Intellia Therapeutics disclosed that a patient dosed with its in vivo CRISPR candidate nexiguran ziclumeran (nex‑z) has died following severe liver injury, and the company paused dosing across its pivotal MAGNITUDE trials. Intellia reported Grade 4 transaminase elevations and increased bilirubin in the hospitalized man in his early 80s, prompting the FDA to place the MAGNITUDE and MAGNITUDE‑2 studies on clinical hold. The company said the event emerged roughly three to four weeks after dosing and that it is working with clinical investigators, external experts and the FDA to investigate the liver signal and design risk‑mitigation measures. Nex‑z is an LNP‑delivered, Regeneron‑partnered in vivo CRISPR therapy targeting TTR for transthyretin amyloidosis with cardiomyopathy; Intellia noted the observed Grade 4 liver events remain rare across the >650 enrolled ATTR‑CM patients. Intellia reported the death as part of its Q3 update and said it has instructed sites to increase early post‑dose laboratory monitoring while it develops exclusion criteria to reduce risk. Investors have reacted sharply to the safety disclosures; the company is awaiting the FDA’s formal clinical‑hold letter as it gathers more data and expert input.