The biotech firm announced late Monday that federal regulators found the current data set insufficient to prove the treatment's efficacy. According to the company, the agency did not agree that the provided evidence offered substantial proof that RGX-121 effectively addresses the underlying causes of the genetic condition, which impairs the body's ability to break down complex sugars.

Hunter syndrome currently has no known cure and frequently leads to severe physical and cognitive decline. Despite the regulatory setback, Regenxbio management stated they intend to identify a path forward and resubmit the biologics license application as quickly as possible to bring the therapy to market.

Market Reaction and Financial Impact

Investors reacted swiftly to the regulatory hurdle, sending Regenxbio shares down 9.2% to $9.36 during early trading hours. The rejection marks a significant delay for the Maryland-based company as it seeks to pivot from research to commercial-scale operations in the competitive gene therapy space.