A few short days after announcing an FDA pivot on a separate asset, REGENXBIO is planning to test the agency’s apparent newfound rare disease outlook on another late-stage gene therapy.
REGENXBIO is aiming for an accelerated approval its Duchenne muscular dystrophy gene therapy amid changing FDA sentiment toward rare diseases, despite adverse events that marred a recent data drop.
Since the departure of former FDA Commissioner Marty Makary and Center for Biologics Evaluation and Research ex-director Vinay Prasad, the agency has backtracked several controversial stances, including REGENXBIO’s own Hunter syndrome gene therapy, which was rejected in February. Earlier this week, the FDA reversed its earlier concerns about REGENXBIO’s RGX-121, now deeming existing data sufficient for an accelerated approval submission without a requirement for further studies or a new control arm—a move that echoes a similar shift for uniQure’s Huntington’s therapy.
Now, the biotech is counting on the FDA’s seemingly restored flexibility in rare diseases for another candidate, this one for Duchenne muscular dystrophy (DMD). The severe degenerative muscle disease eventually leads to loss of movement, required breathing support, cardiomyopathy and early death. REGENXBIO plans to file a Biologics License Application under the accelerated approval pathway in the third quarter for its gene therapy RGX-202, according to a Wednesday release.
RGX‑202 is an AAV8 gene therapy that delivers a version of the microdystrophin gene designed to partially restore dystrophin function in muscle. In May, REGENXBIO reported that the Phase 3 portion of its AFFINITY DUCHENNE trial hit the main endpoint, with the majority (93%) of 30 boys achieving at least 10% microdystrophin expression at week 12. The microdystrophin expression was linked with a statistically significant improvement in function, which should support an accelerated application with the FDA, according to REGENXBIO.
But two patients experienced serious adverse events: one case of liver injury and another of myocarditis, or inflammation of the heart. While the company said that both cases were “easily managed and resolved within weeks,” Leerink told investors in May that the events “muddy the update.”
At the time, REGENXBIO said the FDA recommended a randomized controlled trial, with the biotech planning to meet with the agency to discuss the data and alternative proposals.
Now, REGENXBIO CEO Curran Simpson said the biotech is “encouraged by the recent FDA trends in rare disease development,” citing the “collaborative discussion” regarding its Hunter Syndrome program. The company did not say anything about agency regulators changing their minds on RGX-202 specifically.
“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,” Simpson added.
REGENXBIO believes it could secure a potential approval decision by the second half of 2027. In anticipation of approval, the biotech is preparing for market launch at its end-to-end, in-house manufacturing center in Maryland, where pre-commercial production started last year.
