Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H21/00—Compounds containing two or more mononucleotide units having separate phosphate or polyphosphate groups linked by saccharide radicals of nucleoside groups, e.g. nucleic acids
  • C07H21/04—Compounds containing two or more mononucleotide units having separate phosphate or polyphosphate groups linked by saccharide radicals of nucleoside groups, e.g. nucleic acids with deoxyribosyl as saccharide radical

Definitions

• the present invention relates to methods of characterizing samples containing oligomeric compounds, including oligonucleotides synthesis.
• the invention further provides compounds and synthetic methods useful for the same.
• Oligonucleotides have been used in various biological and biochemical applications. They have been used as primers and probes for the polymerase chain reaction (PCR), as antisense agents used in target validation, drug discovery and development, as ribozymes, as aptamers, and as general stimulators of the immune system. As the popularity of oligonucleotides has increased, the need for producing greater sized batches, and greater numbers of small-sized batches, has increased at pace. Additionally, there has been an increasing emphasis on reducing the costs of oligonucleotide synthesis, and on improving the purity and increasing the yield of oligonucleotide products.
• PCR polymerase chain reaction
• oligonucleotide synthesis A number of innovations have been introduced to the art of oligonucleotide synthesis. Amongst these innovations have been the development of excellent orthogonal protecting groups, activators, reagents, and synthetic conditions.
• the oligonucleotides themselves have been subject to a variety of modifications and improvements. Amongst these are chemistries that improve the affinity of an oligonucleotide for a specific target, that improve the stability of an oligonucleotide in vivo, that enhance the pharmacokinetic (PK) and toxicological (Tox) properties of an oligonucleotide, etc. These novel chemistries generally involve a chemical modification to one or more of the constituent parts of the oligonucleotide.
• PK pharmacokinetic
• Tox toxicological
• oligonucleotide thus embraces a class of compounds that include naturally- occurring, as well as modified, oligonucleotides. Both naturally-occurring and modified oligonucleotides have proven useful in a variety of settings, and both may be made by similar processes, with appropriate modifications made to account for the specific modifications adopted.
• a naturally occurring oligonucleotide i.e. a short strand of DNA or RNA may be envisioned as being a member of the following generic formulas, denominated oligo-RNA and oligo-DNA, respectively, below: Naturally-Occurring Oligonucleotides
• oligo-RNA oligo-DNA wherein m is an integer of from 1 to about 100, and Bx is one of the naturally occurring nucleobases.
• an oligonucleotide occurs as the anion, as the phosphate easily dissociates at neutral pH, and an oligonucleotide will generally occur in solid phase, whether amoiphous or crystalline, as a salt.
• the term "oligonucleotide” encompasses each of the anionic, salt and free acid forms above.
• oligonucleotide may be thought of as being an oligomer of m monomeric subunits represented by the following nucleotides:
• each Bx is a nucleobase, wherein the last residue is a nucleoside (i.e. a nucleotide without the 3 ' -phosphate group) .
• oligonucleotide As mentioned above, various chemistry modifications have been made to oligonucleotides, in order to improve their affinity, stability, PK, Tox, and other properties, hi general, the term oligonucleotide, as now used in the art, encompasses inter alia compounds of the formula: Oligonucletoides (General)
• each Gi is O or S
• each G 2 is OH or SH
• each G 3 is O, S, CH 2 , or NH
• each R 2 ' is H, OH, O-rg, wherein rg is a removable protecting group, a 2'-substituent, or together with R 4 ' forms a bridge
• each R 3 ' is H, a substituent, or together with R 4 ' forms a bridge
• each R 4 ' is H, a substitutent, together with R 2 ' forms a bridge, together with R 3 .
• each q is 0 or 1
• each R 5 ' is H, a substituent, or together with R 4 ' forms a bridge
• each Ge is O, S, CH 2 or NH
• each G 7 is H, PO 3 H 2 , or a conjugate group
• each Bx is a protected or unprotected, naturally occurring or non-naturally occurring nucleobase, as described herein (i.e. naturally occurring or modified).
• oligonucleotides include the solid phase methods first described by Caruthers et al. (See, for example, US Patent No. 5,750,666, incorporated herein by reference, especially columns 3-58, wherein starting materials and general methods of making oligonucleotides, and especially phosphorothioate oligonucleotides, are disclosed, which parts are specifically incorporated herein by reference.) These methods were later improved upon by Koster et al. (See, for example, US Patent No. RE 34,069, which is incorporated herein by reference, especially columns , wherein are disclosed, which parts are specifically incorporated herein by reference.) These methods have further been improved upon by various inventors, as discussed in more detail below.
• a primer support is prepared by covalently linking a suitable nucleoside to a support (SS) through a linker.
• SS support
• LL is a linking group that links the nucleoside to the support via G 3 .
• the linking group is generally a di-functional group, covalently binds the ultimate 3 '-nucleoside (and thus the nascent oligonucleotide) to the solid support during synthesis, but which is cleaved under conditions orthogonal to the conditions under which the 5'-protecting group, and if applicable any T- protecting group, are removed.
• T' is a removable protecting group, and the remaining variables have already been defined, and are described in more detail herein.
• Suitable primer supports may be acquired from Amersham Biosciences under the brand name Primer Support 200TM.
• the primer support may then be swelled in a suitable solvent, e.g. acetonitrile, and introduced into a column of a suitable solid phase synthesis instrument, such as one of the synthesizers available form Amersham Biosciences, such as an AKTAoligopilotTM, or OligoProcessTM brand DNA/RNA synthesizer.
• a suitable solvent e.g. acetonitrile
• a suitable solid phase synthesis instrument such as one of the synthesizers available form Amersham Biosciences, such as an AKTAoligopilotTM, or OligoProcessTM brand DNA/RNA synthesizer.
• T' is selected to be removable under conditions orthogonal to those used to cleave the oligonucleotide from the solid support at the end of synthesis, as well as those used to remove other protecting groups used during synthesis.
• An art-recognized protecting group for oligonucleotide synthesis is DMT (4,4'-dimethoxytrityl).
• the DMT group is especially useful as it is removable under weakly acid conditions.
• an acceptable removal reagent is 3% DCA in a suitable solvent, such as acetonitrile.
• the wash solvent if used, may conveniently be acetonitrile.
• the support may be controlled pore glass or a polymeric bead support.
• Some polymeric supports are disclosed in the following patents: US 6,016,895; US 6,043,353; US 5,391,667 and US 6,300,486, each of which is specifically incorporated herein by reference.
• pg is a phosphorus protecting group, such as a cyanoethyl group.
• NR N1 R N2 is an amine leaving group, such as diisopropyl amino, and for teaching of suitable activator (e.g. tetrazole).
• suitable amidites, and methods of manufacturing amidites are set forth in the following patents: US 6,133,438; US 5,646,265; US 6,124,450; US 5,847,106; US 6,001,982; US 5,705,621; US 5,955,600; US 6,160,152; US 6,335,439; US 6,274,725; US 6,329,519, each of which is specifically incorporated herein by reference, especially as they relate to manufacture of amidites.
• Suitable activators are set forth in the Caruther et al. patent and in the K ⁇ ster et al. patent.
• Especially suitable activators are set forth in the following patents: US 6,031,092 and US 6,476,216, each of which is expressly incorporated herein by reference.
• the oxidant is an oxidizing agent suitable for introducing Gj.
• Gj is oxygen
• a suitable oxidant is set forth in the Caruthers et al. patent, above.
• G 2 is sulfur
• the oxidant may also be referred to as a thiation agent or a sulfur-transfer reagent.
• Suitable thiation agents include the so-called Beaucage reagent, 3H-l,2-benzothiol, phenylacetyl disulfide (also referred to as PADS; see, for example the patents: US 6,114,519 and 6,242,591, each of which is incorporated herein by reference) and thiouram disulfides (e.g. N,N,N',N'-tetramethylthiouram disulfide, disclosed by US patent No. 5,166,387).
• the wash may be a suitable solvent, such as acetonitrile.
• the oxidation step is followed by a capping step, which although not illustrated herein, is an important step for synthesis, as it causes free 5'-OH groups, which did not undergo coupling in step 1, to be blocked from being coupled in subsequent synthetic cycles.
• Suitable capping reagents are set forth in Caruthers et al., K ⁇ ster et al., and other patents described herein. Suitable capping reagents include a combination of acetic anhydride and N-methylimidazole.
• the protecting group pg may be removed by a method as described by Caruthers et al. or K ⁇ ster et al., supra.
• pg is a cyanoethyl group
• the methodology of K ⁇ ster et al., e.g. reaction with a basic solution is generally suitable for removal of the phosphorus protecting group.
• TAA triethylamine
• nucleobases are protected, they are deprotected under basic conditions.
• the deprotected oligonucleotide is cleaved from the support to give the following 5 '-protected oligonucleotide:
• oligonucleotide may be visualized as having the formula:
• the present invention provides compounds having the structure of Formula I:
• each Bx is a naturally occurring or modified nucleobase; provided that at least one Bx has one of the structures Bm, Bn or Bo:
• the present invention provides compounds as describe above, having the formula:
• W 4 is H, a protecting group, or an internucleoside linkage optionally connected to an oligonucleotide
• the present invention provides compounds having the structure of Formula II:
• Pg is a protecting group; m is an integer from 1 to about 100; n and o are each identical integers from 0 to about 100, provided that when n and o are 0, then each
• Gio is an independently selected nucleoside linked to a solid support; and each Bx is a naturally occurring or modified nucleobase;
• the present invention provides compounds having the formula:
• m is an integer from 1 to about 100; n and o are each identical integers from 0 to about 100, provided that when n and o are 0, then W 2 and
• W 3 are each an independently selected nucleoside linked to a solid support; each R 2' is independently selected from the group consisting of H, OH, O-Pg and an independently selected 2'-substituent; W 2 and W 3 are each independently OH, O-Pg, a nucleoside, a nucleotide, or a nucleoside linked to a solid support or to a conjugate group;
• Pg is a protecting group
• W 4 is H, a capping group, or a protecting group, a nucleotide or an oligonucleotides
• the present invention provides methods of characterizing a sample comprising one or more oligomers and at least one impurity, the method comprising: providing said sample comprising one or more oligomers and at least one impurity; obtaining an impurity sample signal from said impurity in said sample; comparing the impurity sample signal with a standard signal to determine the amount of said impurity in said sample; and either rejecting said sample if the amount of the impurity is greater than a predetermined critical impurity threshold, or accepting said sample if the amount of the impurity is less than or equal to said predetermined impurity threshold; wherein said impurity has the formula I:
• R 4 ' forms a bridge; each R 3 ' is H, a substituent, or together with R 4 ' forms abridge; each R 4 ' is H, a substituent, or together with R 2 ' forms abridge, together with R 3 . forms a bridge, or together with R5' forms a bridge; each q is 0 or 1; each R 5 ' is H, a substituent, or together with R 4 ' forms abridge; each G 6 is O 5 S, CH 2 or NH; each G 7 is H, PO 3 H 2 , or a conjugate group; and each Bx is a naturally occurring or modified nucleobase; wherein at least one Bx has one of the structures Bm, Bn or Bo:
• said impurity has the formula:
• the present invention provides methods of characterizing an sample comprising one or more oligomers and at least one impurity, the method comprising: providing said sample comprising one or more oligomers and at least one impurity; obtaining an impurity sample signal from said impurity in said sample; comparing the impurity sample signal with a standard signal to determine the amount of said impurity in said sample; and either rejecting said sample if the amount of the impurity is greater than a predetermined critical impurity threshold, or accepting said sample if the amount of the impurity is less than or equal to said predetermined impurity threshold; wherein said impurity has the Formula II:
• R 4 ' forms abridge; each R 3 ' is H, a substituent, or together with R 4 ' forms a bridge; each R 4 ' is H, a substituent, or together with R 2 ' forms a bridge, together with R 3 > forms a bridge, or together with R 5 ' forms a bridge; each q is 0 or 1; each R 5 ' is H, a substituent, or together with R 4 ' forms abridge; each G 5 is O, S, CH 2 or NH;
• G 8 is H or a protecting group
• Gio is OH, O-Pg, a nucleoside, a nucleotide, or a nucleoside linked to a solid support or to a conjugate group;
• Pg is a protecting group; m is an integer from 1 to about 100; n and o are each identical integers from 0 to about 100, provided that when n and o are 0, then each
• Gio is an independently selected nucleoside linked to a solid support; and each Bx is a naturally occurring or modified nucleobase; wherein either: i) said standard signal is obtained from an internal standard in said determination having said formula II; or ii) said standard signal is a property of said impurity.
