The first US clinical sites will be opening to restart Pfizer’s Duchenne muscular dystrophy (DMD) gene therapy trial, as published in the company’s press release. This is following the lifting of the trial’s hold by the US Food and Drug Administration (FDA).

The global randomized, placebo-controlled phase 3 clinical trial, called CIFFREO, (NCT04281485) is investigating a gene therapy called fordadistrogene movaparvovec (PF-06939926) for the treatment of ambulatory DMD in boys between the ages of 4 and 8 years old. The therapy involves a shortened version of the human dystrophin gene (mini-dystrophin) delivered via a recombinant adeno-associated virus serotype 9 vector.

“[DMD] is a devastating disease with very limited treatment options, and we believe that gene therapy has the potential to significantly impact disease progression,” said Brenda Cooperstone, chief development officer of rare disease at Pfizer.

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The study has been ongoing in 11 countries but was paused in December 2021 following a fatal serious adverse event in a separate phase 1b study (NCT03362502) investigating fordadistrogene movaparvovec in nonambulatory boys with DMD. The patient in that study had advanced disease with underlying cardiac dysfunction.

Following the incident, all trials were paused and the FDA placed a clinical hold on Pfizer’s Investigational New Drug application as the data were reviewed by the independent external Data Monitoring Committee.

The FDA has now lifted the hold after Pfizer addressed its requests regarding potency assay data and a protocol amendment to the trial. The protocol amendment includes the addition of a 7-day hospitalization period after the gene therapy infusion to enable close monitoring and management of patients.

The phase 3 trial has also been approved to restart by regulatory agencies in the United Kingdom, Canada, Taiwan, Spain, and Belgium. Pfizer anticipates that nearly all CIFFREO study sites will open by the end of June 2022.

“Pfizer is pleased to progress CIFFREO and is working as quickly as possible to activate trial sites as local regulatory and ethics approvals occur,” Cooperstone said. “We thank the participants in our clinical trials and their families, as well as the broader Duchenne community, for their ongoing trust and collaboration as we work to advance our investigational gene therapy.”


Pfizer to open first U.S. sites in phase 3 trial of investigational gene therapy for ambulatory patients with Duchenne muscular dystrophy. News release. Pfizer; April 28, 2022.