FDA places hold on REGENXBIO's Hunter syndrome gene therapy after spinal nodules found, company pauses resubmission

The FDA placed a clinical hold on RGX-121, REGENXBIO's gene therapy for Hunter syndrome, after MRI scans showed small nodules or cystic masses in the spines of five trial participants.

The findings were asymptomatic and the patients remained clinically stable or improved on neurocognitive and neurobehavioral tests, according to the company's press release.

REGENXBIO said it does not expect to resubmit the biologics license application in the near term, after the agency had already rejected the filing in February and now recommended a new study with more patients and a placebo arm.

The news sent REGENXBIO shares down about 22% in pre‑market trading on Monday, reflecting investor concern over the setback.