Mechanisms Underlying Hypotensive Response to ARB/NEP Inhibition - Aim 3

LCZ696, a molecular complex of the angiotensin receptor blocker (ARB) valsartan with an inhibitor of neprilysin (NEP, neutral endopeptidase-24.11) sacubitril improved mortality compared to enalapril in patients with heart failure (HF), reduced ejection fraction (EF), and increased brain natriuretic peptide (BNP) or N-terminal pro-BNP (NT-proBNP) in the PARADIGM-HF trial. The PIONEER-HF study demonstrated the efficacy of LCZ696 in preventing rehospitalization in patients with acutely decompensated HF. LCZ696 has been underutilized in heart failure, in part due to concerns about hypotension. NEP degrades several vasodilator peptides including bradykinin, substance P and brain-type natriuretic peptide. Decreased degradation of endogenous substance P could contribute to hypotension at initiation of LCZ696 through vasodilation or through increased natriuresis and diuresis. Antagonism of the NK1 receptor using aprepitant would be expected to prevent this effect. Objectives The main objectives of this mechanistic randomized, double-blind, crossover-design study are: The primary objective is to test the hypothesis that endogenous substance P contributes to effects of ARB/NEP inhibition on blood pressure, natriuresis, and diuresis at initiation. The secondary objective is to test the hypothesis that endogenous substance P contributes to effects of ARB/NEP inhibition on blood pressure, natriuresis, and diuresis after up-titration. Eighty (80) subjects with stable heart failure who meet all inclusion/exclusion criteria will be enrolled. Subjects who qualify will collect their urine for 24 hours before each study day for measurement of volume, sodium and potassium. At the start of the study, they will stop their regular angiotensin-converting enzyme (ACE) inhibitor or ARB. After a 48-hour washout, they will undergo a study day in which they are given a single dose of 50 mg LCZ696. They will also receive either the NK1 receptor antagonist aprepitant or placebo vehicle in random order (double-blind). After a 96-hour washout, they will repeat the study day and receive a single dose of 50 mg LCZ696 and the opposite study drug (aprepitant or placebo). After completion of the two acute study days, subjects will take LCZ696 50 mg bid for two weeks, followed by LCZ696 100 mg bid for three weeks, and then LCZ696 200 mg bid, following the conservative up-titration protocol from the TITRATION study. Criteria for continuing up-titration appears in the full study protocol. On the 7th and 10th day of the 200 mg bid or highest tolerated dose, subjects will again undergo two more study days three days apart in which they are randomized to receive either aprepitant or vehicle.

Mechanisms Underlying Hypotensive Response to ARB/NEP Inhibition - Aim 3

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