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Nippon Shinyaku DMD Drug Falters in Phase III Confirmatory Study

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NEW YORK – Nippon Shinyaku this week said it is conducting additional analyses on clinical trial data of its Duchenne muscular dystrophy (DMD) antisense oligonucleotide drug Viltepso (viltolarsen) after preliminary results of a confirmatory Phase III study did not meet the primary endpoint.

DMD is a rare disease without many treatment options caused by mutations in the DMD gene that result in a deficiency of the dystrophin protein, leading to progressive muscular weakness.

Viltepso is specifically designed for patients with certain DMD mutations amenable to exon 53 skipping. The drug aims to bind to exon 53, so that it is excluded during mRNA processing.

The US Food and Drug Administration granted Nippon Shinyaku's NS Pharma, a subsidiary based in Paramus, New Jersey, accelerated approval for Viltepso in patients with those certain DMD mutations after reviewing data from two clinical trials, one of which showed patients treated with the drug experienced an increase in dystrophin production, which the agency said was reasonably likely to predict clinical benefit. The FDA last year granted accelerated approval to Sarepta Therapeutics for its DMD gene therapy Elevidys (delandistrogene moxeparvovec) based on a similar surrogate endpoint.

As part of the accelerated approval for Viltepso, the FDA required NS Pharma to conduct a confirmatory clinical trial to validate clinical benefits.

In the global randomized-controlled Phase III confirmatory trial, known as the RACER53 study, 77 boys with ambulatory DMD received either a weekly dose of Viltepso or placebo for 48 weeks.

The primary endpoint of the study was time to stand from a supine position. However, while the treatment group showed a trend of increased velocity from baseline after 48 weeks of treatment, the placebo group also showed a similar trend, according to Nippon Shinyaku, which is based in Kyoto, Japan. There was no statistically significant difference between the groups.

The company said it will work closely with regulatory authorities to determine a path forward.

"We have a confidence that viltolarsen is a beneficial medicine," the company wrote in a statement. "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)."

In addition to previous clinical trials that demonstrated an increase in dystrophin production, in an open-label Phase II extension study, patients demonstrated an improvement in average change from baseline for time to stand from a supine position compared to a historical control group at 205 weeks after treatment, the company said.