Ziltivekimab's ZEUS Failure Uncouples hsCRP Reduction from MACE Benefit, Challenging Inflammation Hypothesis

Novo Nordisk's Ziltivekimab Fails Phase III MACE Reduction Trial

Novo Nordisk's monoclonal antibody, ziltivekimab, failed to meet its primary endpoint in the Phase III ZEUS study (NCT05021835). The trial, involving 6,385 patients with atherosclerotic cardiovascular disease (ASCVD), chronic kidney disease (CKD), and inflammation (hsCRP ≥2 mg/L), aimed to reduce major adverse cardiovascular events (MACE) defined as CV death, non-fatal heart attack, or non-fatal stroke. Despite demonstrating target engagement and inhibition of the IL-6 pathway, leading to expected reductions in free IL-6 and hsCRP, ziltivekimab did not translate this into a MACE reduction benefit. The company noted similar overall adverse event rates to placebo, though serious infections were higher with ziltivekimab. Novo Nordisk maintains its commitment to cardiovascular disease research, with two other ziltivekimab trials ongoing in heart failure and acute heart attack patients, expected to read out in H1 2027. The outcome will result in a non-cash impairment charge in Q3 2026.

• The Phase III ZEUS study (NCT05021835) of ziltivekimab, a monoclonal antibody, did not achieve its primary endpoint of reducing major adverse cardiovascular events (MACE) in 6,385 patients with atherosclerotic cardiovascular disease, chronic kidney disease, and inflammation. MACE was defined as cardiovascular death, non-fatal heart attack, or non-fatal stroke. This outcome represents a significant setback for the drug's development in this specific patient population.
• Despite the failure to reduce MACE, ziltivekimab successfully demonstrated target engagement and inhibition of the IL-6 pathway. This was evidenced by expected reductions in free IL-6 and high-sensitivity C-reactive protein (hsCRP) levels, confirming the drug's biological activity. However, this observed anti-inflammatory effect did not translate into the desired clinical benefit for MACE reduction in the study population.
• The safety profile of ziltivekimab in the ZEUS trial showed overall adverse event rates similar to placebo, though a higher proportion of serious infections was observed, consistent with its IL-6 inhibition mechanism. Novo Nordisk plans to continue two other ongoing cardiovascular outcomes trials for ziltivekimab in heart failure (NCT05636176) and acute heart attack (NCT06118281), with results anticipated in the first half of 2027, indicating continued strategic commitment to cardiovascular research.

Addressing the Unmet Need in ASCVD, CKD, and Inflammation

Despite decades of progress in cardiovascular pharmacotherapy, a substantial gap remains between guideline-recommended care and real-world outcomes for patients with ASCVD, CKD, and elevated systemic inflammation. Current standard-of-care agents leave significant residual risk unaddressed, while inflammation-targeted therapies face translational, evidentiary, and practical adoption barriers that limit their integration into routine practice.

• Residual cardiovascular risk despite optimal therapy: Statins and anti-platelet agents — the mainstay of primary and secondary prevention — fail to prevent 30–40% of major cardiovascular events, and roughly 20% of patients with established ASCVD experience recurrent events despite maximal pharmacological treatment, underscoring an unmet need for therapies targeting inflammatory and immune pathways beyond lipid lowering.

• CKD-specific therapeutic gaps: Conventional regimens show limited efficacy in the CKD population, where cardiovascular disease accounts for nearly half of all deaths. Elevated inflammatory mediators, activated renin-angiotensin signaling, and dysregulated vascular calcification drive accelerated atherosclerosis, yet targeted pharmacotherapies adopted from non-CKD or cardio-rheumatology trials remain in early clinical testing, with most supporting evidence derived from small trials using biomarker rather than hard cardiovascular endpoints.

• Lack of anti-inflammatory drugs in routine clinical use: Despite identification of promising molecular targets — particularly the NLRP3 inflammasome/IL-1β/IL-6/CRP pathway — no anti-inflammatory agent has achieved widespread adoption in clinical practice. Clinical benefits demonstrated by canakinumab and colchicine have renewed interest in inflammation as a therapeutic target, but selecting the optimal immunomodulatory agent and identifying patients most likely to benefit remain substantial unresolved challenges.

• Persistent knowledge–practice disconnect on hsCRP and inflammation testing: Recent survey data reveal that while 73.3% of physicians view systemic inflammation as a key driver of cardiovascular events, only 35.2% discuss it with patients, and unprompted recognition of hsCRP as a relevant marker was just 29.7% (versus 87.7% when prompted). Non-testing is commonly attributed to a perceived lack of impact on clinical decisions (71.3%), absence of guideline direction (44.0%), and limited downstream treatment options (37.2%).

• Underutilization of colchicine despite trial evidence: Fewer than one-quarter of eligible ASCVD and/or CKD patients would be prescribed colchicine in practice, with barriers including limited clinician experience (55.2%), concerns over contraindications (54.1%), and side-effect profile (47.1%) — notably, earlier trial data also showed an excess of diarrhea with colchicine without significant reduction in absolute hs-CRP levels.

• Long-term treatment and translational hurdles for novel agents: Because atherosclerosis is a chronic process requiring sustained intervention, safety, cost-effectiveness, and the risk of drug resistance remain major barriers to adopting new inflammation-oriented therapies. Emerging modalities such as nanoparticle-based cytokine delivery and nanozyme interventions face additional translational challenges, including biosafety concerns, pharmacokinetic limitations, and the need for scalable, standardized manufacturing before clinical application is feasible.

