FDA Approves First Drug for Duchenne Muscular Dystrophy

On Sept. 19, 2016, FDA announced that it has granted accelerated approval to Exondys 51 (eteplirsen), an injection for the treatment of Duchenne muscular dystrophy (DMD). The drug is marketed by Sarepta Therapeutics in the United States and is currently the only approved treatment for DMD. In light of the approval, Sarepta shares catapulted 76%, Seeking Alpha reported.

The drug spurred controversy earlier this year after an FDA panel questioned its efficacy. In an executive summary, FDA noted the data from eteplirsen trials “did not provide statistical evidence to support the efficacy of eteplirsen.” The committee expressed concern that the drug did not significantly increase the production of dystrophin, a protein associated with strengthening muscle fibers to increase movement, compared with placebo. Another key issue was the small size of the eteplirsen study, which FDA said may not accurately represent the DMD population on whole.

Because of this concern, FDA is requiring Sarepta to conduct an additional trial to confirm eteplirsen’s clinical benefit, the agency said in a press announcement. This new study will assess whether or not the drug improves motor function in patients with a mutation of the dystrophin gene amendable to exon 51 skipping. FDA said it can revoke the approval of eteplirsen if this new trial fails to demonstrate clinical benefit.

“In rare diseases, new drug development is especially challenging due to the small numbers of people affected by each disease and the lack of medical understanding of many disorders,” Janet Woodcock, MD, director of the FDA’s Center for Drug Evaluation and Research, said in a statement. “Accelerated approval makes this drug available to patients based on initial data, but we eagerly await learning more about the efficacy of this drug through a confirmatory clinical trial that the company must conduct after approval.”

Pressure to approve drugs for DMD has increased recently as patient advocacy groups lobby FDA. In a letter to Woodcock, dated August 11, 2016, the Parent Project Muscular Dystrophy (PPMD) asked FDA to provide clear communication on the status of muscular dystrophy drugs like eteplirsen. PPMD later released a statement in response to FDA’s approval of eteplirsen saying it was “beyond thrilled” with the agency's decision.

Source: FDA, Seeking Alpha, PPMD