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Ziltivekimab Setback Deepens After Earlier Cardiovascular Failure

Novo Nordisk has halted two additional late-stage trials of its experimental heart drug ziltivekimab, a fresh blow to the Danish company's ambition to build growth engines beyond its blockbuster obesity and diabetes franchise. 

The decision, announced on Monday, comes after an independent data monitoring committee concluded there was a "low likelihood" that either study would produce a different result from an earlier failed cardiovascular trial.

The two discontinued studies—named HERMES and ATHENA—were testing ziltivekimab in patients with heart failure and inflammation. Each trial was designed to evaluate a different clinical outcome, including time to cardiovascular death, heart-failure hospitalisation, urgent heart-failure visits and quality of life.

A String of Disappointments in Cardiology

The latest move follows a July announcement in which Novo reported that ziltivekimab failed to reduce the risk of major adverse cardiovascular events—such as death, non-fatal heart attack and non-fatal stroke—compared with placebo in a late-stage trial. That trial, ZEUS, enrolled patients with atherosclerotic cardiovascular disease compounded by chronic kidney disease and inflammation, and showed that despite lowering inflammatory markers, the drug did not translate into better clinical outcomes. 

With HERMES and ATHENA now terminated, Novo has only one remaining pivotal trial for ziltivekimab in the cardiovascular space: ARTEMIS, which is evaluating the drug as an acute treatment in patients recovering from a heart attack. Results from ARTEMIS are expected in the first half of 2027. 

Strategic Implications for Novo's Pipeline

The setbacks are significant for Novo Nordisk, which has been actively trying to diversify its pipeline beyond its core areas of diabetes, obesity and rare diseases. While the company's GLP-1 franchise (including Wegovy and Ozempic) continues to drive outsized revenue, investors and analysts have been watching closely for evidence that Novo can replicate similar success in other therapeutic areas, particularly cardiology.

Ziltivekimab is an IL-6 inhibitor, part of a broader industry effort to target inflammation as a pathway to reduce cardiovascular risk. The hypothesis has faced scrutiny after not only Novo's failures but also a late-stage trial failure by Novartis for its experimental cardiovascular drug, which similarly did not reduce the risk of death, heart attack or stroke. 

Market Reaction and Investor Concerns

The news adds to concerns about Novo's ability to meaningfully expand its addressable market beyond obesity and diabetes. While the company remains financially robust on the back of strong demand for its weight-loss and diabetes medicines, the cardiology disappointments raise questions about the sustainability of growth rates that have outpaced most large pharmaceutical peers. 

Investors will now be watching ARTEMIS closely, as it represents the last major cardiovascular test for ziltivekimab. A positive result could still salvage part of the drug's clinical and commercial potential, but repeated failures have already dampened expectations for IL-6 inhibition as a broad cardiovascular strategy.

The Bigger Picture: Inflammation Hypothesis Under Pressure

The setbacks extend beyond Novo alone. The broader "inflammation hypothesis"—that dampening inflammatory pathways can substantially reduce cardiovascular events—has underpinned billions of dollars in drug development across the industry. With multiple high-profile failures, cardiologists and biotech investors are reassessing how much risk reduction can realistically be achieved through anti-inflammatory mechanisms alone. 

For Novo Nordisk, the immediate focus remains on maximising its obesity and diabetes portfolio while recalibrating its cardiovascular ambitions. The company's long-term growth story now hinges less on ziltivekimab and more on whether it can identify alternative pathways—or entirely new drug classes—that can deliver the diversification investors have been expecting.