Muscle-targeting complexes and their use for treating friedreich's ataxia - Patents.com

Abstract

This application relates to oligonucleotides (e.g., antisense oligonucleotides such as gapmers) designed to target FXN RNA and targeting complexes for delivering oligonucleotides to cells (e.g., muscle cells) and their uses, particularly for the treatment of disease. In some embodiments, the muscle targeting agent specifically binds to an internalizing cell surface receptor on muscle cells. In some embodiments, the molecular payload increases the expression or activity of FXN alleles that contain disease-associated repeats.

Description

[Technical field]

[0001] Related Applications This application claims priority under 35 USC § 119(e) to U.S. Provisional Application No. 63 / 212,816, entitled “MUSCLE-TARGETING COMPLEXES AND USES THEREOF FOR TREATING FRIEDREICH'S ATAXIA,” filed June 21, 2021, the entire contents of which are incorporated herein by reference.

[0002] Reference to a sequence listing submitted as a text file via EFS-WEB It has been submitted in ASCII format via EFS-Web and is incorporated herein by reference in its entirety. The ASCII copy, created on Jun. 17, 2022, is designated D082470049WO00-SEQ-ZJG and is 191,024 bytes in size.

[0003] FIELD OF THEINVENTION This application relates to oligonucleotides designed to target FXN RNA and targeting complexes for delivering oligonucleotides to cells (e.g., muscle cells) and their uses, particularly for the treatment of disease. [Background technology]

[0004] background Friedreich's ataxia is a rare autosomal recessive disorder that results in progressive damage to muscle tissue and the nervous system. The disease is characterized by severe cardiac conditions, including hypertrophic cardiomyopathy, myocardial fibrosis and heart failure, and degeneration of nerve fibers in the spinal cord and peripheral nervous system. Friedreich's ataxia results from mutations in the FXN gene, which codes for frataxin, a protein described to function in iron homeostasis. Specifically, subjects with the disease have an expanded trinucleotide GAA sequence that results in reduced levels of frataxin. Friedreich's ataxia is the most common form of hereditary ataxia, with an incidence of approximately 1 in 50,000. In the most severe cases, subjects with the disease are unable to walk freely by age 10-20, and many subjects have a shortened life expectancy. In Friedreich's ataxia, the decrease in FXN expression may be due to epigenetic silencing and / or may result from a reduced ability to splice out the first intron of the FXN pre-mRNA, which contains an expanded GAA repeat. Except for supportive therapy to address the symptoms of the disease, there is currently no effective treatment available for Friedreich's ataxia. Summary of the Invention

[0005] overview According to some aspects, the disclosure provides oligonucleotides designed to target FXN RNA. In some embodiments, the disclosure provides oligonucleotides complementary to FXN RNA, useful for increasing the level of functional FXN by blocking FXN RNA containing expanded GAA repeats in subjects with or suspected of having Friedreich's ataxia, for example. In some embodiments, the oligonucleotides are designed to direct RNase H-mediated degradation of FXN RNA containing expanded GAA repeats. In some embodiments, the oligonucleotides are designed to inhibit the formation of an RNA loop (R-loop) by FXN RNA containing expanded GAA repeats with chromosomal DNA. In some embodiments, the oligonucleotides are designed to enhance FXN protein levels by inhibiting the formation of an RNA loop (R-loop) between FXN RNA containing expanded GAA repeats and chromosomal DNA. In some embodiments, the oligonucleotides are designed to have desirable bioavailability and / or serum stability. In some embodiments, the oligonucleotides are designed to have desirable binding affinity properties. In some embodiments, the oligonucleotides are designed to have desirable toxicity profiles. In some embodiments, the oligonucleotides are designed to have low complement activation and / or cytokine inducing properties.

[0006] In some embodiments, the oligonucleotides provided herein are conjugated to other molecules, e.g., targeting agents, e.g., muscle targeting agents. Thus, in some aspects, the disclosure provides complexes that target specific cell types for the purpose of delivering oligonucleotides to those cells. For example, in some embodiments, the disclosure provides complexes that target muscle cells for the purpose of delivering oligonucleotides to muscle cells. In some embodiments, the complexes provided herein are particularly useful for delivering molecular payloads that increase the expression or activity of functional FXN protein by reducing the level of FXN RNA containing expanded disease-associated repeats, e.g., in subjects with or suspected of having Friedreich's ataxia. In some embodiments, the complexes provided herein include a muscle targeting agent (e.g., a muscle targeting antibody) that specifically binds to a receptor on the surface of a muscle cell for the purpose of delivering the molecular payload to the muscle cell. In some embodiments, the complexes are taken up into the cell via receptor-mediated internalization, whereupon the molecular payload may be released inside the cell to perform its function. For example, a complex engineered to deliver an oligonucleotide may release the oligonucleotide so that the oligonucleotide can block mutant FXN in the muscle cell. In some embodiments, the oligonucleotide is released by endosomal cleavage of a covalent linker that connects the oligonucleotide and the muscle-targeting agent of the complex.

[0007] Some aspects of the disclosure provide a complex comprising a muscle targeting agent covalently linked to an oligonucleotide configured to increase FXN expression, wherein the oligonucleotide comprises a region of complementarity to a repeat region of FXN RNA that contains an expanded GAA repeat associated with a disease, the repeat region comprising a target sequence set forth in any one of SEQ ID NOs: 162-164, and the region of complementarity is at least 12 nucleotides in length.

[0008] In some embodiments, the muscle targeting agent is an anti-transferrin receptor 1 (TfR1) antibody.

[0009] In some embodiments, the oligonucleotide comprises at least 16 contiguous nucleotides of any one of SEQ ID NOs: 165-176, where each U is optionally and independently T. In some embodiments, the oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-176, where each U is optionally and independently T.

[0010] In some embodiments, the oligonucleotide comprises a 5'-XYZ-3' configuration, where X comprises 3 to 5 linked nucleosides, at least one of the nucleosides in X is a 2'-modified nucleoside, Y comprises 6 to 14 linked 2'-deoxyribonucleosides, each cytidine in Y is optionally independently a 5-methyl-cytidine, and Z comprises 3 to 5 linked nucleosides, at least one of the nucleosides in Z is a 2'-modified nucleoside.

[0011] In some embodiments, the oligonucleotide comprises a nucleotide sequence of any one of SEQ ID NOs: 165-167, wherein X comprises 5 linked nucleosides, each nucleoside in X is a 2'-MOE modified nucleoside, Y comprises 10 linked 2'-deoxyribonucleosides, each cytidine in Y is optionally independently a 5-methyl-cytidine, and Z comprises 5 linked nucleosides, each nucleoside in Z is a 2'-MOE modified nucleoside.

[0012] In some embodiments, the oligonucleotide comprises a nucleotide sequence of any one of SEQ ID NOs: 165-167, wherein X comprises 5 linked nucleosides, each nucleoside in X is an LNA nucleoside, Y comprises 10 linked 2'-deoxyribonucleosides, each cytidine in Y is optionally independently a 5-methyl-cytidine, and Z comprises 5 linked nucleosides, each nucleoside in Z is an LNA nucleoside.

[0013] In some embodiments, the oligonucleotide comprises a nucleotide sequence of any one of SEQ ID NOs: 171-173, wherein X comprises 3 linked nucleosides, each nucleoside in X is an LNA nucleoside, Y comprises 14 linked 2'-deoxyribonucleosides, each cytidine in Y is optionally independently a 5-methyl-cytidine, and Z comprises 3 linked nucleosides, each nucleoside in Z is an LNA nucleoside.

[0014] In some embodiments, the oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 168-170, and each nucleoside of the oligonucleotide is a 2'-MOE modified nucleoside.

[0015] In some embodiments, the oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 168-170, wherein each T in the oligonucleotide is an LNA nucleoside and each C in the oligonucleotide is a 5-methyl-deoxycytidine.

[0016] In some embodiments, the oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 174-176, wherein each C in the oligonucleotide is an LNA nucleoside and each T is a deoxythymidine.

[0017] In some embodiments, the oligonucleotide comprises one or more phosphorothioate internucleoside linkages. In some embodiments, each internucleoside linkage in the oligonucleotide is a phosphorothioate internucleoside linkage.

[0018] In some embodiments, the oligonucleotide is selected from the following: [Table A] In the table, "xdC" indicates 5-methyl-deoxycytidine, "dN" indicates 2'-deoxyribonucleoside, "+N" indicates LNA nucleoside, "oN" indicates 2'-MOE modified ribonucleoside, "oC" indicates 5-methyl-2'-MOE-cytidine, "+C" indicates 5-methyl-2'-4'-bicyclic-cytidine (2'-4' methylene bridge), "oU" indicates 5-methyl-2'-MOE-uridine, "+U" indicates 5-methyl-2'-4'-bicyclic uridine (2'-4' methylene bridge), and "*" indicates a phosphorothioate internucleoside bond.

[0019] In some embodiments, the anti-TfR1 antibody comprises heavy chain complementarity determining region 1 (CDR-H1), heavy chain complementarity determining region 2 (CDR-H2), heavy chain complementarity determining region 3 (CDR-H3), light chain complementarity determining region 1 (CDR-L1), light chain complementarity determining region 2 (CDR-L2), and light chain complementarity determining region 3 (CDR-L3) of any of the anti-TfR1 antibodies listed in Table 2.

[0020] In some embodiments, the anti-TfR1 antibody comprises the heavy chain variable region (VH) and light chain variable region (VL) of any of the anti-TfR1 antibodies listed in Table 3. In some embodiments, the anti-TfR1 antibody is a Fab. In some embodiments, the Fab comprises the heavy and light chains of any of the anti-TfR1 Fabs listed in Table 5.

[0021] In some embodiments, the muscle targeting agent and the oligonucleotide are covalently linked via a linker. In some embodiments, the linker comprises a valine-citrulline sequence.

[0022] Some aspects of the disclosure provide a method for increasing FXN expression in a muscle cell, the method comprising contacting the muscle cell with an effective amount of a complex described herein to promote internalization of an oligonucleotide into the muscle cell.

[0023] Some aspects of the present disclosure provide a method of treating Friedreich's ataxia (FA), the method comprising administering to a subject in need thereof an effective amount of a complex described herein, wherein the subject has a mutant FXN allele that includes a disease-associated GAA repeat.

[0024] In some embodiments, administration of the complex results in an increase in FXN protein levels.

[0025] Some aspects of the disclosure provide an oligonucleotide selected from: [Table B-1] [Table B-2] In the table, "xdC" indicates 5-methyl-deoxycytidine, "dN" indicates 2'-deoxyribonucleoside, "+N" indicates LNA nucleoside, "oN" indicates 2'-MOE modified ribonucleoside, "oC" indicates 5-methyl-2'-MOE-cytidine, "+C" indicates 5-methyl-2'-4'-bicyclic-cytidine (2'-4' methylene bridge), "oU" indicates 5-methyl-2'-MOE-uridine, "+U" indicates 5-methyl-2'-4'-bicyclic uridine (2'-4' methylene bridge), and "*" indicates a phosphorothioate internucleoside bond.

[0026] Compositions comprising the oligonucleotides described herein in sodium salt form are also provided. [Brief description of the drawings]

[0027] [Figure 1A-D]Figure 1A-1H show that a conjugate having an anti-TfR1 Fab conjugated to a DMPK-targeting oligonucleotide reduced mouse DMPK expression in various muscle tissues of a mouse model expressing human TfR1. The DMPK-targeting oligonucleotide was conjugated to anti-TfR1 Fab 3M12-VH4 / VK3. Figure 1A shows that the conjugate reduced mouse wild-type Dmpk in the tibialis anterior muscle by 79%. Figure 1B shows that the conjugate reduced mouse wild-type Dmpk in the gastrocnemius muscle by 76%. Figure 1C shows that the conjugate reduced mouse wild-type Dmpk in the heart by 70%. Figure 1D shows that the conjugate reduced mouse wild-type Dmpk in the diaphragm by 88%. [Figure 1E-H] Figure 1E-H show oligonucleotide distribution in the tibialis anterior (Figure 1E), gastrocnemius (Figure 1F), heart (Figure 1G) and diaphragm (Figure 1H). All tissues showed increased levels of oligonucleotide compared to vehicle controls. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Detailed Description According to some aspects, the disclosure provides oligonucleotides designed to target FXN RNA. In some embodiments, the disclosure provides oligonucleotides complementary to FXN RNA, useful for increasing the level of functional FXN-blocking FXN RNA containing expanded GAA repeats, for example in subjects with or suspected of having Friedreich's ataxia. In some embodiments, the oligonucleotides are designed to direct RNase H-mediated degradation of FXN RNA containing expanded GAA repeats. In some embodiments, the oligonucleotides are designed to inhibit the formation of RNA loops (R-loops) by FXN RNA containing expanded GAA repeats with chromosomal DNA. In some embodiments, the oligonucleotides are designed to have desirable bioavailability and / or serum stability. In some embodiments, the oligonucleotides are designed to have desirable binding affinity properties. In some embodiments, the oligonucleotides are designed to have desirable toxicity profiles. In some embodiments, the oligonucleotides are designed to have low complement activation and / or cytokine induction properties.

[0029] In some embodiments, the oligonucleotides provided herein are conjugated to other molecules, e.g., targeting agents, e.g., muscle targeting agents. Thus, in some aspects, the disclosure provides complexes that target specific cell types for the purpose of delivering oligonucleotides to those cells. For example, in some embodiments, the disclosure provides complexes that target muscle cells for the purpose of delivering oligonucleotides to muscle cells. In some embodiments, the complexes provided herein are particularly useful for delivering molecular payloads that increase the expression or activity of functional FXN protein by reducing the level of FXN RNA containing expanded disease-associated repeats, e.g., in subjects with or suspected of having Friedreich's ataxia. In some embodiments, the complexes provided herein include a muscle targeting agent (e.g., a muscle targeting antibody) that specifically binds to a receptor on the surface of a muscle cell for the purpose of delivering the molecular payload to the muscle cell. In some embodiments, the complexes are taken up into the cell via receptor-mediated internalization, whereupon the molecular payload may be released inside the cell to perform its function. For example, a complex engineered to deliver an oligonucleotide may release the oligonucleotide so that the oligonucleotide can block mutant FXN in the muscle cell. In some embodiments, the oligonucleotide is released by endosomal cleavage of a covalent linker that connects the oligonucleotide and the muscle-targeting agent of the complex.

[0030] As an example, oligonucleotides can target the R-loop portion of FXN with an expansion of GAA repeats to increase frataxin expression. In some embodiments, as an example, inhibition of R-loop formation by a molecular payload that can bind to the expanded GAA repeats can allow normal expression of the FXN gene and treatment of disease. In some embodiments, the complexes provided herein can include a molecular payload, such as an antisense oligonucleotide (ASO), that can target the disease-associated repeat GAA sequence of FXN or a sequence in its vicinity. Further aspects of the disclosure, including a description of defined terms, are provided below.

[0031] I. Definition Administering: As used herein, the term "administering" or "administration" means providing a conjugate to a subject in a physiologically and / or (for example and) pharmacologically useful manner (for example, to treat a disease in a subject).

[0032] about: As used herein, the term "approximately" or "about" when applied to one or more values ​​of interest refers to a value similar to a stated reference value. In certain embodiments, the term "approximately" or "about" refers to a broad range of values ​​that fall within plus or minus (greater or less than) 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, or less of the stated reference value, unless otherwise stated or clear from the context (except where such number exceeds 100% of a feasible value).

[0033] antibody: As used herein, the term "antibody" refers to a polypeptide that includes at least one immunoglobulin variable domain or at least one antigenic determinant, e.g., a paratope, that specifically binds to an antigen. In some embodiments, the antibody is a full-length antibody. In some embodiments, the antibody is a chimeric antibody. In some embodiments, the antibody is a humanized antibody. However, in some embodiments, the antibody is a Fab fragment, a Fab' fragment, a F(ab')2 fragment, an Fv fragment, or an scFv fragment. In some embodiments, the antibody is a nanobody derived from a camelid antibody or a nanobody derived from a shark antibody. In some embodiments, the antibody is a bispecific antibody. In some embodiments, the antibody comprises a framework having human germline sequences. In another embodiment, the antibody comprises a heavy chain constant region selected from the group consisting of IgG, IgG1, IgG2, IgG2A, IgG2B, IgG2C, IgG3, IgG4, IgA1, IgA2, IgD, IgM, and IgE constant regions. In some embodiments, the antibody comprises a heavy (H) chain variable region (abbreviated herein as VH) and / or (for example and) a light (L) chain variable region (abbreviated herein as VL). In some embodiments, the antibody comprises a constant region, for example an Fc region. Immunoglobulin constant region refers to heavy or light chain constant regions. Human IgG heavy and light chain constant region amino acid sequences and functional variants thereof are known. With respect to the heavy chain, the heavy chain of the antibody described herein in some embodiments can be an alpha (α), delta (Δ), epsilon (ε), gamma (γ), or mu (μ) heavy chain. In some embodiments, the heavy chain of the antibody described herein can comprise a human alpha (α), delta (Δ), epsilon (ε), gamma (γ), or mu (μ) heavy chain. In specific embodiments, the antibody described herein comprises a human gamma 1 CH1 domain, CH2 domain, and / or (for example and) a CH3 domain. In some embodiments, the amino acid sequence of the VH domain comprises the amino acid sequence of a human gamma (γ) heavy chain constant region, such as any sequence known in the art.Non-limiting examples of human constant region sequences are described in the art, see, for example, U.S. Patent No. 5,693,780 and Kabat EA et al., (1991) supra. In some embodiments, the VH domain comprises an amino acid sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, 98%, or at least 99% identical to any of the variable chain constant regions provided herein. In some embodiments, the antibody is modified (e.g., modified via glycosylation, phosphorylation, sumoylation, and / or (e.g., and) methylation). In some embodiments, the antibody is a glycosylated antibody conjugated to one or more sugar or carbohydrate molecules. In some embodiments, one or more sugar or carbohydrate molecules are conjugated to the antibody via N-glycosylation, O-glycosylation, C-glycosylation, glypiation (GPI anchor attachment), and / or (e.g., and) phosphoglycosylation. In some embodiments, the one or more sugar or carbohydrate molecules are monosaccharides, disaccharides, oligosaccharides, or glycans. In some embodiments, the one or more sugar or carbohydrate molecules are branched oligosaccharides or branched glycans. In some embodiments, the one or more sugar or carbohydrate molecules include mannose units, glucose units, N-acetylglucosamine units, N-acetylgalactosamine units, galactose units, fucose units, or phospholipid units. In some embodiments, the antibody is a construct comprising a linker polypeptide or a polypeptide comprising one or more antigen-binding fragments of the present disclosure linked to an immunoglobulin constant region. The linker polypeptide comprises two or more amino acid residues linked together by peptide bonds and is used to link one or more antigen-binding moieties. Examples of linker polypeptides have been reported (see, e.g., Holliger, P., et al. (1993) Proc. Natl. Acad. Sci. USA 90:6444-6448; Poljak, RJ, et al. (1994) Structure 2:1121-1123).Furthermore, an antibody may be part of a larger immunoadhesion molecule formed by covalent or non-covalent association of the antibody or antibody portion with one or more other proteins or peptides. Examples of such immunoadhesion molecules include the use of streptavidin core regions to generate tetrameric scFv molecules (Kipriyanov, SM, et al. (1995) Human Antibodies and Hybridomas 6:93-101), and the use of cysteine ​​residues, marker peptides, and C-terminal polyhistidine tags to generate bivalent and biotinylated scFv molecules (Kipriyanov, SM, et al. (1994) Mol. Immunol. 31:1047-1058).

[0034] CDR: As used herein, the term "CDR" refers to the complementarity determining region in an antibody variable sequence. A typical antibody molecule comprises a heavy chain variable region (VH) and a light chain variable region (VL), which are usually involved in antigen binding. The VH and VL regions can be further subdivided into hypervariable regions, also known as "complementarity determining regions" ("CDRs"), interspersed with more conserved regions known as "framework regions" ("FRs"). Each VH and VL is typically composed of three CDRs and four FRs, arranged from the amino terminus to the carboxy terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4. The extent of the framework regions and CDRs can be precisely identified using methodologies known in the art, for example, by the Kabat definition, the IMGT definition, the Chothia definition, the AbM definition, and / or (for example and) the contact definition, all of which are well known in the art.For example, Kabat, EA, et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, USDepartment of Health and Human Services, NIH Publication No. 91-3242; IMGT (registered trademark), the international ImMunoGeneTics information system (registered trademark) www.imgt.org, Lefranc, M.-P. et al., Nucleic Acids. Res.,27:209-212(1999);Ruiz,M.et al.,Nucleic Acids Res.,28:219-221(2000);Lefranc,M.-P.,Nucleic Acids Res.,29:207-209(2001);Lefranc,M.-P.,Nucleic Acids Res.,31:307-310(2003);Lefranc,M.-P.et al.,In Silico Biol.,5,0006(2004)[Epub],5:45-60(2005);Lefranc,M.-P.et al.,Nucleic Acids Res.,33:D593-597(2005);Lefranc,M.-P.et al.,Nucleic Acids Res.,37:D1006-1012(2009);Lefranc,M.-P.et al.,Nucleic Acids Res.,43:D413-422(2015);Chothia et al.,(1989)Nature 342:877;Chothia,C.et al. (1987) J. Mol. Biol. 196:901-917, Al-lazikani et al. al (1997) J. Molec. Biol. 273:927-948; and Almagro, J. Mol. Recognit. 17:132-143 (2004). See also hgmp.mrc.ac.uk and bioinf.org.uk / abs. As used herein, CDRs may refer to CDRs defined by any method known in the art.Two antibodies having the same CDR, as determined by the same method, e.g., the IMGT definition, means that the two antibodies have the same amino acid sequence of that CDR.

[0035] There are three CDRs in each of the heavy and light chain variable regions, which are designated CDR1, CDR2, and CDR3 for each variable region. The term "CDR set" as used herein refers to a group of three CDRs occurring in a single variable region capable of binding to an antigen. The exact boundaries of these CDRs are defined differently according to different systems. The system described by Kabat (Kabat et al., Sequence of Proteins of Immunological Interest, National Institutes of Health, Bethesda, Md. (1987) and (1991)) not only provides an unambiguous residue numbering system applicable to any variable region of an antibody, but also provides precise residue boundaries defining the three CDRs. These CDRs are sometimes referred to as Kabat CDRs. Sub-portions of the CDRs are sometimes designated L1, L2, and L3, or H1, H2, and H3, where "L" and "H" designate the light chain and heavy chain regions, respectively. These regions are sometimes referred to as Chothia CDRs, which have boundaries that overlap with the Kabat CDRs. Other boundaries defining CDRs that overlap with the Kabat CDRs are described by Padlan (FASEB J. 9:133-139 (1995)) and MacCallum (J Mol Biol 262(5):732-45(1996)). Still other CDR boundary definitions may not strictly adhere to one of the above systems, but may still overlap with the Kabat CDRs, and may be shortened or extended in light of predictions or experimental findings that specific residues or groups of residues, or even entire CDRs, do not significantly affect antigen binding. The methods used herein may utilize CDRs defined according to any of these systems. Examples of CDR definition systems are shown in Table 1. [Table 1]

[0036] CDR-grafted antibodies: The term "CDR-grafted antibody" refers to an antibody that contains heavy and light chain variable region sequences from one species but in which the sequence of one or more of the CDR regions of its VH and / or (for example and) VL have been replaced with CDR sequences of another species, such as an antibody having murine heavy and light chain variable regions but in which one or more of the murine CDRs (for example, CDR3) have been replaced with human CDR sequences.

[0037] Chimeric antibodies: The term "chimeric antibody" refers to an antibody that contains heavy and light chain variable region sequences from one species and constant region sequences from another species, such as an antibody having murine heavy and light chain variable regions linked to a human constant region.

[0038] Complementary: As used herein, the term "complementary" refers to the ability for precise pairing between two nucleosides or two sets of nucleosides.In particular, complementary is a term that characterizes the degree of hydrogen bond pairing that results in binding between two nucleosides or two sets of nucleosides.For example, if the base of an oligonucleotide at a position can hydrogen bond with the base of a target nucleic acid (e.g., mRNA) at a corresponding position, then the bases are considered to be complementary to each other at that position.Base pairing may include both standard Watson-Crick base pairing and non-Watson-Crick base pairing (e.g., Wobble base pairing and Hoogsteen base pairing). For example, in some embodiments, for complementary base pairing, an adenosine-type base (A) is complementary to a thymidine-type base (T) or a uracil-type base (U), a cytosine-type base (C) is complementary to a guanosine-type base (G), and a universal base such as 3-nitropyrrole or 5-nitroindole can hybridize with any A, C, U, or T. Inosine (I) is also considered to be a universal base in the art and is considered to be complementary to any A, C, U, or T.

[0039] Conservative Amino Acid Substitutions: As used herein, "conservative amino acid substitution" refers to an amino acid substitution that does not change the relative charge or size characteristics of the protein in which the amino acid substitution is made.Variants can be prepared according to methods for modifying polypeptide sequences known to those skilled in the art, for example, references that summarize such methods, such as Molecular Cloning: A Laboratory Manual, J. Sambrook, et al., eds., Fourth Edition, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, 2012, or Current Protocols in Molecular Biology, FMAusubel, et al., eds., John Wiley & Sons, Inc., New York.Conservative amino acid substitutions include those made to amino acids in the following groups: (a) M, I, L, V; (b) F, Y, W; (c) K, R, H; (d) A, G; (e) S, T; (f) Q, N; and (g) E, D.

[0040] Covalently linked: As used herein, the term "covalently linked" refers to the characteristic of two or more molecules being linked together through at least one covalent bond. In some embodiments, two molecules can be covalently linked together by a single bond (e.g., a disulfide bond or a disulfide bridge) that acts as an intermolecular linker. However, in some embodiments, two or more molecules can be covalently linked together through a molecule that acts as a linker that connects two or more molecules together through multiple covalent bonds. In some embodiments, the linker can be a cleavable linker. However, in some embodiments, the linker can be a non-cleavable linker.

[0041] Cross-reacting: As used herein, and in the context of targeting agents (e.g., antibodies), the term "cross-reacting" refers to the property of an agent that can specifically bind to more than one antigen of the same type or class (e.g., multiple homologs, paralogs, or orthologs of antigens) with similar affinity or avidity. For example, in some aspects, an antibody that cross-reacts to a similar type or class of human and non-human primate antigens (e.g., human transferrin receptor and non-human primate transferrin receptor) can bind to a human antigen and a non-human primate antigen with similar affinity or avidity. In some embodiments, the antibody cross-reacts to a similar type or class of human antigen and rodent antigen. In some embodiments, the antibody cross-reacts to a similar type or class of rodent antigen and non-human primate antigen. In some embodiments, the antibody cross-reacts to a similar type or class of human antigen, non-human primate antigen, and rodent antigen.

[0042] Disease-associated repeats: As used herein, the term "disease-associated repeat" refers to a repeated nucleotide sequence at a genomic location where several units of the repeated nucleotide sequence correlate with and / or (for example, and) directly or indirectly contribute to or cause a genetic disease. Each repeat unit of the disease-associated repeat can be 2, 3, 4, 5 or more nucleotides long. For example, in some embodiments, the disease-associated repeat is a dinucleotide repeat. In some embodiments, the disease-associated repeat is a trinucleotide repeat. In some embodiments, the disease-associated repeat is a tetranucleotide repeat. In some embodiments, the disease-associated repeat is a pentanucleotide repeat. In some embodiments, the disease-associated repeat comprises a GAA repeat, or any nucleotide complement thereof. In some embodiments, the disease-associated repeat is in a non-coding portion of a gene. However, in some embodiments, the disease-associated repeat is in a coding region of a gene. In some embodiments, the disease-associated repeat is extended from a normal state to a length that directly or indirectly contributes to or causes a genetic disease. In some embodiments, the disease-associated repeat is in an RNA (for example, an RNA transcript). In some embodiments, the disease-associated repeats are in DNA (e.g., chromosomes, plasmids). In some embodiments, the disease-associated repeats are expanded in a chromosome of a germline cell. In some embodiments, the disease-associated repeats are expanded in a chromosome of a somatic cell. In some embodiments, the disease-associated repeats are expanded into a number of repeat units associated with congenital onset. In some embodiments, the disease-associated repeats are expanded into a number of repeat units associated with childhood onset of the disease. In some embodiments, the disease-associated repeats are expanded into a number of repeat units associated with adult onset of the disease.

[0043] Framework: As used herein, the term "framework" or "framework sequence" refers to the remaining sequence of the variable region minus the CDRs. Since the exact definition of the CDR sequence can be determined by various systems, the meaning of the framework sequence is subject to correspondingly different interpretations. The six CDRs (CDR-L1, CDR-L2, and CDR-L3 of the light chain, and CDR-H1, CDR-H2, and CDR-H3 of the heavy chain) also divide the framework region on the light chain and the heavy chain into four subregions (FR1, FR2, FR3, and FR4) on each chain, where CDR1 is located between FR1 and FR2, CDR2 is located between FR2 and FR3, and CDR3 is located between FR3 and FR4. The framework region that does not specify a specific subregion as FR1, FR2, FR3, or FR4, when referred to by others, represents the combined FR(s) in the variable region of a naturally occurring single immunoglobulin chain. As used herein, FR refers to one of the four subregions, and FR refers to two or more of the four subregions that contain framework regions. Human heavy and light chain acceptor sequences are known in the art. In one embodiment, acceptor sequences known in the art may be used in the antibodies disclosed herein.

[0044] Friedreich's ataxia: As used herein, the term "Friedreich's ataxia" refers to an autosomal recessive genetic disease caused by mutations in the FXN gene, characterized by progressive damage to muscle tissue and nervous system.Friedreich's ataxia is associated with the expansion of GAA trinucleotide repeats in the FXN gene, which leads to reduced expression of FXN.The expanded GAA trinucleotide repeats located in the first intron form an R-loop that can disrupt normal transcription process, reducing FXN gene expression. While FXN alleles in healthy individuals contain fewer than 36 GAA repeats, in FRDA patients, GAA expansions ranging from 70 to 1700 GAA repeats result in FXN mRNA deficiency and subsequently reduced levels of frataxin, an essential nuclear-encoded mitochondrial protein (see, for example, Silva et al., "Expanded GAA repeats impair FXN gene expression and reposition the FXN locus to the nuclear lamina in single cells." Hum. Molec. Genet., 2015, Vol. 24, No. 12 3457-3471). Friedreich's ataxia, the genetic basis of the disease, and associated symptoms have been described in the art (see, e.g., Montermini, L. et al. "The Friedreich's ataxia GAA triplet repeat: premutation and normal alleles." Hum. Molec. Genet., 1997, 6:1261-1266.; Filla, A. et al. "The relationship between trinucleotide (GAA) repeat length and clinical features in Friedreich's ataxia." Am. J. Hum. Genet. 1996, 59:554-560.; Pandolfo, M. Friedreich's ataxia: the clinical picture. J. Neurol. 2009, 256, 3-8).Friedreich's ataxia is linked to Online Mendelian Inheritance in Man (OMIM) Entry #229300.

