Antibodies for synaptinoglycan-deficient disorders

Abstract

The present invention relates to a MuSK antibody-based molecule for use in the prevention or treatment of a disease or condition caused by a synaptinan deficiency in a human subject.

Description

TECHNICAL FIELD

[0001] The present invention relates to antibody-based molecules for preventing, delaying, reversing or treating a disease or disorder caused by agrin deficiency in a human subject. In one embodiment, such antibody-based molecule is an anti-MuSK antibody. BACKGROUND

[0002] The development and maintenance of the neuromuscular junction (NMJ) relies largely on the agrin / LRP4 / MuSK pathway whereby the active neuronal form of agrin is secreted by the nerve terminal, which binds to its receptor LRP4 on the surface of the muscle fiber. This induces phosphorylation of MuSK, which recruits DOK7 and leads to rapsyn-mediated clustering of acetylcholine receptors (AChRs). Many neuromuscular disorders are characterized by impaired neuromuscular junction (NMJ) and are caused by genetic defects.

[0003] Agrin is a large proteoglycan encoded by the human AGRN gene and plays a key role in the development of the neuromuscular junction and in the clustering of acetylcholine receptors during synaptogenesis. Agrin functions by activating the MuSK (Muscle-Specific Kinase) protein, a receptor tyrosine kinase required for neuromuscular junction formation and maintenance. Defects in agrin can lead to congenital myasthenic syndromes and myasthenia gravis.

[0004] Congenital myasthenic syndromes (CMS) are a heterogeneous group of inherited disorders caused by mutations affecting structures at the neuromuscular junction (NMJ). Characteristic features are fatigue and transient or permanent ocular, facial, bulbar or limb muscle weakness, and the disorder can present at birth or in childhood, however it can also appear in adolescence or adulthood.

[0005] CMS does not have standardized treatment guidelines. Current treatments aim to improve symptoms, but dosing, duration, treatment combinations, and side effects are often ambiguous. The most common drug used for CMS is acetylcholinesterase inhibitors, and 3,4-diaminopyridine (3,4-DAP) is the most common alternative or additional drug treatment. However, acetylcholinesterase inhibitors or 3,4-DAP often do not work for patients with specific CMS subtypes. Other drugs that can be used to control symptoms include salbutamol, albuterol, ephedrine, and fluoxetine, depending on the specific CMS subtype.

[0006] Thus, there is still a need for new treatments for CMS and other diseases associated with synaptopodin deficiency. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1 Treatment and testing protocol for mice.

[0008] Three groups of animals were studied, an untreated wild-type control group and 2 groups below: Agrn nmf380 Mice. Several functional tests were performed between P5 and P50 mice, at P50 mice were culled and tissues were collected for further processing.

[0009] Figure 2: Agrn nmf380 Survival and body weight of mice.

[0010] WT, Agrn nmf380 (Mot) and Agrn nmf380 (3B2) mice. Vertical dashed lines indicate injections. Error bars indicate sd. WT n = 6, Agrn nmf380 (Mot) n = 6, Agrn nmf380 (3B2) n = 6.

[0011] Figure 3: Tube test (hanging tail test) in Agrn nmf380 Mice at P7-9.

[0012] Agrn nmf380(Mot) n = 6, Agrn nmf380 (Mot) n = 6, Agrn nmf380 (Mot) n = 6, Agrn nmf380 (3B2) n = 6.

[0013] Figure 1 : Agrn nmf380 Grip assessment in mice.

[0014] Animals were tested using a grip strength meter at P23 and P48 days. For forelimb assessment (A), the animals' tails were held and they were made to grip the bar; for hindlimb assessment (B), the animals were placed above the bar while restrained until they gripped the bar with their hindlimbs. Three trials were averaged. To determine the forelimb ratio (C) and hindlimb ratio (D), the values were divided by the body weight. Two-way ANOVA and Tukey's multiple comparison correction. WT n = 6, Agrn nmf380 (Mot) n = 3, Agrn nmf380 (3B2) n = 6, WT n = 6, Agrn nmf380 (Mot) n = 1, Agrn nmf380 (3B2) n = 6.

[0015] Figure 2: Agrn nmf380 Inverted hanging wire time in mice.

[0016] Animals were given a 30-second adaptation period on the grid and then inverted above a cushioned box. The time the animals held on was recorded. This was repeated three times with at least 15 minutes of interval between each attempt. By P48, WT animals held on longer than Agrn nmf380 (Mot) and Agrn nmf380 (3B2) animals held on significantly longer (A). WT animals also held on longer than treated and untreated Agrn nmf380 animals when the suspension ratio (B) was determined. Two-way ANOVA and Tukey's multiple comparison correction. WT n = 6, Agrn nmf380 (Mot) n = 3, Agrnnmf380 (3B2) n = 6, WT n = 6, Agrn nmf380 (Mot) n = 1, Agrn nmf380 (3B2) n = 6.

[0017] Figure 3: Agrn nmf380 Muscle harvest weights of mice.

[0018] At sacrifice and tissue extraction, muscles were blotted dry and weighed (A). To normalize the data, weights were also determined as a percentage of body weight (B). Two-way ANOVA and Tukey’s multiple comparison correction. WT n = 6, Agrn nmf380 (Mot) n = 6, Agrn nmf380 (3B2) n = 6. .

[0019] Figure 4: Agrn nmf380 Fiber size and MHC type in gastrocnemius muscle of mice, as well as MuSK, p-MuSK, and p-MuSK:MuSK.

[0020] Muscle cross sections were labeled and analyzed for fiber size and type. (A-1) Hematoxylin and eosin were used to label WT (left), Agrn nmf380 (Mot) (middle), and Agrn nmf380 (3B2) (right) muscle cross sections of mouse quadriceps. (A-2) In the quadriceps, Agrn nmf380 (Mot) mice had significantly reduced muscle fiber size. (A-3) The same pattern was present in the gastrocnemius muscle, these changes were not significant. One-way ANOVA and Tukey’s multiple comparison correction. Quadriceps: WT n = 6, Agrn nmf380 (Mot) n = 4, Agrn nmf380 (3B2) n = 6. Gastrocnemius: WT n = 6, Agrn nmf380 (Mot) n = 3 (note unequal genders), Agrn nmf380 (3B2) n = 4, .

[0021] (B-1) Muscle cross sections were labeled and analyzed for fiber and type, muscles were labeled and the number of each type of fiber was recorded. (B-2) Gastrocnemius muscles were labeled and the number of each type of fiber was recorded. Agrn nmf380 (3B2) mice demonstrated a significant reduction in Agrn nmf380Complete rescue of fiber type conversion observed in (Mot) mice. Two-way ANOVA and Tukey multiple comparison correction. WT n = 6, Agrn nmf380 (Mot) n = 4, Agrn nmf380 (3B2) n = 6. (B-3) and Agrn nmf380 Compared to (Mot) mice, WT mice exhibit significantly larger slow-speed type 1 fibers. In fast-speed type IIa (B-4), IIx (B-5), and IIb (B-6) fibers, WT mice show a greater proportion of Agrn fibers. nmf380 Differences between (Mot) mice and in Agrn nmf380 The rescue was more pronounced in (3B2) mice. .

[0022] (C-1) Muscle cross-sections were labeled and the area and mean strength values ​​were analyzed, which were used to generate integrated density values. (C-2) MuSK was significantly higher in WT animals than in Agrn. nmf380 (Mot) or Agrn nmf380 (3B2) Animal. (C-3) However, adding 3B2 restores Agrn. nmf380 (3B2) p-MuSK levels in animals. (C-4) Agrn when calculating the ratio of Musk to p-MuSK. nmf380 (3B2) The p-MuSK in animals was significantly higher than that in Agrn. nmf380 (Mot) or WT animals. One-way ANOVA and Tukey multiple comparison correction. .

[0023] (D-1) The muscle was run on the WB imprint (A) and the gray bands were quantized. (B) Agrn nmf380 The p-MuSK levels in (Mot) animals were significantly lower than those in WT animals. However, this was completely reversed in the 3B2 treatment. One-way ANOVA and Tukey multiple comparison correction were used. .

[0024] Figure 8: Postnatal injection of MuSK agonist antibody 3B2 shows synaptic proteoglycans ΔZ / ΔZ Moderate effect on mouse survival or weight gain. A. Synaptic proteoglycans ΔZ / ΔZ C57BL / 6 offspring (born from individuals injected with 3B2 synaptic glycans during pregnancy) ΔZ / + C57BL / 6 female mice ultimately showed disease relapse at approximately P30. Dark gray squares indicate natural death or euthanasia at the disease endpoint (approximately 20% weight loss); light gray squares indicate the end of the experiment. B. Synaptic proteoglycans ΔZ / ΔZC57BL / 6 offspring (born from C57BL / 6 females injected with 3B2 synaptoproteins ΔZ / + C57BL / 6 female mice) eventually showed disease relapse around P30. When they lost weight (about 10% weight loss), they were re-injected with 3B2 (10 mg / kg) and monitored. The figure shows the values for each mouse over time. Dark grey squares indicate natural death or sacrifice at disease endpoint (about 20% weight loss).

[0025] Figure 9: Synaptoproteins ΔZ / ΔZ Mice showed respiratory, energy expenditure, activity, water intake, food intake and body weight deficits.

[0026] P40 synaptoproteins ΔZ / ΔZ C57BL / 6 mice (born from C57BL / 6 females injected with 3B2 synaptoproteins ΔZ / + C57BL / 6 female mice) were placed in metabolic chambers and monitored 24h per day for 4 days. O2 consumption, CO2 production, energy expenditure, total activity, water intake, food intake and body weight measurements were collected. Scatter plots show the values for 10 control (wild type or synaptoproteins ΔZ / + ) mice and 10 synaptoproteins ΔZ / ΔZ mice as well as the percentage average values normalized to the wild type mice average values ± SEM values. Two-sided Student t-test (p, *<0.05). .

[0027] Figure 10 : Synaptoproteins ΔZ / ΔZ Mice showed motor deficits at disease relapse.

[0028] Synaptoproteins ΔZ / ΔZ mice (born from C57BL / 6 females injected with 3B2 synaptoproteins ΔZ / + C57BL / 6 female mice) showed motor deficits at disease onset (10% weight loss) as assessed by latency to fall off a rotating rotarod. The figure shows individual data points and the percentage average values normalized to the non-injected mice average values ± SEM. Two-sided Student t-test (p, *<0.05).

[0029] Figure 11: Synaptoproteins ΔZ / + C57BL / 6 female animals synaptoproteins ΔZ / ΔZ 3B2 partially restored synapse development in P40 synaptoproteins

[0030] Diaphragm from P10 and P40 mice were stained with Alexa 488-a-BGT to label AChR (red) and with antibodies against beta-lll tubulin / synaptophysin to label motor axons / nerve terminals (green). Scale bar, 10 μm. SUMMARY

[0031] Provided herein are antibody-based molecules for preventing or treating a disease or disorder caused by a synaptophysin glycan defect in a human subject. In some embodiments, the antibody-based molecule is an anti-MuSK antibody. In some embodiments, the antibody-based molecule binds to the MuSK Frizzled (Fz)-like domain sequence of SEQ ID NO: 130.

[0032] In some embodiments, the disease or disorder caused by a synaptophysin glycan defect is such that the defective synaptophysin glycan can no longer bind its receptor LRP4.

[0033] In some embodiments, the disease or disorder caused by a synaptophysin glycan defect is such that the defective synaptophysin glycan can still bind its natural receptor LRP4, but has impaired / reduced affinity and / or has a lower ability to activate MuSK phosphorylation compared to its corresponding wild-type synaptophysin glycan. In one embodiment, the antibody-based molecule can elicit a higher ability to activate MuSK phosphorylation compared to the defective synaptophysin glycan.

[0034] In some embodiments, the disease or disorder caused by a synaptophysin glycan defect is such that the expression level of MuSK is lower than the expression level of MuSK in a subject without a synaptophysin glycan defect. In one embodiment, wherein the antibody-based molecule can elicit a higher ability to activate MuSK phosphorylation compared to the defective synaptophysin glycan.

[0035] In some embodiments, the disease or disorder caused by a synaptophysin glycan defect is such that the binding of LRP4 to MuSK is impaired / antagonized, which in turn results in impaired MuSK activation. In one embodiment, the antibody-based molecule can elicit a higher ability to activate MuSK phosphorylation compared to the defective synaptophysin glycan.

[0036] In some embodiments, the antibody-based molecule is an agonist MuSK antibody and / or has reduced or eliminated effector function. In some embodiments, the antibody-based molecule induces MuSK phosphorylation. In some embodiments, the antibody-based molecule comprises a heavy chain variable region (VH) and a light chain variable region (VL) as identified in Table 3 and / or CDRs as identified in Table 1 or 2.

[0037] In some embodiments, the antibody-based molecule comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein:

[0038] The VH comprises:

[0039] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0040] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0041] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0042] The VL comprises:

[0043] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0044] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0045] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 183 (3B2).

[0046] In some embodiments, the antibody-based molecule comprises:

[0047] - a heavy chain variable domain (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202, and

[0048] - a light chain variable domain (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203 (3B2).

[0049] In some embodiments, the antibody-based molecule comprises:

[0050] - a heavy chain variable domain (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202, and

[0051] a light chain variable domain (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203, and wherein:

[0052] the heavy chain variable domain comprises:

[0053] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147,

[0054] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and

[0055] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[0056] the light chain variable domain comprises:

[0057] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159,

[0058] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[0059] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

[0060] In some embodiments, the antibody-based molecule comprises:

[0061] - a full length heavy chain comprising SEQ ID NO: 282,

[0062] - a full length light chain comprising SEQ ID NO: 283, and wherein:

[0063] - the full length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

[0064] In some embodiments, the antibody-based molecule comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein:

[0065] the VH comprises:

[0066] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 147,

[0067] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 153, and

[0068] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 (3B2g2m1), and

[0069] the VL comprises:

[0070] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 159,

[0071] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[0072] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

[0073] In some embodiments, the antibody-based molecule comprises:

[0074] - a heavy chain variable region (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 234, and

[0075] - a light chain variable region (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 235.

[0076] In some embodiments, the antibody-based molecule comprises:

[0077] - a heavy chain variable region (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 234, and

[0078] - a light chain variable region (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 235, and wherein:

[0079] VH comprises:

[0080] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 147,

[0081] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 153, and

[0082] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 (3B2g2m1), and

[0083] VL comprises:

[0084] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 159,

[0085] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[0086] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

[0087] In some embodiments, the antibody-based molecule comprises:

[0088] - a full length heavy chain comprising SEQ ID NO: 268, and

[0089] - a full length light chain comprising SEQ ID NO: 269, and

[0090] - wherein the full length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

[0091] In a second aspect, there is provided herein a polynucleotide for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said polynucleotide comprising a nucleotide sequence encoding the antibody-based molecule or the VH or VL or CDR thereof of any of the preceding embodiments.

[0092] In a third aspect, there is provided herein an expression vector for use in preventing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said expression vector comprising the polynucleotide of the second aspect of the application, preferably operably linked to a regulatory region allowing expression of the antibody or antigen-binding fragment thereof or the VH or VL or CDR thereof in a host cell or a cell-free expression system.

[0093] In a fourth aspect, there is provided herein a host cell or a cell-free expression system for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said host cell or cell-free expression system comprising the expression vector of the third aspect of the application.

[0094] In a fifth aspect, there is provided herein a composition for use in preventing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said composition comprising the antibody-based molecule as defined in any of the preceding embodiments, the polynucleotide of the second aspect of the application or the expression vector of the third aspect of the application, preferably said composition comprising at least one pharmaceutically acceptable carrier or excipient.

[0095] In some embodiments, the antibody-based molecule, polynucleotide, expression vector, host cell, cell-free expression system, or composition for use according to any of the preceding aspects and embodiments of the application, wherein the disease or disorder is characterized by impaired neuromuscular transmission and / or denervation at the NMJ (neuromuscular junction). In some embodiments, the disease is a neuromuscular disease. In some embodiments, the neuromuscular disease is selected from the group consisting of amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), myasthenia gravis (MG), congenital myasthenia, congenital myasthenic syndrome (CMS), Lambert-Eaton myasthenic syndrome (LEMS), Lyme disease, polio, post-polio, heavy metal poisoning, Kennedy syndrome, adult-onset Tay-Sachs disease, hereditary spastic paraplegia, multifocal neuropathy, cervical spondylosis, extramedullary tumor with compressive radiculopathy and myelopathy, inclusion body myositis, progressive bulbar palsy, progressive muscular atrophy, motor neuron syndrome, and thyrotoxic myopathy. In some embodiments, the disease is CMS, preferably the disease is presynaptic CMS or synaptophysin glycan-induced CMS. In some embodiments, the disease is ALS or SMA.

[0096] In some embodiments, the subject has at least one symptom selected from the group consisting of early onset of disease after birth, impaired neuromuscular performance, muscle weakness, fatigue, slow muscle fiber predominance, NMJ disassembly leading to remodeling, functional denervation, subsynaptic fold enlargement, and premature death.

[0097] In some embodiments, the administration of the antibody-based molecule, polynucleotide, expression vector, or pharmaceutical composition to the human subject results in one or more of the following therapeutic effects:

[0098] - an increase and maintenance of the number or percentage of fully innervated NMJs in the subject,

[0099] - an improvement of motor performance and / or grip strength in the subject,

[0100] - an improvement of muscle contraction properties at the NMJ in the subject,

[0101] - an improvement of muscle resistance to fatigue at the NMJ in the subject,

[0102] - an increase in muscle weight at the NMJ of the subject,

[0103] - an increase in muscle mass of the subject,

[0104] - an increase in muscle volume of the subject,

[0105] - an increase in nerve terminal area and complexity, acetylcholine perimeter and / or terminal plate area, and / or

[0106] - stabilization of the condition. DETAILED DESCRIPTION

[0107] General Definitions

[0108] The following terms or definitions are provided only to aid understanding of the present application. Unless specifically defined herein, all terms used herein have the same meaning as they would to one skilled in the art of the present application. For definitions and terms not specifically defined herein, practitioners are particularly referred to Sambrook et al., Molecular Cloning: A Laboratory Manual, Second Edition, Cold Spring Harbor Press, Plainsview, New York (1989); and Ausubel et al., Current Protocols in Molecular Biology (Supplement 47), John Wiley & Sons, New York (1999). The definitions provided herein are not to be construed as having a scope less than understood by one of ordinary skill in the art.

[0109] Unless otherwise indicated, it will be apparent to one skilled in the art that all methods, procedures, techniques and manipulations can be carried out in a manner known per se and have been carried out without being specifically detailed. For example, reference is again made to the standard manuals, the general background art mentioned above and further references cited therein.

[0110] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. The terms "condition" and "disease" are used interchangeably herein. As used herein, the term "comprising" and variations thereof as used herein are synonymous with "including", "containing", "comprehending" and variations thereof and are inclusive or open-ended and do not exclude additional, non-recited members, compounds, products, elements or method steps. The expression "consisting essentially of, used in the context of a product or composition, means that additional molecules can be present, but such molecules do not change the characteristic / activity / functionality of the product or composition. For example, if the composition itself would exhibit similar characteristic / activity / functionality to one of the antibodies or one of the antibody fragments, the composition can consist essentially of the antibody or antibody fragment. The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective range, as well as the recited endpoints.

[0111] The term "about" as used herein when referring to a measurable value such as a parameter, a quantity, a temporal duration, and the like, is meant to encompass variations that can exist in the values that are prepared to operate in the disclosed application. It is understood that the value intended to be covered is specifically and primarily disclosed. The term "about" is used herein to describe embodiments that deviate from the nominal or ideal value by no more than 10% or less, preferably by no more than 5% or less, more preferably by no more than 1% or less, and still more preferably by no more than 0.1% or less, of the nominal or ideal value, within the range such variations are suitable to be implemented in the disclosed application. It is understood that the value intended to be covered is specifically and preferably disclosed.

[0112] Amino acid residues as used herein will be represented by their full names or according to the standard three-letter or one-letter amino acid code. The terms "polypeptide" or "protein" as used herein are used interchangeably and refer to a polymer of amino acids of any length (which can include coded and non-coded amino acids, chemically or biochemically modified or derivatized amino acids) and polypeptides having modified peptide backbones. A "peptide" is also a polymer of amino acids, typically up to 50 amino acids in length. A polypeptide or peptide is represented by an amino acid sequence.

[0113] The terms "nucleic acid molecule," "polynucleotide," "polynucleic acid," "nucleic acid" are used interchangeably herein and refer to a polymeric form of nucleotides of any length, either deoxyribonucleotides or ribonucleotides or their analogs. Nucleic acid molecules are represented by nucleic acid sequences, which are primarily characterized by the sequence of their bases. Polynucleotides can have any three-dimensional structure and can perform any function, known or unknown. Non-limiting examples of polynucleotides include genetic

[0114] The term "homology" as used herein denotes at least secondary structure identity or similarity between two macromolecules, particularly between two polypeptides or polynucleotides, from the same or different taxonomic units, wherein said similarity is due to a common ancestry. Thus, the term "homolog" denotes such related macromolecules having said secondary and optionally tertiary structure similarity. For comparing two or more nucleotide sequences, the "sequence identity (in %)" between a first nucleotide sequence and a second nucleotide sequence can be calculated using methods known to the person skilled in the art, for example by dividing the number of nucleotides in the first nucleotide sequence which are identical to the nucleotides at the corresponding positions in the second nucleotide sequence by the total number of nucleotides in the first nucleotide sequence and multiplying by 100%, or by using known computer algorithms for sequence alignment, such as NCBI Blast. When determining the degree of sequence similarity between two amino acid sequences, the person skilled in the art can take into account so-called "conservative" amino acid substitutions, which can generally be described as amino acid replacements in which one amino acid residue is replaced with another amino acid residue having a similar chemical structure and having little or no effect on the function, activity or other biological properties of the polypeptide. Possible conservative amino acid substitutions have been exemplified herein. Amino acid sequences and nucleic acid sequences are said to be "identical" if they have 100% sequence identity over their entire length.

[0115] Throughout this application, each time a specific amino acid sequence SEQ ID NO (as exemplified by SEQ ID NO: Y) is mentioned, it can be replaced by: a polypeptide comprising an amino acid sequence having at least 80% sequence identity or similarity to the amino acid sequence SEQ ID NO: Y. Throughout this application, the expression "a sequence which is at least X% identical to another sequence" can be replaced by "a sequence which has at least X% sequence identity to another sequence".

