein refers to the base pair interactions between cognate nucleobases that occurs on the Watson-Crick face of a target nucleobase (e.g., in a target sequence).
  • Watson-Crick face binding between cognate nucleobase pairs is distinct from Hoogsteen face binding between the same cognate nucleobase pairs; for example, in a tcPNA, a nucleobase of a target sequence (e.g. a target DNA sequence) can engage in simultaneous WC face binding with a first PNA subunit nucleobase and Hoogsteen face binding with a second PNA subunit nucleobase, e.g., to form a PNA/DNA/PNA triplex. See, for example, FIGS.2A-2B and FIG.3.
  • a target sequence e.g. a target DNA sequence
  • a “Watson-Crick hydrogen bond” is a hydrogen bond between cognate base pairs that occurs on the Watson-Crick face of the target nucleobase (e.g., in a target sequence).
  • Peptide Nucleic Acids [0038] The present disclosure features PNA oligomers capable of targeting nucleic acid sequences that include one or more pyrimidine nucleobasesand compositions and related methods of use thereof.
  • the PNA oligomer is a tail-clamp peptide nucleic acid (tcPNA).
  • triplex-forming molecules include a “tail” added to the end of the Watson-Crick binding portion of a PNA oligomer to bind the target strand outside the triple helix.
  • a tcPNA can mediate DNA binding that encompasses both triplex and duplex formation.
  • a tcPNA can comprise a first region comprising a plurality of PNA subunits that participate in binding to the Hoogsteen face of a target sequence, wherein the target sequence comprises a pyrimidine nucleobase (e.g., a cytosine or thymine) at a first pyrimidine position in the target sequence, and, at the position corresponding to the first pyrimidine position, the tcPNA comprises a pyrimidine-compliant PNA subunit (PC PNA subunit).
  • PC PNA subunit pyrimidine-compliant PNA subunit
  • the tcPNA further comprises a second region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target nucleic acid sequence, wherein the first region and second region are covalently linked through a linker (e.g., a polyethylene-glycol linker).
  • the tcPNA further comprises a third region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target tail nucleic acid sequence.
  • the tcPNA further comprises a positively charged region comprising positively charged amino acids (e.g., lysine residues) on at least one terminus of the tcPNA.
  • the tcPNA comprises one or more PNA subunits comprising a substituent at the gamma-position. In some embodiments, the tcPNA comprises one or more PNA subunits comprising a mini-PEG moiety at the gamma-position. [0040] In some embodiments, a tcPNA can comprise a PNA oligomer as shown in FIG.1C.
  • a peptide nucleic acid (PNA) oligomer comprising: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase (X); (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA, and where
  • a PNA oligomer of the disclosure can comprise from about 5 to about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits.
  • a PNA oligomer of the disclosure can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0042] In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits.
  • a first plurality of PNA subunits of a tcPNA can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits.
  • a first plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits.
  • a first plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0043] In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits.
  • a second plurality of PNA subunits can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits.
  • a second plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits.
  • a second plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0044] In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits.
  • a third plurality of PNA subunits can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits.
  • a third plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits.
  • a third plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits.
  • a linker can comprise C 2-50 heteroalkylene. In some embodiments, the linker can comprise polyethylene glycol. In some embodiments, the linker comprises PEG2.
  • the linker comprises PEG2PEG2. In some embodiments, the linker comprises PEG3. In some embodiments, the linker comprises PEG2PEG2. In some embodiments, the linker comprises PEG3PEG3. [0046] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA.
  • the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA.
  • the first plurality of PNA subunits, the first region of the dsDNA, and the second plurality of PNA subunits form a triplex structure.
  • the first region of the PNA oligomer further comprises (a’) a first positively charged region comprising a first positively charged amino acid, wherein the first positively charged region is covalently bound to a second terminal end of the first region of the PNA oligomer.
  • the first positively charged amino acid is lysine.
  • the second region of the PNA oligomer participates in Watson Crick binding with the first region of the dsDNA and the second region of the dsDNA.
  • the second region of the PNA oligomer further comprises a second positively charged amino acid, wherein the second positively charged amino acid is covalently bound to a second terminal end of the second region of the PNA oligomer.
  • the second positively charged amino acid is lysine.
  • the first region of the PNA oligomer comprises a gamma- modified PNA subunit.
  • the second region of the PNA oligomer comprises a gamma-modified PNA subunit.
  • the third region of the PNA oligomer comprises a gamma-modified PNA subunit.
  • the first region of the PNA oligomer comprises a first gamma-modified PNA subunit
  • the second region of the PNA oligomer comprises a second gamma-modified PNA subunit
  • the third region of the PNA oligomer comprises a third gamma-modified PNA subunit.
  • Pyrimidine Compliant PNA Subunits [0049] A PNA subunit refers to a subunit within a PNA oligomer, and comprises a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid, e.g., as shown in FIG.1A-1C.
  • a PNA subunit comprises a nucleobase and a backbone moiety.
  • the nucleobase of the PNA subunit can form one or more hydrogen bonds with the nucleobase of a target nucleic acid sequence.
  • the backbone moiety of the PNA subunit typically comprises a first terminus and a second terminus.
  • the first terminus is an amine terminus (i.e., N-terminus)
  • the second terminus is a carboxyl terminus (i.e., C-terminus), e.g., as shown in FIG.1A.
  • the backbone moiety also comprises an atom to which the nucleobase is bound, typically through a spacer moiety.
  • PC PNA subunits which are capable of accommodating a pyrimidine nucleobase in a target sequence, and can comprise an HCB PNA subunit or an HTB PNA monomer or subunit.
  • the PC PNA subunit is a compound of Formula (I): wherein P 1 is a first terminus, e.g., an amine or a carboxyl terminus, which can participate in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer; P 5 is a second terminus, e.g., an amine or a carboxyl terminus, which can participate in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer; each P 3 and P 4 is independently absent or a backbone unit, e.g., alkylene optionally substituted with one or more R A ; Z is X-R a or X-L-B; X is N or CR
  • P 1 is an amine terminus (e.g., -NH 2 or -NH-, wherein -NH- participates in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer).
  • P 5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH 3 , - C(O)NH 2 , or -C(O)-, wherein -C(O)- participates in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer).
  • P 1 is an amine terminus and P 5 is a carboxyl terminus.
  • each P 3 and P 4 is independently a backbone subunit. In some embodiments, each P 3 and P 4 is independently C 1-12 alkylene optionally substituted with one or more R A . In some embodiments, P 3 is C 1-12 alkylene optionally substituted with one or more R A . In some embodiments, P 3 is C 1-12 alkylene. In some embodiments, P 3 is C 1-6 alkylene. In some embodiments, P 3 is C 1-4 alkylene. In some embodiments, P 3 is C 1-12 alkylene substituted with one or more R A (e.g., 1 R A , e.g., heteroalkyl or oxo).
  • R A e.g., 1 R A , e.g., heteroalkyl or oxo
  • P 4 is C 1-12 alkylene optionally substituted with one or more R A . In some embodiments, P 4 is C 1-12 alkylene. In some embodiments, P 4 is C 1-6 alkylene. In some embodiments, P 4 is C 1-4 alkylene. [0053] In some embodiments, each P 3 and P 4 is independently methylene or ethylene optionally substituted with one or more R A . In some embodiments, P 3 is ethylene optionally substituted with one or more R A . In some embodiments, P 3 is ethylene. In some embodiments, P 3 is ethylene substituted with one or more R A (e.g., 1 R A , e.g., heteroalkyl or oxo).
  • R A e.g., 1 R A , e.g., heteroalkyl or oxo
  • P 4 is methylene optionally substituted with one or more R A . In some embodiments, P 4 is methylene. [0054] In some embodiments, each P 3 or P 4 is independently substituted with 0, 1, 2, 3, 4, 5, or 6 R A . In some embodiments, each P 3 or P 4 is independently substituted with 1 R A (e.g., heteroalkyl or oxo). In some embodiments, each instance of R A is independently oxo or C 1-30 heteroalkyl. In some embodiments, R A is oxo.
  • R A is heteroalkyl, e.g., a C 1-30 polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG moiety comprising between 2 and 6 PEG units).
  • R A has the structure of Formula (IV-a) or (IV-b): wherein R 12 is hydrogen or alkyl (e.g., C 1-4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5, and “ ” denotes an attachment point to P 3 or P 4 .
  • R 12 is hydrogen or methyl, and y is 1. In some embodiments, R 12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R 12 is methyl or tert-butyl, and y is 1. In some embodiments, R 12 is hydrogen and y is 1. In some embodiments, R 12 is methyl and y is 1. In some embodiments, R 12 is tert-butyl and y is 1. [0056] In some embodiments, Z is X-R a , wherein R a is hydrogen. In some embodiments, Z is NH. In some embodiments, Z is X-L-B. In some embodiments, Z is N-L-B.
  • X is CR b , wherein R b is hydrogen, deuterium, fluorine, or C 1- 4 alkyl. In some embodiments, X is N.
  • L is C 1-12 alkylene or C 1-12 heteroalkylene, each of which is optionally substituted with one or more R B . In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one R B . In some embodiments, L is C 1- 12heteroalkylene substituted with one R B . In some embodiments, R B is oxo. [0059] In some embodiments, L is selected from and . In some embodiments, L is .
  • L is . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X.
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) as described herein.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0061] In some embodiments, each P 1 , P 3 , P 4 , and P 5 is independently selected such that, when two or more PNA subunits are coupled, the distance between the nucleobase of each PNA subunit is fixed.
  • the distance between the nucleobase of each PNA subunit allows alignment and interaction of the PNA subunit nucleobases with the complementary nucleobase in a target nucleic acid. In some embodiments, the interaction is forming one or more hydrogen bonds between the PNA subunit nucleobase and the complementary nucleobase in a target nucleic acid.
  • the PC PNA subunit is a compound of Formula (II-a): wherein P 1 is a first terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer; P 5 is a second terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer; each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(R C )(R D ), halo (e.g., fluorine), -OR E , or the side-chain of an amino acid; X is N or CR b ; L is alkylene, alkenylene, heteroalkylene, cyclo
  • P 1 is an amine terminus (e.g., -NH 2 or -NH-, wherein -NH- participates in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer).
  • P 5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH 3 , - C(O)NH 2 , or -C(O)-, wherein -C(O)- participates in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer).
  • P 1 is an amine terminus and P 5 is a carboxyl terminus.
  • each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen or C 1- 30 heteroalkyl. In some embodiments, each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen. In some embodiments, each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen or C 1- 30heteroalkyl, e.g., a C 1-30 polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG moiety comprising between 2 and 6 PEG units).
  • PEG polyethylene glycol
  • each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen or has the structure of Formula (IV-a) or (IV-b): wherein R 12 is hydrogen or alkyl (e.g., C 1-4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5, and “ ” denotes an attachment point to the PNA subunit.
  • R 12 is hydrogen or methyl, and y is 1.
  • R 12 is hydrogen or tert-butyl, and y is 1.
  • R 12 is methyl or tert-butyl, and y is 1. In some embodiments, R 12 is hydrogen and y is 1. In some embodiments, R 12 is methyl and y is 1. In some embodiments, R 12 is tert-butyl and y is 1. [0066] In some embodiments, X is N. [0067] In some embodiments, L is C 1-12 alkylene or C 1-12 heteroalkylene, each of which is optionally substituted with one or more R B . In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one R B . In some embodiments, L is C 1- 12 heteroalkylene substituted with one R B .
  • R B is oxo.
  • L is selected from and . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is . In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X.
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one.
  • the PNA subunit is a PNA subunit of Formula (II-b): [0071] wherein R 2 is hydrogen, deuterium or alkyl (e.g., C 1- C 4 alkyl); each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen, deuterium, C 1- C 4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or has structure of Formula (IV-a) or (IV-b): ; L is alkylene, alkenylene, or heteroalkylene, each of which is optionally substituted with one or more R B ; B is a PNA nucleobase; R 12 is hydrogen or alkyl (e.g., C 1 -C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; each R B is independently
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0073] In some embodiments, each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R 3 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen, and R 4 has structure of Formula (IV-a). In some embodiments, each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen.
  • R 12 is hydrogen or alkyl (e.g., C 1- C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer from 1 to 5. In some embodiments, R 12 is hydrogen or methyl, and y is 1. In some embodiments, R 12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R 12 is methyl or tert-butyl, and y is 1. In some embodiments, R 12 is hydrogen and y is 1. In some embodiments, R 12 is methyl and y is 1. In some embodiments, R 12 is tert-butyl and y is 1.
  • L is C 1-12 alkylene or C 1-12 heteroalkylene, each of which is optionally substituted with one or more R B .
  • L is ethylene, propylene, or butylene, each of which is substituted with one R B .
  • L is C 1- 12heteroalkylene substituted with one R B .
  • R B is oxo.
  • L is selected from , , , and In some embodiments, L is . In some embodiments, L is . In some embodiments, L is in either orientation. In some embodiments, L is . In some embodiments, L is with the carbonyl carbon linked to N.
  • L is with the carbonyl carbon linked to N. In some embodiments, L is with the carbonyl carbon linked to N. In some embodiments, L is with the carbonyl carbon linked to N. In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • V Formula
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one.
  • the PNA subunit is a PNA subunit of Formula (II-c): wherein R 2 is hydrogen, deuterium or C 1 -C 4 alkyl; each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, deuterium, C 1- C 4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or the structure of Formula (IV-a) or (IV-b): L is alkylene, alkenylene, or heteroalkylene, each of which is optionally substituted with one or more R B ; B is a PNA nucleobase; R 12 is hydrogen or alkyl (e.g., C 1 -C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; each R B is independently deuterium, alkyl, halo (e.g., fluorine),
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0080] In some embodiments, each R 3 , R 4 , R 5 , and R 6 , is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R 3 , R 5 , and R 6 is independently hydrogen, and R 4 has structure of Formula (IV-a). In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen.
  • R 12 is hydrogen or alkyl (e.g., C 1- C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5 (inclusive), and “ denotes an attachment point to the methylene or ethylene moiety of the PNA subunit.
  • R 12 is hydrogen or methyl, and y is 1.
  • R 12 is hydrogen or tert-butyl, and y is 1.
  • R 12 is methyl or tert-butyl, and y is 1.
  • R 12 is hydrogen and y is 1.
  • R 12 is methyl and y is 1.
  • R 12 is tert-butyl and y is 1.
  • L is C 1-12 alkylene or C 1-12 heteroalkylene, each of which is optionally substituted with one or more R B .
  • L is ethylene, propylene, or butylene, each of which is substituted with one R B .
  • L is C 1- 12heteroalkylene substituted with one R B .
  • R B is oxo.
  • L is selected from and .
  • L is .
  • L is In some embodiments, L is . In some embodiments, L is . In some embodiments, L is .
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • V Formula
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one.
  • the PNA subunit is a PNA subunit of Formula (II-d): wherein R 2 is hydrogen, deuterium or C 1- C 4 alkyl; each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, deuterium, C 1- C 4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or has the structure of Formula (IV-a) or (IV-b): ; eac 9 10 h R and R is independently hydrogen, deuterium, C 1- C 4 alkyl, or halo (e.g., fluorine); B is PNA nucleobase; n is an integer between 0 and 4; R 12 is hydrogen or alkyl (e.g., C 1 -C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; and each “ ” independently denote
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0087] In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R 3 , R 5 , and R 6 is independently hydrogen, and R 4 has structure of Formula (IV-a). In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen. [0088] In some embodiments, R 12 is hydrogen or methyl, and y is 1. In some embodiments, R 12 is hydrogen or tert-butyl, and y is 1.
  • R 12 is methyl or tert-butyl, and y is 1. In some embodiments, R 12 is hydrogen and y is 1. In some embodiments, R 12 is methyl and y is 1. In some embodiments, R 12 is tert-butyl and y is 1. [0089]
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • V Formula
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0090] In some embodiments, n is an integer between 0 and 2.
  • n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2. [0091]
  • the PNA subunit is a PNA subunit of Formula (II-e): wherein R 2 is hydrogen, deuterium or C 1 -C 4 alkyl; each R 3 , R 5 , and R 6 is independently hydrogen, deuterium, C 1 -C 4 alkyl, halo (e.g., fluorine), or the side-chain of an amino acid; each R 9 and R 10 is independently hydrogen, deuterium, C 1- C 4 alkyl, or halo (e.g., fluorine); R 12 is hydrogen or alkyl (e.g., C 1- C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; n is an integer from 0 to 4; m is an integer from
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0093] In some embodiments, each R 3 , R 5 , and R 6 is independently hydrogen. In some embodiments, each R 9 and R 10 is independently hydrogen. [0094] In some embodiments, R 12 is hydrogen or methyl, and m is 1. In some embodiments, R 12 is hydrogen or tert-butyl, and m is 1. In some embodiments, R 12 is methyl or tert-butyl, and m is 1. In some embodiments, R 12 is hydrogen and m is 1. In some embodiments, R 12 is methyl and m is 1. In some embodiments, R 12 is tert-butyl and m is 1.
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0096] In some embodiments, n is an integer between 0 and 2. In some embodiments, n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2.
  • the PNA subunit is a PNA subunit of Formula (II-f): wherein R 2 is hydrogen, deuterium or C 1- C 4 alkyl; each R 4 , R 5 , and R 6 is independently hydrogen, deuterium, C 1- C 4 alkyl, halo (e.g., fluorine) or the side-chain of an amino acid; each R 9 and R 10 is independently hydrogen, deuterium, C 1 -C 4 alkyl, or halo (e.g., fluorine); R 12 is hydrogen or alkyl (e.g., C 1 -C 4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; n is an integer from 0 to 4; m is an integer from 1 to 3; and each independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0099] In some embodiments, each R 4 , R 5 , and R 6 is independently hydrogen. In some embodiments, each R 9 and R 10 is independently hydrogen. [0100] In some embodiments, R 12 is hydrogen or methyl, and m is 1. In some embodiments, R 12 is hydrogen or tert-butyl, and m is 1. In some embodiments, R 12 is methyl or tert-butyl, and m is 1. In some embodiments, R 12 is hydrogen and m is 1. In some embodiments, R 12 is methyl and m is 1. In some embodiments, R 12 is tert-butyl and m is 1.
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0102] In some embodiments, n is an integer from 0 to 2. In some embodiments, n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2.
  • the PNA subunit is selected from: wherein R 12 is hydrogen or alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; and each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer.
  • R 12 is hydrogen, or alkyl (e.g., methyl, ethyl, isopropyl, tert- butyl). In some embodiments, R 12 is hydrogen. In some embodiments, R 12 is methyl.
  • R 12 is tert-butyl.
  • B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one.
  • each “ ” independently denotes an attachment point to an atom of the N-terminus of the PNA oligomer (e.g., a hydrogen), to an atom of the C-terminus of the PNA oligomer (e.g., -OH or -NH 2 ), or to another PNA subunit.
  • one “ ” is an attachment point to an atom of the C-terminus of the PNA oligomer and one “ ” is an attachment point to another monomer/PNA subunit.
  • one “ ” is an attachment point to an atom of the N-terminus of the PNA oligomer and one “ ” is an attachment point to another PNA subunit.
  • both “ ” are attachment points to other PNA subunits.
  • one “ ” is an attachment point to a linker.
  • one “ ” is an attachment point to an amino acid.
  • the PC PNA subunit is a compound of Formula (III-a): wherein P 1 is a first terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer; P 5 is a second terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer; each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(R C )(R D ), halo (e.g., fluor
  • P 1 is an amine terminus (e.g., -NH 2 or -NH-, wherein -NH- participates in a covalent bond to the P 5 group of another PNA subunit within the PNA oligomer).
  • P 5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH 3 , - C(O)NH 2 , or -C(O)-, wherein -C(O)- participates in a covalent bond to the P 1 group of another PNA subunit within the PNA oligomer).
  • P 1 is an amine terminus and P 5 is a carboxyl terminus.
  • each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, heteroalkyl, or the side-chain of an amino acid. In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen. [0110] In some embodiments, X is N, and R a is hydrogen. In some embodiments, X is N, and R a is methyl. In some embodiments, Y is –C(O)-.
  • the PC PNA subunit is a compound of Formula (III-b): wherein R 2 is hydrogen, deuterium or alkyl (e.g., C 1- C 4 alkyl); each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(R C )(R D ), halo (e.g., fluorine), -OR E , or the side-chain of an amino acid; R a is hydrogen or alkyl (e.g., methyl); each R C , R D , and R E is independently hydrogen, alkyl, or heteroalkyl; and each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer.
  • R 2 is hydrogen, deuterium or alkyl (e.g., C 1- C 4 alkyl); each R 3 , R
  • R 2 is hydrogen or methyl. In some embodiments, R 2 is hydrogen. [0113] In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen, heteroalkyl, or the side-chain of an amino acid. In some embodiments, each R 3 , R 4 , R 5 , and R 6 is independently hydrogen. In some embodiments, R a is hydrogen. In some embodiments, R a is methyl.
  • the PC PNA subunit is a compound of Formula (III-c): wherein each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv).
  • the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase (e.g., B) has the structure of formula (V-i).
  • X 1 is N or C.
  • X 1 is N.
  • X 1 is C.
  • X 2 is N.
  • X 2 is CH.
  • X 3 is CH.
  • X 3 is C-NH 2 .
  • X 4 is C or N. In some embodiments, X 4 is N.
  • R 20 is absent or hydrogen. In some embodiments, R 20 is absent. In some embodiments, R 20 is hydrogen.
  • X 1 is C
  • X 2 is CH
  • X 3 is C-NH 2
  • X 4 is N.
  • each R 20 , R 21 , and R 35 is H.
  • each n and m is independently 1.
  • R 21 is hydrogen, deuterium, alkyl (e.g., methyl), or alkynyl. In some embodiments, R 21 is hydrogen.
  • the PNA nucleobase e.g., B
  • the PNA nucleobase comprises a structure of Formula (V-b): wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein.
  • the PNA nucleobase (e.g., B) comprises a structure of Formula (V-c): wherein R 21 is hydrogen, deuterium, halo, alkyl (e.g., methyl), alkenyl, or alkynyl; and “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein. [0126] In some embodiments, R 21 is hydrogen, or alkyl (e.g., methyl). In some embodiments, R 21 is hydrogen.
  • the nucleobase (e.g., B) of a PNA subunit comprises a structure of Formula (V-d): wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein.
  • the nucleobase (e.g., B) of a PNA subunit comprises a structure of Formula (V-e): wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein.
  • the PC PNA subunit is a PNA subunit of one of the following formula:
  • R 12 is hydrogen or alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl), each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer.
  • R 12 is hydrogen, or alkyl (e.g., methyl, ethyl, isopropyl, tert- butyl).
  • R 12 is hydrogen.
  • R 12 is C 1-4 alkyl.
  • R 12 is methyl.
  • R 12 is ethyl.
  • R 12 is tert-butyl.
  • the PNA subunit is selected from:
  • each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer.
  • each “ ” independently denotes an attachment point to the C- terminus of the PNA oligomer (e.g., -OH or -NH 2 ), or to another PNA subunit.
  • one “ ” is an attachment point to an atom of the C-terminus of the PNA oligomer and one” ” is an attachment point to another PNA subunit.
  • one “ ” is an attachment point to an atom of the N-terminus of the PNA oligomer and one “ ” is an attachment point to another PNA subunit. In some embodiments, both “ ” are attachment points to other PNA subunits.
  • the abbreviations used herein have the conventional meaning within the chemical and biological arts. The chemical structures and formulae set forth herein are constructed according to the standard rules of chemical valency known in the chemical arts. [0134] When a range of values is listed, it is intended to encompass each value and sub–range within the range.
  • C 1- C 6 alkyl is intended to encompass, C 1 ,C 2 , C 3 , C 4 , C 5 , C 6 , C 1 -C 6 , C 1 -C 5 , C 1 -C 4 , C 1 -C 3 , C 1 -C 2 , C 2 -C 6 , C 2 -C 5 , C 2 -C 4 , C 2 -C 3 , C 3 -C 6 , C 3 -C 5 , C 3 -C 4 , C 4 -C 6 , C 4 - C 5 , and C 5 -C 6 alkyl.
  • alkyl refers to a radical of a straight–chain or branched saturated hydrocarbon group.
  • An alkyl group can have, for example, from 1 to 36 carbon atoms (“C 1- C 36 alkyl”). In some embodiments, an alkyl group has 1 to 32 carbon atoms (“C 1 -C 32 alkyl”). In some embodiments, an alkyl group has 1 to 24 carbon atoms (“C 1 -C 24 alkyl”). In some embodiments, an alkyl group has 1 to 18 carbon atoms (“C 1- C 18 alkyl”).
  • an alkyl group has 1 to 12 carbon atoms (“C 1- C 12 alkyl”). In some embodiments, an alkyl group has 1 to 8 carbon atoms (“C 1- C 8 alkyl”). In some embodiments, an alkyl group has 1 to 7 carbon atoms (“C 1 -C 7 alkyl”). In some embodiments, an alkyl group has 1 to 6 carbon atoms (“C 1 -C 6 alkyl”). In some embodiments, an alkyl group has 1 to 5 carbon atoms (“C 1- C 5 alkyl”). In some embodiments, an alkyl group has 1 to 4 carbon atoms (“C 1- C 4 alkyl”).
  • an alkyl group has 1 to 3 carbon atoms (“C 1 -C 3 alkyl”). In some embodiments, an alkyl group has 1 to 2 carbon atoms (“C 1- C 2 alkyl”). In some embodiments, an alkyl group has 1 carbon atom (“C 1 alkyl”). In some embodiments, an alkyl group has 2 to 6 carbon atoms (“C 2 -C 6 alkyl”).
  • C 1 -C 24 alkyl groups include methyl (C 1 ), ethyl (C 2 ), n–propyl (C 3 ), isopropyl (C 3 ), n–butyl (C 4 ), tert–butyl (C 4 ), sec–butyl (C 4 ), iso–butyl (C 4 ), n–pentyl (C 5 ), 3–pentanyl (C 5 ), amyl (C 5 ), neopentyl (C 5 ), 3–methyl–2–butanyl (C 5 ), tert–amyl (C 5 ), n–hexyl (C 6 ), octyl (C 8 ), nonyl (C 9 ), decyl (C 10 ), undecyl (C 1 1), dodecyl (or lauryl) (C 12 ), tridecyl (C 1 3), tetradecyl (or myristyl) (
  • alkyl group can be independently, optionally substituted, i.e., unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents; e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent.
  • alkenyl refers to a radical of a straight–chain or branched hydrocarbon group having one or more carbon–carbon double bonds, and no triple bonds (“C 2 -C 36 alkenyl”).
  • An alkenyl group can have, for example, 2 to 36 carbon atoms.
  • an alkenyl group has 2 to 32 carbon atoms (“C 2 -C 32 alkenyl”). In some embodiments, an alkenyl group has 2 to 24 carbon atoms (“C 2 -C 24 alkenyl”). In some embodiments, an alkenyl group has 2 to 18 carbon atoms (“C 2 -C 18 alkenyl”). In some embodiments, an alkenyl group has 2 to 12 carbon atoms (“C 2 -C 12 alkenyl”). In some embodiments, an alkenyl group has 2 to 8 carbon atoms (“C 2 - C 8 alkenyl”). In some embodiments, an alkenyl group has 2 to 7 carbon atoms (“C 2 -C 7 alkenyl”).
  • an alkenyl group has 2 to 8 carbon atoms (“C 2 -C 8 alkenyl”). In some embodiments, an alkenyl group has 2 to 6 carbon atoms (“C 2 -C 6 alkenyl”). In some embodiments, an alkenyl group has 2 to 5 carbon atoms (“C 2 -C 5 alkenyl”). In some embodiments, an alkenyl group has 2 to 4 carbon atoms (“C 2 -C 4 alkenyl”). In some embodiments, an alkenyl group has 2 to 3 carbon atoms (“C 2 -C 3 alkenyl”). In some embodiments, an alkenyl group has 2 carbon atoms (“C 2 alkenyl”).
  • the one or more carbon– carbon double bonds can be internal (such as in 2–butenyl) or terminal (such as in 1–butenyl).
  • the one or more carbon double bonds can have cis, trans, E, or Z geometry.
  • Examples of C 2 -C 4 alkenyl groups include ethenyl (C 2 ), 1–propenyl (C 3 ), 2–propenyl (C 3 ), 1–butenyl (C 4 ), 2– butenyl (C 4 ), butadienyl (C 4 ), and the like.
  • C 2 -C 24 alkenyl groups include the aforementioned C 2 –4 alkenyl groups and pentenyl (C 5 ), pentadienyl (C 5 ), hexenyl (C 6 ), and the like.
  • alkenyl examples include heptenyl (C 7 ), octenyl (C 8 ), octatrienyl (C 8 ), nonenyl (C 9 ), nonadienyl (C 9 ), decenyl (C 10 ), decadienyl (C 10 ), undecenyl (C 1 1), undecadienyl (C 1 1), dodecenyl (C 12 ), dodecadienyl (C 12 ), tridecenyl (C 1 3), tridecadienyl (C 13 ), tetradecenyl (C 14 ), tetradecadienyl (e.g., myristoleyl) (C 14 ), pentadecenyl (C 15 ), pentadecadienyl (C 15 ), hexadecenyl (e.g., palmitoleyl) (C 16 ), hexadecadienyl (C 16
  • alkenyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkenyl”) or substituted (a “substituted alkenyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent.
  • the alkenyl group is unsubstituted C 2–10 alkenyl.
  • alkynyl refers to a radical of a straight–chain or branched hydrocarbon group having one or more carbon–carbon triple bonds.
  • An alkynyl group can have, for example, from 2 to 36 carbon atoms (“C 2 -C 36 alkynyl”). In some embodiments, an alkynyl group has 2 to 32 carbon atoms (“C 2 -C 3 2 alkynyl”). In some embodiments, an alkynyl group has 2 to 24 carbon atoms (“C 2 -C 24 alkynyl”). In some embodiments, an alkynyl group has 2 to 18 carbon atoms (“C 2 -C 18 alkynyl”). In some embodiments, an alkynyl group has 2 to 12 carbon atoms (“C 2 -C 12 alkynyl”).
  • an alkynyl group has 2 to 8 carbon atoms (“C 2 - C 8 alkynyl”). In some embodiments, an alkynyl group has 2 to 6 carbon atoms (“C 2 -C 6 alkynyl”). In some embodiments, an alkynyl group has 2 to 5 carbon atoms (“C 2 -C 5 alkynyl”). In some embodiments, an alkynyl group has 2 to 4 carbon atoms (“C 2 -C 4 alkynyl”). In some embodiments, an alkynyl group has 2 to 3 carbon atoms (“C 2 -C 3 alkynyl”). In some embodiments, an alkynyl group has 2 carbon atoms (“C 2 alkynyl”).
  • the one or more carbon– carbon triple bonds can be internal (such as in 2–butynyl) or terminal (such as in 1–butynyl).
  • Examples of C 2 -C 4 alkynyl groups include ethynyl (C 2 ), 1–propynyl (C 3 ), 2–propynyl (C 3 ), 1– butynyl (C 4 ), 2–butynyl (C 4 ), and the like.
  • Each instance of an alkynyl group can be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkynyl”) or substituted (a “substituted alkynyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent.
  • the alkynyl group is unsubstituted C 2 –10 alkynyl.
  • the alkynyl group is substituted C 2 –6 alkynyl.
  • heteroalkyl refers to a non-cyclic stable straight or branched alkyl, alkenyl, or alkynyl chains, or combinations thereof, including at least one carbon atom for heteroalkyl and at least two carbon atoms for heteroalkenyl and heteroalkynyl and at least one heteroatom selected from the group consisting of O, N, P, Si, and S, and wherein the nitrogen and sulfur atoms can optionally be oxidized, and the nitrogen heteroatom can optionally be quaternized.
  • alkylene alkenylene
  • alkynylene alkynylene
  • heteroalkylene alone or as part of another substituent, mean, unless otherwise stated, a divalent radical derived from an alkyl, alkenyl, alkynyl, or heteroalkyl, respectively.
  • alkenylene alone or as part of another substituent, means, unless otherwise stated, a divalent radical derived from an alkene.
  • alkylene, alkenylene, alkynylene, or heteroalkylene group can be described as, e.g., a C 1- C 6 - membered alkylene, C 1 -C 6 -membered alkenylene, C 1 -C 6 -membered alkynylene, or C 1 -C 6 - membered heteroalkylene, wherein the term “membered” refers to the non-hydrogen atoms within the moiety.
  • heteroatoms can also occupy either or both of the chain termini (e.g., alkyleneoxy, alkylenedioxy, alkyleneamino, alkylenediamino, and the like).
  • alkylene and heteroalkylene linking groups no orientation of the linking group is implied by the direction in which the formula of the linking group is written.
  • the formula -C(O) 2 R’- can represent both -C(O) 2 R’- and –R’C(O) 2 -.
  • Each instance of an alkylene, alkenylene, alkynylene, or heteroalkylene group can be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkylene”) or substituted (a “substituted heteroalkylene”) with one or more substituents.
  • aryl refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 ⁇ electrons shared in a cyclic array) having 6–14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“C 6 -C 14 aryl”).
  • aromatic ring system e.g., having 6, 10, or 14 ⁇ electrons shared in a cyclic array
  • an aryl group has six ring carbon atoms (“C 6 aryl”; e.g., phenyl).
  • an aryl group has ten ring carbon atoms (“C 10 aryl”; e.g., naphthyl such as 1–naphthyl and 2–naphthyl). In some embodiments, an aryl group has fourteen ring carbon atoms (“C 14 aryl”; e.g., anthracyl).
  • An aryl group can be described as, e.g., a C 6 -C 10 - membered aryl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety.
  • Aryl groups include phenyl, naphthyl, indenyl, and tetrahydronaphthyl.
  • Each instance of an aryl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents.
  • the aryl group is unsubstituted C 6 -C 14 aryl.
  • the aryl group is substituted C 6 -C 14 aryl.
  • cycloalkyl refers to a radical of a non–aromatic cyclic hydrocarbon group having, for example, from 3 to 7 ring carbon atoms (“C 3 -C 7 cycloalkyl”) and zero heteroatoms in the non–aromatic ring system.
  • a cycloalkyl group has 3 to 6 ring carbon atoms (“C 3 -C 6 cycloalkyl”).
  • a cycloalkyl group has 5 to 7 ring carbon atoms (“C 5 -C 7 cycloalkyl”).
  • a cycloalkyl group may be described as, e.g., a C 4 -C 7 - membered cycloalkyl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety.
  • C 3 -C 6 cycloalkyl groups include, without limitation, cyclopropyl (C 3 ), cyclopropenyl (C 3 ), cyclobutyl (C 4 ), cyclobutenyl (C 4 ), cyclopentyl (C 5 ), cyclopentenyl (C 5 ), cyclohexyl (C 6 ), cyclohexenyl (C 6 ), cyclohexadienyl (C 6 ), and the like.
  • C 3 -C 7 cycloalkyl groups include, without limitation, the aforementioned C 3 -C 6 cycloalkyl groups as well as cycloheptyl (C 7 ), cycloheptenyl (C 7 ), cycloheptadienyl (C 7 ), and cycloheptatrienyl (C 7 ), bicyclo[2.1.1]hexanyl (C 6 ), bicyclo[3.1.1]heptanyl (C 7 ), and the like.
  • the cycloalkyl group is either monocyclic (“monocyclic cycloalkyl”) or contain a fused, bridged, or spiro ring system such as a bicyclic system (“bicyclic cycloalkyl”) and can be saturated or can be partially unsaturated.
  • “Cycloalkyl” also includes ring systems wherein the cycloalkyl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is on the cycloalkyl ring, and in such instances, the number of carbons continue to designate the number of carbons in the cycloalkyl ring system.
  • cycloalkyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted cycloalkyl”) or substituted (a “substituted cycloalkyl”) with one or more substituents.
  • halo refers to a fluorine, chlorine, bromine, or iodine radical (i.e., -F, -Cl, -Br, and -I, respectively).
  • heteroaryl refers to an aromatic heterocycle that comprises 1, 2, 3, or 4 heteroatoms selected, independently of the others, from nitrogen, sulfur and oxygen.
  • heteroaryl refers to a group that can be substituted or unsubstituted.
  • a heteroaryl can be fused to one or two rings, such as a cycloalkyl, an aryl, or a heteroaryl ring.
  • the point of attachment of a heteroaryl to a molecule can be on the heteroaryl, cycloalkyl, heterocycloalkyl or aryl ring, and the heteroaryl group can be attached through carbon or a heteroatom.
  • heteroaryl groups include imidazolyl, furyl, pyrrolyl, thienyl, thiazolyl, isoxazolyl, isothiazolyl, thiadiazolyl, oxadiazolyl, pyridinyl, pyrimidyl, pyrazinyl, pyridazinyl, quinolyl, isoquinolinyl, indazolyl, benzoxazolyl, benzisooxazolyl, benzofuryl, benzothiazolyl, indolizinyl, imidazopyridinyl, pyrazolyl, triazolyl, oxazolyl, tetrazolyl, benzimidazolyl, benzoisothiazolyl, benzothiadiazolyl, benzoxadiazolyl, indolyl, tetrahydroindolyl, azaindolyl, imidazopyridyl, quina
  • hydroxy refers to the radical -OH.
  • Compounds described herein can comprise one or more asymmetric centers, and thus can exist in various isomeric forms, e.g., enantiomers and/or diastereomers.
  • the compounds described herein can be in the form of an individual enantiomer, diastereomer, or geometric isomer, or can be in the form of a mixture of stereoisomers, including racemic mixtures and mixtures enriched in one or more stereoisomer.
  • Isomers can be isolated from mixtures by methods including chiral high-performance liquid chromatography (HPLC); or preferred isomers can be prepared by asymmetric syntheses.
  • HPLC high-performance liquid chromatography
  • the invention additionally encompasses compounds described herein as individual isomers substantially free of other isomers, and alternatively, as mixtures of various isomers.
  • a pure enantiomeric compound is substantially free from other enantiomers or stereoisomers of the compound (i.e., in enantiomeric excess).
  • an “S” form of the compound is substantially free from the “R” form of the compound and is, thus, in enantiomeric excess of the “R” form.
  • ‘substantially free’ refers to: (i) an aliquot of an “R” form compound that contains less than 2% “S” form; or (ii) an aliquot of an “S” form compound that contains less than 2% “R” form.
  • the term “enantiomerically pure” or “pure enantiomer” denotes that the compound comprises more than 90% by weight, more than 91% by weight, more than 92% by weight, more than 93% by weight, more than 94% by weight, more than 95% by weight, more than 96% by weight, more than 97% by weight, more than 98% by weight, more than 99% by weight, more than 99.5% by weight, or more than 99.9% by weight, of the single enantiomer.
  • the weights are based upon total weight of all enantiomers or stereoisomers of the compound.
  • an enantiomerically pure compound can be present with other active or inactive ingredients.
  • a pharmaceutical composition comprising enantiomerically pure “R” form compound can comprise, for example, about 90% excipient and about 10% enantiomerically pure “R” form compound.
  • the enantiomerically pure “R” form compound in such compositions can, for example, comprise, at least about 95% by weight “R” form compound and at most about 5% by weight “S” form compound, by total weight of the compound.
  • a pharmaceutical composition comprising enantiomerically pure “S” form compound can comprise, for example, about 90% excipient and about 10% enantiomerically pure “S” form compound.
  • the enantiomerically pure “S” form compound in such compositions can, for example, comprise, at least about 95% by weight “S” form compound and at most about 5% by weight “R” form compound, by total weight of the compound.
  • the active ingredient can be formulated with little or no excipient or carrier.
  • “ ” denotes an attachment point to a spacer or linker moiety.
  • “ ” denotes an attachment point to a nucleobase.
  • “ ” refers to an attachment point to the N-terminus or N-terminal atom (e.g., hydrogen) of the of the PNA oligomer. In one embodiment, “ ” refers to an attachment point to C-terminus or terminal atom (e.g., oxygen, carboxylic acid or amide group) of the PNA oligomer. In another embodiment, “ ” refers to an attachment point to another PNA subunit or other region within a PNA oligomer.
  • “ ” can refer to an attachment point to a linker (e.g., a polyethylene glycol linker) or a positively charged region comprising one or more positively charged moieties (e.g., positively charged amino acids such as lysine, ornithine or arginine).
  • a linker e.g., a polyethylene glycol linker
  • a positively charged region comprising one or more positively charged moieties (e.g., positively charged amino acids such as lysine, ornithine or arginine).
  • a compound herein can be least 1% pure, at least 2% pure, at least 3% pure, at least 4% pure, at least 5% pure, at least 6% pure, at least 7% pure, at least 8% pure, at least 9% pure, at least 10% pure, at least 11% pure, at least 12% pure, at least 13% pure, at least 14% pure, at least 15% pure, at least 16% pure, at least 17% pure, at least 18% pure, at least 19% pure, at least 20% pure, at least 21% pure, at least 22% pure, at least 23% pure, at least 24% pure, at least 25% pure, at least 26% pure, at least 27% pure, at least 28% pure, at least 29% pure, at least 30% pure, at least 31% pure, at least 32% pure, at least 33% pure, at least 34% pure, at least 35% pure, at least 36% pure, at least 37% pure, at least 38% pure, at least 39% pure, at least 40% pure, at least 41% pure, at least 42% pure, at least 4
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv).
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.3 nm, as determined by X-ray crystallography.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.35 nm, as determined by X-ray crystallography.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.4 nm, as determined by X-ray crystallography.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode cytosine-binding nucleobase.
  • the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode thymine- binding subunit. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a cytosine nucleobase in the single strand of the dsDNA. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-iii), or (V-iv) binds to a thymine nucleobase in the single strand of the dsDNA.
  • Pharmaceutically-acceptable salts include, for example, acid- addition salts and base-addition salts.
  • the acid that is added to the compound to form an acid- addition salt can be an organic acid or an inorganic acid.
  • a base that is added to the compound to form a base-addition salt can be an organic base or an inorganic base.
  • a pharmaceutically-acceptable salt is a metal salt.
  • a pharmaceutically- acceptable salt is an ammonium salt.
  • Metal salts can arise from the addition of an inorganic base to a compound of the invention.
  • the inorganic base consists of a metal cation paired with a basic counterion, such as, for example, hydroxide, carbonate, bicarbonate, or phosphate.
  • the metal can be an alkali metal, alkaline earth metal, transition metal, or main group metal.
  • the metal is lithium, sodium, potassium, cesium, cerium, magnesium, manganese, iron, calcium, strontium, cobalt, titanium, aluminum, copper, cadmium, or zinc.
  • a metal salt is a lithium salt, a sodium salt, a potassium salt, a cesium salt, a cerium salt, a magnesium salt, a manganese salt, an iron salt, a calcium salt, a strontium salt, a cobalt salt, a titanium salt, an aluminum salt, a copper salt, a cadmium salt, or a zinc salt.
  • Ammonium salts can arise from the addition of ammonia or an organic amine to a compound of the invention.
  • the organic amine is triethyl amine, diisopropyl amine, ethanol amine, diethanol amine, triethanol amine, morpholine, N- methylmorpholine, piperidine, N-methylpiperidine, N-ethylpiperidine, dibenzylamine, piperazine, pyridine, pyrrazole, pipyrrazole, imidazole, pyrazine, or pipyrazine.
  • an ammonium salt is a triethyl amine salt, a diisopropyl amine salt, an ethanol amine salt, a diethanol amine salt, a triethanol amine salt, a morpholine salt, an N-methylmorpholine salt, a piperidine salt, an N-methylpiperidine salt, an N-ethylpiperidine salt, a dibenzylamine salt, a piperazine salt, a pyridine salt, a pyrrazole salt, a pipyrrazole salt, an imidazole salt, a pyrazine salt, or a pipyrazine salt.
  • Acid addition salts can arise from the addition of an acid to a compound of the invention.
  • the acid is organic.
  • the acid is inorganic.
  • the acid is hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, nitrous acid, sulfuric acid, sulfurous acid, a phosphoric acid, isonicotinic acid, lactic acid, salicylic acid, tartaric acid, ascorbic acid, gentisinic acid, gluconic acid, glucaronic acid, saccaric acid, formic acid, benzoic acid, glutamic acid, pantothenic acid, acetic acid, propionic acid, butyric acid, fumaric acid, succinic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, citric acid, oxalic acid, or maleic acid.
  • the salt is a hydrochloride salt, a hydrobromide salt, a hydroiodide salt, a nitrate salt, a nitrite salt, a sulfate salt, a sulfite salt, a phosphate salt, isonicotinate salt, a lactate salt, a salicylate salt, a tartrate salt, an ascorbate salt, a gentisinate salt, a gluconate salt, a glucaronate salt, a saccarate salt, a formate salt, a benzoate salt, a glutamate salt, a pantothenate salt, an acetate salt, a propionate salt, a butyrate salt, a fumarate salt, a succinate salt, a methanesulfonate (mesylate) salt, an ethanesulfonate salt, a benzenesulfonate salt, a p- tolu
  • Exemplary lipids include ionizable lipids, phospholipids, sterol lipids, alkylene glycol lipids (e.g., polyethylene glycol lipids), sphingolipids, glycerolipids, glycerophospholipids, prenol lipids, saccharolipids, fatty acids, and polyketides.
  • the LNP comprises a single type of lipid.
  • the LNP comprises a plurality of lipids.
  • An LNP may comprise one or more of an ionizable lipid, a phospholipid, a sterol, or an alkylene glycol lipid (e.g., a polyethylene glycol lipid).
  • the LNP comprises an ionizable lipid.
  • An ionizable lipid is a lipid that comprises an ionizable moiety capable of bearing a charge (e.g., a positive charge e.g., a cationic lipid, or a negative charge, e.g., an anionic lipid) under certain conditions (e.g., at a certain pH range, e.g., under physiological conditions).
  • An ionizable moiety can comprise an amine, carboxylic acid, hydroxyl, phenol, phosphate, sulfonyl, thiol, or a combination thereof.
  • An ionizable lipid can be a cationic lipid or an anionic lipid.
  • an ionizable lipid can contain an alkyl or alkenyl group, e.g., greater than six carbon atoms in length (e.g., greater than about 8 carbons, 10 carbons, 12 carbons, 14 carbons, 16 carbons, 18 carbons, 20 carbons or more in length).
  • ionizable lipids examples include dilinoleylmethyl-4- dimethylaminobutyrate (DLin-MC3-DMA), 2,2-dilinoleyl-4-dimethylamino-1,3]-dioxolane (DLin-K-DMA), 2,2-dilinoleyl-4-(2-dimethylaminoethyl)-1,3]-dioxolane (DLin-KC 2 -DMA), 2,2-dilinoleyl-4-N-chloromethyl-N,N-dimethylamino-1,3]-dioxolane (DLin-KC 2 -CIMDMA), 2,2-dilinoleyl-4-(3-dimethylaminopropyl)-1,3]-dioxolane (DLin-KC 3 -DMA), 2,2-dilinoleyl-4- (4-dimethylaminobutyl)-1,3]-dioxolane (DLin-KC4-
  • the ionizable lipid comprises DLin-MC3-DMA, DLin-KC 2 -DMA, D-LinK-DMA, D-Lin-DAP, 98N12-5, C 1 2-200, or DODMA.
  • a LNP comprises an ionizable lipid having a structure of Formula (VI): (VI), or a pharmaceutically acceptable salt thereof, wherein Y is , , , ; each R 22 is independently alkyl, alkenyl, alkynyl, or heteroalkyl, each of which is optionally substituted with R B ; each R B is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; n is an integer between 1 and 10 (inclusive); and “ ” denotes the attachment point.
  • Y is .
  • each R 22 is independently alkyl (e.g., C 2 -C 32 alkyl, C 4 -C 28 alkyl, C 8 -C 24 alkyl, C 12 -C 22 alkyl, or C 16 -C 20 alkyl).
  • each R 22 is independently alkenyl (e.g., C 2 -C 32 alkenyl, C 4 -C 28 alkenyl, C 8 -C 24 alkenyl, C 12 -C 22 alkenyl, or C 16 -C 20 alkenyl).
  • each R 22 is independently C 16 -C 20 alkenyl.
  • each R 22 is independently C 18 alkenyl.
  • each R 22 is independently linoleyl (or cis,cis-9,12-octadecadienyl). In some embodiments, each R 22 is the same. In some embodiments, each R 22 is different. [0166] In some embodiments, n is an integer between 1 and 10, 1 and 8, 1 and 6, or 1 and 4. In some embodiments, n is 1, 2, 3, or 4. In some embodiments, n is 1, 2, or 3. In some embodiments, n is 1 or 2. In some embodiments, n is 1. In some embodiments, n is 2. In some embodiments, n is 3. [0167] In some embodiments, the ionizable lipid is DLin-MC3-DMA.
  • the ionizable lipid is DLin-KC 2 -DMA. In some embodiments, the ionizable lipid is D-LinK-DMA. In some embodiments, the ionizable lipid is DLinDAP. In some embodiments, the ionizable lipid is 98N12-5. In some embodiments, the ionizable lipid is C 1 2-200. In some embodiments, the ionizable lipid is DODMA. [0168] An LNP can comprise an ionizable lipid at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an ionizable lipid at a concentration of greater than about 1 mol%, about 2 mol%, about 4 mol%, about 8 mol%, about 20 mol%, about 40 mol%, about 50 mol%, about 60 mol%, or about 80 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an ionizable lipid at a concentration of greater than about 20 mol%, about 40 mol%, or about 50 mol%.
  • the LNP comprises an ionizable lipid at a concentration between about 1 mol% to about 95 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an ionizable lipid at a concentration between about 2 mol% to about 90 mol%, about 4 mol% to about 80 mol%, about 10 mol% to about 70 mol%, about 20 mol% to about 60 mol%, about 40 mol% to about 55 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an ionizable lipid at a concentration between about 20 mol% to about 60 mol%.
  • the LNP comprises an ionizable lipid at a concentration between about 40 mol% to about 55 mol%.
  • the LNP comprises a phospholipid.
  • a phospholipid is a lipid that comprises a phosphate group and at least one alkyl, alkenyl, or heteroalkyl chain.
  • a phospholipid can be naturally occurring or non-naturally occurring (e.g., a synthetic phospholipid).
