An experimental cardiovascular medication called pelacarsen reduced a sticky, genetically driven blood fat known as lipoprotein(a) by roughly 78% in a major clinical trial, yet it completely failed to lower the rate of heart attacks, strokes, or cardiovascular deaths among 8,350 high-risk patients, stunning cardiologists.
Pelacarsen Slashes Cholesterol Levels Without Reducing Cardiovascular Events
- Lipoprotein(a) [Lp(a)]: A specialized, inherited type of cholesterol packaged in a protein shell. Elevated levels promote blood clotting and inflammation in the arterial walls, creating a double threat for cardiovascular events.
- Pelacarsen: An investigational drug designed to interfere with the body’s ability to produce Lp(a), effectively dropping blood concentrations by nearly 80%.
- The Clinical Paradox: Despite successfully slashing Lp(a) levels, the placebo-controlled study showed zero decreases in stroke, heart attack, cardiovascular deaths, or procedures to open blocked arteries or restore blood flow to the heart.
Unanticipated Trial Outcomes Stun Preventive Cardiology
The stark findings from the Horizon clinical trial were presented on a Saturday at the American Heart Association’s annual scientific sessions in Chicago and published in the New England Journal of Medicine and NEJM Evidence. Dr. Steven Nissen, chief academic officer of the Heart, Vascular & Thoracic Institute at the Cleveland Clinic, led the study. Researchers called the outcome a massive blow to preventive cardiology, given that expectations for the drug were uniformly positive.
The trial enrolled 8,350 adults who had previously experienced a cardiovascular event—such as a heart attack or stroke—within the prior decade and carried elevated blood levels of Lp(a). Participants received either monthly injections of pelacarsen or a placebo. After five years, the drop in Lp(a) did not translate into saving people from cardiovascular complications. Dr. Harlan Krumholz, a Yale University cardiologist, described the high expectations as the primary reason the outcome resonated so heavily across the medical field.
| Trial Parameter | Pelacarsen Arm | Placebo Arm |
|---|---|---|
| Biomarker Reduction | ~78% decrease in Lp(a) | ~13% decrease |
Rethinking the Genetic Target of Cardiovascular Risk
Approximately 20% of the global population inherits genetic variants that instruct the liver to produce elevated levels of Lp(a), with higher baseline frequencies observed in individuals of African or South Asian ancestry. Because these concentrations are largely stable across a person’s lifetime and resistant to diet, exercise, or lifestyle modifications, physicians have long sought targeted pharmacological interventions. Yet, the failure of pelacarsen forces scientists to reconsider whether Lp(a) is a direct causative driver of vascular disease or merely an associative biomarker.
Alternative pharmaceutical developers are currently evaluating distinct mechanisms of action. Amgen is studying olpasiran, and Eli Lilly is investigating lepodisiran, with both compounds demonstrating Lp(a) reductions of approximately 95%. Phase 3 results for Amgen’s candidate are anticipated in early 2028, while Lilly’s trials are expected in 2029. Stanford University cardiologist Dr. David Maron, who serves as president of the American Society for Preventive Cardiology, suggested that a higher Lp(a) level should perhaps have been required for entry into the trial, and several experts said the study may only benefit people whose blood pressure and bad cholesterol were not as well controlled.
Lacks Approved Targeted Drugs in Clinical Practice
No approved targeted drug specifically lowers Lp(a) in clinical practice.
Future Directions in Lipid-Lowering Therapeutics
Despite the setback, investigators emphasize that negative clinical trials provide crucial data that shapes future scientific inquiry. Dr. Fatima Rodriguez, chief of preventive cardiology at Stanford University, who was not involved in the research, noted that there is no signal from the trial. Nissen suggested that patients in the trial were older, so perhaps they were past a point in their heart disease where lowering Lp(a) offered any benefit, and noted that other, stronger Lp(a)-lowering medications are already in clinical trials.
References
- New England Journal of Medicine
- NEJM Evidence
- American Heart Association