[0045] FXN: As used herein, the term "FXN" refers to the gene encoding frataxin, a protein involved in iron homeostasis. In some embodiments, FXN can be a human (gene ID: 2395), non-human primate (e.g., gene ID: 737660), or rodent gene (e.g., gene ID: 14297, gene ID: 499335). In humans, the GAA repeat expansion in the first intron of FXN is associated with Friedreich's ataxia. In addition, multiple human transcript variants (e.g., annotated with GenBank RefSeq accession numbers NM_000144.4 and NM_181425.2) that code for different protein isoforms have been characterized.

[0046] FXN allele: As used herein, the term "FXN allele" refers to any one of the alternative forms (e.g., wild type or mutant) of the FXN gene. In some embodiments, the FXN allele can encode wild type frataxin that retains its normal and typical function. In some embodiments, the FXN allele can contain one or more disease-associated repeat expansions. In some embodiments, a normal subject has two FXN alleles that contain less than 36 GAA trinucleotide repeat units. In some embodiments, a normal subject has two FXN alleles that contain GAA trinucleotide repeat units in the range of 8 to 33. In some embodiments, the number of GAA repeat units in the FXN allele of a subject with Friedreich's ataxia ranges from about 70 to about 1700. In some embodiments, the number of GAA repeat units in the FXN allele of a subject with Friedreich's ataxia ranges from about 90 to about 1300, with the higher number of repeats being associated with increased disease severity. In some embodiments, subjects with mildly affected Friedreich's ataxia have at least one FXN allele with repeat units in the range of 90 to 150. In some embodiments, subjects with classical Friedreich's ataxia have at least one FXN allele with repeat units in the range of 90 to 1,000 or more.

[0047] Human antibodies: The term "human antibody" as used herein is intended to include antibodies having variable and constant regions derived from human germline immunoglobulin sequences. Human antibodies of the present disclosure may include, for example, amino acid residues in the CDRs, particularly CDR3, that are not encoded by human germline immunoglobulin sequences (e.g., mutations introduced by random or site-specific mutagenesis in vitro or by somatic mutation in vivo). However, the term "human antibody" as used herein is not intended to include antibodies in which CDR sequences derived from the germline of another mammalian species, such as a mouse, are grafted onto human framework sequences.

[0048] Humanized antibodies: The term "humanized antibody" refers to an antibody that contains heavy and light chain variable region sequences from a non-human species (e.g., mouse), but where at least a portion of the VH and / or (e.g., and) VL sequences have been altered to be more "human-like", i.e., more similar to human germline variable sequences. One type of humanized antibody is a CDR-grafted antibody, where human CDR sequences are introduced onto non-human VH and VL sequences to replace the corresponding non-human CDR sequences. In one embodiment, humanized anti-transferrin receptor (TfR1) antibodies and antigen-binding portions are provided. Such antibodies can be produced by obtaining a mouse anti-transferrin receptor (TfR1) monoclonal antibody using existing hybridoma technology, followed by humanization using in vitro genetic engineering (such as that disclosed in Kasaian et al., WO 2005 / 123126).

[0049] Internalizing cell surface receptors: As used herein, the term "internalizing cell surface receptor" refers to a cell surface receptor that is internalized by a cell upon an external stimulus (e.g., a ligand binding to the receptor). In some embodiments, the internalizing cell surface receptor is internalized by endocytosis. In some embodiments, the internalizing cell surface receptor is internalized by clathrin-mediated endocytosis. However, in some embodiments, the internalizing cell surface receptor is internalized by a clathrin-independent pathway, such as phagocytosis, macropinocytosis, caveolae- and raft-mediated uptake, or clathrin-independent constitutive endocytosis. In some embodiments, the internalizing cell surface receptor comprises an intracellular domain, a transmembrane domain, and / or (e.g., and), an extracellular domain, which optionally further comprises a ligand-binding domain. In some embodiments, the cell surface receptor becomes internalized by a cell after ligand binding. In some embodiments, the ligand may be a muscle-targeting agent or a muscle-targeting antibody. In some embodiments, the internalizing cell surface receptor is a transferrin receptor.

[0050] Isolated antibodies: An "isolated antibody," as used herein, is intended to refer to an antibody that is substantially free of other antibodies having different antigenic specificities (by way of example, an isolated antibody that specifically binds to the transferrin receptor is substantially free of antibodies that specifically bind to antigens other than the transferrin receptor). However, an isolated antibody that specifically binds to the transferrin receptor complex may have cross-reactivity to other antigens, such as transferrin receptor molecules from other species. Moreover, an isolated antibody may be substantially free of other cellular material and / or (by way of example and) chemicals.

[0051] Kabat numbering: The terms "Kabat numbering", "Kabat definition" and "Kabat labeling" are used interchangeably herein. These terms, while recognized in the art, refer to a system for numbering amino acid residues that are more variable (i.e., more variable) than other amino acid residues in the heavy and light chain variable regions of an antibody or its antigen-binding portion (Kabat et al. (1971) Ann. NY Acad, Sci. 190:382-391 and Kabat, EA, et al. (1991) Sequences of Proteins of Immunological Interest, Fifth Edition, USDepartment of Health and Human Services, NIH Publication No. 91-3242). In the heavy chain variable region, the hypervariable region spans amino acid positions 31-35 for CDR1, amino acid positions 50-65 for CDR2, and amino acid positions 95-102 for CDR3. In the light chain variable region, the hypervariable region spans amino acid positions 24-34 for CDR1, amino acid positions 50-56 for CDR2, and amino acid positions 89-97 for CDR3.

[0052] Molecular payload: As used herein, the term "molecular payload" refers to a molecule or species that functions to modulate a biological outcome. In some embodiments, the molecular payload is linked or otherwise associated with a muscle targeting agent. In some embodiments, the molecular payload is covalently linked to the muscle targeting agent. In some embodiments, the molecular payload is a small molecule, a protein, a peptide, a nucleic acid, or an oligonucleotide. In some embodiments, the molecular payload functions to modulate the transcription of a DNA sequence, to modulate the expression of a protein, or to modulate the activity of a protein. In some embodiments, the molecular payload is an oligonucleotide that includes a strand having a region of complementarity to a target gene.

[0053] Muscle-targeting agents: As used herein, the term "muscle targeting agent" refers to a molecule that specifically binds to an antigen expressed on a muscle cell. The antigen in or on a muscle cell may be a membrane protein, such as an integral membrane protein or a peripheral membrane protein. Typically, a muscle targeting agent specifically binds to an antigen on a muscle cell that facilitates internalization of the muscle targeting agent (and any associated molecular payload) into the muscle cell. In some embodiments, the muscle targeting agent specifically binds to an internalizing cell surface receptor on muscle and is capable of being internalized into the muscle cell through receptor-mediated internalization. In some embodiments, the muscle targeting agent is a small molecule, a protein, a peptide, a nucleic acid (e.g., an aptamer), or an antibody. In some embodiments, the muscle targeting agent is linked to a molecular payload.

[0054] Muscle targeting antibodies: As used herein, the term "muscle-targeting antibody" refers to a muscle targeting agent that is an antibody that specifically binds to an antigen found in or on a muscle cell. In some embodiments, the muscle-targeting antibody specifically binds to an antigen on a muscle cell that facilitates internalization of the muscle-targeting antibody (and any attached molecular payload) into the muscle cell. In some embodiments, the muscle-targeting antibody specifically binds to an internalizing cell surface receptor present on a muscle cell. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds to the transferrin receptor.

[0055] Oligonucleotides: As used herein, the term "oligonucleotide" refers to an oligomeric nucleic acid compound of up to 200 nucleotides in length. Examples of oligonucleotides include, but are not limited to, RNAi oligonucleotides (e.g., siRNA, shRNA), microRNA, gapmers, mixmers, phosphorodiamidates, morpholinos, peptide nucleic acids, aptamers, guide nucleic acids (e.g., Cas9 guide RNA), and the like. Oligonucleotides may be single-stranded or double-stranded. In some embodiments, oligonucleotides may contain one or more modified nucleosides (e.g., 2'-O-methyl sugar modifications, purine or pyrimidine modifications). In some embodiments, oligonucleotides may contain one or more modified internucleoside linkages. In some embodiments, oligonucleotides may contain one or more phosphorothioate linkages that may be in Rp or Sp stereochemical configuration.

[0056] Recombinant antibodies: The term "recombinant human antibody," as used herein, refers to any human antibody that is prepared, expressed, created, or isolated by recombinant means, e.g., antibodies expressed using a recombinant expression vector transfected into a host cell (as described in more detail in this disclosure), antibodies isolated from a recombinant combinatorial human antibody library (Hoogenboom HR, (1997) TIB Tech. 15:62-70; Azzazy H., and Highsmith WE, (2002) Clin. Biochem. 35:425-445; Gavilondo JV, and Larrick JW (2002) BioTechniques 29:128-145; Hoogenboom H., and Chames P. (2000) Immunology Today 21:371-378), antibodies isolated from a human immunoglobulin gene transgenic animal (e.g., a mouse) (see, e.g., Taylor, LD, et al., J. Immunology 29:128-145; Hoogenboom H., and Chames P. (2000) Immunology Today 21:371-378), or antibodies isolated from a human immunoglobulin gene transgenic animal (e.g., a mouse) (see, e.g., Taylor, LD, et al., J. Immunology 29:128-145; Hoogenboom ... al. (1992) Nucl. Acids Res. 20:6287-6295; Kellermann SA., and Green LL (2002) Current Opinion in Biotechnology 13:593-597; Little M. et al (2000) Immunology Today 21:364-370), or any other means involving splicing of human immunoglobulin gene sequences with other DNA sequences. Such recombinant human antibodies have variable and constant regions derived from human germline immunoglobulin sequences. However, in certain embodiments, such recombinant human antibodies are subjected to in vitro mutagenesis (or, when human Ig sequence transgenic animals are used, in vivo somatic mutagenesis) such that the amino acid sequences of the VH and VL regions of the recombinant antibodies, while derived from and related to human germline VH and VL sequences, are sequences that may not naturally occur within the germline repertoire of human antibodies in vivo.One embodiment of the present disclosure provides fully human antibodies capable of binding to the human transferrin receptor that can be generated using techniques well known in the art, such as, but not limited to, techniques using human Ig phage libraries (such as those disclosed in WO 2005 / 007699 to Jermutus et al.).

[0057] Complementarity region: As used herein, the term "complementary region" refers to a nucleotide sequence (e.g., a nucleotide sequence of an oligonucleotide) that is sufficiently complementary to a cognate nucleotide sequence (e.g., a nucleotide sequence of a target nucleic acid) such that the two nucleotide sequences can anneal to each other under physiological conditions (e.g., in a cell). In some embodiments, the complementary region is fully complementary to the cognate nucleotide sequence of the target nucleic acid. However, in some embodiments, the complementary region is partially complementary (e.g., at least 80%, 90%, 95%, or 99% complementary) to the cognate nucleotide sequence of the target nucleic acid. In some embodiments, the complementary region contains 1, 2, 3, or 4 mismatches compared to the cognate nucleotide sequence of the target nucleic acid.

[0058] Specific binding to: As used herein, the term "specifically binds" refers to the ability of a molecule to bind to a binding partner with a degree of affinity or avidity that can be used to distinguish the binding partner from an appropriate control in a binding assay or other binding context. With respect to an antibody, the term "specifically binds" refers to the ability of an antibody to bind to a particular antigen, as compared to an appropriate reference antigen, or an antigen that can be used to distinguish the particular antigen from other antigens, with a degree of affinity or avidity (e.g., a degree that allows preferential targeting to certain cells (e.g., muscle cells) through binding to the antigen, as described herein). In some embodiments, an antibody has at least about 10% affinity for binding to a target. -4 M, 10 -5M, 10 -6 M, 10 -7 M, 10 -8 M, 10 -9 M, 10 -10 M, 10 -11 M, 10 -12 M, 10 -13 M or less than this K D In some embodiments, the antibody specifically binds to a transferrin receptor, e.g., an epitope in the apical domain of the transferrin receptor.

[0059] subject: As used herein, the term "subject" refers to a mammal. In some embodiments, the subject is a non-human animal of the primate order or a rodent. In some embodiments, the subject is a human. In some embodiments, the subject is a patient with or suspected of having a disease, for example, a human patient. In some embodiments, the subject is a human patient with or suspected of having a disease caused by a disease-associated repeat expansion, for example, in the FXN allele.

[0060] Transferrin Receptor: As used herein, the term "transferrin receptor" (also known as TFRC, CD71, p90, TFR, or TFR1) refers to an internalizing cell surface receptor that binds to transferrin to facilitate iron uptake by endocytosis. In some embodiments, the transferrin receptor may originate from humans (NCBI Gene ID 7037), non-human primates (e.g., NCBI Gene ID 711568 or NCBI Gene ID 102136007), or rodents (e.g., NCBI Gene ID 22042). In addition, multiple human transcript variants encoding different isoforms of the receptor have been characterized (e.g., as annotated with GenBank RefSeq accession numbers: NP_001121620.1, NP_003225.2, NP_001300894.1, and NP_001300895.1).

[0061] 2' Modified Nucleosides: As used herein, the terms "2'-modified nucleoside" and "2'-modified ribonucleoside" are used interchangeably and refer to a nucleoside having a sugar moiety modified at the 2'-position. In some embodiments, the 2'-modified nucleoside is a 2'-4' bicyclic nucleoside, in which the 2' and 4' positions of the sugar are bridged (e.g., by a methylene, ethylene, or (S)-constrained ethyl bridge). In some embodiments, the 2'-modified nucleoside is a non-bicyclic 2'-modified nucleoside, in which the 2' position of the sugar moiety is substituted. Non-limiting examples of 2' modified nucleosides include 2' deoxy, 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'-O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), 2'-ON-methylacetamide (2'-O-NMA), locked nucleic acid (LNA, methylene bridged nucleic acid), ethylene bridged nucleic acid (ENA), and (S)-constrained ethyl bridged nucleic acid (cEt). In some embodiments, the 2' modified nucleosides described herein are high affinity modified nucleosides, and oligonucleotides comprising the 2' modified nucleosides have increased affinity for target sequences compared to unmodified oligonucleotides. Examples of 2' modified nucleosides structures are provided below: [ka] Although the examples are shown with a phosphate group, any internucleoside linkage is contemplated between the 2'-modified nucleosides.

[0062] II. Complex Further provided herein is a conjugate comprising a targeting agent, for example an antibody, covalently linked to a molecular payload. In some embodiments, the conjugate comprises a muscle-targeting antibody covalently linked to an oligonucleotide. The conjugate may comprise an antibody that specifically binds to a single antigen site, or an antibody that binds to at least two antigen sites, which may be present on the same antigen or on different antigens.

[0063] The complex may be used to modulate the activity or function of at least one gene, protein, and / or (for example, and) nucleic acid. In some embodiments, the molecular payload present with the complex is responsible for the modulation of the gene, protein, and / or (for example, and) nucleic acid. The molecular payload may be a small molecule, a protein, a nucleic acid, an oligonucleotide, or any molecular entity capable of modulating the activity or function of the gene, protein, and / or (for example, and) nucleic acid in a cell. In some embodiments, the molecular payload is an oligonucleotide that targets disease-associated repeats in muscle cells.

[0064] In some embodiments, the conjugate comprises a muscle targeting agent, e.g., an anti-transferrin receptor 1 (TfR1) antibody, covalently linked to a molecular payload, e.g., an antisense oligonucleotide that targets a disease-associated repeat, e.g., an FXN allele.

[0065] A. Muscle-targeting Agents Some aspects of the present disclosure provide muscle targeting agents, e.g., muscle targeting agents for delivering molecular payloads to muscle cells. In some embodiments, such muscle targeting agents are capable of binding to muscle cells and delivering the associated molecular payload to muscle cells, e.g., via specific binding to an antigen on the muscle cell. In some embodiments, the molecular payload is bound (e.g., covalently bound) to the muscle targeting agent and is internalized into the muscle cell, e.g., via endocytosis, when the muscle targeting agent binds to the antigen on the muscle cell. Of course, various types of muscle targeting agents can be used in accordance with the present disclosure. Of course, various types of muscle targeting agents can be used in accordance with the present disclosure, and any muscle target (e.g., muscle surface protein) can be targeted by any type of muscle targeting agent described herein. For example, the muscle targeting agent can include or consist of a small molecule, a nucleic acid (e.g., DNA or RNA), a peptide (e.g., an antibody), a lipid (e.g., a microvesicle), or a sugar moiety (e.g., a polysaccharide). Exemplary muscle-targeting agents are described in further detail herein, although it will be understood that the exemplary muscle-targeting agents provided herein are not intended to be limiting.

[0066] Some aspects of the disclosure provide muscle targeting agents that specifically bind to antigens on muscles, such as skeletal, smooth, or cardiac muscles. In some embodiments, any of the muscle targeting agents provided herein bind (e.g., specifically bind) to antigens on skeletal muscle cells, smooth muscle cells, and / or (e.g., and) cardiac muscle cells.

[0067] Through interaction with muscle-specific cell surface recognition elements (e.g., cell membrane proteins), both tissue localization and selective uptake into muscle cells can be achieved. In some embodiments, molecules that are substrates for muscle uptake transporters are useful for delivering molecular payloads into muscle tissue. Binding to muscle surface recognition elements followed by endocytosis can allow even macromolecules such as antibodies to enter muscle cells. As another example, molecular payloads conjugated to transferrin or anti-transferrin receptor 1 (TfR1) antibodies can be taken up by muscle cells via binding to the transferrin receptor and then endocytosed, e.g., via clathrin-mediated endocytosis.

[0068] The use of muscle targeting agents can be useful to concentrate molecular payloads (e.g., oligonucleotides) in muscle while reducing toxicity associated with effects in other tissues. In some embodiments, muscle targeting agents concentrate bound molecular payloads in muscle cells compared to other cell types in a subject. In some embodiments, muscle targeting agents concentrate bound molecular payloads in muscle cells (e.g., skeletal muscle cells, smooth muscle cells, or cardiomyocytes) to at least 1-fold, 2-fold, 3-fold, 4-fold, 5-fold, 6-fold, 7-fold, 8-fold, 9-fold, 10-fold, 15-fold, 20-fold, 30-fold, 40-fold, 50-fold, 60-fold, 70-fold, 80-fold, 90-fold, or 100-fold greater than the amount in non-muscle cells (e.g., liver cells, nerve cells, blood cells, or fat cells). In some embodiments, the toxicity in a subject of a molecular payload when conjugated to a muscle targeting agent is reduced by at least 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 90%, or 95% when delivered to a subject.

[0069] In some embodiments, a muscle recognition element (e.g., a muscle cell antigen) may be required to achieve muscle selectivity. As an example, the muscle targeting agent may be a small molecule that is a substrate for a muscle-specific uptake transporter. As another example, the muscle targeting agent may be an antibody that enters muscle cells via transporter-mediated endocytosis. As another example, the muscle targeting agent may be a ligand that binds to a cell surface receptor on muscle cells. Of course, while a transporter-based approach provides a direct pathway for cell entry, receptor-based targeting may involve stimulated endocytosis to reach the desired site of action.

[0070] i. Muscle targeting antibody In some embodiments, the muscle targeting agent is an antibody. In general, the high specificity of antibodies to their target antigens allows them to selectively target muscle cells (e.g., skeletal muscle cells, smooth muscle cells, and / or (e.g., and) cardiomyocytes). This specificity may also limit off-target toxicity. Examples of antibodies capable of targeting surface antigens of muscle cells have been reported and are within the scope of this disclosure. For example, antibodies that target the surface of muscle cells are described in Arahata K., et al. "Immunostaining of skeletal and cardiac muscle surface membrane with antibody against Duchenne muscular dystrophy peptide" Nature 1988;333:861-3; Song KS, et al. "Expression of caveolin-3 in skeletal, cardiac, and smooth muscle cells. Caveolin-3 is a component of the sarcolemma and co-fractionates with dystrophin and dystrophin-associated glycoproteins" J Biol Chem 1996;271:15160-5; and Weisbart RH et al., "Cell type specific targeted intracellular delivery into muscle of a monoclonal antibody that binds myosin IIb" Mol Immunol. 2003 Mar,39(13):78309, the entire contents of each of which are incorporated herein by reference.

[0071] a. Anti-transferrin receptor 1 (TfR1) antibody Some aspects of the present disclosure are based on the recognition that agents that bind to the transferrin receptor, e.g., anti-transferrin receptor antibodies, can target muscle cells. The transferrin receptor is an internalizing cell surface receptor that transports transferrin across the cell membrane and participates in the regulation and homeostasis of intracellular iron levels. Some aspects of the present disclosure provide transferrin receptor binding proteins that can bind to the transferrin receptor. Thus, aspects of the present disclosure provide binding proteins (e.g., antibodies) that bind to the transferrin receptor. In some embodiments, the binding proteins that bind to the transferrin receptor are internalized into muscle cells along with any molecular payloads attached. As used herein, antibodies that bind to the transferrin receptor may be interchangeably referred to as transferrin receptor antibodies, anti-transferrin receptor antibodies, or anti-TfR1 antibodies. Antibodies that bind, e.g., specifically bind, to the transferrin receptor can be internalized into cells, e.g., through receptor-mediated endocytosis, upon binding to the transferrin receptor.

[0072] It is understood that anti-TfR1 antibodies can be produced, synthesized, and / or (for example and) derivatized using several known methodologies, for example, library design using phage display. Exemplary methodologies have been characterized in the art and are incorporated by reference (Diez, P. et al. "High-throughput phage-display screening in array format", Enzyme and Microb Technol, 2015, 79, 34-41.; Hammers CM and Stanley, JR, "Antibody Phage Display: Technique and Applications" J Invest Dermatol. 2014, 134:2.; Engleman, Edgar (Ed.) "Human Hybridomas and Monoclonal Antibodies." 1985, Springer.). In other embodiments, anti-TfR1 antibodies have been previously characterized or disclosed.Antibodies that specifically bind to the transferrin receptor are known in the art (see, e.g., U.S. Pat. No. 4,364,934, filed December 4, 1979, entitled "Monoclonal antibody to a human early thymocyte antigen and methods for preparing same"; U.S. Pat. No. 8,409,573, filed June 14, 2006, entitled "Anti-CD71 monoclonal antibodies and uses thereof for treating malignant tumor cells"; U.S. Pat. No. 9,708,406, filed May 20, 2014, entitled "Anti-transferrin receptor antibodies and methods of use"; U.S. Pat. No. 9,611,323, filed December 19, 2014, entitled "Low affinity blood brain barrier receptor antibodies and uses therefor"; WO 2015 / 098989, filed December 24, 2014, entitled "Novel anti-transferrin receptor antibody that passes through blood-brain barrier"; Schneider C. et al. al. “Structural features of the cell surface receptor for transferrin that is recognized by the monoclonal antibody OKT9.” J Biol Chem.1982,257:14,8516-8522. Lee et al. “Targeting Rat Anti-Mouse Transferrin Receptor Monoclonal Antibodies through Blood-Brain Barrier in Mouse” 2000, J (See Pharmacol. Exp. Ther., 292:1048-1052).

[0073] In some embodiments, the anti-TfR1 antibodies described herein bind to the transferrin receptor with high specificity and affinity. In some embodiments, the anti-TfR1 antibodies described herein specifically bind to any extracellular epitope of the transferrin receptor or epitope that becomes exposed to the antibody. In some embodiments, the anti-TfR1 antibodies provided herein specifically bind to transferrin receptor from humans, non-human animals of the primate order, mice, rats, etc. In some embodiments, the anti-TfR1 antibodies provided herein bind to the human transferrin receptor. In some embodiments, the anti-TfR1 antibodies described herein bind to an amino acid segment of the human or non-human primate transferrin receptor, such as those provided in SEQ ID NOs: 105-108. In some embodiments, the anti-TfR1 antibodies described herein bind to an amino acid segment corresponding to amino acids 90-96 of the human transferrin receptor as set forth in SEQ ID NO: 105, which is not in the apical domain of the transferrin receptor.

[0074] An example of a human transferrin receptor amino acid sequence, which corresponds to the NCBI sequence NP_003225.2 (transferrin receptor protein 1 isoform 1, Homo sapiens), is as follows: (SEQ ID NO:105)

[0075] An example of a primate non-human animal transferrin receptor amino acid sequence, which corresponds to the NCBI sequence NP_001244232.1 (Transferrin receptor protein 1, Macaca mulatta), is as follows: MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNSHVEMKLGVDEEENTDNNTKPNGTKPKRCGGNICYGTIAVIIFFLIGFMIGYLGYCKGVEPKTECERLAGTESPAREEPEEDFPAAPRLYWDDLKRKLSEKLDTTDFTSTIKLLNENLYVPREAGSQKDENLALYIENQFREFKLSKVWRDQHFVKI QVKDSAQNSVIIVDKNGGLVYLVENPGGYVAYSKAATVTGKLVHANFGTKKDFEDLDSPVNGSIVIVRAGKITFAEKVANAESLNAIGVLIYMDQTKFPIVKADLSFFGHAHLGTGDPYTPGFPSFNHTQFPPSQSSGLPNIPVQTISRAAAEKLFGNMEGDCPSDWKTDSTCKMVTSENKSVKLTVSNV LKETKILNIFGVIKGFVEPDHYVVVGAQRDAWGPGAAKSSVGTALLLKLAQMFSDMVLKDGFQPSRSIIFASWSAGDFGSVGATEWLEGYLSSLHLKAFTYINLDKAVLGTSNFKVSASPLLYTLIEKTMQDVKHPVTGRSLYQDSNWASKVEKLTLDNAAFPFLAYSGIPAVSFCFCEDTDYPYLGTTM DTYKELVERIPELNKVARAAAEVAGQFVIKLTHDTELNLDYERYNSQLLLFLRDLNQYRADVKEMGLSLQWLYSARGDFFRATSRLTTDFRNAEKRDKFVMKKLNDRVMRVEYYFLSPYVSPKESPFRHVFWGSGSHTLSALLESLKLRRQNNSAFNETLFRNQLALATWTIQGAANALSGDVWDIDNEF (SEQ ID NO:106)

[0076] An example of a primate non-human animal transferrin receptor amino acid sequence that corresponds to the NCBI sequence XP_005545315.1 (transferrin receptor protein 1, Macaca fascicularis) is as follows: (SEQ ID NO:107)

[0077] An example of a mouse transferrin receptor amino acid sequence, which corresponds to the NCBI sequence NP_001344227.1 (transferrin receptor protein 1, Mus musculus), is as follows: MMDQARSAFSNLFGGEPLSYTRFSLARQVDGDNHVEMKLAADEEENADNNMKASVRKPKRFNGRLCFAAIALVIFFLIGFMSGYLGYCKRVEQKEECVKLAETEETDKSETMETEDVPTSSRLYWADLKTLLSEKLNSIEFADTIKQLSQNTYTPREAGSQKDESLAYYIENQFHEFKFSKVWRDEHYV KIQVKSSIGQNMVTIVQSNGNLDPVESPEGYVAFSKPTEVSGKLVHANFGTKKDFEELSYSVNGSLVIVRAGEITFAEKVANAQSFNAIGVLIYMDKNKFPVVEADLALFGHAHLGTGDPYTPGFPSFNHTQFPPSQSSGLPNIPVQTISRAAAEKLFGKMEGSCPARWNIDSSCKLELSQNQNVKLIVKN VLKERRILNIFGVIKGYEEPDRYVVVGAQRDALGAGVAAKSSVGTGLLLKLAQVFSDMISKDGFRPSRSIIFASWTAGDFGAVGATEWLEGYLSSLHLKAFTYINLDKVVLGTSNFKVSASPLLYTLMGKIMQDVKHPVDGKSLYRDSNWISKVEKLSFDNAAYPFLAYSGIPAVSFCFCEDADYPYLGTR LDTYEALTQKVPQLNQMVRTAAEVAGQLIIKLTHDVELNLDYEMYNSKLLSFMKDLNQFKTDIRDMGLSLQWLYSARGDYFRATSRLTTDFHNAEKTNRFVMREINDRIMKVEYHFLSPYVSPRESPFRHIFWGSGSHTLSALVENLKLRQKNITAFNETLFRNQLALATWTIQGVANALSGDIWNIDNEF (SEQ ID NO:108)

[0078] In some embodiments, the anti-TfR1 antibody binds to a receptor such as: FVKIQVKDSAQNSVIIVDKNGRLVYLVENPGGYVAYSKAATVTGKLVHANFGTKKDFEDLYTPVNGSIVIVRAGKITFAEKVANAESLNAIGVLIYMDQTKFPIVNAELSFFGHAHLGTGDPYTPGFPSFNHTQFPPSRSSGLPNIPVQTISRAAAEKLFGNMEGDCPSDWKTDSTCRMVTSESKNVKLTVSNVLKE (SEQ ID NO: 109) and does not inhibit the binding interaction between the transferrin receptor and transferrin and / or (by way of example and) human hemochromatosis protein (also known as HFE). In some embodiments, the anti-TfR1 receptor antibodies described herein do not bind to the epitope of SEQ ID NO: 109.

[0079] Suitable methodologies may be used to obtain and / or (for example and) produce antibodies, antibody fragments, or antigen-binding agents, for example through the use of recombinant DNA protocols. In some embodiments, antibodies may also be produced through the generation of hybridomas (see, for example, Kohler, G and Milstein, C. "Continuous cultures of fused cells secreting antibody of predefined specificity" Nature, 1975, 256:495-497). An antigen of interest may be used as an immunogen of any type or entity, for example, recombinant or naturally occurring type or entity. Hybridomas are screened using standard methods, for example, ELISA screening, to find at least one hybridoma that produces an antibody that targets a specific antigen. Antibodies may also be produced through screening of protein expression libraries (for example, phage display libraries) that express antibodies. Phage display library design may also be used in some embodiments (see, e.g., U.S. Pat. No. 5,223,409, filed March 1, 1991, entitled "Directed evolution of novel binding proteins," WO 1992 / 18619, filed April 10, 1992, entitled "Heterodimeric receptor libraries using phagemids," WO 1991 / 17271, filed May 1, 1991, entitled "Recombinant library screening methods," WO 1992 / 20791, filed May 15, 1992, entitled "Methods for producing members of specific binding pairs," and WO 1992 / 15679, filed February 28, 1992, entitled "Improved epitope displaying phage"). In some embodiments, the antigen of interest may be used to immunize a non-human animal, e.g., a rodent animal or a goat.In some embodiments, once the antibody is obtained from the non-human animal, it may then be optionally modified using a number of methodologies, for example using recombinant DNA techniques. Additional examples of antibody production and methodologies are also known in the art (see, for example, Harlow et al. "Antibodies: A Laboratory Manual", Cold Spring Harbor Laboratory, 1988).