  • a phospholipid can comprise an amine, amide, ester, carboxyl, choline, hydroxyl, acetal, ether, carbohydrate, sterol, or a glycerol.
  • a phospholipid can comprise a phosphocholine, phosphosphingolipid, or a plasmalogen.
  • phospholipids examples include 1,2- dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3- phosphocholine (DSPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE), 1-myristoyl-2-oleoyl-sn-glycero-3-phosphocholine (MOPC), 1,2-diarachidonoyl-sn- glycero-3-phosphocholine (DAPC), 1-palmitoyl-2-linoleoy
  • a LNP comprises a phospholipid having a structure of Formula (VII), or a pharmaceutically acceptable salt thereof, wherein each R 23 is independently alkyl, alkenyl, or heteroalkyl; wherein each alkyl, alkenyl, or heteroalkyl is optionally substituted with R C ; each R 25 is independently hydrogen or alkyl; R 24 is absent, hydrogen, or alkyl; each R C is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; m is an integer between 1 and 4 (inclusive); and u is 2 or 3.
  • Formula (VII) Formula (VII), or a pharmaceutically acceptable salt thereof, wherein each R 23 is independently alkyl, alkenyl, or heteroalkyl; wherein each alkyl, alkenyl, or heteroalkyl is optionally substituted with R C ; each R 25 is independently hydrogen or alkyl; R 24 is absent, hydrogen, or alkyl; each R C is independently alkyl,
  • each R 23 is independently alkyl (e.g., C 2 -C 3 2 alkyl, C 4 -C 28 alkyl, C 8 -C 24 alkyl, C 12 -C 22 alkyl, or C 16 -C 20 alkyl).
  • each R 23 is independently alkenyl (e.g., C 2 -C 32 alkyl, C 4 -C 28 alkenyl, C 8 -C 24 alkenyl, C 12 -C 22 alkenyl, or C 16 -C 20 alkenyl).
  • each R 23 is independently heteroalkyl (e.g., C 4 -C 28 heteroalkyl, C 8 -C 24 heteroalkyl, C 12 -C 22 heteroalkyl, C 16 -C 20 heteroalkyl). In some embodiments, each R 23 is independently C 16 -C 20 alkyl. In some embodiments, each R 23 is independently C 17 alkyl. In some embodiments, each R 23 is independently heptadecyl. In some embodiments, each R 23 is the same. In some embodiments, each R 23 is different. In some embodiments, each R 23 is optionally substituted with R C .
  • R C is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl.
  • one of R 25 is hydrogen. In some embodiments, one of R 25 is alkyl. In some embodiments, one of R 25 is methyl. In some embodiments, each R 25 is independently alkyl. In some embodiments, each R 25 is independently methyl. In some embodiments, each R 25 is independently methyl and u is 2. In some embodiments, each R 25 is independently methyl and u is 3. [0173] In some embodiments, R 24 is absent, and the oxygen to which R 24 is attached carries a negative charge. In some embodiments, R 24 is hydrogen.
  • m is an integer between 1 and 10, 1 and 8, 1 and 6, 1 and 4. In some embodiments, m is 1, 2, 3, or 4. In some embodiments, m is 1. In some embodiments, m is 2. In some embodiments, m is 3. [0175] In some embodiments, the phospholipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). In some embodiments, the phospholipid is 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). In some embodiments, the phospholipid is 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC).
  • DSPC 1,2-distearoyl-sn-glycero-3-phosphocholine
  • DOPC 1,2-dioleoyl-sn-glycero-3-phosphocholine
  • DPPC 1,2-dipalmitoyl-sn-glycero-3- phosphocholine
  • the phospholipid is 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine (DOPE).
  • DOPE 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine
  • the LNP comprises a phospholipid at a concentration of greater than about 0.5 mol%, greater than about 1 mol%, greater than about 1.5 mol%, greater than about 2 mol%, greater than about 3 mol%, greater than about 4 mol%, greater than about 5 mol%, greater than about 6 mol%, greater than about 8 mol%, greater than about 10 mol%, greater than about 12 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 50 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a phospholipid at a concentration of greater than about 1 mol%, greater than about 5 mol%, or greater than about 10 mol%. In some embodiments, the LNP comprises a phospholipid at a concentration between about 0.1 mol% to about 50 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a phospholipid at a concentration between about 0.5 mol% to about 40 mol%, about 1 mol% to about 30 mol%, about 5 mol% to about 25 mol%, about 10 mol% to about 20 mol%, about 10 mol% to about 15 mol%, or about 15 mol% to about 20 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a phospholipid at a concentration between about 5 mol% to about 25 mol%.
  • the LNP comprises a phospholipid at a concentration between about 10 mol% to 20 mol%.
  • the LNP comprises a sterol.
  • a sterol is a lipid that comprises a polycyclic structure and an optionally a hydroxyl or ether substituent, and can be naturally occurring or non-naturally occurring (e.g., a synthetic sterol).
  • Sterols can comprise no double bonds, a single double bond, or multiple double bonds.
  • Sterols can further comprise an alkyl, alkenyl, halo, ester, ketone, hydroxyl, amine, polyether, carbohydrate, or cyclic moiety.
  • An example listing of sterols includes cholesterol, dehydroergosterol, ergosterol, campesterol, ⁇ - sitosterol, stigmasterol, lanosterol, dihydrolanosterol, desmosterol, brassicasterol, lathosterol, zymosterol, 7-dehydrodesmosterol, avenasterol, campestanol, lupeol, and cycloartenol.
  • the sterol comprises cholesterol, dehydroergosterol, ergosterol, campesterol, ⁇ - sitosterol, or stigmasterol.
  • a LNP comprises a sterol having a structure of Formula (VIII): (VIII) or a pharmaceutically acceptable salt thereof, wherein R 26 is hydrogen, alkyl, heteroalkyl, or -C(O)R D , R 27 is hydrogen, alkyl, or -OR E ; each R D and R E is independently hydrogen, alkyl, alkenyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl or heteroaryl, wherein each alkyl, alkenyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl or heteroaryl is optionally substituted with alkyl, halo, or carbonyl; and each “ is either a single or double bond, and wherein each carbon atom participating in the single or double bond is bound to 0, 1, or 2 hydrogens, valency permitting.
  • R 26 is hydrogen, alkyl, heteroalkyl, or -C(O)R D
  • R 27 is hydrogen, alkyl, or
  • R 26 is hydrogen. In some embodiments, R 26 is alkyl (e.g., C 1 -C 4 alkyl, C 4 -C 8 alkyl, C 8 -C 12 alkyl). In some embodiments, R 26 is C(O)R D , wherein R D is alkyl (e.g., C 1- C 4 alkyl, C 4 -C 8 alkyl, C 8 -C 12 alkyl) or heteroaryl (e.g., a nitrogen-containing heteroaryl). In some embodiments, R 26 is heteroalkyl (e.g., C 1 -C 4 heteroalkyl, C 4 -C 8 heteroalkyl, C 8 -C 12 heteroalkyl).
  • R D is alkyl (e.g., C 1- C 4 alkyl, C 4 -C 8 alkyl, C 8 -C 12 alkyl) or heteroaryl (e.g., a nitrogen-containing heteroaryl).
  • R 26 is heteroalkyl (e.g
  • R 26 is heteroalkyl (e.g., C 1- C 4 heteroalkyl, C 4 -C 8 heteroalkyl, C 8 -C 12 heteroalkyl) substituted with carbonyl.
  • R 27 is hydrogen.
  • R 27 is alkyl (e.g., C 1 -C 4 alkyl, C 4 -C 8 alkyl, C 8 -C 12 alkyl).
  • one of “ is a single bond.
  • one of “ ” is a double bond.
  • two of “ ” are single bonds.
  • two of “ ” are double bonds.
  • each “ ” is a single bond. In some embodiments, each “ ” is a double bond.
  • the sterol is cholesterol. In some embodiments, the sterol is dehydroergosterol. In some embodiments, the sterol is ergosterol. In some embodiments, the sterol is campesterol. In some embodiments, the sterol is ⁇ -sitosterol. In some embodiments, the sterol is stigmasterol. In some embodiments, the sterol is a corticosteroid (e.g., corticosterone, hydrocortisone, cortisone, or aldosterone).
  • corticosteroid e.g., corticosterone, hydrocortisone, cortisone, or aldosterone.
  • a LNP can comprise a sterol at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a sterol at a concentration greater than about 0.5 mol%, greater than about 1 mol%, greater than about 5 mol%, greater than about 10 mol%, greater than about 15 mol%, greater than about 20 mol%, greater than about 25 mol%, greater than about 30%, greater than about 35 mol%, greater than about 40 mol%, greater than about 45 mol%, greater than about 50 mol%, greater than about 55 mol%, greater than about 60 mol%, greater than about 65 mol%, or greater than about 70 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a sterol at a concentration greater than about 10 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 25 mol%. In some embodiments, the LNP comprises a sterol at a concentration about 1 mol% to about 95 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a sterol at a concentration of about 5 mol% to about 90 mol%, about 10 mol% to about 85 mol%, about 20 mol% to about 80 mol%, about 20 mol% to about 60 mol%, about 20 mol% to about 50 mol%, or about 20 mol% to 40 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises a sterol at a concentration between about 20 mol% to about 50 mol%.
  • the LNP comprises a sterol at a concentration between about 30 mol% to about 60 mol%.
  • the LNP comprises an alkylene glycol-containing lipid.
  • An alkylene glycol-containing lipid is a lipid that comprises at least one alkylene glycol moiety, for example, a methylene glycol or an ethylene glycol moiety.
  • the alkylene glycol-containing lipid comprises a polyethylene glycol (PEG).
  • An alkylene glycol-containing lipid can be a PEG-containing lipid.
  • a PEG-containing lipid can further comprise an amine, amide, ester, carboxyl, phosphate, choline, hydroxyl, acetal, ether, heterocycle, or carbohydrate.
  • PEG-containing lipids can comprise at least one alkyl or alkenyl group, e.g., greater than six carbon atoms in length (e.g., greater than about 8 carbons, 10 carbons, 12 carbons, 14 carbons, 16 carbons, 18 carbons, 20 carbons or more in length), e.g., in addition to a PEG moiety.
  • a PEG-containing lipid comprises a PEG moiety comprising at least 20 PEG monomers, e.g., at least 30 PEG monomers, at least 40 PEG monomers, at least 45 PEG monomers, at least 50 PEG monomers, at least 100 PEG monomers, at least 200 PEG monomers, at least 300 PEG monomers, at least 500 PEG monomers, at least 1,000 PEG monomers, or at least 2,000 PEG monomers.
  • PEG-containing lipids examples include PEG-DMG (e.g., DMG- PEG2k), PEG-c-DOMG, PEG-DSG, PEG-DPG, PEG-DSPE, PEG-DMPE, PEG-DPPE, PEG- DOPE, and PEG-DLPE.
  • the PEG-lipids include PEG-DMG (e.g., DMG- PEG2k), PEG-c-DOMG, PEG-DSG, and PEG-DPG.
  • an LNP comprises an alkylene glycol-containing lipid having a structure of Formula (IX): (IX) or a pharmaceutically acceptable salt thereof, wherein each R 28 is independently alkyl, alkenyl, or heteroalkyl, each of which is optionally substituted with R F ; A is absent, O, CH 2 , C(O), or NH; E is absent, alkyl, or heteroalkyl, wherein alkyl or heteroalkyl is optionally substituted with carbonyl; each R F is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; and z is an integer between 10 and 200.
  • Formula (IX): (IX) or a pharmaceutically acceptable salt thereof wherein each R 28 is independently alkyl, alkenyl, or heteroalkyl, each of which is optionally substituted with R F ; A is absent, O, CH 2 , C(O), or NH; E is absent, alkyl, or heteroalkyl,
  • each R 28 is independently alkyl. In some embodiments, each R 28 is independently heteroalkyl. In some embodiments, each R 28 is independently alkenyl. [0187] In some embodiments, A is O or NH. In some embodiments, A is CH 2 . In some embodiments, A is carbonyl. In some embodiments, A is absent. [0188] In some embodiments, E is alkyl. In some embodiments, E is heteroalkyl. In some embodiments, both A and E are not absent. In some embodiments, A is absent. In some embodiments, E is absent. In some embodiments, either one of A or E is absent. In some embodiments, both A and E is independently absent.
  • z is an integer between 10 and 200 (e.g., between 20 and 180, between 20 and 160, between 20 and 120, between 20 and 100, between 40 and 80, between 40 and 60, between 40 and 50). In some embodiments, z is 45.
  • the PEG-lipid is PEG-DMG (e.g., DMG-PEG2k). In some embodiments, the PEG-lipid is PEG-c-DOMG. In some embodiments, the PEG-lipid is PEG- DSG. In some embodiments, the PEG-lipid is PEG-DPG.
  • a LNP can comprise an alkylene glycol-containing lipid at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an alkylene glycol-containing lipid at a concentration of greater than about 0.5 mol%, greater than about 1 mol%, greater than about 1.5 mol%, greater than about 2 mol%, greater than about 3 mol%, greater than about 4 mol%, greater than about 5 mol%, greater than about 6 mol%, greater than about 8 mol%, greater than about 10 mol%, greater than about 12 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 50 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an alkylene glycol-containing lipid at a concentration of greater than about 1 mol%, greater than about 4 mol%, or greater than about 6 mol%. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration between about 0.1 mol% to about 50 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an alkylene glycol-containing lipid at a concentration between about 0.5 mol% to about 40 mol%, about 1 mol% to about 35 mol%, about 1.5 mol% to about 30 mol%, about 2 mol% to about 25 mol%, about 2.5 mol% to about 20%, about 3 mol% to about 15 mol%, about 3.5 mol% to about 10 mol%, or about 4 mol% to 9 mol%, e.g., of the total lipid composition of the LNP.
  • the LNP comprises an alkylene glycol-containing lipid at a concentration between about 3.5 mol% to about 10 mol%.
  • the LNP comprises an alkylene glycol-containing lipid at a concentration between about 4 mol% to 9 mol%.
  • the LNP comprises at least two types of lipids.
  • the LNP comprises two of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid.
  • the LNP comprises at least three types of lipids.
  • the LNP comprises three of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid.
  • the LNP comprises at least four types of lipids.
  • the LNP comprises each of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid.
  • the LNP e.g., as described herein
  • the LNP can comprise one or more of the following components: (i) an ionizable lipid at a concentration between about 1 mol% to about 95 mol% (e.g. about 20 mol% to about 80 mol%); (ii) a phospholipid at a concentration between 0.1 mol% to about 50 mol% (e.g. between about 2.5 mol% to about 20 mol%); (iii) a sterol at a concentration between about 1 mol% to about 95 mol% (e.g.
  • the LNP comprises one of (i)-(iv). In some embodiments, the LNP comprises two of (i)-(iv). In some embodiments, the LNP comprises three of (i)-(iv). In some embodiments, the LNP comprises each of (i)-(iv). In some embodiments, the LNP comprises (i) and (ii). In some embodiments, the LNP comprises (i) and (iii). In some embodiments, the LNP comprises (i) and (iv).
  • the LNP comprises (ii) and (iii). In some embodiments, the LNP comprises (ii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (i), (ii), and (iii). In some embodiments, the LNP comprises (i), (ii), and (iv). In some embodiments, the LNP comprises (ii), (iii), and (iv). In some embodiments, the LNP comprises (ii), (iii), and (iv). [0194]
  • the LNP (e.g., as described herein) can comprise one or more of the following components: (i) DLin-MC3-DMA at a concentration between about 1 mol% to about 95 mol% (e.g.
  • the LNP comprises two of (i)-(iv). In some embodiments, the LNP comprises three of (i)-(iv).
  • the LNP comprises each of (i)-(iv). In some embodiments, the LNP comprises (i) and (ii). In some embodiments, the LNP comprises (i) and (iii). In some embodiments, the LNP comprises (i) and (iv). In some embodiments, the LNP comprises (ii) and (iii). In some embodiments, the LNP comprises (ii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (i), (ii), and (iii). In some embodiments, the LNP comprises (i), (ii), and (iv).
  • the LNP comprises (ii), (iii), and (iv). [0195] In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 50:1 to about 1:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 50:1, about 40:1, about 32:3, about 6:1, about 7:1, about 5:1, about 24:5, about 26:5, about 10:3, about 15:2, about 16:7, about 18:1, about 3:1, about 3:2, or about 1:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 15:2.
  • the LNP comprises a ratio of ionizable lipid to phospholipid of about 5:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to a sterol of about 10:1 to about 1:10.
  • the LNP comprises a ratio of ionizable lipid to a sterol of about 9:1, about 8:1, about 8:7, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9.
  • the LNP comprises a ratio of ionizable lipid to an alkylene- containing lipid of about 1:10 to about 10:1.
  • the LNP comprises a ratio of ionizable lipid to an alkylene-containing lipid of about 1:9, about 1:8, about 7:8, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9.
  • the LNP comprises a ratio of phospholipid to an alkylene-containing lipid of about 10:1 to about 1:10.
  • the LNP comprises a ratio of phospholipid to an alkylene-containing lipid of about 9:1, about 8:1, about 8:7, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9.
  • the LNP comprises a ratio of a sterol to an alkylene-containing lipid of about 50:1 to about 1:1.
  • the LNP comprises a ratio of a sterol to an alkylene-containing lipid of about 40:1, about 32:3, about 6:1, about 7:1, about 5:1, about 24:1, about 22:1, about 20:1, about 22:5, about 24:5, about 26:5, about 10:3, about 15:2, about 16:7, about 18:1, about 3:1, about 3:2, or about 1:1.
  • An LNP e.g., described herein
  • An LNP (e.g., described herein) comprises three of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid (e.g., PEG-containing lipid).
  • An LNP (e.g., described herein) comprises each of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid (e.g., PEG-containing lipid).
  • Synthetic Polymer Nanoparticles [0197] The present disclosure features a synthetic polymer nanoparticle comprising a nucleic acid mimic (e.g., an PNA) and a synthetic polymer.
  • Examples of synthetic polymers include polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(4- hydroxy-L-proline ester, other degradable polyesters, polyanhydrides, poly(ortho)esters, polyesters, polyurethanes, poly(butyric acid), poly(valeric acid), poly(caprolactone), poly(hydroxyalkanoates), poly(lactide-co-caprolactone), poly(amine-co-ester) polymers, and a combination of any two or more of the foregoing.
  • the synthetic polymer comprises a structure of Formula (X): wherein each R 29 and R 30 is independently hydrogen and alkyl; each R 31 , R 32 , R 33 , and R 34 is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more R G ; R G is hydrogen or alkyl; each xa and xb is an integer from 0 to 100, wherein each xa and xb cannot simultaneously be 0; and xc is an integer from 1 to 10,000.
  • R G is hydrogen or alkyl
  • each xa and xb is an integer from 0 to 100, wherein each xa and xb cannot simultaneously be 0
  • xc is an integer from
  • each R 29 and R 30 is independently hydrogen. In some embodiments, each R 29 and R 30 is independently alkyl. In some embodiments, one of R 31 and R 32 is hydrogen and the other of R 31 and R 32 is alkyl (e.g., methyl). In some embodiments, each R 33 and R 34 is independently hydrogen. [0200] In some embodiments, xa is an integer greater than 0 and xb is an integer greater than 0. In some embodiments, xb is 0. In some embodiments, xb is an integer between 1 and 50 (inclusive), between 1 and 25, between 1 and 10, or between 1 and 5. In some embodiments, xb is 1. In some embodiments, xa is 0.
  • xa is an integer between 1 and 50 (inclusive), between 1 and 25, between 1 and 10, or between 1 and 5. In some embodiments, xa is 1. [0201] In some embodiments, xc is an integer from 1 to 10,000, from 1 to 5,000, from 1 to 2,500, from 1 to 1,000, from 1 to 750, from 1 to 500, from 1 to 250, from 1 to 100, or from 1 to 50. [0202] In some embodiments, the synthetic polymer having a structure of Formula (X) is selected from poly(lactic-co-glycolic acid) (PLGA), polyglycolic acid (PGA), and polylactic acid (PLA). In some embodiments, the synthetic polymer having a structure of Formula (X) is PLGA.
  • the synthetic polymer having a structure of Formula (X) is PGA. In some embodiments, the synthetic polymer having a structure of Formula (X) is PLA. [0203] In some embodiments, the synthetic polymer further comprises a polyethylene glycol moiety. For example, the synthetic polymer comprising a structure of Formula (X) can further comprise a PEG moiety. An example of a synthetic polymer comprises mPEG-PLA. [0204] In some embodiments, a nanoparticle comprises a single type of synthetic polymer. In some embodiments, the nanoparticle comprises a plurality of synthetic polymers. For example, a nanoparticle of the present disclosure can comprise PLGA, or can comprise PLGA and a second synthetic polymer.
  • the amount of a synthetic polymer encapsulated and/or entrapped within the nanoparticle can vary depending on the identity of the synthetic polymer or plurality of synthetic polymer.
  • the amount of a synthetic polymer can be between 0.05% and 40% by weight of synthetic polymers to the total weight of the nanoparticle.
  • the amount of a synthetic polymer in the nanoparticle is greater than about 0.05%.
  • the amount of a synthetic polymer in the nanoparticle is greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, or greater than about 40% by weight of synthetic polymers to the total weight of the nanoparticle.
  • the amount of a synthetic polymer in the nanoparticle is between 0.5% and 20% by weight of synthetic polymers to the total weight of the nanoparticle, or between 1% and 10% by weight of a synthetic polymer to the total weight of the nanoparticle, or between 2% to 5% by weight of a synthetic polymer to the total weight of the nanoparticle.
  • a nanoparticle or plurality of nanoparticles further comprises an alkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG described herein).
  • PEG polyethylene glycol
  • a polyalkylene glycol can be any size, for example, a PEG between 2 PEG subunits and 5,000 subunits.
  • At least about 5% of the nanoparticles in the plurality comprise a PEG. In some embodiments, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 99% of the nanoparticles in the plurality comprise a PEG.
  • Load Components [0207]
  • a nanoparticle e.g., an LNP, or a synthetic polymer nanoparticle
  • a load component e.g., an LNP, or a synthetic polymer nanoparticle
  • the load component is an additional biological component (e.g., a polymeric biological component), for example, a nucleic acid or polypeptide.
  • the load component is a nucleic acid.
  • the nucleic acid is double stranded.
  • the nucleic acid is single stranded.
  • the load component is an oligonucleotide.
  • the load component is a single stranded DNA.
  • the load component is a single stranded RNA.
  • the load component is a double stranded DNA.
  • the load component is a double stranded RNA.
  • the load component is mRNA. In some embodiments, the load component is siRNA. In some embodiments, the load component is an antisense oligomer (e.g., PNA, DNA, morpholinos (also known as PMOs), pyrrolidine-amide oligonucleotide mimics (POMs), morpholinoglycine oligonucleotides (MGOs), and methyl phosphonates.
  • the load component is a nucleic acid (e.g., DNA) between 5 and 250 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 10 and 200 nucleotides in length.
  • the load component is a nucleic acid (e.g., DNA) between 18 and 100 nucleotides in length). In some embodiments, the load component is a nucleic acid (e.g., DNA) between 20 and 80 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 25 and 70 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 35 and 65 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 20 and 40 nucleotides in length.
  • a nucleic acid e.g., DNA
  • the load component is a single stranded nucleic acid (e.g., DNA) between 20 and 70 nucleotides in length. In some embodiments, the load component is a double stranded nucleic acid (e.g., DNA), with each strand being independently between 20 and 70 nucleotides in length. [0209] In some embodiments, the load component is a nucleic acid and comprises one or more phosphorothioate linkages at a terminus (e.g., the 5’ terminus and/or the 3’ terminus). In some embodiments, the load component is a nucleic acid and comprises one or more phosphorothioate linkages at an internucleotide linkage.
  • the load component comprises more than one phosphorothioate linkages (e.g., 2, 3, or 4) at each terminus, for example, at each of the 3’ and 5’ termini.
  • the nucleic acid comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more phosphorothioate internucleotide linkages.
  • the load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence to which the PNA oligomer, e.g., a clamp system, e.g., a tail clamp system, e.g., a PNA oligomer comprising a sequence of Compound No.
  • a load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Hoogsteen homology.
  • a load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence that is within 1,000, 500, 200, 100, 75, 60, or 40 base pairs of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Watson Crick homology.
  • the load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence that is within 1,000, 500, or 200 base pairs of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Hoogsteen homology.
  • a nanoparticle e.g., an LNP, or a synthetic polymer nanoparticle
  • the ratio of PNA oligomer to load component is equal (i.e.1:1).
  • the ratio of PNA oligomer to load component is greater than 1:1, for example, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.5, about 1:2, about 1:3, about 1:4, about 1:5, about 1:10, about 1:20, about 1:25, about 1:50, about 1:75, or about 1:100 PNA oligomer to load component.
  • the ratio of load component to PNA oligomer greater than 1:1, for example, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.5, about 1:2, about 1:3, about 1:4, about 1:5, about 1:10, about 1:20, about 1:25, about 1:50, about 1:75, or about 1:100 load component to PNA oligomer.
  • the ratio of PNA oligomer to load component is about 1:1. In some embodiments, the ratio of PNA oligomer to load component is about 1:2. In some embodiments, the ratio of PNA oligomer to load component is about 1:5.
  • a nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle; e.g. PLGA) described herein comprises a nucleic acid mimic, for example, a PNA oligomer (e.g., a tcPNA), and related preparations and methods of making and using the same.
  • the PNA comprises a PNA oligomer. In some embodiments, the PNA comprises a tcPNA oligomer.
  • the PNA oligomer is a tcPNA oligomer disclosed herein.
  • the PNA is a PNA oligomer comprising greater than 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 PNA subunits.
  • the PNA is a PNA oligomer comprising between 10 to 25 PNA subunits.
  • the PNA is a PNA oligomer comprising between 20 to 35 PNA subunits.
  • the PNA is a PNA oligomer comprising between about 2 to 50 PNA subunits, e.g., between about 10 and 45, 15 and 40, 17 and 35, 18 and 30, and 25 and 38 PNA subunits.
  • the PNA oligomer is a tail-clamp PNA oligomer (tcPNA).
  • tcPNA tail-clamp PNA oligomer
  • the PNA oligomer has a sequence shown in Table 3 herein.
  • the PNA oligomer comprises a trilysine sequence (i.e., KKK) on the N-terminus.
  • the PNA oligomer comprises a trilysine sequence (i.e., KKK) on the C- terminus. In some embodiments, the PNA oligomer comprises a trilysine sequence (i.e., KKK) on both the N-terminus and the C-terminus. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 2-thiouracil nucleobase. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 2,6-diaminopurine nucleobase. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 7-deazaguanine nucleobase.
  • the PNA oligomer comprises a Gly-Gly sequence and a 2-aminopyridine nucleobase. [0215] In some embodiments, the PNA oligomer has the sequence of Compound No.1. In some embodiments, the PNA oligomer has the sequence of Compound No.2. In some embodiments, the PNA oligomer has the sequence of Compound No.3. In some embodiments, the PNA oligomer has the sequence of Compound No.4. In some embodiments, the PNA oligomer has the sequence of Compound No.5. In some embodiments, the PNA oligomer has the sequence of Compound No.6. In some embodiments, the PNA oligomer has the sequence of Compound No. 7.
  • the PNA oligomer has the sequence of Compound No.8.
  • a nanoparticle e.g., an LNP, or a synthetic polymer nanoparticle
  • a nanoparticle comprises 1 PNA oligomer.
  • a nanoparticle comprises a plurality of PNA oligomers, for example, at least 2 PNAs, at least 3 PNAs, at least 4 PNAs, at least 5 PNAs, at least 6 PNAs, at least 7 PNAs, at least 8 PNAs, at least 9 PNAs, at least 10 PNAs, at least 15 PNAs, at least 20 PNAs, at least 25 PNAs, at least 30 PNAs, at least 40 PNAs, at least 50 PNAs, at least 60 PNAs, at least 70 PNAs, at least 80 PNAs, at least 90 PNAs, at least 100 PNAs, at least 150 PNAs, at least 200 PNAs, at least 300 PNAs, at least 400 PNAs, at least 500 PNAs, at least 600 PNAs, at least 700 PNAs, at least 800 PNAs, at least 900 PNAs, or at least 1,000 PNAs.
  • PNA oligomers for example, at least 2 PNAs, at least 3
  • a nanoparticle comprises 10-50 PNA oligomers. In some embodiments, a nanoparticle comprises 2-5 PNA oligomers. In some embodiments, a nanoparticle comprises 3- 10 PNA oligomers. In some embodiments, a nanoparticle comprises 5-20 PNA oligomers. In some embodiments, a nanoparticle comprises 10-35 PNA oligomers. In some embodiments, a nanoparticle comprises 10-100 PNA oligomers. In some embodiments, a nanoparticle comprises between 100-1,000 PNA oligomers. In some embodiments, a nanoparticle comprises between 500-1,000 PNA oligomers.
  • the amount of a PNA (e.g., a PNA oligomer) encapsulated and/or entrapped within the nanoparticle (e.g., an LNP, or a synthetic nanoparticle) can vary depending on the identity of the PNA or plurality of PNAs.
  • the amount of PNA can be between 0.001% and 50% by weight of PNAs to the total weight of the nanoparticle.
  • the amount of PNA in the nanoparticle is greater than about 0.001%, e.g., greater than about 0.05%, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, greater than about 40%, greater than about 45%, or greater than about 50% by weight of PNA to the total weight of the nanoparticle.
  • the amount of PNA oligomer in the nanoparticle is greater than about 0.001%, greater than about 0.05%, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, greater than about 40%, greater than about 45%, or greater than about 50% by weight of PNA oligomer to the total weight of the nanoparticle.
  • the amount of PNA oligomer in the nanoparticle is between 0.001% and 50% by weight of PNA oligomers to the total weight of the nanoparticle, or between 0.001% and 30% by weight of PNA oligomers to the total weight of the nanoparticle, or between 1% and 25% by weight of PNA oligomers to the total weight of the nanoparticle, or between 1% and 10% by weight of PNA oligomer to the total weight of the nanoparticle, or between 2% to 5% by weight of PNA oligomer to the total weight of the nanoparticle.
  • a nanoparticle e.g., an LNP, or a synthetic polymer nanoparticle described herein can comprise a single type of PNA (e.g., a single type of PNA oligomer, or a PNA oligomer of a single sequence), or can comprise multiple types of PNAs.
  • the nanoparticle comprises a single type of PNA.
  • the nanoparticle comprises a plurality of types of PNAs (e.g., a plurality of PNA oligomers).
  • a nanoparticle e.g., an LNP, or a synthetic polymer nanoparticle
  • the LNP described herein can comprise a particular ratio of a lipid or a plurality of lipids to an PNA.
  • the ratio of a plurality of lipids to a PNA is between 100:1 to 1:100. PNA.
  • the ratio of a plurality of lipids to a PNA is about 75:1 to 1:75, about 60:1 to 1:60, 100:1 to about 5:1, 80:1 to about 5:1, 60:1 to about 5:1, or about 50:1 to about 5:1.
  • the ratio of a plurality of lipids to an PNA is about 100:1, about 95:1, about 90:1, about 85:1, about 80:1, about 75:1, about 70:1, about 65:1, about 60:1, about 55:1, about 50:1, about 45:1, about 40:1, about 35:1, about 30:1, about 28:1, about 26:1, about 24:1, about 25:1, about 22:1, about 20:1, about 18:1, about 16:1, about 14:1, about 12:1, about 10:1, about 8:1, about 6:1, about 4:1, about 2:1, about 1:1, about 1:2, about 1:4, about 1:6, about 1:8, about 1:10, about 1:12, about 1:14, about 1:16, about 1:18, about 1:20, about 1:22, about 1:24, about 1:25, about 1:26, about 1:28, about 1:30, about 1:35, about 1:40, about 1:45, about 1:50, about 1:55, about 1:60, about 1:65, about 1:70, about 1:
  • a LNP described herein has a diameter between 5 and 500 nm, e.g., between 10 and 400 nm, 20 and 350 nm, 25 and 325 nm, 30 and 300 nm, 50 and 250 nm, 60 and 200 nm, 75 and 190 nm, 80 and 180 nm, 100 and 200 nm, 200 and 300 nm, and 150 and 250 nm.
  • the diameter of an LNP can be determined, for example, dynamic light scattering, transmission electron microscopy (TEM) or scanning electron microscopy (SEM).
  • a LNP has a diameter between 50 and 100 nm, between 70 and 100 nm, and between 80 and 100 nm. In some embodiments, a LNP has a diameter of about 90 nm. In some embodiments, a LNP described herein has a diameter greater than about 30 nm.
  • a LNP has a diameter greater than about 35 nm, greater than about 40 nm, greater than about 45 nm, greater than about 50 nm, greater than about 60 nm, greater than about 70 nm, greater than about 80 nm, greater than about 90 nm, greater than about 100 nm, greater than about 120 nm, greater than about 140 nm, greater than about 160 nm, greater than about 180 nm, greater than about 200 nm, greater than about 225 nm, greater than about 250 nm, greater than about 275 nm, or greater than about 300 nm. In some embodiments, a LNP has a diameter greater than about 70 nm.
  • an LNP has a diameter greater than about 90 nm. In some embodiments, an LNP has a diameter greater than about 180 nm. [0221] In some embodiments, a plurality of LNPs described herein has an average diameter greater than about 30 nm.
  • a plurality of LNPs has an average diameter greater than about 35 nm, greater than about 40 nm, greater than about 45 nm, greater than about 50 nm, greater than about 60 nm, greater than about 70 nm, greater than about 80 nm, greater than about 90 nm, greater than about 100 nm, greater than about 120 nm, greater than about 140 nm, greater than about 160 nm, greater than about 180 nm, greater than about 200 nm, greater than about 220 nm, greater than about 240 nm, greater than about 260 nm, greater than about 280 nm, or greater than about 300 nm.
  • a plurality of LNPs has an average diameter greater than about 70 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 90 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 180 nm.
  • a synthetic polymer nanoparticle or a plurality of nanoparticles have an average diameter between 5 and 500 nm, e.g., between 10 and 400 nm, 20 and 350 nm, 25 and 325 nm, 30 and 300 nm, 50 and 250 nm, 60 and 200 nm, 75 and 190 nm, 80 and 180 nm, 100 and 200 nm, 200 and 300 nm, and 150 and 250 nm.
  • a plurality of nanoparticles has an average diameter between 150 and 300 nm, between 35 and 100 nm, and between 75 and 220 nm.
  • At least 5% e.g., at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99%
  • at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the nanoparticles of a plurality of nanoparticles have a diameter between 5 and 500 nm.
  • the nanoparticles can range in diameter from about 10 to about 400 nm, about 20 to about 300 nm, about 25 to about 250 nm, about 30 to about 150 nm, about 35 to about 125 nm, about 40 to about 100 nm, about 80 to about 180 nm, about 100 to about 200 nm, about 200 to about 300 nm, and about 150 to about 250 nm.
  • the nanoparticles can range in diameter from about 100 to about 200 nm, about 20 to about 100 nm, about 20 to about 80 nm, and from about 20 to about 60 nm.
  • a nanoparticle or plurality of nanoparticles described herein has an average neutral to negative surface charge of less than -100 mv, for example, less than -90 mv, less than -80 mv, less than -70 mv, less than -60 mv, less than -50 mv, less than -40 mv, less than -30 mv, or less than -20 mv.
  • a nanoparticle or plurality of nanoparticles has a neutral to negative surface charge of between -100 mv and 100 mv, between -75 mv to 0, or between -50 mv and -10 mv.
  • At least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 99% of the nanoparticles of a plurality of nanoparticles have an average neutral to negative surface charge of less than about -100 mv.
  • a nanoparticle or plurality of nanoparticles has an average neutral to negative surface charge of between -100 mv and 100 mv, between -75 mv and 0, or between -50 mv and -10 mv.
  • the PNA oligomer binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence.
  • the PNA oligomer binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence that comprises at least seven base pairs.
  • the specific location in the nucleic acid sequence comprises only purines.
  • the specific location in the nucleic acid sequence comprises a mixture of purines and pyrimidines.
  • the PNA oligomer binds to a target nucleic acid sequence corresponding to a sequence provided in Table 1.
  • each sequence is a region within a target nucleic acid sequence (in the 5′ to 3′ direction); each P is a purine nucleobase (adenine or guanine); and each X is a pyrimidine nucleobase (cytosine, thymine, or uracil).
  • the PNA oligomer e.g., a tcPNA oligomer
  • the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence that comprises at least seven nucleobases.
  • the specific location in the nucleic acid sequence comprises only purines.
  • the specific location in the nucleic acid sequence comprises a mixture of purines and pyrimidines.
  • the PNA oligomer binds to a target nucleic acid sequence corresponding to a sequence listed in Table 2.
  • each sequence is a region within a target nucleic acid sequence (in the 5′ to 3′ direction); each G is guanine, each A is adenine; each X is a pyrimidine (cytosine, thymine, or uracil).
  • a pharmaceutical composition of the invention can be used, for example, before, during, or after treatment of a subject with, for example, another pharmaceutical agent.
  • Subjects can be, for example, elderly adults, adults, adolescents, pre-adolescents, children, toddlers, infants, neonates, and non-human animals. In some embodiments, a subject is a patient.
  • a pharmaceutical composition of the invention can be a combination of any pharmaceutical compounds described herein with other chemical components, such as carriers, stabilizers, diluents, dispersing agents, suspending agents, thickening agents, and/or excipients.
  • the pharmaceutical composition facilitates administration of the compound to an organism.
  • Pharmaceutical compositions can be administered in therapeutically-effective amounts as pharmaceutical compositions by various forms and routes including, for example, intravenous, subcutaneous, intramuscular, oral, parenteral, ophthalmic, subcutaneous, transdermal, nasal, vaginal, and topical administration.
  • a pharmaceutical composition can be administered in a local manner, for example, via injection of the compound directly into an organ, optionally in a depot or sustained release formulation or implant.
  • compositions can be provided in the form of a rapid release formulation, in the form of an extended release formulation, or in the form of an intermediate release formulation.
  • a rapid release form can provide an immediate release.
  • An extended release formulation can provide a controlled release or a sustained delayed release.
  • pharmaceutical compositions can be formulated by combining the active compounds with pharmaceutically-acceptable carriers or excipients. Such carriers can be used to formulate liquids, gels, syrups, elixirs, slurries, or suspensions, for oral ingestion by a subject.
  • Non-limiting examples of solvents used in an oral dissolvable formulation can include water, ethanol, isopropanol, saline, physiological saline, DMSO, dimethylformamide, potassium phosphate buffer, phosphate buffer saline (PBS), sodium phosphate buffer, 4-2-hydroxyethyl-1- piperazineethanesulfonic acid buffer (HEPES), 3-(N-morpholino)propanesulfonic acid buffer (MOPS), piperazine-N,N′-bis(2-ethanesulfonic acid) buffer (PIPES), and saline sodium citrate buffer (SSC).
  • PBS phosphate buffer saline
  • MOPS 4-2-hydroxyethyl-1- piperazineethanesulfonic acid buffer
  • MOPS 3-(N-morpholino)propanesulfonic acid buffer
  • PES piperazine-N,N′-bis(2-ethanesulfonic acid) buffer
  • SSC saline sodium citrate buffer
  • Non-limiting examples of co-solvents used in an oral dissolvable formulation can include sucrose, urea, cremaphor, DMSO, and potassium phosphate buffer.
  • Pharmaceutical preparations can be formulated for intravenous administration.
  • the pharmaceutical compositions can be in a form suitable for parenteral injection as a sterile suspension, solution or emulsion in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing and/or dispersing agents.
  • Pharmaceutical formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form. Suspensions of the active compounds can be prepared as oily injection suspensions.
  • Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl oleate or triglycerides, or liposomes.
  • the suspension can also contain suitable stabilizers or agents that increase the solubility of the compounds to allow for the preparation of highly concentrated solutions.
  • the active ingredient can be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen-free water, before use.
  • the active compounds can be administered topically and can be formulated into a variety of topically administrable compositions, such as solutions, suspensions, lotions, gels, pastes, medicated sticks, balms, creams, and ointments.
  • compositions can contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives.
  • the compounds of the invention can be applied topically to the skin, or a body cavity, for example, oral, vaginal, bladder, cranial, spinal, thoracic, or pelvic cavity of a subject.
  • the compounds of the invention can be applied to an accessible body cavity.
  • the compounds can also be formulated in rectal compositions such as enemas, rectal gels, rectal foams, rectal aerosols, suppositories, jelly suppositories, or retention enemas, containing conventional suppository bases such as cocoa butter or other glycerides, and synthetic polymers such as polyvinylpyrrolidone, and PEG.
  • rectal compositions such as enemas, rectal gels, rectal foams, rectal aerosols, suppositories, jelly suppositories, or retention enemas
  • conventional suppository bases such as cocoa butter or other glycerides
  • synthetic polymers such as polyvinylpyrrolidone, and PEG.
  • a low-melting wax such as a mixture of fatty acid glycerides, optionally in combination with cocoa butter, can be melted.
  • therapeutically-effective amounts of the compounds described herein are administered in pharmaceutical compositions to a subject having a disease or condition to be treated.
  • the subject is a mammal such as a human.
  • a therapeutically-effective amount can vary widely depending on the severity of the disease, the age and relative health of the subject, the potency of the compounds used, and other factors.
  • the compounds can be used singly or in combination with one or more therapeutic agents as components of mixtures.
  • Pharmaceutical compositions can be formulated using one or more physiologically- acceptable carriers comprising excipients and auxiliaries, which facilitate processing of the active compounds into preparations that can be used pharmaceutically. Formulations can be modified depending upon the route of administration chosen.
  • compositions comprising a compound described herein can be manufactured, for example, by mixing, dissolving, emulsifying, encapsulating, entrapping, or compression processes.
  • the pharmaceutical compositions can include at least one pharmaceutically-acceptable carrier, diluent, or excipient and compounds described herein as free-base or pharmaceutically- acceptable salt form.
  • Pharmaceutical compositions can contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives.
  • Methods for the preparation of compositions comprising the compounds described herein include formulating the compounds with one or more inert, pharmaceutically-acceptable excipients or carriers to form a solid, semi-solid, or liquid composition.
  • Solid compositions include, for example, powders, tablets, dispersible granules, capsules, and cachets.
  • Liquid compositions include, for example, solutions in which a compound is dissolved, emulsions comprising a compound, or a solution containing liposomes, micelles, or nanoparticles comprising a compound as disclosed herein.
  • Semi-solid compositions include, for example, gels, suspensions and creams. The compositions can be in liquid solutions or suspensions, solid forms suitable for solution or suspension in a liquid prior to use, or as emulsions. These compositions can also contain minor amounts of nontoxic, auxiliary substances, such as wetting or emulsifying agents, pH buffering agents, and other pharmaceutically-acceptable additives.
  • Non-limiting examples of dosage forms suitable for use in the invention include liquid, powder, gel, nanosuspension, nanoparticle, microgel, aqueous or oily suspensions, emulsion, and any combination thereof.
  • Non-limiting examples of pharmaceutically-acceptable excipients suitable for use in the invention include binding agents, disintegrating agents, anti-adherents, anti-static agents, surfactants, anti-oxidants, coating agents, coloring agents, plasticizers, preservatives, suspending agents, emulsifying agents, anti-microbial agents, spheronization agents, and any combination thereof.
  • a composition of the invention can be, for example, an immediate release form or a controlled release formulation.
  • An immediate release formulation can be formulated to allow the compounds to act rapidly.
  • immediate release formulations include readily dissolvable formulations.
  • a controlled release formulation can be a pharmaceutical formulation that has been adapted such that release rates and release profiles of the active agent can be matched to physiological and chronotherapeutic requirements or, alternatively, has been formulated to effect release of an active agent at a programmed rate.
  • Non-limiting examples of controlled release formulations include granules, delayed release granules, hydrogels (e.g., of synthetic or natural origin), other gelling agents (e.g., gel-forming dietary fibers), matrix-based formulations (e.g., formulations comprising a polymeric material having at least one active ingredient dispersed through), granules within a matrix, polymeric mixtures, and granular masses.
  • a controlled release formulation is a delayed release form.
  • a delayed release form can be formulated to delay a compound’s action for an extended period of time.
  • a delayed release form can be formulated to delay the release of an effective dose of one or more compounds, for example, for about 4, about 8, about 12, about 16, or about 24 hours.
  • a controlled release formulation can be a sustained release form.
  • a sustained release form can be formulated to sustain, for example, the compound’s action over an extended period of time.
  • a sustained release form can be formulated to provide an effective dose of any compound described herein (e.g., provide a physiologically-effective blood profile) over about 4, about 8, about 12, about 16 or about 24 hours.
  • nanoparticles e.g.
  • lipid nanoparticles LNPs
  • synthetic polymer nanoparticles e.g., poly(lactic-co-glycolic acid (PLGA) nanoparticles
  • PNA poly(lactic-co-glycolic acid
  • a nanoparticle is a LNP and refers to a particle that comprises a lipid and a nucleic acid mimic, for example, a PNA.
  • a LNP can further comprise one or more lipids, for example, at least one or more of an ionizable lipid, phospholipid, a sterol, or an alkylene glycol-containing lipid (e.g., a PEG-containing lipid), as well as a load component (e.g., a nucleic acid).
  • a nanoparticle is a synthetic polymer nanoparticle and refers to a particle that comprises a synthetic polymer (e.g., PLGA) and a nucleic acid mimic, for example, one or more PNA oligomers.
  • a synthetic polymer nanoparticle may further comprise a synthetic polymer, or a plurality of synthetic polymers, for example, at least one or more of a non- naturally occurring polymer, including co-polymers, block polymers, block co-polymers, polymer mixtures, and polymer blends, as well as a load component (e.g., a nucleic acid).
  • a load component e.g., a nucleic acid.
  • a PNA oligomer comprising a PC PNA subunit can be prepared through the stepwise addition of individual subunits, e.g., by reacting the amine of a first PNA subunit with a carboxylic acid of a second PNA subunit (e.g., an activated form of a carboxylic acid of a second subunit).
  • a PNA oligomer is prepared by the stepwise addition of a first amino acid (e.g., lysine) to a second or subsequent amino acid (e.g., lysine).
  • a PNA oligomer is prepared by the stepwise addition of a PNA subunit to an amino acid (e.g. a lysine).
  • a PNA oligomer is prepared by the stepwise addition of an amino acid (e.g., a lysine) to a PNA subunit.
  • a PNA oligomer can also be prepared through coupling smaller PNA oligomers comprising more than one subunit (e.g., through block synthesis).
  • a PNA oligomer can be synthesized in solution or on a solid support, or by using a combination of both techniques. PNA oligomers can be prepared using automated methods, for example, using an automated peptide synthesizer.
  • the PNA oligomer is synthesized on a solid support.
  • a solid support can be supplied in the form beads, and can be of different shapes (e.g. spherical beads) and sizes (e.g., 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, or 500 mesh).
  • a solid support can comprise, for example, plastic, polymer, polystyrene, polyacrylate, polyacrylamide, or polyethyleneglycol. Polymers used in solid supports can be cross-linked (e.g., with 1-2% divinylbenzene), or uncrosslinked.
  • a solid support can be a functionalized polymer (e.g., a Merrifield resin, Wang resin, brominated Wang resin, 4-(1′,1′- dimethyl-1′-hydroxypropyl)phenoxyacetyl (DHPP) resin, Kaiser resin, 4-hydroxymethyl- phenylacetamidomethyl (PAM) resin, benzhydrylamine (BHA) resin, 4-methylbenzhydrylamine (MBHA) resin, diphenyldiazomethane (PDDM) resin, TentaGel resin, 4-(hydroxymethyl) phenoxyacetic acid (HMPA) resin, 4-(4-hydroxymethyl-3-methoxyphenoxy)butyric acid (HMPB) resin, 2-chlorotrityl resin, 4-carboxytrityl resin, Rink acid resin, Rink amide resin, peptide amide linker (PAL) resin, Sieber resin, 4-(hydroxymethyl)benzoylaminomethyl (HMBA) resin, 4-sulfamoylbenzoyl resin, or
  • a solid support can comprise a functional group suitable for coupling to a subunit.
  • the functional group is an amine, a carboxylic acid, a halide, an oxime, a hydroxyl, a sulfamoyl, a hydrazine, or an aldehyde.
  • the functional group is an amine.
  • solid supports include Merrifield resin, Wang resin, MBHA resin, and Rink amide resin.
  • the PNA oligomer is synthesized on rink amide TentaGel resin (Rapp polymer, R28023). [0252] In some embodiments, the PNA oligomer is formed by anchoring a first subunit onto a solid support.
  • the first subunit is an amino acid (e.g., lysine) or a PNA subunit.
  • the first subunit can comprise one or more protecting groups, for example, a PNA subunit comprising a nucleobase that optionally comprises a protecting group, a PNA subunit with an activated carboxylic acid, a PNA subunit with a protected amine, a PNA subunit with an ⁇ -side chain that is optionally protected, a PNA subunit with a ⁇ -side chain that is optionally protected, a PNA subunit with a ⁇ -side chain that is optionally protected, or any combination thereof.
  • the first subunit can comprise a protecting group (PG) on the amino terminus, such as Fmoc or Boc.
  • the anchoring of the first subunit to a solid support can further require use of a base (e.g., an organic base, e.g., diisopropylethylamine (DIPEA), triethylamine (TEA), collidine, pyridine, piperidine, methyldicyclohexylamine (MDCHA).
  • a base e.g., an organic base, e.g., diisopropylethylamine (DIPEA), triethylamine (TEA), collidine, pyridine, piperidine, methyldicyclohexylamine (MDCHA).
  • DIPEA diisopropylethylamine
  • TAA triethylamine
  • MDCHA methyldicyclohexylamine
  • the anchoring of the first subunit to a solid support can further require an activating agent such as a carbodiimide (e.g., N,N’-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC)), benzotriazole (e.g., hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one (DEPBT)), a phosphonium salt (e.g.
