Novo Nordisk (NYSE: NVO) suffered one of its worst single-session trading days in months after its experimental heart drug Ziltivekimab failed the primary goal of a major late-stage clinical trial.
The Danish drugmaker’s U.S.-listed shares dropped 8.6% in early trading on July 31, while its Danish-listed shares fell approximately 7.5% on the same day, according to CNBC.
The drug was being tested in the ZEUS trial, a large late-stage study that enrolled more than 6,300 patients with atherosclerotic cardiovascular disease, chronic kidney disease, and elevated inflammation.
The trial tested whether Ziltivekimab, a once-monthly injection targeting the IL-6 inflammatory pathway, could reduce the risk of cardiovascular death, non-fatal heart attack, or non-fatal stroke compared with a placebo.
The hazard ratio came in at 0.99, with a 95% confidence interval of 0.88 to 1.11, meaning the drug produced no meaningful reduction in cardiovascular risk, the company said.
Ziltivekimab did successfully lower levels of free interleukin-6 and high-sensitivity C-reactive protein, demonstrating measurable pharmacological activity against its intended biological targets.
Despite those anti-inflammatory effects, the therapy failed to produce a statistically significant reduction in major adverse cardiovascular events when compared with placebo.
Higher serious infection rates were also observed in the treatment group, though total mortality remained comparable between the two groups.
Investors have been closely watching Novo’s efforts to diversify beyond its blockbuster GLP-1 drugs Wegovy and Ozempic, making the ZEUS outcome a significant blow to that broader growth strategy.
The failure is seen as particularly damaging because Ziltivekimab was considered the company’s primary candidate for establishing a meaningful revenue stream outside of its weight-loss and diabetes franchise.
ZEUS was the first of three late-stage trials for Ziltivekimab to report results, with two additional trials named Hermes and Artemis expected to conclude in the first half of 2027.
The lack of a cardiovascular risk reduction in the ZEUS population raises questions about the likelihood of success in those two remaining trials, given the overlapping patient profiles.
Novo Nordisk confirmed that the ZEUS outcome will not affect its adjusted operating profit forecast for the full 2026 fiscal year.
The company also stated it intends to continue its cardiovascular research efforts despite the setback, and full results from the ZEUS trial will be presented at a scientific conference later in 2026.
