Sarepta Therapeutics said a patient taking its treatment for Duchenne muscular dystrophy has died from acute liver failure. The pharmaceutical firm said that "acute liver injury is a known possible side effect of Elevidys.

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.

The company behind the drug, Sarepta Therapeutics, said that the patient suffered acute liver injury, a known side effect, The Associated Press reported. However, the "severity" of this case had not been seen before, the company noted. Elevidys has been used in more than 800 patients, the company stated.