Regenxbio's RGX-202 Hits Primary Endpoint in Pivotal Duchenne Trial, Clearing Path to a 2027 Accelerated-Approval Filing
Regenxbio's gene therapy RGX-202 met the primary endpoint of its pivotal Phase III AFFINITY DUCHENNE trial, with 93% of participants reaching the microdystrophin expression threshold.
Overview
Regenxbio said on May 14 that its investigational gene therapy RGX-202 met the primary endpoint of the pivotal Phase III portion of its AFFINITY DUCHENNE trial, with 93% of participants achieving microdystrophin expression above 10% at Week 12 (p<0.0001), according to the company’s PR Newswire announcement. The result positions the company to pursue accelerated approval for a therapy aimed at Duchenne muscular dystrophy, a fatal muscle-wasting disease.
What We Know
The trial is formally designated the Phase I/II/III AFFINITY DUCHENNE trial. As of an April 16, 2026 data cutoff, 31 participants had received RGX-202 at a dose of 2x10^14 GC/kg in the pivotal portion, according to the company announcement.
On the biomarker measures, Regenxbio reported that microdystrophin expression averaged 71.1% across all participants and 41.6% in older boys aged over 8 years, and that 80% of participants achieved expression above 40%, per the PR Newswire release. BioPharma Dive reported the underlying breakdown: 28 of the 30 study participants who received muscle biopsies produced at least 10% of normal levels of microdystrophin, with average expression of about 71% across all treatment recipients and almost 42% in boys over 8 years of age.
Regenxbio also reported a link between the biomarker and how patients functioned. The company said RGX-202 microdystrophin expression at Week 12 “demonstrated a statistically significant correlation with functional improvement at one year as measured by NSAA change from baseline (correlation=.094, p=0.0002),” referring to the North Star Ambulatory Assessment, according to the PR Newswire announcement. BioPharma Dive noted that nine volunteers with at least one year of follow-up demonstrated statistically significant improvements on multiple tests of motor function.
Steve Pakola, M.D., Chief Medical Officer of Regenxbio, said RGX-202 “is the first gene therapy in development for Duchenne to demonstrate strong, statistically significant correlation between microdystrophin expression and functional improvement,” according to the company announcement.
On safety, the company reported two serious adverse events. As described in the PR Newswire release, one case of subacute myocarditis was reported in an 8-year-old participant whose most recent cardiac MRI confirmed no heart muscle fibrosis and no change in ejection fraction, and one case of asymptomatic liver injury was reported in a 10-year-old participant. BioPharma Dive reported that both serious events were easily managed and resolved within weeks, and that average liver inflammation markers did not surpass the upper limit of normal.
Aravindhan Veerapandiyan, M.D., a principal investigator at Arkansas Children’s Hospital, said it was “encouraging to see robust microdystrophin expression, correlation with functional outcomes, and a manageable safety profile,” per the company announcement. Pat Furlong, Founding President of Parent Project for Muscular Dystrophy, said the “topline results are exciting for the Duchenne community,” according to the same release.
Regenxbio said it plans to pursue accelerated approval for RGX-202 and is preparing for a potential commercial launch in 2027, according to the PR Newswire announcement. In its first-quarter operational highlights, the company said it expects to have completed dosing in all 60 patients across the pivotal and confirmatory trials by mid-year, with more than 20 additional participants enrolled in the confirmatory trial, and reported $150.5 million in cash, cash equivalents and marketable securities as of March 31, 2026, according to a separate PR Newswire release. President and CEO Curran Simpson said the company remains “focused on advancing RGX-202 for Duchenne toward potential BLA submission,” per that release.
What We Don’t Know
Regenxbio has not yet filed its Biologics License Application. BioPharma Dive reported that Simpson said the company intends to wait before filing an application given the FDA leadership transition underway, but is banking on an approval in 2027 — leaving the exact filing date and the regulatory outcome open.
The functional data rest on a small follow-up cohort. The one-year NSAA improvement was measured in nine participants, as reported by both the company and BioPharma Dive, and longer-term durability across the full trial population is not yet established.
Investor reaction was not uniformly positive. BioPharma Dive reported that a Leerink Partners analyst characterized the update as “more mixed than we had hoped,” citing safety concerns that “muddy the update.”
Context
Duchenne muscular dystrophy has drawn sustained drug-development activity across multiple therapeutic approaches. The Machine Herald previously reported on Precision Biosciences winning FDA Fast Track designation for a gene-editing therapy targeting Duchenne — a distinct modality from Regenxbio’s AAV gene-replacement approach. RGX-202’s pivotal readout adds a Phase III data point to a field that has been closely watched following safety questions around earlier Duchenne gene therapies.