ZEUS trial finds a sharp biomarker drop without fewer major cardiovascular events
A powerful anti-inflammatory signal did not translate into fewer heart attacks, strokes, or cardiovascular deaths in ZEUS, a phase III trial that tested ziltivekimab in very high-risk adults with atherosclerotic cardiovascular disease and chronic kidney disease. The drug drove down blood markers of inflammation, yet the primary cardiovascular endpoint remained essentially unchanged versus placebo. In a population this sick, the disconnect is clinically sobering.
Investigators enrolled 6,376 adults across 757 research sites in 38 countries and followed them for a median of 29.1 months. Participants were older, medically complex, and heavily burdened by risk: average age was 69.4 years, 27.5% were women, 92% had hypertension, nearly 66% had type 2 diabetes, and 42% had heart failure. More than 92% were already receiving cholesterol-lowering therapy, which makes the neutral outcome harder to dismiss as undertreated background risk. These were not early-stage patients with room for a large rescue effect; this was an advanced cardiometabolic cohort with multiple competing threats.
Inflammation markers fell, but event curves did not separate
Ziltivekimab, a monoclonal antibody that blocks interleukin-6, reduced hs-CRP by 64% and IL-6 by 76% compared with placebo. Those are large biologic effects. They confirm the drug reached its intended pathway and substantially altered circulating inflammatory signaling.
Yet the clinical endpoint did not budge in a meaningful way. The primary endpoint of heart attack, stroke, or cardiovascular death occurred in 561 participants assigned to ziltivekimab and 565 assigned to placebo. Deaths were similarly close: 538 in the treatment group and 542 in the placebo group. A biomarker win without an outcomes win forces a hard question in cardiovascular medicine: how much inflammatory suppression is enough, and at what disease stage does the biology become less reversible?
The answer may lie in the timing and the substrate of disease. Atherosclerosis in the setting of chronic kidney disease is not just a plaque problem; it is a systemic state of vascular injury, calcification, endothelial dysfunction, and recurrent inflammatory stress. Once that burden is advanced, lowering one signaling pathway may not be sufficient to pull back the full cardiovascular risk architecture.
High inflammation still tracked with higher risk throughout follow-up
Even with a neutral trial result, baseline inflammation remained prognostically important. Participants entering ZEUS with higher hs-CRP or IL-6 levels continued to face greater cardiovascular risk over the trial period. That pattern reinforces inflammation as a real biologic driver, not a laboratory curiosity.
The challenge is therapeutic precision. Interleukin-6 sits downstream in the inflammatory cascade, and blocking it can lower circulating inflammatory markers without necessarily reversing the vascular damage already present. In a cohort with established ASCVD and clinically significant CKD, much of the event burden may have been locked in by preexisting plaque instability, diffuse vascular disease, or non-inflammatory mechanisms that no single biologic agent can overcome. In other words, the pathway matters, but so does the point in the disease course at which the pathway is targeted.
A second point stands out: serious infections were more common with ziltivekimab, 20% versus 18% with placebo. Overall side effect rates were similar, but any therapy that suppresses inflammation carries a tradeoff between vascular benefit and immune defense. In a medically fragile kidney disease population, even small infection differences can matter at the bedside.
Advanced kidney disease may have narrowed the treatment window
ZEUS participants were at exceptionally high risk, and more than 6% died during the study, a rate described as double that seen in other contemporary atherosclerosis trials without severe kidney disease. The combination of ASCVD and CKD is especially unforgiving: reduced renal function amplifies vascular calcification, worsens blood pressure control, raises thrombotic risk, and often coexists with diabetes and heart failure. The trial population reflected that complexity.
The median 29.1-month treatment period and 85.6% adherence suggest the negative result was not simply a matter of poor exposure. Survival status was confirmed for 99% of participants, which gives the findings substantial internal credibility. The issue appears less about execution and more about biology. If disease burden is already extensive enough, downstream IL-6 inhibition may arrive after the most preventable phase of risk has passed.
That interpretation fits the pattern of prior anti-inflammatory cardiovascular studies. Earlier work with other agents has shown that inflammation can be a modifiable driver of cardiovascular events, but the signal has not been universal across all drugs, pathways, or patient groups. ZEUS strengthens the case that inflammation matters while also showing that not every anti-inflammatory strategy will work in every population.
What ZEUS means for anti-inflammatory cardiovascular therapy
The findings do not erase inflammation as a treatment target. They instead narrow the field. Researchers are now looking at downstream IL-6 inhibition in patients with less severe disease and at upstream targeting of the NLRP3 inflammasome, which sits even earlier in inflammatory activation. That direction makes biological sense: earlier intervention may preserve more of the vascular tree before plaque biology and kidney-related injury become too entrenched.
For clinicians, the practical message remains straightforward. Inflammation should be measured, not assumed. Patients with ASCVD and CKD still need aggressive management of blood pressure, lipids, glucose, tobacco exposure, and lifestyle factors, because those interventions remain the backbone of risk reduction while the next generation of anti-inflammatory trials sorts out which pathway, which stage, and which patient profile will actually benefit.
ZEUS leaves one central uncertainty unresolved: whether stronger clinical benefit will emerge in earlier disease, with a different anti-inflammatory target, or in a population less damaged by combined vascular and renal disease. Until then, the most advanced cases may be the least likely to respond to a single biologic intervention, even when the laboratory data move in the right direction.