Danicamtiv affected isometric force and cross-bridge kinetics similarly in skinned myocardial strips from male and female rats.

Myotropes are pharmaceuticals that have recently been developed or are under investigation for the treatment of heart diseases. Myotropes have had varied success in clinical trials. Initial research into myotropes have widely focused on animal models of cardiac dysfunction in comparison with normal animal cardiac physiology-primarily using males. In this study we examined the effect of danicamtiv, which is one type of myotrope within the class of myosin activators, on contractile function in permeabilized (skinned) myocardial strips from male and female Sprague-Dawley rats. We found that danicamtiv increased steady-state isometric force production at sub-maximal calcium levels, leading to greater Ca2+-sensitivity of contraction for both sexes. Danicamtiv did not affect maximal Ca2+-activated force for either sex. Sinusoidal length-perturbation analysis was used to assess viscoelastic myocardial stiffness and cross-bridge cycling kinetics. Data from these measurements did not vary with sex, and the data suggest that danicamtiv slows cross-bridge cycling kinetics. These findings imply that danicamtiv increases force production via increasing cross-bridge contributions to activation of contraction, especially at sub-maximal Ca2+-activation. The inclusion of both sexes in animal models during the formative stages of drug development could be helpful for understanding the efficacy or limitation of a drug's therapeutic impact on cardiac function.

The Effect of Omecamtiv Mecarbil in Hospitalized Patients as Compared With Outpatients With HFrEF: An Analysis of GALACTIC-HF.

BACKGROUND: In the Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF) trial, omecamtiv mecarbil, compared with placebo, reduced the risk of worsening heart failure (HF) events, or cardiovascular death in patients with HF and reduced ejection fraction. The primary aim of this prespecified analysis was to evaluate the safety and efficacy of omecamtiv mecarbil by randomization setting, that is, whether participants were enrolled as outpatients or inpatients. METHODS AND RESULTS: Patients were randomized either during a HF hospitalization or as an outpatient, within one year of a worsening HF event (hospitalization or emergency department visit). The primary outcome was a composite of worsening HF event (HF hospitalization or an urgent emergency department or clinic visit) or cardiovascular death. Of the 8232 patients analyzed, 2084 (25%) were hospitalized at randomization. Hospitalized patients had higher N-terminal prohormone of B-type natriuretic peptide concentrations, lower systolic blood pressure, reported more symptoms, and were less frequently treated with a renin-angiotensin system blocker or a beta-blocker than outpatients. The rate (per 100 person-years) of the primary outcome was higher in hospitalized patients (placebo group = 38.3/100 person-years) than in outpatients (23.1/100 person-years); adjusted hazard ratio 1.21 (95% confidence interval 1.12-1.31). The effect of omecamtiv mecarbil versus placebo on the primary outcome was similar in hospitalized patients (hazard ratio 0.89, 95% confidence interval 0.78-1.01) and outpatients (hazard ratio 0.94, 95% confidence interval 0.86-1.02) (interaction P = .51). CONCLUSIONS: Hospitalized patients with HF with reduced ejection fraction had a higher rate of the primary outcome than outpatients. Omecamtiv mecarbil decreased the risk of the primary outcome both when initiated in hospitalized patients and in outpatients.

Cardiomyocyte external mechanical unloading activates modifications of α-actinin differently from sarcomere-originated unloading.

