Sarepta Therapeutics disclosed on Tuesday that a patient passed away while undergoing treatment with its gene therapy for muscular dystrophy, resulting in a sharp decline in the company's stock prices in morning trading. The individual's death was attributed to acute liver injury, a known side effect of the therapy named Elevidys. Sarepta noted that the severity of this particular case was unprecedented in relation to the therapy, which has been administered to over 800 patients without previous fatal incidents.

Elevidys, which was granted accelerated approval by the FDA in 2023, has faced skepticism regarding its effectiveness in treating Duchenne muscular dystrophy. Despite concerns raised by FDA scientists, it was the first gene therapy sanctioned in the U.S. for the rare muscle-wasting disease that predominantly affects males, leading to muscle weakness, decreased mobility, and premature death.

The FDA granted full approval for Elevidys in 2022 specifically for Duchenne patients with a specific genetic mutation, extending its eligibility to individuals aged 4 and above, regardless of their mobility status. Previously, the therapy was only accessible to younger patients who maintained their ability to walk.

Sarepta stated that the deceased patient had recently suffered from an infection, which might have contributed to the liver injury. The company intends to revise the prescribing information for Elevidys to incorporate this case.

Following the news, shares of Sarepta, based in Cambridge, Massachusetts, saw a significant drop of over 23% to approximately $78 per share during morning trading.

Elevidys functions by employing a disabled virus to introduce a replacement gene that supports dystrophin production in patient cells. The treatment costs $3.2 million for a one-time session.

Since 2016, Sarepta has been granted accelerated approval by the FDA for three other drugs aimed at Duchenne muscular dystrophy, although their efficacy has not yet been definitively proven, as studies for full FDA approval are still ongoing.

(Note: The Associated Press Health and Science Department acknowledges support from the Howard Hughes Medical Institute’s Science and Educational Media Group and the Robert Wood Johnson Foundation. The AP retains full responsibility for all content.)