Pfizer's Duchenne gene therapy misses key trial goals

Pfizer's experimental gene therapy for Duchenne muscular dystrophy has failed to improve motor functions in young boys participating in a late-stage trial. This much-anticipated study was intended to provide a clear verdict on the treatment's potential but did not meet its primary or secondary goals when compared to a placebo, the company announced on Wednesday afternoon.

The Phase 3 trial, named Ciffreo, assessed participants using a rating scale that measures motor abilities and timed tests for walking and standing up. Dan Levy, Pfizer's head of Duchenne muscular dystrophy development, expressed disappointment over the results, noting that the expected improvement in motor function did not materialize. Despite the setback, Pfizer intends to share detailed study data at forthcoming medical and patient advocacy meetings. The company is also continuing to monitor participants and is considering appropriate next steps for the program.

Known as fordadistrogene movaparvovec, Pfizer's gene therapy primarily caused side effects that were mild to moderate in severity. However, the Ciffreo study is currently paused following the death of a Duchenne patient in a separate study involving younger boys, who experienced cardiac arrest.

This failure follows a similar disappointment with Sarepta Therapeutics' gene therapy, Elevidys, which also did not achieve its main goal in a confirmatory, placebo-controlled Phase 3 trial conducted seven months earlier. However, Sarepta reported that Elevidys showed consistent benefits on secondary study measures, prompting the biotechnology company to seek FDA approval for its treatment in all Duchenne patients with specific gene mutations. A decision from the FDA is anticipated by June 21. Last June, the FDA granted accelerated approval to Elevidys for certain boys aged 4 to 5 with Duchenne, based on the therapy's ability to produce microdystrophin, a diminutive protein believed likely to offer benefits.

Pfizer's gene therapy also aims to produce a shortened form of dystrophin, mimicking the muscle-protecting protein that Duchenne patients lack. However, the two therapies are composed of different components, and Pfizer's treatment has faced safety concerns even before the recent death, including cardiac complications.

Duchenne muscular dystrophy predominantly affects boys and is typically diagnosed in early childhood. The disorder disrupts the production of dystrophin, leading to progressive muscle weakness that eventually results in loss of mobility. Patients with this condition often face severe heart and lung complications, which can be life-threatening by their 30s.

While the outcome of Pfizer's trial is disappointing, the company is committed to further analysis and sharing insights from the study. This ongoing research and dialogue with the medical community aim to pave the way for future developments in the treatment of Duchenne muscular dystrophy.