The Food and Drug Administration (FDA) has approved viltolarsen (Viltepso; NS Pharma, Paramus, NJ) injection for individuals with Duchenne muscular dystrophy (DMD) who are amenable to exon 53 skipping therapy. In clinical trials, viltolarsen treatment increased levels of dystrophin by approximately tenfold improved time function testing for all 16 participants. Because a lack of dystrophin is the underlying cause of DMD, increasing dystrophin as much and as early as possible is a key goal in the treatment of DMD. Viltolarsen is the first and only exon 53-skipping therapy to demonstrate an increase in dystrophin in children age 4 years or less. The continued approval of viltolarsen may be contingent on confirmation of a clinical benefit in a phase 3 confirmatory trial.
Prior to its approval, viltolarsen was granted priority review as well as rare pediatric disease, orphan drug and fast track designations.
The viltolarsen new drug application (NDA) submission included results from a phase 2, 2-period study in participants aged 4 to less than 10 years of age conducted in North America (Study 1, N=16) and a multicenter, open-label study in boys 5 to less than 18 years of age conducted in Japan (Study 2, N=16).
In Study 1 (NCT04060199), of those participants who received the recommended dose of 80 mg/kg/wk (N=8), 100% of participants (8/8) showed an increase in dystrophin levels after treatment with viltolarsen and 88% of participants (7/8) showed dystrophin levels of 3% or more than normal. Overall, after 20 to 24 weeks of treatment a mean increase in dystrophin expression to nearly 6% of normal was observed with viltolarsen (80 mg/kg/wk) vs 0.6% at baseline.
Treatment with viltolarsen infusions can be administered at home, in the hospital, or at an outpatient treatment center. Viltolarsen is administered by a trained healthcare professional as an 80 mg per kg of body weight 60-minute weekly intravenous infusion.
The most common adverse events of viltolarsen included upper respiratory tract infection, injection site reaction, cough, and fever.
James Geyer, MD, and Thomas Patton, MD
Tzu-Ying Chuang, MD, PhD, and Dhanashri Miskin, MD