Patent Grant
9175289
The invention pertains to the field of RNA interference (RNAi). The invention more specifically relates to nucleic acid molecules with improved in vivo delivery properties without the use of a delivering agent and their use in efficient gene silencing.
Complementary oligonucleotide sequences are promising therapeutic agents and useful research tools in elucidating gene functions. However, prior art oligonucleotide molecules suffer from several problems that may impede their clinical development, and frequently make it difficult to achieve intended efficient inhibition of gene expression (including protein synthesis) using such compositions in vivo.
A major problem has been the delivery of these compounds to cells and tissues. Conventional double-stranded RNAi compounds, 19-29 bases long, form a highly negatively-charged rigid helix of approximately 1.5 by 10-15 nm in size. This rod type molecule cannot get through the cell-membrane and as a result has very limited efficacy both in vitro and in vivo. As a result, all conventional RNAi compounds require some kind of a delivery vehicle to promote their tissue distribution and cellular uptake. This is considered to be a major limitation of the RNAi technology.
There have been previous attempts to apply chemical modifications to oligonucleotides to improve their cellular uptake properties. One such modification was the attachment of a cholesterol molecule to the oligonucleotide. A first report on this approach was by Letsinger et al., in 1989. Subsequently, ISIS Pharmaceuticals, Inc. (Carlsbad, Calif.) reported on more advanced techniques in attaching the cholesterol molecule to the oligonucleotide (Manoharan, 1992).
With the discovery of siRNAs in the late nineties, similar types of modifications were attempted on these molecules to enhance their delivery profiles. Cholesterol molecules conjugated to slightly modified (Soutschek, 2004) and heavily modified (Wolfrum, 2007) siRNAs appeared in the literature. Yamada et al., 2008 also reported on the use of advanced linker chemistries which further improved cholesterol mediated uptake of siRNAs. In spite of all this effort, the uptake of these types of compounds appears to be inhibited in the presence of biological fluids resulting in highly limited efficacy in gene silencing in vivo, limiting the applicability of these compounds in a clinical setting.
Therefore, it would be of great benefit to improve upon the prior art oligonucleotides by designing oligonucleotides that have improved delivery properties in vivo and are clinically meaningful.
Described herein are asymmetric chemically modified nucleic acid molecules with minimal double stranded regions, and the use of such molecules in gene silencing. RNAi molecules associated with the invention contain single stranded regions and double stranded regions, and can contain a variety of chemical modifications within both the single stranded and double stranded regions of the molecule. Additionally, the RNAi molecules can be attached to a hydrophobic conjugate such as a conventional and advanced sterol-type molecule. This new class of RNAi molecules has superior efficacy both in vitro and in vivo than previously described RNAi molecules.
Aspects of the invention relate to asymmetric nucleic acid molecules including a guide strand, with a minimal length of 16 nucleotides, and a passenger strand forming a double stranded nucleic acid, having a double stranded region and a single stranded region, the double stranded region having 8-15 nucleotides in length, the single stranded region having 5-12 nucleotides in length, wherein the passenger strand is linked to a lipophilic group, wherein at least 40% of the nucleotides of the double stranded nucleic acid are modified, and wherein the single stranded region has at least 2 phosphorothioate modifications. In some embodiments position 1 of the guide strand is 5′ phosphorylated. In certain embodiments, position 1 of the guide strand is 2′O-methyl modified and 5′ phosphorylated.
Aspects of the invention relate to isolated double stranded nucleic acid molecules including a longer strand of 15-21 nucleotides in length that has complementarily to a miRNA sequence, a shorter strand of 8-15 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the longer strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the longer strand has a 3′ single stranded region of 2-13 nucleotides in length, comprising at least two phosphorothioate modification, and at least 50% nucleotides are modified.
Further aspects of the invention relate to isolated double stranded nucleic acid molecules including a guide strand of 17-21 nucleotides in length that has complementarity to a target gene, a passenger strand of 8-16 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide strand has a 3′ single stranded region of 2-13 nucleotides in length, each nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide strand has a 5′ phosphate modification and wherein at least 50% of C and U nucleotides in the double stranded region include at least one 2′ O-methyl modification or 2′-fluoro modification.
In another aspect, the invention is an isolated double stranded nucleic acid molecule having a guide strand of 17-21 nucleotides in length that has complementarity to a target gene, a passenger strand of 10-16 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide strand has a 3′ single stranded region of 5-11 nucleotides in length, at least two nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide strand has a 5′ phosphate modification and wherein at least 50% of C and U nucleotides in the double stranded region are 2′ O-methyl modification or 2′-fluoro modified.
The invention in another aspect is an isolated double stranded nucleic acid molecule having a guide strand of 17-21 nucleotides in length that has complementarity to a target gene, a passenger strand of 8-16 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide strand has a 3′ single stranded region of 6-8 nucleotides in length, each nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide strand has a 5′ phosphate modification, wherein the passenger strand includes at least two phosphorothioate modifications, wherein at least 50% of C and U nucleotides in the double stranded region include a 2′ O-methyl modification or 2′-fluoro modification, and wherein the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang.
An isolated double stranded nucleic acid molecule having a guide strand of 17-21 nucleotides in length that has complementarity to a target gene, a passenger strand of 8-16 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide strand has a 3′ single stranded region, each nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide strand has a 5′ phosphate modification, wherein every C and U nucleotide in position 11-18 of the guide strand has a 2′ O-methyl modification, wherein every nucleotide of the passenger strand is 2′ O-methyl modified, and wherein the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang is provided in other aspects of the invention.
In another aspect the invention is an isolated double stranded nucleic acid molecule having a guide strand of 17-21 nucleotides in length that has complementarity to a target gene, a passenger strand of 8-15 nucleotides in length linked at the 3′ end to a lipophilic group, wherein the lipophilic group is selected from the group consisting of cholesterol and a sterol type molecule with C17 polycarbon chain of 5-7 or 9-18 carbons in length, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide strand has a 3′ single stranded region, each nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide strand has a 5′ phosphate modification, wherein every C and U nucleotide in position 11-18 of the guide strand has a 2′ O-methyl modification, wherein every C and U nucleotide in position 2-10 of the guide strand has a 2′F modification, wherein every nucleotide of the passenger strand is 2′ O-methyl modified, and wherein the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang.
In yet another aspect the invention is an isolated nucleic acid molecule having a guide sequence that has complementarity to a target gene, a passenger sequence linked at the 3′ end to a lipophilic group, wherein the guide sequence and the passenger sequence form a nucleic acid molecule having a double stranded region and a single stranded region, wherein the guide sequence has a 3′ single stranded region of 2-13 nucleotides in length, each nucleotide within the single stranded region having a phosphorothioate modification, wherein the guide sequence has a 5′ phosphate modification, wherein at least 50% of C and U nucleotides in the double stranded region include at least one 2′ O-methyl modification or 2′-fluoro modification, and wherein the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang.
An isolated double stranded nucleic acid molecule having a guide strand and a passenger strand, wherein the region of the molecule that is double stranded is from 8-14 nucleotides long, wherein the guide strand contains a single stranded region that is 4-12 nucleotides long, and wherein the single stranded region of the guide strand contains 2-12 phosphorothioate modifications is provided in other aspects of the invention.
In some embodiments the guide strand contains 6-8 phosphorothioate modifications. In other embodiments the single stranded region of the guide strand is 6 nucleotides long.
In yet other embodiments the double stranded region is 13 nucleotides long. Optionally the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang.
In another aspect the invention is an isolated double stranded nucleic acid molecule having a guide strand, wherein the guide strand is 16-28 nucleotides long and has complementarity to a target gene, wherein the 3′ terminal 10 nucleotides of the guide strand include at least two phosphate modifications, and wherein the guide strand has a 5′ phosphate modification and includes at least one 2′ O-methyl modification or 2′-fluoro modification, and a passenger strand, wherein the passenger strand is 8-14 nucleotides long and has complementarity to the guide strand, wherein the passenger strand is linked to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule.
In some embodiments the nucleotide in position one of the guide strand or sequence has a 2′-O-methyl modification. In other embodiments at least one C or U nucleotide in positions 2-10 of the guide strand or sequence has a 2′-fluoro modification. In yet other embodiments every C and U nucleotide in positions 2-10 of the guide strand or sequence has a 2′-fluoro modification. At least one C or U nucleotide in positions 11-18 of the guide strand or sequence may have a 2′-O-methyl modification. In some embodiments every C and U nucleotide in positions 11-18 of the guide strand or sequence has a 2′-O-methyl modification.
In yet other embodiments the 3′ terminal 10 nucleotides of the guide strand include at least four phosphate modifications. Optionally the 3′ terminal 10 nucleotides of the guide strand include at least eight phosphate modifications. In some embodiments the guide strand includes 4-14 phosphate modifications. In other embodiments the guide strand includes 4-10 phosphate modifications. In yet other embodiments the 3′ terminal 6 nucleotides of the guide strand all include phosphate modifications. The phosphate modifications may be phosphorothioate modifications.
In some embodiments every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In other embodiments every nucleotide on the passenger strand has a 2′-O-methyl modification. In an embodiment at least one nucleotide on the passenger strand is phosphorothioate modified. At least two nucleotides on the passenger strand are phosphorothioate modified in other embodiments.
The lipophilic molecule may be a sterol, such as cholesterol.
In some embodiments the guide strand is 18-19 nucleotides long. In other embodiments the passenger strand is 11-13 nucleotides long.
The double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang in other embodiments.
In other aspects the invention is an isolated double stranded nucleic acid molecule comprising a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has at least two chemical modifications. In some embodiments the at least two chemical modifications include at least two phosphorothioate modifications. In some embodiments the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang.
In some aspects the invention is an isolated double stranded nucleic acid molecule comprising a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has a single stranded 3′ region that is 5 nucleotides or longer and a 5′ region that is 1 nucleotide or less. The single stranded region may contain at least 2 phosphorothioate modifications.
An isolated double stranded nucleic acid molecule having a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-16 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has a single stranded 3′ region that is 5 nucleotides or longer and a passenger strand has a sterol type molecule with C17 attached chain longer than 9 is provided in other aspects of the invention.
A duplex polynucleotide is provided in other aspects of the invention. The polynucleotide has a first polynucleotide wherein said first polynucleotide is complementary to a second polynucleotide and a target gene; and a second polynucleotide wherein said second polynucleotide is at least 6 nucleotides shorter than said first polynucleotide, wherein said first polynucleotide includes a single stranded region containing modifications selected from the group consisting of 40-90% hydrophobic base modifications, 40-90% phosphorothioates, and 40-90% modifications of the ribose moiety, or any combination thereof.
In other aspects the invention is a duplex polynucleotide having a first polynucleotide wherein said first polynucleotide is complementary to a second polynucleotide and a target gene; and a second polynucleotide wherein said second polynucleotide is at least 6 nucleotides shorter than said first polynucleotide, wherein the duplex polynucleotide includes a mismatch between nucleotides 9, 11, 12, 13 or 14 on the first polynucleotide and the opposite nucleotide on the second polynucleotide.
In other aspects the invention is a method for inhibiting the expression of a target gene in a mammalian cell, comprising contacting the mammalian cell with an isolated double stranded nucleic acid molecule of any one of claims 1-41 or a duplex polynucleotide of claim 43 or 44.
A method of inducing RNAi in a subject is provided in other aspects of the invention. The method involves administering to a subject an effective amount for inducing RNAi of an mRNA of a target gene, an isolated double stranded nucleic acid molecule of any one of claims 1-41 or a duplex polynucleotide of claim 43 or 44. In other embodiment the subject is a human. In other embodiments the target gene is PPIB, MAP4K4, or SOD1.
In other aspects an isolated hydrophobic modified polynucleotide having a polynucleotide, wherein the polynucleotide is double stranded RNA, attached to a hydrophobic molecule, wherein the hydrophobic molecule is attached to a base, a ribose or a backbone of a non-terminal nucleotide and wherein the isolated double stranded nucleic acid molecule comprises a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand is provided.
In one embodiment the hydrophobic molecule is attached to the guide strand of the double stranded RNA. In another embodiment the 3′ terminal 10 nucleotides of the guide strand include at least two phosphate modifications, and wherein the guide strand has a 5′ phosphate modification and includes at least one 2′ O-methyl modification or 2′-fluoro modification. In yet another embodiment the hydrophobic molecule is attached to the passenger strand of the double stranded RNA.
The invention provides an isolated hydrophobic modified polynucleotide having a polynucleotide non-covalently complexed to a hydrophobic molecule, wherein the hydrophobic molecule is a polycationic molecule. In some embodiments the polycationic molecule is selected from the group consisting of protamine, arginine rich peptides, and spermine.
In other aspects the invention an isolated hydrophobic modified polynucleotide having a polynucleotide, wherein the polynucleotide is double stranded RNA, directly complexed to a hydrophobic molecule without a linker, wherein the hydrophobic molecule is not cholesterol.
A composition having a hydrophobic modified polynucleotide, wherein the polynucleotide is double stranded RNA, attached to a hydrophobic molecule, wherein the double stranded nucleic acid molecule comprises a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, wherein position 1 of the guide strand is 5′ phosphorylated or has a 2′ O-methyl modification, wherein at least 40% of the nucleotides of the double stranded nucleic acid are modified, and wherein the double stranded nucleic acid molecule has one end that is blunt or includes a one-two nucleotide overhang; a neutral fatty mixture; and optionally a cargo molecule, wherein the hydrophobic modified polynucleotide and the neutral fatty mixture forms a micelle is provided in other aspects of the invention.
In some embodiments the 3′ end of the passenger strand is linked to the hydrophobic molecule. In other embodiments the composition is sterile. In yet other embodiments the neutral fatty mixture comprises a DOPC (dioleoylphosphatidylcholine). In further embodiments the neutral fatty mixture comprises a DSPC (distearoylphosphatidylcholine). The neutral fatty mixture further comprises a sterol such as cholesterol in other embodiments.
In yet other embodiments the composition includes at least 20% DOPC and at least 20% cholesterol. The hydrophobic portion of the hydrophobic modified polynucleotide is a sterol in other embodiments. The sterol may be a cholesterol, a cholesteryl or modified cholesteryl residue. In other embodiments the hydrophobic portion of the hydrophobic modified polynucleotide is selected from the group consisting of bile acids, cholic acid or taurocholic acid, deoxycholate, oleyl litocholic acid, oleoyl cholenic acid, glycolipids, phospholipids, sphingolipids, isoprenoids, vitamins, saturated fatty acids, unsaturated fatty acids, fatty acid esters, triglycerides, pyrenes, porphyrines, Texaphyrine, adamantane, acridines, biotin, coumarin, fluorescein, rhodamine, Texas-Red, digoxygenin, dimethoxytrityl, t-butyldimethylsilyl, t-butyldiphenylsilyl, cyanine dyes (e.g. Cy3 or Cy5), Hoechst 33258 dye, psoralen, and ibuprofen.
In yet other embodiments the hydrophobic portion of the hydrophobic modified polynucleotide is a polycationic molecule, such as, for instance, protamine, arginine rich peptides, and/or spermine.
The composition optionally includes a cargo molecule such as a lipid, a peptide, vitamin, and/or a small molecule. In some embodiments the cargo molecule is a commercially available fat emulsions available for a variety of purposes selected from the group consisting of parenteral feeding. In some embodiments the commercially available fat emulsion is an intralipid or a nutralipid. In other embodiments the cargo molecule is a fatty acid mixture containing more then 74% of linoleic acid, a fatty acid mixture containing at least 6% of cardiolipin, or a fatty acid mixture containing at least 74% of linoleic acid and at least 6% of cardiolipin. In another embodiment the cargo molecule is a fusogenic lipid, such as for example, DOPE, and preferably is at least 10% fusogenic lipid
In some embodiments the polynucleotide includes chemical modifications. For instance it may be at least 40% modified.
A method of inducing RNAi in a subject is provided in another aspect of the invention. The method involves administering to a subject an effective amount for inducing RNAi of mRNA of a target gene, an isolated double stranded nucleic acid molecule or a duplex polynucleotide or a composition of the invention, wherein the polynucleotide has at least a region of sequence correspondence to the target gene, wherein the step of administering is systemic, intravenous, intraperitoneal, intradermal, topical, intranasal, inhalation, oral, intramucosal, local injection, subcutaneous, oral tracheal, or intraocular.
In other embodiment the subject is a human. In other embodiments the target gene is PPIB, MAP4K4, or SOD1.
In some aspects the invention is a single-stranded RNA of less than 35 nucleotides in length that forms a hairpin structure, said hairpin includes a double-stranded stem and a single-stranded loop, said double-stranded stem having a 5′-stem sequence having a 5′-end, and a 3′-stem sequence having a 3′-end; and said 5′-stem sequence and at least a portion of said loop form a guide sequence complementary to a transcript of a target gene, wherein said polynucleotide mediates sequence-dependent gene silencing of expression of said target gene, wherein each nucleotide within the single-stranded loop region has a phosphorothioate modification, and wherein at least 50% of C and U nucleotides in the double stranded region include a 2′ O-methyl modification or 2′-fluoro modification. In one embodiment every C and U nucleotide in position 11-18 of the guide sequence has a 2′ O-methyl modification.
A polynucleotide construct is provided in other aspects, the polynucleotide having two identical single-stranded polynucleotides, each of said single-stranded polynucleotide comprising a 5′-stem sequence having a 5′-end, a 3′-stem sequence having a 3′-end, and a linker sequence linking the 5′-stem sequence and the 3′-stem sequence, wherein: (1) the 5′-stem sequence of a first single-stranded polynucleotide hybridizes with the 3′-stem sequence of a second single-stranded polynucleotide to form a first double-stranded stem region; (2) the 5′-stem sequence of the second single-stranded polynucleotide hybridize with the 3′-stem sequence of the first single-stranded polynucleotide to form a second double-stranded stem region; and, (3) the linker sequences of the first and the second single-stranded polynucleotides form a loop or bulge connecting said first and said second double-stranded stem regions, wherein the 5′-stem sequence and at least a portion of the linker sequence form a guide sequence complementary to a transcript of a target gene, wherein said polynucleotide construct mediates sequence-dependent gene silencing of expression of said target gene, wherein each nucleotide within the single-stranded loop region has a phosphorothioate modification, and wherein at least 50% of C and U nucleotides in the double stranded regions include a 2′ O-methyl modification or 2′-fluoro modification.
In one embodiment every C and U nucleotide in position 11-18 of the guide sequence has a 2′ O-methyl modification.
In some embodiments, the guide strand is 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, or 29 nucleotides long. In some embodiments, the passenger strand is 8, 9, 10, 11, 12, 13 or 14 nucleotides long. In some embodiments, the nucleic acid molecule has a thermodynamic stability (ΔG) of less than −20 kkal/mol.
Aspects of the invention relate to nucleic acid molecules that are chemically modified. In some embodiments, the chemical modification is selected from the group consisting of 5′ Phosphate, 2′-O-methyl, 2′-O-ethyl, 2′-fluoro, ribothymidine, C-5 propynyl-dC (pdC), C-5 propynyl-dU (pdU), C-5 propynyl-C (pC), C-5 propynyl-U (pU), 5-methyl C, 5-methyl U, 5-methyl dC, 5-methyl dU methoxy, (2,6-diaminopurine), 5′-Dimethoxytrityl-N4-ethyl-2′-deoxyCytidine, C-5 propynyl-fC (pfC), C-5 propynyl-fU (pfU), 5-methyl fC, 5-methyl fU, C-5 propynyl-mC (pmC), C-5 propynyl-fU (pmU), 5-methyl mC, 5-methyl mU, LNA (locked nucleic acid), MGB (minor groove binder) and other base modifications which increase base hydrophobicity. More than one chemical modification may be present in the same molecule. In some embodiments, chemical modification increases stability and/or improves thermodynamic stability (ΔG). In some embodiments, at least 90% of CU residues on a nucleic acid molecule are modified.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification.
In some embodiments, nucleic acid molecules associated with the invention contain a stretch of at least 4 nucleotides that are phosphorothioate modified. In certain embodiments, the stretch of nucleotides that are phosphorothioate modified is at least 12 nucleotides long. In some embodiments, the stretch of nucleotides that are phosphorothioate modified is not fully single stranded.
Nucleic acid molecules associated with the invention may be attached to a conjugate. In some embodiments, the conjugate is attached to the guide strand, while in other embodiments the conjugate is attached to the passenger strand. In some embodiments, the conjugate is hydrophobic. In some embodiments, the conjugate is a sterol such as cholesterol. In some embodiments, nucleic acid molecules associated with the invention are blunt-ended.
Aspects of the invention relate to double stranded nucleic acid molecule including a guide strand and a passenger strand, wherein the region of the molecule that is double stranded is from 8-14 nucleotides long, and wherein the molecule has a thermodynamic stability (ΔG) of less than −13 kkal/mol.