  • a carbodiimide e.g., N,N’-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC)
  • benzotriazole e.g., hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt
  • benzotriazol-1-yloxy tris(dimethylamino)phosphonium hexafluorophosphate (BOP), benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), bromotripyrrolidinophosphonium hexafluorophosphate (PyBroP)), a uronium salt (e.g., hexafluorophosphate benzotriazole tetramethyl uronium (HBTU), 2-(1H-benzotriazole-1-yl)- 1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU), hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU), O-(7-azabenzotriazol-1-yl)-N,N,N’N’-tetramethyl uronium tetrafluoroborate (TATU
  • the reaction that anchors the subunit to the solid support can be carried out in any appropriate solvent (e.g., dimethylformamide (DMF), dimethylacetamide (DMA), dimethylsulfoxide (DMSO), N- methylpyrrolidone (NMP), tetrahydrofuran (THF), dioxane, dichloromethane (DCM), or mixtures thereof.
  • solvent e.g., dimethylformamide (DMF), dimethylacetamide (DMA), dimethylsulfoxide (DMSO), N- methylpyrrolidone (NMP), tetrahydrofuran (THF), dioxane, dichloromethane (DCM), or mixtures thereof.
  • the solvent is an aprotic organic solvent.
  • each cycle comprises three steps, deprotection, coupling and capping.
  • the first step of each cycle involves removal of a protecting group (PG) such as Fmoc or Boc from the terminus (e.g., the N-terminus) of the solid-supported PNA using a suitable reagent (i.e. deprotection).
  • PG protecting group
  • removal of the PG is achieved with an organic base (e.g., piperidine, 1,8-diazabicyclo5.4.0]undec-7-ene (DBU), DIPEA or collidine) or an acid (e.g., TFA, trifluoromethanesulfonic acid (TFMSA), hydrochloric acid, or hydrofluoric acid).
  • an organic base e.g., piperidine, 1,8-diazabicyclo5.4.0]undec-7-ene (DBU), DIPEA or collidine
  • an acid e.g., TFA, trifluoromethanesulfonic acid (TFMSA), hydrochloric acid, or hydrofluoric acid
  • the second step of the cycle i.e. the coupling step
  • involves contacting the solid-supported PNA with a second or subsequent subunit(s) dissolved in a solvent e.g., DMF, NMP, or a mixture of solvents.
  • the second step of the cycle can also involve activation of the free carboxylic acid of the second or subsequent subunit(s). Activation can require use of a base (e.g., DIPEA, TEA, collidine, pyridine, or piperidine).
  • a base e.g., DIPEA, TEA, collidine, pyridine, or piperidine.
  • the carboxylic acid of the first subunit is activated with an activating agent such as a carbodiimide (e.g., DCC, DIC), benzotriazole (e.g., HOBt, HOAt, DEPBT), a phosphonium salt (e.g.
  • BOP, PyBOP, PyBrop or uronium salt (e.g., HBTU, TBTU, HATU, TATU, TOTU), or a fluoroformamidinium salt (e.g., TFFH, BTFFH).
  • uronium salt e.g., HBTU, TBTU, HATU, TATU, TOTU
  • fluoroformamidinium salt e.g., TFFH, BTFFH
  • the ratio of the first subunit to the second subunit is about 1:1, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.4, about 1:1.5; about 1.1.75; about 1:2, about 1:2.5, about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10. In some embodiments, an excess of the second or subsequent subunit(s) is used.
  • the ratio of the second or subsequent subunit(s) to the first subunit is about 1:1, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.4, about 1:1.5; about 1.1.75; about 1:2, about 1:2.5, about 1:3, 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10.
  • the third step of the cycle can entail capping. Capping is used to terminate elongation of any particular oligomer that has not undergone elongation during the coupling step. In this way, oligomers possessing a deleted subunit are not created and can be easily purified away from the desired product post synthesis.
  • the subunit is a PNA subunit, an amino acid (e.g., lysine), a linker a label, or a solubility enhancer.
  • the linker is a polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a C 6 -C 20 PEG linker (e.g., a PEG2 or PEG3 linker as illustrated in FIGS.8B and 8D, respectively).
  • the subunit is a C 12 -PEG linker.
  • a PNA oligomer comprises one type of subunit.
  • a PNA oligomer comprises more than one type of subunit. In some embodiments, a PNA oligomer comprises all types of subunits (e.g. PNA subunits, amino acids, linkers, labels, solubility enhancers and the like).
  • the solid-supported PNA is washed with an appropriate solvent (e.g., dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, tetrahydrofuran, dioxane, dichloromethane, or mixtures thereof) and filtered between each coupling step. In some embodiments, each coupling step is also carried out in one or more of these solvents.
  • the solid-supported PNA oligomer is extended through multiple cycles of the above described steps. These steps can be carried out manually, or by using the semi-automated or fully-automated instruments discussed above, or any combination of these methods. [0260] Once the desired subunits and other components are added to the PNA oligomer, the synthesis can be terminated, or the PNA oligomer can be modified further, for example, through acetylation or other end-capping methods. In some embodiments, the PNA oligomer is subjected to selective deprotection of the PNA side chains or PNA nucleobases. In some embodiments, the PNA oligomer is fully deprotected before cleavage.
  • the fully deprotected PNA oligomer is modified prior to cleavage.
  • a final step involving cleavage of the PNA oligomer from the solid support is carried out. This step can involve treatment of the solid-supported PNA oligomer with an acid, base, nucleophile, phenol (e.g. meta cresol), thiol, or photolysis, or combination of two or more of the foregoing.
  • a PNA oligomer can be cleaved from the solid support through incubation with an acid (e.g., trifluoroacetic acid, hydrofluoric acid, trifluoromethanesulfonic acid, trimethylsilyl trifluoromethanesulfonate, hydrobromic acid) or in some cases an alcohol (e.g., hexafluoroisopropanol).
  • an acid e.g., trifluoroacetic acid, hydrofluoric acid, trifluoromethanesulfonic acid, trimethylsilyl trifluoromethanesulfonate, hydrobromic acid
  • an alcohol e.g., hexafluoroisopropanol
  • cleavage of the PNA oligomer from the solid support can also effect removal of the protecting groups from the PNA side chains and/or the PNA nucleobases.
  • scavengers such as water, sulfides, thiols, phenols, and silanes can be used in the final cleavage step to prevent side- reactions or racemization of any chiral centers in the PNA oligomer.
  • residual acid or other reagents or side-products from the cleavage step can be removed through trituration, filtration, dialysis, chromatography, or other purification methods.
  • a PNA oligomer can be synthesized using solution phase synthesis. Many of the same methods outlined above for solid-phase peptide synthesis apply to solution phase peptide synthesis.
  • solution phase peptide synthesis does not use a solid support (e.g., a resin or beads).
  • a solid support e.g., a resin or beads.
  • each step of the repeating cycle to grow the PNA oligomer can require purifying the oligomer from the reaction mixture using techniques such as extraction, trituration, column chromatography, HPLC, or other common purification techniques.
  • no solid support is used in solution phase peptide synthesis, no cleavage from a resin is required. However, more steps are required to remove at least one or all protecting groups from the PNA oligomer.
  • a PNA oligomer can be synthesized using a combination of solid phase and solution phase methods.
  • the PNA oligomer is purified after synthesis. Examples of methods of purification include silica gel chromatography, high performance liquid chromatography (HPLC), extraction, and/or trituration.
  • a PNA oligomer can be purified on a C18 reverse phase column using a solvent system (e.g., 1% TFA, acetonitrile and water). In some embodiments, an isocratic elution is used. In some embodiments, a gradient elution is used. [0265] In some embodiments, the PNA oligomer is at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 97%, at least 98%, at least 99%, at least 99.5%, or at least 99.9% pure. Purity of a PNA oligomer can be determined by any suitable method, for example, through HPLC analysis.
  • the PNA oligomer can be characterized to confirm the identity of the PNA sequence. Characterization methods include mass spectrometry (including liquid chromatography mass spectrometry (LCMS), nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy, infrared spectroscopy, HPLC, fluorimetry, and X-ray crystallography.
  • mass spectrometry including liquid chromatography mass spectrometry (LCMS), nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy, infrared spectroscopy, HPLC, fluorimetry, and X-ray crystallography.
  • the individual subunits in the oligomerization reaction are vacuum dried prior to use in the reaction.
  • the individual subunits in the oligomerization reaction are freshly distilled over a drying agent (e.g., with CaH 2 or K 2 CO 3 ), purified, recrystallized, or dried prior to use in the reaction.
  • a drying agent e.g., with CaH 2 or
  • the individual subunits in the oligomerization reaction are synthesized prior to use. In some embodiments, the individual subunits in the oligomerization reaction are commercially available.
  • Methods of Making Nanoparticles [0268] Described herein are methods for producing a nanoparticle that comprises PNA oligomers comprising a pyrimidine-compliant PNA subunit, and optionally other components (e.g., nucleic acids).
  • the nanoparticle is a lipid nanoparticle (LNP).
  • the nanoparticle is a nanoparticle comprising a synthetic polymer (e.g., a nanoparticle comprising PLGA).
  • a method of forming such nanoparticles can require a double emulsion process, single emulsion process, or a process involving mixing premade solutions to effect nanoprecipitation.
  • Lipid Nanoparticles [0269]
  • the method of making an LNP comprising a PNA oligomer can entail mixing a first solution with a second solution.
  • the first solution comprises a lipid or a plurality of lipids and a PNA oligomer, e.g., a tcPNA oligomer, in a solvent.
  • the solvent can be any water miscible solvent (e.g., ethanol, methanol, isopropanol, acetonitrile, dimethylformamide, dimethylsulfoxide, dioxane or tetrahydrofuran).
  • the first solution comprises a small percentage of water.
  • the first solution can comprise up to at least 60% by volume of water, up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of water.
  • the first solution comprises between about 0.05% and 60% by volume of water, e.g., between about 0.05% and about 50%, about 0.05% and about 40%, or about 5% and about 20% by volume of water.
  • the first solution can comprise a single type of PNA oligomer or a plurality of PNA oligomers, e.g., of different PNA sequences.
  • the first solution comprises a single type of PNA oligomer (e.g., a tcPNA oligomer).
  • the first solution comprises a plurality of PNA oligomers (e.g., tcPNA oligomers), wherein the PNAs comprise different sequences and bind to different target nucleic acid sequences.
  • the first solution comprises a single type of lipid, for example, an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid.
  • the first solution comprises a plurality of lipids.
  • the plurality comprises an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid.
  • the plurality of lipids comprise cholesterol, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dimyristoyl-rac-glycero-3-methylpolyoxyethylene2000 (DMG-PEG2k), and dilinoleylmethyl-4-dimethylaminobutyrate (DLin-MC3-DMA).
  • the plurality of lipids can exist in any ratio.
  • the plurality of lipids comprises an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid of the above lipids in a particular ratio (e.g., a ratio described herein).
  • the second solution is water.
  • the second solution is an aqueous buffer.
  • the second solution can comprise a load component, e.g., a nucleic acid (e.g., a single-stranded DNA).
  • the nucleic acid is a DNA oligomer (e.g. a donor DNA).
  • the second solution can comprise a small percentage of water- miscible organic solvent.
  • the second solution can comprise up to at least about 60% by volume of at least one water miscible organic solvent.
  • the second solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of at least one organic solvent (e.g., a water miscible organic solvent).
  • organic solvent e.g., a water miscible organic solvent
  • the second solution comprises between about 0.05% and about 60% by volume of organic solvent, e.g., between about 0.05% and about 50%, about 0.05% and about 40%, or about 5% and about 20% by volume of organic solvent (e.g., a water miscible organic solvent).
  • the aqueous buffer solution can be an aqueous solution of citrate buffer.
  • the aqueous buffer solution is a citrate buffer solution with a pH between 4-6.
  • the aqueous buffer solution is a citrate buffer solution with a pH of about 4, about 5, or about 6.
  • the aqueous buffer solution is a citrate buffer solution with a pH of about 6.
  • the solution comprising a mixture of the first and second solutions comprising the LNP suspension can be diluted.
  • the pH of the solution comprising a mixture of the first and second solutions comprising the LNP suspension can be adjusted. Dilution or adjustment of the pH of the LNP suspension can be achieved with the addition of water, acid, base, or aqueous buffer. In some embodiments, no dilution or adjustment of the pH of the LNP suspension is carried out. In some embodiments, both dilution and adjustment of the pH of the LNP suspension is carried out.
  • excess reagents, solvents, free PNA or free nucleic acid can be removed from the LNP suspension by tangential flow filtration (TFF) (e.g., diafiltration).
  • TFF tangential flow filtration
  • the organic solvent (e.g., ethanol) and buffer can also be removed from the LNP suspension with TFF.
  • the LNP suspension is subjected to dialysis and not TFF.
  • the LNP suspension is subjected to TFF and not dialysis.
  • the LNP suspension is subjected to both dialysis and TFF.
  • the present disclosure features a method comprising treating a sample of LNPs comprising PNAs and optionally nucleic acids, with a fluid comprising a detergent (e.g., Triton X-100) for a period of time suitable to degrade the lipid layer and thereby release the encapsulated and/or entrapped PNA(s) and optionally nucleic acid(s).
  • a detergent e.g., Triton X-100
  • the method further comprises analyzing the sample for the presence, absence, and/or amount of the released PNA(s) and optionally nucleic acid(s).
  • the present disclosure features a method of manufacturing, or evaluating, a LNP or preparation of LNPs comprising providing a preparation of LNPs described herein, and acquiring, directly or indirectly, a value for a preparation parameter.
  • the method further comprises making the preparation of LNPs by a method described herein.
  • the method further comprises evaluating the value for the preparation parameter, e.g., by comparing the value with a standard or reference value.
  • the method further comprises selecting a course of action, and optionally, performing the action.
  • the method can comprise providing a preparation of LNPs comprising a PNA, acquiring a value for a preparation parameter (e.g., average particle size), evaluating the preparation the value of the preparation parameter by comparing the value with a standard or reference value, selecting a course of action (e.g., selecting to administer the preparation of LNPs to a subject), and performing the action (administering the preparation of LNPs to a subject).
  • a preparation parameter e.g., average particle size
  • evaluating the preparation the value of the preparation parameter by comparing the value with a standard or reference value
  • selecting a course of action e.g., selecting to administer the preparation of LNPs to a subject
  • performing the action administering the preparation of LNPs to a subject.
  • Synthetic Polymer Nanoparticles [0277]
  • the method of making a synthetic polymer nanoparticle comprising a PNA oligomer can entail mixing a first solution with a second solution.
  • the first solution comprises a P
  • the first solution comprises a small percentage of water.
  • the first solution can comprise up to at least 60% by volume of at water.
  • the first solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of water.
  • the first solution comprises between about 0.05% and 60% by volume water, between about 0.05% and 50%, between about 0.05% and 40%, or between about 5% and 20% by volume water.
  • the first solution can comprise a single type of PNA oligomer or a plurality of PNA oligomers, e.g., of different PNA sequences.
  • the first solution comprises a single type of PNA oligomer, e.g., a tcPNA oligomer.
  • the first solution comprises a plurality of PNA oligomers, e.g., tcPNA oligomer, wherein the PNAs comprise different sequences and bind to different target nucleic acid sequences.
  • the synthetic polymer is polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(4-hydroxy-L-proline ester), a polyester, a polyanhydride, a poly(ortho)ester, a polyurethane, a poly(butyric acid), poly(valeric acid), poly(caprolactone), a poly(hydroxyalkanoate), a poly(lactide-co-caprolactone), a poly(amine-co- ester) polymer, or a combination of any two or more thereof.
  • the synthetic polymer is PLGA.
  • the second solution is acqueous.
  • the second solution is an aqueous buffer.
  • the second solution can comprise a load component, e.g., a nucleic acid (e.g., a single-stranded DNA).
  • the nucleic acid is a DNA oligomer (e.g., a donor DNA).
  • the second solution can comprise a small percentage of water miscible organic solvent.
  • the second solution can comprise up to at least about 60% by volume of at least one water miscible organic solvent.
  • the second solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of at least one organic solvent (e.g., a water miscible organic solvent).
  • organic solvent e.g., a water miscible organic solvent
  • the second solution comprises between about 0.05% and 60%, between about 0.05% and 50%, between about 0.05% and 40%, or between about 5% and 20% by volume organic solvent (e.g., a water miscible organic solvent).
  • the aqueous buffer solution can be an aqueous solution of citrate buffer.
  • the aqueous buffer solution is a citrate buffer solution with a pH between 4-6.
  • the aqueous buffer solution is a citrate buffer solution with a pH of about 4, about 5, or about 6.
  • the aqueous buffer solution is a citrate buffer solution with a pH of about 6.
  • the process involves mixing the above solutions to produce nanoparticles that encapsulate the PNA oligomer and, optionally, a nucleic acid load component.
  • the process can further require dilution (e.g., with water or a buffer).
  • the process involves the introduction of a surface stabilizer (e.g., trehalose, sucrose, or cyclodextrin).
  • the process can involve diafiltration to remove excess reagents, non-encapsulated PNA oligomers or DNA, solvents, or buffers from the nanoparticles.
  • dialysis is used to remove excess reagents, non-encapsulated PNA oligomers or DNA, solvents, or buffers from the nanoparticles.
  • the process can further require sterilization of the nanoparticles, for example by filtration through a filter of a select pore size (e.g., 0.2 ⁇ M) to remove microbes.
  • the method can additionally feature the addition of cryoprotectants, excipients, or other components.
  • the method can require transferring the nanoparticles to containers suitable for distribution and use for administration.
  • the nanoparticles can be stored at low temperatures, such as at 0 °C, -20 °C, -80°C lower.
  • the loading of PNA oligomer and other components in the nanoparticle are analyzed through many methods.
  • analysis involves digesting nanoparticles by treatment with ammonia or dimethylsulfoxide (DMSO) to release encapsulated PNA oligomers and any other encapsulated components (e.g., DNA).
  • DMSO dimethylsulfoxide
  • the amount of total PNA and DNA in the digest can then be determined by spectroscopic methods (e.g., UV absorbance), HPLC, or other methods (e.g., OliGreen/RiboGreen methods).
  • nanoparticles are analyzed by scanning electron microscopy (SEM) techniques.
  • nanoparticles can be coated in platinum and imaged using SEM to determine size and morphology of the nanoparticles.
  • Gene Targeting Compositions and Methods of Treatment [0283] Described herein are pyrimidine-compliant PNA oligomers and compositions thereof, and methods of using the same to alter a target nucleic acid sequence.
  • the methods of using the pyrimidine-compliant PNA oligomers can be performed in vitro (e.g., in an in vitro cell system) or in vivo (e.g., in a subject, e.g., a human subject). In some embodiments, the method is performed in an in vitro cell free system. In some embodiments, the method is performed in a cell.
  • the cell can be a cultured cell, e.g., a cell from a cell line, or can be a cell derived from a subject.
  • the method is performed in vivo, e.g., in a subject.
  • the subject can be a mammal (e.g., a mouse, other non-human primate or a human).
  • the target nucleic acid sequence used in the described methods can be single-stranded or double-stranded.
  • altering a target nucleic acid sequence comprises altering a target double-stranded nucleic acid sequence.
  • Altering a target double-stranded nucleic acid sequence can comprise one or more of: a) altering the state of association of the two strands of a target double-stranded nucleic acid sequence; b) altering the helical structure of a target double-stranded nucleic acid sequence; c) altering the topology in a strand of a double-stranded nucleic acid sequence, for example, by introducing a kink or bend in a strand of the target double-stranded nucleic acid sequence; d) recruiting a nucleic acid-modifying protein (e.g., enzyme), for example, a member of the nucleotide excision repair pathway, to a target double stranded nucleic acid.
  • a nucleic acid-modifying protein e.g., enzyme
  • Examples of members of the nucleotide excision repair pathway include XPA, RPA, XPF, and XPG, or a functional variant or fragment thereof; e) cleaving a strand of a target double stranded nucleic acid; or f) altering the sequence of a target double stranded nucleic acid.
  • the sequence of a target double stranded nucleic acid is altered to the sequence of a template nucleic acid.
  • the sequence of a target double stranded nucleic acid is altered from a mutant or disorder-associated sequence (e.g., allele) to a non-mutant or non-disease associated sequence (e.g., allele) a subject having a disease, disorder, or condition.
  • altering a nucleic acid comprises two of (a)-(f). In some embodiments, altering a nucleic acid comprises three of (a)-(f). In some embodiments, altering a nucleic acid comprises four of (a)-(f). In some embodiments, altering a nucleic acid comprises five of (a)-(f).
  • altering a nucleic acid comprises each of (a)-(f). In some embodiments, altering a nucleic acid comprises (a). In some embodiments, altering a nucleic acid comprises (b). In some embodiments, altering a nucleic acid comprises (c). In some embodiments, altering a nucleic acid comprises (d). In some embodiments, altering a nucleic acid comprises (e). In some embodiments, altering a nucleic acid comprises (f). [0286]
  • the PNA oligomer comprising a PC PNA subunit can promote a particular effect in a target nucleic acid sequence. For example, the PNA oligomer can bind a target nucleic acid sequence.
  • This binding can provide a decrease in the melting point (Tm) of the target nucleic acid sequence of at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, and can promote melting or dissociation of the strands of the target nucleic acid sequence.
  • Tm melting point
  • a PNA oligomer can decrease the melting point of the target nucleic acid sequence of at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%. This decrease can promote melting or dissociation of the strands of the target sequence.
  • a PNA oligomer can cleave the target nucleic acid sequence and effect cleavage in at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50% of target nucleic acid sequences.
  • a PNA oligomer can edit at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50% of the strands of the target sequence.
  • the PNA oligomer comprising a PC PNA subunit can induce gene modification in at least one target allele to occur at frequency of at least about 0.1%, at least about 0.2%, at least about 0.3%, at least about 0.4%, at least about 0.5%, at least about 0.6%, at least about 0.7%, at least about 0.8%, at least about 0.9%, at least about 1%, at least about 2%, at least about 3%, at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24, or at least about 25% of target cells.
  • gene modification occurs in at least one target allele at a frequency of about 0.1-25%, or 0.5- 25%, or 1-25% 2-25%, or 3-25%, or 4-25% or 5-25% or 6-25%, or 7-25%, or 8-25%, or 9-25%, or 10-25%, 11-25%, or 12-25%, or 13%-25% or 14%-25% or 15-25%, or 2-20%, or 3-20%, or 4-20% or 5-20% or 6-20%, or 7-20%, or 8-20%, or 9-20%, or 10-20%, 11-20%, or 12-20%, or 13%-20% or 14%-20% or 15-20%, 2-15%, or 3-15%, or 4-15% or 5-15% or 6-15%, or 7-15%, or 8-15%, or 9-15%, or 10-15%, 11-15%, or 12-15%, or 13%-15% or 14%-15%.
  • a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell, of greater than about 5%, greater than about 8%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 16%, greater than about 17%, greater than about 18%, or greater than about 19%.
  • a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of greater than about 10%.
  • a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of greater than about 15%. In some embodiments, a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of about 5% to about20%, about 8% to about 12%, about 10% to about 20%, about 10% to about 15%, about 12.5% to about 20%, about 15% to about 18%, or about 15% to about 20%.
  • a PNA oligomer comprising a PC PNA subunit or a composition thereof is administered at a particular dosage, e.g., a therapeutically effective dosage.
  • dosages can be expressed in mg/kg of the subject, and can be, for example, about 0.1 mg/kg to about 1,000 mg/kg, or about 0.5 mg/kg to about 1,000 mg/kg, or about 1 mg/kg to about 1,000 mg/kg, or about 10 mg/kg to about 500 mg/kg, or about 20 mg/kg to about 500 mg/kg per dose, or about 20 mg/kg to about 100 mg/kg per dose, or about 25 mg/kg to about 75 mg/kg per dose.
  • a PNA oligomer can be administered at a dose of at least about 25 mg/kg, at least about 30 mg/kg, at least about 35 mg/kg, at least about 40 mg/kg, at least about 45 mg/kg, at least about 50 mg/kg, at least about 55 mg/kg, at least about 60 mg/kg, at least about 65 mg/kg, at least about 70 mg/kg, or at least about 75 mg/kg per dose.
  • a PNA oligomer can be administered at a dose of about 25 mg/kg, about 30 mg/kg, about 35 mg/kg, about 40 mg/kg, about 45 mg/kg, about 50 mg/kg, about 55 mg/kg, about 60 mg/kg, about 65 mg/kg, about 70 mg/kg, or about 75 mg/kg per dose.
  • the PNA oligomer comprising a PC PNA subunit alters a target nucleic acid sequence with little to no off-target effects.
  • off-target modification of a nucleic acid is undetectable using routine analysis, e.g., nucleic acid sequencing.
  • off-target modification of a nucleic acid occurs at a frequency of 0-1%, or 0-0.1%, or 0-0.01%, or 0-0.001%, or 0-0.0001%, or 0-0000.1%, or 0- 0.000001%. In some embodiments, off-target modification of a nucleic acid occurs at a frequency that is about 10 2 , about 10 3 , about 10 4 , or about 10 5 -fold lower than at the target nucleic acid sequence.
  • the method comprises administering to a subject a PNA oligomer comprising a PC PNA subunit or a composition thereof (e.g., a nanoparticle comprising the PNA oligomer).
  • the PNA oligomer comprising a PC subunit is administered to the subject in a therapeutically effective amount, e.g., a dosage sufficient to reduce a likelihood of, treat, or inhibit a symptom of a disease, disorder or condition.
  • the disease, disorder, or condition is a human genetic disease, for example, in which at least one addition, deletion or mutation is present in an allele compared to a non-disease control.
  • diseases, disorders, or conditions that may be treated with the PNA oligomers and compositions thereof described herein include cystic fibrosis, hemophilia, and a globinopathy (e.g., sickle cell anemia, beta-thalassemia), xeroderma pigmentosum, a lysosomal storage disease, or a cancer (e.g., a cancer related to PD-1).
  • the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat cystic fibrosis in a subject.
  • the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat hemophilia in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a globinopathy (e.g., sickle cell anemia, beta- thalassemia) in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat xeroderma pigmentosum in a subject.
  • a globinopathy e.g., sickle cell anemia, beta- thalassemia
  • the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a lysosomal storage disease in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a cancer in a subject.
  • PNA oligomers, nucleic acids, nanoparticles (e.g., LNPs or synthetic polymer nanoparticles), and compositions thereof provided herein can be prepared from starting materials using modifications to the specific synthetic protocols set forth below.
  • Examples of PNA oligomers, nucleic acids, nanoparticles (e.g., LNPs or synthetic polymer nanoparticles), and compositions thereof can be prepared using any of the strategies described below.
  • PNA Monomers Except for the specialty PNA monomers comprising pyrimidine compliant nucleobases (i.e.
  • PC monomers used to produce PNA subunits in PNA oligomers prepared as set forth below (which monomers were prepared in-house), classic Fmoc PNA monomers (monomers having an unsubstituted 2-aminoethylglycine backbone) were purchased from commercial sources and/or prepared by a vendor on a custom synthesis basis.
  • Fmoc gamma miniPEG monomers were prepared by a vendor on a custom synthesis basis by generally following published procedures.
  • Fmoc gamma miniPEG PNA monomers could be prepared using the Mitsunobu route using a properly protected serinol intermediate.
  • Amino acids e.g., N-alpha-Fmoc-N-epsilon-Fmoc-L-lysine and N-alpha- Fmoc-N-epsilon-boc-L-lysine
  • Amino acids were purchased from commercial sources such as Chem Impex International, Bachem and Matrix Innovations and used without any analysis.
  • PNA oligomers comprising a Gly-Gly PNA subunit (a.k.a.
  • a “Gly-Gly bridge”) in the Hoogsteen segment of the oligomer a single coupling of the commercially available dimer Fmoc-Gly-Gly- OH was used instead of two back-to-back couplings of the amino acid Fmoc-Gly-OH.
  • a PNA oligomer comprising a Gly-Gly bridge can be prepared using any suitable method.
  • a single synthetic cycle comprised: 1) deprotection of the N-terminal Fmoc group; 2) coupling of a new monomer, linker, amino acid or synthon to the growing polyamide; and 3) capping of the unreacted amino groups.
  • the resin was washed extensively with N,N’-dimethylformamide (DMF) to remove unreacted reagents and other unwanted impurities and side products of the reaction.
  • DMF N,N’-dimethylformamide
  • Protocol for Small Scale Synthesis Approximately 45 mg (5.8 ⁇ mol) rink amide TentaGel resin was placed in the reaction column of the Intavis and treated with 800 ⁇ L dichloromethane (DCM) for 15 minutes (min) to swell the resin prior to initiation of the PNA oligomer synthesis. The resin was then treated twice with 600 ⁇ L of 20% (v/v) piperidine/DMF for 5 min each to remove the Fmoc group.
  • DCM dichloromethane
  • N,N’-diisopropylethylamine DIEA; approximately 56 ⁇ mol
  • NMP dry N-methyl pyrrolidone
  • HATU 1- bis(dimethylamino)methylene]-1H-1,2,3-triazolo4,5-b]pyridinium 3-oxid hexafluorophosphate
  • 2,6-lutidine can be added to the DIEA solution in a ratio of approximately 1/1.5 DIEA/2.6-lutidine (v/v).
  • the reaction mixture was then drained from the reaction vessel and the resin was washed extensively with DMF.
  • the capping step was then performed by treating the resin with 600 ⁇ L of capping solution (5% acetic anhydride and 6% lutidine in DMF (v/v)) while agitating the resin for 5 min. These three steps were repeated sequentially for each new PNA monomer, linker, amino acid or other building block until the PNA oligomer was completely assembled.
  • the protocol was modified so that the final Fmoc deprotection step was eliminated so that the PNA oligomer remained Fmoc-ON.
  • ThermoFisher Preparative HPLC system equipped with an automated fraction collector. Output from the detector and fraction collector were used to determine which fractions should be collected and pooled as product. In some cases, fractions were analyzed by analytical HPLC to determine whether the fractions should be pooled. The pooled product provided by combined fractions was then reanalyzed by ThermoFisher analytical HPLC (to determine purity) and on a Waters-Q-TOF LCMS to confirm the identity (by mass/charge ratio) of the PNA oligomer and subsequently lyophilized to obtain the purified Fmoc-ON PNA oligomers (i.e.
  • FIG.10 contains the HPLC traces for 6 representative bis-Fmoc PNA oligomers evaluated using these analytical separation conditions.
  • the (bis) Fmoc-On purified lyophilized PNA oligomer from the 5.8 ⁇ mol scale synthesis was dissolved in about 400 ⁇ L of dimethylsulfoxide (DMSO).
  • DMSO dimethylsulfoxide
  • the PNA oligomer containing tube was washed with 100 ⁇ L of dry DMSO and that wash solution was also transferred to the tube containing the PIR.
  • the tube containing the PNA oligomer and PIR was then inserted into a holder on a shaker rack and shaken for 24 hrs.
  • the tube containing the PNA oligomer was removed from the shaker and analyzed for completeness of Fmoc removal.
  • a 1-2 ⁇ L aliquot of the liquid in the tube was transferred to an Eppendorf tube containing 40 ⁇ L of 5% aqueous acetonitrile and the solution was thoroughly mixed.
  • the solution was then transferred to a spin cartridge containing a 0.22 ⁇ m cutoff filter and the cartridge was spun by centrifuge to filter off any particles in the liquid.
  • the filtrate was then transferred to a tube suitable for analysis in a Waters-Q-TOF LCMS to access whether or not the Fmoc groups were completely removed from PNA oligomer in the sample.
  • FIG.9 contains the HPLC traces for 6 representative (crude) fully-deprotected PNA oligomers evaluated using these analytical separation conditions.
  • FIG.9 shows the analytical HPLC profile of crude fully deprotected PNA oligomers for each of the PNA oligomers listed in the table.
  • FIG.10 shows the analytical HPLC profile of each of the same PNA oligomers, wherein each PNA oligomer comprises an N-terminal bis-Fmoc protected L-lysine moiety.
  • Step 1 Synthesis of 3-(2-oxopyrimidin-1-(2H)-yl) propanoic acid (2) [0314] To 5 g of 2-hydroxypyrimidine ⁇ HCl (1; 38 mmol) was added 22.5 mL of 5N NaOH with stirring until the solid dissolved. Then, 5.8 g of 3-bromopropionic acid (38 mmol) was added to the solution, which was allowed to stir at about 60 °C overnight. The reaction was then cooled and neutralized with aqueous hydrochloric acid (HCl). The resulting mixture was then extracted 3 times with 50 mL of dichloromethane (DCM). The organic (DCM) layers were combined, dried over granular MgSO 4 and evaporated.
  • Step 3 Synthesis of N-(2-((((9H-fluoren-9-yl) methoxy) carbonyl) amino) ethyl)-N-(3-(2- oxopyrimidin-1(2H)-yl) propanoyl) glycine (5)
  • N-(2-(((9H-fluoren-9-yl) methoxy) carbonyl) amino) ethyl)-N-(3-(2- oxopyrimidin-1(2H)-yl) propanoyl) glycinate 4; 2.1 mmol
  • Example 3 Synthesis of “M-monomer”; a.k.a Fmoc-aeg-M(boc)-OH
  • Step 1 Synthesis of 1-(tert-butyl) 3-ethyl 2-(6-nitropyridin-3-yl)malonate (7)
  • NaH sodium hydride
  • DMF dry N,N’-dimethylformamide
  • Step 2 Synthesis of ethyl 2-(6-nitropyridin-3-yl)acetate (8) [0318] To a stirring solution of 8.17 g of 1-(tert-butyl) 3-ethyl 2-(6-nitropyridin-3-yl) malonate (7; 26 mmol) in 50 mL of dry dichloromethane (DCM) in a round-bottom flask in an ice-bath was added 8.17 mL of trifluoracetic acid (TFA) dropwise. The resulting solution was heated to reflux with heat set at 90 o C for 16 hours. The reaction was cooled and concentrated before being diluted with ice-cold water.
  • DCM dry dichloromethane
  • TFA trifluoracetic acid
  • Step 3 Synthesis of ethyl 2-(6-aminopyridin-3-yl)acetate (9)
  • Ethyl 2-(6-nitropyridin-3-yl) acetate, 5.33 g (8; 25 mmol), 33.6 g of ammonium chloride (628 mmol) and 16.50 g of zinc dust (252 mmol) were placed in a 500 mL round bottom flask. 175 mL of 2:1, (v/v) MeOH:H 2 O was added, and the mixture was stirred at room temperature for 1 hour. Reaction progress was monitored by TLC and LCMS. After the reaction was complete, the mixture was diluted with EtOAc and filtered through Celite.
  • Step 4 Synthesis of ethyl 2-(6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetate (10) [0320] To 9.94 g of ethyl 2-(6-aminopyridin-3-yl) acetate (9; 55 mmol) and 14.47 g of di-tert- butyl dicarbonate (66 mmol) was added 147 mL of tert-butyl alcohol under argon.9.25 mL of triethylamine (66 mmol) was added, and the reaction was stirred for 3 hours at 50 o C.
  • Step 5 Synthesis of 2-(6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetic acid (11) [0321] To 10.97 g of ethyl 2-(6-((tert-butoxycarbonyl) amino) pyridin-3-yl) acetate (10; 39 mmol) in a 500 mL round bottom flask was dissolved 150 mL of acetonitrile:ethanol:water in 2:2:1 (v/v/v) ratio. Some heat was applied to dissolve all the ester. The mixture was then placed on ice-bath for 20 min.
  • Step 6 Synthesis of 2-iodoethyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(2- (6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetyl)glycinate (13) [0322] Ethyl 2-(6-((tert-butoxycarbonyl) amino) pyridin-3-yl) acetate 8.29 g (11; 33 mmol), 25.02 grams of hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU) (66 mmol), and 18.25 g Fmoc protected iodoe
  • Step 7 Synthesis of N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(2-(6-((tert- butoxycarbonyl)amino)pyridin-3-yl)acetyl)glycine (14)
  • TXE Buffer was made by combining 50 mmol KH 2 PO 4 , 25 mmol of ethylenediaminetetraacetic acid (EDTA) and 25 mmol of ethylenediaminetetraacetic acid zinc disodium salt hydrate (EDTA-Zn . H 2 O) in 150 mL of deionized water and 50 mL of glacial acetic acid (HOAc).
  • aqueous layer was then combined the organic layer and washed twice with 50 mL (a total of 100 mL) of extraction buffer (Extraction Buffer is 1g KH 2 PO 4 and 0.5g KHSO 4 per 10 mL of deionized water).
  • extraction Buffer is 1g KH 2 PO 4 and 0.5g KHSO 4 per 10 mL of deionized water.
  • the organic layer was then dried over MgSO 4 (granular), filtered, and evaporated.
  • the crude compound was purified by flash chromatography in 0 to 100% hexane:EtOAc to yield 12.56 g, (93% yield 14). Further purification in DCM:MeOH gave product that was greater than 98% pure. Notes: 1. Use Zn Powder average 4-7 micron 97.5% powder or flakes.
  • Example 4 Synthesis of “E-monomer” a,k.a. Fmoc-aeg-E(boc)-OH monomer
  • Step 1 Synthesis of 3-((6-bromopyridazin-3-yl)amino)propanoic acid (16) [0325] Combined 25g of 2,5-dibromopyridazine (15) with 11.22g of b-alanine and 17.43g of potassium carbonate. Added to this mixture was 60 mL of EtOH and then the resulting solution was heated under reflux with stirring for a total of 6 hours during which everything dissolved to a thick, gooey mixture that eventually crystallized into a white mass. The reaction was cooled and partitioned between EtOAc and water.
  • Step 4 Synthesis of methyl 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoate (19) [0328] 16.3 g of methyl 3-((6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoate (18) was taken up in 140 mL dry dioxane and to the resultant mixture were added 28 g of di-tert-butyl dicarbonate and by 0.618 of DMAP. Gas was slowly evolved from this solution with stirring. at the mixture was heated to 70 o C in an oil bath and CO 2 release became steady and then slowed.
  • Step 5 Synthesis of 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoic acid (20) [0330] 18.3g ( ⁇ 44 mmol) of compound 19 was taken up in 130 mL of THF and cooled on ice. 130 mL of 1M LiOH monohydrate in methanol was added and the ice bath was removed. After stirring for 6 hours, the reaction was ⁇ 90% complete.2N HCl was added slowly with rapid stirring. At ⁇ pH 8 a large amount of solid formed. The mixture was concentrated to almost dryness.
  • Step 6 Synthesis of allyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoyl)glycinate (21) [0331] 6.72 g of 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoic acid (20) was taken into 90mL of dry acetonitrile (ACN) and reconcentrated.
  • ACN dry acetonitrile
  • the test quench showed good mixed anhydride formation.8.38 of Fmoc allyl backbone tosyl salt (3) was added. The reaction was stirred for 30 min. TLC in 5% MeOH/DCM showed almost complete conversion of backbone to monomer ester. The reaction was then concentrated and the resulting oil was dissolved in EtOAc and washed 1x with 50% saturated KHSO 4 , 1x with 5% NaHCO 3 , and once with brine. The EtOAc layer was dried over MgSO 4 and evaporated to give a foam. The foam was dissolved in 40% EtOAc/Hex and loaded on a column equilibrated at 20% EtOAc/Hex, and ran to 90% EtOAc to yield 9 g of very pure material (21).
  • Step 7 Synthesis of N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-oxo-1,6-dihydropyridazin-3-yl)amino)propanoyl)glycine (22) [0332] 1 mmol of allyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)-amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoyl)glycinate (21) was taken up into 10 mL of dry THF and purged under N 2 .
  • the DNA solution (300 ⁇ L, 8.33 uM) was loaded into ITC reaction cell and the reference cell was loaded with degassed HPLC grade water.
  • PNA stock solution (20 ⁇ L, 0.24 mM) was evaporated to dryness and the solid was dissolved in 60 ⁇ L of Phosphate Buffer. After degassing, the PNA solution (60 ⁇ L, 0.08 mM) was loaded in titration syringe and loaded on to the calorimeter.
  • Tables 9A-9B below show the association constants (Ka) for the binding of each PNA oligomer (Compound Nos.1, 2, 7, and 8) binding to the particular ssDNA oligomers screened (SEQ ID NOs: 7-12).
  • Table 9A Association Constants (Ka) from ITC measurements
  • Table 9B Association Constants (Ka) from ITC measurements Results
  • the PNA oligomer containing the P nucleobase (Compound No.1) designed to Hoogsteen bind to the lone pyrimidine in a homopurine tract, was found to bind target DNA (SEQ ID NO: 7) to form a “tail clamp triplex”.
  • the “GlyGly” skip PNA reacted with essentially equivalent affinity to the “E” skip in two cases, SEQ ID NOs: 10 and 11, in the other two cases, SEQ ID NOs: 9 and 12, the “E” skip PNA showed an increased affinity as compared to the “GlyGly” PNA.
  • the overall affinity of the “E” skip PNA to SEQ ID NO: 12 was by far greater than any other KA recorded in the experiment, and approximately double the K A of the “GlyGly” PNA to the same DNA target.
  • the DNA target region for sequence for Compound Nos.3 and 5 is 5’ AGGAGCAGGGAGGG 3’ and the DNA target region sequence for Compound Nos.4 and 6 is 5’ GGGGCAAGGTGAACG 3’; where the underlined base of each sequence is the pyrimidine.
  • An experiment was performed to contact PNA oligomers containing either a “GlyGly” bridge (i.e. Compound Nos.3 and 5) or “P” nucleobase (i.e. Compound Nos.4 and 6) with a double stranded DNA amplicon prepared as described below (and the sequence of which is provided in the Table above (i.e. SEQ ID NO: 13)).
  • the PNA oligomers were designed such that the P nucleobase or the GlyGly subunits (i.e. “GlyGly bridge”) are placed in the clamp portion of the molecule on the Hoogsteen binding segment.
  • the DNA amplicon was generated by polymerase chain reaction (PCR) from a plasmid containing a segment of the sickle cell variant of the human beta-globin gene.
  • the amplicon was a 516 bp molecule with binding sites for PNA constructs Compound Nos.3 and 5 and Compound Nos.4 and 6 beginning at positions 62 and 224 respectively.
  • the DNA target region sequence for constructs Compound Nos.3 and 5 is 5’ AGGAGCAGGGAGGG 3’; and the DNA target region sequence for constructs Compound Nos. 4 and 6 is 5’ GGGGCAAGGTGAACG 3’; wherein the underlined nucleobase of each sequence is the pyrimidine to be evaluated for “pyrimidine compliance” with nucleobase P or the Gly-Gly bridge.
  • Amplicon and PNA oligomer were combined in a 1:15 ratio (0.05 ⁇ M: 0.75 ⁇ M) plus 100 ⁇ M KCL in a total volume of 10 ⁇ L and incubated at 37 °C for 0.5 or 18.0 hr (Figs.12A and 12B, respectively).
  • the reaction contained residual salts and buffers from the PCR reaction which comprised half (5 ⁇ L) of the total volume. Reactant species were separated electrophoretically and visualized on the Agilent TapeStation 4200 using the HSD1000 gel cassette.
  • the lanes are as follows, lane A1, size marker; lane B1, 993 + amplicon; lane C1, 1258 + amplicon; lane D1, 1238 + amplicon; lane E1, 1259 + amplicon, lane F1, amplicon only.
  • PNA oligomers tested alone in control experiments do not migrate into the gel or produce banding patterns.
  • Embodiment 2 The PNA oligomer of embodiment 1, wherein the PNA oligomer is a PNA tail-clamp (tcPNA) oligomer.
  • Embodiment 3 The PNA oligomer of embodiment 1 or 2, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA.
  • Embodiment 5. The PNA oligomer of any one of embodiments 1-4, wherein the first region of the PNA oligomer further comprises (a’) a first positively charged region comprising a first positively charged amino acid, wherein the first positively charged region is covalently bound to a second terminal end of the first region of the PNA oligomer.
  • Embodiment 6. The PNA oligomer of embodiment 5, wherein the first positively charged amino acid is lysine.
  • Embodiment 8 The PNA oligomer of any one of embodiments 1-7, wherein the second region of the PNA oligomer further comprises a second positively charged amino acid, wherein the second positively charged amino acid is covalently bound to a second terminal end of the second region of the PNA oligomer.
  • Embodiment 9. The PNA oligomer of embodiment 8, wherein the second positively charged amino acid is lysine.
  • Embodiment 11 The PNA oligomer of any one of embodiments 1-10, wherein the second region of the PNA oligomer comprises a gamma-modified PNA subunit.
  • Embodiment 12 The PNA oligomer of any one of embodiments 1-11, wherein the third region of the PNA oligomer comprises a gamma-modified PNA subunit.
  • Embodiment 13 Embodiment 13.
  • the first region of the PNA oligomer comprises a first gamma-modified PNA subunit
  • the second region of the PNA oligomer comprises a second gamma-modified PNA subunit
  • the third region of the PNA oligomer comprises a third gamma-modified PNA subunit.
  • Embodiment 15 The PNA oligomer of embodiment 14, wherein P 1 is an amine terminus.
  • Embodiment 16 The PNA oligomer of embodiment 14, wherein P 1 is a carboxyl terminus.
  • Embodiment 17 The PNA oligomer of embodiment 14, wherein P 1 forms a covalent bond with a P 5 group of a second PNA monomer within the first region of the PNA oligomer.
  • Embodiment 18 The PNA oligomer of embodiment 14, wherein P 5 is an amine terminus.
  • Embodiment 19 The PNA oligomer of embodiment 14, wherein P 5 is a carboxyl terminus.
  • Embodiment 20 The PNA oligomer of embodiment 14, wherein P 5 is a carboxyl terminus.
  • Embodiment 21 The PNA oligomer of embodiment 14, wherein P 1 is an amine terminus and P 5 is a carboxyl terminus.
  • Embodiment 22 The PNA oligomer of any one of embodiments 14-21, wherein X is N.
  • Embodiment 23 The PNA oligomer of any one of embodiments 14-21, wherein X is N.
  • Embodiment 24 The PNA oligomer of any one of embodiments 14-23, wherein L is alkylene or heteroalkylene, each of which is optionally substituted with one or more R B .
  • Embodiment 25 Embodiment 25.
  • Embodiment 24 The PNA oligomer of embodiment 24, wherein L is ethylene, propylene, or butylene.
  • Embodiment 26 The PNA oligomer of embodiment 24, wherein R B is oxo.
  • Embodiment 27 The PNA oligomer of any one of embodiments 14-23, wherein L is selected from the group consisting of , and .
  • Embodiment 28 The PNA oligomer of any one of embodiments 14-27, wherein each R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 is independently hydrogen or heteroalkyl.
  • Embodiment 29 Embodiment 29.
  • Embodiment 32 The PNA oligomer of embodiment 31, wherein heteroalkyl is C 2-30 heteroalkyl.
  • Embodiment 33 The PNA oligomer of embodiment 31, wherein heteroalkyl is polyalkylene glycol.
  • Embodiment 34 The PNA oligomer of embodiment 31, wherein heteroalkyl is polyethylene glycol.
  • Embodiment 35 The PNA oligomer of any one of embodiments 30-34, wherein one of R 3 and R 4 comprises a C 2 -C 30 heteroalkyl and each R 5 and R 6 is independently hydrogen.
  • Embodiment 36 Embodiment 36.
  • Embodiment 37 The PNA oligomer of embodiment 31, wherein each R 3 , R 4 , R 5 , and R 6 is independently hydrogen or has the structure of Formula (IV-a) or (IV-b): wherein R 12 is hydrogen or alkyl; and y is 1, 2, 3, 4, or 5.
  • Embodiment 38 The PNA oligomer of embodiment 37, wherein R 12 is C 1-4 alkyl.
  • Embodiment 39 The PNA oligomer of embodiment 38, wherein R 12 is methyl, ethyl, isopropyl, or tert-butyl.
  • Embodiment 40 The PNA oligomer of embodiment 37, wherein R 12 is hydrogen or methyl.
  • Embodiment 41 The PNA oligomer of embodiment 37, wherein R 12 is hydrogen or tert- butyl.
  • Embodiment 42 The PNA oligomer of embodiment 37, wherein R 12 is methyl or tert- butyl.
  • Embodiment 43 The PNA oligomer of any one of embodiments 37-42, wherein y is 1.
  • Embodiment 44 The PNA oligomer of any one of embodiments 37-42, wherein y is 2.
  • Embodiment 45 The PNA oligomer of any one of embodiments 37-42, wherein y is 2.
  • Embodiment 46 The PNA oligomer of embodiment 45, wherein R 2 is C 1-4 alkyl.
  • Embodiment 47 The PNA oligomer of embodiment 45, wherein R 2 is hydrogen.
  • Embodiment 48 The PNA oligomer of any one of embodiments 14-47, wherein each R 5 and R 6 is independently hydrogen.
  • Embodiment 49 The PNA oligomer of any one of embodiments 14-48, wherein R 3 has structure of Formula (IV-a) or (IV-b) and R 4 is hydrogen.
  • Embodiment 50 Embodiment 50.
  • Embodiment 51 The PNA oligomer of any one of embodiments 30-50, wherein n is 1.
  • Embodiment 52 The PNA oligomer of any one of embodiments 30-50, wherein n is 2.
  • Embodiment 53 The PNA oligomer of any one of embodiments 30-50, wherein n is 2.
  • Embodiment 54 The PNA oligomer of embodiment 1, wherein the PNA nucleobase has the Formula (V-i), [0397] Embodiment 55.
  • Embodiment 56 The PNA oligomer of embodiment 54 or 55, wherein each n and m is independently 1.
  • Embodiment 57 The PNA oligomer of any one of embodiments 54-56, wherein each R 21 and R 35 is hydrogen.
  • Embodiment 59 Embodiment 59.
  • Embodiment 60 The PNA oligomer of embodiments 54, 58, or 59, wherein each R 21 and R 35 is hydrogen.
  • Embodiment 61 The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer is selected from the group consisting of:
  • Embodiment 62 The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyridazin-3(2H)-one.
  • Embodiment 63 The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyrimidin-2(1H)-one.
  • Embodiment 64 Embodiment 64.
  • Embodiment 65 The PNA oligomer of any one of embodiment 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the target sequence.
  • Embodiment 66 Embodiment 66.
  • Embodiment 67 The PNA oligomer of embodiment 66, wherein the hydrogen bond has a length of at least about 0.35 nm.
  • Embodiment 68 The PNA oligomer of embodiment 66, wherein the hydrogen bond has a length of at least about 0.4 nm.
  • Embodiment 69 The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode cytosine- binding nucleobase.
  • Embodiment 70 The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode thymine- binding subunit.
  • Embodiment 71 Embodiment 71.
