Comparison of candoxatril and atrial natriuretic factor in healthy men. Effects on hemodynamics, sympathetic activity, heart rate variability, and endothelin

Angiotensin receptor-neprilysin inhibitor improves coronary collateral perfusion

Background

We investigated the pleiotropic effects of an angiotensin receptor-neprilysin inhibitor (ARNi) on collateral-dependent myocardial perfusion in a rat model of coronary arteriogenesis, and performed comprehensive analyses to uncover the underlying molecular mechanisms.

Methods

A rat model of coronary arteriogenesis was established by implanting an inflatable occluder on the left anterior descending coronary artery followed by a 7-day repetitive occlusion procedure (ROP). Coronary collateral perfusion was measured by using a myocardial particle infusion technique. The putative ARNi-induced pro-arteriogenic effects were further investigated and compared with an angiotensin-converting enzyme inhibitor (ACEi). Expression of the membrane receptors and key enzymes in the natriuretic peptide system (NPS), renin-angiotensin-aldosterone system (RAAS) and kallikrein-kinin system (KKS) were analyzed by quantitative polymerase chain reaction (qPCR) and immunoblot assay, respectively. Protein levels of pro-arteriogenic cytokines were measured by enzyme-linked immunosorbent assay, and mitochondrial DNA copy number was assessed by qPCR due to their roles in arteriogenesis. Furthermore, murine heart endothelial cells (MHEC5-T) were treated with a neprilysin inhibitor (NEPi) alone, or in combination with bradykinin receptor antagonists. MHEC5-T proliferation was analyzed by colorimetric assay.

Results

The in vivo study showed that ARNis markedly improved coronary collateral perfusion, regulated the gene expression of KKS, and increased the concentrations of relevant pro-arteriogenic cytokines. The in vitro study demonstrated that NEPis significantly promoted MHEC5-T proliferation, which was diminished by bradykinin receptor antagonists.

Conclusion

ARNis improve coronary collateral perfusion and exert pro-arteriogenic effects via the bradykinin receptor signaling pathway.

Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions

This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.

Effects of BNP and Sacubitrilat/Valsartan on Atrial Functional Reserve and Arrhythmogenesis in Human Myocardium

Background

Although the angiotensin receptor-neprilysin inhibitor (ARNI) sacubitril/valsartan started a new era in heart failure (HF) treatment, less is known about the tissue-level effects of the drug on the atrial myocardial functional reserve and arrhythmogenesis.

Methods and Results

Right atrial (RA) biopsies were retrieved from patients (n = 42) undergoing open-heart surgery, and functional experiments were conducted in muscle strips (n = 101). B-type natriuretic peptide (BNP) did not modulate systolic developed force in human myocardium during β-adrenergic stimulation, but it significantly reduced diastolic tension (p < 0.01) and the probability of arrhythmias (p < 0.01). In addition, patient's plasma NTproBNP positively correlated with isoproterenol-induced contractile reserve in atrial tissue in vitro (r = 0.65; p < 0.01). Sacubitrilat+valsartan (Sac/Val) did not show positive inotropic effects on atrial trabeculae function but reduced arrhythmogeneity. Atrial and ventricular biopsies from patients with end-stage HF (n = 10) confirmed that neprilysin (NEP) is equally expressed in human atrial and ventricular myocardium. RA NEP expression correlates positively with RA ejection fraction (EF) (r = 0.806; p < 0.05) and left ventricle (LV) NEP correlates inversely with left atrial (LA) volume (r = −0.691; p < 0.05).

Conclusion

BNP ameliorates diastolic tension during adrenergic stress in human atrial myocardium and may have positive long-term effects on the inotropic reserve. BNP and Sac/Val reduce atrial arrhythmogeneity during adrenergic stress in vitro. Myocardial NEP expression is downregulated with declining myocardial function, suggesting a compensatory mechanism in HF.

Kidney Angiotensin in Cardiovascular Disease: Formation and Drug Targeting

The concept of local formation of angiotensin II in the kidney has changed over the last 10-15 years. Local synthesis of angiotensinogen in the proximal tubule has been proposed, combined with prorenin synthesis in the collecting duct. Binding of prorenin via the so-called (pro)renin receptor has been introduced, as well as megalin-mediated uptake of filtered plasma-derived renin-angiotensin system (RAS) components. Moreover, angiotensin metabolites other than angiotensin II [notably angiotensin-(1-7)] exist, and angiotensins exert their effects via three different receptors, of which angiotensin II type 2 and Mas receptors are considered renoprotective, possibly in a sex-specific manner, whereas angiotensin II type 1 (AT1) receptors are believed to be deleterious. Additionally, internalized angiotensin II may stimulate intracellular receptors. Angiotensin-converting enzyme 2 (ACE2) not only generates angiotensin-(1-7) but also acts as coronavirus receptor. Multiple, if not all, cardiovascular diseases involve the kidney RAS, with renal AT1 receptors often being claimed to exert a crucial role. Urinary RAS component levels, depending on filtration, reabsorption, and local release, are believed to reflect renal RAS activity. Finally, both existing drugs (RAS inhibitors, cyclooxygenase inhibitors) and novel drugs (angiotensin receptor/neprilysin inhibitors, sodium-glucose cotransporter-2 inhibitors, soluble ACE2) affect renal angiotensin formation, thereby displaying cardiovascular efficacy. Particular in the case of the latter three, an important question is to what degree they induce renoprotection (e.g., in a renal RAS-dependent manner). This review provides a unifying view, explaining not only how kidney angiotensin formation occurs and how it is affected by drugs but also why drugs are renoprotective when altering the renal RAS. SIGNIFICANCE STATEMENT: Angiotensin formation in the kidney is widely accepted but little understood, and multiple, often contrasting concepts have been put forward over the last two decades. This paper offers a unifying view, simultaneously explaining how existing and novel drugs exert renoprotection by interfering with kidney angiotensin formation.

