Regenxbio has guided its Duchenne muscular dystrophy (DMD) gene therapy candidate through another test, reporting a clean safety profile and functional improvements as it heads toward pivotal data.
The biotech expects to publish pivotal top-line data on the gene therapy, RGX-202, early in the second quarter. Wednesday, Regenxbio shared a new cut of data from the phase 1/2 trial that underpinned its decision to take RGX-202 into the pivotal study, generating more evidence that its gene therapy may be free from the liver toxicity issues that have affected Sarepta Therapeutics’ Elevidys.
None of the 13 patients in the interim phase 1/2 safety dataset had serious adverse events or adverse events of special interest—including drug-induced liver injury—up to 24 months after treatment. Mean levels of two liver damage biomarkers among the 10 patients who received the pivotal dose were below the upper limit of normal up to 24 months.
Regenxbio, which shared an earlier cut of the data in January, posted its updated safety results alongside the latest efficacy readout. The readout included one-year disease trajectory data, as measured on the North Star Ambulatory Assessment (NSAA), on more patients who received the pivotal dose.
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The expanded dataset provided more evidence that patients who receive RGX-202 outperform external controls and the expected disease trajectory on the NSAA. One-year data favored RGX-202 on other function tests such as time to stand. Regenxbio also shared data on the three patients who received a lower dose showing NSAA performance exceeded the expected disease trajectory after two years.
Pivotal data are the next milestone for RGX-202. The new phase 1/2 results say little about whether the pivotal trial will hit its primary endpoint, which looks at the proportion of participants whose RGX-202 microdystrophin expression is 10% or higher at Week 12.
Regenxbio included data on the expression of microdystrophin—a shortened version of the protein that is at the root of DMD—in the latest update but largely repeated figures shared in January. The addition of a child aged between 1 and 3 years to the analysis affected the data slightly. Regenxbio reported expression levels of 39.7% to 97.3% across three age-based cohorts that received the pivotal dose.
All patients had microdystrophin expression levels above 10% at Week 12. Regenxbio will hit its primary endpoint if it replicates that result in the pivotal trial, although questions about whether the biotech will have enough for FDA approval will remain even if the study succeeds. The agency recently rejected another Regenxbio gene therapy over trial design issues and ordered uniQure to run a sham-controlled study.
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The biotech plans to request a meeting to discuss a filing for accelerated approval of RGX-202 in mid-2026. By the time the FDA is reviewing RGX-202, Regenxbio could have 12-month functional data from most of its pivotal trial patients and have largely enrolled its 30-participant confirmatory study.
Regenxbio CEO Curran Simpson said on an earnings call last week that the company left its end-of-phase 2 meeting with the FDA believing similar efficacy and improved safety compared to Elevidys could be a route to accelerated approval. Yet Regenxbio reached alignment on its DMD program with the Biden-era FDA, making it unclear whether the current administration holds the same views.