[0116] In other preferred embodiments, each of the amino acid sequences described herein has at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or higher identity with a given amino acid sequence by virtue of its respective percentage identity to the given amino acid sequence (at least 80%). In a preferred embodiment, sequence identity is determined by comparing the full length of the sequences as identified herein. In other preferred embodiments, each of the amino acid sequences described herein has at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or higher similarity with a given amino acid sequence by virtue of its respective percentage similarity to the given amino acid sequence (at least 80%). In a preferred embodiment, sequence similarity is determined by comparing the full length of the sequences as identified herein. Unless otherwise specified herein, identity or similarity with a given SEQ ID NO means identity or similarity based on the full length of the sequence (i.e. over the full length or as a whole).

[0117] "Sequence identity" is defined herein as a relationship between two or more amino acid (polypeptide or protein) sequences or two or more nucleic acid (polynucleotide) sequences, as determined by comparing the sequences. Identity between two amino acid sequences is preferably determined by assessing their identity over the entire SEQ ID NO as identified herein or a portion thereof. A portion thereof can mean at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90% of the length of the SEQ ID NO.

[0118] In the art, "identity" also means the degree of sequence relatedness between amino acid sequences, as the case can be, as determined by matches between strings of such sequences. "Similarity" between two amino acid sequences is determined by comparing the amino acid sequence of one polypeptide and its conserved amino acid substitutes with the sequence of a second polypeptide. "Identity" and "similarity" can be readily calculated by known methods, including but not limited to those described in:

[0119]

[0120] Preferred methods for determining identity are designed to give the largest match between the sequences tested. Methods to determine identity and similarity are codified in publicly available computer programs. Preferred computer program methods to determine identity and similarity between two sequences include, for example, the GCG program package (Devereux, J., et al., Nucleic Acids Research 12(1): 387 (1984)), BestFit, FASTA, BLASTN, and BLASTP (Altschul, S. F. et al., J. Mol. Biol. 215:403-410 (1990)), EMBOSS Needle (Madeira, F., et al., Nucleic Acids Research 47(W1): W636-W641 (2019)). The BLAST programs are publicly available from NCBI and other sources (BLAST Manual, Altschul, S., et al., NCBI NLM NIH Bethesda, MD 20894; Altschul, S., et al., J. Mol. Biol. 215:403-410 (1990)). The EMBOSS programs are publicly available from EMBL-EBI. The well-known Smith Waterman algorithm can also be used to determine identity. The EMBOSS Needle program is the preferred program to use.

[0121] Preferred parameters for polypeptide sequence comparisons include the following: algorithm: Needleman and Wunsch, J. Mol. Biol. 48 (3):443-453 (1970); comparison matrix: BLOSUM62, from Henikoff and Henikoff, Proc. Natl. Acad. Sci. USA. 89:10915-10919 (1992); gap open penalty: 10, and gap extension penalty: 0.5. A program useful with these parameters is publicly available as the EMBOSS Needle program from EMBL-EBI. The foregoing parameters are the default parameters for protein global pairwise sequence alignment (and no penalty for terminal gaps).

[0122] Preferred parameters for nucleic acid comparison include the following: algorithm: Needleman and Wunsch, J. Mol. Biol. 48:443-453 (1970); comparison matrix: DNAfull; gap opening penalty: 10; gap extension penalty: 0.5. A program useful in the context of these parameters is publicly available as the EMBOSS Needle program from EMBL-EBI. The aforementioned parameters are the default parameters for global pairwise sequence alignment of nucleotide sequences (and no penalty for end gaps).

[0123] Also provided herein are embodiments wherein any embodiment described herein can be combined with any one or more additional embodiments, as long as the combination is not mutually exclusive.

[0124] Antibody-based molecules

[0125] The present application is based on the surprising finding that syncan deficiency can be rescued by treatment with MuSK antibodies. As exemplified in the examples, these treated syncan deficient animals show an improvement in at least one of the following parameters and / or symptoms: number or percentage of fully innervated NMJs in the subject, motor performance and / or grip strength, muscle contraction properties at the NMJ, muscle resistance to fatigue at the NMJ, muscle weight at the NMJ, muscle mass of the subject, muscle volume of the subject, nerve terminal area and complexity, acetylcholine perimeter, endplate area, stability of the condition, muscle fiber size, NMJ morphology, muscle strength of the subject, body weight / muscle weight of the subject, and survival.

[0126] All antibody-based molecules as defined herein are encompassed in the present application as such. In the context of the present application, the expression "antibody-based molecule" can be replaced by the word "antibody" or by the expression "antibody or functional fragment thereof" or by the expression "antibody or antigen binding fragment".

[0127] In a first aspect of the present application, there is provided an antibody-based molecule for preventing, delaying, reversing or treating a disease or condition caused by syncan deficiency in a human subject.

[0128] All of these features are further defined herein. Antibody-based molecules include, but are not limited to, antibodies, intact antibodies, epitope-binding fragments of intact antibodies, antigen-binding fragments of intact antibodies, and antibody derivatives. Epitope-binding fragments of antibodies can be obtained by actual fragmentation of a parent antibody (e.g., Fab or (Fab)2 fragments). Alternatively, an epitope-binding fragment is an amino acid sequence comprising a portion of the amino acid sequence of such a parent antibody. As used herein, a molecule is referred to as a "derivative" of an antibody if it is obtained by actual chemical modification of a parent antibody or portion thereof, or if it comprises an amino acid sequence that is substantially similar to the amino acid sequence of such a parent antibody or relevant portion thereof (e.g., differs from such a parent antibody or such a relevant portion thereof by less than 30%, less than 20%, less than 10%, or less than 5%, or differs from such a parent antibody or relevant portion thereof by 10 amino acid residues or fewer, or fewer than 10, 9, 8, 7, 6, 5, 4, 3, or 2 amino acid residues).

[0129] In one embodiment, the antibody-based molecules of the present application are intact immunoglobulins or molecules having a binding epitope of 333 acids encoded by a fragment in a recombinant cell (see, e.g., Evans et al., "Rapid Expression Of An Anti-Human C5 Chimeric Fab Utilizing A Vector That Replicates In COS And 293 Cells," J. Immunol. Meth. 184: 123-38 (1995), which is hereby incorporated by reference in its entirety). For example, a chimeric gene encoding a portion of a F(ab')2 fragment can include DNA sequences encoding the heavy chain CH1 domain and hinge region, followed by a translation termination codon, to produce such a truncated antibody fragment molecule. Suitable fragments capable of binding to a desired epitope can be readily screened for use in the same manner as intact antibodies.

[0130] Antibody derivatives include those molecules that contain at least one epitope binding domain of an antibody, and are typically formed using recombinant techniques. One exemplary antibody derivative includes a single chain Fv (scFv). A scFv is formed from two domains of an Fv fragment, VL and VH, which can be encoded by different genes. Using recombinant methods, such gene sequences or their encoding cDNAs are linked together by a flexible linker (typically of about 10, 12, 15 or more amino acid residues) such that they can be made into a single protein chain, with the VL and VH associating to form a monovalent epitope binding molecule (see, e.g., Bird et al., “Single-Chain Antigen-Binding Proteins,” Science 242:423-426 (1988); and Huston et al., “Protein Engineering Of Antibody Binding Sites: Recovery Of Specific Activity In An Anti-Digoxin Single-Chain Fv Analogue Produced In Escherichia coli,” Proc. Natl. Acad. Sci. (U.S.A.) 85:5879-5883 (1988), which are hereby incorporated by reference in their entireties). Alternatively, by using a less short (e.g., not fewer than about 9 residues) flexible linker to enable the VL and VH of different individual polypeptide chains to associate together, it can form a bispecific antibody having binding specificity for two different epitopes.

[0131] In another embodiment, the antibody derivative is a divalent or bivalent single-chain variable fragment that is engineered by linking two scFv together in tandem (i.e., tandem scFv) or dimerizing them to form a diabody (Holliger et al., "Diabodies': Small Bivalent And Bispecific Antibody Fragments," Proc. Natl. Acad. Sci. (U.S.A.) 90(14), 6444-8 (1993), which is hereby incorporated by reference in its entirety). In another embodiment, the antibody is a triabody, i.e., a trivalent single-chain variable fragment that is engineered by linking three scFv together in tandem or as a trimer to form a triabody. In another embodiment, the antibody is a tetrabody of four single-chain variable fragments. In another embodiment, the antibody is a "linear antibody," which is an antibody comprising a pair of tandem Fd segments (VH-CH1-VH-CH1) that form a pair of antigen binding regions (see Zapata et al., Protein Eng. 8(10): 1057-1062 (1995), which is hereby incorporated by reference in its entirety). In another embodiment, the antibody derivative is a minibody, which consists of a single-chain Fv region coupled to a CH3 region (i.e., scFv-CH3).

[0132] These and other useful antibody fragments and derivatives in the context of the present application are also discussed herein. It will also be understood that, unless otherwise specified, the term antibody-based molecule also includes antibody-like polypeptides, such as chimeric antibodies and humanized antibodies, antigen binding fragments, as well as antibody fragments that retain the ability to specifically bind with antigen (epitope binding fragments, antigen binding fragments, or functional fragments), provided by any known technique, such as enzymatic cleavage, peptide synthesis, and recombinant technology.

[0133] Antibodies produced as herein can be of any isotype. As used herein, "isotype" refers to an immunoglobulin class (e.g., IgGl, IgG2, IgG3, IgG4, IgD, IgA, IgE, or IgM) that is encoded by heavy chain constant region genes. The choice of isotype is generally guided by the effector functions desired, e.g., induction of antibody-dependent cellular cytotoxicity (ADCC). Exemplary isotypes are IgGl, IgG2, IgG3, and IgG4. Particularly useful isotypes of the MuSK antibodies disclosed herein include IgGl and IgG2. Any of the human light chain constant regions, kappa or lambda, can be used. If desired, the class of the MuSK antibodies of the application can be switched by known methods. For example, an antibody of the application that is originally IgM can be class switched to an IgG antibody of the application. In addition, class switching techniques can be used to switch one IgG subclass to another, e.g., from IgGl to IgG2. Thus, the effector functions of the antibodies of the application can be changed by isotype switching to, for example, IgGl, IgG2, IgG3, IgG4, IgD, IgA, IgE, or IgM antibodies for a variety of therapeutic uses.

[0134] In one embodiment, one, two or more amino acid substitutions are introduced into the IgG constant region Fc region to alter the effector function of the antibody-based molecule. For example, amino acid residues selected from 234, 235, 236, 237, 238, 239, 243, 265, 267, 268, 292, 297, 300, 318, 320, 322, 327, 328, 329, 330, 331, 332, and 396 (according to EU numbering system (Kabat, E. A., et al. (1991) Sequences of Proteins of Immunological Interest, 5th Ed. Public Health Service, National Institutes of Health, Bethesda, MD) https: / / www.imgt.org / IMGTScientificChart / Numbering / Hu_ IGHGnber.html#notesone or more amino acid substitutions of one or more amino acids of an antibody-based molecule of the application with different amino acid residues such that the antibody-based molecule has altered affinity for an effector ligand but retains antigen binding ability. In one embodiment, amino acid 234 or 235 has been substituted. In another embodiment, amino acids 234 and 235 have been substituted. In this context, a preferred amino acid sequence of a human IgG constant Fc region comprises SEQ ID NO: 266 or 267. In this context, for example, amino acids 234 and 235 numbered according to the EU numbering system correspond to amino acids 7 and 8 in SEQ ID NO: 266 and 267 (i.e., the human IgG constant Fc region of the antibody-based molecules disclosed herein), or amino acids 238 and 239 in SEQ ID NO: 268 and 270 and 282 (i.e., the human full length heavy chains of the antibody-based molecules disclosed herein). The positions are generally different because of the difference in length of the variable region, which introduces a "delta" between the numbering. In the case described above, this delta is 4. Thus, the same is true for the other amino acid positions identified above numbered according to the EU numbering system (i.e., 236, 237, 238, 239, 243, 265, 267, 268, 292, 297, 300, 318, 320, 322, 327, 328, 329, 330, 331, 332, and 396) when identifying the corresponding position in SEQ ID NO: 266 or 267 or 268 or 270 or 282. In the application as filed, the position of the amino acid can be referred to using the EU numbering system or using the actual position in a given Fc region (e.g., SEQ ID NO: 266 or 267) or in a full length heavy chain (e.g., SEQ ID NO: 268 or 270 or 282).

[0135] Accordingly, in one embodiment, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 amino acid substitutions are introduced into SEQ ID NO: 266 or 267. In one embodiment, 1, 2, 3, 4 amino acid substitutions are introduced into SEQ ID NO: 266 or 267. In one embodiment, 1 or 2 amino acid substitutions are introduced into SEQ ID NO: 266 or 267. Accordingly, in one embodiment, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17 amino acid substitutions are introduced into SEQ ID NO: 266 or 267, and the substitutions are introduced at amino acid positions selected from the group consisting of amino acid residues 234, 235, 236, 237, 239, 243, 267, 292, 297, 300, 318, 320, 322, 328, 330, 332, and 396 of said sequence, numbered in accordance with the EU numbering system. In one embodiment, 1 or 2 amino acid substitutions are introduced into SEQ ID NO: 266 or 267. In one embodiment, amino acid 234 or 235 of SEQ ID NO: 266 or 267, numbered in accordance with the EU numbering system, has been replaced. In another embodiment, amino acids 234 and 235 of SEQ ID NO: 266 or 267, numbered in accordance with the EU numbering system, have been replaced.

[0136] The effector ligand with which affinity is altered can be, for example, an Fc receptor or the Cl component of complement. This approach is described in greater detail in U.S. Patent Nos. 5,624,821 and 5,648,260, each of which is incorporated herein by reference in its entirety. In one embodiment, one or more amino acid substitutions can be introduced into the Fc region of an antibody-based molecule described herein to remove potential glycosylation sites on the Fc region, which can reduce Fc receptor binding (see, e.g., Shields RL et al, (2001) J Biol Chem 276: 6591-604, which is incorporated herein by reference in its entirety). In one embodiment, binding to an effector ligand is reduced at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or the binding is no longer detectable, as compared to the binding of an antibody having no amino acid substitutions in its human IgG constant Fc region to the same ligand.

[0137] In a first embodiment, one or more of the following mutations have been introduced into the constant region of an antibody-based molecule described herein (all numbered according to the EU numbering system): N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; or P396L substitution.

[0138] In a second embodiment, one or more of the following mutations have been introduced into the constant region of an antibody-based molecule described herein (all numbered according to the EU numbering system): L234A and / or L235A substitutions; L234A and L235A substitutions; L234A, L235A and P329G substitutions; L234A, L235A and G236K substitutions; L234A, L235A and G236E substitutions; L234A, L235A and G236R substitutions; L234A and G236R substitutions; L234A, L235S and G236R substitutions; L234A, L235T and G236R substitutions; L234D, L235H and G236R substitutions; L234D, L235K and G236R substitutions; L234D and G236R substitutions; L234D, L235Q and G236R substitutions; L234D, L235S and G236R substitutions; L234E, L235D and G236R substitutions; L234E, L235H and G236R substitutions; L234E, L235I and G236R substitutions; L234G, L235H and G236R substitutions; L234G, L235Q and G236R substitutions; L234G, L235S and G236R substitutions; L234H, L235I and G236R substitutions; L234H, L235S and G236R substitutions; L234K, L235Q and G236R substitutions; L234K, L235R and G236R substitutions; L234K, L235S and G236R substitutions; L234K, L235T and G236R substitutions; L234K, L235V and G236R substitutions; L234Q, L235A and G236R substitutions; L234Q, L235D and G236R substitutions; L234Q, L235H and G236R substitutions; L234Q and G236R substitutions; L234Q, L235Q and G236R substitutions; L234Q, L235R and G236R substitutions; L234Q, L235S and G236R substitutions; L234Q, L235T and G236R substitutions; L234Q, L235V and G236R substitutions; L234R, L235D and G236R substitutions; L234R, L235E and G236R substitutions; L234R, L235H and G236R substitutions; L234R, L235I and G236R substitutions; L234R, L235K and G236R substitutions; L234R and G236R substitutions; L234R, L235Q and G236R substitutions; L234R, L235R and G236R substitutions; L234R, L235T and G236R substitutions; L234S, L235E and G236R substitutions; L234S, L235G and G236R substitutions; L234S, L235H and G236R substitutions;L234S, L235I and G236R substitutions; L234S and G236R substitutions; L234S, L235R and G236R substitutions; L234S, L235T and G236R substitutions; L234S, L235V and G236R substitutions; L234T, L235A and G236R substitutions; L234T, L235D and G236R, L234T, L235H and G236R substitutions; L234T, L235I and G236R substitutions; L234T, L235K and G236R substitutions; L234T, L235Q and G236R substitutions; L234T, L235R and G236R substitutions; L234T, L235S and G236R substitutions; L234T, L235T and G236R substitutions; L234T, L235V and G236R substitutions; G236R and L328R substitutions; L234A, L235A, G237A, P238S, H268A, A330S and P331S substitutions; E233P, L234V, L235A, G326 deletion, A327G, A330S and P331S substitutions; L235A and G236R substitutions; L235S and G236R substitutions.

[0139] In a third embodiment, one or more of the following mutations have been introduced into the Fc region of an antibody-based molecule described herein (all numbered according to the EU numbering system): N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; or P396L substitution.

[0140] In a fourth embodiment, one or more of the following mutations have been introduced into the Fc region of an antibody-based molecule described herein (all numbered according to the EU numbering system): L234A and / or L235A substitutions; L234A and L235A substitutions; L234A, L235A and P329G substitutions; L234A, L235A and G236K substitutions; L234A, L235A and G236E substitutions; L234A, L235A and G236R substitutions; L234A and G236R substitutions; L234A, L235S and G236R substitutions; L234A, L235T and G236R substitutions; L234D, L235H and G236R substitutions; L234D, L235K and G236R substitutions; L234D and G236R substitutions; L234D, L235Q and G236R substitutions; L234D, L235S and G236R substitutions; L234E, L235D and G236R substitutions; L234E, L235H and G236R substitutions; L234E, L235I and G236R substitutions; L234G, L235H and G236R substitutions; L234G, L235Q and G236R substitutions; L234G, L235S and G236R substitutions; L234H, L235I and G236R substitutions; L234H, L235S and G236R substitutions; L234K, L235Q and G236R substitutions; L234K, L235R and G236R substitutions; L234K, L235S and G236R substitutions; L234K, L235T and G236R substitutions; L234K, L235V and G236R substitutions; L234Q, L235A and G236R substitutions; L234Q, L235D and G236R substitutions; L234Q, L235H and G236R substitutions; L234Q and G236R substitutions; L234Q, L235Q and G236R substitutions; L234Q, L235R and G236R substitutions; L234Q, L235S and G236R substitutions; L234Q, L235T and G236R substitutions; L234Q, L235V and G236R substitutions; L234R, L235D and G236R substitutions; L234R, L235E and G236R substitutions; L234R, L235H and G236R substitutions; L234R, L235I and G236R substitutions; L234R, L235K and G236R substitutions; L234R and G236R substitutions; L234R, L235Q and G236R substitutions; L234R, L235R and G236R substitutions; L234R, L235T and G236R substitutions; L234S, L235E and G236R substitutions; L234S, L235G and G236R substitutions;L234S, L235H and G236R substitutions; L234S, L235I and G236R substitutions; L234S and G236R substitutions; L234S, L235R and G236R substitutions; L234S, L235T and G236R substitutions; L234S, L235V and G236R substitutions; L234T, L235A and G236R substitutions; L234T, L235D and G236R, L234T, L235H and G236R substitutions; L234T, L235I and G236R substitutions; L234T, L235K and G236R substitutions; L234T, L235Q and G236R substitutions; L234T, L235R and G236R substitutions; L234T, L235S and G236R substitutions; L234T, L235T and G236R substitutions; L234T, L235V and G236R substitutions; G236R and L328R substitutions; L234A, L235A, G237A, P238S, H268A, A330S and P331S substitutions; E233P, L234V, L235A, G326 deletion, A327G, A330S and P331S substitutions; L235A and G236R substitutions; L235S and G236R substitutions.

[0141] In one embodiment, one or more of the following mutations are introduced into the Fc region of the antibody-based molecule described herein: L234A and / or L235A substitutions (numbered according to the EU numbering system). In one embodiment, the following mutations are introduced into the Fc region of the antibody-based molecule described herein: L234A and L235A substitutions (numbered according to the EU numbering system). This embodiment results in an antibody-based molecule having a heavy chain represented by SEQ ID NO: 268 or 270 or 282. Such antibodies with altered, diminished or even abrogated effector functions are of interest in the context of the present application.

[0142] MuSK antibody-based molecules

[0143] The present application also relates to anti-MuSK antibodies, epitope binding domains thereof, antigen binding fragments thereof and antibody derivatives thereof for use in preventing, delaying, reversing or treating a disease or disorder caused by synapse proteoglycan deficiency in a human subject. The term "anti-MuSK antibodies" can be replaced by the term "MuSK antibodies". Any anti-MuSK antibodies, epitope binding domains thereof, antigen binding fragments thereof and antibody derivatives capable of binding muscle-specific tyrosine-protein kinase (MuSK) are encompassed within the present application.

[0144] The present application provides the insight that such antibody-based molecules can be used for preventing or treating a disease or disorder in which the subject needs an increased MuSK signaling or MuSK phosphorylation, e.g. a neuromuscular disease or disorder associated with synapse proteoglycan deficiency. In one embodiment, such anti-MuSK antibodies are capable of activating or inducing MuSK signaling and / or MuSK phosphorylation.

