S arepta Therapeutics suffered a surprise setback on Monday when the Food and Drug Administration rejected its request to commercialize a second medicine to treat children with Duchenne Muscular Dystrophy, a rare hereditary muscle wasting disease.  In a statement, Sarepta said the FDA has refused to approve its medicine called Vyondys 53 because of the risk of intravenous infusion and kidney toxicity infections seen in animal studies.
Sarepta shares fell 13% to $ 105 after-hours trading. The stock closed the regular trading session by 4%.
The FDA did not make a separate statement for its negative decision, but the rejection of Vyondys 53 is an unusual case in which the agency has fought against a company seeking this. Fast approval for a drug for Rare diseases based on an early biomarker ̵
Rapid approvals for orphan drugs have grown rapidly in recent years and have become almost routine, as the FDA intended to accelerate the development of medicines for the medical need. The decision to reject Vyondys 53 could therefore constitute a new and more restrictive regulatory policy for the FDA that could affect any company developing orphan drugs.
It could also be just Sarepta, which had a controversial relationship "We are very surprised that we received the full answer letter this afternoon," said Doug Ingram, CEO of Sarepta, in a statement. "Throughout the reporting period, the Agency has not raised any issues that point to the inadmissibility of Golodirsen, including the issues that formed the basis for the full response." Golodirsen is the scientific name for Vyondy's 53.
The company provided FDA data showing that Vyondy's 53, administered via a weekly infusion, caused a small increase in an important muscle protein called dystrophin, which is normally found in children with Duchenne missing.
However, no data was collected or transmitted showing Vyondys This may improve the muscle function of Duchenne patients or slow the progression of the disease. Sarepta initially opted for rapid approval by the FDA, before treatment success was confirmed in a later clinical trial.
Sarepta used this strategy in 2016 to obtain an accelerated approval for its first Duchenne drug, called Exondys 51, to be disputed. External FDA advisers – and even some of the agency's staff – concluded that there is not enough evidence for the efficacy of Exondys 51 in the treatment of Duchenne.
Top officials of the FDA, led by Dr. Ing. Janet Woodcock, anyway, ignored the negative recommendations and approval of the drug, also due to the heavy pressure of families with children with Duchenne.
With approval in 2016, Sarepta was able to expand Exondys 51 into a product that generates sales of $ 300 to $ 400 million annually. However, the company has been lagging behind for years when it has completed the FDA-mandated clinical trials to confirm the true benefit of the drug, STAT reported last week.
Sareptas delinquency at Exondys 51 could have upset the FDA enough to play a role in the EU's decision to reject the agency on Monday, Vyondys 53.
Sarepta said it plans to meet with the FDA to resolve the issues that led the FDA to reject the drug. A confirmatory study on Vyondys 53 is currently in progress, but data to improve muscle function are not expected until three or four years have passed.
Vyondys 53 was developed to treat patients whose Duchenne is caused by a defect in the DNA sequence known as exon 53. Approximately 8% of the 5,000 Duchenne patients in the US have the exon 53 defect. Exondys 51 is used to treat 13% of patients with diseases caused by a defect in the DNA sequence called exon 51.