PARADIGM-HF

Participants in the PARADIGM-HF trial were adult patients (mean age 63.8 years) with chronic heart failure and reduced ejection fraction (HFrEF, left ventricular ejection fraction [LVEF] "less than or equal to" 40% at screening, later amended to "less than or equal to" 35% for the majority of the trial). Key characteristics included symptomatic heart failure (NYHA class II, III, or IV), elevated plasma natriuretic peptide levels (BNP "greater than or equal to" 150 pg/mL or NT-proBNP "greater than or equal to" 600 pg/mL, or BNP "greater than or equal to" 100 pg/mL or NT-proBNP "greater than or equal to" 400 pg/mL if hospitalized for HF within the previous 12 months). The mean LVEF was 29.5%. Patients were required to be on stable doses of an ACE inhibitor or an ARB for at least 4 weeks, and a beta-blocker if tolerated, for at least 4 weeks prior to screening. Over 70% were NYHA class II. Mean systolic blood pressure was 122 mmHg. Approximately 79% of patients were male, and 67% were white.

The PARADIGM-HF trial involved a sequential run-in design followed by 1:1 randomization. After screening, eligible patients entered an open-label enalapril run-in period (10 mg twice daily for 2 weeks) to assess tolerance. Patients tolerating enalapril then entered an open-label sacubitril/valsartan (LCZ696) run-in period, starting with 100 mg twice daily for 1-2 weeks, followed by 200 mg twice daily for 3-4 weeks to assess tolerance. Patients tolerating both run-in phases were then randomized 1:1 to receive either sacubitril/valsartan 200 mg twice daily (target dose) or enalapril 10 mg twice daily. Randomization was stratified by region and NYHA functional class. The trial was double-blind and double-dummy. A total of 8,399 patients were randomized: 4,209 to sacubitril/valsartan and 4,190 to enalapril. The median follow-up duration was 27 months.

The primary endpoint was a composite of cardiovascular (CV) death or first hospitalization for heart failure. The trial was stopped early after a median follow-up of 27 months due to overwhelming efficacy. At the time of the interim analysis, the primary endpoint occurred in 914 patients (21.8%) in the sacubitril/valsartan group and 1117 patients (26.5%) in the enalapril group. This represented a statistically significant 20% reduction in the risk of the primary outcome with sacubitril/valsartan compared to enalapril (Hazard Ratio [HR] 0.80; 95% Confidence Interval [CI] 0.73-0.87; P < 0.001). The statistical method used was a Cox proportional-hazards model. Subgroup analyses consistently favored sacubitril/valsartan across various predefined subgroups, including age, sex, race, geographic region, NYHA class, LVEF, etiology of heart failure, and baseline kidney function, with no evidence of heterogeneity of treatment effect.

Several secondary outcomes were assessed:

• Cardiovascular Death: Occurred in 558 patients (13.3%) in the sacubitril/valsartan group and 693 patients (16.5%) in the enalapril group (HR 0.80; 95% CI 0.71-0.89; P < 0.001). This was a significant reduction.
• First Hospitalization for Heart Failure: Occurred in 537 patients (12.8%) in the sacubitril/valsartan group and 658 patients (15.7%) in the enalapril group (HR 0.79; 95% CI 0.71-0.89; P < 0.001). This was a significant reduction.
• All-cause Mortality: Occurred in 711 patients (16.9%) in the sacubitril/valsartan group and 835 patients (19.8%) in the enalapril group (HR 0.84; 95% CI 0.76-0.93; P < 0.001). This was a significant reduction.
• Total Number of Hospitalizations for Heart Failure: Total hospitalizations for heart failure (including first and recurrent events) were reduced by 21% in the sacubitril/valsartan group compared to the enalapril group (Rate Ratio 0.79; 95% CI 0.71-0.89; P < 0.001), using a negative binomial regression model.
• Quality of Life (Kansas City Cardiomyopathy Questionnaire [KCCQ] clinical summary score and overall summary score): Sacubitril/valsartan led to a greater improvement in KCCQ scores from baseline compared to enalapril (P < 0.001 for both scores at 8 months, using a mixed-model repeated-measures analysis).
• Renal Function: The sacubitril/valsartan group experienced a slower decline in estimated glomerular filtration rate (eGFR) over time compared to the enalapril group, though a higher incidence of hypotension was observed. The change in eGFR from baseline to 8 months was -2.0 mL/min/1.73 m² in the sacubitril/valsartan group vs -3.0 mL/min/1.73 m² in the enalapril group (P < 0.001).

The PARADIGM-HF trial conclusively demonstrated that sacubitril/valsartan was superior to enalapril in reducing the risk of cardiovascular death and hospitalization for heart failure in patients with chronic heart failure and reduced ejection fraction. The trial was stopped early due to the highly significant benefits observed. Sacubitril/valsartan also significantly reduced all-cause mortality and improved quality of life. While sacubitril/valsartan was associated with a higher incidence of symptomatic hypotension, it led to less renal dysfunction, hyperkalemia, and cough compared to enalapril. This trial established sacubitril/valsartan as a foundational therapy for HFrEF, changing clinical guidelines and becoming a standard of care. The overall verdict is overwhelmingly positive, indicating a major advancement in the management of HFrEF.

One limitation is the run-in design, where patients who could not tolerate enalapril or sacubitril/valsartan were excluded from randomization. This approach may select for a more tolerant patient population, potentially limiting generalizability to all patients with HFrEF, especially those more prone to adverse effects. The exclusion of patients with a history of angioedema also means that the risk of angioedema with sacubitril/valsartan in such patients is not fully characterized. While the trial involved a broad population, patients with lower blood pressure at baseline were underrepresented, and the generalizability to patients with very low blood pressure or those who cannot tolerate standard ACE inhibitor/ARB doses might be limited. The trial was also terminated early, which, while indicating strong efficacy, means that longer-term effects and very rare adverse events might not have been fully captured.

PARADIGM-HF built upon decades of research establishing the benefits of ACE inhibitors, ARBs, beta-blockers, and mineralocorticoid receptor antagonists in HFrEF. It directly compared sacubitril/valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI), to enalapril, a standard ACE inhibitor. Other key trials in HFrEF include SOLVD (enalapril), CHARM (candesartan), CIBIS (bisoprolol), MERIT-HF (metoprolol), RALES (spironolactone), and EMPHASIS-HF (eplerenone), which demonstrated the benefits of their respective drug classes. Following PARADIGM-HF, trials like PIONEER-HF explored initiating sacubitril/valsartan in hospitalized patients with acute decompensated heart failure. The PARAGON-HF trial evaluated sacubitril/valsartan in patients with heart failure with preserved ejection fraction (HFpEF), showing a non-significant reduction in the primary endpoint but suggesting potential benefits in certain subgroups, particularly women and those with lower LVEF in the HFpEF range.