US20210260210A1 - Anti-her2 biparatopic antibody-drug conjugates and methods of use - Google Patents

Anti-her2 biparatopic antibody-drug conjugates and methods of use Download PDF

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Publication number
US20210260210A1
US20210260210A1 US16/980,318 US201916980318A US2021260210A1 US 20210260210 A1 US20210260210 A1 US 20210260210A1 US 201916980318 A US201916980318 A US 201916980318A US 2021260210 A1 US2021260210 A1 US 2021260210A1
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Prior art keywords
antibody
her2
antigen
drug conjugate
linker
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US16/980,318
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Inventor
Kevin Hamblett
Rupert H. Davies
James R. RICH
Gerald J. Rowse
Vincent K.C. Fung
Stuart D. Barnscher
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Zymeworks BC Inc
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Zymeworks Inc Canada
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Priority to US16/980,318 priority Critical patent/US20210260210A1/en
Assigned to ZYMEWORKS INC. reassignment ZYMEWORKS INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ZYMEWORKS BIOPHARMACEUTICALS INC.
Assigned to ZYMEWORKS INC. reassignment ZYMEWORKS INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BARNSCHER, STUART DANIEL
Assigned to ZYMEWORKS BIOPHARMACEUTICALS INC. reassignment ZYMEWORKS BIOPHARMACEUTICALS INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DAVIES, Rupert H., HAMBLETT, Kevin
Assigned to ZYMEWORKS INC. reassignment ZYMEWORKS INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ROWSE, GERALD JAMES, Fung, Vincent K.C., RICH, James R.
Publication of US20210260210A1 publication Critical patent/US20210260210A1/en
Assigned to ZYMEWORKS BC INC. reassignment ZYMEWORKS BC INC. CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: ZYMEWORKS INC.
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    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/60—Immunoglobulins specific features characterized by non-natural combinations of immunoglobulin fragments
    • C07K2317/62—Immunoglobulins specific features characterized by non-natural combinations of immunoglobulin fragments comprising only variable region components
    • C07K2317/622—Single chain antibody (scFv)
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07K—PEPTIDES
    • C07K2317/00—Immunoglobulins specific features
    • C07K2317/70—Immunoglobulins specific features characterized by effect upon binding to a cell or to an antigen
    • C07K2317/73—Inducing cell death, e.g. apoptosis, necrosis or inhibition of cell proliferation

Definitions

  • the present disclosure relates to the field of cancer therapeutics and, in particular, to antibody-drug conjugates comprising a biparatopic anti-HER2 antibody and an auristatin analogue.
  • HER2 is a transmembrane surface-bound receptor tyrosine kinase that is a member of the ErbB family of receptor tyrosine kinases and is normally involved in the signal transduction pathways leading to cell growth and differentiation.
  • HER2 is a promising target for treatment of breast cancer as it was found to be overexpressed in about one-quarter of breast cancer patients (Bange et al, Nature Medicine 7:548 (2001)).
  • Herceptin® (trastuzumab, U.S. Pat. No. 5,821,337) was the first monoclonal antibody developed for the treatment of HER2-positive breast cancer and has increased survival times for patients so that they are now the same as for patients with HER2-negative breast cancer.
  • Pertuzumab (Perjeta®, U.S. Pat. No. 7,862,817) is a humanized monoclonal antibody, which is designed specifically to prevent the HER2 receptor from pairing (dimerizing) with other HER receptors (EGFR/HER1, HER3 and HER4) on the surface of cells, a process that is believed to play a role in tumour growth and survival.
  • Perjeta binds to domain II of HER2, essential for dimerization, while trastuzumab binds to extracellular domain IV of HER2.
  • the present disclosure relates to an antibody-drug conjugate comprising an anti-HER2 biparatopic antibody conjugated to an auristatin analogue via a linker (L) at a low average drug-to-antibody ratio (DAR), wherein the anti-HER2 biparatopic antibody comprises a first antigen-binding polypeptide construct which binds a first HER2 epitope and a second antigen-binding polypeptide construct which binds a second HER2 epitope, the first and second HER2 epitopes being different epitopes, and wherein the low average DAR is an average DAR of less than 3.9.
  • L linker
  • DAR drug-to-antibody ratio
  • the auristatin analogue-linker has general Formula (II):
  • the low average DAR of the antibody-drug conjugate is between 0.5 and 3.5, or between 0.5 and 2.5.
  • the antibody-drug conjugate comprises 5% or more DAR0 species or 15% or more DAR0 species. In some embodiments, the antibody-drug conjugate comprises between about 5% and about 50% DAR0 species, or between about 10% and about 30% DAR0 species, or between about 10% and about 25% DAR0 species, or between about 15% and about 25% DAR0 species.
  • the antibody-drug conjugate comprises 25% or less DAR6 or greater species, or 15% or less DAR6 or greater species. In some embodiments, the antibody-drug conjugate comprises between 0% and about 15% DAR6 or greater species, or between about 0% and about 10% DAR6 or greater species.
  • Another aspect of the present disclosure relates to a pharmaceutical composition
  • a pharmaceutical composition comprising an anti-HER2 biparatopic antibody-drug conjugate as described herein and a pharmaceutically acceptable carrier or diluent.
  • Another aspect relates to a method of treating a HER2-expressing cancer comprising administering to a subject having a HER2-expressing cancer an effective amount of an anti-HER2 biparatopic antibody-drug conjugate as described herein.
  • Another aspect relates to an antibody-drug conjugate as described herein for use in therapy.
  • Another aspect relates to an antibody-drug conjugate as described herein for use to treat a HER2-expressing cancer in a subject in need thereof.
  • Another aspect relates to a use of an antibody-drug conjugate as described herein in the manufacture of a medicament for the treatment of a HER2-expressing cancer.
  • Another aspect relates to an antibody-drug conjugate composition
  • FIG. 1 shows non-reducing and reducing SDS-PAGE of (A) v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4), and (B) v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2), each compared to parent anti-HER2 biparatopic antibody (v10000).
  • FIG. 2 shows hydrophobic interaction chromatography (HIC) traces for (A) parent anti-HER2 biparatopic antibody v0000, (B) v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 showing an average DAR of 3.92), and (C) v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 showing an average DAR of 2.07).
  • the individual contributions of the DAR0, DAR2, DAR4 and DAR6 species to the average DAR of the purified ADCs is shown in (D) and (E).
  • FIG. 3 shows size-exclusion chromatography (SEC) traces for (A) parent anti-HER2 biparatopic antibody v10000, (B) v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4), and (C) v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2).
  • SEC size-exclusion chromatography
  • FIG. 4 shows the results of flow cytometry binding assays on antigen-positive cells, comparison of v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4) and v10000 (parent biparatopic anti-HER2 antibody) binding to (A) JIMT-1 breast carcinoma cells, and (B) RT-112 bladder carcinoma cells, and (C) comparison of v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2) and v0000 (parent anti-HER2 biparatopic antibody) binding to JIMT-1 breast carcinoma cells.
  • FIG. 5 shows the results of treating the HER2-expressing breast carcinoma cell lines BT-474 (A), SK-BR-3 (B), HCC1954 (C), JIMT-1 (D) and ZR-75-1 (E), and the HER2 negative cell line MDA-MB-468 (F) with v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4) and v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2).
  • FIG. 6 shows the results of treating the HER2-expressing ovarian carcinoma cell line SK-OV-3 (A), and the breast carcinoma cell lines ZR-75-1 (B) and JIMT-1 (C) with antibody-drug conjugates comprising v10000 conjugated to Linker-Toxin 001 at various average DAR.
  • the individual contributions of the DAR0, DAR2, DAR4 and DAR6 species to the average DAR of the ADCs having an average DAR of 0.7, 2.2 and 3.9 is shown in (D).
  • FIG. 7 shows the results of treating HBCx-13b breast cancer patient derived xenograft mice g14d x2 with the noted doses of (A) v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4) and (B) v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2).
  • v15496 vehicle.
  • FIG. 8 shows the results of treating ST-910 breast cancer patient derived xenograft mice qdx1 with the noted doses of (A) v17597 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR4) and (B) v21252 (anti-HER2 biparatopic antibody conjugated to Linker-Toxin 001 at DAR2).
  • v15496 vehicle.
  • FIG. 13 shows internalization of pHAb-conjugated v21252 compared to pHAb-conjugated Trastuzumab-Linker-Toxin 001 and negative control into (A) SKBR3 cells, and (B) JIMT-1 cells.
  • FIG. 14 shows internalization of pHAb-conjugated v21252 (A) compared to pHAb-conjugated Trastuzumab-Linker-Toxin 001 (B) into SKBR3 cells at various time points as indicated. Nuclei are shown in grey, and pHAb is shown in white.
  • FIG. 15 shows comparative exposure in cynomolgus monkeys and mice treated with v21252 at the indicated doses: (A) exposure in cynomolgus monkeys and mice subcutaneously implanted with high HER2 patient derived tumour (HBCx-13b), (B) exposure in cynomolgus monkeys and mice subcutaneously implanted with low HER2 patient derived tumour (ST-910).
  • FIG. 16 shows the results of treating LTL-654 ovarian cancer patient derived xenograft mice qwk x4 with 3 mg/kg of vehicle or v21252.
  • FIG. 17 provides the survival results for mice intracranially implanted with BT-474 breast tumour cells after weekly i.v. administration of vehicle, control conjugate (humanized antibody against respiratory syncytial virus conjugated to Linker-Toxin 001), v21252, v7155 (T-DM1, DAR3.5) and v24029 (trastuzumab conjugated at DAR8 to an exatecan-derivative topoisomerase I inhibitor (DXd)), each at 6 mg/kg weekly for 12 total injections.
  • control conjugate humanized antibody against respiratory syncytial virus conjugated to Linker-Toxin 001
  • v21252, v7155 T-DM1, DAR3.5
  • v24029 trastuzumab conjugated at DAR8 to an exatecan-derivative topoisomerase I inhibitor (DXd)
  • FIG. 18 provides the survival results for mice intracranially implanted with BT-474 breast tumour cells after i.v. administration of vehicle, control conjugate (humanized antibody against respiratory syncytial virus conjugated to Linker-Toxin 001), or v7155 (T-DM1, DAR3.5) at 6 mg/kg weekly for 12 total injections or v21252 or v24029 (trastuzumab conjugated at DAR8 to an exatecan-derivative topoisomerase I inhibitor (DXd)), each at 6 mg/kg every two weeks for 6 total injections.
  • control conjugate humanized antibody against respiratory syncytial virus conjugated to Linker-Toxin 001
  • v7155 T-DM1, DAR3.5
  • DXd exatecan-derivative topoisomerase I inhibitor
  • the present disclosure relates to anti-HER2 biparatopic antibody-drug conjugates (ADCs) in which the drug is an auristatin analogue and is conjugated to the antibody at a low average drug-to-antibody ratio (DAR).
  • ADCs anti-HER2 biparatopic antibody-drug conjugates
  • the low average DAR ( ⁇ 3.9) ADCs as described herein have improved tolerability and decreased toxicity as compared to a corresponding ADC having a DAR ⁇ 3.9 when administered at the same toxin (auristatin analogue) dose.
  • the present disclosure also relates to methods of using the ADCs described herein in the treatment of a HER2-expressing cancer.
  • the term “subject,” as used herein, refers to an animal, in some embodiments a mammal, which is the object of treatment, observation or experiment.
  • the animal may be a human, a non-human primate, a companion animal (for example, dog, cat, or the like), farm animal (for example, cow, sheep, pig, horse, or the like) or a laboratory animal (for example, rat, mouse, guinea pig, non-human primate, or the like).
  • the subject is a human.
  • mammal includes but is not limited to humans, non-human primates, canines, felines, murines, bovines, equines and porcines. In certain embodiments, the mammal is a human.
  • the term “about” refers to an approximately +/ ⁇ 10% variation from a given value. It is to be understood that such a variation is always included in any given value provided herein, whether or not it is specifically referred to.
  • compositions, use or method denotes that additional elements and/or method steps may be present, but that these additions do not materially affect the manner in which the recited composition, method or use functions.
  • Consisting of when used herein in connection with a composition, use or method, excludes the presence of additional elements and/or method steps.
  • a composition, use or method described herein as comprising certain elements and/or steps may also, in certain embodiments consist essentially of those elements and/or steps, and in other embodiments consist of those elements and/or steps, whether or not these embodiments are specifically referred to.
  • the antibody-drug conjugates (ADCs) of the present disclosure comprise an anti-HER2 biparatopic antibody conjugated to a toxin via a linker at a low average drug-to-antibody ratio (DAR), the toxin being an auristatin-based toxin (or “auristatin analogue”).
  • DAR drug-to-antibody ratio
  • auristatin-based toxins are known in the art.
  • the auristatin analogue is a compound of general Formula (I):
  • Low DAR is defined as an average DAR of less than 3.9, but more than 0.5. In some embodiments, the average DAR of the ADCs is less than 3.5. In some embodiments, the average DAR of the ADCs is less than 3.4, for example, less than 3.3, less than 3.2 or less than 3.1. In some embodiments, the average DAR of the ADCs is 3.0 or less. In some embodiments, the average DAR of the ADCs is 2.9 or less, for example, 2.8 or less, 2.7 or less, or 2.6 or less. In some embodiments, the average DAR of the ADCs is 2.5 or less, for example, 2.4 or less, 2.3 or less, or 2.2 or less. In some embodiments, the average DAR of the ADCs is about 2.0.
  • the average DAR of the ADCs is between 0.5 and 3.8, for example, between 0.5 and 3.5, or between 0.5 and 2.5. In some embodiments, the average DAR of the ADCs is between 0.7 and 3.8, for example, between 0.7 and 3.5, between 0.7 and 3.0, or between 0.7 and 2.5. In some embodiments, the average DAR of the ADCs is between 1.0 and 3.8, for example, between 1.0 and 3.5, between 1.0 and 3.0, or between 1.0 and 2.5. In some embodiments, the average DAR of the ADCs is between 1.5 and 3.8, for example, between 1.5 and 3.5, between 1.5 and 3.0, or between 1.5 and 2.5.
  • the average DAR of the ADCs is between 1.6 and 3.8, for example, between 1.6 and 3.5, between 1.6 and 3.0, or between 1.6 and 2.5. In some embodiments, the average DAR of the ADCs is between 1.8 and 2.8, for example, between 1.8 and 2.5.
  • the low average DAR ( ⁇ 3.9) ADCs as described herein have improved tolerability and decreased toxicity as compared to a corresponding ADC having a DAR ⁇ 3.9 when administered at the same toxin dose.
  • the majority of conjugation methods yield an ADC composition that includes various DAR species, with the reported DAR being the average of the individual DAR species.
  • the higher tolerability and decreased toxicity of the low DAR ADC may be due to one or both of a decrease in high DAR (6 or greater) species in the ADC composition and/or an increase in the DAR0 species in the ADC composition.
  • the low DAR ADC composition may include 5% or more DAR0 species. In some embodiments, the low DAR ADC composition may include 10% or more DAR0 species. In some embodiments, the low DAR ADC composition may include 15% or more DAR0 species, for example, 20% or more DAR0 species. In some embodiments, the low DAR ADC composition may include between about 5% and about 50% DAR0 species.
  • the low DAR ADC composition may include between about 10% and about 50% DAR0 species, for example, between about 10% and about 40%, between about 10% and about 30% DAR0 species, or between about 10% and about 25% DAR0 species. In some embodiments, the low DAR ADC composition may include between about 12% and about 28% DAR0 species, for example, between about 12% and about 28% DAR0 species, or between about 15% and about 25% DAR0 species.
  • the low DAR ADC composition may include less than about 35% DAR6 or greater species. In some embodiments, the low DAR ADC composition may include 30% or less DAR6 or greater species. In some embodiments, the low DAR ADC composition may include 25% or less DAR6 or greater species, for example, 20% or less, 15% or less, or 10% or less DAR6 or greater species. In some embodiments, the low DAR ADC composition may include 9% or less DAR6 or greater species, for example, 8% or less, 7% or less, 6% or less, or 5% or less DAR6 or greater species.
  • the low DAR ADC composition may include between 0% and about 35% DAR6 or greater species. In some embodiments, the low DAR ADC composition may include between 0% and about 30% DAR6 or greater species, for example, between 0% and about 25%, or between 0% and about 20% DAR6 or greater species. In some embodiments, the low DAR ADC composition may include between 0% and about 15% DAR6 or greater species, for example, between about 0% and about 10%, between about 0% and about 8%, or between 0% and about 5% DAR6 or greater species.
  • ADCs that comprise an anti-HER2 biparatopic antibody conjugated to an auristatin analogue via a linker (L) at a low average drug-to-antibody ratio (DAR), the auristatin analogue-linker having general Formula (II):
  • Certain embodiments relate to an ADC having general Formula (III):
  • the ADCs described herein comprise an anti-HER2 biparatopic antibody that binds to two different epitopes of HER2.
  • antibody generally refers to a proteinaceous binding molecule with immunoglobulin-like functions. Typical examples of an antibody are immunoglobulins, as well as derivatives or functional fragments thereof which still retain binding specificity. Techniques for the production of antibodies are well known in the art.
  • antibody may also include immunoglobulins of different classes (i.e. IgA, IgG, IgM, IgD and IgE) and subclasses (such as IgG 1 , IgG 2 , IgG 3 , IgG 4 , IgA 1 and IgA 2 ).
  • an antibody is whole antibodies and antigen-binding fragments thereof, such as Fab fragments, F(ab′) 2 , Fv fragments, single-chain Fv fragments (scFv), diabodies, domain antibodies, and combinations thereof.
  • Domain antibodies may be single domain antibodies, single variable domain antibodies or immunoglobulin single variable domain having only one variable domain, which may be a heavy chain variable domain or a light chain variable domain, that specifically bind an antigen or epitope independently of other variable regions or domains.
  • the term “antibody” also includes embodiments such as chimeric, single chain and humanized antibodies.
  • a typical whole antibody comprises at least two heavy (H) chains and two light (L) chains interconnected by disulfide bonds.
