Intellia and partner Regeneron reported that an elderly participant dosed with nex‑z, their in vivo CRISPR therapy for ATTR amyloidosis, was hospitalized with severe liver injury and subsequently died, prompting increased monitoring and a clinical hold on MAGNITUDE/MAGNITUDE‑2 sites pending FDA review. The company told investors it has mandated closer lab monitoring at all sites and is awaiting a formal FDA clinical‑hold letter. Nex‑z aims to inactivate TTR in the liver with a single infusion to deliver durable reductions in transthyretin protein; the programs together enrolled hundreds of patients across ATTR‑CM and ATTRv‑PN indications. Intellia said Grade 4 transaminase elevations remained rare (<1% across MAGNITUDE) but that the recent event triggered immediate risk‑mitigation and consultation with external experts. Regulatory risk has materialized into an operational challenge: Intellia paused enrollment and dosing, increased post‑dose monitoring windows, and is assessing additional safety steps while preserving the program’s development timeline where possible. Investors and trial sites will watch the FDA letter and Intellia/Regeneron's forthcoming analyses for implications on dosing, eligibility and monitoring plans.