NS Pharma's Duchenne Therapy Viltepso Fails Trial

NS Pharma's Duchenne muscular dystrophy (DMD) drug Viltepso, also known as viltolarsen, received accelerated FDA approval in 2020. Sales have steadily increased since its launch, with the company projecting revenues of 20,100 trillion Japanese yen (approximately $128 million) this year. However, the drug’s regulatory status is now in question following disappointing preliminary results from a confirmatory trial.

The trial, which included 77 boys, aimed to validate Viltepso’s efficacy by comparing how quickly patients could stand after 48 weeks of treatment. While Viltepso did help patients stand faster, the control group also showed similar improvements. This lack of a statistically significant difference between the two groups has cast doubt on the drug's effectiveness.

NS Pharma’s CEO, Tsugio Tanaka, expressed the company's commitment to further analyze the trial data to identify any factors that could have influenced the outcomes. Tanaka emphasized confidence in Viltepso’s potential benefits, citing previous clinical studies that indicated the drug's effectiveness.

NS Pharma, based in New Jersey and a subsidiary of Japan’s Nippon Shinyaku, is investigating several variables that might have affected the trial results. These include the age of the participants, the duration of the treatment period, and the impact of concurrent medications such as glucocorticoid therapy.

Viltepso initially received FDA approval for treating DMD patients with exon 53 skipping based on a phase 2, open-label study involving 16 participants aged 4 to 10. Over 205 weeks of treatment, these patients demonstrated significant improvement in their time to stand compared to a historical control group. Additionally, two trials showed that Viltepso increased dystrophin levels, a crucial protein for muscle function that DMD patients lack due to their genetic disorder.

The FDA’s decision to approve Viltepso based on biomarker data has stirred controversy, especially given past experiences in the DMD field. Sarepta Therapeutics faced scrutiny for its DMD drugs, Vyondys 53 and Exondys 51. These drugs were approved mainly because they could increase dystrophin production, despite a lack of evidence showing they could improve symptoms or slow disease progression. The FDA's approval of Exondys 51 came despite its own reviewers' recommendations against it and a narrow vote against approval by an independent panel of experts. This internal conflict within the FDA led to high-profile resignations. Similarly, Vyondys 53 was initially rejected, but following Sarepta's challenge to the FDA's complete response letter, the agency reversed its decision.

The situation with Viltepso mirrors these past controversies, highlighting the complexities and challenges of approving treatments based on biomarker data. As NS Pharma continues to analyze the recent trial results, the future of Viltepso’s regulatory status remains uncertain.