Pfizer Gene Therapy for Ambulatory Boys with DMD Fails Late-Stage Study

Rare Daily Staff

Pfizer reported that the CIFFREO late-stage trial of its experimental mini-dystrophin gene therapy did not meet its primary endpoint of improvement in motor function among boys 4 to 7 years of age with Duchenne muscular dystrophy compared to placebo.

The primary endpoint in the final analysis was assessed by change in the North Star Ambulatory Assessment (NSAA) at one year after treatment. Key secondary endpoints, including 10-meter run/walk velocity and time to rise from floor velocity, also did not show a significant difference between participants treated with fordadistrogene movaparvovec and placebo.

Duchenne muscular dystrophy (DMD) is a serious genetic disease characterized by progressive muscle degeneration and weakness. Symptoms usually manifest in early childhood between the ages of 3 and 5. The disease primarily affects boys. Muscle weakness can begin as early as age 3, first affecting the muscles of the hips, pelvic area, thighs, and shoulders, and later the skeletal (voluntary) muscles in the arms, legs, and trunk. By their early teens, patients typically lose their ability to walk and the heart and respiratory muscles are also affected, ultimately resulting in premature death. DMD is the most common form of muscular dystrophy worldwide with an incidence of 1 in every 5,000 live male births.

“We are extremely disappointed that these results did not demonstrate the relative improvement in motor function that we had hoped,” said Dan Levy, development head for Duchenne muscular dystrophy at Pfizer. “We plan to share more detailed results from the study at upcoming medical and patient advocacy meetings, with the goal of ensuring that learnings from this trial can help improve future clinical research and development of treatment options that can improve care for boys living with Duchenne muscular dystrophy.”

The overall safety profile of fordadistrogene movaparvovec in the CIFFREO trial was manageable, with mostly mild to moderate adverse events, and treatment-related serious adverse events generally responding to clinical management.

Pfizer said it will continue to closely monitor all participants enrolled in the study and is evaluating appropriate next steps for the program.

CIFFREO is a phase 3 global, multi-center, randomized, double-blind, placebo-controlled study to assess the safety and efficacy of fordadistrogene movaparvovec investigational gene therapy in ambulatory male participants, aged 4 to 7 years, with a genetic diagnosis of DMD who are on a stable daily regimen of glucocorticoids. The primary endpoint of the study is a change from baseline to one year in the North Star Ambulatory Assessment total score.

The CIFFREO study is currently on a dosing pause due to a fatal serious adverse event in the phase 2 DAYLIGHT trial. DAYLIGHT is a study that is evaluating the safety and tolerability of fordadistrogene movaparvovec in participants 2 years to 3 years of age with DMD. Pfizer is actively working to gather additional information on the event to understand the potential cause.