Safety and Efficacy of Istaroxime 1.0 and 1.5 µg/kg/min for Patients With Pre-Cardiogenic Shock

INTRODUCTION

Istaroxime was shown, in a small study, to increase systolic blood pressure (SBP) in patients with pre-cardiogenic shock (CS) due to acute heart failure (AHF).

OBJECTIVES

In the current analysis, we describe the effects of 2 doses of istaroxime 1.0 (Ista-1) and 1.5 µg/kg/min (Ista-1.5).

METHODS

The target dose of istaroxime, administered in a double-blind, placebo-controlled fashion, was 1.5 µg/kg/min in the first cohort (n = 24), and it was reduced to 1.0 µg/kg/min in subsequent patients (n = 36).

RESULTS

Ista-1 was associated with numerically larger effects on SBP area under the curve, with a 93.6% relative increase from baseline during the first 6 hours with Ista-1 vs 39.5% for Ista-1.5, and with a 49.4% and 24.3% relative increase, respectively, at 24 hours. Compared to placebo, Ista-1.5 had more worsening HF events until day 5 and fewer days alive out of hospital (DAOH) through day 30. Ista-1 had no worsening HF events, and DAOH to day 30 were significantly increased. Effects on echocardiographic measures were similar, although decreases in left ventricular end systolic and diastolic volumes were numerically larger in the Ista-1 group. Ista-1, but not Ista-1.5, showed numerically smaller creatinine increases and larger decreases in natriuretic peptides as compared to placebo. There were 5 serious adverse events in Ista-1.5 (4 of which were cardiac) but only 1 in Ista-1.

CONCLUSIONS

In patients with pre-CS due to AHF, istaroxime 1.0 µg/kg/min induced beneficial effects on SBP and DAOH. Clinical benefits appear to be reached at dosages less than 1.5 ug/kg/min.

Safety and Efficacy of Istaroxime in Patients With Acute Heart Failure: A Meta-Analysis of Randomized Controlled Trials

The aim of this study was to assess the efficacy and safety of istaroxime in patients with heart failure. Following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines, a search was conducted on the EMBASE and Medline databases to identify articles related to the safety and efficacy of istaroxime in patients with heart failure. The search covered the period from inception to May 31st, 2023, without any restrictions on the year of publication. The search strategy utilized relevant terms such as "istaroxime," "heart failure", "efficacy," and other related terms, along with their corresponding Medical Subject Headings (MeSH) terms. The outcomes assessed in this meta-analysis included the change in left ventricular ejection fraction (LVEF), E to A ratio (a marker of left ventricle function), cardiac index in L/min/m2, systolic blood pressure (SBP) in mmHg, left ventricular end-systolic volume (LVESV) in ml, and left ventricular end-diastolic volume (LVDSV) in ml. For safety analysis, gastrointestinal events and cardiovascular events were assessed. A total of three randomized controlled trials (RCTs) were included in this meta-analysis encompassing 211 patients with heart failure. Pooled analysis showed that istaroxime was effective in increasing LVEF (MD: 1.26, 95% CI: 0.91 to 1.62, p-value: 0.001), reducing E to A ratio (MD: -0.39, 95% CI: -0.60 to -0.19, p-value: 0.001), increasing cardiac index (MD: 0.22, 95% CI: 0.18 to 0.25, p-value: 0.001), reducing LVESV (MD: -11.84, 95% CI: -13.91 to -9.78, p-value: 0.001), reducing LVEDV (MD: -12.25, 95% CI: -14.63 to -9.87, p-value: 0.001) and increasing SBP (MD: 8.41, 95% CI: 5.23 to 11.60, p-value: 0.001) compared to the placebo group. However, risk of gastrointestinal events was significantly higher in patients receiving istaroxime compared to the placebo group (RR: 2.64, 95% CI: 1.53 to 4.57, p-value: 0.0005). These findings support the enhancement of heart function with istaroxime administration, aligning with previous clinical and experimental evidence.

Efficacy of the New Inotropic Agent Istaroxime in Acute Heart Failure

Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.

