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FDA Advisory Committee in Close Vote Backs Approval of Sarepta Therapeutics' DMD Gene Therapy

NEW YORK – In a close vote Friday, an advisory committee for the US Food and Drug Administration voted in favor of approving Sarepta Therapeutics' investigational gene therapy for Duchenne muscular dystrophy (DMD).

The FDA's Cellular, Tissue, and Gene Therapies Advisory Committee voted 8-6 in support of accelerated approval for SRP-9001 (delandistrogene moxeparvovec). Recommendations from the FDA's advisory committees are nonbinding, but the agency usually follows the advice of its independent expert panels.

The FDA is expected to issue a decision on Sarepta's SRP-9001 biologics license application (BLA) on May 29. "With the May 29 action date our top priority, we will work collaboratively with the FDA to complete the review of our BLA for SRP-9001," Sarepta President and CEO Doug Ingram said in a statement.

SRP-9001 is an adeno-associated virus vector-based gene therapy designed to treat ambulatory patients with DMD, a rare and inherited disorder characterized by progressive muscle weakness, and with a confirmed mutation in the DMD gene that results in a lack of the dystrophin protein. SRP-9001 delivers a gene that encodes for microdystrophin, an engineered protein developed by Sarepta that the firm has said can carry out the normal functions of dystrophin.

Sarepta is seeking accelerated approval based on change in expression of microdystrophin at 12 weeks after an infusion of SRP-9001 as a surrogate endpoint. The company submitted Phase II trial data to the FDA that showed the drug successfully increased the quantity of microdystrophin protein expression. However, when compared with a placebo group, the drug did not statistically significantly improve DMD patients' functional motor abilities over baseline as measured by the North Star Ambulatory Assessment rating scale. 

Ahead of the advisory committee meeting last week, reviewers from the FDA released a briefing document raising concerns about the extent to which microdystrophin functions similarly to other dystrophin proteins and safety issues seen with the therapy. During the advisory committee meeting, Sarepta showed data from natural history studies to argue that the drug did clinically benefit patients and showed that no patients died or discontinued treatment due to adverse events in trials. 

After weighing the divergent interpretations of FDA and Sarepta experts, the advisory committee members narrowly voted to recommend accelerated approval, while Sarepta continues to test the gene therapy in a Phase III trial that is expected to provide confirmatory data on the drug's efficacy.