High-Profile Trial Failures Shakes the Cardiovascular Community
On November 7, 2026, at the annual meeting of the American Heart Association in The Straits Times, detailed results from major clinical trials revealed that two highly anticipated heart drugs—Novartis’s pelacarsen and Novo Nordisk’s ziltivekimab—failed to reduce cardiovascular disease outcomes despite successfully hitting their biological targets. Published simultaneously in New York Times reports, the findings left researchers and clinicians stunned, as preliminary expectations suggested these treatments would usher in a new era of preventive cardiology.
The trial for pelacarsen, which involved more than 8,300 patients, demonstrated that a monthly dose successfully cut levels of the Lp(a) blood protein by 78 percent over nearly five years. However, Dr. Steven Nissen of the Cleveland Clinic, who presented the data, reported that the treatment did not reduce deaths, non-fatal heart attacks, strokes, or emergency procedures to unblock clogged arteries. Similarly, the Zeus study evaluating Novo Nordisk’s ziltivekimab in 6,376 high-risk patients showed that while the drug successfully reduced inflammation by blocking the interleukin-6 (IL-6) protein, it failed to provide any protective benefit against major heart events.
Challenging Foundational Theories in Cardiology
The total lack of clinical efficacy has forced researchers to re-examine long-held hypotheses regarding the underlying mechanisms of cardiovascular disease. For decades, high levels of Lp(a) and chronic inflammation were widely considered direct causal agents in plaque accumulation, heart attacks, and strokes. The neutral results—described by Dr. Karol Watson of UCLA’s preventive cardiology program as “about as neutral as they can be”—raise profound questions over whether these biological markers are true drivers of disease or merely secondary indicators of broader pathological progression.
Dr. Paul Ridker of Mass General Brigham, the principal investigator for the Zeus study, noted that every subgroup in the trial fared identically to those receiving a placebo. While reflecting on the unexpected outcome, researchers proposed several possibilities, including whether patient populations had disease that was too advanced to reverse, whether existing background therapies such as anti-clotting medications and controlled cholesterol levels masked any potential benefit, or if the underlying medical hypotheses themselves require fundamental revision.
Examining Alternative Hypotheses and Patient Populations
Cardiologists and trial investigators have scrambled to interpret why interventions that successfully modified their intended biological targets yielded no clinical improvements. Dr. Roger Blumenthal, director of the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease, pointed out that participants in trials like the Horizon study often had other well-managed risk factors, such as blood pressure and LDL cholesterol, which were already optimized through existing standard-of-care treatments. In such tightly controlled cohorts, the marginal impact of further reducing Lp(a) may become statistically undetectable or physiologically irrelevant.
Furthermore, investigators discussed whether the timing of the intervention played a critical role. Because the trials predominantly enrolled individuals who had already experienced a major cardiac event or suffered from advanced kidney disease alongside severe heart pathology, experts like Dr. Priscilla Hsue of UCLA suggested that the chronic inflammatory cascades or structural vascular damage might have already reached an irreversible threshold. In essence, as Dr. Ridker metaphorically questioned during discussions of the Zeus data, researchers are confronting the possibility that “the horse was out of the barn” before the therapies were ever administered.
Looking Ahead: Future R&D and Ongoing Investigations
Despite the setbacks, the scientific community is divided on the next steps for cardiovascular research. Dr. Nissen cautioned that the disappointing findings might discourage patient participation in other active trials testing distinct Lp(a)-lowering therapies, such as small interfering RNA (siRNA) compounds like Amgen’s olpasiran and Eli Lilly’s lepodisiran, which achieve even greater reductions in Lp(a) levels and are being tested in broader populations that include patients without prior heart attacks.
Meanwhile, pharmaceutical developers are assessing how to adjust future compound designs, patient selection criteria, and intervention strategies. Novo Nordisk continues to evaluate ziltivekimab in a separate population of patients who have experienced a heart attack, with that trial scheduled to conclude next year, even as studies involving heart failure patients were discontinued in September following independent committee reviews. Researchers emphasize that while the specific pathways targeted by pelacarsen and ziltivekimab did not yield clinical benefits in these trials, the broader search for effective targeted therapies remains ongoing.