In some embodiments, the region of the molecule that is double stranded is 8, 9, 10, 11, 12, 13, or 14 nucleotides long. In some embodiments, the molecule has a thermodynamic stability (ΔG) of less than −20 kkal/mol. The nucleic acid molecules, in some embodiments are chemically modified. In certain embodiments, the chemical modification is selected from the group consisting of 5′ Phosphate, 2′-O-methyl, 2′-β-ethyl, 2′-fluoro, ribothymidine, C-5 propynyl-dC (pdC), C-5 propynyl-dU (pdU), C-5 propynyl-C (pC), C-5 propynyl-U (pU), 5-methyl C, 5-methyl U, 5-methyl dC, 5-methyl dU methoxy, (2,6-diaminopurine), 5′-Dimethoxytrityl-N4-ethyl-2′-deoxyCytidine, C-5 propynyl-fC (pfC), C-5 propynyl-fU (pfU), 5-methyl fC, 5-methyl fU, C-5 propynyl-mC (pmC), C-5 propynyl-fU (pmU), 5-methyl mC, 5-methyl mU, LNA (locked nucleic acid), MGB (minor groove binder) and other base modifications which increase base hydrophobicity. More than one chemical modification may be present in the same molecule. In some embodiments, chemical modification increases stability and/or improves thermodynamic stability (ΔG). In some embodiments, at least 90% of CU residues on a nucleic acid molecule are modified.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification.
The nucleic acid molecules associated with the invention may contain a stretch of at least 4 nucleotides that are phosphorothioate modified. In certain embodiments, the stretch of nucleotides that are phosphorothioate modified is at least 12 nucleotides long. In some embodiments, the stretch of nucleotides that are phosphorothioate modified is not fully single stranded. In some embodiments, the nucleic acid molecules are attached to a conjugate. In some embodiments, the conjugate is attached to the guide strand, while in other embodiments the conjugate is attached to the passenger strand. In some embodiments, the conjugate is hydrophobic. In some embodiments, the conjugate is a sterol such as cholesterol. In some embodiments, nucleic acid molecules associated with the invention are blunt-ended. In some embodiments, the nucleic acid molecules are blunt ended at the 5′ end. In certain embodiments, the nucleic acid molecules are blunt ended at the 5′ end where the region of complementarity between the two strands of the molecule begins.
Aspects of the invention relate to methods for inhibiting the expression of a target gene in a mammalian cell. Methods include contacting the mammalian cell with an isolated double stranded nucleic acid molecule including a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and has complementarity to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, and wherein the double stranded nucleic acid molecule has a thermodynamic stability (ΔG) of less than −13 kkal/mol.
The cell may be contacted in vivo or in vitro. In some embodiments, the guide strand is 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, or 29 nucleotides long. In some embodiments, the passenger strand is 8, 9, 10, 11, 12, 13 or 14 nucleotides long. In some embodiments, the nucleic acid molecule has a thermodynamic stability (ΔG) of less than −20 kkal/mol.
The nucleic acid molecules associated with methods described herein may be chemically modified. In some embodiments, the chemical modification is selected from the group consisting of 5′ Phosphate, 2′-O-methyl, 2′-O-ethyl, 2′-fluoro, ribothymidine, C-5 propynyl-dC (pdC), C-5 propynyl-dU (pdU), C-5 propynyl-C (pC), C-5 propynyl-U (pU), 5-methyl C, 5-methyl U, 5-methyl dC, 5-methyl dU methoxy, (2,6-diaminopurine), 5′-Dimethoxytrityl-N4-ethyl-2′-deoxyCytidine, C-5 propynyl-fC (pfC), C-5 propynyl-fU (pfU), 5-methyl fC, 5-methyl fU, C-5 propynyl-mC (pmC), C-5 propynyl-fU (pmU), 5-methyl mC, 5-methyl mU, LNA (locked nucleic acid), MGB (minor groove binder) and other base modifications which increase base hydrophobicity. More than one chemical modification may be present in the same molecule. In some embodiments, chemical modification increases stability and/or improves thermodynamic stability (ΔG). In some embodiments, at least 90% of CU residues on a nucleic acid molecule are modified.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification.
In some embodiments, nucleic acid molecules associated with the invention contain a stretch of at least 4 nucleotides that are phosphorothioate modified. In certain embodiments, the stretch of nucleotides that are phosphorothioate modified is at least 12 nucleotides long. In some embodiments, the stretch of nucleotides that are phosphorothioate modified is not fully single stranded.
Nucleic acid molecules associated with the invention may be attached to a conjugate. In some embodiments, the conjugate is attached to the guide strand, while in other embodiments the conjugate is attached to the passenger strand. In some embodiments, the conjugate is hydrophobic. In some embodiments, the conjugate is a sterol such as cholesterol. In some embodiments, nucleic acid molecules associated with the invention are blunt-ended.
Methods for inhibiting the expression of a target gene in a mammalian cell described herein include contacting the mammalian cell with an isolated double stranded nucleic acid molecule including a guide strand and a passenger strand, wherein the region of the molecule that is double stranded is from 8-14 nucleotides long, and wherein the molecule has a thermodynamic stability (ΔG) of less than −13 kkal/mol.
In some embodiments, the region of the molecule that is double stranded is 8, 9, 10, 11, 12, 13, or 14 nucleotides long. In some embodiments, the molecule has a thermodynamic stability (ΔG) of less than −20 kkal/mol. The nucleic acid molecules, in some embodiments are chemically modified. In certain embodiments, the chemical modification is selected from the group consisting of 5′ Phosphate, 2′-O-methyl, 2′-β-ethyl, 2′-fluoro, ribothymidine, C-5 propynyl-dC (pdC), C-5 propynyl-dU (pdU), C-5 propynyl-C (pC), C-5 propynyl-U (pU), 5-methyl C, 5-methyl U, 5-methyl dC, 5-methyl dU methoxy, (2,6-diaminopurine), 5′-Dimethoxytrityl-N4-ethyl-2′-deoxyCytidine, C-5 propynyl-fC (pfC), C-5 propynyl-fU (pfU), 5-methyl fC, 5-methyl fU, C-5 propynyl-mC (pmC), C-5 propynyl-fU (pmU), 5-methyl mC, 5-methyl mU, LNA (locked nucleic acid), MGB (minor groove binder) and other base modifications which increase base hydrophobicity. More than one chemical modification may be present in the same molecule. In some embodiments, chemical modification increases stability and/or improves thermodynamic stability (ΔG). In some embodiments, at least 90% of CU residues on a nucleic acid molecule are modified.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification.
The nucleic acid molecules associated with the invention may contain a stretch of at least 4 nucleotides that are phosphorothioate modified. In certain embodiments, the stretch of nucleotides that are phosphorothioate modified is at least 12 nucleotides long. In some embodiments, the stretch of nucleotides that are phosphorothioate modified is not fully single stranded. In some embodiments, the nucleic acid molecules are attached to a conjugate. In some embodiments, the conjugate is attached to the guide strand, while in other embodiments the conjugate is attached to the passenger strand. In some embodiments, the conjugate is hydrophobic. In some embodiments, the conjugate is a sterol such as cholesterol. In some embodiments, nucleic acid molecules associated with the invention are blunt-ended.
In another embodiment, the invention provides a method for selecting an siRNA for gene silencing by (a) selecting a target gene, wherein the target gene comprises a target sequence; (b) selecting a candidate siRNA, wherein said candidate siRNA comprises a guide strand of 16-29 nucleotide base pairs and a passenger strand of 8-14 nucleotide base pairs that form a duplex comprised of an antisense region and a sense region and said antisense region of said candidate siRNA is at least 80% complementary to a region of said target sequence; (c) determining a thermodynamic stability (ΔG) of the candidate siRNA; and (e) selecting said candidate siRNA as an siRNA for gene silencing, if said thermodynamic stability is less than −13 kkal/mol.
Aspects of the invention relate to isolated double stranded nucleic acid molecules including a guide strand and a passenger strand, wherein the guide strand is 18-19 nucleotides long and has complementarity to a target gene, wherein the passenger strand is 11-13 nucleotides long and has complementarity to the guide strand, and wherein the double stranded nucleic acid molecule has a thermodynamic stability (ΔG) of less than −13 kkal/mol.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification.
In some embodiments, the guide strand contains a stretch of at least 4 nucleotides that are phosphorothioate modified. In certain embodiments, the guide strand contains a stretch of at least 8 nucleotides that are phosphorothioate modified. In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification. In some embodiments, at least one, or at least two nucleotides on the passenger strand is phosphorothioate modified. The nucleic acid molecule can be attached to a conjugate on either the guide or passenger strand. In some embodiments, the conjugate is a sterol such as cholesterol.
Aspects of the invention relate to isolated double stranded nucleic acid molecules including a guide strand, wherein the guide strand is 16-28 nucleotides long and has complementarity to a target gene, wherein the 3′ terminal 10 nucleotides of the guide strand include at least two phosphate modifications, and wherein the guide strand includes at least one 2′ O-methyl modification or 2′-fluoro modification, and a passenger strand, wherein the passenger strand is 8-28 nucleotides long and has complementarity to the guide strand, wherein the passenger strand is linked to a lipophilic group, wherein the guide strand and the passenger strand form the double stranded nucleic acid molecule.
In some embodiments, the nucleotide in position one of the guide strand has a 2′-O-methyl modification and/or a 5′ Phosphate modification. In some embodiments, at least one C or U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In certain embodiments, every C and U nucleotide in positions 2-10 of the guide strand has a 2′-fluoro modification. In some embodiments, at least one C or U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification. In certain embodiments, every C and U nucleotide in positions 11-18 of the guide strand has a 2′-O-methyl modification.
In some embodiments, the 3′ terminal 10 nucleotides of the guide strand include at least four, or at least eight phosphate modifications. In certain embodiments, the guide strand includes 2-14 or 4-10 phosphate modifications. In some embodiments, the 3′ terminal 6 nucleotides of the guide strand all include phosphate modifications. In certain embodiments, the phosphate modifications are phosphorothioate modifications.
In some embodiments, every C and U nucleotide on the passenger strand has a 2′-O-methyl modification. In certain embodiments, every nucleotide on the passenger strand has a 2′-O-methyl modification. In some embodiments, at least one, or at least two nucleotides on the passenger strand is phosphorothioate modified. In some embodiments, the lipophilic molecule is a sterol such as cholesterol. In some embodiments, the guide strand is 18-19 nucleotides long and the passenger strand is 11-13 nucleotides long.
Aspects of the invention relate to isolated double stranded nucleic acid molecules including a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has at least two chemical modifications. In some embodiments, the two chemical modifications are phosphorothioate modifications.
Further aspects of the invention relate to isolated double stranded nucleic acid molecule comprising a guide strand and a passenger strand, wherein the guide strand is from 16-29 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 8-14 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has a single stranded 3′ region that is 5 nucleotides or longer. In some embodiments, the single stranded region contains at least 2 phosphorothioate modifications.
Further aspects of the invention relate to isolated double stranded nucleic acid molecules including a guide strand and a passenger strand, wherein the guide strand is from 18-21 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 11-14 nucleotides long and has complementarity to the guide strand, and wherein position one of the guide stand has 2-OMe and 5′ phosphate modifications, every C and U in positions 2 to 11 of the guide strand are 2-F modified, every C and U in positions 12-18 of the guide strand are 2′OMe modified, and 80% of Cs and Us on the passenger strand are 2′OMe modified
Another aspect of the invention relates to isolated double stranded nucleic acid molecules including a guide strand and a passenger strand, wherein the guide strand is from 18-21 nucleotides long and is substantially complementary to a target gene, wherein the passenger strand is from 11-14 nucleotides long and has complementarity to the guide strand, and wherein the guide stand has 2-OMe and 5′ phosphate modifications at position 1, every C and U in positions 2 to 11 of the guide strand are 2-F modified, every C and U in positions 12-18 of the guide strand are 2′OMe modified, 80% of Cs and Us on the passenger strand are 2′OMe and the 3′ end of the passenger strand is attached to a conjugate. In some embodiments the conjugate is selected from sterols, sterol-type molecules, hydrophobic vitamins or fatty acids.
Each of the limitations of the invention can encompass various embodiments of the invention. It is, therefore, anticipated that each of the limitations of the invention involving any one element or combinations of elements can be included in each aspect of the invention. This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:
Aspects of the invention relate to methods and compositions involved in gene silencing. The invention is based at least in part on the surprising discovery that asymmetric nucleic acid molecules with a double stranded region of a minimal length such as 8-14 nucleotides, are effective in silencing gene expression. Molecules with such a short double stranded region have not previously been demonstrated to be effective in mediating RNA interference. It had previously been assumed that that there must be a double stranded region of 19 nucleotides or greater. The molecules described herein are optimized through chemical modification, and in some instances through attachment of hydrophobic conjugates.
The invention is based at least in part on another surprising discovery that asymmetric nucleic acid molecules with reduced double stranded regions are much more effectively taken up by cells compared to conventional siRNAs. These molecules are highly efficient in silencing of target gene expression and offer significant advantages over previously described RNAi molecules including high activity in the presence of serum, efficient self delivery, compatibility with a wide variety of linkers, and reduced presence or complete absence of chemical modifications that are associated with toxicity.
In contrast to single-stranded polynucleotides, duplex polynucleotides have been difficult to deliver to a cell as they have rigid structures and a large number of negative charges which makes membrane transfer difficult. Unexpectedly, it was found that the polynucleotides of the present invention, although partially double-stranded, are recognized in vivo as single-stranded and, as such, are capable of efficiently being delivered across cell membranes. As a result the polynucleotides of the invention are capable in many instances of self delivery. Thus, the polynucleotides of the invention may be formulated in a manner similar to conventional RNAi agents or they may be delivered to the cell or subject alone (or with non-delivery type carriers) and allowed to self deliver. In one embodiment of the present invention, self delivering asymmetric double-stranded RNA molecules are provided in which one portion of the molecule resembles a conventional RNA duplex and a second portion of the molecule is single stranded.
The polynucleotides of the invention are referred to herein as isolated double stranded or duplex nucleic acids, oligonucleotides or polynucleotides, nano molecules, nano RNA, sd-rxRNAnano, sd-rxRNA or RNA molecules of the invention.
The oligonucleotides of the invention in some aspects have a combination of asymmetric structures including a double stranded region and a single stranded region of 5 nucleotides or longer, specific chemical modification patterns and are conjugated to lipophilic or hydrophobic molecules. This new class of RNAi like compounds have superior efficacy in vitro and in vivo. Based on the data described herein it is believed that the reduction in the size of the rigid duplex region in combination with phosphorothioate modifications applied to a single stranded region are new and important for achieving the observed superior efficacy. Thus, the RNA molecules described herein are different in both structure and composition as well as in vitro and in vivo activity.
In a preferred embodiment the RNAi compounds of the invention comprise an asymmetric compound comprising a duplex region (required for efficient RISC entry of 10-15 bases long) and single stranded region of 4-12 nucleotides long; with a 13 nucleotide duplex. A 6 nucleotide single stranded region is preferred in some embodiments. The single stranded region of the new RNAi compounds also comprises 2-12 phosphorothioate internucleotide linkages (referred to as phosphorothioate modifications). 6-8 phosphorothioate internucleotide linkages are preferred in some embodiments. Additionally, the RNAi compounds of the invention also include a unique chemical modification pattern, which provides stability and is compatible with RISC entry. The combination of these elements has resulted in unexpected properties which are highly useful for delivery of RNAi reagents in vitro and in vivo.
The chemically modification pattern, which provides stability and is compatible with RISC entry includes modifications to the sense, or passenger, strand as well as the antisense, or guide, strand. For instance the passenger strand can be modified with any chemical entities which confirm stability and do not interfere with activity. Such modifications include 2′ ribo modifications (O-methyl, 2′ F, 2 deoxy and others) and backbone modification like phosphorothioate modifications. A preferred chemical modification pattern in the passenger strand includes Omethyl modification of C and U nucleotides within the passenger strand or alternatively the passenger strand may be completely Omethyl modified.
The guide strand, for example, may also be modified by any chemical modification which confirms stability without interfering with RISC entry. A preferred chemical modification pattern in the guide strand includes the majority of C and U nucleotides being 2′ F modified and the 5′ end being phosphorylated. Another preferred chemical modification pattern in the guide strand includes 2′ Omethyl modification of position 1 and C/U in positions 11-18 and 5′ end chemical phosphorylation. Yet another preferred chemical modification pattern in the guide strand includes 2′ Omethyl modification of position 1 and C/U in positions 11-18 and 5′ end chemical phosphorylation and 2′F modification of C/U in positions 2-10.
It was surprisingly discovered according to the invention that the above-described chemical modification patterns of the oligonucleotides of the invention are well tolerated and actually improved efficacy of asymmetric RNAi compounds. See, for instance,
It was also demonstrated experimentally herein that the combination of modifications to RNAi when used together in a polynucleotide results in the achievement of optimal efficacy in passive uptake of the RNAi. Elimination of any of the described components (Guide strand stabilization, phosphorothioate stretch, sense strand stabilization and hydrophobic conjugate) or increase in size results in sub-optimal efficacy and in some instances complete lost of efficacy. The combination of elements results in development of compound, which is fully active following passive delivery to cells such as HeLa cells. (
The data shown in
The data in the Examples presented below demonstrates high efficacy of the oligonucleotides of the invention both in vitro in variety of cell types (supporting data) and in vivo upon local and systemic administration. For instance, the data compares the ability of several competitive RNAi molecules having different chemistries to silence a gene. Comparison of sd-rxRNA (oligonucleotides of the invention) with RNAs described in Soucheck et al. and Wolfrum at al., as applied to the same targeting region, demonstrated that only sd-rxRNA chemistry showed a significant functionality in passive uptake. The composition of the invention achieved EC50 values of 10-50 μM. This level of efficacy is un-attainable with conventional chemistries like those described in Sauthceck at al and Accell. Similar comparisons were made in other systems, such as in vitro (RPE cell line), in vivo upon local administration (wounded skin) and systemic (50 mg/kg) as well as other genes (
Significant amounts of data also demonstrate the in vivo efficacy of the compounds of the invention. For instance
The sd-rxRNA can be further improved in some instances by improving the hydrophobicity of compounds using of novel types of chemistries. For example one chemistry is related to use of hydrophobic base modifications. Any base in any position might be modified, as long as modification results in an increase of the partition coefficient of the base. The preferred locations for modification chemistries are positions 4 and 5 of the pyrimidines. The major advantage of these positions is (a) ease of synthesis and (b) lack of interference with base-pairing and A form helix formation, which are essential for RISC complex loading and target recognition. Examples of these chemistries is shown in
This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.
Thus, aspects of the invention relate to isolated double stranded nucleic acid molecules comprising a guide (antisense) strand and a passenger (sense) strand. As used herein, the term “double-stranded” refers to one or more nucleic acid molecules in which at least a portion of the nucleomonomers are complementary and hydrogen bond to form a double-stranded region. In some embodiments, the length of the guide strand ranges from 16-29 nucleotides long. In certain embodiments, the guide strand is 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, or 29 nucleotides long. The guide strand has complementarity to a target gene. Complementarity between the guide strand and the target gene may exist over any portion of the guide strand. Complementarity as used herein may be perfect complementarity or less than perfect complementarity as long as the guide strand is sufficiently complementary to the target that it mediates RNAi. In some embodiments complementarity refers to less than 25%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, or 1% mismatch between the guide strand and the target. Perfect complementarity refers to 100% complementarity. Thus the invention has the advantage of being able to tolerate sequence variations that might be expected due to genetic mutation, strain polymorphism, or evolutionary divergence. For example, siRNA sequences with insertions, deletions, and single point mutations relative to the target sequence have also been found to be effective for inhibition. Moreover, not all positions of a siRNA contribute equally to target recognition. Mismatches in the center of the siRNA are most critical and essentially abolish target RNA cleavage. Mismatches upstream of the center or upstream of the cleavage site referencing the antisense strand are tolerated but significantly reduce target RNA cleavage. Mismatches downstream of the center or cleavage site referencing the antisense strand, preferably located near the 3′ end of the antisense strand, e.g. 1, 2, 3, 4, 5 or 6 nucleotides from the 3′ end of the antisense strand, are tolerated and reduce target RNA cleavage only slightly.
While not wishing to be bound by any particular theory, in some embodiments, the guide strand is at least 16 nucleotides in length and anchors the Argonaute protein in RISC. In some embodiments, when the guide strand loads into RISC it has a defined seed region and target mRNA cleavage takes place across from position 10-11 of the guide strand. In some embodiments, the 5′ end of the guide strand is or is able to be phosphorylated. The nucleic acid molecules described herein may be referred to as minimum trigger RNA.