[0080] In some embodiments, the antibody is modified (e.g., modified via glycosylation, phosphorylation, sumoylation, and / or (e.g., and) methylation). In some embodiments, the antibody is a glycosylated antibody conjugated to one or more sugar or carbohydrate molecules. In some embodiments, the one or more sugar or carbohydrate molecules are conjugated to the antibody via N-glycosylation, O-glycosylation, C-glycosylation, glypiation (GPI anchor attachment), and / or (e.g., and) phosphoglycosylation. In some embodiments, the one or more sugar or carbohydrate molecules are monosaccharides, disaccharides, oligosaccharides, or glycans. In some embodiments, the one or more sugar or carbohydrate molecules are branched oligosaccharides or branched glycans. In some embodiments, the one or more sugar or carbohydrate molecules include mannose units, glucose units, N-acetylglucosamine units, N-acetylgalactosamine units, galactose units, fucose units, or phospholipid units. In some embodiments, the sugar molecules are present in an amount of about 1-10, about 1-5, about 5-10, about 1-4, about 1-3, or about 2. In some embodiments, the glycosylated antibody is fully or partially glycosylated. In some embodiments, the antibody is glycosylated by chemical reaction or by enzymatic means. In some embodiments, the antibody is glycosylated in vitro or intracellularly, and optionally may be deficient in an enzyme (e.g., glycosyltransferase) in the N- or O-glycosylation pathway. In some embodiments, the antibody is functionalized with a sugar or carbohydrate molecule as described in WO2014065661, published May 1, 2014, entitled "Modified antibody, antibody-conjugate and process for the preparation thereof."

[0081] In some embodiments, the anti-TfR1 antibody of the present disclosure comprises a VL domain and / or (for example and) a VH domain of any one of the anti-TfR1 antibodies selected from any one of Tables 2-7, and comprises a constant region comprising the amino acid sequence of the constant region of an immunoglobulin molecule of an IgG, IgE, IgM, IgD, IgA, or IgY, any class (for example, IgG1, IgG2, IgG3, IgG4, IgA1, and IgA2), or any subclass (for example, IgG2a and IgG2b). Non-limiting examples of human constant regions are described in the art, see, for example, Kabat EA et al., (1991), supra.

[0082] In some embodiments, agents that bind to transferrin receptor, e.g., anti-TfR1 antibodies, can target muscle cells and / or mediate transport of agents across the blood-brain barrier (e.g., and). Transferrin receptor is an internalizing cell surface receptor that transports transferrin across cell membranes and participates in the regulation and homeostasis of intracellular iron levels. Some aspects of the present disclosure provide transferrin receptor binding proteins that can bind to transferrin receptor. Antibodies that bind, e.g., specifically bind, to transferrin receptor can be internalized into cells upon binding to transferrin receptor, e.g., through receptor-mediated endocytosis.

[0083] In some aspects, provided herein are humanized antibodies that bind to the transferrin receptor with high specificity and affinity. In some embodiments, the humanized anti-TfR1 antibodies described herein specifically bind to any extracellular epitope of the transferrin receptor, or an epitope that becomes exposed to the antibody. In some embodiments, the humanized anti-TfR1 antibodies provided herein specifically bind to transferrin receptor from humans, non-human animals of the primate order, mice, rats, etc. In some embodiments, the humanized anti-TfR1 antibodies provided herein bind to the human transferrin receptor. In some embodiments, the humanized anti-TfR1 antibodies described herein bind to an amino acid segment of the human or non-human primate transferrin receptor, such as those provided in SEQ ID NOs: 105-108. In some embodiments, the humanized anti-TfR1 antibodies described herein bind to an amino acid segment corresponding to amino acids 90-96 of the human transferrin receptor as set forth in SEQ ID NO: 105, which is not in the apical domain of the transferrin receptor. In some embodiments, the humanized anti-TfR1 antibodies described herein bind to TfR1 but not to TfR2.

[0084] In some embodiments, the anti-TfR1 antibodies described herein (e.g., anti-TfR1 clone 8 in Table 2 below) bind to an epitope of TfR1, the epitope comprising residues of amino acids 214-241 and / or amino acids 354-381 of SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein bind to an epitope comprising residues of amino acids 214-241 and amino acids 354-381 of SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein bind to an epitope comprising one or more of residues Y222, T227, K231, H234, T367, S368, S370, T376, and S378 of human TfR1 as set forth in SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein bind to an epitope that includes residues Y222, T227, K231, H234, T367, S368, S370, T376 and S378 of human TfR1 as set forth in SEQ ID NO:105.

[0085] In some embodiments, the anti-TfR1 antibodies described herein (e.g., 3M12 and its humanized variants in Table 2 below) bind to an epitope of TfR1 that includes residues of amino acids 258-291 and / or amino acids 358-381 of SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein (e.g., 3M12 and its humanized variants in Table 2 below) bind to an epitope that includes residues of amino acids 258-291 and amino acids 358-381 of SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein (e.g., 3M12 and its humanized variants in Table 2 below) bind to an epitope that includes one or more of residues K261, S273, Y282, T362, S368, S370, and K371 of human TfR1 as shown in SEQ ID NO: 105. In some embodiments, the anti-TfR1 antibodies described herein (e.g., 3M12 and its humanized variants in Table 2 below) bind to an epitope including residues K261, S273, Y282, T362, S368, S370, and K371 of human TfR1 as set forth in SEQ ID NO:105.

[0086] In some embodiments, the anti-TfR1 antibody is at least about 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M, 10 -9 M, 10 -10 M, 10 -11 M, 10 -12 M, 10 -13In some embodiments, the anti-TfR1 antibodies described herein bind to TfR1 (e.g., human or non-human primate TfR1) with a binding affinity (e.g., as indicated by a Kd) of 10 M or less. In some embodiments, the anti-TfR1 antibodies described herein bind to TfR1 with a Kd in the sub-nanomolar range. In some embodiments, the anti-TfR1 antibodies described herein selectively bind to transferrin receptor 1 (TfR1) but not to transferrin receptor 2 (TfR2). In some embodiments, the anti-TfR1 antibodies described herein bind to human TfR1 and cynomolgus TfR1 (e.g., 10 -7 M, 10 -8 M, 10 -9 M, 10 -10 M, 10 -11 M, 10 -12 M, 10 -13 M or smaller Kd) to mouse TfR1. The affinity and binding kinetics of the anti-TfR1 antibodies can be tested using any suitable method, including but not limited to biosensor technology (e.g., OCTET or BIACORE). In some embodiments, the binding of any one of the anti-TfR1 antibodies described herein does not compete with or inhibit transferrin binding to TfR1. In some embodiments, the binding of any one of the anti-TfR1 antibodies described herein does not compete with or inhibit HFE-beta2-microglobulin binding to TfR1.

[0087] Non-limiting examples of anti-TfR1 antibodies are shown in Table 2. [Table 2-1] [Table 2-2] [Table 2-3] [Table 2-4]

[0088] In some embodiments, the anti-TfR1 antibodies of the disclosure are humanized variants of any one of the anti-TfR1 antibodies shown in Table 2. In some embodiments, the anti-TfR1 antibodies of the disclosure comprise the same CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 as the CDR-H1, CDR-H2, and CDR-H3 of any one of the shown anti-TfR1 antibodies provided in Table 2, and comprise a humanized heavy chain variable region and / or (by way of example and) a humanized light chain variable region.

[0089] Exemplary amino acid sequences of anti-TfR1 antibodies described herein are shown in Table 3. [Table 3-1] [Table 3-2] [Table 3-3]

[0090] In some embodiments, an anti-TfR1 antibody of the present disclosure comprises a VH comprising CDR-H1, CDR-H2, and CDR-H3 of any one of the anti-TfR1 antibodies provided in Table 3, and comprises one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) amino acid mutations compared to the respective humanized VH provided in Table 3. Alternatively, or in addition (e.g., in addition), an anti-TfR1 antibody of the present disclosure comprises a VL comprising CDR-L1, CDR-L2, and CDR-L3 of any one of the anti-TfR1 antibodies provided in Table 3, and comprises one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more) amino acid mutations compared to the respective humanized VL provided in Table 3.

[0091] In some embodiments, the anti-TfR1 antibody of the present disclosure comprises a VH comprising CDR-H1, CDR-H2, and CDR-H3 of any one of the anti-TfR1 antibodies shown in Table 3, and comprising an amino acid sequence that is at least 70% (e.g., at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 99%) identical in the framework region compared to each VH shown in Table 3. Alternatively or in addition (e.g., in addition), the anti-TfR1 antibody of the present disclosure comprises a VL comprising CDR-L1, CDR-L2, and CDR-L3 of any one of the anti-TfR1 antibodies shown in Table 3, and comprising an amino acid sequence that is at least 70% (e.g., at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 99%) identical in the framework region compared to each VL shown in Table 3.

[0092] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:69 and a humanized VL comprising the amino acid sequence of SEQ ID NO:70.

[0093] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:71 and a humanized VL comprising the amino acid sequence of SEQ ID NO:70.

[0094] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:72 and a humanized VL comprising the amino acid sequence of SEQ ID NO:70.

[0095] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:73 and a humanized VL comprising the amino acid sequence of SEQ ID NO:74.

[0096] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:73 and a humanized VL comprising the amino acid sequence of SEQ ID NO:75.

[0097] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:76 and a humanized VL comprising the amino acid sequence of SEQ ID NO:74.

[0098] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:76 and a humanized VL comprising the amino acid sequence of SEQ ID NO:75.

[0099] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:77 and a humanized VL comprising the amino acid sequence of SEQ ID NO:78.

[0100] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:79 and a humanized VL comprising the amino acid sequence of SEQ ID NO:80.

[0101] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:77 and a humanized VL comprising the amino acid sequence of SEQ ID NO:80.

[0102] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO:154 and a humanized VL comprising the amino acid sequence of SEQ ID NO:155.

[0103] In some embodiments, the anti-TfR1 antibodies described herein are full-length IgG, which may include heavy and light chain constant regions from a human antibody. In some embodiments, the heavy chain of any of the anti-TfR1 antibodies described herein may include a heavy chain constant region (CH) or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof). The heavy chain constant region may be derived from any suitable source, e.g., human, mouse, rat, or rabbit. In one particular example, the heavy chain constant region is derived from human IgG (gamma heavy chain), e.g., IgG1, IgG2, or IgG4. An example of a human IgG1 constant region is as follows: ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO: 81)

[0104] In some embodiments, the heavy chain of any of the anti-TfR1 antibodies described herein comprises a mutant human IgG1 constant region. For example, the introduction of LALA mutations on the CH2 domain of human IgG1 (a mutant derived from mAb b12 mutated to replace the lower hinge residues Leu234 and Leu235 with Ala234 and Ala235) is known to reduce Fcγ receptor binding (Bruhns, P., et al. (2009) and Xu, D. et al. (2000)). The mutant human IgG1 constant region is shown below (mutations are bolded and underlined): [ka] (SEQ ID NO:82)

[0105] In some embodiments, the light chain of any of the anti-TfR1 antibodies described herein may further comprise a light chain constant region (CL), which may be any CL known in the art. In some examples, the CL is a kappa light chain. In other examples, the CL is a lambda light chain. In some embodiments, the CL is a kappa light chain, the sequence of which is given below: RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 83)

[0106] Heavy and light chain constant regions of other antibodies are well known in the art and include, for example, those provided in the IMGT database (www.imgt.org) or at www.vbase2.org / vbstat.php., both of which are incorporated herein by reference.

[0107] In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 81 or SEQ ID NO: 82. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region that contains 25 or less amino acid mutations (e.g., 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or less amino acid mutations) compared to SEQ ID NO: 81 or SEQ ID NO: 82. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region as shown in SEQ ID NO: 81. In some embodiments, the anti-TfR1 antibodies described herein comprise any one of the VHs listed in Table 3 or any variant thereof, and a heavy chain comprising the heavy chain constant region set forth in SEQ ID NO:82.

[0108] In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 83. In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region that contains 25 or less amino acid mutations (e.g., 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or less amino acid mutations) compared to SEQ ID NO: 83. In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region as represented by SEQ ID NO: 83.

[0109] Examples of IgG heavy and light chain amino acid sequences of the described anti-TfR1 antibodies are shown in Table 4 below. [Table 4-1] [Table 4-2] [Table 4-3] [Table 4-4]

[0110] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain that contains 25 or fewer amino acid mutations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid mutations) compared to the heavy chain set forth in any one of SEQ ID NOs: 84, 86, 87, 88, 91, 92, 94, and 156. Alternatively or in addition (for example, additionally), an anti-TfR1 antibody of the disclosure includes a light chain that contains 25 or fewer amino acid mutations (for example, no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid mutations) compared to the light chain set forth in any one of SEQ ID NOs: 85, 89, 90, 93, 95, and 157.

[0111] In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 84, 86, 87, 88, 91, 92, 94, and 156. Alternatively, or in addition (e.g., in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 85, 89, 90, 93, 95, and 157. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 84, 86, 87, 88, 91, 92, 94, and 156. Alternatively or additionally (by way of example, in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising the amino acid sequence of any one of SEQ ID NOs: 85, 89, 90, 93, 95 and 157.

[0112] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:84 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0113] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:86 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0114] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:87 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0115] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:88 and a light chain comprising the amino acid sequence of SEQ ID NO:89.

[0116] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:88 and a light chain comprising the amino acid sequence of SEQ ID NO:90.

[0117] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:91 and a light chain comprising the amino acid sequence of SEQ ID NO:89.

[0118] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:91 and a light chain comprising the amino acid sequence of SEQ ID NO:90.

[0119] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:92 and a light chain comprising the amino acid sequence of SEQ ID NO:93.

[0120] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:94 and a light chain comprising the amino acid sequence of SEQ ID NO:95.

[0121] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:92 and a light chain comprising the amino acid sequence of SEQ ID NO:95.

[0122] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:156 and a light chain comprising the amino acid sequence of SEQ ID NO:157.

[0123] In some embodiments, the anti-TfR1 antibody is a Fab fragment, a Fab' fragment, or a F(ab')2 fragment of an intact antibody (full-length antibody). An antigen-binding fragment of an intact antibody (full-length antibody) can be prepared by conventional methods (e.g., recombinantly or by digesting the heavy chain constant region of a full-length IgG using an enzyme such as papain). For example, an F(ab')2 fragment can be produced by pepsin or papain digestion of an antibody molecule, and an Fab fragment can be generated by reducing disulfide bridges of an F(ab')2 fragment. In some embodiments, the heavy chain region of the Fab fragment of the anti-TfR1 antibody described herein comprises the amino acid sequence of ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHT (SEQ ID NO: 96).

[0124] In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 96. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region that contains 25 or less amino acid mutations (e.g., 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or less amino acid mutations) compared to SEQ ID NO: 96. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising any one of the VHs or any variants thereof listed in Table 3, and a heavy chain constant region as set forth in SEQ ID NO: 96.

[0125] In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region that is at least 80%, at least 85%, at least 90%, at least 95%, or at least 99% identical to SEQ ID NO: 83. In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region that contains 25 or less amino acid mutations (e.g., 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or less amino acid mutations) compared to SEQ ID NO: 83. In some embodiments, the anti-TfR1 antibodies described herein comprise a light chain comprising any one of the VLs or any variants thereof listed in Table 3, and a light chain constant region as represented by SEQ ID NO: 83.

[0126] Examples of Fab heavy and light chain amino acid sequences of the described anti-TfR1 antibodies are shown in Table 5 below. [Table 5-1] [Table 5-2] [Table 5-3]

[0127] In some embodiments, an anti-TfR1 antibody of the present disclosure comprises a heavy chain that contains 25 or fewer amino acid mutations (e.g., no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid mutation) compared to a heavy chain set forth in any one of SEQ ID NOs: 97-103, 158, and 159. Alternatively or in addition (for example, additionally), an anti-TfR1 antibody of the disclosure includes a light chain that contains 25 or fewer amino acid mutations (for example, no more than 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 amino acid mutations) compared to the light chain set forth in any one of SEQ ID NOs: 85, 89, 90, 93, 95, and 157.

[0128] In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 97-103, 158, and 159. Alternatively, or in addition (e.g., in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 85, 89, 90, 93, 95, and 157. In some embodiments, the anti-TfR1 antibodies described herein comprise a heavy chain comprising an amino acid sequence at least 75% (e.g., 75%, 80%, 85%, 90%, 95%, 98%, or 99%) identical to any one of SEQ ID NOs: 97-103, 158, and 159. Alternatively or additionally (by way of example, in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising the amino acid sequence of any one of SEQ ID NOs: 85, 89, 90, 93, 95 and 157.

[0129] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:97 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0130] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:98 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0131] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:99 and a light chain comprising the amino acid sequence of SEQ ID NO:85.

[0132] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:100 and a light chain comprising the amino acid sequence of SEQ ID NO:89.

[0133] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:100 and a light chain comprising the amino acid sequence of SEQ ID NO:90.

[0134] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:101 and a light chain comprising the amino acid sequence of SEQ ID NO:89.

[0135] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:101 and a light chain comprising the amino acid sequence of SEQ ID NO:90.

[0136] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:102 and a light chain comprising the amino acid sequence of SEQ ID NO:93.

[0137] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:103 and a light chain comprising the amino acid sequence of SEQ ID NO:95.

[0138] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:102 and a light chain comprising the amino acid sequence of SEQ ID NO:95.

[0139] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:158 and a light chain comprising the amino acid sequence of SEQ ID NO:157.

[0140] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a heavy chain comprising the amino acid sequence of SEQ ID NO:159 and a light chain comprising the amino acid sequence of SEQ ID NO:157.

[0141] Other known anti-TfR1 antibodies Any other suitable anti-TfR1 antibody known in the art can be used as muscle targeting agent in the conjugate disclosed herein. Examples of known anti-TfR1 antibodies (including related references and binding epitopes) are listed in Table 6. In some embodiments, the anti-TfR1 antibody comprises any of the complementarity determining regions (CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3) of the anti-TfR1 antibodies provided herein, for example, the anti-TfR1 antibodies listed in Table 6. [Table 6-1] [Table 6-2] [Table 6-3]

[0142] In some embodiments, an anti-TfR1 antibody of the disclosure comprises one or more of the CDR-H (e.g., CDR-H1, CDR-H2, and CDR-H3) amino acid sequences from any one of the anti-TfR1 antibodies selected from Table 6. In some embodiments, an anti-TfR1 antibody comprises CDR-L1, CDR-L2, and CDR-L3 provided for any one of the anti-TfR1 antibodies selected from Table 6. In some embodiments, an anti-TfR1 antibody comprises CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 provided for any one of the anti-TfR1 antibodies selected from Table 6.

[0143] In some embodiments, the anti-TfR1 antibodies of the disclosure include any antibody that comprises a heavy chain variable domain and / or (by way of example and) a light chain variable domain of any anti-TfR1 antibody, such as any one of the anti-TfR1 antibodies selected from Table 6. In some embodiments, the anti-TfR1 antibodies of the disclosure include any antibody, such as any one of the anti-TfR1 antibodies selected from Table 6, that comprises a heavy chain variable pair and a light chain variable pair of any anti-TfR1 antibody.

[0144] Aspects of the present disclosure provide anti-TfR1 antibodies having heavy chain variable (VH) and / or (for example and) light chain variable (VL) domain amino acid sequences homologous to any of those described herein. In some embodiments, the anti-TfR1 antibody comprises a heavy chain variable sequence or a light chain variable sequence that is at least 75% (for example, 80%, 85%, 90%, 95%, 98%, or 99%) identical to the heavy chain variable sequence and / or any light chain variable sequence of any anti-TfR1 antibody, such as any one of the anti-TfR1 antibodies selected from Table 6. In some embodiments, the homologous heavy chain variable and / or (for example and) light chain variable amino acid sequence does not vary in any of the CDR sequences provided herein. For example, in some embodiments, a degree of sequence variation (for example, 75%, 80%, 85%, 90%, 95%, 98%, or 99%) may occur within the heavy chain variable and / or (for example and) light chain variable sequence excluding any of the CDR sequences provided herein. In some embodiments, any of the anti-TfR1 antibodies provided herein comprise heavy and light chain variable sequences that comprise framework sequences that are at least 75%, 80%, 85%, 90%, 95%, 98%, or 99% identical to the framework sequences of any anti-TfR1 antibody, such as any one of the anti-TfR1 antibodies selected from Table 6.

[0145] An example of a transferrin receptor antibody that may be used in accordance with the present disclosure is described in WO 2016 / 081643, which is incorporated herein by reference. The amino acid sequence of this antibody is shown in Table 7. [Table 7-1] [Table 7-2]

[0146] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a CDR-H1, CDR-H2, and CDR-H3 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 7. Alternatively, or in addition (by way of example, in addition), an anti-TfR1 antibody of the disclosure comprises a CDR-L1, CDR-L2, and CDR-L3 that are the same as the CDR-L1, CDR-L2, and CDR-L3 shown in Table 7.

[0147] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a CDR-L3 that comprises no more than three amino acid mutations (e.g., no more than three, two, or one amino acid mutations) compared to the CDR-L3 shown in Table 7. In some embodiments, an anti-TfR1 antibody of the disclosure comprises a CDR-L3 that contains one amino acid mutation compared to the CDR-L3 shown in Table 7. In some embodiments, an anti-TfR1 antibody of the disclosure comprises a CDR-L3 of QHFAGTPLT (SEQ ID NO: 126) according to the Kabat and Chothia definition system) or QHFAGTPL (SEQ ID NO: 127) according to the Contact definition system). In some embodiments, an anti-TfR1 antibody of the disclosure comprises a CDR-H1, CDR-H2, CDR-H3, CDR-L1, and CDR-L2 that are the same as the CDR-H1, CDR-H2, and CDR-H3 shown in Table 7, and comprises a CDR-L3 of QHFAGTPLT (SEQ ID NO: 126) according to the Kabat and Chothia definition system) or QHFAGTPL (SEQ ID NO: 127) according to the Contact definition system).

[0148] In some embodiments, anti-TfR1 antibodies of the disclosure comprise heavy chain CDRs that, collectively, are at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the heavy chain CDRs shown in Table 7. Alternatively, or in addition (e.g., in addition), anti-TfR1 antibodies of the disclosure comprise light chain CDRs that, collectively, are at least 80% (e.g., 80%, 85%, 90%, 95%, or 98%) identical to the light chain CDRs shown in Table 7.

[0149] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 124. Alternatively, or in addition (for example, in addition), an anti-TfR1 antibody of the disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 125.

[0150] In some embodiments, an anti-TfR1 antibody of the disclosure comprises a VH comprising the amino acid sequence of SEQ ID NO: 128. Alternatively, or in addition (for example, in addition), an anti-TfR1 antibody of the disclosure comprises a VL comprising the amino acid sequence of SEQ ID NO: 129.

[0151] In some embodiments, the anti-TfR1 antibodies of the present disclosure include a VH that contains 25 or fewer amino acid mutations (e.g., 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or fewer amino acid mutations) compared to the VH set forth in SEQ ID NO: 128. Alternatively, or in addition (e.g., in addition), the anti-TfR1 antibodies of the present disclosure include a VL that contains 15 or fewer amino acid mutations (e.g., 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 9, 8, 7, 6, 5, 4, 3, 2, or 1 or fewer amino acid mutations) compared to the VL set forth in SEQ ID NO: 129.

[0152] In some embodiments, the anti-TfR1 antibodies of the present disclosure are full-length IgG1 antibodies, which may include heavy and light chain constant regions from a human antibody. In some embodiments, the heavy chain of any of the anti-TfR1 antibodies described herein may include a heavy chain constant region (CH) or a portion thereof (e.g., CH1, CH2, CH3, or a combination thereof). The heavy chain constant region may be derived from any suitable source, e.g., human, mouse, rat, or rabbit. In one particular example, the heavy chain constant region is derived from human IgG (gamma heavy chain), e.g., IgG1, IgG2, or IgG4. An example of a human IgG1 constant region is as follows: ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSRDELTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLSLSPGK (SEQ ID NO: 81)

[0153] In some embodiments, the light chain of any of the anti-TfR1 antibodies described herein may further comprise a light chain constant region (CL), which may be any CL known in the art. In some examples, the CL is a kappa light chain. In other examples, the CL is a lambda light chain. In some embodiments, the CL is a kappa light chain, the sequence of which is given below: RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFNRGEC (SEQ ID NO: 83)

[0154] In some embodiments, the anti-TfR1 antibodies described herein are chimeric antibodies comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 132. Alternatively, or in addition (for example, in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising the amino acid sequence of SEQ ID NO: 133.

[0155] In some embodiments, the anti-TfR1 antibodies described herein are fully human antibodies comprising a heavy chain comprising the amino acid sequence of SEQ ID NO: 134. Alternatively, or in addition (for example, in addition), the anti-TfR1 antibodies described herein comprise a light chain comprising the amino acid sequence of SEQ ID NO: 135.

[0156] In some embodiments, the anti-TfR1 antibody is an antigen-binding fragment (Fab) of an intact antibody (full-length antibody). In some embodiments, the anti-TfR1 Fab described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 136. Alternatively, or in addition (for example, in addition), the anti-TfR1 Fab described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 133. In some embodiments, the anti-TfR1 Fab described herein comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 137. Alternatively, or in addition (for example, in addition), the anti-TfR1 Fab described herein comprises a light chain comprising the amino acid sequence of SEQ ID NO: 135.

[0157] The anti-TfR1 antibodies described herein can be any antibody form, including, but not limited to, intact (i.e., full-length) antibodies, antigen-binding fragments thereof (Fab, Fab', F(ab')2, Fv, etc.), single-chain antibodies, bispecific antibodies, or nanobodies. In some embodiments, the anti-TfR1 antibodies described herein are scFv. In some embodiments, the anti-TfR1 antibodies described herein are scFv-Fab (e.g., scFv fused to a portion of a constant region). In some embodiments, the anti-TfR1 antibodies described herein are scFv fused to a constant region (e.g., the human IgG1 constant region set forth in SEQ ID NO:81).

[0158] In some embodiments, conservative mutations can be introduced into an antibody sequence (e.g., CDR or framework sequences) at positions where the residues are unlikely to be involved in interactions with a target antigen (e.g., transferrin receptor), as determined, for example, based on a crystal structure. In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region (e.g., in the CH2 domain (residues 231-340 of human IgG1), and / or (e.g., in the CH3 domain (residues 341-447 of human IgG1), and / or (e.g., in the hinge region), numbered according to the Kabat numbering system (e.g., EU index of Kabat)) of an anti-TfR1 antibody described herein to alter one or more functional properties of the antibody, such as serum half-life, complement binding, Fc receptor binding, and / or (e.g., and) antigen-dependent cellular cytotoxicity to cells.

[0159] In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the hinge region of the Fc region (CH1 domain) such that the number of cysteine ​​residues in the hinge region can be varied (e.g., increased or decreased) as described, e.g., in U.S. Patent No. 5,677,425. The number of cysteine ​​residues in the hinge region of the CH1 domain can be altered, e.g., to facilitate association of the light and heavy chains, or to alter (e.g., increase or decrease) the stability of the antibody, or to facilitate conjugation of a linker.

[0160] In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region of a muscle-targeting antibody described herein (e.g., in the CH2 domain (residues 231-340 of human IgG1), and / or (e.g., and) in the CH3 domain (residues 341-447 of human IgG1), and / or (e.g., and) in the hinge region, numbered according to the Kabat numbering system (e.g., EU index of Kabat)) to increase or decrease the affinity of the antibody for an Fc receptor (e.g., an activated Fc receptor) on the surface of an effector cell. Mutations in the Fc region of an antibody that increase or decrease the affinity of the antibody for an Fc receptor, and techniques for introducing such mutations into an Fc receptor or fragment thereof, are known to those of skill in the art. Examples of mutations in the Fc receptors of antibodies that can be made to alter the affinity of the antibody to the Fc receptor are described, by way of example, in Smith P et al., (2012) PNAS 109:6181-6186, U.S. Patent No. 6,737,056, and WO 02 / 060919, WO 98 / 23289, and WO 97 / 34631, which are incorporated herein by reference.

[0161] In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to alter (e.g., increase or decrease) the half-life of the antibody in vivo. For example, see WO 02 / 060919, WO 98 / 23289, and WO 97 / 34631, as well as U.S. Patent Nos. 5,869,046, 6,121,022, 6,277,375, and 6,165,745 for examples of mutations that may alter (e.g., increase or decrease) the half-life of the antibody in vivo.

[0162] In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to decrease the half-life of the anti-TfR1 antibody in vivo. In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to increase the half-life of the antibody in vivo. In some embodiments, the antibody may have one or more amino acid mutations (e.g., substitutions) in the second constant (CH2) domain (residues 231-340 of human IgG1) and / or (e.g., and) in the third constant (CH3) domain (residues 341-447 of human IgG1) numbered according to the EU index of Kabat (Kabat EA et al., (1991) supra). In some embodiments, the IgG1 constant region of the antibody described herein comprises a methionine (M) to tyrosine (Y) substitution at position 252, a serine (S) to threonine (T) substitution at position 254, and a threonine (T) to glutamic acid (E) substitution at position 256, numbered according to the EU index as in Kabat. See U.S. Patent No. 7,658,921, which is incorporated herein by reference. This type of mutant IgG, referred to as a "YTE mutant", has been shown to exhibit a 4-fold increased half-life compared to the wild-type version of the same antibody (see Dall'Acqua WF et al., (2006) J Biol Chem 281:23514-24). In some embodiments, the antibody comprises an IgG constant region comprising one, two, three or more amino acid substitutions of amino acid residues at positions 251-257, 285-290, 308-314, 385-389, and 428-436, numbered according to the EU index as in Kabat.

[0163] In some embodiments, one, two or more amino acid substitutions are introduced into the IgG constant region Fc region to change the effector function of anti-TfR1 antibody. The effector ligand with altered affinity to itself can be, for example, an Fc receptor or the C1 component of complement. This approach is described in more detail in U.S. Patent Nos. 5,624,821 and 5,648,260. In some embodiments, deletion or inactivation of constant region domains (through point mutations or other means) can reduce the binding of circulating antibodies to Fc receptors, thereby increasing tumor localization. For a description of mutations that delete or inactivate constant regions, thereby increasing tumor localization, see, for example, U.S. Patent Nos. 5,585,097 and 8,591,886. In some embodiments, one or more amino acid substitutions may be introduced in the Fc region of an antibody described herein to remove potential glycosylation sites in the Fc region, which may reduce binding to Fc receptors (see, e.g., Shields RL et al., (2001) J Biol Chem 276:6591-604).

[0164] In some embodiments, one or more amino acid residues in the constant region of the anti-TfR1 antibodies described herein may be replaced with different amino acid residues such that the antibody may have altered C1q binding and / or (by way of example and) reduced or eliminated complement-dependent cytotoxicity (CDC). This approach is described in more detail in U.S. Pat. No. 6,194,551 (Idusogie et al.). In some embodiments, one or more amino acid residues in the N-terminal region of the CH2 domain of the antibodies described herein are altered to thereby alter the antibody's ability to fix complement. This approach is described in more detail in WO 94 / 29351. In some embodiments, the Fc region of the antibodies described herein is modified to increase the antibody's ability to mediate antibody-dependent cellular cytotoxicity (ADCC) to cells and / or (by way of example and) to increase the affinity of the antibody to Fcγ receptors. This approach is described in more detail in WO 00 / 42072.

