Nippon Shinyaku's Viltepso Faces Setback in Duchenne Trial

On Monday, NS Pharma, a subsidiary of Nippon Shinyaku, announced that their Phase III clinical trial for Viltepso (viltolarsen), a treatment for Duchenne muscular dystrophy (DMD), did not meet its primary endpoint. Viltepso, which received FDA accelerated approval in 2020, is intended for patients with a specific mutation on the dystrophin gene that can be treated by skipping exon 53.

The FDA approval was initially based on two clinical trials with a total of 32 boys. In one of these trials, 16 DMD patients received the recommended dose of Viltepso, and the results indicated an increase in dystrophin levels from 0.6% to 5.9% of normal levels over a period of 25 weeks.

In the recent confirmatory RACER53 study, the primary endpoint was the improvement in the time it takes for participants to stand up from a lying position. After 48 weeks of treatment, NS Pharma reported that while there was a "trend of increased velocity" in patients treated with Viltepso, a similar trend was observed in the placebo group. Consequently, there was no significant difference between the two groups in terms of the primary endpoint.

Regarding safety, all adverse events reported during the trial were of mild to moderate severity, and no patients discontinued the treatment due to side effects.

NS Pharma president Tsugio Tanaka commented on the outcome, stating, "We are currently conducting further detailed data analyses and identifying factors that may have influenced the results." Despite the inconclusive results of the Phase III study, Tanaka expressed confidence in Viltepso's potential, citing prior clinical studies that demonstrated the drug's benefits. He referred to a previous Phase II extension study where Viltepso showed significant improvement in a time-to-stand test at year four compared to historical control data matched for key factors.

The company remains committed to understanding the factors behind the Phase III trial results and continues to analyze the data to identify elements that might have affected the outcomes. They believe that the drug still holds promise as a treatment for patients with Duchenne muscular dystrophy who have the amenable mutation.

In summary, Viltepso's Phase III trial for DMD did not achieve the desired primary endpoint, mirroring similar improvements in both the treatment and placebo groups. However, the treatment was well-tolerated with no severe side effects leading to discontinuation. NS Pharma plans to continue analyzing the trial data and remains optimistic about Viltepso's potential based on earlier studies that showed significant improvements in DMD patients.