Another gene therapy death of a Duchenne patient has some parents and doctors criticizing the FDA's actions, even as other parents still push for the therapy.

Shares of biotech company Sarepta Therapeutics (NASDAQ:SRPT) fell 44.4% in the afternoon session after the company reported a second death linked to its Duchenne muscular dystrophy gene therapy. Elevidys.

The startup, which is backed by the venture arms of Sanofi, Roche and Novartis, is using dual adeno-associated viruses to help overcome the packaging constraints of current genetic medicines.

Sarepta Therapeutics, Inc. (NASDAQ:SRPT), the leader in precision genetic medicine for rare diseases, today provided a safety update regarding ELEVIDYS (delandistrogene moxeparvovec-rokl), the only approved gene therapy for patients with Duchenne muscular dystrophy,

Gene therapies have ridden investor mania to huge valuations but commercialization challenges have pushed market caps to the floor. At an FDA roundtable last week, FDA leaders promised faster approvals and broad support to the industry.