Several Food and Drug Administration staffers were leaning heavily toward rejecting a highly watched gene therapy from Sarepta Therapeutics, according to a report Thursday that sent SRPT stock into a dive.
That gene therapy is in testing for treating the muscle-wasting disease Duchenne muscular dystrophy. Duchenne is marked by a lack of dystrophin protein in patients' bodies. Without that protein, the muscles degenerate. Sarepta's gene therapy prompts the body to make a miniature version of that protein, called microdystrophin.
But some FDA staffers questioned whether the presence of microdystrophin in patients' blood proves the gene therapy is doing its job, according to Stat News. Sarepta is asking for accelerated approval based on microdystrophin levels and functional improvements.
The battle is likely to play out at an FDA advisory committee meeting next month. Independent experts will weigh the merits and risks of the drug.
"We acknowledge this may add uncertainty, if indeed there is more debate within the agency, and could make the briefing documents ahead of the advisory committee more mixed," RBC Capital Markets analyst Brian Abrahams said in a note to clients.
On today's stock market, SRPT stock tumbled 9.4% to close at 124.72.
SRPT Stock: Internal Strife At FDA?
Inside the FDA, some staff members decided to reject Sarepta's gene therapy. But Peter Marks, director of the Center for Biologics Evaluation and Research, reportedly stepped in. He directed staff to schedule an advisory committee meeting for May 12.
The advisory committee meeting will be key. Sarepta's controversial Duchenne muscular dystrophy drug, Exondys 51, gained accelerated approval. It came after an advisory committee meeting that featured comments from numerous patients and advocates.
"We continue to believe the support of DMD patient advocacy groups, such as PPMD (Parent Project Muscular Dystrophy), will play an influential role as the group is likely to make compelling testimonies in favor of approval at the advisory committee meeting," SVB Securities analyst Joseph Schwartz said in his note to clients. He has an outperform rating on SRPT stock.
Importantly, both Schwartz and Abrahams say Sarepta believes the discord at the FDA came from Wilson Bryan. Bryan is a more conservative staffer who retired from the FDA earlier this year. Since then, CBER's Marks and Celia Witten, the group's deputy director, have been closely involved with the Sarepta review, Schwartz said.
Confirmatory Study Already Underway
RBC's Abrahams expects the FDA decision on Sarepta's gene therapy to set an important precedent at the FDA. Marks is a vocal proponent of using the accelerated approval pathway to bring more gene therapies to market faster.
Abrahams also has an outperform rating on SRPT stock.
The company has already finished enrolling patients in a final-phase study called Embark with results due in the fourth quarter. Also, if Sarepta's therapy gains accelerated approval, the Embark study will act as a necessary confirmatory study, SVB's Schwartz said.
Follow Allison Gatlin on Twitter at @IBD_AGatlin.
