The US Food and Drug Administration has accepted NS Pharma’s application for its Duchenne Muscular Dystrophy (DMD) drug viltolarsen, setting a final decision date for the third quarter of this year.
Viltolarsen has been granted a priority review, as well as fast track, orphan drug and rare disease designations. NS Pharma submitted the drug for approval in October last year, and if approved in the third quarter it could enter the market before the end of the year.
DMD causes progressive weakness and atrophy of skeletal, heart and pulmonary muscles, and overwhelmingly affects males.
NS Pharma’s drug is designed to treat DMD patients with exon 53 mutations – the exact same mutation which rival Sarepta’s Vyondys 53 targets. Viltolarsen is an antisense oligonucleotide that promotes the production of functional dystrophin by masking exon 53 in the dystrophin gene.
Sarepta won a surprise approval for its Vyondys 53 in December last year, after the FDA had originally rejected the drug because of concerns about kidney toxicity observed in preclinical studies.
However, after an appeal of the decision, Sarepta was granted an approval for its second DMD medicine – after its exon 51 targeting Exondys 51 – the FDA deemed that the drug has a “reasonably likely” clinical benefit.
NS Pharma’s FDA application is based on results from a phase 2 study and its long-term extension study in North America, as well as a phase 1 and a phase 1/2 study in Japan. These trials measured changes in dystrophin levels and motor function across two doses – 40mg/kg and 80mg/kg administered weekly.
The results from these studies were promising, with those receiving viltolarsen treatment demonstrating restored dystrophin production in the muscles of boys aged four to ten. The treatment also proved safe and was well tolerated.
Viltolarsen will be the second treatment option for DMD patients after Sarpeta’s Vyondys 53, and the two will battle it out for market share if the former is approved later this year. NS Pharma could price its drug below Sarepta’s to gain an edge – Sarepta has indicated it will price Vyondys 53 “at parity” with Exondys 51, which costs around $300,000 per year, ahead of rebates and discounts.
NS Pharma and its parent company Nippon Shinyaku are currently enrolling patients for a phase 3 study in Japan and the US – named RACER53. It will further assess the efficacy of viltolarsen in ambulant boys amenable to exon 53 skipping, with functional tests including the time to stand test, time to run/walk ten metres test and the six-minute walk test.