Rationale and design of the enoximone clinical trials program

Advanced heart failure: guideline-directed medical therapy, diuretics, inotropes, and palliative care

Heart failure (HF) is a major cause of mortality, hospitalizations, and reduced quality of life and a major burden for the healthcare system. The number of patients that progress to an advanced stage of HF is growing. Only a limited proportion of these patients can undergo heart transplantation or mechanical circulatory support. The purpose of this review is to summarize medical management of patients with advanced HF. First, evidence-based oral treatment must be implemented although it is often not tolerated. New therapeutic options may soon become possible for these patients. The second goal is to lessen the symptomatic burden through both decongestion and haemodynamic improvement. Some new treatments acting on cardiac function may fulfil both these needs. Inotropic agents acting through an increase in intracellular calcium have often increased risk of death. However, in the recent Global Approach to Lowering Adverse Cardiac Outcomes Through Improving Contractility in Heart Failure (GALACTIC-HF) trial, omecamtiv mecarbil was safe and effective in the reduction of the primary outcome of cardiovascular death or HF event compared with placebo (hazard ratio, 0.92; 95% confidence interval, 0.86-0.99; P = 0.03) and its effects were larger in those patients with more severe left ventricular dysfunction. Patients with severe HF who received omecamtiv mecarbil experienced a significant treatment benefit, whereas patients without severe HF did not (P = 0.005 for interaction). Lastly, clinicians should take care of the end of life with an appropriate multidisciplinary approach. Medical treatment of advanced HF therefore remains a major challenge and a wide open area for further research.

Why has positive inotropy failed in chronic heart failure? Lessons from prior inotrope trials

Current pharmacological therapies for heart failure with reduced ejection fraction are largely either repurposed anti‐hypertensives that blunt overactivation of the neurohormonal system or diuretics that decrease congestion. However, they do not address the symptoms of heart failure that result from reductions in cardiac output and reserve. Over the last few decades, numerous attempts have been made to develop and test positive cardiac inotropes that improve cardiac haemodynamics. However, definitive clinical trials have failed to show a survival benefit. As a result, no positive inotrope is currently approved for long‐term use in heart failure. The focus of this state‐of‐the‐art review is to revisit prior clinical trials and to understand the causes for their findings. Using the learnings from those experiences, we propose a framework for future trials of such agents that maximizes their potential for success. This includes enriching the trials with patients who are most likely to derive benefit, using biomarkers and imaging in trial design and execution, evaluating efficacy based on a wider range of intermediate phenotypes, and collecting detailed data on functional status and quality of life. With a rapidly growing population of patients with advanced heart failure, the epidemiologic insignificance of heart transplantation as a therapeutic intervention, and both the cost and morbidity associated with ventricular assist devices, there is an enormous potential for positive inotropic therapies to impact the outcomes that matter most to patients.

Preliminary results of the Multicenter Observational Study with Enoximone in Cardiac surgery (MOSEC)

BACKGROUND

Perioperative administration of Enoximone has been shown to improve hemodynamics, organ function, and inflammatory response. Aim of the present study was to evaluate the effects of Enoximone after on-pump cardiac surgery.

METHODS

A protocol for a multicenter observational study was reviewed and approved by local ethic committee. This preliminary report involves the first 29 patients enrolled, in whom Enoximone was perioperatively administered in the context of on-pump cardiac surgery. All patients enrolled were propensity-matched 1:1 with controls not receiving Enoximone, renal function was evaluated in terms of estimated glomerular filtration rate (eGFR) with the CKD-EPI equation.

RESULTS

After propensity matching, the two cohorts of patients receiving Enoximone or not did not show any significant differences among baseline characteristics. Patients receiving Enoximone showed a progressive improvement of eGFR at each time-point of follow-up: roughly +4.3, +10.0, and +12.3 mL/min/1.73 m² on postoperative days 2, 7, and 30; respectively. Consistently, maximum difference versus baseline was +12.6 mL/min/1.73 m² (or +19.3%) among Enoximone patients vs +3.3 mL/min/1.73 m² (or +4.4%) among controls (p = 0.02). Multivariable regression analysis (R²-adjusted 0.47) showed only age (β -0.53; p = 0.01), preoperative eGFR (β -0.39; p = 0.02), diabetes (β 2.1; p = 0.01), cardio-pulmonary bypass duration (β 0.08; p = 0.05), and Enoximone administration (β -0.74; p = 0.05) to be independently correlated with delta eGFR variation on day 30.

