NS Pharma's DMD Drug Viltespo Fails Phase III Trial

NS Pharma recently disclosed that its potential treatment for Duchenne muscular dystrophy (DMD), Viltepso (viltolarsen), did not achieve the desired outcomes in the pivotal Phase III RACER53 trial. The study was designed to assess Viltepso’s efficacy in improving motor function among boys with DMD but ended without significant positive results.

In the RACER53 trial, a randomized and double-blinded study, 77 ambulatory boys with DMD received either an 80 mg/kg dose of Viltepso weekly or a placebo. The study’s primary endpoint was the time it took for patients to stand up from a lying position, a measure of motor function improvement post-treatment.

Over the 48-week treatment period, although there was a “trend of increased velocity” in the Viltepso group according to NS Pharma, the placebo group also demonstrated improvements in their ability to rise. This parallel improvement led to an outcome where there was “no statistically significant difference” between the two groups.

On a positive note, the safety profile of Viltepso was deemed favorable, with most adverse events reported as mild or moderate, and no patients discontinuing due to side effects.

NS Pharma’s President, Tsugio Tanaka, expressed continued confidence in Viltepso despite the trial’s failure, believing it still holds potential as a beneficial treatment for certain DMD patients. The company is conducting a thorough analysis of the RACER53 data to identify any factors that might have influenced these results, including patient age, duration of treatment, and other concurrent medications.

NS Pharma, a subsidiary of Nippon Shinyaku, intends to collaborate with the FDA and other regulatory bodies to decide on the next steps following a detailed review of the trial’s outcomes.

Viltepso is designed as an antisense oligonucleotide therapy that targets exon 53 of the dystrophin pre-mRNA. By binding to this exon, Viltepso facilitates its exclusion during mRNA processing, which can lead to the production of a truncated but functionally viable dystrophin protein in patients with specific genetic mutations.

The FDA had previously granted Viltepso accelerated approval in August 2020. This approval allows its use in patients with exon 53 skipping-amenable mutations, contingent on DNA sequencing analysis.

NS Pharma’s recent setback with Viltepso comes on the heels of a similar incident involving Pfizer, which had to halt its Phase III CIFFREO study due to a sudden patient death in the Phase II DAYLIGHT trial of its gene therapy candidate, fordadistrogene movaparvovec.

Additionally, Sarepta’s Elevidys (delandistrogene moxeparvovec-rokl), also an accelerated approval recipient, has encountered criticisms over its efficacy data and a hefty price tag of $3.1 million.

While the RACER53 results are disappointing, NS Pharma remains committed to furthering the development of Viltepso and exploring its potential benefits for DMD patients. The company’s ongoing analysis and regulatory consultations will determine the future course of this therapy.