Regenxbio falls after FDA rejects rare disease therapy

Shares of drug developer Regenxbio RGNX.O fall 19.4% to $8.31 after hours

Co says US FDA declined to approve its gene therapy RGX-121 for the treatment of a rare neurodegenerative disease called Hunter syndrome

Co says FDA outlined several reasons for not approving the gene therapy, including uncertainty regarding the study eligibility criteria

Co plans to work with FDA on a path forward to resubmit the marketing application

RGNX gained 86.3% in 2025