Cardiologists were taken aback recently when a highly anticipated drug designed to reduce levels of the blood protein lipoprotein(a), or Lp(a), failed to demonstrate a reduction in heart attacks and strokes despite significantly lowering Lp(a). The trial, conducted by Novartis and announced on September 4, showed that while the drug could reduce Lp(a) levels by as much as 80 percent, it did not translate into improved cardiovascular outcomes.

Lp(a) has long been considered an important factor in cardiovascular risk. Roughly 20 percent of Americans have elevated Lp(a) levels, which can increase the likelihood of heart attack by two to three times. Many clinicians have been hopeful that lowering Lp(a) could help patients who experience cardiovascular events despite having normal cholesterol, blood pressure, and without common risk factors such as diabetes, obesity, or smoking.

“This result was a surprise and raises fundamental questions about our understanding of Lp(a),” said Dr. John Alexander, a cardiologist at Duke University. The findings have led experts to question whether Lp(a) is a causal factor in heart disease or merely a marker indicating other underlying problems. Dr. David Maron, president of the American Society for Preventive Cardiology, described this uncertainty as a “nagging question” in the field.

Some researchers caution against abandoning the hypothesis that Lp(a) contributes directly to cardiovascular disease. They point out that the full data from Novartis’s trial will not be publicly available until its presentation at the American Heart Association meeting in November, allowing for deeper analysis. Dr. Sadiya Khan of Northwestern University emphasized that more investigation is needed before drawing definitive conclusions.

Several possible explanations have been proposed for the trial's unexpected outcome. Dr. Daniel Rader, a lipid specialist at the University of Pennsylvania, suggested that the study population—patients with very high Lp(a) who had already experienced heart attacks or strokes—may have been too advanced in their disease course for the treatment to show benefit. Earlier intervention in patients at high risk but without prior events could yield different results. Additionally, Rader noted, it is uncertain whether lowering Lp(a) by 80 percent is sufficient to reduce cardiovascular risk.

Yale cardiologist Dr. Harlan Krumholz offered an alternative perspective, highlighting that Lp(a) levels are genetically determined and stable throughout life. He speculated that lowering Lp(a) in adulthood might be less effective if damage has accumulated over decades and that long-term, perhaps lifelong, lowering might be necessary to observe clinical benefit.

Further research is ongoing, including trials by pharmaceutical companies Lilly and Amgen testing other Lp(a)-lowering therapies. These forthcoming studies will be critical in reassessing whether targeting Lp(a) can help prevent cardiovascular events. If they also fail to show clinical benefit, some experts, including Dr. Rader, warn that enthusiasm for Lp(a) as a therapeutic target may diminish significantly.