Distribution and Temporal Changes of Autoantibody-Mediated Pathogenic Mechanisms among Acetylcholine Receptor-Positive Myasthenia Gravis Patients

Objective: Given that acetylcholine receptor-positive (AChR+) myasthenia gravis (MG) is mediated by AChR-specific autoantibodies, the emergence of new therapeutics underscores the importance of investigating AChR-specific autoantibody repertoire. This study aimed to assess the distribution of AChR-specific autoantibody isotypes, IgG subclasses, and the pathogenic mechanisms they mediate in AChR+ MG patients. Furthermore, we investigated longitudinal changes in autoantibody repertoire and the associated pathogenic mechanisms. Methods: Serum samples (N=210) from 50 AChR+ generalized MG patients collected longitudinally over two years as part of the B-Cell Targeted Treatment in MG (BeatMG) study were evaluated using a set of cell-based assays. Results: In cross-sectional samples, IgA and IgM AChR-specific autoantibodies were observed in the co-occurrence of IgG in 10% and 12% of patients, respectively. Among them, 4% had all three isotypes. AChR-IgG1 was found in 67.4%, followed by IgG3 (21.7%) and IgG2 (17.4%). Complement was active in 84.8%, followed by AChR internalization (63%) and blocking (30.4%). Complement and AChR internalization were simultaneously active in 45.6%, complement and blocking were active in 10.8%, and all three pathomechanisms were active in 17.4%. Blocking alone was active in only 2.1%; AChR internalization alone was not found. Temporal fluctuations of autoantibody isotypes/ IgG subclasses and the associated pathogenic mechanisms were observed. Interpretation: These results demonstrate that a subset of patients have autoantibodies that can mediate pathogenic mechanisms and include isotypes/IgG subclasses that current therapeutics may not effectively target. Accordingly, defining individual patient AChR-specific autoantibody profiles may afford more accurate application of therapeutics designed to target specific autoantibody-mediated mechanisms. ### Competing Interest Statement KCO has received research support from Ra Pharma, now (UCB Pharma), Alexion Rare Disease (Astra Zeneca), Viela Bio (Horizon Therapeutics/Amgen), argenx, and Seismic Therapeutic. KCO is an equity shareholder of Cabaletta Bio. KCO has served on advisory boards for Roche, Merck (EMD Serono), and IgM Biosciences, and received speaking fees from Amgen and argenx. BR has been a consultant/advisor for Alexion (now part of AstraZeneca), Takeda, and argenx. Additionally, BR has received research support from the Martin Shubik Fund for IBM at Yale University, NIH, Abcuro Pharmaceuticals, Immunovant, Takeda. RJN has received research support from the NIH, Genentech, Alexion (Astra Zeneca), argenx, Annexon Biosciences, Ra Pharmaceuticals (now UCB), Myasthenia Gravis Foundation of America, Momenta (now Janssen), Immunovant, Grifols, and Viela Bio (Horizon Therapeutics, now Amgen). RJN has also served as a consultant/advisor for Alexion (Astra Zeneca), argenx, Cabaletta Bio, CSL Behring, Grifols, Ra Pharmaceuticals (now UCB Pharma), Immunovant, Momenta (now Janssen), Viela Bio (Horizon Therapeutics, now Amgen). The authors have no additional financial interests. All other authors declare no competing financial interests. ### Clinical Trial NCT02110706 ### Funding Statement This study was supported by the National Institute of Allergy and Infectious Diseases (NIAID) of the NIH under award numbers R01-AI114780 and R21-AI142198 (to KCO), and through an award provided by the Rare Diseases Clinical Research Consortia of the NIH and MGNet, under award number U54-NS115054 (to KCO). The BeatMG study was funded by the National Institute of Neurologic Disorders and Stroke (NINDS) of the NIH under award U01NS084495 (to RJN). The BeatMG study included additional infrastructure support which was provided under the following NINDS awards: U01NS077179 (Clinical Coordination Center), U01NS077352 (Data Coordination Center). FKH is supported by the Jackie McSpadden Postdoctoral Fellowship from the Myasthenia Gravis Foundation of America (MGFA). BR has received research support from the NIH, Martin Shubik Fund for IBM at Yale University, under award number R01NS132860. MCP is supported by the NIH T32 predoctoral training grant, under award number T32AI007019-46. BF is supported by the award of funds at the Medical University of Lodz to support international mobility of doctoral students under the program of the National Agency for Academic Exchange STER-Internationalisation of Doctoral Schools grant BPI/STE/2021/1/00032. The funders had no role in the decision to publish or in the preparation of the manuscript. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This study was approved by the Yale University Institutional Review Board. A centralized institutional review board and independent ethics committee approved the study protocol and all amendments. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. 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