• the impurity has the formula:
• m is an integer from 1 to about 100; n and o are each identical integers from 0 to about 100, provided that when n and o are 0, men W 2 and
• W 3 are each an independently selected nucleoside linked to a solid support; each R 2 - is independently selected from the group consisting of H and an independently selected 2'- substituent;
• W 2 and W 3 are each independently OH, O-Pg, a nucleoside, a nucleotide, or a nucleoside linked to a solid support or to a conjugate group;
• Pg is a protecting group
• W 4 is H, a capping group, or a protecting group, a nucleotide or an oligonucleotide.
• the present invention provides methods for synthesizing a nucleosidic compound bearing a nucleobase of formula IV, V or VI:
• R 2 o is an optionally protected nucleoside sugar, or an optionally protected nucleoside phosphoramidite; the method comprising: a) reacting a compound of formula:
• the methods wherein the compound of formula of formula VII, VIII or IX that is reacted with the 4- oxo-2-pentenal is a nucleoside; the method further comprises: b) protecting the 3 ' -hydroxyl of the product of step (a) with a protecting group suitable for oligonuclotide synthesis; c) reacting the protected nucleoside from step (b) with a reagent effective to transform the 3'- hydroxyl thereof to a group of formula -0-P(OCH 2 CH 2 CN)(N(Z-Pr) 2 ), thus forming a nucleoside phosphoramidite synthon; and d) performing oligonucleotide synthesis using at least one of said nucleoside phosphoramidite synthon therein.
• the reagent in step (b) is 2-cyanoethyl te
• the invention provides methods for synthesizing an oligomeric compound comprising a moiety of formula:
• Pg is a protecting group; comprising the steps of: a) providing a diamidite of formula:
• Bx of said amidite is selected from optionally protected A, T, G, C, or 5-methyl C.
• the present invention provides compounds having the formula:
• G 8 is H or a protecting group
• Gio is OH, O-Pg, a nucleoside, a nucleotide, or a nucleoside linked to a solid support or to a conjugate group;
• Pg is a protecting group
• m is an integer from 0 to about 100
• n is an integer from 1 to about 100
• each Bx is a naturally occurring or modified nucleobase
• the compounds have the formula:
• R 30 is H or a protecting group
• R 3I is H, a protecting group, PO 3 H 2 , or a conjugate group.
• the present invention provides oliogonucleotides comprising one or more internucleoside linkages of formula:
• the invention provides methods of characterizing a sample comprising one or more oligomers and at least one impurity, the method comprising: providing said sample comprising one or more oligomers and at least one impurity; obtaining an impurity sample signal from said impurity in said sample; comparing the impurity sample signal with a standard signal to determine the amount of said impurity in said sample; and either rejecting said sample if the amount of the impurity is greater than a predetermined critical impurity threshold, or accepting said sample if the amount of the impurity is less than or equal to said predetermined impurity threshold; wherein said impurity has the formula LL, LLI or LLII; wherein either: i) said standard signal is obtained from an internal standard in said determination having said formula I; or ii) said standard signal is a property of said impurity.
• the standard signal is a property of said impurity, for example a HPLC retention time, NMR signal or MS peak characteristic of said impur
• the present invention provides methods for the synthesis of a compound of fo ⁇ nula:
• each Pg is an independently selected protecting group
• Bx is a nucleobase; and R 2 - is H, OH, O-Pg or a 2'-substituent group; Comprising the steps of: a) providing a 3 '-protected nucleoside of formula:
• step (b) reacting said compound formed in step (b) with a 5 '-protected nucleoside phosphoramidite, and then 3'-deprotetced to form a compound of formula:
• the present invention provides methods for preparing an oligonucleotide comprising one or more internucleoside linkages of formula:
• the Pg at the 5 '-positions are DMT
• the PG groups attached to the internucleoside linkages are beta cyanoethyl groups.
• the present invention further provides synthetic methods comprising: a) providing a compound of formula L:
• Pg is a protecting group
• B is a nucleobase
• R 2 is H, OH, O-Pg or a 2'-substituent group; under conditions effective to form a compound of formula LI:
• the compound provided in step (a) is prepared by reacting a compound of formula:
• the methods further comprising the step of performing oligonucleotide synthesis using at least one of said nucleoside phosphoramidite synthons of formula LI therein.
• the invention provides methods of characterizing a sample comprising one or more compounds, said compounds comprising oligomers and / or nucleoside phosphoramidites, and at least one impurity, the method comprising: providing said sample comprising one or more of said compoundsand at least one impurity; obtaining an impurity sample signal from said impurity in said sample; comparing the impurity sample signal with a standard signal to determine the amount of said impurity in said sample; and either rejecting said sample if the amount of the impurity is greater than a predetermined critical impurity threshold, or accepting said sample if the amount of the impurity is less than or equal to said predetermined impurity threshold; wherein said impurity has the formula I:
• Pg is a protecting group
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• B is a nucleobase
• the standard signal is a property of said impurity, for example a HPLC retention time, NMR signal or MS peak characteristic of said impurity.
• the present invention further provides compounds having one of the formulas:
• Pg is a protecting group; R 2 - is H, OH, O-Pg or a 2'-substituent group; B is a nucleobase; wherein said compound is at least one percent pure.
• Pg is DMT.
• the invention provides compounds having the formula LX:
• Wio is a H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wi i is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• the invention provides compounds having one of the formulas LX, LXI or LXII:
• each Wio is H or a protecting group
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• the invention provides oligomeric compounds comprising a moiety of formula LXIII or LXIV:
• Wio is H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group; wherein said compound is at least one percent pure.
• the invention provides compounds having the formula LXV:
• Wio is a H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• the present invention further provides compounds of formula LXX:
• each Wio is independently H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2' is H, OH, O-Pg or a 2'-substituent group
• the present invention further provides compounds having the formula LXXX:
• each Wio is independently H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• the present invention further provides compounds having the fo ⁇ nula:
• W 2O is a 3 '-oxygen atom of a nucleoside or an oligonucleotide, wherein said oligonucleoside or said oligonucleotide is optionally connected to a linker connected to a solid support;
• W 2 i is a 3 '-oxygen atom of a nucleoside or an oligonucleotide;
• Bx is a nucleobase; and
• R 2 ' is H, OH, O-Pg or a 2'-substituent group;
• the present invention further provides compounds having the formula: wherein:
• W 31 is a 3 '-oxygen atom of a nucleoside or an oligonucleotide
• W 2I is a 3 '-oxygen atom of a nucleoside or an oligonucleotide
• Bx is a nucleobase
• R 2 ' is H, OH, O-Pg or a 2'-substituent group
• the present invention further provides methods of characterizing a sample comprising one or more compounds, and at least one impurity, the method comprising: providing said sample comprising one or more compounds of interest, and at least one impurity; obtaining an impurity sample signal from said impurity in said sample; comparing the impurity sample signal with a standard signal to determine the amount of said impurity in said sample; and either . rejecting said sample if the amount of the impurity is greater than a predetermined critical impurity threshold, or accepting said sample if the amount of the impurity is less than or equal to said predetermined impurity threshold; wherein said impurity has one of the formulas:
• Pg is a protecting group
• R 2' is H, OH, O-Pg or a 2'-substituent group
• B is a nucleobase
• Wio is a H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2' is H, OH, O-Pg or a 2'-substituent group
• each Wio is H or a protecting group
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• W 10 is a H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• W 10 is a H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• W n is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2' is H, OH, O-Pg or a 2'-substituent group
• each Wio is independently H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wi i is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 ' is H, OH, O-Pg or a 2'-substiruent group
• each Wio is independently H, a protecting group, a nucleotide or an oligonucleotide having an internucleoside linkage attached to the 3 '-terminal thereof;
• Wn is H, a protecting group, a linker connected to a solid support; an internucleoside linkage connected to nucleoside linked to a solid support, or an internucleoside linkage connected to an oligonucleotide, wherein said oligonucleoside is optionally connected to a linker connected to a solid support;
• Bx is a nucleobase
• R 2 > is H, OH, O-Pg or a 2'-substituent group
• W 20 is a 3 '-oxygen atom of a nucleoside or an oligonucleotide, wherein said oligonucleoside or said oligonucleotide is optionally connected to a linker connected to a solid support;
• W 2 i is a 3 '-oxygen atom of a nucleoside or an oligonucleotide;
• Bx is a nucleobase; and
• R 2' is H, OH, O-Pg or a 2'-substituent group; or wherein:
• W 31 is a 3 '-oxygen atom of a nucleoside or an oligonucleotide
• W 2I is a 3 '-oxygen atom of a nucleoside or an oligonucleotide
• Bx is a nucleobase
• R 2 - is H, OH, O-Pg or a 2'-substituent group; or wherein either: i) said standard signal is obtained from an internal standard in said determination having said formula I; or ii) said standard signal is a property of said impurity.
• said standard signal is a property of said impurity, for example a HPLC retention time, NMR signal or MS peak characteristic of said impurity.
• the present invention further provides a synthetic method comprising: providing a compound of formula:
• Pg is a protecting group
• R 2 is H, OH, O-Pg or a 2'-substituent group
• B is a nucleobase
• the present invention further provides a synthetic method comprising: providing a compound of formula:
• Pg is a protecting group
• R 2' is H, OH, O-Pg or a 2'-substituent group
• B is a nucleobase
• the present invention further provides a synthetic method comprising: providing a compound of formula: wherein: each Pg is a protecting group;
• R 2 > is H, OH, O-Pg or a 2'-substiruent group
• LSS is a linker connected to a solid support; and performing solid phase oligonucleotide synthesis on said compound to form a compound of formula:
• each W 6J is OH, an internucleoside linkage, or an internucleoside linkage attached to the 3 '-oxygen atom of a nucleoside or an oligonucleotide; each Bx is a nucleobase; and R 2' is H, OH, O-Pg or a 2'-substituent group.
• the present invention further provides A synthetic method comprising: providing a compound of formula: wherein: each Pg is a protecting group;
• R 2 - is H, OH, O-Pg or a 2'-substituent group
• LSS is a linker connected to a solid support; and performing solid phase oligonucleotide synthesis on said compound to form a compound of formula:
• each W 6 i is OH, an internucleoside linkage, or an internucleoside linkage attached to the 3 '-oxygen atom of a nucleoside or an oligonucleotides.
