NS Pharma’s Duchenne muscular dystrophy drug Viltepso failed its confirmatory study. Despite the failure, the company is keeping faith in the drug and running further analyses to see if other factors were to blame.
According to preliminary results from the 77-patient RACER53 trial, patients in the Viltepso and placebo groups both showed a trend of standing faster after treatment for 48 weeks — the primary endpoint — with no “statistically significant” difference between the two groups.
“We are currently conducting further detailed data analyses and identifying factors that may have influenced the results,” NS Pharma president Tsugio Tanaka wrote in a statement. He listed age, the length of the study and the effects of steroids as possible influences, and added: “Considering the results of prior clinical studies, we have confidence that viltolarsen can be a beneficial treatment for amenable patients with Duchenne.”
NS Pharma, which is a US subsidiary of Japanese drugmaker Nippon Shinyaku, added that it’s now conducting post-hoc analyses and will work with regulatory bodies on how to move forward.
Viltepso, approved as the third Duchenne drug in the US in 2020, is an injection therapy for patients with a subset of the disease — those who have a mutation of the dystrophin gene that is amenable to exon 53 skipping. It’s also scored an approval in Japan.
The accelerated approval was based off of two studies, including a 16-patient Phase 2 trial that NS Pharma noted in its Monday announcement. In that trial, the patients did show statistically significant improvement change in time to stand after 205 weeks of treatment when compared to a historical control group.
In another trial that formed the basis of the drug’s approval, patients taking Viltepso saw an increase in dystrophin, a lack of which is the underlying cause of the rare disease.
The company said during its medium-term plan presentation that patients taking a steroid treatment prior to the study may have impacted the results, Jefferies analysts wrote in a Tuesday note. While the patients were steroid-free for the three months leading up to the trial start, “the company now thinks that this washout period was too short,” Jefferies analysts wrote.
“It also thinks that the frequency of steroid treatment, which differed quite widely from patient to patient, may have also affected the results,” the analysts continued. “The company says that it is still conducting analyses and has not yet set up a meeting with FDA to discuss the results.”