A Duchenne muscular dystrophy patient died of cardiac arrest on Friday in a Phase 2 trial of Pfizer’s gene therapy, the pharma company confirmed.
The patient received fordadistrogene movaparvovec in early 2023 as part of Pfizer’s DAYLIGHT study enrolling patients 2 and 3 years old. As a result of the boy’s death, Pfizer is pausing dosing in the crossover portion of its Phase 3 CIFFREO study in patients 4 to 7 years old.
“We do not yet have complete information and are actively working with the trial site investigator to understand what happened,” Pfizer said in a letter posted on Parent Project Muscular Dystrophy’s website.
STAT first reported the news.
Pfizer previously disclosed a separate patient death that occurred in an open-label Phase 1b study of fordadistrogene movaparvovec in 2021. In 2022, Pfizer said the patient “had more advanced disease with underlying cardiac dysfunction.”
“Beyond CIFFREO, the dosing pause does not apply to other ongoing trials in the fordadistrogene movaparvovec program as dosing has been completed in those studies,” Pfizer said in the letter.
“We are working with the investigator to gather information,” a Pfizer spokesperson told Endpoints News on Tuesday. “Pfizer, together with the independent external Data Monitoring Committee, is in the process of reviewing the data to understand the potential cause. We are working diligently and with the utmost care to evaluate our investigational gene therapy while protecting the safety of the participants, which is our top priority.”