Regenxbio reports ‘positive’ results from Phase I/II/III CAMPSIITE trial

Regenxbio (RGNX) announced new, positive data from the Phase I/II/III CAMPSIITE trial of clemidsogene lanparvovec (RGX-121) for the treatment of patients with Mucopolysaccharidosis Type II, also known as Hunter syndrome, at the International Congress of Inborn Errors of Metabolism 2025. REGENXBIO submitted these longer-term pivotal results to the U.S. FDA in response to an information request in the ongoing Biologics License Application review of RGX-121. “These positive biomarker and functional data provide further evidence of the long-term potential of RGX-121 to change the trajectory of Hunter syndrome for boys with this devastating, degenerative disease,” said Steve Pakola, M.D., Chief Medical Officer of REGENXBIO. “The sustained reductions in CSF HS D2S6 and evidence of the strong correlation between biomarker level and neurodevelopmental improvement are highly encouraging as we look toward potential accelerated approval early next year.” In the pivotal phase of the CAMPSIITE trial, participants through one year sustained an 82% median reduction of cerebrospinal fluid levels of heparan sulfate D2S6, a key biomarker of MPS II brain disease that is reasonably likely to predict clinical benefit. These longer-term data are consistent with previously reported topline pivotal results from the CAMPSIITE trial, which met its primary endpoint of proportion of participants with CSF HS D2S6 below maximum attenuated levels at week 16 with statistical significance. Similar results were previously reported for the pivotal dose in the dose-finding phase of the study, with 85% reductions of CSF HS D2S6 sustained through two years. Positive neurodevelopmental outcomes were observed in the pivotal and dose-finding phases of the CAMPSIITE trial. Pivotal participants demonstrated neurodevelopmental skill acquisition or stability on all sub-scales of the Bayley Scales of Infant and Toddler Development, 3rd Edition at one year. New data from both the dose-finding and pivotal phases of the CAMPSIITE trial demonstrate a strong correlation between measured CSF HS D2S6 levels at week 16 and neurocognitive outcomes at one year. This correlation supports the use of CSF HS D2S6, a type of glycosaminoglycan, as a surrogate endpoint reasonably likely to predict clinical benefit under the accelerated approval pathway, as the buildup of GAGs in MPS II leads to clinical manifestations including neurodevelopmental deficits.