FDA advisers weigh Sarepta’s Duchenne gene therapy

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Advisers to the U.S. Food and Drug Administration are meeting on Friday to review Sarepta Therapeutics Inc’s first-of-its-kind gene therapy for Duchenne muscular dystrophy (DMD) ahead of an approval decision expected later this month.

If approved, the potential one-time therapy could change the way patients with the muscle-wasting disease are treated, although the FDA earlier this week raised questions about whether there was enough evidence to show that it works.

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DMD is estimated to affect one-in-3,500 male births worldwide, according to the National Organization for Rare Disorders, causing progressive muscle failure. Most people with DMD do not survive beyond their thirties.

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Sarepta’s currently approved DMD therapies only treat a subset of patients with certain gene mutations. Other treatments include corticosteroids that have side effects if used long-term, such as excess weight gain and osteoporosis.

Top FDA official Peter Marks told the panel that the agency had decided to hold the advisory meeting, after initially not planning one, with the idea that an open public discussion would be important for Sarepta’s approval application.

In a mid-stage trial, Sarepta’s gene therapy was able to produce a mini version of the dystrophin protein needed to help keep muscles intact, but did not improve patient clinical outcomes like walking and standing ability.

Sarepta is hoping to gain approval through the FDA’s accelerated pathway based on the current data, and is conducting a late-stage trial to confirm the therapy’s patient benefits. That data is expected later this year.

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In briefing documents published on Wednesday, FDA reviewers said Sarepta’s mid-stage trial did not provide “unambiguous evidence” that the gene therapy will benefit patients with DMD.

On Friday, staff reviewers in a presentation said patients likely have only one chance to receive this type of therapy for DMD, and it is critical that what they get be effective and safe.

The panel will vote later during Friday’s meeting on whether the available data provided by Sarepta supports accelerated FDA approval for the gene therapy.

The FDA typically follows the advice of its independent experts but is not obligated to do so. The agency is expected to make a final decision on the therapy by the end of the month.

Pfizer Inc is also testing a DMD gene therapy.

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Marks said in March the FDA is moving to encourage use of disease related biomarkers that may predict efficacy for gene therapies for diseases with small patient populations.

Investors are hoping it will gain an accelerated approval, which would allow the treatment on the market based on surrogate biomarkers that predict the likelihood of benefit, versus hard clinical outcomes, such as improved physical function or extended survival.

Evercore ISI analysts put the chance of approval at 50%-60%, while SVB Securities analyst Joseph Schwartz said the FDA briefing documents create a shaky backdrop for the advisory panel. (Reporting by Leroy Leo and Aditya Samal in Bengaluru; Editing by Manas Mishra and Bill Berkrot)