  • Embodiment 73 Embodiment 73.
  • Embodiment 79 A PNA oligomer comprising: (a) a first region comprising a pyrimidine-compliant PNA subunit (PC PNA subunit), wherein the PC PNA subunit comprises: - a nucleobase capable of recognizing a pyrimidine nucleobase in a target sequence; and - a polyethylene glycol moiety in the gamma position; and (b) a second region comprising a plurality of PNA subunits that participate in Watson-Crick binding with a target sequence.
  • PC PNA subunit pyrimidine-compliant PNA subunit
  • Embodiment 80 Embodiment 80.
  • Embodiment 81 The PNA oligomer of embodiment 79, wherein R 12 is methyl, ethyl, isopropyl, or tert-butyl.
  • Embodiment 81 The PNA oligomer of embodiment 79, wherein the PNA nucleobase forms no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA.
  • Embodiment 82 The PNA oligomer of embodiment 79, wherein the PNA nucleobase does not engage in hydrogen bonding with an adenine or a guanosine; or wherein the PNA nucleobase engages in impaired hydrogen bonding.
  • Embodiment 83 Embodiment 83.
  • Embodiment 85 The PNA oligomer of any one of embodiments 1-82, wherein the PNA nucleobase is a Hoogsteen-mode cytosine-binding subunit or a Hoogsteen-mode thymine- binding subunit.
  • Embodiment 84 The PNA oligomer of any one of embodiments 1-83, wherein the PNA nucleobase binds to a cytosine nucleobase or a thymine nucleobase in the single strand of the dsDNA.
  • Embodiment 85 Embodiment 85.
  • Embodiment 86. The PNA oligomer of any one of embodiments 3-85, wherein the first pyrimidine position in the single strand of the dsDNA comprises a cytosine.
  • the PNA oligomer of any one of embodiments 3-85 wherein the first pyrimidine position in the single strand of the dsDNA comprises a cytosine; and the first region of the PNA oligomer comprises, at the position corresponding to the first pyrimidine position, an HCB PNA subunit.
  • Embodiment 88 The PNA oligomer of embodiment 87, wherein the PNA subunit at the corresponding position of the first region of the PNA oligomer comprises 2-pyridone.
  • Embodiment 89 The PNA oligomer of any one of embodiments 3-85, wherein the first pyrimidine position in the single strand of the dsDNA comprises a thymine.
  • Embodiment 90 The PNA oligomer of embodiment 89, wherein the first pyrimidine position in the single strand of the dsDNA comprises a thymine; and the first region of the PNA oligomer comprises, at the position corresponding to the first pyrimidine position, an HTB PNA subunit.
  • Embodiment 91 The PNA oligomer of embodiment 90, wherein the PNA subunit at the corresponding position of the first region of the PNA oligomer comprises 3-oxo-2,3- dihydropyridazine.
  • Embodiment 92 Embodiment 92.
  • PNA peptide nucleic acid
  • Embodiment 93 A peptide nucleic acid (PNA) oligomer comprising: (a) a first region comprising a first plurality of PNA subunits, and wherein the first region further comprises a pyrimidine-compliant PNA subunit; (b) a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence; and (c) at least one PNA subunit comprising a gamma modification.
  • PNA peptide nucleic acid
  • Embodiment 95 A lipid nanoparticle (LNP) comprising: (a) one or more or all of: - an ionizable lipid; - a phospholipid; - a sterol; and - an alkylene glycol-containing lipid; and (b) a peptide nucleic acid (PNA) oligomer comprising: a first region comprising a plurality of PNA subunits that bind to a target sequence, wherein: - the target sequence comprises a pyrimidine nucleobase at a first pyrimidine position in the target sequence; and - the first region comprises, at the position corresponding to the first pyrimidine position, a pyrimidine-compliant PNA subunit (PC PNA subunit); and a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence.
  • LNP lipid
  • Embodiment 96 The LNP of embodiment 95, wherein the PNA oligomer is a PNA oligomer of any one of embodiments 1-86.
  • Embodiment 97 The LNP of any one of embodiments 95 or 96, wherein the amount of PNA oligomer encapsulated and/or entrapped within the LNP is between 0.1% to 50% by weight of PNA oligomers to the total weight of the LNP.
  • Embodiment 98 The LNP of any one of embodiments 95-97, wherein the LNP further comprises a load component.
  • Embodiment 99 The LNP of embodiment 98, wherein the load component comprises a nucleic acid.
  • Embodiment 100 The LNP of embodiment 99, wherein the nucleic acid comprises a DNA.
  • Embodiment 101 The LNP of embodiments 99 or 100, wherein the nucleic acid comprises between about 20 and about 100 nucleotides.
  • Embodiment 102 The LNP of any one of embodiments 99-101, wherein the nucleic acid comprises a phosphorothioate linkage.
  • Embodiment 103 Embodiment 103.
  • a nanoparticle comprising: (a) a synthetic polymer; and (b) peptide nucleic acid (PNA) oligomer comprising: (a) a first region comprising a plurality of PNA subunits that bind to a target sequence, wherein: the target sequence comprises a pyrimidine nucleobase at a first pyrimidine position in the target sequence; and the first region comprises, at the position corresponding to the first pyrimidine position, a pyrimidine-compliant PNA subunit (PC PNA subunit); and (b) a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence, wherein the nanoparticle comprises one of the following properties: (1) the amount of a PNA oligomer encapsulated and/or entrapped within the nanoparticle is greater than or equal to 2 percent (2%) by weight of PNA oligomers to the total weight of the nanoparticle(s); (2) the diameter of the nanoparticle is between about 30 to
  • Embodiment 104 The nanoparticle of embodiment 103, wherein the PNA oligomer is a PNA oligomer of any one of embodiments 1-93.
  • Embodiment 105 The nanoparticle of any one of embodiments 103-104, wherein the synthetic polymer comprises polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co- glycolic acid) (PLGA), poly(4-hydroxy-L-proline ester, other degradable polyesters, polyanhydrides, poly(ortho)esters, polyesters, polyurethanes, poly(butyric acid), poly(valeric acid), poly(caprolactone), poly(hydroxyalkanoates), poly(lactide-co-caprolactone), poly(amine- co-ester) polymers, or a combination of any two or more of the foregoing.
  • PLA polylactic acid
  • PGA polyglycolic acid
  • PLGA poly(lactic-co- glycolic acid)
  • PLGA poly(4-
  • Embodiment 106 A preparation of peptide nucleic acid (PNA) oligomers, comprising a property of any one of embodiments 1-93.
  • Embodiment 107 A method of treating a disease in a subject, the method comprising administering to the subject a peptide nucleic acid (PNA) oligomer of any one of embodiments 1-93.
  • Embodiment 108 The method of embodiment 107, wherein the disease comprises a blood disorder.
  • Embodiment 109 The method of embodiment 108, wherein the blood disorder is a red blood cell disorder.
  • Embodiment 110 Embodiment 110.
  • red blood cell disorder is beta-thalassemia.
  • Embodiment 111 The method of embodiment 109, wherein the red blood cell disorder is sickle cell disease.

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Abstract

Disclosed herein are PNA oligomers capable of targeting nucleic acid sequences (including genomic DNA, such as genomic DNA in a living organism) that include one or more pyrimidine nucleobases within the target nucleic acid sequence, and compositions and related methods of use thereof.

Description

PYRIMIDINE-COMPLIANT PEPTIDE NUCLEIC ACID COMPOSITIONS AND METHODS OF USE THEREOF CROSS-REFERENCE [0001] This application claims priority to U.S. Provisional Application No.63/215,698 filed June 28, 2021, which is incorporated herein by reference in its entirety. BACKGROUND [0002] Gene editing typically entails direct modification of the genome in a cell and represents a powerful tool for correcting defective genes in a subject with an inherited disease. Several methods of gene editing currently exist. Those methods include use of targeted nucleases such as zinc finger nucleases (ZFNs), transcription activator-like effector-based nucleases (TALENs), and the clustered regularly interspaced short palindromic repeat system (CRISPR/Cas9). INCORPORATION BY REFERENCE [0003] All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. SUMMARY [0004] Disclosed herein is a peptide nucleic acid (PNA) oligomer comprising: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv):
Figure imgf000003_0001
wherein: - each X1 or X4 is independently N or C; - X2 is N, CH, or C=O; - X3 is CH, C=O, or C-NH2; - each X5 , X6, and X8 is independently N or CH; - X7 is CH or C=O; - R20 is absent or hydrogen; - each R21, R35, R36, R37, R38, and R39 is independently hydrogen, deuterium, halo, alkyl, alkenyl, alkynyl, heteroalkyl, cyano, -OH, -NH2, or NO2; - R40 is hydrogen or alkyl; - R41 is hydrogen, alkyl, or absent; - R42 is hydrogen, deuterium, alkyl, or heteroalkyl; - each n and m is independently an integer of 1 or 2; - each p is 1, 2, 3, or 4; - each
Figure imgf000004_0001
is independently a single or double bond; and wherein when X2 is C=O, then X3 is not C=O; when X3 is C=O, then X2 is not C=O; and when X3 is C-NH2, then X2 is not C=O; (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (c) a linker, wherein a first terminus of the first region of the PNA oligomer is covalently bound to a first terminus of the linker, and wherein a first terminus of the second region of the PNA oligomer is covalently bound to a second terminus of the linker. BRIEF DESCRIPTION OF DRAWINGS [0005] FIG.1A is an illustration of a generic peptide nucleic acid (PNA) subunit where B represents a nucleobase, and α, β, and γ represent optionally substituted positions on the PNA backbone. [0006] FIG.1B is an illustration of an example tail-clamp PNA (tcPNA) oligomer bound to a double stranded DNA (dsDNA). [0007] FIG.1C illustrates the various components in an illustration of an example tcPNA oligomer bound to a dsDNA. [0008] FIGS.2A-2B are illustrations of the Hoogsteen face (HG face) and Watson-Crick face (WC face) of cytosine (C) (FIG.2A) and thymine (T) (FIG.2B), where R indicates a nucleic acid backbone. [0009] FIG.3 is an illustration of Hoogsteen (i.e., HG-binding) interactions between nucleobases (e.g., a nucleobase of a PNA subunit) and a canonical nucleobase in a Watson-Crick base pair (e.g., a base pair in double-stranded DNA). The nucleobases shown are pyridin-2- amine (i.e., “M”) HG-binding to the guanine of a G-C base pair (M*G-C), pseudoisocytosine (i.e., “J”) HG-binding to the guanine of a G-C base pair (J*G-C), 2-thiopseudoisocytosine (i.e., “L”) HG-binding to the guanine of a G-C base pair (L*G-C), thymine (i.e., “T”) HG-binding to the adenine of an A-T base pair (T*A-T), pyrimidin-2(1H)-one HG-binding to the cytosine of a C-G base pair (P*C-G), and pyridazin-3(2H)-one HG-binding to the thymine of a T-A base pair (E*T-A). The dashed lines indicate hydrogen bonds, and R indicates a PNA backbone or DNA backbone. [0010] FIG.4 is an illustration of several common (but non-limiting) unprotected nucleobases (identified as “B” in FIG.1) that can be linked to a PNA monomer (or subunit of a polymer/oligomer). [0011] FIG.5 is an illustration of various nucleobases used in PNA synthesis. [0012] FIGS.6A-6B are illustrations of the complexes formed between tcPNA oligomers and nucleic acids, where “WC” indicates the Watson-Crick binding segment, and “HS” indicates the Hoogsteen-binding segment of the tcPNAs. FIG.6A depicts the complex of Compound No.1 (when X is pyrimidin-2(1H)-one) or Compound No.2 (when X is “GlyGly”) with the nucleic acid sequence SEQ ID NO: 7. FIG.6B depicts the complex of Compound Nos.1 or 2 with the nucleic acid sequence SEQ ID NO: 8. [0013] FIGS.7A-7B is an illustration of various side chains that can be linked to a PNA subunit, including the side-chains of amino acids. [0014] FIG.8A is an illustration of the PEG2 linker monomer used in some embodiments herein. [0015] FIG.8B is an illustration of the PEG2 linker residue as incorporated as a subunit of a PNA oligomer used in some embodiments herein. [0016] FIG.8C is an illustration of the PEG3 linker monomer used in some embodiments herein. [0017] FIG.8D is an illustration of the PEG3 linker residue as incorporated as a subunit of a PNA oligomer used in some embodiments herein. [0018] FIG.9 is an image of 6 HPLC chromatographs; each chromatogram demonstrating the separation obtained by analysis of a crude sample of a different fully-deprotected PNA oligomer. [0019] FIG.10 is an image of 6 HPLC chromatographs; each chromatogram demonstrating the separation obtained by analysis of a crude sample of the same 6 PNA oligomers illustrated in FIG.9. However, in this case, each PNA oligomer is a partially protected PNA oligomer comprising two Fmoc protecting groups, one linked to the N-terminal alpha amine group and one linked to the N-terminal epsilon amine group of an N-terminal lysine residue. [0020] FIGS.11A-11D are images of isothermal titration calorimetry (ITC) (top) and the corresponding graphical representations (bottom), following complexing tcPNA oligomers (Compounds 1 or 2) with DNA oligonucleotides (SEQ ID NO: 7 or 8). FIG.11A are the results from Compound No.1 + SEQ ID NO: 7, FIG.11B are the results from Compound No.1 + SEQ ID NO: 8, FIG.11C are the results from Compound No.2 + SEQ ID NO: 7, and FIG.11D are the results from Compound No: 2 + SEQ ID NO: 8. [0021] FIGS.12A-12B are images of electrophoretic separations performed after incubating a DNA amplicon (SEQ ID NO: 13) with different PNA oligomers (Compound Nos.3-6). FIG. 12A is the separation after 0.5 hours of incubation, and FIG.12B is the separation after 18 hours of incubation. In each, bp] indicates the size (base-pair), lane A1 is a size marker, lane B1 is Compound No.5 + amplicon, lane C1 is Compound No.6 + amplicon, lane D1 is Compound No.3 + amplicon, lane E1 is Compound No.4 + amplicon, and lane F1 is amplicon only. DETAILED DESCRIPTION [0022] Peptide nucleic acids (PNAs) are small polymeric nucleic acid mimics that can bind directly to a target nucleic acid sequence with high affinity and sequence specificity. PNAs can form a number of structures upon interacting with a target nucleic acid, including stable PNA/DNA/PNA triplexes. PNA-based methods involving the formation of triplex structure can require a stretch of purine nucleobases as the target nucleic acid sequence (e.g., target DNA sequence). For example, triplex formation can involve the formation of a complex whereby one polypyrimidine segment of a PNA oligomer binds to a homopurine target nucleic acid sequence by Watson-Crick face binding and another polypyrimidine segment of a PNA oligomer (optionally from the same or a different PNA oligomer) binds to the homopurine target nucleic acid sequence by Hoogsteen face binding. Disclosed herein are PNA oligomers capable of targeting nucleic acid sequences (including genomic DNA, such as genomic DNA in a living organism) that include one or more pyrimidine nucleobases within the target nucleic acid sequence, and compositions and related methods of use thereof. PNA oligomers, e.g., tail clamp PNA oligomers, that can target pyrimidine-containing nucleic acid sequences are sometimes referred to herein as “pyrimidine-compliant” or “pyrimidine-target-compliant.” In some embodiments, a pyrimidine-compliant PNA oligomer participates in Hoogsteen binding with a pyrimidine nucleobase in a target nucleic acid sequence (e.g., a target DNA sequence). In some embodiments, a pyrimidine-compliant PNA oligomer does not participate in Hoogsteen binding with a pyrimidine nucleobase in a target nucleic acid sequence (e.g., a target DNA sequence). Embodiments of the PNA oligomers disclosed herein can be used in various applications such as diagnostic assays, nucleic acid sequencing (e.g. nanopore sequencing) and antisense applications. [0023] The PNA oligomers and methods disclosed herein can exhibit improved ease of administration and relatively low off target effects. [0024] Described herein are peptide nucleic acids (PNAs) comprising a pyrimidine-compliant nucleobase, and compositions and related methods of use thereof. Definitions [0025] “Hoogsteen face binding” or “HF binding,” as used herein, refers to the base pair interactions between cognate nucleobases that occurs on the Hoogsteen face of a target nucleobase (e.g., in a target sequence; e.g. a target DNA sequence). Hoogsteen face binding between cognate nucleobase pairs is distinct from Watson-Crick face binding (or WC face binding) between the same cognate nucleobase pairs; for example, a nucleobase typically engages in simultaneous Hoogsteen face binding with a first PNA subunit nucleobase and Watson-Crick face binding with a second PNA subunit nucleobase, e.g., to form a PNA/DNA/PNA triplex. See, for example, FIGS.2A-2B and FIG.3. A “Hoogsteen face hydrogen bond” is a hydrogen bond between cognate base pairs that occurs on the Hoogsteen face of the target nucleobase (e.g., in a target sequence; e.g. a target DNA sequence). [0026] A “Hoogsteen mode cytosine-binding PNA subunit” or “HCB PNA subunit,” as used herein, refers to a PNA subunit which can bind to a cytosine in a target nucleic acid sequence (e.g., a target DNA sequence or target RNA sequence), e.g., as shown in FIG.3. An HCB PNA subunit comprises an “HCB nucleobase” that exhibits one or more of the following properties: i. the HCB nucleobase participates in Hoogsteen face binding with a target sequence cytosine, wherein said target sequence cytosine also participates in Watson-Crick face binding through at least two canonical Watson-Crick hydrogen bonds with a second PNA subunit comprising a guanine or derivative thereof, e.g., 7-deazaguanine, hypoxanthine or 7- deazahypoxanthine; ii. the HCB nucleobase comprises at least one hydrogen bond acceptor, e.g., a carbonyl oxygen atom and/or one hydrogen bond donor, e.g., an amine hydrogen atom; iii. the HCB nucleobase participates in at least one Hoogsteen hydrogen bond with a target sequence cytosine that is not a canonical cytosine-guanine Watson-Crick hydrogen bond; iv. a carbonyl oxygen atom in the HCB nucleobase participates in a Hoogsteen hydrogen bond with a hydrogen bond donor (e.g., an amine hydrogen atom) in the target sequence cytosine; v. the bond length of a Hoogsteen hydrogen bond between the HCB nucleobase and the target sequence cytosine is between 0.1 Å and 10 Å (e.g., between 1 Å and 5 Å), e.g., as determined by X-ray crystallography; e.g., the bond length of the hydrogen bond between a nitrogen atom in the HCB nucleobase and the amine hydrogen atom of the target sequence cytosine is between 0.1 Å and 10 Å (e.g., between 1 Å and 5 Å), e.g., as determined by X-ray crystallography; vi. the bond length of the cytosine hydrogen at N4-PNA subunit hydrogen bond on the Watson-Crick face is between 1 Å and 5 Å; vii. the bond length of the cytosine N3 nitrogen-PNA subunit hydrogen bond on the Watson- Crick face is between 1 Å and 5 Å; viii. the bond length of the cytosine carbonyl oxygen at C2-PNA subunit hydrogen bond on the Watson-Crick face is between 0.1 Å and 10 Å (e.g., between 1 Å and 5 Å); or ix. the gel shift of a complex formed between a PNA oligomer comprising the HCB nucleobase and a target nucleic acid sequence comprising a cognate cytosine is greater than or equal to the gel shift of the target nucleic acid. [0027] In some embodiments, the HCB nucleobase has one of properties i)-ix). In some embodiments, the HCB nucleobase has two of properties i)-ix). In some embodiments, the HCB nucleobase has three of properties i)-ix). In some embodiments, the HCB nucleobase has four of properties i)-ix). In some embodiments, the HCB nucleobase has five of properties i)-ix). In some embodiments, the HCB nucleobase has six of properties i)-ix). In some embodiments, the HCB nucleobase has seven of properties i)-ix). In some embodiments, the HCB nucleobase has eight of properties i)-ix). In some embodiments, the HCB nucleobase has each of properties i)- ix). [0028] In some embodiments, the HCB nucleobase participates in at least one hydrogen bond with a target sequence cytosine that is other than a canonical Watson-Crick cytosine-guanine bond. For example, a carbonyl oxygen atom or nitrogen atom of the HCB nucleobase participates in a hydrogen bond with an amine hydrogen atom in the target sequence cytosine that is not involved in Watson-Crick face binding. In some embodiments, the HCB PNA subunit comprises pyrimidin-2(1H)-one. In some embodiments, the HCB nucleobase is P. [0029] A “Hoogsteen-mode thymine binding PNA subunit” or “HTB PNA subunit,” as used herein, refers to a PNA subunit which can bind to a thymine or uracil in a target nucleic acid sequence (e.g., a target DNA sequence or a target RNA sequence), e.g., as shown in FIG.3. An HTB PNA subunit comprises an HTB nucleobase that exhibits one or more of the following properties: i. the HTB nucleobase participates in Hoogsteen face binding with a target sequence thymine or uracil, wherein said target sequence thymine or uracil also participates in Watson- Crick face binding through at least one canonical Watson-Crick hydrogen bond with a second PNA subunit comprising an adenine or derivative thereof, e.g., 7-deazaadenine, 2,6- diaminopurine, or 7-deaza-2,6-diaminopurine; ii. the HTB nucleobase comprises at least one hydrogen bond donor, e.g., an amine hydrogen atom and/or one hydrogen bond acceptor, e.g., a carbonyl oxygen atom; iii. the HTB nucleobase participates in at least one Hoogsteen hydrogen bond with a target sequence thymine (or uracil) that is not a canonical thymine-adenine (or uracil-adenine) Watson- Crick hydrogen bond; iv. a hydrogen atom in the HTB nucleobase participates in a Hoogsteen hydrogen bond with a hydrogen bond acceptor (e.g., a carbonyl oxygen atom) in the target sequence thymine (or uracil); v. the bond length of a Hoogsteen hydrogen bond between the HTB nucleobase and the target sequence thymine (or uracil) is between 0.1 Å and 10 Å (e.g., between 1 Å and 5 Å), e.g., as determined by X-ray crystallography; e.g., the bond length of the hydrogen bond between a hydrogen atom in the HTB nucleobase and the carbonyl oxygen atom of the target sequence thymine (or uracil) is between 1 Å and 5 Å, e.g., as determined by X-ray crystallography; vi. the bond length of the thymine (or uracil) carbonyl oxygen at C4-PNA subunit hydrogen bond on the Watson-Crick face is between 1 Å and 5 Å; vii. the bond length of the thymine (or uracil) hydrogen at N3-PNA subunit hydrogen bond on the Watson-Crick face is between 1 Å and 5 Å; viii. the bond length of the thymine (or uracil) carbonyl oxygen at C2-PNA subunit hydrogen bond on the Watson-Crick face is between 0.1 Å and 10 Å (e.g., between 1 Å and 5 Å); or ix. the gel shift of a complex formed between a PNA oligomer comprising the HTB nucleobase and a target nucleic acid sequence comprising a cognate thymine (or uracil) is greater than or equal to the gel shift of the target nucleic acid. [0030] In some embodiments, the HTB nucleobase has one of properties i)-ix). In some embodiments, the HTB nucleobase has two of properties i)-ix). In some embodiments, the HTB nucleobase has three of properties i)-ix). In some embodiments, the HTB nucleobase has four of properties i)-ix). In some embodiments, the HTB nucleobase has five of properties i)-ix). In some embodiments, the HTB nucleobase has six of properties i)-ix). In some embodiments, the HTB nucleobase has seven of properties i)-ix). In some embodiments, the HTB nucleobase has eight of properties i)-ix). In some embodiments, the HTB nucleobase has each of properties i)- ix). [0031] In some embodiments, the HTB nucleobase participates in at least one hydrogen bond with a target sequence thymine (or uracil) that is other than a canonical Watson-Crick thymine- adenine bond (or uracil-adenine bond). For example, a hydrogen atom of the HTB nucleobase participates in a hydrogen bond with a carbonyl oxygen atom in the target sequence thymine (or uracil) that is not involved in Watson-Crick face binding. In some embodiments, the HTB PNA subunit comprises pyridazin-3(2H)-one. In some embodiments, the HTB nucleobase is E. [0032] “Peptide nucleic acid,” “PNA,” or “PNA oligomer” as used herein, refers to a non-natural polymer composition comprising linked nucleobases capable of sequence specifically hybridizing to a nucleic acid. A PNA oligomer is comprised of PNA subunits, each of which comprise a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid. The term “peptide nucleic acid”, “PNA”, or “PNA oligomer” also applies to polymers comprising two or more PNA subunits, phosphono-PNA analogues (pPNAs); trans-4-hydroxy-L-proline nucleic acids (HypNAs); and (1S,2R/1R,2S)-cis- cyclopentyl PNAs (cpPNAs). [0033] A “PNA monomer,” (also sometimes referred to as a “PNA synthon”) as used herein, refers to a single discrete building block for PNA synthesis. A PNA monomer comprises a backbone moiety and optionally a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid. To form a PNA oligomer, a first PNA monomer is activated, for example, by exposure to an activating group (e.g., a carboxyl activating group such as PyBOP or HATU). The PNA monomer is then coupled to a particular reactive moiety (e.g., a free amine terminus (i.e., N-terminus)) on a second deprotected PNA monomer or a PNA oligomer to form a growing PNA oligomer chain. Examples of PNA monomers include Fmoc/Bhoc PNA monomers, Fmoc/t-boc PNA monomers, boc/Z PNA monomers, boc/cbz PNA monomers, and others. [0034] A “PNA subunit” as used herein, refers to a subunit within a PNA oligomer. A PNA subunit comprises a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid, e.g., as shown in FIG.1A. In some embodiments, a PNA subunit comprises an aminoethylglycine backbone with an amine terminus (i.e., N-terminus) and a carboxyl terminus (i.e., C-terminus), and a nucleobase moiety attached to the backbone through a methylene carbonyl linker. PNA subunits can include Watson-Crick (i.e., WC-binding) PNA subunits which mediate WC-binding to nucleobases in a target nucleic acid sequence, and can include Hoogsteen (i.e., HG-binding) PNA subunits that mediate HG-binding to nucleobases in a target nucleic acid sequence. The nucleobases within a PNA subunit may be naturally occurring or non-naturally occurring. Examples of nucleobases include adenine, guanine, thymine, cytosine, uracil, pseudoisocytosine, 2-thiopseudoisocytosine, 5- methylcytosine, 5-hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine (or 2,6- diaminopurine), 2-thiouracil, 2-thiothymine, 2-thiocytosine, 5-chlorouracil, 5-bromouracil, 5- iodouracil, 5-chlorocytosine, 5-bromocytosine, 5-iodocytosine, 5-propynyl uracil, 5-propynyl cytosine, 6-azo uracil, 6-azo cytosine, 6-azo thymine, 7-methylguanine, 7-methyladenine, 8- azaguanine, 8-azaadenine, 7-deazaguanine, 7-deazaadenine, 3-deazaguanine, 3-deazaadenine, 7- deaza-8-aza guanine, 7-deaza-8-aza adenine, 5-propynyl uracil, 2-thio-5-propynyl uracil, pyridazin-3(2H)-one (E), pyrimidin-2(1H)-one (P), and pyridin-2-amine (M), and tautomeric forms thereof. In some embodiments, a PNA subunit does not comprise a nucleobase (i.e., is abasic). For example, a PNA subunit can be a “Gly-Gly” subunit comprising two glycine residues covalently linked by an amide bond, neither of which comprises a nucleobase i.e., does not comprise a nucleobase moiety (e.g., a Gly-Gly bridge). [0035] A “pyrimidine-compliant PNA subunit” or “PC PNA subunit” is a PNA subunit that allows for a pyrimidine nucleobase in a target sequence (e.g., a target nucleic acid sequence). In some embodiments, a PC PNA subunit comprises a PNA nucleobase capable of Hoogsteen binding to a pyrimidine nucleobase in a target sequence. For example, a PC PNA subunit can be an HCB PNA subunit or an HTB PNA subunit, and a PNA nucleobase can be an HCB nucleobase or an HTB nucleobase. In some embodiments, a PC PNA subunit accommodates a nucleobase (e.g., a pyrimidine nucleobase) in a target sequence by forming no bonds to the nucleobase (e.g., does not participate in hydrogen binding with the nucleobase in a target sequence). In some embodiments, a PC PNA subunit does not comprise a nucleobase (i.e., is abasic). For example, a PC PNA subunit may be a “Gly-Gly” subunit comprising two glycine residues covalently linked by an amide bond, neither of which comprises a nucleobase. [0036] A “tail-clamp PNA,” “tail-clamp PNA oligomer,” or “tcPNA,” as used herein, refers to a PNA oligomer capable of forming a PNA/DNA/PNA triplex upon binding to a target sequence (e.g., a target nucleic acid sequence, e.g. a target DNA sequence, e.g. a double stranded target DNA sequence). A tcPNA comprises: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase; (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (c) a linker, wherein a first terminus of the first region of the PNA oligomer is covalently bound to a first terminus of the linker, and wherein a first terminus of the second region of the PNA oligomer is covalently bound to a second terminus of the linker. In some embodiments, a tcPNA comprises i) a first region of the PNA oligomer comprising a plurality of PNA subunits that participate in binding to the Hoogsteen face of a target nucleic acid sequence and ii) a second region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target nucleic acid sequence. In some embodiments, the first region and second region of PNA subunits are linked by a linker (e.g., a polyethylene glycol linker, e.g., PEG2 depicted in FIG.8B, or PEG3 depicted in FIG.8D). A tcPNA may further comprise iii) a third region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target tail nucleic acid sequence and/or iv) a positively charged region comprising one or more positively charged moieties (e.g., positively charged amino acids such as lysine, ornithine or arginine), which can be present on a terminus of the tcPNA. In some embodiments, a tcPNA comprises i), ii) and iii). In some embodiments, a tcPNA comprises i), ii), iii), and iv). In some embodiments, a tcPNA comprises a PC PNA subunit (e.g., an HCB PNA subunit or an HTB PNA subunit) in the first region of the PNA oligomer. An example of tcPNA is depicted in FIG.1B. [0037] “Watson-Crick face binding,” or “WC face binding” as used herein, refers to the base pair interactions between cognate nucleobases that occurs on the Watson-Crick face of a target nucleobase (e.g., in a target sequence). Watson-Crick face binding between cognate nucleobase pairs is distinct from Hoogsteen face binding between the same cognate nucleobase pairs; for example, in a tcPNA, a nucleobase of a target sequence (e.g. a target DNA sequence) can engage in simultaneous WC face binding with a first PNA subunit nucleobase and Hoogsteen face binding with a second PNA subunit nucleobase, e.g., to form a PNA/DNA/PNA triplex. See, for example, FIGS.2A-2B and FIG.3. A “Watson-Crick hydrogen bond” is a hydrogen bond between cognate base pairs that occurs on the Watson-Crick face of the target nucleobase (e.g., in a target sequence). Peptide Nucleic Acids [0038] The present disclosure features PNA oligomers capable of targeting nucleic acid sequences that include one or more pyrimidine nucleobasesand compositions and related methods of use thereof. In some embodiments, the PNA oligomer is a tail-clamp peptide nucleic acid (tcPNA). In some embodiments, triplex-forming molecules include a “tail” added to the end of the Watson-Crick binding portion of a PNA oligomer to bind the target strand outside the triple helix. In some embodiments, a tcPNA can mediate DNA binding that encompasses both triplex and duplex formation. [0039] A tcPNA can comprise a first region comprising a plurality of PNA subunits that participate in binding to the Hoogsteen face of a target sequence, wherein the target sequence comprises a pyrimidine nucleobase (e.g., a cytosine or thymine) at a first pyrimidine position in the target sequence, and, at the position corresponding to the first pyrimidine position, the tcPNA comprises a pyrimidine-compliant PNA subunit (PC PNA subunit). In some embodiments, the tcPNA further comprises a second region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target nucleic acid sequence, wherein the first region and second region are covalently linked through a linker (e.g., a polyethylene-glycol linker). In some embodiments, the tcPNA further comprises a third region comprising a plurality of PNA subunits that participate in binding to the Watson-Crick face of a target tail nucleic acid sequence. In some embodiments, the tcPNA further comprises a positively charged region comprising positively charged amino acids (e.g., lysine residues) on at least one terminus of the tcPNA. In some embodiments, the tcPNA comprises one or more PNA subunits comprising a substituent at the gamma-position. In some embodiments, the tcPNA comprises one or more PNA subunits comprising a mini-PEG moiety at the gamma-position. [0040] In some embodiments, a tcPNA can comprise a PNA oligomer as shown in FIG.1C. In some embodiments, a peptide nucleic acid (PNA) oligomer comprising: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase (X); (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (c) a linker, wherein a first terminus of the first region of the PNA oligomer is covalently bound to a first terminus of the linker, and wherein a first terminus of the second region of the PNA oligomer is covalently bound to a second terminus of the linker. [0041] In some embodiments, a PNA oligomer of the disclosure can comprise from about 5 to about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a PNA oligomer of the disclosure can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0042] In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits. In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits. In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits. In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a first plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0043] In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits. In some embodiments, a second plurality of PNA subunits can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits. In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits. In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a second plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0044] In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise from about 5 to about 50 PNA subunits. In some embodiments, a third plurality of PNA subunits can comprise from about 5 to about 10, from about 10 to about 15, from about 15 to about 20, from about 20 to about 25, from about 25 to about 30, from about 30 to about 35, from about 35 to about 40, from about 40 to about 45, or from about 45 to about 50 PNA subunits. In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise at least about 5, at least about 10, at least about 15, at least about 20, at least about 25, at least about 30, at least about 35, at least about 40, at least about 45, or at least about 50 PNA subunits. In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise about 5, about 10, about 15, about 20, about 25, about 30, about 35, about 40, about 45, or about 50 PNA subunits. In some embodiments, a third plurality of PNA subunits of a tcPNA can comprise at most about 5, at most about 10, at most about 15, at most about 20, at most about 25, at most about 30, at most about 35, at most about 40, at most about 45, or at most about 50 PNA subunits. [0045] In some embodiments, a linker can comprise C2-50 heteroalkylene. In some embodiments, the linker can comprise polyethylene glycol. In some embodiments, the linker comprises PEG2. In some embodiments, the linker comprises PEG2PEG2. In some embodiments, the linker comprises PEG3. In some embodiments, the linker comprises PEG2PEG2. In some embodiments, the linker comprises PEG3PEG3. [0046] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). [0047] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA. In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA. In some embodiments, the first plurality of PNA subunits, the first region of the dsDNA, and the second plurality of PNA subunits form a triplex structure. In some embodiments, the first region of the PNA oligomer further comprises (a’) a first positively charged region comprising a first positively charged amino acid, wherein the first positively charged region is covalently bound to a second terminal end of the first region of the PNA oligomer. In some embodiments, the first positively charged amino acid is lysine. In some embodiments, the second region of the PNA oligomer participates in Watson Crick binding with the first region of the dsDNA and the second region of the dsDNA. In some embodiments, the second region of the PNA oligomer further comprises a second positively charged amino acid, wherein the second positively charged amino acid is covalently bound to a second terminal end of the second region of the PNA oligomer. In some embodiments, the second positively charged amino acid is lysine. [0048] In some embodiments, the first region of the PNA oligomer comprises a gamma- modified PNA subunit. In some embodiments, the second region of the PNA oligomer comprises a gamma-modified PNA subunit. In some embodiments, the third region of the PNA oligomer comprises a gamma-modified PNA subunit. In some embodiments, the first region of the PNA oligomer comprises a first gamma-modified PNA subunit, the second region of the PNA oligomer comprises a second gamma-modified PNA subunit, and the third region of the PNA oligomer comprises a third gamma-modified PNA subunit. Pyrimidine Compliant PNA Subunits [0049] A PNA subunit refers to a subunit within a PNA oligomer, and comprises a backbone moiety and, optionally, a nucleobase moiety that can form hydrogen bonds with the nucleobase of a target nucleic acid, e.g., as shown in FIG.1A-1C. In some embodiments, a PNA subunit comprises a nucleobase and a backbone moiety. The nucleobase of the PNA subunit can form one or more hydrogen bonds with the nucleobase of a target nucleic acid sequence. The backbone moiety of the PNA subunit typically comprises a first terminus and a second terminus. In some embodiments, the first terminus is an amine terminus (i.e., N-terminus), and the second terminus is a carboxyl terminus (i.e., C-terminus), e.g., as shown in FIG.1A. The backbone moiety also comprises an atom to which the nucleobase is bound, typically through a spacer moiety. Disclosed herein are PC PNA subunits which are capable of accommodating a pyrimidine nucleobase in a target sequence, and can comprise an HCB PNA subunit or an HTB PNA monomer or subunit. [0050] In one aspect, the PC PNA subunit is a compound of Formula (I):
Figure imgf000016_0001
wherein P1 is a first terminus, e.g., an amine or a carboxyl terminus, which can participate in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer; P5 is a second terminus, e.g., an amine or a carboxyl terminus, which can participate in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer; each P3 and P4 is independently absent or a backbone unit, e.g., alkylene optionally substituted with one or more RA; Z is X-Ra or X-L-B; X is N or CRb; L is a spacer moiety, e.g., alkylene, alkenylene, heteroalkylene, cycloalkylene, or heterocyclene, each of which is optionally substituted with one or more RB; B is a PNA nucleobase; each Ra and Rb is independently hydrogen, deuterium, halo, or alkyl; each RA and RB is independently deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo (e.g., fluorine), oxo, -ORE, or the side-chain of an amino acid (see for example FIGS.7A-7B); each RC, RD, and RE is independently hydrogen, alkyl, or heteroalkyl; and each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer; provided that i) when P1 is an amine terminus, P5 is a carboxyl terminus; and ii) when P5 is an amine terminus, P1 is a carboxyl terminus. [0051] In some embodiments, P1 is an amine terminus (e.g., -NH2 or -NH-, wherein -NH- participates in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer). In some embodiments, P5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH3, - C(O)NH2, or -C(O)-, wherein -C(O)- participates in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer). In some embodiments, P1 is an amine terminus and P5 is a carboxyl terminus. [0052] In some embodiments, each P3 and P4 is independently a backbone subunit. In some embodiments, each P3 and P4 is independently C1-12alkylene optionally substituted with one or more RA. In some embodiments, P3 is C1-12alkylene optionally substituted with one or more RA. In some embodiments, P3 is C1-12alkylene. In some embodiments, P3 is C1-6alkylene. In some embodiments, P3 is C1-4alkylene. In some embodiments, P3 is C1-12alkylene substituted with one or more RA (e.g., 1 RA, e.g., heteroalkyl or oxo). In some embodiments, P4 is C1-12alkylene optionally substituted with one or more RA. In some embodiments, P4 is C1-12alkylene. In some embodiments, P4 is C1-6alkylene. In some embodiments, P4 is C1-4alkylene. [0053] In some embodiments, each P3 and P4 is independently methylene or ethylene optionally substituted with one or more RA. In some embodiments, P3 is ethylene optionally substituted with one or more RA. In some embodiments, P3 is ethylene. In some embodiments, P3 is ethylene substituted with one or more RA (e.g., 1 RA, e.g., heteroalkyl or oxo). In some embodiments, P4 is methylene optionally substituted with one or more RA. In some embodiments, P4 is methylene. [0054] In some embodiments, each P3 or P4 is independently substituted with 0, 1, 2, 3, 4, 5, or 6 RA. In some embodiments, each P3 or P4 is independently substituted with 1 RA (e.g., heteroalkyl or oxo). In some embodiments, each instance of RA is independently oxo or C1-30heteroalkyl. In some embodiments, RA is oxo. In some embodiments, RA is heteroalkyl, e.g., a C1-30polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG moiety comprising between 2 and 6 PEG units). [0055] In some embodiments, RA has the structure of Formula (IV-a) or (IV-b):
Figure imgf000017_0001
wherein R12 is hydrogen or alkyl (e.g., C1-4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5, and “ ” denotes an attachment point to P3 or P4. In some embodiments, R12 is hydrogen or methyl, and y is 1. In some embodiments, R12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R12 is methyl or tert-butyl, and y is 1. In some embodiments, R12 is hydrogen and y is 1. In some embodiments, R12 is methyl and y is 1. In some embodiments, R12 is tert-butyl and y is 1. [0056] In some embodiments, Z is X-Ra, wherein Ra is hydrogen. In some embodiments, Z is NH. In some embodiments, Z is X-L-B. In some embodiments, Z is N-L-B. [0057] In some embodiments, X is CRb, wherein Rb is hydrogen, deuterium, fluorine, or C1- 4alkyl. In some embodiments, X is N. [0058] In some embodiments, L is C1-12alkylene or C1-12heteroalkylene, each of which is optionally substituted with one or more RB. In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one RB. In some embodiments, L is C1- 12heteroalkylene substituted with one RB. In some embodiments, RB is oxo. [0059] In some embodiments, L is selected from
Figure imgf000018_0001
and
Figure imgf000018_0002
. In some embodiments, L is
Figure imgf000018_0004
. In some embodiments, L is . In some embodiments, L is
Figure imgf000018_0005
. In some embodiments, L is
Figure imgf000018_0003
. In some embodiments, L is
Figure imgf000018_0006
with the carbonyl carbon linked to X. In some embodiments, L is
Figure imgf000018_0007
with the carbonyl carbon linked to X. In some embodiments, L is
Figure imgf000018_0008
with the carbonyl carbon linked to X. In some embodiments, L is
Figure imgf000018_0009
with the carbonyl carbon linked to X. [0060] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) as described herein. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0061] In some embodiments, each P1, P3, P4, and P5 is independently selected such that, when two or more PNA subunits are coupled, the distance between the nucleobase of each PNA subunit is fixed. In some embodiments, the distance between the nucleobase of each PNA subunit allows alignment and interaction of the PNA subunit nucleobases with the complementary nucleobase in a target nucleic acid. In some embodiments, the interaction is forming one or more hydrogen bonds between the PNA subunit nucleobase and the complementary nucleobase in a target nucleic acid. [0062] In some embodiments, the PC PNA subunit is a compound of Formula (II-a):
Figure imgf000019_0001
wherein P1 is a first terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer; P5 is a second terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer; each R3, R4, R5, R6, R7, and R8 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo (e.g., fluorine), -ORE, or the side-chain of an amino acid; X is N or CRb; L is alkylene, alkenylene, heteroalkylene, cycloalkylene, or heterocyclylene, each of which is optionally substituted with one or more RB; B is a PNA nucleobase; Rb is hydrogen, deuterium, halo, or alkyl; each RB is independently deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo (e.g., fluorine), oxo, or -ORE; each RC, RD, and RE is independently hydrogen, alkyl, or heteroalkyl; and each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer; provided that i) when P1 is an amine terminus, P5 is a carboxyl terminus; and ii) when P5 is an amine terminus, P1 is a carboxyl terminus. [0063] In some embodiments, P1 is an amine terminus (e.g., -NH2 or -NH-, wherein -NH- participates in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer). In some embodiments, P5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH3, - C(O)NH2, or -C(O)-, wherein -C(O)- participates in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer). In some embodiments, P1 is an amine terminus and P5 is a carboxyl terminus. [0064] In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen or C1- 30heteroalkyl. In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen. In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen or C1- 30heteroalkyl, e.g., a C1-30polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG moiety comprising between 2 and 6 PEG units). [0065] In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen or has the structure of Formula (IV-a) or (IV-b):
Figure imgf000019_0002
wherein R12 is hydrogen or alkyl (e.g., C1-4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5, and “ ” denotes an attachment point to the PNA subunit. In some embodiments, R12 is hydrogen or methyl, and y is 1. In some embodiments, R12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R12 is methyl or tert-butyl, and y is 1. In some embodiments, R12 is hydrogen and y is 1. In some embodiments, R12 is methyl and y is 1. In some embodiments, R12 is tert-butyl and y is 1. [0066] In some embodiments, X is N. [0067] In some embodiments, L is C1-12alkylene or C1-12heteroalkylene, each of which is optionally substituted with one or more RB. In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one RB. In some embodiments, L is C1- 12heteroalkylene substituted with one RB. In some embodiments, RB is oxo. [0068] In some embodiments, L is selected from
Figure imgf000020_0001
and
Figure imgf000020_0002
. In some embodiments, L is
Figure imgf000020_0003
. In some embodiments, L is . In some embodiments, L is
Figure imgf000020_0005
. In some embodiments, L is
Figure imgf000020_0004
. In some embodiments, L is
Figure imgf000020_0006
with the carbonyl carbon linked to X. In some embodiments, L is
Figure imgf000020_0007
with the carbonyl carbon linked to X. In some embodiments, L is with the carbonyl carbon linked to X. In some embodiments,
Figure imgf000020_0008
L is
Figure imgf000020_0009
with the carbonyl carbon linked to X. [0069] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0070] In some embodiments, the PNA subunit is a PNA subunit of Formula (II-b):
Figure imgf000021_0001
[0071] wherein R2 is hydrogen, deuterium or alkyl (e.g., C1-C4 alkyl); each R3, R4, R5, R6, R7, and R8 is independently hydrogen, deuterium, C1-C4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or has structure of Formula (IV-a) or (IV-b):
Figure imgf000021_0005
; L is alkylene, alkenylene, or heteroalkylene, each of which is optionally substituted with one or more RB; B is a PNA nucleobase; R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; each RB is independently deuterium, alkyl, halo (e.g., fluorine), or oxo; and each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0072] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0073] In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R3, R5, R6, R7, and R8 is independently hydrogen, and R4 has structure of Formula (IV-a). In some embodiments, each R3, R4, R5, R6, R7, and R8 is independently hydrogen. [0074] In some embodiments, R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer from 1 to 5. In some embodiments, R12 is hydrogen or methyl, and y is 1. In some embodiments, R12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R12 is methyl or tert-butyl, and y is 1. In some embodiments, R12 is hydrogen and y is 1. In some embodiments, R12 is methyl and y is 1. In some embodiments, R12 is tert-butyl and y is 1. [0075] In some embodiments, L is C1-12alkylene or C1-12heteroalkylene, each of which is optionally substituted with one or more RB. In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one RB. In some embodiments, L is C1- 12heteroalkylene substituted with one RB. In some embodiments, RB is oxo. [0076] In some embodiments, L is selected from
Figure imgf000021_0002
, , , and
Figure imgf000021_0003
In some embodiments, L is
Figure imgf000021_0004
. In some embodiments, L is
Figure imgf000022_0001
. In some embodiments, L is
Figure imgf000022_0002
in either orientation. In some embodiments, L is
Figure imgf000022_0003
. In some embodiments, L is with the carbonyl
Figure imgf000022_0004
carbon linked to N. In some embodiments, L is
Figure imgf000022_0005
with the carbonyl carbon linked to N. In some embodiments, L is
Figure imgf000022_0006
with the carbonyl carbon linked to N. In some embodiments, L is
Figure imgf000022_0007
with the carbonyl carbon linked to N. [0077] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0078] In some embodiments, the PNA subunit is a PNA subunit of Formula (II-c):
Figure imgf000022_0008
wherein R2 is hydrogen, deuterium or C1-C4 alkyl; each R3, R4, R5, and R6 is independently hydrogen, deuterium, C1-C4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or the structure of Formula (IV-a) or (IV-b):
Figure imgf000022_0010
L is alkylene, alkenylene, or heteroalkylene, each of which is optionally substituted with one or more RB; B is a PNA nucleobase; R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; each RB is independently deuterium, alkyl, halo (e.g., fluorine), or oxo; and each “
Figure imgf000022_0009
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0079] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0080] In some embodiments, each R3, R4, R5, and R6, is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R3, R5, and R6 is independently hydrogen, and R4 has structure of Formula (IV-a). In some embodiments, each R3, R4, R5, and R6 is independently hydrogen. [0081] In some embodiments, R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl), y is an integer between 1 and 5 (inclusive), and “
Figure imgf000023_0010
denotes an attachment point to the methylene or ethylene moiety of the PNA subunit. In some embodiments, R12 is hydrogen or methyl, and y is 1. In some embodiments, R12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R12 is methyl or tert-butyl, and y is 1. In some embodiments, R12 is hydrogen and y is 1. In some embodiments, R12 is methyl and y is 1. In some embodiments, R12 is tert-butyl and y is 1. [0082] In some embodiments, L is C1-12alkylene or C1-12heteroalkylene, each of which is optionally substituted with one or more RB. In some embodiments, L is ethylene, propylene, or butylene, each of which is substituted with one RB. In some embodiments, L is C1- 12heteroalkylene substituted with one RB. In some embodiments, RB is oxo. [0083] In some embodiments, L is selected from
Figure imgf000023_0001
and
Figure imgf000023_0002
. In some embodiments, L is
Figure imgf000023_0003
. In some embodiments, L is In some embodiments, L is
Figure imgf000023_0005
. In some embodiments, L is
Figure imgf000023_0004
. In some embodiments, L is
Figure imgf000023_0006
with the carbonyl carbon linked to N. In some embodiments, L is
Figure imgf000023_0007
with the carbonyl carbon linked to N. In some embodiments, L is
Figure imgf000023_0008
with the carbonyl carbon linked to N. In some embodiments, L is
