DMD: encouraging results for the PF-06939926 gene therapy product

A phase Ib trial of PF-06939926 in Duchenne muscular dystrophy among 9 patients shows that this gene therapy product allows dystrophin to be produced in the muscle and improves motor function, 12 months after the treatment has been injected.

PF-06939926, developed by Pfizer, is a gene therapy drug candidate being evaluated for Duchenne muscular dystrophy (DMD), consisting of an AAV9 vector and a dystrophin mini-gene.
During the American Society of Gene and Cell Therapy (ASGCT) e-conference, which took place from 12 to 15 May 2020, Pfizer presented extensive results from the phase Ib trial, which is still ongoing, to evaluate a low and high dose of PF-06939926 in 9 outpatient children aged 6 to 12 years (mean age 8 years).

Production of dystrophin and functional improvement

The results announced at the ASGCT conference relate to protein and functional tests 12 months after the injection of PF-06939926 in 9 children, 6 treated with a high dose of PF-06939926 (3E14 Vg/Kg) and 3 with a low dose (1E14 Vg/Kg).

  • They show that dystrophin is produced in the muscles and is, indeed, localised under the membrane, with 21.2% ‘dystrophin-positive’ muscle fibres in the 3 children treated with the low dose, and 50.6% in 3 of the 6 children treated with the high dose for whom the measurement could be performed.
  • Motor performance improved by 3.5 points (NSAA scale) in 6 of the patients treated with the low and high doses, compared to control patients with DMD from other clinical trials.
  • MRI imaging of the muscles of patients treated with the high dose shows a reduction in fatty tissue in the muscle, which is not the case for the low dose.

A phase III trial is currently in preparation to evaluate the long-term efficacy of PF-06939926 in a greater number of patients.


Access Pfizer press release May 15, 2020 “Pfizer’s New Phase 1b Results of Gene Therapy in Ambulatory Boys with Duchenne Muscular Dystrophy (DMD) Support Advancement into Pivotal Phase 3 Study”