Sarepta Therapeutics will restart a clinical trial previously put on hold over safety concerns after reaching an agreement with the Food and Drug Administration on changes to the study’s plan.
Moving forward, the biotechnology company will expand patient monitoring in the trial to watch for low magnesium levels, which had resulted in a serious adverse reaction in one study participant that led the FDA to suspend testing earlier this year.
“We will implement the changes in the protocol to resume dosing in the U.S. as quickly as possible,” said Louise Rodino-Klapac, Sarepta’s chief scientific officer, in a company statement Tuesday.
The drug being tested, called SRP-5051, treats Duchenne muscular dystrophy and is meant to be a more potent successor to Sarepta’s approved medicine Exondys 51. Both treatments work by what’s known as “exon-skipping” and are designed for the roughly 13% of Duchenne patients who have mutations to a gene that encodes for the muscle-building protein that they lack.
SRP-5051 is based on a different chemistry platform than Exondys 51 that Sarepta claims could improve its effectiveness and allow for less frequent dosing. It’s the most advanced of six experimental Duchenne medicines Sarepta is advancing based on the same technology.
But in June, trial investigators reported that one patient in the SRP-5051 trial had experienced notably low magnesium levels, which can lead to heart risks and seizures. That case followed others which had been judged less serious.
In response, the FDA halted further dosing of SRP-5051 and asked Sarepta to provide additional information, which the company has since provided.
“Our monitoring plan is designed to mitigate the risks of hypomagnesemia,” added Rodino-Klapac, in Sarepta’s statement. “[The trial] has continued enrolling participants outside the U.S., and we remain on track to complete enrollment by the end of 2022.”
Sarepta currently sells three medicines for Duchenne, each of which are approved for different subsets of patients. Collectively, they earned the company $400 million in sales through the first six months of 2022.
But its most closely watched program is an experimental gene therapy for Duchenne, for which it intends to apply this fall for FDA approval. In December 2019, Roche paid Sarepta $1.2 billion for rights to the therapy in markets outside the U.S.