A new class of drugs for systolic heart failure: The PARADIGM-HF study
ABSTRACTThe PARADIGM-HF trial (Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) found a combination drug containing sacubitril (a neprilysin inhibitor) and valsartan (an angiotensin II receptor blocker) superior to enalapril (an angiotensin-converting enzyme inhibitor) in patients with systolic heart failure. Recently approved by the US Food and Drug Administration, sacubitril-valsartan is the first new drug in over a decade to decrease death rates in patients with systolic heart failure.
KEY POINTS
- Neprilysin is an endogenous enzyme that degrades vasoactive peptides such as bradykinin and natriuretic peptides. Inhibition of neprilysin raises the levels of these peptides, leading to less cardiac remodeling, less sodium retention, and less vasoconstriction.
- Neprilysin inhibition must be combined with inhibition of the renin-angiotensin-aldosterone system, optimally with an angiotensin II receptor blocker.
- PARADIGM-HF showed a 20% reduction in the primary outcome of death from cardiovascular causes or hospitalization for heart failure with sacubitril-valsartan 200 mg twice daily vs enalapril 10 mg twice daily at a median follow-up of 27 months.
- The ultimate role of combined neprilysin and angiotensin receptor inhibitors remains to be determined.
QUESTIONS AND CONCERNS
Although this study, which was funded by the manufacturer, showed consistent benefit for sacubitril-valsartan over enalapril, questions remain.
Are the findings generalizable?
Despite the study’s rigorous run-in period, 12% of patients dropped out because of adverse events, and thus the patients who completed the study may not be representative of the general population of heart failure patients. The authors included this double-level wash-out to ensure patient tolerance of both drugs. But in everyday practice, a significant number of patients may be unable to tolerate one of these drugs.
Moreover, after adjusting for the difference in the run-in periods, patients actually withdrew more often during the enalapril run-in period than during the sacubitril-valsartan run-in period. However, there may be overlap in tolerability in these two drugs, which both affect the renin-angiotensin-aldosterone system. Thus, the enalapril run-in period may have contributed to the lower tolerability of this drug compared with sacubitril-valsartan.
Were patients receiving the best possible therapy?
Another important point when considering how we treat heart failure patients in the United States is how few patients in this study were using cardiac implantable electronic devices. Only 15% of the patients in this study had an implantable cardioverter-defibrillator despite a mean left ventricular ejection fraction less than 30%. This likely reflects differences in practice internationally; however, based on American College of Cardiology, American Heart Association, and Heart Rhythm Society guidelines, these patients would have a class I indication for an implantable cardioverter-defibrillator for primary prevention of sudden cardiac death.23
Therefore, based on these recommendations, the patients in this study were not necessarily on optimal medical and device therapy and furthermore may not be representative of heart failure patients in the United States.
Was enalapril 10 mg twice a day a fair comparison?
Another concern about the results of this study relates to the dosages used in the two treatment groups. The sacubitril-valsartan formulation included full-dose valsartan, whereas the ACE inhibitor group received enalapril at less than a full dose.
Although the authors explained that the dose of enalapril chosen for the study was based on the one used in previous studies that showed survival benefit, this raises the question of whether the significant difference in outcomes in this trial was due to a greater inhibition of the renin-angiotensin-aldosterone system related to a higher dose of drug in the sacubitril-valsartan group.
What about black patients taking hydralazine-isosorbide?
Only about 5% of patients in the PARADIGM-HF trial were black. Based on the A-HeFT study results, black patients can be prescribed an ACE inhibitor as well as hydralazine and isosorbide dinitrate as tolerated to decrease the risk of death. Does sacubitril-valsartan offer benefit to these patients compared with a regimen of an ACE inhibitor, hydralazine, and isosorbide dinitrate?
Another concern is that the incidence of angioedema observed with ACE inhibitors and omapatrilat is higher in black patients.15,21 Thus, it would be prudent to investigate whether the risk of angioedema with sacubitril-valsartan would be higher if more black patients are studied.