• the nucleobases are optionally protected, and are independently selected from adenine, guanine, thymine, cytosine, uracil and 5-methylcytosine.
• said standard signal is a property of said impurity, for example a HPLC retention time, NMR signal or MS peak characteristic of said impurity.
• the compound is greater than about 1% pure, or greater than about 2% pure, 5% pure, 10% pure, 20% pure, 30% pure, 40% pure, 50% pure, 60% pure, 70% pure, 80% pure, 90% pure, 950% pure, 98% pure, 99% pure or substantially 100% pure as determined by weight with reference to the other components of the system.
• the present invention further provides products of the processes described herein.
• Figure 1 shows the average mass spectrum of the main UV peak obtained by ion pair- liquid chromatography analysis of a typical batch of ISIS 3521 drug substance.
• Figure 3 shows ion pair-liquid chromatogram of ISIS 3521 drug substance.
• Figure 8 shows an average mass spectrum of trimer 4 (late eluting peaks).
• Figure 9 shows IP-LC-MS analysis of 1.
• Figure 10 shows IP-LC-MS analysis of 2.
• Figure 11 shows IP-LC-UV analysis of a) ISIS 3521 drug substance, b) ISIS 3521 drug substance spiked with 1% of 1, c) ISIS 3521 drug substance spiked with 1% of 2 and d) 1 : 1 mixture of 1 and 2.
• Figure 12 shows UV chromatograms of the control and X twelve-mer.
• Figure 13 shows a UV chromatogram of impurity XI twelve-mer.
• Figure 14 shows a UV chromatogram of the XVIII synthesis.
• the present invention provides compounds of Formula I, II or III: j
• each R 1 , R 2 , R 3 and R 4 is independently a 2'-O-, 3'-O-, or 5'-O- linked nucleoside optionally attached to solid support, a 2'-O-, 3'-O-, or 5'-O- linked oligonucleotide optionally attached to solid support, -N 1 Pr 2 , -O(CH 2 ) 2 CN, -OH or -SH, and each G is independently O or S.
• R 1 , R 2 , R 3 and R 4 are-N'Pr 2 or -O(CH 2 ) 2 CN.
• At least one of R 1 , R 2 , R 3 or R 4 is a 2'-0-, 3'-0-, or 5'-
• O- linked nucleoside optionally attached to solid support or a 2'-0-, 3'-0-, or 5'-O- linked oligonucleotide optionally attached to solid support.
• R 1 , R 2 , R 3 or R 4 are 2'-0-, 3'-0-, or 5'-O- linked nucleosides optionally attached to solid support or 2'-0 ⁇ , 3'-0-, or 5'-O- linked oligonucleotides optionally attached to solid support.
• R 1 , R 2 , R 3 or R 4 are 2'-O-, 3'-0-, or 5'-O- linked nucleosides optionally attached to solid support or 2'-0-, 3'-0-, or 5'-O- linked oligonucleotides optionally attached to solid support.
• R 1 , R 2 , R 3 and R 4 are 2'-0-, 3'-0-, or 5'-O- linked nucleosides optionally attached to solid support or 2'-0-, 3'-0-, or 5'-O- linked oligonucleotides optionally attached to solid support.
• the compounds of Formula I, II or III are not attached to solid support.
• the present invention provides compounds of Formula VI:
• each R 4 , R 5 and R 6 is independently a 2-0-, 3'-0-, or 5'-O- linked nucleoside optionally attached to solid support, a 2'-0-, 3'-0-, or 5'-O- linked oligonucleotide optionally attached to solid support, and
• G is O or S.
• R 4 , R 5 or R 6 when one of R 4 , R 5 or R 6 is attached to solid support, then the remainder are not attached to solid support.
• the compounds of Formula IV are not attached to solid support.
• the present invention provides compounds of Formula V:
• R 7 and R 8 are independently a 2'-O-, 3'-O-, or 5'-O- linked nucleoside optionally attached to solid support, a T-O-, 3'-O-, or 5'-O- linked oligonucleotide optionally attached to solid support, -SH or -OH, each G is independently O or S, and
• R 2 ' is H, OH, O-rg wherein rg is a removable protecting group, or a 2' substituent.
• rg is a removable protecting group, or a 2' substituent.
• the compounds of formula I, II, III, IV, or V are at least 1 percent pure. In another embodiment of the invention the compounds of formula I, II, III, IV, or V are greater than about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 percent puer. In a preferred embodiment, the compounds of formula I, II, III, IV, or V are greater than 10 percent pure. In other preferred embodiments, the compounds of formula I, II, III, IV, or V are greater than 50 percent pure.
• any of the compounds disclosed herein are greater than about 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 percent pure.
• the present invention is concerned with the art of oligonucleotide synthesis, and in particular with providing starting materials of excellent purity, the use of which will provide oligonucleotides having excellent purity.
• the invention provides, in some embodiments, methods of identifying samples as starting materials having purity profiles suitable for synthesizing oligonucleotides having excellent purity, and in some embodiments purity sufficient to qualify the oligonucleotides for inclusion in drug preparations.
• the methods according to the present invention comprise identifying an impurity, identifying at least one impurity signal that is representative of the impurity concentration in the sample, detecting said impurity signal in the sample, determining from the impurity signal the impurity concentration, comparing the quantity of impurity with a predetermined impurity threshold, rejecting the sample if the quantity of impurity exceeds the predetermined impurity threshold, or accepting the sample as a starting material if the quantity of the identified impurity does not exceed the impurity threshold.
• the impurity may be further classified as either a critical impurity or a non-critical impurity.
• a critical impurity is an impurity that reacts with a nascent oligonucleotide chain during synthesis, and which permits further chain extension upon reaction. Certain critical impurities react with the 5'- OH of the nascent oligonucleotide chain, and themselves are capable of reacting with an amidite, thereby giving rise to oligonucleotides having incorporated therein the impurity as a constituent part.
• critical impurities react with the nascent oligonucleotide chain at positions other than the 5'- OH, and are incorporated into the oligonucleotide as adducts. Some critical impurities give rise to branchmers. Other critical impurities give rise to adducts. Exemplary critical impurities will be illustrated in more detail below.
• Non-critical impurities are impurities that are either inert with respect to the nascent oligonucleotide chain or non-inert.
• Inert non-critical impurities are those impurities that do not react with the nascent oligonucleotide.
• Non-inert non-critical impurities are those impurities that react with the oligonucleotide chain but result in the termination of the oligonucleotide sequence, and thus are similar in chemical behavior to capping.
• a non-inert non- critical impurity may be referred to as a capping impurity.
• Impurities may arise out of one or more of the process steps used to make the components of the sample, or may result from degradation of components of the sample.
• nucleobase Bx is one of the moieties:
• the impurity signal may be a signal that is representative of the concentration of the impurity in a sample.
• Suitable signals may include an absorption signal, a fluorescence signal, a phosphorescence signal, a mass spectrometry signal, etc.
• An absorption signal includes ultraviolet light absorption signal, a nuclear magnetic resonance signal, a visible light absorption signal, etc. Such a signal may be gathered by, for example, an HPLC instrument with an absorption detector, e.g. an ultraviolet detector.
• a mass spectrometry signal may include an HPLC-mass spectrometry signal.
• the impurity signal may vary linearly, log-linearly, log-log, or otherwise with respect to the impurity concentration.
• an authentic impurity may be prepared and subjected to HPLC, whereby there is produced an impurity signal, the impurity signal comprising an HPLC retention time and a detector signal strength that varies in a consistent relationship to the amount of authentic impurity applied to the HPLC column.
• an impurity signal may be multidimensional, comprising a first signal component representing the identity of the impurity (in the case of HPLC, retention time; in the case of mass-spectrometry, m/z) and a second signal component representative of impurity concentration (in the case of HPLC, UV absorbance; in the case of mass-spectrometry, electrode signal strength).
• the signal component that is representative of impurity identity may be thought of as a qualitative component, while the signal component that is representative of the impurity's concentration in the sample may be thought of as a quantitative component.
• a sample may be subjected to the same testing method to determine whether the impurity is present in the sample (a qualitative determination) and if so, at what concentration (quantitative determination). For example in HPLC, a portion of a sample is applied to a column and the retention times and areas of at least two peaks (one representing a desired compound, and one representing the impurity) are recorded. The retention times are used to identify the signals relating to the compound of interest and the impurity, while the relative areas of the elution peaks of the compound and impurity are used to determine the concentration of impurity relative to the compound in the sample.
• impurity concentration expressed as % impurity, is:
• % impurity 100 % x (Aj / (A; + A A )), where A; is the area under the impurity's elution peak and A A is the area under the elution peak of the compound of interest.
• the concentration of the impurity in the sample is then compared to a predetermined impurity limit.
• a sample having an impurity concentration greater than the impurity limit is classified as rejected.
• a rejected sample may be destroyed, recycled, further purified, or otherwise disposed of, but not used in oligonucleotide synthesis.
• a sample in which no impurity's concentration exceeds its predetermined impurity limit is then classified as a starting material, which may be used as a starting material for making oligonucleotide.
• the impurity is not a starting material, but rather is generated during synthesis. I such cases, the sample is rejected or accepted as an oligomeric sample suitable for further processing to make the desired oligonucleotide.
• a signal may be identified for each of the n impurities. The concentration for impurity X is then calculated as:
• %X 100% x Ax/(A A + ⁇ Ai) ,
• a x is the area of the peak corresponding to impurity X, where X is an integer from 1 to n, A A is the area of the peak corresponding to the compound of interest, and each Ai is the area of the zth impurity peak, wherein i is an integer from 1 to n.
• a predetermined impurity limit is selected for each impurity. If any impurity concentration exceeds its predetermined impurity threshold, the sample is rejected. If each impurity concentration is less than or equal to its impurity threshold, the sample is classified as a starting material, which may be used in oligonucleotide synthesis, or a sample suitable for further processing.
• sample refers to a composition of matter, which contains a compound of interest, and optionally a detectable amount of at least one impurity.
• a sample may further be classified as a “starting material” or as suitable for further processing, or as “rejected,” as described in more detail herein.
• starting material refers to a composition of matter, which contains a compound of interest and optionally a detectable amount of at least one impurity, and which has been classified as “starting material” according to a method of the present invention. In many cases, more than one impurity will be present in the "starting material.” Thus, a starting material is a sample that has been subjected to testing as described herein, and has been determined to contain no more than the impurity threshold of each impurity tested for.
• Hie term "rejected sample” refers to a sample that has been subjected to testing by the inventive method described herein, and has been found to contain at least one impurity at a concentration greater than its impurity threshold. It should be noted that if there are n identified impurities potentially in a sample, there will potentially be n signals corresponding to the n impurities. There also may be a signal relating to the compound of interest itself.
• the term "signal" refers to a voltage, UV absorbance, current, or other value, whether analog or digital, that represents some characteristic of an impurity or a compound of interest.
• a signal may comprise more man one component, e.g. a qualitative component and a quantitative component.
• an HPLC chromatogram comprises a time component (retention time), useful for identifying the signal relating to an impurity or compound of interest, and an absorbance component (UV absorbance), useful for determining the amount of impurity or compound of interest in the sample.