  • Each heavy chain is comprised of a heavy chain variable region (VH) and a heavy chain constant region (CH).
  • the heavy chain constant region comprises three domains: CH1, CH2 and CH3.
  • the heavy chain constant domains that correspond to the different classes of immunoglobulins are known as ⁇ (IgA), ⁇ (IgD), ⁇ (IgE), ⁇ (IgG) and ⁇ (IgM).
  • Each light chain is comprised of a light chain variable region (VL) and a light chain constant region.
  • the light chain constant region comprises just one domain: CL. Light chains are classified as either kappa or lambda.
  • VH and VL regions can be further subdivided into regions of hypervariability, termed Complementarity Determining Regions (CDR), interspersed with regions that are more conserved, termed framework regions (FW).
  • CDR Complementarity Determining Regions
  • FW framework regions
  • Each VH and VL is composed of three CDRs and four FWs, arranged from amino-terminus to carboxy-terminus in the following order: FW1, CDR1, FW2, CDR2, FW3, CDR3, FW4.
  • the variable regions of the heavy and light chains contain a binding domain (a paratope) that interacts with an antigen.
  • the constant regions of the antibodies can mediate the binding of the immunoglobulin to host tissues or factors, including various cells of the immune system (such as effector cells) and C1q, which is a component of the complement system.
  • the anti-HER2 biparatopic antibodies for inclusion in the ADCs described herein comprise two antigen-binding polypeptide constructs, each of which binds to a different epitope of HER2.
  • An “antigen-binding polypeptide construct,” as used herein, may be an immunoglobulin-based construct, for example, an antibody fragment, or it may be a non-immunoglobulin-based antibody mimetic format, such as an anticalin, a fynomer, an affimer, an alphabody, a DARPin or an avimer.
  • the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may be immunoglobulin-based constructs.
  • the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may be antibody fragments.
  • the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may each independently be a Fab fragment, a Fab′ fragment, an scFv or an sdAb. In some embodiments, the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may each independently be a Fab fragment or an scFv. In some embodiments, one antigen-binding polypeptide construct comprised by the anti-HER2 biparatopic antibody may be a Fab fragment and the other antigen-binding polypeptide construct may be an scFv.
  • At least one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may be a Fab fragment or a Fab′ fragment.
  • a “Fab fragment” contains the constant domain of the light chain (CL) and the first constant domain of the heavy chain (CH1) along with the variable domains of the light and heavy chains (VL and VH, respectively).
  • Fab′ fragments differ from Fab fragments by the addition of a few amino acid residues at the C-terminus of the heavy chain CH1 domain, including one or more cysteines from the antibody hinge region.
  • a Fab fragment may also be a single-chain Fab molecule, i.e.
  • Fab molecule in which the Fab light chain and the Fab heavy chain are connected by a peptide linker to form a single peptide chain.
  • the C-terminus of the Fab light chain may be connected to the N-terminus of the Fab heavy chain in the single-chain Fab molecule.
  • At least one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may be a single-chain Fv (scFv).
  • An “scFv” includes a heavy chain variable domain (VH) and a light chain variable domain (VL) of an antibody in a single polypeptide chain.
  • the scFv may optionally further comprise a polypeptide linker between the VH and VL domains which enables the scFv to form a desired structure for antigen binding.
  • an scFv may include a VL connected from its C-terminus to the N-terminus of a VH by a polypeptide linker.
  • an scFv may comprise a VH connected through its C-terminus to the N-terminus of a VL by a polypeptide chain or linker (see review in Pluckthun in The Pharmacology of Monoclonal Antibodies , vol. 113, Rosenburg and Moore eds., Springer-Verlag, New York, pp. 269-315 (1994)).
  • At least one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody may be in a single domain antibody (sdAb) format.
  • An sdAb format refers to a single immunoglobulin domain.
  • the sdAb may be, for example, of camelid origin. Camelid antibodies lack light chains and their antigen-binding sites consist of a single domain, termed a “VHH.”
  • An sdAb comprises three CDR/hypervariable loops that form the antigen-binding site: CDR1, CDR2 and CDR3.
  • sdAbs are fairly stable and easy to express, for example, as a fusion with the Fc chain of an antibody (see, for example, Harmsen & De Haard, Appl. Microbiol Biotechnol. 77(1): 13-22 (2007)).
  • the anti-HER2 biparatopic antibodies for inclusion in the ADCs described herein may have various formats.
  • the minimal components of the anti-HER2 biparatopic antibody are a first antigen-binding polypeptide construct that binds to a first HER2 epitope and a second antigen-binding polypeptide construct that binds to a second HER2 epitope, with the first and second HER2 epitopes being different.
  • An antibody that comprises two antigen-binding polypeptide constructs that bind to different HER2 epitopes may be considered to be a bivalent, biparatopic antibody.
  • Certain embodiments relate to bivalent, anti-HER2 biparatopic antibodies.
  • the anti-HER2 biparatopic antibody may comprise one or more additional antigen-binding polypeptide constructs, each of which bind to either the first or second HER2 epitope.
  • the anti-HER2 biparatopic antibody may be trivalent or tetravalent.
  • the anti-HER2 biparatopic antibody further comprises a linker that links the first and second antigen-binding polypeptide constructs.
  • the anti-HER2 biparatopic antibody further comprises a scaffold and the first and second antigen-binding polypeptide constructs are operably linked to the scaffold.
  • operably linked means that the components described are in a relationship permitting them to function in their intended manner.
  • the anti-HER2 biparatopic antibodies may thus be considered to have a modular architecture that includes two antigen-binding polypeptide construct modules and optionally one or both of a linker module and a scaffold module.
  • these modules may be combined in various ways to provide anti-HER2 biparatopic antibodies having different formats. These formats are based generally on antibody formats known in the art (see, for example, review by Brinkmann & Kontermann, MABS, 9(2):182-212 (2017), and Müller & Kontermann, “ Bispecific Antibodies ” in Handbook of Therapeutic Antibodies , Wiley-VCH Verlag GmbH & Co. (2014)).
  • the anti-HER2 biparatopic antibody comprises two antigen-binding polypeptide constructs operably linked to a scaffold. Suitable scaffolds are described below. In some embodiments, the anti-HER2 biparatopic antibody comprises two antigen-binding polypeptide constructs operably linked to a scaffold, and at least one of the antigen-binding polypeptide constructs is an scFv. In some embodiments, the anti-HER2 biparatopic antibody comprises two antigen-binding polypeptide constructs operably linked to a scaffold, and at least one of the antigen-binding polypeptide constructs is a Fab.
  • the anti-HER2 biparatopic antibody may comprise three or four antigen-binding polypeptide constructs and a scaffold.
  • at least the first and second antigen-binding constructs are operably linked to the scaffold.
  • the third and optional fourth antigen-binding polypeptide constructs may each independently be operably linked to the scaffold or to the first antigen-binding polypeptide construct or to the second antigen-binding polypeptide construct.
  • Anti-HER2 biparatopic antibodies that lack a scaffold typically comprise two antigen-binding polypeptide constructs operably linked by one or more linkers.
  • the antigen-binding polypeptide constructs may be in the form of scFvs, Fabs, sdAbs, or a combination thereof.
  • scFvs as the antigen-binding polypeptide constructs, formats such as a tandem scFv ((scFv) 2 or taFv) may be constructed, in which the scFvs are connected together by a flexible linker.
  • scFvs may also be used to construct diabody formats, which comprise two scFvs connected by a short linker (usually about 5 amino acids in length).
  • the restricted length of the linker results in dimerization of the scFvs in a head-to-tail manner.
  • the scFvs may be further stabilized by inclusion of an interdomain disulfide bond.
  • a disulfide bond may be introduced between VL and VH through introduction of an additional cysteine residue in each chain (for example, at position 44 in VH and 100 in VL) (see, for example, Fitzgerald et al., Protein Engineering, 10:1221-1225 (1997)), or a disulfide bond may be introduced between two VHs to provide construct having a DART format (see, for example, Johnson et al., J Mol. Biol., 399:436-449 (2010)).
  • formats comprising two sdAbs, such as VHs or VHHs, connected together through a suitable linker may be employed in some embodiments.
  • an scFv or a sdAb may be fused to the C-terminus of either or both of the light and heavy chain of a Fab fragment resulting in a bivalent (Fab-scFv/sdAb) construct.
  • the anti-HER2 biparatopic antibody may comprise two antigen-binding polypeptide constructs and one or more linkers, and does not include a scaffold.
  • the anti-HER2 biparatopic antibody comprises two antigen-binding polypeptide constructs which are scFvs, Fabs, sdAbs, or a combination thereof, and one or more linkers, and does not include a scaffold.
  • Anti-HER2 biparatopic antibodies comprising a scaffold may be constructed by linking the two antigen-binding polypeptide constructs to a suitable scaffold.
  • the antigen-binding polypeptide constructs may be in one or a combination of the forms described above (for example, scFvs, Fabs and/or sdAbs).
  • suitable scaffolds include, but are not limited to, immunoglobulin Fc regions, albumin, albumin analogs and derivatives, heterodimerizing peptides (such as leucine zippers, heterodimer-forming “zipper” peptides derived from Jun and Fos, IgG CH1 and CL domains or bamase-barstar toxins), cytokines, chemokines or growth factors.
  • Other examples include antibodies based on the DOCK-AND-LOCKTM (DNLTM) technology developed by IBC Pharmaceuticals, Inc. and Immunomedics, Inc. (see, for example, Chang, et al., Clin Cancer Res 13:5586s-5591s (2007)).
  • the anti-HER2 biparatopic antibodies comprise two or more antigen-binding polypeptide constructs and a scaffold. In some embodiments, the anti-HER2 biparatopic antibodies comprise two antigen-binding polypeptide constructs operably linked to a scaffold.
  • a scaffold may be a peptide, polypeptide, polymer, nanoparticle or other chemical entity. Where the scaffold is a polypeptide, each antigen-binding polypeptide construct of the anti-HER2 biparatopic antibody may be linked to either the N- or C-terminus of the polypeptide scaffold.
  • Anti-HER2 biparatopic antibodies comprising a polypeptide scaffold in which one or more of the antigen-binding polypeptide constructs are linked to a region other than the N- or C-terminus, for example, via the side chain of an amino acid with or without a linker, are also contemplated in certain embodiments.
  • the antigen-binding polypeptide constructs may be linked to the scaffold by genetic fusion or chemical conjugation.
  • the antigen-binding polypeptide constructs are linked to the scaffold by genetic fusion.
  • the antigen-binding polypeptide constructs may be linked to the scaffold by chemical conjugation.
  • a number of protein domains are known in the art that comprise selective pairs of two different polypeptides and may be used to form a scaffold.
  • An example is leucine zipper domains such as Fos and Jun that selectively pair together (Kostelny, et al., J Immunol, 148:1547-53 (1992); Wranik, et al., J. Biol. Chem., 287: 43331-43339 (2012)).
  • protein scaffolds include immunoglobulin Fc regions, albumin, albumin analogues and derivatives, toxins, cytokines, chemokines and growth factors.
  • the use of protein scaffolds in combination with antigen-binding moieties has been described (see, for example, Müller et al., J Biol Chem, 282:12650-12660 (2007); McDonaugh et al., Mol Cancer Ther, 11:582-593 (2012); Vallera et al., Clin Cancer Res, 11:3879-3888 (2005); Song et al., Biotech Appl Biochem, 45:147-154 (2006), and U.S. Patent Application Publication No. 2009/0285816).
  • Antigen-binding moieties such as scFvs, diabodies or single chain diabodies to albumin has been shown to improve the serum half-life of the antigen-binding moieties (Müller et al., ibid.).
  • Antigen-binding moieties may be fused at the N- and/or C-termini of albumin, optionally via a linker.
  • albumin in the form of heteromultimers that comprise two transporter polypeptides obtained by segmentation of an albumin protein such that the transporter polypeptides self-assemble to form quasi-native albumin have been described (see International Patent Application Publication Nos. WO 2012/116453 and WO 2014/012082).
  • the heteromultimer includes four termini and thus can be fused to up to four different antigen-binding moieties, optionally via linkers.
  • the anti-HER2 biparatopic antibody may comprise a protein scaffold. In some embodiments, the anti-HER2 biparatopic antibody may comprise a protein scaffold that is based on an immunoglobulin Fc region, an albumin or an albumin analogue or derivative. In some embodiments, the anti-HER2 biparatopic antibody may comprise a protein scaffold that is based on an immunoglobulin Fc region, for example, an IgG Fc region.
  • the anti-HER2 biparatopic antibody may comprise a protein scaffold that is based on an albumin, for example human serum albumin (HSA), or an albumin analogue or derivative.
  • HSA human serum albumin
  • the anti-HER2 biparatopic antibody may comprise a protein scaffold that is based on an albumin derivative as described in International Patent Application Publication No. WO 2012/116453 or WO 2014/012082.
  • Fc region refers to a C-terminal region of an immunoglobulin heavy chain that contains at least a portion of the constant region.
  • the term includes native sequence Fe regions and variant Fe regions. Unless otherwise specified herein, numbering of amino acid residues in the Fc region or constant region is according to the EU numbering system, also called the EU index, as described in Kabat et al, Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, Md. (1991).
  • the anti-HER2 biparatopic antibodies may comprise a scaffold that is based on an immunoglobulin Fc region.
  • the Fc region may be dimeric and composed of two Fc polypeptides. In some embodiments, the Fc region may be composed of a single polypeptide.
  • an “Fc polypeptide” of a dimeric Fc refers to one of the two polypeptides forming the dimeric Fc domain, i.e. a polypeptide comprising one or more C-terminal constant regions of an immunoglobulin heavy chain that is capable of stable self-association.
  • the terms “first Fc polypeptide” and “second Fc polypeptide” may be used interchangeably provided that the Fc region comprises one first Fc polypeptide and one second Fc polypeptide.
  • An Fc region comprises a CH3 domain or both a CH3 and a CH2 domain.
  • an Fc polypeptide of a dimeric IgG Fc region comprises an IgG CH2 and an IgG CH3 constant domain sequence.
  • the CH3 domain comprises two CH3 sequences, one from each of the two Fc polypeptides of the dimeric Fc region.
  • the CH2 domain comprises two CH2 sequences, one from each of the two Fc polypeptides of the dimeric Fc region.
  • the anti-HER2 biparatopic antibody may comprise a scaffold that is based on an IgG Fc region. In some embodiments, the anti-HER2 biparatopic antibody may comprise a scaffold that is based on a human Fc region. In some embodiments, the anti-HER2 biparatopic antibody may comprise a scaffold based on a human IgG Fc region, for example a human IgG1 Fc region.
  • the anti-HER2 biparatopic antibody may comprise a scaffold based on an IgG Fc region, which is a heterodimeric Fc region, comprising a first Fc polypeptide and a second Fc polypeptide, each comprising a CH3 sequence, and optionally a CH2 sequence.
  • the anti-HER2 biparatopic antibody may comprise a scaffold based on an Fc region which comprises first and second Fc polypeptides, and the first antigen-binding polypeptide construct is operably linked to the first Fc polypeptide and the second antigen-binding polypeptide construct is operably linked to the second Fc polypeptide.
  • the anti-HER2 biparatopic antibody may comprise a scaffold based on an Fc region which comprises first and second Fc polypeptides, in which the first antigen-binding polypeptide construct is operably linked to the first Fc polypeptide and the second antigen-binding polypeptide construct is operably linked to the second Fc polypeptide, and in which the first and second antigen-binding polypeptide constructs are independently a Fab fragment or an scFv.
  • the anti-HER2 biparatopic antibody may comprise a scaffold based on an Fc region which comprises two CH3 sequences, at least one of which comprises one or more amino acid modifications. In some embodiments, the anti-HER2 biparatopic antibody may comprise a scaffold based on an Fc region which comprises two CH3 sequences and two CH2 sequences, at least one of the CH2 sequences comprising one or more amino acid modifications.
  • the anti-HER2 biparatopic antibody comprises a heterodimeric Fc region comprising a modified CH3 domain, wherein the modified CH3 domain is an asymmetrically modified CH3 domain.
  • the first Fc polypeptide of the heterodimeric Fc comprises a first CH3 sequence and the second Fc polypeptide comprises a second CH3 sequence.
  • asymmetric amino acid modification refers to a modification where an amino acid at a specific position on a first CH3 sequence is different to the amino acid on a second CH3 sequence at the same position.
  • first and second CH3 sequence will typically preferentially pair to form a heterodimer, rather than a homodimer.
  • These asymmetric amino acid modifications can be a result of modification of only one of the two amino acids at the same respective amino acid position on each sequence, or different modifications of both amino acids on each sequence at the same respective position on each of the first and second CH3 sequences.
  • Each of the first and second CH3 sequence of a heterodimeric Fc may comprise one or more than one asymmetric amino acid modification.
  • the anti-HER2 biparatopic antibody may comprise a scaffold based on a modified Fc region as described in International Patent Application Publication No. WO 2012/058768 or WO 2013/063702.
  • Table 1 provides the amino acid sequence of the human IgG1 Fc sequence (SEQ ID NO:1), corresponding to amino acids 231 to 447 of the full-length human IgG1 heavy chain.
  • the CH3 sequence comprises amino acids 341-447 of the full-length human IgG1 heavy chain.
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold comprising a modified CH3 domain that comprises asymmetric amino acid modifications that promote formation of a heterodimeric Fc rather than a homodimeric Fc.
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold which includes modifications at one or more of the following positions: L351, F405, Y407, T366, K392, T394, T350, S400 and/or N390, using EU numbering.
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc comprising a modified CH3 domain having a first polypeptide sequence that comprises amino acid modifications at positions F405 and Y407, and optionally further comprises an amino acid modification at position L351, and a second polypeptide sequence that comprises amino acid modifications at positions T366 and T394, and optionally further comprises an amino acid modification at position K392.
