FDA hold stalls Regenxbio's RGX-121 refiling amid spine MRI findings

The FDA has placed a clinical hold on Regenxbio’s RGX-121 due to asymptomatic spine MRI findings, derailing plans to refile for approval in MPS II (Hunter syndrome). The hold follows a prior safety signal in RGX-111 and expanded monitoring that identified five patients with likely benign spinal nodules; researchers will continue imaging and use FDA feedback to determine next steps, while Regenxbio forges ahead with RGX-202 and surabgene lomparvovec. Regenxbio’s stock declined in premarket trading.