Neprilysin, cardiovascular, and Alzheimer's diseases: the therapeutic split?

Neprilysin inhibitors and risk of Alzheimer's disease: A future perspective

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disease with multifaceted neuropathological disorders. AD is characterized by intracellular accumulation of phosphorylated tau proteins and extracellular deposition of amyloid beta (Aβ). Various protease enzymes, including neprilysin (NEP), are concerned with the degradation and clearance of Aβ. Indeed, a defective neuronal clearance pathway due to the dysfunction of degradation enzymes might be a possible mechanism for the accumulation of Aβ and subsequent progression of AD neuropathology. NEP is one of the most imperative metalloproteinase enzymes involved in the clearance of Aβ. This review aimed to highlight the possible role of NEP inhibitors in AD. The combination of sacubitril and valsartan which is called angiotensin receptor blocker and NEP inhibitor (ARNI) may produce beneficial and deleterious effects on AD neuropathology. NEP inhibitors might increase the risk of AD by the inhibition of Aβ clearance, and increase brain bradykinin (BK) and natriuretic peptides (NPs), which augment the pathogenesis of AD. These verdicts come from animal model studies, though they may not be applied to humans. However, clinical studies revealed promising safety findings regarding the use of ARNI. Moreover, NEP inhibition increases various neuroprotective peptides involved in inflammation, glucose homeostasis and nerve conduction. Also, NEP inhibitors may inhibit dipeptidyl peptidase 4 (DPP4) expression, ameliorating insulin and glucagon-like peptide 1 (GLP-1) levels. These findings proposed that NEP inhibitors may have a protective effect against AD development by increasing GLP-1, neuropeptide Y (NPY) and substance P, and deleterious effects by increasing brain BK. Preclinical and clinical studies are recommended in this regard.

Plasma Amyloid-β in Relation to Cardiac Function and Risk of Heart Failure in General Population

BACKGROUND

Amyloid-β (Aβ) may be related to cardiac function. However, there are limited data on the association of plasma Aβ with cardiac function and risk of heart failure (HF) in the general population.

OBJECTIVES

This study sought to determine the associations of plasma amyloid-β40 (Aβ40) and amyloid-β42 (Aβ42) with echocardiographic measurements of cardiac dysfunction and with incident HF in the general population.

METHODS

The study included 4,156 participants of the population-based Rotterdam Study (mean age: 71.4 years; 57.1% women), who had plasma Aβ samples collected between 2002 and 2005 and had no established dementia and HF at baseline. Multivariable linear regression models were used to explore the cross-sectional association of plasma Aβ with echocardiographic measures. Participants were followed up until December 2016. Cox proportional hazards models were used to assess the association of Aβ levels with incident HF. Models were adjusted for cardiovascular risk factors.

RESULTS

A per 1-SD increase in log-transformed plasma Aβ40 was associated with a 0.39% (95% CI: -0.68 to -0.10) lower left ventricular ejection fraction and a 0.70 g/m² (95% CI: 0.06-1.34) larger left ventricular mass indexed by body surface area. Aβ42 was not significantly associated with echocardiographic measures cross-sectionally. During follow-up (median: 10.2 years), 472 incident HF cases were identified. A per 1-SD increase in log-transformed Aβ40 was associated with a 32% greater risk of HF (HR: 1.32; 95% CI: 1.15-1.51), and the association was significant in men, but not in women. Higher plasma Aβ42 levels were associated with an increased risk of HF (HR: 1.12; 95% CI: 1.02-1.24), although the association was attenuated after further adjustment for concomitant Aβ40 (HR: 1.03; 95% CI: 0.92-1.16).

CONCLUSIONS

Higher levels of Aβ40 were associated with worse cardiac function and higher risk of new onset HF in the general population, in particular among men.