  • a first polypeptide sequence of the modified CH3 domain may comprise amino acid modifications at positions F405 and Y407, and optionally further comprises an amino acid modification at position L351, and a second polypeptide sequence of the modified CH3 domain comprises amino acid modifications at positions T366 and T394, and optionally further comprises an amino acid modification at position K392, and the amino acid modification at position F405 is F405A, F405I, F405M, F405S, F405T or F405V; the amino acid modification at position Y407 is Y407I or Y407V; the amino acid modification at position T366 is T366I, T366L or T366M; the amino acid modification at position T394 is T394W; the amino acid modification at position L351 is L351Y, and the amino acid modification at position K392 is K392F, K392L or K392M.
  • the amino acid modification at position F405 is F405A, F
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc comprising a modified CH3 domain having a first Fc polypeptide sequence comprising amino acid modifications at positions F405 and Y407, and optionally further comprises an amino acid modification at position L351, and a second Fc polypeptide sequence comprising amino acid modifications at positions T366 and T394, and optionally further comprises an amino acid modification at position K392, and the amino acid modification at position F405 is F405A, F405I, F405M, F405S, F405T or F405V; the amino acid modification at position Y407 is Y407I or Y407V; the amino acid modification at position T366 is T366I, T366L or T366M; the amino acid modification at position T394 is T394W; the amino acid modification at position L351 is L351Y, and the amino acid modification at position K392 is K392F, K392L or K392M,
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc comprising a modified CH3 domain as described above, in which the first Fe polypeptide sequence comprises amino acid modifications at positions F405 and Y407, and optionally further comprises an amino acid modification at position L351, and the second Fc polypeptide sequence comprises amino acid modifications at positions T366 and T394, and optionally further comprises an amino acid modification at position K392, and in which the first Fc polypeptide sequence further comprises an amino acid modification at one or both of positions S400 or Q347 and/or the second Fe polypeptide sequence further comprises an amino acid modification at one or both of positions K360 or N390, where the amino acid modification at position 5400 is S400E, S400D, S400R or S400K; the amino acid modification at position Q347 is Q347R, Q347E or Q347K; the amino acid modification at position K360 is K360D or K360E, and the amino acid modification at position N390 is N390R, N390
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold having a modified CH3 domain comprising the modifications of any one of Variant 1, Variant 2, Variant 3, Variant 4 or Variant 5, as shown in Table 1.
  • IgG1 Fc sequences Human IgG1 APELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVS Fc sequence HEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVS 231-447 (EU- VLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKG numbering) QPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIA VEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKS RWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQID NO: 1) Variant IgG1 Fc sequence Chain Mutations 1 A L351Y_F405A_Y407V B T366L_K392M_T394W 2 A L351Y_F405A_Y407V B T366L_K392L_T394W 3 A T350V_L351Y_F
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold having a modified CH3 domain with a first CH3 sequence comprising one or more amino acid modifications selected from L351Y, F405A, and Y407V, and the second CH3 sequence comprising the amino acid modifications T366L or T366I; K392L or K392M, and T394W, and one or both of the first and second CH3 sequences may optionally further comprise the amino acid modification T350V.
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold having a modified CH3 domain comprising asymmetric amino acid modifications as described above that promote the formation of a heterodimeric Fc in which the heterodimeric CH3 domain has a stability that is comparable to a wild-type homodimeric CH3 domain.
  • the stability of the CH3 domain may be assessed by measuring the melting temperature (Tm) of the CH3 domain, for example by differential scanning calorimetry (DSC).
  • the one or more asymmetric amino acid modifications promote the formation of a heterodimeric Fc domain in which the CH3 domain has a stability as observed via the melting temperature (Tm) in a differential scanning calorimetry study that is within about 8° C., for example, within about 7° C., about 6° C., about 5° C., or about 4° C., of that observed for the corresponding symmetric wild-type homodimeric CH3 domain.
  • Tm melting temperature
  • a heterodimeric Fc comprising modified CH3 sequences may be formed with a purity of at least about 75% as compared to homodimeric Fc in the expressed product.
  • the anti-HER2 biparatopic antibody may comprise a heterodimeric Fc scaffold having a modified CH3 domain comprising asymmetric amino acid modifications that promote the formation of a heterodimeric Fc with a purity greater than about 80%, greater than about 85%, greater than about 90%, greater than about 95% or greater than about 97%.
  • Additional methods for modifying monomeric Fc polypeptides to promote heterodimeric Fc formation include, for example, those described in International Patent Application Publication No. WO 96/027011 (knobs into holes); Gunasekaran et al. J Biol Chem, 285, 19637-46 (2010) (electrostatic design to achieve selective heterodimerization); Davis et al., Prot Eng Des Sel, 23(4):195-202 (2010) (strand exchange engineered domain (SEED) technology), and Labrijn et al., Proc Natl Acad Sci USA, 110(13):5145-50 (2013) (Fab-arm exchange).
  • SEED strand exchange engineered domain
  • the heterodimeric Fc also comprises a CH2 domain.
  • the CH2 domain is a modified CH2 domain.
  • FcRs Fc receptors
  • Fe receptors include receptors of the Fc ⁇ RI, Fc ⁇ RII, and Fc ⁇ RIII subclasses, including allelic variants and alternatively spliced forms of these receptors.
  • the term FcR may also include in certain embodiments the neonatal receptor, FcRn.
  • Modifications in the CH2 domain can affect the binding of FcRs to the Fc.
  • a number of amino acid modifications in the Fc region are known in the art for selectively altering the affinity of the Fc for different Fc ⁇ receptors.
  • the modified CH2 domain may comprise one or more modifications to promote selective binding of Fc ⁇ receptors.
  • Non-limiting examples of modifications that alter the binding of the Fe by FcRs include S298A/E333A/K334A and S298A/E333A/K334A/K326A (Lu, et al., J Immunol Methods, 365(1-2):132-41 (2011)); F243L/R292P/Y300L/V305I/P396L and F243L/R292P/Y300L/L235V/P396L (Stavenhagen, et al., Cancer Res, 67(18):8882-90 (2007) and Nordstrom J L, et al., Breast Cancer Res, 13(6):R123 (2011)); F243L (Stewart, et al., Protein Eng Des Sel.
  • Fc binding by FcRs Additional modifications that affect Fc binding by FcRs are described in Therapeutic Antibody Engineering (Strohl & Strohl, Woodhead Publishing series in Biomedicine No 11, ISBN 1907568 37 9, October 2012, page 283). Fc regions that comprise asymmetric modifications that affect binding by FcRs are described in International Patent Publication No. WO 2014/190441.
  • Fc regions may be made to improve their ability to mediate effector function.
  • modifications are known in the art and include afucosylation, or engineering of the affinity of the Fc towards an activating receptor, mainly Fc ⁇ RIIIa for ADCC, and towards C1q for CDC.
  • the anti-HER2 biparatopic antibody may comprise an Fc region modified to improve its ability to mediate effector function.
  • the anti-HER2 biparatopic antibody may comprise an Fc region that is aglycosylated.
  • the anti-HER2 biparatopic antibody may be fully afucosylated (i.e.
  • the anti-HER2 biparatopic antibody contains less than 95%, less than 85%, less than 75%, less than 65%, less than 55%, less than 45%, less than 35%, less than 25%, less than 15% or less than 5%, or any amount therebetween, of the amount of fucose normally detected for a similar construct produced by a mammalian expression system.
  • Fc modifications reducing Fc ⁇ R and/or complement binding and/or effector function are known in the art and include those described above.
  • Various publications describe strategies that have been used to engineer antibodies with reduced or silenced effector activity (see, for example, Strohl, Curr Opin Biotech 20:685-691 (2009), and Strohl & Strohl, “ Antibody Fc engineeringfor optimal antibody performance ” In Therapeutic Antibody Engineering , Cambridge: Woodhead Publishing (2012), pp 225-249). These strategies include reduction of effector function through modification of glycosylation, use of IgG2/IgG4 scaffolds, or the introduction of mutations in the hinge or CH2 regions of the Fc (see also, U.S. Patent Publication No. 2011/0212087, International Patent Publication No. WO 2006/105338, U.S. Patent Publication No. 2012/0225058, U.S. Patent Publication No. 2012/0251531 and Strop et al., J. Mol. Biol. 420: 204-219
  • amino acid modifications to reduce Fc ⁇ R or complement binding to the Fc include those identified in Table 2.
  • the anti-HER2 biparatopic antibody may comprise an Fc region that comprises a modified CH2 domain having one or more mutations identified in Table 2. In some embodiments, the anti-HER2 biparatopic antibody may comprise an Fc region comprising a modified CH2 domain having amino acid modifications at positions L234, L235 and/or D265. In some embodiments, the anti-HER2 biparatopic antibody may comprise an Fc region comprising a modified CH2 domain having the amino acid modifications L234A, L235A and D265S.
  • the two antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody each bind to a different epitope of HER2, that is, a first antigen-binding polypeptide construct binds to a first HER2 epitope and a second antigen-binding polypeptide construct binds to a second HER2 epitope.
  • each of the antigen-binding polypeptide constructs specifically binds to its target epitope.
  • Specifically binds or “specific binding” mean that the binding is selective for the antigen and can be discriminated from unwanted or non-specific interactions.
  • the ability of an antigen-binding polypeptide construct to bind to a specific epitope can be measured, for example, through an enzyme-linked immunosorbent assay (ELISA), surface plasmon resonance (SPR) techniques (analyzed on a BIAcore instrument) (Liljeblad et al, Glyco J 17, 323-329 (2000)) or traditional binding assays (Heeley, Endocr Res 28, 217-229 (2002)).
  • ELISA enzyme-linked immunosorbent assay
  • SPR surface plasmon resonance
  • the antigen-binding polypeptide construct is considered to specifically bind to its target epitope when the extent of binding of the antigen-binding polypeptide construct to an unrelated protein is less than about 10% of the binding of the antigen-binding polypeptide construct to its target epitope as measured, for example, by SPR.
  • HER2 also known as ErbB2 refers to human HER2 protein described, for example, in Semba et al., PNAS (USA), 82:6497-6501 (1985) and Yamamoto et al., Nature, 319:230-234 (1986) (GenBank accession number X03363).
  • the terms “erbB2” and “neu” refer to the gene encoding human HER2 protein.
  • the terms p185 or p185neu may also be used to refer to the protein product of the neu gene.
  • HER2 comprises an extracellular domain, which typically binds a HER ligand, a lipophilic transmembrane domain, a conserved intracellular tyrosine kinase domain and a carboxyl-terminal signaling domain harboring several tyrosine residues which can be phosphorylated.
  • the extracellular (ecto) domain of HER2 comprises four domains, Domains I-IV.
  • the sequence of HER2 is provided in Table 3 (SEQ ID NO:2).
  • the Extracellular Domain (ECD) boundaries are: Domain I—approximately amino acids 1-165; Domain II—approximately amino acids 166-322; Domain III—approximately amino acids 323-488, and Domain IV—approximately amino acids 489-607.
  • Epitopope 2C4 is the region in the extracellular domain of HER2 to which the antibody 2C4 binds and comprises residues from Domain II in the extracellular domain of HER2 (also referred to as ECD2). 2C4 and Pertuzumab bind to the extracellular domain of HER2 at the junction of Domains I, II and III (Franklin et al. Cancer Cell 5:317-328 (2004)).
  • Epitope 4D5 is the region in the extracellular domain of HER2 to which the antibody 4D5 (ATCC CRL 10463) and trastuzumab bind. This epitope is close to the transmembrane domain of HER2, and within Domain IV of HER2 (also referred to as ECD4).
  • the anti-HER2 biparatopic antibody of the present disclosure will bind to epitopes within the extracellular domains of HER2.
  • the first and second HER2 epitopes bound by the first and second antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody are non-overlapping epitopes.
  • the first and second HER2 epitopes bound by the first and second antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody are on different extracellular domains of HER2.
  • the first antigen-binding polypeptide construct of the anti-HER2 biparatopic antibody binds to a first HER2 epitope on a first domain of HER2, and the second antigen-binding polypeptide construct binds to a second HER2 epitope on a second domain of HER2.
  • the first domain of HER2 is ECD2 and the second domain of HER2 is ECD4.
  • one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody competes with trastuzumab for binding to HER2. In some embodiments, one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody competes with Pertuzumab for binding to HER2. In some embodiments, one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody competes with trastuzumab for binding to HER2, and the other antigen-binding polypeptide construct competes with Pertuzumab for binding to HER2.
  • one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody is in a Fab or scFv format and competes with trastuzumab for binding to HER2, and the other antigen-binding polypeptide construct is in a Fab or scFv format and competes with Pertuzumab for binding to HER2.
  • one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody is in a Fab format and competes with trastuzumab for binding to HER2, and the other antigen-binding polypeptide construct is in an scFv format and competes with Pertuzumab for binding to HER2.
  • one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody binds to the same epitope on HER2 as trastuzumab. In some embodiments, one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody binds to the same epitope on HER2 as Pertuzumab. In some embodiments, one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody binds to the same epitope on HER2 as trastuzumab, and the other antigen-binding polypeptide construct binds to the same epitope on HER2 as Pertuzumab.
  • one of the antigen-binding polypeptide constructs comprised by the anti-HER2 biparatopic antibody comprises the CDR sequences of trastuzumab or a variant thereof comprising one or more mutations known to increase HER2 binding
  • the other antigen-binding polypeptide construct comprises the CDRs of pertuzumab or a variant thereof comprising one or more mutations known to increase HER2 binding.
  • anti-HER2 biparatopic antibodies are known in the art and may be suitable candidate antibodies for inclusion in the ADCs described herein. Examples include antibodies described in U.S. Patent Application Publication Nos. 2014/0170148; 2015/0284463; 2016/0289335; 2017/0029529; 2017/0291955 and 2018/0022820, and International Patent Application Publication No. WO 2016/179707.
  • the anti-HER2 biparatopic antibody is one of the biparatopic antibodies described in U.S. Patent Application Publication No. 2016/0289335. In some embodiments, the anti-HER2 biparatopic antibody is one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717 (see Tables 6, 6A and 6B, and Sequence Tables).
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence and a VL sequence from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence and a VL sequence from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717
  • the other antigen-binding polypeptide construct comprises a VH sequence and a VL sequence from the ECD4-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises the CDR sequences from the ECD2-binding arm of one of v5019, v5020, v7091, v0000, v6902, v6903 or v6717.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises the CDR sequences from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717
  • the other antigen-binding polypeptide construct comprises the CDR sequences from the ECD4-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a set of CDRs (i.e.
  • heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3) that have 90% or greater, 95% or greater, 98% or greater, 99% or greater, or 100% sequence identity to a set of CDRs from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a variant of these CDR sequences comprising between 1 and 10 amino acid substitutions across the six CDRs (that is, the CDRs may be modified by including up to 10 amino acid substitutions with any combination of CDRs being modified), for example, between 1 and 7 amino acid substitutions, between 1 and 5 amino acid substitutions, between 1 and 4 amino acid substitutions, between 1 and 3 amino acid substitutions, between 1 and 2 amino acid substitutions, or 1 amino acid substitution, across the CDRs, wherein the variant retains the ability to bind ECD2.
  • amino acid substitutions will be conservative amino acid substitutions.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a set of CDRs (i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3) that have 90% or greater, 95% or greater, 98% or greater, 99% or greater, or 100% sequence identity to a set of CDRs from the ECD2-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • CDRs i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VH sequence from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VL sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VL sequence from the ECD2-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VH sequence from the ECD2-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VL sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VL sequence from the ECD2-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD2.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a set of CDRs (i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3) that have 90% or greater, 95% or greater, 98% or greater, 99% or greater, or 100% sequence identity to a set of CDRs from the ECD4-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • CDRs i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a variant of these CDR sequences comprising between 1 and 10 amino acid substitutions across the six CDRs (that is, the CDRs may be modified by including up to 10 amino acid substitutions with any combination of CDRs being modified), for example, between 1 and 7 amino acid substitutions, between 1 and 5 amino acid substitutions, between 1 and 4 amino acid substitutions, between 1 and 3 amino acid substitutions, between 1 and 2 amino acid substitutions, or 1 amino acid substitution, across the CDRs, wherein the variant retains the ability to bind ECD4. Typically, such amino acid substitutions will be conservative amino acid substitutions.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a set of CDRs (i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3) that have 90% or greater, 95% or greater, 98% or greater, 99% or greater, or 100% sequence identity to a set of CDRs from the ECD4-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • CDRs i.e. heavy chain CDR1, CDR2 and CDR3, and light chain CDR1, CDR2 and CDR3
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VH sequence from the ECD4-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VL sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VL sequence from the ECD4-binding arm of one of v5019, v5020, v7091, v10000, v6902, v6903 or v6717, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VH sequence from the ECD4-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VL sequence that is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% identical to the VL sequence from the ECD4-binding arm of v10000, wherein the antigen-binding polypeptide construct retains the ability to bind ECD4.
  • the anti-HER2 biparatopic antibody is one of the biparatopic antibodies described in International Patent Application Publication No. WO 2016/179707.
  • This application describes high-affinity variants of the anti-HER2 antibody pertuzumab, including biparatopic antibodies comprising sequences from a high-affinity variant as one antigen-binding domain.
  • the anti-HER2 biparatopic antibody is one of v7133, v15079, v15080, v15081, v15082, v15083, v15084 or v15085 (see Tables 7 and 7A, and Sequence Tables).
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence and a VL sequence from the ECD2-binding arm of one of v7133, v15079, v15080, v15081, v15082, v15083, v15084 or v15085.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises the CDR sequences from the ECD2-binding arm of one of v7133, v15079, v15080, v15081, v15082, v15083, v15084 or v15085.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises a VH sequence and a VL sequence from the ECD2-binding arm of one of v7133, v15079, v15080, v15081, v15082, v15083, v15084 or v15085, and the other antigen-binding polypeptide construct comprises the VH sequence and VL sequence from trastuzumab.
  • one of the antigen-binding polypeptide constructs of the anti-HER2 biparatopic antibody comprises the CDR sequences from the ECD2-binding arm of one of v7133, v15079, v15080, v15081, v15082, v15083, v15084 or v15085, and the other antigen-binding polypeptide construct comprises the CDR sequences from trastuzumab.