[0145] MuSK is a receptor tyrosine kinase that is expressed in skeletal muscle and has a key, primary role in forming and maintaining neuromuscular synapses (Burden et al., “The Role of MuSK in Synapse Formation and Neuromuscular Disease,” Cold Spring Harb. Perspect. Biol. 5:a009167 (2013), which is hereby incorporated by reference in its entirety). MuSK is a single-pass, 120 kDa transmembrane protein composed of an extracellular region containing three Ig-like domains and a Frizzled (Fz)-like domain and an intracellular region containing a juxtamembrane region, a kinase domain, and a short cytoplasmic tail (Jennings et al., “Muscle-Specific trk-Related Receptor with a Kringle Domain Defines a Distinct Class of Receptor Tyrosine Kinases,” Proc. Natl. Acad. Sci. USA 90:2895-2899 (1993) and Valenzuela et al., “Receptor Tyrosine Kinase Specific for the Skeletal Muscle Lineage: Expression in Embryonic muscle, at the Neuromuscular Junction, and After Injury,” Neuron 15: 573-584 (1995), which are hereby incorporated by reference in their entireties). MuSK phosphorylation is stimulated by agrin, a signal provided by motor neurons. Once activated, MuSK stimulates pathways that (1) cluster and anchor AChRs and additional muscle proteins that are critical for synaptic transmission, (2) enhance transcription of genes encoding synaptic proteins in muscle “synaptic nuclei,” and (3) promote generation of retrograde signals that promote presynaptic differentiation and attachment of motor nerve terminals to muscle. In the absence of MuSK, neuromuscular synapses cannot form (Burden et al., “The Role of MuSK in Synapse Formation and Neuromuscular Disease,” Cold Spring Harb. Perspect. Biol. 5:a009167 (2013), which is hereby incorporated by reference in its entirety).In addition to its role in synapse formation, MuSK is required to maintain adult synapses, as inhibition of MuSK expression in adult muscle results in severe defects in presynaptic and postsynaptic differentiation (Kong et al., “Inhibition of Synapse Assembly in Mammalian Muscle in vivo by RNA Interference,” EMBO Rep 5: 183-188 (2004) and Hesser et al., “Synapse Disassembly and Formation of New Synapses in Postnatal Muscle Upon Conditional Inactivation of MuSK,” Mol. Cell. Neurosci. 31 :470-480 (2006), which are hereby incorporated by reference in their entireties). Consistent with these findings in mice, mutations that impair MuSK kinase activity or inhibit MuSK downstream signaling steps result in congenital myasthenic (CM), characterized by synaptic structural and functional defects, leading to muscle weakness and fatigue (Beeson et al., “Dok-7 Mutations Underlie a Neuromuscular Junction Synaptopathy,” Science 313:1975-1978 (2006); Muller et al., “Phenotypical Spectrum of DOK7 Mutations in Congenital Myasthenic Syndromes,” Brain 130:1497-1506 (2007); and Selcen et al., “A Compensatory Subpopulation of Motor Neurons in a Mouse Model of Amyotrophic Lateral Sclerosis,” J. Comp. Neurol. 490:209-219 (2008), which are hereby incorporated by reference in their entireties).

[0146] The amino acid sequence of human MuSK has the amino acid sequence of SEQ ID NO: 129.

[0147]

[0148] In some embodiments, the antibody-based molecules of the present application bind to the MuSK Frizzled (Fz)-like domain sequence of SEQ ID NO: 130.

[0149] According to the present application, the MuSK antibody-based molecules described herein bind to an epitope within the Frizzled (Fz)-like domain of the MuSK protein. The Fz-like domain of MuSK has the amino acid sequence of SEQ ID NO: 130 as shown below.

[0150] .

[0151] The MuSK antibody-based molecules bind to the Fz-like domain of human MuSK.

[0152] The term "epitope" as used herein refers to an antigenic determinant to which an antibody binds. Epitopes usually consist of surface groupings of molecules such as amino acids or sugar side chains and usually have specific three-dimensional structural characteristics, as well as specific charge characteristics. The distinction between conformational and non-conformational epitopes is based on the fact that binding to the former, but not the latter, is lost in the presence of denaturing solvents. The epitope can include amino acid residues that directly participate in binding (also referred to as the immunodominant components of the epitope) and other amino acid residues that do not directly participate in binding, such as amino acid residues that are effectively blocked by a particular antigen binding peptide (in other words, the amino acid residues are within the "footprint" of the particular antigen binding peptide). Epitopes include usually at least 3, and more usually at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or more amino acids in a unique spatial conformation.

[0153] In one embodiment, the MuSK antibody-based molecules applied according to the present application bind to the MuSK Frizzled (Fz)-like domain. In one embodiment, the MuSK antibody or antigen binding fragment immunospecifically binds to an epitope in the MuSK Fz-like domain sequence of SEQ ID NO: 130 more frequently, more rapidly, more persistently, and / or with stronger affinity or avidity than an alternative epitope. In one embodiment, the MuSK antibody-based molecules described herein immunospecifically bind to any 2, 3, 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 or more amino acid residues of SEQ ID NO: 130. The terms "affinity", "specifically binds", "binds", "immunospecifically binds", "binding activity", or "specific binding activity" as used herein refer to the degree of binding of an antibody or antibody fragment as defined herein to an epitope within the MuSK-Fz-like domain sequence of SEQ ID NO: 130.

[0154] In one embodiment, a MuSK antibody-based molecule as disclosed herein binds to the MuSK Fz-like domain with an affinity corresponding to a KD of about 10 -7 M or less. For example, a MuSK antibody-based molecule as disclosed herein binds to the MuSK Fz-like domain with an affinity corresponding to a KD of about 10 -8 M, about 10 -9 M, about 10 -10 M, about 10 -11 M, about 10 -12 M or lower, as determined by, for example, surface plasmon resonance (SPR) technology in a Biacore 3000 instrument, preferably using the antibody as the ligand and MuSK as the analyte. A MuSK antibody-based molecule as disclosed herein binds to the MuSK Fz-like domain with an affinity that is at least 10-fold lower, for example at least 100-fold lower, for example at least 1,000-fold lower, for example at least 10,000-fold lower, for example at least 100,000-fold lower, of the affinity with which the MuSK antibody-based molecule binds to a non-specific antigen (e.g., bovine serum albumin, casein, etc.). The amount of reduction in affinity depends on the KD of the antibody, so when the KD of the antibody is very low (i.e., the antibody is highly specific), then the amount of affinity for the antigen is at least 10,000-fold lower than the affinity for the non-specific antigen. The term "kd" (sec"1or 1 / s) as used herein refers to the dissociation rate constant of a particular antibody-antigen interaction. This value is also referred to as the koff value and reflects the avidity of an antibody for its target. The term "ka" (M"1sec"1or 1 / Ms) as used herein refers to the association rate constant of a particular antibody-antigen interaction. The term "KD" (M) as used herein refers to the dissociation equilibrium constant of a particular antibody-antigen interaction and is obtained by dividing the kd by the ka. The term "KA" (M"1or 1 / M) as used herein refers to the association equilibrium constant of a particular antibody-antigen interaction and is obtained by dividing the ka by the kd.

[0155] ​In one embodiment, the MuSK antibody-based molecules described herein have pH-dependent binding affinity for MuSK, which allows antibody recirculation to enhance antigen binding. For example, in one embodiment, the association rate constant or dissociation rate constant can be different at acidic versus neutral versus basic pH conditions. In one embodiment, the MuSK antibody-based molecules described herein have a higher dissociation rate constant at acidic pH conditions (e.g., pH < 7.0) compared to neutral pH conditions (e.g., pH of about 7.0 to 7.9). In some embodiments, the MuSK antibody-based molecules described herein have 2-fold to 3-fold higher dissociation rate constant (i.e., decreased binding affinity) at acidic pH (e.g., pH of about 5.5) compared to neutral pH (pH of about 7.4). In one embodiment, the MuSK antibody-based molecules bind to the MuSK Fz-like domain with higher affinity at neutral pH conditions than at acidic pH conditions. In other words, in one embodiment, the MuSK antibody-based molecules bind to the MuSK Fz-like domain with higher dissociation rate at acidic pH conditions than at neutral pH conditions. Neutral pH conditions can be defined as comprising a pH of 7.0 to 7.9. Acidic pH conditions can be defined as a pH less than 7.0. Higher can mean at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200%, 250%, 300% higher. Antibodies with this pH-dependent dissociation characteristic dissociate from the antigen after binding and activation but before lysosomal degradation. Once dissociated, the antibodies are transported back into the circulation through the neonatal Fc receptor and released to bind more antigen.

[0156] In some embodiments, the MuSK antibody-based molecules induce or activate MuSK phosphorylation. In some embodiments, the binding of the MuSK antibodies of the application to their respective epitopes activates MuSK signaling. Preferably, the epitopes are within the Fz-like domain and the binding to said epitopes activates MuSK signaling. In particular, when the MuSK antibodies of the application bind to their respective epitopes in the MuSK Fz-like domain, such binding induces MuSK phosphorylation and activation. Relative to the MuSK phosphorylation induced by agrin activation, the MuSK antibodies of the application induce from about 50% to about 100% of MuSK phosphorylation (as measured, for example, in a C2C12 phosphorylation assay). In this embodiment, the MuSK phosphorylation induced by the MuSK antibodies of the application is compared to the MuSK phosphorylation induced by wild-type agrin. In one embodiment, the MuSK antibodies of the application induce about 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, or 100% of MuSK phosphorylation (relative to the MuSK phosphorylation induced by agrin activation in the absence of a dystroglycan deficiency). In one embodiment, the MuSK antibody-based molecules of the application induce from about 90% to about 100% of MuSK phosphorylation upon MuSK binding (relative to the MuSK phosphorylation induced by agrin activation in the absence of a dystroglycan deficiency). In this context, MuSK phosphorylation is assessed in subjects that are not deficient in dystroglycan, thus enabling a proper assessment of the level of MuSK phosphorylation. The phosphorylation of MuSK can be assessed using techniques known to those skilled in the art, such as western blot or C2C12 myotube phosphorylation assays. Such antibodies that activate MuSK signaling (i.e., induce dimerization of MuSK, induce tyrosine phosphorylation of MuSK) are agonist antibodies.

[0157] In some embodiments, the MuSK antibodies of the application, preferably MuSK antibodies that bind to the Fz-domain of MuSK, do not interfere (i.e., do not block, hinder, inhibit, or reduce) natural ligand binding and stimulation of MuSK. Some known MuSK binding proteins (or ligands) include lrp4 / titinin and ColQ. In some embodiments, the MuSK antibodies of the application enhance natural MuSK activation, i.e., phosphorylation, induced by natural ligand binding. In the context of the present application, titinin can be considered a natural ligand that activates MuSK by binding to LRP4. Such MuSK antibodies are agonist antibodies. In some embodiments, the antibodies of the application, in combination with the natural ligand, activate MuSK (i.e., MuSK phosphorylation) to > 20% of the level of endogenous activation, e.g., at least 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 130%, 150%, 200% of the level of endogenous activation. MuSK phosphorylation can be assessed using techniques known to the skilled person. Such techniques can be western blotting.

[0158] Thus, in one embodiment, the activity of the MuSK antibody-based molecule of the application comprises: (i) binding to an epitope of human muscle-specific tyrosine-protein kinase (MuSK), preferably the epitope is present in the MuSK frizzled (Fz)-like domain sequence of SEQ ID NO: 130, wherein the antibody-based molecule upon binding to its epitope induces MuSK phosphorylation, and / or (ii) binding to its epitope, preferably the MuSK Fz-like domain does not block, hinder, or inhibit the phosphorylation induced by a natural or endogenous MuSK ligand and can enhance the phosphorylation induced by the natural or endogenous MuSK ligand, and (iii) the binding to its epitope, preferably the MuSK Fz-like domain, occurs with higher affinity under neutral pH conditions than under acidic pH conditions. In one embodiment, the MuSK antibody-based molecule binds to the human Fz-like domain of human MuSK (SEQ ID NO: 130).

[0159] In one embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing, or treating a disease or disorder caused by titinin deficiency in a human subject is an agonist MuSK antibody and / or has reduced or eliminated effector function.

[0160] In a first embodiment, the disease or disorder caused by syncan deficiency is such that the deficient syncan can no longer bind its receptor LRP4. In one embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating a disease or disorder caused by syncan deficiency: (i) binds to an epitope of human MuSK, preferably the epitope is preferably present in the MuSK Frizzled (Fz)-like domain sequence of SEQ ID NO: 130, and (ii) induces MuSK phosphorylation upon binding to its epitope. In one such embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating a disease or disorder caused by syncan deficiency: (i) binds to an epitope of human MuSK, preferably the epitope is preferably present in the MuSK Frizzled (Fz)-like domain sequence of SEQ ID NO: 130, (ii) induces MuSK phosphorylation upon binding to its epitope, and (iii) wherein the binding mimics the binding of the natural ligand of MuSK, i.e. syncan or LRP / synscan.

[0161] In a second embodiment, the disease or disorder caused by syncan deficiency is such that the deficient syncan is still able to bind its natural receptor LRP4, but has impaired / reduced affinity to and / or has reduced ability to activate MuSK phosphorylation compared to its corresponding wild-type syncan. In this embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating a disease or disorder caused by syncan deficiency can elicit a higher ability to activate MuSK phosphorylation than the deficient syncan.

[0162] In this context, the affinity can be assessed using techniques known to the skilled person, as previously defined herein. Techniques to assess MuSK phosphorylation are also known to the skilled person and are also previously defined herein.

[0163] In this embodiment, the impaired / reduced affinity of the deficient syncan to LRP4 can be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% lower than the corresponding affinity of wild-type syncan to LRP4.

[0164] In this embodiment, the ability of the deficient syncan to activate MuSK phosphorylation can be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% lower than the corresponding ability of wild-type syncan.

[0165] In this embodiment, the higher capacity of the MuSK antibody-based molecule to activate MuSK phosphorylation is at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 200%, 500%, 1000% higher than the corresponding capacity of the defective syncan.

[0166] In a third embodiment, the disease or disorder caused by the syncan deficiency is such that the expression level of MuSK is lower than the MuSK expression level in a subject without the syncan deficiency (as exemplified in Figure 7C-2 In this embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating the disease or disorder caused by the syncan deficiency can elicit a higher capacity to activate MuSK phosphorylation than the defective syncan (as exemplified in Figure 7C-4 In this embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating the disease or disorder caused by the syncan deficiency can elicit a higher capacity to activate MuSK phosphorylation than the defective syncan (as exemplified in

[0167] Such a property allows to compensate for the lower expression level of MuSK.

[0168] Each of these features has been previously defined in this document.

[0169] In this embodiment, the lower expression of MuSK can be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% lower than the corresponding expression of MuSK in a subject expressing a wild-type syncan.

[0170] In a fourth embodiment, the disease or disorder caused by the syncan deficiency is such that the binding of LRP4 to MuSK is impaired / antagonized, which in turn results in impaired MuSK activation. The binding of LRP4 to MuSK can be considered as impaired / antagonized when the binding affinity of LRP4 to MuSK is lower than the binding affinity of LRP4 to MuSK in a subject without the syncan deficiency. In this embodiment, the MuSK antibody-based molecule for preventing, delaying, reversing or treating the disease or disorder caused by the syncan deficiency can elicit a higher capacity to activate MuSK phosphorylation than the defective syncan.

[0171] Such a property allows to compensate for the impaired / antagonized binding of LRP4 to MuSK and / or the impaired MuSK activation.

[0172] Each of these features has been previously defined in this document.

[0173] In this embodiment, lower binding affinity means that the binding affinity is at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% lower than the corresponding binding affinity in a subject expressing wild-type syncan. In this embodiment, impaired MuSK activation can be at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% lower than the corresponding MuSK activation in a subject expressing wild-type syncan.

[0174] Each of the first, third and / or fourth embodiments defined above can be combined. Each of the second, third and / or fourth embodiments defined above can be combined.

[0175] The present application assumes that a syncan deficiency can result in reduced or no activation of MuSK, and thus a reduced activation of the MuSK signaling pathway can occur. As a result, the NMJ can be impaired, which in turn can have an impact on the MuSK expression level. Therefore, it was unexpected and surprising that a therapeutic result can be obtained using a MuSK antibody-based molecule when the MuSK expression level is reduced.

[0176] The MuSK antibody-based molecule can reduce or eliminate effector function. As previously described herein, reduced or eliminated effector function can be obtained by introducing mutations into the human IgG constant Fc region. Preferably, at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17 amino acid substitutions are introduced into said Fc region. Preferably, at least 1, 2, 3, 4 amino acid substitutions are introduced into said Fc region. Said Fc region can comprise SEQ ID NO: 266 or 267 and said substitutions are introduced at amino acid positions selected from the group consisting of amino acid residues 234, 235, 236, 237, 238, 239, 243, 265, 267, 268, 292, 297, 300, 318, 320, 322, 327, 328, 329, 330, 331, 332 and 396 of said sequences, numbered according to the EU numbering system.

[0177] In one embodiment, said Fc region can comprise SEQ ID NO: 266 or 267 and said substitutions are introduced at amino acid positions selected from the group consisting of amino acid residues 234 or 235 of said sequences, numbered according to the EU numbering system. In one embodiment, said Fc region can comprise SEQ ID NO: 266 or 267 and said substitutions are introduced at amino acid positions selected from the group consisting of amino acid residues 234 and 235 of said sequences, numbered according to the EU numbering system.

[0178] In one embodiment, one or more (all numbered according to the EU numbering system) of the following mutations are introduced into the human IgG constant Fc region of the antibody-based molecules described herein: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; or P396L substitution.

[0179] In one embodiment, each of the combinations of the foregoing mutations described in the fourth embodiment of the application can be made in the human IgG constant Fc region of the antibody-based molecules described herein.

[0180] In one preferred embodiment, a L234A or L235A substitution is introduced into the human IgG constant Fc region of the antibody-based molecules described herein. In a more preferred embodiment, a L234A and L235A substitution is introduced into the human IgG constant Fc region of the antibody-based molecules described herein. This embodiment results in an antibody-based molecule having a heavy chain represented by SEQ ID NO: 268 or 270 or 282.

[0181] In an even more preferred embodiment, the anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0182] a) a heavy chain variable domain (VH) comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and

[0183] b) a light chain variable domain (VL) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 235.

[0184] In this context, the identity or similarity is at least 81 %, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%.

[0185] A preferred anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0186] a) a full length heavy chain comprising SEQ ID NO: 268, and

[0187] b) a full length light chain comprising SEQ ID NO: 269.

[0188] A preferred anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0189] a) a full length heavy chain comprising SEQ ID NO: 270, and

[0190] b) a full length light chain comprising SEQ ID NO: 271.

[0191] In another even more preferred embodiment, the anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0192] a) a heavy chain variable domain (VH) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 202, and

[0193] b) a light chain variable domain (VL) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 203.

[0194] In this context, the identity or similarity is at least 81 %, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91 %, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%.

[0195] A preferred anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0196] a) a full length heavy chain comprising SEQ ID NO: 282, and

[0197] b) a full length light chain comprising SEQ ID NO: 283.

[0198] In one embodiment, the antibody-based molecules of the present application are "humanized," particularly if they are to be used for therapeutic purposes. The term "humanized" refers to chimeric molecules, typically prepared using recombinant techniques, that have an antigen-binding site derived from an immunoglobulin from a non-human species and the remaining immunoglobulin structure and / or sequence based on a human immunoglobulin. The antigen-binding site can comprise the entire non-human antibody variable domain fused to a human constant domain, or only the complementarity determining regions (CDRs) of such a variable domain grafted onto an appropriate human framework region of a human variable domain. The framework residues of such humanized molecules can be wild type (e.g., fully human), or they can be modified to contain one or more amino acid substitutions not found in the human antibody from which the humanization was based. Humanization reduces or eliminates the likelihood that the constant region of the molecule will act as an immunogen in a human individual, but the likelihood of an immune response to the foreign variable region remains unchanged (LoBuglio, A.F. et al., "Mouse / Human Chimeric Monoclonal Antibody In Man: Kinetics And Immune Response," Proc. Natl. Acad. Sci. USA 86:4220-4224 (1989), which is hereby incorporated by reference in its entirety). Another approach focuses not only on providing a constant region of human origin, but also on modifying the variable region to reconfigure it as close as possible to the human form. The variable regions of both the heavy and light chains contain three complementarity determining regions (CDRs), which vary in response to the antigen in question and determine the binding capacity. The CDRs are flanked by four framework regions (FRs), which are relatively conserved within a given species and are assumed to provide a scaffold for the CDRs. When a non-human antibody is prepared against a particular antigen, the variable region can be "reconfigured" or "humanized" by grafting the CDRs derived from the non-human antibody onto the FRs present in a human antibody to be modified. Suitable methods for humanizing a non-human antibody described herein are known in the art, see, e.g., U.S. Patent No. 6,180,716, which is hereby incorporated by reference in its entirety.

[0199] ,

[0200] which is hereby incorporated by reference in its entirety. In some embodiments, the humanized MuSK antibodies of the present application retain all CDR sequences (e.g., a humanized antibody comprising all six CDRs from a llama or mouse antibody). In other embodiments, the humanized MuSK antibodies of the present application have one or more CDRs (one, two, three, four, five, six) altered relative to the original antibody. Methods of humanizing antibodies are well known in the art and are suitable for humanizing the antibodies disclosed herein (see, e.g., U.S. Patent No. 5,225,539 to Winter; U.S. Patent Nos. 5,530,101 and 5,585,089 to Queen and Selick; U.S. Patent No. 5,859,205 to Robert et al.; U.S. Patent No. 6,407,213 to Carter; and U.S. Patent No. 6,881,557 to Foote, which are hereby incorporated by reference in their entirety).

[0201] In some antibodies, only a portion of the CDRs is required, i.e., a subset of the CDR residues required for binding, referred to as "specificity determining residues" ("SDRs"), to retain the binding of the antibody. CDR residues that do not contact the antigen and that are not in SDRs can be identified based on previous studies of Kabat CDR regions located outside of Chothia hypervariable loops (see Kabat et al., SEQUENCES OF PROTEINS OF IMMUNOLOGICAL INTEREST, National Institutes of Health Publication No. 91-3242 (1992); Chothia, C. et al., "Canonical Structures For The Hypervariable Regions Of Immunoglobulins," J. Mol. Biol. 196:901-917 (1987), which are hereby incorporated by reference in their entireties) by molecular modeling and / or empirically or as described in Gonzales, N.R. et al., "SDR Grafting Of A Murine Antibody Using Multiple Human Germline Templates To Minimize Its Immunogenicity," Mol. Immunol. 41 :863-872 (2004), which is hereby incorporated by reference in its entirety. In such humanized antibodies, where one or more donor CDR residues are absent or where an entire donor CDR is omitted, the amino acid residue occupying the position can be the amino acid residue occupying the corresponding position in the acceptor antibody sequence (by Kabat numbering). The number of such replacements of donors for acceptors of amino acids in the included CDRs reflects a balance of competing considerations. Such replacements can be advantageous to reduce the number of non-human amino acids in the humanized antibody and thereby reduce potential immunogenicity. However, replacements can also cause changes in affinity, and significant decreases in affinity are preferably avoided. Replacements can also lead to changes in activity. Replacements that lead to significant decreases in activity are also preferably avoided. In this case, the antibody or antibody fragment should still exhibit a detectable activity of the antibody as previously defined herein or at least exhibit the activity of the antibody to some extent. The replacement positions and amino acids to be replaced within the CDRs can also be selected empirically.