• Dialysis-specific cardiovascular burden: In dialysis patients, cardiovascular mortality remains unacceptably high despite advances in dialysis technology, with inflammation implicated in accelerated atherosclerosis, vascular calcification, malnutrition, and anemia — yet anti-cytokine treatment strategies to improve survival in this population remain insufficiently studied.

The Path Forward: Ziltivekimab's Future in Other CV Indications

Beyond its established investigation in ASCVD, CKD, and elevated inflammatory burden (hsCRP ≥2 mg/L), the current literature does not point to dedicated ziltivekimab trials in other indications. The core evidence base remains anchored in this population: the ZEUS trial (NCT05021835), a multinational, double-blind, placebo-controlled, event-driven randomized study enrolling 6,376 participants with ASCVD, CKD, and hsCRP ≥2 mg/L, randomized 1:1 to ziltivekimab 15 mg subcutaneously monthly versus matching placebo. Earlier phase 2 work — RESCUE (40 US sites, 1:1:1:1 randomization to placebo or ziltivekimab 7.5 mg, 15 mg, or 30 mg every 4 weeks through 24 weeks) and RESCUE-2 (a 12-week Japanese trial randomizing patients to placebo or ziltivekimab 15 mg or 30 mg at Weeks 0, 4, and 8) — similarly focused on CKD patients with heightened inflammatory markers and elevated atherosclerotic risk. Two additional phase 3 studies, HERMES and ARTEMIS, are referenced by name in the literature, though specific details on their target indications or intervention models are not yet available.

Where IL-6 inhibition more broadly is being explored outside this core cardiorenal-inflammatory axis, cancer cachexia emerges as a notable area of interest, with anti-IL-6 antibody approaches listed among promising emerging agents — alongside selective COX-2 inhibitors, ghrelin mimetics, oxandrolone, selective androgen receptor modulators (e.g., ostarine), and olanzapine. Importantly, this class is not yet considered standard of care, and the prevailing view is that the greatest therapeutic benefit will likely come from multitargeted combination regimens rather than IL-6 blockade as monotherapy, consistent with the recognized multifactorial pathophysiology of cancer cachexia. No specific intervention model or trial design details for ziltivekimab (or anti-IL-6 antibodies generally) in this setting have been reported.

A related but mechanistically distinct dataset comes from rheumatoid arthritis, where a retrospective cohort study of 196 patients evaluated predictive factors for selecting IL-6 inhibition (tocilizumab) versus TNF inhibition (etanercept) as first- or later-line biologics. While this study does not involve ziltivekimab directly, it offers class-level insight relevant to IL-6 pathway targeting: patients were stratified into four groups (TCZ-first, TCZ-second/third, ETN-first, ETN-second/third), and clinical improvement — measured via CRP, MMP-3, VAS, CDAI, and mHAQ over six months — correlated with baseline CRP, RA duration, and radiographic Sharp scores. Multivariate analysis found that CDAI improvement was significantly associated with yearly radiographic erosion progression in the TCZ-first group and negatively associated with RA duration in the ETN-first group, underscoring how baseline inflammatory and disease-duration profiles may inform IL-6-targeted therapy selection across indications.

IL-6 Inhibition's Setback in Inflammatory CVD

The recent announcement regarding ziltivekimab's failure to meet its primary endpoint in the Phase III ZEUS study marks a pivotal moment for the field of inflammatory cardiovascular disease. For years, the scientific community has recognized the critical role of inflammation in the development and progression of atherosclerotic cardiovascular disease (ASCVD) and chronic kidney disease (CKD). Ziltivekimab, a monoclonal antibody designed to inhibit the IL-6 ligand, was poised to address the significant unmet need of residual inflammatory risk in these high-risk patient populations.

Earlier Phase II data from trials like RESCUE had shown promising results, demonstrating ziltivekimab's ability to significantly reduce key inflammatory biomarkers such as high-sensitivity C-reactive protein (hsCRP) and the neutrophil-lymphocyte ratio (NLR), and even improve markers of anemia and iron homeostasis in CKD patients. This robust biomarker modulation fueled optimism that targeting the IL-6 pathway could translate into a reduction in major adverse cardiovascular events (MACE), similar to how IL-1β inhibition with canakinumab showed benefit. However, the ZEUS trial's outcome suggests that while ziltivekimab effectively engaged its target and reduced inflammation, this did not confer a clinical benefit in MACE reduction. This outcome underscores the complex interplay of inflammatory pathways in cardiovascular disease and the challenge of translating biomarker improvements into hard clinical endpoints.

Furthermore, the trial noted a higher incidence of serious infections with ziltivekimab, a known risk associated with immune-modulating monoclonal antibodies. This safety signal, combined with the lack of efficacy, will undoubtedly influence the strategic direction for Novo Nordisk's remaining ziltivekimab trials in heart failure and acute myocardial infarction, which are expected to read out in 2027. The pharmaceutical industry will likely re-evaluate the specific role of IL-6 inhibition in cardiovascular disease, potentially exploring more nuanced approaches to targeting IL-6 signaling or shifting focus to alternative inflammatory pathways that have demonstrated clinical efficacy.