In some embodiments, the length of the passenger strand ranges from 8-14 nucleotides long. In certain embodiments, the passenger strand is 8, 9, 10, 11, 12, 13 or 14 nucleotides long. The passenger strand has complementarity to the guide strand. Complementarity between the passenger strand and the guide strand can exist over any portion of the passenger or guide strand. In some embodiments, there is 100% complementarity between the guide and passenger strands within the double stranded region of the molecule.
Aspects of the invention relate to double stranded nucleic acid molecules with minimal double stranded regions. In some embodiments the region of the molecule that is double stranded ranges from 8-14 nucleotides long. In certain embodiments, the region of the molecule that is double stranded is 8, 9, 10, 11, 12, 13 or 14 nucleotides long. In certain embodiments the double stranded region is 13 nucleotides long. There can be 100% complementarity between the guide and passenger strands, or there may be one or more mismatches between the guide and passenger strands. In some embodiments, on one end of the double stranded molecule, the molecule is either blunt-ended or has a one-nucleotide overhang. The single stranded region of the molecule is in some embodiments between 4-12 nucleotides long. For example the single stranded region can be 4, 5, 6, 7, 8, 9, 10, 11 or 12 nucleotides long. However, in certain embodiments, the single stranded region can also be less than 4 or greater than 12 nucleotides long. In certain embodiments, the single stranded region is 6 nucleotides long.
RNAi constructs associated with the invention can have a thermodynamic stability (AG) of less than −13 kkal/mol. In some embodiments, the thermodynamic stability (AG) is less than −20 kkal/mol. In some embodiments there is a loss of efficacy when (AG) goes below −21 kkal/mol. In some embodiments a (ΔG) value higher than −13 kkal/mol is compatible with aspects of the invention. Without wishing to be bound by any theory, in some embodiments a molecule with a relatively higher (ΔG) value may become active at a relatively higher concentration, while a molecule with a relatively lower (ΔG) value may become active at a relatively lower concentration. In some embodiments, the (ΔG) value may be higher than −9 kkcal/mol. The gene silencing effects mediated by the RNAi constructs associated with the invention, containing minimal double stranded regions, are unexpected because molecules of almost identical design but lower thermodynamic stability have been demonstrated to be inactive (Rana et al 2004).
Without wishing to be bound by any theory, results described herein suggest that a stretch of 8-10 bp of dsRNA or dsDNA will be structurally recognized by protein components of RISC or co-factors of RISC. Additionally, there is a free energy requirement for the triggering compound that it may be either sensed by the protein components and/or stable enough to interact with such components so that it may be loaded into the Argonaute protein. If optimal thermodynamics are present and there is a double stranded portion that is preferably at least 8 nucleotides then the duplex will be recognized and loaded into the RNAi machinery.
In some embodiments, thermodynamic stability is increased through the use of LNA bases. In some embodiments, additional chemical modifications are introduced. Several non-limiting examples of chemical modifications include: 5′ Phosphate, 2′-O-methyl, 2′-O-ethyl, 2′-fluoro, ribothymidine, C-5 propynyl-dC (pdC) and C-5 propynyl-dU (pdU); C-5 propynyl-C (pC) and C-5 propynyl-U (pU); 5-methyl C, 5-methyl U, 5-methyl dC, 5-methyl dU methoxy, (2,6-diaminopurine), 5′-Dimethoxytrityl-N4-ethyl-2′-deoxyCytidine and MGB (minor groove binder). It should be appreciated that more than one chemical modification can be combined within the same molecule.
Molecules associated with the invention are optimized for increased potency and/or reduced toxicity. For example, nucleotide length of the guide and/or passenger strand, and/or the number of phosphorothioate modifications in the guide and/or passenger strand, can in some aspects influence potency of the RNA molecule, while replacing 2′-fluoro (2′F) modifications with 2′-O-methyl (2′OMe) modifications can in some aspects influence toxicity of the molecule. Specifically, reduction in 2′F content of a molecule is predicted to reduce toxicity of the molecule. The Examples section presents molecules in which 2′F modifications have been eliminated, offering an advantage over previously described RNAi compounds due to a predicted reduction in toxicity. Furthermore, the number of phosphorothioate modifications in an RNA molecule can influence the uptake of the molecule into a cell, for example the efficiency of passive uptake of the molecule into a cell. Preferred embodiments of molecules described herein have no 2′F modification and yet are characterized by equal efficacy in cellular uptake and tissue penetration. Such molecules represent a significant improvement over prior art, such as molecules described by Accell and Wolfrum, which are heavily modified with extensive use of 2′F.
In some embodiments, a guide strand is approximately 18-19 nucleotides in length and has approximately 2-14 phosphate modifications. For example, a guide strand can contain 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or more than 14 nucleotides that are phosphate-modified. The guide strand may contain one or more modifications that confer increased stability without interfering with RISC entry. The phosphate modified nucleotides, such as phosphorothioate modified nucleotides, can be at the 3′ end, 5′ end or spread throughout the guide strand. In some embodiments, the 3′ terminal 10 nucleotides of the guide strand contains 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 phosphorothioate modified nucleotides. The guide strand can also contain 2′F and/or 2′OMe modifications, which can be located throughout the molecule. In some embodiments, the nucleotide in position one of the guide strand (the nucleotide in the most 5′ position of the guide strand) is 2′OMe modified and/or phosphorylated. C and U nucleotides within the guide strand can be 2′F modified. For example, C and U nucleotides in positions 2-10 of a 19 nt guide strand (or corresponding positions in a guide strand of a different length) can be 2′F modified. C and U nucleotides within the guide strand can also be 2′OMe modified. For example, C and U nucleotides in positions 11-18 of a 19 nt guide strand (or corresponding positions in a guide strand of a different length) can be 2′OMe modified. In some embodiments, the nucleotide at the most 3′ end of the guide strand is unmodified. In certain embodiments, the majority of Cs and Us within the guide strand are 2′F modified and the 5′ end of the guide strand is phosphorylated. In other embodiments, position 1 and the Cs or Us in positions 11-18 are 2′OMe modified and the 5′ end of the guide strand is phosphorylated. In other embodiments, position 1 and the Cs or Us in positions 11-18 are 2′OMe modified, the 5′ end of the guide strand is phosphorylated, and the Cs or Us in position 2-10 are 2′F modified.
In some aspects, an optimal passenger strand is approximately 11-14 nucleotides in length. The passenger strand may contain modifications that confer increased stability. One or more nucleotides in the passenger strand can be 2′OMe modified. In some embodiments, one or more of the C and/or U nucleotides in the passenger strand is 2′OMe modified, or all of the C and U nucleotides in the passenger strand are 2′OMe modified. In certain embodiments, all of the nucleotides in the passenger strand are 2′OMe modified. One or more of the nucleotides on the passenger strand can also be phosphate-modified such as phosphorothioate modified. The passenger strand can also contain 2′ ribo, 2′F and 2 deoxy modifications or any combination of the above. As demonstrated in the Examples, chemical modification patterns on both the guide and passenger strand are well tolerated and a combination of chemical modifications is shown herein to lead to increased efficacy and self-delivery of RNA molecules.
Aspects of the invention relate to RNAi constructs that have extended single-stranded regions relative to double stranded regions, as compared to molecules that have been used previously for RNAi. The single stranded region of the molecules may be modified to promote cellular uptake or gene silencing. In some embodiments, phosphorothioate modification of the single stranded region influences cellular uptake and/or gene silencing. The region of the guide strand that is phosphorothioate modified can include nucleotides within both the single stranded and double stranded regions of the molecule. In some embodiments, the single stranded region includes 2-12 phosphorothioate modifications. For example, the single stranded region can include 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 phosphorothioate modifications. In some instances, the single stranded region contains 6-8 phosphorothioate modifications.
Molecules associated with the invention are also optimized for cellular uptake. In RNA molecules described herein, the guide and/or passenger strands can be attached to a conjugate. In certain embodiments the conjugate is hydrophobic. The hydrophobic conjugate can be a small molecule with a partition coefficient that is higher than 10. The conjugate can be a sterol-type molecule such as cholesterol, or a molecule with an increased length polycarbon chain attached to C17, and the presence of a conjugate can influence the ability of an RNA molecule to be taken into a cell with or without a lipid transfection reagent. The conjugate can be attached to the passenger or guide strand through a hydrophobic linker. In some embodiments, a hydrophobic linker is 5-12C in length, and/or is hydroxypyrrolidine-based. In some embodiments, a hydrophobic conjugate is attached to the passenger strand and the CU residues of either the passenger and/or guide strand are modified. In some embodiments, at least 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95% of the CU residues on the passenger strand and/or the guide strand are modified. In some aspects, molecules associated with the invention are self-delivering (sd). As used herein, “self-delivery” refers to the ability of a molecule to be delivered into a cell without the need for an additional delivery vehicle such as a transfection reagent.
Aspects of the invention relate to selecting molecules for use in RNAi. Based on the data described herein, molecules that have a double stranded region of 8-14 nucleotides can be selected for use in RNAi. In some embodiments, molecules are selected based on their thermodynamic stability (ΔG). In some embodiments, molecules will be selected that have a (AG) of less than −13 kkal/mol. For example, the (ΔG) value may be −13, −14, −15, −16, −17, −18, −19, −21, −22 or less than −22 kkal/mol. In other embodiments, the (ΔG) value may be higher than −13 kkal/mol. For example, the (AG) value may be −12, −11, −10, −9, −8, −7 or more than −7 kkal/mol. It should be appreciated that ΔG can be calculated using any method known in the art. In some embodiments ΔG is calculated using Mfold, available through the Mfold internet site (http://mfold.bioinfo.rpi.edu/cgi-bin/rna-form1.cgi). Methods for calculating ΔG are described in, and are incorporated by reference from, the following references: Zuker, M. (2003) Nucleic Acids Res., 31(13):3406-15; Mathews, D. H., Sabina, J., Zuker, M. and Turner, D. H. (1999) J. Mol. Biol. 288:911-940; Mathews, D. H., Disney, M. D., Childs, J. L., Schroeder, S. J., Zuker, M., and Turner, D. H. (2004) Proc. Natl. Acad. Sci. 101:7287-7292; Duan, S., Mathews, D. H., and Turner, D. H. (2006) Biochemistry 45:9819-9832; Wuchty, S., Fontana, W., Hofacker, I. L., and Schuster, P. (1999) Biopolymers 49:145-165.
Aspects of the invention relate to using nucleic acid molecules described herein, with minimal double stranded regions and/or with a (ΔG) of less than −13 kkal/mol, for gene silencing. RNAi molecules can be administered in vivo or in vitro, and gene silencing effects can be achieved in vivo or in vitro.
In certain embodiments, the polynucleotide contains 5′- and/or 3′-end overhangs. The number and/or sequence of nucleotides overhang on one end of the polynucleotide may be the same or different from the other end of the polynucleotide. In certain embodiments, one or more of the overhang nucleotides may contain chemical modification(s), such as phosphorothioate or 2′-OMe modification.
In certain embodiments, the polynucleotide is unmodified. In other embodiments, at least one nucleotide is modified. In further embodiments, the modification includes a 2′-H or 2′-modified ribose sugar at the 2nd nucleotide from the 5′-end of the guide sequence. The “2nd nucleotide” is defined as the second nucleotide from the 5′-end of the polynucleotide.
As used herein, “2′-modified ribose sugar” includes those ribose sugars that do not have a 2′-OH group. “2′-modified ribose sugar” does not include 2′-deoxyribose (found in unmodified canonical DNA nucleotides). For example, the 2′-modified ribose sugar may be 2′-O-alkyl nucleotides, 2′-deoxy-2′-fluoro nucleotides, 2′-deoxy nucleotides, or combination thereof.
In certain embodiments, the 2′-modified nucleotides are pyrimidine nucleotides (e.g., C/U). Examples of 2′-O-alkyl nucleotides include 2′-O-methyl nucleotides, or 2′-O-allyl nucleotides.
In certain embodiments, the miniRNA polynucleotide of the invention with the above-referenced 5′-end modification exhibits significantly (e.g., at least about 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or more) less “off-target” gene silencing when compared to similar constructs without the specified 5′-end modification, thus greatly improving the overall specificity of the RNAi reagent or therapeutics.
As used herein, “off-target” gene silencing refers to unintended gene silencing due to, for example, spurious sequence homology between the antisense (guide) sequence and the unintended target mRNA sequence.
According to this aspect of the invention, certain guide strand modifications further increase nuclease stability, and/or lower interferon induction, without significantly decreasing RNAi activity (or no decrease in RNAi activity at all).
In some embodiments, the 5′-stem sequence may comprise a 2′-modified ribose sugar, such as 2′-O-methyl modified nucleotide, at the 2nd nucleotide on the 5′-end of the polynucleotide and, in some embodiments, no other modified nucleotides. The hairpin structure having such modification may have enhanced target specificity or reduced off-target silencing compared to a similar construct without the 2′-O-methyl modification at said position.
Certain combinations of specific 5′-stem sequence and 3′-stem sequence modifications may result in further unexpected advantages, as partly manifested by enhanced ability to inhibit target gene expression, enhanced serum stability, and/or increased target specificity, etc.
In certain embodiments, the guide strand comprises a 2′-O-methyl modified nucleotide at the 2nd nucleotide on the 5′-end of the guide strand and no other modified nucleotides.
In other aspects, the miniRNA structures of the present invention mediates sequence-dependent gene silencing by a microRNA mechanism. As used herein, the term “microRNA” (“miRNA”), also referred to in the art as “small temporal RNAs” (“stRNAs”), refers to a small (10-50 nucleotide) RNA which are genetically encoded (e.g., by viral, mammalian, or plant genomes) and are capable of directing or mediating RNA silencing. An “miRNA disorder” shall refer to a disease or disorder characterized by an aberrant expression or activity of an miRNA.
microRNAs are involved in down-regulating target genes in critical pathways, such as development and cancer, in mice, worms and mammals. Gene silencing through a microRNA mechanism is achieved by specific yet imperfect base-pairing of the miRNA and its target messenger RNA (mRNA). Various mechanisms may be used in microRNA-mediated down-regulation of target mRNA expression.
miRNAs are noncoding RNAs of approximately 22 nucleotides which can regulate gene expression at the post transcriptional or translational level during plant and animal development. One common feature of miRNAs is that they are all excised from an approximately 70 nucleotide precursor RNA stem-loop termed pre-miRNA, probably by Dicer, an RNase III-type enzyme, or a homolog thereof. Naturally-occurring miRNAs are expressed by endogenous genes in vivo and are processed from a hairpin or stem-loop precursor (pre-miRNA or pri-miRNAs) by Dicer or other RNAses. miRNAs can exist transiently in vivo as a double-stranded duplex but only one strand is taken up by the RISC complex to direct gene silencing.
In some embodiments a version of sd-rxRNA compounds, which are effective in cellular uptake and inhibiting of miRNA activity are described. Essentially the compounds are similar to RISC entering version but large strand chemical modification patterns are optimized in the way to block cleavage and act as an effective inhibitor of the RISC action. For example, the compound might be completely or mostly Omethyl modified with the PS content described previously. For these types of compounds the 5′ phosphorilation is not necessary. The presence of double stranded region is preferred as it is promotes cellular uptake and efficient RISC loading.
Another pathway that uses small RNAs as sequence-specific regulators is the RNA interference (RNAi) pathway, which is an evolutionarily conserved response to the presence of double-stranded RNA (dsRNA) in the cell. The dsRNAs are cleaved into ˜20-base pair (bp) duplexes of small-interfering RNAs (siRNAs) by Dicer. These small RNAs get assembled into multiprotein effector complexes called RNA-induced silencing complexes (RISCs). The siRNAs then guide the cleavage of target mRNAs with perfect complementarity.
Some aspects of biogenesis, protein complexes, and function are shared between the siRNA pathway and the miRNA pathway. The subject single-stranded polynucleotides may mimic the dsRNA in the siRNA mechanism, or the microRNA in the miRNA mechanism.
In certain embodiments, the modified RNAi constructs may have improved stability in serum and/or cerebral spinal fluid compared to an unmodified RNAi constructs having the same sequence.
In certain embodiments, the structure of the RNAi construct does not induce interferon response in primary cells, such as mammalian primary cells, including primary cells from human, mouse and other rodents, and other non-human mammals. In certain embodiments, the RNAi construct may also be used to inhibit expression of a target gene in an invertebrate organism.
To further increase the stability of the subject constructs in vivo, the 3′-end of the hairpin structure may be blocked by protective group(s). For example, protective groups such as inverted nucleotides, inverted abasic moieties, or amino-end modified nucleotides may be used. Inverted nucleotides may comprise an inverted deoxynucleotide. Inverted abasic moieties may comprise an inverted deoxyabasic moiety, such as a 3′,3′-linked or 5′,5′-linked deoxyabasic moiety.
The RNAi constructs of the invention are capable of inhibiting the synthesis of any target protein encoded by target gene(s). The invention includes methods to inhibit expression of a target gene either in a cell in vitro, or in vivo. As such, the RNAi constructs of the invention are useful for treating a patient with a disease characterized by the overexpression of a target gene.
The target gene can be endogenous or exogenous (e.g., introduced into a cell by a virus or using recombinant DNA technology) to a cell. Such methods may include introduction of RNA into a cell in an amount sufficient to inhibit expression of the target gene. By way of example, such an RNA molecule may have a guide strand that is complementary to the nucleotide sequence of the target gene, such that the composition inhibits expression of the target gene.
The invention also relates to vectors expressing the nucleic acids of the invention, and cells comprising such vectors or the nucleic acids. The cell may be a mammalian cell in vivo or in culture, such as a human cell.
The invention further relates to compositions comprising the subject RNAi constructs, and a pharmaceutically acceptable carrier or diluent.
Another aspect of the invention provides a method for inhibiting the expression of a target gene in a mammalian cell, comprising contacting the mammalian cell with any of the subject RNAi constructs.
The method may be carried out in vitro, ex vivo, or in vivo, in, for example, mammalian cells in culture, such as a human cell in culture.
The target cells (e.g., mammalian cell) may be contacted in the presence of a delivery reagent, such as a lipid (e.g., a cationic lipid) or a liposome.
Another aspect of the invention provides a method for inhibiting the expression of a target gene in a mammalian cell, comprising contacting the mammalian cell with a vector expressing the subject RNAi constructs.
In one aspect of the invention, a longer duplex polynucleotide is provided, including a first polynucleotide that ranges in size from about 16 to about 30 nucleotides; a second polynucleotide that ranges in size from about 26 to about 46 nucleotides, wherein the first polynucleotide (the antisense strand) is complementary to both the second polynucleotide (the sense strand) and a target gene, and wherein both polynucleotides form a duplex and wherein the first polynucleotide contains a single stranded region longer than 6 bases in length and is modified with alternative chemical modification pattern, and/or includes a conjugate moiety that facilitates cellular delivery. In this embodiment, between about 40% to about 90% of the nucleotides of the passenger strand between about 40% to about 90% of the nucleotides of the guide strand, and between about 40% to about 90% of the nucleotides of the single stranded region of the first polynucleotide are chemically modified nucleotides.
In an embodiment, the chemically modified nucleotide in the polynucleotide duplex may be any chemically modified nucleotide known in the art, such as those discussed in detail above. In a particular embodiment, the chemically modified nucleotide is selected from the group consisting of 2′ F modified nucleotides, 2′-β-methyl modified and 2′ deoxy nucleotides. In another particular embodiment, the chemically modified nucleotides results from “hydrophobic modifications” of the nucleotide base. In another particular embodiment, the chemically modified nucleotides are phosphorothioates. In an additional particular embodiment, chemically modified nucleotides are combination of phosphorothioates, 2′-O-methyl, 2′ deoxy, hydrophobic modifications and phosphorothioates. As these groups of modifications refer to modification of the ribose ring, back bone and nucleotide, it is feasible that some modified nucleotides will carry a combination of all three modification types.
In another embodiment, the chemical modification is not the same across the various regions of the duplex. In a particular embodiment, the first polynucleotide (the passenger strand), has a large number of diverse chemical modifications in various positions. For this polynucleotide up to 90% of nucleotides might be chemically modified and/or have mismatches introduced.
In another embodiment, chemical modifications of the first or second polynucleotide include, but not limited to, 5′ position modification of Uridine and Cytosine (4-pyridyl, 2-pyridyl, indolyl, phenyl (C6H5OH); tryptophanyl (C8H6N)CH2CH(NH2)CO), isobutyl, butyl, aminobenzyl; phenyl; naphthyl, etc), where the chemical modification might alter base pairing capabilities of a nucleotide. For the guide strand an important feature of this aspect of the invention is the position of the chemical modification relative to the 5′ end of the antisense and sequence. For example, chemical phosphorylation of the 5′ end of the guide strand is usually beneficial for efficacy. O-methyl modifications in the seed region of the sense strand (position 2-7 relative to the 5′ end) are not generally well tolerated, whereas 2′F and deoxy are well tolerated. The mid part of the guide strand and the 3′ end of the guide strand are more permissive in a type of chemical modifications applied. Deoxy modifications are not tolerated at the 3′ end of the guide strand.
