The FDA granted Denali Therapeutics accelerated approval for Avlayah (tividenofusp alfa), a Hunter syndrome gene therapy, in a decision that runs counter to recent rare-disease rejection patterns and noted agency scrutiny. Avlayah’s approval follows a calendar that includes an earlier rejection of a Regenxbio Hunter syndrome gene therapy, which had prompted concerns among patient advocates about evidence thresholds. For Denali, the accelerated approval framework could shorten time to access while requiring post-marketing confirmation; for investors and the rare-disease ecosystem, the decision is a concrete signal that some programs can still clear the agency’s bar quickly. The approval also comes as regulatory expectations for rare therapies continue to evolve amid political and evidentiary debate around the definition of “substantial evidence.”