Study of the possible effect of sacubitril/valsartan combination versus valsartan on the cognitive function in Alzheimer's disease model in rats

Objectives: Alzheimer's disease (AD) is an irreversible, progressive neurodegenerative disorder. The proportion of elderly individuals at risk for AD and cardiovascular problems increases by raising life expectancy. The present study was designed to investigate the effect of the sacubitril/valsartan combination compared to that of valsartan alone in a rat model of AD. Methods: 72 male adult Wistar rats were divided into seven groups; control untreated rats received saline, control valsartan-treated rats received valsartan orally, control sacubitril/valsartan treated rats received sacubitril/valsartan orally, model rats received aluminum chloride i.p., model valsartan treated rats received aluminum chloride i.p. and valsartan orally and model sacubitril/valsartan treated rats received aluminum chloride i.p. and sacubitril/valsartan combination orally. All previous treatments continued on a daily basis for 6 weeks. At the second, fourth, and sixth weeks of the experiment, behavioral changes were evaluated using the Morris water maze and novel object recognition tests, and systolic blood pressure was measured. In the end, rat brain malondialdehyde and amyloid-beta 1-42 levels were measured, and the isolated hippocampus was evaluated histopathologically. Results: Valsartan improved AD symptoms in the aluminum-induced rat model, while the sacubitril/valsartan combination significantly worsened all tested parameters in both control and model rats compared with untreated and valsartan-treated animals. Conclusion: Based on the current study's findings, valsartan did not increase the risk for AD development in control rats and improved AD symptoms in a rat model, while sacubitril/valsartan combination increased the risk of AD in control rats and worsened the condition in a rat model.

New paradigm shift in the pharmacotherapy for heart failure-where are we now and where are we heading?

Over the past 30 years, accumulating evidence has shown that three main therapies including angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers, ß-blockers, and mineralocorticoid receptor antagonists are the standard treatment for patients with heart failure (HF) who exhibit reduced ejection fraction (EF). However, lessons learned from recent large-scale clinical trials have added a paradigm shift including angiotensin receptor-neprilysin inhibitor, sodium glucose co-transporter 2 inhibitor, and ivabradine. In addition, soluble guanyl cyclase stimulator and omecamtiv mecarbil are also suggested as next generation therapeutic measures for these patients. From these clinical trials, we learned some patients with preserved EF will benefit from certain agents, which has been one of the largest unmet needs over these decades. This article will review these paradigm shifts over the past 10 years and address a new therapeutic algorithm for patients with HF.

Vascular smooth muscle cell dysfunction in neurodegeneration

Vascular smooth muscle cells (VSMCs) are the key moderators of cerebrovascular dynamics in response to the brain's oxygen and nutrient demands. Crucially, VSMCs may provide a sensitive biomarker for neurodegenerative pathologies where vasculature is compromised. An increasing body of research suggests that VSMCs have remarkable plasticity and their pathophysiology may play a key role in the complex process of neurodegeneration. Furthermore, extrinsic risk factors, including environmental conditions and traumatic events can impact vascular function through changes in VSMC morphology. VSMC dysfunction can be characterised at the molecular level both preclinically, and clinically ex vivo. However the identification of VSMC dysfunction in living individuals is important to understand changes in vascular function at the onset and progression of neurological disorders such as dementia, Alzheimer's disease, and Parkinson's disease. A promising technique to identify changes in the state of cerebral smooth muscle is cerebrovascular reactivity (CVR) which reflects the intrinsic dynamic response of blood vessels in the brain to vasoactive stimuli in order to modulate regional cerebral blood flow (CBF). In this work, we review the role of VSMCs in the most common neurodegenerative disorders and identify physiological systems that may contribute to VSMC dysfunction. The evidence collected here identifies VSMC dysfunction as a strong candidate for novel therapeutics to combat the development and progression of neurodegeneration, and highlights the need for more research on the role of VSMCs and cerebrovascular dynamics in healthy and diseased states.

Recent advances in the pharmacological therapy of chronic heart failure: Evidence and guidelines

Heart failure (HF) is a clinical syndrome with symptoms and or signs caused by a structural and/or functional cardiac abnormality and associated with elevated natriuretic peptide levels and/or objective evidence of pulmonary or systemic congestion. It is classified according to left ventricular ejection fraction (LVEF): HF with reduced EF (HFrEF) with an LVEF of ≤40%, HF with mildly reduced EF (HFmrEF) with an LVEF of 41 to 49%, HF with preserved EF (HFpEF) with an LVEF of ≥50%, and HF with improved EF (HFimpEF) with a baseline LVEF of ≤40%, a ≥ 10% increase from baseline LVEF, and a second measurement of LVEF of >40%. Despite the remarkable progress in the management of HF over the past decades, its prognosis is still poor with higher rates of mortality and hospitalization due to worsening HF. Therefore, the development of novel strategies including pharmacologic therapy is needed to further improve its prognosis. Recent large-scale clinical trials have demonstrated the efficacy of newer pharmacological agents including angiotensin II receptor/neprilysin inhibitor (ARNI), sacubitril/valsartan, type 2 sodium-glucose cotransporter (SGLT2) inhibitors, dapagliflozin, empagliflozin and sotagliflozin, and soluble guanylyl cyclase (sGC) stimulator, vericiguat, and cardiac myosin activator, omecamtiv mecarbil. This review focuses the recent advances in the pharmacological agents for treatment of chronic heart failure, including their mechanisms of action, the evidence based on the clinical trials, and the guideline recommendations for their use.

