Pfizer Pauses Enrollment in DMD Gene Therapy Study After Patient Death

Rare Daily Staff

Pfizer, in a May 7 letter to Duchenne muscular dystrophy patient advocacy organizations, reported that a participant in its phase 2 DAYLIGHT study of its experimental gene therapy for the treatment of Duchenne muscular dystrophy died suddenly and that it is pausing enrollment in the crossover portion of its CIFFREO study.

The company said that the patient received the investigational gene therapy, fordadistrogene movaparvovec, in early 2023. Initial dosing for the placebo-controlled, randomized phase 3 CIFFREO trial, which utilizes a crossover trial design, was also completed in 2023.

Pfizer said it is working with regulators and the independent external Data Monitoring Committee as it learns more about the event. The company said other trial activities are continuing as scheduled as dosing in other studies have been completed.

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 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 caused by an absence of dystrophin, a protein that helps keep muscle cells intact. In the absence of dystrophin, muscle cells deteriorate.

Fordadistrogene movaparvovec is an experimental recombinant adeno-associated virus serotype 9 (AAV9) capsid carrying a shortened version of the human dystrophin gene (mini-dystrophin) under the control of a human muscle-specific promotor. The AAV9 capsid was chosen as the delivery mechanism because of its potential to target muscle tissue.

Pfizer’s DAYLIGHT and CIFFREO trials are investigating fordadistrogene movaparvovec in patients with DMD, in different age cohorts. DAYLIGHT is a study in boys 2 years to less than 4 years of age, and CIFFREO is a study in boys 4 to less than 8 years of age.

“The safety and well-being of the patients in our clinical trials remains our top priority, and we are committed to sharing more information with the medical and patient community as soon as we can,” Pfizer said in the letter.

Pat Furlong, president and CEO of Parent Project Muscular Dystrophy in a note posted on the organization’s website, expressed the patient community’s grief in response to the news.

“This journey is not without its challenges, and yet, it is also instilled with resilience, determination, and unwavering hope.” she said. “In the face of adversity, we find the courage to persevere, fueled by the knowledge that every step forward brings us closer to our shared goal of ending Duchenne.”

Photo: Pat Furlong, president and CEO of Parent Project Muscular Dystrophy