Loss of myocardial mass in a neonatal rat cardiomyocyte culture is studied to determine whether there is a distinguishable cellular response based on the origin of mechano-signals. The approach herein compares the sarcomeric assembly and disassembly processes in heart cells by imposing mechano-signals at the interface with the extracellular matrix (extrinsic) and at the level of the myofilaments (intrinsic). Experiments compared the effects of imposed internal (inside/out) and external (outside/in) loading and unloading on modifications in neonatal rat cardiomyocytes. Unloading of the cellular substrate by myosin inhibition (1 µm mavacamten), or cessation of cyclic strain (1 Hz, 10% strain) after preconditioning, led to significant disassembly of sarcomeric α-actinin by 6 h. In myosin inhibition, this was accompanied by redistribution of intracellular poly-ubiquitin K48 to the cellular periphery relative to the poly-ubiquitin K48 reservoir at the I-band. Moreover, loading and unloading of the cellular substrate led to a three-fold increase in post-translational modifications (PTMs) when compared to the myosin-specific activation or inhibition. Specifically, phosphorylation increased with loading while ubiquitination increased with unloading, which may involve extracellular signal-regulated kinase 1/2 and focal adhesion kinase activation. The identified PTMs, including ubiquitination, acetylation, and phosphorylation, are proposed to modify internal domains in α-actinin to increase its propensity to bind F-actin. These results demonstrate a link between mechanical feedback and sarcomere protein homeostasis via PTMs of α-actinin that exemplify how cardiomyocytes exhibit differential responses to the origin of force. The implications of sarcomere regulation governed by PTMs of α-actinin are discussed with respect to cardiac atrophy and heart failure.

Acyl ghrelin improves cardiac function in heart failure and increases fractional shortening in cardiomyocytes without calcium mobilization.

BACKGROUND AND AIMS: Ghrelin is an endogenous appetite-stimulating peptide hormone with potential cardiovascular benefits. Effects of acylated (activated) ghrelin were assessed in patients with heart failure and reduced ejection fraction (HFrEF) and in ex vivo mouse cardiomyocytes. METHODS AND RESULTS: In a randomized placebo-controlled double-blind trial, 31 patients with chronic HFrEF were randomized to synthetic human acyl ghrelin (0.1 µg/kg/min) or placebo intravenously over 120 min. The primary outcome was change in cardiac output (CO). Isolated mouse cardiomyocytes were treated with acyl ghrelin and fractional shortening and calcium transients were assessed. Acyl ghrelin but not placebo increased cardiac output (acyl ghrelin: 4.08 ± 1.15 to 5.23 ± 1.98 L/min; placebo: 4.26 ± 1.23 to 4.11 ± 1.99 L/min, P < 0.001). Acyl ghrelin caused a significant increase in stroke volume and nominal increases in left ventricular ejection fraction and segmental longitudinal strain and tricuspid annular plane systolic excursion. There were no effects on blood pressure, arrhythmias, or ischaemia. Heart rate decreased nominally (acyl ghrelin: 71 ± 11 to 67 ± 11 b.p.m.; placebo 69 ± 8 to 68 ± 10 b.p.m.). In cardiomyocytes, acyl ghrelin increased fractional shortening, did not affect cellular Ca2+ transients, and reduced troponin I phosphorylation. The increase in fractional shortening and reduction in troponin I phosphorylation was blocked by the acyl ghrelin antagonist D-Lys 3. CONCLUSION: In patients with HFrEF, acyl ghrelin increased cardiac output without causing hypotension, tachycardia, arrhythmia, or ischaemia. In isolated cardiomyocytes, acyl ghrelin increased contractility independently of preload and afterload and without Ca2+ mobilization, which may explain the lack of clinical side effects. Ghrelin treatment should be explored in additional randomized trials. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT05277415.

Effects of omecamtiv mecarbil in heart failure with reduced ejection fraction according to blood pressure: the GALACTIC-HF trial.