[0202] Phage display technology can alternatively be used to increase (or decrease) the CDR affinity of an antibody-based molecule of the present application. This technique, referred to as affinity maturation, employs mutagenesis or "CDR walking" and reselection using the target antigen or antigenic fragment thereof to identify antibodies having CDRs that bind to the antigen with higher (or lower) affinity when compared to the original or parent antibody (see, e.g., Glaser et al., "Antibody Engineering By Codon-Based Mutagenesis In A Filamentous Phage Vector System," J. Immunology 149:3903-3913 (1992), which is hereby incorporated by reference in its entirety). Mutagenizing entire codons rather than single nucleotides results in semi-random libraries of amino acid mutations. The library can be composed of a pool of variant clones, each variant clone differing from another member of such a library by a single amino acid change in a single CDR, and which contains variants that can represent every possible amino acid replacement for each CDR residue. Mutants with increased (or decreased) binding affinity for the antigen can be selected by contacting immobilized mutants with labeled antigen. Any screening method known in the art can be used to identify variant antibody-based binding molecules with increased or decreased affinity for the antigen (e.g., ELISA) (see Wu, H. et al., "Stepwise In Vitro Affinity Maturation Of Vitaxin, An Alpha v Beta 3-Specific Humanized mAb," Proc. Natl. Acad. Sci. USA 95:6037-6042 (1998); Yelton et al., "Affinity Maturation Of The BR96 Anti-Carcinoma Antibody By Codon-Based Mutagenesis," J. Immunology 155:1994 (1995), which are hereby incorporated by reference in their entireties)."CDR walking" that randomizes the light chain (see Schier, R. et al., "Isolation Of Picomolar Affinity Anti-c-erbB-2 Single-Chain Fv By Molecular Evolution Of The Complementarity Determining Regions In The Center Of The Antibody Binding Site," J. Mol. Biol. 263:551-567 (1996), which is hereby incorporated by reference in its entirety).

[0203] Methods for affinity maturation of MuSK antibody molecules are described and disclosed herein, for example, in

[0204] ,

[0205] which is hereby incorporated by reference in its entirety.

[0206] In the context of the present application, an amino acid alteration (change or modification) can be an amino acid substitution, addition, deletion, or chemical modification.

[0207] In one embodiment, a MuSK antibody-based molecule as described herein comprises the amino acid sequence of any one, any two, any three, any four, any five, or any six CDRs as provided in Tables 1 and 2 herein.

[0208] In one embodiment, an antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0209] (i) a complementarity determining region 1 (CDR-H1) comprising the amino acid sequence of any one of SEQ ID NOs: 1-16, 135, 136, 147-149, or a modified amino acid sequence of any one of SEQ ID NOs: 1-16, 135, 136, 147-149 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NOs: 1-16, 135, 136, 147-149;

[0210] (ii) a Complementarity Determining Region 2 (CDR-H2) comprising an amino acid sequence of any one of SEQ ID NOs: 17-32, 137, 138, 150-155, or a modified amino acid sequence of any one of SEQ ID NOs: 17-32, 137, 138, 150-155 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NOs: 17-32, 137, 138, 150-155; and

[0211] (iii) a Complementarity Determining Region 3 (CDR-H3) comprising an amino acid sequence of any one of SEQ ID NOs: 33-48, 139, 140, 156-158, 240-251, or a modified amino acid sequence of any one of SEQ ID NOs: 33-48, 139, 140, 156-158, or 240-251 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NOs: 33-48, 139, 140, 156-158, or 240-251.

[0212] In one embodiment, an antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises:

[0213] (i) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 1 or a CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 1, a CDR-H2 of SEQ ID NO: 17 or a CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 17, and a CDR-H3 of SEQ ID NO: 33 or a CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 33;

[0214] (ii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 2 or a CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18 or a CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 34 or a CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 34;

[0215] (iii) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 3 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 3, CDR-H2 of SEQ ID NO: 19 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 19, and CDR-H3 of SEQ ID NO: 35 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 35;

[0216] (iv) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 4 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 4, CDR-H2 of SEQ ID NO: 20 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 20, and CDR-H3 of SEQ ID NO: 36 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 36;

[0217] (v) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 5 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 5, CDR-H2 of SEQ ID NO: 21 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 21, and CDR-H3 of SEQ ID NO: 37 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 37;

[0218] (vi) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 6 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 6, CDR-H2 of SEQ ID NO: 22 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 22, and CDR-H3 of SEQ ID NO: 38 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 38;

[0219] (vii) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 7 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 7, CDR-H2 of SEQ ID NO: 23 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 23, and CDR-H3 of SEQ ID NO: 39 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 39;

[0220] (viii) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 8 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 8, CDR-H2 of SEQ ID NO: 24 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 24, and CDR-H3 of SEQ ID NO: 40 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 40;

[0221] (ix) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 9 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 9, CDR-H2 of SEQ ID NO: 25 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 25, and CDR-H3 of SEQ ID NO: 41 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 41;

[0222] (x) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 10 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 10, CDR-H2 of SEQ ID NO: 26 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 26, and CDR-H3 of SEQ ID NO: 42 or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 42;

[0223] (xi) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 11 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 11, a CDR-H2 of SEQ ID NO: 27 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 27, and a CDR-H3 of SEQ ID NO: 43 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 43;

[0224] (xii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 12 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 12, a CDR-H2 of SEQ ID NO: 28 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 28, and a CDR-H3 of SEQ ID NO: 44 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 44;

[0225] (xiii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 13 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 13, a CDR-H2 of SEQ ID NO: 29 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 29, and a CDR-H3 of SEQ ID NO: 45 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 45;

[0226] (xiv) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 14 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 14, a CDR-H2 of SEQ ID NO: 30 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 30, and a CDR-H3 of SEQ ID NO: 46 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 46;

[0227] (xvii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 135 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 139; or

[0228] (xvi) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 16 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 16, a CDR-H2 of SEQ ID NO: 32 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 32, and a CDR-H3 of SEQ ID NO: 48 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 48;

[0229] (xvii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 135 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 139; or

[0230] (xviii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 136 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 136, a CDR-H2 of SEQ ID NO: 138 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 138, and a CDR-H3 of SEQ ID NO: 140 or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 140. The sequences of the heavy chain CDRs are provided in Table 1.

[0231] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises:

[0232] (ii.a) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 240 (X2ml) or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 240;

[0233] (ii.b) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 241 (X2m2) or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 241;

[0234] (ii.c) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 242 (X2m3) or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 242;

[0235] (ii.d) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 or CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 243 (X2m4) or CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 243;

[0236] (ii.e) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 of SEQ ID NO: 2 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, CDR-H2 of SEQ ID NO: 18 or CDR-H2 of SEQ ID NO: 18 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, and CDR-H3 of SEQ ID NO: 244 (X2m5) or CDR-H3 of SEQ ID NO: 244 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto;

[0237] (ii.f) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 of SEQ ID NO: 2 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, CDR-H2 of SEQ ID NO: 18 or CDR-H2 of SEQ ID NO: 18 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, and CDR-H3 of SEQ ID NO: 245 (X2m6) or CDR-H3 of SEQ ID NO: 245 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto;

[0238] (ii.g) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 of SEQ ID NO: 2 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, CDR-H2 of SEQ ID NO: 18 or CDR-H2 of SEQ ID NO: 18 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, and CDR-H3 of SEQ ID NO: 246 (X2m7) or CDR-H3 of SEQ ID NO: 246 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto; or

[0239] (ii.h) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 of SEQ ID NO: 2 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, CDR-H2 of SEQ ID NO: 18 or CDR-H2 of SEQ ID NO: 18 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto, and CDR-H3 of SEQ ID NO: 247 (X2m8) or CDR-H3 of SEQ ID NO: 247 having 1, 2, 3, 4 or 5 amino acid alterations relative thereto.

[0240] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises:

[0241] (xvii.a) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 135 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 248 (X17ml) or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 248;

[0242] (xvii.b) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 135 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 249 (X17m2) or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 249;

[0243] (xvii.c) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 135 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 250 (X17m3) or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 250; or

[0244] (xvii.d) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 135 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 251 (X17m6) or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 251.

[0245] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0246] (xix) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 147 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 156;

[0247] (xx) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 148 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 148, CDR-H2 of SEQ ID NO: 151 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 151, and CDR-H3 of SEQ ID NO: 157 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 157; or

[0248] (xxi) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 149 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 149, CDR-H2 of SEQ ID NO: 152 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 152, and CDR-H3 of SEQ ID NO: 158 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 158.

[0249] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0250] (xxii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 147 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 153 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 153, and a CDR-H3 of SEQ ID NO: 156 (3B2glml / 3B2g2ml) or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156;

[0251] (xxiii) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 147 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 154 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 154, and a CDR-H3 of SEQ ID NO: 156 (3B2glm2 / 3B2g2m2) or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156; or

[0252] (xxiv) a heavy chain variable domain comprising: a CDR-H1 of SEQ ID NO: 147 or a CDR-H1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 155 or a CDR-H2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 155, and a CDR-H3 of SEQ ID NO: 156 (3B2glm4 / 3B2g2m4) or a CDR-H3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156. The sequences of the heavy chain CDRs are provided in Table 1.

[0253] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) contains:

[0254] (i) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 1, a CDR-H2 of SEQ ID NO: 17, and a CDR-H3 of SEQ ID NO: 33;

[0255] (ii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 34;

[0256] (iii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 3, a CDR-H2 of SEQ ID NO: 19, and a CDR-H3 of SEQ ID NO: 35;

[0257] (iv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 4, a CDR-H2 of SEQ ID NO: 20, and a CDR-H3 of SEQ ID NO: 36;

[0258] (v) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 5, a CDR-H2 of SEQ ID NO: 21, and a CDR-H3 of SEQ ID NO: 37;

[0259] (vi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 6, a CDR-H2 of SEQ ID NO: 22, and a CDR-H3 of SEQ ID NO: 38;

[0260] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 7, a CDR-H2 of SEQ ID NO: 23, and a CDR-H3 of SEQ ID NO: 39;

[0261] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 8, a CDR-H2 of SEQ ID NO: 24, and a CDR-H3 of SEQ ID NO: 40;

[0262] (ix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 25, and a CDR-H3 of SEQ ID NO: 41;

[0263] (x) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 10, a CDR-H2 of SEQ ID NO: 26, and a CDR-H3 of SEQ ID NO: 42;

[0264] (xi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 11, a CDR-H2 of SEQ ID NO: 27, and a CDR-H3 of SEQ ID NO: 43;

[0265] (xii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 12, a CDR-H2 of SEQ ID NO: 28, and a CDR-H3 of SEQ ID NO: 44;

[0266] (xiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 13, a CDR-H2 of SEQ ID NO: 29, and a CDR-H3 of SEQ ID NO: 45;

[0267] (xiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 14, a CDR-H2 of SEQ ID NO: 30, and a CDR-H3 of SEQ ID NO: 46;

[0268] (xv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 15, a CDR-H2 of SEQ ID NO: 31, and a CDR-H3 of SEQ ID NO: 47;

[0269] (xvi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 16, a CDR-H2 of SEQ ID NO: 32, and a CDR-H3 of SEQ ID NO: 48;

[0270] (xvii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139; or

[0271] (xviii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 136, a CDR-H2 of SEQ ID NO: 138, and a CDR-H3 of SEQ ID NO: 140. The sequences of the heavy chain CDR sequences are provided in Table 1 below.

[0272] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) contains:

[0273] (ii.a) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 240 (X2m1);

[0274] (ii.b) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 241 (X2m2);

[0275] (ii.c) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 242 (X2m3);

[0276] (ii.d) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 243 (X2m4);

[0277] (ii.e) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 244 (X2m5);

[0278] (ii.f) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 245 (X2m6);

[0279] (ii.g) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 246 (X2m7); or

[0280] (ii.h) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 247 (X2m8).

[0281] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises:

[0282] (xvii.a) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 248 (X17m1);

[0283] (xvii.b) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 249 (X17m2);

[0284] (xvii.c) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 250 (X17m3); or

[0285] (xvii.d) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 251 (X17m6).

[0286] In one embodiment, an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) comprises:

[0287] (xix) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156;

[0288] (xx) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 148, CDR-H2 of SEQ ID NO: 151, and CDR-H3 of SEQ ID NO: 157; or

[0289] (xxi) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 149, CDR-H2 of SEQ ID NO: 152, and CDR-H3 of SEQ ID NO: 158.

[0290] In one embodiment, an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) comprises:

[0291] (xxii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 153, and CDR-H3 of SEQ ID NO: 156 (3B2g1m1 / 3B2g2m1);

[0292] (xxiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 154, and a CDR-H3 of SEQ ID NO: 156 (3B2glm2 / 3B2g2m2); or

[0293] (xxiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 155, and a CDR-H3 of SEQ ID NO: 156 (3B2glm4 / 3B2g2m4). The sequences of the heavy chain CDR sequences are provided in Table 1 below.

[0294] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 153, or a CDR-H2 amino acid sequence having at least 0, 1, 2, 3, 4, or 5 alterations relative to SEQ ID NO: 153, and a CDR-H3 of SEQ ID NO: 156 (3B2g2ml). In one embodiment, the CDR-H2 amino acid sequence has at least 0, 1, 2, 3, 4, or 5 alterations relative to SEQ ID NO: 153. In accordance with this embodiment, the CDR-H2 amino acid sequence has at least 0, 1, 2, 3, 4, or 5 alterations relative to SEQ ID NO: 153, wherein the alterations are at residues 1, 2, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or any combination thereof.

[0295] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0296] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0297] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0298] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156.

[0299] In one embodiment, the antibody's CDR-H2 contains proline (P) at position 3, tryptophan (W)30 at position 4, and serine (S) or asparagine (N) at position 5. In a preferred embodiment, the antibody's CDR-H2 contains proline (P) at position 3, tryptophan (W) at position 4, and asparagine (N) at position 5.

[0300] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) includes a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0301] - Contains the CDR-H1 amino acid sequence of SEQ ID NO: 147 or composed of SEQ ID NO: 147.

[0302] - Contains the CDR-H2 amino acid sequence of SEQ ID NO: 150 or composed of SEQ ID NO: 150, and

[0303] - Contains the CDR-H3 amino acid sequence consisting of SEQ ID NO: 156 or SEQ ID NO: 156 (3B2).

[0304] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) includes a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0305] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[0306] - Contains a CDR-H2 amino acid sequence modified by 1, 2, 3, 4, or 5 amino acids relative to SEQ ID NO: 153, and

[0307] - Contains a CDR-H3 amino acid sequence (3B2g2m1) that has SEQ ID NO: 156 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156.

[0308] In one embodiment, the antibody's CDR-H2 contains proline (P) at position 3, tryptophan (W) at position 4, and serine (S) or asparagine (N) at position 5.

[0309] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain comprises:

[0310] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0311] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0312] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2m1).

[0313] Table 1 below provides the sequences of the heavy chain CDR sequences.

[0314]

[0315]

[0316] In some embodiments, the MuSK antibody-based molecules disclosed herein further comprise a light chain variable domain. The light chain variable domain comprises:

[0317] (i) a complementarity determining region 1 (CDR-L1) having an amino acid sequence of any one of SEQ ID NOs: 49-64, 141, 142, 159-169, or a modified amino acid sequence of any one of SEQ ID NOs: 49-64, 141, 142, or 159-169 that has at least 80% sequence identity to any one of SEQ ID NOs: 49-64, 141, 142, or 159-169;

[0318] (ii) a complementarity determining region 2 (CDR-L2) having an amino acid sequence of any one of SEQ ID NOs: 65-80, 143, 144, 170-179, or a modified amino acid sequence of any one of SEQ ID NOs: 65-80, 143, 144, or 170-179 that has at least 80% sequence identity to any one of SEQ ID NOs: 65-80, 143, 144, or 170-179; and

[0319] (iii) Complementarity Determining Region 3 (CDR-L3) having an amino acid sequence of any one of SEQ ID NOs: 81-96, 145, 146, 180-195, or a modified amino acid sequence of any one of SEQ ID NOs: 81-96, 145, 146, or 180-195 that has at least 80% sequence identity to any one of SEQ ID NOs: 81-96, 145, 146, or 180-195.

[0320] In some embodiments, the MuSK antibody-based molecules disclosed herein further comprise a light chain variable domain. The light chain variable domain comprises:

[0321] (iv) Complementarity Determining Region 1 (CDR-L1) having an amino acid sequence of any one of SEQ ID NOs: 49-64, 141, 142, 159-169, or a modified amino acid sequence of any one of SEQ ID NOs: 49-64, 141, 142, or 159-169 that has 1, 2, 3, 4, or 5 amino acid changes relative to any one of SEQ ID NOs: 49-64, 141, 142, or 159-169;

[0322] (v) Complementarity Determining Region 2 (CDR-L2) having an amino acid sequence of any one of SEQ ID NOs: 65-80, 143, 144, 170-179, or a modified amino acid sequence of any one of SEQ ID NOs: 65-80, 143, 144, or 170-179 that has 1, 2, 3, 4, or 5 amino acid changes relative to any one of SEQ ID NOs: 65-80, 143, 144, or 170-179; and

[0323] (vi) Complementarity Determining Region 3 (CDR-L3) having an amino acid sequence of any one of SEQ ID NOs: 81-96, 145, 146, 180-195, or a modified amino acid sequence of any one of SEQ ID NOs: 81-96, 145, 146, or 180-195 that has 1, 2, 3, 4, or 5 amino acid changes relative to any one of SEQ ID NOs: 81-96, 145, 146, or 180-195.

[0324] In one embodiment, the light chain variable domain of the MuSK antibody-based molecules disclosed herein comprises:

[0325] (i) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 1 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 1, CDR-H2 of SEQ ID NO: 17 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 17, and CDR-H3 of SEQ ID NO: 33 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 33;

[0326] (ii) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 2 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 34 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 34;

[0327] (iii) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 3 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 3, CDR-H2 of SEQ ID NO: 19 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 19, and CDR-H3 of SEQ ID NO: 35 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 35;

[0328] (iv) a heavy chain variable domain comprising: CDR-H1 of SEQ ID NO: 4 or CDR-H1 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 4, CDR-H2 of SEQ ID NO: 20 or CDR-H2 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 20, and CDR-H3 of SEQ ID NO: 36 or CDR-H3 having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 36;

[0329] (vii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 55 or a CDR-L1 of SEQ ID NO: 55 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71 or a CDR-L2 of SEQ ID NO: 71 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87 or a CDR-L3 of SEQ ID NO: 87 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 87;

[0330] (vii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 55 or a CDR-L1 of SEQ ID NO: 55 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71 or a CDR-L2 of SEQ ID NO: 71 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87 or a CDR-L3 of SEQ ID NO: 87 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 87;

[0331] (vii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 55 or a CDR-L1 of SEQ ID NO: 55 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71 or a CDR-L2 of SEQ ID NO: 71 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87 or a CDR-L3 of SEQ ID NO: 87 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 87;

[0332] (vii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 55 or a CDR-L1 of SEQ ID NO: 55 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71 or a CDR-L2 of SEQ ID NO: 71 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87 or a CDR-L3 of SEQ ID NO: 87 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 87;

[0333] (ix) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 57 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 57, a CDR-L2 of SEQ ID NO: 73 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 73, and a CDR-L3 of SEQ ID NO: 89 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 89;

[0334] (x) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 58 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 58, a CDR-L2 of SEQ ID NO: 74 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 74, and a CDR-L3 of SEQ ID NO: 90 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 90;

[0335] (xi) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 59 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 59, a CDR-L2 of SEQ ID NO: 75 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 75, and a CDR-L3 of SEQ ID NO: 91 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 91;

[0336] (xii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 60 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 60, a CDR-L2 of SEQ ID NO: 76 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 76, and a CDR-L3 of SEQ ID NO: 92 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 92;

[0337] (xiii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 61 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 61, a CDR-L2 of SEQ ID NO: 77 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 77, and a CDR-L3 of SEQ ID NO: 93 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 93;

[0338] (xiv) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 62 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 62, a CDR-L2 of SEQ ID NO: 78 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 78, and a CDR-L3 of SEQ ID NO: 94 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 94;

[0339] (xv) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 63 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 63, a CDR-L2 of SEQ ID NO: 79 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 79, and a CDR-L3 of SEQ ID NO: 95 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 95;

[0340] (xvi) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 64 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 64, a CDR-L2 of SEQ ID NO: 80 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 80, and a CDR-L3 of SEQ ID NO: 96 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 96;

[0341] (xvii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 141 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 141, a CDR-L2 of SEQ ID NO: 143 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 143, and a CDR-L3 of SEQ ID NO: 145 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 145; or

[0342] (xviii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 142 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 142, a CDR-L2 of SEQ ID NO: 144 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 144, and a CDR-L3 of SEQ ID NO: 146 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 146. The sequences of the light chain CDRs are provided in Table 2 below.

[0343] In one embodiment, the light chain variable domain of the MuSK antibody-based molecules disclosed herein comprises:

[0344] (xix) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 170 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 170, and a CDR-L3 of SEQ ID NO: 180 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations with respect to SEQ ID NO: 180;

[0345] (xx) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 181 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 181;

[0346] (xxi) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 160 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 160, a CDR-L2 of SEQ ID NO: 172 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 182 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 182;

[0347] (xxii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 183;

[0348] (xxiii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 184 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 184;

[0349] (xxiv) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 185 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 185;

[0350] (xxv) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 159 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 186 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 186;

[0351] (xxvi) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 161 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 187;

[0352] (xxvii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 162 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 162, a CDR-L2 of SEQ ID NO: 174 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 188;

[0353] (xxviii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 163 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 188;

[0354] (xxix) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 164 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 189;

[0355] (xxx) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 165 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 165, a CDR-L2 of SEQ ID NO: 175 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 175, and a CDR-L3 of SEQ ID NO: 190 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 190;

[0356] (xxxi) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 166 or a CDR-L1 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 166, a CDR-L2 of SEQ ID NO: 176 or a CDR-L2 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 176, and a CDR-L3 of SEQ ID NO: 191 or a CDR-L3 having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 191;

[0357] (xxxiii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 169 or a CDR-L1 of SEQ ID NO: 169 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 169, a CDR-L2 of SEQ ID NO: 179 or a CDR-L2 of SEQ ID NO: 179 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 179, and a CDR-L3 of SEQ ID NO: 194 or a CDR-L3 of SEQ ID NO: 194 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 194.

[0358] (xxxiii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 169 or a CDR-L1 of SEQ ID NO: 169 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 169, a CDR-L2 of SEQ ID NO: 179 or a CDR-L2 of SEQ ID NO: 179 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 179, and a CDR-L3 of SEQ ID NO: 194 or a CDR-L3 of SEQ ID NO: 194 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 194.