Sympathoinhibitory effect of sacubitril-valsartan in heart failure with reduced ejection fraction: A pilot study

Chronic sympathetic nervous system (SNS) overactivity, characteristic of heart failure (HF) with reduced ejection fraction (HFrEF), is associated with poor prognosis and contributes to increased mortality risk. Sacubitril-valsartan is a recently approved, first-in-class, angiotensin receptor neprilysin inhibitor (ARNI) drug that markedly reduces the risks of death from cardiovascular causes and hospitalization for HF in patients with HFrEF, but the physiological mechanisms underlying these benefits are not fully understood. This single-arm, open-label, prospective study sought to test the hypothesis that short-term treatment with sacubitril-valsartan reduces SNS activity, measured directly via muscle sympathetic nerve activity (MSNA), in patients with HFrEF. MSNA, heart rate (HR), and arterial blood pressure (BP) were assessed in stable Class II and III patients with HFrEF (n = 9, 69 ± 8 yrs.; 28.6 ± 3.6 kg/m²) on contemporary, guideline-directed medical treatment who were subsequently started on sacubitril-valsartan. These measurements were repeated after two months of treatment with sacubitril-valsartan. Sacubitril-valsartan reduced MSNA burst frequency (baseline: 43 ± 10 bursts/min; 2-month: 36 ± 10 bursts/min, p = 0.05) and burst incidence (baseline: 68 ± 16 bursts/100 heartbeats; 2-month: 55 ± 16 bursts/100 heartbeats, p = 0.02), while HR and BP were unchanged following of treatment (p > 0.05). These preliminary findings provide new evidence regarding the ability of sacubitril-valsartan to rapidly reduce SNS activity in patients with HFrEF, suggesting the presence of a novel sympathoinhibitory effect of this new drug class.

Angiotensin-neprilysin inhibition confers renoprotection in rats with diabetes and hypertension by limiting podocyte injury

OBJECTIVES

Combined angiotensin receptor--neprilysin inhibition (ARNI) reduces glomerulosclerosis better than single angiotensin receptor blockade (ARB) in diabetic, hypertensive rats. The renoprotective mechanism remains unknown, but may depend on superior blood pressure control, improved renal hemodynamics, suppressed renal inflammation or prevention of podocyte loss.

METHODS

To address this, TGR(mREN2)27 rats (a model of angiotensin II-dependent hypertension) were made diabetic for 12 weeks and treated with vehicle (n = 10), valsartan (ARB; n = 7) or sacubitril/valsartan (ARNI; n = 8) for the final 3 weeks. Arterial pressure was measured via radiotelemetry.

RESULTS

Sacubitril/valsartan lowered mean arterial pressure by -50 ± 4 mmHg and valsartan by -43 ± 4 mmHg (P = 0.3). Both treatments lowered albuminuria, but only sacubitril/valsartan maintained high urinary atrial natriuretic peptide, improved glycemic control and protected podocyte integrity, reflected by increased nephrin expression and suppression of transient receptor potential canonical 6 and regulator of calcineurin 1. This resulted in markedly reduced glomerulosclerosis (P < 0.05 vs. control and valsartan). Despite higher effective renal plasma flow and glomerular filtration rates, sacubitril/valsartan did neither improve filtration fraction nor renal immune cell infiltration.

CONCLUSION

Sacubitril/valsartan offers drug-class-specific renoprotection in a preclinical model of diabetes and hypertension. Renoprotection is unrelated to antihypertensive efficacy, renal hemodynamics or inflammation, but may be related to protective effects of natriuretic peptides on podocyte integrity.

The effect of neprilysin and renin inhibition on the renal dysfunction following ischemia-reperfusion injury in the rat

The natriuretic peptide (NP) system counter-regulates the renin-angiotensin system (RAS), so enhancing the activity of natriuretic peptides (NPs) may be beneficial in conditions when RAS is activated such as ischemia-reperfusion injury (IRI). Neprilysin is the key enzyme responsible for the degradation of NPs. The effects of neprilysin inhibition or the combination of neprilysin inhibition and RAS inhibition on renal IRI-induced renal dysfunction have not been investigated yet. To investigate this, rats underwent sham surgery or bilateral IRI for 20 min. G-Als, G-Scb, and G-Als+Scb underwent similar protocol but received aliskiren (renin inhibitor), sacubitril (neprilysin inhibitor) or a combination of both pre- and post-IRI, respectively. IRI caused significant alterations in all renal functional parameters, markers of acute renal injury, pro-inflammatory and pro-fibrotic cytokines, and histological features. All these alterations were significantly attenuated in G-Als, G-Scb, and G-Als+Scb. The attenuations in the alterations in serum creatinine, creatinine clearance, and histological features were larger in G-Als+Scb compared to either G-Als or G-Scb. We conclude that RAS blockade by a renin inhibitor (aliskiren) or neprilysin inhibition by sacubitril separately led to significant attenuation in the renal IRI-induced renal dysfunction. The combination of aliskiren and sacubitril was more effective than either one alone.

The Role of Neprilysin Inhibitors in the Treatment of Heart Failure with Preserved Ejection Fraction

Clinical and hemodynamic aggravation of heart failure with preserved ejection fraction (HFpEF) is largely due to progression of left ventricular (LV) diastolic dysfunction. The key role in the normal maintenance of diastolic function is played by a high level of activity of the intracellular signaling axis, cyclic guanosine-monophosphate-protein kinase G, the activity of which is significantly reduced in HFpEF. The activity of this axis can be increased by increasing the bioavailability of natriuretic peptides by blocking the enzyme neutral endopeptidase (neprilisin), which is responsible for the destruction of natriuretic peptides.This review presents experimental and clinical data on the use of neprilysin inhibitors in HFpEF and addresses prospects of this treatment.

Neprilysin: A Potential Therapeutic Target of Arterial Hypertension?

Arterial hypertension is the most prevalent chronic disease in the adult population of developed countries and it constitutes a significant risk factor in the development of cardiovascular disease, contributing to the emergence of many comorbidities, among which heart failure excels, a clinical syndrome that nowadays represents a major health problem with uncountable hospitalizations and the indolent course of which progressively worsens until quality of life decreases and lastly death occurs prematurely. In the light of this growing menace, each day more efforts are invested in the field of cardiovascular pharmacology, searching for new therapeutic options that allow us to modulate the physiological systems that appear among these pathologies. Therefore, in the later years, the study of natriuretic peptides has become so relevant, which mediate beneficial effects at the cardiovascular level such as diuresis, natriuresis, and decreasing cardiac remodeling; their metabolism is mediated by neprilysin, a metalloproteinase, widely expressed in the human and capable of catalyzing many substrates. The modulation of these functions has been studied by decades, giving room to Sacubitril, the first neprilysin inhibitor, which in conjunction with an angiotensin receptor blocker has provided a high efficacy and tolerability among patients with heart failure, for whom it has already been approved and recommended. Nonetheless, in the matter of arterial hypertension, significant findings have arisen that demonstrate the potential role that it will play among the pharmacological alternatives in the upcoming years.