A unique feature of this aspect of the invention involves the use of hydrophobic modification on the bases. In one embodiment, the hydrophobic modifications are preferably positioned near the 5′ end of the guide strand, in other embodiments, they localized in the middle of the guides strand, in other embodiment they localized at the 3′ end of the guide strand and yet in another embodiment they are distributed thought the whole length of the polynucleotide. The same type of patterns is applicable to the passenger strand of the duplex.
The other part of the molecule is a single stranded region. The single stranded region is expected to range from 7 to 40 nucleotides.
In one embodiment, the single stranded region of the first polynucleotide contains modifications selected from the group consisting of between 40% and 90% hydrophobic base modifications, between 40%-90% phosphorothioates, between 40%-90% modification of the ribose moiety, and any combination of the preceding.
Efficiency of guide strand (first polynucleotide) loading into the RISC complex might be altered for heavily modified polynucleotides, so in one embodiment, the duplex polynucleotide includes a mismatch between nucleotide 9, 11, 12, 13, or 14 on the guide strand (first polynucleotide) and the opposite nucleotide on the sense strand (second polynucleotide) to promote efficient guide strand loading.
More detailed aspects of the invention are described in the sections below.
Duplex Characteristics
Double-stranded oligonucleotides of the invention may be formed by two separate complementary nucleic acid strands. Duplex formation can occur either inside or outside the cell containing the target gene.
As used herein, the term “duplex” includes the region of the double-stranded nucleic acid molecule(s) that is (are) hydrogen bonded to a complementary sequence. Double-stranded oligonucleotides of the invention may comprise a nucleotide sequence that is sense to a target gene and a complementary sequence that is antisense to the target gene. The sense and antisense nucleotide sequences correspond to the target gene sequence, e.g., are identical or are sufficiently identical to effect target gene inhibition (e.g., are about at least about 98% identical, 96% identical, 94%, 90% identical, 85% identical, or 80% identical) to the target gene sequence.
In certain embodiments, the double-stranded oligonucleotide of the invention is double-stranded over its entire length, i.e., with no overhanging single-stranded sequence at either end of the molecule, i.e., is blunt-ended. In other embodiments, the individual nucleic acid molecules can be of different lengths. In other words, a double-stranded oligonucleotide of the invention is not double-stranded over its entire length. For instance, when two separate nucleic acid molecules are used, one of the molecules, e.g., the first molecule comprising an antisense sequence, can be longer than the second molecule hybridizing thereto (leaving a portion of the molecule single-stranded). Likewise, when a single nucleic acid molecule is used a portion of the molecule at either end can remain single-stranded.
In one embodiment, a double-stranded oligonucleotide of the invention contains mismatches and/or loops or bulges, but is double-stranded over at least about 70% of the length of the oligonucleotide. In another embodiment, a double-stranded oligonucleotide of the invention is double-stranded over at least about 80% of the length of the oligonucleotide. In another embodiment, a double-stranded oligonucleotide of the invention is double-stranded over at least about 90%-95% of the length of the oligonucleotide. In another embodiment, a double-stranded oligonucleotide of the invention is double-stranded over at least about 96%-98% of the length of the oligonucleotide. In certain embodiments, the double-stranded oligonucleotide of the invention contains at least or up to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 mismatches.
Modifications
The nucleotides of the invention may be modified at various locations, including the sugar moiety, the phosphodiester linkage, and/or the base.
Sugar moieties include natural, unmodified sugars, e.g., monosaccharide (such as pentose, e.g., ribose, deoxyribose), modified sugars and sugar analogs. In general, possible modifications of nucleomonomers, particularly of a sugar moiety, include, for example, replacement of one or more of the hydroxyl groups with a halogen, a heteroatom, an aliphatic group, or the functionalization of the hydroxyl group as an ether, an amine, a thiol, or the like.
One particularly useful group of modified nucleomonomers are 2′-O-methyl nucleotides. Such 2′-O-methyl nucleotides may be referred to as “methylated,” and the corresponding nucleotides may be made from unmethylated nucleotides followed by alkylation or directly from methylated nucleotide reagents. Modified nucleomonomers may be used in combination with unmodified nucleomonomers. For example, an oligonucleotide of the invention may contain both methylated and unmethylated nucleomonomers.
Some exemplary modified nucleomonomers include sugar- or backbone-modified ribonucleotides. Modified ribonucleotides may contain a non-naturally occurring base (instead of a naturally occurring base), such as uridines or cytidines modified at the 5′-position, e.g., 5′-(2-amino)propyl uridine and 5′-bromo uridine; adenosines and guanosines modified at the 8-position, e.g., 8-bromo guanosine; deaza nucleotides, e.g., 7-deaza-adenosine; and N-alkylated nucleotides, e.g., N6-methyl adenosine. Also, sugar-modified ribonucleotides may have the 2′-OH group replaced by a H, alxoxy (or OR), R or alkyl, halogen, SH, SR, amino (such as NH2, NHR, NR2), or CN group, wherein R is lower alkyl, alkenyl, or alkynyl.
Modified ribonucleotides may also have the phosphodiester group connecting to adjacent ribonucleotides replaced by a modified group, e.g., of phosphorothioate group. More generally, the various nucleotide modifications may be combined.
Although the antisense (guide) strand may be substantially identical to at least a portion of the target gene (or genes), at least with respect to the base pairing properties, the sequence need not be perfectly identical to be useful, e.g., to inhibit expression of a target gene's phenotype. Generally, higher homology can be used to compensate for the use of a shorter antisense gene. In some cases, the antisense strand generally will be substantially identical (although in antisense orientation) to the target gene.
The use of 2′-O-methyl modified RNA may also be beneficial in circumstances in which it is desirable to minimize cellular stress responses. RNA having 2′-O-methyl nucleomonomers may not be recognized by cellular machinery that is thought to recognize unmodified RNA. The use of 2′-O-methylated or partially 2′-O-methylated RNA may avoid the interferon response to double-stranded nucleic acids, while maintaining target RNA inhibition. This may be useful, for example, for avoiding the interferon or other cellular stress responses, both in short RNAi (e.g., siRNA) sequences that induce the interferon response, and in longer RNAi sequences that may induce the interferon response.
Overall, modified sugars may include D-ribose, 2′-O-alkyl (including 2′-β-methyl and 2′-O-ethyl), i.e., 2′-alkoxy, 2′-amino, 2′-S-alkyl, 2′-halo (including 2′-fluoro), 2′-methoxyethoxy, 2′-allyloxy (—OCH2CH═CH2), 2′-propargyl, 2′-propyl, ethynyl, ethenyl, propenyl, and cyano and the like. In one embodiment, the sugar moiety can be a hexose and incorporated into an oligonucleotide as described (Augustyns, K., et al., Nucl. Acids. Res. 18:4711 (1992)). Exemplary nucleomonomers can be found, e.g., in U.S. Pat. No. 5,849,902, incorporated by reference herein.
The term “alkyl” includes saturated aliphatic groups, including straight-chain alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.), branched-chain alkyl groups (isopropyl, tert-butyl, isobutyl, etc.), cycloalkyl (alicyclic) groups (cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl), alkyl substituted cycloalkyl groups, and cycloalkyl substituted alkyl groups. In certain embodiments, a straight chain or branched chain alkyl has 6 or fewer carbon atoms in its backbone (e.g., C1-C6 for straight chain, C3-C6 for branched chain), and more preferably 4 or fewer. Likewise, preferred cycloalkyls have from 3-8 carbon atoms in their ring structure, and more preferably have 5 or 6 carbons in the ring structure. The term C1-C6 includes alkyl groups containing 1 to 6 carbon atoms.
Moreover, unless otherwise specified, the term alkyl includes both “unsubstituted alkyls” and “substituted alkyls,” the latter of which refers to alkyl moieties having independently selected substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents can include, for example, alkenyl, alkynyl, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromatic or heteroaromatic moiety. Cycloalkyls can be further substituted, e.g., with the substituents described above. An “alkylaryl” or an “arylalkyl” moiety is an alkyl substituted with an aryl (e.g., phenylmethyl (benzyl)). The term “alkyl” also includes the side chains of natural and unnatural amino acids. The term “n-alkyl” means a straight chain (i.e., unbranched) unsubstituted alkyl group.
The term “alkenyl” includes unsaturated aliphatic groups analogous in length and possible substitution to the alkyls described above, but that contain at least one double bond. For example, the term “alkenyl” includes straight-chain alkenyl groups (e.g., ethylenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, etc.), branched-chain alkenyl groups, cycloalkenyl (alicyclic) groups (cyclopropenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl), alkyl or alkenyl substituted cycloalkenyl groups, and cycloalkyl or cycloalkenyl substituted alkenyl groups. In certain embodiments, a straight chain or branched chain alkenyl group has 6 or fewer carbon atoms in its backbone (e.g., C2-C6 for straight chain, C3-C6 for branched chain). Likewise, cycloalkenyl groups may have from 3-8 carbon atoms in their ring structure, and more preferably have 5 or 6 carbons in the ring structure. The term C2-C6 includes alkenyl groups containing 2 to 6 carbon atoms.
Moreover, unless otherwise specified, the term alkenyl includes both “unsubstituted alkenyls” and “substituted alkenyls,” the latter of which refers to alkenyl moieties having independently selected substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents can include, for example, alkyl groups, alkynyl groups, halogens, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromatic or heteroaromatic moiety.
The term “alkynyl” includes unsaturated aliphatic groups analogous in length and possible substitution to the alkyls described above, but which contain at least one triple bond. For example, the term “alkynyl” includes straight-chain alkynyl groups (e.g., ethynyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, octynyl, nonynyl, decynyl, etc.), branched-chain alkynyl groups, and cycloalkyl or cycloalkenyl substituted alkynyl groups. In certain embodiments, a straight chain or branched chain alkynyl group has 6 or fewer carbon atoms in its backbone (e.g., C2-C6 for straight chain, C3-C6 for branched chain). The term C2-C6 includes alkynyl groups containing 2 to 6 carbon atoms.
Moreover, unless otherwise specified, the term alkynyl includes both “unsubstituted alkynyls” and “substituted alkynyls,” the latter of which refers to alkynyl moieties having independently selected substituents replacing a hydrogen on one or more carbons of the hydrocarbon backbone. Such substituents can include, for example, alkyl groups, alkynyl groups, halogens, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromatic or heteroaromatic moiety.
Unless the number of carbons is otherwise specified, “lower alkyl” as used herein means an alkyl group, as defined above, but having from one to five carbon atoms in its backbone structure. “Lower alkenyl” and “lower alkynyl” have chain lengths of, for example, 2-5 carbon atoms.
The term “alkoxy” includes substituted and unsubstituted alkyl, alkenyl, and alkynyl groups covalently linked to an oxygen atom. Examples of alkoxy groups include methoxy, ethoxy, isopropyloxy, propoxy, butoxy, and pentoxy groups. Examples of substituted alkoxy groups include halogenated alkoxy groups. The alkoxy groups can be substituted with independently selected groups such as alkenyl, alkynyl, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkyl amino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido), amidino, imino, sulffiydryl, alkylthio, arylthio, thiocarboxylate, sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromatic or heteroaromatic moieties. Examples of halogen substituted alkoxy groups include, but are not limited to, fluoromethoxy, difluoromethoxy, trifluoromethoxy, chloromethoxy, dichloromethoxy, trichloromethoxy, etc.
The term “heteroatom” includes atoms of any element other than carbon or hydrogen. Preferred heteroatoms are nitrogen, oxygen, sulfur and phosphorus.
The term “hydroxy” or “hydroxyl” includes groups with an —OH or —O− (with an appropriate counterion).
The term “halogen” includes fluorine, bromine, chlorine, iodine, etc. The term “perhalogenated” generally refers to a moiety wherein all hydrogens are replaced by halogen atoms.
The term “substituted” includes independently selected substituents which can be placed on the moiety and which allow the molecule to perform its intended function. Examples of substituents include alkyl, alkenyl, alkynyl, aryl, (CR′R″)0-3NR′R″, (CR′R″)0-3CN, NO2, halogen, (CR′R″)0-3C(halogen)3, (CR′R″)0-3CH(halogen)2, (CRR″)0-3CH2(halogen), (CR′R″)0-3CONR′R″, (CR′R″)0-3S(O)1-2NR′R″, (CR′R″)0-3CHO, (CR′R″)0-3O(CR′R″)0-3H, (CR′R″)0-3S(O)0-2R′, (CR′R″)0-3O(CR′R″)0-3H, (CR′R″)0-3COR′, (CR′R″)0-3CO2R′, or (CR′R″)0-3OR′ groups; wherein each R′ and R″ are each independently hydrogen, a C1-C5 alkyl, C2-C5 alkenyl, C2-C5 alkynyl, or aryl group, or R′ and R″ taken together are a benzylidene group or a —(CH2)2—O—(CH2)2— group.
The term “amine” or “amino” includes compounds or moieties in which a nitrogen atom is covalently bonded to at least one carbon or heteroatom. The term “alkyl amino” includes groups and compounds wherein the nitrogen is bound to at least one additional alkyl group. The term “dialkyl amino” includes groups wherein the nitrogen atom is bound to at least two additional alkyl groups.
The term “ether” includes compounds or moieties which contain an oxygen bonded to two different carbon atoms or heteroatoms. For example, the term includes “alkoxyalkyl,” which refers to an alkyl, alkenyl, or alkynyl group covalently bonded to an oxygen atom which is covalently bonded to another alkyl group.
The term “base” includes the known purine and pyrimidine heterocyclic bases, deazapurines, and analogs (including heterocyclic substituted analogs, e.g., aminoethyoxy phenoxazine), derivatives (e.g., 1-alkyl-, 1-alkenyl-, heteroaromatic- and 1-alkynyl derivatives) and tautomers thereof. Examples of purines include adenine, guanine, inosine, diaminopurine, and xanthine and analogs (e.g., 8-oxo-N6-methyladenine or 7-diazaxanthine) and derivatives thereof. Pyrimidines include, for example, thymine, uracil, and cytosine, and their analogs (e.g., 5-methylcytosine, 5-methyluracil, 5-(1-propynyl)uracil, 5-(1-propynyl)cytosine and 4,4-ethanocytosine). Other examples of suitable bases include non-purinyl and non-pyrimidinyl bases such as 2-aminopyridine and triazines.
In a preferred embodiment, the nucleomonomers of an oligonucleotide of the invention are RNA nucleotides. In another preferred embodiment, the nucleomonomers of an oligonucleotide of the invention are modified RNA nucleotides. Thus, the oligonucleotides contain modified RNA nucleotides.
The term “nucleoside” includes bases which are covalently attached to a sugar moiety, preferably ribose or deoxyribose. Examples of preferred nucleosides include ribonucleosides and deoxyribonucleosides. Nucleosides also include bases linked to amino acids or amino acid analogs which may comprise free carboxyl groups, free amino groups, or protecting groups. Suitable protecting groups are well known in the art (see P. G. M. Wuts and T. W. Greene, “Protective Groups in Organic Synthesis”, 2nd Ed., Wiley-Interscience, New York, 1999).
The term “nucleotide” includes nucleosides which further comprise a phosphate group or a phosphate analog.
As used herein, the term “linkage” includes a naturally occurring, unmodified phosphodiester moiety (—O—(PO2−)—O—) that covalently couples adjacent nucleomonomers. As used herein, the term “substitute linkage” includes any analog or derivative of the native phosphodiester group that covalently couples adjacent nucleomonomers. Substitute linkages include phosphodiester analogs, e.g., phosphorothioate, phosphorodithioate, and P-ethyoxyphosphodiester, P-ethoxyphosphodiester, P-alkyloxyphosphotriester, methylphosphonate, and nonphosphorus containing linkages, e.g., acetals and amides. Such substitute linkages are known in the art (e.g., Bjergarde et al. 1991. Nucleic Acids Res. 19:5843; Caruthers et al. 1991. Nucleosides Nucleotides. 10:47). In certain embodiments, non-hydrolizable linkages are preferred, such as phosphorothiate linkages.
In certain embodiments, oligonucleotides of the invention comprise hydrophobicly modified nucleotides or “hydrophobic modifications.” As used herein “hydrophobic modifications” refers to bases that are modified such that (1) overall hydrophobicity of the base is significantly increased, and/or (2) the base is still capable of forming close to regular Watson-Crick interaction. Several non-limiting examples of base modifications include 5-position uridine and cytidine modifications such as phenyl, 4-pyridyl, 2-pyridyl, indolyl, and isobutyl, phenyl (C6H5OH); tryptophanyl (C8H6N)CH2CH(NH2)CO), Isobutyl, butyl, aminobenzyl; phenyl; and naphthyl.
In certain embodiments, oligonucleotides of the invention comprise 3′ and 5′ termini (except for circular oligonucleotides). In one embodiment, the 3′ and 5′ termini of an oligonucleotide can be substantially protected from nucleases e.g., by modifying the 3′ or 5′ linkages (e.g., U.S. Pat. No. 5,849,902 and WO 98/13526). For example, oligonucleotides can be made resistant by the inclusion of a “blocking group.” The term “blocking group” as used herein refers to substituents (e.g., other than OH groups) that can be attached to oligonucleotides or nucleomonomers, either as protecting groups or coupling groups for synthesis (e.g., FITC, propyl (CH2—CH2—CH3), glycol (—O—CH2—CH2—O—) phosphate (PO32−), hydrogen phosphonate, or phosphoramidite). “Blocking groups” also include “end blocking groups” or “exonuclease blocking groups” which protect the 5′ and 3′ termini of the oligonucleotide, including modified nucleotides and non-nucleotide exonuclease resistant structures.
Exemplary end-blocking groups include cap structures (e.g., a 7-methylguanosine cap), inverted nucleomonomers, e.g., with 3′-3′ or 5′-5′ end inversions (see, e.g., Ortiagao et al. 1992. Antisense Res. Dev. 2:129), methylphosphonate, phosphoramidite, non-nucleotide groups (e.g., non-nucleotide linkers, amino linkers, conjugates) and the like. The 3′ terminal nucleomonomer can comprise a modified sugar moiety. The 3′ terminal nucleomonomer comprises a 3′-O that can optionally be substituted by a blocking group that prevents 3′-exonuclease degradation of the oligonucleotide. For example, the 3′-hydroxyl can be esterified to a nucleotide through a 3′→3′ internucleotide linkage. For example, the alkyloxy radical can be methoxy, ethoxy, or isopropoxy, and preferably, ethoxy. Optionally, the 3′→3′ linked nucleotide at the 3′ terminus can be linked by a substitute linkage. To reduce nuclease degradation, the 5′ most 3′→5′ linkage can be a modified linkage, e.g., a phosphorothioate or a P-alkyloxyphosphotriester linkage. Preferably, the two 5′ most 3′→5′ linkages are modified linkages. Optionally, the 5′ terminal hydroxy moiety can be esterified with a phosphorus containing moiety, e.g., phosphate, phosphorothioate, or P-ethoxyphosphate.
Another type of conjugates that can be attached to the end (3′ or 5′ end), the loop region, or any other parts of the miniRNA might include a sterol, sterol type molecule, peptide, small molecule, protein, etc. In some embodiments, a miniRNA may contain more than one conjugates (same or different chemical nature). In some embodiments, the conjugate is cholesterol.
Another way to increase target gene specificity, or to reduce off-target silencing effect, is to introduce a 2′-modification (such as the 2′-O methyl modification) at a position corresponding to the second 5′-end nucleotide of the guide sequence. This allows the positioning of this 2′-modification in the Dicer-resistant hairpin structure, thus enabling one to design better RNAi constructs with less or no off-target silencing.
In one embodiment, a hairpin polynucleotide of the invention can comprise one nucleic acid portion which is DNA and one nucleic acid portion which is RNA. Antisense (guide) sequences of the invention can be “chimeric oligonucleotides” which comprise an RNA-like and a DNA-like region.
The language “RNase H activating region” includes a region of an oligonucleotide, e.g., a chimeric oligonucleotide, that is capable of recruiting RNase H to cleave the target RNA strand to which the oligonucleotide binds. Typically, the RNase activating region contains a minimal core (of at least about 3-5, typically between about 3-12, more typically, between about 5-12, and more preferably between about 5-10 contiguous nucleomonomers) of DNA or DNA-like nucleomonomers. (See, e.g., U.S. Pat. No. 5,849,902). Preferably, the RNase H activating region comprises about nine contiguous deoxyribose containing nucleomonomers.
The language “non-activating region” includes a region of an antisense sequence, e.g., a chimeric oligonucleotide, that does not recruit or activate RNase H. Preferably, a non-activating region does not comprise phosphorothioate DNA. The oligonucleotides of the invention comprise at least one non-activating region. In one embodiment, the non-activating region can be stabilized against nucleases or can provide specificity for the target by being complementary to the target and forming hydrogen bonds with the target nucleic acid molecule, which is to be bound by the oligonucleotide.
