WASHINGTON -- Viltolarsen (Viltepso) injection has been (DMD) in patients with a confirmed mutation in the DMD gene amenable to exon 53 skipping, the FDA said Wednesday.
About 8% of DMD patients have this type of mutation. Viltolarsen, a novel antisense oligonucleotide, is the second targeted treatment for these patients, the first being golodirsen (Vyondys 53), which was approved in December 2019.
"The FDA is committed to fostering drug development for serious neurological disorders like Duchenne muscular dystrophy," Billy Dunn, MD, director of the Office of Neuroscience in the FDA's Center for Drug Evaluation and Research, said in a statement. "Today's approval of Viltepso provides an important treatment option for Duchenne muscular dystrophy patients with this confirmed mutation."
DMD is caused by an absence of dystrophin. First symptoms of DMD usually are seen when patients are ages 3 to 5 years and worsen over time. People with DMD progressively lose the ability to perform activities independently and often require a wheelchair by their early teens; as the disease progresses, life-threatening heart and respiratory conditions can occur.
DMD occurs in approximately one out of every 3,600 male infants worldwide; in rare cases, it can affect females, the agency noted.
Viltolarsen won approval through the FDA's for drugs that treat serious or life-threatening diseases. Under this pathway, approval can be based on studies that show a drug has an effect on a that is likely to predict clinical benefit.
Viltolarsen was evaluated in two clinical studies that included a total of 32 boys with genetically confirmed DMD. showed an in eight boys treated with viltolarsen at 80 mg/kg per week, with dystrophin levels increasing on average from 0.6% of normal at baseline to 5.9% of normal at week 25.
The agency concluded that this "demonstrated an increase in dystrophin production that is reasonably likely to predict clinical benefit in patients with DMD who have a confirmed mutation of the dystrophin gene amenable to exon 53 skipping."
Clinical benefit of viltolarsen has not been established, the FDA pointed out. An ongoing study will assess whether viltolarsen improves time to stand in DMD patients; if the trial fails to verify clinical benefit, the agency may start proceedings to withdraw approval.
In the two studies, the most common side effects observed in patients treated with 80 mg/kg once a week were upper respiratory tract infection, injection site reaction, cough, and fever.
"Although kidney toxicity was not observed in the Viltepso clinical studies, the clinical experience with Viltepso is limited, and kidney toxicity, including potentially fatal glomerulonephritis, has been observed after administration of some antisense oligonucleotides," the FDA warned. "Kidney function should be monitored in patients taking Viltepso."
Patients receiving viltolarsen will have the option of or treatment center, drugmaker NS Pharma said. The drug will be administered by a trained healthcare professional in 60-minute weekly intravenous infusions.