  • a corresponding bivalent monospecific antibody may comprise two of the first antigen-binding polypeptide constructs, or two of the second antigen-binding polypeptide constructs that are comprised by the biparatopic antibody.
  • the anti-HER2 biparatopic antibodies show an increased binding (i.e. bind with a higher affinity) to HER2 compared to a corresponding bivalent monospecific antibody.
  • Increased binding may be shown, for example, by a decrease in dissociation constant and/or an increase in maximal binding.
  • a dissociation constant or (K D ) refers to the equilibrium dissociation constant of a particular ligand-protein interaction, such as antibody-antigen interactions.
  • the K D measures the propensity of two proteins (e.g. AB) to dissociate reversibly into smaller components (A+B), and is defined as the ratio of the rate of dissociation (also called the “off-rate” or k off ) to the association rate (also called the “on-rate” or k on ).
  • K D equals k off /k on and is expressed as a molar concentration (M). It follows that the smaller the K D , the stronger the affinity of binding.
  • K D values for antibodies can be determined using methods well established in the art. Examples of such methods include surface plasmon resonance (SPR), typically using a biosensor system such as a Biacore® system, and isothermal titration calorimetry (ITC).
  • SPR surface plasmon resonance
  • ITC isothermal titration calori
  • Apparent K D represents the antibody concentration at which half maximal cell binding is observed.
  • the apparent K D is dependent on the conditions of the cell binding experiment, such as different receptor levels expressed on the cells and incubation conditions, and thus the apparent K D is generally different from the K D values determined from cell-free molecular experiments such as SPR and ITC. However, there is generally good agreement between the different methods.
  • Maximal binding refers to the maximum antibody binding level on the cells at saturating concentrations of antibody. This parameter can be reported in the arbitrary unit MFI for relative comparisons, or converted into an absolute value corresponding to the number of antibodies bound to the cell with the use of a standard curve.
  • Bmax and apparent K D can be determined by various techniques.
  • One example is the measurement of binding to target antigen-expressing cells by flow cytometry.
  • the target antigen-expressing cells are incubated with antibodies at different concentrations, washed, incubated with a secondary agent for detecting the antibody, washed, and analyzed in the flow cytometer to measure the median fluorescent intensity (MFI) representing the strength of detection signal on the cells, which in turn is related to the number of antibodies bound to the cells.
  • MFI median fluorescent intensity
  • the antibody concentration vs. MFI data is then fitted into a saturation binding equation to yield Bmax and apparent K D .
  • the anti-HER2 biparatopic antibody displays an increase in Bmax to a target cell displaying HER2 as compared to a corresponding reference antibody.
  • a corresponding reference antibody would be a bivalent monospecific antibody that comprises two of the first antigen-binding polypeptide constructs, or two of the second antigen-binding polypeptide constructs.
  • the Bmax determined for the anti-HER2 biparatopic antibody is at least about 110% of the Bmax of a corresponding reference antibody.
  • the Bmax determined for the anti-HER2 biparatopic antibody is at least about 125% of the Bmax for a corresponding reference antibody, for example, about 150% of the Bmax of the corresponding reference antibody, or at least about 200% of the Bmax of the corresponding reference antibody.
  • the Bmax determined for the anti-HER2 biparatopic antibody is 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0 times the Bmax of a reference antibody.
  • the anti-HER2 biparatopic antibodies show a higher internalization into HER2-expressing cells than a corresponding reference bivalent monospecific antibody.
  • the anti-HER2 biparatopic antibodies are internalized in HER2+ cells through binding to the receptor HER2.
  • the anti-HER2 biparatopic antibodies thus can be considered as being able to induce receptor internalization in HER2+ cells.
  • Antibody internalization may be measured using art-known methods, for example, by a direct internalization method according to the protocol detailed in Schmidt, M. et al., Cancer Immunol Immunother, 57:1879-1890 (2008).
  • cancer cells may express HER2 at various levels.
  • One method of classifying HER2 expressing cells is as HER2 1+, 2+ or 3+(low, medium and high, respectively).
  • the anti-HER2 biparatopic antibody shows a higher internalization than a corresponding reference bivalent monospecific antibody in cells expressing HER2 at the 3+ level.
  • the anti-HER2 biparatopic antibody shows a higher internalization than a corresponding reference bivalent monospecific antibody in cells expressing HER2 at the 2+ level. In some embodiments, the anti-HER2 biparatopic antibody shows a higher internalization than a corresponding reference bivalent monospecific antibody in cells expressing HER2 at the 1+ level. Examples of cell lines expressing different levels of HER2 are described in more detail below.
  • an anti-HER2 biparatopic antibody is considered to demonstrate a higher internalization into HER2-expressing cells than a corresponding reference bivalent monospecific antibody when the amount of anti-HER2 biparatopic antibody internalized into the HER2-expressing cells is at least 1.2 times greater than the amount of reference bivalent monospecific antibody internalized into the same HER2-expressing cells.
  • the amount of internalized antibody is determined by the direct internalization method according to the protocol detailed in Schmidt, M. et al., Cancer Immunol Immunother, 57:1879-1890 (2008).
  • the amount of internalized antibody is determined in HER2-expressing cells that express HER2 at the 2+ level.
  • an anti-HER2 biparatopic antibody is considered to demonstrate a higher internalization into HER2-expressing cells than a corresponding reference bivalent monospecific antibody when the amount of anti-HER2 biparatopic antibody internalized into the HER2-expressing cells is at least 1.3 times greater than the amount of reference bivalent monospecific antibody internalized into the same HER2-expressing cells.
  • an anti-HER2 biparatopic antibody is considered to demonstrate a higher internalization into HER2-expressing cells than a corresponding reference bivalent monospecific antibody when the amount of anti-HER2 biparatopic antibody internalized into the HER2-expressing cells is at least 1.4 times greater, for example, at least 1.5 times greater, 1.6 times greater, 1.7 times greater, 1.8 times greater, 1.9 times greater, or 2.0 times greater, than the amount of reference bivalent monospecific antibody internalized into the same HER2-expressing cells.
  • the amount of internalized antibody is determined by the direct internalization method according to the protocol detailed in Schmidt, M. et al., Cancer Immunol Immunother, 57:1879-1890 (2008).
  • the amount of internalized antibody is determined in HER2-expressing cells that express HER2 at the 2+ level.
  • the ADCs described herein comprise an auristatin-based toxin (or “auristatin analogue”).
  • auristatin analogues are known in the art. Examples include, but are not limited to, monomethylauristatin F (MMAF), monomethylauristatin E (MMAE), auristatin EB (AEB), auristatin EVB (AEVB) and auristatin F phenylenediamine (AFP).
  • MMAF monomethylauristatin F
  • MMAE monomethylauristatin E
  • AEB auristatin EB
  • AEVB auristatin EVB
  • AFP auristatin F phenylenediamine
  • the auristatin analogue included in the ADCs described herein may be an auristatin analogue as described in International Patent Application Publication No. WO 2016/041082.
  • the auristatin analogue included the ADCs described herein is a compound of general Formula (I):
  • R 1 is selected from:
  • X is absent.
  • the compound of general Formula (I) has general Formula (IV):
  • R 1 is selected from:
  • R 1 is:
  • R 1 is:
  • the compound of general Formula (I) has general Formula (V):
  • R 1 is selected from:
  • R 1 is:
  • R 1 is:
  • Compounds of general Formula (I) may be prepared by standard synthetic organic chemistry protocols from commercially available starting materials. Exemplary methods are provided in International Patent Application Publication No. WO 2016/041082 and in the Examples section below.
  • the ADC of the present disclosure comprises an anti-HER2 biparatopic antibody conjugated to an auristatin analogue (toxin) via a linker (L), in which the linker-toxin has general Formula (II):
  • R 1 is selected from:
  • X is absent.
  • L is a cleavable linker
  • L is a peptide-containing linker.
  • the linker-toxin of general Formula (II) has general Formula (X):
  • R 1 is selected from:
  • R 1 is:
  • R 1 is:
  • L is a cleavable linker
  • L is a peptide-containing linker.
  • L is a protease-cleavable linker.
  • the linker-toxin of general Formula (II) has general Formula (XI):
  • R 1 is selected from:
  • R 1 is:
  • R 1 is:
  • L is a cleavable linker
  • L is a peptide-containing linker.
  • L is a protease-cleavable linker.
  • ADCs comprising an anti-HER2 biparatopic antibody conjugated to a linker-toxin of general Formula (II), Formula (X) or Formula (XI), in which the linker has general Formula (VIII) or (IX) as shown below.
  • the ADC comprises a linker-toxin having the structure:
  • the ADC of the present disclosure comprising an anti-HER2 biparatopic antibody conjugated to an auristatin analogue (toxin) via a linker (L) has general Formula (III):
  • R 1 is selected from:
  • X is absent.
  • R 1 is:
  • R 1 is:
  • X is —C(O)NHCH(CH 2 R 2 )—
  • R 1 is:
  • R 1 is:
  • L is a cleavable linker
  • L is a peptide-containing linker
  • L is a protease-cleavable linker.
  • n is between 0.5 and 3.8.
  • n is between 0.7 and 3.8, between 0.7 and 3.5, between 0.7 and 3.0, or between 0.7 and 2.5.
  • n is between 1.0 and 3.8, between 1.0 and 3.5, between 1.0 and 3.0, or between 1.0 and 2.5.
  • n is between 1.5 and 3.8, between 1.5 and 3.5, between 1.5 and 3.0, or between 1.5 and 2.5.
  • n is between 1.6 and 3.8, between 1.6 and 3.5, between 1.6 and 3.0, or between 1.6 and 2.5.
  • n is between 1.8 and 2.8, or between 1.8 and 2.5.
  • the anti-HER2 biparatopic antibody is linked to the auristatin analogue (toxin) by a linker.
  • Linkers are bifunctional or multifunctional moieties capable of linking one or more toxin molecules to an antibody.
  • a linker may be bifunctional (or monovalent) such that it links a single drug to a single site on the antibody, or it may be multifunctional (or polyvalent) such that it links more than one toxin molecule to a single site on the antibody.
  • Linkers capable of linking one toxin molecule to more than one site on the antibody may also be considered to be multifunctional.
  • Attachment of a linker to an antibody can be accomplished in a variety of ways, such as through surface lysines on the antibody, reductive-coupling to oxidized carbohydrates on the antibody, or through cysteine residues on the antibody liberated by reducing interchain disulfide linkages.
  • attachment of a linker to an antibody may be achieved by modification of the antibody to include additional cysteine residues (see, for example, U.S. Pat. Nos.
  • non-natural amino acids that provide reactive handles, such as selenomethionine, p-acetylphenylalanine, formylglycine or p-azidomethyl-L-phenylalanine (see, for example, Hofer et al., Biochemistry, 48:12047-12057 (2009); Axup et al., PNAS, 109:16101-16106 (2012); Wu et al., PNAS, 106:3000-3005 (2009); Zimmerman et al., Bioconj. Chem., 25:351-361 (2014)), to allow for site-specific conjugation.
  • selenomethionine such as selenomethionine, p-acetylphenylalanine, formylglycine or p-azidomethyl-L-phenylalanine
  • Linkers include a functional group capable of reacting with the target group or groups on the antibody, and one or more functional groups capable of reacting with a target group on the toxin.
  • Suitable functional groups are known in the art and include those described, for example, in Bioconjugate Techniques (G. T. Hermanson, 2013, Academic Press).
  • Non-limiting examples of functional groups for reacting with free cysteines or thiols include maleimide, haloacetamide, haloacetyl, activated esters such as succinimide esters, 4-nitrophenyl esters, pentafluorophenyl esters, tetrafluorophenyl esters, anhydrides, acid chlorides, sulfonyl chlorides, isocyanates and isothiocyanates.
  • maleimide haloacetamide
  • haloacetyl activated esters such as succinimide esters, 4-nitrophenyl esters, pentafluorophenyl esters, tetrafluorophenyl esters, anhydrides, acid chlorides, sulfonyl chlorides, isocyanates and isothiocyanates.
  • self-stabilizing maleimides as described in Lyon et al., Nat. Biotechnol., 32:1059-1062 (2014).
  • Non-limiting examples of functional groups for reacting with surface lysines on an antibody and free amines on a toxin include activated esters such as N-hydroxysuccinamide (NHS) esters, sulfo-NHS esters, imido esters such as Traut's reagent, isothiocyanates, aldehydes and acid anhydrides such as diethylenetriaminepentaacetic anhydride (DTPA).
  • Other examples include succinimido-1,1,3,3-tetra-methyluronium tetrafluoroborate (TSTU) and benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP).
  • Non-limiting examples of functional groups capable of reacting with an electrophilic group on the antibody or toxin include hydrazide, oxime, amino, hydrazine, thiosemicarbazone, hydrazine carboxylate and arylhydrazide.
  • linkers include those having a functional group that allows for bridging of two interchain cysteines on the antibody, such as a ThioBridgeTM linker (Badescu et al., Bioconjug. Chem., 25:1124-1136 (2014)), a dithiomaleimide (DTM) linker (Behrens et al., Mol. Pharm., 12:3986-3998 (2015)), a dithioaryl(TCEP)pyridazinedione based linker (Lee et al., Chem. Sci., 7:799-802 (2016)), a dibromopyridazinedione based linker (Maruani et al., Nat. Commun., 6:6645 (2015)) and others known in the art.
  • ThioBridgeTM linker Bodescu et al., Bioconjug. Chem., 25:1124-1136 (2014)
  • DTM dithiomaleimide
  • TCEP dithioaryl
  • a linker may comprise one or more linker components.
  • a linker will comprise two or more linker components.
  • Exemplary linker components include functional groups for reaction with the antibody, functional groups for reaction with the toxin, stretchers, peptide components, self-immolative groups, self-elimination groups, hydrophilic moieties, and the like.
  • Various linker components are known in the art, some of which are described below.
  • Certain useful linker components can be obtained from various commercial sources, such as Pierce Biotechnology, Inc. (now Thermo Fisher Scientific, Waltham, Mass.) and Molecular Biosciences Inc. (Boulder, Colo.), or may be synthesized in accordance with procedures described in the art (see, for example, Toki et al., J. Org. Chem., 67:1866-1872 (2002); Dubowchik, et al., Tetrahedron Letters, 38:5257-60 (1997); Walker, M. A., J. Org. Chem., 60:5352-5355 (1995); Frisch, et al., Bioconjugate Chem., 7:180-186 (1996); U.S. Pat. Nos. 6,214,345 and 7,553,816, and International Patent Application Publication No. WO 02/088172).
  • linker components include, but are not limited to, N-( ⁇ -maleimidopropyloxy)-N-hydroxy succinimide ester (BMPS), N-(s-maleimidocaproyloxy) succinimide ester (EMCS), N-[ ⁇ -maleimidobutyryloxy]succinimide ester (GMBS), 1,6-hexane-bis-vinylsulfone (HBVS), succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxy-(6-amidocaproate) (LC-SMCC), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), 4-(4-N-Maleimidophenyl)butyric acid hydrazide (MPBH), succinimidyl 3-(bromoacetamido)propionate (SBAP), succinimidyl iodoacetate (SIA), succinimidyl (4-io
  • bis-maleimide reagents such as dithiobismaleimidoethane (DTME), bis-maleimido-trioxyethylene glycol (BMPEO), 1,4-bismaleimidobutane (BMB), 1,4 bismaleimidyl-2,3-dihydroxybutane (BMDB), bismaleimidohexane (BMH), bismaleimidoethane (BMOE), BM(PEG) 2 and BM(PEG) 3 ; bifunctional derivatives of imidoesters (such as dimethyl adipimidate HCl), active esters (such as disuccinimidyl suberate), aldehydes (such as glutaraldehyde), bis-azido compounds (such as bis (p-azidobenzoyl) hexanediamine), bis-diazonium derivatives (such as bis-(p-diazoniumbenzoyl)-ethylenediamine), diisocyanates (such as tol, di
  • Suitable linkers typically are more chemically stable to conditions outside the cell than to conditions inside the cell, although less stable linkers may be contemplated in certain situations, such as when the toxin is selective or targeted and has a low toxicity to normal cells.
  • Linkers may be “cleavable linkers” or “non-cleavable linkers.”
  • a cleavable linker is typically susceptible to cleavage under intracellular conditions, for example, through lysosomal processes. Examples include linkers that are protease-sensitive, acid-sensitive, reduction-sensitive or photolabile.
  • Non-cleavable linkers by contrast, rely on the degradation of the antibody in the cell, which typically results in the release of an amino acid-linker-toxin moiety.
  • Suitable cleavable linkers include, for example, linkers comprising a peptide component that includes two or more amino acids and is cleavable by an intracellular protease, such as lysosomal protease or an endosomal protease.
  • a peptide component may comprise amino acid residues that occur naturally and/or minor amino acids and/or non-naturally occurring amino acid analogues, such as citrulline.
  • Peptide components may be designed and optimized for enzymatic cleavage by a particular enzyme, for example, a tumour-associated protease, cathepsin B, C or D, or a plasmin protease.
  • the linker included in the ADCs may be a dipeptide-containing linker, such as a linker containing valine-citrulline (Val-Cit) or phenylalanine-lysine (Phe-Lys).
  • suitable dipeptides for inclusion in linkers include Val-Lys, Ala-Lys, Me-Val-Cit, Phe-homoLys, Phe-Cit, Leu-Cit, Ile-Cit, Trp-Cit, Phe-Arg, Ala-Phe, Val-Ala, Met-Lys, Asn-Lys, Ile-Pro, Ile-Val, Asp-Val, His-Val, Met-(D)Lys, Asn-(D)Lys, Val-(D)Asp, NorVal-(D)Asp, Ala-(D)Asp, Me 3 Lys-Pro, PhenylGly-(D)Lys, Met-(D)Lys, Asn-(D)Lys, Pro-(D)Lys and Met-(D)Lys.