In one embodiment, at least a portion of the contiguous polynucleotides are linked by a substitute linkage, e.g., a phosphorothioate linkage.
In certain embodiments, most or all of the nucleotides beyond the guide sequence (2′-modified or not) are linked by phosphorothioate linkages. Such constructs tend to have improved pharmacokinetics due to their higher affinity for serum proteins. The phosphorothioate linkages in the non-guide sequence portion of the polynucleotide generally do not interfere with guide strand activity, once the latter is loaded into RISC.
Antisense (guide) sequences of the present invention may include “morpholino oligonucleotides.” Morpholino oligonucleotides are non-ionic and function by an RNase H-independent mechanism. Each of the 4 genetic bases (Adenine, Cytosine, Guanine, and Thymine/Uracil) of the morpholino oligonucleotides is linked to a 6-membered morpholine ring. Morpholino oligonucleotides are made by joining the 4 different subunit types by, e.g., non-ionic phosphorodiamidate inter-subunit linkages. Morpholino oligonucleotides have many advantages including: complete resistance to nucleases (Antisense & Nucl. Acid Drug Dev. 1996. 6:267); predictable targeting (Biochemica Biophysica Acta. 1999. 1489:141); reliable activity in cells (Antisense & Nucl. Acid Drug Dev. 1997. 7:63); excellent sequence specificity (Antisense & Nucl. Acid Drug Dev. 1997. 7:151); minimal non-antisense activity (Biochemica Biophysica Acta. 1999. 1489:141); and simple osmotic or scrape delivery (Antisense & Nucl. Acid Drug Dev. 1997. 7:291). Morpholino oligonucleotides are also preferred because of their non-toxicity at high doses. A discussion of the preparation of morpholino oligonucleotides can be found in Antisense & Nucl. Acid Drug Dev. 1997. 7:187.
The chemical modifications described herein are believed, based on the data described herein, to promote single stranded polynucleotide loading into the RISC. Single stranded polynucleotides have been shown to be active in loading into RISC and inducing gene silencing. However, the level of activity for single stranded polynucleotides appears to be 2 to 4 orders of magnitude lower when compared to a duplex polynucleotide.
The present invention provides a description of the chemical modification patterns, which may (a) significantly increase stability of the single stranded polynucleotide (b) promote efficient loading of the polynucleotide into the RISC complex and (c) improve uptake of the single stranded nucleotide by the cell.
In yet another embodiment, the present invention provides a description of the chemical modifications patterns, which improve functionality of RISC inhibiting polynucleotides. Single stranded polynucleotides have been shown to inhibit activity of a preloaded RISC complex through the substrate competition mechanism. For these types of molecules, conventionally called antagomers, the activity usually requires high concentration and in vivo delivery is not very effective. The present invention provides a description of the chemical modification patterns, which may (a) significantly increase stability of the single stranded polynucleotide (b) promote efficient recognition of the polynucleotide by the RISC as a substrate and/or (c) improve uptake of the single stranded nucleotide by the cell.
The modifications provided by the present invention are applicable to all polynucleotides. This includes single stranded RISC entering polynucleotides, single stranded RISC inhibiting polynucleotides, conventional duplexed polynucleotides of variable length (15-40 bp), asymmetric duplexed polynucleotides, and the like. Polynucleotides may be modified with wide variety of chemical modification patterns, including 5′ end, ribose, backbone and hydrophobic nucleoside modifications.
Synthesis
Oligonucleotides of the invention can be synthesized by any method known in the art, e.g., using enzymatic synthesis and/or chemical synthesis. The oligonucleotides can be synthesized in vitro (e.g., using enzymatic synthesis and chemical synthesis) or in vivo (using recombinant DNA technology well known in the art).
In a preferred embodiment, chemical synthesis is used for modified polynucleotides. Chemical synthesis of linear oligonucleotides is well known in the art and can be achieved by solution or solid phase techniques. Preferably, synthesis is by solid phase methods. Oligonucleotides can be made by any of several different synthetic procedures including the phosphoramidite, phosphite triester, H-phosphonate, and phosphotriester methods, typically by automated synthesis methods.
Oligonucleotide synthesis protocols are well known in the art and can be found, e.g., in U.S. Pat. No. 5,830,653; WO 98/13526; Stec et al. 1984. J. Am. Chem. Soc. 106:6077; Stec et al. 1985. J. Org. Chem. 50:3908; Stec et al. J. Chromatog. 1985. 326:263; LaPlanche et al. 1986. Nucl. Acid. Res. 1986. 14:9081; Fasman G. D., 1989. Practical Handbook of Biochemistry and Molecular Biology. 1989. CRC Press, Boca Raton, Fla.; Lamone. 1993. Biochem. Soc. Trans. 21:1; U.S. Pat. No. 5,013,830; U.S. Pat. No. 5,214,135; U.S. Pat. No. 5,525,719; Kawasaki et al. 1993. J. Med. Chem. 36:831; WO 92/03568; U.S. Pat. No. 5,276,019; and U.S. Pat. No. 5,264,423.
The synthesis method selected can depend on the length of the desired oligonucleotide and such choice is within the skill of the ordinary artisan. For example, the phosphoramidite and phosphite triester method can produce oligonucleotides having 175 or more nucleotides, while the H-phosphonate method works well for oligonucleotides of less than 100 nucleotides. If modified bases are incorporated into the oligonucleotide, and particularly if modified phosphodiester linkages are used, then the synthetic procedures are altered as needed according to known procedures. In this regard, Uhlmann et al. (1990, Chemical Reviews 90:543-584) provide references and outline procedures for making oligonucleotides with modified bases and modified phosphodiester linkages. Other exemplary methods for making oligonucleotides are taught in Sonveaux. 1994. “Protecting Groups in Oligonucleotide Synthesis”; Agrawal. Methods in Molecular Biology 26:1. Exemplary synthesis methods are also taught in “Oligonucleotide Synthesis—A Practical Approach” (Gait, M. J. IRL Press at Oxford University Press. 1984). Moreover, linear oligonucleotides of defined sequence, including some sequences with modified nucleotides, are readily available from several commercial sources.
The oligonucleotides may be purified by polyacrylamide gel electrophoresis, or by any of a number of chromatographic methods, including gel chromatography and high pressure liquid chromatography. To confirm a nucleotide sequence, especially unmodified nucleotide sequences, oligonucleotides may be subjected to DNA sequencing by any of the known procedures, including Maxam and Gilbert sequencing, Sanger sequencing, capillary electrophoresis sequencing, the wandering spot sequencing procedure or by using selective chemical degradation of oligonucleotides bound to Hybond paper. Sequences of short oligonucleotides can also be analyzed by laser desorption mass spectroscopy or by fast atom bombardment (McNeal, et al., 1982, J. Am. Chem. Soc. 104:976; Viari, et al., 1987, Biomed. Environ. Mass Spectrom. 14:83; Grotjahn et al., 1982, Nuc. Acid Res. 10:4671). Sequencing methods are also available for RNA oligonucleotides.
The quality of oligonucleotides synthesized can be verified by testing the oligonucleotide by capillary electrophoresis and denaturing strong anion HPLC(SAX-HPLC) using, e.g., the method of Bergot and Egan. 1992. J. Chrom. 599:35.
Other exemplary synthesis techniques are well known in the art (see, e.g., Sambrook et al., Molecular Cloning: a Laboratory Manual, Second Edition (1989); DNA Cloning, Volumes I and II (D N Glover Ed. 1985); Oligonucleotide Synthesis (M J Gait Ed, 1984; Nucleic Acid Hybridisation (B D Hames and S J Higgins eds. 1984); A Practical Guide to Molecular Cloning (1984); or the series, Methods in Enzymology (Academic Press, Inc.)).
In certain embodiments, the subject RNAi constructs or at least portions thereof are transcribed from expression vectors encoding the subject constructs. Any art recognized vectors may be use for this purpose. The transcribed RNAi constructs may be isolated and purified, before desired modifications (such as replacing an unmodified sense strand with a modified one, etc.) are carried out.
Delivery/Carrier
Uptake of Oligonucleotides by Cells
Oligonucleotides and oligonucleotide compositions are contacted with (i.e., brought into contact with, also referred to herein as administered or delivered to) and taken up by one or more cells or a cell lysate. The term “cells” includes prokaryotic and eukaryotic cells, preferably vertebrate cells, and, more preferably, mammalian cells. In a preferred embodiment, the oligonucleotide compositions of the invention are contacted with human cells.
Oligonucleotide compositions of the invention can be contacted with cells in vitro, e.g., in a test tube or culture dish, (and may or may not be introduced into a subject) or in vivo, e.g., in a subject such as a mammalian subject. Oligonucleotides are taken up by cells at a slow rate by endocytosis, but endocytosed oligonucleotides are generally sequestered and not available, e.g., for hybridization to a target nucleic acid molecule. In one embodiment, cellular uptake can be facilitated by electroporation or calcium phosphate precipitation. However, these procedures are only useful for in vitro or ex vivo embodiments, are not convenient and, in some cases, are associated with cell toxicity.
In another embodiment, delivery of oligonucleotides into cells can be enhanced by suitable art recognized methods including calcium phosphate, DMSO, glycerol or dextran, electroporation, or by transfection, e.g., using cationic, anionic, or neutral lipid compositions or liposomes using methods known in the art (see e.g., WO 90/14074; WO 91/16024; WO 91/17424; U.S. Pat. No. 4,897,355; Bergan et al. 1993. Nucleic Acids Research. 21:3567). Enhanced delivery of oligonucleotides can also be mediated by the use of vectors (See e.g., Shi, Y. 2003. Trends Genet. 2003 Jan. 19:9; Reichhart J M et al. Genesis. 2002. 34(1-2):1604, Yu et al. 2002. Proc. Natl. Acad. Sci. USA 99:6047; Sui et al. 2002. Proc. Natl. Acad. Sci. USA 99:5515) viruses, polyamine or polycation conjugates using compounds such as polylysine, protamine, or Ni, N12-bis(ethyl) spermine (see, e.g., Bartzatt, R. et al. 1989. Biotechnol. Appl. Biochem. 11:133; Wagner E. et al. 1992. Proc. Natl. Acad. Sci. 88:4255).
In certain embodiments, the miniRNA of the invention may be delivered by using various beta-glucan containing particles, such as those described in US 2005/0281781 A1, WO 2006/007372, and WO 2007/050643 (all incorporated herein by reference). In certain embodiments, the beta-glucan particle is derived from yeast. In certain embodiments, the payload trapping molecule is a polymer, such as those with a molecular weight of at least about 1000 Da, 10,000 Da, 50,000 Da, 100 kDa, 500 kDa, etc. Preferred polymers include (without limitation) cationic polymers, chitosans, or PEI (polyethylenimine), etc.
Such beta-glucan based delivery system may be formulated for oral delivery, where the orally delivered beta-glucan/miniRNA constructs may be engulfed by macrophages or other related phagocytic cells, which may in turn release the miniRNA constructs in selected in vivo sites. Alternatively or in addition, the miniRNA may changes the expression of certain macrophage target genes.
The optimal protocol for uptake of oligonucleotides will depend upon a number of factors, the most crucial being the type of cells that are being used. Other factors that are important in uptake include, but are not limited to, the nature and concentration of the oligonucleotide, the confluence of the cells, the type of culture the cells are in (e.g., a suspension culture or plated) and the type of media in which the cells are grown.
Encapsulating Agents
Encapsulating agents entrap oligonucleotides within vesicles. In another embodiment of the invention, an oligonucleotide may be associated with a carrier or vehicle, e.g., liposomes or micelles, although other carriers could be used, as would be appreciated by one skilled in the art. Liposomes are vesicles made of a lipid bilayer having a structure similar to biological membranes. Such carriers are used to facilitate the cellular uptake or targeting of the oligonucleotide, or improve the oligonucleotide's pharmacokinetic or toxicologic properties.
For example, the oligonucleotides of the present invention may also be administered encapsulated in liposomes, pharmaceutical compositions wherein the active ingredient is contained either dispersed or variously present in corpuscles consisting of aqueous concentric layers adherent to lipidic layers. The oligonucleotides, depending upon solubility, may be present both in the aqueous layer and in the lipidic layer, or in what is generally termed a liposomic suspension. The hydrophobic layer, generally but not exclusively, comprises phopholipids such as lecithin and sphingomyelin, steroids such as cholesterol, more or less ionic surfactants such as diacetylphosphate, stearylamine, or phosphatidic acid, or other materials of a hydrophobic nature. The diameters of the liposomes generally range from about 15 nm to about 5 microns.
The use of liposomes as drug delivery vehicles offers several advantages. Liposomes increase intracellular stability, increase uptake efficiency and improve biological activity. Liposomes are hollow spherical vesicles composed of lipids arranged in a similar fashion as those lipids which make up the cell membrane. They have an internal aqueous space for entrapping water soluble compounds and range in size from 0.05 to several microns in diameter. Several studies have shown that liposomes can deliver nucleic acids to cells and that the nucleic acids remain biologically active. For example, a lipid delivery vehicle originally designed as a research tool, such as Lipofectin or LIPOFECTAMINE™ 2000, can deliver intact nucleic acid molecules to cells.
Specific advantages of using liposomes include the following: they are non-toxic and biodegradable in composition; they display long circulation half-lives; and recognition molecules can be readily attached to their surface for targeting to tissues. Finally, cost-effective manufacture of liposome-based pharmaceuticals, either in a liquid suspension or lyophilized product, has demonstrated the viability of this technology as an acceptable drug delivery system.
In some aspects, formulations associated with the invention might be selected for a class of naturally occurring or chemically synthesized or modified saturated and unsaturated fatty acid residues. Fatty acids might exist in a form of triglycerides, diglycerides or individual fatty acids. In another embodiment, the use of well-validated mixtures of fatty acids and/or fat emulsions currently used in pharmacology for parenteral nutrition may be utilized.
Liposome based formulations are widely used for oligonucleotide delivery. However, most of commercially available lipid or liposome formulations contain at least one positively charged lipid (cationic lipids). The presence of this positively charged lipid is believed to be essential for obtaining a high degree of oligonucleotide loading and for enhancing liposome fusogenic properties. Several methods have been performed and published to identify optimal positively charged lipid chemistries. However, the commercially available liposome formulations containing cationic lipids are characterized by a high level of toxicity. In vivo limited therapeutic indexes have revealed that liposome formulations containing positive charged lipids are associated with toxicity (i.e. elevation in liver enzymes) at concentrations only slightly higher than concentration required to achieve RNA silencing.
New liposome formulations, lacking the toxicity of the prior art liposomes have been developed according to the invention. These new liposome formulations are neutral fat-based formulations for the efficient delivery of oligonucleotides, and in particular for the delivery of the RNA molecules of the invention. The compositions are referred to as neutral nanotransporters because they enable quantitative oligonucleotide incorporation into non-charged lipids mixtures. The lack of toxic levels of cationic lipids in the neutral nanotransporter compositions of the invention is an important feature.
The neutral nanotransporters compositions enable efficient loading of oligonucleotide into neutral fat formulation. The composition includes an oligonucleotide that is modified in a manner such that the hydrophobicity of the molecule is increased (for example a hydrophobic molecule is attached (covalently or no-covalently) to a hydrophobic molecule on the oligonucleotide terminus or a non-terminal nucleotide, base, sugar, or backbone), the modified oligonucleotide being mixed with a neutral fat formulation (for example containing at least 25% of cholesterol and 25% of DOPC or analogs thereof). A cargo molecule, such as another lipid can also be included in the composition. This composition, where part of the formulation is build into the oligonucleotide itself, enables efficient encapsulation of oligonucleotide in neutral lipid particles.
One of several unexpected observations associated with the invention was that the oligonucleotides of the invention could effectively be incorporated in a lipid mixture that was free of cationic lipids and that such a composition could effectively deliver the therapeutic oligonucleotide to a cell in a manner that it is functional. Another unexpected observation was the high level of activity observed when the fatty mixture is composed of a phosphatidylcholine base fatty acid and a sterol such as a cholesterol. For instance, one preferred formulation of neutral fatty mixture is composed of at least 20% of DOPC or DSPC and at least 20% of sterol such as cholesterol. Even as low as 1:5 lipid to oligonucleotide ratio was shown to be sufficient to get complete encapsulation of the oligonucleotide in a non charged formulation. The prior art demonstrated only a 1-5% oligonucleotide encapsulation with non-charged formulations, which is not sufficient to get to a desired amount of in vivo efficacy. Compared to the prior art using neutral lipids the level of oligonucleotide delivery to a cell was quite unexpected.
Stable particles ranging in size from 50 to 140 nm were formed upon complexing of hydrophobic oligonucleotides with preferred formulations. It is interesting to mention that the formulation by itself typically does not form small particles, but rather, forms agglomerates, which are transformed into stable 50-120 nm particles upon addition of the hydrophobic modified oligonucleotide.
The neutral nanotransporter compositions of the invention include a hydrophobic modified polynucleotide, a neutral fatty mixture, and optionally a cargo molecule. A “hydrophobic modified polynucleotide” as used herein is a polynucleotide of the invention (i.e. sd-rxRNA) that has at least one modification that renders the polynucleotide more hydrophobic than the polynucleotide was prior to modification. The modification may be achieved by attaching (covalently or non-covalently) a hydrophobic molecule to the polynucleotide. In some instances the hydrophobic molecule is or includes a lipophilic group.
The term “lipophilic group” means a group that has a higher affinity for lipids than its affinity for water. Examples of lipophilic groups include, but are not limited to, cholesterol, a cholesteryl or modified cholesteryl residue, adamantine, dihydrotesterone, long chain alkyl, long chain alkenyl, long chain alkynyl, olely-lithocholic, cholenic, oleoyl-cholenic, palmityl, heptadecyl, myrisityl, bile acids, cholic acid or taurocholic acid, deoxycholate, oleyl litocholic acid, oleoyl cholenic acid, glycolipids, phospholipids, sphingolipids, isoprenoids, such as steroids, vitamins, such as vitamin E, fatty acids either saturated or unsaturated, fatty acid esters, such as triglycerides, pyrenes, porphyrines, Texaphyrine, adamantane, acridines, biotin, coumarin, fluorescein, rhodamine, Texas-Red, digoxygenin, dimethoxytrityl, t-butyldimethylsilyl, t-butyldiphenylsilyl, cyanine dyes (e.g. Cy3 or Cy5), Hoechst 33258 dye, psoralen, or ibuprofen. The cholesterol moiety may be reduced (e.g. as in cholestan) or may be substituted (e.g. by halogen). A combination of different lipophilic groups in one molecule is also possible.
The hydrophobic molecule may be attached at various positions of the polynucleotide. As described above, the hydrophobic molecule may be linked to the terminal residue of the polynucleotide such as the 3′ of 5′-end of the polynucleotide. Alternatively, it may be linked to an internal nucleotide or a nucleotide on a branch of the polynucleotide. The hydrophobic molecule may be attached, for instance to a 2′-position of the nucleotide. The hydrophobic molecule may also be linked to the heterocyclic base, the sugar or the backbone of a nucleotide of the polynucleotide.
The hydrophobic molecule may be connected to the polynucleotide by a linker moiety. Optionally the linker moiety is a non-nucleotidic linker moiety. Non-nucleotidic linkers are e.g. abasic residues (dSpacer), oligoethyleneglycol, such as triethyleneglycol (spacer 9) or hexaethylenegylcol (spacer 18), or alkane-diol, such as butanediol. The spacer units are preferably linked by phosphodiester or phosphorothioate bonds. The linker units may appear just once in the molecule or may be incorporated several times, e.g. via phosphodiester, phosphorothioate, methylphosphonate, or amide linkages.
Typical conjugation protocols involve the synthesis of polynucleotides bearing an aminolinker at one or more positions of the sequence, however, a linker is not required. The amino group is then reacted with the molecule being conjugated using appropriate coupling or activating reagents. The conjugation reaction may be performed either with the polynucleotide still bound to a solid support or following cleavage of the polynucleotide in solution phase. Purification of the modified polynucleotide by HPLC typically results in a pure material.
In some embodiments the hydrophobic molecule is a sterol type conjugate, a PhytoSterol conjugate, cholesterol conjugate, sterol type conjugate with altered side chain length, fatty acid conjugate, any other hydrophobic group conjugate, and/or hydrophobic modifications of the internal nucleoside, which provide sufficient hydrophobicity to be incorporated into micelles.
For purposes of the present invention, the term “sterols”, refers or steroid alcohols are a subgroup of steroids with a hydroxyl group at the 3-position of the A-ring. They are amphipathic lipids synthesized from acetyl-coenzyme A via the HMG-CoA reductase pathway. The overall molecule is quite flat. The hydroxyl group on the A ring is polar. The rest of the aliphatic chain is non-polar. Usually sterols are considered to have an 8 carbon chain at position 17.