IMPLICATIONS AND CONSIDERATIONS
In this study, sacubitril-valsartan showed impressive and consistent results, with an almost 20% decrease in the composite end point of heart failure hospitalization or cardiovascular death and a similar decrease in the composite outcomes with a very low number needed to treat (21 patients). It did not show a decrease in the incidence of new-onset atrial fibrillation; however, only 80 cases of atrial fibrillation were reported, so there may have been a lack of statistical power to detect a difference.
To avoid angioedema, wait at least 36 hours after stopping an ACE inhibitor. Sacubitril-valsartan was not associated with an increased risk of severe angioedema, and no patients experienced life-threatening angioedema. In the trial, the sacubitril-valsartan run-in period was started at least 24 hours after enalapril was stopped, and thus the authors recommended at least a 1-day washout period after discontinuing an ACE inhibitor to avoid angioedema in patients starting sacubitril-valsartan.
Hypotension is a concern. Although there was actually a decreased risk of renal dysfunction, hyperkalemia, and cough compared with enalapril, there was a significantly increased rate of symptomatic hypotension in the sacubitril-valsartan group, which raises the question of patient tolerance and physician comfort when prescribing and titrating this drug in clinical practice. This side effect will be an important consideration when attempting to titrate the drug to target doses.
Start treatment early. This trial largely consisted of patients with NYHA class II or III symptoms, with about 70% of patients with class II symptoms. Since this drug showed benefit in patients with mildly to moderately symptomatic heart failure, clinicians who are considering prescribing this drug should not wait until the patient is closer to end-stage disease. Patients with mildly symptomatic heart failure may be followed by a general cardiologist, internist, or both, and thus it is important to emphasize to the entire medical community the need to start this medication early on.
How much will it cost? Cost is a concern that could heavily weigh on the decision to prescribe this drug. Generic ACE inhibitors are relatively inexpensive, and it may difficult to switch from an affordable generic drug to a new drug that is likely to be much more expensive. Arguably, this drug may be cost-effective in the long run owing to a large decrease in heart failure readmissions. We await further analyses to evaluate this issue.
Will patients take a twice-a-day drug as prescribed? Most patients who are prescribed an ACE inhibitor take it just once a day, and switching from a daily to a twice-daily drug may present a challenge for some.
What about other outcomes? Based on this study, it is unclear what effect sacubitril-valsartan has on the incidence of fatal arrhythmias, sudden cardiac death, and pump failure. Furthermore, the effect on quality of life is still uncertain. Quality of life is an integral component in the evaluation of heart failure patients, and in this study the changes in KCCQ scores were not impressive. We hope to see further evaluations of this drug’s impact on quality of life of patients with heart failure. Furthermore, it would be interesting to study if this drug has any long-term effects on the need for advanced therapies such as left ventricular assist devices and orthotopic heart transplant.
What about patients with heart failure with preserved ejection fraction? This study included only patients with heart failure with reduced ejection fraction. However PARAMOUNT, a phase 2 study that evaluated the benefit of sacubitril-valsartan in patients with heart failure with preserved ejection fraction, has shown encouraging results.24 We look forward to further investigation of this agent in patients with heart failure with preserved ejection fraction.
Sacubitril-valsartan, the first ARNI to be studied in humans, has a dual action in that it enhances the activity of the natriuretic peptide system and inhibits that of the renin-angiotensin-aldosterone system. It is the first drug in over a decade to show mortality benefit in patients with chronic systolic heart failure when compared with an already well-established heart failure medication. It appears to decrease rates of mortality and heart failure hospitalization without increasing the risk of severe angioedema in patients with mild or moderate chronic systolic heart failure. Symptomatic hypotension and high cost may pose the largest barriers to the use of this new drug. And we have yet to see how the clinical community and patients with heart failure will respond to it.
