Regenxbio presents interim data from Phase I/II AFFINITY DUCHENNE trial

Regenxbio announced additional interim safety data and initial efficacy data from the Phase I/II AFFINITY DUCHENNE trial of RGX-202 for the treatment of Duchenne Muscular Dystrophy. Results were shared at the 28th Annual International Congress of the World Muscle Society. As of September 28, 2023, RGX-202 was reported to be well tolerated with no drug-related serious adverse events in three patients, aged 4.4, 10.6 and 6.3 years, dosed to date at dose level 1. Time of post-administration follow up ranges from three weeks to more than five months. The two patients who reached three-month follow-up have completed the immunosuppression regimen per study protocol. Initial biomarker data from two patients who completed three-month trial assessments indicate encouraging increases in expression of RGX-202 microdystrophin from bicep muscle biopsies taken at three months following one-time administration of RGX-202. In addition, RGX-202 microdystrophin was detectable by immunofluorescence staining throughout muscle tissue at three months, with RGX-202 microdystrophin protein localized to the sarcolemma. RGX-202 microdystrophin levels were measured using an automated and precise western blot method, and comparable results were confirmed with a proprietary liquid chromatography-mass spectrometry method. In the patient aged 4.4 years old, RGX-202 microdystrophin expression was measured to be 38.8% compared to control. A reduction from baseline in serum creatinine kinase levels of 43% was observed at ten weeks, supporting evidence of clinical improvement. Elevated CK levels are associated with muscle injury and are uniformly elevated in patients with Duchenne. In the patient aged 10.6 years old, RGX-202 microdystrophin expression was measured to be 11.1% compared to control and a reduction from baseline in serum CK levels of 44% was observed at ten weeks.