• impurity includes any compound other than amidite or solvent, if any, whether actually present in the amidite sample or not, and whether identified or not.
• a potential impurity is an impurity that has been hypothesized to be present in a sample, whether actually present or not.
• An unidentified impurity is an impurity whose structure is not known, but which is detected in the sample. In some cases, a group of impurities may be collected into an "unidentified impurity" classification.
• a known impurity is an impurity whose structure is known. In accordance with the present invention, a known impurity in a sample can be identified and its quantity measured by obtaining its characteristic signal from both a reference (authentic compound) and the sample.
• Detection of an impurity in a sample may be conducted using a suitable analytical method, such as HPLC, Mass-Spectrometry, GC-Mass Spec, etc.
• a suitable analytical method such as HPLC, Mass-Spectrometry, GC-Mass Spec, etc.
• HPLC high-LC
• Mass-Spectrometry mass-Spectrometry
• GC-Mass Spec a method capable of unambiguously identifying and quantifying an impurity in a sample will be suitable for the disclosed methodology.
• oligonucleotide has the meaning of an oligomer having m subunits embraced within the brackets [ ] of the formula:
• oligonucleotide to be made is depicted in a single stranded conformation, it is common for oligonucleotides to be used in a double stranded conformation.
• siRNA antisense method
• two strands of RNA or RNA-like oligonucleotide are prepared and annealed together, often with a two-nucleotide overlap at the ends.
• the present invention contemplates manufacture of both single- and double-stranded oligonucleotides.
• the nucleobases Bx may be the same or different, and include naturally occurring nucleobases adenine (A), guanine (G), thymine (T), uracil (U) and cytosine (C), as well as modified nucleobases.
• Modified nucleobases include heterocyclic moieties that are structurally related to the naturally-occurring nucleobases, but which have been chemically modified to impart some property to the modified nucleobase that is not possessed by naturally-occurring nucleobases.
• nucleobase is intended to by synonymous with “nucleic acid base or mimetic thereof.”
• a nucleobase is any substructure that contains one or more atoms or groups of atoms capable of hydrogen bonding to a base of an oligonucleotide.
• unmodified or “natural” nucleobases include the purine bases adenine (A) and guanine (G), and the pyrimidine bases thymine (T), cytosine (C) and uracil (U).
• Modified nucleobases include other synthetic and natural nucleobases such as 5-methylcytosine (5-me-C), 5- hydroxymethyl cytosine, xanthine, hypoxanthine, 2-aminoadenine, 6-methyl and other alkyl derivatives of adenine and guanine, 2-propyl and other alkyl derivatives of adenine and guanine, 2- thiouracil, 2-thiotliymine and 2-thiocytosine, 5-halouracil and cytosine, 5-propynyl (-C ⁇ C-CH 3 ) uracil and cytosine and other alkynyl derivatives of pyrimidine bases, 6-azo uracil, cytosine and thymine, 5- uracil (pseudouracil), 4-thiouracil, 8-halo, 8-amino, 8-thiol, 8-thioalkyl, 8-hydroxyl and other 8- substituted adenines and
• nucleobases include tricyclic pyrimidines such as phenoxazine cytidine(lH-pyrimido[5,4-b][l,4]benzoxazin-2(3H)-one), phenothiazine cytidine (lH-pyrimido[5,4- b][l,4]benzothiazin-2(3H)-one), G-clamps such as a substituted phenoxazine cytidine (e.g.
• nucleobases may also include those in which the purine or pyrimidine base is replaced with other heterocycles, for example 7-deaza-adenine, 7-deazaguanosine, 2-aminopyridine and 2-pyridone. Further nucleobases include those disclosed in United States Patent No.
• 5-substituted pyrimidines include 5-substituted pyrimidines, 6-azapyrimidines and N-2, N-6 and O-6 substituted purines, including 2-aminopro ⁇ yladenine, 5-propynyluracil and 5- propynylcytosine.
• 5-methylcytosine substitutions have been shown to increase nucleic acid duplex stability by 0.6-1.2 0 C (Sanghvi, Y.S., Crooke, S.T. and Lebleu, B., eds., Antisense Research and Applications, CRC Press, Boca Raton, 1993, pp. 276-278) and are presently preferred base substitutions, even more particularly when combined with 2'-O-methoxyethyl sugar modifications.
• Additional modifications may also be made at other positions on the oligonucleotide, particularly the 3' position of the sugar on the 3' terminal nucleotide and the 5' position of 5' terminal nucleotide.
• one additional modification of the ligand conjugated oligonucleotides of the present invention involves chemically linking to the oligonucleotide one or more additional non- ligand moieties or conjugates which enhance the activity, cellular distribution or cellular uptake of the oligonucleotide.
• moieties include but are not limited to lipid moieties such as a cholesterol moiety (Letsinger et al., Proc. Natl. Acad. Sci.
• cholic acid Manoharan et al., Bioorg. Med. Chem. Lett., 1994, 4, 1053
• a thioether e.g., hexyl-S-trityltliiol (Manoharan et al., Ann. N.Y. Acad. Sci., 1992, 660, 306; Manoharan et al., Bioorg. Med. Chem. Let, 1993, 3, 2765
• a thiocholesterol (Oberhauser et al., Nucl.
• oligomeric compounds e.g. oligonucleotides
• polycyclic heterocyclic compounds in place of one or more heterocyclic base moieties.
• a number of tricyclic heterocyclic compounds have been previously reported. These compounds are routinely used in antisense applications to increase the binding properties of the modified strand to a target strand. The most studied modifications are targeted to guanosines hence they have been termed G-clamps or cytidine analogs. Many of these polycyclic heterocyclic compounds have the general formula:
• the gain in helical stability does not compromise the specificity of the oligonucleotides.
• the T n data indicate an even greater discrimination between the perfect match and mismatched sequences compared to dC5 me .
• the tethered amino group serves as an additional hydrogen bond donor to interact with the Hoogsteen face, namely the 06, of a complementary guanine thereby forming 4 hydrogen bonds. This means that the increased affinity of G-clamp is mediated by the combination of extended base stacking and additional specific hydrogen bonding.
• R 1Oa is O, S or N-CH 3 ;
• R Uil is A(Z) xl , wherein A is a spacer and Z independently is a label bonding group bonding group optionally bonded to a detectable label, but R ⁇ a is not amine, protected amine, nitro or cyano;
• Xl is 1, 2 or 3; and
• R u is NO 2 or both R ⁇ and Ri 2 are independently -CH 3 .
• the synthesis of these compounds is dicslosed in United States Patent Serial Number 5,434,257, which issued on July 18, 1995, United States Patent Serial Number 5,502,177, which issued on March 26, 1996, and United States Patent Serial Number 5,646, 269, which issued on July 8, 1997, the contents of which are commonly assigned with this application and are incorporated herein in their entirety.
• Further tricyclic heterocyclic compounds amenable to the present invention also disclosed in the "257, 177 and 269" Patents include those having the formula:
• a and b are independently 0 or 1 with the total of a and b being 0 or 1 ;
• A is N, C or CH;
• Z is taken together with A to form an aryl or heteroaryl ring structure comprising 5 or 6 ring atoms wherein the heteroaryl ring comprises a single O ring heteroatom, a single N ring heteroatom, a single S ring heteroatom, a single O and a single N ring heteroatom separated by a carbon atom, a single S and a single N ring heteroatom separated by a C atom, 2 N ring heteroatoms separated by a carbon atom, or 3 N ring heteroatoms at least 2 of which are separated by a carbon atom, and wherein the aryl or heteroaryl ring carbon atoms are unsubstituted with other than H or at least 1 nonbridging ring
• each Ri 6 is, independently, selected from hydrogen and various substituent groups.
• a 6 is O or S
• a 7 is CH 2 , N-CH 3 , O or S
• each A 8 and A 9 is hydrogen or one of A 8 and A 9 is hydrogen and the other of A 8 and A 9 is selected from the group consisting of: — O-(CH 2 ) pl -G
• each Q 2 is, independently, H or Pg
• a 10 is H, Pg, substituted or unsubstituted C 1 -C 10 alkyl, acetyl, benzyl, -(CH 2 ) P 3NH 2 , -(CH 2
• each dashed line ( — ) indicates a point of attachment to an adjacent phosphorus atom, represents the sugar portion of a general nucleoside or nucleotide as embraced by the present invention.
• Suitable 2 '-substituents corresponding to R' 2 include: OH, F, O-alkyl (e.g. O-methyl), S- alkyl, N-alkyl, O-alkenyl, S-alkenyl, N-alkenyl; 0-alkynyl, S-alkynyl, N-alkynyl; O-alkyl-0-alkyl, wherein the alkyl, alkenyl and alkynyl may be substituted or unsubstituted C 1 to C 10 alkyl or C 2 to C 10 alkenyl or alkynyl, respectively.
• O-alkyl e.g. O-methyl
• S- alkyl e.g. O-methyl
• S- alkyl e.g. O-methyl
• S-alkenyl S-alkenyl, N-alkenyl
• 0-alkynyl S-alkynyl, N-alkynyl
• oligonucleotides comprise one of the following at the 2' position: C 1 to Ci 0 lower alkyl, substituted lower alkyl, alkenyl, alkynyl, alkaryl, aralkyl, O-alkaryl or O-aralkyl, SH, SCH 3 , OCN, Cl, Br, CN, CF 3 , OCF 3 , SOCH 3 , SO 2 CH 3 , ONO 2 , NO 2 , N 3 , NH 2 , heterocycloalkyl, heterocycloalkaryl, aminoalkylamino, polyalkylamino, substituted silyl, an RNA cleaving group, a reporter group, an intercalator, a group for improving the pharmacokinetic properties of an oligonucleotide, or a group for improving the pharmacodynamic properties of an oligonucleotide, and other substituents having similar properties.
• a preferred 2 '-modification includes 2'-methoxyethoxy (2'-0-CH 2 CH 2 OCH 3 , also known as 2'-O-(2-methoxyethyl) or 2'-MOE) (Martin et ah, HeIv. CMm. Acta, 1995, 78, 486-504).
• a further preferred modification includes 2'-dimethylaminooxyethoxy, i.e., a O(CH 2 ) 2 ON(CH 3 ) 2 group, also known as 2'-DMAOE 3 as described in examples hereinbelow, and T- dimethylaminoethoxyethoxy (also known in the art as 2'-O-dimethyl-amino-ethoxy-ethyl or T- DMAEOE), i.e., 2'-O-(CH 2 ) 2 -O-(CH 2)2 -N(CH 3 ) 2 , also described in examples hereinbelow.
• 2'-dimethylaminooxyethoxy i.e., a O(CH 2 ) 2 ON(CH 3 ) 2 group, also known as 2'-DMAOE 3 as described in examples hereinbelow
• T- dimethylaminoethoxyethoxy also known in the art as 2'-O-dimethyl-amino-ethoxy-eth
• R b is O, S or NH;
• Each R s , R t , R u and R v is, independently, hydrogen, C(O)R W , substituted or unsubstituted Q- Cio alkyl, substituted or unsubstituted C 2 -Ci 0 alkenyl, substituted or unsubstituted C 2 -Ci 0 alkynyl, alkylsulfonyl, arylsulfonyl, a chemical functional group or a conjugate group, wherein the substituent groups are selected from hydroxyl, amino, alkoxy, carboxy, benzyl, phenyl, nitro, thiol, thioalkoxy, halogen, alkyl, aryl, alkenyl and alkynyl; or optionally, R u and R v , together fo ⁇ n a phthalimido moiety with the nitrogen atom to which they are attached; each R w is, independently, substituted or unsubstituted Ci-
• R j is alkyl or haloalkyl having 1 to about 10 carbon atoms, alkenyl having 2 to about 10 carbon atoms, alkynyl having 2 to about 10 carbon atoms, aryl having 6 to about 14 carbon atoms, N(R k )(R m ) ORi;, halo, SR k or CN; m a is 1 to about 10; each nib is, independently, 0 or 1; me is 0 or an integer from 1 to 10; md is an integer from 1 to 10; me is from 0, 1 or 2; and provided that when me is 0, md is greater than 1.
