The explanation for the impressive clinical benefits of sacubitril/valsartan in women with heart failure with preserved ejection fraction in the PARAGON-HF trial – but not in the men – remains elusive, Jonathan W. Cunningham, MD, said at the joint scientific sessions of the American College of Cardiology and the World Heart Federation. The meeting was conducted online after its cancellation because of the COVID-19 pandemic.
“We’ve all been trying to unravel the explanation for the differential effects between men and women in the primary trial. I don’t know that this NT-proBNP substudy gives a clear answer because we did see similar reduction in NT-proBNP in the men and women,” saidof Brigham and Women’s Hospital, Boston.
“Unfortunately, I think we’re still looking for the underlying physiological explanation for that very interesting interaction,” he added.
The PARAGON-HF trial included 4,796 patients with heart failure with preserved ejection fraction (HFpEF) who were randomized double-blind to sacubitril/valsartan (Entresto) or valsartan on top of background guideline-directed medical therapy and followed for a median of 34 months (). The sacubitril/valsartan group’s 13% relative risk reduction in the primary composite endpoint of cardiovascular death and total heart failure hospitalizations fell tantalizingly short of statistical significance (P = 0.058).
In women, however, who comprised more than half of the study population, the benefit of sacubitril/valsartan was larger: a 27% relative risk reduction compared to valsartan alone. That’s a statistically significant difference in a prespecified subgroup analysis, but according to the rules of clinical trials and statistics it must be considered hypothesis-generating and nondefinitive, since the overall trial was negative. Men randomized to sacubitril/valsartan had a modest 3% increased risk of the primary endpoint compared to men on valsartan.
Because of the enormous unmet need for effective therapy for HFpEF, and the fact that HFpEF is more common in women than men, the search is on for an explanation that would account for the striking gender difference in outcome in PARAGON-HF. At ACC 2020, Dr. Cunningham presented a secondary analysis of the trial focusing on the relationships between baseline and on-treatment N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels and clinical outcomes.
Among the key findings was that the higher the baseline NT-proBNP, the greater the likelihood of the primary endpoint. Also, sacubitril/valsartan reduced NT-proBNP to a similar extent in men and women: For example, by 20% compared to valsartan in men and by 18% in women when measured 16 weeks after randomization. And reduction in NT-proBNP was associated with reduced risk of cardiovascular death and heart failure hospitalizations; indeed, 60% of participants in PARAGON-HF experienced a decrease in NT-proBNP, and they had a 23% lower event rate compared to patients whose NT-proBNP increased during the course of the study.
Another intriguing finding in the parent PARAGON-HF trial was that HFpEF patients with an LVEF of 45%-57% had a 22% lower rate of the primary endpoint than those with an LVEF of 58% or more. But as with the gender difference in clinical outcomes in response to sacubitril/valsartan, the difference in outcomes based on ejection fraction was not mediated by the drug’s impact on NT-proBNP, since sacubitril/valsartan reduced NT-proBNP to a similar degree in HFpEF patients with an LVEF above or below 57%.
The difference in outcomes by ejection fraction wasn’t entirely surprising, because those low-normal–range ejection fractions where sacubitril/valsartan had a favorable impact approach those characteristic of heart failure with reduced ejection fraction (HFrEF), and guidelines give sacubitril/valsartan a class I recommendation in patients with HFrEF on the strength of the medication’s demonstrated reduction in morbidity and mortality in the PARADIGM-HF trial.
Discussant, predicted this analysis will have an impact on the design of future clinical trials in HFpEF, which up until now have required certain minimum NT-proBNP levels for participation.
“Maybe this is why so many of our trials in HFpEF have been unsuccessful. It’s a very heterogeneous population and perhaps NT-proBNP cutoffs are leading to a lot of mischief or heterogeneity that causes us some difficulty,” said Dr. Goldberg, professor of medicine and chief of the section of advanced heart failure and cardiac transplantation at the University of Pennsylvania, Philadelphia.
Dr. Cunningham reported having no financial conflicts regarding his study. The PARAGON-HF trial was funded by Novartis.
Simultaneously with Dr. Cunningham’s presentation at ACC 2020, the study results were published online (JACC Heart Fail. 2020 Mar 26;.
SOURCE: Cunningham JW. ACC 2020, Abstract 412-08.