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REGENXBIO: Enrollment Complete for Cohort 2 and Positive Interim Data in AFFINITY DUCHENNE® Trial

February 7, 2024

REGENXBIO has completed enrollment at the second dose level of the Phase I/II AFFINITY DUCHENNE trial of RGX-202 in patients with Duchenne muscular dystrophy ages 4 to 11 years old in the United States and has reported positive interim safety and efficacy data.

Press release highlights:

  • Completed enrollment in cohort 2 of the Phase I/II AFFINITY DUCHENNE® trial of RGX-202, a potential one-time AAV Therapeutic for the treatment of Duchenne that includes an optimized transgene for a novel microdystrophin.
  • New three-month assessment in third patient at dose level 1 demonstrates largest increase in microdystrophin expression.
  • Patient aged 6.6 years old had expression level at 83.4% of control.
  • On track to initiate pivotal trial in second half of 2024.

“We are thrilled to see that RGX-202 is demonstrating strong microdystrophin expression across a wide range of patients. RGX-202 microdystrophin is differentiated with important biology most similar to naturally occurring dystrophin that protects from the muscle degradation associated with Duchenne. All boys with Duchenne are in need of new treatment options that can meaningfully impact disease, and we are working with great urgency to accelerate RGX-202 as an option for them.”

Kenneth T. Mills, President and CEO, REGENXBIO

Safety Update
As of February 6, 2024, 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 (1×1014 genome copies (GC)/kg body weight) and dose level 2 (2×1014 GC/kg body weight).

Clinical Program Updates
REGENXIO expects to make a pivotal dose determination in mid-2024. The Company also expects to share initial strength and functional assessment data for both dose levels and the initiation of a pivotal trial in the second half of 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.

AFFINITY DUCHENNE Trial Design
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. In the dose evaluation phase of the trial, four ambulatory, pediatric patients (ages 4 to 11 years old) are expected to enroll in two cohorts with doses of 1×1014 GC/kg body weight (n=2) and 2×1014 GC/kg body weight (n=2). After an independent safety data review for each cohort, a dose expansion phase of the trial may allow for additional patients to be enrolled. Currently recruiting at 3 U.S. sites in Little Rock, Arkansas, San Carlos, California and Chicago, Illinois.

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