• 2'-modifications include 2'-methoxy (2'-0-CH 3 ), T- aminopropoxy (2'-OCH 2 CH 2 CH 2 NH 2 ) and 2'-fluoro (2'-F).
• the 2'-modif ⁇ cation may be in the arabino (up) position or ribo (down) position.
• a preferred 2'-arabino modification is 2'-F.Similar modifications may also be made at other positions on nucleosides and oligomers, particularly the 3' position of the sugar on the 3' terminal nucleoside or at a 3'-position of a nucleoside that has a linkage from the 2'-position such as a 2'-5' linked oligomer and at the 5' position of a 5' terminal nucleoside. Oligomers may also have sugar mimetics such as cyclobutyl moieties in place of the pentofuranosyl sugar. Representative United States patents that teach the preparation of such modified sugars structures include, but are not limited to, U.S.
• acetamido substituent groups are disclosed in United States Patent 6,147,200 which is hereby incorporated by reference in its entirety.
• Representative dimethylaminoethyloxyethyl substituent groups are disclosed in International Patent Application PCT/US99/17895, entitled “2'-O- Dimethylaminoethyloxyethyl-Modified Oligonucleotides", filed August 6, 1999, hereby incorporated by reference in its entirety.
• the phosphate group can be linked to either the 2', 3' or 5' hydroxyl moiety of the sugar.
• the phosphate groups covalently link adjacent nucleosides to one another to form a linear polymeric compound.
• the respective ends of this linear polymeric structure can be joined to form a circular structure by hybridization or by formation of a covalent bond, however, open linear structures are generally preferred.
• the phosphate groups are commonly referred to as forming the internucleoside linkages of the oligonucleotide.
• the normal internucleoside linkage of RNA and DNA is a 3' to 5' phosphodiester linkage.
• RNAse H mechanism whereby a strand of DNA is introduced into a cell, where the DNA hybridizes to a strand of RNA.
• RNAse H endonuclease
• mRNA messenger RNA
• DNA may be employed as an agent for modulating the expression of certain genes.
• RNAse H mechanism can be effectively used to modulate expression of target peptides or proteins.
• an oligonucleotide incorporating a stretch of DNA and a stretch of RNA or 2'-modified RNA can be used to effectively modulate gene expression.
• the oligonucleotide comprises a stretch of DNA flanked by two stretches of 2'- modified RNA.
• Preferred 2 '-modifications include 2'-MOE as described herein.
• the ribosyl sugar moiety has also been extensively studied to evaluate the effect its modification has on the properties of oligonucleotides relative to unmodified oligonucleotides.
• the 2 '-position of the sugar moiety is one of the most studied sites for modification.
• Certain T- substituent groups have been shown to increase the lipohpilicity and enhance properties such as binding affinity to target RNA, chemical stability and nuclease resistance of oligonucleotides. Many of the modifications at the 2 '-position that show enhanced binding affinity also force the sugar ring into the C 3 -endo conformation.
• RNA:RNA duplexes are more stable, or have higher melting temperatures (Tm) than DNA-.DNA duplexes (Sanger et al, Principles of Nucleic Acid Structure, 1984, Springer-Verlag; New York, NY.; Lesnik et al, Biochemistry, 1995, 34, 10807-10815; Conte et al, Nucleic Acids Res., 1997, 25, 2627-2634).
• RNA duplex The increased stability of RNA has been attributed to several structural features, most notably the improved base stacking interactions that result from an A-form geometry (Searle et al, Nucleic Acids Res., 1993, 21, 2051-2056).
• the presence of the 2' hydroxyl in RNA biases the sugar toward a C3' endo pucker, i.e., also designated as Northern pucker, which causes the duplex to favor the A-form geometry.
• deoxy nucleic acids prefer a C2' endo sugar pucker, i.e., also known as Southern pucker, which is thought to impart a less stable B-form geometry (Sanger, W. (1984) Principles of Nucleic Acid Structure, Springer-Verlag, New York, NY).
• the 2' hydroxyl groups of RNA can form a network of water mediated hydrogen bonds that help stabilize the RNA duplex (EgIi et al., Biochemistry, 1996, 35, 8489-8494).
• DNA:RNA hybrid duplexes are usually less stable than pure RNA:RNA duplexes, and depending on their sequence may be either more or less stable than DNA:DNA duplexes (Searle et al, Nucleic Acids Res., 1993, 21, 2051-2056).
• the structure of a hybrid duplex is intermediate between A- and B-form geometries, which may result in poor stacking interactions (Lane et al, Eur. J. Biochem., 1993, 215, 297-306; Fedoroff et al, J. MoI. Biol, 1993, 233, 509-523; Gonzalez et al, Biochemisti ⁇ , 1995, 34, 4969-4982; Horton et al, J.
• the stability of a DNA:RNA hybrid is central to antisense therapies as the mechanism requires the binding of a modified DNA strand to a mRNA strand.
• the antisense DNA should have a very high binding affinity with the mRNA. Otherwise the desired interaction between the DNA and target mRNA strand will occur infrequently, thereby decreasing the efficacy of the antisense oligonucleotide.
• RNA:RNA duplexes are more stable, or have higher melting temperatures (Tm) than DNArDNA duplexes (Sanger et al, Principles of Nucleic Acid Structure, 1984, Springer- Verlag; New York, NY.; Lesnik et al, Biochemistry, 1995, 34, 10807-10815; Conte et al, Nucleic Acids Res., 1997, 25, 2627-2634).
• RNA has been attributed to several structural features, most notably the improved base stacking interactions that result from an A-form geometry (Searle et al, Nucleic Acids Res., 1993, 21, 2051-2056).
• deoxy nucleic acids prefer a C2' endo sugar pucker, i.e., also known as Southern pucker, which is thought to impart a less stable B-form geometry (Sanger, W. (1984) Principles of Nucleic Acid Structure, Springer- Verlag, New York, NY).
• DNA:RNA hybrid duplexes are usually less stable than pure RNA:RNA duplexes and, depending on their sequence, may be either more or less stable than DNA:DNA duplexes (Searle et al, Nucleic Acids Res., 1993, 21, 2051-2056).
• the structure of a hybrid duplex is intermediate between A- and B-form geometries, which may result in poor stacking interactions (Lane et al, Eur. J. Biochem., 1993, 215, 297-306; Fedoroff et al, J. MoI Biol, 1993, 233, 509-523; Gonzalez et al, Biochemistry, 1995, 34, 4969-4982; Horton et al, J.
• the stability of a DNA:RNA hybrid a significant aspect of antisense therapies, as the proposed mechanism requires the binding of a modified DNA strand to a mRNA strand.
• the antisense DNA should have a very high binding affinity with the mRNA. Otherwise, the desired interaction between the DNA and target mRNA strand will occur infrequently, thereby decreasing the efficacy of the antisense oligonucleotide.
• oligonucleotides also have been shown to be antisense inhibitors of gene expression with promising features for in vivo use (Martin, P., HeIv. CMm. Acta, 1995, 78, 486-504; Altmann et al, Chimia, 1996, 50, 168-176; Altmann et al, Biochem. Soc. Trans., 1996, 24, 630-637; and Altmann et al, Nucleosides Nucleotides, 1997, 16, 917-926). Relative to DNA, they display improved RNA affinity and higher nuclease resistance.
• MOE substituted oligonucleotides have shown outstanding promise as antisense agents in several disease states.
• One such MOE substituted oligonucleotide is presently being investigated in clinical trials for the treatment of CMV retinitis.
• LNAs oligonucleotides wherein the 2' and 4' positions are connected by a bridge
• CD Circular dichroism
• spectra show that duplexes involving fully modified LNA (esp. LNAiRNA) structurally resemble an A-form RNA:RNA duplex.
• Nuclear magnetic resonance (NMR) examination of an LNA:DNA duplex confirmed the 3'-endo conformation of an LNA monomer. Recognition of double-stranded DNA has also been demonstrated suggesting strand invasion by LNA. Studies of mismatched sequences show that LNAs obey the Watson-Crick base pairing rules with generally improved selectivity compared to the corresponding unmodified reference strands.
• LNAs in which the 2'-hydroxyl group is linked to the 4' carbon atom of the sugar ring thereby forming a 2'-C,4'-C-oxymethylene linkage thereby forming a bicyclic sugar moiety.
• the linkage may be a methelyne (-CH 2 -) n group bridging the 2' oxygen atom and the 4' carbon atom wherein n is 1 or 2 (Singh et al., Chem. Commun., 1998, 4, 455-456).
• Other preferred bridge groups include the 2'-deoxy-2'-CH 2 OCH 2 -4' bridge.
• Exemplary non-phosphate/phosphorothioate diester linkages contemplated within the skill of the art include: phosphorodithioates, phosphotriesters, aminoalkylphosphotiiesters, methyl and other alkyl phosphonates including 3'-alkylene phosphonates, 5'-alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates including 3 '-amino phosphoramidate and aminoalkylphosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, selenophosphates and boranophosphates.
• Additional linkages include: thiodiester (-O-C(O)-S-), thionocarbamate (-0-C(O)(NJ)-S-), siloxane (-0-Si(J) 2 -O-), carbamate (-0- C(O)-NH- and -NH-C(O)-O-), sulfamate (-0-S(O)(O)-N- and -N-S(O)(O)-N-, morpholino sulfamide (-O-S(O)(N(morpholino)-), sulfonamide (-0-SO 2 -NH-), sulfide (-CH 2 -S-CH 2 -), sulfonate (-0-SO 2 - CH 2 -), N,N'-dimethylhydrazine (-CH 2 -N(CHj)-N(CH 3 )-), thioformacetal (-S-CH 2 -O-), formacetal (-
• J denotes a substituent group which is commonly hydrogen or an alkyl group or a more complicated group that varies from one type of linkage to another.
• linking groups as described above that involve the modification or substitution of the -0-P-O- atoms of a naturally occurring linkage
• linking groups that include modification of the 5'-methylene group as well as one or more of the -0-P-O- atoms.
• Oligonucleotides are generally prepared, as described above, on a support medium, e.g. a solid support medium.
• a first synthon e.g. a monomer, such as a nucleoside
• the oligonucleotide is then synthesized by sequentially coupling monomers to the support-bound synthon. This iterative elongation eventually results in a final oligomeric compound or other polymer such as a polypeptide.
• Suitable support media can be soluble or insoluble, or may possess variable solubility in different solvents to allow the growing support bound polymer to be either in or out of solution as desired.
• support media is intended to include all forms of support known to the art skilled for the synthesis of oligomeric compounds and related compounds such as peptides.
