REGENXBIO Reports Positive Data from CAMPSIITE Trial for Hunter Syndrome Treatment.

REGENXBIO has reported positive data from the Phase I/II/III CAMPSIITE trial of RGX-121, a treatment for Hunter syndrome. The primary endpoint of CSF HS D2S6 reduction at week 16 was met. The company submitted these results to the FDA in response to an information request, with a decision expected by February 8, 2026.

Rockville, Md., Sept. 2, 2025 — REGENXBIO Inc. (Nasdaq: RGNX) has announced positive 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 company presented these results at the International Congress of Inborn Errors of Metabolism (ICIEM) 2025.

The primary endpoint of the trial, a 16-week reduction in cerebrospinal fluid (CSF) levels of heparan sulfate (HS) D2S6, was met. This reduction was sustained through one year, with participants experiencing an 82% median reduction in CSF HS D2S6 levels. This biomarker is considered a surrogate endpoint reasonably likely to predict clinical benefit in MPS II disease [1].

The trial also demonstrated a strong correlation between measured CSF HS D2S6 levels at week 16 and neurocognitive outcomes at one year. Participants showed neurodevelopmental skill acquisition or stability on all sub-scales of the Bayley Scales of Infant and Toddler Development, 3rd Edition (BSID-III) at one year [1].

REGENXBIO submitted these longer-term pivotal results 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 FDA is expected to make a decision on the application by February 8, 2026 [1].

RGX-121 is a potential one-time AAV therapeutic designed to deliver the iduronate-2-sulfatase (IDS) gene to the central nervous system (CNS), providing a permanent source of secreted iduronate-2-sulfatase (I2S) protein beyond the blood-brain barrier. 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 [1].

The CAMPSIITE trial is a multicenter, open-label study for boys aged four months up to five years with neuronopathic MPS II. The primary endpoint is measurement of CSF GAGs, with accurate and sensitive measurements having the potential to be considered a surrogate endpoint under the accelerated approval pathway [1].

References:
[1] https://finance.yahoo.com/news/regenxbio-presents-positive-twelve-month-110500797.html