Pfizer has officially abandoned development of its experimental gene therapy for Duchenne muscular dystrophy following disappointing Phase 3 trial results, the company confirmed Tuesday. The decision eliminates what had been the most advanced alternative to the only approved gene therapy for this progressive and fatal muscle-wasting condition.
"In light of the disappointing results" disclosed from the Phase 3 study in June, Pfizer "does not have plans to continue development" of fordadistrogene movaparvovec, a company spokesperson stated. The therapy missed all of its study objectives in the pivotal trial, contrasting sharply with rival Sarepta Therapeutics' Elevidys, which despite mixed results has secured broad FDA approval.
Financial Impact and Workforce Reduction
The termination carries significant financial consequences for Pfizer, which will take a $230 million impairment charge related to the therapy's discontinuation. The company is also laying off 150 employees at its Sanford, North Carolina facility, which served as the main hub for Duchenne research and produces two gene therapies for hemophilia.
Pfizer expects an additional $400 million charge in the third quarter related to a manufacturing facility it acquired from Abzena in 2023. The company is "reviewing all future options," including a possible sale of the facility, which was scheduled to open by year-end before plans changed following the study failure.
Clinical Development Challenges
Development of fordadistrogene movaparvovec was marked by significant safety concerns throughout its clinical program. A patient death occurred in an earlier study in 2021, leading to a temporary FDA hold on testing. Another young boy enrolled in a Phase 2 study died suddenly in May 2023 from cardiac arrest, though the connection to treatment remained unclear.
These safety events prompted protocol modifications across the Duchenne gene therapy field. Both Pfizer and Sarepta modified their late-stage trials to exclude patients thought to be at higher risk, and Pfizer implemented requirements for week-long hospital monitoring after treatment.
Regulatory Strategy Differences
Pfizer pursued a different regulatory approach than Sarepta, opting for a placebo-controlled Phase 3 trial rather than seeking accelerated approval based on historical comparisons. Dan Levy, Pfizer's development head of rare neurologic diseases, had expressed confidence in this strategy, stating: "We believe the good data is going to come from a placebo-controlled, randomized clinical trial."
However, this approach ultimately proved unsuccessful when the therapy failed to meet any of its study objectives. Meanwhile, Sarepta's Elevidys, despite missing the main goal of its own placebo-controlled trial, won broad FDA approval after Peter Marks, the agency's top gene therapy evaluator, determined that benefits on secondary measures warranted expanded use.
Impact on Duchenne Treatment Landscape
The decision officially removes the near-term possibility of a second gene therapy option for people with Duchenne muscular dystrophy, a condition with no cure and limited available treatments. U.S. regulators granted narrow clearance to Sarepta's Elevidys in 2023 and substantially broadened its use last month, despite clinical results that have left doubts about its effectiveness.
Pfizer originally acquired the medicine through its 2016 purchase of North Carolina-based biotechnology startup Bamboo Therapeutics, part of the company's broader investment in gene therapy. While this effort has produced mixed results, Pfizer did achieve its first U.S. gene therapy approval this year for hemophilia B treatment Beqvez, and recently reported success in a late-stage trial for a hemophilia A therapy.
Future Outlook
Pfizer is not working on any other Duchenne medicines, and there are no other Duchenne gene therapies currently in late-stage testing, though Regenxbio could begin a Phase 3 study this year. The company has committed to continuing monitoring of all participants treated in studies of the discontinued therapy and sharing detailed results at medical and patient advocacy meetings "to ensure that learnings from the trial can help improve future research and development of treatments for boys living with Duchenne."