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.

Newer Drugs to Reduce High Blood Pressure and Mitigate Hypertensive Target Organ Damage

PURPOSE OF REVIEW

This review aims to investigate the blood pressure (BP)-lowering effects of emerging drugs developed to treat diabetic kidney disease and heart failure (HF). We summarize the potential pathophysiological mechanisms responsible for mitigating hypertensive target organ damage and evaluating the available clinical data on these newer drugs.

RECENT FINDINGS

Nonsteroidal dihydropyridine-based mineralocorticoid receptor antagonists (MRAs), dual angiotensin II receptor-neprilysin inhibitors (valsartan with sacubitril), sodium-glucose cotransporter 2 inhibitors (SGLT2i), and soluble guanylate cyclase stimulators are new classes of chemical agents that have distinct mechanisms of action and have been shown to be effective for the treatment of cardiovascular (CV) disease (CVD), HF, and type 2 diabetes mellitus (T2D). These drugs can be used either alone or in combination with other antihypertensive and CV drugs. Among these, SGLT2i and valsartan with sacubitril offer new avenues to reduce CVD mortality. SGLT2i have a mild-to-moderate effect on BP lowering with a favorable effect on CV and renal hemodynamics and have been shown to produce a significant reduction in the incidence of major adverse CVD events (as monotherapy or add-on therapy) compared with controls (placebo or non-SGLT2i treatment). Most of the participants in these studies had hypertension (HTN) at baseline and were receiving antihypertensive therapy, including renin-angiotensin system blockers. The combination of valsartan with sacubitril also lowers BP in the short term and has demonstrated a striking reduction in CVD mortality and morbidity in HF patients with a reduced left ventricular ejection fraction. If widely adopted, these novel therapeutic agents hold significant promise for reducing the public health burden posed by HTN and CVD. Based on the results of several clinical trials and considering the high prevalence of HTN and T2D, these new classes of agents have emerged as powerful therapeutic tools in managing and lowering the BP of patients with diabetic kidney disease and HF.

Current concept in the diagnosis, treatment and rehabilitation of patients with congestive heart failure

Heart failure (HF) is a major public health problem with a prevalence of 1%-2% in developed countries. The underlying pathophysiology of HF is complex and as a clinical syndrome is characterized by various symptoms and signs. HF is classified according to left ventricular ejection fraction (LVEF) and falls into three groups: LVEF ≥ 50% - HF with preserved ejection fraction (HFpEF), LVEF < 40% - HF with reduced ejection fraction (HFrEF), LVEF 40%-49% - HF with mid-range ejection fraction. Diagnosing HF is primarily a clinical approach and it is based on anamnesis, physical examination, echocardiogram, radiological findings of the heart and lungs and laboratory tests, including a specific markers of HF - brain natriuretic peptide or N-terminal pro-B-type natriuretic peptide as well as other diagnostic tests in order to elucidate possible etiologies. Updated diagnostic algorithms for HFpEF have been recommended (H2FPEF, HFA-PEFF). New therapeutic options improve clinical outcomes as well as functional status in patients with HFrEF (e.g., sodium-glucose cotransporter-2 - SGLT2 inhibitors) and such progress in treatment of HFrEF patients resulted in new working definition of the term “HF with recovered left ventricular ejection fraction”. In line with rapid development of HF treatment, cardiac rehabilitation becomes an increasingly important part of overall approach to patients with chronic HF for it has been proven that exercise training can relieve symptoms, improve exercise capacity and quality of life as well as reduce disability and hospitalization rates. We gave an overview of latest insights in HF diagnosis and treatment with special emphasize on the important role of cardiac rehabilitation in such patients.

