Regenxbio Unveils 12-Month Data For Gene Therapy Soon After FDA Delays Review Date

On Friday, REGENXBIO Inc. (NASDAQ:RGNX) shared new 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), also known as Hunter syndrome, at the International Congress of Inborn Errors of Metabolism (ICIEM) 2025.

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.

Also Read: FDA Extends Decision Date On Regenxbio’s Gene Therapy Into Next Year

Data Summary

In the pivotal phase of the CAMPSIITE trial (n=13), participants through one year sustained an 82% median reduction of cerebrospinal fluid (CSF) levels of heparan sulfate (HS) 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 (BSID-III) at one year.

New data from both the dose-finding and pivotal phases of the CAMPSIITE trial demonstrate a 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 (GAG), 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.

Price Action: RGNX stock is up 2.65% at $9.67 at the last check on Friday.

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