Rare Disease Report

FDA Asks Sarepta For More Data

JUNE 07, 2016
James Radke, PhD
Sarepta Therapeutics announced that the FDA has asked for some more data as the agency continues to decide on whether or not to approve eteplirsen for the treatment of boys with Duchenne muscular dystrophy amenable to exon 51 skipping treatment. 
Details are limited but the company did state that the FDA has requested that Sarepta provide “dystrophin data, as measured by western blot, from biopsies already obtained from the ongoing confirmatory study of eteplirsen (Promovi), as part of its ongoing evaluation of the eteplirsen New Drug Application (NDA).” Sarepta stated they plan to submit data from 13 patient biopsy samples at baseline and week 48 of eteplirsen treatment.
As we wrote 10 days ago, the PDUFA date (May 26) for eteplirsen came and went without the FDA making a decision on the drug. And as we also wrote, this is not the first delay that the FDA has announced for the review of this drug. Initially, there was an Advisory Committee Meeting scheduled for January 22 but that got delayed due to a snow storm that hit the Washington DC area. A month and a half later, the FDA announced the new meeting would take place April 25th.  During that meeting, a record 52 people spoke during the public forum in favor of the drug being approved while the FDA briefing documents for that meeting were highly critical of the data. The voting at that meeting was mixed with half the committee in favor of the drug and half of them not.

FDA has had the NDA since August 25, 2015. A normal review process for an orphan drug is 6 months.

The the latest request is a good thing?

Probably. The more data the FDA can have, the better.

Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is caused by lack of a functional dystrophin protein, a protein that helps keep muscle cells intact. Patients with progressive muscle disorder experience symptoms in early childhood, losing the ability to walk as early as age 10. These patients, mostly boys, experience life-threatening heart and lung complications in their late teens and twenties.
There are many subsets of the DMD population based on the type of mutation found in the dystrophin gene. There are currently no drugs approved in the US to directly treat any of these groups.
Eteplirsen is designed to enable RNA to skip over the part of the DNA with a problematic mutation, enabling a functional (though shorter) dystrophin protein to be produced. Specifically, the drug skips a portion of the DNA known as exon 51. About 13% of the 35,000 DMD patients in the US and Europe have a mutation that might theoretically respond to a drug such as eteplirsen. According to Sarepta, the drug’s developer, up to 80% of patients with DMD might respond to this class of drugs, others of which are in development.

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