Cellular Mechanisms Underlying the Low Cardiotoxicity of Istaroxime

Background

Istaroxime is an inhibitor of Na⁺/K⁺ ATPase with proven efficacy to increase cardiac contractility and to accelerate relaxation attributable to a relief in phospholamban‐dependent inhibition of the sarcoplasmic reticulum Ca²⁺ ATPase. We have previously shown that pharmacologic Na⁺/K⁺ ATPase inhibition promotes calcium/calmodulin‐dependent kinase II activation, which mediates both cardiomyocyte death and arrhythmias. Here, we aim to compare the cardiotoxic effects promoted by classic pharmacologic Na⁺/K⁺ ATPase inhibition versus istaroxime.

Methods and Results

Ventricular cardiomyocytes were treated with ouabain or istaroxime at previously tested equi‐inotropic concentrations to compare their impact on cell viability, apoptosis, and calcium/calmodulin‐dependent kinase II activation. In contrast to ouabain, istaroxime neither promoted calcium/calmodulin‐dependent kinase II activation nor cardiomyocyte death. In addition, we explored the differential behavior promoted by ouabain and istaroxime on spontaneous diastolic Ca²⁺ release. In rat cardiomyocytes, istaroxime did not significantly increase Ca²⁺ spark and wave frequency but increased the proportion of aborted Ca²⁺ waves. Further insight was provided by studying cardiomyocytes from mice that do not express phospholamban. In this model, the lower Ca²⁺ wave incidence observed with istaroxime remains present, suggesting that istaroxime‐dependent relief on phospholamban‐dependent sarcoplasmic reticulum Ca²⁺ ATPase 2A inhibition is not the unique mechanism underlying the low arrhythmogenic profile of this drug.

Conclusions

Our results indicate that, different from ouabain, istaroxime can reach a significant inotropic effect without leading to calcium/calmodulin‐dependent kinase II–dependent cardiomyocyte death. Additionally, we provide novel insights regarding the low arrhythmogenic impact of istaroxime on cardiac Ca²⁺ handling.

Functional characterization and anti-cancer action of the clinical phase II cardiac Na+/K+ ATPase inhibitor istaroxime: in vitro and in vivo properties and cross talk with the membrane androgen receptor

Sodium potassium pump (Na⁺/K⁺ ATPase) is a validated pharmacological target for the treatment of various cardiac conditions. Recent published data with Na⁺/K⁺ ATPase inhibitors suggest a potent anti-cancer action of these agents in multiple indications. In the present study, we focus on istaroxime, a Na⁺/K⁺ ATPase inhibitor that has shown favorable safety and efficacy properties in cardiac phase II clinical trials. Our experiments in 22 cancer cell lines and in prostate tumors in vivo proved the strong anti-cancer action of this compound. Istaroxime induced apoptosis, affected the key proliferative and apoptotic mediators c-Myc and caspase-3 and modified actin cystoskeleton dynamics and RhoA activity in prostate cancer cells. Interestingly, istaroxime was capable of binding to mAR, a membrane receptor mediating rapid, non-genomic actions of steroids in prostate and other cells. These results support a multi-level action of Na⁺/K⁺ ATPase inhibitors in cancer cells and collectively validate istaroxime as a strong re-purposing candidate for further cancer drug development.

Istaroxime, a potential anticancer drug in prostate cancer, exerts beneficial functional effects in healthy and diseased human myocardium

The current gold standard for prostate cancer treatment is androgen deprivation therapy and antiandrogenic agents. However, adverse cardiovascular events including heart failure can limit therapeutic use. Istaroxime, which combines Na⁺-K⁺-ATPase (NKA) inhibition with sarco/endoplasmic reticulum Ca²⁺-ATPase 2a (SERCA2a) stimulation, has recently shown promising anti-neoplastic effects in prostate cancer (PC) models and may also improve cardiac function. Considering the promising anticancer effects of istaroxime, we aimed to assess its functional effects on human myocardium.

