The Food and Drug Administration (FDA) has granted Fast Track designation to the investigational gene therapy candidate, PF-06939926 (Pfizer), for the treatment of Duchenne muscular dystrophy (DMD).

PF-06939926 is a recombinant adeno-associated virus serotype 9 (rAAV9) capsid carrying a shortened version of human dystrophin gene under the control of a human muscle-specific promoter. The Company has chosen the rAAV9 capsid due to its potential to target muscle tissue.

The designation was based on data from an ongoing phase 1b study evaluating the safety and tolerability of a single intravenous infusion of PF-06939926 in 9 ambulatory boys with DMD aged 6 to 12 years. Preliminary results showed that PF-06939926 was well tolerated during the infusion period and dystrophin expression levels were sustained over a 12-month period.

The Company plans to launch a double-blind, placebo-controlled phase 3 study to evaluate the efficacy and safety of PF-06939926 in boys with DMD. The study will include patients who are at least 4 years old and less than 8 years old; all participants will need to be on a daily dose of glucocorticoids for at least 3 months prior to enrolling and to stay on daily glucocorticoids for the first 2 years of the study. The primary outcome of the study (change from baseline in North Star Ambulatory Assessment) will be assessed at 52 weeks; patients will be followed for 5 years after treatment.

“The FDA’s decision to grant our investigational gene therapy PF-06939926 Fast Track designation underscores the urgency to address a significant unmet treatment need for Duchenne muscular dystrophy,” said Brenda Cooperstone, MD, Chief Development Officer, Rare Disease, Pfizer Global Product Development. “We are working to advance our planned phase 3 program as quickly as possible.”

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The FDA’s Fast Track designation allows for expedited review of therapies that are meant to treat serious or life-threatening conditions. Generally, the designation is granted to drugs that are expected to have an impact on factors such as survival and daily functioning.

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Pfizer receives FDA Fast Track designation for Duchenne muscular dystrophy investigational gene therapy. Accessed October 2, 2020.