The drop comes the day after the drugmaker said it would add a so-called black-box warning to its gene therapy Elevidys after two teenage boys receiving the treatment died earlier this year.

In a highly unusual move, Cambridge-based Sarepta said late Friday won’t comply with a request from the Food and Drug Administration to halt all shipments of its gene therapy.

The patient, who was being treated with an investigational gene therapy for limb-girdle muscular dystrophy, died of acute liver failure, the same complication responsible for the deaths of two boys taking Sarepta's Duchenne muscular dystrophy treatment Elevidys.