Regenxbio’s RGX-202 shows initial efficacy in Duchenne

Regenxbio reported additional interim safety and efficacy data in the Phase I/II AFFINITY DUCHENNE trial of RGX-202 in patients with Duchenne muscular dystrophy ages 4 to 11 years old, including RGX-202 microdystrophin expression from dose level 2 and video of trial clinic assessments demonstrating initial evidence of strength and functional improvement. As of February 28, RGX-202 has been well tolerated with no drug-related serious adverse events in five patients, aged 4.4 to 12.1 at dose level 1 and 2. Time of post-administration follow up ranges from approximately seven weeks to over eleven months. All patients who reached three-month follow-up have completed the immunosuppression regimen per study protocol. In the first patient, aged 12.1 years, who received RGX-202 at dose level 2, RGX-202 microdystrophin expression was measured to be 75.7% compared to control at three months. A reduction from baseline in serum creatinine kinase levels of 77% was observed at ten weeks. All four patients, across both dose levels, who completed three-month trial assessments indicate encouraging increases in expression of RGX-202 microdystrophin and reduction from baseline in serum CK levels, supporting evidence of clinical improvement. Among patients aged 8 to 11 years old at screening, RGX-202 microdsytrophin expression levels at three months following RGX-202 administration was higher in dose level 2. New recordings of the trial clinic assessments and home videos illustrate patients treated with RGX-202 are demonstrating initial evidence of strength and functional improvement. Regenxbio expects to make a pivotal dose determination in mid-2024. The company also expects to share strength and functional assessment data for both dose levels and the initiation of a pivotal trial in the second half of 2024.