Figure imgf000023_0009
with the carbonyl carbon linked to N. [0084] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0085] In some embodiments, the PNA subunit is a PNA subunit of Formula (II-d):
Figure imgf000024_0001
wherein R2 is hydrogen, deuterium or C1-C4 alkyl; each R3, R4, R5, and R6 is independently hydrogen, deuterium, C1-C4 alkyl, halo (e.g., fluorine), the side-chain of an amino acid, or has the structure of Formula (IV-a) or (IV-b): ; eac 9 10
Figure imgf000024_0002
h R and R is independently hydrogen, deuterium, C1-C4 alkyl, or halo (e.g., fluorine); B is PNA nucleobase; n is an integer between 0 and 4; R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); y is an integer between 1 and 5; and each “
Figure imgf000024_0003
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0086] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0087] In some embodiments, each R3, R4, R5, and R6 is independently hydrogen, or has structure of Formula (IV-a) or (IV-b). In some embodiments, each R3, R5, and R6 is independently hydrogen, and R4 has structure of Formula (IV-a). In some embodiments, each R3, R4, R5, and R6 is independently hydrogen. [0088] In some embodiments, R12 is hydrogen or methyl, and y is 1. In some embodiments, R12 is hydrogen or tert-butyl, and y is 1. In some embodiments, R12 is methyl or tert-butyl, and y is 1. In some embodiments, R12 is hydrogen and y is 1. In some embodiments, R12 is methyl and y is 1. In some embodiments, R12 is tert-butyl and y is 1. [0089] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0090] In some embodiments, n is an integer between 0 and 2. In some embodiments, n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2. [0091] In some embodiments, the PNA subunit is a PNA subunit of Formula (II-e):
Figure imgf000025_0001
wherein R2 is hydrogen, deuterium or C1-C4 alkyl; each R3, R5, and R6 is independently hydrogen, deuterium, C1-C4 alkyl, halo (e.g., fluorine), or the side-chain of an amino acid; each R9 and R10 is independently hydrogen, deuterium, C1-C4 alkyl, or halo (e.g., fluorine); R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; n is an integer from 0 to 4; m is an integer from 1 to 3; and each “
Figure imgf000025_0002
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0092] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0093] In some embodiments, each R3, R5, and R6 is independently hydrogen. In some embodiments, each R9 and R10 is independently hydrogen. [0094] In some embodiments, R12 is hydrogen or methyl, and m is 1. In some embodiments, R12 is hydrogen or tert-butyl, and m is 1. In some embodiments, R12 is methyl or tert-butyl, and m is 1. In some embodiments, R12 is hydrogen and m is 1. In some embodiments, R12 is methyl and m is 1. In some embodiments, R12 is tert-butyl and m is 1. [0095] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0096] In some embodiments, n is an integer between 0 and 2. In some embodiments, n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2. [0097] In some embodiments, the PNA subunit is a PNA subunit of Formula (II-f):
Figure imgf000026_0001
wherein R2 is hydrogen, deuterium or C1-C4 alkyl; each R4, R5, and R6 is independently hydrogen, deuterium, C1-C4 alkyl, halo (e.g., fluorine) or the side-chain of an amino acid; each R9 and R10 is independently hydrogen, deuterium, C1-C4 alkyl, or halo (e.g., fluorine); R12 is hydrogen or alkyl (e.g., C1-C4 alkyl, e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; n is an integer from 0 to 4; m is an integer from 1 to 3; and each
Figure imgf000026_0002
independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N-terminus of a PNA oligomer. [0098] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0099] In some embodiments, each R4, R5, and R6 is independently hydrogen. In some embodiments, each R9 and R10 is independently hydrogen. [0100] In some embodiments, R12 is hydrogen or methyl, and m is 1. In some embodiments, R12 is hydrogen or tert-butyl, and m is 1. In some embodiments, R12 is methyl or tert-butyl, and m is 1. In some embodiments, R12 is hydrogen and m is 1. In some embodiments, R12 is methyl and m is 1. In some embodiments, R12 is tert-butyl and m is 1. [0101] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0102] In some embodiments, n is an integer from 0 to 2. In some embodiments, n is an integer of 0. In some embodiments, n is an integer of 1. In some embodiments, n is an integer of 2. [0103] In some embodiments, the PNA subunit is selected from:
Figure imgf000027_0001
wherein R12 is hydrogen or alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl); B is a PNA nucleobase; and each “
Figure imgf000027_0005
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0104] In some embodiments, R12 is hydrogen, or alkyl (e.g., methyl, ethyl, isopropyl, tert- butyl). In some embodiments, R12 is hydrogen. In some embodiments, R12 is methyl. In some embodiments, R12 is tert-butyl. [0105] In some embodiments, B is a PNA nucleobase described herein, e.g., a PNA nucleobase comprising or consisting of Formula (V) (e.g., any one of Formulas (V-i), (V-ii), (V-iii), (V-iv), (V-a), (V-b), (V-c), (V-d), or (V-e)) shown below. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, B is pyridazin-3(2H)-one. In some embodiments, B is pyrimidin-2(1H)-one. [0106] In some embodiments, each “
Figure imgf000027_0002
” independently denotes an attachment point to an atom of the N-terminus of the PNA oligomer (e.g., a hydrogen), to an atom of the C-terminus of the PNA oligomer (e.g., -OH or -NH2), or to another PNA subunit. In some embodiments, one “
Figure imgf000027_0003
” is an attachment point to an atom of the C-terminus of the PNA oligomer and one “
Figure imgf000027_0004
” is an attachment point to another monomer/PNA subunit. In some embodiments, one “ ” is an attachment point to an atom of the N-terminus of the PNA oligomer and one “ ” is an attachment point to another PNA subunit. In some embodiments, both “ ” are attachment points to other PNA subunits. In some embodiments, one “
Figure imgf000028_0003
” is an attachment point to a linker. In some embodiments, one “ ” is an attachment point to an amino acid. [0107] In some embodiments, the PC PNA subunit is a compound of Formula (III-a):
Figure imgf000028_0001
wherein P1 is a first terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer; P5 is a second terminus, e.g., an amine or a carboxyl terminus, that can participate in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer; each R3, R4, R5, and R6 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo (e.g., fluorine), -ORE, or the side-chain of an amino acid; X is N or CRb; Y is –C(O)- or -CH2-; each Ra and Rb is independently hydrogen, deuterium, halo, or alkyl (e.g., methyl); each RC, RD, and RE is independently hydrogen, alkyl, or heteroalkyl; and each “
Figure imgf000028_0004
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N-terminus of a PNA oligomer; provided that i) when P1 is an amine terminus, P5 is a carboxyl terminus; and ii) when P5 is an amine terminus, P1 is a carboxyl terminus. [0108] In some embodiments, P1 is an amine terminus (e.g., -NH2 or -NH-, wherein -NH- participates in a covalent bond to the P5 group of another PNA subunit within the PNA oligomer). In some embodiments, P5 is a carboxyl terminus (e.g., -C(O)OH, -C(O)CH3, - C(O)NH2, or -C(O)-, wherein -C(O)- participates in a covalent bond to the P1 group of another PNA subunit within the PNA oligomer). In some embodiments, P1 is an amine terminus and P5 is a carboxyl terminus. [0109] In some embodiments, each R3, R4, R5, and R6 is independently hydrogen, heteroalkyl, or the side-chain of an amino acid. In some embodiments, each R3, R4, R5, and R6 is independently hydrogen. [0110] In some embodiments, X is N, and Ra is hydrogen. In some embodiments, X is N, and Ra is methyl. In some embodiments, Y is –C(O)-. [0111] In some embodiments, the PC PNA subunit is a compound of Formula (III-b):
Figure imgf000028_0002
wherein R2 is hydrogen, deuterium or alkyl (e.g., C1-C4 alkyl); each R3, R4, R5, and R6 is independently hydrogen, deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo (e.g., fluorine), -ORE, or the side-chain of an amino acid; Ra is hydrogen or alkyl (e.g., methyl); each RC, RD, and RE is independently hydrogen, alkyl, or heteroalkyl; and each “
Figure imgf000029_0003
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0112] In some embodiments, R2 is hydrogen or methyl. In some embodiments, R2 is hydrogen. [0113] In some embodiments, each R3, R4, R5, and R6 is independently hydrogen, heteroalkyl, or the side-chain of an amino acid. In some embodiments, each R3, R4, R5, and R6 is independently hydrogen. In some embodiments, Ra is hydrogen. In some embodiments, Ra is methyl. [0114] In some embodiments, the PC PNA subunit is a compound of Formula (III-c):
Figure imgf000029_0002
wherein each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0115] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase (e.g., B) comprises a structure of any of Formulas (V-i), (V-ii), (V-iii), and (V-iv):
Figure imgf000029_0001
wherein each X1 or X4 is independently N or C; X2 is N, CH, or C=O; X3 is CH, C=O, or C-NH2; each X5 , X6, and X8 is independently N or CH; X7 is CH or C=O; R20 is absent or hydrogen; each R21, R35, R36, R37, R38, and R39 is independently hydrogen, deuterium, halo, alkyl, alkenyl, alkynyl, heteroalkyl, cyano, -OH, -NH2, or NO2; R40 is hydrogen or alkyl; R41 is hydrogen, alkyl, or absent; R42 is hydrogen, deuterium, alkyl, or heteroalkyl; each n and m is independently an integer of 1 or 2; each p is an integer from 1 to 4; each is independently a single or double bond, valency permitting; and “
Figure imgf000030_0002
” denotes an attachment point to L, wherein L is a spacer moiety described herein; wherein when X2 is C=O, then X3 is not also C=O; when X3 is C=O, then X2 is not also C=O; and when X3 is C-NH2, then X2 is not C=O. [0116] In some embodiments, the PNA nucleobase (e.g., B) has the structure of formula (V-i). In some embodiments, X1 is N or C. In some embodiments, X1 is N. In some embodiments, X1 is C. In some embodiments, X2 is N, CH, or C=O. In some embodiments, X2 is N. In some embodiments, X2 is CH. In some embodiments, X2 is C=O. In some embodiments, X3 is CH, C=O, or C-NH2. In some embodiments, X3 is CH. In some embodiments, X3 is C=O. In some embodiments, X3 is C-NH2. In some embodiments, X4 is C or N. In some embodiments, X4 is N. [0117] In some embodiments, R20 is absent or hydrogen. In some embodiments, R20 is absent. In some embodiments, R20 is hydrogen. [0118] In some embodiments, each R21 and R35 is independently hydrogen, deuterium, alkyl (e.g., methyl), or alkynyl. In some embodiments, each R21 and R35 is independently hydrogen. In some embodiments, each n and m is independently an integer of 1 or 2. In some embodiments, each n and m is independently 1. [0119] In some embodiments, X1 is N, X3 is C=O, and X4 is N. In some embodiments, X1 is C, X2 is CH, X3 is C-NH2, and X4 is N. In some embodiments, each R20, R21, and R35 is H. In some embodiments, each n and m is independently 1. [0120] In some embodiments, the PNA nucleobase (e.g., B) comprises a structure of Formula (V-a):
Figure imgf000030_0001
wherein X1 is N or C; X2 is N, CH, or C=O; X3 is CH, C=O, or C-NH2; R20 is absent or hydrogen; R21 is hydrogen, deuterium, halo, alkyl (e.g., methyl), alkenyl, or alkynyl; each
Figure imgf000030_0003
is independently a single or double bond, valency permitting; and “
Figure imgf000030_0004
” denotes an attachment point to L, wherein L is a spacer moiety described herein; wherein when X2 is C=O, then X3 is not also C=O; when X3 is C=O, then X2 is not also C=O; and when X3 is C-NH2, then X2 is not C=O. [0121] In some embodiments, X1 is N or C. In some embodiments, X1 is N. In some embodiments, X1 is C. In some embodiments, X2 is N, CH, or C=O. In some embodiments, X2 is N. In some embodiments, X2 is CH. In some embodiments, X2 is C=O. In some embodiments, X3 is CH, C=O, or C-NH2. In some embodiments, X3 is CH. In some embodiments, X3 is C=O. In some embodiments, X3 is C-NH2. [0122] In some embodiments, R20 is absent or hydrogen. In some embodiments, R20 is absent. In some embodiments, R20 is hydrogen. [0123] In some embodiments, R21 is hydrogen, deuterium, alkyl (e.g., methyl), or alkynyl. In some embodiments, R21 is hydrogen. [0124] In some embodiments, the PNA nucleobase (e.g., B) comprises a structure of Formula (V-b):
Figure imgf000031_0004
wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein. [0125] In some embodiments, the PNA nucleobase (e.g., B) comprises a structure of Formula (V-c):
Figure imgf000031_0003
wherein R21 is hydrogen, deuterium, halo, alkyl (e.g., methyl), alkenyl, or alkynyl; and “
Figure imgf000031_0005
” denotes an attachment point to L, wherein L is a spacer moiety described herein. [0126] In some embodiments, R21 is hydrogen, or alkyl (e.g., methyl). In some embodiments, R21 is hydrogen. [0127] In some embodiments, the nucleobase (e.g., B) of a PNA subunit comprises a structure of Formula (V-d):
Figure imgf000031_0002
wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein. [0128] In some embodiments, the nucleobase (e.g., B) of a PNA subunit comprises a structure of Formula (V-e):
Figure imgf000031_0001
wherein “ ” denotes an attachment point to L, wherein L is a spacer moiety described herein. [0129] In some embodiments, the PC PNA subunit is a PNA subunit of one of the following formula:
Figure imgf000032_0001
wherein R12 is hydrogen or alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl), each “
Figure imgf000032_0002
” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0130] In some embodiments, R12 is hydrogen, or alkyl (e.g., methyl, ethyl, isopropyl, tert- butyl). In some embodiments, R12 is hydrogen. In some embodiments, R12 is C1-4alkyl. In some embodiments, R12 is methyl. In some embodiments, R12 is ethyl. In some embodiments, R12 is tert-butyl. [0131] In some embodiments, the PNA subunit is selected from:
Figure imgf000033_0001
wherein each “ ” independently denotes an attachment point to a PNA subunit, a protecting group, a linker, an amino acid, or the C-terminus or N- terminus of a PNA oligomer. [0132] In some embodiments, each “
Figure imgf000033_0002
” independently denotes an attachment point to the C- terminus of the PNA oligomer (e.g., -OH or -NH2), or to another PNA subunit. In some embodiments, one “
Figure imgf000033_0003
” is an attachment point to an atom of the C-terminus of the PNA oligomer and one”
Figure imgf000033_0004
” is an attachment point to another PNA subunit. In some embodiments, one “ ” is an attachment point to an atom of the N-terminus of the PNA oligomer and one “ ” is an attachment point to another PNA subunit. In some embodiments, both “
Figure imgf000033_0005
” are attachment points to other PNA subunits. [0133] The abbreviations used herein have the conventional meaning within the chemical and biological arts. The chemical structures and formulae set forth herein are constructed according to the standard rules of chemical valency known in the chemical arts. [0134] When a range of values is listed, it is intended to encompass each value and sub–range within the range. For example, “C1-C6 alkyl” is intended to encompass, C1,C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4- C5, and C5-C6 alkyl. [0135] The following terms are intended to have the meanings presented therewith below and are useful in understanding the description and intended scope of the present invention. [0136] As used herein, “alkyl” refers to a radical of a straight–chain or branched saturated hydrocarbon group. An alkyl group can have, for example, from 1 to 36 carbon atoms (“C1-C36 alkyl”). In some embodiments, an alkyl group has 1 to 32 carbon atoms (“C1-C32 alkyl”). In some embodiments, an alkyl group has 1 to 24 carbon atoms (“C1-C24 alkyl”). In some embodiments, an alkyl group has 1 to 18 carbon atoms (“C1-C18 alkyl”). In some embodiments, an alkyl group has 1 to 12 carbon atoms (“C1-C12 alkyl”). In some embodiments, an alkyl group has 1 to 8 carbon atoms (“C1-C8 alkyl”). In some embodiments, an alkyl group has 1 to 7 carbon atoms (“C1-C7 alkyl”). In some embodiments, an alkyl group has 1 to 6 carbon atoms (“C1-C6 alkyl”). In some embodiments, an alkyl group has 1 to 5 carbon atoms (“C1-C5 alkyl”). In some embodiments, an alkyl group has 1 to 4 carbon atoms (“C1-C4 alkyl”). In some embodiments, an alkyl group has 1 to 3 carbon atoms (“C1-C3 alkyl”). In some embodiments, an alkyl group has 1 to 2 carbon atoms (“C1-C2 alkyl”). In some embodiments, an alkyl group has 1 carbon atom (“C1 alkyl”). In some embodiments, an alkyl group has 2 to 6 carbon atoms (“C2-C6 alkyl”). Examples of C1-C24 alkyl groups include methyl (C1), ethyl (C2), n–propyl (C3), isopropyl (C3), n–butyl (C4), tert–butyl (C4), sec–butyl (C4), iso–butyl (C4), n–pentyl (C5), 3–pentanyl (C5), amyl (C5), neopentyl (C5), 3–methyl–2–butanyl (C5), tert–amyl (C5), n–hexyl (C6), octyl (C8), nonyl (C9), decyl (C10), undecyl (C11), dodecyl (or lauryl) (C12), tridecyl (C13), tetradecyl (or myristyl) (C14), pentadecyl (C15), hexadecyl (or cetyl) (C16), heptadecyl (C17), octadecyl (or stearyl) (C18), nonadecyl (C19), eicosyl (or arachidyl) (C20), henicosanyl (C21), docosanyl (C22), tricosanyl (C23), and tetracosanyl (C24). Each instance of an alkyl group can be independently, optionally substituted, i.e., unsubstituted (an “unsubstituted alkyl”) or substituted (a “substituted alkyl”) with one or more substituents; e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. [0137] As used herein, “alkenyl” refers to a radical of a straight–chain or branched hydrocarbon group having one or more carbon–carbon double bonds, and no triple bonds (“C2-C36 alkenyl”). An alkenyl group can have, for example, 2 to 36 carbon atoms. In some embodiments, an alkenyl group has 2 to 32 carbon atoms (“C2-C32 alkenyl”). In some embodiments, an alkenyl group has 2 to 24 carbon atoms (“C2-C24 alkenyl”). In some embodiments, an alkenyl group has 2 to 18 carbon atoms (“C2-C18 alkenyl”). In some embodiments, an alkenyl group has 2 to 12 carbon atoms (“C2-C12 alkenyl”). In some embodiments, an alkenyl group has 2 to 8 carbon atoms (“C2- C8 alkenyl”). In some embodiments, an alkenyl group has 2 to 7 carbon atoms (“C2-C7 alkenyl”). In some embodiments, an alkenyl group has 2 to 8 carbon atoms (“C2-C8 alkenyl”). In some embodiments, an alkenyl group has 2 to 6 carbon atoms (“C2-C6 alkenyl”). In some embodiments, an alkenyl group has 2 to 5 carbon atoms (“C2-C5 alkenyl”). In some embodiments, an alkenyl group has 2 to 4 carbon atoms (“C2-C4 alkenyl”). In some embodiments, an alkenyl group has 2 to 3 carbon atoms (“C2-C3 alkenyl”). In some embodiments, an alkenyl group has 2 carbon atoms (“C2 alkenyl”). The one or more carbon– carbon double bonds can be internal (such as in 2–butenyl) or terminal (such as in 1–butenyl). The one or more carbon double bonds can have cis, trans, E, or Z geometry. Examples of C2-C4 alkenyl groups include ethenyl (C2), 1–propenyl (C3), 2–propenyl (C3), 1–butenyl (C4), 2– butenyl (C4), butadienyl (C4), and the like. Examples of C2-C24 alkenyl groups include the aforementioned C2–4 alkenyl groups and pentenyl (C5), pentadienyl (C5), hexenyl (C6), and the like. Additional examples of alkenyl include heptenyl (C7), octenyl (C8), octatrienyl (C8), nonenyl (C9), nonadienyl (C9), decenyl (C10), decadienyl (C10), undecenyl (C11), undecadienyl (C11), dodecenyl (C12), dodecadienyl (C12), tridecenyl (C13), tridecadienyl (C13), tetradecenyl (C14), tetradecadienyl (e.g., myristoleyl) (C14), pentadecenyl (C15), pentadecadienyl (C15), hexadecenyl (e.g., palmitoleyl) (C16), hexadecadienyl (C16), heptadecenyl (C17), heptadecadienyl (C17), octadecenyl (e.g., oleyl) (C18), octadecadienyl (e.g., linoleyl) (C18), nonadecenyl (C19), nonadecadienyl (C19), eicosenyl (C20), eicosadienyl (C20), eicosatrienyl (C20), and the like. Each instance of an alkenyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkenyl”) or substituted (a “substituted alkenyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. In some embodiments, the alkenyl group is unsubstituted C2–10 alkenyl. [0138] As used herein, the term “alkynyl” refers to a radical of a straight–chain or branched hydrocarbon group having one or more carbon–carbon triple bonds. An alkynyl group can have, for example, from 2 to 36 carbon atoms (“C2-C36 alkynyl”). In some embodiments, an alkynyl group has 2 to 32 carbon atoms (“C2-C32 alkynyl”). In some embodiments, an alkynyl group has 2 to 24 carbon atoms (“C2-C24 alkynyl”). In some embodiments, an alkynyl group has 2 to 18 carbon atoms (“C2-C18 alkynyl”). In some embodiments, an alkynyl group has 2 to 12 carbon atoms (“C2-C12 alkynyl”). In some embodiments, an alkynyl group has 2 to 8 carbon atoms (“C2- C8 alkynyl”). In some embodiments, an alkynyl group has 2 to 6 carbon atoms (“C2-C6 alkynyl”). In some embodiments, an alkynyl group has 2 to 5 carbon atoms (“C2-C5 alkynyl”). In some embodiments, an alkynyl group has 2 to 4 carbon atoms (“C2-C4 alkynyl”). In some embodiments, an alkynyl group has 2 to 3 carbon atoms (“C2-C3 alkynyl”). In some embodiments, an alkynyl group has 2 carbon atoms (“C2 alkynyl”). The one or more carbon– carbon triple bonds can be internal (such as in 2–butynyl) or terminal (such as in 1–butynyl). Examples of C2-C4 alkynyl groups include ethynyl (C2), 1–propynyl (C3), 2–propynyl (C3), 1– butynyl (C4), 2–butynyl (C4), and the like. Each instance of an alkynyl group can be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkynyl”) or substituted (a “substituted alkynyl”) with one or more substituents e.g., for instance from 1 to 5 substituents, 1 to 3 substituents, or 1 substituent. In certain embodiments, the alkynyl group is unsubstituted C2–10 alkynyl. In certain embodiments, the alkynyl group is substituted C2–6 alkynyl. [0139] As used herein, the terms “heteroalkyl,” “heteroalkenyl,” and “heteroalkynyl,” refer to a non-cyclic stable straight or branched alkyl, alkenyl, or alkynyl chains, or combinations thereof, including at least one carbon atom for heteroalkyl and at least two carbon atoms for heteroalkenyl and heteroalkynyl and at least one heteroatom selected from the group consisting of O, N, P, Si, and S, and wherein the nitrogen and sulfur atoms can optionally be oxidized, and the nitrogen heteroatom can optionally be quaternized. The heteroatom(s) O, N, P, S, and Si can be placed at any position of the heteroalkyl, heteroalkenyl, or heteroalkynyl group. Examples of heteroalkyl, heteroalkenyl, and heteroalkynyl groups include, but are not limited to: -CH2-CH2- O-CH3, -CH2-CH2-NH-CH3, -CH2-CH2-N(CH3)-CH3, -CH2-S-CH2-CH3, -CH2-CH2-S(O)-CH3, - CH2-CH2-S(O)2-CH3, -CH=CH-O-CH3, -Si(CH3)3, -CH2-CH=N-OCH3, -CH=CH-N(CH3)-CH3, - O-CH3, and -O-CH2-CH3. Up to two or three heteroatoms can be consecutive, such as, for example, -CH2-NH-OCH3 and -CH2-O-Si(CH3)3. [0140] The terms “alkylene,” “alkenylene,” “alkynylene,” and “heteroalkylene,” alone or as part of another substituent, mean, unless otherwise stated, a divalent radical derived from an alkyl, alkenyl, alkynyl, or heteroalkyl, respectively. The term “alkenylene,” alone or as part of another substituent, means, unless otherwise stated, a divalent radical derived from an alkene. An alkylene, alkenylene, alkynylene, or heteroalkylene group can be described as, e.g., a C1-C6- membered alkylene, C1-C6-membered alkenylene, C1-C6-membered alkynylene, or C1-C6- membered heteroalkylene, wherein the term “membered” refers to the non-hydrogen atoms within the moiety. In the case of heteroalkylene groups, heteroatoms can also occupy either or both of the chain termini (e.g., alkyleneoxy, alkylenedioxy, alkyleneamino, alkylenediamino, and the like). Still further, for alkylene and heteroalkylene linking groups, no orientation of the linking group is implied by the direction in which the formula of the linking group is written. For example, the formula -C(O)2R’- can represent both -C(O)2R’- and –R’C(O)2-. Each instance of an alkylene, alkenylene, alkynylene, or heteroalkylene group can be independently optionally substituted, i.e., unsubstituted (an “unsubstituted alkylene”) or substituted (a “substituted heteroalkylene”) with one or more substituents. [0141] As used herein, “aryl” refers to a radical of a monocyclic or polycyclic (e.g., bicyclic or tricyclic) 4n+2 aromatic ring system (e.g., having 6, 10, or 14 π electrons shared in a cyclic array) having 6–14 ring carbon atoms and zero heteroatoms provided in the aromatic ring system (“C6-C14 aryl”). In some embodiments, an aryl group has six ring carbon atoms (“C6 aryl”; e.g., phenyl). In some embodiments, an aryl group has ten ring carbon atoms (“C10 aryl”; e.g., naphthyl such as 1–naphthyl and 2–naphthyl). In some embodiments, an aryl group has fourteen ring carbon atoms (“C14 aryl”; e.g., anthracyl). An aryl group can be described as, e.g., a C6-C10- membered aryl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety. Aryl groups include phenyl, naphthyl, indenyl, and tetrahydronaphthyl. Each instance of an aryl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted aryl”) or substituted (a “substituted aryl”) with one or more substituents. In some embodiments, the aryl group is unsubstituted C6-C14 aryl. In some embodiments, the aryl group is substituted C6-C14 aryl. [0142] As used herein, “cycloalkyl” refers to a radical of a non–aromatic cyclic hydrocarbon group having, for example, from 3 to 7 ring carbon atoms (“C3-C7 cycloalkyl”) and zero heteroatoms in the non–aromatic ring system. In some embodiments, a cycloalkyl group has 3 to 6 ring carbon atoms (“C3-C6 cycloalkyl”). In some embodiments, a cycloalkyl group has 5 to 7 ring carbon atoms (“C5-C7 cycloalkyl”). A cycloalkyl group may be described as, e.g., a C4-C7- membered cycloalkyl, wherein the term “membered” refers to the non-hydrogen ring atoms within the moiety. Examples of C3-C6 cycloalkyl groups include, without limitation, cyclopropyl (C3), cyclopropenyl (C3), cyclobutyl (C4), cyclobutenyl (C4), cyclopentyl (C5), cyclopentenyl (C5), cyclohexyl (C6), cyclohexenyl (C6), cyclohexadienyl (C6), and the like. Examples of C3-C7 cycloalkyl groups include, without limitation, the aforementioned C3-C6 cycloalkyl groups as well as cycloheptyl (C7), cycloheptenyl (C7), cycloheptadienyl (C7), and cycloheptatrienyl (C7), bicyclo[2.1.1]hexanyl (C6), bicyclo[3.1.1]heptanyl (C7), and the like. As the foregoing examples illustrate, in some embodiments, the cycloalkyl group is either monocyclic (“monocyclic cycloalkyl”) or contain a fused, bridged, or spiro ring system such as a bicyclic system (“bicyclic cycloalkyl”) and can be saturated or can be partially unsaturated. “Cycloalkyl” also includes ring systems wherein the cycloalkyl ring, as defined above, is fused with one or more aryl groups wherein the point of attachment is on the cycloalkyl ring, and in such instances, the number of carbons continue to designate the number of carbons in the cycloalkyl ring system. Each instance of a cycloalkyl group may be independently optionally substituted, i.e., unsubstituted (an “unsubstituted cycloalkyl”) or substituted (a “substituted cycloalkyl”) with one or more substituents. [0143] As used herein, the term “halo” refers to a fluorine, chlorine, bromine, or iodine radical (i.e., -F, -Cl, -Br, and -I, respectively). [0144] As used herein, the term “heteroaryl,” refers to an aromatic heterocycle that comprises 1, 2, 3, or 4 heteroatoms selected, independently of the others, from nitrogen, sulfur and oxygen. As used herein, the term “heteroaryl” refers to a group that can be substituted or unsubstituted. A heteroaryl can be fused to one or two rings, such as a cycloalkyl, an aryl, or a heteroaryl ring. The point of attachment of a heteroaryl to a molecule can be on the heteroaryl, cycloalkyl, heterocycloalkyl or aryl ring, and the heteroaryl group can be attached through carbon or a heteroatom. Examples of heteroaryl groups include imidazolyl, furyl, pyrrolyl, thienyl, thiazolyl, isoxazolyl, isothiazolyl, thiadiazolyl, oxadiazolyl, pyridinyl, pyrimidyl, pyrazinyl, pyridazinyl, quinolyl, isoquinolinyl, indazolyl, benzoxazolyl, benzisooxazolyl, benzofuryl, benzothiazolyl, indolizinyl, imidazopyridinyl, pyrazolyl, triazolyl, oxazolyl, tetrazolyl, benzimidazolyl, benzoisothiazolyl, benzothiadiazolyl, benzoxadiazolyl, indolyl, tetrahydroindolyl, azaindolyl, imidazopyridyl, quinazolinyl, purinyl, pyrrolo2,3]pyrimidyl, pyrazolo3,4]pyrimidyl, and benzo(b)thienyl, each of which can be optionally substituted. [0145] As used herein, the term “hydroxy” refers to the radical -OH. [0146] As used herein, the terms “carbonyl” and “oxo” each refer to the radical -C=O. [0147] Compounds described herein can comprise one or more asymmetric centers, and thus can exist in various isomeric forms, e.g., enantiomers and/or diastereomers. For example, the compounds described herein can be in the form of an individual enantiomer, diastereomer, or geometric isomer, or can be in the form of a mixture of stereoisomers, including racemic mixtures and mixtures enriched in one or more stereoisomer. Isomers can be isolated from mixtures by methods including chiral high-performance liquid chromatography (HPLC); or preferred isomers can be prepared by asymmetric syntheses. The invention additionally encompasses compounds described herein as individual isomers substantially free of other isomers, and alternatively, as mixtures of various isomers. [0148] As used herein, a pure enantiomeric compound is substantially free from other enantiomers or stereoisomers of the compound (i.e., in enantiomeric excess). In other words, an “S” form of the compound is substantially free from the “R” form of the compound and is, thus, in enantiomeric excess of the “R” form. In some embodiments, ‘substantially free’, refers to: (i) an aliquot of an “R” form compound that contains less than 2% “S” form; or (ii) an aliquot of an “S” form compound that contains less than 2% “R” form. The term “enantiomerically pure” or “pure enantiomer” denotes that the compound comprises more than 90% by weight, more than 91% by weight, more than 92% by weight, more than 93% by weight, more than 94% by weight, more than 95% by weight, more than 96% by weight, more than 97% by weight, more than 98% by weight, more than 99% by weight, more than 99.5% by weight, or more than 99.9% by weight, of the single enantiomer. In certain embodiments, the weights are based upon total weight of all enantiomers or stereoisomers of the compound. [0149] In the compositions provided herein, an enantiomerically pure compound can be present with other active or inactive ingredients. For example, a pharmaceutical composition comprising enantiomerically pure “R” form compound can comprise, for example, about 90% excipient and about 10% enantiomerically pure “R” form compound. In certain embodiments, the enantiomerically pure “R” form compound in such compositions can, for example, comprise, at least about 95% by weight “R” form compound and at most about 5% by weight “S” form compound, by total weight of the compound. For example, a pharmaceutical composition comprising enantiomerically pure “S” form compound can comprise, for example, about 90% excipient and about 10% enantiomerically pure “S” form compound. In certain embodiments, the enantiomerically pure “S” form compound in such compositions can, for example, comprise, at least about 95% by weight “S” form compound and at most about 5% by weight “R” form compound, by total weight of the compound. In some embodiments, the active ingredient can be formulated with little or no excipient or carrier. [0150] The symbol “
Figure imgf000039_0003
” as used herein refers to an attachment point to another moiety or functional group. For example, the “
Figure imgf000039_0004
”can refer to an attachment point to the terminus or terminal atom of a PNA oligomer (e.g., a hydrogen or oxygen) or the attachment point to another region or atom within the PNA oligomer. In some embodiments, “
Figure imgf000039_0005
” denotes an attachment point to a PNA subunit. In some embodiments, “
Figure imgf000039_0006
” denotes an attachment point to a spacer or linker moiety. In some embodiments, “
Figure imgf000039_0009
” denotes an attachment point to a nucleobase. In some embodiments, “
Figure imgf000039_0002
” denotes an attachment point to a backbone moiety. In one embodiment, “ ” refers to an attachment point to the N-terminus or N-terminal atom (e.g., hydrogen) of the of the PNA oligomer. In one embodiment, “
Figure imgf000039_0007
” refers to an attachment point to C-terminus or terminal atom (e.g., oxygen, carboxylic acid or amide group) of the PNA oligomer. In another embodiment, “
Figure imgf000039_0001
” refers to an attachment point to another PNA subunit or other region within a PNA oligomer. For example, in a tcPNA, “
Figure imgf000039_0008
” can refer to an attachment point to a linker (e.g., a polyethylene glycol linker) or a positively charged region comprising one or more positively charged moieties (e.g., positively charged amino acids such as lysine, ornithine or arginine). [0151] Any compound herein can be purified. A compound herein can be least 1% pure, at least 2% pure, at least 3% pure, at least 4% pure, at least 5% pure, at least 6% pure, at least 7% pure, at least 8% pure, at least 9% pure, at least 10% pure, at least 11% pure, at least 12% pure, at least 13% pure, at least 14% pure, at least 15% pure, at least 16% pure, at least 17% pure, at least 18% pure, at least 19% pure, at least 20% pure, at least 21% pure, at least 22% pure, at least 23% pure, at least 24% pure, at least 25% pure, at least 26% pure, at least 27% pure, at least 28% pure, at least 29% pure, at least 30% pure, at least 31% pure, at least 32% pure, at least 33% pure, at least 34% pure, at least 35% pure, at least 36% pure, at least 37% pure, at least 38% pure, at least 39% pure, at least 40% pure, at least 41% pure, at least 42% pure, at least 43% pure, at least 44% pure, at least 45% pure, at least 46% pure, at least 47% pure, at least 48% pure, at least 49% pure, at least 50% pure, at least 51% pure, at least 52% pure, at least 53% pure, at least 54% pure, at least 55% pure, at least 56% pure, at least 57% pure, at least 58% pure, at least 59% pure, at least 60% pure, at least 61% pure, at least 62% pure, at least 63% pure, at least 64% pure, at least 65% pure, at least 66% pure, at least 67% pure, at least 68% pure, at least 69% pure, at least 70% pure, at least 71% pure, at least 72% pure, at least 73% pure, at least 74% pure, at least 75% pure, at least 76% pure, at least 77% pure, at least 78% pure, at least 79% pure, at least 80% pure, at least 81% pure, at least 82% pure, at least 83% pure, at least 84% pure, at least 85% pure, at least 86% pure, at least 87% pure, at least 88% pure, at least 89% pure, at least 90% pure, at least 91% pure, at least 92% pure, at least 93% pure, at least 94% pure, at least 95% pure, at least 96% pure, at least 97% pure, at least 98% pure, at least 99% pure, at least 99.1% pure, at least 99.2% pure, at least 99.3% pure, at least 99.4% pure, at least 99.5% pure, at least 99.6% pure, at least 99.7% pure, at least 99.8% pure, or at least 99.9% pure. [0152] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting essentially of Formula (V-i), (V- ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv). In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA. In some embodiments, the PNA nucleobase consisting of Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.3 nm, as determined by X-ray crystallography. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.35 nm, as determined by X-ray crystallography. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.4 nm, as determined by X-ray crystallography. [0153] In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode cytosine-binding nucleobase. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode thymine- binding subunit. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a cytosine nucleobase in the single strand of the dsDNA. In some embodiments, the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a thymine nucleobase in the single strand of the dsDNA. Pharmaceutically-acceptable salts. [0154] The invention provides the use of pharmaceutically-acceptable salts of any therapeutic compound described herein. Pharmaceutically-acceptable salts include, for example, acid- addition salts and base-addition salts. The acid that is added to the compound to form an acid- addition salt can be an organic acid or an inorganic acid. A base that is added to the compound to form a base-addition salt can be an organic base or an inorganic base. In some embodiments, a pharmaceutically-acceptable salt is a metal salt. In some embodiments, a pharmaceutically- acceptable salt is an ammonium salt. [0155] Metal salts can arise from the addition of an inorganic base to a compound of the invention. The inorganic base consists of a metal cation paired with a basic counterion, such as, for example, hydroxide, carbonate, bicarbonate, or phosphate. The metal can be an alkali metal, alkaline earth metal, transition metal, or main group metal. In some embodiments, the metal is lithium, sodium, potassium, cesium, cerium, magnesium, manganese, iron, calcium, strontium, cobalt, titanium, aluminum, copper, cadmium, or zinc. [0156] In some embodiments, a metal salt is a lithium salt, a sodium salt, a potassium salt, a cesium salt, a cerium salt, a magnesium salt, a manganese salt, an iron salt, a calcium salt, a strontium salt, a cobalt salt, a titanium salt, an aluminum salt, a copper salt, a cadmium salt, or a zinc salt. [0157] Ammonium salts can arise from the addition of ammonia or an organic amine to a compound of the invention. In some embodiments, the organic amine is triethyl amine, diisopropyl amine, ethanol amine, diethanol amine, triethanol amine, morpholine, N- methylmorpholine, piperidine, N-methylpiperidine, N-ethylpiperidine, dibenzylamine, piperazine, pyridine, pyrrazole, pipyrrazole, imidazole, pyrazine, or pipyrazine. [0158] In some embodiments, an ammonium salt is a triethyl amine salt, a diisopropyl amine salt, an ethanol amine salt, a diethanol amine salt, a triethanol amine salt, a morpholine salt, an N-methylmorpholine salt, a piperidine salt, an N-methylpiperidine salt, an N-ethylpiperidine salt, a dibenzylamine salt, a piperazine salt, a pyridine salt, a pyrrazole salt, a pipyrrazole salt, an imidazole salt, a pyrazine salt, or a pipyrazine salt. [0159] Acid addition salts can arise from the addition of an acid to a compound of the invention. In some embodiments, the acid is organic. In some embodiments, the acid is inorganic. In some embodiments, the acid is hydrochloric acid, hydrobromic acid, hydroiodic acid, nitric acid, nitrous acid, sulfuric acid, sulfurous acid, a phosphoric acid, isonicotinic acid, lactic acid, salicylic acid, tartaric acid, ascorbic acid, gentisinic acid, gluconic acid, glucaronic acid, saccaric acid, formic acid, benzoic acid, glutamic acid, pantothenic acid, acetic acid, propionic acid, butyric acid, fumaric acid, succinic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, citric acid, oxalic acid, or maleic acid. [0160] In some embodiments, the salt is a hydrochloride salt, a hydrobromide salt, a hydroiodide salt, a nitrate salt, a nitrite salt, a sulfate salt, a sulfite salt, a phosphate salt, isonicotinate salt, a lactate salt, a salicylate salt, a tartrate salt, an ascorbate salt, a gentisinate salt, a gluconate salt, a glucaronate salt, a saccarate salt, a formate salt, a benzoate salt, a glutamate salt, a pantothenate salt, an acetate salt, a propionate salt, a butyrate salt, a fumarate salt, a succinate salt, a methanesulfonate (mesylate) salt, an ethanesulfonate salt, a benzenesulfonate salt, a p- toluenesulfonate salt, a citrate salt, an oxalate salt , or a maleate salt, Lipid Nanoparticles [0161] The present disclosure features a lipid nanoparticle comprising a nucleic acid mimic (e.g., an PNA) and a lipid. Exemplary lipids include ionizable lipids, phospholipids, sterol lipids, alkylene glycol lipids (e.g., polyethylene glycol lipids), sphingolipids, glycerolipids, glycerophospholipids, prenol lipids, saccharolipids, fatty acids, and polyketides. In some embodiments, the LNP comprises a single type of lipid. In some embodiments, the LNP comprises a plurality of lipids. An LNP may comprise one or more of an ionizable lipid, a phospholipid, a sterol, or an alkylene glycol lipid (e.g., a polyethylene glycol lipid). [0162] In some embodiments, the LNP comprises an ionizable lipid. An ionizable lipid is a lipid that comprises an ionizable moiety capable of bearing a charge (e.g., a positive charge e.g., a cationic lipid, or a negative charge, e.g., an anionic lipid) under certain conditions (e.g., at a certain pH range, e.g., under physiological conditions). An ionizable moiety can comprise an amine, carboxylic acid, hydroxyl, phenol, phosphate, sulfonyl, thiol, or a combination thereof. An ionizable lipid can be a cationic lipid or an anionic lipid. In addition to an ionizable moiety, an ionizable lipid can contain an alkyl or alkenyl group, e.g., greater than six carbon atoms in length (e.g., greater than about 8 carbons, 10 carbons, 12 carbons, 14 carbons, 16 carbons, 18 carbons, 20 carbons or more in length). Examples of ionizable lipids include dilinoleylmethyl-4- dimethylaminobutyrate (DLin-MC3-DMA), 2,2-dilinoleyl-4-dimethylamino-1,3]-dioxolane (DLin-K-DMA), 2,2-dilinoleyl-4-(2-dimethylaminoethyl)-1,3]-dioxolane (DLin-KC2-DMA), 2,2-dilinoleyl-4-N-chloromethyl-N,N-dimethylamino-1,3]-dioxolane (DLin-KC2-CIMDMA), 2,2-dilinoleyl-4-(3-dimethylaminopropyl)-1,3]-dioxolane (DLin-KC3-DMA), 2,2-dilinoleyl-4- (4-dimethylaminobutyl)-1,3]-dioxolane (DLin-KC4-DMA), 1,2-dilinoleyloxy-3- dimethylaminopropane (D-Lin-DMA), 1,2-dilinolenyloxy-dimethyl-3-aminopropane (D-Len- DMA), (1,2-dilinoleoyl-3-dimethylaminopropane (D-Lin-DAP), 1,2-dioleyloxy- dimethylaminopropane (DODMA), 1,2-distearyloxy-dimethyl-3-aminopropane (DSDMA), dioleoyl dimethyl-ammonium propane (DODAP), 1,2-dimyristyloxy-propyl-3-dimethyl-hydroxy ethyl ammonium bromide (DMRIE), dimethyl-2-(sperminecarboxamido)ethyl]-2,3- bis(dioleyloxy)-1-propaniminium or a salt thereof (DOSPA), 98N12-5, and C12-200. In some embodiments, the ionizable lipid comprises DLin-MC3-DMA, DLin-KC2-DMA, D-LinK-DMA, D-Lin-DAP, 98N12-5, C12-200, or DODMA. [0163] In some embodiments, a LNP comprises an ionizable lipid having a structure of Formula (VI):
Figure imgf000043_0001
(VI), or a pharmaceutically acceptable salt thereof, wherein Y is
Figure imgf000043_0002
Figure imgf000043_0003
, , , ; each R22 is independently alkyl, alkenyl, alkynyl, or heteroalkyl, each of which is optionally substituted with RB; each RB is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; n is an integer between 1 and 10 (inclusive); and “ ” denotes the attachment point. [0164] In some embodiments, Y is
Figure imgf000043_0004
. [0165] In some embodiments, each R22 is independently alkyl (e.g., C2-C32 alkyl, C4-C28 alkyl, C8-C24 alkyl, C12-C22 alkyl, or C16-C20 alkyl). In some embodiments, each R22 is independently alkenyl (e.g., C2-C32 alkenyl, C4-C28 alkenyl, C8-C24 alkenyl, C12-C22 alkenyl, or C16-C20 alkenyl). In some embodiments, each R22 is independently C16-C20 alkenyl. In some embodiments, each R22 is independently C18 alkenyl. In some embodiments, each R22 is independently linoleyl (or cis,cis-9,12-octadecadienyl). In some embodiments, each R22 is the same. In some embodiments, each R22 is different. [0166] In some embodiments, n is an integer between 1 and 10, 1 and 8, 1 and 6, or 1 and 4. In some embodiments, n is 1, 2, 3, or 4. In some embodiments, n is 1, 2, or 3. In some embodiments, n is 1 or 2. In some embodiments, n is 1. In some embodiments, n is 2. In some embodiments, n is 3. [0167] In some embodiments, the ionizable lipid is DLin-MC3-DMA. In some embodiments, the ionizable lipid is DLin-KC2-DMA. In some embodiments, the ionizable lipid is D-LinK-DMA. In some embodiments, the ionizable lipid is DLinDAP. In some embodiments, the ionizable lipid is 98N12-5. In some embodiments, the ionizable lipid is C12-200. In some embodiments, the ionizable lipid is DODMA. [0168] An LNP can comprise an ionizable lipid at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an ionizable lipid at a concentration of greater than about 1 mol%, about 2 mol%, about 4 mol%, about 8 mol%, about 20 mol%, about 40 mol%, about 50 mol%, about 60 mol%, or about 80 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an ionizable lipid at a concentration of greater than about 20 mol%, about 40 mol%, or about 50 mol%. In some embodiments, the LNP comprises an ionizable lipid at a concentration between about 1 mol% to about 95 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an ionizable lipid at a concentration between about 2 mol% to about 90 mol%, about 4 mol% to about 80 mol%, about 10 mol% to about 70 mol%, about 20 mol% to about 60 mol%, about 40 mol% to about 55 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an ionizable lipid at a concentration between about 20 mol% to about 60 mol%. In some embodiments, the LNP comprises an ionizable lipid at a concentration between about 40 mol% to about 55 mol%. [0169] In some embodiments, the LNP comprises a phospholipid. A phospholipid is a lipid that comprises a phosphate group and at least one alkyl, alkenyl, or heteroalkyl chain. A phospholipid can be naturally occurring or non-naturally occurring (e.g., a synthetic phospholipid). A phospholipid can comprise an amine, amide, ester, carboxyl, choline, hydroxyl, acetal, ether, carbohydrate, sterol, or a glycerol. In some embodiments, a phospholipid can comprise a phosphocholine, phosphosphingolipid, or a plasmalogen. Examples of phospholipids include 1,2- dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), 1,2-distearoyl-sn-glycero-3- phosphocholine (DSPC), 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC), 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE), 1-myristoyl-2-oleoyl-sn-glycero-3-phosphocholine (MOPC), 1,2-diarachidonoyl-sn- glycero-3-phosphocholine (DAPC), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC), 1-palmitoyl-2-oleoyl-glycero-3-phosphocholine (POPC), 1-stearoyl-2-myristoyl-sn- glycero-3-phosphocholine (SMPC), 1-palmitoyl-2-myristoyl-sn-glycero-3-phosphocholine (PMPC), bis(monoacylglycerol)phosphate (BMP), L-α-phosphatidylcholine, 1,2- Diheptadecanoyl-sn-glycero-3-phosphorylcholine (DHDPC), and 1-stearoyl-2-arachidonoyl-sn- glycero-3-phosphocholine (SAPC). [0170] In some embodiments, a LNP comprises a phospholipid having a structure of Formula
Figure imgf000044_0001
(VII), or a pharmaceutically acceptable salt thereof, wherein each R23 is independently alkyl, alkenyl, or heteroalkyl; wherein each alkyl, alkenyl, or heteroalkyl is optionally substituted with RC; each R25 is independently hydrogen or alkyl; R24 is absent, hydrogen, or alkyl; each RC is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; m is an integer between 1 and 4 (inclusive); and u is 2 or 3. [0171] In some embodiments, each R23 is independently alkyl (e.g., C2-C32 alkyl, C4-C28 alkyl, C8-C24 alkyl, C12-C22 alkyl, or C16-C20 alkyl). In some embodiments, each R23 is independently alkenyl (e.g., C2-C32 alkyl, C4-C28 alkenyl, C8-C24 alkenyl, C12-C22 alkenyl, or C16-C20 alkenyl). In some embodiments, each R23 is independently heteroalkyl (e.g., C4-C28 heteroalkyl, C8-C24 heteroalkyl, C12-C22 heteroalkyl, C16-C20 heteroalkyl). In some embodiments, each R23 is independently C16-C20 alkyl. In some embodiments, each R23 is independently C17 alkyl. In some embodiments, each R23 is independently heptadecyl. In some embodiments, each R23 is the same. In some embodiments, each R23 is different. In some embodiments, each R23 is optionally substituted with RC. In some embodiments, RC is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl. [0172] In some embodiments, one of R25 is hydrogen. In some embodiments, one of R25 is alkyl. In some embodiments, one of R25 is methyl. In some embodiments, each R25 is independently alkyl. In some embodiments, each R25 is independently methyl. In some embodiments, each R25 is independently methyl and u is 2. In some embodiments, each R25 is independently methyl and u is 3. [0173] In some embodiments, R24 is absent, and the oxygen to which R24 is attached carries a negative charge. In some embodiments, R24 is hydrogen. [0174] In some embodiments, m is an integer between 1 and 10, 1 and 8, 1 and 6, 1 and 4. In some embodiments, m is 1, 2, 3, or 4. In some embodiments, m is 1. In some embodiments, m is 2. In some embodiments, m is 3. [0175] In some embodiments, the phospholipid is 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC). In some embodiments, the phospholipid is 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). In some embodiments, the phospholipid is 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC). In some embodiments, the phospholipid is 1,2-dioleoyl-sn-glycero-3- phosphoethanolamine (DOPE). [0176] A LNP may comprise a phospholipid at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a phospholipid at a concentration of greater than about 0.5 mol%, greater than about 1 mol%, greater than about 1.5 mol%, greater than about 2 mol%, greater than about 3 mol%, greater than about 4 mol%, greater than about 5 mol%, greater than about 6 mol%, greater than about 8 mol%, greater than about 10 mol%, greater than about 12 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 50 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a phospholipid at a concentration of greater than about 1 mol%, greater than about 5 mol%, or greater than about 10 mol%. In some embodiments, the LNP comprises a phospholipid at a concentration between about 0.1 mol% to about 50 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a phospholipid at a concentration between about 0.5 mol% to about 40 mol%, about 1 mol% to about 30 mol%, about 5 mol% to about 25 mol%, about 10 mol% to about 20 mol%, about 10 mol% to about 15 mol%, or about 15 mol% to about 20 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a phospholipid at a concentration between about 5 mol% to about 25 mol%. In some embodiments, the LNP comprises a phospholipid at a concentration between about 10 mol% to 20 mol%. [0177] In some embodiments, the LNP comprises a sterol. A sterol is a lipid that comprises a polycyclic structure and an optionally a hydroxyl or ether substituent, and can be naturally occurring or non-naturally occurring (e.g., a synthetic sterol). Sterols can comprise no double bonds, a single double bond, or multiple double bonds. Sterols can further comprise an alkyl, alkenyl, halo, ester, ketone, hydroxyl, amine, polyether, carbohydrate, or cyclic moiety. An example listing of sterols includes cholesterol, dehydroergosterol, ergosterol, campesterol, β- sitosterol, stigmasterol, lanosterol, dihydrolanosterol, desmosterol, brassicasterol, lathosterol, zymosterol, 7-dehydrodesmosterol, avenasterol, campestanol, lupeol, and cycloartenol. In some embodiments, the sterol comprises cholesterol, dehydroergosterol, ergosterol, campesterol, β- sitosterol, or stigmasterol. [0178] In some embodiments, a LNP comprises a sterol having a structure of Formula (VIII):
Figure imgf000046_0001
(VIII) or a pharmaceutically acceptable salt thereof, wherein R26 is hydrogen, alkyl, heteroalkyl, or -C(O)RD, R27 is hydrogen, alkyl, or -ORE; each RD and RE is independently hydrogen, alkyl, alkenyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl or heteroaryl, wherein each alkyl, alkenyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl or heteroaryl is optionally substituted with alkyl, halo, or carbonyl; and each “
Figure imgf000046_0002
is either a single or double bond, and wherein each carbon atom participating in the single or double bond is bound to 0, 1, or 2 hydrogens, valency permitting. [0179] In some embodiments, R26 is hydrogen. In some embodiments, R26 is alkyl (e.g., C1-C4 alkyl, C4-C8 alkyl, C8-C12 alkyl). In some embodiments, R26 is C(O)RD, wherein RD is alkyl (e.g., C1-C4 alkyl, C4-C8 alkyl, C8-C12 alkyl) or heteroaryl (e.g., a nitrogen-containing heteroaryl). In some embodiments, R26 is heteroalkyl (e.g., C1-C4 heteroalkyl, C4-C8 heteroalkyl, C8-C12 heteroalkyl). In some embodiments, R26 is heteroalkyl (e.g., C1-C4 heteroalkyl, C4-C8 heteroalkyl, C8-C12 heteroalkyl) substituted with carbonyl. [0180] In some embodiments, R27 is hydrogen. In some embodiments, R27 is alkyl (e.g., C1-C4 alkyl, C4-C8 alkyl, C8-C12 alkyl). [0181] In some embodiments, one of “
