Novo Nordisk’s ziltivekimab has failed to reduce major adverse cardiovascular events in the Phase 3 ZEUS trial despite producing the expected suppression of the interleukin-6 inflammatory pathway. Among more than 6,300 people with atherosclerotic cardiovascular disease, chronic kidney disease and elevated inflammation, the risk of cardiovascular death, nonfatal heart attack or nonfatal stroke was essentially identical with monthly ziltivekimab and placebo. The primary analysis produced a hazard ratio of 0.99 with a 95% confidence interval from 0.88 to 1.11, showing that a strong effect on inflammatory biomarkers did not translate into a measurable clinical benefit.
The company reported similar overall adverse-event and serious-adverse-event rates between the groups, although serious infections occurred more frequently with ziltivekimab. Novo Nordisk will continue two other cardiovascular outcome trials in heart failure and patients recovering from an acute heart attack, but ZEUS substantially weakens the assumption that IL-6 suppression alone will reduce cardiovascular risk across inflammatory cardiovascular populations.
ZEUS tested monthly IL-6 inhibition in more than 6,300 high-risk patients
ZEUS was a randomized, double-blind and placebo-controlled cardiovascular outcomes trial. It enrolled people with established atherosclerotic cardiovascular disease, chronic kidney disease and evidence of persistent systemic inflammation, defined by a high-sensitivity C-reactive protein level of at least 2 milligrams per litre. Participants continued receiving standard cardiovascular and kidney care while being assigned to ziltivekimab or placebo.
Ziltivekimab was administered as a 15 mg subcutaneous injection once each month. The drug is a fully human monoclonal antibody that binds the IL-6 ligand, preventing it from activating inflammatory signalling through the IL-6 receptor. Novo Nordisk selected this dose after earlier studies demonstrated substantial reductions in hsCRP and other inflammatory and thrombosis-related biomarkers.
The primary endpoint measured the time until the first three-point major adverse cardiovascular event. The composite included cardiovascular death, nonfatal myocardial infarction and nonfatal stroke. A hazard ratio below 1 would have indicated fewer events with ziltivekimab, while a result above 1 would have favoured placebo.
The reported hazard ratio of 0.99 indicates virtually no difference between the two groups. The confidence interval ranged from a possible 12% relative reduction to an 11% relative increase in risk, meaning the available headline analysis does not support a clinically meaningful cardiovascular benefit.
Novo Nordisk has not yet disclosed the number of events in each group, median treatment duration, discontinuation rates or results for the individual components of the primary endpoint. It has also not reported whether any prespecified subgroups appeared to benefit, such as participants with particularly high inflammation, more advanced kidney impairment or specific previous cardiovascular events.
Full results are expected to be presented at a scientific meeting later in 2026. Those data should clarify whether the neutral result was consistent across the population and whether reductions in inflammatory markers were sustained throughout the trial.
Strong biomarker reductions did not become fewer heart attacks, strokes or cardiovascular deaths
The central finding from ZEUS is the separation between biological target engagement and clinical efficacy. Novo Nordisk reported that ziltivekimab reduced free IL-6 and hsCRP as expected, confirming that the antibody reached and inhibited its intended pathway. The reduction did not produce fewer major cardiovascular events.
High-sensitivity C-reactive protein is produced by the liver in response to inflammatory signalling and is associated with cardiovascular risk. Elevated hsCRP can identify patients who remain at increased risk despite receiving medicines that control cholesterol, blood pressure and thrombosis.
Association does not necessarily mean that lowering the biomarker will reduce events. A biomarker may indicate the presence or severity of a disease process without being the single mechanism responsible for clinical outcomes. ZEUS suggests that reducing IL-6-driven inflammation in this particular population was insufficient to change the combined risk of cardiovascular death, heart attack and stroke.
The trial population also had chronic kidney disease, which creates overlapping cardiovascular risks involving vascular calcification, abnormal mineral metabolism, hypertension, anaemia, endothelial dysfunction and metabolic disease. IL-6 inhibition may have successfully addressed one inflammatory pathway while leaving several other drivers of cardiovascular events unchanged.
The neutral result does not prove that inflammation is unimportant in cardiovascular disease. It shows that this specific therapy, dose and treatment strategy did not reduce the selected cardiovascular endpoint in patients with established atherosclerotic disease, kidney impairment and elevated hsCRP.