• Some representative support media that are amenable to the methods of the present invention include but are not limited to the following: controlled pore glass (CPG); oxalyl-controlled pore glass (see, e.g., Alul, et al., Nucleic Acids Research 1991, 19, 1527); silica-containing particles, such as porous glass beads and silica gel such as that formed by the reaction of trichloro-[3-(4-chloromethyl)phenyl]propylsilane and porous glass beads (see Parr and Grohmann, Angew. Chem. Internal. Ed.
• Further support media amenable to the present invention include without limitation PEPS support a polyethylene (PE) film with pendant long-chain polystyrene (PS) grafts (molecular weight on the order of 10 6 , (see Berg, et al, J. Am. Chein. Soc, 1989, 111, 8024 and International Patent Application WO 90/02749),).
• the loading capacity of the film is as high as that of a beaded matrix with the additional flexibility to accomodate multiple syntheses simultaneously.
• the PEPS film may be fashioned in the form of discrete, labeled sheets, each serving as an individual compartment.
• the sheets are kept together in a single reaction vessel to permit concurrent preparation of a multitude of peptides at a rate close to that of a single peptide by conventional methods.
• experiments with other geometries of the PEPS polymer such as, for example, non-woven felt, knitted net, sticks or microwellplates have not indicated any limitations of the synthetic efficacy.
• Further support media amenable to the present invention include without limitation particles based upon copolymers of dimethylacrylamide cross-linked with N,N'-bisacryloylethylenediamine, including a known amount of N-tertbutoxycarbonyl-beta-alanyl-N'-acryloylhexamethylenediamine.
• Several spacer molecules are typically added via the beta alanyl group, followed thereafter by the amino acid residue subunits.
• the beta alanyl-containing monomer can be replaced with an acryloyl safcosine monomer during polymerization to form resin beads. The polymerization is followed by reaction of the beads with ethylenediamine to form resin particles that contain primary amines as the covalently linked functionality.
• the polyacrylamide-based supports are relatively more hydrophilic than are the polystyrene-based supports and are usually used with polar aprotic solvents including dimemylformamide, dimethylacetamide, ⁇ -methylpyrrolidone and the like (see Atherton, et al, J. Am. Chan. Soc, 1975, 97, 6584, Bioorg. Chem. 1979, 8, 351, and J. C. S. Perkin I 538 (1981)).
• Further support media amenable to the present invention include without limitation a composite of a resin and another material that is also substantially inert to the organic synthesis reaction conditions employed.
• One exemplary composite (see Scott, et al, J. Chrom. ScI, 1971, 9, 577) utilizes glass particles coated with a hydrophobic, cross-linked styrene polymer containing reactive chloromethyl groups, and is supplied by ⁇ orthgate Laboratories, Inc., of Hamden, Conn., USA.
• Another exemplary composite contains a core of fluorinated ethylene polymer onto which has been grafted polystyrene (see Kent and Merrifield, Israel J. Chem. 1978, 17, 243 and van Rietschoten in Peptides 1974, Y.
• Contiguous solid supports other than PEPS such as cotton sheets (Lebl and Eichler, Peptide Res. 1989, 2, 232) and hydroxypropylacrylate-coated polypropylene membranes (Daniels, et al, Tetrahedron Lett. 1989, 4345).
• Support bound oligonucleotide synthesis relies on sequential addition of nucleotides to one end of a growing chain.
• a first nucleoside (having protecting groups on any exocyclic amine functionalities present) is attached to an appropriate glass bead support and activated phosphite compounds (typically nucleotide phosphoramidites, also bearing appropriate protecting groups) are added stepwise to elongate the growing oligonucleotide.
• activated phosphite compounds typically nucleotide phosphoramidites, also bearing appropriate protecting groups
• Additional methods for solid-phase synthesis may be found in Caruthers U.S. Patents Nos. 4,415,732; 4,458,066; 4,500,707; 4,668,777; 4,973,679; and 5,132,418; and Koster U.S. Patents Nos. 4,725,677 and Re. 34,069.
• the phosphorus protecting group (pg) is an alkoxy or alkylthio group or O or S having a /3-eliminable group of Hie formula -CH 2 CH 2 -G W , wherein G w is an electron-withdrawing group.
• Suitable examples of pg that are amenable to use in connection with the present invention include those set forth in the Caruthers U.S. Patents Nos. 4,415,732; 4,458,066; 4,500,707; 4,668,777; 4,973,679; and 5,132,418; and Koster U.S. Patents Nos. 4,725,677 and Re. 34,069.
• the alkyl or cyanoethyl withdrawing groups are preferred, as commercially available phosphoramidites generally incorporate either the methyl or cyanoethyl phosphorus protecting group.
• the method for removal of pg depends upon the specific pg to be removed.
• an alkyl group is generally removed by nucleophilic attack on the ⁇ -carbon of the alkyl group.
• Such PGs are described in the Caruthers et al. patents, as cited herein.
• oxidation of P(III) to P(V) can be carried out by a variety of reagents.
• the P(V) species can exist as phosphate triesters, phosphorothioate diesters, or phosphorodithioate diesters.
• Each type of P(V) linkage has uses and advantages, as described herein.
• the term "oxidizing agent" should be understood broadly as being any reagent capable of transforming a P(III) species (e.g. a phosphite) into a P(V) species.
• oxidizing agent includes “sulfurizing agent,” which is also considered to have the same meaning as “thiation reagent.” Oxidation, unless otherwise modified, indicates introduction of oxygen or sulfur, with a concomitant increase in P oxidation state from III to V. Where it is important to indicate that an oxidizing agent introduces an oxygen into a P(III) species to make a P(V) species, the oxidizing agent will be referred to herein is "an oxygen- introducing oxidizing reagent.”
• Oxidizing reagents for making phosphate diester linkages have been described by e.g. Caruthers et al. and K ⁇ ster et al., as cited herein.
• sulfurization reagents which have been used to synthesize oligonucleotides containing phosphorothioate bonds include elemental sulfur, dibenzoyltetrasuli ⁇ de, 3-H-l,2-benzidithiol-3-one 1,1-dioxide (also known as Beaucage reagent), tetraethylthiuram disulfide (TETD), and bis(O,O-diisopropoxy phosphinothioyl) disulfide (known as Stec reagent).
• Oxidizing reagents for making phosphorothioate diester linkages include phenylacetyldisulfide (PADS), as described by Cole et al.
• the phosphorothioate diester and phosphate diester linkages may alternate between sugar subunits. In other embodiments of the present invention, phosphorothioate linkages alone may be employed.
• the thiation reagent may be a dithiuram disulfides. See US 5,166,387 for disclosure of some suitable dithiuram disulfides. It has been surprisingly found that one dithiuram disulfide may be used together with a standard capping reagent, so that capping and oxidation may be conducted in the same step. This is in contrast to standard oxidative reagents, such as Beaucage reagent, which require that capping and oxidation take place in separate steps, generally including a column wash between steps.
• the 5 '-protecting group bg or T' is a protecting group that is orthogonal to the protecting groups used to protect the nucleobases, and is also orthogonal, where appropriate to 2'-O-protecting groups, as well as to the 3'-linker to the solid support.
• the 5'- protecting group is acid labile.
• the 5 '-protecting group is selected from an optionally substituted trityl group and an optionally substituted pixyl group.
• the pixyl group is substituted with one or more substituents selected from alkyl, alkoxy, halo, alkenyl and alkynyl groups.
• the trityl groups are substituted with from about 1 to about 3 alkoxy groups, specifically about 1 to about 3 methoxy groups. In particular embodiments of the invention, the trityl groups are substituted with 1 or 2 methoxy groups at the 4- and (if applicable) 4'- positions.
• a particularly acceptable trityl group is 4,4'-dimethoxytrityl (DMT or DMTr).
• reagent push has the meaning of a volume of solvent that is substantially free of any active compound (i.e. reagent, activator, by-product, or other substance other than solvent), which volume of solvent is introduced to the column for the purpose, and with the effect, of pushing a reagent solution onto and through the column ahead of a subsequent reagent solution.
• a reagent push need not be an entire column volume, although in some cases it may include one or more column volumes.
• a reagent push comprises at least the minimum volume necessary to substantially clear reagent, by-products and/or activator from a cross-section of the column immediately ahead of the front formed by the reagent solution used for the immediately subsequent synthetic step.
• An active compound whether a reagent, by ⁇ product or activator, is considered substantially cleared if the concentration of the compound in a cross-section of the column at which the following reagent solution front is located, is low enough that it does not substantially affect the activity of the following reagent solution.
• the person skilled in the art will recognize that this the volume of solvent required for a "reagent push" will vary depending upon the solvent, the solubility in the solvent of the reagents, activators, by-products, etc., that are on the column, the amounts of reagents, activators, by-products, etc. that are to be cleared from the column, etc. It is considered within the skill of the artisan to select an appropriate volume for each reagent push, especially with an eye toward the Examples, below.
• column wash may imply that at least one column volume is permitted to pass through the column before the subsequent reagent solution is applied to the column. Where a column volume (CV) of the column wash is specified, this indicates that a volume of solvent equivalent to the interior volume of the unpacked column is used for the column wash.
• CV column volume
• a wash solvent is a solvent containing substantially no active compound that is applied to a column between synthetic steps.
• a “wash step” is a step in which a wash solvent is applied to the column. Both "reagent push” and “column wash” are included within this definition of "wash step”.
• a wash solvent may be a pure chemical compound or a mixture of chemical compounds, the solvent being capable of dissolving an active compound.
• a wash solvent used in one of the wash steps may comprise some percentage of acetonitrile, not to exceed 50% v/v.
• capping and oxidation steps may be reversed, if desired. That is, capping may precede or follow oxidation. Also, with selection of a suitable thiation reagent, the oxidation and capping steps may be combined into a single step. For example, it has been surprisingly found that capping with acetic anhydride may be conducted in the presence of N,N'-dimethyldithiuram disulfide.
• Suitable solvents are identified in the Caruthers et al. and Koster et al. patents, cited herein.
• the Cole et al. patent describes acetonitrile as a solvent for phenylacetyldisulfide.
• Other suitable solvents include toluene, xanthenes, dichloromethane, etc.
• Reagents for cleaving an oligonucleotide from a support are set forth, for example, in the Caruthers et al. and Koster et al. patents, as cited herein. It is considered good practice to cleave oligonucleotide containing thymidine (T) nucleotides in the presence of an alkylated amine, such as triethylamine, when the phosphorus protecting group is 0-CH 2 CH 2 CN, because this is now known to avoid the creation if cyano-ethylated thymidine nucleotides (CNET). Avoidance of CNET adducts is described in general in US Patent No. 6,465,628, which is incoiporated herein by reference, and especially the Examples in columns 20-30, which are specifically incorporated by reference.
• CNET cyano-ethylated thymidine nucleotides
• the oligonucleotide may be worked up by standard procedures known in the art, for example by size exclusion chromatography, high performance liquid chromatography (e.g. reverse-phase HPLC), differential precipitation, etc.
• the oligonucleotide is cleaved from a solid support while the 5'-OH protecting group is still on the ultimate nucleoside.
• This so-called DMT-on (or trityl-on) oligonucleotide is then subjected to chromatography, after which the DMT group is removed by treatment in an organic acid, after which the oligonucleotide is de-salted and further purified to form a final product.
• the 5'-hydroxyl protecting groups may be any groups that are selectively removed under suitable conditions.
