The FDA placed REGENXBIO’s RGX-121 gene therapy on clinical hold after expanded monitoring found small, asymptomatic spine nodules or cystic masses in five participants in the CAMPSIITE trial.
The patients, who have Hunter syndrome (MPS II), received RGX-121 roughly three to six years ago. Investigators considered the findings nonserious, and radiologists believed they were likely benign, but their cause and clinical significance remain unknown.
The hold derails REGENXBIO’s plan to promptly refile RGX-121’s biologics license application after the FDA had indicated that existing long-term data could support an accelerated-approval review without additional studies.
The company now says it does not expect to resubmit the application in the near term. It will continue periodic imaging and evaluate further patient scans and follow-up data with partner NS Pharma.
The setback follows a January FDA hold on RGX-121 and related RGX-111 after a separate patient developed an asymptomatic central nervous system tumor; the FDA cited similarities and shared risks between the programs.
REGENXBIO shares reportedly fell sharply after the disclosure, while the company said other programs, including RGX-202 and surabgene lomparvovec, continue advancing.
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