SERCA2a stimulation by istaroxime: a novel mechanism of action with translational implications

Sarcoplasmic reticular (SR) Ca(2+) -ATPase (SERCA2a) is central to cardiac electrophysiological and mechanical function. It ensures full diastolic relaxation minimizing delayed after-potentials that would otherwise compromise membrane electrophysiological stability, and optimizes SR Ca(2+) refilling and systolic contraction. Previous studies demonstrated that the small molecule agent istaroxime stimulates SERCA2a-ATPase activity, restoring its function in failing hearts, and enhancing indices of mechanical, and SR Ca(2+) release and re-uptake, activity. Ferrandi et al (2013) now elegantly demonstrate its ability to dissociate the phospholamdan (PB) bound to cardiac SERCA2a, thereby removing the inhibitory effect of PB on SERCA2a. This effect was independent of the cAMP/PKA system and modified a specific SERCA2a reaction step. They used SERCA-enriched SR preparations from a rigorously validated and realistic physiological, canine model of cardiac failure with established Na(+) -K(+) -ATPase sensitivity to cardiac glycosides and SR Ca(2+) handling features. These findings potentially translate into a novel management of the major and increasingly important public health challenge of chronic cardiac failure.

LINKED ARTICLE

This article is a commentary on Ferrandi et al., pp. 1849-1861 of volume 169 issue 8. To view this paper visit http://dx.doi.org/10.1111/bph.12278.

Istaroxime stimulates SERCA2a and accelerates calcium cycling in heart failure by relieving phospholamban inhibition

BACKGROUND AND PURPOSE

Calcium handling is known to be deranged in heart failure. Interventions aimed at improving cell Ca(2) (+) cycling may represent a promising approach to heart failure therapy. Istaroxime is a new luso-inotropic compound that stimulates cardiac contractility and relaxation in healthy and failing animal models and in patients with acute heart failure (AHF) syndrome. Istaroxime is a Na-K ATPase inhibitor with the unique property of increasing sarcoplasmic reticulum (SR) SERCA2a activity as shown in heart microsomes from humans and guinea pigs. The present study addressed the molecular mechanism by which istaroxime increases SERCA2a activity.

EXPERIMENTAL APPROACH

To study the effect of istaroxime on SERCA2a-phospholamban (PLB) complex, we applied different methodologies in native dog healthy and failing heart preparations and heterologous canine SERCA2a/PLB co-expressed in Spodoptera frugiperda (Sf21) insect cells.

KEY RESULTS

We showed that istaroxime enhances SERCA2a activity, Ca(2) (+) uptake and the Ca(2) (+) -dependent charge movements into dog healthy and failing cardiac SR vesicles. Although not directly demonstrated, the most probable explanation of these activities is the displacement of PLB from SERCA2a.E2 conformation, independently from cAMP/PKA. We propose that this displacement may favour the SERCA2a conformational transition from E2 to E1, thus resulting in the acceleration of Ca(2) (+) cycling.

CONCLUSIONS AND IMPLICATIONS

Istaroxime represents the first example of a small molecule that exerts a luso-inotropic effect in the failing human heart through the stimulation of SERCA2a ATPase activity and the enhancement of Ca(2) (+) uptake into the SR by relieving the PLB inhibitory effect on SERCA2a in a cAMP/PKA independent way.

Agents with inotropic properties for the management of acute heart failure syndromes. Traditional agents and beyond

Treatment with inotropic agents is one of the most controversial topics in heart failure. Initial enthusiasm, based on strong pathophysiological rationale and apparent empirical efficacy, has been progressively limited by results of controlled trials and registries showing poorer outcomes of the patients on inotropic therapy. The use of these agents remains, however, potentially indicated in a significant proportion of patients with low cardiac output, peripheral hypoperfusion and end-organ dysfunction caused by heart failure. Limitations of inotropic therapy seem to be mainly related to their mechanisms of action entailing arrhythmogenesis, peripheral vasodilation, myocardial ischemia and damage, and possibly due to their use in patients without a clear indication, rather than to the general principle of inotropic therapy itself. This review will discuss the characteristics of the patients with a potential indication for inotropic therapy, the main data from registries and controlled trials, the mechanism of the untoward effects of these agents on outcomes and, lastly, perspectives with new agents with novel mechanisms of action.