Pfizer Restricts Enrollment in Duchenne Gene Therapy Trial Following Adverse Events

Pfizer has further restricted enrollment criteria for its ongoing phase 3 CIFFREO trial (NCT04281485) of fordadistrogene movaparvovec for the treatment of Duchenne muscular dystrophy (DMD) following 3 serious adverse events (AEs).¹

In a letter sent to advocacy organization Parent Project Muscular Dystrophy, Pfizer addressed the 3 serious AEs, 2 of which involved myocarditis. Moving forward, patients with DMD who have any mutation affecting exons 9 through 13, inclusive, or deletion affecting both exon 29 and exon 30 will be excluded from participating in the study. Pfizer stated that the excluded mutations are estimated to be present in less than 15% of patients with DMD.

“We know this change will be very difficult news for the community. However, once the new safety findings and risk information were known, it was necessary to take this step to protect the safety of study participants,” Pfizer wrote in the letter.¹

The decision follows a report by Pfizer’s External Data Monitoring Committee that found that these mutations in the dystrophin gene may be associated with adverse event risk after treatment with fordadistrogene movaparvovec. The trial will continue to enroll patients in trial sites outside the US under the new criteria to hit the target enrollment of 99 participants.

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“We understand the sense of urgency for novel therapies among many families globally. We are appreciative of your trust and collaboration and assure you that we are working with the utmost care as we advance our program of gene therapy for Duchenne,” Pfizer concluded.¹

Pfizer dosed the first patient in the CIFFREO trial in January 2021.² The trial’s primary end point is change in North Star Ambulatory Assessment (NSAA) at 1 year from baseline. Participants in the placebo group will be treated with the gene therapy after 1 year and treated participants will switch to placebo after 1 year. Participants will be followed-up for 5 years post-treatment.

Fordadistrogene movaparvovec previously received fast track designation from the FDA in October 2020 as well as orphan drug and rare pediatric disease designations in May 2017.

“DMD is a progressive disorder, and patients and parents are waiting desperately for treatment options,” said Silvia Avila, President, Duchenne Parent Project Spain, in a statement released upon trial initiation.² “The initiation of this study is an important step forward for this community, and it fuels us with hope that one day there may be treatment options for boys impacted with this devastating disease.”

REFERENCES
1. Pfizer announces amendment to ongoing gene therapy phase 3 trial. September 28, 2021. https://www.parentprojectmd.org/pfizer-announces-amendment-to-ongoing-gene-therapy-phase-iii-trial/
2. Pfizer doses first participant in phase 3 study for Duchenne muscular dystrophy investigational gene therapy. News release. Pfizer. January 7, 2021. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-doses-first-participant-phase-3-study-duchenne