[0359] (xxxiii) a light chain variable domain comprising: a CDR-L1 of SEQ ID NO: 169 or a CDR-L1 of SEQ ID NO: 169 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 169, a CDR-L2 of SEQ ID NO: 179 or a CDR-L2 of SEQ ID NO: 179 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 179, and a CDR-L3 of SEQ ID NO: 194 or a CDR-L3 of SEQ ID NO: 194 having 1, 2, 3, 4, or 5 amino acid alterations with respect to SEQ ID NO: 194.

[0360] In one embodiment, the light chain variable domain of a MuSK antibody-based molecule disclosed herein comprises:

[0361] (i) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 49, a CDR-L2 of SEQ ID NO: 65, and a CDR-L3 of SEQ ID NO: 81;

[0362] (ii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82;

[0363] (iii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 51, a CDR-L2 of SEQ ID NO: 67, and a CDR-L3 of SEQ ID NO: 83;

[0364] (iv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 52, a CDR-L2 of SEQ ID NO: 68, and a CDR-L3 of SEQ ID NO: 84;

[0365] (v) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 53, a CDR-L2 of SEQ ID NO: 69, and a CDR-L3 of SEQ ID NO: 85;

[0366] (vi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 54, a CDR-L2 of SEQ ID NO: 70, and a CDR-L3 of SEQ ID NO: 86;

[0367] (vii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87;

[0368] (viii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 56, a CDR-L2 of SEQ ID NO: 72, and a CDR-L3 of SEQ ID NO: 88;

[0369] (ix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 57, a CDR-L2 of SEQ ID NO: 73, and a CDR-L3 of SEQ ID NO: 89;

[0370] (x) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 58, a CDR-L2 of SEQ ID NO: 74, and a CDR-L3 of SEQ ID NO: 90;

[0371] (xi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 59, a CDR-L2 of SEQ ID NO: 75, and a CDR-L3 of SEQ ID NO: 91;

[0372] (xii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 60, a CDR-L2 of SEQ ID NO: 76, and a CDR-L3 of SEQ ID NO: 92;

[0373] (xiii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 61, a CDR-L2 of SEQ ID NO: 77, and a CDR-L3 of SEQ ID NO: 93;

[0374] (xiv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 62, a CDR-L2 of SEQ ID NO: 78, and a CDR-L3 of SEQ ID NO: 94;

[0375] (xv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 63, a CDR-L2 of SEQ ID NO: 79, and a CDR-L3 of SEQ ID NO: 95;

[0376] (xvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 64, a CDR-L2 of SEQ ID NO: 80, and a CDR-L3 of SEQ ID NO: 96;

[0377] (xvii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 141, a CDR-L2 of SEQ ID NO: 143, and a CDR-L3 of SEQ ID NO: 145; or

[0378] (xviii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 142, a CDR-L2 of SEQ ID NO: 144, and a CDR-L3 of SEQ ID NO: 146. The sequences of the light chain CDRs are provided in Table 2 below.

[0379] In one embodiment, the light chain variable domain of the MuSK antibody-based molecule disclosed herein comprises:

[0380] (xix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 170, and a CDR-L3 of SEQ ID NO: 180;

[0381] (xx) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 181;

[0382] (xxxi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 160, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 182;

[0383] (xxxii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183;

[0384] (xxxiii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 184;

[0385] (xxxiv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 185;

[0386] (xxxv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 186;

[0387] (xxxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187;

[0388] (xxxvii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 162, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188;

[0389] (xxxviii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188;

[0390] (xxxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0391] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0392] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0393] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0394] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189; or

[0395] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189.

[0396] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a light chain variable domain, wherein the light chain variable domain contains:

[0397] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159,

[0398] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0399] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 183 (3B2).

[0400] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a light chain variable domain, wherein the light chain variable domain contains:

[0401] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0402] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0403] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 183 (3B2).

[0404] In one embodiment, the light chain variable domain of the MuSK antibody-based molecule disclosed herein comprises a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 195 or a CDR-L3 having 1, 2, 3, 4, or 5 amino acid alterations relative to the amino acid sequence of SEQ ID NO: 195, wherein the alterations are at residues 1, 2, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or any combination thereof.

[0405] In one embodiment, the antibody-based molecule that binds to human muscle- specific tyrosine-protein kinase (MuSK) comprises a light chain variable domain, wherein the light chain variable domain contains:

[0406] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0407] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0408] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0409] In one embodiment, the CDR-L1, CDR-L2, CDR-L3 amino acid sequences have at least 0, 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159, 172, or 195, respectively.

[0410] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain, wherein the heavy chain variable domain contains:

[0411] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 158,

[0412] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 171, and

[0413] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 194.

[0414] The sequences of the heavy chain CDR sequences are provided in Table 1 below.

[0415]

[0416]

[0417] Amino acid modifications of the heavy chain CDR sequences and / or light chain CDR sequences of the MuSK antibody-based molecules disclosed herein that are suitable include, for example, conservative substitutions or functionally equivalent amino acid residue substitutions that result in a variant CDR sequence having binding characteristics that are similar to or enhanced from the binding characteristics of the CDR sequences disclosed herein above. The present application encompasses the CDRs of Table 1 and Table 2 with 1, 2, 3, 4, 5, or more amino acid alterations that maintain or enhance MuSK binding of the antibody, depending on the length of the CDR. Amino acid modifications of the heavy chain CDR sequences of Table 1 and / or the light chain CDR sequences of Table 1 and Table 2 that are suitable include, for example, conservative substitutions or functionally equivalent amino acid residue substitutions that result in a variant CDR sequence having binding characteristics that are similar to or enhanced from the binding characteristics of the CDR sequences of Table 1 and Table 2. Conservative substitutions are those that occur within a family of amino acids that are related in their side chain. Genetically encoded amino acids can be divided into four families: (1) acidic (aspartic acid, glutamic acid); (2) basic (lysine, arginine, histidine); (3) non-polar (alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, tryptophan); and (4) uncharged polar (glycine, asparagine, glutamine, cysteine, serine, threonine, tyrosine). Phenylalanine, tryptophan, and tyrosine are sometimes collectively referred to as aromatic amino acids. Alternatively, the amino acid repertoire can be divided into (1) acidic (aspartic acid, glutamic acid); (2) basic (lysine, arginine, histidine), (3) aliphatic (glycine, alanine, valine, leucine, isoleucine, serine, threonine), with serine and threonine optionally separately divided into aliphatic-hydroxyl; (4) aromatic (phenylalanine, tyrosine, tryptophan); (5) amide (asparagine, glutamine); and (6) sulfur-containing (cysteine and methionine) (Stryer (ed.), Biochemistry, 2nd ed, WH Freeman and Co., 1981, which is hereby incorporated by reference in its entirety). Non-conservative substitutions can also be made to the heavy chain CDR sequences of Table 1 and the light chain CDR sequences of Table 2. Non-conservative substitutions involve replacing one or more amino acid residues of a CDR with one or more amino acid residues from a different class to improve or enhance the binding properties of the CDR. The amino acid sequences of the heavy chain CDRs of Table 1 and / or the light chain CDRs of Table 2 can also comprise one or more internal neutral amino acid insertions or deletions that maintain or enhance MuSK binding.

[0418] In one embodiment, the MuSK antibody-based molecule contains:

[0419] (i) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 1, CDR-H2 of SEQ ID NO: 17, and CDR-H3 of SEQ ID NO: 33, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 49, CDR-L2 of SEQ ID NO: 65, and CDR-L3 of SEQ ID NO: 81;

[0420] (ii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 34, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 50, CDR-L2 of SEQ ID NO: 66, and CDR-L3 of SEQ ID NO: 82;

[0421] (iii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 3, CDR-H2 of SEQ ID NO: 19, and CDR-H3 of SEQ ID NO: 35, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 51, CDR-L2 of SEQ ID NO: 67, and CDR-L3 of SEQ ID NO: 83;

[0422] (iv) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 4, CDR-H2 of SEQ ID NO: 20, and CDR-H3 of SEQ ID NO: 36, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 52, CDR-L2 of SEQ ID NO: 68, and CDR-L3 of SEQ ID NO: 84;

[0423] (v) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 5, CDR-H2 of SEQ ID NO: 21, and CDR-H3 of SEQ ID NO: 37, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 53, CDR-L2 of SEQ ID NO: 69, and CDR-L3 of SEQ ID NO: 85;

[0424] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 7, a CDR-H2 of SEQ ID NO: 23, and a CDR-H3 of SEQ ID NO: 39, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87;

[0425] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 7, a CDR-H2 of SEQ ID NO: 23, and a CDR-H3 of SEQ ID NO: 39, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87;

[0426] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 8, a CDR-H2 of SEQ ID NO: 24, and a CDR-H3 of SEQ ID NO: 40, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 56, a CDR-L2 of SEQ ID NO: 72, and a CDR-L3 of SEQ ID NO: 88;

[0427] (ix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 25, and a CDR-H3 of SEQ ID NO: 41, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 57, a CDR-L2 of SEQ ID NO: 73, and a CDR-L3 of SEQ ID NO: 89;

[0428] (ix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 25, and a CDR-H3 of SEQ ID NO: 41, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 57, a CDR-L2 of SEQ ID NO: 73, and a CDR-L3 of SEQ ID NO: 89;

[0429] (xi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 11, CDR-H2 of SEQ ID NO: 27, and CDR-H3 of SEQ ID NO: 43, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 59, CDR-L2 of SEQ ID NO: 75, and CDR-L3 of SEQ ID NO: 91;

[0430] (xii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 12, CDR-H2 of SEQ ID NO: 28, and CDR-H3 of SEQ ID NO: 44, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 60, CDR-L2 of SEQ ID NO: 76, and CDR-L3 of SEQ ID NO: 92;

[0431] (xiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 13, CDR-H2 of SEQ ID NO: 29, and CDR-H3 of SEQ ID NO: 45, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 61, CDR-L2 of SEQ ID NO: 77, and CDR-L3 of SEQ ID NO: 93;

[0432] (xiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 14, CDR-H2 of SEQ ID NO: 30, and CDR-H3 of SEQ ID NO: 46, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 62, CDR-L2 of SEQ ID NO: 78, and CDR-L3 of SEQ ID NO: 94;

[0433] (xv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 15, CDR-H2 of SEQ ID NO: 31, and CDR-H3 of SEQ ID NO: 47, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 63, CDR-L2 of SEQ ID NO: 79, and CDR-L3 of SEQ ID NO: 95;

[0434] (xvi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 16, a CDR-H2 of SEQ ID NO: 32, and a CDR-H3 of SEQ ID NO: 48, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 64, a CDR-L2 of SEQ ID NO: 80, and a CDR-L3 of SEQ ID NO: 96;

[0435] (xvii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 141, a CDR-L2 of SEQ ID NO: 143, and a CDR-L3 of SEQ ID NO: 145; or

[0436] (xviii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 136, a CDR-H2 of SEQ ID NO: 138, and a CDR-H3 of SEQ ID NO: 140, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 142, a CDR-L2 of SEQ ID NO: 144, and a CDR-L3 of SEQ ID NO: 146.

[0437] In one embodiment, the MuSK antibody-based molecule contains:

[0438] (ii.a) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 240, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2ml);

[0439] (ii.b) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 241, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m2);

[0440] (ii.c) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 242, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m3);

[0441] (ii.d) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 243, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m4);

[0442] (ii.e) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 244, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m5);

[0443] (ii.f) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 245, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m6);

[0444] (ii.g) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 246, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82 (X2m7); or

[0445] (ii.f) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 247, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 50, CDR-L2 of SEQ ID NO: 66, and CDR-L3 of SEQ ID NO: 82 (X2m8).

[0446] In one embodiment, the MuSK antibody-based molecule contains:

[0447] (xvii.a) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 248, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 141, CDR-L2 of SEQ ID NO: 143, and CDR-L3 of SEQ ID NO: 145 (X17ml);

[0448] (xvii.b) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 249, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 141, CDR-L2 of SEQ ID NO: 143, and CDR-L3 of SEQ ID NO: 145 (X17m2);

[0449] (xvii.c) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 250, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 141, CDR-L2 of SEQ ID NO: 143, and CDR-L3 of SEQ ID NO: 145 (X17m3); or

[0450] (xvii.d) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 251, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 141, CDR-L2 of SEQ ID NO: 143, and CDR-L3 of SEQ ID NO: 145 (X17m6).

[0451] In one embodiment, the MuSK antibody-based molecule contains:

[0452] (i) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 170, and CDR-L3 of SEQ ID NO: 180 (14D10);

[0453] (ii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 171, and CDR-L3 of SEQ ID NO: 181 (7G4);

[0454] (iii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 160, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 182 (3C4);

[0455] (iv) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 183 (3B2);

[0456] (v) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 171, and CDR-L3 of SEQ ID NO: 184 (3G3);

[0457] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 150, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 186 (31B7);

[0458] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 150, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 186 (31B7);

[0459] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 148, a CDR-H2 of SEQ ID NO: 151, and a CDR-H3 of SEQ ID NO: 157, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187 (17H10);

[0460] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 148, a CDR-H2 of SEQ ID NO: 151, and a CDR-H3 of SEQ ID NO: 157, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187 (17H10);

[0461] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 148, a CDR-H2 of SEQ ID NO: 151, and a CDR-H3 of SEQ ID NO: 157, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187 (17H10);

[0462] (xi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 148, a CDR-H2 of SEQ ID NO: 151, and a CDR-H3 of SEQ ID NO: 157, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189 (30A11);

[0463] (xii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 165, a CDR-L2 of SEQ ID NO: 175, and a CDR-L3 of SEQ ID NO: 190 (16F11);

[0464] (xiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 166, a CDR-L2 of SEQ ID NO: 176, and a CDR-L3 of SEQ ID NO: 191 (4C11);

[0465] (xiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 167, a CDR-L2 of SEQ ID NO: 177, and a CDR-L3 of SEQ ID NO: 192 (7A12);

[0466] (xv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 168, a CDR-L2 of SEQ ID NO: 178, and a CDR-L3 of SEQ ID NO: 193 (7G12);

[0467] (xvi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 169, a CDR-L2 of SEQ ID NO: 179, and a CDR-L3 of SEQ ID NO: 194 (7B8);

[0468] (xvii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 153, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183 (3B2glml);

[0469] (xviii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 154, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183 (3B2glm2);

[0470] (xix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 155, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183 (3B2glm4);

[0471] (xx) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 153, and a CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 195 (3B2g2ml);

[0472] (xxii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 155, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 195 (3B2g2m4).

[0473] (xxii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 155, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 195 (3B2g2m4).

[0474] In a preferred embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein:

[0475] The VH comprises:

[0476] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0477] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0478] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0479] The VL comprises:

[0480] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0481] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0482] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

[0483] In one embodiment, the CDR-H2 of the antibody comprises proline (P) in position 3, tryptophan (W) in position 4 and serine (S) or asparagine (N) in position 5. In a preferred embodiment, the CDR-H2 of the antibody comprises proline (P) in position 3, tryptophan (W) in position 4 and asparagine (N) in position 5.

[0484] In a more preferred embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain and a light chain variable domain,

[0485] wherein the heavy chain variable domain contains:

[0486] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147 or of SEQ ID NO: 147,

[0487] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 150 or of SEQ ID NO: 150, and

[0488] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 or of SEQ ID NO: 156 (3B2) and

[0489] wherein the light chain variable domain contains:

[0490] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159 or of SEQ ID NO: 159,

[0491] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172 or of SEQ ID NO: 172, and

[0492] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 183 or of SEQ ID NO: 183 (3B2).

[0493] In a preferred embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain and a light chain variable domain,

[0494] wherein the heavy chain variable domain contains:

[0495] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 147,

[0496] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0497] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1 ) and

[0498] wherein the light chain variable domain contains:

[0499] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159,

[0500] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0501] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1 ).

[0502] In one embodiment, the CDR-H2 of the antibody comprises a proline (P) at position 3, a tryptophan (W) at position 4 and a serine (S) or asparagine (N) at position 5.

[0503] In a more preferred embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain and a light chain variable domain,

[0504] wherein the heavy chain variable domain contains:

[0505] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0506] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0507] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2ml) and

[0508] wherein the light chain variable domain contains:

[0509] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0510] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0511] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 (3B2g2ml).

[0512] The MuSK antibody-based molecules described herein can comprise a variable light (VL) chain, a variable heavy (VH) chain, or a combination of VL and VH chains. In some embodiments, the VH chain of a MuSK antibody-based molecule comprises any of the VH amino acid sequences provided in Table 3 below, or an amino acid sequence that is at least 60%, at least 61%, at least 62%, at least 63%, at least 64%, at least 65%, at least 66%, at least 67%, at least 68%, at least 69%, at least 70%, at least 71%, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, 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% identical or similar to any of the VH amino acid sequences listed in Table 3. In some embodiments, the VL chain of a MuSK antibody-based molecule comprises any of the VL amino acid sequences provided in Table 3 below, or an amino acid sequence that is at least 60% identical or similar to any of the VL amino acid sequences listed in Table 3. In one embodiment, the identity or similarity is at least 61%, at least 62%, at least 63%, at least 64%, at least 65%, at least 66%, at least 67%, at least 68%, at least 69%, at least 70%, at least 71%, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, 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%.

[0513]

[0514]

[0515]

[0516]

[0517]

[0518]

[0519]

[0520]

[0521] In one embodiment, the MuSK antibody-based molecules disclosed herein contain:

[0522] (i) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 97 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 98;

[0523] (ii) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to any one of SEQ ID NOs: 99 and 252-259 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 100;

[0524] (iii) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 101 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 102;

[0525] (iv) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 103 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 104;

[0526] (v) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 105 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 106;

[0527] (vi) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 107 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 108;

[0528] (vii) a heavy chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 109 and a light chain variable domain comprising an amino acid sequence at least 80% identical to SEQ ID NO: 110;

[0529] (viii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 111 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 112;

[0530] (ix) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 113 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 114;

[0531] (x) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 115 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 116;

[0532] (xi) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 117 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 118;

[0533] (xii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 119 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 120;

[0534] (xiii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 121 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 122;

[0535] (xiv) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 123 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 124;

[0536] (xv) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 125 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 126;

[0537] (xvi) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 127 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 128;

[0538] (xvii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to any one of SEQ ID NOs: 131 and 260-263 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 132; or

[0539] (xviii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 133 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 134.

[0540] In some embodiments, the MuSK antibody-based molecules disclosed herein contain:

[0541] (i) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 196 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 197;

[0542] (ii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 198 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 199;

[0543] (iii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 200 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 201;

[0544] (iv) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 202 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 203;

[0545] (v) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 204 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 205;

[0546] (vii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 208 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 209;

[0547] (vii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 208 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 209;

[0548] (viii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 210 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 211 ;

[0549] (ix) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 212 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 213;

[0550] (x) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 214 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 215;

[0551] (xi) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 216 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 217;

[0552] (xii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 218 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 219;

[0553] (xiii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 220 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 221 ;

[0554] (xiv) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 222 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 223;

[0555] (xv) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 224 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 225;

[0556] (xvi) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 226 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 227;

[0557] (xvii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 228 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 229;

[0558] (xviii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 230 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 231 ;

[0559] (xix) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 232 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 233;

[0560] (xx) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 234 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 235;

[0561] (xxi) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 236 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 237; or

[0562] (xxii) a heavy chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 238 and a light chain variable domain comprising an amino acid sequence that is at least 80% identical to SEQ ID NO: 239.

[0563] In a preferred embodiment, the MuSK antibody-based molecules disclosed herein (or anti-MuSK antibodies or antigen-binding fragments thereof) contain:

[0564] a heavy chain variable domain (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 234 and a light chain variable domain (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 235.

[0565] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0566] In a preferred embodiment, the MuSK antibody-based molecules disclosed herein contain:

[0567] a heavy chain variable domain comprising the amino acid sequence of SEQ ID NO: 234 and a light chain variable domain comprising the amino acid sequence of SEQ ID NO: 235.

[0568] In a preferred embodiment, the antibody-based molecules that bind to human muscle- specific tyrosine-protein kinase (MuSK) comprise a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 235, and

[0569] wherein the heavy chain variable domain contains:

[0570] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147,

[0571] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and

[0572] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1 ) and

[0573] wherein the heavy chain variable domain contains:

[0574] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159,

[0575] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0576] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1 ).

[0577] In a more preferred embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0578] wherein the heavy chain variable domain contains:

[0579] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0580] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0581] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2m1 ) and

[0582] wherein the heavy chain variable domain contains:

[0583] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0584] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0585] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 (3B2g2m1).

[0586] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises at least 80% sequence identity to SEQ ID NO: 266 or SEQ ID NO: 267, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0587] wherein the heavy chain variable domain contains:

[0588] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0589] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0590] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0591] wherein the light chain variable domain contains:

[0592] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0593] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0594] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0595] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0596] In one embodiment, the CDR-H2 of the antibody comprises proline (P) at position 3, tryptophan (W) at position 4, and serine (S) or asparagine (N) at position 5.

[0597] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or 267, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 235, and

[0598] wherein the heavy chain variable domain contains:

[0599] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0600] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0601] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0602] wherein the light chain variable domain contains:

[0603] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0604] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0605] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0606] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0607] In one embodiment, the CDR-H2 of the antibody comprises proline (P) at position 3, tryptophan (W) at position 4 and serine (S) or asparagine (N) at position 5.

[0608] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein the heavy chain variable domain comprises SEQ ID NO: 234 and the light chain variable domain comprises SEQ ID NO: 235, and

[0609] wherein the heavy chain variable domain contains:

[0610] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 147,

[0611] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0612] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0613] wherein the light chain variable domain contains:

[0614] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 159,

[0615] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0616] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0617] In one embodiment, the CDR-H2 of the antibody comprises proline (P) at position 3, tryptophan (W) at position 4 and serine (S) or asparagine (N) at position 5.

[0618] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein the heavy chain variable domain comprises SEQ ID NO: 234 and the light chain variable domain comprises SEQ ID NO: 235, and

[0619] wherein the heavy chain variable domain contains:

[0620] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0621] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0622] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2m1) and

[0623] wherein the light chain variable domain contains:

[0624] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0625] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0626] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 (3B2g2m1).