CONCLUSION

These preliminary results show that perioperative Enoximone administration improved renal function in patients undergoing on-pump cardiac surgery. Further studies are needed to confirm these findings.

Perioperative administration of enoximone and renal function after cardiac surgery: a propensity-matched analysis

BACKGROUND

Perioperative administration of enoximone has been shown to improve hemodynamics, organ function, and inflammatory response. Aim of the present study is to evaluate the impact of enoximone on postoperative renal function after on-pump cardiac surgery.

METHODS

A total of 3727 patients undergoing cardiac surgery at one Institution between May 2004 and November 2010 were reviewed. A propensity score was built and a 1:1 perfect matching was performed, providing two fairly comparable cohorts of 712 patients each, receiving or not enoximone after surgery. Renal function was evaluated by lower glomerular filtration rate (GFR) value reached postoperatively.

RESULTS

Overall 30-day mortality rate was 4.3% (62/1424). Cumulative incidence of postoperative renal failure (RF) was 157/1424(11%), of which 99/1424(7%) needed renal replacement therapy. Mean lower postoperative GFR in patients who received or not enoximone was 63 ± 30.1 and 53.5 ± 26.1 ml/min/1.73 m(2) (p<0.0001), respectively. At multivariable analysis age (OR2.75, p=0.0004), diabetes (OR1.82, p=0.006), preoperative GFR (OR3.81, p<0.0001), preoperative cardiogenic shock (OR1.65, p=0.004), previous cardiac surgery (OR2.12, p=0.0002), type of intervention (OR1.96, p=0.005), and enoximone (OR0.38, p=0.001) were found to be independently associated with postoperative RF. Logistic regression analysis showed that the administration of enoximone (OR0.41, p=0.0001), and of no inotropes (OR0.27, p<0.0001) were protective vs. the occurrence of postoperative RF.

CONCLUSION

Patients perioperatively receiving enoximone showed a statistically significant better renal function after cardiac surgery.

Treatment of chronic heart failure with β-adrenergic receptor antagonists: a convergence of receptor pharmacology and clinical cardiology

Despite the absence of a systematic development plan, β-blockers have reached the top tier of medical therapies for chronic heart failure. The successful outcome was due to the many dedicated investigators who produced, over a 30-year period, increasing evidence that β-blocking agents should or actually did improve the natural history of dilated cardiomyopathies and heart failure. It took 20 years for supportive evidence to become undeniable, at which time in 1993 the formidable drug development resources of large pharmaceutical companies were deployed into Phase 3 trials. Success then came relatively quickly, and within 8 years multiple agents were on the market in the United States and Europe. Importantly, there is ample room to improve antiadrenergic therapy, through novel approaches exploiting the nuances of receptor biology and/or intracellular signaling, as well as through pharmacogenetic targeting.

Chronic heart failure: current evidence, challenges to therapy, and future directions

Heart failure (HF) is a complex syndrome characterized by the inability of the heart to maintain a normal cardiac output without elevated intracardiac filling pressures, resulting in signs of pulmonary and peripheral edema and symptoms of dyspnea and fatigue. Central to the management of HF is a multifaceted pharmacological intervention to abate the harmful counter-regulatory effects of neurohormonal activation and avid salt and water retention. Whereas up to 40 years ago HF was managed with diuretics and leaf of digitalis, the cornerstones of therapy for HF patients with systolic dysfunction now include ACE inhibitors or angiotensin II type 1 receptor antagonists (angiotensin receptor blockers), β-adrenoceptor antagonists (β-blockers), and aldosterone antagonists, which have significantly improved survival. However, with the increasing number of beneficial therapies, there are challenges to implementing all of them. Specific cardiomyopathies also merit specific considerations with respect to treatment, and - unfortunately - there is no therapy for HF with preserved left ventricular ejection fraction that has been shown to improve survival. Although mortality has improved in HF, the biggest challenge to treatment lies in addressing the morbidity of this disease, which is now the most common reason for hospital admission in our aged population. As such, there are many therapies that may serve to improve the quality of life of HF patients. Future HF treatment regimens may include direct cellular therapy via hormone and cytokine signaling or cardiac regeneration through growth factors or cell therapy.