  • Cleavable linkers may also include longer peptide components such as tripeptides, tetrapeptides or pentapeptides. Examples include, but are not limited to, the tripeptides Met-Cit-Val, Gly-Cit-Val, (D)Phe-Phe-Lys and (D)Ala-Phe-Lys, and the tetrapeptides Gly-Phe-Leu-Gly and Ala-Leu-Ala-Leu.
  • cleavable linkers include disulfide-containing linkers, such as, for example, N-succinimydyl-4-(2-pyridyldithio) butanoate (SPBD) and N-succinimydyl-4-(2-pyridyldithio)-2-sulfo butanoate (sulfo-SPBD).
  • Disulfide-containing linkers may optionally include additional groups to provide steric hindrance adjacent to the disulfide bond in order to improve the extracellular stability of the linker, for example, inclusion of a geminal dimethyl group.
  • Other suitable linkers include linkers hydrolyzable at a specific pH or within a pH range, such as hydrazone linkers. Linkers comprising combinations of these functionalities may also be useful, for example, linkers comprising both a hydrazone and a disulfide are known in the art.
  • a further example of a cleavable linker is a linker comprising a ⁇ -glucuronide, which is cleavable by ⁇ -glucuronidase, an enzyme present in lysosomes and tumour interstitium (see, for example, De Graaf et al., Curr. Pharm. Des., 8:1391-1403 (2002)).
  • Cleavable linkers may optionally further comprise one or more additional components such as self-immolative and self-elimination groups, stretchers or hydrophilic moieties.
  • Self-immolative and self-elimination groups that find use in linkers include, for example, p-aminobenzyloxycarbonyl (PABC) and p-aminobenzyl ether (PABE) groups, and methylated ethylene diamine (MED).
  • PABC p-aminobenzyloxycarbonyl
  • PABE p-aminobenzyl ether
  • MED methylated ethylene diamine
  • Other examples of self-immolative groups include, but are not limited to, aromatic compounds that are electronically similar to the PABC or PABE group such as heterocyclic derivatives, for example 2-aminoimidazol-5-methanol derivatives as described in U.S. Pat. No. 7,375,078.
  • Stretchers that find use in linkers for ADCs include, for example, alkylene groups and stretchers based on aliphatic acids, diacids, amines or diamines, such as diglycolate, malonate, caproate and caproamide.
  • Other stretchers include, for example, glycine-based stretchers, polyethylene glycol (PEG) stretchers and monomethoxy polyethylene glycol (mPEG) stretchers.
  • PEG and mPEG stretchers also function as hydrophilic moieties.
  • components commonly found in cleavable linkers that may find use in the ADCs of the present disclosure in some embodiments include, but are not limited to, SPBD, sulfo-SPBD, hydrazone, Val-Cit, maleidocaproyl (MC or mc), mc-Val-Cit, mc-Val-Cit-PABC, Phe-Lys, mc-Phe-Lys, mc-Phe-Lys-PABC, maleimido triethylene glycolate (MT), MT-Val-Cit, MT-Phe-Lys and adipate (AD).
  • SPBD sulfo-SPBD
  • hydrazone Val-Cit
  • MC or mc maleidocaproyl
  • mc-Val-Cit mc-Val-Cit
  • mc-Val-Cit-PABC Phe-Lys
  • mc-Phe-Lys mc-Phe-
  • the linker included in the ADCs of the present disclosure are peptide-based linkers having general Formula (VI):
  • Z is:
  • Str is selected from:
  • Str is:
  • Str is:
  • AA 1 -[AA 2 ] m is selected from Val-Lys, Ala-Lys, Phe-Lys, Val-Cit, Phe-Cit, Leu-Cit, Ile-Cit, Trp-Cit, Phe-Arg, Ala-Phe, Val-Ala, Met-Lys, Asn-Lys, Ile-Pro, Ile-Val, Asp-Val, His-Val, Met-(D)Lys, Asn-(D)Lys, Val-(D)Asp, NorVal-(D)Asp, Ala-(D)Asp, Me 3 Lys-Pro, PhenylGly-(D)Lys, Met-(D)Lys, Asn-(D)Lys, Pro-(D)Lys, Met-(D)Lys, Met-Cit-Val, Gly-Cit-Val, (D)Phe-Phe-Ly
  • m is 1 (i.e. AA 1 -[AA 2 ] m is a dipeptide).
  • AA 1 -[AA 2 ] m is a dipeptide selected from Val-Lys, Ala-Lys, Phe-Lys, Val-Cit, Phe-Cit, Leu-Cit, Ile-Cit and Trp-Cit.
  • each X is independently selected from p-aminobenzyloxycarbonyl (PABC), p-aminobenzyl ether (PABE) and methylated ethylene diamine (MED).
  • PABC p-aminobenzyloxycarbonyl
  • PABE p-aminobenzyl ether
  • MED methylated ethylene diamine
  • m is 1, 2 or 3.
  • s is 1.
  • o 0.
  • the linker is a disulfide-containing linker and the ADC has general Formula (VII):
  • p and q are each independently an integer between 1 and 4.
  • Y is —(CH 2 ) p — and p is an integer between 1 and 4.
  • each R 1 is independently H or Me.
  • r is 1 or 2.
  • non-cleavable linkers are known in the art for linking drugs to antibodies and may be useful in the ADCs of the present disclosure in certain embodiments.
  • non-cleavable linkers include linkers having an N-succinimidyl ester or N-sulfosuccinimidyl ester moiety for reaction with the antibody, as well as a maleimido- or haloacetyl-based moiety for reaction with the toxin, or vice versa.
  • An example of such a non-cleavable linker is based on sulfosuccinimidyl-4-[N-maleimidomethyl]cyclohexane-1-carboxylate (sulfo-SMCC).
  • linkers include those based on N-succinimidyl 4-(maleimidomethyl)cyclohexanecarboxylate (SMCC), N-succinimidyl-4-(N-maleimidomethyl)-cyclohexane-1-carboxy-(6-amidocaproate) (“long chain” SMCC or LC-SMCC), x-maleimidoundecanoic acid N-succinimidyl ester (KMUA), ⁇ -maleimidobutyric acid N-succinimidyl ester (GMBS), ⁇ -maleimidocaproic acid N-hydroxysuccinimide ester (EMCS), m-maleimidobenzoyl-N-hydroxysuccinimide ester (MBS), N-( ⁇ -maleimidoacetoxy)-succinimide ester (AMAS), succinimidyl-6-( ⁇ -maleimidopropionamido)hexanoate
  • SMCC N
  • haloacetyl-based functional group such as N-succinimidyl-4-(iodoacetyl)-aminobenzoate (SIAB), N-succinimidyl iodoacetate (SIA), N-succinimidyl bromoacetate (SBA) and N-succinimidyl 3-(bromoacetamido)propionate (SBAP).
  • a haloacetyl-based functional group such as N-succinimidyl-4-(iodoacetyl)-aminobenzoate (SIAB), N-succinimidyl iodoacetate (SIA), N-succinimidyl bromoacetate (SBA) and N-succinimidyl 3-(bromoacetamido)propionate (SBAP).
  • non-cleavable linkers include maleimidocarboxylic acids, such as maleimidocaproyl (MC).
  • the linker included in the ADCs of the present disclosure has general Formula (VIII):
  • A-S— is the point of attachment to anti-HER2 biparatopic antibody
  • Y is one or more additional linker components, or is absent, and
  • D is the point of attachment to the auristatin analogue.
  • the linker included in the ADCs of the present disclosure has general Formula (IX):
  • A-S— is the point of attachment to anti-HER2 biparatopic antibody
  • Y is one or more additional linker components, or is absent, and
  • D is the point of attachment to the auristatin analogue.
  • the ADCs of the present disclosure may be prepared by one of several routes known in the art, employing organic chemistry reactions, conditions, and reagents known to those skilled in the art (see, for example, Bioconjugate Techniques (G. T. Hermanson, 2013, Academic Press, and the Examples provided herein).
  • conjugation may be achieved by (1) reaction of a nucleophilic group or an electrophilic group of an antibody with a bifunctional linker to form an antibody-linker intermediate Ab-L, via a covalent bond, followed by reaction with an activated auristatin analogue (D), or (2) reaction of a nucleophilic group or an electrophilic group of an auristatin analogue with a linker to form linker-toxin D-L, via a covalent bond, followed by reaction with the nucleophilic group or an electrophilic group of an antibody.
  • Conjugation methods (1) and (2) may be employed with a variety of antibodies, auristatin analogues, and linkers to prepare the ADCs described herein.
  • the auristatin analogue may be conjugated via an appropriate linker to various groups on the antibody to provide the ADC.
  • conjugation may be through surface lysines, through oxidized carbohydrates or through cysteine residues that have been liberated by reducing one or more interchain disulfide linkages.
  • the antibody may be modified to include additional cysteine residues or non-natural amino acids that provide reactive handles, such as selenomethionine, p-acetylphenylalanine, formylglycine or p-azidomethyl-L-phenylalanine.
  • Such modifications are well-known in the art (see, for example, U.S. Pat. Nos.
  • the ADCs of the present disclosure comprise an auristatin analogue conjugated via an appropriate linker to cysteine residues that have been liberated by reducing one or more interchain disulfide linkages.
  • the anti-HER2 biparatopic antibody is conjugated to the toxin via a linker at a low average drug-to-antibody ratio (DAR), specifically an average DAR of less than 3.9 but more than 0.5, for example, between about 1.5 and about 2.5 in certain embodiments.
  • DAR drug-to-antibody ratio
  • a partial reduction of the antibody interchain disulfide bonds may be conducted followed by conjugation to linker-toxin.
  • Partial reduction can be achieved by limiting the amount of reducing agent used in the reduction reaction (see, for example, Lyon et al., Methods in Enzymology, 502:123-138 (2012), and examples therein, and the Examples provided herein).
  • Suitable reducing agents are known in the art and include, for example, dithiothreitol (DTT), tris(2-carboxyethyl)phosphine (TCEP), 2-mercaptoethanol, cysteamine and a number of water soluble phosphines.
  • TCEP tris(2-carboxyethyl)phosphine
  • 2-mercaptoethanol cysteamine
  • cysteamine and a number of water soluble phosphines.
  • fewer equivalents of linker-toxin may be employed in order to obtain a low average DAR.
  • an engineered antibody may be employed in which one or more of the cysteine residues that make up the interchain disulfide bonds is replaced with a serine residue resulting in fewer available cysteine residues for conjugation (see McDonagh et al., Protein Eng. Des. Sel. PEDS, 19(7):299-307).
  • the engineered antibody can then be treated with reducing agent and conjugated to linker-toxin.
  • Another approach is to employ a bis-thiol linker that bridges two cysteines that normally make up an interchain disulfide bond.
  • Use of a bis-thiol linker that carries only one toxin molecule would produce an ADC with a maximum DAR4 for a full-size antibody, if all four interchain disulfide bonds are reduced and replaced with the bis-thiol linker. Partial reduction of the interchain disulfide bonds and/or fewer equivalents of linker may be used in conjunction with a bis-thiol linker in order to further reduce the DAR.
  • Various bis-thiol linkers are known in the art (see, for example, Badescu et al., Bioconjug.
  • Cysteine engineering approaches may also be employed in order to generate ADCs with a low average DAR. Such approaches involve engineering solvent-accessible cysteines into the antibody in order to provide a site-specific handle for conjugation.
  • a number of appropriate sites for introduction of a cysteine residue have been identified with the IgG structure, and include those described in Junutula, et al., J. Immunol Methods, 332(1-2):41-52 (2008); Junutula, et al., Nat. Biotechnol., 26(8), 925-932 (2008), and U.S. Pat. Nos. 9,315,581; 9,000,130; 8,455,622; 8,507,654 and 7,521,541.
  • Low average DAR ADCs may also be prepared by lysine conjugation employing limiting amounts of activated linker-toxin.
  • Selective reaction at the antibody N-terminal amino acids may also be employed.
  • N-terminal serine may be oxidized to an aldehyde with periodate, then reacted with linker-toxin (see, for example, Thompson, et al., Bioconjug. Chem., 26(10):2085-2096 (2015)).
  • linker-toxin see, for example, Thompson, et al., Bioconjug. Chem., 26(10):2085-2096 (2015).
  • N-terminal cysteine residues can be selectively reacted with aldehydes to give thiazolidinones (see, for example, Bernardes, et al., Nature Protocols, 8:2079-2089).
  • Additional approaches include engineering the antibody to include one or more unnatural amino acids, such as p-acetylphenylalanine (pAcPhe) or selenocysteine (Sec).
  • pAcPhe p-acetylphenylalanine
  • Sec selenocysteine
  • the keto group in pAcPhe can be reacted with a linker-toxin comprising a terminal alkoxyamine or hydrazide to form an oxime or hydrazone bond (see, for example, Axup, et al., PNAS USA, 109:16101-16106 (2012)).
  • Sec-containing antibodies can be reacted with maleimide- or iodoacetamide containing linker-toxins to form a selenoether conjugate (see, for example, Hofer, et al., Biochemistry, 48:12047-12057 (2009)).
  • Antibodies may also be engineered to include peptide tags recognized by certain enzymes to allow for enzyme-catalyzed conjugation.
  • Sortase-A (SortA) recognizes the sequence LPXTG. This pentapeptide may be engineered into the N- or C-terminus of the antibody to allow for SortA-mediated conjugation (see, for example, U.S. Patent Application Publication No. 2016/0136298; Kornberger and Skerra, mAbs, 6(2):354-366 (2014)).
  • Transglutaminases have also been employed to generate DAR2 ADCs by using antibodies that have been deglycosylated at position N297 (which exposes Q295 for enzymatic conjugation) or by engineering antibodies to include a “glutamine tag” (LLQG) (Jeger, et al., Angew. Chem., 49:9995-9997 (2010); Strop, et al., Chem. Biol., 20(2):161-167 (2013)).
  • a formylglycine residue can be introduced into an antibody by engineering an appropriate consensus sequence into the antibody and co-expressing the engineered antibody with formylglycine-generating enzyme (FGE). The aldehyde functionality of the introduced formylglycine may then be used as a handle for conjugation of toxin (see, for example, Drake, et al., Bioconjug. Chem., 25(7):1331-1341 (2014)).
  • Another approach used to generate DAR2 ADCs is by conjugation of linker-toxin to the native sugars found on glycosylated antibodies. Conjugation to glycosylated antibodies may be achieved, for example, by periodate oxidation of terminal sugar residues to yield aldehydes, which may then be conjugated to an appropriate linker-toxin, or by glycoengineering approaches in which native sugars are modified with terminal sialic acid residues, which can then be oxidized to yield aldehydes for conjugation to linker-toxin (Zhou, et al., Bioconjug. Chem., 25(3):510-520 (2014)).
  • UV cross-linking for conjugation of active moieties to antibodies has also been reported.
  • This method uses the nucleotide binding site (NBS) for site-specific covalent functionalization of antibodies with reactive thiol moieties.
  • NBS nucleotide binding site
  • IBA indole-3-butyric acid
  • cysteine was used to site-specifically photo-cross-link a reactive thiol moiety to antibodies at the NBS.
  • the thiol moiety may then be used to conjugate linker-toxin having a thiol reactive group (Alves, et al., Bioconjug. Chem., 25(7):1198-1202 (2014)).
  • ADCs with a low average DAR may be isolated from an ADC preparation containing a mixture of DAR species using chromatographic separation techniques, such as hydrophobic interaction chromatography (see, for example, Hamblett, et al., Clin. Cancer Res., 10:7063-7070 (2004); Sun, et al., Bioconj Chem., 28:1371-81 (2017); U.S. Patent Application Publication No. 2014/0286968).
  • ADC preparations with a low average DAR may also be generated by adding unconjugated (i.e. DAR0) antibody to preparations of ADC having an average DAR ⁇ 3.9.
  • DAR0 unconjugated antibody
  • the majority of conjugation methods yield an ADC preparation that includes various DAR species, with the reported DAR being the average of the individual DAR species.
  • ADC preparations that include a proportion of DAR0 species may be advantageous.
  • the ADC preparation having an average DAR of less than 3.9 may include at least 5% DAR0 species.
  • the ADC preparation may include at least 10% DAR0 species, for example, at least 15% DAR0 species or at least 20% DAR0 species.
  • the ADC preparation may include between about 5% and about 50% DAR0 species. In some embodiments, the ADC preparation may include between about 10% and about 50% DAR0 species, for example, between about 10% and about 40%, or between about 10% and abut 30% DAR0 species.
  • the average DAR for the ADCs may be determined by standard techniques such as UV/VIS spectroscopic analysis, ELISA-based techniques, chromatography techniques such as hydrophobic interaction chromatography (HIC), UV-MALDI mass spectrometry (MS) and MALDI-TOF MS.
  • chromatography techniques such as hydrophobic interaction chromatography (HIC), UV-MALDI mass spectrometry (MS) and MALDI-TOF MS.
  • distribution of drug-linked forms for example, the fraction of DAR0, DAR1, DAR2, etc.
  • MS with or without an accompanying chromatographic separation step
  • HPLC reverse-phase HPLC
  • IEF iso-electric focusing gel electrophoresis
  • the average DAR of the ADCs is determined by hydrophobic interaction chromatography (HIC) techniques.
  • HIC hydrophobic interaction chromatography
  • the ADCs may be purified and separated from unconjugated reactants and/or any conjugate aggregates by purification methods known in the art. Such methods include, but are not limited to, size exclusion chromatography (SEC), hydrophobic interaction chromatography (HIC), ion exchange chromatography, chromatofocusing, ultrafiltration, centrifugal ultrafiltration, and combinations thereof.
  • SEC size exclusion chromatography
  • HIC hydrophobic interaction chromatography
  • ion exchange chromatography chromatofocusing
  • ultrafiltration centrifugal ultrafiltration, and combinations thereof.
  • the anti-cancer activity of the ADCs in HER2-expressing cancer cells may be tested in vitro and/or in vivo using standard techniques.
  • the cytotoxic activity of the ADCs may be measured by exposing HER2-expressing cancer cells to the ADC in a cell culture medium, culturing the cells for an appropriate period of time (for example, about 6 hrs to about 7 days), then measuring cell viability.
  • Non-HER2 expressing cells may be included as a control.
