The ghrelin receptor agonist AC01 improves cardiac function in non-human primates and in mice with heart failure by increasing cardiomyocyte contractility

Abstract Background Current therapy for Heart Failure (HF) includes neurohormonal antagonist and modulator drugs that improve remodelling, symptoms and clinical outcomes. However, these drugs do not target the underlying problem of reduced contractility. Improving cardiac contractility without harmful consequences is an unmet need in heart failure therapy. The human peptide hormone ghrelin increases cardiac output in HF patients and increases contractility in murine cardiomyocytes. Purpose We aim to study the cardiovascular effects of a novel oral small molecule ghrelin receptor agonist, AC01, in in vivo and ex vivo mouse models and in non-human primates. Methods HF mice (N=11) underwent pressure-volume loops analysis of cardiac functional and hemodynamic to assess the effects of intravenous AC01 (N=7) or placebo (N=4). Primary cardiomyocytes isolated from HF (N=3) and SHAM (N=5) mice, were treated with combinations of vehicle, AC01, ghrelin receptor antagonist (D-Lys-3-GHRP-6) and pertussis toxin (PTX, a Gαi signalling inhibitor). Live cell imaging was performed to assess cardiomyocyte fractional shortening and Ca2+ signalling, while biochemistry assays were employed to measure PKA activity, and phosphorylation of cardiac Troponin I (cTnI). Cynomolgus monkeys (N=6) were instrumented with devices to measure pulse contour, central aortic blood pressure and ECG devices. Cardiovascular effects of AC01 following single oral dosing were assessed through pulse contour hemodynamic modelling and analysis of autonomic system activation. Results In HF mice, AC01 significantly improved cardiac output (p< 0.01), stroke volume (p< 0.001), and ejection fraction (p< 0.001), and increased nominally the end-systolic pressure-volume curve relationship. In cardiomyocytes, AC01 dose-dependently improved fractional shortening (p< 0.01) without increasing Ca2+ transient amplitudes. AC01 reduced PKA activity (p< 0.05) and reduced phosphorylation of cTnI at Serine 23-24 (p< 0.01). These effects were blocked by pre-treatment with either D-Lys-3-GHRP-6 or PTX. In monkeys, oral AC01 sustainably increased cardiac output (p< 0.05) and stroke volume (p< 0.05) and reduced heart rate without altering central systolic blood pressure or causing tachycardia or arrhythmia. Conclusions AC01 improved CO, SV, and EF in HF mice by increasing contractility in a load-independent fashion. AC01 increased cardiomyocyte contractility without affecting Ca2+ transient amplitudes, through ghrelin receptor Gαi signalling, leading to reduced phosphorylation of cTnI. AC01 improved left ventricle systolic function in monkeys. AC01 is a first in class novel inotrope, which improves contractility in different species without harmful mobilization of Ca2+. AC01 should be explored for the treatment of patients with heart failure.graphical abstract