Greater benefit in primary prevention?
In this primary prevention group, treatment with bempedoic acid for 40 months was associated with a significant risk reduction for the primary endpoint – a composite of cardiovascular death, nonfatal MI, nonfatal stroke, or coronary revascularization – which occurred in 5.3% of the treatment group versus 7.6% in the placebo group (adjusted hazard ratio, 0.70; P = .002). This represents a 30% relative risk reduction in major cardiovascular events.
Other key secondary endpoints also showed impressive reductions.
The rate of the composite endpoint of cardiovascular death, MI, or stroke was 6.4% in the placebo group and 4.0% with bempedoic acid (HR, 0.64; P < .001); MI occurred in 2.2% versus 1.4% (HR, 0.61), cardiovascular death in 3.1% versus 1.8% (HR, 0.61), and all-cause mortality in 5.2% versus 3.6% (HR, 0.73), respectively.
Adverse effects with bempedoic acid included a higher incidence of gout (2.6% vs 2.0%), cholelithiasis (2.5% vs. 1.1%), and increases in serum creatinine, uric acid, and hepatic enzyme levels.
Dr. Nissen believed these results suggest that there may be a greater benefit of lipid lowering in high-risk primary prevention patients than in the secondary prevention population.
“It may seem paradoxical, but there is actually some history that this may be the case,” he said.
He pointed out that the JUPITER trial of rosuvastatin in 2008 was the last major primary prevention trial of a lipid-lowering agent, which was stopped early with a 44% reduction of the primary endpoint.
He noted that one of the arguments against the use of statins in primary prevention is the belief that absolute risk reductions are quite modest.
“But in this analysis, we found an absolute risk reduction of 2.3% for the primary endpoint. That’s a number needed to treat to prevent 1 event of 43. That’s pretty good,” he said.
Trying to explain why there may be more benefit in the primary prevention population, Dr. Nissen suggested that these patients may have more vulnerable plaques.
“I think high-risk primary prevention patients probably have a lot of lipid-laden plaque – some people call it ‘vulnerable’ plaque. These are softer, cholesterol-laden plaque. We know that treatment with cholesterol-lowering medication causes these plaques to shrink. The lipid core is delipidated and the plaque stabilizes,” he explained. “It may be that in secondary prevention patients to some extent the horse is already out of the barn – they have advanced disease. But primary prevention patients may have plaques that are more amenable to modification by cholesterol lowering.”
He admitted that the idea is only speculation. “But that is a potential explanation for our observations.”
Editorial cautious
In an accompanying editorial, also published in JAMA, Dhruv S. Kazi, MD, Beth Israel Deaconess Medical Center, Boston, said the findings need to be interpreted with caution as they come from one of many subgroup analyses of a larger trial.
Dr. Kazi pointed out that the intervention and control survival curves separate right away, on the first day of follow-up, whereas the true effect of lipid-lowering therapy for primary prevention would be expected to have a somewhat delayed onset, an observation he says supports the argument that this is a chance finding.
Dr. Kazi also reminded clinicians that bempedoic acid should not be regarded as a substitute for statins, which should remain the first-line therapy for primary prevention.
“For now, available evidence suggests that, although bempedoic acid is not a perfect substitute for a statin, it is a reasonable therapeutic choice for primary prevention of ASCVD events in high-risk, statin-intolerant patients,” he concluded.
A version of this article first appeared on Medscape.com.