Patient Hospitalized After Receiving Intellia’s CRISPR Therapy Dies, Prompting FDA Hold on Trials

An elderly patient (early 80s) with a high body mass index, receiving Intellia's experimental CRISPR therapy, nexiguran ziclumeran (nex-z), in a Phase III clinical trial for transthyretin amyloidosis with cardiomyopathy (ATTR-CM), died after developing severe liver dysfunction (Grade 4 liver transaminase elevations and increased total bilirubin) following dosing on September 30, 20251 3 5 6 7.

The patient's hospitalization led Intellia to pause dosing and screening in two Phase III trials (MAGNITUDE and MAGNITUDE-2) in late October 2025, before the FDA imposed a formal clinical hold on both studies1 3 4 5 6 7.

According to Intellia and the patient's treating physician, the death involved 'complicating comorbidities,' and the case is under further evaluation1 3 5 6 7.

The company is working with clinical investigators and external experts to understand the liver-related events and develop a risk mitigation plan as the regulatory review proceeds1 3 5 6 7.

Liver safety concerns are a known risk for CRISPR-based therapies targeting genes in the liver, and this is the most significant safety signal for Intellia after treating hundreds of patients8.

Following news of the death, Intellia's stock experienced a sharp decline (dropping to $12.32 on November 6th, 2025, with expectations of a further drop), reflecting market and stakeholder concerns about the future of the program3.