[0165] In some embodiments, the heavy and / or (by way of example) light chain variable domain sequences of the antibodies provided herein may be used to generate, for example, CDR-grafted, chimeric, humanized, or composite human antibodies, or antigen-binding fragments, as described elsewhere herein. As will be appreciated by one of skill in the art, any variant, CDR-grafted, chimeric, humanized, or composite antibody derived from any of the antibodies provided herein may be useful in the compositions and methods described herein, and will retain specific binding ability to the transferrin receptor, such that the variant, CDR-grafted, chimeric, humanized, or composite antibody may have at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or more binding to the transferrin receptor compared to the original antibody from which it is derived.

[0166] In some embodiments, the antibodies provided herein contain mutations that confer desired properties to the antibody. For example, to avoid potential complications due to Fab-arm exchange that is known to occur in natural IgG4 mAbs, the antibodies provided herein may contain a stabilizing "Adair" mutation (Angal S., et al., "A single amino acid substitution abolishes the heterogeneity of chimeric mouse / human (IgG4) antibody", Mol Immunol 30, 105-108; 1993), in which serine 228 (EU numbering; residue 241 Kabat numbering) is converted to a proline resulting in an IgG1-like hinge sequence. Thus, any of the antibodies may contain a stabilizing "Adair" mutation.

[0167] In some embodiments, the antibody is modified (e.g., modified via glycosylation, phosphorylation, sumoylation, and / or (e.g., and) methylation). In some embodiments, the antibody is a glycosylated antibody conjugated to one or more sugar or carbohydrate molecules. In some embodiments, the one or more sugar or carbohydrate molecules are conjugated to the antibody via N-glycosylation, O-glycosylation, C-glycosylation, glypiation (GPI anchor attachment), and / or (e.g., and) phosphoglycosylation. In some embodiments, the one or more sugar or carbohydrate molecules are monosaccharides, disaccharides, oligosaccharides, or glycans. In some embodiments, the one or more sugar or carbohydrate molecules are branched oligosaccharides or branched glycans. In some embodiments, the one or more sugar or carbohydrate molecules include mannose units, glucose units, N-acetylglucosamine units, N-acetylgalactosamine units, galactose units, fucose units, or phospholipid units. In some embodiments, the sugar molecules are present in an amount of about 1-10, about 1-5, about 5-10, about 1-4, about 1-3, or about 2. In some embodiments, the glycosylated antibody is fully or partially glycosylated. In some embodiments, the antibody is glycosylated by chemical reaction or by enzymatic means. In some embodiments, the antibody is glycosylated in vitro or intracellularly, and optionally may be deficient in an enzyme (e.g., glycosyltransferase) in the N- or O-glycosylation pathway. In some embodiments, the antibody is functionalized with a sugar or carbohydrate molecule as described in WO2014065661, published May 1, 2014, entitled "Modified antibody, antibody-conjugate and process for the preparation thereof."

[0168] In some embodiments, any one of the anti-TfR1 antibodies described herein may include a signal peptide (e.g., an N-terminal signal peptide) on the heavy and / or (e.g., and) light chain sequences. In some embodiments, the anti-TfR1 antibodies described herein include any one of the VH and VL sequences, any one of the IgG heavy and light chain sequences, or any one of the F(ab') heavy and light chain sequences described herein, and further include a signal peptide (e.g., an N-terminal signal peptide). In some embodiments, the signal peptide includes the amino acid sequence of MGWSCIILFLVATATGVHS (SEQ ID NO: 104). In some embodiments, the antibodies provided herein may have one or more post-translational modifications. In some embodiments, N-terminal cyclization, also referred to as pyroglutamic acid formation (pyroGlu), may occur on antibodies during production. In some embodiments, pyroglutamic acid formation may occur on antibodies during production at N-terminal glutamic acid (Glu) and / or glutamine (Gln) residues. Thus, it should be understood that an antibody identified as having a sequence that includes an N-terminal glutamate or glutamine residue includes an antibody that has undergone pyroglutamate formation due to post-translational modification. In some embodiments, pyroglutamic acid formation occurs on heavy chain sequences. In some embodiments, pyroglutamic acid formation occurs on light chain sequences.

[0169] b. Other muscle-targeting antibodies In some embodiments, the muscle-targeting antibody is an antibody that specifically binds to hemojuvelin, caveolin-3, Duchenne muscular dystrophy peptide, myosin IIb, or CD63. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds to a myogenic precursor protein. Exemplary myogenic precursor proteins include, but are not limited to, ABCG2, M-cadherin / cadherin-15, caveolin-1, CD34, FoxK1, integrin alpha7, integrin alpha7 beta1, MYF-5, MyoD, myogenin, NCAM-1 / CD56, Pax3, Pax7, and Pax9. In some embodiments, the muscle-targeting antibody is an antibody that specifically binds to a skeletal muscle protein. Exemplary skeletal muscle proteins include, but are not limited to, alpha-sarcoglycan, beta-sarcoglycan, calpain inhibitor, creatine kinase MM / CKMM, eIF5A, enolase 2 / neuron-specific enolase, epsilon-sarcoglycan, FABP3 / H-FABP, GDF-8 / myostatin, GDF-11 / GDF-8, integrin alpha 7, integrin alpha 7 beta 1, integrin beta 1 / CD29, MCAM / CD146, MyoD, myogenin, myosin light chain kinase inhibitor, NCAM-1 / CD56, and troponin I; in some embodiments, the muscle-targeting antibody is an antibody that specifically binds to a smooth muscle protein. Exemplary smooth muscle proteins include, without limitation, alpha-smooth muscle actin, VE-cadherin, caldesmon / CALD1, calponin 1, desmin, histamine H2 R, motilin R / GPR38, Transgelin / TAGLN, and vimentin, however, it will be understood that antibodies to additional targets are within the scope of this disclosure and that the exemplary list of targets provided herein is not intended to be limiting.

[0170] c. Antibody Features / Modifications In some embodiments, conservative mutations may be introduced into an antibody sequence (e.g., CDR or framework sequences) at positions where the residues are unlikely to be involved in interactions with the target antigen (e.g., transferrin receptor), as determined, for example, based on a crystal structure. In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region (e.g., in the CH2 domain (residues 231-340 of human IgG1), and / or (e.g., in the CH3 domain (residues 341-447 of human IgG1), and / or (e.g., in the hinge region), numbered according to the Kabat numbering system (e.g., EU index of Kabat)) of a muscle-targeting antibody described herein to alter one or more functional properties of the antibody, such as serum half-life, complement binding, Fc receptor binding, and / or (e.g., and) antigen-dependent cellular cytotoxicity to cells.

[0171] In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the hinge region of the Fc region (CH1 domain) such that the number of cysteine ​​residues in the hinge region can be varied (e.g., increased or decreased) as described, e.g., in U.S. Patent No. 5,677,425. The number of cysteine ​​residues in the hinge region of the CH1 domain can be altered, e.g., to facilitate association of the light and heavy chains, or to alter (e.g., increase or decrease) the stability of the antibody, or to facilitate conjugation of a linker.

[0172] In some embodiments, one, two or more mutations (e.g., amino acid substitutions) are introduced into the Fc region of a muscle-targeting antibody described herein (e.g., in the CH2 domain (residues 231-340 of human IgG1), and / or (e.g., and) in the CH3 domain (residues 341-447 of human IgG1), and / or (e.g., and) in the hinge region, numbered according to the Kabat numbering system (e.g., EU index of Kabat)) to increase or decrease the affinity of the antibody for an Fc receptor (e.g., an activated Fc receptor) on the surface of an effector cell. Mutations in the Fc region of an antibody that increase or decrease the affinity of the antibody for an Fc receptor, and techniques for introducing such mutations into an Fc receptor or fragment thereof, are known to those of skill in the art. Examples of mutations in the Fc receptors of antibodies that can be made to alter the affinity of the antibody to the Fc receptor are described, by way of example, in Smith P et al., (2012) PNAS 109:6181-6186, U.S. Patent No. 6,737,056, and WO 02 / 060919, WO 98 / 23289, and WO 97 / 34631, which are incorporated herein by reference.

[0173] In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to alter (e.g., increase or decrease) the half-life of the antibody in vivo. For example, see WO 02 / 060919, WO 98 / 23289, and WO 97 / 34631, as well as U.S. Patent Nos. 5,869,046, 6,121,022, 6,277,375, and 6,165,745 for examples of mutations that may alter (e.g., increase or decrease) the half-life of the antibody in vivo.

[0174] In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to decrease the half-life of the anti-transferrin receptor antibody in vivo. In some embodiments, one, two or more amino acid mutations (i.e., substitutions, insertions, or deletions) are introduced into the IgG constant region or FcRn-binding fragment thereof (preferably, Fc or hinge-Fc domain fragment) to increase the half-life of the antibody in vivo. In some embodiments, the antibody may have one or more amino acid mutations (e.g., substitutions) in the second constant (CH2) domain (residues 231-340 of human IgG1) and / or (e.g., and) in the third constant (CH3) domain (residues 341-447 of human IgG1) numbered according to the EU index of Kabat (Kabat EA et al., (1991) supra). In some embodiments, the IgG1 constant region of the antibody described herein comprises a methionine (M) to tyrosine (Y) substitution at position 252, a serine (S) to threonine (T) substitution at position 254, and a threonine (T) to glutamic acid (E) substitution at position 256, numbered according to the EU index as in Kabat. See U.S. Patent No. 7,658,921, which is incorporated herein by reference. This type of mutant IgG, referred to as a "YTE mutant", has been shown to exhibit a 4-fold increased half-life compared to the wild-type version of the same antibody (see Dall'Acqua WF et al., (2006) J Biol Chem 281:23514-24). In some embodiments, the antibody comprises an IgG constant region comprising one, two, three or more amino acid substitutions of amino acid residues at positions 251-257, 285-290, 308-314, 385-389, and 428-436, numbered according to the EU index as in Kabat.

[0175] In some embodiments, one or more amino acid substitutions are introduced into the IgG constant region Fc region to alter the effector function of the anti-transferrin receptor antibody. The effector ligand with altered affinity to itself can be, for example, an Fc receptor or the C1 component of complement. This approach is described in more detail in U.S. Patent Nos. 5,624,821 and 5,648,260. In some embodiments, deletion or inactivation of the constant region domain (through point mutation or other means) can reduce the binding of circulating antibodies to Fc receptors, thereby increasing tumor localization. See, for example, U.S. Patent Nos. 5,585,097 and 8,591,886 for a description of mutations that delete or inactivate constant regions, thereby increasing tumor localization. In some embodiments, one or more amino acid substitutions may be introduced in the Fc region of an antibody described herein to remove potential glycosylation sites in the Fc region, which may reduce binding to Fc receptors (see, e.g., Shields RL et al., (2001) J Biol Chem 276:6591-604).

[0176] In some embodiments, one or more amino acid residues in the constant region of the muscle-targeting antibody described herein may be replaced with a different amino acid residue such that the antibody may have altered C1q binding and / or (by way of example and) reduced or eliminated complement-dependent cytotoxicity (CDC). This approach is described in more detail in U.S. Pat. No. 6,194,551 (Idusogie et al.). In some embodiments, one or more amino acid residues in the N-terminal region of the CH2 domain of the antibody described herein are altered to thereby alter the antibody's ability to fix complement. This approach is described in more detail in WO 94 / 29351. In some embodiments, the Fc region of the antibody described herein is modified to increase the antibody's ability to mediate antibody-dependent cellular cytotoxicity (ADCC) to cells and / or (by way of example and) to increase the affinity of the antibody to Fcγ receptors. This approach is described in more detail in WO 00 / 42072.

[0177] In some embodiments, the heavy and / or (by way of example) light chain variable domain sequences of the antibodies provided herein may be used to generate, for example, CDR-grafted, chimeric, humanized, or composite human antibodies, or antigen-binding fragments, as described elsewhere herein. As will be appreciated by one of skill in the art, any variant, CDR-grafted, chimeric, humanized, or composite antibody derived from any of the antibodies provided herein may be useful in the compositions and methods described herein, and will retain specific binding ability to the transferrin receptor, such that the variant, CDR-grafted, chimeric, humanized, or composite antibody may have at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, at least 95% or more binding to the transferrin receptor compared to the original antibody from which it is derived.

[0178] In some embodiments, the antibodies provided herein contain mutations that confer desired properties to the antibody. For example, to avoid potential complications due to Fab-arm exchange that is known to occur in natural IgG4 mAbs, the antibodies provided herein may contain a stabilizing "Adair" mutation (Angal S., et al., "A single amino acid substitution abolishes the heterogeneity of chimeric mouse / human (IgG4) antibody", Mol Immunol 30, 105-108; 1993), in which serine 228 (EU numbering; residue 241 Kabat numbering) is converted to a proline resulting in an IgG1-like hinge sequence. Thus, any of the antibodies may contain a stabilizing "Adair" mutation.

[0179] As provided herein, the antibody of the present disclosure may optionally include a constant region or a portion thereof. For example, the VL domain may be attached at its C-terminus to a light chain constant region like Cκ or Cλ. Similarly, the VH domain or a portion thereof may be attached to all or a portion of a heavy chain like IgA, IgD, IgE, IgG, and IgM, and any subclass of isotype. The antibody may include a suitable constant region (see, for example, Kabat et al., Sequences of Proteins of Immunological Interest, No. 91-3242, National Institutes of Health Publications, Bethesda, Md. (1991)). Thus, the antibody within the scope of the present disclosure may include VH and VL domains, or antigen-binding portions thereof, combined with any suitable constant region.

[0180] ii. Muscle-targeting peptides Some aspects of the present disclosure provide muscle-targeting peptides as muscle-targeting agents. Short peptide sequences (e.g., peptide sequences between 5 and 20 amino acids in length) that bind to specific cell types have been described. For example, cell-targeting peptides can be found in Vines e.,et al.,A., "Cell-penetrating and cell-targeting peptides in drug delivery," Biochim Biophys Acta 2008,1786:126-38; Jarver P.,et al., "In vivo biodistribution and efficacy of peptide mediated delivery," Trends Pharmacol Sci 2010;31:528-35; Samoylova TI,et al., "Elucidation of muscle-binding peptides by phage display screening," Muscle Nerve 1999;22:460-6; ​​U.S. Patent No. 6,329,501, issued December 11, 2001, entitled "METHODS AND COMPOSITIONS FOR TARGETING COMPOUNDS TO MUSCLE," and Samoylov AM,et al., "Recognition of cell-specific binding of phage display derived peptides using an acoustic wave sensor." Biomol Eng 2002;18:269-72, the entire contents of each of which are incorporated herein by reference. By designing peptides to interact with specific cell surface antigens (e.g., receptors), selectivity to a desired tissue, e.g., muscle, can be obtained. Skeletal muscle targeting has been explored, and a wide range of molecular payloads can be delivered. These approaches, which do not have many of the practical disadvantages of large antibodies or viral particles, may have high selectivity for muscle tissue. Thus, in some embodiments, the muscle targeting agent is a muscle targeting peptide of 4 to 50 amino acids in length.In some embodiments, the muscle-targeting peptide is 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 amino acids in length. Muscle-targeting peptides can be generated using any of several methods, such as phage display.

[0181] In some embodiments, the muscle targeting peptide may bind to an internalizing cell surface receptor (e.g., transferrin receptor) that is overexpressed or relatively highly expressed in muscle cells compared to certain other cells. In some embodiments, the muscle targeting peptide may target (e.g., bind to) the transferrin receptor. In some embodiments, the transferrin receptor targeting peptide may include a segment of a naturally occurring ligand, e.g., transferrin. In some embodiments, the transferrin receptor targeting peptide is as described in U.S. Patent No. 6,743,893, 11 / 30 / 2000 application, "RECEPTOR-MEDIATED UPTAKE OF PEPTIDES THAT BIND THE HUMAN TRANSFERRIN RECEPTOR." In some embodiments, the transferrin receptor targeting peptide is as described in Kawamoto, M. et al, "A novel transferrin receptor-targeted hybrid peptide disintegrates cancer cell membrane to induce rapid killing of cancer cells." BMC Cancer. 2011 Aug 18;11:359. In some embodiments, the transferrin receptor targeting peptide is as described in U.S. Patent No. 8,399,653, filed 5 / 20 / 2011, "TRANSFERRIN / TRANSFERRIN RECEPTOR-MEDIATED SIRNA DELIVERY."

[0182] As mentioned above, examples of muscle targeting peptides have been reported. For example, muscle-specific peptides have been identified using phage display libraries that display surface heptapeptides. As an example, a peptide having the amino acid sequence ASSLNIA (SEQ ID NO: 130) bound to C2C12 mouse myotubes in vitro and to mouse muscle tissue in vivo. Thus, in some embodiments, the muscle targeting agent comprises the amino acid sequence ASSLNIA (SEQ ID NO: 130). This peptide exhibited improved specificity for binding to cardiac and skeletal muscle tissue after intravenous injection in mice, with reduced binding to liver, kidney, and brain. Additional muscle-specific peptides have been identified using phage display. For example, in the context of treatment for DMD, a 12 amino acid peptide was identified by a phage display library for muscle targeting. See Yoshida D., et al., "Targeting of salicylate to skin and muscle following topical injections in rats." Int J Pharm 2002;231:177-84. The entire contents of which are hereby incorporated by reference herein. Herein, a 12 amino acid peptide having the sequence SKTFNTHPQSTP (SEQ ID NO: 131) was identified, and this muscle-targeting peptide showed improved binding to C2C12 cells compared to the ASSLNIA (SEQ ID NO: 130) peptide.

[0183] Any additional method for identifying peptides selective for muscle (e.g., skeletal muscle) over other cell types includes in vitro selection, as described in Ghosh D., et al., "Selection of muscle-binding peptides from context-specific peptide-presenting phage libraries for adenoviral vector targeting," J Virol 2005;79:13667-72, the entire contents of which are incorporated herein by reference. Non-specific cell binders were selected by pre-incubating a random 12-mer peptide phage display library with a mixture of non-muscle cell types. After repeated selection, the 12 amino acid peptide TARGEHKEEELI (SEQ ID NO: 189) emerged most frequently. Thus, in some embodiments, the muscle targeting agent comprises the amino acid sequence TARGEHKEEELI (SEQ ID NO: 189).

[0184] The muscle targeting agent may be an amino acid-containing molecule or peptide. The muscle targeting peptide may correspond to a sequence of a protein that preferentially binds to a protein receptor found in muscle cells. In some embodiments, the muscle targeting peptide has a strong hydrophobic amino acid (e.g., valine) character such that the peptide may preferentially target muscle cells. In some embodiments, the muscle targeting peptide has not been previously characterized or disclosed. These peptides may be conceived, produced, synthesized, and / or (e.g., and) derivatized using any of several methodologies, e.g., phage-displayed peptide libraries, one-bead one-compound peptide libraries, or positional scanning synthetic peptide combinatorial libraries. Exemplary methodologies are characterized in the art and are incorporated by reference (Gray, BP and Brown, KC "Combinatorial Peptide Libraries: Mining for Cell-Binding Peptides" Chem Rev. 2014, 114:2, 1020-1081.; Samoylova, TI and Smith, BF "Elucidation of muscle-binding peptides by phage display screening." Muscle Nerve, 1999, 22:4.460-6.).In some embodiments, muscle-targeting peptides have been previously disclosed (see, e.g., Writer MJ et al. "Targeted gene delivery to human airway epithelial cells with synthetic vectors incorporating novel targeting peptides selected by phage display." J. Drug Targeting. 2004;12:185; Cai, D. "BDNF-mediated enhancement of inflammation and injury in the aging heart." Physiol Genomics. 2006,24:3,191-7.; Zhang, L. "Molecular profiling of heart endothelial cells." Circulation, 2005,112:11,1601-11.; McGuire, MJ et al. "In vitro selection of a peptide with high selectivity for cardiomyocytes in vivo." J Mol Biol. 2004,342:1,171-82). Exemplary muscle-targeting peptides include the following groups of amino acid sequences: CQAQGQLVC (SEQ ID NO: 201), CSERSMNFC (SEQ ID NO: 202), CPKTRRVPC (SEQ ID NO: 203), WLSEAGPVVTVRALRGTGSW (SEQ ID NO: 204), ASSLNIA (SEQ ID NO: 130), CMQHSMRVC (SEQ ID NO: 205), and DDTRHWG (SEQ ID NO: 206). In some embodiments, muscle-targeting peptides may include about 2-25 amino acids, about 2-20 amino acids, about 2-15 amino acids, about 2-10 amino acids, or about 2-5 amino acids. Muscle-targeting peptides may include naturally occurring amino acids, such as cysteine, alanine, or non-naturally occurring amino acids, or modified amino acids. Non-naturally occurring amino acids include β-amino acids, homo-amino acids, proline derivatives, 3-substituted alanine derivatives, linear core amino acids, N-methyl amino acids, and other amino acids known in the art.In some embodiments, the muscle-targeting peptide can be linear, while in other embodiments, the muscle-targeting peptide can be cyclic (e.g., bicyclic) (see, e.g., Silvana, MGet al. Mol. Therapy, 2018, 26:1, 132-147).

[0185] iii. Muscle-targeted receptor ligands The muscle targeting agent may be a ligand, e.g., a ligand that binds to a receptor protein. The muscle targeting ligand may be a protein, e.g., transferrin, that binds to an internalized cell surface receptor expressed by muscle cells. Thus, in some embodiments, the muscle targeting agent is transferrin or a derivative thereof that binds to the transferrin receptor. The muscle targeting ligand may alternatively be a small molecule, e.g., a lipophilic small molecule that preferentially targets muscle cells over other cell types. Exemplary lipophilic small molecules that may target muscle cells include compounds that include cholesterol, cholesteryl, stearic acid, palmitic acid, oleic acid, oleyl, linoleic acid, linoleic acid, myristic acid, sterol, dihydrotestosterone, testosterone derivatives, glycerin, alkyl chains, trityl groups, and alkoxy acids.

[0186] iv. Muscle-targeting aptamers The muscle targeting agent may be an aptamer, e.g., an RNA aptamer, that preferentially targets muscle cells over other cell types. In some embodiments, the muscle targeting aptamers have not been previously characterized or disclosed. These aptamers may be conceived, produced, synthesized, and / or (e.g., and) derivatized using any of several methodologies, e.g., systematic evolution of ligands by exponential enrichment. Exemplary methodologies have been characterized in the art and are incorporated by reference (Yan, A C and Levy, M. "Aptamers and aptamer targeted delivery" RNA biology, 2009, 6:3, 316-20.; Germer, K. et al. "RNA aptamers and their therapeutic and diagnostic applications." Int. J. Biochem. Mol. Biol. 2013; 4:27-40). In some embodiments, muscle-targeting aptamers have been previously disclosed (see, e.g., Phillippou, S. et al. "Selection and Identification of Skeletal-Muscle-Targeted RNA Aptamers." Mol Ther Nucleic Acids. 2018, 10:199-214.; Thiel, W H et al. "Smooth Muscle Cell-targeted RNA Aptamer Inhibits Neointimal Formation." Mol Ther. 2016, 24:4, 779-87). Exemplary muscle-targeting aptamers include the A01B RNA aptamer and RNA Apt 14. In some embodiments, the aptamer is a nucleic acid-based aptamer, an oligonucleotide aptamer, or a peptide aptamer. In some embodiments, the aptamer may be about 5-15 kDa, about 5-10 kDa, about 10-15 kDa, about 1-5 Da, about 1-3 kDa, or smaller.

[0187] v. Other muscle-targeting agents One strategy for targeting muscle cells (e.g., skeletal muscle cells) is to use a substrate of a muscle transporter protein, such as a transporter protein expressed on the sarcolemma. In some embodiments, the muscle targeting agent is a substrate of an influx transporter specific to muscle tissue. In some embodiments, the influx transporter is specific to skeletal muscle tissue. The two major classes of transporters expressed on the sarcolemma of skeletal muscle are (1) the adenosine triphosphate (ATP)-binding cassette (ABC) superfamily, which facilitates efflux from skeletal muscle tissue, and (2) the solute carrier (SLC) superfamily, which can facilitate the influx of substrates into skeletal muscle. In some embodiments, the muscle targeting agent is a substrate that binds to the ABC or SLC superfamily of transporters. In some embodiments, the substrate that binds to the ABC or SLC superfamily of transporters is a naturally occurring substrate. In some embodiments, the substrate that binds to the ABC or SLC superfamily of transporters is a non-naturally occurring substrate, such as a synthetic derivative thereof that binds to the ABC or SLC superfamily of transporters.

[0188] In some embodiments, the muscle targeting agent is any of the muscle targeting agents described herein that target the SLC superfamily of transporters (e.g., antibodies, nucleic acids, small molecules, peptides, aptamers, lipids, sugar moieties).In some embodiments, the muscle targeting agent is a substrate of the SLC superfamily of transporters.SLC transporters are either equilibria or use the proton or sodium ion gradient created across the membrane to drive transport of the substrate. Exemplary SLC transporters with high expression in skeletal muscle include, without limitation, the SATT transporter (ASCT1; SLC1A4), the GLUT4 transporter (SLC2A4), the GLUT7 transporter (GLUT7; SLC2A7), the ATRC2 transporter (CAT-2; SLC7A2), the LAT3 transporter (KIAA0245; SLC7A6), the PHT1 transporter (PTR4; SLC15A4), the OATP-J transporter (OATP5A1; SLC21A15), the OCT3 transporter (EMT; SLC22A3), the OCTN2 transporter (FLJ46769; SLC22A5), the ENT transporters (ENT1; SLC29A1 and ENT2; SLC29A2), the PAT2 transporter (SLC36A2), and the SAT2 transporter (KIAA1382; SLC38A2). These transporters may facilitate the entry of substrates into skeletal muscle, providing opportunities for muscle targeting.

[0189] In some embodiments, the muscle targeting agent is a substrate of equilibrative nucleoside transporter 2 (ENT2) transporter. Compared to other transporters, ENT2 has one of the highest mRNA expression in skeletal muscle. Human ENT2 (hENT2) is expressed in most body organs, such as brain, heart, placenta, thymus, pancreas, prostate, and kidney, but is particularly abundant in skeletal muscle. Human ENT2 facilitates the uptake of its substrates according to their concentration gradient. ENT2 plays a role in maintaining nucleoside homeostasis by transporting a wide range of purine and pyrimidine nucleobases. hENT2 transporter has low affinity for all nucleosides except inosine (adenosine, guanosine, uridine, thymidine, and cytidine). Thus, in some embodiments, the muscle targeting agent is an ENT2 substrate. Exemplary ENT2 substrates include, but are not limited to, inosine, 2',3'-dideoxyinosine, and clofarabine. In some embodiments, any of the muscle targeting agents provided herein are associated with a molecular payload (e.g., an oligonucleotide payload). In some embodiments, the muscle targeting agent is covalently linked to the molecular payload. In some embodiments, the muscle targeting agent is non-covalently linked to the molecular payload.

[0190] In some embodiments, the muscle targeting agent is a substrate for the organic cation / carnitine transporter (OCTN2), a sodium ion-dependent high affinity carnitine transporter. In some embodiments, the muscle targeting agent is carnitine, mildronate, acetylcarnitine, or any derivative thereof that binds to OCTN2. In some embodiments, carnitine, mildronate, acetylcarnitine, or a derivative thereof is covalently linked to a molecular payload (e.g., an oligonucleotide payload).

[0191] The muscle targeting agent may be a protein, which is a protein that exists in at least one soluble form that targets muscle cells. In some embodiments, the muscle targeting protein may be the protein hemojuvelin (also known as repulsive guidance molecule C or hemochromatosis type 2 protein), which is involved in iron overload and homeostasis. In some embodiments, the hemojuvelin may be full-length or a fragment, or a variant having at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99% sequence identity to a functional hemojuvelin protein. In some embodiments, the hemojuvelin variant may be a soluble fragment, may lack the N-terminal signaling and / or (by way of example and) may lack the C-terminal anchoring domain. In some embodiments, the hemojuvelin may be annotated as GenBank RefSeq accession numbers NM_001316767.1, NM_145277.4, NM_202004.3, NM_213652.3, or NM_213653.3. It will be appreciated that the hemojuvelin may be of human, non-human primate, or rodent origin.

[0192] B. Molecular Payload Some aspects of the disclosure provide molecular payloads, e.g., for modulating a biological outcome (e.g., transcription of a DNA sequence, expression of a protein, or activity of a protein). In some embodiments, the molecular payload is covalently linked to or otherwise associated with the molecular payload. In some embodiments, such molecular payloads are capable of targeting muscle cells, e.g., via specific binding to a nucleic acid or protein in a muscle cell upon delivery to the muscle cell by an associated muscle targeting agent. Of course, various types of muscle targeting agents can be used in accordance with the disclosure. For example, the molecular payload can include or consist of an oligonucleotide (e.g., an antisense oligonucleotide), a peptide (e.g., a peptide that binds to a nucleic acid or protein in a muscle cell associated with a disease), a protein (e.g., a protein that binds to a nucleic acid or protein in a muscle cell associated with a disease), or a small molecule (e.g., a small molecule that modulates the function of a nucleic acid or protein in a muscle cell associated with a disease). In some embodiments, the molecular payload is an oligonucleotide that includes a strand having a region of complementarity to FXN (e.g., GAA repeats). Exemplary molecular payloads are described in further detail herein, although it will be understood that the exemplary molecular payloads provided herein are not intended to be limiting.

[0193] i. Oligonucleotides Any suitable oligonucleotide may be used as described herein as a molecular payload. In some embodiments, the oligonucleotide may be designed to cause degradation of mRNA (e.g., the oligonucleotide may be a gapmer, siRNA, ribozyme, or aptamer that causes degradation). In some embodiments, the oligonucleotide may be designed to block translation of mRNA (e.g., the oligonucleotide may be a mixmer, siRNA, or aptamer that blocks translation). In some embodiments, the oligonucleotide may be designed to block the formation of an R-loop between FXN RNA containing an expanded GAA repeat and chromosomal DNA. In some embodiments, the oligonucleotide is complementary to FXN RNA and is useful, e.g., in subjects with or suspected of having Friedreich's ataxia, to increase the level of functional FXN by blocking FXN RNA containing an expanded GAA repeat. In some embodiments, the oligonucleotide may be designed to cause degradation of mRNA to block its translation. In some embodiments, the oligonucleotide may be a guide nucleic acid (e.g., a guide RNA) to direct the activity of an enzyme (e.g., a gene editing enzyme). Other examples of oligonucleotides are provided herein. Of course, in some embodiments, oligonucleotides of one format (e.g., antisense oligonucleotides) may be suitably adapted to another format (e.g., siRNA oligonucleotides) by incorporating functional sequences from one format (e.g., antisense strand sequences) into the other format.

