The FDA placed clinical holds on two late-stage Intellia Therapeutics trials testing its in vivo CRISPR therapy for transthyretin amyloidosis (ATTR) after a patient developed serious liver injury. Intellia paused dosing earlier this week and the hold formalizes the agency’s review of elevated liver enzymes and on-target toxicity signals tied to nexiguran ziclumeran (nex‑z). A clinical hold prevents new patient dosing and enrollment until sponsors provide safety data and a mitigation plan. Intellia said it had already paused dosing and screening after the safety event; the company and regulators will now investigate causality, timing and whether changes to dosing or monitoring can permit the program to resume. The action removed an on‑target safety debate around in‑vivo editing from the academic sphere to immediate regulatory scrutiny, driving a sharp share decline for the company in after‑hours trading. Industry watchers note this hold will reverberate across the gene‑editing sector, increasing regulatory attention on liver safety for systemically delivered genome editors and potentially complicating investor appetite for in‑vivo editing platforms in the near term.