Efficacy and Safety of LCZ696 for Short-term Management of Essential Hypertension Compared With ARBs: A Meta-analysis of Randomized Controlled Trials

ABSTRACT

Whether LCZ696 (neprilysin inhibitor + valsartan) has greater advantages of blood pressure (BP) lowering than angiotensin II type 1 receptor blockers (ARBs) is unclear. To provide more detailed information about the benefits of LCZ696, we conducted a meta-analysis to evaluate the efficacy and safety of LCZ696 for short-term management of hypertension compared with ARBs. We searched PubMed, EMBASE, the Cochrane Library, and ClinicalTrials.gov, using relevant keywords. We used a random or fixed effects model to calculate the weighted mean difference (WMD) of changes in BP and the risk ratio (RR) for BP control rates and adverse events (AEs). In this meta-analysis, 9 studies were incorporated. Compared with ARBs, LCZ696 revealed a significant reduction in mean sitting systolic BP [msSBP; WMD -4.79 mm Hg; 95% confidence interval (CI): -5.46 to -4.11 mm Hg], mean sitting diastolic BP (msDBP; WMD -2.12 mm Hg; 95% CI: -2.53 to -1.71 mm Hg), mean sitting pulse pressure (msPP; WMD -2.79 mm Hg; 95% CI: -3.52 to -2.07 mm Hg), and mean ambulatory pulse pressure (maPP; WMD -2.96 mm Hg; 95% CI: -3.35 to -2.57 mm Hg). LCZ696 had a higher BP control rate than ARBs (OR = 1.55; 95% CI: 1.39 to 1.73). There was no significant difference between LCZ696 and ARBs in the incidence of AEs (RR = 1.10; 95% CI: 0.96 to 1.25) and discontinuations because of AEs (RR = 0.97; 95% CI: 0.54 to 1.32). Overall, in short-term treatment, LCZ696 has greater advantages of antihypertensive efficacy and the safety is not inferior to ARBs. Further long-term studies are required to rule out the potential risks of beta amyloid accumulation and the potential for Alzheimer's disease.

Sacubitril/valsartan: from the PARADIGM-HF trial results to heart failure patients in internal medicine. A narrative review

Data regarding the treatment of heart failure (HF) patients derived from randomized, controlled clinical trials, which, with rare exceptions, appear to be distant from the real world of internal medicine. Many trials have been conducted in cardiology departments: however, the characteristics of patients admitted to cardiology wards are largely different from those of patients hospitalized in internal medicine wards. Recently, the PARADIGM-HF study established the efficacy of sacubitril-valsartan – the first drug of the angiotensin II receptor neprilysin inhibitor (ARNI) class - versus enalapril in increasing survival and reducing hospitalizations in a selected population of HF patients with reduced ventricular function. Although practical guidance on the use of ARNI has been published, it is not specific to HF patients admitted to internal medicine wards. In this review, we examine all available data in order to understand if the characteristics of HF patients followed in internal medicine departments hinder or contraindicate the use of sacubitril-valsartan and what indications appear more appropriate in this setting.

Do neprilysin inhibitors walk the line? Heart ameliorative but brain threatening!

Sacubitril/valsartan (Entresto™; LCZ696) is the first angiotensin receptor-neprilysin inhibitor (ARNI) drug approved by the US and EU for heart failure (HF) and especially recommended for hypertensive HF (HHF). Sacubitril inhibits the enzyme neprilysin (NEP) which produces both beneficial and adverse effects in the human body. While LCZ696 causes beneficial cardiovascular effects, it may induce memory and cognitive dysfunction, or even exacerbate Alzheimer's disease (AD). This article reviewed data reported by experimental and clinical studies that examined NEP inhibitors and their dementia-related side effects. Based on the literature, LCZ696 increases the risk of memory and cognitive dysfunctions, and clinical trials failed to show compelling evidence for LCZ696 safety for the brain. Together, it was concluded that more experimental and clinical studies with particular focus on LCZ696 side effects on β-amyloid (Aβ) degradation are needed to assess LCZ696 safety for the cognitive function, especially in case of long-term administration.

