Lawlor MW, Schoser B, Margeta M, Sewry CA, Jones KA, Shieh PB, Kuntz NL, Smith BK, Dowling JJ, Müller-Felber W, Bönnemann CG, Seferian AM, Blaschek A, Neuhaus S, Foley AR, Saade DN, Tsuchiya E, Qasim UR, Beatka M, Prom MJ, Ott E, Danielson S, Krakau P, Kumar SN, Meng H, Vanden Avond M, Wells C, Gordish-Dressman H, Beggs AH, Christensen S, Conner E, James ES, Lee J, Sadhu C, Miller W, Sepulveda B, Varfaj F, Prasad S, and Rico S
Background: X-linked myotubular myopathy (XLMTM) is a rare, life-threatening congenital muscle disease caused by mutations in the MTM1 gene that result in profound muscle weakness, significant respiratory insufficiency, and high infant mortality. There is no approved disease-modifying therapy for XLMTM. Resamirigene bilparvovec (AT132; rAAV8-Des-hMTM1) is an investigational adeno-associated virus (AAV8)-mediated gene replacement therapy designed to deliver MTM1 to skeletal muscle cells and achieve long-term correction of XLMTM-related muscle pathology. The clinical trial ASPIRO (NCT03199469) investigating resamirigene bilparvovec in XLMTM is currently paused while the risk:benefit balance associated with this gene therapy is further investigated., Methods: Muscle biopsies were taken before treatment and 24 and 48 weeks after treatment from ten boys with XLMTM in a clinical trial of resamirigene bilparvovec (ASPIRO; NCT03199469). Comprehensive histopathological analysis was performed., Findings: Baseline biopsies uniformly showed findings characteristic of XLMTM, including small myofibres, increased internal or central nucleation, and central aggregates of organelles. Biopsies taken at 24 weeks post-treatment showed marked improvement of organelle localisation, without apparent increases in myofibre size in most participants. Biopsies taken at 48 weeks, however, did show statistically significant increases in myofibre size in all nine biopsies evaluated at this timepoint. Histopathological endpoints that did not demonstrate statistically significant changes with treatment included the degree of internal/central nucleation, numbers of triad structures, fibre type distributions, and numbers of satellite cells. Limited (predominantly mild) treatment-associated inflammatory changes were seen in biopsy specimens from five participants., Interpretation: Muscle biopsies from individuals with XLMTM treated with resamirigene bilparvovec display statistically significant improvement in organelle localisation and myofibre size during a period of substantial improvements in muscle strength and respiratory function. This study identifies valuable histological endpoints for tracking treatment-related gains with resamirigene bilparvovec, as well as endpoints that did not show strong correlation with clinical improvement in this human study., Funding: Astellas Gene Therapies (formerly Audentes Therapeutics, Inc.)., Competing Interests: Declaration of interests MWL has received research funding from Astellas Gene Therapies∗ to his academic institution (Medical College of Wisconsin) and to his company (Diverge Translational Science Laboratory) for work related to the present manuscript; has received research grants or contracts to his academic institution (Medical College of Wisconsin) from Solid Biosciences, Kate Therapeutics, Taysha Therapeutics, Ultragenyx, and Prothelia; has received consulting fees from Astellas Gene Therapies∗, Encoded Therapeutics, Modis Therapeutics, Lacerta Therapeutics, AGADA Biosciences, Dynacure, Affinia, Voyager, BioMarin, Locanabio, and Vertex Pharmaceuticals; has received speaker fees and reimbursement for travel related to sponsored research from Astellas Gene Therapies∗; has received personal fees for scientific advisory board participation for Astellas Gene Therapies∗ and Solid Biosciences, and his institution has received payment from Taysha Therapeutics for his advisory board participation; he is currently CEO, founder, and owner of Diverge Translational Science Laboratory, which continues to work under contracts from many gene therapy companies including Astellas Gene Therapies∗, Solid Biosciences, Rocket Pharma, Kate Therapeutics, Carbon Biosciences, Dynacure, Nationwide Children's Hospital, Taysha Gene Therapies, and Ultragenyx. BS (Schoser) has received grants/contracts, honoraria, and