  • a variety of cancer cell lines expressing HER2 at varying levels, which may be used to test the ADCs are known in the art and many are commercially available (for example, from the American Type Culture Collection, Manassas, Va.; Addexbio Technologies, San Diego, Calif.; DSMZ, Braunschweig, Germany). Examples include the BT-474 (3+), SK-BR-3 (3+), HCC1954 (3+), JEIMT-1 (2+) and ZR-75-1 (1+) cell lines. These and other examples are summarized in Table 8.
  • the ability of the ADCs to inhibit tumour growth in vivo can be determined in an appropriate animal model using standard techniques known in the art (see, for example, Enna, et al., Current Protocols in Pharmacology , J. Wiley &Sons, Inc., New York, N.Y.).
  • current animal models for screening anti-tumour compounds are xenograft models, in which a human tumour has been implanted into an animal, typically a rodent.
  • the ADCs may be tested in vivo on HER2-expressing tumours using mice that are subcutaneously grafted with tumour fragment, or implanted with an appropriate number of cancer cells, on day 0.
  • the tumours are allowed to develop to the desired size, with animals having insufficiently developed tumours being eliminated.
  • ADC treatment generally begins from 3 to 22 days after grafting, depending on the type of tumour.
  • the ADC may be administered to the animals, for example, by intravenous (i.v.) injection.
  • Tumours are measured either after a pre-determined time period or continuously (for example, 2 or 3 times a week) until a pre-determined endpoint for the study, for example, when the tumour reaches a pre-determined size or weight.
  • Tumours expressing HER2 at various levels may be used in the xenograft models.
  • Patient-derived xenografts (PDX) are particularly useful.
  • In vivo toxic effects of the ADCs may initially be evaluated in rodents, for example mice or rats, by measuring their effect on animal body weight during treatment. Hematological profiles and liver enzyme analysis may also be performed on blood samples taken from the animals.
  • In vivo toxicity and pharmacokinetics may be further analyzed in appropriate animal models, for example, rats or non-human primates, following standard protocols. Cynomolgus monkeys are particularly useful in this regard as human and cynomolgus monkey HER2 share 98% sequence homology.
  • the ADCs described herein have improved tolerability and lower toxicity as compared to a corresponding ADC having a DAR ⁇ 3.9 when administered at the same toxin dose.
  • the ADCs show an improvement in tolerability of greater than 2 ⁇ that of a corresponding ADC having a DAR ⁇ 3.9 when administered at the same toxin dose.
  • the ADCs show an improvement in tolerability of greater than 2.2 ⁇ , for example, 2.3 ⁇ , 2.4 ⁇ or 2.5 ⁇ , that of a corresponding ADC having a DAR ⁇ 3.9 when administered at the same toxin dose.
  • Improvement in tolerability may be determined, for example, by comparison of maximal tolerated dose (MTD), no observed adverse event level (NOAEL) or highest non-severely toxic dose (HNSTD) for the ADC of the present disclosure and the corresponding ADC having a DAR ⁇ 3.9.
  • MTD, NOAEL and/or HNSTD may be measured by standard techniques in an appropriate animal model, for example, a rodent or non-human primate.
  • the ADCs may be provided in the form of compositions comprising the ADC and a pharmaceutically acceptable carrier or diluent.
  • the compositions may be prepared by known procedures using well-known and readily available ingredients.
  • compositions may be formulated for administration to a subject by, for example, oral (including, for example, buccal or sublingual), topical, parenteral, rectal or vaginal routes, or by inhalation or spray.
  • parenteral as used herein includes subcutaneous injection, and intradermal, intra-articular, intravenous, intramuscular, intravascular, intrasternal, intrathecal injection or infusion.
  • the pharmaceutical composition will typically be formulated in a format suitable for administration to the subject, for example, as a syrup, elixir, tablet, troche, lozenge, hard or soft capsule, pill, suppository, oily or aqueous suspension, dispersible powder or granule, emulsion, injectable or solution.
  • Pharmaceutical compositions may be provided as unit dosage formulations.
  • compositions comprising the ADCs are formulated for parenteral administration in a unit dosage injectable form, for example as lyophilized formulations or aqueous solutions.
  • Pharmaceutically acceptable carriers are generally nontoxic to recipients at the dosages and concentrations employed.
  • examples of such carriers include, but are not limited to, buffers such as phosphate, citrate, and other organic acids; antioxidants such as ascorbic acid and methionine; preservatives such as octadecyldimethylbenzyl ammonium chloride, hexamethonium chloride, benzalkonium chloride, benzethonium chloride, phenol, butyl alcohol, benzyl alcohol, alkyl parabens (such as methyl or propyl paraben), catechol, resorcinol, cyclohexanol, 3-pentanol and m-cresol; low molecular weight (less than about 10 residues) polypeptides; proteins such as serum albumin or gelatin; hydrophilic polymers such as polyvinylpyrrolidone; amino acids such as glycine, glutamine, asparagine, histidine, arginine
  • the compositions comprising the ADCs may be in the form of a sterile injectable aqueous or oleaginous solution or suspension.
  • a sterile injectable aqueous or oleaginous solution or suspension Such suspensions may be formulated using suitable dispersing or wetting agents and/or suspending agent that are known in the art.
  • the sterile injectable solution or suspension may comprise the ADC in a non-toxic parentally acceptable diluent or carrier. Acceptable diluents and carriers that may be employed include, for example, 1,3-butanediol, water, Ringer's solution or isotonic sodium chloride solution.
  • sterile, fixed oils may be employed as a carrier.
  • various bland fixed oils may be employed, including synthetic mono- or diglycerides.
  • fatty acids such as oleic acid find use in the preparation of injectables.
  • Adjuvants such as local anaesthetics, preservatives and/or buffering agents may also be
  • the composition comprising the ADC may be formulated for intravenous administration to humans.
  • compositions for intravenous administration are solutions in sterile isotonic aqueous buffer.
  • the composition may also include a solubilizing agent and/or a local anaesthetic such as lignocaine to ease pain at the site of the injection.
  • the ingredients are supplied either separately or mixed together in unit dosage form, for example, as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent.
  • the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline.
  • an ampoule of sterile water for injection or saline can be provided so that the ingredients may be mixed prior to administration.
  • compositions and methods of preparing pharmaceutical compositions are known in the art and are described, for example, in “Remington: The Science and Practice of Pharmacy” (formerly “Remingtons Pharmaceutical Sciences”); Gennaro, A., Lippincott, Williams & Wilkins, Philadelphia, Pa. (2000).
  • the ADCs described herein may be used in methods of inhibiting the growth of HER2-expressing tumour cells.
  • the cells may be in vitro or in vivo.
  • the ADCs may be used in methods of treating a HER2-expressing cancer or tumour in a subject.
  • Treatment of a HER2-expressing cancer may result in one or more of alleviation of symptoms, shrinking the size of the tumour, inhibiting growth of the tumour, diminishing one or more direct or indirect pathological consequences of the disease, preventing metastasis, decreasing the rate of disease progression, amelioration or palliation of the disease state, improving survival, increasing progression-free survival, remission and/or improving prognosis.
  • treatment of a HER2-expressing cancer with an ADC as described herein slows the progression of the disease. In some embodiments, treatment of a HER2-expressing cancer with an ADC as described herein results in tumour regression. In some embodiments, treatment of a HER2-expressing cancer with an ADC as described herein results in inhibition of tumour growth.
  • HER2-expressing cancers are typically solid tumours.
  • HER2-expressing solid tumours include, but are not limited to, breast cancer, ovarian cancer, lung cancer, gastric cancer, esophageal cancer, colorectal cancer, urothelial cancer, pancreatic cancer, salivary gland cancer and brain cancer.
  • HER2-expressing breast cancer include estrogen receptor negative (ER ⁇ ) and/or progesterone receptor negative (PR ⁇ ) breast cancers and triple negative (ER ⁇ , PR ⁇ , low HER2) breast cancers.
  • HER2-expressing lung cancers include non-small cell lung cancer (NSCLC) and small cell lung cancer.
  • the ADCs described herein may be used in the treatment of HER2-expressing breast cancer, ovarian cancer, lung cancer or gastric cancer. In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing breast cancer. In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing breast cancer that is also estrogen receptor and progesterone receptor negative. In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing triple negative breast cancer (TNBC). In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing breast cancer that has metastasized to the brain. In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing ovarian cancer.
  • TNBC triple negative breast cancer
  • the ADCs described herein may be used in the treatment of HER2-expressing breast cancer that has metastasized to the brain. In some embodiments, the ADCs described herein may be used in the treatment of HER2-expressing ova
  • HER2-expressing cancers may be characterized by the level of HER2 they express (i.e. by “HER2 status”).
  • HER2 status can be assessed, for example, by immunohistochemistry (IHC), fluorescent in situ hybridization (FISH) and chromogenic in situ hybridization (CISH).
  • IHC immunohistochemistry
  • FISH fluorescent in situ hybridization
  • CISH chromogenic in situ hybridization
  • IHC HER2 protein expression on the cell membrane.
  • Paraffin-embedded tissue sections from a tumour biopsy may be subjected to the IHC assay and accorded a HER2 staining intensity criteria as follows:
  • Tumours with 0 or 1+ scores for HER2 expression are characterized as HER2 negative, whereas those tumours with 2+ or 3+ scores are characterized as HER2 positive.
  • FDA-approved commercial kits available for HER2 detection using IHC include HercepTestTM (Dako Denmark A/S); PATHWAY (Ventana Medical Systems, Inc.); InSiteTMHER2/NEU kit (Biogenex Laboratories, Inc.) and Bond Oracle HER2 IHC System (Leica Biosystems.
  • ADCs as described herein may be useful in the treatment of cancers that express HER2 at various levels.
  • the ADCs may be used in the treatment of cancers that express high levels of HER2 (IHC 3+).
  • the ADCs may be used in the treatment of cancers that express high levels of HER2 (3+ IHC) or moderate levels of HER2 (2+ IHC or 2+/3+ IHC).
  • the ADCs may be used in the treatment of cancers that express high levels of HER2 (3+ IHC), moderate levels of HER2 (2+ IHC or 2+/3+ IHC), or low levels of HER2 (1+ IHC or 1+/2+ IHC).
  • the ADCs described herein may be used in the treatment of cancers that are scored as HER2 negative by IHC.
  • HER2 levels of the cancer to be treated with the ADCs are determined by IHC. In some embodiments, HER2 levels of the cancer to be treated with the ADCs are determined by IHC performed using the HerceptestTM assay.
  • HER2-expressing cancers may be homogeneous in nature (i.e. the majority of tumour cells express a similar amount of HER2) or they may be heterogeneous in nature (i.e. comprise different tumour cell populations expressing different levels of HER2). It is contemplated that the ADCs may be used to treat HER2-expressing cancers that are either homogeneous or heterogeneous with respect to HER2 levels.
  • the ADCs find use in methods for treating a subject having a HER2-expressing cancer that is resistant or becoming resistant to other standard-of-care therapies. In some embodiments, the ADCs find use in methods for treating a subject having a HER2-expressing cancer who is unresponsive to one or more current therapies, such as trastuzumab (Herceptin®), pertuzumab (Perjeta®), T-DM1 (Kadcyla® or trastuzumab emtansine) or taxanes (such as such as paclitaxel, docetaxel, cabazitaxel, and the like).
  • current therapies such as trastuzumab (Herceptin®), pertuzumab (Perjeta®), T-DM1 (Kadcyla® or trastuzumab emtansine) or taxanes (such as such as paclitaxel, docetaxel, cabazitaxel, and the like).
  • the ADCs find use in methods for treating a subject having a HER2-expressing cancer that is resistant to trastuzumab. In some embodiments, the ADCs find use in methods for treating a subject having a HER2-expressing cancer that is resistant to pertuzumab. In some embodiments, the ADCs find use in methods for treating a subject having a HER2-expressing cancer that is resistant to T-DM1. In some embodiments, the ADCs find use in the treatment of metastatic cancer when the patient has progressed on previous anti-HER2 therapy.
  • the ADCs When the ADCs are used in the treatment of subjects having a HER2-expressing cancer that is resistant to, refractory to and/or relapsed from treatment with another therapeutic agent, the ADCs may be part of a second-line therapy, or a third- or fourth-line therapy, depending on the number of prior treatments undergone by the subject.
  • the ADCs described herein may be used in conjunction with an additional anti-tumour agent in the treatment of subjects having a HER2-expressing cancer.
  • the additional anti-tumour agent may be a therapeutic antibody such as those noted above, or a chemotherapeutic agent.
  • Chemotherapeutic agents commonly used for the treatment of HER2-expressing cancers include, for example, cisplatin, carboplatin, paclitaxel, albumin-bound paclitaxel Abraxane®), docetaxel, gemcitabine, vinorelbine, irinotecan, etoposide, vinblastine, pemetrexed, 5-fluorouracil (with or without folinic acid), capecitabine, carboplatin, epirubicin, oxaliplatin, folfirinox, cyclophosphamide, and various combinations of these agents as is known in the art.
  • the additional agent(s) may be administered to the subject concurrently with the ADCs or sequentially.
  • the ADCs described herein may be used to treat a subject having a HER2-expressing cancer who has not undergone any prior anti-cancer treatments (i.e. the ADCs may be used as a first line therapy).
  • the subject being treated with the ADC in the above methods may be a human, a non-human primate or other mammal. In some embodiments, the subject being treated with the ADC in the above methods is a human subject.
  • the amount of the ADC to be administered to a subject will vary in the light of the relevant circumstances, including the condition to be treated, the chosen route of administration, the actual compound administered, the age, weight, and response of the individual subject and the severity of the subject's symptoms, but is a therapeutically effective amount.
  • terapéuticaally effective amount refers to the amount of ADC required to be administered in order to accomplish the goal of the recited method, for example, amelioration of one or more of the symptoms of the disease being treated.
  • the amount of the ADC described herein that will be effective in the treatment of a HER2-expressing cancer can be determined by standard clinical techniques.
  • in vitro assays may optionally be employed to help identify optimal dosage ranges. Effective doses are extrapolated from dose-response curves derived from in vitro or animal model test systems.
  • kits comprising an ADC as described herein.
  • the kit typically will comprise a container and a label and/or package insert on or associated with the container.
  • the label or package insert contains instructions customarily included in commercial packages of therapeutic products, providing information about the indications, usage, dosage, administration, contraindications and/or warnings concerning the use of such therapeutic products.
  • the label or package insert may further include a notice in the form prescribed by a governmental agency regulating the manufacture, use or sale of pharmaceuticals or biological products, which notice reflects approval by the agency of manufacture, for use or sale for human or animal administration.
  • the label or package insert also indicates that the ADC is for use to treat a HER2-expressing cancer.
  • the container holds a composition comprising the ADC and may in some embodiments have a sterile access port (for example, the container may be an intravenous solution bag or a vial having a stopper that may be pierced by a hypodermic injection needle).
  • a sterile access port for example, the container may be an intravenous solution bag or a vial having a stopper that may be pierced by a hypodermic injection needle).
  • the kit may comprise one or more additional containers comprising other components of the kit.
  • a pharmaceutically-acceptable buffer such as bacteriostatic water for injection (BWFI), phosphate-buffered saline, Ringer's solution or dextrose solution; other buffers or diluents.
  • Suitable containers include, for example, bottles, vials, syringes, intravenous solution bags, and the like.
  • the containers may be formed from a variety of materials such as glass or plastic.
  • one or more components of the kit may be lyophilized or provided in a dry form, such as a powder or granules, and the kit can additionally contain a suitable solvent for reconstitution of the lyophilized or dried component(s).
  • the kit may further include other materials desirable from a commercial or user standpoint, such as filters, needles, and syringes.
  • Linker-Toxin 001 that comprises the following auristatin analogue (Compound 9):
  • linker-toxins comprising other auristatin analogues including the following exemplary compounds (see also International Patent Application Publication No. WO 2016/041082):
  • reaction was acidified with the addition of 1 M aqueous HC (50 mL) and concentrated under reduced pressure to remove the dioxane.
  • the remaining reaction mixture was extracted with ethyl acetate (4 ⁇ 50 mL) and the organic phase was pooled, washed with brine (15 mL+2 mL 2 M HCl), dried over MgSO 4 , filtered and concentrated under reduced pressure to yield a light coloured oil.
  • the oil was re-dissolved in diethyl ether ( ⁇ 50 mL) and concentrated under reduced pressure (3 ⁇ ) to facilitate the removal of residual dioxane, affording the title product as a stiff oil (7.81 g 97% yield with some residual dioxane and Compound 4).
  • MS m/z obs. 606.7 (M+1).
  • EDCI N-(3-Dimethylaminopropyl)-N,N-ethylcarbodiimide hydrochloride
  • the reaction was then concentrated under reduced pressure, diluted with ethyl acetate (120 mL) and 40 mL 1:1 NaHCO 3 (sat.): 5% LiCl and transferred to a separating funnel.
  • the aqueous layer was removed and the organic phase was washed with LiC (1 ⁇ 20 mL), NaHCO 3 (sat., 2 ⁇ 20 mL).
  • Aqueous layers were pooled and extracted with EtOAc (3 ⁇ 50 mL).
  • Organic layers were pooled and washed with brine (1 ⁇ 20 mL), dried over sodium sulfate, filtered and concentrated to give a DMF-laden oil which was concentrated via rotary evaporator to remove residual DMF, yielding 7 g of crude straw coloured oil.
  • the reaction was monitored by HPLC-MS for the consumption of starting materials. After 6 days, the reaction was complete with the total consumption of Compound 14, leaving only Compound 15 and a small amount ( ⁇ 5%) of the bis-TFP maleic amide intermediate.
  • the reaction was transferred to a separating funnel, diluted with diethyl ether (75 ml) and washed with 5% LiCl (1 ⁇ 20 mL), 1 M HCl (2 ⁇ 20 mL), sat. NaHCO 3 (5 ⁇ 20 mL) and brine (1 ⁇ 20 mL). The organic layer was dried over Na 2 SO 4 , filtered and evaporated to give brown crude oil with residual DMF.
