Pfizer pauses Duchenne gene therapy trial after patient death

Dec. 21, 2021

The U.S. FDA has placed a clinical hold on Pfizer's gene therapy to treat Duchenne muscular dystrophy, following the death of a patient in an early stage trial.

Pfizer is testing the gene therapy, known as PF-06939926, in a phase 1 study of up to 35 patients. in a letter sent to patient advocacy group Parent Project Muscular Dystrophy, Pfizer acknowledged the death of a patient participating in the non-ambulatory cohort of the drugmaker's phase 1b mini-dystrophin gene therapy trial.

But the drugmaker doesn't quite know what happened yet. According to Pfizer, screening and dosing in the trial have been paused as the drugmaker works with the independent External Data Monitoring Committee to review the data and figure out the cause of death.

DMD is a rare, incurable genetic disease and Pfizer, along with other drugmakers, is searching for a one-time treatment through gene therapy. Pfizer is testing the same candidate, PF-06939926, which is a phase 3 trial, which was recently restarted with restricted enrollment following several adverse events. That trial is assessing the safety and efficacy of Pfizer's investigational gene therapy in 99 ambulatory male participants, ages 4 through 7 years, with a genetic diagnosis of DMD who are on a stable daily regimen of glucocorticoids.

As for the phase 1 trial, regulators have been notified and the FDA has placed the Investigational New Drug (IND) application on clinical hold. Pfizer has promised to share "more information with the medical and patient community as soon as we can."