Figure imgf000047_0002
is a single bond. In some embodiments, one of “
Figure imgf000047_0005
” is a double bond. In some embodiments, two of “
Figure imgf000047_0003
” are single bonds. In some embodiments, two of “ ” are double bonds. In some embodiments, each “
Figure imgf000047_0004
” is a single bond. In some embodiments, each “
Figure imgf000047_0001
” is a double bond. [0182] In some embodiments, the sterol is cholesterol. In some embodiments, the sterol is dehydroergosterol. In some embodiments, the sterol is ergosterol. In some embodiments, the sterol is campesterol. In some embodiments, the sterol is β-sitosterol. In some embodiments, the sterol is stigmasterol. In some embodiments, the sterol is a corticosteroid (e.g., corticosterone, hydrocortisone, cortisone, or aldosterone). [0183] A LNP can comprise a sterol at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a sterol at a concentration greater than about 0.5 mol%, greater than about 1 mol%, greater than about 5 mol%, greater than about 10 mol%, greater than about 15 mol%, greater than about 20 mol%, greater than about 25 mol%, greater than about 30%, greater than about 35 mol%, greater than about 40 mol%, greater than about 45 mol%, greater than about 50 mol%, greater than about 55 mol%, greater than about 60 mol%, greater than about 65 mol%, or greater than about 70 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a sterol at a concentration greater than about 10 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 25 mol%. In some embodiments, the LNP comprises a sterol at a concentration about 1 mol% to about 95 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a sterol at a concentration of about 5 mol% to about 90 mol%, about 10 mol% to about 85 mol%, about 20 mol% to about 80 mol%, about 20 mol% to about 60 mol%, about 20 mol% to about 50 mol%, or about 20 mol% to 40 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises a sterol at a concentration between about 20 mol% to about 50 mol%. In some embodiments, the LNP comprises a sterol at a concentration between about 30 mol% to about 60 mol%. [0184] In some embodiments, the LNP comprises an alkylene glycol-containing lipid. An alkylene glycol-containing lipid is a lipid that comprises at least one alkylene glycol moiety, for example, a methylene glycol or an ethylene glycol moiety. In some embodiments, the alkylene glycol-containing lipid comprises a polyethylene glycol (PEG). An alkylene glycol-containing lipid can be a PEG-containing lipid. A PEG-containing lipid can further comprise an amine, amide, ester, carboxyl, phosphate, choline, hydroxyl, acetal, ether, heterocycle, or carbohydrate. PEG-containing lipids can comprise at least one alkyl or alkenyl group, e.g., greater than six carbon atoms in length (e.g., greater than about 8 carbons, 10 carbons, 12 carbons, 14 carbons, 16 carbons, 18 carbons, 20 carbons or more in length), e.g., in addition to a PEG moiety. In some embodiments, a PEG-containing lipid comprises a PEG moiety comprising at least 20 PEG monomers, e.g., at least 30 PEG monomers, at least 40 PEG monomers, at least 45 PEG monomers, at least 50 PEG monomers, at least 100 PEG monomers, at least 200 PEG monomers, at least 300 PEG monomers, at least 500 PEG monomers, at least 1,000 PEG monomers, or at least 2,000 PEG monomers. Examples of PEG-containing lipids include PEG-DMG (e.g., DMG- PEG2k), PEG-c-DOMG, PEG-DSG, PEG-DPG, PEG-DSPE, PEG-DMPE, PEG-DPPE, PEG- DOPE, and PEG-DLPE. In some embodiments, the PEG-lipids include PEG-DMG (e.g., DMG- PEG2k), PEG-c-DOMG, PEG-DSG, and PEG-DPG. [0185] In some embodiments, an LNP comprises an alkylene glycol-containing lipid having a structure of Formula (IX):
Figure imgf000048_0001
(IX) or a pharmaceutically acceptable salt thereof, wherein each R28 is independently alkyl, alkenyl, or heteroalkyl, each of which is optionally substituted with RF; A is absent, O, CH2, C(O), or NH; E is absent, alkyl, or heteroalkyl, wherein alkyl or heteroalkyl is optionally substituted with carbonyl; each RF is independently alkyl, halo, hydroxy, amino, cycloalkyl, or heterocyclyl; and z is an integer between 10 and 200. [0186] In some embodiments, each R28 is independently alkyl. In some embodiments, each R28 is independently heteroalkyl. In some embodiments, each R28 is independently alkenyl. [0187] In some embodiments, A is O or NH. In some embodiments, A is CH2. In some embodiments, A is carbonyl. In some embodiments, A is absent. [0188] In some embodiments, E is alkyl. In some embodiments, E is heteroalkyl. In some embodiments, both A and E are not absent. In some embodiments, A is absent. In some embodiments, E is absent. In some embodiments, either one of A or E is absent. In some embodiments, both A and E is independently absent. [0189] In some embodiments, z is an integer between 10 and 200 (e.g., between 20 and 180, between 20 and 160, between 20 and 120, between 20 and 100, between 40 and 80, between 40 and 60, between 40 and 50). In some embodiments, z is 45. [0190] In some embodiments, the PEG-lipid is PEG-DMG (e.g., DMG-PEG2k). In some embodiments, the PEG-lipid is PEG-c-DOMG. In some embodiments, the PEG-lipid is PEG- DSG. In some embodiments, the PEG-lipid is PEG-DPG. [0191] A LNP can comprise an alkylene glycol-containing lipid at a concentration greater than about 0.1 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration of greater than about 0.5 mol%, greater than about 1 mol%, greater than about 1.5 mol%, greater than about 2 mol%, greater than about 3 mol%, greater than about 4 mol%, greater than about 5 mol%, greater than about 6 mol%, greater than about 8 mol%, greater than about 10 mol%, greater than about 12 mol%, greater than about 15 mol%, greater than about 20 mol%, or greater than about 50 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration of greater than about 1 mol%, greater than about 4 mol%, or greater than about 6 mol%. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration between about 0.1 mol% to about 50 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration between about 0.5 mol% to about 40 mol%, about 1 mol% to about 35 mol%, about 1.5 mol% to about 30 mol%, about 2 mol% to about 25 mol%, about 2.5 mol% to about 20%, about 3 mol% to about 15 mol%, about 3.5 mol% to about 10 mol%, or about 4 mol% to 9 mol%, e.g., of the total lipid composition of the LNP. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration between about 3.5 mol% to about 10 mol%. In some embodiments, the LNP comprises an alkylene glycol-containing lipid at a concentration between about 4 mol% to 9 mol%. [0192] In some embodiments, the LNP comprises at least two types of lipids. In some embodiments, the LNP comprises two of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid. In some embodiments, the LNP comprises at least three types of lipids. In some embodiments, the LNP comprises three of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid. In some embodiments, the LNP comprises at least four types of lipids. In some embodiments, the LNP comprises each of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid. [0193] The LNP (e.g., as described herein) can comprise one or more of the following components: (i) an ionizable lipid at a concentration between about 1 mol% to about 95 mol% (e.g. about 20 mol% to about 80 mol%); (ii) a phospholipid at a concentration between 0.1 mol% to about 50 mol% (e.g. between about 2.5 mol% to about 20 mol%); (iii) a sterol at a concentration between about 1 mol% to about 95 mol% (e.g. about 20 mol% to about 80 mol%); and (iv) a PEG-containing lipid at a concentration between about 0.1 mol% to about 50 mol% (e.g. between about 2.5 mol% to about 20 mol%). In some embodiments, the LNP comprises one of (i)-(iv). In some embodiments, the LNP comprises two of (i)-(iv). In some embodiments, the LNP comprises three of (i)-(iv). In some embodiments, the LNP comprises each of (i)-(iv). In some embodiments, the LNP comprises (i) and (ii). In some embodiments, the LNP comprises (i) and (iii). In some embodiments, the LNP comprises (i) and (iv). In some embodiments, the LNP comprises (ii) and (iii). In some embodiments, the LNP comprises (ii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (i), (ii), and (iii). In some embodiments, the LNP comprises (i), (ii), and (iv). In some embodiments, the LNP comprises (ii), (iii), and (iv). [0194] The LNP (e.g., as described herein) can comprise one or more of the following components: (i) DLin-MC3-DMA at a concentration between about 1 mol% to about 95 mol% (e.g. about 20 mol% to about 80 mol%); (ii) DSPC at a concentration between 0.1 mol% to about 50 mol% (e.g. between about 2.5 mol% to about 20 mol%); (iii) cholesterol at a concentration between about 1 mol% to about 95 mol% (e.g. about 20 mol% to about 80 mol%); and (iv) DMG-PEG2k at a concentration between about 0.1 mol% to about 50 mol% (e.g. between about 2.5 mol% to about 20 mol%). In some embodiments, the LNP comprises two of (i)-(iv). In some embodiments, the LNP comprises three of (i)-(iv). In some embodiments, the LNP comprises each of (i)-(iv). In some embodiments, the LNP comprises (i) and (ii). In some embodiments, the LNP comprises (i) and (iii). In some embodiments, the LNP comprises (i) and (iv). In some embodiments, the LNP comprises (ii) and (iii). In some embodiments, the LNP comprises (ii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (iii) and (iv). In some embodiments, the LNP comprises (i), (ii), and (iii). In some embodiments, the LNP comprises (i), (ii), and (iv). In some embodiments, the LNP comprises (ii), (iii), and (iv). [0195] In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 50:1 to about 1:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 50:1, about 40:1, about 32:3, about 6:1, about 7:1, about 5:1, about 24:5, about 26:5, about 10:3, about 15:2, about 16:7, about 18:1, about 3:1, about 3:2, or about 1:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 15:2. In some embodiments, the LNP comprises a ratio of ionizable lipid to phospholipid of about 5:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to a sterol of about 10:1 to about 1:10. In some embodiments, the LNP comprises a ratio of ionizable lipid to a sterol of about 9:1, about 8:1, about 8:7, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9. In some embodiments, the LNP comprises a ratio of ionizable lipid to an alkylene- containing lipid of about 1:10 to about 10:1. In some embodiments, the LNP comprises a ratio of ionizable lipid to an alkylene-containing lipid of about 1:9, about 1:8, about 7:8, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9. In some embodiments, the LNP comprises a ratio of phospholipid to an alkylene-containing lipid of about 10:1 to about 1:10. In some embodiments, the LNP comprises a ratio of phospholipid to an alkylene-containing lipid of about 9:1, about 8:1, about 8:7, about 7:1, about 7:5, about 7:3, about 6:1, about 6:5, about 5:1, about 5:3, about 4:1, about 4:3, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 3:4, about 1:4, about 3:5, about 1:5, about 4:5, about 1:6, about 5:6, about 7:6, about 7:8, or about 8:9. In some embodiments, the LNP comprises a ratio of a sterol to an alkylene-containing lipid of about 50:1 to about 1:1. In some embodiments, the LNP comprises a ratio of a sterol to an alkylene-containing lipid of about 40:1, about 32:3, about 6:1, about 7:1, about 5:1, about 24:1, about 22:1, about 20:1, about 22:5, about 24:5, about 26:5, about 10:3, about 15:2, about 16:7, about 18:1, about 3:1, about 3:2, or about 1:1. [0196] An LNP (e.g., described herein) comprises two of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid (e.g., PEG-containing lipid). An LNP (e.g., described herein) comprises three of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid (e.g., PEG-containing lipid). An LNP (e.g., described herein) comprises each of an ionizable lipid, a phospholipid, a sterol, and an alkylene glycol-containing lipid (e.g., PEG-containing lipid). Synthetic Polymer Nanoparticles [0197] The present disclosure features a synthetic polymer nanoparticle comprising a nucleic acid mimic (e.g., an PNA) and a synthetic polymer. Examples of synthetic polymers include polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(4- hydroxy-L-proline ester, other degradable polyesters, polyanhydrides, poly(ortho)esters, polyesters, polyurethanes, poly(butyric acid), poly(valeric acid), poly(caprolactone), poly(hydroxyalkanoates), poly(lactide-co-caprolactone), poly(amine-co-ester) polymers, and a combination of any two or more of the foregoing. [0198] In some embodiments, the synthetic polymer comprises a structure of Formula (X):
Figure imgf000051_0001
wherein each R29 and R30 is independently hydrogen and alkyl; each R31, R32, R33, and R34 is independently hydrogen, alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, or heteroaryl, wherein each alkyl, alkenyl, alkynyl, heteroalkyl, cycloalkyl, heterocyclyl, aryl, and heteroaryl is optionally substituted with one or more RG; RG is hydrogen or alkyl; each xa and xb is an integer from 0 to 100, wherein each xa and xb cannot simultaneously be 0; and xc is an integer from 1 to 10,000. [0199] In some embodiments, each R29 and R30 is independently hydrogen. In some embodiments, each R29 and R30 is independently alkyl. In some embodiments, one of R31 and R32 is hydrogen and the other of R31 and R32 is alkyl (e.g., methyl). In some embodiments, each R33 and R34 is independently hydrogen. [0200] In some embodiments, xa is an integer greater than 0 and xb is an integer greater than 0. In some embodiments, xb is 0. In some embodiments, xb is an integer between 1 and 50 (inclusive), between 1 and 25, between 1 and 10, or between 1 and 5. In some embodiments, xb is 1. In some embodiments, xa is 0. In some embodiments, xa is an integer between 1 and 50 (inclusive), between 1 and 25, between 1 and 10, or between 1 and 5. In some embodiments, xa is 1. [0201] In some embodiments, xc is an integer from 1 to 10,000, from 1 to 5,000, from 1 to 2,500, from 1 to 1,000, from 1 to 750, from 1 to 500, from 1 to 250, from 1 to 100, or from 1 to 50. [0202] In some embodiments, the synthetic polymer having a structure of Formula (X) is selected from poly(lactic-co-glycolic acid) (PLGA), polyglycolic acid (PGA), and polylactic acid (PLA). In some embodiments, the synthetic polymer having a structure of Formula (X) is PLGA. In some embodiments, the synthetic polymer having a structure of Formula (X) is PGA. In some embodiments, the synthetic polymer having a structure of Formula (X) is PLA. [0203] In some embodiments, the synthetic polymer further comprises a polyethylene glycol moiety. For example, the synthetic polymer comprising a structure of Formula (X) can further comprise a PEG moiety. An example of a synthetic polymer comprises mPEG-PLA. [0204] In some embodiments, a nanoparticle comprises a single type of synthetic polymer. In some embodiments, the nanoparticle comprises a plurality of synthetic polymers. For example, a nanoparticle of the present disclosure can comprise PLGA, or can comprise PLGA and a second synthetic polymer. [0205] The amount of a synthetic polymer encapsulated and/or entrapped within the nanoparticle can vary depending on the identity of the synthetic polymer or plurality of synthetic polymer. For example, the amount of a synthetic polymer can be between 0.05% and 40% by weight of synthetic polymers to the total weight of the nanoparticle. In some embodiments, the amount of a synthetic polymer in the nanoparticle is greater than about 0.05%. In some embodiments, the amount of a synthetic polymer in the nanoparticle is greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, or greater than about 40% by weight of synthetic polymers to the total weight of the nanoparticle. In some embodiment, the amount of a synthetic polymer in the nanoparticle is between 0.5% and 20% by weight of synthetic polymers to the total weight of the nanoparticle, or between 1% and 10% by weight of a synthetic polymer to the total weight of the nanoparticle, or between 2% to 5% by weight of a synthetic polymer to the total weight of the nanoparticle. [0206] In some embodiments, a nanoparticle or plurality of nanoparticles further comprises an alkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a PEG described herein). A polyalkylene glycol can be any size, for example, a PEG between 2 PEG subunits and 5,000 subunits. In some embodiments, at least about 5% of the nanoparticles in the plurality comprise a PEG. In some embodiments, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 99% of the nanoparticles in the plurality comprise a PEG. Load Components [0207] In some embodiments, a nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle) further comprises a load component. In some embodiments, the load component is an additional biological component (e.g., a polymeric biological component), for example, a nucleic acid or polypeptide. In some embodiments, the load component is a nucleic acid. In some embodiments, the nucleic acid is double stranded. In some embodiments, the nucleic acid is single stranded. In some embodiments, the load component is an oligonucleotide. In some embodiments, the load component is a single stranded DNA. In some embodiments, the load component is a single stranded RNA. In some embodiments, the load component is a double stranded DNA. In some embodiments, the load component is a double stranded RNA. In some embodiments, the load component is mRNA. In some embodiments, the load component is siRNA. In some embodiments, the load component is an antisense oligomer (e.g., PNA, DNA, morpholinos (also known as PMOs), pyrrolidine-amide oligonucleotide mimics (POMs), morpholinoglycine oligonucleotides (MGOs), and methyl phosphonates. [0208] In some embodiments, the load component is a nucleic acid (e.g., DNA) between 5 and 250 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 10 and 200 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 18 and 100 nucleotides in length). In some embodiments, the load component is a nucleic acid (e.g., DNA) between 20 and 80 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 25 and 70 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 35 and 65 nucleotides in length. In some embodiments, the load component is a nucleic acid (e.g., DNA) between 20 and 40 nucleotides in length. In some embodiments, the load component is a single stranded nucleic acid (e.g., DNA) between 20 and 70 nucleotides in length. In some embodiments, the load component is a double stranded nucleic acid (e.g., DNA), with each strand being independently between 20 and 70 nucleotides in length. [0209] In some embodiments, the load component is a nucleic acid and comprises one or more phosphorothioate linkages at a terminus (e.g., the 5’ terminus and/or the 3’ terminus). In some embodiments, the load component is a nucleic acid and comprises one or more phosphorothioate linkages at an internucleotide linkage. In some embodiments, the load component comprises more than one phosphorothioate linkages (e.g., 2, 3, or 4) at each terminus, for example, at each of the 3’ and 5’ termini. In some embodiments, the nucleic acid comprises 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more phosphorothioate internucleotide linkages. [0210] In some embodiments, the load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence to which the PNA oligomer, e.g., a clamp system, e.g., a tail clamp system, e.g., a PNA oligomer comprising a sequence of Compound No. 1 as described herein, has Watson Crick homology. In some embodiments, a load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Hoogsteen homology. In some embodiments, a load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence that is within 1,000, 500, 200, 100, 75, 60, or 40 base pairs of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Watson Crick homology. In some embodiments, the load component comprises a nucleic acid having a sequence that is the same or the complement of a sequence that is within 1,000, 500, or 200 base pairs of a sequence to which the PNA oligomer, e.g., a tcPNA, e.g., a PNA oligomer comprising a sequence of Compound No.1 as described herein, has Hoogsteen homology. [0211] In some embodiments, a nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle) comprises a PNA oligomer and a load component. In some embodiments, the ratio of PNA oligomer to load component is equal (i.e.1:1). In some embodiments, the ratio of PNA oligomer to load component is greater than 1:1, for example, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.5, about 1:2, about 1:3, about 1:4, about 1:5, about 1:10, about 1:20, about 1:25, about 1:50, about 1:75, or about 1:100 PNA oligomer to load component. In some embodiments, the ratio of load component to PNA oligomer greater than 1:1, for example, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.5, about 1:2, about 1:3, about 1:4, about 1:5, about 1:10, about 1:20, about 1:25, about 1:50, about 1:75, or about 1:100 load component to PNA oligomer. In some embodiments, the ratio of PNA oligomer to load component is about 1:1. In some embodiments, the ratio of PNA oligomer to load component is about 1:2. In some embodiments, the ratio of PNA oligomer to load component is about 1:5. [0212] A nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle; e.g. PLGA) described herein comprises a nucleic acid mimic, for example, a PNA oligomer (e.g., a tcPNA), and related preparations and methods of making and using the same. In some embodiments, the PNA comprises a PNA oligomer. In some embodiments, the PNA comprises a tcPNA oligomer. In some embodiments, the PNA oligomer is a tcPNA oligomer disclosed herein. [0213] In some embodiments, the PNA is a PNA oligomer comprising greater than 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 PNA subunits. In some embodiments, the PNA is a PNA oligomer comprising between 10 to 25 PNA subunits. In some embodiments, the PNA is a PNA oligomer comprising between 20 to 35 PNA subunits. In some embodiments, the PNA is a PNA oligomer comprising between about 2 to 50 PNA subunits, e.g., between about 10 and 45, 15 and 40, 17 and 35, 18 and 30, and 25 and 38 PNA subunits. [0214] In some embodiments, the PNA oligomer is a tail-clamp PNA oligomer (tcPNA). In some embodiments, the PNA oligomer has a sequence shown in Table 3 herein. In some embodiments, the PNA oligomer comprises a trilysine sequence (i.e., KKK) on the N-terminus. In some embodiments, the PNA oligomer comprises a trilysine sequence (i.e., KKK) on the C- terminus. In some embodiments, the PNA oligomer comprises a trilysine sequence (i.e., KKK) on both the N-terminus and the C-terminus. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 2-thiouracil nucleobase. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 2,6-diaminopurine nucleobase. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 7-deazaguanine nucleobase. In some embodiments, the PNA oligomer comprises a Gly-Gly sequence and a 2-aminopyridine nucleobase. [0215] In some embodiments, the PNA oligomer has the sequence of Compound No.1. In some embodiments, the PNA oligomer has the sequence of Compound No.2. In some embodiments, the PNA oligomer has the sequence of Compound No.3. In some embodiments, the PNA oligomer has the sequence of Compound No.4. In some embodiments, the PNA oligomer has the sequence of Compound No.5. In some embodiments, the PNA oligomer has the sequence of Compound No.6. In some embodiments, the PNA oligomer has the sequence of Compound No. 7. In some embodiments, the PNA oligomer has the sequence of Compound No.8. [0216] A nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle) can comprise a single PNA oligomer or a plurality of PNA oligomers. In some embodiments, a nanoparticle comprises 1 PNA oligomer. In some embodiments, a nanoparticle comprises a plurality of PNA oligomers, for example, at least 2 PNAs, at least 3 PNAs, at least 4 PNAs, at least 5 PNAs, at least 6 PNAs, at least 7 PNAs, at least 8 PNAs, at least 9 PNAs, at least 10 PNAs, at least 15 PNAs, at least 20 PNAs, at least 25 PNAs, at least 30 PNAs, at least 40 PNAs, at least 50 PNAs, at least 60 PNAs, at least 70 PNAs, at least 80 PNAs, at least 90 PNAs, at least 100 PNAs, at least 150 PNAs, at least 200 PNAs, at least 300 PNAs, at least 400 PNAs, at least 500 PNAs, at least 600 PNAs, at least 700 PNAs, at least 800 PNAs, at least 900 PNAs, or at least 1,000 PNAs. In some embodiments, a nanoparticle comprises 10-50 PNA oligomers. In some embodiments, a nanoparticle comprises 2-5 PNA oligomers. In some embodiments, a nanoparticle comprises 3- 10 PNA oligomers. In some embodiments, a nanoparticle comprises 5-20 PNA oligomers. In some embodiments, a nanoparticle comprises 10-35 PNA oligomers. In some embodiments, a nanoparticle comprises 10-100 PNA oligomers. In some embodiments, a nanoparticle comprises between 100-1,000 PNA oligomers. In some embodiments, a nanoparticle comprises between 500-1,000 PNA oligomers. [0217] The amount of a PNA (e.g., a PNA oligomer) encapsulated and/or entrapped within the nanoparticle (e.g., an LNP, or a synthetic nanoparticle) can vary depending on the identity of the PNA or plurality of PNAs. For example, the amount of PNA can be between 0.001% and 50% by weight of PNAs to the total weight of the nanoparticle. In some embodiments, the amount of PNA in the nanoparticle is greater than about 0.001%, e.g., greater than about 0.05%, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, greater than about 40%, greater than about 45%, or greater than about 50% by weight of PNA to the total weight of the nanoparticle. In some embodiments, the amount of PNA oligomer in the nanoparticle is greater than about 0.001%, greater than about 0.05%, greater than about 0.1%, greater than about 0.5%, greater than about 1%, greater than about 2%, greater than about 3%, greater than about 4%, greater than about 5%, greater than about 6%, greater than about 7%, greater than about 8%, greater than about 9%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 20%, greater than about 25%, greater than about 30%, greater than about 35%, greater than about 40%, greater than about 45%, or greater than about 50% by weight of PNA oligomer to the total weight of the nanoparticle. In some embodiments the amount of PNA oligomer in the nanoparticle is between 0.001% and 50% by weight of PNA oligomers to the total weight of the nanoparticle, or between 0.001% and 30% by weight of PNA oligomers to the total weight of the nanoparticle, or between 1% and 25% by weight of PNA oligomers to the total weight of the nanoparticle, or between 1% and 10% by weight of PNA oligomer to the total weight of the nanoparticle, or between 2% to 5% by weight of PNA oligomer to the total weight of the nanoparticle. [0218] A nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle) described herein can comprise a single type of PNA (e.g., a single type of PNA oligomer, or a PNA oligomer of a single sequence), or can comprise multiple types of PNAs. In some embodiments, the nanoparticle comprises a single type of PNA. In some embodiments, the nanoparticle comprises a plurality of types of PNAs (e.g., a plurality of PNA oligomers). [0219] A nanoparticle (e.g., an LNP, or a synthetic polymer nanoparticle) described herein (e.g., comprising an PNA, and optionally a load component) can have a certain ratio of components. For example, the LNP described herein can comprise a particular ratio of a lipid or a plurality of lipids to an PNA. In some embodiments, the ratio of a plurality of lipids to a PNA (e.g., a PNA oligomer) is between 100:1 to 1:100. PNA. In some embodiments, the ratio of a plurality of lipids to a PNA (e.g., a PNA oligomer) is about 75:1 to 1:75, about 60:1 to 1:60, 100:1 to about 5:1, 80:1 to about 5:1, 60:1 to about 5:1, or about 50:1 to about 5:1. In some embodiments, the ratio of a plurality of lipids to an PNA (e.g., a PNA oligomer) is about 100:1, about 95:1, about 90:1, about 85:1, about 80:1, about 75:1, about 70:1, about 65:1, about 60:1, about 55:1, about 50:1, about 45:1, about 40:1, about 35:1, about 30:1, about 28:1, about 26:1, about 24:1, about 25:1, about 22:1, about 20:1, about 18:1, about 16:1, about 14:1, about 12:1, about 10:1, about 8:1, about 6:1, about 4:1, about 2:1, about 1:1, about 1:2, about 1:4, about 1:6, about 1:8, about 1:10, about 1:12, about 1:14, about 1:16, about 1:18, about 1:20, about 1:22, about 1:24, about 1:25, about 1:26, about 1:28, about 1:30, about 1:35, about 1:40, about 1:45, about 1:50, about 1:55, about 1:60, about 1:65, about 1:70, about 1:75, about 1:80. about 1:85, about 1:90, about 1:95, or about 1:100. [0220] In some embodiments, a LNP described herein has a diameter between 5 and 500 nm, e.g., between 10 and 400 nm, 20 and 350 nm, 25 and 325 nm, 30 and 300 nm, 50 and 250 nm, 60 and 200 nm, 75 and 190 nm, 80 and 180 nm, 100 and 200 nm, 200 and 300 nm, and 150 and 250 nm. The diameter of an LNP can be determined, for example, dynamic light scattering, transmission electron microscopy (TEM) or scanning electron microscopy (SEM). In some embodiments, a LNP has a diameter between 50 and 100 nm, between 70 and 100 nm, and between 80 and 100 nm. In some embodiments, a LNP has a diameter of about 90 nm. In some embodiments, a LNP described herein has a diameter greater than about 30 nm. In some embodiments, a LNP has a diameter greater than about 35 nm, greater than about 40 nm, greater than about 45 nm, greater than about 50 nm, greater than about 60 nm, greater than about 70 nm, greater than about 80 nm, greater than about 90 nm, greater than about 100 nm, greater than about 120 nm, greater than about 140 nm, greater than about 160 nm, greater than about 180 nm, greater than about 200 nm, greater than about 225 nm, greater than about 250 nm, greater than about 275 nm, or greater than about 300 nm. In some embodiments, a LNP has a diameter greater than about 70 nm. In some embodiments, an LNP has a diameter greater than about 90 nm. In some embodiments, an LNP has a diameter greater than about 180 nm. [0221] In some embodiments, a plurality of LNPs described herein has an average diameter greater than about 30 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 35 nm, greater than about 40 nm, greater than about 45 nm, greater than about 50 nm, greater than about 60 nm, greater than about 70 nm, greater than about 80 nm, greater than about 90 nm, greater than about 100 nm, greater than about 120 nm, greater than about 140 nm, greater than about 160 nm, greater than about 180 nm, greater than about 200 nm, greater than about 220 nm, greater than about 240 nm, greater than about 260 nm, greater than about 280 nm, or greater than about 300 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 70 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 90 nm. In some embodiments, a plurality of LNPs has an average diameter greater than about 180 nm. [0222] In some embodiments, a synthetic polymer nanoparticle or a plurality of nanoparticles have an average diameter between 5 and 500 nm, e.g., between 10 and 400 nm, 20 and 350 nm, 25 and 325 nm, 30 and 300 nm, 50 and 250 nm, 60 and 200 nm, 75 and 190 nm, 80 and 180 nm, 100 and 200 nm, 200 and 300 nm, and 150 and 250 nm. In some embodiments, a plurality of nanoparticles has an average diameter between 150 and 300 nm, between 35 and 100 nm, and between 75 and 220 nm. [0223] In some embodiments, at least 5% (e.g., at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99%) of the nanoparticles of a plurality of nanoparticles have a diameter between 5 and 500 nm. The nanoparticles can range in diameter from about 10 to about 400 nm, about 20 to about 300 nm, about 25 to about 250 nm, about 30 to about 150 nm, about 35 to about 125 nm, about 40 to about 100 nm, about 80 to about 180 nm, about 100 to about 200 nm, about 200 to about 300 nm, and about 150 to about 250 nm. In some embodiments, the nanoparticles can range in diameter from about 100 to about 200 nm, about 20 to about 100 nm, about 20 to about 80 nm, and from about 20 to about 60 nm. [0224] In some embodiments, a nanoparticle or plurality of nanoparticles described herein has an average neutral to negative surface charge of less than -100 mv, for example, less than -90 mv, less than -80 mv, less than -70 mv, less than -60 mv, less than -50 mv, less than -40 mv, less than -30 mv, or less than -20 mv. In some embodiments, a nanoparticle or plurality of nanoparticles has a neutral to negative surface charge of between -100 mv and 100 mv, between -75 mv to 0, or between -50 mv and -10 mv. [0225] In some embodiments, at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, at least about 70%, at least about 80%, at least about 90%, at least about 95%, or at least about 99% of the nanoparticles of a plurality of nanoparticles have an average neutral to negative surface charge of less than about -100 mv. In some embodiments, a nanoparticle or plurality of nanoparticles has an average neutral to negative surface charge of between -100 mv and 100 mv, between -75 mv and 0, or between -50 mv and -10 mv. Target Sequences [0226] In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence. In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence that comprises at least seven base pairs. In some embodiments, the specific location in the nucleic acid sequence comprises only purines. In some embodiments, the specific location in the nucleic acid sequence comprises a mixture of purines and pyrimidines. In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence corresponding to a sequence provided in Table 1.
Table 1. Examples of binding regions in a target nucleic acid sequence.
Figure imgf000060_0001
Legend: each sequence is a region within a target nucleic acid sequence (in the 5′ to 3′ direction); each P is a purine nucleobase (adenine or guanine); and each X is a pyrimidine nucleobase (cytosine, thymine, or uracil). [0227] In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence. In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence at a specific location in the nucleic acid sequence that comprises at least seven nucleobases. In some embodiments, the specific location in the nucleic acid sequence comprises only purines. In some embodiments, the specific location in the nucleic acid sequence comprises a mixture of purines and pyrimidines. In some embodiments, the PNA oligomer (e.g., a tcPNA oligomer) binds to a target nucleic acid sequence corresponding to a sequence listed in Table 2.
Table 2. Examples of binding regions in a target nucleic acid sequence.
Figure imgf000061_0001
Legend: each sequence is a region within a target nucleic acid sequence (in the 5′ to 3′ direction); each G is guanine, each A is adenine; each X is a pyrimidine (cytosine, thymine, or uracil). Pharmaceutical Compositions of the invention. [0228] A pharmaceutical composition of the invention can be used, for example, before, during, or after treatment of a subject with, for example, another pharmaceutical agent. [0229] Subjects can be, for example, elderly adults, adults, adolescents, pre-adolescents, children, toddlers, infants, neonates, and non-human animals. In some embodiments, a subject is a patient. [0230] A pharmaceutical composition of the invention can be a combination of any pharmaceutical compounds described herein with other chemical components, such as carriers, stabilizers, diluents, dispersing agents, suspending agents, thickening agents, and/or excipients. The pharmaceutical composition facilitates administration of the compound to an organism. Pharmaceutical compositions can be administered in therapeutically-effective amounts as pharmaceutical compositions by various forms and routes including, for example, intravenous, subcutaneous, intramuscular, oral, parenteral, ophthalmic, subcutaneous, transdermal, nasal, vaginal, and topical administration. [0231] A pharmaceutical composition can be administered in a local manner, for example, via injection of the compound directly into an organ, optionally in a depot or sustained release formulation or implant. Pharmaceutical compositions can be provided in the form of a rapid release formulation, in the form of an extended release formulation, or in the form of an intermediate release formulation. A rapid release form can provide an immediate release. An extended release formulation can provide a controlled release or a sustained delayed release. [0232] For oral administration, pharmaceutical compositions can be formulated by combining the active compounds with pharmaceutically-acceptable carriers or excipients. Such carriers can be used to formulate liquids, gels, syrups, elixirs, slurries, or suspensions, for oral ingestion by a subject. Non-limiting examples of solvents used in an oral dissolvable formulation can include water, ethanol, isopropanol, saline, physiological saline, DMSO, dimethylformamide, potassium phosphate buffer, phosphate buffer saline (PBS), sodium phosphate buffer, 4-2-hydroxyethyl-1- piperazineethanesulfonic acid buffer (HEPES), 3-(N-morpholino)propanesulfonic acid buffer (MOPS), piperazine-N,N′-bis(2-ethanesulfonic acid) buffer (PIPES), and saline sodium citrate buffer (SSC). Non-limiting examples of co-solvents used in an oral dissolvable formulation can include sucrose, urea, cremaphor, DMSO, and potassium phosphate buffer. [0233] Pharmaceutical preparations can be formulated for intravenous administration. The pharmaceutical compositions can be in a form suitable for parenteral injection as a sterile suspension, solution or emulsion in oily or aqueous vehicles, and can contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Pharmaceutical formulations for parenteral administration include aqueous solutions of the active compounds in water-soluble form. Suspensions of the active compounds can be prepared as oily injection suspensions. Suitable lipophilic solvents or vehicles include fatty oils such as sesame oil, or synthetic fatty acid esters, such as ethyl oleate or triglycerides, or liposomes. The suspension can also contain suitable stabilizers or agents that increase the solubility of the compounds to allow for the preparation of highly concentrated solutions. Alternatively, the active ingredient can be in powder form for constitution with a suitable vehicle, e.g., sterile pyrogen-free water, before use. [0234] The active compounds can be administered topically and can be formulated into a variety of topically administrable compositions, such as solutions, suspensions, lotions, gels, pastes, medicated sticks, balms, creams, and ointments. Such pharmaceutical compositions can contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives. [0235] The compounds of the invention can be applied topically to the skin, or a body cavity, for example, oral, vaginal, bladder, cranial, spinal, thoracic, or pelvic cavity of a subject. The compounds of the invention can be applied to an accessible body cavity. [0236] The compounds can also be formulated in rectal compositions such as enemas, rectal gels, rectal foams, rectal aerosols, suppositories, jelly suppositories, or retention enemas, containing conventional suppository bases such as cocoa butter or other glycerides, and synthetic polymers such as polyvinylpyrrolidone, and PEG. In suppository forms of the compositions, a low-melting wax such as a mixture of fatty acid glycerides, optionally in combination with cocoa butter, can be melted. [0237] In practicing the methods of treatment or use provided herein, therapeutically-effective amounts of the compounds described herein are administered in pharmaceutical compositions to a subject having a disease or condition to be treated. In some embodiments, the subject is a mammal such as a human. A therapeutically-effective amount can vary widely depending on the severity of the disease, the age and relative health of the subject, the potency of the compounds used, and other factors. The compounds can be used singly or in combination with one or more therapeutic agents as components of mixtures. [0238] Pharmaceutical compositions can be formulated using one or more physiologically- acceptable carriers comprising excipients and auxiliaries, which facilitate processing of the active compounds into preparations that can be used pharmaceutically. Formulations can be modified depending upon the route of administration chosen. Pharmaceutical compositions comprising a compound described herein can be manufactured, for example, by mixing, dissolving, emulsifying, encapsulating, entrapping, or compression processes. [0239] The pharmaceutical compositions can include at least one pharmaceutically-acceptable carrier, diluent, or excipient and compounds described herein as free-base or pharmaceutically- acceptable salt form. Pharmaceutical compositions can contain solubilizers, stabilizers, tonicity enhancing agents, buffers and preservatives. [0240] Methods for the preparation of compositions comprising the compounds described herein include formulating the compounds with one or more inert, pharmaceutically-acceptable excipients or carriers to form a solid, semi-solid, or liquid composition. Solid compositions include, for example, powders, tablets, dispersible granules, capsules, and cachets. Liquid compositions include, for example, solutions in which a compound is dissolved, emulsions comprising a compound, or a solution containing liposomes, micelles, or nanoparticles comprising a compound as disclosed herein. Semi-solid compositions include, for example, gels, suspensions and creams. The compositions can be in liquid solutions or suspensions, solid forms suitable for solution or suspension in a liquid prior to use, or as emulsions. These compositions can also contain minor amounts of nontoxic, auxiliary substances, such as wetting or emulsifying agents, pH buffering agents, and other pharmaceutically-acceptable additives. [0241] Non-limiting examples of dosage forms suitable for use in the invention include liquid, powder, gel, nanosuspension, nanoparticle, microgel, aqueous or oily suspensions, emulsion, and any combination thereof. [0242] Non-limiting examples of pharmaceutically-acceptable excipients suitable for use in the invention include binding agents, disintegrating agents, anti-adherents, anti-static agents, surfactants, anti-oxidants, coating agents, coloring agents, plasticizers, preservatives, suspending agents, emulsifying agents, anti-microbial agents, spheronization agents, and any combination thereof. [0243] A composition of the invention can be, for example, an immediate release form or a controlled release formulation. An immediate release formulation can be formulated to allow the compounds to act rapidly. Non-limiting examples of immediate release formulations include readily dissolvable formulations. A controlled release formulation can be a pharmaceutical formulation that has been adapted such that release rates and release profiles of the active agent can be matched to physiological and chronotherapeutic requirements or, alternatively, has been formulated to effect release of an active agent at a programmed rate. Non-limiting examples of controlled release formulations include granules, delayed release granules, hydrogels (e.g., of synthetic or natural origin), other gelling agents (e.g., gel-forming dietary fibers), matrix-based formulations (e.g., formulations comprising a polymeric material having at least one active ingredient dispersed through), granules within a matrix, polymeric mixtures, and granular masses. [0244] In some embodiments, a controlled release formulation is a delayed release form. A delayed release form can be formulated to delay a compound’s action for an extended period of time. A delayed release form can be formulated to delay the release of an effective dose of one or more compounds, for example, for about 4, about 8, about 12, about 16, or about 24 hours. [0245] A controlled release formulation can be a sustained release form. A sustained release form can be formulated to sustain, for example, the compound’s action over an extended period of time. A sustained release form can be formulated to provide an effective dose of any compound described herein (e.g., provide a physiologically-effective blood profile) over about 4, about 8, about 12, about 16 or about 24 hours. [0246] Described herein are nanoparticles (e.g. lipid nanoparticles (LNPs), synthetic polymer nanoparticles, (e.g., poly(lactic-co-glycolic acid (PLGA) nanoparticles) comprising a PNA (e.g., a PNA oligomer, e.g., a tcPNA oligomer) and methods of making and using the same. [0247] In some embodiments, a nanoparticle is a LNP and refers to a particle that comprises a lipid and a nucleic acid mimic, for example, a PNA. A LNP can further comprise one or more lipids, for example, at least one or more of an ionizable lipid, phospholipid, a sterol, or an alkylene glycol-containing lipid (e.g., a PEG-containing lipid), as well as a load component (e.g., a nucleic acid). [0248] In some embodiments, a nanoparticle is a synthetic polymer nanoparticle and refers to a particle that comprises a synthetic polymer (e.g., PLGA) and a nucleic acid mimic, for example, one or more PNA oligomers. A synthetic polymer nanoparticle may further comprise a synthetic polymer, or a plurality of synthetic polymers, for example, at least one or more of a non- naturally occurring polymer, including co-polymers, block polymers, block co-polymers, polymer mixtures, and polymer blends, as well as a load component (e.g., a nucleic acid). Methods of Making Peptide Nucleic Acids [0249] Described herein are methods for making peptide nucleic acid (PNA) oligomers comprising a pyrimidine-compliant PNA subunit (e.g., PC PNA subunit), and compositions thereof. A PNA oligomer comprising a PC PNA subunit can be prepared through the stepwise addition of individual subunits, e.g., by reacting the amine of a first PNA subunit with a carboxylic acid of a second PNA subunit (e.g., an activated form of a carboxylic acid of a second subunit). In some embodiments, a PNA oligomer is prepared by the stepwise addition of a first amino acid (e.g., lysine) to a second or subsequent amino acid (e.g., lysine). In some embodiments, a PNA oligomer is prepared by the stepwise addition of a PNA subunit to an amino acid (e.g. a lysine). In some embodiments, a PNA oligomer is prepared by the stepwise addition of an amino acid (e.g., a lysine) to a PNA subunit. A PNA oligomer can also be prepared through coupling smaller PNA oligomers comprising more than one subunit (e.g., through block synthesis). [0250] A PNA oligomer can be synthesized in solution or on a solid support, or by using a combination of both techniques. PNA oligomers can be prepared using automated methods, for example, using an automated peptide synthesizer. [0251] In some embodiments, the PNA oligomer is synthesized on a solid support. A solid support can be supplied in the form beads, and can be of different shapes (e.g. spherical beads) and sizes (e.g., 100 mesh, 150 mesh, 200 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, or 500 mesh). A solid support can comprise, for example, plastic, polymer, polystyrene, polyacrylate, polyacrylamide, or polyethyleneglycol. Polymers used in solid supports can be cross-linked (e.g., with 1-2% divinylbenzene), or uncrosslinked. A solid support can be a functionalized polymer (e.g., a Merrifield resin, Wang resin, brominated Wang resin, 4-(1′,1′- dimethyl-1′-hydroxypropyl)phenoxyacetyl (DHPP) resin, Kaiser resin, 4-hydroxymethyl- phenylacetamidomethyl (PAM) resin, benzhydrylamine (BHA) resin, 4-methylbenzhydrylamine (MBHA) resin, diphenyldiazomethane (PDDM) resin, TentaGel resin, 4-(hydroxymethyl) phenoxyacetic acid (HMPA) resin, 4-(4-hydroxymethyl-3-methoxyphenoxy)butyric acid (HMPB) resin, 2-chlorotrityl resin, 4-carboxytrityl resin, Rink acid resin, Rink amide resin, peptide amide linker (PAL) resin, Sieber resin, 4-(hydroxymethyl)benzoylaminomethyl (HMBA) resin, 4-sulfamoylbenzoyl resin, or 4-(4-formyl-3-methoxyphenoxy)ethyl (FMP) resin). A solid support can comprise a functional group suitable for coupling to a subunit. In some embodiments, the functional group is an amine, a carboxylic acid, a halide, an oxime, a hydroxyl, a sulfamoyl, a hydrazine, or an aldehyde. In some embodiments, the functional group is an amine. Examples of solid supports include Merrifield resin, Wang resin, MBHA resin, and Rink amide resin. In some embodiments, the PNA oligomer is synthesized on rink amide TentaGel resin (Rapp polymer, R28023). [0252] In some embodiments, the PNA oligomer is formed by anchoring a first subunit onto a solid support. In some embodiments, the first subunit is an amino acid (e.g., lysine) or a PNA subunit. The first subunit can comprise one or more protecting groups, for example, a PNA subunit comprising a nucleobase that optionally comprises a protecting group, a PNA subunit with an activated carboxylic acid, a PNA subunit with a protected amine, a PNA subunit with an α-side chain that is optionally protected, a PNA subunit with a β-side chain that is optionally protected, a PNA subunit with a γ-side chain that is optionally protected, or any combination thereof. The first subunit can comprise a protecting group (PG) on the amino terminus, such as Fmoc or Boc. The anchoring of the first subunit to a solid support can further require use of a base (e.g., an organic base, e.g., diisopropylethylamine (DIPEA), triethylamine (TEA), collidine, pyridine, piperidine, methyldicyclohexylamine (MDCHA). In some embodiments, the anchoring of the first subunit to a solid support can further require an activating agent such as a carbodiimide (e.g., N,N’-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC)), benzotriazole (e.g., hydroxybenzotriazole (HOBt), 1-hydroxy-7-azabenzotriazole (HOAt), 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3H)-one (DEPBT)), a phosphonium salt (e.g. (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), bromotripyrrolidinophosphonium hexafluorophosphate (PyBroP)), a uronium salt (e.g., hexafluorophosphate benzotriazole tetramethyl uronium (HBTU), 2-(1H-benzotriazole-1-yl)- 1,1,3,3-tetramethylaminium tetrafluoroborate (TBTU), hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU), O-(7-azabenzotriazol-1-yl)-N,N,N’N’-tetramethyl uronium tetrafluoroborate (TATU), O-(ethoxycarbonyl)cyanomethylenamino]-N,N,N’,N’-tetra methyluronium tetrafluoroborate (TOTU)), or a fluoroformamidinium salt (e.g., tetramethylfluoroformamidinium hexafluorophosphate (TFFH), bis(tetramethylene)fluoroformamidinium hexafluorophospnate (BTFFH)). The reaction that anchors the subunit to the solid support can be carried out in any appropriate solvent (e.g., dimethylformamide (DMF), dimethylacetamide (DMA), dimethylsulfoxide (DMSO), N- methylpyrrolidone (NMP), tetrahydrofuran (THF), dioxane, dichloromethane (DCM), or mixtures thereof. Generally, the solvent is an aprotic organic solvent. Once anchored to a solid support, the subunit can then be extended by one or more additional subunits (e.g. PNA subunit, amino acid, linker, label, solubility enhancer, etc.) to form an oligomer (e.g., a PNA oligomer). [0253] Synthesis of a PNA oligomer on a solid support typically entails repetition of a cycle of steps to extend the growing PNA oligomer. In general, each cycle comprises three steps, deprotection, coupling and capping. [0254] In some embodiments, the first step of each cycle involves removal of a protecting group (PG) such as Fmoc or Boc from the terminus (e.g., the N-terminus) of the solid-supported PNA using a suitable reagent (i.e. deprotection). In some embodiments, removal of the PG is achieved with an organic base (e.g., piperidine, 1,8-diazabicyclo5.4.0]undec-7-ene (DBU), DIPEA or collidine) or an acid (e.g., TFA, trifluoromethanesulfonic acid (TFMSA), hydrochloric acid, or hydrofluoric acid). [0255] In some embodiments, the second step of the cycle (i.e. the coupling step) involves contacting the solid-supported PNA with a second or subsequent subunit(s) dissolved in a solvent (e.g., DMF, NMP, or a mixture of solvents). The second step of the cycle can also involve activation of the free carboxylic acid of the second or subsequent subunit(s). Activation can require use of a base (e.g., DIPEA, TEA, collidine, pyridine, or piperidine). In some embodiments, the carboxylic acid of the first subunit is activated with an activating agent such as a carbodiimide (e.g., DCC, DIC), benzotriazole (e.g., HOBt, HOAt, DEPBT), a phosphonium salt (e.g. BOP, PyBOP, PyBrop) or uronium salt (e.g., HBTU, TBTU, HATU, TATU, TOTU), or a fluoroformamidinium salt (e.g., TFFH, BTFFH). Once activated, the