Regenxbio Presents 12-Month Data for Gene Therapy Amid FDA Delay

Regenxbio Inc. (RGNX) has unveiled 12-month data from the Phase 1/2/3 CAMPSIITE trial of clemidsogene lanparvovec (RGX-121) for the treatment of patients with Mucopolysaccharidosis Type II (MPS II). The trial data showed an 82% median reduction of cerebrospinal fluid (CSF) levels of heparan sulfate (HS) D2S6, a key biomarker of MPS II brain disease. The company submitted these longer-term pivotal results to the FDA in response to an information request in the ongoing Biologics License Application (BLA) review of RGX-121.

Regenxbio Inc. (RGNX) has announced encouraging 12-month data from the Phase I/II/III CAMPSIITE trial of clemidsogene lanparvovec (RGX-121) for the treatment of Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome. The trial data demonstrated an 82% median reduction of cerebrospinal fluid (CSF) levels of heparan sulfate (HS) D2S6, a key biomarker of MPS II brain disease. This positive data was presented at the International Congress of Inborn Errors of Metabolism (ICIEM) 2025 and submitted to the U.S. Food and Drug Administration (FDA) in response to an information request in the ongoing Biologics License Application (BLA) review of RGX-121.

The 12-month data further solidify the potential of RGX-121 to improve outcomes for patients with MPS II. The pivotal patients in the trial showed a 80% reduction in CSF HS D2S6 levels, which is a significant improvement and sustained over the year. This reduction is correlated with strong neurodevelopmental outcomes, supporting the use of CSF HS D2S6 as a surrogate biomarker reasonably likely to predict clinical benefit under the accelerated approval pathway. The data also indicate that RGX-121 could be the first and only potential one-time, commercially-available therapy designed to directly address the underlying genetic cause of Hunter syndrome.

The FDA is expected to make a decision on the RGX-121 BLA by February 8, 2026. The company has received several designations from the FDA, including Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT) designations. RGX-121 has also been classified as an advanced therapy medicinal product (ATMP) by the European Medicines Agency.

Regenxbio Inc. is a biotechnology company focused on developing gene therapy treatments for rare and retinal diseases. The company's pipeline includes RGX-202 for Duchenne muscular dystrophy, clemidsogene lanparvovec (RGX-121) for MPS II, and surabgene lomparvovec (ABBV-RGX-314) for wet AMD and diabetic retinopathy. Thousands of patients have been treated with REGENXBIO's AAV platform, including those receiving Novartis' ZOLGENSMA®.

References:
[1] https://www.nasdaq.com/articles/regenxbio-reports-positive-data-phase-i-ii-iii-campsiite-trial-rgx-121
[2] https://regenxbio.gcs-web.com/news-releases/news-release-details/regenxbio-presents-positive-twelve-month-pivotal-data-phase