Coronavirus Disease-2019 Conundrum: RAS Blockade and Geriatric-Associated Neuropsychiatric Disorders

Coronavirus Disease 2019 (COVID-19) is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which primarily targets the human respiratory system and may lead to severe pneumonia and ultimately death. Mortality rate is particurlarly high among people beyond the sixth decade of life with cardiovascular and metabolic diseases. The discovery that the SARS-CoV-2 uses the renin-angiotensin system (RAS) component ACE2 as a receptor to invade host epithelial cells and cause organs damage resulted in a debate regarding the role of ACE inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) therapies during COVID-19 pandemic. Some authors proposed the discontinuation of ACEIs and ARBs for cardiovascular, kidney, and metabolic diseases, while expert opinions have discouraged that due to limited empirical evidence of their negative effect on COVID-19 outcomes, and that withdrawing treatment may contribute to clinical decompensation in high-risk patients. Moreover, as cardiovascular and metabolic diseases are associated with neurodegenerative and psychiatric disorders, especially among older adults, a critical appraisal of the potential positive effects of ACEIs and ARBs is highly needed. Herein, we aim to discuss the conundrum of ACEIs and ARBs use in high-risk patients for COVID-19, and their potential protective role on the development and/or progression of geriatric neuropsychiatric disorders.

Myrtus communis subsp. communis improved cognitive functions in ovariectomized diabetic rats

AIM

The purpose of this study was to investigate the possible effects of Myrtus communis subsp. communis (MC) on cognitive impairment in ovariectomized diabetic rats.

MATERIAL AND METHOD

Female Sprague-Dawley rats were divided into 5 groups consisting of 15 rats each; Control (C), Diabetes (D), Ovariectomy and diabetes (OVX + D), Ovariectomy, diabetes and donepezil (OVX + D + Don), Ovariectomy, diabetes and Myrtus communis subsp. communis (OVX + D + MC). Blood glucose measurements were made at the beginning and end of the experiments. The animals underwent the novel object recognition test (NORT) and their performance was evaluated. In hippocampal tissues; amyloid beta (Aβ) and neprilysin levels, acetylcholinesterase (AChE), and choline acetyltransferase (ChAT) activities, polysialylated neural cell adhesion molecule (PSA-NCAM), α7 subunit of neuronal nicotinic acetylcholine receptor (α7-nAChR) and brain derived neurotrophic factor (BDNF) gene expressions were examined.

RESULTS

Animals with ovariectomy and diabetes showed increased levels of blood glucose, AChE activity and Aβ levels, and decreased neprilysin levels, ChAT activity, α7-nAChR, PSA-NCAM and BDNF gene expressions in parallel with a decrease in NORT performance score. On the other hand, in the MC-treated OVX + D group, there was a significant decrease observed in blood glucose levels and AChE activities while there was improvement in NORT performances and an increase in hippocampal ChAT activity, neprilysin levels, α7-nAChR, PSA-NCAM and BDNF expressions.

CONCLUSION

These results suggest that MC extract could improve cognitive and neuronal functions with its anticholinesterase and antihyperglycemic properties.

An evaluation of the fixed-dose combination sacubitril/valsartan for the treatment of arterial hypertension

INTRODUCTION

Essential hypertension is a significant risk factor for cardiovascular disease, renal disease, and mortality with increasing prevalence. Despite the availability of various antihypertensive agents, hypertension is still poorly controlled. Therefore, new chemical compounds with antihypertensive efficacy need to be developed. The dual angiotensin II receptor-neprilysin inhibitor LCZ696 is a single molecule synthesized by co-crystallization of valsartan and the neprilysin inhibitor prodrug sacubitril (1:1 molar ratio).

AREAS COVERED

This review includes an overview of hypertension and the current pharmacotherapy. The authors summarize the LCZ696 drug chemistry, pharmacodynamics, pharmacokinetics, metabolism, randomized control trials (RCTs), and safety concerns. Databases searched included PubMed, Google Scholar, Embase, and ClinicalTrials.gov.

EXPERT OPINION

LCZ696 is effective in hypertension treatment. Short-term RCTs have shown that the highest doses of LCZ696 (200 and 400 mg [q.d.]) were more effective at lowering office and ambulatory blood pressure than angiotensin II receptor blockers (ARB) alone while having a similar tolerability profile. The effects of LCZ696 on hypertensive organ damage are only sparsely investigated and so far no studies have established the impact of LCZ696 on cardiovascular event rates. Future studies should focus on the comparison of LCZ696 and combination therapies already in use such as ARB and calcium channel blockers.