[0627] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

[0628] In one embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain and a light chain variable domain,

[0629] wherein the wild-type human IgG constant Fc region comprises at least 80% sequence identity to SEQ ID NO: 266 or SEQ ID NO: 267, wherein a), wherein one or more of the following mutations (all numbered according to the EU numbering system) has been introduced into the full-length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; P396L substitution; or in the fourth embodiment of the present application a combination of the previously described mutations, preferably the mutation is L234A or L235A, more preferably the mutations are L234A and L235A, and

[0630] wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0631] wherein the heavy chain variable domain contains:

[0632] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147,

[0633] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and

[0634] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156 (3B2g2m1) and

[0635] wherein the light chain variable domain contains:

[0636] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159,

[0637] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[0638] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

[0639] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0640] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain,

[0641] wherein the wild type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein L234A and / or L235A substitutions (numbered according to the EU numbering system) are introduced to said Fc region, and

[0642] wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0643] wherein the heavy chain variable domain contains:

[0644] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0645] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0646] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0647] wherein the light chain variable domain contains:

[0648] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0649] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0650] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0651] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0652] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein L234A and L235A substitutions according to the EU numbering system are introduced to the Fc region, and

[0653] wherein the heavy chain variable domain comprises SEQ ID NO: 234 and the light chain variable domain comprises SEQ ID NO: 235, and

[0654] wherein the heavy chain variable domain contains:

[0655] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0656] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0657] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2m1) and

[0658] wherein the light chain variable domain contains:

[0659] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0660] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0661] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 (3B2g2m1).

[0662] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0663] In one embodiment, the anti-MuSK antibody or antigen-binding fragment thereof contains:

[0664] a) a full length heavy chain comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 268 and

[0665] b) a full length light chain comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 269 and

[0666] c) wherein one or more of the following mutations (all numbered according to the EU numbering system) has been introduced into the full length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; P396L substitution; or a combination of the mutations described in the fourth embodiment of the application above, preferably the mutation is L234A or L235A, more preferably the mutations are L234A and L235A.

[0667] In one embodiment the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0668] In one embodiment the anti-MuSK antibody or antigen binding fragment thereof, contains:

[0669] a) a full length heavy chain comprising SEQ ID NO: 268 and

[0670] b) a full length light chain comprising SEQ ID NO: 269 and

[0671] c) wherein the full length heavy chain comprises L234A and L235A mutations numbered according to the EU numbering system.

[0672] In one embodiment, the anti-MuSK antibody or antigen-binding fragment thereof, comprises:

[0673] a) a full length heavy chain comprising SEQ ID NO: 270 and

[0674] b) a full length light chain comprising SEQ ID NO: 271, and

[0675] c) wherein the full length heavy chain comprises L234A and L235A mutations numbered according to the EU numbering system.

[0676] In one embodiment, the anti-MuSK antibody or antigen-binding fragment thereof, comprises:

[0677] a) a full length heavy chain comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 270 and

[0678] b) a full length light chain comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 271, and

[0679] c) one or more of the following mutations (all numbered according to the EU numbering system) has been introduced into the full-length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; P396L substitution; or each of the combinations of mutations described in the fourth embodiment of the application above, preferably the mutation is L234A or L235A, more preferably the mutations are L234A and L235A.

[0680] In one embodiment the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0681] In one embodiment the anti-MuSK antibody or antigen binding fragment thereof, comprises:

[0682] a) a full-length heavy chain comprising SEQ ID NO: 270 and

[0683] b) a full-length light chain comprising SEQ ID NO: 271 and

[0684] c) wherein the full-length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

[0685] In one preferred embodiment the MuSK antibody-based molecule (or anti-MuSK antibody or antigen binding fragment thereof) disclosed herein comprises:

[0686] a heavy chain variable domain (VH) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202 and a light chain variable domain (VL) comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203.

[0687] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0688] In one preferred embodiment, the MuSK antibody-based molecule disclosed herein comprises a heavy chain variable domain comprising the amino acid sequence of SEQ ID NO: 202 and a light chain variable domain comprising the amino acid sequence of SEQ ID NO: 203.

[0689] In one preferred embodiment, the antibody-based molecule that binds to human muscle- specific tyrosine-protein kinase (MuSK) comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203, and

[0690] wherein the heavy chain variable domain contains:

[0691] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0692] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0693] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0694] - the light chain variable domain contains:

[0695] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0696] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0697] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0698] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises at least 80% sequence identity to SEQ ID NO: 266 or SEQ ID NO: 267, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203, and

[0699] wherein the heavy chain variable domain contains:

[0700] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0701] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0702] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0703] - the light chain variable domain contains:

[0704] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0705] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0706] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156.

[0707] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0708] In one embodiment, the CDR-H2 of the antibody comprises proline (P) at position 3, tryptophan (W) at position 4 and serine (S) or asparagine (N) at position 5. In a preferred embodiment, the CDR-H2 of the antibody comprises proline (P) at position 3, tryptophan (W) at position 4 and asparagine (N) at position 5.

[0709] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein the heavy chain variable domain comprises SEQ ID NO: 202 and the light chain variable domain comprises SEQ ID NO: 203, and wherein:

[0710] The heavy chain variable domain comprises:

[0711] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0712] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 150, and

[0713] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156, and

[0714] The light chain variable domain comprises:

[0715] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0716] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0717] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 183 (3B2).

[0718] In one embodiment, the antibody-based molecule binding to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain and a light chain variable domain,

[0719] wherein the wild-type human IgG constant Fc region comprises at least 80% sequence identity to SEQ ID NO: 266 or SEQ ID NO: 267, wherein one or more of the following mutations (all numbered according to the EU numbering system) has been introduced into the full-length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; P396L substitution; or a combination of the mutations described in the fourth embodiment of the present application above, preferably the mutation is L234A or L235A, more preferably the mutations are L234A and L235A, and

[0720] wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203, and wherein:

[0721] The heavy chain variable domain contains:

[0722] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147,

[0723] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and

[0724] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[0725] The light chain variable domain contains:

[0726] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159,

[0727] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[0728] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

[0729] In one embodiment the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0730] In one embodiment, the antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK) comprises a wild-type human IgG constant Fc region, a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267, wherein L234A and / or L235A numbered according to the EU numbering system is introduced into the Fc region, and

[0731] wherein the heavy chain variable domain comprises SEQ ID NO: 202 and the light chain variable domain comprises SEQ ID NO: 203, and

[0732] wherein the heavy chain variable domain contains:

[0733] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0734] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 150, and

[0735] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2) and

[0736] wherein the light chain variable domain contains:

[0737] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0738] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0739] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 183 (3B2).

[0740] In one embodiment, the anti-MuSK antibody or antigen-binding fragment thereof contains:

[0741] a) a full-length heavy chain comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 282 and

[0742] b) a full-length light chain comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 283, and

[0743] c) one or more of the following mutations (all numbered according to the EU numbering system) has been introduced into the full length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E233P substitution; L234V substitution; C236 deletion; G236E substitution; G236R substitution; G236K substitution; G237A substitution; P238A substitution; F243L substitution; D265A substitution; S267E substitution; H268A substitution; R292P substitution; Y300L substitution; K322A substitution; K322Q substitution; A327Q substitution; L328F substitution; L328R substitution; P329A substitution; P329G substitution; A330L substitution; A330S substitution; P331S substitution; I332E substitution; P396L substitution; or each of the combinations of mutations described in the fourth embodiment of the application above, preferably the mutation is L234A or L235A, more preferably the mutations are L234A and L235A.

[0744] In one embodiment the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0745] In one embodiment the anti-MuSK antibody or antigen binding fragment thereof comprises:

[0746] a) a full length heavy chain comprising SEQ ID NO: 282 and

[0747] b) a full length light chain comprising SEQ ID NO: 283 and

[0748] c) wherein the full length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

[0749] Polynucleotides

[0750] Another aspect of the application relates to isolated polynucleotides encoding the MuSK antibody-based molecules described herein. In one embodiment, the polynucleotides comprise a nucleotide sequence encoding an antibody-based molecule comprising a heavy chain variable region (VH) and a light chain variable region (VL) as identified in Table 3 and / or CDRs as identified in Table 1 or Table 2. Accordingly, the application provides polynucleotides for use in preventing, delaying, reversing or treating a disease or disorder caused by syncan deficiency in a human subject, wherein the polynucleotides comprise a nucleotide sequence encoding an anti-MuSK antibody or antigen binding fragment or a VH, VL or CDR domain thereof as defined in the preceding embodiments. In one embodiment, the polynucleotides encoding the MuSK antibodies of the application comprise a nucleotide sequence encoding any one, any two, any three, any four, any five or any six of the CDRs described above, including the heavy chain CDRs of SEQ ID NOs: 1 to 48, 135 to 140, 147 to 158, 240 to 251 and the light chain CDRs of SEQ ID NOs: 49 to 96, 141 to 146 and 159 to 195.

[0751] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VH domain, wherein the VH domain contains:

[0752] (i) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 1, CDR-H2 of SEQ ID NO: 17 and CDR-H3 of SEQ ID NO: 33;

[0753] (ii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18 and CDR-H3 of SEQ ID NO: 34;

[0754] (iii) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 3, CDR-H2 of SEQ ID NO: 19 and CDR-H3 of SEQ ID NO: 35;

[0755] (iv) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 4, CDR-H2 of SEQ ID NO: 20 and CDR-H3 of SEQ ID NO: 36;

[0756] (v) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 5, CDR-H2 of SEQ ID NO: 21 and CDR-H3 of SEQ ID NO: 37;

[0757] (vi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 6, a CDR-H2 of SEQ ID NO: 22, and a CDR-H3 of SEQ ID NO: 38;

[0758] (vii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 7, a CDR-H2 of SEQ ID NO: 23, and a CDR-H3 of SEQ ID NO: 39;

[0759] (viii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 8, a CDR-H2 of SEQ ID NO: 24, and a CDR-H3 of SEQ ID NO: 40;

[0760] (ix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 9, a CDR-H2 of SEQ ID NO: 25, and a CDR-H3 of SEQ ID NO: 41;

[0761] (x) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 10, a CDR-H2 of SEQ ID NO: 26, and a CDR-H3 of SEQ ID NO: 42;

[0762] (xi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 11, a CDR-H2 of SEQ ID NO: 27, and a CDR-H3 of SEQ ID NO: 43;

[0763] (xii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 12, a CDR-H2 of SEQ ID NO: 28, and a CDR-H3 of SEQ ID NO: 44;

[0764] (xiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 13, a CDR-H2 of SEQ ID NO: 29, and a CDR-H3 of SEQ ID NO: 45;

[0765] (xiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 14, a CDR-H2 of SEQ ID NO: 30, and a CDR-H3 of SEQ ID NO: 46;

[0766] (xvii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139; or

[0767] (xvi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 16, a CDR-H2 of SEQ ID NO: 32, and a CDR-H3 of SEQ ID NO: 48;

[0768] (xvii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 135, a CDR-H2 of SEQ ID NO: 137, and a CDR-H3 of SEQ ID NO: 139; or

[0769] (xviii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 136, a CDR-H2 of SEQ ID NO: 138, and a CDR-H3 of SEQ ID NO: 140.

[0770] In some embodiments, the polynucleotide comprises a nucleotide sequence encoding a VH domain, wherein the VH domain contains:

[0771] (ii.a) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 240 (X2ml);

[0772] (ii.b) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 241 (X2m2);

[0773] (ii.c) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 242 (X2m3);

[0774] (ii.d) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 2, a CDR-H2 of SEQ ID NO: 18, and a CDR-H3 of SEQ ID NO: 243 (X2m4);

[0775] (ii.e) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 244 (X2m5);

[0776] (ii.f) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 245 (X2m6);

[0777] (ii.g) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 246 (X2m7); or

[0778] (ii.h) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 2, CDR-H2 of SEQ ID NO: 18, and CDR-H3 of SEQ ID NO: 247 (X2m8).

[0779] In some embodiments, the polynucleotide comprises a nucleotide sequence encoding a VH domain, wherein the VH domain contains:

[0780] (xvii.a) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 248 (X17ml);

[0781] (xvii.b) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 249 (X17m2);

[0782] (xvii.c) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 250 (X17m3); or

[0783] (xvii.d) a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 135, CDR-H2 of SEQ ID NO: 137, and CDR-H3 of SEQ ID NO: 251 (X17m6).

[0784] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VH domain, wherein the VH domain contains:

[0785] (xix) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 150, and a CDR-H3 of SEQ ID NO: 156;

[0786] (xx) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 148, a CDR-H2 of SEQ ID NO: 151, and a CDR-H3 of SEQ ID NO: 157; or

[0787] (xxi) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 149, a CDR-H2 of SEQ ID NO: 152, and a CDR-H3 of SEQ ID NO: 158.

[0788] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VH domain, wherein the VH domain contains:

[0789] (xxii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 153, and a CDR-H3 of SEQ ID NO: 156;

[0790] (xxiii) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 154, and a CDR-H3 of SEQ ID NO: 156; or

[0791] (xxiv) a heavy chain variable domain comprising a CDR-H1 of SEQ ID NO: 147, a CDR-H2 of SEQ ID NO: 155, and a CDR-H3 of SEQ ID NO: 156.

[0792] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VL domain, wherein the VL domain contains:

[0793] (i) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 49, a CDR-L2 of SEQ ID NO: 65, and a CDR-L3 of SEQ ID NO: 81;

[0794] (ii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 50, a CDR-L2 of SEQ ID NO: 66, and a CDR-L3 of SEQ ID NO: 82;

[0795] (iii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 51, a CDR-L2 of SEQ ID NO: 67, and a CDR-L3 of SEQ ID NO: 83;

[0796] (iv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 52, a CDR-L2 of SEQ ID NO: 68, and a CDR-L3 of SEQ ID NO: 84;

[0797] (v) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 53, a CDR-L2 of SEQ ID NO: 69, and a CDR-L3 of SEQ ID NO: 85;

[0798] (vi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 54, a CDR-L2 of SEQ ID NO: 70, and a CDR-L3 of SEQ ID NO: 86;

[0799] (vii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 55, a CDR-L2 of SEQ ID NO: 71, and a CDR-L3 of SEQ ID NO: 87;

[0800] (viii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 56, a CDR-L2 of SEQ ID NO: 72, and a CDR-L3 of SEQ ID NO: 88;

[0801] (ix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 57, a CDR-L2 of SEQ ID NO: 73, and a CDR-L3 of SEQ ID NO: 89;

[0802] (x) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 58, a CDR-L2 of SEQ ID NO: 74, and a CDR-L3 of SEQ ID NO: 90;

[0803] (xi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 59, a CDR-L2 of SEQ ID NO: 75, and a CDR-L3 of SEQ ID NO: 91 ;

[0804] (xii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 60, a CDR-L2 of SEQ ID NO: 76, and a CDR-L3 of SEQ ID NO: 92;

[0805] (xiii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 61, a CDR-L2 of SEQ ID NO: 77, and a CDR-L3 of SEQ ID NO: 93;

[0806] (xiv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 62, a CDR-L2 of SEQ ID NO: 78, and a CDR-L3 of SEQ ID NO: 94;

[0807] (xv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 63, a CDR-L2 of SEQ ID NO: 79, and a CDR-L3 of SEQ ID NO: 95;

[0808] (xvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 64, a CDR-L2 of SEQ ID NO: 80, and a CDR-L3 of SEQ ID NO: 96;

[0809] (xvii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 141, a CDR-L2 of SEQ ID NO: 143, and a CDR-L3 of SEQ ID NO: 145; or

[0810] (xviii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 142, a CDR-L2 of SEQ ID NO: 144, and a CDR-L3 of SEQ ID NO: 146.

[0811] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VL domain, wherein the VL domain contains:

[0812] (xix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 170, and a CDR-L3 of SEQ ID NO: 180;

[0813] (xx) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 181;

[0814] (xxi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 160, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 182;

[0815] (xxii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 172, and a CDR-L3 of SEQ ID NO: 183;

[0816] (xxiii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 171, and a CDR-L3 of SEQ ID NO: 184;

[0817] (xxiv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 185;

[0818] (xxv) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 159, a CDR-L2 of SEQ ID NO: 173, and a CDR-L3 of SEQ ID NO: 186;

[0819] (xxvi) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 161, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 187;

[0820] (xxvii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 162, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188;

[0821] (xxviii) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 163, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 188;

[0822] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0823] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0824] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0825] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189;

[0826] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189; or

[0827] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189.

[0828] In one embodiment, the polynucleotide comprises a nucleotide sequence encoding a VL domain, wherein the VL domain contains:

[0829] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189; or

[0830] (xxix) a light chain variable domain comprising a CDR-L1 of SEQ ID NO: 164, a CDR-L2 of SEQ ID NO: 174, and a CDR-L3 of SEQ ID NO: 189.

[0831] In one embodiment, the isolated polynucleotide encoding a MuSK antibody-based molecule encodes any of the VH and / or VL domain sequences provided in Table 3. The nucleic acid molecules described herein include isolated polynucleotides, portions of expression vectors, or portions of linear DNA sequences, including linear DNA sequences for in vitro transcription / translation, and vectors compatible with prokaryotic, eukaryotic, or filamentous phage expression, secretion, and / or display of the antibodies or binding fragments thereof described herein.

[0832] In one preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding a VH comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234. In another preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding a VL comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235.

[0833] In one preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0834] wherein the heavy chain variable domain contains:

[0835] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 147,

[0836] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 153, and

[0837] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 156 (3B2g2m1) and

[0838] wherein the light chain variable domain contains:

[0839] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid alterations relative to SEQ ID NO: 159,

[0840] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 172, and

[0841] - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid alterations relative to SEQ ID NO: 195 (3B2g2m1).

[0842] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0843] In a more preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine-protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0844] wherein the heavy chain variable domain contains:

[0845] - a CDR-H1 amino acid sequence comprising or consisting of SEQ ID NO: 147,

[0846] - a CDR-H2 amino acid sequence comprising or consisting of SEQ ID NO: 153, and

[0847] - a CDR-H3 amino acid sequence comprising or consisting of SEQ ID NO: 156 (3B2g2m1) and

[0848] wherein the light chain variable domain contains:

[0849] - a CDR-L1 amino acid sequence comprising or consisting of SEQ ID NO: 159,

[0850] - a CDR-L2 amino acid sequence comprising or consisting of SEQ ID NO: 172, and

[0851] - a CDR-L3 amino acid sequence comprising or consisting of SEQ ID NO: 195 (3B2g2m1).

[0852] In one embodiment, the identity or similarity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0853] In a more preferred embodiment, the polynucleotide comprises or consists of a nucleotide sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 264. In an even more preferred embodiment, the polynucleotide comprises or consists of SEQ ID NO: 264.

[0854] In another more preferred embodiment, the polynucleotide comprises or consists of a nucleotide sequence having at least 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100% identity to SEQ ID NO: 265. In an even more preferred embodiment, the polynucleotide comprises or consists of SEQ ID NO: 265.

[0855] In a more preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain is encoded by a nucleotide sequence having at least 80% identity to SEQ ID NO: 264 and the light chain variable domain is encoded by a nucleotide sequence having at least 80% identity to SEQ ID NO: 265. In one embodiment, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0856] In one embodiment, the polynucleotide comprises:

[0857] a) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 276 encoding a full length heavy chain, and

[0858] b) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 278 encoding a full length light chain.

[0859] In one embodiment, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0860] In one embodiment, the polynucleotide comprises:

[0861] a) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 277 encoding a heavy chain variable domain, and

[0862] b) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 279 encoding a light chain variable domain.

[0863] In one embodiment, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0864] In one embodiment, the polynucleotide comprises:

[0865] a) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 276 encoding a full length heavy chain, wherein the nucleotide sequence comprises a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 277 encoding a heavy chain variable domain, and

[0866] b) a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 278 encoding a full length light chain, wherein the nucleotide sequence comprises a nucleotide sequence that is at least 80% identical to the SEQ ID NO: 279 encoding a light chain variable domain.

[0867] In one embodiment, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%.

[0868] In one embodiment, the polynucleotide comprises:

[0869] a) the nucleotide sequence of SEQ ID NO: 276, and

[0870] b) the nucleotide sequence of SEQ ID NO: 278.

[0871] In another preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding a VL comprising an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203.

[0872] In another preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence that is at least 80% identical or similar to SEQ ID NO: 203, and

[0873] wherein the heavy chain variable domain contains:

[0874] - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 147,

[0875] - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 150, and

[0876] - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 (3B2) and

[0877] wherein the light chain variable domain contains:

[0878] - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 159,

[0879] - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[0880] - Contains SEQ ID NO: 183 or a CDR-L3 amino acid sequence with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

[0881] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0882] In a more preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), said molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203, and

[0883] The heavy-chain variable structural domain contains:

[0884] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[0885] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 150 or SEQ ID NO: 150, and

[0886] - Contains the CDR-H3 amino acid sequence (3B2) consisting of SEQ ID NO: 156 or SEQ ID NO: 156 and

[0887] The variable structural domain of the light chain contains:

[0888] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[0889] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[0890] - Contains the CDR-L3 amino acid sequence consisting of SEQ ID NO: 183 or SEQ ID NO: 183 (3B2).

[0891] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0892] In a more preferred embodiment, the polynucleotide comprises a nucleotide sequence encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), said molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain is encoded by a nucleotide sequence having at least 80% identity with SEQ ID NO: 284 and the light chain variable domain is encoded by a nucleotide sequence having at least 80% identity with SEQ ID NO: 285.

[0893] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0894] In one implementation, the polynucleotide comprises:

[0895] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, and

[0896] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain.

[0897] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0898] In one implementation, the polynucleotide comprises:

[0899] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the heavy chain variable domain, and

[0900] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 285 encoding a light chain variable domain.

[0901] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0902] In one implementation, the polynucleotide comprises:

[0903] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, wherein said nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the variable domain of the heavy chain, and

[0904] b) A nucleotide sequence having at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain, wherein the nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 285 encoding the variable domain of the light chain.

[0905] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0906] In one implementation, the polynucleotide comprises:

[0907] a) Nucleotide sequence SEQ ID NO: 288, and

[0908] b) Nucleotide sequence SEQ ID NO: 289.

[0909] The polynucleotides of the present invention can be generated and assembled into complete single-stranded or double-stranded molecules by chemical synthesis, such as solid-phase polynucleotide synthesis on an automated polynucleotide synthesizer. Alternatively, the polynucleotides can be generated by other techniques such as PCR, followed by conventional cloning. Techniques for generating or obtaining polynucleotides of a given sequence are well known in the art.

[0910] Polynucleotides may contain at least one non-coding sequence, such as a promoter or enhancer sequence, intron, polyadenylation signal, cis sequence that promotes RepA binding, etc. The polynucleotide sequence may also contain additional sequences encoding, for example, adapter sequences, marker or tag sequences (e.g., histidine tags or HA tags) to facilitate the purification or detection of proteins, signal sequences, fusion protein couplers (e.g., RepA, Fc moieties), or phage coat proteins (e.g., pIX or pIII).

