Pfizer’s Duchenne muscular dystrophy gene therapy failed to meet the primary and key secondary endpoints in a Phase 3 study, pointing to a bleak future for the program.
The gene therapy failed to significantly improve motor function at one year in boys with Duchenne, measured using a 17-item scale that evaluates various aspects of mobility called the North Star Ambulatory Assessment. The therapy also did not significantly improve secondary endpoints such as 10-meter run/walk velocity and time-to-rise-from-floor velocity compared to placebo.
“Pfizer will continue to closely monitor all participants enrolled in the study and is evaluating appropriate next steps for the program,” the company said Wednesday in a statement.
Known as CIFFREO, the study enrolled 99 boys aged 4 through 7 with Duchenne muscular dystrophy, according to the federal clinical trials database. The participants received Pfizer’s fordadistrogene movaparvovec or placebo.
There have been two patient deaths in Pfizer’s Duchenne gene therapy clinical studies. In May, Pfizer disclosed that a boy enrolled in a Phase 2 study for the therapy passed away, and it was investigating the patient’s death. As a result, the company paused the administration of the gene therapy to boys who had originally been in the placebo arm of the Phase 3 study. In 2021, Pfizer disclosed a boy in a Phase 1b study of the gene therapy died and later said he “had more advanced disease with underlying cardiac dysfunction.”
The FDA granted accelerated approval last June to Sarepta Therapeutics’ Duchenne muscular dystrophy gene therapy for boys aged 4 to 5. Within the narrow group of patients eligible for Elevidys, demand has been high. The FDA is expected to decide by June 21 on whether to expand the eligible population based on mixed results from a confirmatory study.
Last year, Pfizer took a step back from developing early-stage gene therapies, selling a suite of preclinical programs to AstraZeneca.