FDA approvals

August 13, 2020

Drug Granted Accelerated Approval for Rare Duchenne Muscular Dystrophy Mutation

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THURSDAY, Aug. 13, 2020 -- Accelerated approval has been granted to Viltepso (viltolarsen) injection for treatment of patients with Duchenne muscular dystrophy (DMD) and a mutation of the DMD gene amenable to exon 53 skipping, the U.S. Food and Drug Administration announced Wednesday.

About 8 percent of DMD patients have a mutation amenable to exon 53 skipping, the FDA notes. Viltepso is administered by a health care professional at a dose of 80 mg/kg in 60-minute weekly intravenous infusions at home, a hospital, or a treatment center.

The accelerated approval was based on two clinical studies with 32 male patients with genetically confirmed DMD; one was conducted in the United States and the other was conducted in Japan. In the U.S. study, a phase 2, two-period study of 16 patients ages 4 to 10 years old, eight patients received Viltepso at the recommended dose. All patients treated with Viltepso showed an increase in dystrophin levels. Dystrophin levels increased from 0.6 to 5.9 percent of normal from baseline to week 25. The most commonly reported side effects with Viltepso included upper respiratory tract infection, injection site reaction, cough, and fever.

Based on these data, the FDA determined that the increase in dystrophin production among patients who received Viltepso is "reasonably likely" to predict clinical benefit in this patient population. As part of the accelerated approval, the manufacturer of Viltepso is required to conduct a phase 3 confirmatory clinical trial to confirm the drug's clinical benefit. In the ongoing phase 3 RACER53 trial, which was initiated in October 2019 and is still enrolling patients, researchers will assess whether Viltepso improves the time to stand for DMD patients with the DMD gene amenable to exon 53 skipping. The FDA may move to withdraw approval of the drug if the study does not show clinical benefit.

The approval was granted to NS Pharma Inc.

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