carboxyl group can then react with the PG-free terminus of the solid-supported PNA to form a peptide bond and extend the PNA oligomer. [0256] In some embodiments, an excess of the first subunit is used. In some embodiments, the ratio of the first subunit to the second subunit is about 1:1, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.4, about 1:1.5; about 1.1.75; about 1:2, about 1:2.5, about 1:3, about 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10. In some embodiments, an excess of the second or subsequent subunit(s) is used. In some embodiments, the ratio of the second or subsequent subunit(s) to the first subunit is about 1:1, about 1:1.1, about 1:1.2, about 1:1.3, about 1:1.4, about 1:1.5; about 1.1.75; about 1:2, about 1:2.5, about 1:3, 1:4, about 1:5, about 1:6, about 1:7, about 1:8, about 1:9, or about 1:10. [0257] The third step of the cycle can entail capping. Capping is used to terminate elongation of any particular oligomer that has not undergone elongation during the coupling step. In this way, oligomers possessing a deleted subunit are not created and can be easily purified away from the desired product post synthesis. [0258] In some embodiments, the subunit is a PNA subunit, an amino acid (e.g., lysine), a linker a label, or a solubility enhancer. In some embodiments, the linker is a polyalkylene glycol (e.g., a polyethylene glycol (PEG), e.g., a C6-C20 PEG linker (e.g., a PEG2 or PEG3 linker as illustrated in FIGS.8B and 8D, respectively). In some embodiments, the subunit is a C12-PEG linker. In some embodiments, a PNA oligomer comprises one type of subunit. In some embodiments a PNA oligomer comprises more than one type of subunit. In some embodiments, a PNA oligomer comprises all types of subunits (e.g. PNA subunits, amino acids, linkers, labels, solubility enhancers and the like). [0259] In some embodiments, the solid-supported PNA is washed with an appropriate solvent (e.g., dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, tetrahydrofuran, dioxane, dichloromethane, or mixtures thereof) and filtered between each coupling step. In some embodiments, each coupling step is also carried out in one or more of these solvents. In some embodiments, the solid-supported PNA oligomer is extended through multiple cycles of the above described steps. These steps can be carried out manually, or by using the semi-automated or fully-automated instruments discussed above, or any combination of these methods. [0260] Once the desired subunits and other components are added to the PNA oligomer, the synthesis can be terminated, or the PNA oligomer can be modified further, for example, through acetylation or other end-capping methods. In some embodiments, the PNA oligomer is subjected to selective deprotection of the PNA side chains or PNA nucleobases. In some embodiments, the PNA oligomer is fully deprotected before cleavage. In some embodiments, the fully deprotected PNA oligomer is modified prior to cleavage. [0261] In some embodiments, a final step involving cleavage of the PNA oligomer from the solid support is carried out. This step can involve treatment of the solid-supported PNA oligomer with an acid, base, nucleophile, phenol (e.g. meta cresol), thiol, or photolysis, or combination of two or more of the foregoing. For example, a PNA oligomer can be cleaved from the solid support through incubation with an acid (e.g., trifluoroacetic acid, hydrofluoric acid, trifluoromethanesulfonic acid, trimethylsilyl trifluoromethanesulfonate, hydrobromic acid) or in some cases an alcohol (e.g., hexafluoroisopropanol). In some embodiments, cleavage of the PNA oligomer from the solid support can also effect removal of the protecting groups from the PNA side chains and/or the PNA nucleobases. In some embodiments, scavengers such as water, sulfides, thiols, phenols, and silanes can be used in the final cleavage step to prevent side- reactions or racemization of any chiral centers in the PNA oligomer. In some embodiments, residual acid or other reagents or side-products from the cleavage step can be removed through trituration, filtration, dialysis, chromatography, or other purification methods. [0262] A PNA oligomer can be synthesized using solution phase synthesis. Many of the same methods outlined above for solid-phase peptide synthesis apply to solution phase peptide synthesis. The use of protecting group manipulations, activating agents, and the sequential addition of PNA units to the growing oligomer are similarly applied. One distinction is that solution phase peptide synthesis does not use a solid support (e.g., a resin or beads). Subsequently, each step of the repeating cycle to grow the PNA oligomer can require purifying the oligomer from the reaction mixture using techniques such as extraction, trituration, column chromatography, HPLC, or other common purification techniques. As no solid support is used in solution phase peptide synthesis, no cleavage from a resin is required. However, more steps are required to remove at least one or all protecting groups from the PNA oligomer. Furthermore, in the absence of a solid-support, one or both termini (e.g., the carboxyl terminus and the amine termini) of the PNA oligomer can also be protected during PNA oligomer preparation, and removal of the protecting group(s) or modification to introduce an end-cap or other modification of the PNA oligomer may be required. [0263] A PNA oligomer can be synthesized using a combination of solid phase and solution phase methods. [0264] In some embodiments the PNA oligomer is purified after synthesis. Examples of methods of purification include silica gel chromatography, high performance liquid chromatography (HPLC), extraction, and/or trituration. For example, a PNA oligomer can be purified on a C18 reverse phase column using a solvent system (e.g., 1% TFA, acetonitrile and water). In some embodiments, an isocratic elution is used. In some embodiments, a gradient elution is used. [0265] In some embodiments, the PNA oligomer is at least 80%, at least 85%, at least 90%, at least 92%, at least 95%, at least 97%, at least 98%, at least 99%, at least 99.5%, or at least 99.9% pure. Purity of a PNA oligomer can be determined by any suitable method, for example, through HPLC analysis. [0266] After synthesis, the PNA oligomer can be characterized to confirm the identity of the PNA sequence. Characterization methods include mass spectrometry (including liquid chromatography mass spectrometry (LCMS), nuclear magnetic resonance (NMR) spectroscopy, Raman spectroscopy, infrared spectroscopy, HPLC, fluorimetry, and X-ray crystallography. [0267] In some embodiments, the individual subunits in the oligomerization reaction are vacuum dried prior to use in the reaction. In some embodiments, the individual subunits in the oligomerization reaction are freshly distilled over a drying agent (e.g., with CaH2 or K2CO3), purified, recrystallized, or dried prior to use in the reaction. In some embodiments, the individual subunits in the oligomerization reaction are synthesized prior to use. In some embodiments, the individual subunits in the oligomerization reaction are commercially available. Methods of Making Nanoparticles [0268] Described herein are methods for producing a nanoparticle that comprises PNA oligomers comprising a pyrimidine-compliant PNA subunit, and optionally other components (e.g., nucleic acids). In some embodiments, the nanoparticle is a lipid nanoparticle (LNP). In some embodiments, the nanoparticle is a nanoparticle comprising a synthetic polymer (e.g., a nanoparticle comprising PLGA). A method of forming such nanoparticles can require a double emulsion process, single emulsion process, or a process involving mixing premade solutions to effect nanoprecipitation. Lipid Nanoparticles (LNPs) [0269] The method of making an LNP comprising a PNA oligomer can entail mixing a first solution with a second solution. In some embodiments, the first solution comprises a lipid or a plurality of lipids and a PNA oligomer, e.g., a tcPNA oligomer, in a solvent. The solvent can be any water miscible solvent (e.g., ethanol, methanol, isopropanol, acetonitrile, dimethylformamide, dimethylsulfoxide, dioxane or tetrahydrofuran). In some embodiments, the first solution comprises a small percentage of water. The first solution can comprise up to at least 60% by volume of water, up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of water. In some embodiments, the first solution comprises between about 0.05% and 60% by volume of water, e.g., between about 0.05% and about 50%, about 0.05% and about 40%, or about 5% and about 20% by volume of water. [0270] The first solution can comprise a single type of PNA oligomer or a plurality of PNA oligomers, e.g., of different PNA sequences. In some embodiments, the first solution comprises a single type of PNA oligomer (e.g., a tcPNA oligomer). In some embodiments, the first solution comprises a plurality of PNA oligomers (e.g., tcPNA oligomers), wherein the PNAs comprise different sequences and bind to different target nucleic acid sequences. [0271] In some embodiments, the first solution comprises a single type of lipid, for example, an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid. In some embodiments, the first solution comprises a plurality of lipids. In some embodiments, the plurality comprises an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid. In some embodiments, the plurality of lipids comprise cholesterol, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), 1,2-dimyristoyl-rac-glycero-3-methylpolyoxyethylene2000 (DMG-PEG2k), and dilinoleylmethyl-4-dimethylaminobutyrate (DLin-MC3-DMA). The plurality of lipids can exist in any ratio. In some embodiments, the plurality of lipids comprises an ionizable lipid, a phospholipid, a sterol, or a PEG-containing lipid of the above lipids in a particular ratio (e.g., a ratio described herein). [0272] In some embodiments, the second solution is water. In some embodiments, the second solution is an aqueous buffer. The second solution can comprise a load component, e.g., a nucleic acid (e.g., a single-stranded DNA). In some embodiments, the nucleic acid is a DNA oligomer (e.g. a donor DNA). The second solution can comprise a small percentage of water- miscible organic solvent. The second solution can comprise up to at least about 60% by volume of at least one water miscible organic solvent. In some embodiments, the second solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of at least one organic solvent (e.g., a water miscible organic solvent). In some embodiments, the second solution comprises between about 0.05% and about 60% by volume of organic solvent, e.g., between about 0.05% and about 50%, about 0.05% and about 40%, or about 5% and about 20% by volume of organic solvent (e.g., a water miscible organic solvent). The aqueous buffer solution can be an aqueous solution of citrate buffer. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH between 4-6. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH of about 4, about 5, or about 6. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH of about 6. [0273] In some embodiments, the solution comprising a mixture of the first and second solutions comprising the LNP suspension can be diluted. In some embodiments, the pH of the solution comprising a mixture of the first and second solutions comprising the LNP suspension can be adjusted. Dilution or adjustment of the pH of the LNP suspension can be achieved with the addition of water, acid, base, or aqueous buffer. In some embodiments, no dilution or adjustment of the pH of the LNP suspension is carried out. In some embodiments, both dilution and adjustment of the pH of the LNP suspension is carried out. [0274] In some embodiments, excess reagents, solvents, free PNA or free nucleic acid can be removed from the LNP suspension by tangential flow filtration (TFF) (e.g., diafiltration). The organic solvent (e.g., ethanol) and buffer can also be removed from the LNP suspension with TFF. In some embodiments, the LNP suspension is subjected to dialysis and not TFF. In some embodiments, the LNP suspension is subjected to TFF and not dialysis. In some embodiments, the LNP suspension is subjected to both dialysis and TFF. [0275] In some embodiments, the present disclosure features a method comprising treating a sample of LNPs comprising PNAs and optionally nucleic acids, with a fluid comprising a detergent (e.g., Triton X-100) for a period of time suitable to degrade the lipid layer and thereby release the encapsulated and/or entrapped PNA(s) and optionally nucleic acid(s). In some embodiments, the method further comprises analyzing the sample for the presence, absence, and/or amount of the released PNA(s) and optionally nucleic acid(s). [0276] In some embodiments, the present disclosure features a method of manufacturing, or evaluating, a LNP or preparation of LNPs comprising providing a preparation of LNPs described herein, and acquiring, directly or indirectly, a value for a preparation parameter. In some embodiments, the method further comprises making the preparation of LNPs by a method described herein. In some embodiments, the method further comprises evaluating the value for the preparation parameter, e.g., by comparing the value with a standard or reference value. In some embodiments, wherein responsive to the evaluation, the method further comprises selecting a course of action, and optionally, performing the action. For example, the method can comprise providing a preparation of LNPs comprising a PNA, acquiring a value for a preparation parameter (e.g., average particle size), evaluating the preparation the value of the preparation parameter by comparing the value with a standard or reference value, selecting a course of action (e.g., selecting to administer the preparation of LNPs to a subject), and performing the action (administering the preparation of LNPs to a subject). Synthetic Polymer Nanoparticles [0277] The method of making a synthetic polymer nanoparticle comprising a PNA oligomer can entail mixing a first solution with a second solution. In some embodiments, the first solution comprises a PNA oligomer (e.g. a tcPNA oligomer) and synthetic polymer (e.g., PLGA) or mixture of synthetic polymers in a solvent. The solvent can be any water-miscible solvent (e.g., ethanol, methanol, isopropanol, acetonitrile, dimethylformamide, dioxane, tetrahydrofuran). In some embodiments, the first solution comprises a small percentage of water. The first solution can comprise up to at least 60% by volume of at water. In some embodiments, the first solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of water. In some embodiments, the first solution comprises between about 0.05% and 60% by volume water, between about 0.05% and 50%, between about 0.05% and 40%, or between about 5% and 20% by volume water. [0278] The first solution can comprise a single type of PNA oligomer or a plurality of PNA oligomers, e.g., of different PNA sequences. In some embodiments, the first solution comprises a single type of PNA oligomer, e.g., a tcPNA oligomer. In some embodiments, the first solution comprises a plurality of PNA oligomers, e.g., tcPNA oligomer, wherein the PNAs comprise different sequences and bind to different target nucleic acid sequences. [0279] In some embodiments, the synthetic polymer is polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co-glycolic acid) (PLGA), poly(4-hydroxy-L-proline ester), a polyester, a polyanhydride, a poly(ortho)ester, a polyurethane, a poly(butyric acid), poly(valeric acid), poly(caprolactone), a poly(hydroxyalkanoate), a poly(lactide-co-caprolactone), a poly(amine-co- ester) polymer, or a combination of any two or more thereof. In some embodiments, the synthetic polymer is PLGA. [0280] In some embodiments the second solution is acqueous. In some embodiments, the second solution is an aqueous buffer. The second solution can comprise a load component, e.g., a nucleic acid (e.g., a single-stranded DNA). In some embodiments, the nucleic acid is a DNA oligomer (e.g., a donor DNA). The second solution can comprise a small percentage of water miscible organic solvent. The second solution can comprise up to at least about 60% by volume of at least one water miscible organic solvent. In some embodiments, the second solution can comprise up to at least about 0.05%, up to at least about 0.1%, up to at least about 0.5%, up to at least about 1%, up to at least about 2%, up to at least about 3%, up to at least about 4%, up to at least about 5%, up to at least about 10%, up to at least about 15%, up to at least about 20%, up to at least about 25%, up to at least about 30%, up to at least about 35%, up to at least about 40%, up to at least about 45%, up to at least about 50%, up to at least about 55% or up to at least about 60% by volume of at least one organic solvent (e.g., a water miscible organic solvent). In some embodiments, the second solution comprises between about 0.05% and 60%, between about 0.05% and 50%, between about 0.05% and 40%, or between about 5% and 20% by volume organic solvent (e.g., a water miscible organic solvent). The aqueous buffer solution can be an aqueous solution of citrate buffer. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH between 4-6. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH of about 4, about 5, or about 6. In some embodiments, the aqueous buffer solution is a citrate buffer solution with a pH of about 6. [0281] In some embodiments, the process involves mixing the above solutions to produce nanoparticles that encapsulate the PNA oligomer and, optionally, a nucleic acid load component. The process can further require dilution (e.g., with water or a buffer). In some embodiments, the process involves the introduction of a surface stabilizer (e.g., trehalose, sucrose, or cyclodextrin). The process can involve diafiltration to remove excess reagents, non-encapsulated PNA oligomers or DNA, solvents, or buffers from the nanoparticles. In some embodiments, dialysis is used to remove excess reagents, non-encapsulated PNA oligomers or DNA, solvents, or buffers from the nanoparticles. The process can further require sterilization of the nanoparticles, for example by filtration through a filter of a select pore size (e.g., 0.2 µM) to remove microbes. The method can additionally feature the addition of cryoprotectants, excipients, or other components. The method can require transferring the nanoparticles to containers suitable for distribution and use for administration. The nanoparticles can be stored at low temperatures, such as at 0 °C, -20 °C, -80°C lower. [0282] In some embodiments, the loading of PNA oligomer and other components in the nanoparticle are analyzed through many methods. In some embodiments, analysis involves digesting nanoparticles by treatment with ammonia or dimethylsulfoxide (DMSO) to release encapsulated PNA oligomers and any other encapsulated components (e.g., DNA). The amount of total PNA and DNA in the digest can then be determined by spectroscopic methods (e.g., UV absorbance), HPLC, or other methods (e.g., OliGreen/RiboGreen methods). In some embodiments, nanoparticles are analyzed by scanning electron microscopy (SEM) techniques. For example, nanoparticles can be coated in platinum and imaged using SEM to determine size and morphology of the nanoparticles. Gene Targeting Compositions and Methods of Treatment [0283] Described herein are pyrimidine-compliant PNA oligomers and compositions thereof, and methods of using the same to alter a target nucleic acid sequence. The methods of using the pyrimidine-compliant PNA oligomers can be performed in vitro (e.g., in an in vitro cell system) or in vivo (e.g., in a subject, e.g., a human subject). In some embodiments, the method is performed in an in vitro cell free system. In some embodiments, the method is performed in a cell. The cell can be a cultured cell, e.g., a cell from a cell line, or can be a cell derived from a subject. In some embodiments, the method is performed in vivo, e.g., in a subject. The subject can be a mammal (e.g., a mouse, other non-human primate or a human). [0284] The target nucleic acid sequence used in the described methods can be single-stranded or double-stranded. In some embodiments, altering a target nucleic acid sequence comprises altering a target double-stranded nucleic acid sequence. Altering a target double-stranded nucleic acid sequence can comprise one or more of: a) altering the state of association of the two strands of a target double-stranded nucleic acid sequence; b) altering the helical structure of a target double-stranded nucleic acid sequence; c) altering the topology in a strand of a double-stranded nucleic acid sequence, for example, by introducing a kink or bend in a strand of the target double-stranded nucleic acid sequence; d) recruiting a nucleic acid-modifying protein (e.g., enzyme), for example, a member of the nucleotide excision repair pathway, to a target double stranded nucleic acid. Examples of members of the nucleotide excision repair pathway include XPA, RPA, XPF, and XPG, or a functional variant or fragment thereof; e) cleaving a strand of a target double stranded nucleic acid; or f) altering the sequence of a target double stranded nucleic acid. In some embodiments, the sequence of a target double stranded nucleic acid is altered to the sequence of a template nucleic acid. In some embodiments, the sequence of a target double stranded nucleic acid is altered from a mutant or disorder-associated sequence (e.g., allele) to a non-mutant or non-disease associated sequence (e.g., allele) a subject having a disease, disorder, or condition. [0285] In some embodiments, altering a nucleic acid comprises two of (a)-(f). In some embodiments, altering a nucleic acid comprises three of (a)-(f). In some embodiments, altering a nucleic acid comprises four of (a)-(f). In some embodiments, altering a nucleic acid comprises five of (a)-(f). In some embodiments, altering a nucleic acid comprises each of (a)-(f). In some embodiments, altering a nucleic acid comprises (a). In some embodiments, altering a nucleic acid comprises (b). In some embodiments, altering a nucleic acid comprises (c). In some embodiments, altering a nucleic acid comprises (d). In some embodiments, altering a nucleic acid comprises (e). In some embodiments, altering a nucleic acid comprises (f). [0286] The PNA oligomer comprising a PC PNA subunit can promote a particular effect in a target nucleic acid sequence. For example, the PNA oligomer can bind a target nucleic acid sequence. This binding can provide a decrease in the melting point (Tm) of the target nucleic acid sequence of at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, and can promote melting or dissociation of the strands of the target nucleic acid sequence. In some embodiments, a PNA oligomer can decrease the melting point of the target nucleic acid sequence of at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%. This decrease can promote melting or dissociation of the strands of the target sequence. In some embodiments, a PNA oligomer can cleave the target nucleic acid sequence and effect cleavage in at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50% of target nucleic acid sequences. In some embodiments, a PNA oligomer can edit at least about 0.5%, at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50% of the strands of the target sequence. [0287] In some embodiments, the PNA oligomer comprising a PC PNA subunit can induce gene modification in at least one target allele to occur at frequency of at least about 0.1%, at least about 0.2%, at least about 0.3%, at least about 0.4%, at least about 0.5%, at least about 0.6%, at least about 0.7%, at least about 0.8%, at least about 0.9%, at least about 1%, at least about 2%, at least about 3%, at least about 4%, at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, at least about 10%, at least about 11%, at least about 12%, at least about 13%, at least about 14%, at least about 15%, at least about 16%, at least about 17%, at least about 18%, at least about 19%, at least about 20%, at least about 21%, at least about 22%, at least about 23%, at least about 24, or at least about 25% of target cells. In some embodiments, gene modification occurs in at least one target allele at a frequency of about 0.1-25%, or 0.5- 25%, or 1-25% 2-25%, or 3-25%, or 4-25% or 5-25% or 6-25%, or 7-25%, or 8-25%, or 9-25%, or 10-25%, 11-25%, or 12-25%, or 13%-25% or 14%-25% or 15-25%, or 2-20%, or 3-20%, or 4-20% or 5-20% or 6-20%, or 7-20%, or 8-20%, or 9-20%, or 10-20%, 11-20%, or 12-20%, or 13%-20% or 14%-20% or 15-20%, 2-15%, or 3-15%, or 4-15% or 5-15% or 6-15%, or 7-15%, or 8-15%, or 9-15%, or 10-15%, 11-15%, or 12-15%, or 13%-15% or 14%-15%. [0288] In some embodiments, a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell, of greater than about 5%, greater than about 8%, greater than about 10%, greater than about 12.5%, greater than about 15%, greater than about 16%, greater than about 17%, greater than about 18%, or greater than about 19%. In some embodiments, a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of greater than about 10%. In some embodiments, a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of greater than about 15%. In some embodiments, a PNA oligomer comprising a PC PNA subunit exhibits a percent gene editing in a cell (e.g., a bone marrow cell, e.g., as described in Example 7) of about 5% to about20%, about 8% to about 12%, about 10% to about 20%, about 10% to about 15%, about 12.5% to about 20%, about 15% to about 18%, or about 15% to about 20%. [0289] In some embodiments, a PNA oligomer comprising a PC PNA subunit or a composition thereof is administered at a particular dosage, e.g., a therapeutically effective dosage. Examples of dosages can be expressed in mg/kg of the subject, and can be, for example, about 0.1 mg/kg to about 1,000 mg/kg, or about 0.5 mg/kg to about 1,000 mg/kg, or about 1 mg/kg to about 1,000 mg/kg, or about 10 mg/kg to about 500 mg/kg, or about 20 mg/kg to about 500 mg/kg per dose, or about 20 mg/kg to about 100 mg/kg per dose, or about 25 mg/kg to about 75 mg/kg per dose. In some embodiments, a PNA oligomer can be administered at a dose of at least about 25 mg/kg, at least about 30 mg/kg, at least about 35 mg/kg, at least about 40 mg/kg, at least about 45 mg/kg, at least about 50 mg/kg, at least about 55 mg/kg, at least about 60 mg/kg, at least about 65 mg/kg, at least about 70 mg/kg, or at least about 75 mg/kg per dose. In some embodiments, a PNA oligomer can be administered at a dose of about 25 mg/kg, about 30 mg/kg, about 35 mg/kg, about 40 mg/kg, about 45 mg/kg, about 50 mg/kg, about 55 mg/kg, about 60 mg/kg, about 65 mg/kg, about 70 mg/kg, or about 75 mg/kg per dose. [0290] In some embodiments, the PNA oligomer comprising a PC PNA subunit alters a target nucleic acid sequence with little to no off-target effects. In some embodiments, off-target modification of a nucleic acid is undetectable using routine analysis, e.g., nucleic acid sequencing. In some embodiments, off-target modification of a nucleic acid occurs at a frequency of 0-1%, or 0-0.1%, or 0-0.01%, or 0-0.001%, or 0-0.0001%, or 0-0000.1%, or 0- 0.000001%. In some embodiments, off-target modification of a nucleic acid occurs at a frequency that is about 102, about 103, about 104, or about 105 -fold lower than at the target nucleic acid sequence. Methods of Treatment [0291] The PNA oligomer comprising a PC PNA subunit or a composition thereof (e.g. a nanoparticle) can further be used in a method to treat a subject having a particular disease, disorder or condition. In some embodiments, the method comprises administering to a subject a PNA oligomer comprising a PC PNA subunit or a composition thereof (e.g., a nanoparticle comprising the PNA oligomer). In some embodiments, the PNA oligomer comprising a PC subunit is administered to the subject in a therapeutically effective amount, e.g., a dosage sufficient to reduce a likelihood of, treat, or inhibit a symptom of a disease, disorder or condition. In some embodiments, the disease, disorder, or condition is a human genetic disease, for example, in which at least one addition, deletion or mutation is present in an allele compared to a non-disease control. Examples of diseases, disorders, or conditions that may be treated with the PNA oligomers and compositions thereof described herein include cystic fibrosis, hemophilia, and a globinopathy (e.g., sickle cell anemia, beta-thalassemia), xeroderma pigmentosum, a lysosomal storage disease, or a cancer (e.g., a cancer related to PD-1). In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat cystic fibrosis in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat hemophilia in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a globinopathy (e.g., sickle cell anemia, beta- thalassemia) in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat xeroderma pigmentosum in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a lysosomal storage disease in a subject. In some embodiments, the PNA oligomer comprising a PC PNA subunit or a composition thereof is used in a method to treat a cancer in a subject. EXAMPLES [0292] In order that the disclosure described herein may be more fully understood, the following examples are set forth. The examples described in this application are offered to illustrate the peptide nucleic acids, compositions, and methods provided herein and are not to be construed in any way as limiting their scope. [0293] The PNA oligomers, nucleic acids, nanoparticles (e.g., LNPs or synthetic polymer nanoparticles), and compositions thereof provided herein can be prepared from starting materials using modifications to the specific synthetic protocols set forth below. [0294] Examples of PNA oligomers, nucleic acids, nanoparticles (e.g., LNPs or synthetic polymer nanoparticles), and compositions thereof can be prepared using any of the strategies described below. Example 1. Synthesis of PNA Oligomers [0295] PNA Monomers: Except for the specialty PNA monomers comprising pyrimidine compliant nucleobases (i.e. PC monomers used to produce PNA subunits in PNA oligomers) prepared as set forth below (which monomers were prepared in-house), classic Fmoc PNA monomers (monomers having an unsubstituted 2-aminoethylglycine backbone) were purchased from commercial sources and/or prepared by a vendor on a custom synthesis basis. Fmoc gamma miniPEG monomers were prepared by a vendor on a custom synthesis basis by generally following published procedures. Fmoc gamma miniPEG PNA monomers could be prepared using the Mitsunobu route using a properly protected serinol intermediate. Identity, purity and chiral purity (if applicable) were confirmed for all PNA monomers after receipt using 1H-NMR (proton nuclear magnetic resonance) and LCMS (liquid chromatography mass spectrometry) of the PNA monomers and/or PNA oligomers prepared therefrom. [0296] Linkers: Fmoc protected PEG2 and PEG3 linkers were purchased from commercial sources such as PurePEG and used without any analysis. [0297] Amino Acids: Amino acids (e.g., N-alpha-Fmoc-N-epsilon-Fmoc-L-lysine and N-alpha- Fmoc-N-epsilon-boc-L-lysine) were purchased from commercial sources such as Chem Impex International, Bachem and Matrix Innovations and used without any analysis. For PNA oligomers comprising a Gly-Gly PNA subunit (a.k.a. a “Gly-Gly bridge”) in the Hoogsteen segment of the oligomer, a single coupling of the commercially available dimer Fmoc-Gly-Gly- OH was used instead of two back-to-back couplings of the amino acid Fmoc-Gly-OH. however, a PNA oligomer comprising a Gly-Gly bridge can be prepared using any suitable method. [0298] General Procedure for Synthesis of PNA Oligomers: All PNA oligomers were synthesized on an Intavis MultiPep RSi automated peptide synthesizer using Fmoc solid phase peptide synthesis protocol using rink amide TentaGel resin (Rapp polymer, R28023) as the solid support. The synthesis protocol comprised three synthetic steps (in addition to washing steps) wherein each of the steps was repeated for each new PNA monomer, linker, amino acid or other building block (e.g., synthon) until the polyamide was completely assembled. Specifically, a single synthetic cycle comprised: 1) deprotection of the N-terminal Fmoc group; 2) coupling of a new monomer, linker, amino acid or synthon to the growing polyamide; and 3) capping of the unreacted amino groups. Between each step in the cycle, the resin was washed extensively with N,N’-dimethylformamide (DMF) to remove unreacted reagents and other unwanted impurities and side products of the reaction. [0299] Protocol for Small Scale Synthesis: Approximately 45 mg (5.8 µmol) rink amide TentaGel resin was placed in the reaction column of the Intavis and treated with 800 µL dichloromethane (DCM) for 15 minutes (min) to swell the resin prior to initiation of the PNA oligomer synthesis. The resin was then treated twice with 600 µL of 20% (v/v) piperidine/DMF for 5 min each to remove the Fmoc group. After five washes with DMF, approximately 45 µmol of a PNA monomer, linker, amino acid (e.g., lysine) or other synthon (as applicable based on the sequence of the PNA oligomer to be prepared) was delivered to the resin from a solution comprising PNA monomer, linker, amino acid, or synthon dissolved in dry DMF. To the resin was also delivered a mixture of N,N’-diisopropylethylamine (DIEA; approximately 56 µmol) dissolved in dry N-methyl pyrrolidone (NMP) and approximately 42 µmol of 1- bis(dimethylamino)methylene]-1H-1,2,3-triazolo4,5-b]pyridinium 3-oxid hexafluorophosphate (HATU) in dry DMF. Also, 2,6-lutidine can be added to the DIEA solution in a ratio of approximately 1/1.5 DIEA/2.6-lutidine (v/v). Once all the reagents were delivered for the reaction column, the resin was agitated for 30 min. The reaction mixture was then drained from the reaction vessel and the resin was washed extensively with DMF. The capping step was then performed by treating the resin with 600 µL of capping solution (5% acetic anhydride and 6% lutidine in DMF (v/v)) while agitating the resin for 5 min. These three steps were repeated sequentially for each new PNA monomer, linker, amino acid or other building block until the PNA oligomer was completely assembled. However, for bis-Fmoc PNA oligomers the protocol was modified so that the final Fmoc deprotection step was eliminated so that the PNA oligomer remained Fmoc-ON. Hence, after the final capping step, the instrument did not execute a final step that removed the terminal Fmoc moiety but rather, the resin was simply washed extensively with DCM and then dried. For all bis-Fmoc PNA oligomers, the final coupling was performed using N-alpha-Fmoc-N-epsilon-Fmoc-L-lysine. [0300] PNA oligomer synthesis could be scaled using adaptations of the above described protocol wherein volumes, reagent amounts and reaction times were altered, with some optimization, to produce similar results as are obtained with the 5.8 µmol scale synthesis. Other representative scales included 15 µmol and 52 µmol. [0301] General Protocol for Cleavage and Deprotection of PNA Oligomers: Crude PNA oligomers were obtained by treating the dried resin with 1 mL of cleavage mixture containing, trifluoracetic acid (TFA), m-cresol, water, and thioanisole (in a ratio of 95/2/2/1: v/v/v/v) for 2 hours (hrs) at room temperature. The sample was then filtered to remove the resin and the filtrate was subsequently treated with cold diethyl ether to cause precipitation of the PNA oligomer. After repeated suspension and pelleting of the PNA oligomer with cold diethyl ether, the crude PNA oligomer was dissolved in approximately 2 mL of a 1/1 (v/v) water/acetonitrile mixture. The crude PNA oligomer was then obtained for purification by lyophilization of this solution. [0302] HPLC Purification Procedure for bis-Fmoc PNA Oligomers: After lyophilization, crude PNA oligomers were dissolved in 1 mL of 5% aqueous acetonitrile and analyzed on a ThermoFisher analytical HPLC system to obtain a crude analytical profile. Thereafter, the crude PNA oligomers were purified on a ThermoFisher Preparative HPLC system equipped with an automated fraction collector. Output from the detector and fraction collector were used to determine which fractions should be collected and pooled as product. In some cases, fractions were analyzed by analytical HPLC to determine whether the fractions should be pooled. The pooled product provided by combined fractions was then reanalyzed by ThermoFisher analytical HPLC (to determine purity) and on a Waters-Q-TOF LCMS to confirm the identity (by mass/charge ratio) of the PNA oligomer and subsequently lyophilized to obtain the purified Fmoc-ON PNA oligomers (i.e. bis-Fmoc PNA oligomers). [0303] Analytical HPLC Separation Conditions for bis-Fmoc PNA oligomers: Solvent A: 0.1% TFA in Water; Solvent B: 0.1% TFA in acetonitrile Analytical HPLC Column: Waters Xbridge Peptide C18, 3.5 µm, 4.6X150 mm Column Temperature: 55 oC; Flow Rate: 1.5 mL/min Gradient (Table 3): Table 3.
Figure imgf000080_0001
[0304] FIG.10 contains the HPLC traces for 6 representative bis-Fmoc PNA oligomers evaluated using these analytical separation conditions. [0305] Preparative HPLC Separation Conditions for bis-Fmoc PNA oligomers: Preparative HPLC Column: Waters Xbridge Peptide C18, 5 µm, 19X150 mm Column Temperature: Room Temperature; Flow Rate: 18 mL/min Gradient (Table 4): Table 4
Figure imgf000081_0001
[0306] Fmoc Removal Procedure With Piperazine Immobilized Resin: For removal of the bis- Fmoc groups from each PNA oligomer, approximately 250 mg of Piperazine Immobilized Resin (“PIR”; such as: Silicycle, 0.97 mmol/gram; 3-(1-Piperazino)propyl functionalized silica gel from Sigma at 0.8 mmol/gram or Piperazine, polymer-bound from Sigma with 1-2 mmol/g loading) was weighed into a 13 mL plastic tube. The (bis) Fmoc-On purified lyophilized PNA oligomer from the 5.8 µmol scale synthesis was dissolved in about 400 µL of dimethylsulfoxide (DMSO). The purified (bis) Fmoc-On PNA oligomer, now dissolved in DMSO, was then transferred by pipet to the PIR. After complete transfer of the solution to the tube containing the PIR, the PNA oligomer containing tube was washed with 100 µL of dry DMSO and that wash solution was also transferred to the tube containing the PIR. The tube containing the PNA oligomer and PIR was then inserted into a holder on a shaker rack and shaken for 24 hrs. [0307] After 24 hours of agitation at room temperature, the tube containing the PNA oligomer was removed from the shaker and analyzed for completeness of Fmoc removal. A 1-2 µL aliquot of the liquid in the tube was transferred to an Eppendorf tube containing 40 µL of 5% aqueous acetonitrile and the solution was thoroughly mixed. The solution was then transferred to a spin cartridge containing a 0.22 µm cutoff filter and the cartridge was spun by centrifuge to filter off any particles in the liquid. The filtrate was then transferred to a tube suitable for analysis in a Waters-Q-TOF LCMS to access whether or not the Fmoc groups were completely removed from PNA oligomer in the sample. If the analysis on the Waters-Q-TOF LCMS indicated that Fmoc- ON PNA oligomer was still present, the reaction was allowed to continue to run – either under the same conditions or with added PIR if a large amount of Fmoc-ON PNA oligomer was observed. The sample could be reanalyzed until the analysis indicated essentially complete removal of the terminal Fmoc protecting groups from the PNA oligomer. Whenever analysis indicated complete removal of the Fmoc groups from the PNA oligomer, the entirety of the remaining reaction mixture (and combined washings of the tube) was transferred to a 5 mL centrifuge tube containing a 0.45 mm cutoff filter and centrifugation produced the crude PNA oligomer ready for purification by HPLC to obtain purified fully-deprotected PNA oligomer. [0308] Analytical HPLC Separation Conditions for fully-deprotected PNA oligomers: Solvent A: 0.1% TFA in Water; Solvent B: 0.1% TFA in acetonitrile Analytical HPLC Column: Waters Xbridge Peptide C18, 3.5 µm, 4.6X150 mm Column Temperature: 55 oC; Flow Rate: 1.5 mL/min Gradient (Table 5): Table 5
Figure imgf000082_0001
[0309] FIG.9 contains the HPLC traces for 6 representative (crude) fully-deprotected PNA oligomers evaluated using these analytical separation conditions. In this case, the PNA oligomers were not first purified by the Fmoc-ON process described herein but these traces illustrate the crude purity of the synthesis when the Fmoc-ON purification step is not performed. [0310] Preparative HPLC Separation Conditions for fully-deprotected PNA oligomers: Preparative HPLC Column: Waters Xbridge Peptide C18, 5 µm, 19X150 mm Column Temperature: Room Temperature; Flow Rate: 18 mL/min Gradient (Table 6): Table 6
Figure imgf000082_0002
[0311] The above described procedures have been applied to tens, if not hundreds, of successful PNA oligomer purification runs. Table 7 (Table of PNA Oligomers) presented below is illustrative of six tail-clamp PNA oligomers that have been successfully purified using the methodology described above. FIG.9 shows the analytical HPLC profile of crude fully deprotected PNA oligomers for each of the PNA oligomers listed in the table. [0312] In contrast, FIG.10 shows the analytical HPLC profile of each of the same PNA oligomers, wherein each PNA oligomer comprises an N-terminal bis-Fmoc protected L-lysine moiety. In the Figure, for each PNA, the bis-Fmoc protected PNA oligomer is labeled “Fmoc PNA” and the truncates and impurities (identified as “deletion sequences” in the chromatographs) are identified and clearly separated from the PNA oligomer product. This result illustrates the power of this separation for longer PNA oligomers, particularly tail-clamp PNA oligomers. Table 7. Exemplary PNA Oligomers (Compound Nos.1-8)
Figure imgf000083_0002
Legend: Each K refers to the amino acid L-lysine; Gly is the amino acid glycine; PEG2 is a long chain linker construct as illustrated in FIG.8B; PEG3 is a long chain linker construct as illustrated in FIG.8D; each letter corresponds to the nucleobase in the sequence (e.g., t = thymine; j = pseudoisocytosine, c = cytosine; a = adenine; g = guanine; e = 3-oxo-2,3- dihydropyridazine; p = 2-pyrimidinone); a lower-case letter indicates use of a classic (i.e. an unsubstituted aminoethylglycine) PNA monomer subunit; an upper-case letter indicates a right- handed gamma miniPEG (-CH2-(OCH2CH2)2-OH) substituted aminoethylglycine PNA monomer subunit was used. All PNA oligomers are illustrated in the N-terminal to C-terminal direction. The -NH2 at the C-terminus of the PNA oligomer indicates a C-terminal amide group. Example 2: Synthesis of “P-monomer”; a.k.a. Fmoc-aeg-P-OH [0313] Fmoc-AEG-P-OH monomer were prepared as outlined below. Step 1: Synthesis of 3-(2-oxopyrimidin-1-(2H)-yl) propanoic acid (2)
Figure imgf000083_0001
[0314] To 5 g of 2-hydroxypyrimidine·HCl (1; 38 mmol) was added 22.5 mL of 5N NaOH with stirring until the solid dissolved. Then, 5.8 g of 3-bromopropionic acid (38 mmol) was added to the solution, which was allowed to stir at about 60 °C overnight. The reaction was then cooled and neutralized with aqueous hydrochloric acid (HCl). The resulting mixture was then extracted 3 times with 50 mL of dichloromethane (DCM). The organic (DCM) layers were combined, dried over granular MgSO4 and evaporated. The resulting crude product was purified by flash chromatography using 0 to 10% DCM:Methanol (MeOH) gradient to yield 2.66 g of 2, (42% yield). Step 2: Synthesis of Allyl N-(2-((((9H-fluoren-9-yl) methoxy) carbonyl) amino) ethyl)-N-(3-(2- oxopyrimidin-1(2H)-yl) propanoyl) glycinate (4)
Figure imgf000084_0001
[0315] To 548 mg of 3-(2-oxopyrimidin-1-(2H)-yl) propanoic acid (2; 3.3 mmol), 1.5 g of Fmoc-allyl-aminoethylglycine tosyl salt (3; 2.7 mmol – purchased from a custom synthesis vendor who used the procedures described in WO 2018/175927) and 2.1 g of hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU, 5.4 mmol) in a dry, nitrogen filled round bottom flask was added 150 mL of dry dimethylformamide (DMF) and this solution was allowed to stir until the contents dissolved. To this stirring solution was then added 0.94 mL of diisopropylethylamine (DIPEA, 5.4 mmol). The reaction was stirred for 1 hour, checking reaction progress by TLC and LCMS. After 1 hour, the DMF was evaporated and the residue re- dissolved in a minimal amount of DCM for purification by flash chromatography using a 0 to 100% hexane:ethyl acetate (EtOAc) gradient to give 1.1 g of product 4 (77% yield). Step 3: Synthesis of N-(2-((((9H-fluoren-9-yl) methoxy) carbonyl) amino) ethyl)-N-(3-(2- oxopyrimidin-1(2H)-yl) propanoyl) glycine (5)
Figure imgf000084_0002
[0316] To 1.1 g of allyl N-(2-((((9H-fluoren-9-yl) methoxy) carbonyl) amino) ethyl)-N-(3-(2- oxopyrimidin-1(2H)-yl) propanoyl) glycinate (4; 2.1 mmol) was added 50 mL of dry tetrahydrofuran (THF) in a nitrogen-filled round bottom flask, and this solution was stirred until the solid dissolved. Then 250 µL of N-ethyl aniline (2 mmol) and 101.3 mg of tetrakis (triphenylphosphine) palladium (0) (0.09 mmol) were added and the reaction was stirred for 2 hours. When complete, the THF was removed by evaporation and the residue was re-dissolved in 10 mL methanol and added 5 g of silica. The methanol was then evaporated until the silica was dry enough for dry-loading flash chromatography using a 0 to 10% MeOH: EtOAc gradient to yield 630 mg of 5 (62% yield). Example 3: Synthesis of “M-monomer”; a.k.a Fmoc-aeg-M(boc)-OH Step 1: Synthesis of 1-(tert-butyl) 3-ethyl 2-(6-nitropyridin-3-yl)malonate (7)
Figure imgf000085_0001
[0317] In an oven-dried 500 mL round bottom flask was suspended 9.37 g of sodium hydride (NaH) (234 mmol) 57-63% oil dispersion, in dry N,N’-dimethylformamide (DMF) under argon. The suspension was chilled on an ice-bath, and 44.4 mL of tert-butyl ethyl malonate (234 mmol) was added dropwise over 10 minutes. The reaction mixture was stirred for 1 hour after which 38.71 g of 5-bromo-2-nitropyridine (6; 191 mmol) was added and the reaction was stirred at room temperature overnight. The reaction was quenched by the addition of water, the solvent was evaporated, and the residue re-dissolved in ethyl acetate (EtOAc) and washed with water and brine. The EtOAc layer was dried over MgSO4 and concentrated. The resulting slurry was dissolved in a minimal amount of EtOAc and kept overnight. The precipitate which formed was collected by vacuum filtration to afford after drying 58.35 g of crude solid product (7; 98% yield) which was used in the next step without further purification. Step 2: Synthesis of ethyl 2-(6-nitropyridin-3-yl)acetate (8)
Figure imgf000085_0002
[0318] To a stirring solution of 8.17 g of 1-(tert-butyl) 3-ethyl 2-(6-nitropyridin-3-yl) malonate (7; 26 mmol) in 50 mL of dry dichloromethane (DCM) in a round-bottom flask in an ice-bath was added 8.17 mL of trifluoracetic acid (TFA) dropwise. The resulting solution was heated to reflux with heat set at 90 oC for 16 hours. The reaction was cooled and concentrated before being diluted with ice-cold water. A solution of 5% (w/v) sodium bicarbonate was added to neutralize excess acid and then extracted with EtOAc. The EtOAc was concentrated in vacuo and to the resulting oil was added minimal amount of EtOAc and this mixture was to crystalize at room temperature overnight. The precipitate was removed by filtration and the remaining material was further purified by flash chromatography using a gradient of 0 to 100% hexane:EtOAc to yield 5.33 g oil (8; 96% yield). Notes: 1. The main side product or impurity precipitates out of EtOAc and multiple recrystallizations of this impurity lead to purer product. Step 3: Synthesis of ethyl 2-(6-aminopyridin-3-yl)acetate (9)
Figure imgf000086_0001
[0319] Ethyl 2-(6-nitropyridin-3-yl) acetate, 5.33 g (8; 25 mmol), 33.6 g of ammonium chloride (628 mmol) and 16.50 g of zinc dust (252 mmol) were placed in a 500 mL round bottom flask. 175 mL of 2:1, (v/v) MeOH:H2O was added, and the mixture was stirred at room temperature for 1 hour. Reaction progress was monitored by TLC and LCMS. After the reaction was complete, the mixture was diluted with EtOAc and filtered through Celite. The filtrate was washed with water and extracted with EtOAc. The organic layers were combined and dried over MgSO4, filtered and evaporated to give 3.96 g (9; 87% yield) of product, which was used in the next step without further purification. Step 4: Synthesis of ethyl 2-(6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetate (10)
Figure imgf000086_0002
[0320] To 9.94 g of ethyl 2-(6-aminopyridin-3-yl) acetate (9; 55 mmol) and 14.47 g of di-tert- butyl dicarbonate (66 mmol) was added 147 mL of tert-butyl alcohol under argon.9.25 mL of triethylamine (66 mmol) was added, and the reaction was stirred for 3 hours at 50 o C. After confirming that the reaction was complete by TLC and LCMS, the solution was concentrated on a rotoevaporator and the residue was redissolved in EtOAc. The ethyl acetate solution was then washed with water and brine, dried over granular MgSO4, concentrated and purified by flash chromatography in 0 to 100% hexane:EtOAc to yield 8.34 g (10; 54% yield) as a solid. Step 5: Synthesis of 2-(6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetic acid (11)
Figure imgf000086_0003
[0321] To 10.97 g of ethyl 2-(6-((tert-butoxycarbonyl) amino) pyridin-3-yl) acetate (10; 39 mmol) in a 500 mL round bottom flask was dissolved 150 mL of acetonitrile:ethanol:water in 2:2:1 (v/v/v) ratio. Some heat was applied to dissolve all the ester. The mixture was then placed on ice-bath for 20 min. A solution of 16.42 g of LiOH monohydrate (391 mmol) dissolved in 156 mL of water (2.5M solution) was added. The reaction mixture was briskly stirred for 10 minutes and quenched by the rapid addition of 195.6 mL of 2M HCl. The pH was brought down to ~5 using saturated KHSO4 upon which the compound precipitated out. The mixture was filtered to obtain 8.29 g of a pure solid (11; 84% yield). Notes: 1. When the dissolved starting material is placed in the ice-bath, the material precipitates out of the solution but in a form with enough moisture to allow de-esterification by LiOH. 2. Upon acidification, not all product precipitates out of solution. About 10% is left in solution and can be recovered by extraction into DCM. 3. Lowering the pH below 4 leads to product going back into solution due to protonation of the pyridine nitrogen. Thus, pH of about 5 is optimal for precipitation and collection of product. Step 6: Synthesis of 2-iodoethyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(2- (6-((tert-butoxycarbonyl)amino)pyridin-3-yl)acetyl)glycinate (13)
Figure imgf000087_0001
[0322] Ethyl 2-(6-((tert-butoxycarbonyl) amino) pyridin-3-yl) acetate 8.29 g (11; 33 mmol), 25.02 grams of hexafluorophosphate azabenzotriazole tetramethyl uronium (HATU) (66 mmol), and 18.25 g Fmoc protected iodoethyl ester backbone tosyl salt (12; 27 mmol – purchased from a custom synthesis vendor who used the procedures described in WO 2018/175927, published 27 September 2018) were dissolved in dry DMF under argon.11.46 mL of N’N diisopropylethylamine (DIPEA) (66 mmol) was added and the reaction was stirred for an hour. After TLC/LCMS confirmed reaction was complete, the DMF was removed by rotary evaporation. The oil was re-dissolved in DCM and extracted with saturated sodium bicarbonate, followed by water and brine. The organic layer was dried over granular MgSO4 then concentrated and the compound was purified by flash chromatography in 0 to 100% hexanes:EtOAc to yield 18.94 g of product (13; 95% yield). Step 7: Synthesis of N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(2-(6-((tert- butoxycarbonyl)amino)pyridin-3-yl)acetyl)glycine (14)
Figure imgf000088_0001