Antihypertensive agents in Alzheimer's disease: beyond vascular protection

Introduction: Midlife hypertension has been consistently linked with increased risk of cognitive decline and Alzheimer's disease (AD). Observational studies and randomized trials show that the use of antihypertensive therapy is associated with a lesser incidence or prevalence of cognitive impairment and dementia. However, whether antihypertensive agents specifically target the pathological process of AD remains elusive.Areas covered: This review of literature provides an update on the clinical and preclinical arguments supporting anti-AD properties of antihypertensive drugs. The authors focused on validated all classes of antihypertensive treatments such as angiotensin-converting enzyme inhibitors (ACEi), angiotensin receptor blockers (ARB), calcium channel blockers (CCB), β-blockers, diuretics, neprilysin inhibitors, and other agents. Three main mechanisms can be advocated: action on the concurrent vascular pathology, action on the vascular component of Alzheimer's pathophysiology, and action on nonvascular targets.Expert opinion: In 2019, while there is no doubt that hypertension should be treated in primary prevention of vascular disease and in secondary prevention of stroke and mixed dementia, the place of antihypertensive agents in the secondary prevention of 'pure' AD remains an outstanding question.

Do plasma neprilysin activity and plasma neprilysin concentration predict cardiac events in chronic kidney disease patients?

Background

Since the introduction of sacubitril/valsartan in clinical cardiology, neprilysin has become a major target for heart failure treatment. Plasma neprilysin concentration has been discussed as a novel biomarker that predicts cardiac events. Natriuretic peptides may inhibit plasma neprilysin. As they accumulate in chronic kidney disease (CKD), we hypothesized that high plasma neprilysin loses its predictive role in CKD patients.

Methods

We measured plasma levels of neprilysin concentration, neprilysin activity and brain natriuretic peptide (BNP) in 542 CKD G2-G4 patients within the CARE FOR HOMe study. Patients were followed for predefined endpoints of hospitalization for acute decompensated heart failure and incident atherosclerotic cardiovascular events.

Results

During 5.1 ± 2.1 years, 63 patients had acute decompensated heart failure and 125 patients had incident atherosclerotic cardiovascular events. In both Kaplan-Meier and multivariate Cox regression analyses, high plasma BNP and low, rather than elevated, neprilysin activity predicted future hospitalization for acute decompensated heart failure; neprilysin concentration was not predictive. Furthermore, only BNP was an independent predictor of incident atherosclerotic cardiovascular events.

Conclusions

In line with experimental studies, high natriuretic peptides may inhibit neprilysin activity in CKD. Therefore, high neprilysin activity and concentrations are not predictors of adverse cardiovascular outcome in CKD patients. Thus neprilysin inhibitors should be implemented with caution in patients with advanced CKD.

Neutral Endopeptidase (Neprilysin) in Therapy and Diagnostics: Yin and Yang

Neprilysin (NEP) is a zinc-dependent metalloproteinase that exists in organisms in both transmembrane and soluble forms. NEP substrates are involved in regulating the cardiovascular and nervous systems. In this review, we discuss some of the biochemical characteristics and physiological functions of this enzyme with special emphasis on the use of NEP as a therapeutic target. The history and various physiological aspects of applying NEP inhibitors for treating heart failure and attempts to increase NEP activity when treating Alzheimer's disease using gene and cell therapies are described. Another important issue discussed is the role of NEP as a potential marker for predicting the risk of cardiovascular disease complications. The diagnostic and prognostic performance of soluble NEP in various types of heart failure is analyzed and presented. We also discuss the methods and approaches for measuring NEP activity for prognosis and diagnosis, as well as a possible new role of natriuretic peptides (NEP substrates) in cardiovascular diagnostics.

Therapeutic Progress and Knowledge Basis on the Natriuretic Peptide System in Heart Failure

Notwithstanding substantial improvements in diagnosis and treatment, Heart Failure (HF) remains a major disease burden with high prevalence and poor outcomes worldwide. Natriuretic Peptides (NPs) modulate whole cardiovascular system and exhibit multiple cardio-protective effects, including the counteraction of the Renin-Angiotensin-Aldosterone System (RAAS) and Sympathetic Nervous System (SNS), promotion of vasodilatation and natriuresis, and inhibition of hypertrophy and fibrosis. Novel pharmacological therapies based on NPs may achieve a valuable shift in managing patients with HF from inhibiting RAAS and SNS to a reversal of neurohormonal imbalance. Enhancing NP bioavailability through exogenous NP administration and inhibiting Neutral Endopeptidase (NEP) denotes valuable therapeutic strategies for HF. On the one hand, NEP-resistant NPs may be more specific as therapeutic choices in patients with HF. On the other hand, NEP Inhibitors (NEPIs) combined with RAAS inhibitors have proved to exert beneficial effects and reduce adverse events in patients with HF. Highly effective and potentially safe Angiotensin Receptor Blocker Neprilysin Inhibitors (ARNIs) have been developed after the failure of NEPIs and Vasopeptidase Inhibitors (VPIs) due to lacking efficacy and safety. Therapeutic progress and knowledge basis on the NP system in HF are summarized in the current review.

