The first publication of the results of the phase II clinical trial of Viltolarsen in 16 boys with DMD aged between 4 and 9 years in May 2020 showed that it induced a significant increase in the overall level of dystrophin in the muscle, accompanied by functional improvement after six months of treatment. In this double-blind, placebo-controlled trial, the two doses of viltolarsen tested (40 and 80 mg/kg) were also well tolerated.
Following these positive results, an open-label extension trial was launched to assess the long-term safety and efficacy (192 weeks) of this oligonucleotide, which targets skipping of exon 53 of the DMD gene. Now complete, the results of the trial have been published in two parts: after 2 years of treatment in 2022 and then 4 years in 2023. They show :
- Viltolarsen was well tolerated at the 2 doses tested, throughout the duration of the trial;
- maintenance of motor function compared with the motor decline observed in untreated patients in an external control cohort (CINRG DNHS natural history study) during the first two years;
- a slowdown in disease progression over the following two years, again compared with untreated patients.
Viltolarsen is currently being evaluated in several clinical trials, including a real-life study in the United States and Canada, as well as a phase II trial (Galactic53) in participants who have lost their ability to walk.
