Sarepta Therapeutics failed to win the European drug regulator's backing for its muscle disorder gene therapy on Friday, as the company faces intense regulatory scrutiny after two recent patient deaths tied to the treatment.

Three patient deaths linked to gene therapies developed by Sarepta Therapeutics (SRPT) have drawn FDA scrutiny on the viral vector used in the drugs. Read more here.

The Revell family hoped a gene therapy could buy time for their sons, who have a rare and fatal disease. After two patients died, the drug’s manufacturer halted dosing under pressure from the FDA.