NS Pharma, Inc. has received preliminary analysis results from the global Phase 3 clinical trial (RACER53 study, NCT04060199) of NS-065/NCNP-01.

Viltolarsen was approved by the United States (US) Food and Drug Administration (FDA) in 2020 under the brand name VILTEPSO – for the treatment of Duchenne muscular dystrophy (Duchenne) in patients who have a confirmed mutation of the dystrophin gene that is amenable to exon 53 skipping, under the FDA accelerated approval pathway based on an increase in dystrophin production in skeletal muscle observed in treated patients. In the US, continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial.

The RACER53 Study is a randomized, double-blind, placebo-controlled, comparative study of 77 ambulatory boys with Duchenne. The study evaluated the efficacy and safety of an 80 mg/kg once weekly dosing of the treatment – versus placebo – for 48 weeks and was intended to serve as a confirmatory study.

The primary endpoint of the study was Time to Stand from Supine evaluated as velocity (rise/sec). The viltolarsen group showed a trend of increased velocity from baseline after treatment for 48 weeks. However, the placebo group also showed a trend of increased velocity, and there was no statistically significant difference between the viltolarsen group and the placebo group.

Preliminary safety results indicated that all adverse events that occurred under viltolarsen treatment were mild or moderate. There were no treatment emergent adverse events that led to discontinuation of the drug during the study.

"We are currently conducting further detailed data analyses and identifying factors that may have influenced the results (e.g. age, treatment period, and effect of concomitant drugs including glucocorticoid therapy)," said Tsugio Tanaka, President, NS Pharma.

"Considering the results of prior clinical studies, we have confidence that viltolarsen can be a beneficial treatment for amenable patients with Duchenne," Tanaka added.

Specifically, in addition to the increase in dystrophin production in skeletal muscle that formed the basis of the FDA approval, a previously reported Phase 2, open-label, long-term extension study evaluated viltolarsen in 16 subjects between the ages of four and 10 with Duchenne amenable to exon 53 skipping.

NS Pharma is currently conducting further detailed data analyses, including post-hoc data analyses, and plans to work closely with regulatory authorities to determine how to proceed based on the results of this analysis and in the best interests of patients. The company will report on additional analyses and discussions with the regulatory authorities at a later date.