AIM: Patients with heart failure with reduced ejection fraction and low systolic blood pressure (SBP) have high mortality, hospitalizations, and poorly tolerate evidence-based medical treatment. Omecamtiv mecarbil may be particularly helpful in such patients. This study examined its efficacy and tolerability in patients with SBP ≤100 mmHg enrolled in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF). METHODS AND RESULTS: The GALACTIC-HF enrolled patients with baseline SBP ≥85 mmHg with a primary outcome of time to cardiovascular death or first heart failure event. In this analysis, patients were divided according to their baseline SBP (≤100 vs. >100 mmHg). Among the 8232 analysed patients, 1473 (17.9%) had baseline SBP ≤100 mmHg and 6759 (82.1%) had SBP >100 mmHg. The primary outcome occurred in 715 (48.5%) and 2415 (35.7%) patients with SBP ≤100 and >100 mmHg, respectively. Patients with lower SBP were at higher risk of adverse outcomes. Omecamtiv mecarbil, compared with placebo, appeared to be more effective in reducing the primary composite endpoint in patients with SBP ≤100 mmHg [hazard ratio (HR), 0.81; 95% confidence interval (CI), 0.70-0.94] compared with those with SBP >100 mmHg (HR, 0.95; 95% CI, 0.88-1.03; P-value for interaction = 0.051). In both groups, omecamtiv mecarbil did not change SBP values over time and did not increase the risk of adverse events, when compared with placebo. CONCLUSION: In GALACTIC-HF, risk reduction of heart failure outcomes with omecamtiv mecarbil compared with placebo was large and significant in patients with low SBP. Omecamtiv mecarbil did not affect SBP and was well tolerated independent of SBP values.

Inotropic therapies in heart failure and cardiogenic shock: an educational review.

Reduced systolic function is central to the pathophysiology and clinical sequelae of acute decompensated heart failure (ADHF) with reduced ejection fraction and cardiogenic shock. These clinical entities are the final common pathway for marked deterioration of right or left ventricular function and can occur in multiple clinical presentations including severe ADHF, myocardial infarction, post-cardiac surgery, severe pulmonary hypertension, and advanced or end-stage chronic heart failure. Inotropic therapies improve ventricular systolic function and may be divided into three classes on the basis of their mechanism of action (calcitropes, mitotropes, and myotropes). Most currently available therapies for cardiogenic shock are calcitropes which can provide critical haemodynamic support, but also may increase myocardial oxygen demand, ischaemia, arrhythmia, and mortality. Emerging therapies to improve cardiac function such as mitotropes (e.g. perhexiline, SGLT2i) or myotropes (e.g. omecamtiv mecarbil) may provide useful alternatives in the future.

Effect of Ejection Fraction on Clinical Outcomes in Patients Treated With Omecamtiv Mecarbil in GALACTIC-HF.

BACKGROUND: In GALACTIC-HF (Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure) (n = 8,256), the cardiac myosin activator, omecamtiv mecarbil, significantly reduced the primary composite endpoint (PCE) of time-to-first heart failure event or cardiovascular death in patients with heart failure and reduced ejection fraction (EF) (≤35%). OBJECTIVES: The purpose of this study was to evaluate the influence of baseline EF on the therapeutic effect of omecamtiv mecarbil. METHODS: Outcomes in patients treated with omecamtiv mecarbil were compared with placebo according to EF. RESULTS: The risk of the PCE in the placebo group was nearly 1.8-fold greater in the lowest EF (≤22%) compared with the highest EF (≥33%) quartile. Amongst the pre-specified subgroups, EF was the strongest modifier of the treatment effect of omecamtiv mecarbil on the PCE (interaction as continuous variable, p = 0.004). Patients receiving omecamtiv mecarbil had a progressively greater relative and absolute treatment effect as baseline EF decreased, with a 17% relative risk reduction for the PCE in patients with baseline EF ≤22% (n = 2,246; hazard ratio: 0.83; 95% confidence interval: 0.73 to 0.95) compared with patients with EF ≥33% (n = 1,750; hazard ratio: 0.99; 95% confidence interval: 0.84 to 1.16; interaction as EF by quartiles, p = 0.013). The absolute reduction in the PCE increased with decreasing EF (EF ≤22%; absolute risk reduction, 7.4 events per 100 patient-years; number needed to treat for 3 years = 11.8), compared with no reduction in the highest EF quartile. CONCLUSIONS: In heart failure patients with reduced EF, omecamtiv mecarbil produced greater therapeutic benefit as baseline EF decreased. These findings are consistent with the drug's mechanism of selectively improving systolic function and presents an important opportunity to improve the outcomes in a group of patients at greatest risk. (Registrational Study With Omecamtiv Mecarbil/AMG 423 to Treat Chronic Heart Failure With Reduced Ejection Fraction [GALACTIC-HF]; NCT02929329).

