A Single Gene Edit Holds At One Year
One Infusion, One Year
CRISPR Therapeutics infused 15 patients with a single dose of an experimental gene editor called CTX310, then waited to find out whether the edit would keep working. All had a form of familial hypercholesterolemia or severe high triglycerides that statins and PCSK9 inhibitor injections had failed to control, the group doctors reach for once the standard drugs run out of room. CTX310 uses CRISPR-Cas9 to permanently disable a single gene in the liver called ANGPTL3, a one-time infusion, not a daily or biweekly drug. It is one infusion, then nothing, and that is exactly what made the trial's real question hard to answer early: does a one-time edit behave like a drug that wears off, or like a switch that stays flipped? The company ran five escalating doses, from 0.1 to 0.8 milligrams per kilogram of lean body weight, delivered intravenously with Cleveland Clinic as a trial site. An early readout at 60 days, presented at the American Heart Association meeting, showed lipids falling. But 60 days is not long enough to tell a durable edit from a slow-fading one, and gene editing carries a safety bar a pill does not: there is no taking it back once the cut is made.
The Numbers Hold
All 15 patients reached the one-year mark, and CRISPR Therapeutics presented the full results at the European Society of Cardiology Congress on August 28, 2026, with the New England Journal of Medicine publishing the same data simultaneously. At the highest dose tested, 0.8 mg/kg, ANGPTL3 protein levels were down 79 percent on average a year after the single infusion, with triglycerides down 48 percent and LDL cholesterol down 53 percent from baseline. Individual patients did better still: one hit an 89 percent ANGPTL3 reduction, another a 78 percent triglyceride drop. Steven Nissen at Cleveland Clinic said the reductions 'have persisted out to one year, suggesting a sustained biological effect,' which is the specific claim a durability study exists to test. Safety looked manageable rather than clean: three patients had Grade 2 infusion reactions, one had a temporary rise in liver enzymes, and none had a serious treatment-related adverse event or a dose pulled for toxicity. Luke Laffin, principal investigator and Medical Director of the Cleveland Clinic Coordinating Center for Clinical Research, framed the appeal in practical terms: a therapy that works once a lifetime instead of once a day, or once every two weeks by injection, 'could help close that adherence gap' for patients who quietly stop taking cholesterol drugs because remembering is hard and the drugs have side effects of their own.
Why One Gene Matters
ANGPTL3 makes a protein whose job is to block two enzymes, lipoprotein lipase and endothelial lipase, that clear triglycerides and LDL particles out of the bloodstream. Switch ANGPTL3 off and those clearing enzymes run unopposed, which is why people born with rare natural mutations that break the gene tend to have unusually low cholesterol and less heart disease. That is the natural experiment CTX310 is trying to reproduce on purpose, in adults who did not win that genetic lottery. CRISPR Therapeutics already has one approved edit on the market, Casgevy, which treats sickle cell disease by removing a patient's blood stem cells, editing them outside the body, and returning them. CTX310 is a different kind of edit: it goes directly into the patient by IV, finds its way to liver cells, and cuts the gene where it sits, no cell extraction required. That is a harder trick to control and a more permanent one if it goes wrong, and it is that IV liver-targeting risk that keeps this stage of the trial small: 15 patients, five doses. The company has not announced a Phase 2 or Phase 3 timeline, and the trial's own protocol calls for tracking these same patients for years beyond the one-year mark just reported. Whether it fades at year three or year eight is what the mandated follow-up will show.
Fifteen patients, one infusion each, one year of data that did not fade. What is not on the record is whether the edit holds at three years or five, since Cleveland Clinic and CRISPR Therapeutics are still watching this same cohort for exactly that. No Phase 2 has been announced.
Sources
- CRISPR Therapeutics Presents Phase 1a Data for CTX310 at ESC Congress 2026 (globenewswire.com)
- Durability of CRISPR-Cas9 Gene Editing Targeting ANGPTL3 with CTX310 (nejm.org)
- Cleveland Clinic First In Human CRISPR Trial Lowers Cholesterol and Triglycerides for a Full Year (consultqd.clevelandclinic.org)
- First-in-human trial of CRISPR gene editing therapy safely lowered cholesterol, triglycerides (newsroom.heart.org)