An elderly patient dosed with Intellia Therapeutics’ in vivo CRISPR candidate nexiguran ziclumeran (nex‑z) died after developing severe liver dysfunction, prompting the biotech to pause dosing and screening in its two Phase 3 MAGNITUDE studies and triggering an FDA clinical hold. Intellia said the man was in his early 80s and had complicating comorbidities; the company and investigators are working with external experts to investigate the liver events. The FDA has placed both MAGNITUDE trials on hold while it evaluates safety data; Intellia and partner Regeneron face uncertainty on timing and design of any restart. Clarification: a clinical hold is an FDA action that stops enrollment or dosing in a trial pending safety review.