REGENXBIO’s DMD Gene Therapy RGX-202 Generates Microdystrophin Expression in Additional Patients Treated in Phase 1/2 Trial
One of the patients, who was aged 3 years at the time of treatment, achieved 122.3% microdystrophin expression compared to control.
REGENXBIO’s RGX-202, an investigational adeno-associated virus (AAV) vector-based gene therapy intended to treat Duchenne muscular dystrophy (DMD), has continued to demonstrate the ability to produce microdystrophin at “consistent, robust” levels in data from 2 new patients treated in the phase 1/2 portion of the AFFINITY DUCHENNE clinical trial (NCT05693142).1 The results were presented at the 2025 Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, held March 16-19 in Dallas, Texas, by Fei Cao, the medical program lead at Genethon.
One of the patients, who was aged 3 years at the time of treatment, achieved 122.3% microdystrophin expression compared to control. In the other patient, who was treated at 7 years of age, microdystrophin expression was found to be 31.5% compared to control.
Furthermore, REGENXBIO reported that in all patients RGX-202 was localized to the sarcolemma, as intended. The company also stated that in patients aged 8 years of age and older who are ambulatory, microdystrophin expression has been reported at levels higher than other approved or investigational DMD gene therapy products. In addition, REGENXBIO noted that on qPCR RGX-202 demonstrates vector genome copies from 4.9 to 55.4, which are the highest reported across approved and investigational DMD gene therapy products.
With regard to safety, RGX-202 was characterized as “well-tolerated" as of the February 21, 2025 data cutoff. There were no serious adverse events (AEs) or AEs of special interest (AESI) in patients treated at any dose level. Potential AESIs included central or peripheral neurotoxicity, drug-induced liver injury, and thrombocytopenia; these did not occur in any patients. Nausea, vomiting, and fatigue were noted to be common AEs related to RGX-202, but all of these are typically associated with gene therapy products and resolved.
"RGX-202 is the only next generation gene therapy for Duchenne in a pivotal phase trial,” Steve Pakola, MD, the chief medical officer at REGENXBIO, said in a statement.1 “The new data from the age 1-3 cohort builds on the favorable safety and efficacy profile seen in ages 4 and older and reinforces the potential of RGX-202 to serve a wide age range of patients. The consistent, robust microdystrophin levels seen across the age range as well as the functional improvements previously reported support RGX-202's potential to alter the course of this devastating disease. We look forward to sharing additional phase 1/2 functional data in the first half of 2025. We also continue to rapidly advance the pivotal trial towards completing enrollment this year and BLA submission mid2026."
In November 2024, REGENXBIO announced that the first patient had been dosed in the pivotal phase 3 portion of AFFINITY DUCHENNE.2 REGENXBIO noted that the phase 3 portion of the trial is utilizing 2×1014 GC/kg, which was dose level 2 (DL2) in the study’s dose expansion portion, as the pivotal dose, in accordance with an End of Phase 2 meeting that the FDA held with the company. Furthermore, REGENXBIO anticipates that it will submit a biologics license application for RGX-202 in 2026 via an accelerated approval pathway.
"Patients with Duchenne continue to be in need of treatment options that could meaningfully impact the course of disease," Carolina Tesi-Rocha, MD, of Stanford Children's Hospital, added to the statement.1 "The microdystrophin expression and biomarker data presented represent key indicators of potential therapeutic effect. Combined with the safety and functional data to date, I am highly encouraged by the profile of RGX-202."
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