CAMBRIDGE, Massachusetts: A third patient death linked to gene therapy technology has intensified scrutiny on Sarepta Therapeutics, whose Duchenne muscular dystrophy treatment, Elevidys, remains at the centre of safety concerns.

Despite a request from U.S. regulators to halt shipments, the company is refusing to pause deliveries for ambulatory patients.

On July 18, the Food and Drug Administration confirmed that it had asked Sarepta to voluntarily stop distributing Elevidys, a gene therapy for Duchenne muscular dystrophy. The request came during a meeting between the agency and the company.

Sarepta declined the FDA's request, stating it would continue shipping Elevidys to patients who are able to walk while maintaining an existing pause for non-ambulatory patients — a halt implemented by the company on June 15 after reporting a case of acute liver failure.

Sarepta said its decision to continue shipping to ambulatory patients was "based on our comprehensive scientific interpretation of the data, which shows no new or changed safety signals in the ambulant patient population."

The most recent patient death — a 51-year-old man with limb girdle muscular dystrophy — did not involve Elevidys but another experimental therapy using similar gene technology. The FDA said clinical trials involving limb girdle muscular dystrophy have now been placed on hold due to safety concerns.

Earlier this year, two teenage boys receiving Elevidys died of acute liver failure. All three deaths occurred in non-ambulatory patients. These events have raised alarm among regulators, investors, and patient advocacy groups.

Elevidys received traditional FDA approval in 2024 for ambulatory patients aged four and older with Duchenne muscular dystrophy. It was also granted accelerated approval for non-ambulatory patients, despite the therapy failing to meet its primary goal in a late-stage trial.

In a further regulatory setback, the FDA also revoked Sarepta's platform technology designation for its AAVrh74 gene therapy — a status that would have streamlined approval for similar treatments.

Following the news of the third death and the regulatory developments, Sarepta shares plunged 36 percent on July 18 to US$14.08, briefly hitting a more than nine-year low.

The FDA is continuing to investigate the risk of acute liver failure linked to Sarepta's platform technology. Some analysts have said this could make patients and families more reluctant to consider the therapy.

"Families with Duchenne muscular dystrophy are grappling with a mix of disappointment, concern... and uncertainty about choices they are making for their children or themselves," said Debra Miller, founder of the non-profit CureDuchenne.

Sarepta said earlier this week that it is working with the FDA to update Elevidys' packaging to include a warning about liver toxicity risks.

However, the company is also facing criticism for its communication handling. During an investor call, analysts questioned why Sarepta had not disclosed the latest patient death earlier in the week when it announced 500 layoffs and financial restructuring. CEO Doug Ingram responded that the death was "neither material nor central" to that announcement.

Some analysts, including those at BMO Capital Markets, have warned that how the disclosure was managed could damage Sarepta's credibility with investors.