Eteplirsen Earns Accelerated Approval for Duchenne Muscular Dystrophy

The US Food and Drug Administration (FDA) has granted accelerated approval to Sarepta’s eteplirsen for the treatment of Duchenne muscular dystrophy (DMD) in patients with mutations amendable to exon 51 skipping.

The drug is the first approved treatment for DMD in the US.

The approval process for the drug, which will be marketed as Exondys 51, was not without complications. In April, an FDA advisory panel failed to recommend the drug for approval, citing lackluster data on dystrophin, a key biomarker of efficacy. The FDA had since requested 2 extensions on its decision deadline as pressure from advocacy groups mounted.

The accelerated approval means patients will have earlier access to the drug – which is administered as a once-weekly infusion – while the manufacturer completes a required confirmatory clinical trial to verify the predicted clinical benefit.

The FDA concluded that “the data submitted by the applicant demonstrated an increase in dystrophin production that is reasonably likely to predict clinical benefit in some patients with DMD who have a confirmed mutation of the dystrophin gene amenable to exon 51 skipping.” However, the agency also pointed out that a “clinical benefit of Exondys 51, including improved motor function, has not been established.” If the post-approval trial fails to show a clinical benefit, the FDA will begin proceedings to withdraw approval.

DMD drug development has been plagued by weak clinical trials and questionable clinical benefits. Nearly a year ago in November 2015, the FDA denied BioMarin Pharmaceutical’s drisapersen, meant to treat the same DMD variant as eteplirsen. The approval process has been complicated by a very vocal advocacy population, who showed up in the hundreds for eteplirsen’s public comment period.

Only recently has the light begun to show through. Early last month, the FDA granted priority review to Marathon’s deflazacort, meant to treat DMD regardless of genetic etiology. The drug met its primary endpoint of improved muscle strength in a randomized, double-blind, placebo-controlled study of 196 patients.

As for Exondys 51, Sarepta said it plans to launch the drug commercially immediately.

References

1. FDA grants accelerated approval to first drug for Duchenne muscular dystrophy [news release]. US FDA newsroom; September 19, 2016.
2. Sarepta Therapeutics Announces FDA Accelerated Approval of EXONDYS 51™ (eteplirsen) injection, an Exon Skipping Therapy to Treat Duchenne Muscular Dystrophy (DMD) Patients Amenable to Skipping Exon 51 [news release]. Cambridge, MA: Sarepta Therapeutics newsroom; September 19, 2016.