[0194] Examples of oligonucleotides useful for targeting FXN and / or otherwise compensating for frataxin deficiency can be found in Li, L. et al., "Activating frataxin expression by repeat-targeted nucleic acids," Nat. Comm. 2016, 7:10606., WO 2016 / 094374, published June 16, 2016; "Compositions and methods for treatment of Friedreich's ataxia.", WO 2015 / 020993, published February 12, 2015; "RNAi COMPOSITIONS AND METHODS FOR TREATMENT OF FRIEDREICH'S ATAXIA," WO 2017 / 186815, published November 2, 2017; and "Antisense oligonucleotides for enhanced expression of "Compositions and methods for modulating expression of frataxin", WO 2008 / 018795, published February 14, 2008; "Methods and means for treating DNA repeat instability associated genetic disorders", U.S. Patent Application Publication No. 2018 / 0028557, published February 1, 2018; "Hybrid oligonucleotides and uses thereof", WO 2015 / 023975, published February 19, 2015; "Compositions and methods for modulating RNA", WO 2015 / 023939, published February 19, 2015; "Compositions and methods for modulating expression of frataxin", U.S. Patent Application Publication No. 2017 / 0281643, published October 5, 2017; "Compounds and methods for modulating frataxin expression", Li L. et al., "Activating frataxin expression by repeat-targeted nucleic acids," Nature Communications, published February 4, 2016, and Li L. et al., "Activation of Frataxin Protein Expression by Antisense Oligonucleotides Targeting the Mutant Expanded Repeat," Nucleic Acid Ther. 2018 Feb;28(1):23-33, the entire contents of each of which are incorporated herein by reference.

[0195] In some embodiments, the oligonucleotide payload is configured to inhibit expression of natural antisense transcripts that inhibit FXN expression (e.g., as a gapmer or RNAi oligonucleotide), as disclosed, for example, in U.S. Pat. No. 9,593,330, filed 6 / 9 / 2011, entitled "Treatment of frataxin (FXN) related diseases by inhibition of natural antisense transcript to FXN," the entire contents of which are incorporated herein by reference.

[0196] Examples of oligonucleotides for facilitating FXN gene editing include those described in WO 2016 / 094845, published June 16, 2016, entitled "Compositions and methods for editing nucleic acids in cells utilizing oligonucleotides," WO 2015 / 089354, published June 18, 2015, entitled "Compositions and methods of use of CRISPR-Cas systems in nucleotide repeat disorders," WO 2015 / 139139, published September 24, 2015, entitled "CRISPR-based methods and products for increasing frataxin levels and uses thereof," and WO 2018 / 002783, published January 4, 2018, entitled "Materials and methods for treatment of Friedreich ataxia and other related disorders," the contents of each of which are incorporated herein in their entirety.

[0197] Examples of oligonucleotides for promoting FXN gene expression through targeting non-FXN genes, such as epigenetic regulators of FXN, are described in International Publication No. WO 2015 / 023938, published February 19, 2015, entitled "Epigenetic regulators of frataxin," the entire contents of which are incorporated herein by reference.

[0198] In some embodiments, the oligonucleotide may have a region of complementarity to a sequence defined as the FXN gene from human (Gene ID 2395; NC_000009.12) and / or the FXN gene from mouse (Gene ID 14297; NC_000085.6). In some embodiments, the oligonucleotide may have a region of complementarity to a mutant form of FXN, as reported, for example, in Montermini, L. et al. "The Friedreich ataxia GAA triplet repeat: premutation and normal alleles." Hum. Molec. Genet., 1997, 6:1261-1266.; Filla, A. et al. "The relationship between trinucleotide (GAA) repeat length and clinical features in Friedreich ataxia." Am. J. Hum. Genet. 1996, 59:554-560.; Pandolfo, M. Friedreich ataxia: the clinical picture. J. Neurol. 2009, 256, 3-8. (the entire contents of each of which are incorporated herein by reference).

[0199] An exemplary human FXN gene nucleotide sequence corresponding to gene ID 2395; NM_000144.5 is as follows:

[0200] An exemplary mouse FXN gene nucleotide sequence corresponding to gene ID 2395; NM_008044.3 is as follows:

[0201] Oligonucleotide size / sequence Oligonucleotides may be of a variety of different lengths, for example depending on the format. In some embodiments, the oligonucleotides are 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, 75, or more nucleotides long. In some embodiments, the oligonucleotides are 8-50 nucleotides long, 8-40 nucleotides long, 8-30 nucleotides long, 10-15 nucleotides long, 10-20 nucleotides long, 15-25 nucleotides long, 21-23 nucleotides long, 20-25 nucleotides long, etc.

[0202] In some embodiments, the nucleic acid sequence of an oligonucleotide for the purposes of this disclosure is "complementary" to a target nucleic acid if it can specifically hybridize to the target nucleic acid. In some embodiments, an oligonucleotide that hybridizes to a target nucleic acid (e.g., an mRNA or pre-mRNA molecule) results in the modulation of the activity or expression of the target (e.g., reduced mRNA translation, altered pre-mRNA splicing, exon skipping, target mRNA degradation, etc.). In some embodiments, the nucleic acid sequence of an oligonucleotide has a sufficient degree of complementarity to its target nucleic acid so that it does not hybridize to non-target sequences under conditions where it is desired to avoid non-specific binding, e.g., physiological conditions. Thus, in some embodiments, an oligonucleotide can be at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% complementary to consecutive nucleotides of a target nucleic acid. In some embodiments, complementary nucleotide sequence can specifically hybridize to target nucleic acid or does not need to be 100% complementary to the sequence of the target specific to target nucleic acid.In certain embodiments, oligonucleotide comprises one or more mismatched nucleobases with respect to target nucleic acid.In certain embodiments, target-related activity is reduced by such mismatch, but non-target-related activity is reduced to a greater extent (i.e., selectivity for target nucleic acid is increased and off-target effect is reduced).

[0203] In some embodiments, the FXN targeting oligonucleotide comprises a nucleotide sequence comprising a region complementary to a target region comprising at least 10 consecutive nucleotides (e.g., at least 10, at least 12, at least 14, at least 16, at least 18, at least 20, or more consecutive nucleotides) in SEQ ID NO: 160 or SEQ ID NO: 161. In some embodiments, the FXN targeting oligonucleotide comprises a nucleotide sequence comprising a region complementary to a target region comprising a GAA trinucleotide repeat. In some embodiments, the FXN targeting oligonucleotide comprises a nucleotide sequence comprising a region complementary to an extended GAA trinucleotide repeat. In some embodiments, the region of complementarity is complementary to at least 8 consecutive nucleotides of the target nucleic acid. In some embodiments, the oligonucleotide may contain 1, 2, or 3 base mismatches compared to a portion of consecutive nucleotides of the target nucleic acid. In some embodiments, the oligonucleotide may have up to 3 mismatches for 15 bases or up to 2 mismatches for 10 bases.

[0204] In some embodiments, the oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 contiguous nucleotides of a sequence comprising any one of SEQ ID NOs: 165-176. In some embodiments, the oligonucleotide comprises a sequence comprising any one of SEQ ID NOs: 165-176. In some embodiments, the oligonucleotide comprises a sequence that shares at least 70%, 75%, 80%, 85%, 90%, 95%, or 97% sequence identity with at least 12 or at least 15 contiguous nucleotides of any one of SEQ ID NOs: 165-176.

[0205] In some embodiments, the oligonucleotide comprises a region of complementarity to a target sequence set forth in any one of SEQ ID NOs: 162-164. In some embodiments, the oligonucleotide comprises at least 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleotides (e.g., consecutive nucleotides) that are complementary to a nucleotide sequence set forth in any one of SEQ ID NOs: 162-164. In some embodiments, the oligonucleotide comprises a sequence that is at least 70%, 75%, 80%, 85%, 90%, 95%, 97%, 99%, or 100% complementary to at least 12 or at least 15 consecutive nucleotides of any one of SEQ ID NOs: 162-164.

[0206] In some embodiments, the oligonucleotide is complementary (e.g., at least 85%, at least 90%, at least 95%, or 100%) to the target sequence of any one of the oligonucleotides provided herein (e.g., the oligonucleotides listed in Table 8). In some embodiments, such target sequence is 100% complementary to the oligonucleotides listed in Table 8.

[0207] In some embodiments, it is understood that methylation of the nucleobase uracil at the C5 position forms thymine. Thus, in some embodiments, a nucleotide or nucleoside having a C5 methylated uracil (or 5-methyl-uracil) may be equivalently identified as a thymine nucleotide or nucleoside.

[0208] In some embodiments, any one or more of the thymine bases (T) in any one of the oligonucleotides provided herein (e.g., the oligonucleotides listed in Table 8) can optionally be uracil bases (U), and / or any one or more of the U can optionally be T.

[0209] b. Oligonucleotide modification The oligonucleotides described herein may be modified, including, for example, modified sugar moieties, modified internucleoside linkages, modified nucleotides or nucleosides, and / or combinations thereof.In addition, in some embodiments, the oligonucleotides may exhibit one or more of the following properties: do not mediate alternative splicing; are not immunostimulatory; are nuclease resistant; have improved cellular uptake compared to unmodified oligonucleotides; are not toxic to cells or mammals; have improved endosomal exit in cells; minimize TLR stimulation; or avoid pattern recognition receptors.Any modified chemical nature or format of the oligonucleotides described herein may be combined with each other.For example, one, two, three, four, five or more different types of modifications may be included in the same oligonucleotide.

[0210] In some embodiments, specific nucleotide or nucleoside modifications can be used that make the oligonucleotides they are incorporated into more resistant to nuclease digestion than natural oligodeoxynucleotide or oligoribonucleotide molecules, and these modified oligonucleotides remain intact for longer periods than unmodified oligonucleotides.Specific examples of modified oligonucleotides include those that contain modified backbones, such as phosphorothioates, phosphotriesters, methylphosphonates, short alkyl or cycloalkyl intersugar linkages, or short heteroatom or heterocyclic intersugar linkages.Thus, the oligonucleotides of the present disclosure can be stabilized against nucleic acid degradation by modifications, such as the incorporation of nucleotide or nucleoside modifications.

[0211] In some embodiments, the oligonucleotides can be up to 50 nucleotides in length or up to 100 nucleotides in length, with 2-10, 2-15, 2-16, 2-17, 2-18, 2-19, 2-20, 2-25, 2-30, 2-40, 2-45, or more nucleotides or nucleosides of the oligonucleotide being modified nucleotides / nucleosides. The oligonucleotides can be 8 to 30 nucleotides in length, with 2-10, 2-15, 2-16, 2-17, 2-18, 2-19, 2-20, 2-25, 2-30 nucleotides or nucleosides of the oligonucleotide being modified nucleotides / nucleosides. The oligonucleotide may be 8-15 nucleotides in length, and 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, 2-10, 2-11, 2-12, 2-13, 2-14 nucleotides or nucleosides of the oligonucleotide are modified nucleotides / nucleosides. Optionally, the oligonucleotide may be modified at all nucleotides or nucleosides except 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 nucleotides / nucleosides. Oligonucleotide modifications are described in more detail herein.

[0212] C modified nucleosides In some embodiments, the oligonucleotides described herein comprise at least one nucleoside modified at the 2' position of the sugar. In some embodiments, the oligonucleotide comprises at least one 2' modified nucleoside. In some embodiments, all of the nucleosides on the oligonucleotide are 2' modified nucleosides.

[0213] In some embodiments, the oligonucleotides described herein contain one or more non-bicyclic 2'-modified nucleosides, such as 2'-deoxy, 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'-O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), or 2'-O-N-methylacetamido (2'-O-NMA) modified nucleosides.

[0214] In some embodiments, the oligonucleotides described herein include one or more 2'-4' bicyclic nucleosides, in which the ribose ring in the nucleoside includes a bridging moiety that connects two atoms in the ring (e.g., the 2'-O atom to the 4'-C atom via a methylene (LNA) bridge, an ethylene (ENA) bridge, or an (S)-constrained ethyl (cEt) bridge). Examples of LNAs are described in International Publication No. 2008 / 043753, entitled "RNA Antagonist Compounds For The Modulation Of PCSK9," published April 17, 2008, the contents of which are incorporated herein by reference in their entirety. Examples of ENAs are provided in International Publication No. 2005 / 042777, published May 12, 2005, entitled "APP / ENA Antisense," Morita et al., Nucleic Acid Res., Suppl 1:241-242, 2001; Surono et al., Hum. Gene Ther., 15:749-757, 2004; Koizumi, Curr. Opin. Mol. Ther., 8:144-149, 2006; and Horie et al., Nucleic Acids Symp. Ser(Oxf), 49:171-172, 2005, the disclosures of which are incorporated herein by reference in their entireties. Examples of cEt are given in US Pat. No. 7,101,993, US Pat. No. 7,399,845 and US Pat. No. 7,569,686, each of which is incorporated herein by reference in its entirety.

[0215] In some embodiments, the oligonucleotides are disclosed in the following U.S. patents or published patent applications: U.S. Patent No. 7,399,845, issued July 15, 2008, entitled "6-Modified Bicyclic Nucleic Acid Analogs," U.S. Patent No. 7,741,457, issued June 22, 2010, entitled "6-Modified Bicyclic Nucleic Acid Analogs," U.S. Patent No. 8,022,193, issued September 20, 2011, entitled "6-Modified Bicyclic Nucleic Acid Analogs," U.S. Patent No. 7,569,686, issued August 4, 2009, entitled "Compounds And Methods For Synthesis Of Bicyclic Nucleic Acid Analogs," and U.S. Patent No. 7,335,765, issued February 26, 2008, entitled "Novel Nucleoside And Oligonucleotide Analogs." No. 7,314,923, issued Jan. 1, 2008, entitled "Novel Nucleoside And Oligonucleotide Analogues," U.S. Pat. No. 7,816,333, issued Oct. 19, 2010, entitled "Oligonucleotide Analogues And Methods Utilizing The Same," and U.S. Patent Application Publication No. 2011 / 0009471, now U.S. Pat. No. 8,957,201, issued Feb. 17, 2015, entitled "Oligonucleotide Analogues And Methods Utilizing The Same," the entire contents of each of which are incorporated herein by reference for all purposes.

[0216] In some embodiments, an oligonucleotide comprises at least one modified nucleoside that results in an increase in the Tm of the oligonucleotide in the range of 1° C., 2° C., 3° ​​C., 4° C., or 5° C., compared to an oligonucleotide that does not have at least one modified nucleoside. An oligonucleotide may have multiple modified nucleosides that, in total, result in an increase in the Tm of the oligonucleotide in the range of 2° C., 3° ​​C., 4° C., 5° C., 6° C., 7° C., 8° C., 9° C., 10° C., 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., or more, compared to an oligonucleotide that does not have the modified nucleoside.

[0217] An oligonucleotide may contain a mixture of different kinds of nucleosides. For example, an oligonucleotide may contain a mixture of 2'-deoxyribonucleosides or ribonucleosides and 2'-fluoro modified nucleosides. An oligonucleotide may contain a mixture of deoxyribonucleosides or ribonucleosides and 2'-O-Me modified nucleosides. An oligonucleotide may contain a mixture of 2'-fluoro modified nucleosides and 2'-O-methyl modified nucleosides. An oligonucleotide may contain a mixture of bridged nucleosides and 2'-fluoro or 2'-O-methyl modified nucleotides. An oligonucleotide may contain a mixture of non-bicyclic 2' modified nucleosides (e.g., 2'-O-MOE) and 2'-4' bicyclic nucleosides (e.g., LNA, ENA, cEt). The oligonucleotide may comprise a mixture of 2'-fluoro and 2'-O-Me modified nucleosides. The oligonucleotide may comprise a mixture of 2'-4' bicyclic nucleosides and 2'MOE, 2'-fluoro or 2'-O-Me modified nucleosides. The oligonucleotide may comprise a mixture of non-bicyclic 2' modified nucleosides (e.g., 2'-MOE, 2'-fluoro or 2'-O-Me) and 2'-4' bicyclic nucleosides (e.g., LNA, ENA, cEt).

[0218] Oligonucleotides may contain different types of alternating nucleosides. For example, oligonucleotides may contain alternating 2'-deoxyribonucleosides or ribonucleosides and 2'-fluoro modified nucleosides. Oligonucleotides may contain alternating deoxyribonucleosides or ribonucleosides and 2'-O-Me modified nucleosides. Oligonucleotides may contain alternating 2'-fluoro modified nucleosides and 2'-O-Me modified nucleosides. Oligonucleotides may contain alternating bridged nucleotides and 2'-fluoro or 2'-O-methyl modified nucleotides. Oligonucleotides may contain alternating non-bicyclic 2' modified nucleosides (e.g., 2'-O-MOE) and 2'-4' bicyclic nucleosides (e.g., LNA, ENA, cEt). The oligonucleotides may contain alternating 2'-4' bicyclic nucleosides and 2'-MOE, 2'-fluoro, or 2'-O-Me modified nucleosides. The oligonucleotides may contain alternating non-bicyclic 2' modified nucleosides (e.g., 2'-MOE, 2'-fluoro, or 2'-O-Me) and 2'-4' bicyclic nucleosides (e.g., LNA, ENA, cEt).

[0219] In some embodiments, the oligonucleotides described herein comprise a 5'-vinylphosphonate modification, one or more abasic residues, and / or one or more reverse abasic residues.

[0220] d. Internucleoside linkage / backbone In some embodiments, the oligonucleotide may contain phosphorothioate or other modified internucleoside linkages. In some embodiments, the oligonucleotide contains phosphorothioate internucleoside linkages. In some embodiments, the oligonucleotide contains phosphorothioate internucleoside linkages between at least two nucleosides. In some embodiments, the oligonucleotide contains phosphorothioate internucleoside linkages between all nucleosides. For example, in some embodiments, the oligonucleotide contains modified internucleoside linkages at the first, second, and / or (for example, and) third internucleoside linkages at the 5' or 3' end of the nucleotide sequence.

[0221] Phosphorus-containing linkages which may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkyl phosphotriesters, methyl and other alkyl phosphonates (including 3' alkylene phosphonates and chiral phosphonates), phosphinates, phosphoramidates (including 3'-amino phosphoramidates and aminoalkyl phosphoramidates), thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates, having normal 3'-5' linkages, 2'-5' linked analogs thereof, and those of reverse polarity (where adjacent pairs of nucleoside units are linked 3'-5' to 5'-3' or 2'-5' to 5'-2'), as described in U.S. Pat. No. 3,687,808, U.S. Pat. Nos. 4,469,863, 4,476,301, 5,023,243, 5,177,196, 5,188,897, 5,264,423, 5,276,019, 5,278,302, 5,286,717, 5,321,131, 5,399,676, 5,405,939, 5, See U.S. Patent Nos. 5,453,496, 5,455,233, 5,466,677, 5,476,925, 5,519,126, 5,536,821, 5,541,306, 5,550,111, 5,563,253, 5,571,799, 5,587,361, and 5,625,050.

[0222] In some embodiments, oligonucleotides may have heteroatom backbones such as methylene (methylimino) or MMI backbones, amide backbones (see De Mesmaeker et al. Ace. Chem. Res. 1995, 28:366-374), morpholino backbones (see Summerton and Weller, U.S. Pat. No. 5,034,506), or peptide nucleic acid (PNA) backbones (in which the phosphodiester backbone of the oligonucleotide is replaced by a polyamide backbone and the nucleotides are attached directly or indirectly to aza nitrogen atoms of the polyamide backbone, see Nielsen et al., Science 1991, 254, 1497).

[0223] e. Stereospecific oligonucleotides In some embodiments, the phosphorus atom between oligonucleotides of oligonucleotides is chiral, and the properties of the oligonucleotide are adjusted based on the configuration of the chiral phosphorus atom. In some embodiments, suitable methods can be used to synthesize P-chiral oligonucleotide analogs with stereocontrolled aspects (e.g., as described in Oka N, Wada T, Stereocontrolled synthesis of oligonucleotide analogs containing chiral internucleotidic phosphorus atoms. Chem Soc Rev. 2011 Dec; 40(12): 5829-43). In some embodiments, phosphorothioate-containing oligonucleotides are provided that include nucleoside units linked together by either substantially all Sp phosphorothioate intersugar linkages or substantially all Rp phosphorothioate intersugar linkages. In some embodiments, such phosphorothioate oligonucleotides with substantially chiral pure intersugar linkages are prepared by enzymatic synthesis or chemical synthesis, for example, as described in U.S. Patent No. 5,587,261, issued December 12, 1996, the contents of which are incorporated herein by reference in their entirety. In some embodiments, chiral controlled oligonucleotides provide selective cleavage patterns of target nucleic acid.For example, in some embodiments, chiral controlled oligonucleotides provide single cleavage sites within the complementary sequence of nucleic acid, as described, for example, in U.S. Patent Application Publication No. 20170037399, entitled "CHIRAL DESIGN," published on February 2, 2017 (the contents of which are incorporated herein by reference in their entirety).

[0224] f. gapmer In some embodiments, the oligonucleotides described herein are gapmers. Gapmer oligonucleotides generally have the formula 5'-XYZ-3' with X and Z as flanking regions around the gap region Y. In some embodiments, the flanking region X of the formula 5'-XYZ-3' is also referred to as the X region, flanking sequence X, 5' wing region X, or 5' wing segment. In some embodiments, the flanking region Z of the formula 5'-XYZ-3' is also referred to as the Z region, flanking sequence Z, 3' wing region Z, or 3' wing segment. In some embodiments, the gap region Y of the formula 5'-XYZ-3' is also referred to as the Y region, Y segment, or gap segment Y. In some embodiments, each nucleoside of the gap region Y is a 2'-deoxyribonucleoside, and neither the 5' wing region X nor the 3' wing region Z contains a 2'-deoxyribonucleoside.

[0225] In some embodiments, the Y region is a contiguous stretch of nucleotides, e.g., six or more DNA nucleotides, that can recruit RNases, such as RNase H. In some embodiments, the gapmer binds to a target nucleic acid, at which point RNases can be recruited and cleave the target nucleic acid from it. In some embodiments, the Y region is flanked on the 5' and 3' by regions X and Z that contain high affinity modified nucleosides, e.g., one to six high affinity modified nucleosides. Examples of high affinity modified nucleosides include, but are not limited to, 2' modified nucleosides (e.g., 2'-MOE, 2'O-Me, 2'-F) or 2'-4' bicyclic nucleosides (e.g., LNA, cEt, ENA). In some embodiments, the flanking sequences X and Z can be 1-20 nucleotides long, 1-8 nucleotides long, or 1-5 nucleotides long. The flanking sequences X and Z can be of similar or dissimilar length. In some embodiments, the gap segment Y can be a nucleotide sequence that is 5 to 20 nucleotides in length, 5 to 15, 12 nucleotides in length, or 6 to 10 nucleotides in length.

[0226] In some embodiments, the gap region of the gapmer oligonucleotide may contain, in addition to DNA nucleotides, modified nucleotides such as C4'-substituted nucleotides, acyclic nucleotides, and arabino-type nucleotides that are known to be permissive for efficient RNase H action. In some embodiments, the gap region contains one or more unmodified internucleosides. In some embodiments, one or both flanking regions each independently contain one or more phosphorothioate internucleoside linkages (e.g., phosphorothioate internucleoside linkages or other linkages) between at least two, at least three, at least four, at least five, or more nucleotides. In some embodiments, the gap region and the two flanking regions each independently contain modified internucleoside linkages (e.g., phosphorothioate internucleoside linkages or other linkages) between at least two, at least three, at least four, at least five, or more nucleotides.

[0227] Gapmers may be produced using any suitable method. Representative U.S. patents, U.S. patent application publications, and international publications that teach the preparation of gapmers include, but are not limited to, U.S. Pat. No. 5,013,830, U.S. Pat. No. 5,149,797, U.S. Pat. No. 5,220,007, U.S. Pat. No. 5,256,775, U.S. Pat. No. 5,366,878, U.S. Pat. No. 5,403,711, U.S. Pat. No. 5,491,133, U.S. Pat. No. 5,565,350, U.S. Pat. US Patent No. 5,623,065, US Patent No. 5,652,355, US Patent No. 5,652,356, US Patent No. 5,700,922, US Patent No. 5,898,031, US Patent No. 7,015,315, US Patent No. 7,101,993, US Patent No. 7,399,845, US Patent No. 7,432,250, US Patent No. 7,569,686, US Patent No. 7,683,036, US Patent No. 7,750, 131, U.S. Patent No. 8,580,756, U.S. Patent No. 9,045,754, U.S. Patent No. 9,428,534, U.S. Patent No. 9,695,418, U.S. Patent No. 10,017,764, U.S. Patent No. 10,260,069, U.S. Patent No. 9,428,534, U.S. Patent No. 8,580,756, U.S. Patent Application Publication No. 20050074801, U.S. Patent Application Publication No. 20090221685, U.S. Patent Application Publication No. No. 20090286969, U.S. Patent Application Publication No. 20100197762, and U.S. Patent Application Publication No. 20110112170, WO 2004069991, WO 2005023825, WO 2008049085, and WO 2009090182, and European Patent No. 2,149,605, each of which is incorporated herein by reference in its entirety.

[0228] In some embodiments, the gapmer is 10-40 nucleosides in length. For example, the gapmer can be 10-40, 10-35, 10-30, 10-25, 10-20, 10-15, 15-40, 15-35, 15-30, 15-25, 15-20, 20-40, 20-35, 20-30, 20-25, 25-40, 25-35, 25-30, 30-40, 30-35, or 35-40 nucleosides in length. In some embodiments, the gapmer is 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 nucleosides in length.

[0229] In some embodiments, the gap region Y of the gapmer is 5-20 nucleosides in length. For example, the gap region Y can be 5-20, 5-15, 5-10, 10-20, 10-15, or 15-20 nucleosides in length. In some embodiments, the gap region Y is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleosides in length. In some embodiments, each nucleoside in the gap region Y is a 2'-deoxyribonucleoside. In some embodiments, all nucleosides in the gap region Y are 2'-deoxyribonucleosides. In some embodiments, one or more of the nucleosides in the gap region Y are modified nucleosides (e.g., 2'-modified nucleosides such as those described herein). In some embodiments, one or more cytidines in the gap region Y are optionally 5-methylcytidines. In some embodiments, each cytidine in the gap region Y is a 5-methylcytidine.

[0230] In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') are independently 1 to 20 nucleosides in length. For example, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') can independently be 1 to 20, 1 to 15, 1 to 10, 1 to 7, 1 to 5, 1 to 3, 1 to 2, 2 to 5, 2 to 7, 3 to 5, 3 to 7, 5 to 20, 5 to 15, 5 to 10, 10 to 20, 10 to 15, or 15 to 20 nucleosides in length. In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') are independently 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nucleosides in length. In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') are the same length. In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') are different lengths. In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') is longer than the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3'). In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') is shorter than the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3').

[0231] In some embodiments, the gapmer is 5-10-5, 4-12-4, 3-14-3, 2-16-2, 1-18-1, 3-10-3, 2-10-2, 1-10-1, 2-8-2, 4-6-4, 3-6-3, 2-6-2, 4-7-4, 3-7-3, 2-7-2, 4-8-4, 3-8-3, 2-8-2, 1-8-1, 2-9-2, 1-9-1, 2-10-2, 1-10-1, 1-12-1, 1-16-1, 2-15-1, 1-15-2, 1-14-3, 3-14-1, 2-14-2, 1-13-4, 4-13-1, 2-13-3, 3-13-2, 1-12- 5, 5-12-1, 2-12-4, 4-12-2, 3-12-3, 1-11-6, 6-11-1, 2-11-5, 5-11-2, 3-11-4, 4-11-3, 1-17-1, 2-16-1, 1-16-2, 1-15-3, 3-15-1, 2-15-2, 1-14-4, 4-14 -1, 2-14-3, 3-14-2, 1-13-5, 5-13-1, 2-13-4, 4-13-2, 3-13-3, 1-12-6, 6-12-1, 2-12-5, 5-12-2, 3-12-4, 4-12-3, 1-11-7, 7-11-1, 2-11-6, 6-11-2, 3-1 1-5, 5-11-3, 4-11-4, 1-18-1, 1-17-2, 2-17-1, 1-16-3, 1-16-3, 2-16-2, 1-15-4, 4-15-1, 2-15-3, 3-15-2, 1-14-5, 5-14-1, 2-14-4, 4-14-2, 3-14-3, 1- 13-6, 6-13-1, 2-13-5, 5-13-2, 3-13-4, 4-13-3, 1-12-7, 7-12-1, 2-12-6, 6-12-2, 3-12-5, 5-12-3, 1-11-8, 8-11-1, 2-11-7, 7-11-2, 3-11-6, 6-11-3, 4 -11-5, 5-11-4, 1-18-1, 1-17-2, 2-17-1, 1-16-3, 3-16-1, 2-16-2, 1-15-4, 4-15-1, 2-15-3, 3-15-2, 1-14-5, 2-14-4, 4-14-2, 3-14-3, 1-13-6, 6-13-1, 2-13-5, 5-13-2, 3-13-4, 4-13-3, 1-12-7, 7-12-1, 2-12-6, 6-12-2, 3-12-5, 5-12-3, 1-11-8, 8-11-1, 2-11-7, 7-11-2, 3-11-6, 6-11-3, 4-11-5, 5-11-4,1-19-1、1-18-2、2-18-1、1-17-3、3-17-1、2-17-2、1-16-4、4-16-1、2-16-3、3-16-2、1-15-5、2-15-4、4-15-2、3-15-3、1-14-6、6-14-1、2-14-5、5-14-2、3-14-4、4-14-3、1-13-7、7-13-1、2-13-6、6-13-2、3-13-5、5-13-3、4-13-4、1-12-8、8-12-1、2-12-7、7-12-2、3-12-6、6-12-3、4-12-5、5-12-4、2-11-8、8-11-2、3-11-7、7-11-3、4-11-6、6-11-4、5-11-5、1-20-1、1-19-2、2-19-1、1-18-3、3-18-1、2-18-2、1-17-4、4-17-1、2-17-3、3-17-2、1-16-5、2-16-4、4-16-2、3-16-3、1-15-6、6-15-1、2-15-5、5-15-2、3-15-4、4-15-3、1-14-7、7-14-1、2-14-6、6-14-2、3-14-5、5-14-3、4-14-4、1-13-8、8-13-1、2-13-7、7-13-2、3-13-6、6-13-3、4-13-5、5-13-4、2-12-8、8-12-2、3-12-7、7-12-3、4-12-6、6-12-4、5-12-5、3-11-8、8-11-3、4-11-7、7-11-4、5-11-6、6-11-5、1-21-1、1-20-2、2-20-1、1-20-3、3-19-1、2-19-2、1-18-4、4-18-1、2-18-3、3-18-2、1-17-5、2-17-4、4-17-2、3-17-3、1-16-6、6-16-1、2-16-5、5-16-2、3-16-4、4-16-3、1-15-7、7-15-1、2-15-6、6-15-2、3-15-5、5-15-3、4-15-4、1-14-8、8-14-1、2-14-7、7-14-2、3-14-6、6-14-3、4-14-5、5-14-4、2-13-8、8-13-2、3-13-7、7-13-3、4-13-6、6-13-4、5-13-5、1-12-10、10-12-1、2-12-9、9-12-2、3-12-8、8-12-3、4-12-7、7-12-4、5-12-6、6-12-5、4-11-8, 8-11-4, 5-11-7, 7-11-5, 6-11-6, 1-22-1, 1-21-2, 2-21-1, 1-21-3, 3-20-1, 2-20-2, 1-19-4, 4-19-1, 2-19-3, 3-19-2, 1-18-5, 2-18-4, 4-18-2, 3-18-3, 1-17-6, 6-17-1, 2-17-5, 5-17-2, 3-17-4, 4-17-3, 1-16-7, 7-16-1, 2-16-6, 6-16-2, 3-16-5, 5-16-3, 4-16-4, 1 -15-8, 8-15-1, 2-15-7, 7-15-2, 3-15-6, 6-15-3, 4-15-5, 5-15-4, 2-14-8, 8-14-2, 3-14-7, 7-14-3, 4-14-6, 6-14-4, 5-14-5, 3-13-8, 8-13-3, 4-13-7, 7-13-4, 5-13-6, 6-13-5, 4-12-8, 8-12-4, 5-12-7, 7-12-5, 6-12-6, 5-11-8, 8-11-5, 6-11-7, or 7-11-6 5'-XYZ-3'. The numbers indicate the number of nucleosides in the X, Y, and Z regions in the 5'-XYZ-3' gapmer.

