Pfizer Updates on Phase 3 Gene Therapy Study for Duchenne Muscular Dystrophy Boys

Pfizer Inc. has announced that the CIFFREO Phase 3 global study, which evaluated the experimental gene therapy fordadistrogene movaparvovec in young boys with Duchenne muscular dystrophy (DMD), failed to meet its primary endpoint. The study aimed to improve motor function in ambulatory boys aged 4 to 7 years but did not show significant enhancements compared to placebo.

The primary measure of the study was the North Star Ambulatory Assessment (NSAA) score, assessed one year post-treatment. Unfortunately, the results did not demonstrate notable improvements in motor function in the boys who received the gene therapy compared to those who received a placebo. Furthermore, key secondary outcomes, such as the 10-meter run/walk speed and the time taken to rise from the floor, also did not show significant differences between the treatment and placebo groups.

The safety profile of fordadistrogene movaparvovec was considered manageable. Most adverse events were mild to moderate, and serious treatment-related adverse events were generally responsive to clinical management.

Dan Levy, MD, PhD, Development Head for Duchenne muscular dystrophy at Pfizer, expressed disappointment with the results, emphasizing the company’s commitment to advancing treatment options for DMD. Levy acknowledged the contributions of the participants, their families, and advocates, and stressed the importance of learning from this trial to enhance future research and development of DMD treatments.

Pfizer will continue monitoring all participants in the study and is evaluating the next steps for the program.

The CIFFREO study is a Phase 3 global, multicenter, randomized, double-blind, placebo-controlled trial. It aims to assess the safety and efficacy of fordadistrogene movaparvovec in ambulatory male participants aged 4 to 7 years who have a genetic diagnosis of DMD and are on a stable regimen of glucocorticoids. The primary goal is to observe changes in the NSAA score from baseline to one year.

Currently, the CIFFREO study is paused due to a serious adverse event that resulted in a fatality during the Phase 2 DAYLIGHT trial, which is evaluating the safety of the same gene therapy in younger participants aged 2 to 3 years with DMD. Pfizer is working to gather more information to understand the cause of this adverse event.

DMD is a severe genetic disorder characterized by progressive muscle degeneration and weakness, typically manifesting in early childhood. The disease predominantly affects boys, beginning with muscle weakness in the hips, thighs, and shoulders, and progressively impacting the skeletal muscles in the arms, legs, and trunk. By the early teens, patients generally lose the ability to walk, and the condition also affects the heart and respiratory muscles, leading to premature death. DMD is the most common form of muscular dystrophy worldwide, affecting 1 in every 5,000 live male births.