Bioactive Signaling in Next-Generation Pharmacotherapies for Heart Failure: A Review

Importance

The standard pharmacotherapy for heart failure (HF), particularly HF with reduced ejection fraction (HFrEF), is primarily through the use of receptor antagonists, notably inhibition of the renin-angiotensin system by either angiotensin-converting enzyme inhibition or angiotensin II receptor blockade (ARB). However, the completed Prospective Comparison of ARNI With an ACE-Inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial identified that the use of a single molecule (sacubitril/valsartan), which is an ARB and the neutral endopeptidase inhibitor (NEPi) neprilysin, yielded improved clinical outcomes in HFrEF compared with angiotensin-converting enzyme inhibition alone.

Observations

This review examined specific bioactive signaling pathways that would be potentiated by NEPi and how these would affect key cardiovascular processes relevant to HFrEF. It also addressed potential additive/synergistic effects of ARB. A number of biological signaling pathways that may be potentiated by sacubitril/valsartan were identified, including some novel candidate molecules, which will act in a synergistic manner to favorably alter the natural history of HFrEF.

Conclusions and Relevance

This review identified that activation rather than inhibition of specific receptor pathways provided favorable cardiovascular effects that cannot be achieved by renin-angiotensin system inhibition alone. Thus, an entirely new avenue of translational and clinical research lies ahead in which HF pharmacotherapies will move beyond receptor antagonist strategies.

Novel Therapeutic Approaches Targeting the Renin-Angiotensin System and Associated Peptides in Hypertension and Heart Failure

Despite the success of renin-angiotensin system (RAS) blockade by angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 receptor (AT1R) blockers, current therapies for hypertension and related cardiovascular diseases are still inadequate. Identification of additional components of the RAS and associated vasoactive pathways, as well as new structural and functional insights into established targets, have led to novel therapeutic approaches with the potential to provide improved cardiovascular protection and better blood pressure control and/or reduced adverse side effects. The simultaneous modulation of several neurohumoral mediators in key interconnected blood pressure-regulating pathways has been an attractive approach to improve treatment efficacy, and several novel approaches involve combination therapy or dual-acting agents. In addition, increased understanding of the complexity of the RAS has led to novel approaches aimed at upregulating the ACE2/angiotensin-(1-7)/Mas axis to counter-regulate the harmful effects of the ACE/angiotensin II/angiotensin III/AT1R axis. These advances have opened new avenues for the development of novel drugs targeting the RAS to better treat hypertension and heart failure. Here we focus on new therapies in preclinical and early clinical stages of development, including novel small molecule inhibitors and receptor agonists/antagonists, less conventional strategies such as gene therapy to suppress angiotensinogen at the RNA level, recombinant ACE2 protein, and novel bispecific designer peptides.

Neprilysin inhibition for pulmonary arterial hypertension: a randomized, double-blind, placebo-controlled, proof-of-concept trial

BACKGROUND AND PURPOSE

Pulmonary arterial hypertension (PAH) is an incurable, incapacitating disorder resulting from increased pulmonary vascular resistance, pulmonary arterial remodelling, and right ventricular failure. In preclinical models, the combination of a PDE5 inhibitor (PDE5i) with a neprilysin inhibitor augments natriuretic peptide bioactivity, promotes cGMP signalling, and reverses the structural and haemodynamic deficits that characterize PAH. Herein, we conducted a randomized, double-blind, placebo-controlled trial to assess the efficacy and safety of repurposing the neprilysin inhibitor, racecadotril, in PAH.

EXPERIMENTAL APPROACH

Twenty-one PAH patients stable on PDE5i therapy were recruited. Acute haemodynamic and biochemical changes following a single dose of racecadotril or matching placebo were determined; this was followed by a 14-day safety and efficacy evaluation. The primary endpoint in both steps was the maximum change in circulating atrial natriuretic peptide (ANP) concentration (Δ_max ), with secondary outcomes including pulmonary and systemic haemodynamics plus mechanistic biomarkers.

KEY RESULTS

Acute administration of racecadotril (100 mg) resulted in a 79% increase in the plasma ANP concentration and a 106% increase in plasma cGMP levels, with a concomitant 14% fall in pulmonary vascular resistance. Racecadotril (100 mg; t.i.d.) treatment for 14 days resulted in a 19% rise in plasma ANP concentration. Neither acute nor chronic administration of racecadotril resulted in a significant drop in mean arterial BP or any serious adverse effects.

CONCLUSIONS AND IMPLICATIONS

This Phase IIa evaluation provides proof-of-principle evidence that neprilysin inhibitors may have therapeutic utility in PAH and warrants a larger scale prospective trial.

New antihypertensive medications and clinical implications

Hypertension remains a global public health issue and is a leading preventable risk factor for many causes of mortality and morbidity. Although it is generally managed as an outpatient chronic disease, anaesthetists will inevitably encounter patients with hypertension, ranging from undiagnosed asymptomatic to chronic forms with end-organ damage(s). An understanding of perioperative management of anti-hypertensive pharmacotherapy is crucial. Although many drugs are familiar, new drug groups that have relevance for blood pressure control and perioperative care have evolved in recent years. This article also describes new antihypertensive agents currently available or under development that could impact perioperative management.

Sacubitril/valsartan in cardiovascular disease: evidence to date and place in therapy

Cardiovascular (CV) disease is a major cause of morbidity and mortality in the developing and the developed world. Mortality from CV disease had plateaued in the recent years raising concerning alarms about the sustained efficacy of available preventive and treatment options. Heart failure (HF) is among the major contributors to the CV-related health care burden, a persisting concern despite the use of clinically proven guideline-directed therapies. A requirement for more efficient medical therapies coupled with recent advances in bio-innovation led to the creation of sacubitril/valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI), which demonstrated substantial CV benefit when compared with the standard of care, enalapril, in patients with HF and reduced ejection fraction. Further investigations of this novel combination ARNI at the tissue level shed light into the anti-remodeling and cardioprotective effects of sacubitril/valsartan, while clinical studies in the phenotypes of HF with preserved ejection fraction, hypertension and subsets, coronary outcomes, postmyocardial infarction, and renal disease suggested that this combination could be beneficial across a wide spectrum of CV disease. Sacubitril/valsartan is a much-needed therapeutic advance in the avenue of CV disease.

