REGENXBIO Stock Falls on FDA Clinical Hold for MPS II Gene Therapy

By EC Assets · Published 24 August 2026

REGENXBIO Inc. stock declined after the U.S. Food and Drug Administration (FDA) issued a clinical hold. The hold concerns RGX-121 (clemidsogene lanparvovec), an investigational gene therapy. This therapy is developed for the treatment of Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome. REGENXBIO confirmed a regulatory update regarding its RGX-121 program for MPS II. The company also announced that the FDA issued a Complete Response Letter for RGX-121. This letter was for the treatment of Mucopolysaccharidosis II (MPS II). REGENXBIO plans to collaborate with the FDA to determine a path forward. The company's goal is to facilitate the review and potential approval of RGX-121. RGX-121 is designed to treat patients with MPS II. The FDA previously extended its review period for the Biologics License Application (BLA) for RGX-121. Despite recent setbacks, REGENXBIO's NAV AAV platform offers a diversified pipeline. The company has other primary value drivers, including RGX-314 and RGX-202. These programs have promising catalysts scheduled for 2026. REGENXBIO is developing RGX-314 in partnership. This article is intended for informational purposes only. It does not constitute investment advice.