An elderly participant in Intellia Therapeutics’ in vivo CRISPR program died after being hospitalized with severe liver injury, prompting intensified safety reviews and an FDA clinical-hold process. Intellia and partner Regeneron disclosed the event while noting the company has increased post-dose laboratory monitoring at MAGNITUDE trial sites and is consulting external experts. The death follows reports of rare Grade 4 transaminase elevations in a small fraction of trial participants. Intellia reiterated belief in nex‑z’s therapeutic potential for ATTR amyloidosis but said it is awaiting a formal FDA clinical‑hold letter and exploring additional risk‑mitigation measures. Industry watchers said the case underscores the safety tradeoffs inherent to in vivo gene‑editing therapies and the likelihood of heightened regulatory scrutiny for similar platform candidates. Clinical investigators and regulators will be focused on mechanistic explanations for hepatotoxicity and on whether monitoring or dosing changes can manage the observed risks.