** Shares of therapy developer Regenxbio RGNX.O fall 1.26% to $8.60 after the bell

** U.S. Food and Drug Administration has extended its review for co's therapy for the treatment of Mucopolysaccharidosis II, which is also known as Hunter syndrome, a rare inherited disorder

** Co adds FDA extends action date from November 9 to February 8, 2026

** The extension follows co's submission of longer-term data in response to an FDA information request

** Co is studying the therapy clemidsogene lanparvovec, or RGX-121, as a potential one-time treatment to directly address the underlying genetic cause of Hunter syndrome, in which the body doesn't properly break down certain sugar molecules

** Co expects the commercial launch plans to remain on track — CEO Curran Simpson

** Stock up ~13% YTD

(Reporting by Sriparna Roy in Bengaluru)

((Sriparna.Roy@thomsonreuters.com))