support for attending meetings from Astellas Gene Therapies∗ has participated in Advisory Boards for Dynacure. MM has received personal fees and study funding to her institution from Astellas Gene Therapies∗ in relation to the present manuscript. CAS has received royalties from Elsevier for the book “Muscle Biopsy. A Practical Approach”. KAJ has received consulting fees from Astellas Gene Therapies∗ in relation to the present manuscript and other activities. PBS has received research funding from Astellas Gene Therapies∗ to support clinical trial investigations relating to the present manuscript; has received research contracts from Biogen, Dyne, Fulcrum, Pfizer, PTC Therapeutics, Reveragen, Sanofi, Sarepta, and Solid Biosciences; has received consulting fees from Alexion, Argenx, Biogen, Novartis Gene Therapies, Pfizer, UCB, and Sarepta; has received honoraria for lectures or presentations from Alexion, Argenx, Biogen, Catalyst, CSL Behring, Genentech, and Grifols; and has participated on Independent Data Monitoring Committees for Encoded Therapeutics, Excision BioTherapeutics, and Taysha. NLK reports research grants paid to her institution from AMO Pharma, Argenx, Astellas Gene Therapies∗, Biogen, Biohaven, Novartis, NS Pharma, Sarepta, Reveragen, Roche, and Scholar Rock; has received payment for educational presentations from Sarepta; and has participated in a Data Safety Monitoring Board for Sarepta and Advisory Boards for Argenx, BioMarin, Fibrogen, Roche, and Sarepta. BKS has received institutional research grants or contracts to serve as an INCEPTUS and ASPIRO study site from Astellas Gene Therapies∗. JJD has received research grants from NIH, CIHR, and Astellas Gene Therapies∗; has received support for attending annual meetings from the World Muscle Society (as Executive Board Member) and TREAT NMD (as Chair of Executive Board); and receives annual honoraria as a Scientific Advisory Board member for the RYR1 Foundation. WMF has received support for study materials and study personnel relating to the present manuscript from Astellas Gene Therapies∗; consulting fees from Sarepta, PTC Therapeutics, Novartis, and Roche; personal compensation from Novartis and Biogen, and institutional funding from Roche, for lectures; and has served on Scientific Advisory Boards for DGM and Glykogenosis e.V. CGB reports study funding relating to the present manuscript paid to NINDS; and has participated in data safety monitoring or advisory boards without financial compensation, in his capacity of representing NIH. AMS is a principal investigator in the ASPIRO study. AB has received speaker's honoraria from Pfizer and Roche; and has participated in advisory boards at for Pfizer and Roche. SN, ARF, DNS, ET, and URQ report no conflicts of interests. MB and MJP are full-time employees of Diverge Translational Science Laboratory. EO and SD report no conflicts of interest. PK is a full-time employee of Diverge Translational Science Laboratory. SNK report no conflicts of interest. HM is a full-time employee of Diverge Translational Science Laboratory. MVA, CW, and HGD report no conflicts of interest. AHB received study funding relating to the present manuscript; reports grants or contracts received from NIH, MDA (USA), and the Chan Zuckerberg Initiative, and from AFM Telethon, Alexion Pharmaceuticals Inc., Avidity, Dynacure SAS, Kate Therapeutics, and Pfizer Inc. He has received consulting fees from Astellas Gene Therapies∗, Dynacure, GLG Inc., Guidepoint Global, Kate Therapeutics, and Roche; has received support for attending meetings from Kate Therapeutics and MDA; holds equity in Kate Therapeutics and Kinea Bio, and is an inventor on a US patent describing a method for gene therapy of XLMTM. SC, EC, JL, CS, WM, BS (Sepulveda), FV are former employees of Astellas Gene Therapies∗. ESJ and SR are former employees and stockholders in Astellas Gene Therapies∗. SP was Chief Medical Officer and a stockholder in Astellas Gene Therapies∗ when the study was designed and initiated; he is no longer a stockholder and currently consults independently with a wide variety of companies and academic institutions primarily on Clinical Development matters. ∗Formerly Audentes Therapeutics, Inc., (Copyright © 2023. Published by Elsevier B.V.)