Novo Nordisk's ZEUS trial has failed despite biomarker target engagement for ziltivekimab, the company's anti-IL-6 monoclonal antibody, dealing a setback to the hypothesis that targeting cardiovascular inflammation in a high-risk cardiorenal population would translate into fewer major adverse cardiovascular events (MACE). Novo Nordisk reported on July 31 that the drug produced no MACE benefit versus placebo despite confirmed suppression of both free interleukin-6 (IL-6) and high-sensitivity C-reactive protein (hsCRP).
The result is a direct challenge to the residual inflammatory risk thesis that has driven investment in anti-inflammatory cardiovascular therapies since the CANTOS trial demonstrated that Novartis's Ilaris (canakinumab) reduced MACE in patients with elevated hsCRP — without ever securing a cardiovascular indication from the FDA.
Ziltivekimab is a fully human monoclonal antibody that binds the IL-6 ligand, blocking downstream signaling through a pro-inflammatory cytokine implicated in atherosclerotic plaque progression and cardiovascular risk. The drug produced the anticipated biological effect: reductions in both free IL-6 and hsCRP were observed, confirming target engagement. That engagement did not, however, reduce the primary endpoint of cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke. The hazard ratio was 0.99 (95% confidence interval, 0.88–1.11), a result statistically indistinguishable from no effect.
ZEUS enrolled more than 6,300 patients with established atherosclerotic cardiovascular disease (ASCVD), chronic kidney disease (CKD), and systemic inflammation defined by hsCRP ≥2 mg/L — a population selected precisely because elevated inflammation was expected to be a modifiable risk factor. The trial compared once-monthly subcutaneous ziltivekimab 15 mg against placebo on top of standard of care. Overall rates of adverse events and serious adverse events were similar between arms, though serious infections were more frequent with ziltivekimab, consistent with IL-6 pathway inhibition. No difference in all-cause mortality was reported.
The failure raises a pointed mechanistic question: if IL-6 suppression, confirmed by biomarker data, does not reduce MACE in this population, does the inflammatory pathway play a causal role in outcomes — or is elevated hsCRP a marker rather than a driver of residual risk in ASCVD-CKD patients? The CANTOS data with canakinumab, which targets IL-1β upstream of IL-6, and the subsequent FDA approval of Agepha Pharma's LoDoco (colchicine 0.5 mg) for chronic ASCVD prevention via NLRP3 inflammasome inhibition, had supported the broader inflammatory hypothesis. ZEUS does not refute that hypothesis entirely, but it suggests that IL-6 inhibition specifically may not be the operative mechanism in this cardiorenal phenotype.