By MATTHEW PERRONE, Associated Press

WASHINGTON (AP) — Shares of Sarepta Therapeutics plunged Monday after the biotech drugmaker reported a second death in connection with its gene therapy for muscular dystrophy.

Sarepta reported the death over the weekend and provided additional details about its response, which includes pausing shipments of the therapy, Elevidys, for older patients who are no longer able to walk. The one-time treatment is approved for children with a genetic variant of Duchenne’s muscular dystrophy, which causes weakness, loss of mobility and early death in males.

Elevidys is the first gene therapy approved in the U.S. for the rare muscle-wasting condition, but it has faced scrutiny since its accelerated approval in 2023.

The second death, like an earlier one reported in March, occurred in a teenage boy who suffered a fatal case of acute liver injury, a known side effect of the therapy. Older patients receive a larger dose of the therapy.

Sarepta said it would pause a study in those patients and assemble an expert panel to recommend new safety protocols for taking the drug. Those changes are expected to include increased use of immune-system suppressing drugs, company executives said Monday. The liver injury associated with the therapy is thought to be connected to the immune system’s response.

Sarepta said it was cooperating with the Food and Drug Administration, which would have to sign off on any changes to the product’s use.

Elevidys received expedited approval despite concerns from some FDA scientists about its effectiveness in treating Duchenne’s.

The FDA granted full approval last year and expanded the therapy’s use to patients 4 years and older, regardless of whether they are still able to walk. Previously it was only available for younger patients who were still walking.

Shares of the Cambridge, Massachusetts-based company fell more than 42% to close at about $21 in trading.

Wall Street analysts speculated that FDA officials, including new vaccine chief Dr. Vinay Prasad, might impose more restrictions on the drug or even block its use. Prasad has been highly critical of the therapy since its approval under the agency’s previous leadership.

“Now with two deaths reported in this segment of the market, it seems incrementally more possible that the FDA could step in and remove the therapy from the market in non-ambulatory patients,” said Leerink Partners analyst Joseph Schwartz, in a Sunday research note.

Elevidys uses a disabled virus to insert a replacement gene for producing dystrophin into patient cells. It costs $3.2 million for a one-time infusion.

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