To evaluate safety and efficacy of RGX-202 in patients with Duchenne muscular dystrophy (DMD) aged 4 to 11 years.

Duchenne is a rare, X-linked, progressive muscle disease due to pathogenic variants in the DMD gene which encodes dystrophin. The absence of functional dystrophin results in muscle cell damage and ultimately death with progressive weakness of skeletal muscle, loss of ambulation, and cardiac/diaphragm weakness.

RGX-202 is an investigational, one-time AAV therapeutic for Duchenne, using the NAV® AAV8 vector to deliver a transgene for a novel microdystrophin that includes the functional elements of the C-Terminal domain as well as a muscle-specific promoter to support a targeted therapy for improved resistance to muscle damage associated with Duchenne.

As of September 28, 2023, RGX-202 was reported to be well tolerated with no drug-related serious adverse events in three patients at dose level 1, 1x10¹⁴ genome copies (GC)/kg, with 3 weeks to over 5 months follow-up. The prophylactic immune suppression for gene therapy with RGX-202 has been well tolerated.  Initial biomarker data from two patients indicate increased expression of RGX-202 microdystrophin from bicep biopsies taken three months following one-time RGX-202 administration. In the patient aged 4.4 years, RGX-202 microdystrophin expression was measured to be 38.8% compared to control. A reduction from baseline in serum creatine kinase (CK) levels of 43% was observed at ten weeks, supporting evidence of clinical improvement. In the patient aged 10.6 years, 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. Additionally, RGX-202 microdystrophin was detectable by immunofluorescence staining in muscle at three months, with RGX-202 microdystrophin protein localized to the sarcolemma. Updated interim results will be presented.