Sanofi's biotech arm Genzyme has launched a legal challenge against Sarepta Therapeutics, alleging patent infringement in the production of the latter's Duchenne muscular dystrophy (DMD) treatment Elevidys (delandistrogene moxeparvovec-rokl). The lawsuit, filed late last week in the US District Court for the District of Delaware, claims that Sarepta's manufacturing process for its $3.2-million, one-time infusion treads on two of Genzyme's patents related to recombinant adeno-associated viral (rAAV) vector technologies.The dispute centres on US patent nos. 9,051,542 and 7,704,721, with claims on both set to expire on June 1, 2025. According to Genzyme, the patents cover crucial methods and compositions that prevent the aggregation of gene therapy virus particles during production. The company says its scientists invented a method to manufacture gene therapies that Sarepta allegedly mimics in the production of Elevidys."Manufacturing rAAV-based therapeutics is a highly technical, multi-phase process involving rAAV vector production, which includes the creation of the vector genome, or genetic payload carrying the transgene, encapsulation of the vector genome in a protein shell called a capsid, followed by purification and formulation. A major concern during production is that the rAAV vector particles will become insoluble and aggregate into clusters of viral particles, which can result in production difficulties and loss of vector functionality," the complaint notes.The timing of the lawsuit comes on the heels of Elevidys' recent label expansion. Initially approved by the FDA last year for ambulatory paediatric patients aged 4 through 5 years with DMD, Elevidys saw its indication broadened this past June to include both non-ambulatory boys with DMD and those aged four years and older. The expansion has been met with scrutiny, as it was enabled by an unusual decision from Peter Marks, director of the FDA's Center for Biologics Evaluation and Research (CBER), who essentially overruled other agency members.Sarepta's Elevidys generated $200.4 million in product revenue in 2023. The expanded label is expected to further boost sales, with Wall Street analysts anticipating strong continued performance. The company is scheduled to report its second quarter earnings on August 7.