From ARB to ARNI in Cardiovascular Control

Coexistence of hypertension, diabetes mellitus and chronic kidney disease synergistically aggravates the risk of cardiovascular and renal morbidity and mortality. These high-risk, multi-morbid patient populations benefit less from currently available anti-hypertensive treatment. Simultaneous angiotensin II type 1 receptor blockade and neprilysin inhibition (‘ARNI’) with valsartan/sacubitril (LCZ696) might potentiate the beneficial effects of renin-angiotensin-aldosterone inhibition by reinforcing its endogenous counterbalance, the natriuretic peptide system. This review discusses effects obtained with this approach in animals and humans. In animal models of hypertension, either alone or in combination with myocardial infarction or diabetes, ARNI consistently reduced heart weight and cardiac fibrosis in a blood pressure-independent manner. Additionally, LCZ696 treatment reduced proteinuria, focal segmental glomerulosclerosis and retinopathy, thus simultaneously demonstrating favourable effects on microvascular complications. These results were confirmed in patient populations. Besides blood pressure reductions in hypertensive patients and greatly improved (cardiovascular) mortality in heart failure patients, ventricular wall stress and albuminuria were reduced particularly in diabetic patients. The exact underlying mechanism remains unknown, but may involve improved renal haemodynamics and reduced glomerulosclerosis, e.g. related to a rise in natriuretic peptide levels. However, the assays of these peptides are hampered by methodological artefacts. Moreover, since sacubitrilat is largely renally cleared, drug accumulation may occur in patients with impaired renal function and thus hypotension is a potential side effect in patients with chronic kidney disease. Further caution is warranted since neprilysin also degrades endothelin-1 and amyloid beta in animal models. Accumulation of the latter may increase the risk of Alzheimer’s disease.

Neprilysin inhibition and endothelin-1 elevation: Focus on the kidney

Increasing the degree of renin-angiotensin system (RAS) blockade by combining ≥2 RAS blockers marginally increases efficacy, but results in more side effects. Hence, interference with other systems is currently being investigated, like potentiation of natriuretic peptides with neprilysin inhibitors. However, the neprilysin inhibitor thiorphan was recently found to increase endothelin-1 when administered to TGR(mREN2)27 (Ren2) rats on top of RAS blockade. Here we investigated whether this effect is thiorphan-specific, by comparing the neprilysin inhibitors thiorphan and sacubitril, administered by osmotic minipumps at a low or high dose for 7 days, in Ren2 rats. Plasma and urinary levels of endothelin-1, atrial and brain natriuretic peptide (ANP, BNP) and their second messenger cyclic guanosine 3'5' monophosphate (cGMP) were monitored. No significant differences were found in the plasma concentrations of endothelin-1, cGMP, ANP and BNP after treatment, although plasma ANP tended to be higher in the high-dose thiorphan treatment group and the low- and high-dose sacubitril treatment groups, compared with vehicle. Urinary endothelin-1 increased in the low-dose thiorphan and high-dose sacubitril groups, compared with baseline, although significance was reached for the former only. Urinary cGMP rose significantly in the high-dose sacubitril treatment group compared with baseline. Both urinary endothelin-1 and cGMP were significantly higher in the high-dose sacubitril group compared with the low-dose sacubitril group. In conclusion, endothelin-1 upregulation occurs with both thiorphan and sacubitril, and is particularly apparent in neprilysin-rich organs like the kidney. High renal neprilysin levels most likely also explain why sacubitril increased cGMP in urine only.

Renin angiotensin aldosterone inhibition in the treatment of cardiovascular disease

A collective century of discoveries establishes the importance of the renin angiotensin aldosterone system in maintaining blood pressure, fluid volume and electrolyte homeostasis via autocrine, paracrine and endocrine signaling. While research continues to yield new functions of angiotensin II and angiotensin-(1-7), the gap between basic research and clinical application of these new findings is widening. As data accumulates on the efficacy of angiotensin converting enzyme inhibitors and angiotensin II receptor blockers as drugs of fundamental importance in the treatment of cardiovascular and renal disorders, it is becoming apparent that the achieved clinical benefits is suboptimal and surprisingly no different than what can be achieved with other therapeutic interventions. We discuss this issue and summarize new pathways and mechanisms effecting the synthesis and actions of angiotensin II. The presence of renin-independent non-canonical pathways for angiotensin II production are largely unaffected by agents inhibiting renin angiotensin system activity. Hence, new efforts should be directed to develop drugs that can effectively block the synthesis and/or action of intracellular angiotensin II. Improved drug penetration into cardiac or renal sites of disease, inhibiting chymase the primary angiotensin II forming enzyme in the human heart, and/or inhibiting angiotensinogen synthesis would all be more effective strategies to inhibit the system. Additionally, given the role of angiotensin II in the maintenance of renal homeostatic mechanisms, any new inhibitor should possess greater selectivity of targeting pathogenic angiotensin II signaling processes and thereby limit inappropriate inhibition.

Neprilysin Inhibitors in Cardiovascular Disease

Mortality from heart failure remains high despite advances in medical therapy over the last three decades. Angiotensin receptor-neprilysin inhibitor (ARNI) combinations are the latest addition to the heart failure medical armamentarium, which is built on the cornerstone regimen of beta blockers, angiotensin converting enzyme (ACE) inhibitors/angiotensin receptor blockers, and aldosterone antagonists. Recent trial data have shown a significant mortality benefit from ARNIs, which, as of May 2016, have now received a class I recommendation for use in patients with heart failure and reduced ejection fraction from the major American and European cardiology societies.