For purposes of the present invention, the term “sterol type molecules”, refers to steroid alcohols, which are similar in structure to sterols. The main difference is the structure of the ring and number of carbons in a position 21 attached side chain.
For purposes of the present invention, the term “PhytoSterols” (also called plant sterols) are a group of steroid alcohols, phytochemicals naturally occurring in plants. There are more then 200 different known PhytoSterols
For purposes of the present invention, the term “Sterol side chain” refers to a chemical composition of a side chain attached at the position 17 of sterol-type molecule. In a standard definition sterols are limited to a 4 ring structure carrying a 8 carbon chain at position 17. In this invention, the sterol type molecules with side chain longer and shorter than conventional are described. The side chain may branched or contain double back bones.
Thus, sterols useful in the invention, for example, include cholesterols, as well as unique sterols in which position 17 has attached side chain of 2-7 or longer then 9 carbons. In a particular embodiment, the length of the polycarbon tail is varied between 5 and 9 carbons.
Alternatively the polynucleotide may be bound to a protein, peptide or positively charged chemical that functions as the hydrophobic molecule. The proteins may be selected from the group consisting of protamine, dsRNA binding domain, and arginine rich peptides. Exemplary positively charged chemicals include spermine, spermidine, cadaverine, and putrescine.
In another embodiment hydrophobic molecule conjugates may demonstrate even higher efficacy when it is combined with optimal chemical modification patterns of the polynucleotide (as described herein in detail), containing but not limited to hydrophobic modifications, phosphorothioate modifications, and 2′ ribo modifications.
In another embodiment the sterol type molecule may be a naturally occurring PhytoSterols such as those shown in
The hydrophobic modified polynucleotide is mixed with a neutral fatty mixture to form a micelle. The neutral fatty acid mixture is a mixture of fats that has a net neutral or slightly net negative charge at or around physiological pH that can form a micelle with the hydrophobic modified polynucleotide. For purposes of the present invention, the term “micelle” refers to a small nanoparticle formed by a mixture of non charged fatty acids and phospholipids. The neutral fatty mixture may include cationic lipids as long as they are present in an amount that does not cause toxicity. In preferred embodiments the neutral fatty mixture is free of cationic lipids. A mixture that is free of cationic lipids is one that has less than 1% and preferably 0% of the total lipid being cationic lipid. The term “cationic lipid” includes lipids and synthetic lipids having a net positive charge at or around physiological pH. The term “anionic lipid” includes lipids and synthetic lipids having a net negative charge at or around physiological pH.
The neutral fats bind to the oligonucleotides of the invention by a strong but non-covalent attraction (e.g., an electrostatic, van der Waals, pi-stacking, etc. interaction).
The neutral fat mixture may include formulations selected from a class of naturally occurring or chemically synthesized or modified saturated and unsaturated fatty acid residues. Fatty acids might exist in a form of triglycerides, diglycerides or individual fatty acids. In another embodiment the use of well-validated mixtures of fatty acids and/or fat emulsions currently used in pharmacology for parenteral nutrition may be utilized.
The neutral fatty mixture is preferably a mixture of a choline based fatty acid and a sterol. Choline based fatty acids include for instance, synthetic phosphocholine derivatives such as DDPC, DLPC, DMPC, DPPC, DSPC, DOPC, POPC, and DEPC. DOPC (chemical registry number 4235-95-4) is dioleoylphosphatidylcholine (also known as dielaidoylphosphatidylcholine, dioleoyl-PC, dioleoylphosphocholine, dioleoyl-sn-glycero-3-phosphocholine, dioleylphosphatidylcholine). DSPC (chemical registry number 816-94-4) is distearoylphosphatidylcholine (also known as 1,2-Distearoyl-sn-Glycero-3-phosphocholine).
The sterol in the neutral fatty mixture may be for instance cholesterol. The neutral fatty mixture may be made up completely of a choline based fatty acid and a sterol or it may optionally include a cargo molecule. For instance, the neutral fatty mixture may have at least 20% or 25% fatty acid and 20% or 25% sterol.
For purposes of the present invention, the term “Fatty acids” relates to conventional description of fatty acid. They may exist as individual entities or in a form of two- and triglycerides. For purposes of the present invention, the term “fat emulsions” refers to safe fat formulations given intravenously to subjects who are unable to get enough fat in their diet. It is an emulsion of soy bean oil (or other naturally occurring oils) and egg phospholipids. Fat emulsions are being used for formulation of some insoluble anesthetics. In this disclosure, fat emulsions might be part of commercially available preparations like Intralipid, Liposyn, Nutrilipid, modified commercial preparations, where they are enriched with particular fatty acids or fully de novo-formulated combinations of fatty acids and phospholipids.
In one embodiment, the cells to be contacted with an oligonucleotide composition of the invention are contacted with a mixture comprising the oligonucleotide and a mixture comprising a lipid, e.g., one of the lipids or lipid compositions described supra for between about 12 hours to about 24 hours. In another embodiment, the cells to be contacted with an oligonucleotide composition are contacted with a mixture comprising the oligonucleotide and a mixture comprising a lipid, e.g., one of the lipids or lipid compositions described supra for between about 1 and about five days. In one embodiment, the cells are contacted with a mixture comprising a lipid and the oligonucleotide for between about three days to as long as about 30 days. In another embodiment, a mixture comprising a lipid is left in contact with the cells for at least about five to about 20 days. In another embodiment, a mixture comprising a lipid is left in contact with the cells for at least about seven to about 15 days.
50%-60% of the formulation can optionally be any other lipid or molecule. Such a lipid or molecule is referred to herein as a cargo lipid or cargo molecule. Cargo molecules include but are not limited to intralipid, small molecules, fusogenic peptides or lipids or other small molecules might be added to alter cellular uptake, endosomal release or tissue distribution properties. The ability to tolerate cargo molecules is important for modulation of properties of these particles, if such properties are desirable. For instance the presence of some tissue specific metabolites might drastically alter tissue distribution profiles. For example use of Intralipid type formulation enriched in shorter or longer fatty chains with various degrees of saturation affects tissue distribution profiles of these type of formulations (and their loads).
An example of a cargo lipid useful according to the invention is a fusogenic lipid. For instance, the zwiterionic lipid DOPE (chemical registry number 4004-5-1,1,2-Dioleoyl-sn-Glycero-3-phosphoethanolamine) is a preferred cargo lipid.
Intralipid may be comprised of the following composition: 1 000 mL contain: purified soybean oil 90 g, purified egg phospholipids 12 g, glycerol anhydrous 22 g, water for injection q.s. ad 1 000 mL. pH is adjusted with sodium hydroxide to pH approximately 8. Energy content/L: 4.6 MJ (190 kcal). Osmolality (approx.): 300 mOsm/kg water. In another embodiment fat emulsion is Liposyn that contains 5% safflower oil, 5% soybean oil, up to 1.2% egg phosphatides added as an emulsifier and 2.5% glycerin in water for injection. It may also contain sodium hydroxide for pH adjustment. pH 8.0 (6.0-9.0). Liposyn has an osmolarity of 276 m Osmol/liter (actual).
Variation in the identity, amounts and ratios of cargo lipids affects the cellular uptake and tissue distribution characteristics of these compounds. For example, the length of lipid tails and level of saturability will affect differential uptake to liver, lung, fat and cardiomyocytes. Addition of special hydrophobic molecules like vitamins or different forms of sterols can favor distribution to special tissues which are involved in the metabolism of particular compounds. Complexes are formed at different oligonucleotide concentrations, with higher concentrations favoring more efficient complex formation (
In another embodiment, the fat emulsion is based on a mixture of lipids. Such lipids may include natural compounds, chemically synthesized compounds, purified fatty acids or any other lipids. In yet another embodiment the composition of fat emulsion is entirely artificial. In a particular embodiment, the fat emulsion is more then 70% linoleic acid. In yet another particular embodiment the fat emulsion is at least 1% of cardiolipin. Linoleic acid (LA) is an unsaturated omega-6 fatty acid. It is a colorless liquid made of a carboxylic acid with an 18-carbon chain and two cis double bonds.
In yet another embodiment of the present invention, the alteration of the composition of the fat emulsion is used as a way to alter tissue distribution of hydrophobicly modified polynucleotides. This methodology provides for the specific delivery of the polynucleotides to particular tissues (
In another embodiment the fat emulsions of the cargo molecule contain more then 70% of Linoleic acid (C18H32O2) and/or cardiolipin are used for specifically delivering RNAi to heart muscle.
Fat emulsions, like intralipid have been used before as a delivery formulation for some non-water soluble drugs (such as Propofol, re-formulated as Diprivan). Unique features of the present invention include (a) the concept of combining modified polynucleotides with the hydrophobic compound(s), so it can be incorporated in the fat micelles and (b) mixing it with the fat emulsions to provide a reversible carrier. After injection into a blood stream, micelles usually bind to serum proteins, including albumin, HDL, LDL and other. This binding is reversible and eventually the fat is absorbed by cells. The polynucleotide, incorporated as a part of the micelle will then be delivered closely to the surface of the cells. After that cellular uptake might be happening though variable mechanisms, including but not limited to sterol type delivery.
Complexing Agents
Complexing agents bind to the oligonucleotides of the invention by a strong but non-covalent attraction (e.g., an electrostatic, van der Waals, pi-stacking, etc. interaction). In one embodiment, oligonucleotides of the invention can be complexed with a complexing agent to increase cellular uptake of oligonucleotides. An example of a complexing agent includes cationic lipids. Cationic lipids can be used to deliver oligonucleotides to cells. However, as discussed above, formulations free in cationic lipids are preferred in some embodiments.
The term “cationic lipid” includes lipids and synthetic lipids having both polar and non-polar domains and which are capable of being positively charged at or around physiological pH and which bind to polyanions, such as nucleic acids, and facilitate the delivery of nucleic acids into cells. In general cationic lipids include saturated and unsaturated alkyl and alicyclic ethers and esters of amines, amides, or derivatives thereof. Straight-chain and branched alkyl and alkenyl groups of cationic lipids can contain, e.g., from 1 to about 25 carbon atoms. Preferred straight chain or branched alkyl or alkene groups have six or more carbon atoms. Alicyclic groups include cholesterol and other steroid groups. Cationic lipids can be prepared with a variety of counterions (anions) including, e.g., Cl—, Br—, I—, F—, acetate, trifluoroacetate, sulfate, nitrite, and nitrate.
Examples of cationic lipids include polyethylenimine, polyamidoamine (PAMAM) starburst dendrimers, Lipofectin (a combination of DOTMA and DOPE), Lipofectase, LIPOFECTAMINE™ (e.g., LIPOFECTAMINE™ 2000), DOPE, Cytofectin (Gilead Sciences, Foster City, Calif.), and Eufectins (JBL, San Luis Obispo, Calif.). Exemplary cationic liposomes can be made from N-[1-(2,3-dioleoloxy)-propyl]-N,N,N-trimethylammonium chloride (DOTMA), N-[1-(2,3-dioleoloxy)-propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP), 3β-[N—(N′,N′-dimethylaminoethane)carbamoyl]cholesterol (DC-Chol), 2,3,-dioleyloxy-N-[2(sperminecarboxamido)ethyl]-N,N-dimethyl-1-propanaminium trifluoroacetate (DOSPA), 1,2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide; and dimethyldioctadecylammonium bromide (DDAB). The cationic lipid N-(1-(2,3-dioleyloxy)propyl)-N,N,N-trimethylammonium chloride (DOTMA), for example, was found to increase 1000-fold the antisense effect of a phosphorothioate oligonucleotide. (Vlassov et al., 1994, Biochimica et Biophysica Acta 1197:95-108). Oligonucleotides can also be complexed with, e.g., poly(L-lysine) or avidin and lipids may, or may not, be included in this mixture, e.g., steryl-poly(L-lysine).
Cationic lipids have been used in the art to deliver oligonucleotides to cells (see, e.g., U.S. Pat. Nos. 5,855,910; 5,851,548; 5,830,430; 5,780,053; 5,767,099; Lewis et al. 1996. Proc. Natl. Acad. Sci. USA 93:3176; Hope et al. 1998. Molecular Membrane Biology 15:1). Other lipid compositions which can be used to facilitate uptake of the instant oligonucleotides can be used in connection with the claimed methods. In addition to those listed supra, other lipid compositions are also known in the art and include, e.g., those taught in U.S. Pat. No. 4,235,871; U.S. Pat. Nos. 4,501,728; 4,837,028; 4,737,323.
In one embodiment lipid compositions can further comprise agents, e.g., viral proteins to enhance lipid-mediated transfections of oligonucleotides (Kamata, et al., 1994. Nucl. Acids. Res. 22:536). In another embodiment, oligonucleotides are contacted with cells as part of a composition comprising an oligonucleotide, a peptide, and a lipid as taught, e.g., in U.S. Pat. No. 5,736,392. Improved lipids have also been described which are serum resistant (Lewis, et al., 1996. Proc. Natl. Acad. Sci. 93:3176). Cationic lipids and other complexing agents act to increase the number of oligonucleotides carried into the cell through endocytosis.
In another embodiment N-substituted glycine oligonucleotides (peptoids) can be used to optimize uptake of oligonucleotides. Peptoids have been used to create cationic lipid-like compounds for transfection (Murphy, et al., 1998. Proc. Natl. Acad. Sci. 95:1517). Peptoids can be synthesized using standard methods (e.g., Zuckermann, R. N., et al. 1992. J. Am. Chem. Soc. 114:10646; Zuckermann, R. N., et al. 1992. Int. J. Peptide Protein Res. 40:497). Combinations of cationic lipids and peptoids, liptoids, can also be used to optimize uptake of the subject oligonucleotides (Hunag, et al., 1998. Chemistry and Biology. 5:345). Liptoids can be synthesized by elaborating peptoid oligonucleotides and coupling the amino terminal submonomer to a lipid via its amino group (Hunag, et al., 1998. Chemistry and Biology. 5:345).
It is known in the art that positively charged amino acids can be used for creating highly active cationic lipids (Lewis et al. 1996. Proc. Natl. Acad. Sci. U.S.A. 93:3176). In one embodiment, a composition for delivering oligonucleotides of the invention comprises a number of arginine, lysine, histidine or ornithine residues linked to a lipophilic moiety (see e.g., U.S. Pat. No. 5,777,153).
In another embodiment, a composition for delivering oligonucleotides of the invention comprises a peptide having from between about one to about four basic residues. These basic residues can be located, e.g., on the amino terminal, C-terminal, or internal region of the peptide. Families of amino acid residues having similar side chains have been defined in the art. These families include amino acids with basic side chains (e.g., lysine, arginine, histidine), acidic side chains (e.g., aspartic acid, glutamic acid), uncharged polar side chains (e.g., glycine (can also be considered non-polar), asparagine, glutamine, serine, threonine, tyrosine, cysteine), nonpolar side chains (e.g., alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan), beta-branched side chains (e.g., threonine, valine, isoleucine) and aromatic side chains (e.g., tyrosine, phenylalanine, tryptophan, histidine). Apart from the basic amino acids, a majority or all of the other residues of the peptide can be selected from the non-basic amino acids, e.g., amino acids other than lysine, arginine, or histidine. Preferably a preponderance of neutral amino acids with long neutral side chains are used.
In one embodiment, a composition for delivering oligonucleotides of the invention comprises a natural or synthetic polypeptide having one or more gamma carboxyglutamic acid residues, or γ-Gla residues. These gamma carboxyglutamic acid residues may enable the polypeptide to bind to each other and to membrane surfaces. In other words, a polypeptide having a series of γ-Gla may be used as a general delivery modality that helps an RNAi construct to stick to whatever membrane to which it comes in contact. This may at least slow RNAi constructs from being cleared from the blood stream and enhance their chance of homing to the target.
The gamma carboxyglutamic acid residues may exist in natural proteins (for example, prothrombin has 10 γ-Gla residues). Alternatively, they can be introduced into the purified, recombinantly produced, or chemically synthesized polypeptides by carboxylation using, for example, a vitamin K-dependent carboxylase. The gamma carboxyglutamic acid residues may be consecutive or non-consecutive, and the total number and location of such gamma carboxyglutamic acid residues in the polypeptide can be regulated/fine tuned to achieve different levels of “stickiness” of the polypeptide.
In one embodiment, the cells to be contacted with an oligonucleotide composition of the invention are contacted with a mixture comprising the oligonucleotide and a mixture comprising a lipid, e.g., one of the lipids or lipid compositions described supra for between about 12 hours to about 24 hours. In another embodiment, the cells to be contacted with an oligonucleotide composition are contacted with a mixture comprising the oligonucleotide and a mixture comprising a lipid, e.g., one of the lipids or lipid compositions described supra for between about 1 and about five days. In one embodiment, the cells are contacted with a mixture comprising a lipid and the oligonucleotide for between about three days to as long as about 30 days. In another embodiment, a mixture comprising a lipid is left in contact with the cells for at least about five to about 20 days. In another embodiment, a mixture comprising a lipid is left in contact with the cells for at least about seven to about 15 days.
For example, in one embodiment, an oligonucleotide composition can be contacted with cells in the presence of a lipid such as cytofectin CS or GSV (available from Glen Research; Sterling, Va.), GS3815, GS2888 for prolonged incubation periods as described herein.
In one embodiment, the incubation of the cells with the mixture comprising a lipid and an oligonucleotide composition does not reduce the viability of the cells. Preferably, after the transfection period the cells are substantially viable. In one embodiment, after transfection, the cells are between at least about 70% and at least about 100% viable. In another embodiment, the cells are between at least about 80% and at least about 95% viable. In yet another embodiment, the cells are between at least about 85% and at least about 90% viable.
In one embodiment, oligonucleotides are modified by attaching a peptide sequence that transports the oligonucleotide into a cell, referred to herein as a “transporting peptide.” In one embodiment, the composition includes an oligonucleotide which is complementary to a target nucleic acid molecule encoding the protein, and a covalently attached transporting peptide.
The language “transporting peptide” includes an amino acid sequence that facilitates the transport of an oligonucleotide into a cell. Exemplary peptides which facilitate the transport of the moieties to which they are linked into cells are known in the art, and include, e.g., HIV TAT transcription factor, lactoferrin, Herpes VP22 protein, and fibroblast growth factor 2 (Pooga et al. 1998. Nature Biotechnology. 16:857; and Derossi et al. 1998. Trends in Cell Biology. 8:84; Elliott and O'Hare. 1997. Cell 88:223).
Oligonucleotides can be attached to the transporting peptide using known techniques, e.g., (Prochiantz, A. 1996. Curr. Opin. Neurobiol. 6:629; Derossi et al. 1998. Trends Cell Biol. 8:84; Troy et al. 1996. J. Neurosci. 16:253), Vives et al. 1997. J. Biol. Chem. 272:16010). For example, in one embodiment, oligonucleotides bearing an activated thiol group are linked via that thiol group to a cysteine present in a transport peptide (e.g., to the cysteine present in the (3 turn between the second and the third helix of the antennapedia homeodomain as taught, e.g., in Derossi et al. 1998. Trends Cell Biol. 8:84; Prochiantz. 1996. Current Opinion in Neurobiol. 6:629; Allinquant et al. 1995. J. Cell Biol. 128:919). In another embodiment, a Boc-Cys-(Npys)OH group can be coupled to the transport peptide as the last (N-terminal) amino acid and an oligonucleotide bearing an SH group can be coupled to the peptide (Troy et al. 1996. J. Neurosci. 16:253).
In one embodiment, a linking group can be attached to a nucleomonomer and the transporting peptide can be covalently attached to the linker. In one embodiment, a linker can function as both an attachment site for a transporting peptide and can provide stability against nucleases. Examples of suitable linkers include substituted or unsubstituted C1-C20 alkyl chains, C2-C20 alkenyl chains, C2-C20 alkynyl chains, peptides, and heteroatoms (e.g., S, O, NH, etc.). Other exemplary linkers include bifunctional crosslinking agents such as sulfosuccinimidyl-4-(maleimidophenyl)-butyrate (SMPB) (see, e.g., Smith et al. Biochem J 1991.276: 417-2).
In one embodiment, oligonucleotides of the invention are synthesized as molecular conjugates which utilize receptor-mediated endocytotic mechanisms for delivering genes into cells (see, e.g., Bunnell et al. 1992. Somatic Cell and Molecular Genetics. 18:559, and the references cited therein).
Targeting Agents
The delivery of oligonucleotides can also be improved by targeting the oligonucleotides to a cellular receptor. The targeting moieties can be conjugated to the oligonucleotides or attached to a carrier group (i.e., poly(L-lysine) or liposomes) linked to the oligonucleotides. This method is well suited to cells that display specific receptor-mediated endocytosis.