• the 4,4'-dimethoxytriphenylmethyl (DMT) group is a favored group for protecting at the 5 '-position, because it is readily cleaved under acidic conditions (e.g. in the presence of dichlroacetic acid (DCA), trichloroacetic acid (TCA), or acetic acid.
• DCA dichlroacetic acid
• TCA trichloroacetic acid
• acetic acid e.g. about 3 to about 10 percent DCA (v/v) in a suitable solvent.
• DCA e.g. about 3 to about 10 percent DCA (v/v) in a suitable solvent.
• Removal of oligonucleotide after cleavage from the support is generally performed with acetic acid.
• oligonucleotides can be prepared as chimeras with other oligomeric moieties.
• the term "oligomeric compound” refers to a polymeric structure capable of hybridizing a region of a nucleic acid molecule, and an "oligomeric moiety" a portion of such an oligomeric compound.
• Oligomeric compounds include oligonucleotides, oligonucleosides, oligonucleotide analogs, modified oligonucleotides and oligonucleotide mimetics. Oligomeric compounds can be linear or circular, and may include branching.
• an oligomeric compound comprises a backbone of linked monomeric subunits where each linked monomeric subunit is directly or indirectly attached to a heterocyclic base moiety.
• the linkages joining the monomeric subunits, the monomeric subunits and the heterocyclic base moieties can be variable in structure giving rise to a plurality of motifs for the resulting oligomeric compounds including hemimers, gapmers and chimeras.
• a nucleoside is a base-sugar combination. The base portion of the nucleoside is normally a heterocyclic base moiety.
• oligonucleoside refers to nucleosides that are joined by internucleoside linkages that do not have phosphorus atoms. Internucleoside linkages of this type include short chain alkyl, cycloalkyl, mixed heteroatom alkyl, mixed heteroatom cycloalkyl, one or more short chain heteroatomic and one or more short chain heterocyclic.
• internucleoside linkages include but are not limited to siloxane, sulfide, sulfoxide, sulfone, acetyl, fo ⁇ nacetyl, thioformacetyl, methylene formacetyl, thioformacetyl, alkeneyl, sulfamate; methyleneimino, methylenehydrazino, sulfonate, sulfonamide, amide and others having mixed N, O, S and CH 2 component parts.
• WO 91/08213 WO 90/15065; WO 91/15500; WO 92/20822; WO 92/20823; WO 91/15500; WO 89/12060; EP 216860; PCT/US 92/04294; PCT/US 90/03138; PCT/US 91/06855; PCT/US 92/03385; PCT/US 91/03680; U.S. Application Nos.
• Phosphoramidites used in the synthesis of oligonucleotides are available from a variety of commercial sources (included are: Glen Research, Sterling, Virginia; Amersham Pharmacia Biotech Inc., Piscataway, New Jersey; Cruachem Inc., Aston, Pennsylvania; Chemgenes Corporation, Waltham, Massachusetts; Proligo LLC, Boulder, Colorado; PE Biosystems, Foster City California; Beckman Coulter Inc., Fullerton, California). These commercial sources sell high purity phosphoramidites generally having a purity of better than 98%. Those not offering an across the board purity for all amidites sold will in most cases include an assay with each lot purchased giving at least the purity of the particular phosphoramidite purchased.
• Phosphoramidites are prepared for the most part for automated DNA synthesis and as such are prepared for immediate use for synthesizing desired sequences of oligonucleotides.
• Phosphoramidites may be prepared by methods disclosed by e.g. Caruthers et al. (US 4,415,732; 4,458,066; 4,500,707; 4,668,777; 4,973,679; and 5,132,418) and K ⁇ ster et al. (US RE 34,069).
• Double stranded oligonucleotides such as double-stranded RNA, may be manufactured according to methods according to the present invention, as described herein.
• RNA synthesis it is necessary to protect the 2'-OH of the amidite reagent with a suitable removable protecting groups.
• Suitable protecting groups for 2'-OH are described in US Patent Nos. 6,008,400, 6,111,086 and 5,889,136.
• a particularly suitable 2'-protecting group for RNA synthesis is the ACE protecting group as described in US 6,111,086.
• Suitable 5'-protecting groups are set forth in US 6,008,400.
• a particularly suitable 5'- ⁇ rotecting group is the trimethylsilyloxy (TMSO) group as taught in US 6,008,400. See especially example 1, columns 10- 13.
• TMSO trimethylsilyloxy
• the separate strands of the double stranded RNA may be separately synthesized and then annealed to form the double stranded (duplex) oligonucleotide.
• Exemplary preferred antisense compounds include DNA or RNA sequences that comprise at least the 8 consecutive nucleobases from the 5 '-terminus of one of the illustrative preferred antisense compounds (the remaining nucleobases being a consecutive stretch of the same DNA or RNA beginning immediately upstream of the 5'-terminus of the antisense compound which is specifically hybridizable to the target nucleic acid and continuing until the DNA or RNA contains about 8 to about 80 nucleobases).
• preferred antisense compounds are represented by DNA or RNA sequences that comprise at least the 8 consecutive nucleobases from the 3 '-terminus of one of the illustrative preferred antisense compounds (the remaining nucleobases being a consecutive stretch of the same DNA or RNA beginning immediately downstream of the 3 '-terminus of the antisense compound which is specifically hybridizable to the target nucleic acid and continuing until the DNA or RNA contains about 8 to about 80 nucleobases).
• One having skill in the art once armed with the empirically-derived preferred antisense compounds illustrated herein will be able, without undue experimentation, to identify further preferred antisense compounds.
• Antisense and other compounds of the invention which hybridize to the target and inhibit expression of the target, are identified through experimentation, and representative sequences of these compounds are herein identified as preferred embodiments of the invention. While specific sequences of the antisense compounds are set forth herein, one of skill in the art will recognize that these serve to illustrate and describe particular embodiments within the scope of the present invention. Additional preferred antisense compounds may be identified by one having ordinary skill.
• oligonucleotides containing modified backbones or non-natural internucleoside linkages include those that retain a phosphorus atom in the backbone and those that do not have a phosphorus atom in the backbone.
• modified oligonucleotides that do not have a phosphorus atom in their internucleoside backbone can also be considered to be oligonucleosides.
• Antisense technology involves directing oligonucleotides, or analogs thereof, to a specific, target messenger RNA (rnRNA) sequence.
• rnRNA target messenger RNA
• the interaction of exogenous "antisense” molecules and endogenous mRNA modulates transcription by a variety of pathways. Such pathways include transcription arrest, RNAse H recruitment, and RNAi (e.g. siRNA).
• Antisense technology permits modulation of specific protein activity in a relatively predictable manner.
• cytosine or 5-methylcytosine
• adenine residues present in the parent oligonucleotide.
• the structures of the cytosine (I), 5-methylcytosine (II) and adenine (III) adducts are shown below.
• R HOrOCH 2 CH 2 OCH 3
• the present invention provides a novel class of impurities in phosphorothioate oligonucleotides. These have been synthesized using solid phase phosphoramidite chemistry. These impurities were characterized by a variety of analytical techniques and take the general form I shown below: Structures of ⁇ -mer impurities
• a 5'-terminal deletion sequence is attached to a molecule of the parent sequence via a phosphorothioate triester linkage.
• the members of this family are distinguished from each other by the location of the triester linkage within the parent sequence.
• the two strands located 3' of the triester linkage are the same lengths.
• These components possess one 5' and two 3' ends.
• Drawn in the shape shown in Figure 1 they resemble the Greek letter lambda ( ⁇ ); for this reason we refer to this class of impurity as " ⁇ -mers.”
• Ion-pair liquid-chromatography mass spectrometry (IP-LC-MS) analysis of ISIS 3521 drug substance revealed the presence of low levels of an impurity with a molecular weight 147 amu greater than the parent compound. Evidence from other sequences suggested this impurity was almost certainly composed of a family of chloral hydrate modified oligonucleotides. In order to confirm this hypothesis, an unambiguous chemical synthesis of a member of this group of impurities was undertaken. The mass spectral properties of this material and the native impurity were identical. The chromatographic properties of the native and synthetic materials were also very similar.
• Synthesis of trichloroacetaldehyde modified ISIS 3521 Synthesis was performed on an OligoPilot II DNA/RNA synthesizer using Primer HL-30 (6.3 mL). Phosphoramidites were dissolved to a concentration of 0.2 M in anhydrous acetonitrile and activated with 0.45 M solution of lH-tetrazole in acetonitrile. Detritylation was effected by treatment with a 10% v/v solution of dichloroacetic acid in toluene and sulfurization was achieved with a 0.2 M solution of phenylacetyl disulfide in 3-picoline-acetonitrile (1:1 v/v).
• the support-bound oligonucleotide was suspended in ammonium hydroxide (60 mL) and the products heated at 60 0 C for 14 h then allowed to cool to room temperature.
• the support was removed by filtration and washed with ethanol-water (1:1 v/v, 50 mL). The combined filtrate and washings were concentrated under vacuum to a volume of about 45 mL.
• the residue was purified by reversed phase HPLC using a gradient of methanol in aqueous sodium acetate. The fractions that eluted with 50% methanol were combined and evaporated to a volume of approximately 40 mL.
• the purified product was precipitated by the addition of cold (-20 0 C) ethanol (200 mL) and isolated by centrifugation. The precipitate was dissolved in water (2 mL) and aqueous sodium acetate solution (10 mM, pH 2.9, 6 mL) added. The products incubated for 1 h at room temperature then precipitated by addition of aqueous sodium acetate (2.5 M, pH 8, 1 mL) and cold (-20 0 C) ethanol (20 mL). The detritylated oligonucleotide collected by centrifugation and washed with ethanol (10 mL). The residue was dissolved in water (6 mL) and lyophilized.
• Chloral hydrate modified ISIS 3521 was synthesized by incorporation of modified dimer phosphoramidite 4 into the ISIS 3521 sequence.
• the route used to synthesize 4 is outlined in the Scheme below:
• dimer phosphoramidite 4 was used to prepare the chloral hydrate modified ISIS 3521 sequence 5 shown in below: Choral hydrate modified ISIS 3521
• the relative retention times were not identical is probably due to the fact that the native impurity is actually composed of a group of related species, each with a modified internucleotide linkage at a different location within the sequence. Each species could exhibit slightly different chromatographic properties with the result that the reported relative retention time is an average of all components.
• the synthetic material is a single sequence that elutes as a sharper peak.
• Ion-pair liquid chromatography mass spectrometry (IP-LC-MS) analysis of ISIS 3521 drug substance revealed the presence of a late-eluting impurity.
• the data presented in this report supports the hypothesis that the impurity is a 39-mer oligonucleotide formed by the addition of 19-mer oligonucleotides to the 5 '-hydroxy and N 5 positions of a single 2'- deoxyadenosine residue (structure 2).
• the ion pair-liquid chromatogram of a typical batch of ISIS 3521 drug substance is shown in figure 3.
• An impurity with a relative retention time (rrt) of about 1.3 (indicated) is clearly visible as the latest eluting component in the sample.
• Succinic anhydride (1.05g, 10.5 mmol) and 4-dimethylaminopyridine (DMAP, 0.054 g, 0.4 mmol) were added to a stirred solution of 5'-O-N 5 -Di-(4,4'-dimethoxytrityl)-2'- deoxyadenosine (7.5 g, 8.8 mmol) and TEA (1.5 rnL, 10.5mmol) in anhydrous methylene chloride (50 mL). The mixture was stirred for 16 h then additional succinic anhydride (0.5g, 5 mmol) added.