Neprilysin Inhibition and the Treatment of Heart Failure: Recent Steps in the Right Direction

Numerous investigators have attempted to target the natriuretic peptide system in the treatment of heart failure since it was first described over 30 years ago. The history of neprilysin inhibition as a treatment for heart failure has been characterized by numerous setbacks. Recently, the PARADIGM-HF trial has shown favorable results, which may bring neprilysin inhibition into the mainstream of clinical practice. This article will review the history of the natriuretic peptide system and the investigations into it as a target for heart failure treatment, culminating in the positive results of the PARADIGM-HF trial, as well as planned and potential future directions for research.

The evolution of natriuretic peptide augmentation in management of heart failure and the role of sacubitril/valsartan

Heart failure (HF) is one of the leading causes of morbidity, mortality, and health care expenditures in the US and worldwide. For three decades, the pillars of treatment of HF with reduced ejection fraction (HFrEF) were medications that targeted the sympathetic nervous system (SNS) and the renin-angiotensin-aldosterone system (RAAS). Prior attempts to augment the natriuretic peptide system (NPS) for the management of HF failed either due to lack of significant clinical benefit or due to the unacceptable side effect profile. This review article will discuss the NPS, the failure of early drugs which targeted the NPS as therapies for HF, and the sequence of events which led to the development of sacubitril plus valsartan (Entresto; LCZ696; Novartis). LCZ696 has been shown to be superior to the standard of care available for treatment of HFrEF in several substantial hard endpoints including heart failure hospitalizations, cardiovascular mortality, and all-cause mortality.

Focus on the Novel Cardiovascular Drug LZC696: from Evidence to Clinical Consideration

LCZ696, a first-in-class angiotensin receptor neprilysin inhibitor (ARNI), is comprised of the angiotensin receptor blocker valsartan and the neprilysin inhibitor pro-drug sacubitril (AHU377). After oral administration, AHU377 is rapidly metabolized to the active neprilysin inhibitor LBQ657. LCZ696 exerts its effects of diuresis, natriuresis, vasodilation and aldosterone secretion inhibition through simultaneous renin-angiotensin-aldosterone system (RAAS) blockade and natriuretic peptides system (NPS) enhancement. Powerful evidence including PARAMETER and PRARDIGM-HF trials have shown that LCZ696 outperforms RAAS inhibition in treating patients with hypertension and heart failure with reduced ejection fraction (HFrEF), and is well tolerated. In addition, accumulating evidence also suggests its potential use in heart failure with preserved ejection fraction (HFpEF), chronic kidney disease (CKD), post-myocardium infarction (post-MI) and stroke. Both the FDA and CHMP have approved LCZ696 for treatment of HFrEF. Despite all this, some special issues (e.g. use in specific subgroups, adverse events, contraindications and cost-effectiveness analysis) should be considered before its implementation in clinical practice.

Sacubitril/Valsartan (LCZ696) in Heart Failure

It has been known since the 1990s that long-term morbidity and mortality is improved in patients with heart failure with reduced ejection fraction (HFrEF) by treatments that target the renin-angiotensin-aldosterone system (RAAS). It has also long been thought that enhancement of the activity of natriuretic peptides (NPs) could potentially benefit patients with HFrEF, but multiple attempts to realize this benefit had failed over the years - until 2014, when a large, phase III, randomized, controlled clinical trial (PARADIGM-HF) was completed comparing sacubitril/valsartan with enalapril, a well-established treatment for HFrEF. Sacubitril/valsartan (formerly known as LCZ696) is a first-in-class angiotensin receptor neprilysin inhibitor (ARNI) that simultaneously suppresses RAAS activation through blockade of angiotensin II type 1 receptors and enhances vasoactive peptides including NPs through inhibition of neprilysin, the enzyme responsible for their degradation. In PARADIGM-HF, patients with HFrEF treated with sacubitril/valsartan had 20% less risk for cardiovascular death or hospitalization for heart failure (the primary endpoint), 20% less risk for cardiovascular death, 21% less risk for first hospitalization for heart failure, and 16% less risk for death from any cause, compared with enalapril (all p < 0.001). Concerning tolerability, the sacubitril/valsartan group had higher proportions of patients with hypotension and nonserious angioedema but lower proportions with renal impairment, hyperkalemia, and cough, compared with the enalapril group. The use of sacubitril/valsartan has been endorsed by the latest heart failure treatment guidelines in Europe and the USA. This chapter reviews the discoveries, scientific reasoning, and clinical evidence that led to the development of sacubitril/valsartan, the first novel therapy in a new drug class to improve survival in HFrEF in the last 15 years.

Long-term neprilysin inhibition - implications for ARNIs

Neprilysin has a major role in both the generation and degradation of bioactive peptides. LCZ696 (valsartan/sacubitril, Entresto), the first of the new ARNI (dual-acting angiotensin-receptor-neprilysin inhibitor) drug class, contains equimolar amounts of valsartan, an angiotensin-receptor blocker, and sacubitril, a prodrug for the neprilysin inhibitor LBQ657. LCZ696 reduced blood pressure more than valsartan alone in patients with hypertension. In the PARADIGM-HF study, LCZ696 was superior to the angiotensin-converting enzyme inhibitor enalapril for the treatment of heart failure with reduced ejection fraction, and LCZ696 was approved by the FDA for this purpose in 2015. This approval was the first for chronic neprilysin inhibition. The many peptides metabolized by neprilysin suggest many potential consequences of chronic neprilysin inhibitor therapy, both beneficial and adverse. Moreover, LBQ657 might inhibit enzymes other than neprilysin. Chronic neprilysin inhibition might have an effect on angio-oedema, bronchial reactivity, inflammation, and cancer, and might predispose to polyneuropathy. Additionally, inhibition of neprilysin metabolism of amyloid-β peptides might have an effect on Alzheimer disease, age-related macular degeneration, and cerebral amyloid angiopathy. Much of the evidence for possible adverse consequences of chronic neprilysin inhibition comes from studies in animal models, and the relevance of this evidence to humans is unknown. This Review summarizes current knowledge of neprilysin function and possible consequences of chronic neprilysin inhibition that indicate a need for vigilance in the use of neprilysin inhibitor therapy.

