REGENXBIO announced on June 24 that it is pursuing an accelerated approval for its Duchenne muscular dystrophy gene therapy, RGX-202, as the Food and Drug Administration shows changing attitudes toward rare disease treatments. The company aims to file a Biologics License Application under the accelerated pathway in the third quarter of this year.
The announcement follows recent developments at the FDA, which has shifted several positions since former Commissioner Marty Makary and Center for Biologics Evaluation and Research ex-director Vinay Prasad left their posts. Earlier in the week, REGENXBIO received confirmation from the agency that existing data for its Hunter syndrome gene therapy (RGX-121) would be sufficient to support an accelerated approval submission without requiring additional studies or a new control arm. This move was similar to a recent decision regarding uniQure’s Huntington’s disease gene therapy.
RGX-202 is designed as an AAV8 gene therapy delivering a version of the microdystrophin gene intended to partially restore dystrophin function in muscle tissue. In May, REGENXBIO reported that 93% of boys enrolled in its Phase 3 AFFINITY DUCHENNE trial achieved at least 10% microdystrophin expression by week 12. The company said this expression correlated with statistically significant functional improvement and should support their application with regulators.
However, two patients experienced serious adverse events during trials: one suffered liver injury and another myocarditis. Both cases were described by REGENXBIO as "easily managed and resolved within weeks." Despite these incidents, Leerink told investors in May that such events "muddy the update." At that time, REGENXBIO said it was advised by the FDA to conduct a randomized controlled trial, but planned further discussions about alternative proposals.
Chief Executive Officer Curran Simpson said he is “encouraged by the recent FDA trends in rare disease development,” referencing what he called “collaborative discussion” around their Hunter syndrome program. Simpson also stated, “The RGX-202 pivotal dataset directly aligns with the established accelerated approval criteria: the magnitude of clinical effect seen in functional improvement from baseline, correlation between the biomarker and functional outcomes, and a differentiated safety profile.”
REGENXBIO anticipates a potential approval decision by late 2027 and has begun pre-commercial production at its manufacturing center in Maryland.
