NS Pharma, a subsidiary of Nippon Shinyaku, announced Monday that its Duchenne muscular dystrophy candidate Viltepso failed a late-stage confirmatory trial, showing no significant motor function improvements over placebo.
NS Pharma announced Monday that its Duchenne muscular dystrophy candidate Viltepso (viltolarsen) failed the confirmatory Phase III RACER53 study, unable to significantly improve motor function versus placebo.
RACER53, a randomized and double-blinded study, enrolled 77 ambulatory boys with Duchenne muscular dystrophy (DMD) who were administered Viltepso at an 80-mg/kg dose once-weekly. Its primary outcome was time to stand from supine, which measures the velocity at which patients go from lying on their backs to standing upright after treatment.
After 48 weeks of treatment, boys who were given Viltepso showed a “trend of increased velocity,” according to NS Pharma. However, placebo comparators also saw improvements in their rising velocity, which in turn resulted in “no statistically significant difference” between patients treated with Viltepso and placebo.
In terms of safety, preliminary data from RACER53 showed that adverse events associated with Viltepso were mild or moderate. None of the patients dropped out due to side effects.
Despite failing its confirmatory Phase III study, NS Pharma President Tsugio Tanaka in a statement said the company still has “confidence that viltolarsen can be a beneficial treatment for amenable patients with Duchenne.”
The biotech is conducting a more detailed analysis of RACER53 and identifying potential factors that could have influenced its outcomes, such as patient age, treatment period and concomitant medications, according to Tanaka.
NS Pharma, a subsidiary of Nippon Shinyaku, will work with the FDA and other regulatory authorities to “determine how to proceed based on the results of this analysis and in the best interest of patients,” the company announced.
Viltepso is an antisense oligonucleotide therapy that works by targeting and binding to exon 53 of the dystrophin pre-mRNA, according to its label. This mechanism of action allows Viltepso to exclude exon 53 from the mature dystrophin mRNA, which in patients harboring certain mutations results in a truncated but partially functional protein.
The FDA granted Viltepso accelerated approval in August 2020, allowing its use in patients with mutations that make them amenable to exon 53 skipping, as assessed by DNA sequencing analysis.
Monday’s Phase III failure for NS Pharma follows a similar DMD stumble by Pfizer, which earlier this month announced that it was pausing the Phase III CIFFREO study following a sudden patient death in the Phase II DAYLIGHT trial. Both studies are evaluating Pfizer’s experimental gene therapy fordadistrogene movaparvovec.
Meanwhile, Sarepta’s Elevidys (delandistrogene moxeparvovec-rokl), which won accelerated approval in June 2023, has recently come under fire for having weak efficacy data to back its use and for its $3.1 million price tag.
Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at tristan@tristanmanalac.com or tristan.manalac@biospace.com.