Sacubitril/valsartan in heart failure: latest evidence and place in therapy

Despite significant therapeutic advances, patients with chronic heart failure (HF) remain at high risk for HF progression and death. Sacubitril/valsartan (previously known as LCZ696) is a first-in-class medicine that contains a neprilysin (NEP) inhibitor (sacubitril) and an angiotensin II (Ang-II) receptor blocker (valsartan). NEP is an endopeptidase that metabolizes different vasoactive peptides including natriuretic peptides, bradykinin and Ang-II. In consequence, its inhibition increases mainly the levels of both, natriuretic peptides (promoting diuresis, natriuresis and vasodilatation) and Ang-II whose effects are blocked by the angiotensin receptor blocker, valsartan (reducing vasoconstriction and aldosterone release). Results from the 8442 patient PARADIGM-HF study showed in patients with New York Heart Association (NYHA) class II-IV and reduced ejection fraction treated with LCZ696 (versus enalapril), the following benefits: reduction of the risk of death from cardiovascular causes by 20%; reduction of HF hospitalizations by 21%; reduction of the risk of all-cause mortality by 16%. Overall there was a 20% risk reduction on the primary endpoint, composite measure of cardiovascular (CV) death or time to first HF hospitalization. PARADIGM-HF was stopped early after a median follow up of 27 months. Post hoc analyses of PARADIGM-HF as well as the place in therapy of sacubitril/valsartan, including future directions, are included in the present review.

Combined Angiotensin Receptor Antagonism and Neprilysin Inhibition

Heart failure affects ≈5.7 million people in the United States alone. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, β-blockers, and aldosterone antagonists have improved mortality in patients with heart failure and reduced ejection fraction, but mortality remains high. In July 2015, the US Food and Drug Administration approved the first of a new class of drugs for the treatment of heart failure: Valsartan/sacubitril (formerly known as LCZ696 and currently marketed by Novartis as Entresto) combines the angiotensin receptor blocker valsartan and the neprilysin inhibitor prodrug sacubitril in a 1:1 ratio in a sodium supramolecular complex. Sacubitril is converted by esterases to LBQ657, which inhibits neprilysin, the enzyme responsible for the degradation of the natriuretic peptides and many other vasoactive peptides. Thus, this combined angiotensin receptor antagonist and neprilysin inhibitor addresses 2 of the pathophysiological mechanisms of heart failure: activation of the renin-angiotensin-aldosterone system and decreased sensitivity to natriuretic peptides. In the Prospective Comparison of ARNI With ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure (PARADIGM-HF) trial, valsartan/sacubitril significantly reduced mortality and hospitalization for heart failure, as well as blood pressure, compared with enalapril in patients with heart failure, reduced ejection fraction, and an elevated circulating level of brain natriuretic peptide or N-terminal pro-brain natriuretic peptide. Ongoing clinical trials are evaluating the role of valsartan/sacubitril in the treatment of heart failure with preserved ejection fraction and hypertension. We review here the mechanisms of action of valsartan/sacubitril, the pharmacological properties of the drug, and its efficacy and safety in the treatment of heart failure and hypertension.

MicroRNA and receptor mediated signaling pathways as potential therapeutic targets in heart failure

INTRODUCTION

Cardiac remodelling is a complex pathogenetic pathway involving genome expression, molecular, cellular, and interstitial changes that cause changes in size, shape and function of the heart after cardiac injury. Areas covered: We will review recent advances in understanding the role of several receptor-mediated signaling pathways and micro-RNAs, in addition to their potential as candidate target pathways in the pathogenesis of heart failure. The myocyte is the main target cell involved in the remodelling process via ischemia, cell necrosis and apoptosis (by means of various receptor pathways), and other mechanisms mediated by micro-RNAs. We will analyze the role of some receptor mediated signaling pathways such as natriuretic peptides, mediators of glycogen synthase kinase 3 and ERK1/2 pathways, beta-adrenergic receptor subtypes and relaxin receptor signaling mechanisms, TNF/TNF receptor family and TWEAK/Fn14 axis, and some micro-RNAs as candidate target pathways in pathogenesis of heart failure. These mediators of receptor-mediated pathways and micro-RNA are the most addressed targets of emerging therapies in modern heart failure treatment strategies. Expert opinion: Future treatment strategies should address mediators involved in multiple steps within heart failure pathogenetic pathways.

Spotlight on valsartan-sacubitril fixed-dose combination for heart failure: the evidence to date

Heart failure is a global problem with elevated prevalence, and it is associated with substantial cardiovascular morbidity and mortality. Treating heart-failure patients has been a very challenging task. This review highlights the main pharmacological developments in the field of heart failure with reduced ejection fraction, giving emphasis to a drug that has a dual-acting inhibition of the neprilysin and renin–angiotensin–aldosterone system. Neprilysin is an enzyme that participates in the breakdown of biologically active natriuretic peptides and several other vasoactive compounds. The inhibition of neprilysin has been a therapeutic target for several drugs tested in cardiovascular disease, mainly for heart failure and/or hypertension. However, side effects and a lack of efficacy led to discontinuation of their development. LCZ696 is a first-in-class neprilysin- and angiotensin-receptor inhibitor that has been developed for use in heart failure. This drug is composed of two molecular moieties in a single crystalline complex: a neprilysin-inhibitor prodrug (sacubitril) and the angiotensin-receptor blocker (valsartan). The PARADIGM-HF trial demonstrated that this drug was superior to an angiotensin-converting enzyme inhibitor (enalapril) in reducing mortality in patients with heart failure with reduced ejection fraction. The ability to block the angiotensin receptor and augment the endogenous natriuretic peptide system provides a distinctive mechanism of action in cardiovascular disease.

Current Understanding of the Compensatory Actions of Cardiac Natriuretic Peptides in Cardiac Failure: A Clinical Perspective

Natriuretic peptides play a crucial role in maintaining cardiovascular homeostasis. Among their properties are vasodilation, natriuresis, diuresis, and inhibition of cardiac remodeling. As heart failure progresses, however, natriuretic peptides fail to compensate. Knowledge of their processing and signaling pathways has guided the development of pharmacological therapies aimed at bolstering their effects. The drugs that have achieved the most clinical success have also stirred the most controversy. Nesiritide, the synthetic B-type natriuretic peptide, yielded significant symptomatic relief and improved haemodynamics but its use was plagued with questions surrounding its possibly harmful impact on renal function. More recently, compounds containing inhibitors of neprilysin, the enzyme responsible for degrading natriuretic peptides, have demonstrated morbidity and mortality benefit, but have also been linked to possible negative side effects. Clearly, potentiating the actions of natriuretic peptides for the benefit of patients is not as simple as just raising their serum concentration. This article reviews the current understanding of the compensatory actions of cardiac natriuretic peptides in heart failure and how this knowledge is revolutionizing heart failure therapy.

