Regenxbio tumbles as FDA halts rare‑disease gene therapy trials after tumor case

Shares of therapy developer Regenxbio RGNX.O fall 34% to $8.82 premarket

Co says FDA paused studies of its experimental treatments for two rare childhood disorders

The two disorders are Hurler syndrome and Hunter syndrome, conditions that cause severe physical and cognitive decline, per co

Co says a brain tumor was found in a child who received RGX‑111 four years earlier

Early tests linked therapy DNA near a cancer‑related gene, but causality is unclear, says co

Co says no similar cases seen in other children treated with RGX‑111 or RGX‑121

RGX‑111 and RGX‑121 are experimental gene therapies that co is developing for two rare childhood genetic disorders

Shares up ~86% in 2025