For instance, oligonucleotide conjugates to 6-phosphomannosylated proteins are internalized 20-fold more efficiently by cells expressing mannose 6-phosphate specific receptors than free oligonucleotides. The oligonucleotides may also be coupled to a ligand for a cellular receptor using a biodegradable linker. In another example, the delivery construct is mannosylated streptavidin which forms a tight complex with biotinylated oligonucleotides. Mannosylated streptavidin was found to increase 20-fold the internalization of biotinylated oligonucleotides. (Vlassov et al. 1994. Biochimica et Biophysica Acta 1197:95-108).
In addition specific ligands can be conjugated to the polylysine component of polylysine-based delivery systems. For example, transferrin-polylysine, adenovirus-polylysine, and influenza virus hemagglutinin HA-2 N-terminal fusogenic peptides-polylysine conjugates greatly enhance receptor-mediated DNA delivery in eucaryotic cells. Mannosylated glycoprotein conjugated to poly(L-lysine) in aveolar macrophages has been employed to enhance the cellular uptake of oligonucleotides. Liang et al. 1999. Pharmazie 54:559-566.
Because malignant cells have an increased need for essential nutrients such as folic acid and transferrin, these nutrients can be used to target oligonucleotides to cancerous cells. For example, when folic acid is linked to poly(L-lysine) enhanced oligonucleotide uptake is seen in promyelocytic leukaemia (HL-60) cells and human melanoma (M-14) cells. Ginobbi et al. 1997. Anticancer Res. 17:29. In another example, liposomes coated with maleylated bovine serum albumin, folic acid, or ferric protoporphyrin IX, show enhanced cellular uptake of oligonucleotides in murine macrophages, KB cells, and 2.2.15 human hepatoma cells. Liang et al. 1999. Pharmazie 54:559-566.
Liposomes naturally accumulate in the liver, spleen, and reticuloendothelial system (so-called, passive targeting). By coupling liposomes to various ligands such as antibodies are protein A, they can be actively targeted to specific cell populations. For example, protein A-bearing liposomes may be pretreated with H-2K specific antibodies which are targeted to the mouse major histocompatibility complex-encoded H-2K protein expressed on L cells. (Vlassov et al. 1994. Biochimica et Biophysica Acta 1197:95-108).
Other in vitro and/or in vivo delivery of RNAi reagents are known in the art, and can be used to deliver the subject RNAi constructs. See, for example, U.S. patent application publications 20080152661, 20080112916, 20080107694, 20080038296, 20070231392, 20060240093, 20060178327, 20060008910, 20050265957, 20050064595, 20050042227, 20050037496, 20050026286, 20040162235, 20040072785, 20040063654, 20030157030, WO 2008/036825, WO04/065601, and AU2004206255B2, just to name a few (all incorporated by reference).
Administration
The optimal course of administration or delivery of the oligonucleotides may vary depending upon the desired result and/or on the subject to be treated. As used herein “administration” refers to contacting cells with oligonucleotides and can be performed in vitro or in vivo. The dosage of oligonucleotides may be adjusted to optimally reduce expression of a protein translated from a target nucleic acid molecule, e.g., as measured by a readout of RNA stability or by a therapeutic response, without undue experimentation.
For example, expression of the protein encoded by the nucleic acid target can be measured to determine whether or not the dosage regimen needs to be adjusted accordingly. In addition, an increase or decrease in RNA or protein levels in a cell or produced by a cell can be measured using any art recognized technique. By determining whether transcription has been decreased, the effectiveness of the oligonucleotide in inducing the cleavage of a target RNA can be determined.
Any of the above-described oligonucleotide compositions can be used alone or in conjunction with a pharmaceutically acceptable carrier. As used herein, “pharmaceutically acceptable carrier” includes appropriate solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, it can be used in the therapeutic compositions. Supplementary active ingredients can also be incorporated into the compositions.
Oligonucleotides may be incorporated into liposomes or liposomes modified with polyethylene glycol or admixed with cationic lipids for parenteral administration. Incorporation of additional substances into the liposome, for example, antibodies reactive against membrane proteins found on specific target cells, can help target the oligonucleotides to specific cell types.
Moreover, the present invention provides for administering the subject oligonucleotides with an osmotic pump providing continuous infusion of such oligonucleotides, for example, as described in Rataiczak et al. (1992 Proc. Natl. Acad. Sci. USA 89:11823-11827). Such osmotic pumps are commercially available, e.g., from Alzet Inc. (Palo Alto, Calif.). Topical administration and parenteral administration in a cationic lipid carrier are preferred.
With respect to in vivo applications, the formulations of the present invention can be administered to a patient in a variety of forms adapted to the chosen route of administration, e.g., parenterally, orally, or intraperitoneally. Parenteral administration, which is preferred, includes administration by the following routes: intravenous; intramuscular; interstitially; intraarterially; subcutaneous; intra ocular; intrasynovial; trans epithelial, including transdermal; pulmonary via inhalation; ophthalmic; sublingual and buccal; topically, including ophthalmic; dermal; ocular; rectal; and nasal inhalation via insufflation.
Pharmaceutical preparations for parenteral administration include aqueous solutions of the active compounds in water-soluble or water-dispersible form. In addition, suspensions of the active compounds as appropriate oily injection suspensions may be administered. Suitable lipophilic solvents or vehicles include fatty oils, for example, sesame oil, or synthetic fatty acid esters, for example, ethyl oleate or triglycerides. Aqueous injection suspensions may contain substances which increase the viscosity of the suspension include, for example, sodium carboxymethyl cellulose, sorbitol, or dextran, optionally, the suspension may also contain stabilizers. The oligonucleotides of the invention can be formulated in liquid solutions, preferably in physiologically compatible buffers such as Hank's solution or Ringer's solution. In addition, the oligonucleotides may be formulated in solid form and redissolved or suspended immediately prior to use. Lyophilized forms are also included in the invention.
Pharmaceutical preparations for topical administration include transdermal patches, ointments, lotions, creams, gels, drops, sprays, suppositories, liquids and powders. In addition, conventional pharmaceutical carriers, aqueous, powder or oily bases, or thickeners may be used in pharmaceutical preparations for topical administration.
Pharmaceutical preparations for oral administration include powders or granules, suspensions or solutions in water or non-aqueous media, capsules, sachets or tablets. In addition, thickeners, flavoring agents, diluents, emulsifiers, dispersing aids, or binders may be used in pharmaceutical preparations for oral administration.
For transmucosal or transdermal administration, penetrants appropriate to the barrier to be permeated are used in the formulation. Such penetrants are known in the art, and include, for example, for transmucosal administration bile salts and fusidic acid derivatives, and detergents. Transmucosal administration may be through nasal sprays or using suppositories. For oral administration, the oligonucleotides are formulated into conventional oral administration forms such as capsules, tablets, and tonics. For topical administration, the oligonucleotides of the invention are formulated into ointments, salves, gels, or creams as known in the art.
Drug delivery vehicles can be chosen e.g., for in vitro, for systemic, or for topical administration. These vehicles can be designed to serve as a slow release reservoir or to deliver their contents directly to the target cell. An advantage of using some direct delivery drug vehicles is that multiple molecules are delivered per uptake. Such vehicles have been shown to increase the circulation half-life of drugs that would otherwise be rapidly cleared from the blood stream. Some examples of such specialized drug delivery vehicles which fall into this category are liposomes, hydrogels, cyclodextrins, biodegradable nanocapsules, and bioadhesive microspheres.
The described oligonucleotides may be administered systemically to a subject. Systemic absorption refers to the entry of drugs into the blood stream followed by distribution throughout the entire body. Administration routes which lead to systemic absorption include: intravenous, subcutaneous, intraperitoneal, and intranasal. Each of these administration routes delivers the oligonucleotide to accessible diseased cells. Following subcutaneous administration, the therapeutic agent drains into local lymph nodes and proceeds through the lymphatic network into the circulation. The rate of entry into the circulation has been shown to be a function of molecular weight or size. The use of a liposome or other drug carrier localizes the oligonucleotide at the lymph node. The oligonucleotide can be modified to diffuse into the cell, or the liposome can directly participate in the delivery of either the unmodified or modified oligonucleotide into the cell.
The chosen method of delivery will result in entry into cells. Preferred delivery methods include liposomes (10-400 nm), hydrogels, controlled-release polymers, and other pharmaceutically applicable vehicles, and microinjection or electroporation (for ex vivo treatments).
The pharmaceutical preparations of the present invention may be prepared and formulated as emulsions. Emulsions are usually heterogeneous systems of one liquid dispersed in another in the form of droplets usually exceeding 0.1 μm in diameter. The emulsions of the present invention may contain excipients such as emulsifiers, stabilizers, dyes, fats, oils, waxes, fatty acids, fatty alcohols, fatty esters, humectants, hydrophilic colloids, preservatives, and anti-oxidants may also be present in emulsions as needed. These excipients may be present as a solution in either the aqueous phase, oily phase or itself as a separate phase.
Examples of naturally occurring emulsifiers that may be used in emulsion formulations of the present invention include lanolin, beeswax, phosphatides, lecithin and acacia. Finely divided solids have also been used as good emulsifiers especially in combination with surfactants and in viscous preparations. Examples of finely divided solids that may be used as emulsifiers include polar inorganic solids, such as heavy metal hydroxides, nonswelling clays such as bentonite, attapulgite, hectorite, kaolin, montrnorillonite, colloidal aluminum silicate and colloidal magnesium aluminum silicate, pigments and nonpolar solids such as carbon or glyceryl tristearate.
Examples of preservatives that may be included in the emulsion formulations include methyl paraben, propyl paraben, quaternary ammonium salts, benzalkonium chloride, esters of p-hydroxybenzoic acid, and boric acid. Examples of antioxidants that may be included in the emulsion formulations include free radical scavengers such as tocopherols, alkyl gallates, butylated hydroxyanisole, butylated hydroxytoluene, or reducing agents such as ascorbic acid and sodium metabisulfite, and antioxidant synergists such as citric acid, tartaric acid, and lecithin.
In one embodiment, the compositions of oligonucleotides are formulated as microemulsions. A microemulsion is a system of water, oil and amphiphile which is a single optically isotropic and thermodynamically stable liquid solution. Typically microemulsions are prepared by first dispersing an oil in an aqueous surfactant solution and then adding a sufficient amount of a 4th component, generally an intermediate chain-length alcohol to form a transparent system.
Surfactants that may be used in the preparation of microemulsions include, but are not limited to, ionic surfactants, non-ionic surfactants, Brij 96, polyoxyethylene oleyl ethers, polyglycerol fatty acid esters, tetraglycerol monolaurate (ML310), tetraglycerol monooleate (MO310), hexaglycerol monooleate (PO310), hexaglycerol pentaoleate (PO500), decaglycerol monocaprate (MCA750), decaglycerol monooleate (MO750), decaglycerol sequioleate (S0750), decaglycerol decaoleate (DA0750), alone or in combination with cosurfactants. The cosurfactant, usually a short-chain alcohol such as ethanol, 1-propanol, and 1-butanol, serves to increase the interfacial fluidity by penetrating into the surfactant film and consequently creating a disordered film because of the void space generated among surfactant molecules.
Microemulsions may, however, be prepared without the use of cosurfactants and alcohol-free self-emulsifying microemulsion systems are known in the art. The aqueous phase may typically be, but is not limited to, water, an aqueous solution of the drug, glycerol, PEG300, PEG400, polyglycerols, propylene glycols, and derivatives of ethylene glycol. The oil phase may include, but is not limited to, materials such as Captex 300, Captex 355, Capmul MCM, fatty acid esters, medium chain (C8-C12) mono, di, and tri-glycerides, polyoxyethylated glyceryl fatty acid esters, fatty alcohols, polyglycolized glycerides, saturated polyglycolized C8-C10 glycerides, vegetable oils and silicone oil.
Microemulsions are particularly of interest from the standpoint of drug solubilization and the enhanced absorption of drugs. Lipid based microemulsions (both oil/water and water/oil) have been proposed to enhance the oral bioavailability of drugs.
Microemulsions offer improved drug solubilization, protection of drug from enzymatic hydrolysis, possible enhancement of drug absorption due to surfactant-induced alterations in membrane fluidity and permeability, ease of preparation, ease of oral administration over solid dosage forms, improved clinical potency, and decreased toxicity (Constantinides et al., Pharmaceutical Research, 1994, 11:1385; Ho et al., J. Pharm. Sci., 1996, 85:138-143). Microemulsions have also been effective in the transdermal delivery of active components in both cosmetic and pharmaceutical applications. It is expected that the microemulsion compositions and formulations of the present invention will facilitate the increased systemic absorption of oligonucleotides from the gastrointestinal tract, as well as improve the local cellular uptake of oligonucleotides within the gastrointestinal tract, vagina, buccal cavity and other areas of administration.
In an embodiment, the present invention employs various penetration enhancers to affect the efficient delivery of nucleic acids, particularly oligonucleotides, to the skin of animals. Even non-lipophilic drugs may cross cell membranes if the membrane to be crossed is treated with a penetration enhancer. In addition to increasing the diffusion of non-lipophilic drugs across cell membranes, penetration enhancers also act to enhance the permeability of lipophilic drugs.
Five categories of penetration enhancers that may be used in the present invention include: surfactants, fatty acids, bile salts, chelating agents, and non-chelating non-surfactants. Other agents may be utilized to enhance the penetration of the administered oligonucleotides include: glycols such as ethylene glycol and propylene glycol, pyrrols such as 2-15 pyrrol, azones, and terpenes such as limonene, and menthone.
The oligonucleotides, especially in lipid formulations, can also be administered by coating a medical device, for example, a catheter, such as an angioplasty balloon catheter, with a cationic lipid formulation. Coating may be achieved, for example, by dipping the medical device into a lipid formulation or a mixture of a lipid formulation and a suitable solvent, for example, an aqueous-based buffer, an aqueous solvent, ethanol, methylene chloride, chloroform and the like. An amount of the formulation will naturally adhere to the surface of the device which is subsequently administered to a patient, as appropriate. Alternatively, a lyophilized mixture of a lipid formulation may be specifically bound to the surface of the device. Such binding techniques are described, for example, in K. Ishihara et al., Journal of Biomedical Materials Research, Vol. 27, pp. 1309-1314 (1993), the disclosures of which are incorporated herein by reference in their entirety.
The useful dosage to be administered and the particular mode of administration will vary depending upon such factors as the cell type, or for in vivo use, the age, weight and the particular animal and region thereof to be treated, the particular oligonucleotide and delivery method used, the therapeutic or diagnostic use contemplated, and the form of the formulation, for example, suspension, emulsion, micelle or liposome, as will be readily apparent to those skilled in the art. Typically, dosage is administered at lower levels and increased until the desired effect is achieved. When lipids are used to deliver the oligonucleotides, the amount of lipid compound that is administered can vary and generally depends upon the amount of oligonucleotide agent being administered. For example, the weight ratio of lipid compound to oligonucleotide agent is preferably from about 1:1 to about 15:1, with a weight ratio of about 5:1 to about 10:1 being more preferred. Generally, the amount of cationic lipid compound which is administered will vary from between about 0.1 milligram (mg) to about 1 gram (g). By way of general guidance, typically between about 0.1 mg and about 10 mg of the particular oligonucleotide agent, and about 1 mg to about 100 mg of the lipid compositions, each per kilogram of patient body weight, is administered, although higher and lower amounts can be used.
The agents of the invention are administered to subjects or contacted with cells in a biologically compatible form suitable for pharmaceutical administration. By “biologically compatible form suitable for administration” is meant that the oligonucleotide is administered in a form in which any toxic effects are outweighed by the therapeutic effects of the oligonucleotide. In one embodiment, oligonucleotides can be administered to subjects. Examples of subjects include mammals, e.g., humans and other primates; cows, pigs, horses, and farming (agricultural) animals; dogs, cats, and other domesticated pets; mice, rats, and transgenic non-human animals.
Administration of an active amount of an oligonucleotide of the present invention is defined as an amount effective, at dosages and for periods of time necessary to achieve the desired result. For example, an active amount of an oligonucleotide may vary according to factors such as the type of cell, the oligonucleotide used, and for in vivo uses the disease state, age, sex, and weight of the individual, and the ability of the oligonucleotide to elicit a desired response in the individual. Establishment of therapeutic levels of oligonucleotides within the cell is dependent upon the rates of uptake and efflux or degradation. Decreasing the degree of degradation prolongs the intracellular half-life of the oligonucleotide. Thus, chemically-modified oligonucleotides, e.g., with modification of the phosphate backbone, may require different dosing.
The exact dosage of an oligonucleotide and number of doses administered will depend upon the data generated experimentally and in clinical trials. Several factors such as the desired effect, the delivery vehicle, disease indication, and the route of administration, will affect the dosage. Dosages can be readily determined by one of ordinary skill in the art and formulated into the subject pharmaceutical compositions. Preferably, the duration of treatment will extend at least through the course of the disease symptoms.
Dosage regim may be adjusted to provide the optimum therapeutic response. For example, the oligonucleotide may be repeatedly administered, e.g., several doses may be administered daily or the dose may be proportionally reduced as indicated by the exigencies of the therapeutic situation. One of ordinary skill in the art will readily be able to determine appropriate doses and schedules of administration of the subject oligonucleotides, whether the oligonucleotides are to be administered to cells or to subjects.
Physical methods of introducing nucleic acids include injection of a solution containing the nucleic acid, bombardment by particles covered by the nucleic acid, soaking the cell or organism in a solution of the nucleic acid, or electroporation of cell membranes in the presence of the nucleic acid. A viral construct packaged into a viral particle would accomplish both efficient introduction of an expression construct into the cell and transcription of nucleic acid encoded by the expression construct. Other methods known in the art for introducing nucleic acids to cells may be used, such as lipid-mediated carrier transport, chemical-mediated transport, such as calcium phosphate, and the like. Thus the nucleic acid may be introduced along with components that perform one or more of the following activities: enhance nucleic acid uptake by the cell, inhibit annealing of single strands, stabilize the single strands, or other-wise increase inhibition of the target gene.
Nucleic acid may be directly introduced into the cell (i.e., intracellularly); or introduced extracellularly into a cavity, interstitial space, into the circulation of an organism, introduced orally or by inhalation, or may be introduced by bathing a cell or organism in a solution containing the nucleic acid. Vascular or extravascular circulation, the blood or lymph system, and the cerebrospinal fluid are sites where the nucleic acid may be introduced.
The cell with the target gene may be derived from or contained in any organism. The organism may a plant, animal, protozoan, bacterium, virus, or fungus. The plant may be a monocot, dicot or gymnosperm; the animal may be a vertebrate or invertebrate. Preferred microbes are those used in agriculture or by industry, and those that are pathogenic for plants or animals.
Alternatively, vectors, e.g., transgenes encoding a siRNA of the invention can be engineered into a host cell or transgenic animal using art recognized techniques.
Another use for the nucleic acids of the present invention (or vectors or transgenes encoding same) is a functional analysis to be carried out in eukaryotic cells, or eukaryotic non-human organisms, preferably mammalian cells or organisms and most preferably human cells, e.g. cell lines such as HeLa or 293 or rodents, e.g. rats and mice. By administering a suitable nucleic acid of the invention which is sufficiently complementary to a target mRNA sequence to direct target-specific RNA interference, a specific knockout or knockdown phenotype can be obtained in a target cell, e.g. in cell culture or in a target organism.
Thus, a further subject matter of the invention is a eukaryotic cell or a eukaryotic non-human organism exhibiting a target gene-specific knockout or knockdown phenotype comprising a fully or at least partially deficient expression of at least one endogenous target gene wherein said cell or organism is transfected with at least one vector comprising DNA encoding an RNAi agent capable of inhibiting the expression of the target gene. It should be noted that the present invention allows a target-specific knockout or knockdown of several different endogenous genes due to the specificity of the RNAi agent.
Gene-specific knockout or knockdown phenotypes of cells or non-human organisms, particularly of human cells or non-human mammals may be used in analytic to procedures, e.g. in the functional and/or phenotypical analysis of complex physiological processes such as analysis of gene expression profiles and/or proteomes. Preferably the analysis is carried out by high throughput methods using oligonucleotide based chips.
Assays of Oligonucleotide Stability
In some embodiments, the oligonucleotides of the invention are stabilized, i.e., substantially resistant to endonuclease and exonuclease degradation. An oligonucleotide is defined as being substantially resistant to nucleases when it is at least about 3-fold more resistant to attack by an endogenous cellular nuclease, and is highly nuclease resistant when it is at least about 6-fold more resistant than a corresponding oligonucleotide. This can be demonstrated by showing that the oligonucleotides of the invention are substantially resistant to nucleases using techniques which are known in the art.