Should Angiotensin Receptor Neprilysin Inhibitors Replace Angiotensin-converting Enzyme Inhibitors in Heart Failure With a Reduced Ejection Fraction?

Angiotensin-converting enzyme inhibitors (ACEIs) have been the cornerstone of treatment of heart failure with reduced ejection fraction (HFrEF) for over two decades. Inhibition of neprilyisin augments vasoactive substances including natriuretic peptides, which may have multiple advantageous effects in chronic HF. Early studies of neprilyisin inhibition led to drug discontinuation due to lack of efficacy or safety concerns. Sacubitril/valsartan is a first-in-class combined angiotensin receptor/neprilysin inhibitor (ARNI). The PARADIGM-HF study demonstrated robust superiority of ARNI compared with enalapril in patients with chronic symptomatic HFrEF, raising the question of whether ACEI should still have a role in the management of HFrEF.

The Mechanism of Action of LCZ696

Heart failure (HF) represents a growing financial burden on healthcare systems and despite therapeutic advances, mortality remains high. Current treatments focus on blocking neurohormonal pathways, such as the renin-angiotensin aldosterone system (RAAS). Recent research has focused on the natriuretic peptide system, which confers beneficial effects in HF, whereas activation of the RAAS and of the sympathetic nervous system has detrimental effects. LCZ696 (sacubutril/valsartan), a first-in-class angiotensin II AT[1] receptor neprilysin inhibitor, has a unique mode of action that targets both pathways. Clinical studies to date indicate that LCZ696 is effective and safe in mild to moderate arterial hypertension and in HF patients with preserved ejection fraction, and has been shown to be superior to enalapril in patients with moderate to severe HF due to reduced left ventricular ejection fraction.

The natriuretic peptides system in the pathophysiology of heart failure: from molecular basis to treatment

After its discovery in the early 1980s, the natriuretic peptide (NP) system has been extensively characterized and its potential influence in the development and progression of heart failure (HF) has been investigated. HF is a syndrome characterized by the activation of different neurohormonal systems, predominantly the renin-angiotensin (Ang)-aldosterone system (RAAS) and the sympathetic nervous system (SNS), but also the NP system. Pharmacological interventions have been developed to counteract the neuroendocrine dysregulation, through the down modulation of RAAS with ACE (Ang-converting enzyme) inhibitors, ARBs (Ang receptor blockers) and mineralcorticoid antagonists and of SNS with β-blockers. In the last years, growing attention has been paid to the NP system. In the present review, we have summarized the current knowledge on the NP system, focusing on its role in HF and we provide an overview of the pharmacological attempts to modulate NP in HF: from the negative results of the study with neprilysin (NEP) inhibitors, alone or associated with an ACE inhibitor and vasopeptidase inhibitors, to the most recently and extremely encouraging results obtained with the new pharmacological class of Ang receptor and NEP inhibitor, currently defined ARNI (Ang receptor NEP inhibitor). Indeed, this new class of drugs to manage HF, supported by the recent results and a vast clinical development programme, may prompt a conceptual shift in the treatment of HF, moving from the inhibition of RAAS and SNS to a more integrated target to rebalance neurohormonal dysregulation in HF.

Blood pressure-independent renoprotection in diabetic rats treated with AT1 receptor-neprilysin inhibition compared with AT1 receptor blockade alone

ARNI [dual AT1 (angiotensin II type 1) receptor-neprilysin inhibition] exerts beneficial effects on blood pressure and kidney function in heart failure, compared with ARB (AT1 receptor blockade) alone. We hypothesized that ARNI improves cardiac and kidney parameters in diabetic TGR(mREN2)27 rats, an angiotensin II-dependent hypertension model. Rats were made diabetic with streptozotocin for 5 or 12 weeks. In the final 3 weeks, rats were treated with vehicle, irbesartan (ARB) or irbesartan+thiorphan (ARNI). Blood pressure, measured by telemetry in the 5-week group, was lowered identically by ARB and ARNI. The heart weight/tibia length ratio in 12-week diabetic animals was lower after ARNI compared with after ARB. Proteinuria and albuminuria were observed from 8 weeks of diabetes onwards. ARNI reduced proteinuria more strongly than ARB, and a similar trend was seen for albuminuria. Kidneys of ARNI-treated animals showed less severe segmental glomerulosclerosis than those of ARB-treated animals. After 12 weeks, no differences between ARNI- and ARB-treated animals were found regarding diuresis, natriuresis, plasma endothelin-1, vascular reactivity (acetylcholine response) or kidney sodium transporters. Only ARNI-treated rats displayed endothelin type B receptor-mediated vasodilation. In conclusion, ARNI reduces proteinuria, glomerulosclerosis and heart weight in diabetic TGR(mREN2)27 rats more strongly than does ARB, and this occurs independently of blood pressure.

LCZ696: the next step in improving RAS inhibition?

LCZ696 is a single molecule which combines the angiotensin receptor blocker valsartan with the neprilysn inhibitor sacubitril (AHU377). In the recently published PARADIGM-HF trial, LCZ696 proved superior to enalapril in reducing overall mortality, heart failure hospitalizations, and other endpoints in patients with systolic dysfunction heart failure. Increases in counter-regulatory natriuretic peptides which oppose sodium retention, vasoconstriction, and the deleterious structural changes which follow neurohormonal activation are thought to account for these improved outcomes. In two large hypertension studies, LCZ696 has proved to be a potent, effective antihypertensive agent with tolerability similar to valsartan and placebo and potency comparable to amlodipine. Although several have occurred in the heart failure population, there have been no cases of angioedema noted in the hypertension trials, although few black patients-a group at high risk for its occurrence-have been studied. Whether LCZ696 will displace angiotensin-converting enzyme inhibitors and angiotensin II receptor blockers (ARBs) as preferred renin-angiotensin system (RAS) blocking agents in hypertension will require demonstration of improved long-term outcomes compared with currently preferred first-line drugs. In this regard, experience has shown that it is difficult to extrapolate results achieved in heart failure to the treatment of hypertension, a condition in which neurohormonal activation is less critical in determining long-term prognosis. It will be particularly important to demonstrate renal protection with LCZ696 in patients with diabetes, proteinuria, and hypertension-the only therapeutic area other than heart failure in which RAS blockade has proved essential for optimal endpoint reduction. Superiority over available RAS blockers in terms of 'vascular protection' in high-risk populations represents another path to acceptance of LCZ696 as a preferred agent in cardiovascular medicine.