This distinction is clinically important because early drug development often relies on changes in laboratory measurements to select doses and justify larger studies. Target engagement demonstrates that a medicine is biologically active. Only a properly designed outcomes trial can determine whether that activity improves how patients feel, function or survive.
Phase 2 RESCUE findings supported ZEUS but were not designed to prove cardiovascular benefit
Development of ziltivekimab advanced largely because of the Phase 2 RESCUE study. That trial enrolled 264 people with moderate-to-severe chronic kidney disease and elevated hsCRP and assigned them to placebo or one of three monthly ziltivekimab doses.
Ziltivekimab produced large, dose-dependent reductions in hsCRP and other markers associated with inflammation and thrombosis. The results supported selection of the 15 mg monthly dose for the cardiovascular outcomes program and generated the hypothesis that direct IL-6 ligand inhibition could address residual inflammatory cardiovascular risk.
RESCUE was not large enough or long enough to determine whether ziltivekimab prevented heart attacks, strokes or cardiovascular deaths. Its primary purpose was to evaluate biological activity, dose response and safety. ZEUS was required because improvement in inflammatory biomarkers cannot be assumed to produce improvement in cardiovascular outcomes.
The difference between the two trials does not mean the Phase 2 data were incorrect. Ziltivekimab appears to have reduced the intended biomarkers in both studies. The development hypothesis failed at the next stage because the laboratory changes did not result in a detectable reduction in clinical events.
The full ZEUS dataset may help explain why. Event curves could show whether the treatment groups remained similar throughout follow-up or separated temporarily before converging. Additional biomarker analyses may identify patients with deeper inflammatory suppression, although any subgroup findings would need cautious interpretation after a neutral primary endpoint.
Novo Nordisk may also examine whether competing causes of cardiovascular events reduced the ability of IL-6 inhibition to provide benefit. Participants with chronic kidney disease frequently have several advanced risk factors, making it difficult for a single additional treatment to improve outcomes when layered onto modern standard care.
Serious infections and two continuing trials will shape ziltivekimab’s future
Overall adverse-event and serious-adverse-event rates were similar with ziltivekimab and placebo. Serious infections were more common among patients receiving the IL-6 inhibitor, an outcome consistent with suppressing an immune pathway involved in the response to infection. No difference in all-cause mortality was observed.
Novo Nordisk has not yet published the infection rates, types, severity or relationship to treatment. Those details will be important because a preventive cardiovascular medicine may be administered for years to patients who are not experiencing an immediate life-threatening condition.
Even a modest increase in serious infections can materially affect the benefit-risk assessment when cardiovascular efficacy is absent. A neutral primary endpoint means there is currently no demonstrated reduction in major cardiovascular events to offset the additional infection signal in the ZEUS population.
Ziltivekimab remains under investigation in the HERMES and ARTEMIS cardiovascular outcome trials. HERMES is studying patients with heart failure, while ARTEMIS is evaluating treatment after an acute myocardial infarction. Novo Nordisk expects both studies to report results during the first half of 2027.
The company plans to continue those trials because their populations and disease settings differ from ZEUS. Inflammation may play a different role in heart failure or during the period following an acute heart attack, when inflammatory activity can contribute to tissue injury, healing and cardiac remodelling.
ZEUS nevertheless lowers confidence that biomarker suppression will automatically produce positive outcomes in the remaining studies. HERMES and ARTEMIS must independently demonstrate clinical benefit on their prespecified endpoints.
Novo Nordisk said the failed trial will result in a non-cash impairment charge during the third quarter of 2026 but will not change its previously issued adjusted operating-profit outlook. That financial consequence does not determine the clinical future of the drug, but it confirms that the company has reduced the value assigned to the program following the neutral result.
Ziltivekimab is not approved for cardiovascular disease, chronic kidney disease, heart failure or any other indication. The ZEUS findings do not change established treatment recommendations for people with atherosclerotic cardiovascular disease or kidney disease.
The trial provides a clear scientific result: direct IL-6 inhibition produced substantial biochemical effects but did not reduce major cardiovascular events in the population studied. The remaining ziltivekimab program will now test whether a more specific disease setting can convert the same anti-inflammatory mechanism into measurable clinical benefit.