[0323] TXE Buffer was made by combining 50 mmol KH2PO4, 25 mmol of ethylenediaminetetraacetic acid (EDTA) and 25 mmol of ethylenediaminetetraacetic acid zinc disodium salt hydrate (EDTA-Zn.H2O) in 150 mL of deionized water and 50 mL of glacial acetic acid (HOAc). This mixture was permitted to stir overnight, after which 100 mL of tetrahydrofuran (THF) was added and after 30 minutes of additional stirring, the solids were removed by filtration and the resulting filtrate was used as TXE Buffer. Fmoc M iodoethyl ester, 16.95 g (13; 23 mmol) was dissolved in a mixture of 161 mL of TXE buffer and 161 mL of THF. The mixture was placed on a salt-bath for 30 minutes. When the reaction was cold, 23 mL of HOAc, 23 mL of H2O and 23 mL of chilled, saturated KH2PO4 were added to the reaction in that order (this is roughly 1 mL of each reagent per milli mole of monomer). Then 5.07 g of Zn dust (77.5 mmol, a third of total Zn required) was added. The mixture was stirred for 20 minutes, then the above liquid reagents were added in the order listed with another 5.07 g of Zn dust. The mixture was stirred for another 20 minutes and the liquid reagents were added in the prescribed order a third time along with a final addition of 5.07 g of Zn dust. The mixture was then stirred for an addition hour with monitoring by TLC and LCMS (always keeping the reaction cold in a salt/ice bath). [0324] After the reaction was complete, the mixture was filtered through celite and washed with a solution of THF:H2O (4:1; v/v) containing a couple of drops of acetic acid. The resulting solution was concentrated in vacuo to remove all the THF until the solution began to freeze on the roto-evaporator (no heat added to the flask via water bath). At this point, 100 mL of water was added, the aqueous layer was extracted three times with 150 mL aliquots of DCM. The aqueous layer was then combined the organic layer and washed twice with 50 mL (a total of 100 mL) of extraction buffer (Extraction Buffer is 1g KH2PO4 and 0.5g KHSO4 per 10 mL of deionized water). The organic layer was then dried over MgSO4 (granular), filtered, and evaporated. The crude compound was purified by flash chromatography in 0 to 100% hexane:EtOAc to yield 12.56 g, (93% yield 14). Further purification in DCM:MeOH gave product that was greater than 98% pure. Notes: 1. Use Zn Powder average 4-7 micron 97.5% powder or flakes. Using granular Zn, for instance Zn powder -140 +325 mesh with 99.9% (metal basis) leads to very sparing hydrolysis of iodoethyl group. 2. Crude product can be dissolved in minimum DCM and precipitated by dropwise addition to a briskly stirring solution of hexanes or hexanes/diethyl ether (generally in a ratio of about 5/1 to 10/1. After allowing to stir for 2 hours, the product was collected by vacuum filtration and vacuum dried. 3. Purification in hexanes and EtOAc is unnecessary. The best mobile phase for monomer purification is starting at 2% MeOH in DCM to 10% MeOH in DCM over 14 column volumes on Teledyne ISCO. Example 4: Synthesis of “E-monomer” a,k.a. Fmoc-aeg-E(boc)-OH monomer Step 1: Synthesis of 3-((6-bromopyridazin-3-yl)amino)propanoic acid (16)
Figure imgf000089_0001
[0325] Combined 25g of 2,5-dibromopyridazine (15) with 11.22g of b-alanine and 17.43g of potassium carbonate. Added to this mixture was 60 mL of EtOH and then the resulting solution was heated under reflux with stirring for a total of 6 hours during which everything dissolved to a thick, gooey mixture that eventually crystallized into a white mass. The reaction was cooled and partitioned between EtOAc and water. The water layer was separated and acidified with 2N HCl until pH was ~5, at which point copious off-white solid formed. This solid was collected by vacuum filtration and washed with water and then diethyl ether. After drying under high vacuum overnight to constant weight, 20.3 g (82 mmol) of pure product (16) was obtained (yield 78%). Notes: 1. If desired, the reaction may be allowed to reflux overnight. 2. TLC using 3/1, hexane/EtOAc may be used to follow the course of the reaction by checking for the disappearance of the 2,5-dibromopyridazine. Step 2: Synthesis of 3-((6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoic acid (17)
Figure imgf000090_0001
[0326] 216 mL DMSO and 48.6 g of potassium t-butoxide were combined and placed the mixture under N2 and stirred for 10 min at room temperature. When most (or all) of the t- butoxide had dissolved, 108 mL of 4-methoxybenzyl alcohol was added and stirring continued under N2 for 10 minutes at room temperature. Then 26.6 g of 3-((6-bromopyridazin-3- yl)amino)propanoic acid (16) was added and the reaction was stirred for an additional 10 minutes at room temperature. The reaction mixture was then placed with stirring in an oil bath set to 90 oC for 1.5 hours. During this time, all of the starting material dissolved and the reaction mixture became dark brown and clarified. LCMS was used to follow the reaction progress. Complete disappearance of starting material was observed after 90 minutes. The mixture then was cooled somewhat and poured into 600 g of ice water. The resulting aqueous solution was then transferred to a separatory funnel and washed twice w/DCM (~400 mL in total - the DCM washes were discarded). The water layer was then acidified with stirring to pH ~4 using saturated KHSO4 whereupon a large amount of tan solid formed. The solid was collected by vacuum filtration and washed with ice cold water, followed by washing with ice cold acetonitrile. After drying overnight, 33.3g of off-white solid was obtained. This amount was overweight. The material was dissolved in ~500 mL of hot DMF, leaving behind a white hard solid crystal (an inorganic salt). The hot DMF solution was filtered through a cotton plug to remove the inorganic solids. Water (250 mL) was added to the DMF solution, whereupon a tan solid formed. The mixture was allowed to cool to RT with stirring. The solid was collected by vacuum filtration and the resulting solid was washed with ice cold water and ice cold acetonitrile as before. Drying under high vacuum overnight provided 18.1g of pure product (17), 55% yield. Step 3: Synthesis of methyl 3-((6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoate (18)
Figure imgf000091_0001
[0327] A total of 18.1 g of 3-((6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoic acid (17) was dissolved in 90 mL of dry dioxane and to this mixture was added 2 equivalents of di- tert-butyl dicarbonate (26 g), followed by 1.5 equivalents N,N’-diisopropylethyamine (15.5 mL), and 0.1 equivalents of DMAP (0.728 g). Copious CO2 was liberated and then the mixture solidified into a thick brown mass, which was broken up and the slurry stirred for three hours. Then the reaction was briefly heated to 50 oC until no more CO2 evolution occurred. Then 250 mL of MeOH was added. The reaction was continuously stirred, and a new solid formed. TLC of a methanol dilution of the reaction showed complete reaction (product Rf 0.7 in 5% MeOH/DCM). The mixture was then concentrated to a gummy solid and dissolved in a large volume of EtOAc (~1.7 L), which was extracted with water twice and then brine. The organic layer was dried over MgSO4, then concentrated to a brown solid. This solid was re-crystallized from a minimal amount of boiling EtOAc (~300 mL). After standing overnight, the crystalline solid was collected by vacuum filtration and dried to give 16.28g (51.3 mmol) of 18 (yield, 86%). Step 4: Synthesis of methyl 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoate (19)
Figure imgf000091_0002
[0328] 16.3 g of methyl 3-((6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoate (18) was taken up in 140 mL dry dioxane and to the resultant mixture were added 28 g of di-tert-butyl dicarbonate and by 0.618 of DMAP. Gas was slowly evolved from this solution with stirring. at the mixture was heated to 70 oC in an oil bath and CO2 release became steady and then slowed. The mixture stirred at 70 oC overnight. TLC in 5% MeOH/DCM showed disappearance of starting material and complete reaction. The mixture was cooled to room temperature and added 5 mL water and 100 mg DMAP and stirred until no further gas was evolved. The mixture was concentrated the mixture to a thick oil and was placed on high vacuum overnight.23.5 g of oil was obtained. This amount was two grams overweight. The oil was placed again on high vacuum pump overnight to provide 22.5 g, still about one gram overweight. The oil was placed in a refrigerator at 5 oC overnight and the oil solidified into crystals with some brown liquid being expelled. The product was put back under high vacuum and all of the liquid was evaporated to give 19.8 g of a crystalline solid. [0329] The solid was taken up in 30 mL of xylenes and heated until complete dissolution. Then 30 mL of hexanes was added. A small portion of the mixture was removed and scratched to induce crystallization. The resultant crystals were added to the bulk solution. Once crystallization was apparent in the bulk mixture, the mixture was placed at 4 oC overnight. The next morning the solid was collected by filtration, washed with cold 1/1, xylenes/hexanes, and dried to give 18.53 g of a solid (19) that was pure by TLC (3/1 hex/EtAc, Rf 0.4). Yield 87%. Step 5: Synthesis of 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoic acid (20)
Figure imgf000092_0001
[0330] 18.3g (~44 mmol) of compound 19 was taken up in 130 mL of THF and cooled on ice. 130 mL of 1M LiOH monohydrate in methanol was added and the ice bath was removed. After stirring for 6 hours, the reaction was ~90% complete.2N HCl was added slowly with rapid stirring. At ~ pH 8 a large amount of solid formed. The mixture was concentrated to almost dryness. Then 300 mL of DCM was added, followed by 300 mL of water.2N HCl was added with vigorous shaking until all of the solid had dissolved and the pH was ~2. The mixture was separated and the DCM layer washed with water twice, then brine. The organic layer was dried over Mg2SO4 and concentrated to give a tan solid. This solid was crystallized from a minimal amount of ACN/water, 9/1. A gave a first crop of 7.2 g of pure material and a s,,econd crop of 3.4g of impure material were obtained. Notes: 1. Appreciable loss of the pMB was observed during the acidification and work-up of the reaction and during recrystallization. Step 6: Synthesis of allyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoyl)glycinate (21)
Figure imgf000093_0001
[0331] 6.72 g of 3-((tert-butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3- yl)amino)propanoic acid (20) was taken into 90mL of dry acetonitrile (ACN) and reconcentrated. The resulting residue was dissolved in 120 mL of dry ACN with warming and then cooled to 0 oC under N2 with rapid stirring, whereupon a fine white crystal formed. To this mixture was added 7.58 mL of dry N-methylmorpholine (NMM) followed immediately by 2.30 mL of trimethylacetyl chloride (TMAC), whereupon everything dissolved and a small amount of NMM salt was formed. The yellow mixture was stirred for 20 min at 0 oC. Then a test quench (quench was performed by adding one drop of phenethylamine to about 1 mL of ACN and then adding one drop of the reaction mixture to 100 µL of the phenethylamine in ACN solution) was performed. The test quench showed good mixed anhydride formation.8.38 of Fmoc allyl backbone tosyl salt (3) was added. The reaction was stirred for 30 min. TLC in 5% MeOH/DCM showed almost complete conversion of backbone to monomer ester. The reaction was then concentrated and the resulting oil was dissolved in EtOAc and washed 1x with 50% saturated KHSO4, 1x with 5% NaHCO3, and once with brine. The EtOAc layer was dried over MgSO4 and evaporated to give a foam. The foam was dissolved in 40% EtOAc/Hex and loaded on a column equilibrated at 20% EtOAc/Hex, and ran to 90% EtOAc to yield 9 g of very pure material (21). Step 7: Synthesis of N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-oxo-1,6-dihydropyridazin-3-yl)amino)propanoyl)glycine (22)
Figure imgf000094_0001
[0332] 1 mmol of allyl N-(2-((((9H-fluoren-9-yl)methoxy)carbonyl)-amino)ethyl)-N-(3-((tert- butoxycarbonyl)(6-((4-methoxybenzyl)oxy)pyridazin-3-yl)amino)propanoyl)glycinate (21) was taken up into 10 mL of dry THF and purged under N2. To this mixture was added 3 equivalents of N-ethyl analine (378 µL) and stirred/purged with N2.10 mol% tetrakis (0.115g) was added, and the resultant mixture was purged and stirred rapidly under N2 for 3 hours. TLC 5% showed complete consumption of the starting material ester. The mixture was concentrated to thick oil, which was partitioned with EtOAc and water.1.5 mL of 2N HCl (3mmol, 1 equ. based on the analine) was added until pH by paper was ~2. Layers were separated and EtOAc layer was washed twice with water and then brine. The EtOAc layer was dried over MgSO4 and concentrated to a thick oil. [0333] The above reaction was repeated with remaining 21 (8.23g, 10.74 mmol).21 was dissolved in 100 mL THF and 4.06 mL of N-ethyl analine was added. The reaction flask was purged with N2 and 1.23 g of tetrakis was added. The mixture was stirred for about 3 hours at RT at which time analysis indicated complete reaction. The reaction mixture was concentrated to a thick oil, partitioned between EtOAc and water.16.11 mL of 2N HCl (1 equ to analine) was added, whereupon pH by paper was ~2. The layers were separated and washed with 2x dilute KHSO4, then brine. The EtOAc layer was dried over MgSO4 and concentrated to obtain a foam, 8.8g. [0334] The products of the two reactions were combined in ~25 mL of 2% MeOH/DCM and loaded on a flash column (80 g silica gel), which was run over a 2-8% methanol gradient. The product was repurified on silica using a methanol gradient of 0% to 6%. The resulting product was dried over MgSO4, concentrated and purified by flash chromatography to yield a total of 4.2g of product. The product was dissolved in DCM and precipitated into hexanes to give 4.0 g of powder, yield 56%. Example 5: Isothermal Titration Calorimetry (ITC) Table 8. Table of Exemplary DNA oligomers
Figure imgf000095_0001
[0335] ITC experiments were performed to determine whether tcPNA oligomers containing the nucleobase “P” (Compound No.1), “E” (Compound No.7), or a “GlyGly” skip motif (Compound No.2) could bind target to a complementary DNA oligonucleotide (SEQ ID NOs: 7- 12, see Table 8 above) and, if so, to determine whether the hybrid formation exhibited sequence selectivity (See Figs.6A-6B for an illustration of the triplex to be formed). ITC directly measures enthalpy of binding. For this purpose, a Malvern Microcal-iTC200 instrument was used to analyze the hybridization reactions. Complementary DNA oligonucleotides were obtained as lyophilized powders from a commercial source (Integrated DNA Technologies, Skokie, Illinois, USA). Each DNA oligonucleotide was diluted in deionized water to form a DNA stock solution (10 μL, 0.24 mM). This stock solution was evaporated to dryness and then resuspended with 300 µL of phosphate buffer (100 mM of sodium chloride, 6.8 mM of Na2HPO4, 3.2 mM NaH2PO4, 0.1 mM EDTA, pH = 7.4, the “Phosphate Buffer”). After degassing, the DNA solution (300 µL, 8.33 uM) was loaded into ITC reaction cell and the reference cell was loaded with degassed HPLC grade water. PNA stock solution (20 μL, 0.24 mM) was evaporated to dryness and the solid was dissolved in 60 μL of Phosphate Buffer. After degassing, the PNA solution (60 μL, 0.08 mM) was loaded in titration syringe and loaded on to the calorimeter. Other ITC Experimental Parameters: MicroCalPEAQ-ITC control software version1.10 Temperature: 25 °C 41.9 mJ/sec (10 mcal/sec) reference power Stirring speed: 750rpm Injection delay: 60 sec Total of 17 injections, 150 sec apart Reference Cell: deionized water The heat output due to PNA-DNA interaction per injection creates a temperature difference between the reference cell and sample cell. This temperature difference is converted to power and directly read out as raw data (FIGS.11A-11D, top). The raw data are then fitted, using MicroCalPEAQ-ITC control software version1.10, to give association constant (Ka), binding enthalpy (ΔH), and binding order (stoichiometry) (FIGS.11A-11D, bottom). Tables 9A-9B below show the association constants (Ka) for the binding of each PNA oligomer (Compound Nos.1, 2, 7, and 8) binding to the particular ssDNA oligomers screened (SEQ ID NOs: 7-12). Table 9A: Association Constants (Ka) from ITC measurements
Figure imgf000096_0001
Table 9B: Association Constants (Ka) from ITC measurements
Figure imgf000096_0002
Results [0336] The PNA oligomer containing the P nucleobase (Compound No.1), designed to Hoogsteen bind to the lone pyrimidine in a homopurine tract, was found to bind target DNA (SEQ ID NO: 7) to form a “tail clamp triplex”. The “GlyGly” skip motif designed to accommodate the lack of natural bases that Hoogsteen bind to pyrimidine interruption C-G and A-T resulting in triplex formation worked. This compound bound to both the C-G pyrimidine interruption or “skip” and T-A pyrimidine interruption. P nucleobase in P-containing PNAs allows that the tail clamp PNA form triplexes via P forming an unnatural Hoogsteen base pairing with the pyrimidine C, leading to triplex formation. [0337] In the case of Compound Nos.7 and 8, both PNA oligomers were found to bind to all four DNAs, although with significant differences in affinity. In fact, the “GlyGly” skip PNA reacted with essentially equivalent affinity to the “E” skip in two cases, SEQ ID NOs: 10 and 11, in the other two cases, SEQ ID NOs: 9 and 12, the “E” skip PNA showed an increased affinity as compared to the “GlyGly” PNA. Importantly, the overall affinity of the “E” skip PNA to SEQ ID NO: 12 was by far greater than any other KA recorded in the experiment, and approximately double the KA of the “GlyGly” PNA to the same DNA target. Taken together, these data suggest that the use of the “E” base confers increased affinity and specificity to DNA targets containing a thymine residue as compared to the “GlyGly”, abasic “hybrid”. Example 6: Hybridization of PNAs Containing Pyrimidine Compliant Bases to dsDNA Table 10
Figure imgf000097_0001
[0338] In Table 10 above, the target region for Compound Nos.3 and 5 and Compound Nos.4 and 6 are underlined in SEQ ID NO: 13. Specifically, the DNA target region for sequence for Compound Nos.3 and 5 is 5’ AGGAGCAGGGAGGG 3’ and the DNA target region sequence for Compound Nos.4 and 6 is 5’ GGGGCAAGGTGAACG 3’; where the underlined base of each sequence is the pyrimidine. [0339] An experiment was performed to contact PNA oligomers containing either a “GlyGly” bridge (i.e. Compound Nos.3 and 5) or “P” nucleobase (i.e. Compound Nos.4 and 6) with a double stranded DNA amplicon prepared as described below (and the sequence of which is provided in the Table above (i.e. SEQ ID NO: 13)). The PNA oligomers were designed such that the P nucleobase or the GlyGly subunits (i.e. “GlyGly bridge”) are placed in the clamp portion of the molecule on the Hoogsteen binding segment. The DNA amplicon was generated by polymerase chain reaction (PCR) from a plasmid containing a segment of the sickle cell variant of the human beta-globin gene. The amplicon was a 516 bp molecule with binding sites for PNA constructs Compound Nos.3 and 5 and Compound Nos.4 and 6 beginning at positions 62 and 224 respectively. The DNA target region sequence for constructs Compound Nos.3 and 5 is 5’ AGGAGCAGGGAGGG 3’; and the DNA target region sequence for constructs Compound Nos. 4 and 6 is 5’ GGGGCAAGGTGAACG 3’; wherein the underlined nucleobase of each sequence is the pyrimidine to be evaluated for “pyrimidine compliance” with nucleobase P or the Gly-Gly bridge. [0340] Amplicon and PNA oligomer were combined in a 1:15 ratio (0.05 µM: 0.75 µM) plus 100 µM KCL in a total volume of 10 µL and incubated at 37 °C for 0.5 or 18.0 hr (Figs.12A and 12B, respectively). The reaction contained residual salts and buffers from the PCR reaction which comprised half (5 µL) of the total volume. Reactant species were separated electrophoretically and visualized on the Agilent TapeStation 4200 using the HSD1000 gel cassette. [0341] With reference to FIGS.12A-12B, the lanes are as follows, lane A1, size marker; lane B1, 993 + amplicon; lane C1, 1258 + amplicon; lane D1, 1238 + amplicon; lane E1, 1259 + amplicon, lane F1, amplicon only. PNA oligomers tested alone in control experiments (data not shown) do not migrate into the gel or produce banding patterns. In FIG.12A very little change is visible in any of the PNA-dsDNA reactions, as compared to the amplicon only. In contrast, at 18.0 hr as seen in FIG.12B, all PNA-dsDNA reactions produce new slower migrating species (apparent higher molecular weight in the image), which was not observed at 30 minutes. The species migrating higher in the gel are complexes (believed to be stable triplexes) formed by strand invasion of the amplicon by the PNA. There does not appear to be much difference between the result of hybridization for Compound Nos.5 and 6. Likewise, the hybridization for Compound Nos.3 and 4 show similar relative amounts of gel retardation. Taken together these data suggest that there is a negligible effect of using P as compared to GlyGly but that both can form stable triplexes when interacting with dsDNA. Thus, both P and Gly-Gly appear to be suitable for use as ‘pyrimidine compliant’ nucleobases. EMBODIMENTS [0342] The following non-limiting embodiments provide illustrative examples of the invention, but do not limit the scope of the invention. [0343] Embodiment 1. A peptide nucleic acid (PNA) oligomer comprising: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv): wherein:
Figure imgf000098_0001
- each X1 or X4 is independently N or C; - X2 is N, CH, or C=O; - X3 is CH, C=O, or C-NH2; - each X5 , X6, and X8 is independently N or CH; - X7 is CH or C=O; - R20 is absent or hydrogen; - each R21, R35, R36, R37, R38, and R39 is independently hydrogen, deuterium, halo, alkyl, alkenyl, alkynyl, heteroalkyl, cyano, -OH, -NH2, or NO2; - R40 is hydrogen or alkyl; - R41 is hydrogen, alkyl, or absent; - R42 is hydrogen, deuterium, alkyl, or heteroalkyl; - each n and m is independently an integer of 1 or 2; - each p is 1, 2, 3, or 4; - each is independently a single or double bond; and wherein when X2 is C=O, then X3 is not C=O; when X3 is C=O, then X2 is not C=O; and when X3 is C-NH2, then X2 is not C=O; (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (c) a linker, wherein a first terminus of the first region of the PNA oligomer is covalently bound to a first terminus of the linker, and wherein a first terminus of the second region of the PNA oligomer is covalently bound to a second terminus of the linker. [0344] Embodiment 2. The PNA oligomer of embodiment 1, wherein the PNA oligomer is a PNA tail-clamp (tcPNA) oligomer. [0345] Embodiment 3. The PNA oligomer of embodiment 1 or 2, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA. [0346] Embodiment 4. The PNA oligomer of any one of embodiments 1-3, wherein the first plurality of PNA subunits, the first region of the dsDNA, and the second plurality of PNA subunits form a triplex structure. [0347] Embodiment 5. The PNA oligomer of any one of embodiments 1-4, wherein the first region of the PNA oligomer further comprises (a’) a first positively charged region comprising a first positively charged amino acid, wherein the first positively charged region is covalently bound to a second terminal end of the first region of the PNA oligomer. [0348] Embodiment 6. The PNA oligomer of embodiment 5, wherein the first positively charged amino acid is lysine. [0349] Embodiment 7. The PNA oligomer of any one of embodiments 1-6, wherein the second region of the PNA oligomer participates in Watson Crick binding with the first region of the dsDNA and the second region of the dsDNA. [0350] Embodiment 8. The PNA oligomer of any one of embodiments 1-7, wherein the second region of the PNA oligomer further comprises a second positively charged amino acid, wherein the second positively charged amino acid is covalently bound to a second terminal end of the second region of the PNA oligomer. [0351] Embodiment 9. The PNA oligomer of embodiment 8, wherein the second positively charged amino acid is lysine. [0352] Embodiment 10. The PNA oligomer of any one of embodiments 1-9, wherein the first region of the PNA oligomer comprises a gamma-modified PNA subunit. [0353] Embodiment 11. The PNA oligomer of any one of embodiments 1-10, wherein the second region of the PNA oligomer comprises a gamma-modified PNA subunit. [0354] Embodiment 12. The PNA oligomer of any one of embodiments 1-11, wherein the third region of the PNA oligomer comprises a gamma-modified PNA subunit. [0355] Embodiment 13. The PNA oligomer of any one of embodiments 1-12, wherein the first region of the PNA oligomer comprises a first gamma-modified PNA subunit, the second region of the PNA oligomer comprises a second gamma-modified PNA subunit, and the third region of the PNA oligomer comprises a third gamma-modified PNA subunit. [0356] Embodiment 14. The PNA oligomer of any one of embodiments 1-13, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer has the Formula (II-a):
Figure imgf000100_0001
wherein: - P1 is a first terminus of the PNA monomer; - P5 is a second terminus of the PNA monomer; - each R3, R4, R5, R6, R7, and R8 is independently alkyl, heteroalkyl, -N(RC)(RD), -ORE, or an amino acid side chain, each of which is substituted or unsubstituted; or hydrogen, deuterium, or halo; - X is N or CRb, wherein Rb is substituted or unsubstituted alkyl, hydrogen, deuterium, or halo; - L is alkylene, alkenylene, heteroalkylene, cycloalkylene, or heterocyclylene, each of which is optionally substituted with one or more RB, wherein each RB is independently deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo, oxo, or -ORE; - B is the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv); - each RC, RD, and RE is independently substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, or hydrogen; and - each “ ” independently denotes an attachment point to another PNA monomer, a protecting group, the linker, an amino acid, or a C-terminus or an N- terminus of the first region of the PNA oligomer or the second region of the PNA oligomer, provided that i) when P1 is an amine terminus, P5 is a carboxyl terminus; or ii) when P5 is an amine terminus, P1 is a carboxyl terminus. [0357] Embodiment 15. The PNA oligomer of embodiment 14, wherein P1 is an amine terminus. [0358] Embodiment 16. The PNA oligomer of embodiment 14, wherein P1 is a carboxyl terminus. [0359] Embodiment 17. The PNA oligomer of embodiment 14, wherein P1 forms a covalent bond with a P5 group of a second PNA monomer within the first region of the PNA oligomer. [0360] Embodiment 18. The PNA oligomer of embodiment 14, wherein P5 is an amine terminus. [0361] Embodiment 19. The PNA oligomer of embodiment 14, wherein P5 is a carboxyl terminus. [0362] Embodiment 20. The PNA oligomer of embodiment 14, wherein P5 forms a covalent bond with a P1 group of a second PNA monomer within the first region of the PNA oligomer. [0363] Embodiment 21. The PNA oligomer of embodiment 14, wherein P1 is an amine terminus and P5 is a carboxyl terminus. [0364] Embodiment 22. The PNA oligomer of any one of embodiments 14-21, wherein X is N. [0365] Embodiment 23. The PNA oligomer of embodiment 14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer has the Formula (II-b):
Figure imgf000102_0004
wherein R2 is substituted or unsubstituted alkyl, hydrogen, or deuterium. [0366] Embodiment 24. The PNA oligomer of any one of embodiments 14-23, wherein L is alkylene or heteroalkylene, each of which is optionally substituted with one or more RB. [0367] Embodiment 25. The PNA oligomer of embodiment 24, wherein L is ethylene, propylene, or butylene. [0368] Embodiment 26. The PNA oligomer of embodiment 24, wherein RB is oxo. [0369] Embodiment 27. The PNA oligomer of any one of embodiments 14-23, wherein L is selected from the group consisting of , and
Figure imgf000102_0001
Figure imgf000102_0002
. [0370] Embodiment 28. The PNA oligomer of any one of embodiments 14-27, wherein each R3, R4, R5, R6, R7, and R8 is independently hydrogen or heteroalkyl. [0371] Embodiment 29. The PNA oligomer of any one of embodiments 14-28, wherein one of R3 and R4 comprises a C2-C30 heteroalkyl and each R5, R6, R7, and R8 is independently hydrogen. [0372] Embodiment 30. The PNA oligomer of any one of embodiments 14-29, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer has the Formula (II-d):
Figure imgf000102_0003
wherein: - each R9 and R10 is independently hydrogen, deuterium, C1-4 alkyl, or halo; and - n is 0, 1, 2, 3, or 4. [0373] Embodiment 31. The PNA oligomer of embodiment 30, wherein each R3, R4, R5, and R6 is independently hydrogen or heteroalkyl. [0374] Embodiment 32. The PNA oligomer of embodiment 31, wherein heteroalkyl is C2-30 heteroalkyl. [0375] Embodiment 33. The PNA oligomer of embodiment 31, wherein heteroalkyl is polyalkylene glycol. [0376] Embodiment 34. The PNA oligomer of embodiment 31, wherein heteroalkyl is polyethylene glycol. [0377] Embodiment 35. The PNA oligomer of any one of embodiments 30-34, wherein one of R3 and R4 comprises a C2-C30 heteroalkyl and each R5 and R6 is independently hydrogen. [0378] Embodiment 36. The PNA oligomer of embodiment 35, wherein one of R3 and R4 comprises C2-30 polyethylene glycol. [0379] Embodiment 37. The PNA oligomer of embodiment 31, wherein each R3, R4, R5, and R6 is independently hydrogen or has the structure of Formula (IV-a) or (IV-b):
Figure imgf000103_0001
wherein R12 is hydrogen or alkyl; and y is 1, 2, 3, 4, or 5. [0380] Embodiment 38. The PNA oligomer of embodiment 37, wherein R12 is C1-4 alkyl. [0381] Embodiment 39. The PNA oligomer of embodiment 38, wherein R12 is methyl, ethyl, isopropyl, or tert-butyl. [0382] Embodiment 40. The PNA oligomer of embodiment 37, wherein R12 is hydrogen or methyl. [0383] Embodiment 41. The PNA oligomer of embodiment 37, wherein R12 is hydrogen or tert- butyl. [0384] Embodiment 42. The PNA oligomer of embodiment 37, wherein R12 is methyl or tert- butyl. [0385] Embodiment 43. The PNA oligomer of any one of embodiments 37-42, wherein y is 1. [0386] Embodiment 44. The PNA oligomer of any one of embodiments 37-42, wherein y is 2. [0387] Embodiment 45. The PNA oligomer of any one of embodiments 23-44, wherein R2 is hydrogen. [0388] Embodiment 46. The PNA oligomer of embodiment 45, wherein R2 is C1-4 alkyl. [0389] Embodiment 47. The PNA oligomer of embodiment 45, wherein R2 is hydrogen. [0390] Embodiment 48. The PNA oligomer of any one of embodiments 14-47, wherein each R5 and R6 is independently hydrogen. [0391] Embodiment 49. The PNA oligomer of any one of embodiments 14-48, wherein R3 has structure of Formula (IV-a) or (IV-b) and R4 is hydrogen. [0392] Embodiment 50. The PNA oligomer of any one of embodiments 14-48, wherein R4 has structure of Formula (IV-a) or (IV-b) and R3 is hydrogen. [0393] Embodiment 51. The PNA oligomer of any one of embodiments 30-50, wherein n is 1. [0394] Embodiment 52. The PNA oligomer of any one of embodiments 30-50, wherein n is 2. [0395] Embodiment 53. The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer is selected from the group consisting of:
Figure imgf000104_0001
wherein R12 is hydrogen or alkyl. [0396] Embodiment 54. The PNA oligomer of embodiment 1, wherein the PNA nucleobase has the Formula (V-i),
Figure imgf000105_0002
[0397] Embodiment 55. The PNA oligomer of embodiment 54, wherein: X1 is C; X2 is N; X3 is C=O; X4 is N; and R20 is H. [0398] Embodiment 56. The PNA oligomer of embodiment 54 or 55, wherein each n and m is independently 1. [0399] Embodiment 57. The PNA oligomer of any one of embodiments 54-56, wherein each R21 and R35 is hydrogen. [0400] Embodiment 58. The PNA oligomer of embodiment 54, wherein X1 is N; X2 is C=O; X3 is CH; X4 is N; and R20 is absent. [0401] Embodiment 59. The PNA oligomer of embodiment 54 or 58, wherein each n and m is independently 1. [0402] Embodiment 60. The PNA oligomer of embodiments 54, 58, or 59, wherein each R21 and R35 is hydrogen. [0403] Embodiment 61. The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer is selected from the group consisting of:
Figure imgf000105_0001
Figure imgf000106_0001
wherein R12 is hydrogen or alkyl. [0404] Embodiment 62. The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyridazin-3(2H)-one. [0405] Embodiment 63. The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyrimidin-2(1H)-one. [0406] Embodiment 64. The PNA oligomer of any one of embodiments 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is 3-oxo-2,3-dihydropyridazine. [0407] Embodiment 65. The PNA oligomer of any one of embodiment 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the target sequence. [0408] Embodiment 66. The PNA oligomer of any one of embodiment 1-14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.3 nm, as determined by X-ray crystallography. [0409] Embodiment 67. The PNA oligomer of embodiment 66, wherein the hydrogen bond has a length of at least about 0.35 nm. [0410] Embodiment 68. The PNA oligomer of embodiment 66, wherein the hydrogen bond has a length of at least about 0.4 nm. [0411] Embodiment 69. The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode cytosine- binding nucleobase. [0412] Embodiment 70. The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode thymine- binding subunit. [0413] Embodiment 71. The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a cytosine nucleobase in the single strand of the dsDNA. [0414] Embodiment 72. The PNA oligomer of any one of embodiments 1-68, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a thymine nucleobase in the single strand of the dsDNA. [0415] Embodiment 73. The PNA oligomer of embodiment 1, wherein the PNA oligomer comprises from about 20 to about 50 PNA subunits. [0416] Embodiment 74. The PNA oligomer of embodiment 1, wherein the PNA oligomer comprises from about 30 to about 40 PNA subunits. [0417] Embodiment 75. The PNA oligomer of embodiment 1, wherein the linker comprises polyethylene glycol. [0418] Embodiment 76. The PNA oligomer of embodiment 1, wherein the linker comprises PEG2. [0419] Embodiment 77. The PNA oligomer of embodiment 1, wherein the linker comprises PEG2PEG2. [0420] Embodiment 78. The PNA oligomer of embodiment 1, wherein the linker comprises PEG3. [0421] Embodiment 79. A PNA oligomer comprising: (a) a first region comprising a pyrimidine-compliant PNA subunit (PC PNA subunit), wherein the PC PNA subunit comprises: - a nucleobase capable of recognizing a pyrimidine nucleobase in a target sequence; and - a polyethylene glycol moiety in the gamma position; and (b) a second region comprising a plurality of PNA subunits that participate in Watson-Crick binding with a target sequence. [0422] Embodiment 80. The PNA oligomer of embodiment 79, wherein R12 is methyl, ethyl, isopropyl, or tert-butyl. [0423] Embodiment 81. The PNA oligomer of embodiment 79, wherein the PNA nucleobase forms no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA. [0424] Embodiment 82. The PNA oligomer of embodiment 79, wherein the PNA nucleobase does not engage in hydrogen bonding with an adenine or a guanosine; or wherein the PNA nucleobase engages in impaired hydrogen bonding. [0425] Embodiment 83. The PNA oligomer of any one of embodiments 1-82, wherein the PNA nucleobase is a Hoogsteen-mode cytosine-binding subunit or a Hoogsteen-mode thymine- binding subunit. [0426] Embodiment 84. The PNA oligomer of any one of embodiments 1-83, wherein the PNA nucleobase binds to a cytosine nucleobase or a thymine nucleobase in the single strand of the dsDNA. [0427] Embodiment 85. The PNA oligomer of any one of embodiments 1-84, wherein the PNA oligomer comprises at least 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50 PNA subunits. [0428] Embodiment 86. The PNA oligomer of any one of embodiments 3-85, wherein the first pyrimidine position in the single strand of the dsDNA comprises a cytosine. [0429] Embodiment 87. The PNA oligomer of any one of embodiments 3-85, wherein the first pyrimidine position in the single strand of the dsDNA comprises a cytosine; and the first region of the PNA oligomer comprises, at the position corresponding to the first pyrimidine position, an HCB PNA subunit. [0430] Embodiment 88. The PNA oligomer of embodiment 87, wherein the PNA subunit at the corresponding position of the first region of the PNA oligomer comprises 2-pyridone. [0431] Embodiment 89. The PNA oligomer of any one of embodiments 3-85, wherein the first pyrimidine position in the single strand of the dsDNA comprises a thymine. [0432] Embodiment 90. The PNA oligomer of embodiment 89, wherein the first pyrimidine position in the single strand of the dsDNA comprises a thymine; and the first region of the PNA oligomer comprises, at the position corresponding to the first pyrimidine position, an HTB PNA subunit. [0433] Embodiment 91. The PNA oligomer of embodiment 90, wherein the PNA subunit at the corresponding position of the first region of the PNA oligomer comprises 3-oxo-2,3- dihydropyridazine. [0434] Embodiment 92. The PNA oligomer of any one of embodiments 1-91, wherein the PNA nucleobase comprises a compound recited in Table 3. [0435] Embodiment 93. A peptide nucleic acid (PNA) oligomer comprising: (a) a first region comprising a first plurality of PNA subunits, and wherein the first region further comprises a pyrimidine-compliant PNA subunit; (b) a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence; and (c) at least one PNA subunit comprising a gamma modification. [0436] Embodiment 94. A PNA oligomer of any one of embodiments 1-93, formulated as a nanoparticle. [0437] Embodiment 95. A lipid nanoparticle (LNP) comprising: (a) one or more or all of: - an ionizable lipid; - a phospholipid; - a sterol; and - an alkylene glycol-containing lipid; and (b) a peptide nucleic acid (PNA) oligomer comprising: a first region comprising a plurality of PNA subunits that bind to a target sequence, wherein: - the target sequence comprises a pyrimidine nucleobase at a first pyrimidine position in the target sequence; and - the first region comprises, at the position corresponding to the first pyrimidine position, a pyrimidine-compliant PNA subunit (PC PNA subunit); and a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence. [0438] Embodiment 96. The LNP of embodiment 95, wherein the PNA oligomer is a PNA oligomer of any one of embodiments 1-86. [0439] Embodiment 97. The LNP of any one of embodiments 95 or 96, wherein the amount of PNA oligomer encapsulated and/or entrapped within the LNP is between 0.1% to 50% by weight of PNA oligomers to the total weight of the LNP. [0440] Embodiment 98. The LNP of any one of embodiments 95-97, wherein the LNP further comprises a load component. [0441] Embodiment 99. The LNP of embodiment 98, wherein the load component comprises a nucleic acid. [0442] Embodiment 100. The LNP of embodiment 99, wherein the nucleic acid comprises a DNA. [0443] Embodiment 101. The LNP of embodiments 99 or 100, wherein the nucleic acid comprises between about 20 and about 100 nucleotides. [0444] Embodiment 102. The LNP of any one of embodiments 99-101, wherein the nucleic acid comprises a phosphorothioate linkage. [0445] Embodiment 103. A nanoparticle comprising: (a) a synthetic polymer; and (b) peptide nucleic acid (PNA) oligomer comprising: (a) a first region comprising a plurality of PNA subunits that bind to a target sequence, wherein: the target sequence comprises a pyrimidine nucleobase at a first pyrimidine position in the target sequence; and the first region comprises, at the position corresponding to the first pyrimidine position, a pyrimidine-compliant PNA subunit (PC PNA subunit); and (b) a second region comprising a plurality of PNA subunits that participate in Watson Crick binding with the target sequence, wherein the nanoparticle comprises one of the following properties: (1) the amount of a PNA oligomer encapsulated and/or entrapped within the nanoparticle is greater than or equal to 2 percent (2%) by weight of PNA oligomers to the total weight of the nanoparticle(s); (2) the diameter of the nanoparticle is between about 30 to about 200 nanometers; or (3) the neutral to negative surface charge of the nanoparticle is less than about - 100 mv. [0446] Embodiment 104. The nanoparticle of embodiment 103, wherein the PNA oligomer is a PNA oligomer of any one of embodiments 1-93. [0447] Embodiment 105. The nanoparticle of any one of embodiments 103-104, wherein the synthetic polymer comprises polylactic acid (PLA), polyglycolic acid (PGA), poly(lactic-co- glycolic acid) (PLGA), poly(4-hydroxy-L-proline ester, other degradable polyesters, polyanhydrides, poly(ortho)esters, polyesters, polyurethanes, poly(butyric acid), poly(valeric acid), poly(caprolactone), poly(hydroxyalkanoates), poly(lactide-co-caprolactone), poly(amine- co-ester) polymers, or a combination of any two or more of the foregoing. [0448] Embodiment 106. A preparation of peptide nucleic acid (PNA) oligomers, comprising a property of any one of embodiments 1-93. [0449] Embodiment 107. A method of treating a disease in a subject, the method comprising administering to the subject a peptide nucleic acid (PNA) oligomer of any one of embodiments 1-93. [0450] Embodiment 108. The method of embodiment 107, wherein the disease comprises a blood disorder. [0451] Embodiment 109. The method of embodiment 108, wherein the blood disorder is a red blood cell disorder. [0452] Embodiment 110. The method of embodiment 109, wherein the red blood cell disorder is beta-thalassemia. [0453] Embodiment 111. The method of embodiment 109, wherein the red blood cell disorder is sickle cell disease. [0454] Embodiment 112. The method of embodiment 109, wherein the red blood cell disorder is sickle cell anemia.

Claims

CLAIMS WHAT IS CLAIMED IS: 1. A peptide nucleic acid (PNA) oligomer comprising: (a) a first region of the PNA oligomer comprising a first plurality of PNA subunits, wherein the first plurality of PNA subunits binds to a first region of a single strand of a double-stranded deoxyribonucleic acid (dsDNA), and wherein the first region of the PNA oligomer comprises a PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv):
Figure imgf000112_0001
wherein: - each X1 or X4 is independently N or C; - X2 is N, CH, or C=O; - X3 is CH, C=O, or C-NH2; - each X5 , X6, and X8 is independently N or CH; - X7 is CH or C=O; - R20 is absent or hydrogen; - each R21, R35, R36, R37, R38, and R39 is independently hydrogen, deuterium, halo, alkyl, alkenyl, alkynyl, heteroalkyl, cyano, -OH, -NH2, or NO2; - R40 is hydrogen or alkyl; - R41 is hydrogen, alkyl, or absent; - R42 is hydrogen, deuterium, alkyl, or heteroalkyl; - each n and m is independently an integer of 1 or 2; - each p is 1, 2, 3, or 4; - each
Figure imgf000112_0002
is independently a single or double bond; and wherein when X2 is C=O, then X3 is not C=O; when X3 is C=O, then X2 is not C=O; and when X3 is C-NH2, then X2 is not C=O; (b) a second region of the PNA oligomer comprising a second plurality of PNA subunits and a third plurality of PNA subunits, wherein the second plurality of PNA subunits binds to the first region of the single strand of the dsDNA and the third plurality of PNA subunits binds to a second region of the single strand of the dsDNA, and wherein the first region of the dsDNA and the second region of the single strand of the dsDNA are adjacent sequences; and (c) a linker, wherein a first terminus of the first region of the PNA oligomer is covalently bound to a first terminus of the linker, and wherein a first terminus of the second region of the PNA oligomer is covalently bound to a second terminus of the linker.
2. The PNA oligomer of claim 1, wherein the PNA oligomer is a PNA tail-clamp (tcPNA) oligomer.
3. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is at a position corresponding to a first pyrimidine position of the dsDNA.
4. The PNA oligomer of claim 1, wherein the first plurality of PNA subunits, the first region of the dsDNA, and the second plurality of PNA subunits form a triplex structure.
5. The PNA oligomer of claim 1, wherein the first region of the PNA oligomer further comprises (a’) a first positively charged region comprising a first positively charged amino acid, wherein the first positively charged region is covalently bound to a second terminal end of the first region of the PNA oligomer.
6. The PNA oligomer of claim 5, wherein the first positively charged amino acid is lysine.
7. The PNA oligomer of claim 1, wherein the second region of the PNA oligomer participates in Watson Crick binding with the first region of the dsDNA and the second region of the dsDNA.
8. The PNA oligomer of claim 1, wherein the second region of the PNA oligomer further comprises a second positively charged amino acid, wherein the second positively charged amino acid is covalently bound to a second terminal end of the second region of the PNA oligomer.
9. The PNA oligomer of claim 8, wherein the second positively charged amino acid is lysine.
10. The PNA oligomer of claim 1, wherein the first region of the PNA oligomer comprises a gamma-modified PNA subunit.
11. The PNA oligomer of claim 1, wherein the second region of the PNA oligomer comprises a gamma-modified PNA subunit.
12. The PNA oligomer of claim 1, wherein the third region of the PNA oligomer comprises a gamma-modified PNA subunit.
13. The PNA oligomer of claim 1, wherein the first region of the PNA oligomer comprises a first gamma-modified PNA subunit, the second region of the PNA oligomer comprises a second gamma-modified PNA subunit, and the third region of the PNA oligomer comprises a third gamma-modified PNA subunit.
14. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer of the Formula (II-a):
Figure imgf000114_0001
wherein: - P1 is a first terminus of the PNA monomer; - P5 is a second terminus of the PNA monomer; - each R3, R4, R5, R6, R7, and R8 is independently alkyl, heteroalkyl, -N(RC)(RD), -ORE, or an amino acid side chain, each of which is substituted or unsubstituted; or hydrogen, deuterium, or halo; - X is N or CRb, wherein Rb is substituted or unsubstituted alkyl, hydrogen, deuterium, or halo; - L is alkylene, alkenylene, heteroalkylene, cycloalkylene, or heterocyclylene, each of which is optionally substituted with one or more RB, wherein each RB is independently deuterium, alkyl, heteroalkyl, -N(RC)(RD), halo, oxo, or -ORE; - B is the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv); - each RC, RD, and RE is independently substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, or hydrogen; and - each “ ” independently denotes an attachment point to another PNA monomer, a protecting group, the linker, an amino acid, or a C-terminus or an N- terminus of the first region of the PNA oligomer or the second region of the PNA oligomer, provided that i) when P1 is an amine terminus, P5 is a carboxyl terminus; or ii) when P5 is an amine terminus, P1 is a carboxyl terminus.
15. The PNA oligomer of claim 14, wherein P1 is an amine terminus.
16. The PNA oligomer of claim 14, wherein P1 is a carboxyl terminus.
17. The PNA oligomer of claim 14, wherein P1 forms a covalent bond with a P5 group of a second PNA monomer within the first region of the PNA oligomer.
18. The PNA oligomer of claim 14, wherein P5 is an amine terminus.
19. The PNA oligomer of claim 14, wherein P5 is a carboxyl terminus.
20. The PNA oligomer of claim 14, wherein P5 forms a covalent bond with a P1 group of a second PNA monomer within the first region of the PNA oligomer.
21. The PNA oligomer of claim 14, wherein P1 is an amine terminus and P5 is a carboxyl terminus.
22. The PNA oligomer of claim 14, wherein X is N.
23. The PNA oligomer of claim 14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer has the Formula (II-b):
Figure imgf000115_0001
wherein R2 is substituted or unsubstituted alkyl, hydrogen, or deuterium.
24. The PNA oligomer of claim 14, wherein L is alkylene or heteroalkylene, each of which is optionally substituted with one or more RB.
25. The PNA oligomer of claim 24, wherein L is ethylene, propylene, or butylene.
26. The PNA oligomer of claim 24, wherein RB is oxo.
27. The PNA oligomer of any one of claims 14-23, wherein L is selected from the group consisting of
Figure imgf000115_0002
28. The PNA oligomer of claim 14, wherein each R3, R4, R5, R6, R7, and R8 is independently hydrogen or heteroalkyl.
29. The PNA oligomer of claim 14, wherein one of R3 and R4 comprises a C2-C30 heteroalkyl and each R5, R6, R7, and R8 is independently hydrogen.
30. The PNA oligomer of claim 14, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer has the Formula (II-d):
Figure imgf000115_0003
wherein: - each R9 and R10 is independently hydrogen, deuterium, C1-4 alkyl, or halo; and - n is 0, 1, 2, 3, or 4.
31. The PNA oligomer of claim 30, wherein each R3, R4, R5, and R6 is independently hydrogen or heteroalkyl.
32. The PNA oligomer of claim 31, wherein heteroalkyl is C2-30 heteroalkyl.
33. The PNA oligomer of claim 31, wherein heteroalkyl is polyalkylene glycol.
34. The PNA oligomer of claim 31, wherein heteroalkyl is polyethylene glycol.
35. The PNA oligomer of claim 30, wherein one of R3 and R4 comprises a C2-C30 heteroalkyl and each R5 and R6 is independently hydrogen.
36. The PNA oligomer of claim 35, wherein one of R3 and R4 comprises C2-30 polyethylene glycol.
37. The PNA oligomer of claim 30, wherein each R3, R4, R5, and R6 is independently hydrogen or has a structure of Formula (IV-a) or (IV-b):
Figure imgf000116_0001
wherein R12 is hydrogen or alkyl; and y is 1, 2, 3, 4, or 5.
38. The PNA oligomer of claim 37, wherein R12 is C1-4 alkyl.
39. The PNA oligomer of claim 37, wherein R12 is methyl, ethyl, isopropyl, or tert-butyl.
40. The PNA oligomer of claim 37, wherein R12 is hydrogen or methyl.
41. The PNA oligomer of claim 37, wherein R12 is hydrogen or tert-butyl.
42. The PNA oligomer of claim 37, wherein R12 is methyl or tert-butyl.
43. The PNA oligomer of claim 37, wherein y is 1.
44. The PNA oligomer of claim 37, wherein y is 2.
45. The PNA oligomer of claim 30, wherein R2 is hydrogen or C1-4 alkyl.
46. The PNA oligomer of claim 30, wherein R2 is C1-4 alkyl.
47. The PNA oligomer of claim 30, wherein R2 is hydrogen.
48. The PNA oligomer of claim 14, wherein each R5 and R6 is independently hydrogen.
49. The PNA oligomer of claim 14, wherein R3 has structure of Formula (IV-a) or (IV-b) and R4 is hydrogen.
50. The PNA oligomer of claim 14, wherein R4 has structure of Formula (IV-a) or (IV-b) and R3 is hydrogen.
51. The PNA oligomer of claim 30, wherein n is 1.
52. The PNA oligomer of claim 30, wherein n is 2.
53. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer is selected from the group consisting of:
Figure imgf000117_0001
wherein R12 is hydrogen or alkyl.
54. The PNA oligomer of claim 1, wherein the PNA nucleobase has the Formula (V-i),
Figure imgf000117_0002
55. The PNA oligomer of claim 54, wherein: X1 is C; X2 is N; X3 is C=O; X4 is N; and R20 is H.
56. The PNA oligomer of claim 55, wherein each n and m is independently 1.
57. The PNA oligomer of claim 55, wherein each R21 and R35 is hydrogen.
58. The PNA oligomer of claim 54, wherein X1 is N; X2 is C=O; X3 is CH; X4 is N; and R20 is absent.
59. The PNA oligomer of claim 58, wherein each n and m is independently 1.
60. The PNA oligomer of claim 58, wherein each R21 and R35 is hydrogen.
61. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is part of a PNA monomer of the first plurality of PNA subunits, wherein the PNA monomer is selected from the group consisting of:
Figure imgf000118_0001
wherein R12 is hydrogen or alkyl.
62. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyridazin-3(2H)-one.
63. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is pyrimidin-2(1H)-one.
64. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is 3-oxo-2,3-dihydropyridazine.
65. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) engages in no more than one hydrogen bond with a nucleobase in the single strand of the dsDNA.
66. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) forms a hydrogen bond with a nucleobase in the single strand of the dsDNA, wherein the hydrogen bond has a length of at least about 0.3 nm, as determined by X- ray crystallography.
67. The PNA oligomer of claim 66, wherein the hydrogen bond has a length of at least about 0.35 nm.
68. The PNA oligomer of claim 66, wherein the hydrogen bond has a length of at least about 0.4 nm.
69. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode cytosine-binding nucleobase.
70. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) is a Hoogsteen-mode thymine-binding subunit.
71. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a cytosine nucleobase in the single strand of the dsDNA.
72. The PNA oligomer of claim 1, wherein the PNA nucleobase comprising Formula (V-i), (V-ii), (V-iii), or (V-iv) binds to a thymine nucleobase in the single strand of the dsDNA.
73. The PNA oligomer of claim 1, wherein the PNA oligomer comprises from about 20 to about 50 PNA subunits.
74. The PNA oligomer of claim 1, wherein the PNA oligomer comprises from about 30 to about 40 PNA subunits.
75. The PNA oligomer of claim 1, wherein the linker comprises polyethylene glycol.
76. The PNA oligomer of claim 1, wherein the linker comprises PEG2.
77. The PNA oligomer of claim 1, wherein the linker comprises PEG2PEG2.
78. The PNA oligomer of claim 1, wherein the linker comprises PEG3.
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