[0911] Vectors

[0912] In another aspect, a vector (preferably an expression vector) is provided for generating a MuSK antibody-based molecule for the prevention, delay, reversal, or treatment in human subjects of a disease or condition caused by a synaptic glycan deficiency, the vector comprising a polynucleotide encoding a MuSK antibody-based molecule (or an anti-MuSK antibody or its antigen-binding fragment) as described herein.

[0913] Such vectors include, but are not limited to, plasmid vectors, viral vectors, including but not limited to vaccinia vectors, lentiviral vectors, adenovirus vectors, adeno-associated virus vectors, vectors for baculovirus expression, transposon-based vectors, or any other vector suitable for introducing the polynucleotides described herein into a given organism or genetic background in any way to promote the expression of encoded antibody peptides. In one embodiment, a polynucleotide encoding a heavy chain variable domain, alone or together with a polynucleotide encoding a light chain variable domain as described herein, is combined with a promoter, a translation initiation region (e.g., a ribosome-binding sequence and a start codon), a 3' untranslated region, a polyadenylation signal, a stop codon, and a transcription termination sequence to form one or more expression vector constructs.

[0914] In one embodiment, the vector is an adenovirus-associated viral (AAV) vector. Many therapeutic AAV vectors suitable for delivering polynucleotides encoding the antibodies described herein to the central nervous system are known in the art. See, for example, Deverman et al., “Gene Therapy for Neurological Disorders: Progress and Prospects,” Nature Rev. 17:641-659 (2018), which is incorporated herein by reference in its entirety. Suitable AAV vectors include serotypes AAV1, AAV2, AAV3, AAV4, AAV5, AAV6, AAV7, AAV8, AAV9, AAV10, or AAV11, either in their natural form or modified for enhanced tropism. Known CNS-tropy AAV vectors particularly suitable for the therapeutic expression of the MuSK antibodies described herein include AAV1, AAV2, AAV4, AAV5, AAV8, and AAV9, either in their natural form or modified for enhanced tropism. In one embodiment, the AAV vector is an AAV2 vector. In another embodiment, the AAV vector is an AAV5 vector (Vitale et al., “Anti-tauConformational scFv MC1 Antibody Efficiently Reduces Pathological Tau Species in Adult JNPL3 Mice,” Acta Neuropathol. Commun. 6:82 (2018), which is incorporated herein by reference in its entirety). In yet another embodiment, the AAV vector is an AAV9 vector (Haiyan et al., “Targeting RootCause by Systemic scAAV9-hIDS Gene Delivery: Functional Correction and Reversal of Severe MPSII in Mice,” Mol. Ther. Methods Clin. Dev. 10:327-340 (2018), which is incorporated herein by reference in its entirety).In another implementation, the AAV vector is the AAVrh10 vector (Liu et al., “Vectored Intracerebral Immunizations with the Anti-Tau Monoclonal Antibody PHF1 Markedly Reduces Tau Pathology in Mutant Transgenic Mice,” J.Neurosci. 36(49): 12425-35 (2016), which is incorporated herein by reference in its entirety).

[0915] In another embodiment, the AAV vector is a heterozygous vector containing the genome of one serotype (e.g., AAV2) and the capsid protein of another serotype (e.g., AAV1 or AAV3 to 9) to control tropism. See, for example, Broekman et al., “Adeno-associated Virus Vectors Serotyped with AAV8 Capsid are More Efficient than AAV-1 or -2 Serotypes for Widespread Gene Delivery to the Neonatal Mouse Brain,” Neuroscience 138:501-510 (2006), which is incorporated herein by reference in its entirety. In one embodiment, the AAV vector is an AAV2 / 8 heterozygous vector (Ising et al., “AAV-mediated Expression of Anti-Tau ScFv Decreases Tau Accumulation in a Mouse Model of Tauopathy,” J. Exp. Med. 214(5):1227 (2017), which is incorporated herein by reference in its entirety). In another implementation, the AAV vector is an AAV2 / 9 hybrid vector (Simon et al., “A Rapid Gene Delivery-Based Mouse Model for Early-Stage Alzheimer Disease-Type Tauopathy,” J. Neuropath.Exp. Neurol. 72(11): 1062-71 (2013), which is incorporated herein by reference in its entirety).

[0916] In another embodiment, the AAV vector is an AAV vector modified or selected for the following: enhanced CNS transduction after intraplasmic administration, such as AAV-DJ (Grimm et al., J. Viol. 82:5887-5911 (2008), which is incorporated herein by reference in its entirety); enhanced transduction of neural stem cells and progenitor cells, such as SCH9 and AAV4.18 (Murlidharan et al., J. Virol. 89: 3976-3987 (2015) and Ojala et al., Mol. Ther. 26:304-319 (2018), which is incorporated herein by reference in its entirety); enhanced retrograde transduction, such as rAAV2-retro (Muller et al., Nat. Biotechnol. 21:1040-1046). (2003), which is incorporated herein by reference in its entirety; selective transduction to brain endothelial cells, such as AAV-BRI (Korbelin et al., EMBO Mol.Med. 8: 609-625 (2016), which is incorporated herein by reference in its entirety); or enhanced adult CNS transduction following IV administration, such as AAV-PHP.B and AAVPHP.eB (Deverman et al., Nat. Biotechnol. 34: 204-209 (2016) and Chan et al., Nat. Neurosci. 20: 1172-1179 (2017), which is incorporated herein by reference in its entirety).

[0917] According to this embodiment, the expression vector construct encoding a MuSK antibody-based molecule comprises a polynucleotide encoding a heavy chain polypeptide, a functional fragment thereof, a variant thereof, or a combination thereof. Alternatively, the expression construct may comprise a nucleic acid sequence encoding a light chain polypeptide, a functional fragment thereof, a variant thereof, or a combination thereof. In one embodiment, the expression vector construct comprises nucleic acid sequences encoding a heavy chain polypeptide, a functional fragment thereof, or a variant thereof, and a light chain polypeptide, a functional fragment thereof, or a variant thereof.

[0918] In one embodiment, the expression construct further comprises a promoter sequence suitable for driving the expression of a MuSK antibody-based molecule. Suitable promoter sequences include, but are not limited to, the elongation factor 1-α promoter (EF1a), the phosphoglycerate kinase-1 promoter (PGK), the cytomegalovirus immediate early gene promoter (CMV), the chimeric liver-specific promoter (LSP), the cytomegalovirus enhancer / chicken β-actin promoter (CAG), the tetracycline-responsive promoter (TRE), the thyroxine transporter promoter (TTR), the simian virus 40 promoter (SV40), and the CK6 promoter. Other promoters known in the art suitable for driving gene expression in mammalian cells are also suitable for inclusion in the expression constructs disclosed herein.

[0919] In one implementation, the expression construct (or expression vector) also encodes an adapter sequence. The adapter sequence may encode an amino acid sequence that spatially separates and / or connects one or more components of the expression construct (the heavy and light chain components of the encoded antibody).

[0920] In a preferred embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235.

[0921] The heavy-chain variable structural domain contains:

[0922] - Contains the CDR-H1 amino acid sequence of SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[0923] - Contains the CDR-H2 amino acid sequence of SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and

[0924] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 and

[0925] The variable structural domain of the light chain contains:

[0926] - Contains the CDR-L1 amino acid sequence of SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[0927] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[0928] - Contains SEQ ID NO: 195 or a CDR-L3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195.

[0929] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0930] In a more preferred embodiment, the expression vector comprises nucleotides encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235.

[0931] The heavy-chain variable structural domain contains:

[0932] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[0933] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 153 or SEQ ID NO: 153, and

[0934] - Contains the CDR-H3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 156 or SEQ ID NO: 156 and

[0935] The variable structural domain of the light chain contains:

[0936] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[0937] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[0938] - Contains the CDR-L3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 195 or SEQ ID NO: 195.

[0939] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0940] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0941] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 276 encoding the full-length heavy chain, and

[0942] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 278 encoding the full-length light chain.

[0943] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0944] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0945] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 277 encoding the heavy chain variable domain, and

[0946] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 279 encoding a light chain variable domain.

[0947] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0948] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0949] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 276 encoding the full-length heavy chain, wherein said nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 277 encoding the variable domain of the heavy chain, and

[0950] b) A nucleotide sequence having at least 80% identity with SEQ ID NO: 278 encoding the full-length light chain, wherein the nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 279 encoding the variable domain of the light chain.

[0951] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0952] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0953] a) Nucleotide sequence SEQ ID NO: 276, and

[0954] b) Nucleotide sequence SEQ ID NO: 278.

[0955] In a preferred embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[0956] The heavy-chain variable structural domain contains:

[0957] - Contains the CDR-H1 amino acid sequence of SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[0958] - Contains the CDR-H2 amino acid sequence of SEQ ID NO: 150 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and

[0959] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2) having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 and

[0960] The variable structural domain of the light chain contains:

[0961] - Contains the CDR-L1 amino acid sequence of SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[0962] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[0963] - Contains SEQ ID NO: 183 or a CDR-L3 amino acid sequence with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

[0964] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0965] In a more preferred embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and comprises a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[0966] The heavy-chain variable structural domain contains:

[0967] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[0968] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 150 or SEQ ID NO: 150, and

[0969] - Contains the CDR-H3 amino acid sequence (3B2) consisting of SEQ ID NO: 156 or SEQ ID NO: 156 and

[0970] The variable structural domain of the light chain contains:

[0971] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[0972] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[0973] - Contains the CDR-L3 amino acid sequence consisting of SEQ ID NO: 183 or SEQ ID NO: 183 (3B2).

[0974] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0975] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0976] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, and

[0977] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain.

[0978] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0979] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0980] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the heavy chain variable domain, and

[0981] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 285 encoding a light chain variable domain.

[0982] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0983] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0984] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, wherein said nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the variable domain of the heavy chain, and

[0985] b) A nucleotide sequence having at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain, wherein the nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 285 encoding the variable domain of the light chain.

[0986] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[0987] In one embodiment, the expression vector comprises a polynucleotide encoding an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK) and includes:

[0988] a) Nucleotide sequence SEQ ID NO: 288, and

[0989] b) Nucleotide sequence SEQ ID NO: 289.

[0990] Host cells

[0991] Another aspect of the invention is a host cell or cell-free expression system for producing MuSK antibody-based molecules for the prevention, delay, reversal, or treatment in human subjects of diseases or conditions caused by synaptic glycan defects, wherein the cells contain an expression vector encoding a MuSK antibody (or an antigen-binding fragment thereof) and optionally produce the MuSK antibody described herein.

[0992] As is well known in the art, the MuSK-based antibody molecules described herein may optionally be generated from cell lines, mixed cell lines, immortalized cells, or clonal populations of immortalized cells (see, for example, Ausubel et al., ed., Current Protocols in Molecular Biology, John Wiley & Sons, Inc., NY, NY (1987–2001); Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd edition, Cold Spring Harbor, NY (1989); Harlow and Lane, Antibodies, a Laboratory Manual, Cold Spring Harbor, NY (1989); Colligan et al., eds., Current Protocols in Immunology, John Wiley & Sons, Inc., NY (1994–2001); Colligan et al., Current Protocols in Protein Science, John Wiley & Sons, NY). NY, (1997-2001), which is incorporated herein by reference in its entirety.

[0993] In some embodiments, the selected host cell for expression may be of mammalian origin. Suitable mammalian host cells include, but are not limited to, COS-1 cells, COS-7 cells, HEK293 cells, BHK21 cells, CHO cells, BSC-1 cells, HeG2 cells, SP2 / 0 cells, HeLa cells, mammalian myeloma cells, mammalian lymphoma cells, or any derived, immortalized, or transformed cells thereof. Other suitable host cells include, but are not limited to, yeast cells, insect cells, and plant cells. Alternatively, the host cell may be selected from species or organisms that cannot glycosylate the polypeptide, such as prokaryotic cells or organisms, such as BL21, BL21(DE3), BL21-GOLD(DE3), XL1-Blue, JM109, HMS174, HMS174(DE3), and any natural or modified strains of Escherichia coli, Klebsiella, or Pseudomonas.

[0994] The MuSK-based antibody molecules described herein can be prepared using any of a variety of techniques employing the isolated polynucleotides, vectors, and host cells described above. Generally, antibodies can be generated using cell culture techniques, including the production of monoclonal antibodies using conventional techniques, or by transfecting antibody genes, heavy chains, and / or light chains into suitable bacterial or mammalian cell hosts to allow antibody production, where the antibodies can be recombinant. In one embodiment, the MuSK-based antibody molecules described herein are monoclonal antibodies or functional binding fragments thereof. Standard molecular biology techniques are used to prepare recombinant expression vectors, transfect host cells, select transformants, culture host cells, and recover antibodies from the culture medium. Transfection of host cells can be performed using a variety of techniques commonly used to introduce exogenous DNA into prokaryotic or eukaryotic host cells, such as electroporation, calcium phosphate precipitation, DEAE-dextran transfection, etc. Although the antibodies described herein can be expressed in prokaryotic or eukaryotic host cells, expression of antibodies in eukaryotic cells, particularly mammalian cells, is sometimes preferred because such eukaryotic cells (and particularly mammalian cells) are more likely than prokaryotic cells to assemble and secrete properly folded and immunologically active antibodies.

[0995] As described above, exemplary mammalian host cells for expressing the recombinant antibodies of the present invention include Chinese hamster ovary (CHO) cells (including dhfr-CHO cells, described in Urlaub and Chasin, Proc. Natl. Acad. Sci. USA, 77: 4216-4220 (1980), which is incorporated herein by reference in its entirety). Other suitable mammalian host cells include, but are not limited to, NSO myeloma cells, COS cells, and SP2 cells. When a recombinant expression vector encoding an antibody gene is introduced into a mammalian host cell, the antibody is produced by culturing the host cell for a period of time sufficient to allow the antibody to be expressed in the host cell or, more preferably, to allow the antibody to be secreted into the culture medium in which the host cell is cultured.

[0996] Host cells can also be used to generate functional antibody fragments, such as Fab fragments or scFv molecules. It is understood that variations of the above operations are within the scope of this invention. For example, it may be desirable to transfect host cells with DNA encoding functional fragments of the light and / or heavy chains of the antibodies described herein. Recombinant DNA technology can also be used to remove some or all of the DNA encoding either or both of the light and heavy chains that are not essential for binding to the target antigen. Molecules expressed from such truncated DNA molecules are also included in the antibodies described herein.

[0997] Antibodies and antibody-binding fragments are recovered and purified from recombinant cell cultures using known methods, including but not limited to protein A purification, ammonium sulfate or ethanol precipitation, acid extraction, anion or cation exchange chromatography, cellulose phosphate chromatography, hydrophobic interaction chromatography, affinity chromatography, hydroxyapatite chromatography, and lectin chromatography. High-performance liquid chromatography (“HPLC”) can also be used for purification.

[0998] In a preferred embodiment, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[0999] The heavy-chain variable structural domain contains:

[1000] - Contains the CDR-H1 amino acid sequence of SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1001] - Contains the CDR-H2 amino acid sequence of SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and

[1002] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 156 and

[1003] The variable structural domain of the light chain contains:

[1004] - Contains the CDR-L1 amino acid sequence of SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1005] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 172, and

[1006] - Contains SEQ ID NO: 195 or a CDR-L3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195.

[1007] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1008] In a more preferred embodiment, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), said molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234 and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[1009] The heavy-chain variable structural domain contains:

[1010] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1011] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 153 or SEQ ID NO: 153, and

[1012] - Contains the CDR-H3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 156 or SEQ ID NO: 156 and

[1013] The variable structural domain of the light chain contains:

[1014] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1015] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1016] - Contains the CDR-L3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 195 or SEQ ID NO: 195.

[1017] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1018] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1019] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 276 encoding the full-length heavy chain, and

[1020] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 278 encoding the full-length light chain.

[1021] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1022] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1023] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 277 encoding the heavy chain variable domain, and

[1024] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 279 encoding a light chain variable domain.

[1025] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1026] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1027] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 276 encoding the full-length heavy chain, wherein said nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 277 encoding the variable domain of the heavy chain, and

[1028] b) A nucleotide sequence having at least 80% identity with SEQ ID NO: 278 encoding the full-length light chain, wherein the nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 279 encoding the variable domain of the light chain.

[1029] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1030] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1031] a) Nucleotide sequence SEQ ID NO: 276, and

[1032] b) Nucleotide sequence SEQ ID NO: 278.

[1033] In a preferred embodiment, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), the molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[1034] The heavy-chain variable structural domain contains:

[1035] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1036] - Contains a CDR-H2 amino acid sequence that is SEQ ID NO: 150 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and

[1037] - Contains a CDR-H3 amino acid sequence (3B2) with SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[1038] The variable structural domain of the light chain contains:

[1039] - Contains a CDR-L1 amino acid sequence that is SEQ ID NO: 159 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1040] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[1041] - Contains a CDR-L3 amino acid sequence (3B2) with SEQ ID NO: 183 or with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183.

[1042] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1043] In a more preferred embodiment, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), said molecule comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[1044] The heavy-chain variable structural domain contains:

[1045] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1046] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 150 or SEQ ID NO: 150, and

[1047] - Contains the CDR-H3 amino acid sequence (3B2) consisting of SEQ ID NO: 156 or SEQ ID NO: 156 and

[1048] The variable structural domain of the light chain contains:

[1049] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1050] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1051] Contains the CDR-L3 amino acid sequence consisting of SEQ ID NO: 183 or SEQ ID NO: 183 (3B2).

[1052] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1053] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1054] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, and

[1055] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain.

[1056] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1057] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1058] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the heavy chain variable domain, and

[1059] b) A nucleotide sequence that has at least 80% identity with SEQ ID NO: 285 encoding a light chain variable domain.

[1060] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1061] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1062] a) A nucleotide sequence having at least 80% identity with SEQ ID NO: 288 encoding the full-length heavy chain, wherein said nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 284 encoding the variable domain of the heavy chain, and

[1063] b) A nucleotide sequence having at least 80% identity with SEQ ID NO: 289 encoding the full-length light chain, wherein the nucleotide sequence comprises a nucleotide sequence having at least 80% identity with SEQ ID NO: 285 encoding the variable domain of the light chain.

[1064] In one implementation, the identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1065] In one implementation, the host cell expresses an antibody-based molecule that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1066] a) Nucleotide sequence SEQ ID NO: 288, and

[1067] b) Nucleotide sequence SEQ ID NO: 289.

[1068] Compositions comprising MuSK antibody-based molecules

[1069] The MuSK antibody-based molecules of the present invention or the polynucleotides encoding MuSK antibody-based molecules can be advantageously applied as compositions.

[1070] Therefore, in another aspect, compositions are provided for the prevention, delay, reversal, or treatment in human subjects of diseases or conditions caused by synaptic proteoglycan (Agrin) deficiency, said compositions comprising an antibody or antigen-binding fragment, a polynucleotide, or an expression vector as defined herein.

[1071] In one embodiment, the composition is a pharmaceutical composition. In another embodiment, the pharmaceutical composition comprises at least one pharmaceutically acceptable carrier or excipient.

[1072] In one embodiment, such a composition is a pharmaceutical composition comprising an active therapeutic agent (i.e., a MuSK antibody) and one or more other pharmaceutically acceptable components. See REMINGTON: THE SCIENCE AND PRACTICE OF PHARMACY (21st edition) (2005) (Troy, DB et al. (Eds.) Lippincott Williams & Wilkins (Publs.), Baltimore MD), which is incorporated herein by reference in its entirety. Preferred forms depend on the intended method of administration and therapeutic application. Depending on the desired formulation, the composition may also comprise pharmaceutically acceptable, nontoxic carriers, excipients, diluents, fillers, salts, buffers, detergents (e.g., nonionic detergents, such as Tween-20 or Tween-80), stabilizers (e.g., sugars or protein-free amino acids), preservatives, tissue fixatives, solubilizers, and / or other substances suitable for inclusion in the pharmaceutical composition, and these are typically used to formulate pharmaceutical compositions for animal or human administration. Diluents are selected so as not to affect the bioactivity of the composition. Examples of such diluents include distilled water, physiological phosphate-buffered saline, Ringer's solution, dextran solution, and Hank's solution. Additionally, pharmaceutical compositions or formulations may contain other carriers, or non-toxic, non-therapeutic, non-immunogenic stabilizers, etc. Examples of suitable aqueous and non-aqueous carriers that can be used in the pharmaceutical compositions of this invention include water, saline, phosphate-buffered saline, ethanol, dextran, polyols (e.g., glycerol, propylene glycol, polyethylene glycol, etc.) and suitable mixtures thereof, vegetable oils (e.g., olive oil, corn oil, peanut oil, cottonseed oil, and sesame oil), carboxymethyl cellulose colloidal solutions, tragacanth gum, and injectable organic esters (e.g., ethyl oleate), and / or various buffers. Other carriers are well known in the pharmaceutical industry.

[1073] Pharmaceutically acceptable carriers include sterile aqueous solutions or dispersions, as well as sterile powders for the provisional preparation of sterile injectable solutions or dispersions. The use of such media and reagents for pharmaceutically active substances is known in the art. Their use in the pharmaceutical compositions of the present invention is contemplated unless any conventional media or reagent is incompatible with the active compound.

[1074] The composition may also comprise large, slowly metabolizing macromolecules such as proteins, polysaccharides (e.g., chitosan), polylactic acid, polyglycolic acid, and copolymers (e.g., latex-functionalized agarose, agarose, cellulose, etc.), polymeric amino acids, amino acid copolymers, and lipid aggregates (e.g., oil droplets or liposomes). The suitability of the carrier and other components of the pharmaceutical composition is determined based on the absence of a significant negative impact on the desired biological properties of the active antibody-based molecules of the present invention (e.g., a less than significant effect on antigen binding (e.g., 10% or less relative inhibition, 5% or less relative inhibition, etc.)).

[1075] The pharmaceutical compositions of the present invention may also contain pharmaceutically acceptable antioxidants, such as (1) water-soluble antioxidants, such as ascorbic acid, cysteine ​​hydrochloride, sodium bisulfate, sodium metabisulfite, sodium sulfite, etc.; (2) oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate, α-tocopherol, etc.; and (3) metal chelating agents, such as citric acid, ethylenediaminetetraacetic acid (EDTA), sorbitol, tartaric acid, phosphoric acid, etc.

[1076] The pharmaceutical compositions of the present invention may also contain isotonic agents, such as sugars, polyols, such as mannitol, sorbitol, glycerol, or sodium chloride.

