By Leroy Leo and Aditya Samal
(Reuters) - The U.S. health regulator has granted accelerated approval to Sarepta Therapeutics (NASDAQ:SRPT)' first-of-its-kind gene therapy for Duchenne muscular dystrophy (DMD), an inherited progressive muscle-wasting disorder that almost always affects young boys.
Sarepta said on Thursday the Food and Drug Administration had approved the treatment for children aged between 4 and 5 years who can walk. It was initially seeking approval for all DMD patients who can walk.
The therapy's wholesale acquisition cost is $3.2 million, CEO Douglas Ingram said on a conference call with investors.
The world's most expensive treatment, a gene therapy for bleeding disorder hemophilia from Australian drugmaker CSL (OTC:CSLLY) Ltd, carries a list price of $3.5 million.
The agency's decision comes after several delays and questions over the effectiveness of the therapy, which will be sold under the brand name Elevidys.
Elevidys could change the way that DMD patients, who rarely survive beyond their thirties, are treated. Currently, approved steroids and some therapies for specific genetic mutations only control symptoms and slow disease progression.
In a mid-stage trial, Sarepta's gene therapy was able to produce a mini version of the dystrophin protein needed to help keep muscles intact, but did not improve patient clinical outcomes like their ability to walk and stand.
A late-stage study to confirm the treatment's effectiveness is underway and initial data from it is expected by December.
Current options for DMD patients are limited. Of four new "exon-skipping" therapies - intended for a smaller group of patients with specific genetic mutations - three are from Sarepta.
They require weekly infusions and work by skipping specific parts of genes, called exons, with the aim of allowing the body to form shorter forms of the dystrophin protein. Elevidys should not be used in patients with any deletion in exon 8 and exon 9 in the DMD gene, the company said on Thursday.
Sarepta's infrastructure is prepared to support the launch of Elevidys and it could take about four months to get to patients even with a limited target population, Ingram said ahead of the approval.
DMD affects an estimated one-in-3,500 male births worldwide, according to the National Organization for Rare Disorders.
"We will have a very successful launch and I think we'll expand this label successfully early next year," Sarepta's Ingram said.
Elevidys could become a multibillion-dollar product, William Blair analyst Tim Lugo said in a note.
A green light for Sarepta's treatment could open the doors for more effective gene therapies, experts and analysts have said. Pfizer (NYSE:PFE) is also developing a gene therapy for DMD.
A late-stage trial of 126 patients is ongoing at Sarepta, and will be pivotal in expanding the patient population and gaining a traditional approval.
Roche acquired the commercial rights to Elevidys outside the United States under a 2019 deal. Sarepta remains in charge of clinical development, but it splits the costs with Roche.
Sarepta's shares were up nearly 1% in extended trading.