FDA Approves NS Pharma’s Targeted Treatment for Patients with Rare DMD Mutation

Rare Daily Staff

The U.S. Food and Drug Administration granted accelerated approval to NS Pharma’s Viltepso injection for the treatment of Duchenne muscular dystrophy (DMD) in patients who have a confirmed mutation of the DMD gene that is amenable to exon 53 skipping.

It is the second drug approved by the FDA to treat this patient group, which comprises approximately 8 percent of patients with Duchenne muscular dystrophy. Sarepta Pharmaceuticals’ Vyondys 53 injection was granted accelerated approval by the agency in December 2019 that has to be confirmed with a post-marketing trial expected to conclude in 2024.

Duchenne muscular dystrophy (DMD) is a rare genetic disorder characterized by progressive muscle deterioration and weakness. It is the most common type of muscular dystrophy. DMD is caused by an absence of dystrophin, a protein that helps keep muscle cells intact. The first symptoms are usually seen between three and five years of age and worsen over time. The disease often occurs in people without a known family history of the condition and primarily affects boys, but in rare cases it can affect girls. DMD occurs in about one out of every 3,600 male infants worldwide.

“The FDA is committed to fostering drug development for serious neurological disorders like Duchenne muscular dystrophy,” said Billy Dunn, director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research. “Today’s approval of Viltepso provides an important treatment option for Duchenne muscular dystrophy patients with this confirmed mutation.”

Viltepso, the antisense oligonucleotide viltolarsen, was evaluated in two clinical studies with a total of 32 patients, all of whom were male and had genetically confirmed DMD. The increase in dystrophin production was established in one of those two studies, a study that included 16 DMD patients, with 8 patients receiving Viltepso at the recommended dose. In the study, dystrophin levels increased, on average, from 0.6 percent of normal at baseline to 5.9 percent of normal at week 25.

Although a clinical benefit of the drug has not been established, the FDA considered the potential risks associated with the drug, the life threatening and debilitating nature of the disease, and the lack of available therapies in its decision to approve Viltepso.

As part of the accelerated approval process, the FDA is requiring the company to conduct a clinical trial to confirm the drug’s clinical benefit. The ongoing study is designed to assess whether Viltepso improves the time to stand for DMD patients with this confirmed mutation. If the trial fails to verify clinical benefit, the FDA may initiate proceedings to withdraw approval of the drug.

The most common side effects observed in DMD patients (pooled from the two studies) treated with 80 mg/kg once a week were upper respiratory tract infection, injection site reaction, cough and fever.

Viltepso, which has Priority Review designation, was approved under the FDA’s accelerated approval pathway, which provides for the approval of drugs that treat serious or life-threatening diseases and generally offer a meaningful advantage over existing treatments. Approval under this pathway can be based on adequate and well-controlled studies showing the drug has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit to patients, for example how patients feel or function or whether they survive. This pathway provides earlier patient access to promising new drugs while the company conducts clinical trials to verify the predicted clinical benefit.