Intellia Therapeutics Inc. (NASDAQ:NTLA) shares tumbled after the company said it had temporarily paused patient dosing and screening in its Phase 3 MAGNITUDE and MAGNITUDE-2 trials of its experimental CRISPR therapy, nexiguran ziclumeran (nex-z), following a serious liver-related adverse event in one participant.
The company described the pause as a precautionary step while it works with regulators and medical experts to assess the incident.
According to Intellia, the issue arose after a report on October 24 showed elevated liver transaminases and bilirubin in a patient treated on September 30. The individual remains hospitalized and under close medical supervision.
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CEO John Leonard, M.D., said the company moved quickly “in line with our commitment to patient safety,” adding that Intellia is developing a plan to safely resume enrollment. The ongoing MAGNITUDE trials are designed to evaluate nex-z in patients with transthyretin amyloidosis with cardiomyopathy (ATTR-CM) and/or polyneuropathy (ATTR-PN).
More than 650 patients with ATTR-CM and 47 with ATTR-PN are enrolled across the MAGNITUDE trials, with over 450 estimated to have received nex-z.
Promising Phase 1 Data Backed Program Expansion
In September, Intellia released long-term follow-up data from its Phase 1 trial of nex-z in hereditary ATTR amyloidosis with polyneuropathy (ATTRv-PN). Results presented at the International ATTR Amyloidosis Annual Meeting and published in the New England Journal of Medicine showed sustained, deep reductions in transthyretin (TTR) protein levels after a single treatment.
Among patients receiving a dose of 0.3 mg/kg or higher, mean TTR levels fell by 92% at 24 months and 90% at 36 months, demonstrating durable and consistent target engagement. Clinical and biomarker outcomes also indicated stabilization or improvement in most patients, with 72% achieving a clinically meaningful improvement in neuropathy scores.
Secondary measures such as modified body mass index, quality-of-life scores, and neurofilament light chain levels trended toward improvement. The therapy was generally well-tolerated, with only mild to moderate infusion-related reactions reported and no treatment-related discontinuations as of the April 2025 data cutoff.
Intellia began dosing patients in the MAGNITUDE-2 Phase 3 trial in April 2025 and expects enrollment to conclude in the first half of 2026.
Price Action: NTLA shares were trading lower by 43.09% to $14.57 at last check Monday.
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