[1077] The pharmaceutical compositions of the present invention may also contain one or more excipients suitable for the chosen route of administration, such as preservatives, wetting agents, emulsifiers, dispersants, or buffers, which may improve the shelf life or efficacy of the pharmaceutical composition. The antibodies of the present invention may be prepared with a carrier that protects the antibody from rapid release, such as a controlled-release formulation, including implants, transdermal patches, and microencapsulated delivery systems. Such carriers may include gelatin, glyceryl monostearate, glyceryl distearate, biodegradable, biocompatible polymers (e.g., ethylene vinyl acetate, polyanhydride, polyglycolic acid, collagen, polyorthoesters, and polylactic acid alone or in combination with waxes), or other substances known in the art. Methods for preparing such formulations are generally known to those skilled in the art. See, for example, *SUSTAINED AND CONTROLLED RELEASE DRUG DELIVERY SYSTEMS*, JR Robinson, ed., MarcelDekker, Inc., New York, 1978.

[1078] In one embodiment, the antibody of the present invention can be formulated to ensure proper distribution in vivo. Pharmaceutically acceptable carriers for parenteral administration include sterile aqueous solutions or dispersions, as well as sterile powders for the provisional preparation of sterile injectable solutions or dispersions. The use of such media and reagents for pharmaceutically active substances is known in the art.

[1079] Injectable pharmaceutical compositions must generally be sterile and stable under the conditions of preparation and storage. The composition can be formulated as a solution, microemulsion, liposome, or other ordered structure suitable for achieving high drug concentrations. The carrier can be an aqueous or non-aqueous solvent or dispersion medium comprising, for example, water, ethanol, polyols (e.g., glycerol, propylene glycol, polyethylene glycol, etc.) and suitable mixtures thereof, vegetable oils (e.g., olive oil), and injectable organic esters (e.g., ethyl oleate). Suitable flowability can be maintained, for example, by using coatings (e.g., lecithin), in the case of dispersions by maintaining the desired particle size, and by using surfactants. In many cases, isotonic agents, such as sugars, polyols (e.g., glycerol, mannitol, sorbitol), or sodium chloride, will be preferably included in the composition. Prolonged absorption of the injectable composition can be achieved by including a delayed-absorption agent (e.g., monostearate and gelatin) in the composition. Sterile injectable solutions can be prepared by incorporating the desired amount of the active compound with one or a combination of the ingredients listed above (as needed) into a suitable solvent, followed by sterile microfiltration. Typically, dispersions are prepared by incorporating the active compound into a sterile carrier containing a basic dispersion medium and other desired components. In the case of sterile powders used to prepare sterile injectable solutions, some examples of preparation methods are vacuum drying and freeze-drying (lyophilization), which produce a powder containing the active ingredient plus any additional desired components from its previously sterile filtered solution.

[1080] For parenteral administration, the pharmaceutical preparations of the present invention are typically formulated together with a pharmaceutical carrier in an injectable dose of a physiologically acceptable diluent, such as water, oil, saline, glycerin, or ethanol. Additionally, excipients may be present in the composition, such as wetting agents or emulsifiers, surfactants, pH buffers, etc. Other components of the pharmaceutical composition are of petroleum, animal, plant, or synthetic origin. Peanut oil, soybean oil, and mineral oil are examples of suitable substances. Generally, glycols (e.g., propylene glycol or polyethylene glycol) are preferred liquid carriers, particularly for injectable solutions. The pharmaceutical preparations of the present invention can be administered in the form of reservoir injections or implants, formulated in a manner that allows for sustained release of the active ingredient.

[1081] Typically, compositions are prepared as injectable formulations, as liquid solutions or suspensions; they can also be prepared in solid forms suitable for dissolving or suspending in a liquid carrier prior to injection. Formulations may also be emulsified or encapsulated in liposomes or microparticles (e.g., polylactide, polyglycolic acid, or copolymers) to enhance the excipient effect (Langer, et al., Science 249:1527 (1990); Hanes, et al., Advanced Drug Delivery Reviews 28:97-119 (1997), which are incorporated herein by reference in their entirety). Additional formulations suitable for other routes of administration include intranasal and pulmonary formulations, suppositories, and transdermal applications.

[1082] In one embodiment, the composition comprises an anti-MuSK antibody (or antigen-binding fragment) containing: a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 153, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain (3B2g2m1) comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 195.

[1083] In one embodiment, the composition comprises an anti-MuSK antibody (or antigen-binding fragment) containing: a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 153, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain (3B2g1m1) comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 183.

[1084] In one embodiment, the anti-MuSK antibody (or antigen-binding fragment) comprises: a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 154, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain (3B2g1m2) comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 183.

[1085] In one embodiment, the anti-MuSK antibody (or antigen-binding fragment) comprises: a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 154, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain (3B2g2m2) comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 195.

[1086] In one embodiment, the anti-MuSK antibody (or antigen-binding fragment) comprises: a heavy chain variable domain comprising CDR-H1 of SEQ ID NO: 147, CDR-H2 of SEQ ID NO: 150, and CDR-H3 of SEQ ID NO: 156, and a light chain variable domain comprising CDR-L1 of SEQ ID NO: 159, CDR-L2 of SEQ ID NO: 172, and CDR-L3 of SEQ ID NO: 183 (3B2).

[1087] In a preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235.

[1088] The heavy-chain variable structural domain contains:

[1089] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1090] - Contains a CDR-H2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 153, and

[1091] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[1092] The variable structural domain of the light chain contains:

[1093] - Contains a CDR-L1 amino acid sequence that is SEQ ID NO: 159 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1094] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[1095] - Contains a CDR-L3 amino acid sequence (3B2g2m1) with SEQ ID NO: 195 or with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195.

[1096] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1097] In a more preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235.

[1098] The heavy-chain variable structural domain contains:

[1099] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1100] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 153 or SEQ ID NO: 153, and

[1101] - Contains the CDR-H3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 156 or SEQ ID NO: 156, and

[1102] The variable structural domain of the light chain contains:

[1103] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1104] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1105] - Contains the CDR-L3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 195 or SEQ ID NO: 195.

[1106] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1107] In a preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a constant Fc region of wild-type human IgG, a heavy chain variable domain, and a light chain variable domain, wherein the constant Fc region of wild-type human IgG comprises SEQ ID NO: 266 or SEQ ID NO: 267; the heavy chain variable domain and the light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[1108] The heavy-chain variable structural domain contains:

[1109] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1110] - Contains a CDR-H2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 153, and

[1111] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[1112] The variable structural domain of the light chain contains:

[1113] - Contains a CDR-L1 amino acid sequence that is SEQ ID NO: 159 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1114] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[1115] - Contains a CDR-L3 amino acid sequence (3B2g2m1) with SEQ ID NO: 195 or with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195.

[1116] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1117] In a more preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a constant Fc region of wild-type human IgG, a heavy chain variable domain, and a light chain variable domain, wherein the constant Fc region of wild-type human IgG comprises SEQ ID NO: 266 or SEQ ID NO: 267; the heavy chain variable domain and the light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[1118] The heavy-chain variable structural domain contains:

[1119] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1120] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 153 or SEQ ID NO: 153, and

[1121] - Contains the CDR-H3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 156 or SEQ ID NO: 156, and

[1122] The variable structural domain of the light chain contains:

[1123] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1124] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1125] - Contains the CDR-L3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 195 or SEQ ID NO: 195.

[1126] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1127] In a preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a constant Fc region of wild-type human IgG (in which L234A and / or L235A substitutions according to the EU numbering system are introduced into the Fc region), a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267; the heavy chain variable domain and the light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[1128] The heavy-chain variable structural domain contains:

[1129] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1130] - Contains a CDR-H2 amino acid sequence having 1, 2, 3, 4, or 5 amino acid changes relative to SEQ ID NO: 153, and

[1131] - Contains SEQ ID NO: 156 or a CDR-H3 amino acid sequence (3B2g2m1) with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[1132] The variable structural domain of the light chain contains:

[1133] - Contains a CDR-L1 amino acid sequence that is SEQ ID NO: 159 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1134] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[1135] - Contains a CDR-L3 amino acid sequence (3B2g2m1) with SEQ ID NO: 195 or with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195.

[1136] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1137] In a more preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a constant Fc region of wild-type human IgG (in which L234A and / or L235A substitutions according to the EU numbering system are introduced into the Fc region), a heavy chain variable domain, and a light chain variable domain, wherein the wild-type human IgG constant Fc region comprises SEQ ID NO: 266 or SEQ ID NO: 267; the heavy chain variable domain and the light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 235, and

[1138] The heavy-chain variable structural domain contains:

[1139] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1140] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 153 or SEQ ID NO: 153, and

[1141] - Contains the CDR-H3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 156 or SEQ ID NO: 156, and

[1142] The variable structural domain of the light chain contains:

[1143] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1144] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1145] - Contains the CDR-L3 amino acid sequence (3B2g2m1) consisting of SEQ ID NO: 195 or SEQ ID NO: 195.

[1146] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1147] In one embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1148] a) A full-length heavy chain containing an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 268, and

[1149] b) A full-length light chain containing an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 269, and

[1150] c) One or more of the following mutations (all numbered according to the EU numbering system) have been introduced into the full-length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E23 3P replacement; L234V replacement; C236 deletion; G236E replacement; G236R replacement; G236K replacement; G237A replacement; P238A replacement; F243L replacement; D265A replacement; S267E replacement; H268A replacement; R292P replacement; Y300L replacement; K322A replacement; K322Q replacement; A327Q replacement; L328F replacement; L328R replacement; P329A replacement; P329G replacement; A330L replacement; A330S replacement; P331S replacement; I332E replacement; P396L replacement; or each combination of mutations in the fourth embodiment of this application described above, preferably L234A or L235A, more preferably L234A and L235A.

[1151] In one embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1152] a) A full-length heavy chain containing SEQ ID NO: 268, and

[1153] b) Contains a full-length light chain of SEQ ID NO: 269, and

[1154] c) The full-length heavy chain contains L234A and L235A mutations numbered according to the EU numbering system.

[1155] In one embodiment, the anti-MuSK antibody or its antigen-binding fragment contains:

[1156] a) Containing a full-length heavy chain of SEQ ID NO: 270, and

[1157] b) Contains a full-length light chain of SEQ ID NO: 271, and

[1158] c) The full-length heavy chain contains L234A and L235A mutations numbered according to the EU numbering system.

[1159] In one implementation, the binding to the same ligand is reduced by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or becomes undetectable compared to the binding of an antibody to an effector ligand that does not have any amino acid substitutions in its constant Fc region of human IgG.

[1160] In one embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1161] a) A full-length heavy chain containing an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 270, and

[1162] b) A full-length light chain containing an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 271, and

[1163] c) One or more of the following mutations (all numbered according to the EU numbering system) have been introduced into the full-length heavy chain: N297A substitution; N297Q substitution; L234A substitution; L234D substitution; L234E substitution; L234G substitution; L234H substitution; L234F substitution; L234K substitution; L234Q substitution; L234R substitution; L234S substitution; L234T substitution; L235A substitution; L235D substitution; L235E substitution; L235F substitution; L235G substitution; L235V substitution; L235H substitution; L235I substitution; L235K substitution; L235R substitution; L235S substitution; L235T substitution; L235Q substitution; L237A substitution; S239D substitution; E23 3P replacement; L234V replacement; C236 deletion; G236E replacement; G236R replacement; G236K replacement; G237A replacement; P238A replacement; F243L replacement; D265A replacement; S267E replacement; H268A replacement; R292P replacement; Y300L replacement; K322A replacement; K322Q replacement; A327Q replacement; L328F replacement; L328R replacement; P329A replacement; P329G replacement; A330L replacement; A330S replacement; P331S replacement; I332E replacement; P396L replacement; or each combination of mutations in the fourth embodiment of this application described above, preferably L234A or L235A, more preferably L234A and L235A.

[1164] In one embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising:

[1165] a) A full-length heavy chain, comprising SEQ ID NO: 270, and

[1166] b) A full-length light chain containing SEQ ID NO: 271, and

[1167] c) The full-length heavy chain contains L234A and L235A mutations numbered according to the EU numbering system.

[1168] In one implementation, the binding to the same ligand is reduced by at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or becomes undetectable compared to the binding of an antibody to an effector ligand that does not have any amino acid substitutions in its constant Fc region of human IgG.

[1169] In a preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[1170] The heavy-chain variable structural domain contains:

[1171] - Contains a CDR-H1 amino acid sequence that is SEQ ID NO: 147 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147.

[1172] - Contains a CDR-H2 amino acid sequence that is SEQ ID NO: 150 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and

[1173] - Contains a CDR-H3 amino acid sequence (3B2) with SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and

[1174] The variable structural domain of the light chain contains:

[1175] - Contains a CDR-L1 amino acid sequence that is SEQ ID NO: 159 or has 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159.

[1176] - Contains SEQ ID NO: 172 or a CDR-L2 amino acid sequence having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and

[1177] - Contains a CDR-L3 amino acid sequence (3B2) with SEQ ID NO: 183 or with 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183.

[1178] In one implementation, the similarity or identity is at least 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, and 99%.

[1179] In a more preferred embodiment, the composition comprises an antibody or antigen-binding fragment that binds to human muscle-specific tyrosine protein kinase (MuSK), comprising a heavy chain variable domain and a light chain variable domain, wherein the heavy chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 202, and the light chain variable domain comprises an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 203.

[1180] The heavy-chain variable structural domain contains:

[1181] - Contains the CDR-H1 amino acid sequence consisting of SEQ ID NO: 147 or SEQ ID NO: 147.

[1182] - Contains the CDR-H2 amino acid sequence consisting of SEQ ID NO: 150 or SEQ ID NO: 150, and

[1183] - Contains the CDR-H3 amino acid sequence (3B2) consisting of SEQ ID NO: 156 or SEQ ID NO: 156, and

[1184] The variable structural domain of the light chain contains:

[1185] - Contains the CDR-L1 amino acid sequence consisting of SEQ ID NO: 159 or SEQ ID NO: 159.

[1186] - Contains the CDR-L2 amino acid sequence consisting of SEQ ID NO: 172 or SEQ ID NO: 172, and

[1187] - Contains the CDR-L3 amino acid sequence consisting of SEQ ID NO: 183 or SEQ ID NO: 183 (3B2).

[1188] In...

Claims

1. An antibody-based molecule for use in preventing, delaying, reversing or treating a disease or disorder caused by synaptogyrin deficiency in a human subject.

2. The antibody-based molecule for use according to claim 1, wherein the antibody-based molecule is an anti-MuSK antibody.

3. The antibody-based molecule for use according to claim 1 or claim 2, wherein the antibody-based molecule binds to the MuSK Frizzled (Fz)-like domain sequence of SEQ ID NO:

130.

4. The antibody-based molecule for use according to any one of claims 1 to 3, wherein the disease or disorder caused by synaptogyrin deficiency is such that the deficient synaptogyrin can no longer bind its receptor LRP4.

5. The antibody-based molecule for use according to any one of claims 1 to 3, wherein the disease or disorder caused by synaptogyrin deficiency is such that the deficient synaptogyrin can still bind its natural receptor LRP4, but has impaired / reduced affinity and / or has a lower ability to activate MuSK phosphorylation compared to its corresponding wild-type synaptogyrin.

6. The antibody-based molecule for use according to claim 5, wherein the antibody-based molecule elicits a higher ability to activate MuSK phosphorylation compared to the deficient synaptogyrin.

7. The antibody-based molecule for use according to any one of claims 1 to 6, wherein the disease or disorder caused by synaptogyrin deficiency is such that the expression level of MuSK is lower than in a subject without synaptogyrin deficiency.

8. The antibody-based molecule for use according to claim 7, wherein the antibody-based molecule elicits a higher ability to activate MuSK phosphorylation compared to the deficient synaptogyrin.

9. The antibody-based molecule for use according to any one of claims 1 to 8, wherein the disease or disorder caused by synaptogyrin deficiency is such that the binding of LRP4 to MuSK is impaired / antagonized, which in turn leads to impaired MuSK activation.

10. The antibody-based molecule for use according to claim 9, wherein the antibody-based molecule elicits a higher ability to activate MuSK phosphorylation compared to the deficient synaptogyrin.

11. The antibody-based molecule for use according to any one of the preceding claims, which is an agonist MuSK antibody and / or has reduced or eliminated effector function.

12. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule induces MuSK phosphorylation.

13. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule comprises a heavy chain variable region (VH) and a light chain variable region (VL) according to those identified in Table 3 and / or CDRs according to those identified in Table 1 or 2.

14. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule comprises a heavy chain variable domain (VH) and a light chain variable domain (VL), wherein: the VH comprises: the VL comprises: - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147, - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and the VL comprises: - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159, - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

15. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule comprises: - a heavy chain variable domain (VH) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 202, and - a light chain variable domain (VL) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 203 (3B2).

16. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule comprises: - a heavy chain variable domain (VH) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 202, and - a light chain variable domain (VL) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 203, and wherein: the heavy chain variable domain comprises: - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147, - a CDR-H2 amino acid sequence comprising SEQ ID NO: 150 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 150, and - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156, and the light chain variable domain comprises: - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159, - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and - a CDR-L3 amino acid sequence comprising SEQ ID NO: 183 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 183 (3B2).

17. The antibody-based molecule for use according to any one of the preceding claims, wherein the antibody-based molecule comprises: - a full length heavy chain comprising SEQ ID NO: 282, - a full length light chain comprising SEQ ID NO: 283, and wherein: - the full length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

18. The antibody-based molecule for use according to any one of claims 1 to 13, wherein the antibody-based molecule comprises a heavy chain variable region (VH) and a light chain variable region (VL), wherein: the VH comprises: - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147, - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156 (3B2g2m1), and the VL comprises: - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159, - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

19. The antibody-based molecule for use according to any one of claims 1 to 13 and 18, wherein the antibody-based molecule comprises: - a heavy chain variable region (VH) comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO: 234, and - a light chain variable region (VL) comprising an amino acid sequence having at least 80% identity or similarity to SEQ ID NO:

235.

20. The antibody-based molecule for use according to any one of claims 1 to 13 and 18 to 19, wherein the antibody-based molecule comprises: - a heavy chain variable region (VH) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 234, and - a light chain variable region (VL) comprising an amino acid sequence which is at least 80% identical or similar to SEQ ID NO: 235, and wherein: the VH comprises: - a CDR-H1 amino acid sequence comprising SEQ ID NO: 147 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 147, - a CDR-H2 amino acid sequence comprising SEQ ID NO: 153 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 153, and - a CDR-H3 amino acid sequence comprising SEQ ID NO: 156 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 156 (3B2g2m1), and the VL comprises: - a CDR-L1 amino acid sequence comprising SEQ ID NO: 159 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 159, - a CDR-L2 amino acid sequence comprising SEQ ID NO: 172 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 172, and - a CDR-L3 amino acid sequence comprising SEQ ID NO: 195 or having 1, 2, 3, 4 or 5 amino acid changes relative to SEQ ID NO: 195 (3B2g2m1).

21. The antibody-based molecule for use according to any one of claims 1 to 13 and 18 to 20, wherein the antibody-based molecule comprises: - a full length heavy chain comprising SEQ ID NO: 268, and - a full length light chain comprising SEQ ID NO: 269, and - wherein the full length heavy chain comprises L234A and L235A mutations, numbered according to the EU numbering system.

22. A polynucleotide for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said polynucleotide comprising a nucleotide sequence encoding the antibody-based molecule of any one of claims 1 to 21 or a VH or VL or CDR thereof.

23. An expression vector for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said expression vector comprising the polynucleotide of claim 22, preferably operably linked to a regulatory region allowing expression of the antibody or antigen binding fragment thereof or a VH or VL or CDR thereof in a host cell or a cell-free expression system.

24. A host cell or a cell-free expression system for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said host cell or cell-free expression system comprising the expression vector of claim 23.

25. A composition for use in preventing, delaying, reversing or treating a disease or disorder caused by synuclein glycan deficiency in a human subject, said composition comprising an antibody-based molecule as defined in any one of claims 1 to 21, a polynucleotide as defined in claim 22, an expression vector as defined in claim 23 or a host cell or cell-free expression system as defined in claim 24, preferably said composition comprises at least one pharmaceutically acceptable carrier or excipient.

26. The antibody-based molecule, polynucleotide, expression vector or composition for use according to any one of the preceding claims, wherein the disease or disorder is characterized by impaired neuromuscular transmission and / or denervation at the NMJ (neuromuscular junction).

27. The antibody-based molecule, polynucleotide, expression vector or composition for use according to any one of the preceding claims, wherein the disease is a neuromuscular disease.

28. The antibody-based molecule, polynucleotide, expression vector or composition for use according to claim 27, wherein the neuromuscular disease is selected from the group consisting of amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), myasthenia gravis (MG), congenital myasthenia, congenital myasthenic syndrome (CMS), Lambert-Eaton myasthenic syndrome (LEMS), Lyme disease, poliomyelitis, post-polio, heavy metal poisoning, Kennedy syndrome, adult-onset Tay-Sachs disease, hereditary spastic paraplegia, multifocal neuropathy, cervical spondylosis, extramedullary tumor with compressive radiculopathy and myelopathy, inclusion body myositis, progressive bulbar palsy, progressive muscular atrophy, motor neuron syndrome and thyrotoxic myopathy.

29. The antibody-based molecule, polynucleotide, expression vector, pharmaceutical composition for use according to claim 28, wherein the disease is CMS, preferably the disease is presynaptic CMS or synuclein glycan-induced CMS.

30. The antibody-based molecule, polynucleotide, expression vector or pharmaceutical composition for use according to claim 28, wherein the disease is ALS or SMA.

31. The antibody-based molecule, polynucleotide, expression vector or pharmaceutical composition for use according to any one of the preceding claims, wherein the subject suffers from at least one symptom selected from the group consisting of early postnatal onset of disease, impaired neuromuscular performance, muscle weakness, fatigue, slow muscle fiber predominance, NMJ disorganization leading to remodeling, functional denervation, increased subsynaptic folds and premature death.

32. The antibody-based molecule, polynucleotide, expression vector or pharmaceutical composition for use according to any one of the preceding claims, wherein administration of the antibody-based molecule, polynucleotide, expression vector or pharmaceutical composition to the human subject results in one or more of the following therapeutic effects: - an increase and maintenance of the number or percentage of fully innervated NMJs in the subject, - an improvement in motor performance and / or grip strength of the subject, - an improvement in muscle contraction properties at the NMJ of the subject, - an improvement in muscle resistance to fatigue at the NMJ of the subject, - an induction of muscle weight increase at the NMJ of the subject, - an increase in muscle mass of the subject, - an increase in muscle volume of the subject, - an increase in nerve terminal area and complexity, acetylcholine perimeter and / or terminal plate area, and / or - a stabilization of the condition.

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