A clinical hold tied to an imaging finding in a rare-disease trial wiped nearly a quarter of REGENXBIO’s market value Monday, the second time in seven months the FDA has paused a program in the company’s CNS-directed gene-therapy franchise.
REGENXBIO shares fell 24.8% Monday, closing at $8.06 on volume nearly six times the stock’s trailing five-session average. The FDA placed a clinical hold on the company’s trial of RGX-121, a gene therapy for Hunter syndrome, after a small, asymptomatic nodule or cystic mass was found on spine imaging in five trial participants dosed three to six years earlier. Radiologists judged the findings likely benign; the company found no brain nodules or masses. REGENXBIO does not expect to resubmit RGX-121’s regulatory application in the near term.
Chief Executive Curran Simpson said the company believes “these findings are unique and limited to our Hunter Syndrome program,” pointing to a Duchenne muscular dystrophy therapy and a wet age-related macular degeneration therapy developed with AbbVie, both built on a different viral capsid and delivery route.
This is REGENXBIO’s second FDA clinical-hold action this year on its intrathecal and intracisternal programs. A January hold followed a different finding, a pediatric brain tumor with a specific oncogene-integration signature, in a related trial. Three sell-side analysts publicly called that selloff an overreaction within days. No analyst has yet weighed in on Monday’s event. Only the company’s own statement currently stands behind the isolated-and-benign reading.
The two findings do not appear related biologically. What is unresolved is whether a second FDA intervention on this class of CNS-directed delivery programs signals something about platform-level risk that a single-incident framing misses.
Peer gene-therapy stocks moved only modestly Monday, and no trading halt or competing catalyst accompanied REGENXBIO’s decline. The company has said it plans to submit its Duchenne application this quarter, on a different delivery route that this week’s hold does not touch.