The US Food and Drug Administration (FDA) has approved viltolarsen (Viltepso, NS Pharma), the second drug therapy for Duchenne muscular dystrophy in patients with a confirmed mutation amenable to exon 53 skipping.
“The FDA is committed to fostering drug development for serious neurological disorders like Duchenne muscular dystrophy,” Billy Dunn, MD, director, Office of Neuroscience of the FDA’s Center for Drug Evaluation and Research, said in a statement.
The approval of viltolarsen provides “an important treatment option for Duchenne muscular dystrophy patients with this confirmed mutation,” Dunn said.
Viltolarsen is an antisense oligonucleotide that promotes production of functional dystrophin by masking exon 53 in the dystrophin gene. It was evaluated in two studies involving 32 male patients.
In one study of 16 patients, the increase in dystrophin production was established in eight patients receiving viltolarsen at the recommended dose. In this study, dystrophin levels increased, on average, from 0.6% of normal at baseline to 5.9% of normal at week 25.
The increase in dystrophin production is “reasonably likely to predict clinical benefit,” but a “clinical benefit of the drug has not been established,” the FDA said.
In making their decision, 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.
Viltolarsen 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.
As part of the accelerated approval, the FDA requires the company to do a clinical trial to confirm the drug’s clinical benefit. If the trial fails to verify clinical benefit, the FDA may start proceedings to withdraw approval of the drug, the agency said.
The most common side effects with viltolarsen are upper respiratory tract infection, injection-site reaction, cough, and fever.
Kidney toxicity was not observed in the clinical studies, but the clinical experience with the drug is limited, and kidney toxicity, including potentially fatal glomerulonephritis, has been observed with some antisense oligonucleotides.
“Kidney function should be monitored in patients taking Viltepso,” the FDA advises.