FDA Lifts Gene Therapy Trial Hold
The FDA has lifted its clinical hold on Intellia Therapeutics' gene therapy trial for a rare heart disease (ATTR-CM), allowing the MAGNITUDE Phase 3 trial to proceed. This marks an important milestone in gene-based cardiovascular therapies targeting heart muscle diseases.
The now-lifted clinical hold on the MAGNITUDE trial was initiated on October 29, 2025. The halt came after a patient in the study experienced Grade 4 liver enzyme elevations and subsequently died. A similar hold on a related trial, MAGNITUDE-2, which focuses on a different form of the disease, was lifted in January 2026. The therapy at the center of the trial, nexiguran ziclumeran (also known as nex-z), is a CRISPR-based gene editing treatment. It's designed to be a one-time treatment that works by inactivating the TTR gene, which is responsible for producing the protein that misfolds and causes the disease. Transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive and often fatal disease where misfolded transthyretin proteins build up in the heart. This buildup stiffens the heart muscle, leading to heart failure. The condition has a median survival of just over three years from diagnosis. Current treatments for ATTR-CM include "stabilizer" drugs like tafamidis and acoramidis, which prevent the protein from misfolding, and "silencer" therapies that reduce the production of the TTR protein. Unlike these lifelong treatments, nex-z aims to permanently halt the disease with a single dose. The MAGNITUDE trial is a large-scale, Phase 3 study designed to enroll approximately 1,200 patients with ATTR-CM. Its primary goal is to measure a combination of cardiovascular-related events, including mortality, to determine the therapy's effectiveness. To move forward, Intellia has agreed with the FDA on enhanced safety protocols. These include more rigorous monitoring of liver lab tests and excluding patients with certain liver abnormalities or a recent history of cardiovascular instability.
