FDA issues a complete response letter for REGENXBIO's gene therapy RGX-121 intended for mucopolysaccharidosis type 2 (MPS II), also known as Hunter syndrome. The agency raised concerns regarding clinical trial eligibility criteria and differentiation between disease types.

The FDA issued a complete response letter to REGENXBIO for its gene therapy RGX-121, intended for mucopolysaccharidosis type 2 (MPS II), also known as Hunter syndrome. The agency raised concerns regarding clinical trial eligibility criteria and its ability to differentiate between disease types.

Regenxbio's RGX-202 gene therapy for Duchenne muscular dystrophy (DMD) demonstrated significant improvements in patient outcomes, exceeding expected disease progression at 12 and 18 months post-treatment in a pivotal trial. The company plans to submit a Biologics License Application (BLA) in mid-2026 via an accelerated approval pathway.