Date Time Pfizer Doses First Participant in Phase 3 CIFFREO study NEW YORK–(BUSINESS WIRE)– Pfizer Inc. (NYSE: PFE) today announced that the first participant has been dosed in the Phase 3 CIFFREO study, which will evaluate the efficacy and safety of investigational gene therapy candidate PF-06939926 in boys with Duchenne muscular dystrophy (DMD). The CIFFREO trial is expected to enroll 99 ambulatory male patients, ages 4 through 7, across 55 clinical trial sites in 15 countries. The first patient was dosed at a site in Barcelona, Spain on December 29, 2020. CIFFREO is a Phase 3 global, multicenter, randomized, double-blind, placebo-controlled study. The primary endpoint of the study is the change from baseline in the North Star Ambulatory Assessment (NSAA) at one year. The NSAA is a 17-item test that measures gross motor function in boys with DMD. Regardless of cohort, eligible participants are scheduled to receive the investigational gene therapy, either at the start of the study or after one year following treatment with placebo. Participants will be followed in the CIFFREO study for five years after treatment with the investigational gene therapy. Trial participants will receive commercially representative drug product manufactured at Pfizer’s state-of-the-art gene therapy manufacturing facility in Sanford, North Carolina.