[0232] In some embodiments, one or more nucleosides in the 5' wing region of a gapmer (X in the 5'-XYZ-3' formula) or the 3' wing region of a gapmer (Z in the 5'-XYZ-3' formula) are modified nucleotides (e.g., high affinity modified nucleosides). In some embodiments, the modified nucleoside (e.g., high affinity modified nucleoside) is a 2' modified nucleoside. In some embodiments, the 2' modified nucleoside is a 2'-4' bicyclic nucleoside or a non-bicyclic 2' modified nucleoside. In some embodiments, the high affinity modified nucleoside is a 2'-4' bicyclic nucleoside (e.g., LNA, cEt, or ENA) or a non-bicyclic 2'-modified nucleoside (e.g., 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'-O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), or 2'-ON-methylacetamide (2'-O-NMA)).

[0233] In some embodiments, one or more nucleosides in the 5' wing region of the gapmer (X in the 5'-XYZ-3' formula) are high affinity modified nucleosides. In some embodiments, each nucleoside in the 5' wing region of the gapmer (X in the 5'-XYZ-3' formula) is a high affinity modified nucleoside. In some embodiments, one or more nucleosides in the 3' wing region of the gapmer (Z in the 5'-XYZ-3' formula) are high affinity modified nucleosides. In some embodiments, each nucleoside in the 3' wing region of the gapmer (Z in the 5'-XYZ-3' formula) is a high affinity modified nucleoside. In some embodiments, one or more nucleosides in the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') are high affinity modified nucleosides and one or more nucleosides in the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') are high affinity modified nucleosides. In some embodiments, each nucleoside in the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') is a high affinity modified nucleoside and each nucleoside in the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') is a high affinity modified nucleoside.

[0234] In some embodiments, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') comprises the same high affinity nucleosides as the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3'). For example, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') may comprise one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me). In another example, the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') may comprise one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, each nucleoside in the 5' wing region of the gapmer (X in the 5'-XYZ-3' formula) and the 3' wing region of the gapmer (Z in the 5'-XYZ-3' formula) is a non-bicyclic 2' modified nucleoside (e.g., 2'-MOE or 2'-O-Me). In some embodiments, each nucleoside in the 5' wing region of the gapmer (X in the 5'-XYZ-3' formula) and the 3' wing region of the gapmer (Z in the 5'-XYZ-3' formula) is a 2'-4' bicyclic nucleoside (e.g., LNA or cEt).

[0235] In some embodiments, a gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 1 to 7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6 to 10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, each nucleoside of X and Z is a non-bicyclic 2'-modified nucleoside (e.g., 2'-MOE or 2'-O-Me), and each nucleoside of Y is a 2' deoxyribonucleoside. In some embodiments, a gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 1 to 7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6 to 10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, each nucleoside of X and Z is a 2'-4' bicyclic nucleoside (e.g., LNA or cEt), and each nucleoside of Y is a 2' deoxyribonucleoside. In some embodiments, the 5' wing region of the gapmer (X of the 5'-XYZ-3' formula) comprises a different high affinity nucleoside than the 3' wing region of the gapmer (Z of the 5'-XYZ-3' formula). For example, the 5' wing region of the gapmer (X of the 5'-XYZ-3' formula) may include one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and the 3' wing region of the gapmer (Z of the 5'-XYZ-3' formula) may include one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt). In another example, the 3' wing region of the gapmer (Z of the 5'-XYZ-3' formula) may include one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and the 5' wing region of the gapmer (X of the 5'-XYZ-3' formula) may include one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt).

[0236] In some embodiments, a gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 1-7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, each nucleoside of X is a non-bicyclic 2' modified nucleoside (e.g., 2'-MOE or 2'-O-Me), each nucleoside of Z is a 2'-4' bicyclic nucleoside (e.g., LNA or cEt), and each nucleoside of Y is a 2'-deoxyribonucleoside. In some embodiments, a gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 1 to 7 (e.g., 1, 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6 to 10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, each nucleoside of X is a 2'-4' bicyclic nucleoside (e.g., LNA or cEt), each nucleoside of Z is a non-bicyclic 2' modified nucleoside (e.g., 2'MOE or 2'-O-Me), and each nucleoside of Y is a 2'-deoxyribonucleoside.

[0237] In some embodiments, the 5' wing region of the gapmer (X of the 5'-XYZ-3' formula) comprises one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, the 3' wing region of the gapmer (Z of the 5'-XYZ-3' formula) comprises one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt). In some embodiments, both the 5' wing region of the gapmer (X of the formula 5'-XYZ-3') and the 3' wing region of the gapmer (Z of the formula 5'-XYZ-3') comprise one or more non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and one or more 2'-4' bicyclic nucleosides (e.g., LNA or cEt).

[0238] In some embodiments, the gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, at least one but not all (e.g., 1, 2, 3, 4, 5, or 6) of positions 1, 2, 3, 4, 5, 6, or 7 of X (the 5'-most position is position 1) is a non-bicyclic 2' modified nucleoside (e.g., 2'-MOE or 2'-O-Me), the remainder of the nucleosides of both X and Z are 2'-4' bicyclic nucleosides (e.g., LNA or cEt), and each nucleoside of Y is a 2' deoxyribonucleoside. In some embodiments, the gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, at least one but not all (e.g., 1, 2, 3, 4, 5, or 6) of positions 1, 2, 3, 4, 5, 6, or 7 of Z (the 5'-most position is position 1) is a non-bicyclic 2' modified nucleoside (e.g., 2'-MOE or 2'-O-Me), the remainder of the nucleosides of both X and Z are 2'-4' bicyclic nucleosides (e.g., LNA or cEt), and each nucleoside of Y is a 2' deoxyribonucleoside.In some embodiments, a gapmer comprises a 5'-XYZ-3' configuration, where X and Z are independently 2-7 (e.g., 2, 3, 4, 5, 6, or 7) nucleosides in length, Y is 6-10 (e.g., 6, 7, 8, 9, or 10) nucleosides in length, and at least one, but not all (e.g., 1, 2, 3, 4, 5, 6, or 7) of positions 1, 2, 3, 4, 5, 6, or 7 of X and Z (the 5'-most position) are 5'-XYZ-3'. At least one of positions 1, 2, 3, 4, 5, 6, or 7, but not all of the nucleosides (e.g., 1, 2, 3, 4, 5, or 6, position 1 being position 1), is a non-bicyclic 2' modified nucleoside (e.g., 2'-MOE or 2'-O-Me), the remainder of the nucleosides of both X and Z are 2'-4' bicyclic nucleosides (e.g., LNA or cEt), and each nucleoside of Y is a 2' deoxyribonucleoside.

[0239] Non-limiting examples of gapmer configurations having mixtures of non-bicyclic 2' modified nucleosides (e.g., 2'-MOE or 2'-O-Me) and 2'-4' bicyclic nucleosides (e.g., LNA or cEt) in the 5' wing region of the gapmer (X in the 5'-XYZ-3' formula) and / or the 3' wing region of the gapmer (Z in the 5'-XYZ-3' formula) include, but are not limited to, BBB-(D)n-BBBAA; KKK-(D)n-KKKAA; LLL-(D)n-LLLAA; BBB-(D)n-BBBEE; KKK-(D)n-KKKEE; LLL-(D )n-LLLEE;BBB-(D)n-BBBAA;KKK-(D)n-KKKAA;LLL-(D)n-LLLAA;BBB-(D)n-BBBEE;KKK-(D)n-KKKEE;LLL-(D)n-LLLEE;BBB-(D)n-BBBAAA;KKK-(D)n -KKKAAA;LLL-(D)n-LLLAAA;BBB-(D)n-BBBEEE;KKK-(D)n-KKKEEE;LLL-(D)n-LLLEEE;BBB-(D)n-BBBAAA;KKK-(D)n-KKKAAA;LLL-(D)n-LLLAAA;BBB- (D)n-BBBEEE;KKK-(D)n-KKKEEE;LLL-(D)n-LLLEEE;BABA-(D)n-ABAB;KAKA-(D)n-AKAK;LALA-(D)n-ALAL;BEBE-(D)n-EBEB;KEKE-(D)n-EKEK;LELE -(D)n-ELEL;BABA-(D)n-ABAB;KAKA-(D)n-AKAK;LALA-(D)n-ALAL;BEBE-(D)n-EBEB;KEKE-(D)n-EKEK;LELE-(D)n-ELEL;ABAB-(D)n-ABAB;AKAK-(D) n-AKAK;ALAL-(D)n-ALAL;EBEB-(D)n-EBEB;EKEK-(D)n-EKEK;ELEL-(D)n-ELEL;ABAB-(D)n-ABAB;AKAK-(D)n-AKAK;ALAL-(D)n-ALAL;EBEB-(D)n-E BEB;EKEK-(D)n-EKEK;ELEL-(D)n-ELEL;AABB-(D)n-BBAA;BBAA-(D)n-AABB;AAKK-(D)n-KKAA;AALL-(D)n-LLAA;EEBB-(D)n-BBEE;EEKK-(D)n-KKEE;EELL-(D)n-LLEE;AABB-(D)n-BBAA;AAKK-(D)n-KKAA;AALL-(D)n-LLAA;EEBB-(D)n-BBEE;EEKK-(D)n-KKEE;EELL-(D)n-LLEE;BBB-(D)n-BBA;KKK-(BBA; D)n-KKA;LLL-(D)n-LLA;BBB-(D)n-BBE;KKK-(D)n-KKE;LLL-(D)n-LLE;BBB-(D)n-BBA;KKK-(D)n-KKA;LLL-(D)n-LLA;BBB-(D)n-BBE; E;LLL-(D)n-LLE;BBB-(D)n-BBA;KKK-(D)n-KKA;LLL-(D)n-LLA;BBB-(D)n-BBE;KKK-(D)n-KKE;LLL-(D)n-LLE;ABBB-(D)n-BBBA;ACC-KK-KKA; ALLL-(D)n-LLLA;EBBB-(D)n-BBBE;EKKK-(D)n-KKKE;ELLL-(D)n-LLLE;ABBB-(D)n-BBBA;AKKK-(D)n-KKKA;ALLL-(D)n-LLLA;EBBB-(D)n-BBBE;EKKK -(D)n-CCKE;ELLL-(D)n-LLLE;ABBB-(D)n-BBBAA;ACC-(D)n-CCKAA;ALLL-(D)n-LLLAA;EBBB-(D)n-BBBEE;ECC-(D)n-CCKEE;ELLL-(D)n-LLLEE;ACC-(D)n-LLLAA; BBB-(D)n-BBBAA;ACC-(D)n-CCKAA;ALLL-(D)n-LLLAA;EBBB-(D)n-BBBEE;CCK-(D)n-CCKEE;ELLL-(D)n-LLLEE;AABBB-(D)n-BBB;AACCC-(D)n-CCKK ;AALLL-(D)n-LLL;EEBBB-(D)n-BBB;EEKKK-(D)n-KKK;EELLL-(D)n-LLL;AABBB-(D)n-BBB;AACKK-(D)n-KKK;AALLL-(D)n-LLL; KKK-(D)n-KKK;EELLL-(D)n-LLL;AABBB-(D)n-BBBA;AACKK-(D)n-KKKA;AALLL-(D)n-LLLA;EEBBB-(D)n-BBBE;EEKK-(D)n-KKKE;EELLL-(D)n-LLLE;AABBB-(D)n-BBBA;AAKKK-(D)n-KKKA;AALLL-(D)n-LLLA;EEBBB-(D)n-BBBE;EEKKK-(D)n-KKKE;EELLL-(D)n-L LLE;ABBAABB-(D)n-BB;AKKAAKK-(D)n-KK;ALLAALLL-(D)n-LL;EBBEEBB-(D)n-BB;EKKEEKK-(D)n-KK;ELLEELL -(D)n-LL;ABBAABB-(D)n-BB;AKKAAKK-(D)n-KK;ALLAALL-(D)n-LL;EBBEEBB-(D)n-BB;EKKEEKK-(D)n-KK;ELL EELL-(D)n-LL;ABBABB-(D)n-BBB;AKKAKK-(D)n-KKK;ALLALLL-(D)n-LLL;EBBEBB-(D)n-BBB;EKKEKK-(D)n-KK K;ELLELL-(D)n-LLL;ABBABB-(D)n-BBB;AKKAKK-(D)n-KKK;ALLALL-(D)n-LLL;EBBEBB-(D)n-BBB;EKKEKK-(D) n-KKK;ELLELL-(D)n-LLL;EEEK-(D)n-EEEEEEEE;EEK-(D)n-EEEEEEEEEE;EK-(D)n-EEEEEEEEEE;EK-(D)n-EEEEKK ;K-(D)n-EEEKEKE;K-(D)n-EEEKEKEE;K-(D)n-EEKEK;EK-(D)n-EEEEKEKE;EK-(D)n-EEEKEK;EEK-(D)n-KEEKE; EK-(D)n-EEKEK;EK-(D)n-KEEK;EEK-(D)n-EEEKEK;EK-(D)n-KEEEKEE;EK-(D)n-EEKEKE;EK-(D)n-EEEKEKE;and EK-(D)n-EEEEKEK;. "A" nucleosides include 2' modified nucleosides, "B" represents a 2'-4' bicyclic nucleoside, "K" represents a constrained ethyl nucleoside (cEt), "L" represents an LNA nucleoside, "E" represents a 2'-MOE modified ribonucleoside, "D" represents a 2' deoxyribonucleoside, and "n" represents the length of the gap segment (Y in the 5'-XYZ-3' configuration) and is an integer between 1 and 20;

[0240] In some embodiments, any one of the gapmers described herein comprises one or more modified internucleoside linkages (e.g., phosphorothioate linkages) in each of the X, Y, and Z regions. In some embodiments, each internucleoside linkage in any one of the gapmers described herein is a phosphorothioate linkage. In some embodiments, each of the X, Y, and Z regions independently comprises a mixture of phosphorothioate and phosphodiester linkages. In some embodiments, each internucleoside linkage in gap region Y is a phosphorothioate linkage, 5' wing region X comprises a mixture of phosphorothioate and phosphodiester linkages, and 3' wing region Z comprises a mixture of phosphorothioate and phosphodiester linkages.

[0241] Non-limiting examples of FXN-targeting oligonucleotides are shown in Table 8. [Table 8-1] [Table 8-2]

[0242] In some embodiments, the FXN-targeting oligonucleotides described herein are 15-20 nucleosides in length (e.g., 15, 16, 17, 18, 19, or 20 nucleosides in length), contain a region of complementarity to at least 15 contiguous nucleosides (e.g., at least 15, at least 16, at least 17, at least 18, at least 19, or at least 20) of any one of SEQ ID NOs: 162-164, and contain a 5'-XYZ-3' configuration, wherein X contains 3-5 (e.g., 3, 4, or 5) linked nucleosides, and at least one of the nucleosides in X is 2-substituted. Y is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, LNA, cEt, or ENA), Y comprises 6 to 10 (e.g., 6, 7, 8, 9, or 10) linked 2'-deoxyribonucleosides, where each cytidine in Y is optionally and independently a 5-methyl-cytidine, and Z comprises 3 to 5 (e.g., 3, 4, or 5) linked nucleosides, where at least one of the nucleosides in Z is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, a 2'-O-Me modified nucleoside, LNA, cEt, or ENA).

[0243] In some embodiments, the FXN-targeting oligonucleotide comprises at least 15 contiguous nucleosides (e.g., at least 15, at least 16, at least 17, at least 18, at least 19, or at least 20) of the nucleotide sequence of any one of SEQ ID NOs: 165-176, and comprises a 5'-XYZ-3' configuration, wherein X comprises 3 to 5 (e.g., 3, 4, or 5) linked nucleosides, and at least one of the nucleosides in X is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, a 2'-O Y comprises 6 to 10 (e.g., 6, 7, 8, 9, or 10) linked 2'-deoxyribonucleosides, where each cytidine in Y is optionally independently a 5-methyl-cytidine, and Z comprises 3 to 5 (e.g., 3, 4, or 5) linked nucleosides, where at least one of the nucleosides in Z is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, a 2'-O-Me modified nucleoside, LNA, cEt, or ENA).

[0244] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-176, and comprises a 5'-XYZ-3' configuration, wherein X comprises 3 to 5 (e.g., 3, 4, or 5) linked nucleosides, at least one of the nucleosides in X is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, a 2'-O-Me modified nucleoside, LNA, cEt, or ENA), and Y is 6 to 10 (e.g., a 2'-MOE modified nucleoside, a 2'-O-Me modified nucleoside, LNA, cEt, or ENA). and Z comprises 3 to 5 (e.g., 3, 4, or 5) linked nucleosides, where at least one of the nucleosides in Z is a 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside, a 2'-O-Me modified nucleoside, LNA, cEt, or ENA).

[0245] In some embodiments, each nucleoside in X is a 2'-modified nucleoside and / or (for example and) each nucleoside in Z is a 2'-modified nucleoside. In some embodiments, the 2'-modified nucleoside is a 2'-4' bicyclic nucleoside (for example, LNA, cEt or ENA) or a non-bicyclic 2'-modified nucleoside (for example, a 2'-MOE modified nucleoside or a 2'-O-Me modified nucleoside).

[0246] In some embodiments, each nucleoside in X is a non-bicyclic 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside) and / or (for example and) each nucleoside in Z is a non-bicyclic 2'-modified nucleoside (e.g., a 2'-MOE modified nucleoside). In some embodiments, each nucleoside in X is a 2'-4' bicyclic nucleoside (e.g., an LNA, cEt or ENA) and / or (for example and) each nucleoside in Z is a 2'-4' bicyclic nucleoside (e.g., an LNA, cEt or ENA).

[0247] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-167 and comprises a 5'-XYZ-3' configuration, wherein X comprises 5 linked nucleosides, each nucleoside in X is a 2'-MOE modified nucleoside, and Y comprises 10 linked 2'-deoxyribonucleosides, wherein each cytidine in Y is optionally and independently a 5-methyl-cytidine, and Z comprises 5 linked nucleosides, each nucleoside in Z is a 2'-MOE modified nucleoside.

[0248] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-167 and comprises a 5'-XYZ-3' configuration, wherein X comprises 5 linked nucleosides, each nucleoside in X is an LNA nucleoside, and Y comprises 10 linked 2'-deoxyribonucleosides, wherein each cytidine in Y is optionally and independently a 5-methyl-cytidine, and Z comprises 5 linked nucleosides, each nucleoside in Z is an LNA nucleoside.

[0249] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 171-173, and comprises a 5'-XYZ-3' configuration, wherein X comprises three linked nucleosides, each nucleoside in X is an LNA nucleoside, and Y comprises 14 linked 2'-deoxyribonucleosides, wherein each cytidine in Y is optionally and independently a 5-methyl-cytidine, and Z comprises three linked nucleosides, each nucleoside in Z is an LNA nucleoside.

[0250] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 168-170, wherein each nucleoside is a 2'-MOE modified nucleoside.

[0251] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 168-170, wherein each T in the oligonucleotide is an LNA nucleoside and each C in the oligonucleotide is a 5-methyl-deoxycytidine.

[0252] In some embodiments, the FXN-targeting oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 174-176, wherein each C in the oligonucleotide is an LNA nucleoside and each T is a deoxythymidine.

[0253] In some embodiments, in any one of the FXN-targeting oligonucleotides described herein, each cytidine (e.g., a 2'-modified cytidine) in X and / or Z is optionally independently a 5-methyl-cytidine, and / or each uridine (e.g., a 2'-modified uridine) in X and / or Z is optionally independently a 5-methyl-uridine.

[0254] In some embodiments, any one of the FXN-targeting oligonucleotides described herein comprises one or more phosphorothioate internucleoside linkages. In some embodiments, each internucleoside linkage in the FXN-targeting oligonucleotide is a phosphorothioate internucleoside linkage.

[0255] In some embodiments, the FXN-targeting oligonucleotide is selected from modified ASO1-18 listed in Table 8. In some embodiments, any one of the FXN-targeting oligonucleotides can be in a salt form, such as, by way of example, a sodium, potassium, or magnesium salt.

[0256] In some embodiments, the 5' or 3' nucleoside (e.g., the terminal nucleoside) of any one of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table 8) is conjugated to an amine group, optionally via a spacer. In some embodiments, the spacer comprises an aliphatic moiety. In some embodiments, the spacer comprises a polyethylene glycol moiety. In some embodiments, a phosphodiester linkage is present between the spacer and the 5' or 3' nucleoside of the oligonucleotide. In some embodiments, the 5' or 3' nucleoside (e.g., the terminal nucleoside) of any one of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table 8) is conjugated to a spacer, which is a substituted or unsubstituted aliphatic, substituted or unsubstituted heteroaliphatic, substituted or unsubstituted carbocyclylene, substituted or unsubstituted heterocyclylene, substituted or unsubstituted arylene, substituted or unsubstituted heteroarylene, -O-, -N(R A )-, -S-, -C(=O)-, -C(=O)O-, -C(=O)NR A -, -NR A C(=O)-, -NR A C(=O)R A -, -C(=O)R A -, -NR A C(=O)O-, -NR A C(=O)N(R A )-, -OC(=O)-, -OC(=O)O-, -OC(=O)N(R A )-, -S(O)NR A -, -NR A S(O)-, or a combination thereof, where each R A are independently hydrogen or substituted or unsubstituted alkyl. In certain embodiments, the spacer is a substituted or unsubstituted alkylene, a substituted or unsubstituted heterocyclylene, a substituted or unsubstituted heteroarylene, -O-, -N(R A )-, or -C(=O)N(R A )2, or a combination of these.

[0257] In some embodiments, the 5' or 3' nucleoside of any one of the oligonucleotides described herein (e.g., the oligonucleotides listed in Table 8) has the formula -NH2-(CH2) n -, where n is an integer from 1 to 12. In some embodiments, n is 6, 7, 8, 9, 10, 11, or 12. In some embodiments, the phosphodiester linkage is of the formula NH2-(CH2) n - is present between the compound of formula NH2-(CH2)6- and the 5' or 3' nucleoside of the oligonucleotide. In some embodiments, the compound of formula NH2-(CH2)6- is conjugated to the oligonucleotide by reaction between 6-amino-1-hexanol (NH2-(CH2)6-OH) and the 5' phosphate of the oligonucleotide.

[0258] In some embodiments, the oligonucleotide is conjugated to a targeting agent, e.g., a muscle targeting agent such as an anti-TfR1 antibody, e.g., via an amine group.

[0259] g. RNA interference (RNAi) In some embodiments, the FXN-targeting oligonucleotides provided herein are small interfering RNAs (siRNAs), also known as small interfering RNAs or silencing RNAs. siRNAs are a class of double-stranded RNA molecules, typically about 20-25 base pairs in length, that target nucleic acids (e.g., mRNAs) for degradation via the RNA interference (RNAi) pathway in cells. The specificity of an siRNA molecule can be determined by the binding of the antisense strand molecule to its target RNA. Effective siRNA molecules are generally less than 30 to 35 base pairs in length to prevent triggering of non-specific RNA interference pathways in cells via the interferon response, although longer siRNAs can also be effective. In some embodiments, the siRNA molecules are 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more base pairs in length. In some embodiments, the siRNA molecule is 8-30 base pairs in length, 10-15 base pairs in length, 10-20 base pairs in length, 15-25 base pairs in length, 19-21 base pairs in length, 21-23 base pairs in length.

[0260] Upon selection of an appropriate target RNA sequence, siRNA molecules containing a nucleotide sequence complementary to all or a portion of the target sequence, i.e., an antisense sequence, can be designed and prepared using suitable methods (see, for example, WO 2004 / 016735, and U.S. Patent Application Publication Nos. 2004 / 0077574 and 2008 / 0081791).

[0261] siRNA molecules can be double-stranded (i.e., dsRNA molecules that contain an antisense strand and a complementary sense strand) or single-stranded (i.e., ssRNA molecules that contain only an antisense strand). siRNA molecules can contain duplexes, asymmetric duplexes, hairpins, or asymmetric hairpins secondary structures with self-complementary sense and antisense strands. In some embodiments, the FXN-targeting oligonucleotides described herein are siRNAs that contain antisense and sense strands.

[0262] In some embodiments, the antisense strand of the siRNA molecule is 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more nucleotides in length. In some embodiments, the antisense strand is 8 to 50 nucleotides in length, 8 to 40 nucleotides in length, 8 to 30 nucleotides in length, 10 to 15 nucleotides in length, 10 to 20 nucleotides in length, 15 to 25 nucleotides in length, 19 to 21 nucleotides in length, 21 to 23 nucleotides in length.

[0263] In some embodiments, the sense strand of the siRNA molecule is 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45, 50, or more nucleotides in length. In some embodiments, the sense strand is 8 to 50 nucleotides in length, 8 to 40 nucleotides in length, 8 to 30 nucleotides in length, 10 to 15 nucleotides in length, 10 to 20 nucleotides in length, 15 to 25 nucleotides in length, 19 to 21 nucleotides in length, 21 to 23 nucleotides in length.

[0264] In some embodiments, the siRNA molecule comprises an antisense strand that comprises a complementary region to a target region on FXN mRNA.In some embodiments, the complementary region is at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, or 100% complementary to the target region of FXN mRNA.In some embodiments, the target region is a region of consecutive nucleotides of FXN mRNA.In some embodiments, the complementary nucleotide sequence does not need to be 100% complementary to the sequence of the target in order to be specifically hybridizable or specific for the target RNA sequence.

[0265] In some embodiments, the siRNA molecule comprises an antisense strand that includes a region of complementarity to the FXN mRNA sequence, the region of complementarity being in the range of 8-15, 8-30, 8-40, or 10-50, or 5-50, or 5-40 nucleotides in length. In some embodiments, the region of complementarity is 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 nucleotides in length. In some embodiments, the region of complementarity is complementary to at least 6, at least 7, at least 8, at least 9, at least 10, at least 11, at least 12, at least 13, at least 14, at least 15, at least 16, at least 17, at least 18, at least 19, at least 20, at least 21, at least 22, at least 23, at least 24, at least 25, or more consecutive nucleotides of the FXN mRNA sequence. In some embodiments, the region of complementarity comprises a nucleotide sequence that comprises no more than 1, 2, 3, 4, or 5 base mismatches compared to the complementary portion of the FXN mRNA sequence. In some embodiments, the region of complementarity comprises a nucleotide sequence with up to 3 mismatches for 15 bases or up to 2 mismatches for 10 bases.

[0266] Double-stranded siRNA may comprise RNA strands of the same or different lengths. Double-stranded siRNA molecules can also be assembled from a single oligonucleotide of stem-loop structure (where the self-complementary sense and antisense regions of the siRNA molecule are linked using a nucleic acid-based or non-nucleic acid-based linker), as well as from a circular single-stranded RNA with two or more loop structures and a stem that comprises self-complementary sense and antisense strands (where the circular RNA can be processed either in vivo or in vitro to generate an active siRNA molecule that can mediate RNAi). Thus, small hairpin RNA (shRNA) molecules are also contemplated herein. These molecules contain a specific antisense sequence in addition to a reverse-complementary (sense) sequence, typically separated by a spacer or loop sequence. Cleavage of the spacer or loop provides the single-stranded RNA molecule and its reverse complement (optionally with an additional processing step that may result in the addition or removal of one, two, three or more nucleotides from the 3'-end and / or (for example and) 5'-end of one or both strands) so that they can anneal to form a dsRNA molecule. The spacer may be of sufficient length to allow the antisense and sense sequences to anneal to form a double-stranded structure (or stem) prior to cleavage of the spacer (and, optionally, subsequent processing steps that may result in the addition or removal of 1, 2, 3, 4 or more nucleotides from the 3' and / or (by way of example) the 5' end of one or both strands). The spacer sequence may be an unrelated nucleotide sequence placed between two complementary nucleotide sequence regions that, once annealed into the double-stranded nucleic acid, will comprise the shRNA.

[0267] The overall length of siRNA molecule can vary from about 14 to about 100 nucleotides depending on the type of siRNA molecule designed.Generally, between about 14 and about 50 of these nucleotides are complementary to RNA target sequence, i.e., constitute the specific antisense sequence of siRNA molecule.For example, when siRNA is double-stranded siRNA or single-stranded siRNA, the length can vary from about 14 to about 50 nucleotides, while when siRNA is shRNA or circular molecule, the length can vary from about 40 nucleotides to about 100 nucleotides.

[0268] The siRNA molecule may include a 3' overhang at one end of the molecule. The other end may be blunt or may have an overhang (5' or 3'). When the siRNA molecule includes an overhang at both ends of the molecule, the length of the overhang may be the same or different. In one embodiment, the siRNA molecule of the present disclosure includes a 3' overhang of about 1 to about 3 (e.g., 1, 2, 3) nucleotides at both ends of the molecule. In some embodiments, the siRNA molecule includes a 3' overhang of about 1 to about 3 nucleotides on the sense strand. In some embodiments, the siRNA molecule includes a 3' overhang of about 1 to about 3 (e.g., 1, 2, 3) nucleotides on the antisense strand. In some embodiments, the siRNA molecule includes a 3' overhang of about 1 to about 3 (e.g., 1, 2, 3) nucleotides on both the sense strand and the antisense strand.

[0269] In some embodiments, the siRNA molecule comprises one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) modified nucleotides. In some embodiments, the siRNA molecule comprises one or more modified nucleotides and / or (e.g., and) one or more modified internucleoside linkages. In some embodiments, the modified nucleotide is a modified sugar moiety (e.g., 2' modified nucleotide). In some embodiments, the siRNA molecule comprises one or more 2' modified nucleotides, such as 2'-deoxy, 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'-O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), or 2'-ON-methylacetamide (2'-O--NMA). In some embodiments, each nucleotide of the siRNA molecule is a modified nucleotide (such as a 2' modified nucleotide). In some embodiments, the siRNA molecule comprises one or more 2'-O-methyl modified nucleotides. In some embodiments, the siRNA molecule comprises one or more 2'-F modified nucleotides. In some embodiments, the siRNA molecule comprises one or more 2'-O-methyl modified nucleotides and 2'-F modified nucleotides.

