Boy Dosed with Pfizer DMD Gene Therapy Dies a Year after Phase II Trial

Pfizer has paused enrollment in a Phase III trial assessing its Duchenne muscular dystrophy (DMD) gene therapy candidate fordadistrogene movaparvovec after acknowledging the sudden death of a young boy who received the treatment last year.

The boy, whose age was not disclosed, was among patients dosed with the gene therapy in the Phase II DAYLIGHT trial (NCT05429372), which is evaluating fordadistrogene movaparvovec in 10 boys ages two to less than four years old. Initial dosing was completed last year in DAYLIGHT, as well as in the Phase III CIFERO trial (NCT04281485), which is studying the gene therapy in boys ages four to less than eight years old.

Pfizer said it has paused dosing associated with the crossover portion of the placebo-controlled, randomized CIFFREO trial, in which patients who originally received placebo are crossed over to the gene therapy, while the company reviews data with regulators and the study’s independent External Data Monitoring Committee.

Fordadistrogene movaparvovec is a recombinant adeno-associated virus, serotype 9 (AAV9) carrying a mini-dystrophin or truncated human dystrophin gene under the control of a...