New data has revealed a robust microdystrophin expression from a pivotal dose of gene therapy RGX-202 for Duchenne muscular dystrophy (Duchenne).

RGX-202 is an investigational one-time AAV therapeutic designed to deliver a novel microdystrophin gene that includes key regions of the naturally occurring dystrophin gene.

It is the only gene therapy approved or in development for Duchenne that encodes for the C-Terminal (CT) domain to produce a microdystrophin that is closer to naturally occurring dystrophin.

In preclinical studies, the CT domain has been shown to protect the muscle from contraction-induced stress and improve its ability to repair itself.

The Phase I/II AFFINITY DUCHENNE trial assessed RGX-202 in patients with Duchenne ages 1 to 11 years old. In patients aged 5.8 and 8.5 who received RGX-202 at dose level 2, RGX-202 microdystrophin expression was measured to be 77.2%, and 46.5%, respectively, compared to control at three months.

All seven patients who completed three-month trial assessments indicate meaningful increases in expression of RGX-202 microdystrophin and reduction from baseline in serum creatinine kinase levels, supporting evidence of clinical improvement.

“With today’s new, positive data, we are seeing a clear dose response and consistent, robust microdystrophin expression levels across all treated patients in the AFFINITY DUCHENNE trial, and, notably, among the highest levels of microdystrophin expression reported in older ambulatory patients,” said Curran Simpson, President and CEO, REGENXBIO. “This data continues to build on the totality of evidence supporting the potential for RGX-202 to be a differentiated, best-in-class treatment for Duchenne.”

REGENXBIO plans to complete enrolment in the dose level 2 expansion cohort early in the third quarter of 2024 and has initiated enrolment in the cohort for boys aged 1-3. Initiation of the pivotal trial is expected in the fourth quarter of 2024.

Diana Spencer, Senior Digital Content Editor, DDW