Medical therapy for chronic heart failure

Understanding of contemporary pharmacological therapy for chronic heart failure continues to evolve. In this Review, we discuss how findings from clinical trials have caused the roles of old therapies to be expanded and past treatment algorithms to be challenged. Several trials investigating preserved ejection fraction as a measure of heart failure had disappointing results, although important studies are in progress. Many novel therapeutic approaches for heart failure have emerged and are discussed in this review. The pharmacological treatments for heart failure continue to change, with many exciting possibilities for the future.

Effects of low-dose oral enoximone administration on mortality, morbidity, and exercise capacity in patients with advanced heart failure: the randomized, double-blind, placebo-controlled, parallel group ESSENTIAL trials

Aims

Use of inotropic agents in patients with heart failure (HF) has been limited by adverse effects on outcomes. However, administration of positive inotropes at lower doses and concomitant treatment with beta-blockers might increase benefit–risk ratio. We investigated the effects of low doses of the positive inotrope enoximone on symptoms, exercise capacity, and major clinical outcomes in patients with advanced HF who were also treated with beta-blockers and other guideline-recommended background therapy.

Methods and results

The Studies of Oral Enoximone Therapy in Advanced HF (ESSENTIAL) programme consisted of two identical, randomized, double-blind, placebo-controlled trials that differed only by geographic location (North and South America: ESSENTIAL-I; Europe: ESSENTIAL-II). Patients with New York Heart Association class III–IV HF symptoms, left ventricular ejection fraction ≤30%, and one hospitalization or two ambulatory visits for worsening HF in the previous year were eligible for participation in the trials. The trials had three co-primary endpoints: (i) the composite of time to all-cause mortality or cardiovascular hospitalization, analysed in the two ESSENTIAL trials combined; (ii) the 6 month change from baseline in the 6 min walk test distance (6MWTD); and (iii) the Patient Global Assessment (PGA) at 6 months, both analysed in each trial separately. ESSENTIAL-I and -II randomized 1854 subjects at 211 sites in 16 countries. In the combined trials, all-cause mortality and the composite, first co-primary endpoint did not differ between the two treatment groups [hazard ratio (HR) 0.97; 95% confidence interval (CI) 0.80–1.17; and HR 0.98; 95% CI 0.86–1.12, respectively, for enoximone vs. placebo]. The two other co-primary endpoints were analysed separately in the two ESSENTIAL trials, as prospectively designed in the protocol. The 6MWTD increased with enoximone, compared with placebo, in ESSENTIAL-I (P = 0.025, not reaching, however, the pre-specified criterion for statistical significance of P < 0.020), but not in ESSENTIAL-II. No difference in PGA was observed in either trial.

Conclusion

Although low-dose enoximone appears to be safe in patients with advanced HF, major clinical outcomes are not improved.

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.

Combination therapy with beta-adrenergic receptor antagonists and phosphodiesterase inhibitors for chronic heart failure

Abstract Rational use of phosphodiesterase inhibitors represents an ongoing controversy in contemporary pharmacotherapy for heart failure. In randomized clinical trials, phosphodiesterase inhibitors increased cardiac output at the expense of worsening the rates of sudden cardiac death and cardiovascular mortality. Preliminary findings from ongoing clinical and preclinical investigations of phosphodiesterase activity suggest that combined use of phosphodiesterase inhibitors with beta-adrenergic antagonists may prevent these adverse outcomes. Compartmentation of cyclic adenosine 3',5'-monophosphate signaling may prove critical in determining myocardial response to combination therapy.

Phosphodiesterase inhibition in heart failure

Drugs that inhibit cyclic nucleotide phosphodiesterase activity act to increase intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) content. In total, 11 families of these enzymes-which differ with respect to affinity for cAMP and cGMP, cellular expression, intracellular localization, and mechanisms of regulation-have been identified. Inhibitors of enzymes in the PDE3 family of cyclic nucleotide phosphodiesterases raise intracellular cAMP content in cardiac and vascular smooth muscle, with inotropic and, to a lesser extent, vasodilatory actions. These drugs have been used for many years in the treatment of patients with heart failure, but their long-term use has generally been shown to increase mortality through mechanisms that remain unclear. More recently, inhibitors of PDE5 cyclic nucleotide phosphodiesterases have been used as cGMP-raising agents in vascular smooth muscle. With respect to cardiovascular disease, there is evidence that these drugs are more efficacious in the pulmonary than in the systemic vasculature, for which reason they are used principally in patients with pulmonary hypertension. Effects attributable to inhibition of myocardial PDE5 activity are less well characterized. New information indicating that enzymes from the PDE1 family of cyclic nucleotide phosphodiesterases constitute the majority of cAMP- and cGMP-hydrolytic activity in human myocardium raises questions as to their role in regulating these signaling pathways in heart failure.