• DMAP 4-dimethylaminopyridine
• Nucleoside dodecanoate or succinate (7 or 10, 0.3 mmol), 0-benzotriazol-l-yl-N, N, N', N'-tetramethyluronium hexafluorophosphate (HBTU, 0.91 g, 2.4 mmol), Hunig's base (0.62 g, 4.8 mmol), DMAP (0.07 g, 0.6 mmol) and amino derivatised PrimerTM support HL 30 (6g) were shaken together in CH 3 CN (25 mL) for 1 h at 25 0 C.
• HBTU 0-benzotriazol-l-yl-N, N, N', N'-tetramethyluronium hexafluorophosphate
• Hunig's base (0.62 g, 4.8 mmol
• DMAP (0.07 g, 0.6 mmol
• amino derivatised PrimerTM support HL 30 (6g) were shaken together in CH 3 CN (25 m
• the support was collected by filtration, washed with MeOH (2 x 25 mL), Et 2 O (2 x 25 mL) and CH 3 CN (2 x 25 mL) then resuspended in a mixture of acetic anhydride-pyridine- CH 3 CN (2:5:5 v/v/v, 10 mL) and NMI-acetonitrile (1:5 v/v, 10 mL) and the products shaken at 25 0 C for 1 to 2 h.
• the support was collected, washed with pyridine, MeOH and Et 2 O then dried by suction.
• the loading of support 8 was estimated at 32 umol/g.
• the loading of support 11 was estimated at 21 umol/g.
• 2'-deoxycytidine phosphoramidite was dissolved to a concentration of 0.2 M in anhydrous acetonitrile and activated with 0.45 M solution of 1-H- tetrazole in acetonitrile.
• Detritylation was effected by treatment with a 3 % v/v solution of dichloroacetic acid in toluene and sulfurization was achieved with a 0.2 M solution of phenylacetyl disulfide in 3-picoline-acetonitrile (1:1 v/v).
• the support-bound material was suspended in ammonium hydroxide (100 mL). The products were heated at 55 0 C for 8 h then cooled to room temperature. The support was removed by filtration and the filtrate concentrated to dryness under reduced pressure.
• Oligonucleotide 1 Synthesis was performed on an OligoPilot II DNA/RNA synthesizer using solid support 8 (3.8 g). Phosphoramidites were dissolved to a concentration of 0.2 M in anhydrous acetonitrile and activated with 0.45 M solution of 1-H-tetrazole in acetonitrile. Detritylation was effected by treatment with a 10 % v/v solution of dichloroacetic acid in toluene and sulfurization was achieved with a 0.2 M solution of phenylacetyl disulfide in 3-picoline-acetonitrile (1:1 v/v).
• the support-bound oligonucleotide was suspended in ammonium hydroxide (150 mL) and the products heated at 65 0 C for 8 h then allowed to cool to room temperature.
• the support was removed by filtration and washed with a 1 : 1 v/v solution of ethanol and water (100 mL).
• the combined filtrate and washings were concentrated under vacuum to a volume of about 40 mL.
• the residue was purified by reversed phase HPLC using a gradient of methanol in aqueous sodium acetate. The fractions that eluted with 50% methanol were combined and evaporated to a volume of approximately 100 mL.
• the purified product was precipitated by the addition of cold (-20 oC) ethanol (500 mL) and isolated by centrifugation. The precipitate was dissolved in aqueous sodium acetate solution (10 niM, pH 3, 10 mL) and the products incubated for 1 h at room temperature. Aqueous sodium acetate (2.5 M, pH 8, 1 mL) was added and the detritylated oligonucleotide collected by centrifugation following precipitation with cold ethanol (50 mL). The product was washed with ethanol (20 mL) then dissolved in water (5 mL) and lyophilized.
• Detritylation was effected by treatment with a 3 % v/v solution of dichloroacetic acid in toluene and sulfurization was achieved with a 0.2 M solution of phenylacetyl disulfide in 3-picoline-acetonitrile (1:1 v/v).
• the support-bound oligonucleotide was suspended in triethylamine-acetonitrile (1:1 v/v, 100 ml) and the mixture incubated at room temperature for 4 h.
• the precipitate was dissolved in water (0.05 ml), aqueous sodium acetate solution (10 mm, ph 3, 0.2 ml) added and the products incubated for 1 h at room temperature, aqueous sodium acetate (2.5 m, ph 8, 0.02 ml) was added and the detritylated oligonucleotide collected by centrifugation following precipitation with cold ethanol (ca 1.3 ml).
• oligonucleotide samples were prepared by diluting stock solutions to an approximate total oligonucleotide concentration of 0.1 mg/mL in water. The samples were analyzed according to the conditions described in AM-OO 141 with the following modifications:
• Derivatised support 11 was detritylated by treatment with 10% DCA in toluene for 15 minutes. An extended detritylation time was required to remove the 4, 4'- dimethoxytrityl group from the exocyclic amino group. Detritylated support was converted to trimer 4 by standard solid phase oligonucleotide chemistry.
• solid supports 8 and 11 were also used to synthesize full- length 2n-dA sequences 1 and 2, respectively.
• the sequences were assembled using standard techniques.
• the crude products were purified by reversed phase HPLC or IP-LC and detritylated with acidic sodium acetate solution.
• the late eluting impurity is a 39-mer oligonucleotide formed by the addition of 19-mer oligonucleotides to the 5'-hydroxy and N 5 positions of a single 2'-deoxyadenosine residue (structure 2).
• structure 1 an alternative structure in which the two 19-mer chains grow from the 5'- and 3'-hydroxy groups of the 3'-terminal T- deoxyadenosine residue
• Tetrabutylammonium fluoride (8 g) was added and the mixture was stirred at for 2 hours. The mixture was diluted with toluene (100 ml), washed with water (2x100 ml) and evaporated. The residue was dissolved in toluene (50 ml). Ethyl diisopropylamine (10 ml) and cyanoethyl chlorophosphoramidite ( 4 ml) were added. After 20min, the mixture was washed with water (100 ml) and evaporated. The residue was purified by column chromatography on silica gel to give the desired product as a colorless solid (ca. 5 g).
• Phosphorus trichloride (218 ml) was added to a solution of diisopropylamine (2.1 L), hexane (5 L) and acetonitrile (0.5 L) and the mixture was stirred for 2 hours at room temperature. Ethylene glycol (62 g) was added and the mixture was stirred for 1 hour. The mixuture was washed with water (4 L) and was evaporated to give an oil (305 g).
• a n+140 amu impurity was identified having the structure:
• Synthesis of O-ethyl modified oligonucleotides was performed on an Applied Biosystems 394 DNA/RNA synthesizer at the 1 ⁇ M scale using thymine loaded cpg columns from Glen Research and at the 10 ⁇ M scale using thymine loaded cpg from Cruachem.
• T- phosphoramidites and O-ethyl authentic impurities were dissolved to a concentration of 0.1 M in anhydrous acetonitrile and activated with 0.45 M solution of lH-tetrazole in acetonitrile.
• Detritylation was effected by treatment with a 3 % solution of trichloroacetic acid in DCM and sulfurization was achieved with a 0.2 M solution of phenylacetyl disulfide in 3-picoline-acetonitrile (1:1 v/v).
• the support-bound oligonucleotide was dried with argon then suspended in ammonium hydroxide (ImI) for 3.5 hours.
• the support was removed by filtration and washed with ethanol-water (1 : 1 v/v, 2 mL).
• the combined filtrate and washings were concentrated under vacuum to a volume of about 1 mL. Oligonucleotide concentrations were measured by UV absorbance.
• Authentic amidite impurities X, XI, and XVIII were each incorporated into a poly T twelve-mer at the tenth base from the 3 ' end on the 1 ⁇ M scale. A poly T twelve-mer control was also made. These four sequences were synthesized in parallel using the same solution of T amidite. An additional poly T four-mer was made with impurity XI at the third base from the 3' end. The four-mer was synthesized at the 10 ⁇ M scale on four columns in parallel and the support- bound oligonucleotide from each column was combined before cleavage. Samples were analyzed by IP-LC-MS unpurified with the 5' DMT attached.
• Impurity X contains only one reactive amidite functionality the second phosphorus being a cyanoethyl phosphite. Once coupled to the growing oligonucleotide the second phosphite is sulfurized and the oligonucleotide is extended from the 5 'OH in a regular manner. In this case a single product is produced, that being the n + 140 amu version of the T twelve-mer.
• the UV chromatograms of the control and the impurity X twelve-mer are presented in figure 12.
• Impurity XI has two reactive phosporoamidite groups and can produce a more complicated mixture of products.
• the UV chromatogram for the impurity XI twelve-mer is shown in figure 13. Part of this complexity is due to the fact that each species has two peaks if the 5' DMT is present when analyzed by this method. There are five primary products produced by this synthesis. Some of the unmodified T twelve-mer produced. There are also the n + 140 amu, n + 156 amu, n + 223 amu impurities, and a fifth impurity much larger than the others with a mass of n + 2,926 amu.
• the unmodified product is most likely formed when the amidite closest to the nucleoside couples and then the O-ethyl functionality is removed during ammonia cleavage.
• Formation of the n + 140 amu impurity likely occurs when the amidite farthest from the nucleoside couples and the second amidite is ultimately converted to a phosphorothioate diester. If this second amidite is converted to a phosphorodithioate, n + 156 amu is formed and if it is converted to a phosporothioamidate, n + 223 amu is formed.
• the structures of the n + 156 amu and n + 223 amu impurities are presented below.
• the final impurity is formed if both amidites couple to the 5' end of different oligonucleotide chains bound to the support.
• the eventual product is one full length twelve-mer with an additional nine-mer 3' tail bridged by an ethyl phosphorothioate diester linkage.
• Impurity XVIII contains two phosphoroamidites and two nucleosides. When it reacts three primary products are formed. Like XI it can produce unmodified twelve-mer if the ethyl linkage is cleaved. If the linkage is not cleaved but the second amidite does not couple, a "Y" shaped oligo is produces as the chain is elongated from both nucleosides. If both amidites couple an "H" shape oligonucleotide is formed where two full length twelve-mers are linked together by an ethyl bridge. The structures of the "Y” and “H” oligonucleotides are shown below. The "Y” and “H” oligonucleotides formed by impurity XVIII
• O-ethyl amidite impurities X and XI are responsible for the n + 140 amu impurity found in synthetic oligonucleotides.
• Impurity XI is also responsible for the n + 156 amu and n + 223 amu impurities. Based on the structure of XI and the mass of these two impurities logical structures have been proposed. While impurity X will only produce the impurity n + 140 amu amidite authentics XI and XVIII can produce some full length unmodified sequence n. However, in addition to those impurities already mentioned XI produces one additional high molecular weight impurity and XVIII produces two.
• O-ethyl amidite impurities are formed by impurities in the phosphitilating reagent used for their preparation. These impurities are caused in turn by the presence of ethylene glycol in the cyanoethanol use to make the phosphitilating reagent.
• the primary commercial vendor of the phosphitilating reagent is aware of this issue and has put controls in place in order to prevent their formation. Impurities X, XI, and XVIII are easily detected by our LC/MS method and unsuitable amidite lots can be rejected before use.

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