CAMBRIDGE, October 27, 2025 – Intellia Therapeutics (NTLA.O) paused two late-stage gene-editing trials after a patient suffered Grade 4 liver toxicity, raising safety concerns for its CRISPR treatment.
The pause affects the company’s lead program for hereditary transthyretin amyloidosis, a rare genetic disorder, potentially delaying commercialization of what could be a breakthrough one-time therapy.
- Patient developed severe liver injury after September dosing
- Two Phase 3 trials temporarily halted for safety review
- CRISPR gene-editing treatment targets rare genetic disease
Safety Event Details
The biotech company said a patient dosed on September 30 developed Grade 4 elevated bilirubin levels, indicating severe liver dysfunction on a scale where Grade 5 represents death 1. This marks a serious adverse event that triggered the immediate suspension of dosing and patient screening in both MAGNITUDE and MAGNITUDE-2 trials 2.
The trials are testing nexiguran ziclumeran (nex-z), Intellia’s experimental CRISPR-based treatment designed to provide a one-time cure for hereditary transthyretin amyloidosis with polyneuropathy. The condition affects an estimated 50,000 people globally and can cause progressive nerve damage and heart problems.
Market Impact and Investor Concerns
Gene-editing stocks have faced scrutiny over safety profiles, with investors closely watching for adverse events that could derail promising treatments. Intellia’s shares have been volatile this year as investors weigh the potential of CRISPR technology against regulatory and safety risks.
The company joins other gene-editing firms navigating safety challenges in late-stage development. Competitor Editas Medicine and CRISPR Therapeutics have also faced regulatory hurdles and safety questions in their respective programs.
Company Response and Next Steps
Intellia said it took “immediate action” to pause enrollment as part of its commitment to patient safety 3. The company is working with regulators and clinical investigators to review the safety data and determine next steps for the trials.
The pause comes as Intellia was preparing to potentially file for regulatory approval based on Phase 3 results. The company had previously reported promising efficacy data showing significant reductions in disease-causing protein levels.
Industry Implications
The development highlights ongoing challenges facing the gene-editing sector as companies transition from early-stage trials to larger patient populations. While CRISPR technology has shown remarkable potential in treating genetic diseases, safety remains paramount for regulatory approval and commercial success.
Intellia said it will provide updates as the safety review progresses. The company maintains that the overall benefit-risk profile of nex-z remains positive based on previous clinical data, though the current pause allows for thorough investigation of the liver toxicity event.
Not investment advice. For informational purposes only.
References
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