A boy has died in Pfizer's phase 2 study of its gene therapy candidate for Duchenne muscular dystrophy, a rare genetic disorder that primarily affects boys, according to a patient advocacy group.
On May 7, Parent Project Muscular Dystrophy published a letter it received from Pfizer announcing the patient's death in the drugmaker's Daylight study. The phase 2 trial is researching the safety and efficacy of fordadistrogene movaparvovec among boys aged 2 to 4. Test sites include hospitals in Florida, Utah, Pennsylvania and Australia.
As it investigates the death, Pfizer paused dosing in its phase 3 Ciffreo study — which overlaps with Daylight — and tests the drug among boys aged 4 to 8. The company is continuing other trial activities.
"We do not yet have complete information and are actively working with the trial site investigator to understand what happened," Pfizer said in the letter. "The patient received the investigational gene therapy, fordadistrogene movaparvovec, in early 2023."
A Pfizer spokesperson told Reuters the death was reported as cardiac arrest, but the company has not verified the letter posted by Parent Project Muscular Dystrophy.
Duchenne muscular dystrophy is a progressive muscle degeneration, and symptom onset usually begins between ages 2 and 3, according to the Muscular Dystrophy Association. The median age of survival in males with DMD is 23.7 years.
Becker's has reached out to Pfizer for comment and will update this article if more information becomes available.