Interim results from a small group of children in a Phase I/II trial are essentially in line with that of Elevidys, according to BMO Capital Markets analysts.
In the race to bring another Duchenne muscular dystrophy treatment to the market, Regenxbio showed new interim Phase I/II data Thursday for its gene therapy RGX-202.
The data, which came from five patients aged 6 to 12 years old in the AFFINITY DUCHENNE trial, demonstrated “consistent, robust microdystrophin expression,” according to the biotech’s press release. The trial tracked patients at 9 and 12 months post treatment.
Analysts from BMO Capital Markets saw the results as being essentially in line with Sarepta’s Duchenne muscular dystrophy (DMD) gene therapy Elevidys, first approved in June 2023. “Although certain [RGX-202] functional improvements appear slightly higher than Elevidys, given the high variability across patients/control and lack of placebo arm, we don’t think the efficacy difference between RGNX/Elevidys is material or could drive/prove differentiated clinical outcomes,” the analysts wrote Thursday morning.
Regenxbio’s stock was down about 16% at the time of publication.
AFFINITY DUCHENNE’s primary endpoint is safety, with a biomarker endpoint of microdystrophin expression. Regenxbio reported no serious adverse effects. Notably, patients taking RGX-202 are given immunosuppressants to tamp down on those effects, something not done with Elevidys, according to the BMO analysts.
As for efficacy, RGX-202 “continues to demonstrate evidence of positively impacting disease trajectory,” according to the company, showing improvements on the North Star Ambulatory Assessment and timed function tests, including time to stand, 10-meter walk-run and time to climb, which exceeded external natural history controls.
Regenxbio is planning a biologics license application sometime in mid-2026 through the FDA’s accelerated approval pathway, with an eye toward an approval in the first half of 2027, according to materials distributed by the company at its data readout.
Regenxbio and Sarepta are close competitors in the DMD space. In 2020, Regenxbio sued Sarepta for infringement of a patent on an adeno-associated virus (AAV) gene therapy cell culture technique. In 2024, a Delaware district ruled in favor of Sarepta, stating that the cell culture technique was not patentable.
The safety of DMD gene therapies has come under a harsh glare after a patient taking Elevidys died of acute liver injury in March. While safety appears to be a positive in Regenxbio’s trial, the BMO analysts noted that “heavy” immunosuppression carries its own risks, and that the viral vector that Regenxbio uses has had its own mortality concerns.
