Sarepta Therapeutics stock plummeted Monday after the company said a second patient receiving its gene therapy died from liver failure, raising serious questions on the drug’s outlook.Shares fell 40% to $21.

Sarepta Therapeutics shares sank to their lowest level in nine years Monday after a second patient taking its Elevidys drug died.

Shares of Sarepta Therapeutics closed down as much as 42% to hit a nine-year low of $18.30 on Monday after a second death of a male teenage patient who had received its gene therapy, Elevidys, raising doubts on the safety and future demand for the treatment.