Although Sarepta initially appeared to have avoided the worst possible outcome for Elevidys—a market withdrawal—thanks to the gene therapy’s new black box warning, the FDA is signaling stronger misgivings about the approved drug in the wake of the death of a third patient who received one of the company's gene therapies.

Shares of Sarepta Therapeutics fell as much as 8% on Tuesday after the company agreed to comply with the U.S. health regulator's request to pause all shipments of its gene therapy Elevidys in the United States.