(Bloomberg) -- A top US Food and Drug Administration official overrode reviewers to give broad approval to Sarepta Therapeutics Inc.’s gene therapy for a rare muscle disease in children, despite a lack of data showing it actually slows overall progression of the disease.

The approval was a victory for parents who’d advocated for the controversial, $3.2 million treatment as well as for the company. The shares rose as much as 40% in New York, the most intraday in six years. 

Under the expanded approval given Thursday, Sarepta can now market the drug for the vast majority of children with Duchenne muscular dystrophy, a lethal genetic disease. It was the best possible outcome for the company, which had been seeking to expand the treatment’s approval even after a trial had failed to clearly show it slowed disease versus a placebo. Earlier, the therapy had only been approved for 4- and 5-year-olds. 

“The sales growth will be enormous,” Sarepta CEO Douglas Ingram said Friday on a conference call. “Patients have been waiting far too long for a therapy like this.”

Sole Provider

The new clearance means Sarepta is likely to have the market to itself in Duchenne muscular dystrophy gene therapy for the time being, as a potential competing product from Pfizer Inc. recently failed in a trial.  

The approval came after two FDA reviewers recommended against it, according to FDA documents, noting that results of two failed trials conducted by Sarepta created uncertainty whether the treatment worked, and in which patients. A statistical review also found that Sarepta’s main trial “did not meet the success criterion.”

But those reviewers were overruled by FDA biologics head Peter Marks, who noted that patients on the drug did better on other measures of disease progression. “The observations regarding the secondary endpoints and exploratory endpoints are compelling,” he wrote in a memo.

Under the new decision, full approval was granted for a broad group of patients ages 4 and up who can still walk. The agency also gave accelerated approval for use in those who can’t walk, meaning the company will need to perform another trial to confirm the benefits in this group.

The new label covers over 80% of boys and men with Duchenne muscular dystrophy, Sarepta executives said on a conference call. The broader label will drive “significant top-line growth for the company in the near term,” Tim Lugo, an analyst at William Blair & Co. said in a note. 

No Strings Attached

Brian Abrahams, an analyst at RBC Capital Markets, called the agency’s decision a “broad, almost ‘no strings attached’” label expansion. Abrahams raised his price target for Sarepta’s shares from $142 to $182. The company’s shares traded as high as $173.25 Friday. 

Called Elevidys, the treatment has highlighted the debate around the FDA’s accelerated approval process, a regulatory shortcut designed to get drugs for devastating diseases to market quickly, often based on preliminary data. When confirmatory trials don’t show clinical benefit, the FDA can pull such drugs from the market. While such fast approvals may help some desperate patients, critics say the system sometimes allows unproven drugs to stay on the market for years. 

The FDA gave Elevidys accelerated approval in June 2023 to treat 4- and 5-year-olds, the age group that appeared to gain the most benefit in studies. 

In October, Sarepta said its confirmatory trial failed to clearly slow the disease in a yearlong study of 125 young children. But secondary measures of patients’ movement in the trial were positive, according to the drugmaker, and the company filed with US regulators for full approval.

Duchenne muscular dystrophy primarily occurs in about 1 in 3,500 male births worldwide. Caused by defects in a protein called dystrophin that helps keep muscle cells intact, the disease leads to severe muscle weakening and atrophy. Most patients die in their 20s, though some are living longer thanks to various treatment options, like steroids and other approved treatments that target a certain genetic mutation.

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