The FDA has accepted the new drug application (NDA) for Nippon Shinyaku’s viltolarsen for the treatment of patients with Duchenne muscular dystrophy (DMD) who are amenable to exon 53 skipping therapy.1

The investigational DMD agent was previously granted fast track, orphan drug, and rare disease designations, in addition to priority review. Viltolarsen’s NDA is supported by the results of a phase 2 study and a long-term extension study. In Japan, additional results from a phase 1 and phase 1/2 study (Japic CTI-163291) were factored into the regulatory decision as well.2

In October 2018, Nippon Shinyaku announced the results of its phase 2 clinical trial (NCT02740972) at the 23rd International Annual Congress of the World Muscle Society. In that study, 16 boys received a dose of either 40 mg/kg or 80 mg/kg of intravenous (IV) viltolarsen for 24 weeks. The trial aimed to evaluate changes in dystrophin levels as well as motor function.3

At the end of the trial,, investigators observed both drug-induced dystrophin and exon-skipping efficiency in both dose groups of viltolarsen-treated patients. Additionally, the drug demonstrated improvements in time to run/walk 10 meters velocity, time to stand from supine velocity, and 6-minute walk test meters in viltolarsen-treated patients compared to their treatment-matched history cohorts.

Only mild or moderate adverse events (AEs) and no treatment-emergent AEs which required discontinuation from the trial or dose reduction were reported.3
 
READ MORE: Ataluren Extends Ability to Walk in Patients With Duchenne Muscular Dystrophy
 
An ongoing open-label extension study (NCT03167255) is assessing safety and tolerability of viltolarsen in patients for an additional 144 weeks. Investigators plan to have finalized trial data in December 2020, according to Nippon Shinyaku.1

In addition,  the company is currently assessing viltolarsen’s safety and efficacy in the phase 3 RACER53 clinical trial (NCT04060199) in ambulatory boys with DMD, age 4 to 7. During the trial, patients will receive 80 mg/kg of viltolarsen or placebo for up to 48 weeks. RACER53 is expected to conclude in late 2024.

Viltolarsen is a morpholino antisense oligonucleotide that was discovered by Nippon
Shinyaku and the National Center of Neurology and Psychiatry. The drug candidate contains an artificial piece of mRNA that masks exon 53, allowing the exon to be “skipped” and generating a partially functional protein. The drug has not proven to be effective on other patients with DMD who do not have a mutation that is amenable to exon 53 skipping.

Viltolarsen’s Prescription Drug User Fee Act (PDUFA) date is set for sometime within the third quarter of 2020.
REFERENCES
1. NDA accepted for filing by the FDA for antisense oligonucleotide viltolarsen (NS-065/NCNP-01) [news release]. Kyoto, Japan and Paramus, NJ: Nippon Shinyaku. February 7, 2020. nippon-shinyaku.co.jp/file/download.php?file_id=2949. Accessed February 13, 2020.
2. Morpholino Oligonucleotide NS-065/NCNP-01 (viltolarsen), Presentation on results of an additional analysis of Phase I/II study in Japan [news release]. Kyoto, Japan: Nippon Shinyaku. October 17, 2019. nippon-shinyaku.co.jp/file/download.php?file_id=2711. Accessed February 13, 2020.
3. NS-065/NCNP-01 (Vitolarsen) of Nippon Shinyaku’ in-house product presentation on results of phase 2 study in US/Canada [news release]. Kyoto, Japan: Nippon Shinyaku. October 3, 2018. nippon-shinyaku.co.jp/file/download.php?file_id=1990. Accessed February 13, 2020.