Pfizer Pauses Gene Therapy Dosing in DMD Trial After Patient's Death

Pfizer recently disclosed the unfortunate passing of a participant in their Phase II clinical trial, known as DAYLIGHT, which was assessing the efficacy of an experimental gene therapy named fordadistrogene movaparvovec. The therapy is designed to treat Duchenne muscular dystrophy (DMD), a genetic disorder leading to muscle degeneration and weakness. The patient's death was reported to have occurred suddenly, and Pfizer is collaborating with the trial's investigators to determine the cause.

This incident has had repercussions on another of Pfizer's clinical trials, the Phase III CIFFREO study, also focused on DMD. While the initial dosing for the trial was completed in 2023, Pfizer has decided to halt the administration of the gene therapy for the cross-over segment of the study. Nonetheless, the trial is expected to proceed as planned.

In a statement, Pfizer emphasized the paramount importance of patient safety and well-being in their clinical trials. They are committed to working with regulatory bodies and an external data monitoring committee to evaluate the situation and will update the medical community and patients as soon as new information becomes available.

The company expressed its condolences to the family and friends of the deceased, as well as to those closely involved in his care. This is not the first time Pfizer has faced such a situation with fordadistrogene movaparvovec; in December 2021, they had to pause another study due to an unexpected patient death. The FDA, however, lifted the clinical hold on the therapy in April 2022, enabling Pfizer to initiate the first U.S. sites for the CIFFREO trial.

DMD typically affects young boys and is caused by mutations in the gene responsible for the production of dystrophin, a protein vital for muscle function. Fordadistrogene movaparvovec aims to provide a functional, albeit shortened, version of the dystrophin gene using an AAV9 capsid to target muscle tissue.

Duchenne muscular dystrophy is a severe condition that not only leads to muscle weakness but can also impact vital organs, including the lungs, potentially causing respiratory failure. The treatment being developed by Pfizer holds the potential to address this debilitating disease by introducing a modified version of the crucial dystrophin gene into the affected muscles.