One way in which substantial stability can be demonstrated is by showing that the oligonucleotides of the invention function when delivered to a cell, e.g., that they reduce transcription or translation of target nucleic acid molecules, e.g., by measuring protein levels or by measuring cleavage of mRNA. Assays which measure the stability of target RNA can be performed at about 24 hours post-transfection (e.g., using Northern blot techniques, RNase Protection Assays, or QC-PCR assays as known in the art). Alternatively, levels of the target protein can be measured. Preferably, in addition to testing the RNA or protein levels of interest, the RNA or protein levels of a control, non-targeted gene will be measured (e.g., actin, or preferably a control with sequence similarity to the target) as a specificity control. RNA or protein measurements can be made using any art-recognized technique. Preferably, measurements will be made beginning at about 16-24 hours post transfection. (M. Y. Chiang, et al. 1991. J Biol Chem. 266:18162-71; T. Fisher, et al. 1993. Nucleic Acids Research. 21 3857).
The ability of an oligonucleotide composition of the invention to inhibit protein synthesis can be measured using techniques which are known in the art, for example, by detecting an inhibition in gene transcription or protein synthesis. For example, Nuclease Si mapping can be performed. In another example, Northern blot analysis can be used to measure the presence of RNA encoding a particular protein. For example, total RNA can be prepared over a cesium chloride cushion (see, e.g., Ausebel et al., 1987. Current Protocols in Molecular Biology (Greene & Wiley, New York)). Northern blots can then be made using the RNA and probed (see, e.g., Id.). In another example, the level of the specific mRNA produced by the target protein can be measured, e.g., using PCR. In yet another example, Western blots can be used to measure the amount of target protein present. In still another embodiment, a phenotype influenced by the amount of the protein can be detected. Techniques for performing Western blots are well known in the art, see, e.g., Chen et al. J. Biol. Chem. 271:28259.
In another example, the promoter sequence of a target gene can be linked to a reporter gene and reporter gene transcription (e.g., as described in more detail below) can be monitored. Alternatively, oligonucleotide compositions that do not target a promoter can be identified by fusing a portion of the target nucleic acid molecule with a reporter gene so that the reporter gene is transcribed. By monitoring a change in the expression of the reporter gene in the presence of the oligonucleotide composition, it is possible to determine the effectiveness of the oligonucleotide composition in inhibiting the expression of the reporter gene. For example, in one embodiment, an effective oligonucleotide composition will reduce the expression of the reporter gene.
A “reporter gene” is a nucleic acid that expresses a detectable gene product, which may be RNA or protein. Detection of mRNA expression may be accomplished by Northern blotting and detection of protein may be accomplished by staining with antibodies specific to the protein. Preferred reporter genes produce a readily detectable product. A reporter gene may be operably linked with a regulatory DNA sequence such that detection of the reporter gene product provides a measure of the transcriptional activity of the regulatory sequence. In preferred embodiments, the gene product of the reporter gene is detected by an intrinsic activity associated with that product. For instance, the reporter gene may encode a gene product that, by enzymatic activity, gives rise to a detectable signal based on color, fluorescence, or luminescence. Examples of reporter genes include, but are not limited to, those coding for chloramphenicol acetyl transferase (CAT), luciferase, beta-galactosidase, and alkaline phosphatase.
One skilled in the art would readily recognize numerous reporter genes suitable for use in the present invention. These include, but are not limited to, chloramphenicol acetyltransferase (CAT), luciferase, human growth hormone (hGH), and beta-galactosidase. Examples of such reporter genes can be found in F. A. Ausubel et al., Eds., Current Protocols in Molecular Biology, John Wiley & Sons, New York, (1989). Any gene that encodes a detectable product, e.g., any product having detectable enzymatic activity or against which a specific antibody can be raised, can be used as a reporter gene in the present methods.
One reporter gene system is the firefly luciferase reporter system. (Gould, S. J., and Subramani, S. 1988. Anal. Biochem., 7:404-408 incorporated herein by reference). The luciferase assay is fast and sensitive. In this assay, a lysate of the test cell is prepared and combined with ATP and the substrate luciferin. The encoded enzyme luciferase catalyzes a rapid, ATP dependent oxidation of the substrate to generate a light-emitting product. The total light output is measured and is proportional to the amount of luciferase present over a wide range of enzyme concentrations.
CAT is another frequently used reporter gene system; a major advantage of this system is that it has been an extensively validated and is widely accepted as a measure of promoter activity. (Gorman C. M., Moffat, L. F., and Howard, B. H. 1982. Mol. Cell. Biol., 2:1044-1051). In this system, test cells are transfected with CAT expression vectors and incubated with the candidate substance within 2-3 days of the initial transfection. Thereafter, cell extracts are prepared. The extracts are incubated with acetyl CoA and radioactive chloramphenicol. Following the incubation, acetylated chloramphenicol is separated from nonacetylated form by thin layer chromatography. In this assay, the degree of acetylation reflects the CAT gene activity with the particular promoter.
Another suitable reporter gene system is based on immunologic detection of hGH. This system is also quick and easy to use. (Selden, R., Burke-Howie, K. Rowe, M. E., Goodman, H. M., and Moore, D. D. (1986), Mol. Cell, Biol., 6:3173-3179 incorporated herein by reference). The hGH system is advantageous in that the expressed hGH polypeptide is assayed in the media, rather than in a cell extract. Thus, this system does not require the destruction of the test cells. It will be appreciated that the principle of this reporter gene system is not limited to hGH but rather adapted for use with any polypeptide for which an antibody of acceptable specificity is available or can be prepared.
In one embodiment, nuclease stability of a double-stranded oligonucleotide of the invention is measured and compared to a control, e.g., an RNAi molecule typically used in the art (e.g., a duplex oligonucleotide of less than 25 nucleotides in length and comprising 2 nucleotide base overhangs) or an unmodified RNA duplex with blunt ends.
The target RNA cleavage reaction achieved using the siRNAs of the invention is highly sequence specific. Sequence identity may determined by sequence comparison and alignment algorithms known in the art. To determine the percent identity of two nucleic acid sequences (or of two amino acid sequences), the sequences are aligned for optimal comparison purposes (e.g., gaps can be introduced in the first sequence or second sequence for optimal alignment). A preferred, non-limiting example of a local alignment algorithm utilized for the comparison of sequences is the algorithm of Karlin and Altschul (1990) Proc. Natl. Acad. Sci. USA 87:2264-68, modified as in Karlin and Altschul (1993) Proc. Natl. Acad. Sci. USA 90:5873-77. Such an algorithm is incorporated into the BLAST programs (version 2.0) of Altschul, et al. (1990) J. Mol. Biol. 215:403-10. Additionally, numerous commercial entities, such as Dharmacon, and Invitrogen provide access to algorithms on their website. The Whitehead Institute also offers a free siRNA Selection Program. Greater than 90% sequence identity, e.g., 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or even 100% sequence identity, between the siRNA and the portion of the target gene is preferred. Alternatively, the siRNA may be defined functionally as a nucleotide sequence (or oligonucleotide sequence) that is capable of hybridizing with a portion of the target gene transcript. Examples of stringency conditions for polynucleotide hybridization are provided in Sambrook, J., E. F. Fritsch, and T. Maniatis, 1989, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y., chapters 9 and 11, and Current Protocols in Molecular Biology, 1995, F. M. Ausubel et al., eds., John Wiley & Sons, Inc., sections 2.10 and 6.3-6.4, incorporated herein by reference.
Therapeutic Use
By inhibiting the expression of a gene, the oligonucleotide compositions of the present invention can be used to treat any disease involving the expression of a protein. Examples of diseases that can be treated by oligonucleotide compositions, just to illustrate, include: cancer, retinopathies, autoimmune diseases, inflammatory diseases (i.e., ICAM-1 related disorders, Psoriasis, Ulcerative Colitus, Crohn's disease), viral diseases (i.e., HIV, Hepatitis C), miRNA disorders, and cardiovascular diseases.
In one embodiment, in vitro treatment of cells with oligonucleotides can be used for ex vivo therapy of cells removed from a subject (e.g., for treatment of leukemia or viral infection) or for treatment of cells which did not originate in the subject, but are to be administered to the subject (e.g., to eliminate transplantation antigen expression on cells to be transplanted into a subject). In addition, in vitro treatment of cells can be used in non-therapeutic settings, e.g., to evaluate gene function, to study gene regulation and protein synthesis or to evaluate improvements made to oligonucleotides designed to modulate gene expression or protein synthesis. In vivo treatment of cells can be useful in certain clinical settings where it is desirable to inhibit the expression of a protein. There are numerous medical conditions for which antisense therapy is reported to be suitable (see, e.g., U.S. Pat. No. 5,830,653) as well as respiratory syncytial virus infection (WO 95/22,553) influenza virus (WO 94/23,028), and malignancies (WO 94/08,003). Other examples of clinical uses of antisense sequences are reviewed, e.g., in Glaser. 1996. Genetic Engineering News 16:1. Exemplary targets for cleavage by oligonucleotides include, e.g., protein kinase Ca, ICAM-1, c-raf kinase, p53, c-myb, and the bcr/abl fusion gene found in chronic myelogenous leukemia.
The subject nucleic acids can be used in RNAi-based therapy in any animal having RNAi pathway, such as human, non-human primate, non-human mammal, non-human vertebrates, rodents (mice, rats, hamsters, rabbits, etc.), domestic livestock animals, pets (cats, dogs, etc.), Xenopus, fish, insects (Drosophila, etc.), and worms (C. elegans), etc.
The invention provides methods for inhibiting or preventing in a subject, a disease or condition associated with an aberrant or unwanted target gene expression or activity, by administering to the subject a nucleic acid of the invention. If appropriate, subjects are first treated with a priming agent so as to be more responsive to the subsequent RNAi therapy. Subjects at risk for a disease which is caused or contributed to by aberrant or unwanted target gene expression or activity can be identified by, for example, any or a combination of diagnostic or prognostic assays known in the art. Administration of a prophylactic agent can occur prior to the manifestation of symptoms characteristic of the target gene aberrancy, such that a disease or disorder is prevented or, alternatively, delayed in its progression. Depending on the type of target gene aberrancy, for example, a target gene, target gene agonist or target gene antagonist agent can be used for treating the subject.
In another aspect, the invention pertains to methods of modulating target gene expression, protein expression or activity for therapeutic purposes. Accordingly, in an exemplary embodiment, the methods of the invention involve contacting a cell capable of expressing target gene with a nucleic acid of the invention that is specific for the target gene or protein (e.g., is specific for the mRNA encoded by said gene or specifying the amino acid sequence of said protein) such that expression or one or more of the activities of target protein is modulated. These methods can be performed in vitro (e.g., by culturing the cell with the agent), in vivo (e.g., by administering the agent to a subject), or ex vivo. The subjects may be first treated with a priming agent so as to be more responsive to the subsequent RNAi therapy if desired. As such, the present invention provides methods of treating a subject afflicted with a disease or disorder characterized by aberrant or unwanted expression or activity of a target gene polypeptide or nucleic acid molecule. Inhibition of target gene activity is desirable in situations in which target gene is abnormally unregulated and/or in which decreased target gene activity is likely to have a beneficial effect.
Thus the therapeutic agents of the invention can be administered to subjects to treat (prophylactically or therapeutically) disorders associated with aberrant or unwanted target gene activity. In conjunction with such treatment, pharmacogenomics (i.e., the study of the relationship between an individual's genotype and that individual's response to a foreign compound or drug) may be considered. Differences in metabolism of therapeutics can lead to severe toxicity or therapeutic failure by altering the relation between dose and blood concentration of the pharmacologically active drug. Thus, a physician or clinician may consider applying knowledge obtained in relevant pharmacogenomics studies in determining whether to administer a therapeutic agent as well as tailoring the dosage and/or therapeutic regimen of treatment with a therapeutic agent. Pharmacogenomics deals with clinically significant hereditary variations in the response to drugs due to altered drug disposition and abnormal action in affected persons.
For the purposes of the invention, ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
Moreover, for the purposes of the present invention, the term “a” or “an” entity refers to one or more of that entity; for example, “a protein” or “a nucleic acid molecule” refers to one or more of those compounds or at least one compound. As such, the terms “a” (or “an”), “one or more” and “at least one” can be used interchangeably herein. It is also to be noted that the terms “comprising”, “including”, and “having” can be used interchangeably. Furthermore, a compound “selected from the group consisting of” refers to one or more of the compounds in the list that follows, including mixtures (i.e., combinations) of two or more of the compounds. According to the present invention, an isolated, or biologically pure, protein or nucleic acid molecule is a compound that has been removed from its natural milieu. As such, “isolated” and “biologically pure” do not necessarily reflect the extent to which the compound has been purified. An isolated compound of the present invention can be obtained from its natural source, can be produced using molecular biology techniques or can be produced by chemical synthesis.
The present invention is further illustrated by the following Examples, which in no way should be construed as further limiting. The entire contents of all of the references (including literature references, issued patents, published patent applications, and co-pending patent applications) cited throughout this application are hereby expressly incorporated by reference.
Transfection of Minimum Length Trigger (mlt) RNA
mltRNA constructs were chemically synthesized (Integrated DNA Technologies, Coralville, Iowa) and transfected into HEK293 cells (ATCC, Manassas, Va.) using the Lipofectamine RNAiMAX (Invitrogen, Carlsbad, Calif.) reagent according to manufacturer's instructions. In brief, RNA was diluted to a 12× concentration and then combined with a 12× concentration of Lipofectamine RNAiMAX to complex. The RNA and transfection reagent were allowed to complex at room temperature for 20 minutes and make a 6× concentration. While complexing, HEK293 cells were washed, trypsinized and counted. The cells were diluted to a concentration recommended by the manufacturer and previously described conditions which was at 1×105 cells/ml. When RNA had completed complexing with the RNAiMAX transfection reagent, 20 ul of the complexes were added to the appropriate well of the 96-well plate in triplicate. Cells were added to each well (100 ul volume) to make the final cell count per well at 1×104 cells/well. The volume of cells diluted the 6× concentration of complex to 1× which was equal to a concentration noted (between 10-0.05 nM). Cells were incubated for 24 or 48 hours under normal growth conditions.
After 24 or 48 hour incubation cells were lysed and gene silencing activity was measured using the QuantiGene assay (Panomics, Freemont, Calif.) which employs bDNA hybridization technology. The assay was carried out according to manufacturer's instructions.
ΔG Calculation
ΔG was calculated using Mfold, available through the Mfold internet site (http://mfold.bioinfo.rpi.edu/cgi-bin/rna-form1.cgi). Methods for calculating ΔG are described in, and are incorporated by reference from, the following references: Zuker, M. (2003) Nucleic Acids Res., 31(13):3406-15; Mathews, D. H., Sabina, J., Zuker, M. and Turner, D. H. (1999) J. Mol. Biol. 288:911-940; Mathews, D. H., Disney, M. D., Childs, J. L., Schroeder, S. J., Zuker, M., and Turner, D. H. (2004) Proc. Natl. Acad. Sci. 101:7287-7292; Duan, S., Mathews, D. H., and Turner, D. H. (2006) Biochemistry 45:9819-9832; Wuchty, S., Fontana, W., Hofacker, I. L., and Schuster, P. (1999) Biopolymers 49:145-165.
Asymmetric double stranded RNAi molecules, with minimal double stranded regions, were developed herein and are highly effective at gene silencing. These molecules can contain a variety of chemical modifications on the sense and/or anti-sense strands, and can be conjugated to sterol-like compounds such as cholesterol.
Chemical modifications of polynucleotides, such as the guide strand in a duplex molecule, can facilitate RISC entry.
The RNA molecules described herein were subject to a variety of chemical modifications on the sense and antisense strands, and the effects of such modifications were observed. RNAi molecules were synthesized and optimized through testing of a variety of modifications. In first generation optimization, the sense (passenger) and anti-sense (guide) strands of the sd-rxRNAnano molecules were modified for example through incorporation of C and U 2′OMe modifications, 2′F modifications, phosphorothioate modifications, phosphorylation, and conjugation of cholesterol. Molecules were tested for inhibition of MAP4K4 expression in cells including HeLa, primary mouse hepatocytes and primary human hepatocytes through both lipid-mediated and passive uptake transfection.
Optimization of the length of the oligonucleotide was also investigated.
The importance of phosphorothioate content of the RNA molecule for unassisted delivery was also investigated.
A summary of 1st generation sd-rxRNA molecules is presented in
Modifications to the sense strand were also developed and tested, as depicted in
Based on the above-described optimization experiments, 2nd generation RNA molecules were developed. As shown in
Linker chemistry was also tested in conjunction with the RNA molecules associated with the invention. As depicted in
Stability of the chemically modified sd-rxRNA molecules described herein in human serum is shown in
Based on the analysis of 2nd generation RNA molecules associated with the invention, a screen was performed to identify functional molecules for targeting the SPP1/PPIB gene. As revealed in
The effect of 5-Methyl C modifications was also examined.
The addition of hydrophobic conjugates to the sd-rxRNA molecules was also explored (
A screen was conducted to identify compounds that could effectively silence expression of SPP1 (Osteopontin). Compounds targeting SPP1 were added to A549 cells (using passive transfection), and the level of SPP1 expression was evaluated at 48 hours. Several novel compounds effective in SPP1 silencing were identified. Compounds that were effective in silencing of SPP1 included 14116, 14121, 14131, 14134, 14139, 14149, and 14152 (
A similar screen was conducted to identify compounds that could effectively silence expression of CTGF (
Methods
Transfection of sd-rxRNAnano
Lipid Mediated Transfection
sd-rxRNAnano constructs were chemically synthesized (Dharmacon, Lafayette, Colo.) and transfected into HEK293 cells (ATCC, Manassas, Va.) using Lipofectamine RNAiMAX (Invitrogen, Carlsbad, Calif.) according to the manufacturer's instructions. In brief, RNA was diluted to a 12× concentration in Opti-MEM®1 Reduced Serum Media (Invitrogen, Carlsbad, Calif.) and then combined with a 12× concentration of Lipofectamine RNAiMAX. The RNA and transfection reagent were allowed to complex at room temperature for 20 minutes and make a 6× concentration. While complexing, HEK293 cells were washed, trypsinized and counted. The cells were diluted to a concentration recommended by the manufacturer and previously described of 1×105 cells/ml. When RNA had completed complexing with the RNAiMAX transfection reagent, 20 ul of the complexes were added to the appropriate well of the 96-well plate in triplicate. Cells were added to each well (100 ul volume) to make the final cell count per well 1×104 cells/well. The volume of cells diluted the 6× concentration of complex to 1× (between 10-0.05 nM). Cells were incubated for 24 or 48 hours under normal growth conditions. After 24 or 48 hour incubation, cells were lysed and gene silencing activity was measured using the QuantiGene assay (Panomics, Freemont, Calif.) which employs bDNA hybridization technology. The assay was carried out according to manufacturer's instructions.
Passive Uptake Transfection
sd-rxRNAnano constructs were chemically synthesized (Dharmacon, Lafayette, Colo.). 24 hours prior to transfection, HeLa cells (ATCC, Manassas, Va.) were plated at 1×104 cells/well in a 96 well plate under normal growth conditions (DMEM, 10% FBS and 1% Penicillin and Streptomycin). Prior to transfection of HeLa cells, sd-rxRNAnano were diluted to a final concentration of 0.01 uM to 1 uM in Accell siRNA Delivery Media (Dharmacon, Lafayette, Colo.). Normal growth media was aspirated off cells and 100 uL of Accell Delivery media containing the appropriate concentration of sd-rxRNAnano was applied to the cells. 48 hours post transfection, delivery media was aspirated off the cells and normal growth media was applied to cells for an additional 24 hours.
After 48 or 72 hour incubation, cells were lysed and gene silencing activity was measured using the QuantiGene assay (Panomics, Freemont, Calif.) according to manufacturer's instructions.
12138
Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.
Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.
All references, including patent documents, disclosed herein are incorporated by reference in their entirety. This application incorporates by reference the entire contents, including all the drawings and all parts of the specification (including sequence listing or amino acid/polynucleotide sequences) of the co-pending U.S. Provisional Application No. 61/135,855, filed on Jul. 24, 2008, entitled “SHORT HAIRPIN RNAI CONSTRUCTS AND USES THEREOF,” and U.S. Provisional Application No. 61/197,768, filed on Oct. 30, 2008, entitled “MINIRNA CONSTRUCTS AND USES THEREOF.”
This application claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application serial number U.S. 61/192,954, entitled “Chemically Modified Polynucleotides and Methods of Using the Same,” filed on Sep. 22, 2008, U.S. 61/149,946, entitled “Minimum Length Triggers of RNA Interference,” filed on Feb. 4, 2009, and U.S. 61/224,031, entitled “Minimum Length Triggers of RNA Interference,” filed on Jul. 8, 2009, the disclosure of each of which is incorporated by reference herein in its entirety.
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| Number | Date | Country | |
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| Parent | 13120342 | US | |
| Child | 14278900 | US |
