REGENXBIO (NASDAQ: RGNX) has reported strong 12-month results from its pivotal CAMPSIITE® trial evaluating RGX-121, a one-time AAV-based gene therapy for Mucopolysaccharidosis Type II (Hunter syndrome, MPS II).
Patients treated with RGX-121 showed an 82% median reduction in cerebrospinal fluid (CSF) levels of heparan sulfate D2S6, the key biomarker of MPS II. The reduction was statistically significant (p<0.0001) and sustained through one year, meeting the trial’s primary endpoint and reinforcing both target engagement and durability of effect. Importantly, the therapy has been well tolerated across all 26 patients, with no new safety concerns reported.
REGENXBIO also confirmed that the FDA has completed its pre-license and bioresearch monitoring inspections with no observations, further underscoring regulatory readiness. A decision on the company’s Biologics License Application (BLA) is expected by February 8, 2026, marking a clear path toward potential approval.
Investor takeaway: These results validate RGX-121 as a potentially transformative treatment for Hunter syndrome—one that addresses the underlying cause of disease with a single administration. With durable biomarker impact, clean safety, and a clear regulatory timeline, REGENXBIO is well positioned to bring the first gene therapy for MPS II to market, creating both significant clinical impact and a meaningful value driver for investors.
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