A major experimental heart drug from Novo Nordisk has flopped in the crucial ZEUS trial, missing the outcome that matters most to patients and forcing cardiologists to rethink one of the field's most influential ideas.
The drug, ziltivekimab, blocked the IL-6 inflammatory pathway as designed, and blood tests confirmed lower levels of inflammation. But across more than 6,300 patients, it did not cut the rate of heart attacks, strokes or cardiovascular deaths compared with placebo.
Novo Nordisk announced the results on July 31, 2026. The hazard ratio was 0.99 (95 percent confidence interval, 0.88 to 1.11), a flat line where the company had hoped to see benefit.
Serious infections were more common in patients on ziltivekimab, and overall mortality did not differ between the groups.
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What the inflammation theory says
For years, researchers have argued that chronic, low-grade inflammation drives the buildup of plaque inside arteries and helps trigger the ruptures that cause heart attacks. High-sensitivity C-reactive protein, or hsCRP, a blood marker of inflammation, tracks with cardiovascular risk even in people whose cholesterol looks fine.
The idea got its strongest boost from the CANTOS trial, published in 2017 in The New England Journal of Medicine. It found that canakinumab, an antibody targeting a different inflammatory protein called interleukin-1 beta, reduced recurrent cardiovascular events in heart-attack survivors with elevated hsCRP.
That was the first hard evidence that damping inflammation, without touching cholesterol, could protect the heart.
Why ZEUS mattered so much
Ziltivekimab was designed to go deeper into the same pathway, targeting IL-6, a cytokine sitting downstream of IL-1 beta. Novo Nordisk gained control of the drug in 2020 through its acquisition of Corvidia Therapeutics, paying $725 million up front in a deal worth up to $2.1 billion in total.
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The ZEUS trial enrolled people with atherosclerotic heart disease and chronic kidney disease, a group with high baseline inflammation and few good treatment options.
"Although ziltivekimab produced the expected biological effect, this did not result in MACE benefits in this population," said Martin Holst Lange, Novo Nordisk's chief scientific officer, in a company statement. MACE is short for major adverse cardiovascular events, meaning heart attack, stroke or cardiovascular death.
Andy Hsieh, an analyst at William Blair, wrote that the lack of any signal, combined with the excess infections, calls into question the role of hsCRP as a target for protecting the heart.
A hypothesis under pressure
Cardiologists were quick to weigh in. One, Sanjay Kaul, invoked the biologist Thomas Huxley's line about beautiful hypotheses being slain by ugly facts.
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Others urged caution. Pablo Corral wrote that "the neutral ZEUS result should not be interpreted as disproving the prognostic association between hsCRP and cardiovascular events." Inflammation may still mark risk, in other words, even if blocking IL-6 does not lower it.
The setback follows another recent disappointment for anti-inflammatory cardiology. Low-dose colchicine, an old gout drug, won FDA approval for cardiovascular use in June 2023 based on the LoDoCo and LoDoCo2 trials, but later failed to show benefit in the CLEAR SYNERGY study of heart-attack patients.
What it means for patients
The result does not change how doctors treat cardiovascular disease today. Statins and blood-pressure medicines remain the cornerstone of prevention, and neither is affected by the ZEUS findings.
Ziltivekimab is not approved and is not available to patients.
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Novo Nordisk said two other ziltivekimab trials will continue. HERMES, in patients with heart failure, and ARTEMIS, in patients after an acute heart attack, are expected to report in the first half of 2027.
Anyone taking a prescribed heart medicine, or worried about their own cardiovascular risk, should discuss it with a doctor.
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