  • Crude oil was dissolved in 8 mL of 1:1 DMF:H 2 O+0.1% TFA, loaded onto a 60 g Biotage® SNAP Ultra C18 column (Biotage AB, Uppsala, Sweden) and purified under a linear 30-100% gradient of ACN/H 2 O+0.1% TFA over 8 column volumes. Pure fractions were pooled and diluted with brine (20 mL), then extracted 3 ⁇ 50 mL Et 2 O. Pooled organics were dried over MgSO 4 , filtered and evaporated to recover a light-yellow oil (1.34 g, 66% yield).
  • the reaction was monitored for completion by HPLC-MS and no change to reaction progress was observed between the samples taken at 30 minutes and 1 h ( ⁇ 95% complete).
  • the reaction was allowed to stir overnight at room temperature, then 2-(2-aminoethylamino)ethanol (0.483 mL, 4.781 mmol, 4 equiv), EtOAc (10 mL) and dH 2 O (5 mL) were added to the stirred suspension, which underwent a colour change to deep blue.
  • the suspension was stirred vigorously for 4 hr as the suspended solids gradually dissolved into the biphasic mixture.
  • This mixture was transferred to a separating funnel and diluted with EtOAc (100 mL) and brine (10 mL), and the aqueous layer was extracted 10% IpOH/EtOAc (4 ⁇ 50 mL). The organic layers were pooled and washed with brine (10 mL), dried over Na 2 SO 4 , and evaporated to yield a faintly blue crude solid.
  • This crude solid was dissolved in a mixture of methanol (0.5 mL) and dichloromethane (6 mL) and purified on a Biotage® SNAP Ultra 100 g silica gel column (2-20% MeOH in CH 2 Cl 2 over 10 column volumes, followed by an 8-column volume plateau at 20% MeOH).
  • Antibody-drug conjugates of the biparatopic anti-HER2 mAb, v10000, and Linker-Toxin 001 were generated by partial reduction of the antibody interchain disulfide bonds, followed by capping of the free cysteine residues by reaction with the maleimide component of the Linker-Toxin.
  • ADCs with average drug-to-antibody ratios of between 0 and 6 may be obtained.
  • ADCs were purified to remove contaminant small molecules and characterized to demonstrate DAR, purity, monomeric content, endotoxin levels, and binding to antigen positive tumour cells.
  • a solution (138.9 mL) of the antibody v10000 (2.0 g) in 10 mM sodium acetate, 9% (w/v) sucrose, pH 4.5 was reduced by addition of a freshly prepared mixture of 200 mM Na 2 HPO 4 , pH 8.9 (15.4 mL), 5 mM DTPA solution (39.5 mL in PBS, pH 7.4), and 10 mM TCEP solution (3.68 mL, 2.3 eq.).
  • the reaction was cooled on ice before addition of an excess of Linker-Toxin 001 (6.41 mL; 8 eq) from a 20 mM DMSO stock solution.
  • the conjugation reaction was quenched after 90 minutes by addition of an excess of a 20 mM N-acetyl cysteine solution (4.81 mL; 6 eq.).
  • a solution (138.9 mL) of the antibody v10000 (2.0 g) in 10 mM sodium acetate, 9% (w/v) sucrose, pH 4.5 was pH-adjusted by addition of 200 mM Na 2 HPO 4 , pH 8.9 (15.4 mL).
  • a DTPA solution 44 mL in PBS, pH 7.4, final concentration 1.0 mM
  • reduction of the interchain disulfides was initiated by addition of an aqueous 10 mM TCEP solution (1.68 mL, 1.05 eq.).
  • Quenched antibody drug conjugate (ADC) solutions were purified with 9-15 diavolumes of 10 mM sodium acetate, 9% (w/v) sucrose, pH 4.5 on a Millipore LabscaleTM Tangential Flow Filtration instrument using a Pellicon® XL Ultrafiltration Module (Ultracel® 30 kDa 0.005 m 2 ; Millipore Sigma). The eluted ADC was sterile filtered (0.22 um). ADCs produced on small scale were purified over 40 KDa MWCO ZebaTM columns (ThermoFisher Scientific, Waltham, Mass.) preconditioned with either PBS or 10 mM sodium acetate, 9% (w/v) sucrose, pH 4.5.
  • HIC hydrophobic interaction chromatography
  • the average drug to antibody ratio (DAR) of an ADC can vary depending on the number of disulphide bonds liberated during the reduction of the antibody.
  • a single conjugation reaction that yields an ADC with a particular average DAR comprises a mixture of species.
  • v17597 and v21252 a mixture of four species was generated: unconjugated antibody, ADC with a DAR of 2, ADC with a DAR of 4 and ADC with a DAR of 6.
  • FIG. 2 The results of the HIC are shown in FIG. 2 and show that v17597 has an average DAR of 3.92 ( FIG. 2A ), and v21252 has an average DAR of 2.07 ( FIG. 2B ).
  • the individual contributions of the DAR0, DAR2, DAR4 and DAR6 species to the average DAR of the purified ADCs were assessed by the integration of the HPLC-HIC chromatogram. Each peak in the HIC chromatogram was isolated by preparative chromatography and the identity of the peak was verified by LC-MS. The % content of individual DAR species for each variant (as determined by HIC) is shown in Table 10 and in FIG. 2D . As can be seen from Table 10 and FIG. 2D , v17597 contains significantly more DAR6 species than v21252, and v21252 contains significantly more DAR0 species than v17597.
  • FIG. 2E illustrates the change in the relative amounts of DAR 0, 2, 4, and 6 species within v10000-Linker Toxin 001 for a series of ADC preparations having average DAR values ranging from 0.5 to 6.
  • the extent of aggregation of the antibody and ADCs was assessed by size exclusion chromatography (SEC) on an ACQUITY UPLC® Protein BEH SEC column (200 angstrom, 1.7 ⁇ m, 4.6 ⁇ 150 mm) (Waters Corporation, Milford, Mass.) using a mobile phase consisting of 150 mM phosphate, pH 6.8 and a flow rate of 400 uL/min. Detection was by absorbance at 280 nm.
  • the results are shown in FIG. 3 and summarized in Table 11.
  • the mAb v10000 is highly monomeric by SEC analysis. No significant increase in aggregation was observed upon conjugation to Linker-Toxin 001.
  • a comparison of v21252 and v17597 indicates that the extent of aggregation is unaffected by increasing the DAR from 2 to 4.
  • ADCs antigen-positive tumour cell lines JIMT-1 (breast carcinoma, Addexbio Technologies, San Diego, Calif.) and RT-112/84 (bladder carcinoma, Sigma-Aldrich, St. Louis, Mo.) was compared to parental antibody (v10000) binding by flow cytometry.
  • Cells were cultured as per vendor instructions. Briefly, cells (50,000 cells/well) were incubated with antibody or ADC serial dilutions for 90 minutes on ice. Following this incubation, cells were washed twice and then incubated with an AlexaFluor® 647 conjugated anti-hIgG (Jackson ImmunoResearch Inc., Westgrove, Pa.) secondary reagent for 60 minutes on ice. Cells were then washed twice and fluorescence was analyzed by flow cytometry (LSRFortessaTM X-20 flow cytometer, BD, San Jose, Calif.).
  • the endotoxin level of formulated ADCs was assessed using a Limulus Amebocyte Lysate (LAL) gelation end point assay (Genscript ToxinSensorTM Single Test Kit; GenScript, Piscataway, N.J.) with a 0.125 EU/mL threshold. All ADCs employed in in vivo experiments (below) were dosed below 5 endotoxin units per kilogram body mass.
  • LAL Limulus Amebocyte Lysate
  • v17597 and v21252 were measured by a cell proliferation assay on antigen-positive tumour cells BT-474 (ductal carcinoma, ATCC, Manassas, Va. (HTB-20)), SK-BR-3 (breast carcinoma, ATCC, Manassas, Va. (HTB-30)), HCC-1954 (breast carcinoma, ATCC (CRL-2338)), JIMT-1 (breast carcinoma, Addexbio Technologies, San Diego, Calif., (C0006005)), ZR-75-1 (breast carcinoma, ATCC (CRL-1500)) and antigen-negative tumour cells MDA-MB-468 (breast carcinoma, Addexbio Technologies (C0006003)).
  • Cells were cultured as per vendor instructions. Briefly, on the day prior to adding the ADC, cells (50 uL/well, 1000 cells/well) were added to sterile, tissue culture (TC) treated, 384-well plates (ThermoFisher Scientific, Waltham, Mass.) and incubated overnight at 37° C./5% CO 2 to allow the cells to adhere to the plate surface. In a sterile, U-bottom, 96-well plate, ADCs were diluted in complete growth medium at 4.3-times the desired final maximum concentration and were titrated 1:3 in the same medium, creating a 10-point dose response titration. Control wells with no ADC (growth medium alone) were included on each microtiter 96-well plate.
  • FIG. 5 The results are shown FIG. 5 and summarized in Table 12. The results show that both v17597 and v21252 demonstrate selective cell killing.
  • HER2 expressing cell lines BT-474, SK-BR-3, HCC1954, JIMT-1, and ZR-75-1 FIG. 5A-E ) were sensitive to both v17597 and v21252.
  • Both v17597 and v21252 were ineffective against MDA-MB-468 cells ( FIG. 5F ), which are from a HER2 negative breast carcinoma cell line.
  • ADCs comprised of v10000 conjugated to Linker-Toxin 001 with an average DAR ranging from 0.7 to 3.9 were prepared by varying the amount of TCEP (0.5 to 10 molar equivalents) utilized in the reduction reaction.
  • the conjugation reaction was conducted in accordance with the procedures outlined in Example 2 and the resulting ADCs were purified using a 40 kDa ZebaTM column, pre-equilibrated with PBS pH 7.4.
  • the in vitro potency of the ADCs was measured by a cell proliferation assay on antigen-positive tumour cells SK-OV-3 (ovarian carcinoma, ATCC, Manassas, Va. (HTB-77)), JIMT-1 (breast carcinoma, DSMZ, Braunschweig, Germany (ACC 589)) and ZR-75-1 (breast carcinoma, ATCC (CRL-1500)).
  • SK-OV-3 ovarian carcinoma, ATCC, Manassas, Va.
  • JIMT-1 breast carcinoma, DSMZ, Braunschweig, Germany
  • ZR-75-1 breast carcinoma, ATCC (CRL-1500)
  • the results are shown in FIG. 6 .
  • the ADCs having average DARs between 3.9 and 1.6 showed comparable potency across the three cell-lines, however, the ADC with average DAR0.7 showed a significant decrease in potency.
  • the approximate amounts of individual DAR species making up the DAR0.7, DAR2.2 and DAR3.9 ADCs are shown in Table 13 and FIG. 6D . It can be seen that the DAR0.7 ADC contains approximately three times as much DAR0 species (approx. 65% vs. approx. 20%) as the DAR1.9 ADC.
  • the DAR2.2 ADC in turn contains significantly more DAR0 species than the DAR3.9 species (approx. 20% vs. ⁇ 3%), however, the DAR2.2 ADC showed comparable in vitro potency to the DAR3.9 ADC.
  • pHAb Dye Promega Corporation, Madison, Wis.
  • a negative control ADC was an anti-RSV Protein F antibody conjugated to Linker-Toxin 001.
  • pHAb-conjugated antibodies can be used to monitor receptor-mediated antibody internalization.
  • Antibody conjugated with pHAb Dye bound to antigen on the cell membrane exhibits minimal fluorescence, but after receptor-mediated internalization and traffic through the endosome and lysosomal system, the antibody-pHAb conjugate is exposed to more acidic pH, causing the antibody-pHAb conjugate to fluoresce.
  • pHAb conjugated v21252, pHAb conjugated trastuzumab-Linker-Toxin 001 and pHAb conjugated control were incubated with the HER2 expressing cell lines SKBR3 and JIMT-1. Briefly, SKBR3 and JIMT-1 HER2+ tumour cells were seeded into a 384-well black optical bottom plate (ThermoFisher Scientific, Waltham, Mass.) at 5,000 cells/well in assay media. The plate was incubated overnight at 37° C.+5% CO 2 . The following day, pHAb-conjugated antibodies were added to plates at 10 ug/ml and 1 ug/mL final in assay media.
  • FIGS. 13 and 14 show that v21252 internalizes and traffics to lysosomes in HER2 expressing cells to a greater level than the monospecific trastuzumab-Linker-Toxin 001.
  • FIG. 7A provides the results for the tumour response in mice subcutaneously implanted with HBCx-13b tumour fragments after i.v. administration of vehicle or v17597.
  • FIG. 7B provides the results for the tumour response in mice subcutaneously implanted with HBCx-13b tumour fragments after i.v. administration of vehicle or v21252.
  • FIG. 8A provides the results for the tumour response in mice subcutaneously implanted with ST-910 tumour fragments after i.v. administration of vehicle or v17597.
  • FIG. 8B provides the results for the tumour response in mice subcutaneously implanted with ST-910 tumour fragments after i.v. administration of vehicle or v21252.
  • ST-910 is a patient derived xenograft (PDX) that represents HER2 1+ breast cancer while HBCx-13b (used in Example 6.1) is a PDX that represents HER2 3+ breast cancer.
  • Examples 6.1 and 6.2 thus demonstrate that both v17597 and v21252 are active in both HER2 3+ and HER2 1+ tumours.
  • pharmacokinetic samples for total antibody were collected at pre-specified time points and were evaluated using an ELISA-based assay for total antibody quantification. Serum concentrations for total antibody for either v21252 or v17597 were analyzed by first coating 384-well ELISA plates with goat anti-human IgG Fc antibody (Jackson ImmunoResearch, West Grove, Pa.) in PBS pH 7.4 and incubating at 4° C. overnight. The following day, plates were washed and blocked using assay diluent and incubated at RT for 1 hr.
  • FIG. 15 shows the total antibody serum concentration-time profile for HBCx-13b (A) and ST-910 (B).
  • the objective of this study was to characterize the pharmacokinetics (PK) and tolerability of v17597 and v21252 in cynomolgus monkeys following a single intravenous (IV) infusion administration.
  • the cynomolgus monkey was selected for the nonclinical safety assessment of both v17597 and v21252 based on sequence homology and binding affinity.
  • Human and cynomolgus monkey HER2 share 98% sequence homology, whereas the sequence homology for dog and mouse/rat HER2 is 93% and 88%, respectively.
  • v17597 3, 6 or 9 mg/kg
  • v21252 9 mg/kg or 12 mg/kg
  • General tolerability was assessed with clinical observations, body weight, food consumption, and clinical pathology (hematology and clinical chemistry).
  • Blood was collected throughout the study for bioanalytical analysis of v17597 or v21252, total antibody, and free toxin (Compound 9). The study design is summarized in Table 14.
  • v17597 and v21252 Serum concentrations of v17597 or v21252 (DAR of 1 or greater) were analyzed using an Electrochemiluminescence assay with Meso Scale Discovery platform (ECL/MSD) (Meso Scale Diagnostics, LLC, Rockville, Md.) with anti-toxin mouse IgG as the capture agent and anti-pertuzumab sulfo-TAG as the detection agent.
  • ECL/MSD Meso Scale Discovery platform
  • Total Antibody The total antibody bioanalytical assay measured the antibody component of v17597 or v21252 regardless of whether the antibody component was conjugated with toxin (at all DARs) or not. Serum concentrations of total antibody were analyzed using an Electrochemiluminescence assay with Meso Scale Discovery platform (ECL/MSD) with anti-pertuzumab antibody as the capture agent and anti-trastuzumab sulfo-TAG as the detection agent.
  • ECL/MSD Electrochemiluminescence assay with Meso Scale Discovery platform
  • Toxin (Compound 9): Serum concentrations of toxin were analyzed using a LC-MS/MS method. Serum samples were precipitated with acetonitrile/methanol (50:50, v/v) and supernatants were analyzed. The liquid chromatography system used was a reverse phase column with a gradient flow consisting of water/acetic acid (100/0.05, v/v) and acetonitrile. Toxin and the internal standard (toxin-d4; deuterated Compound 9) were detected using a triple quadrupole mass spectrometer system equipped with an electrospray ionization (ESI) source operated in the positive ion mode.
  • ESI electrospray ionization
  • Non-compartmental analysis of the serum sample bioanalytical results was used to derive PK parameters (maximum serum concentration [C max ], terminal half-life [T 1/2 ], clearance [CL] and apparent volume of distribution [V ss ]).
  • v17597 v17597 exposure was generally dose proportional between 3 to 9 mg/kg.
  • C max was achieved at the end of the 60-minute infusion (median Tmax) and increased in a dose-proportional manner.
  • Systemic exposure (AUC 0- ⁇ ) increased in a slightly greater than dose-proportional manner.
  • Preliminary mean terminal half-life (T 1/2 ) generally appeared to increase with increasing dose
  • clearance (CL) generally appeared to decease with increasing dose
  • V ss apparent volume of distribution
  • v21252 exposure was generally dose proportional between 9 to 12 mg/kg.
  • C max was achieved at the end of the 60-minute infusion (median Tmax) and increased in a dose-proportional manner.
  • the v21252 serum concentration-time profile is shown in FIG. 9A .
  • Systemic exposure AUC 0- ⁇
  • T 1/2 Preliminary mean terminal half-life
  • CL clearance
  • V ss apparent volume of distribution
  • Total Antibody (conjugated and non-conjugated): Maximum serum concentration of total antibody (C max ) was achieved at the end of the 60-minute infusion (median T max ). The total antibody serum concentration-time profile of v21252 is shown in FIG. 9B .
  • a non-compartment model was used to derive PK parameters.
  • C max increased in a dose-proportional manner, while AUC 0- ⁇ increased in a slightly greater than dose-proportional manner for both v17597 and v21252.
  • the mean terminal half-life of v17597 increased with increasing dose, while serum clearance (CL) and total apparent volume of distribution (V ss ) of total antibody decreased with increasing dose.
  • the mean terminal half-life and total apparent volume of distribution (V ss ) of v21252 increased with increasing dose, while serum clearance (CL) of total antibody decreased with increasing dose.
