Experimental Heart Drug Pelacarsen Fails Clinical Trial Despite Cutting Lp(a) Levels by 78%

An experimental drug once hailed as a breakthrough in preventing heart attacks and strokes has failed a crucial clinical trial, despite successfully lowering a key blood protein linked to cardiovascular disease. Researchers presented the disappointing findings Saturday at an American Heart Association meeting in Chicago, marking a significant setback in the fight against the leading cause of death in developed countries.

The medicine pelacarsen, developed by Novartis, successfully reduced levels of lipoprotein(a), or Lp(a), by approximately 78% in study participants. However, after five years, that dramatic drop failed to translate into fewer cardiovascular complications, leaving cardiologists searching for answers about why the biochemical success didn’t produce clinical benefits.

“I was shocked. I had high hopes for success,” says Steven Nissen, a cardiologist at the Cleveland Clinic who led the study. “Cardiovascular disease is still the leading cause of death in developed countries. And so we really were hoping to find additional therapies that would reduce risk.”

The Promise of Targeting Lipoprotein(a)

The trial aimed to help a frustrating category of patients who seem to do everything right in managing their cardiovascular health. These individuals keep their cholesterol and blood pressure low, eat well, maintain a healthy weight, and exercise regularly, yet many still suffer heart attacks and strokes despite their diligent efforts.

Many of these patients share a common trait: elevated blood levels of lipoprotein(a), a cholesterol-carrying protein that has long been suspected of increasing heart disease risk. About 20% of the global population has elevated Lp(a) levels, affecting approximately one billion people worldwide, making it a common disorder with enormous public health implications.

“That sort of patient we see very frequently, and we were really doing our best to try to find a way to help those patients,” Nissen says.

A Large-Scale Trial with Disappointing Results

Nissen and his colleagues enrolled 8,350 adults who already had heart disease in the study, randomly assigning them to receive either a placebo or pelacarsen. Until recently, doctors lacked any drugs capable of lowering Lp(a) levels, but several pharmaceutical companies have developed experimental medications in recent years that can slash elevated Lp(a) concentrations in the bloodstream.

The drug performed exactly as hoped on a biochemical level, suppressing Lp(a) levels by the substantial margin researchers anticipated. Yet the critical question remained: would lowering this protein actually prevent heart attacks, strokes, and other cardiovascular events? The answer proved unexpectedly negative, with no measurable reduction in cardiovascular complications among patients receiving the active drug compared to those taking a placebo.

“Very disappointing, terribly disappointing,” says Nissen, who presented the first details about the study at an American Heart Association meeting in Chicago Saturday and published more specifics in the New England Journal of Medicine and the NEJM Evidence.

Novartis Confirms the Setback

Drugmaker Novartis, which sponsored the extensive multi-year study, announced last month that the results hadn’t met its goals, though the company withheld specific details at that time. In a statement following the full data release, Novartis said the study “provides meaningful evidence,” though the company did not elaborate on what lessons might be drawn from the failure or whether it would continue pursuing this therapeutic approach.

The trial’s failure raises fundamental questions about the role of lipoprotein(a) in cardiovascular disease. While elevated Lp(a) levels are associated with increased heart attack and stroke risk in observational studies, the new findings suggest that simply lowering these levels may not be sufficient to prevent cardiovascular events, or that Lp(a) may be a marker of risk rather than a direct cause of disease.

Implications for Heart Disease Treatment

This setback arrives at a critical time when cardiovascular disease remains the leading cause of death in developed countries, and researchers continue searching for new therapeutic targets beyond traditional cholesterol management. The failure of pelacarsen follows a pattern seen in other drug development efforts where successfully modifying a biomarker doesn’t always produce the expected clinical benefits.

The research community now faces difficult questions about the mechanism by which elevated Lp(a) contributes to heart disease and whether other approaches to targeting this protein might prove more successful. Several other pharmaceutical companies have invested in similar programs, and they will likely scrutinize these results carefully before deciding how to proceed with their own development efforts.

For the billion people worldwide with elevated Lp(a) levels who remain at increased cardiovascular risk despite optimal management of traditional risk factors, the search for effective therapies continues. Cardiologists and patients alike had hoped pelacarsen would fill a critical gap in cardiovascular prevention, offering protection to those who need it most despite doing everything conventional medicine currently recommends.

The detailed publication of results in the New England Journal of Medicine and NEJM Evidence will allow the broader scientific community to analyze the data and potentially identify insights that might guide future research directions. Understanding why such a dramatic reduction in Lp(a) failed to protect patients may ultimately prove as valuable as a successful trial, potentially redirecting efforts toward more promising therapeutic targets or combination approaches that address multiple pathways simultaneously.