Patients Treated With REGENXBIO’s DMD Gene Therapy RGX-202 Exceed Expected Disease Trajectory on NSAA

Among 4 patients treated with the pivotal dose of REGENXBIO’s RGX-202, an investigational adeno-associated virus (AAV) vector-based gene therapy intended to treat Duchenne muscular dystrophy (DMD), in the phase 1/2 portion of the AFFINITY DUCHENNE clinical trial (NCT05693142), all 4 surpassed expected disease trajectory on the North Star Ambulatory Assessment (NSAA) with utilization of the Collaborative Trajectory Analysis Project (cTAP) disease progression model at 18 months posttreatment.¹

Specifically, REGENXBIO noted that the patients treated with the gene therapy product showed an average improvement of 7.4 points in comparison to cTAP. The company also pointed out that at 12 months posttreatment, the 4 treated patients had improved an average of 6.6 points in comparison to cTAP.

REGENXBIO stated that additional results from the trial covering safety and biomarker data, in addition to more functional data, will be presented this year at the Muscular Dystrophy Association (MDA) Clinical & Scientific Conference, which will be held March 8 to 11 in Orlando, Florida. In the middle of 2026, the company is planning to submit a biologics license application (BLA) for RGX-202 via an accelerated approval pathway. Although the pivotal phase 1/2 trial portion finished enrolling patients in October of last year, a separate confirmatory portion (part 3) is currently enrolling patients and anticipated to have recruited the majority of its participants by the time the BLA is filed. REGENXBIO has planned engagements with the FDA and European Medicines Agency in 2026 in order to support global expansion of the study.

"2026 is set to be a transformative year for REGENXBIO, as we enter commercial stage with two near-term catalysts from our three late-stage assets and a clear path to sustained growth," Curran Simpson, the president and chief executive officer of REGENXBIO, said in a statement.¹ "We are starting the year with exciting new long-term data for our Duchenne program, demonstrating how our comprehensive strategy to maximize the potential for therapeutic benefit across all our programs is resulting in positive outcomes for patients. We are continuing to set the bar high for how potentially life-changing gene therapies are discovered, developed, and manufactured; this year we are sharply focused on advancing our commercial readiness to enable successful launches of these medicines for patients in need.”

In addition to RGX-202, one of REGENXBIO’s other lead programs is clemidsogene lanparvovec (RGX-121), an investigational adeno-associated virus (AAV) vector-based gene therapy for mucopolysaccharidosis type 2 (MPSII, also known as Hunter syndrome).² RGX-121 is currently being evaluated in the pivotal phase 1/2/3 CAMPSIITE clinical trial (NCT03566043). Notably, a BLA for RGX-121 is currently under review by the FDA, with a Prescription Drug User Fee Act (PDUFA) goal date set for February 8, 2026.³

Updated data from CAMPSIITE reported at the International Congress of Inborn Errors of Metabolism (ICIEM), held in Kyoto, Japan, from September 2 to 6, 2025, included the finding that 13 patients treated in the pivotal phase had shown an 82% reduction in heparan sulfate (HS) D2S6 levels in the cerebrospinal fluid (CSF) through 1 year posttreatment.² According to a September 2025 press release, HS D2S6 is “a key biomarker of MPS II brain disease that is reasonably likely to predict clinical benefit.” The company also noted that the updated data is in line with earlier findings: the study previously met its primary end point for the proportion of treated patients showing CSF HS D2S6 under maximum attenuated levels at 16 weeks posttreatment (P < .0001).

REFERENCES
1. REGENXBIO highlights key 2026 catalysts and announces positive long-term functional outcomes in lead Duchenne gene therapy program. News release. REGENXBIO Inc. January 11, 2026. Accessed January 14, 2026. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-highlights-key-2026-catalysts-and-announces-positive
2. REGENXBIO presents positive twelve-month pivotal data from phase I/II/III CAMPSIITE® trial of RGX-121 for treatment of MPS II. News release. REGENXBIO Inc. August 18, 2025. Accessed January 14, 2026. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-presents-positive-twelve-month-pivotal-data-phase
3. REGENXBIO announces FDA review extension of BLA for RGX-121 to treat patients with MPS II. News release. REGENXBIO Inc. August 18, 2025. Accessed January 14, 2026. https://ir.regenxbio.com/news-releases/news-release-details/regenxbio-announces-fda-review-extension-bla-rgx-121-treat