Omecamtiv mecarbil in chronic heart failure with reduced ejection fraction: GALACTIC-HF baseline characteristics and comparison with contemporary clinical trials.

AIMS: The safety and efficacy of the novel selective cardiac myosin activator, omecamtiv mecarbil, in patients with heart failure with reduced ejection fraction (HFrEF) is being tested in the Global Approach to Lowering Adverse Cardiac outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF) trial. Here we describe the baseline characteristics of participants in GALACTIC-HF and how these compare with other contemporary trials. METHODS AND RESULTS: Adults with established HFrEF, New York Heart Association (NYHA) functional class ≥II, ejection fraction ≤35%, elevated natriuretic peptides and either current hospitalization for heart failure or history of hospitalization/emergency department visit for heart failure within a year were randomized to either placebo or omecamtiv mecarbil (pharmacokinetic-guided dosing: 25, 37.5, or 50 mg bid). A total of 8256 patients [male (79%), non-white (22%), mean age 65 years] were enrolled with a mean ejection fraction 27%, ischaemic aetiology in 54%, NYHA class II 53% and III/IV 47%, and median N-terminal pro-B-type natriuretic peptide 1971 pg/mL. Heart failure therapies at baseline were among the most effectively employed in contemporary heart failure trials. GALACTIC-HF randomized patients representative of recent heart failure registries and trials with substantial numbers of patients also having characteristics understudied in previous trials including more from North America (n = 1386), enrolled as inpatients (n = 2084), systolic blood pressure <100 mmHg (n = 1127), estimated glomerular filtration rate <30 mL/min/1.73 m2 (n = 528), and treated with sacubitril/valsartan at baseline (n = 1594). CONCLUSIONS: GALACTIC-HF enrolled a well-treated, high-risk population from both inpatient and outpatient settings, which will provide a definitive evaluation of the efficacy and safety of this novel therapy, as well as informing its potential future implementation.

Effects of danicamtiv, a novel cardiac myosin activator, in heart failure with reduced ejection fraction: experimental data and clinical results from a phase 2a trial.

AIMS: Both left ventricular (LV) and left atrial (LA) dysfunction and remodelling contribute to adverse outcomes in heart failure with reduced ejection fraction (HFrEF). Danicamtiv is a novel, cardiac myosin activator that enhances cardiomyocyte contraction. METHODS AND RESULTS: We studied the effects of danicamtiv on LV and LA function in non-clinical studies (ex vivo: skinned muscle fibres and myofibrils; in vivo: dogs with heart failure) and in a randomized, double-blind, single- and multiple-dose phase 2a trial in patients with stable HFrEF (placebo, n = 10; danicamtiv, n = 30; 50-100 mg twice daily for 7 days). Danicamtiv increased ATPase activity and calcium sensitivity in LV and LA myofibrils/muscle fibres. In dogs with heart failure, danicamtiv improved LV stroke volume (+10.6 mL, P < 0.05) and LA emptying fraction (+10.7%, P < 0.05). In patients with HFrEF (mean age 60 years, 25% women, ischaemic heart disease 48%, mean LV ejection fraction 32%), treatment-emergent adverse events, mostly mild, were reported in 17 patients (57%) receiving danicamtiv and 4 patients (40%) receiving placebo. Danicamtiv (at plasma concentrations ≥2000 ng/mL) increased stroke volume (up to +7.8 mL, P < 0.01), improved global longitudinal (up to -1.0%, P < 0.05) and circumferential strain (up to -3.3%, P < 0.01), decreased LA minimal volume index (up to -2.4 mL/m2 , P < 0.01) and increased LA function index (up to 6.1, P < 0.01), when compared with placebo. CONCLUSIONS: Danicamtiv was well tolerated and improved LV systolic function in patients with HFrEF. A marked improvement in LA volume and function was also observed in patients with HFrEF, consistent with pre-clinical findings of direct activation of LA contractility.