[0270] In some embodiments, the siRNA molecule contains phosphorothioate or other modified internucleotidic linkages. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages between at least two nucleotides. In some embodiments, the siRNA molecule comprises phosphorothioate internucleoside linkages between all nucleotides. For example, in some embodiments, the siRNA molecule comprises modified internucleotidic linkages at the first, second, and / or (for example and) third internucleoside linkages at the 5' or 3' end of the siRNA molecule.

[0271] In some embodiments, the modified internucleotide linkage is a phosphorus-containing linkage. In some embodiments, phosphorus-containing linkages that can be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkyl phosphotriesters, methyl and other alkyl phosphonates, including 3' alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates, including 3'-amino phosphoramidates and aminoalkyl phosphoramidates, thionophosphoramidates, thionoalkyl phosphonates, thionoalkyl phosphotriesters, and boranophosphates, their 2'-5' linked analogs, and those with reverse polarity, in which adjacent pairs of nucleoside units are linked 3'-5' to 5'-3' or 2'-5' to 5'-2', as described in U.S. Patent No. 3,687,808, U.S. Patent No. 4,466,633, and the like. No. 9,863, U.S. Patent No. 4,476,301, U.S. Patent No. 5,023,243, U.S. Patent No. 5,177,196, U.S. Patent No. 5,188,897, U.S. Patent No. 5,264,423, U.S. Patent No. 5,276,019, U.S. Patent No. 5,278,302, U.S. Patent No. 5,286,717, U.S. Patent No. 5,321,131, U.S. Patent No. 5,399,676, U.S. Patent No. 5,405,939, U.S. Patent No. 5,45 See U.S. Patent Nos. 3,496, 5,455,233, 5,466,677, 5,476,925, 5,519,126, 5,536,821, 5,541,306, 5,550,111, 5,563,253, 5,571,799, 5,587,361, and 5,625,050.

[0272] Any modified chemistry or format of the siRNA molecules described herein can be combined with each other, for example, one, two, three, four, five, or more different types of modifications can be included in the same siRNA molecule.

[0273] In some embodiments, the antisense strand comprises one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) modified nucleosides. In some embodiments, the antisense strand comprises one or more modified nucleosides and / or (e.g., and) one or more modified internucleoside linkages. In some embodiments, the modified nucleotides comprise modified sugar moieties (e.g., 2' modified nucleotides). In some embodiments, the antisense strand comprises one or more 2' modified nucleosides, such as 2'-deoxy, 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'-O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), or 2'-ON-methylacetamide (2'-O--NMA). In some embodiments, each nucleoside in the antisense strand is a modified nucleotide (such as a 2' modified nucleoside). In some embodiments, the antisense strand comprises one or more 2'-O-methyl modified nucleosides. In some embodiments, the antisense strand comprises one or more 2'-F modified nucleosides. In some embodiments, the antisense strand comprises one or more 2'-O-methyl and 2'-F modified nucleosides.

[0274] In some embodiments, the antisense strand contains phosphorothioate internucleoside linkages or other modified internucleoside linkages. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages between at least two nucleosides. In some embodiments, the antisense strand comprises phosphorothioate internucleoside linkages between all nucleosides. For example, in some embodiments, the antisense strand comprises modified internucleoside linkages at the first, second, and / or (for example and) third internucleoside linkages at the 5' or 3' end of the siRNA molecule. In some embodiments, the two internucleoside linkages at the 3' end of the antisense strand are phosphorothioate internucleoside linkages.

[0275] In some embodiments, the modified internucleoside linkage is a phosphorus-containing linkage. In some embodiments, phosphorus-containing linkages that can be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkylphosphotriesters, methyl and other alkyl phosphonates, including 3' alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates, including 3'-amino phosphoramidates and aminoalkyl phosphoramidates, thionophosphoramidates, thionoalkylphosphonates, thionoalkylphosphotriesters, and boranophosphates, their 2'-5' linked analogs, and those with reverse polarity, in which adjacent pairs of nucleoside units are linked 3'-5' to 5'-3' or 2'-5' to 5'-2', as described in U.S. Patent No. 3,687,808, U.S. Patent No. 4,466,621, and the like. No. 9,863, U.S. Patent No. 4,476,301, U.S. Patent No. 5,023,243, U.S. Patent No. 5,177,196, U.S. Patent No. 5,188,897, U.S. Patent No. 5,264,423, U.S. Patent No. 5,276,019, U.S. Patent No. 5,278,302, U.S. Patent No. 5,286,717, U.S. Patent No. 5,321,131, U.S. Patent No. 5,399,676, U.S. Patent No. 5,405,939, U.S. Patent No. 5,45 See U.S. Patent Nos. 3,496, 5,455,233, 5,466,677, 5,476,925, 5,519,126, 5,536,821, 5,541,306, 5,550,111, 5,563,253, 5,571,799, 5,587,361, and 5,625,050.

[0276] Any of the antisense strand modified chemistries or formats described herein can be combined with each other, for example, one, two, three, four, five, or more different types of modifications can be included on the same antisense strand.

[0277] In some embodiments, the sense strand comprises one or more (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more) modified nucleotides. In some embodiments, the sense strand comprises one or more modified nucleosides and / or (e.g., and) one or more modified internucleoside linkages. In some embodiments, the modified nucleotides are modified sugar moieties (e.g., 2' modified nucleosides). In some embodiments, the sense strand comprises one or more 2' modified nucleosides, such as 2'-deoxy, 2'-fluoro (2'-F), 2'-O-methyl (2'-O-Me), 2'O-methoxyethyl (2'-MOE), 2'-O-aminopropyl (2'-O-AP), 2'-O-dimethylaminoethyl (2'-O-DMAOE), 2'-O-dimethylaminopropyl (2'-O-DMAP), 2'-O-dimethylaminoethyloxyethyl (2'-O-DMAEOE), or 2'-ON-methylacetamide (2'-O--NMA). In some embodiments, each nucleoside in the sense strand is a modified nucleoside (e.g., a 2' modified nucleoside). In some embodiments, the sense strand comprises one or more phosphorodiamidate morpholinos. In some embodiments, the sense strand is a phosphorodiamidate morpholino oligomer (PMO). In some embodiments, the sense strand comprises one or more 2'-O-methyl modified nucleosides. In some embodiments, the sense strand comprises one or more 2'-F modified nucleosides. In some embodiments, the sense strand comprises one or more 2'-O-methyl modified nucleosides and 2'-F modified nucleosides.

[0278] In some embodiments, the sense strand contains phosphorothioate or other modified internucleoside linkages. In some embodiments, the sense strand includes phosphorothioate internucleoside linkages. In some embodiments, the sense strand includes phosphorothioate internucleoside linkages between at least two nucleosides. In some embodiments, the sense strand includes phosphorothioate internucleoside linkages between all nucleosides. For example, in some embodiments, the sense strand includes modified internucleoside linkages at the first, second, and / or (for example and) third internucleoside linkages at the 5' or 3' end of the sense strand. In some embodiments, the sense strand includes phosphorodiester internucleoside linkages. In some embodiments, the sense strand does not include phosphorothioate internucleoside linkages. In some embodiments, the modified internucleoside linkages are phosphorus-containing linkages.In some embodiments, phosphorus-containing linkages that may be used include, but are not limited to, phosphorothioates, chiral phosphorothioates, phosphorodithioates, phosphotriesters, aminoalkyl phosphotriesters, methyl and other alkyl phosphonates including 3' alkylene phosphonates and chiral phosphonates, phosphinates, phosphoramidates including 3'-amino phosphoramidates and aminoalkyl phosphoramidates, thionophosphoramidates, thionoalkyl phosphonates, thionoalkyl phosphotriesters, and boranophosphates having normal 3'-5' linkages, as well as 2'-5' linked analogs thereof, and those having opposite polarity where adjacent pairs of nucleoside units are linked 3'-5' to 5'-3' or 2'-5' to 5'-2', as described in U.S. Pat. No. 3,687,808, U.S. Pat. No. 4,466,633, and the like. No. 9,863, U.S. Patent No. 4,476,301, U.S. Patent No. 5,023,243, U.S. Patent No. 5,177,196, U.S. Patent No. 5,188,897, U.S. Patent No. 5,264,423, U.S. Patent No. 5,276,019, U.S. Patent No. 5,278,302, U.S. Patent No. 5,286,717, U.S. Patent No. 5,321,131, U.S. Patent No. 5,399,676, U.S. Patent No. 5,405,939, U.S. Patent No. 5,45 See U.S. Patent Nos. 3,496, 5,455,233, 5,466,677, 5,476,925, 5,519,126, 5,536,821, 5,541,306, 5,550,111, 5,563,253, 5,571,799, 5,587,361, and 5,625,050.

[0279] Any of the sense strand modification chemistries or formats described herein can be combined with each other, for example, one, two, three, four, five, or more different types of modifications can be included on the same sense strand.

[0280] In some embodiments, the antisense or sense strand of the siRNA molecule comprises a modification that enhances or reduces RNA-induced silencing complex (RISC) loading. In some embodiments, the antisense strand of the siRNA molecule comprises a modification that enhances RISC loading. In some embodiments, the sense strand of the siRNA molecule comprises a modification that reduces RISC loading and reduces off-target effects. In some embodiments, the antisense strand of the siRNA molecule comprises a 2'-methoxyethyl (2'-MOE) modification. As described in Song et al., (2017) Mol Ther Nucleic Acids 9:242-250, the entirety of which is incorporated herein by reference, the addition of a 2'-methoxyethyl (2'-MOE) group at the cleavage site improves both the specificity and silencing effect of siRNA by facilitating the directional RNA-induced silencing complex (RISC) loading of the modified strand. In some embodiments, the antisense strand of the siRNA molecule contains a 2'-O-Me-phosphorodithioate modification, which increases RISC loading, as described in Wu et al. (2014) Nat Commun 5:3459, which is incorporated by reference in its entirety.

[0281] In some embodiments, the sense strand of the siRNA molecule comprises a 5' morpholino, which reduces RISC loading of the sense strand and improves antisense strand selection and RNAi activity, as described in Kumar et al., (2019) Chem Commun (Camb) 55 (35): 5139-5142, the entirety of which is incorporated herein by reference. In some embodiments, the sense strand of the siRNA molecule is modified with a synthetic RNA-like high affinity nucleotide analogue, locked nucleic acid (LNA). This reduces RISC loading of the sense strand and further enhances antisense strand incorporation into RISC, as described in Elman et al., (2005) Nucleic Acids Res. 33 (1): 439-447, the entirety of which is incorporated herein by reference. In some embodiments, the sense strand of the siRNA molecule comprises 5'unlocked nucleic acid (UNA) modification, which reduces the RISC loading of the sense strand and improves the silencing effect of the antisense strand, as described in Snead et al., (2013) Mol Ther Nucleic Acids 2(7):e103, the entirety of which is incorporated herein by reference.In some embodiments, the sense strand of the siRNA molecule comprises 5-nitroindole modification, which reduces the RNAi potency of the sense strand and reduces off-target effects, as described in Zhang et al., (2012) Chembiochem 13(13):1940-1945, the entirety of which is incorporated herein by reference. In some embodiments, the sense strand contains a 2'-O' methyl (2'-O-Me) modification, which reduces RISC loading and off-target effects of the sense strand, as described in Zheng et al., FASEB (2013) 27(10):4017-4026, which is incorporated by reference in its entirety.In some embodiments, the sense strand of the siRNA molecule is fully substituted with morpholino, 2'-MOE, or 2'-O-Me residues and is not recognized by RISC, as described in Kole et al., (2012) Nature reviews. Drug Discovery 11(2):125-140, which is incorporated herein by reference in its entirety. In some embodiments, the antisense strand of the siRNA molecule comprises an MOE modification and the sense strand comprises a 2'-O-Me modification (see, e.g., Song et al., (2017) Mol Ther Nucleic Acids 9:242-250). In some embodiments, at least one (e.g., at least 2, at least 3, at least 4, at least 5, at least 10) siRNA molecule is linked (e.g., covalently) to a muscle targeting agent. In some embodiments, the muscle targeting agent may comprise or consist of a nucleic acid (e.g., DNA or RNA), a peptide (e.g., an antibody), a lipid (e.g., a microvesicle), or a sugar moiety (e.g., a polysaccharide). In some embodiments, the muscle targeting agent is an antibody. In some embodiments, the muscle targeting agent is an anti-transferrin receptor antibody (e.g., any one of the anti-TfR1 antibodies shown in Tables 2-7). In some embodiments, the muscle targeting agent can be covalently linked to the 5' end of the sense strand of the siRNA molecule. In some embodiments, the muscle targeting agent can be covalently linked to the 3' end of the sense strand of the siRNA molecule. In some embodiments, the muscle targeting agent can be covalently linked internally to the sense strand of the siRNA molecule. In some embodiments, the muscle targeting agent can be covalently linked to the 5' end of the antisense strand of the siRNA molecule. In some embodiments, the muscle targeting agent can be covalently linked to the 3' end of the antisense strand of the siRNA molecule. In some embodiments, the muscle targeting agent can be covalently linked internally to the antisense strand of the siRNA molecule.

[0282] C. Linker The conjugates described herein generally include a linker that covalently links any one of the anti-TfR1 antibodies described herein to a molecular payload. The linker includes at least one covalent bond. In some embodiments, the linker can be a single bond, such as a disulfide bond or a disulfide bridge, that covalently links the anti-TfR1 antibody to the molecular payload. However, in some embodiments, the linker can covalently link any one of the anti-TfR1 antibodies described herein to the molecular payload through multiple covalent bonds. In some embodiments, the linker can be a cleavable linker. However, in some embodiments, the linker can be a non-cleavable linker. The linker is typically stable in vitro and in vivo and can be stable in a particular cellular environment. In addition, the linker typically does not negatively affect the functional properties of either the anti-TfR1 antibody or the molecular payload. Examples and methods of linker synthesis are known in the art (see, e.g., Kline, T. et al. "Methods to Make Homogenous Antibody Drug Conjugates." Pharmaceutical Research, 2015, 32:11, 3480-3493.; Jain, N. et al. "Current ADC Linker Chemistry." Pharm Res. 2015, 32:11, 3526-3540.; McCombs, JR and Owen, S.C. "Antibody Drug Conjugates: Design and Selection of Linker, Payload and Conjugation Chemistry" AAPS J. 2015, 17:2, 339-351.).

[0283] The linker typically comprises two different reactive species that can be attached to both the anti-TfR1 antibody and the molecular payload. In some embodiments, the two different reactive species may be nucleophiles and / or electrophiles. In some embodiments, the linker comprises two different electrophiles or nucleophiles specific for two different nucleophiles or electrophiles. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody via conjugation to a lysine or cysteine ​​residue of the anti-TfR1 antibody. In some embodiments, the linker is covalently linked to a cysteine ​​residue of the anti-TfR1 antibody via a maleimide-containing linker, optionally comprising a maleimidocaproyl or maleimidomethylcyclohexane-1-carboxylate group. In some embodiments, the linker is covalently linked to a cysteine ​​residue of the anti-TfR1 antibody or a thiol-functionalized molecular payload via a 3-arylpropionitrile functional group. In some embodiments, the linker is covalently linked to a lysine residue of the anti-TfR1 antibody. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or the molecular payload (e.g., and) independently via an amide bond, a carbamate bond, a hydrazide, a triazole, a thioether, and / or a disulfide bond.

[0284] i. Cleavable Linker The cleavable linker may be a protease-sensitive linker, a pH-sensitive linker, or a glutathione-sensitive linker, which are typically only cleavable intracellularly and are preferably stable in the extracellular environment, e.g., outside of a muscle cell.

[0285] Protease-sensitive linkers are cleavable by protease enzyme activity. These linkers typically comprise peptide sequences and can be 2-10 amino acids long, about 2-5 amino acids long, about 5-10 amino acids long, about 10 amino acids long, about 5 amino acids long, about 3 amino acids long, or about 2 amino acids long. In some embodiments, the peptide sequence can comprise naturally occurring amino acids, such as cysteine, alanine, or non-naturally occurring or modified amino acids. Non-naturally occurring amino acids include β-amino acids, homo-amino acids, proline derivatives, 3-substituted alanine derivatives, linear core amino acids, N-methyl amino acids, and other amino acids known in the art. In some embodiments, the protease-sensitive linker comprises a valine-citrulline or alanine-citrulline sequence. In some embodiments, the protease-sensitive linker can be cleaved by lysosomal proteases, such as cathepsin B, and / or endosomal proteases (such as and).

[0286] A pH-sensitive linker is a covalent linkage that is easily degraded in a high or low pH environment. In some embodiments, the pH-sensitive linker may be cleaved at a pH in the range of 4 to 6. In some embodiments, the pH-sensitive linker comprises a hydrazone or a cyclic acetal. In some embodiments, the pH-sensitive linker is cleaved in an endosome or lysosome.

[0287] In some embodiments, the glutathione-sensitive linker comprises a disulfide moiety. In some embodiments, the glutathione-sensitive linker is cleaved by disulfide exchange reaction with glutathione species inside the cell. In some embodiments, the disulfide moiety further comprises at least one amino acid, for example a cysteine ​​residue.

[0288] In some embodiments, the linker comprises a valine-citrulline sequence (e.g., as described in U.S. Patent No. 6,214,345, incorporated herein by reference). In some embodiments, prior to conjugation, the linker comprises the following structure: [ka]

[0289] In some embodiments, after conjugation, the linker comprises the following structure: [ka]

[0290] In some embodiments, prior to conjugation, the linker comprises the following structure: [ka] (wherein n is any number from 0 to 10.) In some embodiments, n is 3.

[0291] In some embodiments, the linker comprises the following structure: [ka] (wherein n is any number from 0 to 10, and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4.

[0292] In some embodiments, the linker comprises the following structure: [ka] (wherein n is any number from 0 to 10, and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4.

[0293] ii. Non-cleavable linker In some embodiments, a non-cleavable linker may be used. In general, a non-cleavable linker cannot be easily degraded in a cellular or physiological environment. In some embodiments, a non-cleavable linker comprises an optionally substituted alkyl group, where the substitution may include halogen, hydroxyl group, oxygen species, and other common substitutions. In some embodiments, the linker may comprise an optionally substituted alkyl, an optionally substituted alkylene, an optionally substituted arylene, a heteroarylene, a peptide sequence comprising at least one unnatural amino acid, a truncated glycan, a sugar(s) that cannot be enzymatically degraded, an azide, an alkyne-azide, a peptide sequence comprising an LPXT sequence, a thioether, a biotin, a biphenyl, a repeating unit of polyethylene glycol or an equivalent compound, an acid ester, an acid amide, a sulfamide, and / or an alkoxy-amine linker. In some embodiments, sortase-mediated ligation is carried out by linking an anti-TfR1 antibody comprising an LPXT sequence to a (G) n It can be used to covalently link to molecular payloads containing sequences (see, for example, Proft T. Sortase-mediated protein ligation: an emerging biotechnology tool for protein modification and immobilization. Biotechnol Lett. 2010, 32(1):1-10.).

[0294] In some embodiments, the linker may comprise a substituted alkylene, an optionally substituted alkenylene, an optionally substituted alkynylene, an optionally substituted cycloalkylene, an optionally substituted cycloalkenylene, an optionally substituted arylene, an optionally substituted heteroarylene further comprising at least one heteroatom selected from N, O, and S, an optionally substituted heterocyclylene further comprising at least one heteroatom selected from N, O, and S, an imino, an optionally substituted nitrogen species, an optionally substituted oxygen species O, an optionally substituted sulfur species, or a poly(alkylene oxide), such as polyethylene oxide or polypropylene oxide. In some embodiments, the linker may be a non-cleavable N-gamma-maleimidobutyryl-oxysuccinimide ester (GMBS) linker.

[0295] iii. Linker conjugation In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) the molecular payload via phosphate, thioether, ether, carbon-carbon, carbamate, or amide bond. In some embodiments, the linker is covalently linked to the oligonucleotide via a phosphate or phosphorothioate group, for example, the phosphate at the end of the oligonucleotide backbone. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody via a lysine or cysteine ​​residue present on the anti-TfR1 antibody.

[0296] In some embodiments, the linker or a portion thereof is covalently linked to the anti-TfR1 antibody and / or (for example and) the molecular payload by a cycloaddition reaction between an azide and an alkyne forming a triazole, and the azide or alkyne may be located on the anti-TfR1 antibody, the molecular payload, or the linker. In some embodiments, the alkyne may be a cyclic alkyne, for example, a cyclooctyne. In some embodiments, the alkyne may be a bicyclononyne (also known as bicyclo[6.1.0]nonyne or BCN) or a substituted bicyclononyne. In some embodiments, the cyclooctane is as described in International Publication No. 2011136645, entitled "Fused Cyclooctyne Compounds And Their Use In Metal-free Click Reactions," published November 3, 2011. In some embodiments, the azide may be a sugar or carbohydrate molecule containing an azide. In some embodiments, the azide may be 6-azido-6-deoxygalactose or 6-azido-N-acetylgalactosamine. In some embodiments, the azide-containing sugar or carbohydrate molecule is as described in International Publication No. WO 2016170186, published October 27, 2016, entitled "Process For The Modification Of A Glycoprotein Using A Glycosyltransferase That Is Or Is Derived From A β(1,4)-N-Acetylgalactosaminyltransferase."In some embodiments, the cycloaddition reaction between an azide and an alkyne to form a triazole (wherein the azide and alkyne can be located on the anti-TfR1 antibody, the molecular payload, or the linker) is as described in WO 2014065661, published on May 1, 2014, entitled "Modified antibody, antibody-conjugate and process for the preparation thereof"; or WO 2016170186, published on October 27, 2016, entitled "Process For The Modification Of A Glycoprotein Using A Glycosyltransferase That Is Or Is Derived From A β(1,4)-N-Acetylgalactosaminyltransferase."

[0297] In some embodiments, the linker comprises a spacer, e.g., a polyethylene glycol spacer or an acyl / carbamoyl sulfamide spacer, e.g., a HydraSpace™ spacer. In some embodiments, the spacer is as described in Verkade, JMM et al., "A Polar Sulfamide Spacer Significantly Enhances the Manufacturability, Stability, and Therapeutic Index of Antibody-Drug Conjugates", Antibodies, 2018, 7, 12.

[0298] In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) molecular payload by a Diels-Alder reaction between a dienophile and a diene / hetero-diene, although the dienophile or diene / hetero-diene may be located on the anti-TfR1 antibody, the molecular payload, or the linker. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) molecular payload by other pericyclic reactions such as ene reactions. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) molecular payload by amide, thioamide, or sulfonamide coupling reactions. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) molecular payload by a condensation reaction forming an oxime group, hydrazone group, or semicarbazide group present between the linker and the anti-TfR1 antibody and / or (for example and) molecular payload.

[0299] In some embodiments, the linker is covalently linked to the anti-TfR1 antibody and / or (for example and) the molecular payload by a conjugate addition reaction between a nucleophile, for example an amine group or a hydroxyl group, and an electrophile, for example a carboxylic acid, carbonate, or aldehyde. In some embodiments, prior to the reaction between the linker and the anti-TfR1 antibody or the molecular payload, the nucleophile can be present on the linker, and the electrophile can be present on the anti-TfR1 antibody or the molecular payload. In some embodiments, prior to the reaction between the linker and the anti-TfR1 antibody or the molecular payload, the electrophile can be present on the linker, and the nucleophile can be present on the anti-TfR1 antibody or the molecular payload. In some embodiments, the electrophile may be an azide, pentafluorophenyl, silicon center, carbonyl, carboxylic acid, anhydride, isocyanate, thioisocyanate, succinimidyl ester, sulfosuccinimidyl ester, maleimide, alkyl halide, alkyl pseudohalide, epoxide, episulfide, aziridine, aryl, activated phosphorus center, and / or activated sulfur center. In some embodiments, the nucleophile may be an optionally substituted alkene, an optionally substituted alkyne, an optionally substituted aryl, an optionally substituted heterocyclyl, a hydroxyl group, an amino group, an alkylamino group, an anilide group, and / or a thiol group.

[0300] In some embodiments, the linker comprises a valine-citrulline sequence covalently linked to a reactive chemical moiety (e.g., an azide or BCN moiety for click chemistry). In some embodiments, the linker comprising a valine-citrulline sequence covalently linked to a reactive chemical moiety (e.g., an azide moiety for click chemistry) comprises the following structure: [ka] (wherein n is any number from 0 to 10.) In some embodiments, n is 3.

[0301] In some embodiments, the linker comprising the structure of formula (A) is covalently linked (e.g., optionally via an additional chemical moiety) to a molecular payload (e.g., an oligonucleotide). In some embodiments, the linker comprising the structure of formula (A) is covalently linked to an oligonucleotide, e.g., via nucleophilic displacement by an amine-L1-oligonucleotide forming a carbamate bond, resulting in a compound comprising the following structure: [ka] (wherein n is any number from 0 to 10.) In some embodiments, n is 3.

[0302] In some embodiments, the compound of formula (B) is further covalently linked to an additional moiety via a triazole, which is formed by a click reaction between an azide of formula (A) or formula (B) and an alkyne provided on the bicyclononyne. In some embodiments, the bicyclononyne-containing compound comprises the following structure: [ka] (wherein m is any number from 0 to 10.) In some embodiments, m is 4.

[0303] In some embodiments, an azide of a compound of structure (B) forms a triazole via a click reaction with an alkyne of a compound of structure (C) to form a compound comprising the following structure: [ka] (wherein n is any number from 0 to 10, and m is any number from 0 to 10.) In some embodiments, n is 3, and m is 4.

[0304] In some embodiments, the compound of structure (D) is further covalently linked to a lysine of an anti-TfR1 antibody to form a conjugate comprising the following structure: [ka] (wherein n is any number from 0 to 10 and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4. It will be appreciated that the amide shown adjacent to the anti-TfR1 antibody in formula (E) results from reaction with an amine of the anti-TfR1 antibody, such as a lysine epsilon amine.

[0305] In some embodiments, the compound of Formula (C) is further covalently linked to a lysine of an anti-TfR1 antibody to form a compound comprising the following structure: [ka] (wherein m is 0 to 15 (eg, 4).) It will be appreciated that the amide shown adjacent to the anti-TfR1 antibody in formula (F) results from reaction with an amine of the anti-TfR1 antibody, such as a lysine epsilon amine.

[0306] In some embodiments, the azide of the compound of structure (B) forms a triazole via a click reaction with an alkyne of the compound of structure (F) to form a conjugate comprising the following structure: [ka] (wherein n is any number from 0 to 10 and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4. It will be appreciated that the amide shown adjacent to the anti-TfR1 antibody in formula (E) results from reaction with an amine of the anti-TfR1 antibody, such as a lysine epsilon amine.

[0307] In some embodiments, an azide of a compound of structure (A) forms a triazole via a click reaction with an alkyne of a compound of structure (F) to form a compound comprising the following structure: [ka] (wherein n is any number from 0 to 10 and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4. In some aspects, the oligonucleotide is covalently linked to a compound comprising the structure of formula (G), thereby forming a conjugate comprising the structure of formula (E). It will be appreciated that the amide shown adjacent to the anti-TfR1 antibody in formula (G) results from reaction with an amine of the anti-TfR1 antibody, such as a lysine epsilon amine.

[0308] In some embodiments, in any one of the conjugates described herein, the anti-TfR1 antibody is covalently linked to a molecular payload (e.g., an oligonucleotide) via a lysine of the anti-TfR1 antibody via a linker comprising the following structure: [ka] (wherein n is any number from 0 to 10, and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4.

[0309] In some embodiments, in any one of the conjugates described herein, the anti-TfR1 antibody is covalently linked to a molecular payload (e.g., an oligonucleotide) via a lysine of the anti-TfR1 antibody via a linker comprising the following structure: [ka] (wherein n is any number from 0 to 10, and m is any number from 0 to 10.) In some embodiments, n is 3 and / or (by way of example and) m is 4.

[0310] In some embodiments, in formulas (B), (D), (E), and (I), L is, in some embodiments, a substituted or unsubstituted aliphatic, a substituted or unsubstituted heteroaliphatic, a substituted or unsubstituted carbocyclylene, a substituted or unsubstituted heterocyclylene, a substituted or unsubstituted arylene, a substituted or unsubstituted heteroarylene, -O-, -N(R A )-, -S-, -C(=O)-, -C(=O)O-, -C(=O)NR A -, -NR A C(=O)-, -NR A C(=O)R A -, -C(=O)R A -, -NR A C(=O)O-, -NR A C(=O)N(R A )-, -OC(=O)-, -OC(=O)O-, -OC(=O)N(R A )-, -S(O)NR A -, -NR A S(O)-, or a combination thereof; R A is independently hydrogen or substituted or unsubstituted alkyl. In some embodiments, L is [ka] It is. (Wherein, L2 is [ka] or [ka] a represents a site directly attached to the carbamate moiety of formulas (B), (D), (E) and (I), and b represents a site covalently linked (directly or via an additional chemical moiety) to an oligonucleotide.

[0311] In some embodiments, L1 is [ka] where a represents the site directly linked to the carbamate moiety of formulas (B), (D), (E), and (I), and b represents the site covalently linked (directly or via an additional chemical moiety) to the oligonucleotide.

[0312] In some embodiments, L1 is [ka] It is.

[0313] In some embodiments, L1 is linked to the 5' phosphate of the oligonucleotide. In some embodiments, L1 is linked to the 5' phosphorothioate of the oligonucleotide. In some embodiments, L1 is linked to the 5' phosphoramidate of the oligonucleotide.

[0314] In some embodiments, L1 is linked to the 5' phosphate of the oligonucleotide. In some embodiments, the attachment of L1 to the 5' phosphate of the oligonucleotide forms a phosphodiester bond between L1 and the oligonucleotide.

[0315] In some embodiments, L1 is linked to the 3' phosphate of the oligonucleotide. In some embodiments, the attachment of L1 to the 3' phosphate of the oligonucleotide forms a phosphodiester bond between L1 and the oligonucleotide.

[0316] In some embodiments, L1 is optional (eg, does not have to be present).

[0317] In some embodiments, any one of the conjugates described herein has the following structure: [ka] (wherein n is 0 to 15 (e.g., 3) and m is 0 to 15 (e.g., 4).) It will be appreciated that the amide shown adjacent to the anti-TfR1 antibody in formula (J) results from reaction with an amine of the anti-TfR1 antibody, such as a lysine epsilon amine.

[0318] In some embodiments, any one of the conjugates described herein has the following structure: [ka] (In the formula, n is 0 to 15 (for example, 3), and m is 0 to 15 (for example, 4).)

[0319] In some embodiments, the oligonucleotide is modified to contain an amine group at the 5' or 3' end, or internally (e.g., as an amine-functionalized nucleobase) prior to linking to a compound, e.g., a compound of Formula (A) or Formula (G).

[0320] Although the linker conjugations are described in relation to anti-TfR1 antibodies and oligonucleotide molecular payloads, it will be appreciated that the use of such linker conjugations for other muscle targeting agents, such as other muscle targeting antibodies, and / or other molecular payloads is contemplated.

