When three patients die after taking a cutting-edge drug, most companies hit the brakes. Not Sarepta Therapeutics. The Massachusetts-based biotech company is under fire for refusing a request from the U.

U.S. regulators asked Sarepta Therapeutics on Friday to voluntarily halt shipments of its Elevidys gene therapy after a muscular dystrophy patient who received a different, experimental treatment died,

Shares of Sarepta Therapeutics plunged more than 30% on Friday as the future of its approved gene therapy appeared at risk. Sarepta has reported three patient deaths related to its gene therapies.