A patient has died while taking a closely watched gene therapy for muscular dystrophy. Sarepta Therapeutics announced the death Tuesday morning, sending the company's shares plummeting in morning trading.

A patient has died while receiving Elevidys, a gene therapy for Duchenne muscular dystrophy, marking the first known death linked to the treatment. The company behind the drug, Sarepta Therapeutics, said that the patient suffered acute liver injury,

Shares of Sarepta Therapeutics have struggled for the past year due to concerns about the commercial potential of its gene therapy and broader pipeline. Safety hadn’t been a major worry for investors—