  • Toxin (Compound 9): Following administration of a single dose of v17597 (3, 6 or 9 mg/kg) or v21252 (9 mg/kg or 12 mg/kg), all toxin serum concentrations were below the lower limit of quantitation (LLOQ, ⁇ 5.00 ng/mL).
  • v17597 3, 6 or 9 mg/kg
  • v21252 at doses of 9 or 12 mg/kg was well tolerated. There was no mortality during the course of the study. No treatment-related effects were noted in clinical observations, food consumption, or body weight.
  • a non-GLP toxicity study was conducted to investigate the toxicokinetics and toxicity of v17597 in cynomolgus monkeys. The study was designed based on results from the single-dose pharmacokinetic/tolerability study in female cynomolgus monkeys (Example 6).
  • Vehicle or v17597 was administered by a 1-hr IV infusion weekly on Days 1, 8, 15, 22, 29 and 36 at doses 0, 2.25 and 4.5 mg/kg, and once every other week on Days 1, 15 and 29 at doses of 4.5 and 9 mg/kg. All animals were evaluated for changes in clinical signs, food consumption, body weight, blood pressure, ECGs, respiration rates (visual), clinical pathology (hematology, clinical chemistry, coagulation, urinalysis), organ weights, and macroscopic/microscopic examination of tissues. Blood was collected for toxicokinetic analysis and anti-drug antibody (ADA) analysis. Animals dosed weekly were terminated on Day 42 and animals dosed every other week were terminated on Day 36. The study design is presented in Table 15.
  • v17597 was considered to be adverse at all doses tested in this study.
  • the no adverse effect level (NOAEL) and the highest non-severely toxic dose (HNSTD) for v17597 following weekly or bi-weekly administration for up to 6 weeks was considered to be less than 2.25 mg/kg administered weekly or 4.5 mg/kg administered bi-weekly.
  • v21252 Pharmacokinetics were calculated after repeat administration of v21252. C max was achieved either at the end of the 60-minute infusion or 60 minutes after the end of infusion (median T max ). The v21252 serum concentration-time profile is shown in FIG. 10 . On Day 1, C max and systemic exposure (AUC 0-168h ) increased in a slightly greater than dose-proportional manner. On Day 29, C max and AUC 0-168h increased in an approximately dose-proportional manner. Systemic exposure and AUC 0-168h did not appear to change and showed no accumulation following repeated administration. Mean elimination half-lives (T 1/2 ) increased from the 9 mg/kg group to the 12 mg/kg group. A saturable clearance mechanism for v21252 may account for the difference in T 1/2 and clearance between the low (9 mg/kg) and high (12 mg/kg) dose groups.
  • Total Antibody (conjugated and unconjugated): Total antibody was measured in cynomolgus monkeys after the repeat administrations of v21252. The C max for total antibody was achieved at the end of the 60-minute infusion (median T max ). The total antibody serum concentration-time profile is shown in FIG. 11 . On Day 1, C max and systemic exposure (AUC 0-168h ) increased in a slightly greater than dose-proportional manner. On Day 29, C max and AUC 0-168h increased in an approximately dose-proportional manner. Systemic exposure AUC 0-168h was unchanged and showed no accumulation following repeated administrations. Similar to v21252, mean elimination half-lives (T 1/2 ) for total antibody increased from the 9 mg/kg group to the 12 mg/kg group.
  • v21252 The pharmacokinetics of v21252 as indicated by the serum concentration-time profiles of v21252 and Total Antibody are indicative of minimal linker-toxin loss from v21252 in vivo (see FIG. 12 ).
  • Toxin (Compound 9): Free toxin was measured in cynomolgus monkeys after the repeat administrations of v21252. All payload (Compound 9) serum concentrations were below the limit of quantitation ( ⁇ 0.500 ng/mL) with the exception of one female at 12 mg/kg on Day 1, one female at 9 mg/kg on Day 29, and one male at 12 mg/kg on Day 29.
  • Anti-drug Antibodies Anti-v21252 antibodies were screened in cynomolgus monkeys following the repeat administrations of v21252. ADA were detected in serum of a single female in the 9 mg/kg dosing cohort.
  • the PK analysis confirmed systemic exposure in the v21252-treated animals and mean systemic exposure increased with increasing dose in a dose proportional manner for v21252 and total antibody, while exposure to free toxin (Compound 9) was only seen at low levels in a few animals.
  • Tables 17-20 show a comparison of the results from the PK/tolerability studies and the non-GLP repeat dose studies for v17597 and v21252.
  • HNSTD could not Pain not >12 mg/kg be determined be determined ( ⁇ 2.25 mg/kg) ( ⁇ 4.5 mg/kg)
  • Auristatin analogues of general Formula (I) have been shown to have good in vivo tolerability when administered to mice.
  • Conjugation of Compound 9 to the monospecific anti-HER2 antibody trastuzumab at an average DAR4 produced an ADC that showed excellent tolerability in cynomolgus monkeys with a highest non-severely toxic dose (HNSTD) of 18 mg/kg.
  • HNSTD non-severely toxic dose
  • the ADC comprising Compound 9 conjugated to an anti-HER2 biparatopic antibody, v10000, at an average DAR4 (v17597) showed greatly decreased tolerability with a HNSTD of less than 4.5 mg/kg (Example 8).
  • the decreased tolerability observed for v17597 may be due in part to the increased on-target binding and internalization of the biparatopic antibody compared to the monospecific trastuzumab, leading to increased on-target toxicity, and/or a decreased proportion of DAR0 or naked species in average DAR4 (v17597) compared to average DAR2 (v21252) that increases the toxicity associated with higher DAR species (DAR2, DAR4 and DAR6), and/or increased proportion of DAR6 species in average DAR4 compared to average DAR2 increasing the toxicity associated with the highest DAR species.
  • the ADC comprising Compound 9 conjugated to v10000 at an average DAR2 (v21252) showed much improved tolerability with a HNSTD of 12 mg/kg (Example 9).
  • MMAE monomethyl auristatin E
  • a maytansinoid directly correlates with the total amount of drug attached to the antibody, i.e. the relationship between DAR and the maximum tolerated dose is linear for ADCs (Hamblett, et al., Clin. Cancer Res., 10:7063-7070 (2004); Sun, et al., Bioconj Chem., 28:1371-81 (2017)).
  • the maximum tolerated dose of an ADC with 8 drug molecules per antibody was 50 mg/kg, and the maximum tolerated dose of an ADC with 4 drug molecules per antibody (i.e. half the amount of toxin) was 100 mg/kg (Hamblett, et al., ibid.). That is, an ADC with half the amount of toxin of the DAR8 ADC, when administered at the same antibody dose, showed an MTD that was twice that of the DAR8 ADC.
  • v21252 has a DAR of 2 and thus half the amount of toxin as v17597 when administered at the same antibody dose. Based on previous studies with v17597, therefore, the amount of v21252 that would be tolerated was expected to be less than 9 mg/kg (i.e. 2 ⁇ the maximum dose tolerated for v17597). However, as shown in Example 9, v21252 administered to cynomolgus monkeys at doses of either 9 or 12 mg/kg every two weeks for three doses was tolerated and 12 mg/kg was designated as a no observed adverse event level (NOAEL).
  • NOAEL no observed adverse event level
  • v21252 has less toxicity and more tolerability compared to v17597 when dosed bi-weekly, even though it has greater exposure. Based on the non-GLP toxicology study in the cynomolgus monkeys (Example 8), v17597 was considered to have adverse findings at both bi-weekly doses of 4.5 and 9 mg/kg.
  • v21252 was not considered to have adverse findings at bi-weekly doses of both 9 mg/kg and 12 mg/kg, despite having approximately 1.8 to 4.6 fold increases in exposure (AUC 0-336hr after first dose or AUC 0-168hr last dose) compared to 4.5 mg/kg of v17597 (summarized in Tables 19 and 20).
  • v21252 demonstrated in vivo efficacy at exposure levels shown to be tolerated in cynomolgus monkeys. Specifically, complete responses were achieved in patient derived xenograft models of both high HER2 and low HER2 tumours at exposures tolerated in cynomolgus monkeys, as summarized in FIG. 15 (see also, Example 6).
  • v21252 was administered to cynomolgus monkeys every two weeks at 0, 6, 12 and 18 mg/kg for 4 doses, with a 6 week recovery period.
  • the highest non-severely toxic dose (HNSTD) was determined to be 18 mg/kg.
  • v21252 was well tolerated at all doses. No clinical observations were considered adverse and no mortality was observed in this GLP study. The only consistent clinical observation was increased diarrhea. No change in body weight was observed at all doses and no clinical pathology findings (liver function—aspartate transaminase and alanine transaminase and hematology—neutrophils, platelets, hemoglobin, and lymphocytes) were considered adverse.
  • the exposure (C max and AUC 0-168hr ) of v21252 was virtually identical to that of v10000 (antibody alone). Details of the study are provided below.
  • the objective of this GLP study was to further characterize the toxicokinetics and toxicity of v21252 administered 4 times intravenously to cynomolgus monkeys.
  • v21252 was administered to male and female cynomolgus monkeys on Days 1, 15, 29 and 43 at doses of 0, 6, 12 and 18 mg/kg, with a 6 week recovery period.
  • the no observed adverse event level (NOAEL) was 12 mg/kg and the highest non-severely toxic dose (HNSTD) was 18 mg/kg.
  • vehicle or v21252 was administered to male and female cynomolgus monkeys by a 1-hr IV infusion once every other week on Days 1, 15, 29 and 43 at doses of 0, 6, 12 and 18 mg/kg (4 animals per sex at each dose level and an additional 2 animals per sex at 0, 12 and 18 mg/kg for recovery evaluation). All animals were evaluated for changes in clinical signs, food consumption, body weight, blood pressure, ECGs, respiration rates (visual), clinical pathology (hematology, clinical chemistry, coagulation, urinalysis), organ weights, and macroscopic/microscopic examination of tissues.
  • TK toxicokinetic
  • Compound 9 total antibody, and free toxin
  • ADA anti-drug antibody
  • v21252 Median peak v21252 serum concentrations were observed by 1 hr following the start of infusion (SOI) on Days 1 and 43. Following bi-weekly administration of v21252, mean C max and AUC values for v21252 increased with increasing dose. Increases in C max were approximately proportional to dose on Day 1. On Day 1, a 1:2:3 fold increase in v21252 dose resulted in an approximate 1:2.3:3.3 fold increase in C max values, an approximate 1:2.6:3.8 fold increase in mean AUC 0-168hr values, and an approximate 1:2.9:4.5 fold increase in AUC 0-336hr values. On Day 43, C max and AUC 0-168hr were approximately dose proportional.
  • Total Antibody (conjugated and unconjugated): Median peak Total Antibody serum concentrations were observed by 1 hr following the SOI of v21252 on Days 1 and 43. Following bi-weekly administration of v21252, mean C max and AUC 0-168hr values for Total Antibody increased with increasing dose. On Day 1, a 1:2:3 fold increase in v21252 dose resulted in an approximate 1:2.1:3.3 fold increase in C max values, an approximate 1:2.4:3.8 fold increase in AUC 0-168hr values, and an approximate 1:2.8:4.5 fold increase in mean AUC 0-336hr values.
  • Toxin (Compound 9) Free toxin was measured after the repeat administrations of v21252. Most toxin (Compound 9) serum concentrations were below the limit of quantitation ( ⁇ 0.500 ng/mL). The following exceptions were noted: one female at 12 mg/kg on Day 43 had a single quantifiable toxin (Compound 9) concentration (0.513 ng/ml at 72 hr post dose); one male at 18 mg/kg on Day 29 had a single quantifiable toxin (Compound 9) concentration (0.532 ng/mL at 1 hr following the SOI); two males and two females at 18 mg/kg on Day 43 each had a single quantifiable toxin (Compound 9) concentration (0.555, 0.505, 0.556 and 0.653 ng/mL, respectively, at 24 hr following the SOI); and one male at 18 mg/kg on Day 43 had four consecutive quantifiable toxin (Compound 9) concentrations with an AUC 0-168hr value
  • ADA Anti-drug Antibodies
  • v21252 Repeat-dose administration of v21252 (every other week ⁇ 4) was generally well tolerated. There were no v21252-related deaths and no effects noted in ophthalmic and electrocardiographic evaluations, visual respiration rates, urinalysis, or troponin I assessments. There were no v21252-related changes in body weight parameters noted during the treatment or recovery periods following administration of v21252.
  • v21252 received fluid and/or nutritional supplementation from Day 4 (6 and 18 mg/kg) or Day 8 (12 mg/kg) until the end of the treatment period. Similarly, males receiving repeated administration of v21252 received fluid and/or nutritional supplementation from Day 8 (12 mg/kg) or Day 7 (18 mg/kg) until the end of the treatment period. No fluids or supplementation were provided during the recovery.
  • Test article-related hematology changes included: increases in monocyte counts, morphologic alterations in neutrophils, decreases in reticulocyte counts and red cell mass (RBC, hemoglobin and hematocrit) with concomitant increase in red blood cell distribution width. There were minimal to mild increases in mean fibrinogen concentrations relative to baseline means at Days 8 through 50 in males at 18 mg/kg and in females at ⁇ 12 mg/kg. These changes were test article-related and indicative of an immune or inflammatory stimulus. These changes had resolved at Day 92. Treatment-related changes were observed in AST, phosphorus, total protein, albumin, globulin and citrulline.
  • Tables 22-25 show a comparison of the results from the non-GLP repeat dose studies for v17597 and v21252 and the GLP study for v21252.
  • HNSTD non-severely toxic dose
  • the ADC comprising Compound 9 conjugated to v10000 at an average DAR2 (v21252) showed improved tolerability compared to an ADC with an average DAR4 (v17597) with a HNSTD of 18 mg/kg.
  • This result is unexpected as it has previously been shown that toxin Compound 9 conjugated to v10000 at an average DAR4 (v17597) when administered at a toxin dose of 0.36 mg/kg was associated with mortality either when dosed acutely (with a single dose of 9 mg/kg) or sub-chronically (with two doses of 4.5 mg/kg separated by two weeks) (Example 8).
  • v21252 DAR2
  • Compound 9 a cumulative toxin dose of 1.44 mg/kg
  • NOAEL no observed adverse event level
  • 1.44 mg/kg cumulative dose of toxin was administered with 18 mg/kg of v21252 over 4 doses and was tolerated. This is a four-fold higher dose than the dose of v17597 that was associated with mortality (0.36 mg/kg).
  • v21252 has less toxicity and more tolerability compared to v17597 when dosed every two every weeks, even though it has approximately two times greater exposure (AUC 0-336hr after first dose) and two times longer half-life after first dose when compared at toxin-matched doses (4.5 mg/kg of v17597 v. 9 mg/kg of v21252 and 9 mg/kg of v17597 v. 18 mg/kg of v21252) (summarized in Tables 24 and 25).
  • Example 11 v21252 Inhibits Low HER2 Patient Derived Xenograft Growth In Vivo
  • LTL-654 was derived from an ovarian serous carcinoma patient metastasis and was scored by immunohistochemistry (HC) as HER2 negative. An earlier biopsy was scored by IHC as HER2 equivocal.
  • mice Female NOD Rag gamma (NRG) mice were subcutaneously implanted via the renal capsule with two LTL-654 tumour fragments, approximately 15 mm 3 each. Animals were randomly assigned to one of two blinded treatment groups of six animals each when mean tumour volumes reached 70.3-77.8 mm 3 .
  • Tumour size was measured using a Vevo®3100 imaging system (FUJIFILM VisualSonics, Inc., Toronto, Canada) using three-dimensional (3D)-mode. Multiple images (70 to 100 per tumour) throughout the whole tumour were recorded and analyzed using Vevo® LAB software v2.1.0 (FUJIFILM VisualSonics, Inc.). Tumour size was measured once weekly after randomization up to Day 24. Mice were ethically sacrificed when individual tumours reached a size of 1500 mm 3 . Tumour volumes are reported as the mean ⁇ SEM for each group.
  • FIG. 16 provides the results for the tumour response in mice subcutaneously implanted with LTL-654 tumour fragments after i.v. administration of vehicle or v21252, which demonstrate that treatment of LTL-654 engrafted mice with v21252 inhibited the growth rate of the LTL-654 tumour xenografts.
  • v21252 is effective in a patient derived xenograft in which HER2 expression is sufficiently low to be scored by IHC as HER2 negative.
  • Example 12 v21252 Prolongs Survival of Mice Bearing Intracranially Implanted Human Breast Tumours In Vivo
  • control conjugate humanized antibody against respiratory syncytial virus conjugated to Linker-Toxin 001
  • v21252 v7155
  • v24029 trastuzumab conjugated at DAR8 to an exatecan-derivative topoisomerase I inhibitor (DXd)
  • DXd exatecan-derivative topoisomerase I inhibitor
  • mice Female Balb/c Nude mice (CByJ.Cg-Foxnlnu/J) mice were irradiated with a ⁇ -source (2 Gy, 60 Co, BioMep, Bretenines, France). Anesthetized mice were stereotactically injected with 1 ⁇ 10 5 BT-474 cells in 2 microliters of RPMI 1640 medium without phenol red. Animals were randomized into treatment groups and, starting on day 8, were administered intravenously with vehicle, control conjugate, v21252, v7155 or v24029 at 6 mg/kg every week for twelve total injections (Table 26). Body weights were recorded twice weekly until day 18 and then daily thereafter. Mice were ethically sacrificed when bodyweight loss met or exceeded 20% for 3 consecutive days.
  • FIG. 17 provides the survival results for mice intracranially implanted with BT-474 tumour cells after i.v. administration of vehicle, control conjugate, v21252, v7155, or v24029.
  • FIG. 18 provides the survival results for mice intracranially implanted with BT-474 tumour cells after weekly (qw) i.v. administration of vehicle, control conjugate or v7155, or i.v. administration every two weeks (q2w) of either v21252 or v24029.
  • v21252 is effective in prolonging the survival of mice intracranially implanted with BT-474 breast tumour cells.

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