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.

Elevidys was approved after intense debate at the FDA, as officials and reviewers disagreed over how strong the evidence was and whether it warranted making the drug available for patients facing a fatal disease with few other options.