Natriuretic Peptides and Cardiometabolic Health

Natriuretic peptides are cardiac-derived hormones with a range of protective functions, including natriuresis, diuresis, vasodilation, lusitropy, lipolysis, weight loss, and improved insulin sensitivity. Their actions are mediated through membrane-bound guanylyl cyclases that lead to production of the intracellular second-messenger cyclic guanosine monophosphate. A growing body of evidence demonstrates that genetic and acquired deficiencies of the natriuretic peptide system can promote hypertension, cardiac hypertrophy, obesity, diabetes mellitus, the metabolic syndrome, and heart failure. Clinically, natriuretic peptides are robust diagnostic and prognostic markers, and augmenting natriuretic peptides is a target for therapeutic strategies in cardiometabolic disease. This review will summarize current understanding and highlight novel aspects of natriuretic peptide biology.

Angiotensin receptor-neprilysin inhibitors: clinical potential in heart failure and beyond

Heart failure remains a major concern across the globe as life expectancies and delivery of health care continue to improve. There has been a dearth of new developments in heart failure therapies in the last decade until last year, with the release of the results from the PARADIGM-HF Trial heralding the arrival of a promising new class of drug, ie, the angiotensin receptor-neprilysin inhibitor. In this review, we discuss the evolution of our incremental understanding of the neurohormonal mechanisms involved in the pathophysiology of heart failure, which has led to our success in modulating its various pathways. We start by examining the renin-angiotensin-aldosterone system, followed by the challenges of modulating the natriuretic peptide system. We then delve deeper into the pharmacology and mechanisms by which angiotensin receptor-neprilysin inhibitors achieve their significant cardiovascular benefits. Finally, we also consider the potential application of this new class of drug in other areas, such as heart failure with preserved ejection fraction, hypertension, patients with renal impairment, and following myocardial infarction.

Optimum AT1 receptor-neprilysin inhibition has superior cardioprotective effects compared with AT1 receptor blockade alone in hypertensive rats

Neprilysin inhibitors prevent the breakdown of bradykinin and natriuretic peptides, promoting vasodilation and natriuresis. However, they also increase angiotensin II and endothelin-1. Here we studied the effects of a low and a high dose of the neprilysin inhibitor thiorphan on top of AT1 receptor blockade with irbesartan versus vehicle in TGR(mREN2)27 rats with high renin hypertension. Mean arterial blood pressure was unaffected by vehicle or thiorphan alone. Irbesartan lowered blood pressure, but after 7 days pressure started to increase again. Low- but not high-dose thiorphan prevented this rise. Only during exposure to low-dose thiorphan plus irbesartan did heart weight/body weight ratio, cardiac atrial natriuretic peptide expression, and myocyte size decrease significantly. Circulating endothelin-1 was not affected by low-dose thiorphan with or without irbesartan, but increased after treatment with high-dose thiorphan plus irbesartan. This endothelin-1 rise was accompanied by an increase in renal sodium-hydrogen exchanger 3 protein abundance, and an upregulation of constrictor vascular endothelin type B receptors. Consequently, the endothelin type B receptor antagonist BQ788 no longer enhanced endothelin-1-induced vasoconstriction (indicative of endothelin type B receptor-mediated vasodilation), but prevented it. Thus, optimal neprilysin inhibitor dosing reveals additional cardioprotective effects on top of AT1 receptor blockade in renin-dependent hypertension.

Angiotensin Receptor Neprilysin Inhibitor LCZ696 Attenuates Cardiac Remodeling and Dysfunction After Myocardial Infarction by Reducing Cardiac Fibrosis and Hypertrophy

Background—

Angiotensin receptor neprilysin inhibitors (ARNi), beyond blocking angiotensin II signaling, augment natriuretic peptides by inhibiting their breakdown by neprilysin. The myocardial effects of ARNi have been little studied until recently. We hypothesized that LCZ696 attenuates left ventricular (LV) remodeling after experimental myocardial infarction (MI), and that this may be contributed to by inhibition of hypertrophy and fibrosis in cardiac cells.

Methods and Results—

One week after MI, adult male Sprague–Dawley rats were randomized to treatment for 4 weeks with LCZ696 (68 mg/kg body weight perorally; MI-ARNi, n=11) or vehicle (MI-vehicle, n=6). Five weeks after MI, MI-ARNi versus MI-vehicle demonstrated lower LV end-diastolic diameter (by echocardiography; 9.7±0.2 versus 10.5±0.3 mm), higher LV ejection fraction (60±2 versus 47±5%), diastolic wall strain (0.23±0.02 versus 0.13±0.02), and circular strain (−9.8±0.5 versus −7.3±0.5%; all P <0.05). LV pressure–volume loops confirmed improved LV function. Despite similar infarct size, MI-ARNi versus MI-vehicle had lower cardiac weights ( P <0.01) and markedly reduced fibrosis in peri-infarct and remote myocardium. Angiotensin II–stimulated incorporation of 3[H]leucine in cardiac myocytes and 3[H]proline in cardiac fibroblast was used to evaluate hypertrophy and fibrosis, respectively. The neprilysin inhibitor component of LCZ696, LBQ657, inhibited hypertrophy but not fibrosis. The angiotensin receptor blocker component of LCZ696, valsartan inhibited both hypertrophy and fibrosis. Dual valsartan+LBQ augmented the inhibitory effects of valsartan and the highest doses completely abrogated angiotensin II–mediated effects.

Conclusions—

LCZ696 attenuated cardiac remodeling and dysfunction after MI. This may be contributed to by superior inhibition of LCZ696 on cardiac fibrosis and cardiac hypertrophy than either stand-alone neprilysin inhibitor or angiotensin receptor blocker.