Intellia Therapeutics paused dosing and screening in Phase III and Phase II trials of its in vivo CRISPR candidate nexiguran ziclumeran after a patient experienced severe liver injury. The FDA placed a clinical hold on the related INDs following reported cases meeting Hy’s law criteria, prompting an immediate halt to further enrollment and dosing. The pause highlights safety risks in systemic in vivo genome editing and underscores the agency’s cautious stance on first-in-class genetic medicines. Intellia’s disclosure sent its shares lower and will force the company to work with regulators to define additional monitoring, risk mitigation, or data requirements before resuming enrollment.