Regenxbio Inc’s stock tumbled 24.3% in pre-market trading on Tuesday after the U.S. Food and Drug Administration placed a clinical hold on its RGX-121 gene therapy program, citing asymptomatic spine MRI findings in five participants from the CAMPSIITE study.
The FDA identified small nodules or cystic masses in individuals treated three to six years ago, prompting the hold. Regenxbio said it does not expect to resubmit its Biologics License Application for RGX-121 in the near term. The stock, which had been halted ahead of the announcement, resumed trading at 7:25 AM ET and last traded at $8.12, well below its 52-week high of $16.19 but above its 52-week low of $5.46.
The setback follows a prior clinical hold in January on a related therapy, RGX-111, after a CNS tumor case in a trial participant. Regenxbio also received a Complete Response Letter from the FDA in February 2026 regarding RGX-121.
Analysts have adjusted their outlook amid the regulatory uncertainty. Barclays downgraded Regenxbio from overweight to hold on August 7, while HC Wainwright reduced its price target from $26 to $23 on August 10.
U.S. equity benchmarks showed modest declines on Tuesday, with the S&P 500 slightly lower, the Dow Jones down 0.1%, and the Nasdaq slipping 0.5%.
