The U.S. Food and Drug Administration (FDA) has reversed its decision to reject Regenxbio’s gene therapy for Hunter syndrome (MPS II), known as NAVSUNLI (clemidsogene lanparvovec-sngl, RGX-121). The FDA will now consider existing longer-term data under the accelerated approval pathway without requiring new studies or additional patients, allowing Regenxbio to resubmit the Biologics License Application (BLA) in the third quarter of 2026.
Regenxbio plans to request a Type A meeting with the FDA in July 2026 to review existing longer-term biomarker and clinical data from the CAMPSIITE study. The company expects the FDA to review the resubmission on an expedited basis, with labeling discussions to begin shortly after filing.
This reversal is part of a broader trend of FDA policy shifts on rare disease gene therapies following leadership changes. The agency originally accepted the BLA for RGX-121 under accelerated review in May 2025, but issued a Complete Response Letter (CRL) in February 2026 citing concerns about trial design, patient population definition, external controls, and the surrogate biomarker endpoint (CSF HS D2S6).
Sources:
FDA to reconsider Regenxbio Hunter syndrome gene therapy | STAT
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