Prospects for Regenxbio’s clemidsogene lanparvovec approval in Hunter syndrome

US gene therapy company Regenxbio’s (Nasdaq: RGNX) clemidsogene lanparvovec has a plausible pathway to US Food and Drug Administration (FDA) approval in Hunter syndrome, although the decision will likely hinge on whether biomarker reductions can be convincingly linked to meaningful clinical outcomes, experts tell the insights investigative news team at GlobalData.

Clemidsogene lanparvovec is a CNS-directed gene therapy designed to address the root cause of Hunter syndrome by restoring the functional IDS gene and reducing the accumulation of toxic glycosaminoglycans. If approved, the therapy could become a first-in-class, potentially life-changing option for early-stage patients, while also stabilizing disease in more advanced cases.

The FDA accepted Regenxbio’s biologics license application (BLA) and initially set a Prescription Drug User Fee Act (PDUFA) decision date of November 9, 2025, which has since been extended to February 8, 2026. The extension follows heightened regulatory scrutiny of biomarker-based approvals in rare diseases, highlighted by recent reassessments of accelerated approvals such as Sarepta Therapeutics’ (Nasdaq: SRPT) gene therapy Elevidys (delandistrogene moxeparvovec-rokl) in Duchenne muscular dystrophy.