The U.S. Food and Drug Administration has placed a clinical hold on two Phase 3 trials of Intellia Therapeutics’ CRISPR candidate nexiguran ziclumeran after a participant experienced a grade‑4 liver injury and hospitalization. Intellia paused dosing and enrollment voluntarily earlier in the week and notified investors; the FDA will issue a formal letter within 30 days outlining required information to lift the hold. Nexiguran ziclumeran is being developed to treat transthyretin amyloidosis (ATTR), a rare protein‑misfolding disease that affects heart and nerve function. Intellia had enrolled hundreds of patients across the cardiomyopathy and polyneuropathy trials; the regulatory hold freezes further dosing and could delay readouts by multiple quarters. A clinical hold is a regulatory pause that prevents new dosing until the sponsor addresses safety or protocol concerns. Intellia said it will work with the FDA and independent experts to update safety monitoring and mitigation plans before resuming the studies.