[0321] D. Examples of Antibody-Molecular Payload Conjugates Further provided herein are non-limiting examples of conjugates comprising any one of the anti-TfR1 antibodies described herein covalently linked to any one of the molecular payloads described herein (e.g., oligonucleotides). In some embodiments, the anti-TfR1 antibody (e.g., any one of the anti-TfR1 antibodies shown in Tables 2-7) is covalently linked to the molecular payload (e.g., an oligonucleotide such as the oligonucleotides shown in Table 8) via a linker. Any of the linkers described herein may be used. In some embodiments, when the molecular payload is an oligonucleotide, the linker is covalently linked to the 5' end, 3' end, or internally of the oligonucleotide. In some embodiments, the linker is covalently linked to the anti-TfR1 antibody via a thiol-reactive linkage (e.g., via a cysteine ​​in the anti-TfR1 antibody). In some embodiments, the linker is covalently linked to the antibody (e.g., the anti-TfR1 antibody described herein) via an amine group (e.g., via a lysine in the antibody). In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (eg, an FXN-targeting oligonucleotide listed in Table 8).

[0322] An example structure of a conjugate comprising an anti-TfR1 antibody covalently linked to a molecular payload via a linker is provided below. [ka] (wherein the linker is covalently linked to the antibody via a thiol-reactive linkage (e.g., via a cysteine ​​in the antibody).) In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0323] Another example of the structure of a conjugate comprising an anti-TfR1 antibody covalently linked to a molecular payload via a linker is provided below. [ka] (wherein n is a number from 0 to 10, m is a number from 0 to 10, and the linker is covalently linked to the antibody via an amine group (e.g., on a lysine residue) and / or (for example and) the linker is covalently linked to the oligonucleotide (for example at the 5' end, the 3' end, or internally).) In some embodiments, the linker is covalently linked to the antibody via a lysine, the linker is covalently linked to the oligonucleotide at the 5' end, n is 3, and m is 4. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (for example, the FXN-targeting oligonucleotides listed in Table 8). In some embodiments, L1 is [ka] It is.

[0324] Of course, the antibody may be covalently linked to the molecular payload with various stoichiometries, a property that may be referred to as the drug-antibody ratio (DAR), where the "drug" is the molecular payload. In some embodiments, one molecular payload is covalently linked to the antibody (DAR=1). In some embodiments, two molecular payloads are covalently linked to the antibody (DAR=2). In some embodiments, three molecular payloads are covalently linked to the antibody (DAR=3). In some embodiments, four molecular payloads are covalently linked to the antibody (DAR=4). In some embodiments, a mixture of different conjugates, each having a different DAR, is provided. In some embodiments, the average DAR of the conjugates in such a mixture may range from 1 to 3, 1 to 4, 1 to 5, or more. The DAR may be increased by conjugating the molecular payload to various sites on the antibody and / or (for example and) by conjugating a multimer to one or more sites on the antibody. For example, a DAR of 2 can be achieved by conjugating a single molecular payload to two different sites on an antibody, or by conjugating a dimeric molecular payload to a single site on an antibody.

[0325] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody described herein (e.g., an antibody shown in Tables 2-7) covalently linked to a molecular payload. In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody described herein (e.g., an antibody shown in Tables 2-7) covalently linked to a molecular payload via a linker. In some embodiments, the linker is covalently linked to an antibody (e.g., an anti-TfR1 antibody described herein) via a thiol-reactive linkage (e.g., via a cysteine ​​in the antibody). In some embodiments, the linker is covalently linked to an antibody (e.g., an anti-TfR1 antibody described herein) via an amine group (e.g., via a lysine in the antibody). In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0326] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises the CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 of any one of the antibodies listed in Table 2. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0327] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising the amino acid sequence of SEQ ID NO: 69, SEQ ID NO: 71, or SEQ ID NO: 72, and a VL comprising the amino acid sequence of SEQ ID NO: 70. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0328] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising the amino acid sequence of SEQ ID NO: 73 or SEQ ID NO: 76, and a VL comprising the amino acid sequence of SEQ ID NO: 74. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0329] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising the amino acid sequence of SEQ ID NO: 73 or SEQ ID NO: 76, and a VL comprising the amino acid sequence of SEQ ID NO: 75. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0330] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising SEQ ID NO: 77 and a VL comprising the amino acid sequence of SEQ ID NO: 78. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0331] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising the amino acid sequence of SEQ ID NO: 77 or SEQ ID NO: 79, and a VL comprising the amino acid sequence of SEQ ID NO: 80. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0332] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a VH comprising SEQ ID NO: 154 and a VL comprising the amino acid sequence of SEQ ID NO: 155. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0333] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 84, SEQ ID NO: 86, or SEQ ID NO: 87, and a light chain comprising the amino acid sequence of SEQ ID NO: 85. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0334] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 88 or SEQ ID NO: 91, and a light chain comprising the amino acid sequence of SEQ ID NO: 89. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0335] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 88 or SEQ ID NO: 91, and a light chain comprising the amino acid sequence of SEQ ID NO: 90. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0336] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 92 or SEQ ID NO: 94, and a light chain comprising the amino acid sequence of SEQ ID NO: 95. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0337] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 92 and a light chain comprising the amino acid sequence of SEQ ID NO: 93. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0338] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 156 and a light chain comprising the amino acid sequence of SEQ ID NO: 157. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0339] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 97, SEQ ID NO: 98, or SEQ ID NO: 99, and a VL comprising the amino acid sequence of SEQ ID NO: 85. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0340] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 100 or SEQ ID NO: 101, and a light chain comprising the amino acid sequence of SEQ ID NO: 89. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0341] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 100 or SEQ ID NO: 101, and a light chain comprising the amino acid sequence of SEQ ID NO: 90. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0342] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 102 and a light chain comprising the amino acid sequence of SEQ ID NO: 93. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0343] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 102 or SEQ ID NO: 103, and a light chain comprising the amino acid sequence of SEQ ID NO: 95. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0344] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to a molecular payload, wherein the anti-TfR1 antibody comprises a heavy chain comprising the amino acid sequence of SEQ ID NO: 158 or SEQ ID NO: 159, and a light chain comprising the amino acid sequence of SEQ ID NO: 157. In some embodiments, the molecular payload is an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8).

[0345] In some embodiments, the conjugate described herein comprises an anti-TfR1 antibody covalently linked to the 5' end of an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8) via a lysine in the anti-TfR1 antibody, wherein the anti-TfR1 antibody comprises CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2, and CDR-L3 of any one of the antibodies listed in Table 2, and the conjugate has the following structure: [ka] (wherein n is 3 and m is 4). In some embodiments, L1 is [ka] It is.

[0346] In some embodiments, the conjugate described herein comprises an anti-TfR1 antibody covalently linked to the 5' end of an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8) via a lysine in the anti-TfR1 antibody, wherein the anti-TfR1 antibody comprises the VH and VL of any one of the antibodies listed in Table 3, and the conjugate has the following structure: [ka] (wherein n is 3 and m is 4). In some embodiments, L1 is [ka] It is.

[0347] In some embodiments, the conjugate described herein comprises an anti-TfR1 antibody covalently linked to the 5' end of an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8) via a lysine in the anti-TfR1 antibody, wherein the anti-TfR1 antibody comprises the heavy and light chains of any one of the antibodies listed in Table 4, and the conjugate has the following structure: [ka] (wherein n is 3 and m is 4). In some embodiments, L1 is [ka] It is.

[0348] In some embodiments, the conjugates described herein comprise an anti-TfR1 antibody covalently linked to the 5' end of an FXN-targeting oligonucleotide (e.g., an FXN-targeting oligonucleotide listed in Table 8) via a lysine in the anti-TfR1 Fab, wherein the anti-TfR1 Fab comprises the heavy and light chains of any one of the antibodies listed in Table 5, and the conjugate has the following structure: [ka] (wherein n is 3 and m is 4). In some embodiments, L1 is [ka] It is.

[0349] In some embodiments, L1 is linked to the 5' phosphate of the oligonucleotide. In some embodiments, L1 is linked to the 5' phosphorothioate of the oligonucleotide. In some embodiments, L1 is linked to the 5' phosphoramidate of the oligonucleotide.

[0350] In some embodiments, L1 is linked to the 5' phosphate of the oligonucleotide. In some embodiments, the attachment of L1 to the 5' phosphate of the oligonucleotide forms a phosphodiester bond between L1 and the oligonucleotide.

[0351] In some embodiments, L1 is linked to the 3' phosphate of the oligonucleotide. In some embodiments, the attachment of L1 to the 3' phosphate of the oligonucleotide forms a phosphodiester bond between L1 and the oligonucleotide.

[0352] In some embodiments, L1 is optional (eg, does not have to be present).

[0353] III. Preparations The conjugates provided herein may be formulated in any suitable manner. In general, the conjugates provided herein are formulated in a manner suitable for pharmaceutical use. For example, the conjugates may be delivered to a subject using a formulation that minimizes degradation, facilitates delivery and / or (for example and) uptake, or provides another beneficial property to the conjugate in the formulation. In some embodiments, compositions are provided herein that include the conjugate and a pharma- ceutically acceptable carrier. Such compositions can be appropriately formulated so that, upon administration to a subject, a sufficient amount of the conjugate enters the target muscle cell, either in the environment surrounding the target cell or in the entire body. In some embodiments, the conjugates are formulated in a buffer solution, such as phosphate buffered saline solution, liposomes, micellar structures, and capsids.

[0354] Of course, in some embodiments, a composition may individually include one or more components of the conjugates provided herein (e.g., a muscle targeting agent, a linker, a molecular payload, or a precursor molecule of any one of these).

[0355] In some embodiments, the complex is formulated in water or an aqueous solution (e.g., pH-adjusted water). In some embodiments, the complex is formulated in a basic buffered aqueous solution (e.g., PBS). In some embodiments, the formulation as disclosed herein includes an excipient. In some embodiments, the excipient confers improved stability, improved absorption, improved solubility, and / or (e.g., and) therapeutic enhancement of the active ingredient to the composition. In some embodiments, the excipient is a buffer (e.g., sodium citrate, sodium phosphate, Tris base, or sodium hydroxide) or a vehicle (e.g., a buffer solution, petrolatum, dimethyl sulfoxide, or mineral oil).

[0356] In some embodiments, the complex or a component thereof (e.g., an oligonucleotide or an antibody) is lyophilized to extend its shelf life and then brought into solution prior to use (e.g., administration to a subject). Thus, the excipient in a composition comprising the complex or a component thereof described herein may be a cryoprotectant (e.g., mannitol, lactose, polyethylene glycol, or polyvinylpyrrolidone), or a collapse temperature modifier (e.g., dextran, ficoll, or gelatin).

[0357] In some embodiments, the pharmaceutical composition is formulated to be compatible with its intended route of administration. Examples of routes of administration include parenteral administration, such as intravenous administration, intradermal administration, and subcutaneous administration. Typically, the route of administration is intravenous or subcutaneous administration.

[0358] Pharmaceutical compositions suitable for use in injections include sterile aqueous solutions (wherein they are soluble in water) or dispersions, and sterile powders for extemporaneous preparation of sterile injection solutions or dispersions. Carriers can be, for example, solvents or dispersion media containing water, ethanol, polyols (for example, glycerol, propylene glycol, liquid polyethylene glycol, etc.), and suitable mixtures thereof. In some embodiments, the formulations include isotonic agents in the composition, for example, sugars, polyalcohols such as mannitol, sorbitol, and sodium chloride. Sterile injection solutions can be prepared by incorporating the required amount of the complex with one or a combination of the above-listed ingredients in the selected solvent, and then optionally filtering and sterilizing.

[0359] In some embodiments, the composition may contain at least about 0.1% of the complex or its components, or more, but the percentage of active ingredient may be about 1% to about 80% or more by weight or volume of the total composition. Factors such as solubility, bioavailability, biological half-life, route of administration, shelf life of the product, and other pharmacological considerations will be taken into account by those skilled in the art of preparing such pharmaceutical formulations. Therefore, different dosages and treatment regimes may be desirable.

[0360] IV. Methods of Use / Treatment The complex comprising the muscle targeting agent covalently linked to the molecular payload as described herein is effective for treating Friedreich's ataxia.In some embodiments, FA is associated with the expansion of the GAA trinucleotide repeat in intron 1 of both FXN alleles.In some embodiments, the nucleotide expansion leads to epigenetic changes and the formation of heterochromatin near the repeat, resulting in the reduced expression of FXN.

[0361] In some embodiments, the subject may be a human subject, a non-human primate animal subject, a rodent animal subject, or any suitable mammalian subject. In some embodiments, the subject may have Friedreich's ataxia. In some embodiments, the subject may have an FXN allele, which may optionally include a disease-associated repeat. In some embodiments, the subject may have an FXN allele with an expanded disease-associated repeat comprising about 2-10 repeat units, about 2-50 repeat units, about 2-100 repeat units, about 50-1,000 repeat units, about 50-500 repeat units, about 50-250 repeat units, about 50-100 repeat units, about 500-10,000 repeat units, about 500-5,000 repeat units, about 500-2,500 repeat units, about 500-1,000 repeat units, or about 1,000-10,000 repeat units. In some embodiments, the subject suffers from symptoms of FA, such as hypertrophic cardiomyopathy, muscle atrophy or muscle weakness. In some embodiments, the subject does not suffer from symptoms of FA. In some embodiments, the subject has congenital hypertrophic cardiomyopathy.

[0362] Aspects of the present disclosure include methods involving administering to a subject an effective amount of a complex as described herein. In some embodiments, an effective amount of a pharmaceutical composition comprising a complex comprising a muscle targeting agent covalently linked to a molecular payload may be administered to a subject in need of treatment. In some embodiments, a pharmaceutical composition comprising a complex as described herein may be administered by a suitable route, which may include, for example, intravenous administration by intravenous bolus administration or continuous infusion over a period of time. In some embodiments, intravenous administration may be performed by intramuscular, intraperitoneal, intracerebrospinal, subcutaneous, intraarticular, intrasynovial, or intrathecal routes. In some embodiments, the pharmaceutical composition may be in a solid, aqueous, or liquid form. In some embodiments, the aqueous or liquid form may be sprayed or lyophilized. In some embodiments, the sprayed or lyophilized form may be reconstituted with an aqueous or liquid solution.

[0363] Compositions for intravenous administration may contain various carriers, such as vegetable oils, dimethylacetamide, dimethylformamide, ethyl lactate, ethyl carbonate, isopropyl myristate, ethanol, and polyols (glycerol, propylene glycol, liquid polyethylene glycol, etc.). Water-soluble antibodies for intravenous injection may be administered by drip infusion, whereby a pharmaceutical formulation containing the antibody and a pharma- ceutical acceptable excipient is infused. Physiologically acceptable excipients may include, for example, 5% dextrose, 0.9% saline, Ringer's solution, or other suitable excipients. Intramuscular preparations, for example, a sterile formulation of a suitable soluble salt form of the antibody, may be administered dissolved in a pharmaceutical excipient, such as water for injection, 0.9% saline, or 5% glucose solution.

[0364] In some embodiments, pharmaceutical compositions comprising a conjugate comprising a muscle-targeting agent covalently linked to a molecular payload are administered via site-specific or localized delivery techniques, examples of which include an implanted depot source of the conjugate, a localized delivery catheter, a site-specific carrier, direct injection, or direct application.

[0365] In some embodiments, the pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload is administered at an effective concentration that provides a therapeutic effect to the subject. The effective amount will vary depending on the severity of the disease, the specific characteristics of the subject being treated, such as age, physical condition, health, or weight, the duration of treatment, the nature of any concomitant treatments, the route of administration, and related factors, as will be recognized by those skilled in the art. These related factors are known to those skilled in the art and can be addressed with no more than routine experimentation. In some embodiments, the effective concentration is the maximum dose that is considered safe for the patient. In some embodiments, the effective concentration will be the lowest concentration feasible that provides maximum efficacy.

[0366] Empirical considerations, such as the half-life of the conjugate in the subject, will generally help determine the concentration of pharmaceutical composition used for treatment. Dosing frequency may be empirically determined and adjusted to maximize efficacy of treatment.

[0367] The effectiveness of treatment can be assessed using any suitable method.In some embodiments, the effectiveness of treatment can be evaluated by observing the symptoms associated with FA, such as hypertrophic cardiomyopathy, muscle atrophy, or muscle weakness, through the subject's self-reported outcomes, such as mobility, self-care, normal activity, pain / discomfort, and anxiety / depression, or by quality of life indicators, such as lifespan.

[0368] In some embodiments, a pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload described herein is administered to a subject at an effective concentration sufficient to inhibit target gene activity or expression by at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% as compared to a control (e.g., a baseline level of gene expression prior to treatment).

[0369] In some embodiments, a single dose or administration to a subject of a pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload as described herein is sufficient to inhibit target gene activity or expression for at least 1-5 days, 1-10 days, 5-15 days, 10-20 days, 15-30 days, 20-40 days, 25-50 days, or longer. In some embodiments, a single dose or administration to a subject of a pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload as described herein is sufficient to inhibit target gene activity or expression for at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 15, 20, or 24 weeks. In some embodiments, a single dose or administration to a subject of a pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload as described herein is sufficient to inhibit target gene activity or expression for at least 1-5, 1-10, 2-5, 2-10, 4-8, 4-12, 5-10, 5-12, 5-15, 8-12, 8-15, 10-12, 10-15, 10-20, 12-15, 12-20, 15-20, or 15-25 weeks. In some embodiments, a single dose or administration to a subject of a pharmaceutical composition comprising a conjugate comprising a muscle targeting agent covalently linked to a molecular payload as described herein is sufficient to inhibit target gene activity or expression for at least 1, 2, 3, 4, 5, or 6 months.

[0370] In some embodiments, the pharmaceutical composition may include two or more complexes comprising a muscle targeting agent covalently linked to a molecular payload. In some embodiments, the pharmaceutical composition may further include any other suitable therapeutic agent for treating a subject, for example, a human subject with FA. In some embodiments, the other therapeutic agent may enhance or complement the efficacy of the complexes described herein. In some embodiments, the other therapeutic agent may function to treat a different condition or disease than the complexes described herein.

[0371] example Example 1. In vitro activity of FXN-targeting oligonucleotides (ASOs) In vitro experiments were carried out to examine the activity of the FXN targeting oligonucleotides (ASOs) listed in Table 8. The oligonucleotides target the region of FXN RNA that contains GAA repeats (repeat region). The ability of the oligonucleotide to knock down FXN RNA levels is an indication of the accessibility of the target sequence in the repeat region. The accessible target sequence can be targeted by the oligonucleotide to inhibit R-loop formation between FXN RNA containing expanded repeats and chromosomal DNA, thereby enhancing FXN protein expression.

[0372] To recapitulate the gene expression profile of Friedreich's ataxia, endogenous FXN mRNA was knocked down in LS 174T colorectal adenocarcinoma cells. After knockdown, LS 174T cells were seeded at a density of 15,000 cells / well in 96-well plates and incubated overnight. After overnight incubation, cells were transfected with either 20 nM or 5 nM of FXN-targeted oligonucleotides using Lipofectamine RNAiMax in technical quadruplicates. Cells were then incubated for 72 hours and then harvested. Transcript levels were assessed using a branched DNA assay specific for FXN. All transcript data were normalized to a reference branched DNA assay measuring GAPDH transcript levels. The quadruplicate values ​​were averaged and the average transcript level was recorded. Table 9 shows the average remaining transcript level (%) after treatment with each ASO, with transcript levels normalized to GAPDH transcript levels and recorded as FXN transcript levels averaged over the four replicates. The standard deviation for each quadruplicate set is also recorded. [Table 9]

[0373] Example 2: FXN-targeting ASO-dose response Five FXN mRNA targeting ASOs (Table 10) were tested for their ability to knockdown FXN mRNA in a dose response experiment in LS 174T colorectal adenocarcinoma cells. LS 174T cells were seeded at a density of 15,000 cells / well in 96-well plates and allowed to recover overnight. The following day, cells were transfected with various concentrations of FXN-targeting ASOs using Lipofectamine RNAiMax in technical quadruplicates. Cells were incubated for 72 hours and harvested. A dose response analysis was performed, including calculation of IC20 and IC50 values ​​for the tested ASOs, and the results are shown in Table 10. [Table 10]

[0374] Example 3. In vivo activity of conjugates containing anti-TfR1 Fab conjugated to DMPK-targeted oligonucleotides in mice expressing human TfR1 A conjugate containing anti-TfR1 Fab 3M12-VH4 / VK3 conjugated to a DMPK-targeting oligonucleotide was tested in a mouse model expressing human TfR1. Anti-TfR Fab1 3M12-VH4 / VK3 was conjugated to a DMPK-targeting oligonucleotide via a cleavable linker having the structure of formula (I). The conjugate was administered to mice at a dose equivalent to 10 mg / kg oligonucleotide on days 0 and 7. Mice were sacrificed on day 14, and different muscle tissues were collected and analyzed for dmpk mRNA levels and oligonucleotide concentrations in the tissues. The conjugate reduced mouse wild-type dmpk by 79% in tibialis anterior muscle (Figure 1A), 76% in gastrocnemius muscle (Figure 1B), 70% in heart (Figure 1C), and 88% in diaphragm (Figure 1D). Oligonucleotide distribution in tibialis anterior, gastrocnemius, heart, and diaphragm is shown in Figures 1E-H.

[0375] These data show that anti-TfR Fab1 3M12-VH4 / VK3 enabled cellular internalization of the conjugate to muscle-specific tissue in an in vivo mouse model, whereby the DMPK-targeting oligonucleotide reduced the expression of DMPK. Similarly, anti-TfR1 antibodies (e.g., anti-TfR1 Fab 3M12-VH4 / VK3) can enable cellular internalization of conjugates containing anti-TfR1 antibodies conjugated to FXN-targeting oligonucleotides to enhance FXN protein expression.

[0376] Equivalents and Terminology The disclosure illustratively described herein may suitably be implemented in the absence of any element or limitation not specifically disclosed herein. Thus, for example, in each instance herein, any of the terms "comprise", "consist essentially of" and "consist of" may be replaced by either of the other two terms. The terms and expressions employed are used as terms of description and not of limitation, and the use of such terms and expressions is not intended to exclude any equivalents or portions of the features shown and described, and it is recognized that various modifications are possible within the scope of the present disclosure. Thus, although the present disclosure has been specifically disclosed by preferred embodiments, it should be understood that any features, modifications and variations of the concepts disclosed herein may be resorted to by those skilled in the art, and such modifications and variations are considered to be within the scope of the present disclosure.

[0377] Additionally, where features or aspects of the disclosure are described as a Markush group or other grouping of alternatives, those skilled in the art will recognize that the disclosure is thereby also described as any individual member or subgroup of members of the Markush group or other group.

[0378] Of course, in some embodiments, when describing the structure of an oligonucleotide or other nucleic acid, reference may be made to the sequences presented in the sequence listing. In such embodiments, the actual oligonucleotide or other nucleic acid may have one or more alternative nucleotides or nucleosides (e.g., RNA counterparts of DNA nucleosides, or DNA counterparts of RNA nucleosides) and / or (for example and) one or more modified nucleotides / nucleosides and / or (for example and) one or more modified internucleoside linkages and / or (for example and) one or more other modifications compared to the designated sequence, while retaining essentially the same or similar complementary properties as the designated sequence.

[0379] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the present invention (particularly in the context of the claims below) should be construed to encompass both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms "comprises," "has," "includes," and "containing" should be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise indicated herein. The recitation of ranges of values ​​herein is intended merely to serve as a shorthand method of individually referring to each separate value falling within the range, and each separate value is incorporated herein as if it were individually set forth herein. All methods described herein may be performed in any suitable order, unless otherwise indicated herein or clearly contradicted by context. Unless otherwise asserted, the use of any and all examples or exemplary language provided herein (such as, for example, "etc.") is intended merely to better illuminate the invention and does not impose limitations on the scope of the invention. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0380] Aspects of the invention have been described herein. Variations of those embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description.

[0381] The inventors anticipate that those skilled in the art will adopt such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the present invention unless otherwise indicated herein or clearly contradicted by context. 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.

Claims

**Claim 1**: A complex comprising an anti-transferrin receptor 1 (TfR1) covalently linked to an oligonucleotide configured to increase frataxin (FXN) expression, wherein the oligonucleotide comprises a complementary region to a repetitive region of FXN RNA, wherein the repetitive region comprises a target sequence shown in any one of SEQ ID NOs: 162-164, and wherein the complementary region is at least 12 nucleotides in length, said complex. **Claim 2** The complex according to claim 1, wherein the oligonucleotide comprises at least 16 consecutive nucleotides of any one of SEQ ID NOs: 165-176, wherein each uridine (U) of the oligonucleotide is optionally and independently thymine (T). **Claim 3**: The complex according to claim 1, wherein the oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-176, and wherein each U of the oligonucleotide is optionally and independently T. **Claim 4** The oligonucleotide comprises a 5'-X-Y-Z-3' configuration, wherein X comprises 3 to 5 linked nucleosides, wherein at least 1 of the nucleosides in X is a 2'-modified nucleoside; Y comprises 6 to 14 linked 2'-deoxyribonucleosides; and Z comprises 3 to 5 linked nucleosides, wherein at least 1 of the nucleosides in Z is a 2'-modified nucleoside, the complex according to claim 1. **Claim 5** The oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-167, X comprises 5 linked nucleosides, wherein each nucleoside in X is a 2'-MOE modified nucleoside; Y comprises 10 linked 2'-deoxyribonucleosides; and Z comprises 5 linked nucleosides, wherein each nucleoside in Z is a 2'-MOE modified nucleoside, the complex according to claim 4. **Claim 6** The oligonucleotide comprises the nucleotide sequence of any one of SEQ ID NOs: 165-167, X comprises 5 linked nucleosides, wherein each nucleoside in X is a locked nucleic acid (LNA) nucleoside; Y comprises 10 linked 2'-deoxyribonucleosides; and The complex according to claim 4, wherein Z comprises 5 linked nucleosides, and each nucleoside in Z is an LNA nucleoside.

7. The oligonucleotide comprises any one of the nucleotide sequences of SEQ ID NOs: 171 to 173, X comprises 3 linked nucleosides, and each nucleoside in X is an LNA nucleoside; Y comprises 14 linked 2'-deoxyribonucleosides; and Z comprises 3 linked nucleosides, and each nucleoside in Z is an LNA nucleoside, the complex according to claim 4.

8. The complex according to claim 4, wherein each cytidine in Y is optionally and independently 5-methyl-cytidine.

9. The oligonucleotide comprises any one of the nucleotide sequences of SEQ ID NOs: 168 to 170, and each nucleoside of the oligonucleotide is a 2'-MOE modified nucleoside, the complex according to claim 1.

10. The oligonucleotide comprises any one of the nucleotide sequences of SEQ ID NOs: 168 to 170, and each T in the oligonucleotide is an LNA nucleoside, and each C in the oligonucleotide is 5-methyl-deoxycytidine, the complex according to claim 1.

11. The oligonucleotide comprises any one of the nucleotide sequences of SEQ ID NOs: 174 to 176, and each C in the oligonucleotide is an LNA nucleoside, and each T is deoxythymidine, the complex according to claim 1.

12. The complex according to claim 1, wherein the oligonucleotide comprises one or more phosphorothioate internucleoside linkages.

13. The complex according to claim 1, wherein each internucleoside linkage in the oligonucleotide is a phosphorothioate internucleoside linkage.

14. The oligonucleotide is 【Table 1-1】 【Table 1-2】 (Here, "xdC" represents 5-methyl-deoxycytidine; "dN" represents 2'-deoxyribonucleoside; "+N" represents LNA nucleoside; "oN" represents 2'-MOE-modified ribonucleoside; "oC" represents 5-methyl-2'-MOE-cytidine; "+C" represents 5-methyl-2'-4'-bicyclic-cytidine (2'-4' methylene bridge); "oU" represents 5-methyl-2'-MOE-uridine; "+U" represents 5-methyl-2'-4'-bicyclic uridine (2'-4' methylene bridge); "*" represents a phosphorothioate internucleoside linkage) The complex according to claim 1, selected from

15. The complex according to claim 1, wherein the anti-TfR1 antibody comprises heavy chain complementarity determining region 1 (CDR-H1) of SEQ ID NO: 33, heavy chain complementarity determining region 2 (CDR-H2) of SEQ ID NO: 34, heavy chain complementarity determining region 3 (CDR-H3) of SEQ ID NO: 35, light chain complementarity determining region 1 (CDR-L1) of SEQ ID NO: 36, light chain complementarity determining region 2 (CDR-L2) of SEQ ID NO: 37, and light chain complementarity determining region 3 (CDR-L3) of SEQ ID NO:

32.

16. The complex according to claim 1, wherein the anti-TfR1 antibody comprises a heavy chain variable region (VH) comprising an amino acid sequence that is at least 85% identical in the framework region compared to the framework region of SEQ ID NO: 76 and / or a light chain variable region (VL) comprising an amino acid sequence that is at least 85% identical in the framework region compared to the framework region of SEQ ID NO:

75.

17. The complex according to claim 1, wherein the anti-TfR1 antibody is a Fab.

18. The complex according to claim 17, wherein the Fab comprises a heavy chain comprising an amino acid sequence that is at least 85% identical to SEQ ID NO: 101 and / or a light chain comprising an amino acid sequence that is at least 85% identical to SEQ ID NO:

90.

19. The complex according to claim 1, wherein the anti-TfR1 antibody comprises an N-terminal pyroglutamate.

20. The complex according to claim 1, wherein the muscle targeting agent and the oligonucleotide are covalently linked via a linker.

21. The complex according to claim 20, wherein the linker comprises a valine-citrulline sequence.

22. The complex according to claim 1, wherein the muscle targeting agent and the oligonucleotide are covalently linked via a non-cleavable linker.

23. The complex according to claim 22, wherein the non-cleavable linker contains an alkyl group.

24. The complex according to claim 1, wherein the anti-TfR1 antibody is covalently linked to the oligonucleotide via conjugation to a lysine residue of the antibody.

25. A composition for treating Friedreich's ataxia (FA) in a subject having a mutant FXN allele containing a disease-related GAA repeat, the composition comprising an effective amount of the complex according to claim 1.

26. 【Table 2】 (wherein "xdC" represents 5-methyl-deoxycytidine; "dN" represents 2'-deoxyribonucleoside; "+N" represents LNA nucleoside; "oN" represents 2'-MOE-modified ribonucleoside; "oC" represents 5-methyl-2'-MOE-cytidine; "+C" represents 5-methyl-2'-4'-bicyclic-cytidine (2'-4' methylene bridge); "oU" represents 5-methyl-2'-MOE-uridine; "+U" represents 5-methyl-2'-4'-bicyclic uridine (2'-4' methylene bridge); "*" represents a phosphorothioate internucleoside linkage) An oligonucleotide selected from

27. A composition comprising the oligonucleotide according to claim 26 in sodium salt form.

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