FDA Giving SRP-9001, DMD Gene Therapy, Priority Review

Agency decision on treatment for ambulatory Duchenne patients possible in May

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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The U.S. Food and Drug Administration (FDA) has given priority review Sarepta Therapeutics‘ application seeking accelerated approval of SRP-9001 (delandistrogene moxeparvovec), the company’s experimental gene therapy for Duchenne muscular dystrophy (DMD) in patients who can walk.

An FDA decision is expected on or before May 29, 2023.

“We are delighted to announce that the FDA has accepted Sarepta’s [application] for SRP-9001 for filing and priority review,” Doug Ingram, Sarepta’s president and CEO, said in a company press release. Sarepta is developing the gene therapy in partnership with Roche.

The accelerated approval pathway allows the FDA to grant conditional marketing authorization to treatments based on early clinical evidence of likely effectiveness. As a condition for accelerated approval, the therapy’s developers are required to conduct additional clinical testing in order to confirm efficacy.

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Sarepta Asks FDA to Approve Gene Therapy SRP-9001 for DMD

Gene therapy allows micro-dystrophin production in muscle cells

An accelerated approval review “is a tremendously important milestone in our effort to bring a potentially life-changing gene therapy to Duchenne patients as rapidly as possible and we look forward to working with the FDA through the review process,” Ingram said.

The application is supported by data from a proof-of-concept Phase 1/2 clinical trial (NCT03375164), which tested a single dose of SRP-9001 in four boys with DMD. Results found better motor function and walking abilities at three years post-treatment.

It also is supported by data from a Phase 2 trial (NCT03769116) showing SRP-9001 improved motor function in 41 boys with DMD. Safety and other efficacy data from the open-label, Phase 1 ENDEAVOR (NCT04626674) study were also given for FDA review.

More than 80 DMD patients have been treated with SRP-9001 across these studies, and the therapy has shown “positive results at multiple time points, including one-, two- and up to four-years after treatment, in addition to demonstrating a consistent safety profile,” Sarepta reported in its release.

A Phase 3 trial called EMBARK (NCT05096221) is testing SRP-9001 against a placebo, with a main goal of comparing one-year changes in motor function with treatment. The study has enrolled 125 boys with DMD, ages 4 to 7 and all able to walk; it is expected to conclude in November 2024.

Should the FDA grant SRP-9001 accelerated approval and the EMBARK trial report positive data, Sarepta has proposed that its Phase 3 trial’s findings be allowed to serve as proof of efficacy in support of the therapy’s full approval.

SRP-9001 is designed to deliver a copy of a gene encoding micro-dystrophin — a shortened but functional version of the dystrophin protein, whose lack causes DMD — to muscle cells using a lab-engineered, harmless virus as a vector.

Sarepta announced plans to launch a clinical trial testing the antibody-cleaving therapy imlifidase as a pre-treatment for SRP-9001 in Duchenne patients with pre-existing antibodies against the viral vector.