How long does it take for Vyondys 53 to work?

Vyondys 53 (golodirsen) is a treatment for Duchenne muscular dystrophy (DMD) in patients with a DMD gene mutation amenable to exon 53 skipping. It works by increasing dystrophin protein production in skeletal muscle and it is thought that this will provide a clinical benefit to DMD patients who are exon 53 amenable.

Clinical Trial Results

Results from a small phase I/II clinical trial show that treatment with Vyondys 53 increases dystrophin protein levels within 48 weeks of starting treatment.

• Muscle biopsies were needed to confirm that Vyondys 53 increased dystrophin protein levels and these were taken at the beginning of the trial and again at 48 weeks after starting treatment.
• Vyondys 53-treated patients had a significant increase in exon 53 skipping, which was linked with a 16-fold increase in dystrophin protein expression at 48 weeks compared with baseline levels. The mean percent of normal dystrophin was 1.019% (range, 0.09% to 4.30%). The dystrophin protein expression was localized to the sarocolemma, the plasma membrane of the muscle cell.

FDA Approval and Ongoing Research

DMD is a rare genetic degenerative neuromuscular disease, so results from the phase I/II trial, which was conducted in 39 patients, were enough to enable Accelerated FDA Approval of Vyondys 53 in the US in 2019.

Continued approval of Vyondys 53 requires confirmation that the drug provides a clinical benefit. A post-marketing trial called ESSENCE is being conducted to confirm Vyondys 53s clinical benefit. The trial is expected to be completed in late 2025.