A Phase 1 trial of CTX310, a lipid-nanoparticle-delivered CRISPR-Cas9 therapy targeting ANGPTL3, produced dose-dependent lipid reductions in 15 adults with uncontrolled dyslipidemia, per the study published in the New England Journal of Medicine in November 2025. At the highest dose, circulating ANGPTL3 fell by a mean of 73% (maximum 89%) with no dose-limiting toxic effects, per the company's disclosure.
What did the Phase 1 trial actually measure?
The trial was an ascending-dose Phase 1 study in adults with uncontrolled hypercholesterolemia, hypertriglyceridemia or mixed dyslipidemia who were already receiving maximally tolerated lipid-lowering therapy. Each participant received a single intravenous dose of CTX310 at one of five dose levels from 0.1 to 0.8 mg per kilogram of body weight. The primary endpoint was adverse events, including dose-limiting toxic effects; 15 participants received CTX310 and had at least 60 days of follow-up, per the journal record.
No dose-limiting toxic effects related to CTX310 occurred, and serious adverse events occurred in two participants (13%), per the published report. The lipid results by the company's disclosure at the highest dose were as follows:
| Measure | Mean reduction | Maximum reduction |
|---|---|---|
| Circulating ANGPTL3 | -73% | -89% |
| Triglycerides | -55% | -84% |
| LDL cholesterol | -49% | -87% |
How does the editing mechanism work?
CTX310 delivers Cas9 messenger RNA and a guide RNA in a lipid nanoparticle, targeting the hepatic ANGPTL3 gene to induce a loss-of-function mutation, per the published methods. ANGPTL3 inhibits lipoprotein and endothelial lipases; people who carry loss-of-function variants naturally have lower LDL cholesterol and triglycerides and a decreased lifetime risk of atherosclerotic cardiovascular disease, which is the genetic rationale for the target. The trial was run by investigators at the Cleveland Clinic and collaborating sites together with CRISPR Therapeutics, which presented the data at the AHA Scientific Sessions on November 8, 2025 and published them simultaneously in the journal.
What stands between a Phase 1 paper and a medicine?
The gap is the honest caveat in any early editing readout. Fifteen participants and 60 days of minimum follow-up establish feasibility and short-term safety, not durability or outcomes. A follow-up correspondence in the journal has since reported on one-year durability of the reductions, per the journal record. CRISPR Therapeutics has said it is advancing CTX310 into Phase 1b clinical trials, prioritizing severe hypertriglyceridemia and mixed dyslipidemia, per the company's November 8 statement.
The method translation is the part worth watching. A single-course intravenous infusion that behaves like a permanent lipid-lowering exposure would compete with daily statins and injectable inhibitors on a different logic, but only if editing efficiency, off-target profile and durability hold across larger populations. The published trial record is the source for the design and safety figures above; effect sizes beyond the reported cohort have not yet been disclosed.
This article is provided for informational purposes only and does not constitute medical advice. Consult a qualified healthcare professional regarding any treatment or diagnostic decision.
