REGENXBIO Inc. announced that the first patient received RGX-202 at dose level 2 in the Phase I/II AFFINITY DUCHENNE®? trial. RGX-202 is an investigational one-time AAV Therapeutic for Duchenne muscular dystrophy (Duchenne), using the NAV®?

AAV8 vector to deliver a transgene for a novel microdystrophin that includes the functional elements of the C-Terminal (CT) domain as well as a muscle-specific promoter to support a targeted therapy for improved resistance to muscle damage associated with Duchenne. In recently completed preclinical efficacy studies, RGX-202 at dose levels showed improvement in functional performance, compared to dose level 1, as determined by forelimb muscle strength and treadmill exhaustion in mdx mice. REGENXBIO expects to share initial strength and functional assessment data for both dose levels and anticipates pivotal dose determination and the initiation of a pivotal program in 2024.

The Company plans to use RGX-202 microdystrophin expression as a surrogate endpoint to support a Biologics License Application (BLA) filing using the accelerated approval pathway. The Phase I/II AFFinITY DUCHENNE trial is a multicenter, open-label dose escalation and dose expansion clinical study to evaluate the safety, tolerability and clinical efficacy of a one-time intravenous (IV) dose of RGX-202 in patients with Duchenne. Additional design features, including codon optimization and reduction of CpG content, may potentially improve gene expression, increase translational efficiency and reduce immunogenicity.

RGX-202 is designed to support the delivery and targeted expression of genes throughout skeletal and heart muscle using the NAV AAV8 vector, a vector used in numerous clinical trials, and a well-characterized muscle-specific promoter (Spc5-12).