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Pfizer gene therapy for Duchenne fails to meet goals of key trial

Pfizer’s experimental gene therapy for Duchenne muscular dystrophy didn’t improve the motor function of young boys enrolled in a late-stage trial meant to provide a decisive verdict on the treatment’s potential.

Results from a final analysis showed the treatment failed to meet the main and secondary goals of the study compared to placebo, the company said Wednesday afternoon. Participants in the Phase 3 trial, called Ciffreo, were assessed on a rating scale used to measure motor abilities, as well as timed tests of how quickly they walked or stood up.

“We are extremely disappointed that these results did not demonstrate the relative improvement in motor function that we had hoped,” said Dan Levy, Pfizer’s development head of Duchenne muscular dystrophy, in a statement.

The company plans to share detailed data from the study at upcoming medical and patient advocacy meetings, Levy said. It continues to monitor all participants in the study and is “evaluating appropriate next steps for the program.”

Side effects related to Pfizer’s therapy, known as fordadistrogene movaparvovec, were mostly mild to moderate in severity, Pfizer said. The Ciffreo study is currently paused due to the death of a Duchenne patient in another study testing the treatment in younger boys with the muscle-wasting condition.

The study failure comes about seven months after a similar gene therapy from Sarepta Therapeutics, Elevidys, also missed its main goal in a confirmatory, placebo-controlled Phase 3 trial.

Unlike Pfizer, Sarepta said Elevidys was associated with consistent benefit on secondary study measures. The biotechnology company has since asked the FDA to approve its treatment for all Duchenne patients with specific mutations in the gene that’s linked to the disease. A decision is expected by June 21.

The FDA had granted accelerated approval to Elevidys last June for certain boys with Duchenne who are between 4 and 5 years of age. The agency’s decision was based on that therapy’s ability to produce a diminutive protein, microdystrophin, the agency deemed “reasonably likely” to predict a benefit.

Pfizer’s gene therapy is also designed to help produce a shortened form of dystrophin that mimics the muscle-protecting protein Duchenne patients lack. But they’re made of different components and Pfizer’s has hit safety setbacks even before the recent death, which was due to cardiac arrest.

Duchenne almost always affects boys and typically is diagnosed in early childhood. Disruption of dystrophin production leads to progressive muscle weakness that eventually takes away patients’ ability to walk. People with the condition can die from heart and lung complications in their 30s. 


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