FDA places Regenxbio's Hunter syndrome gene therapy on clinical hold

The FDA has placed Regenxbio's experimental RGX-121 gene therapy for Hunter syndrome on clinical hold, Regenxbio said, after spinal scans found abnormalities in five study participants. The company said the affected patients had received the treatment about three to six years earlier. RGX-121 uses an AAV9 vector to deliver a gene intended to produce a missing enzyme. Regenxbio and partner NS Pharma plan to review additional imaging and longer-term follow-up data while awaiting the agency's full hold letter.