Pfizer has started dosing in a phase 3 study evaluating its investigational gene therapy, PF-06939926, in young male patients with Duchenne muscular dystrophy (DMD).

The trial plans to enroll 99 boys aged 4 to 7 years across 55 sites in 15 countries. PF-06939926 received Fast-Track designation from the FDA in October.

The agency previously granted the gene therapy Orphan Drug and Rare Pediatric Disease designations in 2017.

Meanwhile, Sarepta Therapeutics reported disappointing top-line results from a phase 2 trial evaluating SRP-9001, its gene therapy for DMD.

Patients receiving the infusion did not achieve statistically significant muscle function following 48 weeks of treatment.