This week, Pfizer announced the sudden death of a participant in its phase 2 DAYLIGHT study, evaluating its new gene therapy for Duchenne muscular dystrophy (DMD) in pediatric patients.
In a statement, Pfizer revealed that the patient was undergoing fordadistrogene movaparvovec treatment, first administered in early 2023. In response to the death, the drugmaker has paused dosing in the crossover portion of the subsequent phase 3 CIFFREO trial, which targets a slightly older age cohort of boys aged 4 to less than 8 years. The CIFFREO trial, which had just completed its initial dosing phase last year, utilizes a placebo-controlled, randomized crossover design.
Despite the pause, Pfizer confirmed that other activities within the CIFFREO trial will proceed as scheduled, and that the dosing suspension does not affect other ongoing trials within the fordadistrogene movaparvovec program, as dosing in those has been completed.
The trial had been previously paused in December of 2021, due to the death of a patient in the non-ambulatory cohort of the phase 1b study, which Pfizer later attributed to advanced disease and underlying cardiac dysfunction. After the pause, Pfizer amended the trial protocol to include a seven-day hospital stay for monitoring post-dosing, and resumed the study in March of 2022.
Fordadistrogene movaparvovec works by using a modified virus to deliver a functional version of the dystrophin gene directly into muscle cells. This gene encodes a shortened version of the dystrophin protein, called micro-dystrophin, which helps improve muscle function and slow disease progression. The therapy aims to provide a long-term treatment option by compensating for the defective gene responsible for DMD.
