REGENXBIO has shared encouraging new data from their ongoing Phase I/II AFFINITY DUCHENNE trial of RGX-202, an investigational gene therapy for Duchenne muscular dystrophy (DMD). This update follows the presentation of the data at the Muscular Dystrophy Association (MDA) conference.
Safety
One of the most important questions in any clinical trial is whether the treatment is safe. The latest data, cut on January 5, 2026, continues to show a positive safety picture for RGX-202:
- No serious adverse events (SAEs) and no adverse events of special interest (AESIs) have been reported in the Phase I/II study.
- There is no evidence of liver injury, based on blood markers including GGT and total bilirubin.
- Participants showed a mean reduction in creatine kinase (CK), a marker of muscle damage, one year after receiving gene therapy. This was supported by reductions seen in ALT, AST, and LDH.
- The trial uses a short-course immune suppression protocol to manage any potential side effects of the gene therapy.
What are CK, ALT, AST, GGT and LDH? These are enzymes (proteins) found in the blood. In DMD, elevated levels can signal muscle damage or stress on the liver and other tissues. Seeing reductions in these markers after treatment is an encouraging sign that the therapy may be reducing ongoing muscle damage.
Functional Data
This update included functional data from seven participants who received RGX-202 at the same dose currently being used in the Phase III confirmatory trial — the “pivotal dose.”
- At one year following treatment, pivotal dose participants showed improved performance on the North Star Ambulatory Assessment (NSAA) – a standard measure of walking and movement ability in DMD – as well as timed function tests including Time to Stand, 10 Metre Walk-run, and Time to Climb.
- Their results exceeded what would be expected based on the natural course of the disease and external controls.
- Notably, five of the seven participants were aged 8 or older at the time of dosing – an age at which functional decline is typically expected in DMD.
What is the NSAA? The North Star Ambulatory Assessment is a set of 17 movement-based activities used to track how well ambulatory (walking) boys and men with DMD are able to function over time. It is one of the main tools used to measure whether a treatment is working.
Cardiac Function
Pivotal dose participants showed cardiac stability one year after treatment, as measured by cardiac MRI.
Biomarker Data
Biomarker testing from the Phase I/II study continues to support consistent, high-level expression of RGX-202 microdystrophin – the shortened, functional version of the dystrophin protein that the gene therapy is designed to produce.
What is microdystrophin? Dystrophin is a protein that helps protect muscle fibres during movement. In DMD, a faulty gene means this protein is missing. Gene therapies like RGX-202 aim to deliver a working, slightly shortened version (called microdystrophin) to help compensate for this.
Phase III Enrolment
REGENXBIO is continuing to enrol approximately 30 participants aged 1 and older in the confirmatory Phase III portion of the AFFINITY DUCHENNE study. The Study is currently enrolling across the U.S. and Canada.
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