Low-dose oral enoximone enhances the ability to wean patients with ultra-advanced heart failure from intravenous inotropic support: results of the oral enoximone in intravenous inotrope-dependent subjects trial

BACKGROUND

We determined whether low-dose oral enoximone could wean patients with ultra-advanced heart failure (UA-HF) from intravenous (i.v.) inotropic support. Chronic parenteral inotropic therapy in UA-HF is costly and requires an indwelling catheter. An effective and safe oral inotrope would have value.

METHODS

In this placebo-controlled study, 201 subjects with UA-HF requiring i.v. inotropic therapy were randomized to enoximone or placebo. Subjects receiving intermittent i.v. inotropes were administered study medication of 25 or 50 mg 3 times a day (tid). Subjects receiving continuous i.v. inotropes were administered 50 or 75 mg tid for 1 week, which was reduced to 25 or 50 mg tid. The ability of subjects to remain alive and free of inotropic therapy was assessed for up to 182 days.

RESULTS

Thirty days after weaning, 51 (51%) subjects on placebo and 62 (61.4%) subjects in the enoximone group were alive and free of i.v. inotropic therapy (unadjusted primary end point P = 0.14, adjusted for etiology P = .17). At 60 days, the wean rate was 30% in the placebo group and 46.5% in the enoximone group (unadjusted P = .016) Kaplan-Meier curves demonstrated a trend toward a decrease in the time to death or reinitiation of i.v. inotropic therapy over the 182-day study period (hazard ratio 0.76 [95% CI 0.55-1.04]) and a reduction at 60 days (0.62 [95% CI 0.43-0.89], P = .009) and 90 days (0.69 [95% CI 0.49-0.97], P = .031) after weaning in the enoximone group.

CONCLUSIONS

Although there was no benefit over placebo in weaning patients from i.v. inotropes from 0 to 30 days, the EMOTE data suggest that low-dose oral enoximone can be used to wean a modest percentage of subjects from i.v. inotropic support for up to 90 days after initiation of therapy.

Inotropic drugs and neurohormonal antagonists in the treatment of HF in the elderly

Heart failure (HF) is the most common reason for hospital admission among individuals over age 65 years and results in more than 1 million admissions each year. The overall annual death rate for HF is approximately 20%. HF results from decreased contractile function of the heart, and neurohormonal dysregulation plays a major part in the morbidity and mortality of the heart. The purpose of this article is to review recent studies on inotropic drugs and neurohormonal antagonists used in the treatment of patients who have HF, especially the elderly.

Inotropic drugs and neurohormonal antagonists in the treatment of HF in the elderly

HF (HF) is the most common reason for hospital admission among individuals over age 65 years and results in more than 1 million admissions each year. The overall annual death rate for HF is approximately 20%. HF results from decreased contractile function of the heart, and neurohormonal dysregulation plays a major part in the morbidity and mortality of the heart. The purpose of this article is to review recent studies on inotropic drugs and neurohormonal antagonists used in the treatment of patients who have HF, especially the elderly.

Acute heart failure: inotropic agents and their clinical uses

Inotropic agents are indispensable for the improvement of cardiac contractile dysfunction in acute or decompensated heart failure. Clinically available agents, including sympathomimetic amines (dopamine, dobutamine, noradrenaline) and selective phosphodiesterase-3 inhibitors (amrinone, milrinone, olprinone and enoximone) act via cAMP/protein kinase A (PKA)-mediated facilitation of intracellular Ca2+ mobilisation. Phosphodiesterase-3 inhibitors also have a vasodilatory action, which plays a role in improving haemodynamic parameters in certain patients, and are termed inodilators. The available inotropic agents suffer from risks of Ca2+ overload leading to arrhythmias, myocardial cell injury and ultimately, cell death. In addition, they are energetically disadvantageous because of an increase in activation energy and cellular metabolism. Furthermore, they lose their effectiveness under pathophysiological conditions, such as acidosis, stunned myocardium and heart failure. Pimobendan and levosimendan (that act by a combination of an increase in Ca2+ sensitivity and phosphodiesterase-3 inhibition) appear to be more beneficial among existing agents. Novel Ca2+ sensitisers that are under basic research warrant clinical trials to replace available inotropic agents.