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’s shares crashed 41% in premarket trading Monday morning to $21.01 after the biotech reported a second death from acute liver failure, a known side effect of adeno-associated virus-based gene therapies.

Duchenne muscular dystrophy patient died after being treated with the gene therapy delandistrogene moxeparvovec (Elevidys), Sarepta Therapeutics said Sunday. Like the first case reported, this patient developed acute liver failure (ALF) that resulted in death.