Sacubitril/valsartan: from a large clinical trial to clinical practice

: The Prospective Comparison of Angiotensin Receptor Antagonist and Neprilysin Inhibitor with Angiotensin-Converting Enzyme Inhibitor to Determine Impact on Global Mortality and Morbidity in Heart Failure Trial (PARADIGM-HF) has shown a reduction in the risk of death and heart failure hospitalizations with sacubitril/valsartan, compared with enalapril, in patients with heart failure and reduced ejection fraction. Guidelines now recommend the substitution of angiotensin-converting enzyme inhibitors or AT1 blockers with sacubitril/valsartan in patients with heart failure and reduced ejection fraction. The aim of this review is to discuss factors that may have an impact on the implementation of these guidelines into clinical practice. The main limitation is that, based on the inclusion criteria of PARADIGM-HF, sacubitril/valsartan is not indicated in patients with heart failure and preserved ejection fraction, although they may be the majority of the patients with heart failure. The trial enrolled ambulatory patients and thus start of sacubitril/valsartan is not indicated in those hospitalized for heart failure. A drug's tolerability may be limited by hypotension with, however, a lower rate of renal dysfunction, compared with enalapril. The cost of the new treatment is also an issue. Similarly to what occurred when other neurohormonal antagonists have been introduced in clinical practice, increased awareness of poor heart failure outcomes and better patients' management programs may be of utmost importance for the implementation of this new agent.

Sacubitril/Valsartan: From Clinical Trials to Real-world Experience

PURPOSE OF REVIEW

Compared to enalapril, use of angiotensin-receptor blocker and neprilysin inhibitor sacubitril/valsartan to treat patients with heart failure and reduced ejection fraction (HFrEF) is associated with substantial reductions in both cardiovascular mortality and heart failure progression. The purpose of this review is to discuss the real-world experience of sacubitril/valsartan.

RECENT FINDINGS

In the years following the publication of the landmark PARADIGM-HF trial in 2014 and its subsequent FDA approval, a growing evidence base supports the safety and efficacy of sacubitril/valsartan in a broad spectrum of patients with HFrEF. Updated clinical practice guidelines have embraced the use of sacubitril/valsartan in preference to ACE inhibitors or ARBs in selected patients. In this review, we highlight the clinical trials that led to these key updates to clinical guidelines, offer practical strategies for patient selection and utilization in clinical practice, and identify important areas of uncertainty that require future research.

Augmentation of glucagon-like peptide-1 receptor signalling by neprilysin inhibition: potential implications for patients with heart failure

Augmentation of glucagon-like peptide-1 (GLP-1) receptor signalling is an established approach to the treatment of type 2 diabetes. However, endogenous GLP-1 and long-acting GLP-1 receptor analogues are degraded not only by dipeptidyl peptidase-4, but also by neprilysin. This observation raises the possibilities that endogenous GLP-1 contributes to the clinical effects of neprilysin inhibition and that patients concurrently treated with sacubitril/valsartan and incretin-based drugs may experience important drug-drug interactions. Specifically, potentiation of GLP-1 receptor signalling may underlie the antihyperglycaemic actions of sacubitril/valsartan. Neprilysin inhibitors may also be able to augment the effects of long-acting GLP-1 analogues to increase heart rate and myocardial cyclic AMP, and thus, potentiate these deleterious actions; if so, concomitant treatment with GLP-1 receptor agonists may limit the efficacy of neprilysin inhibitors in patients with both heart failure and diabetes. For patients not concurrently treated with GLP-1 analogues, the action of neprilysin to enhance the effects of GLP-1 may be particularly relevant in the brain, where augmentation of GLP-1 and other endogenous peptides may act to inhibit amyloid-induced neuroinflammation and cytotoxicity and improve memory formation and executive functioning. Experimentally, neprilysin inhibitors may also potentiate the effects of endogenous GLP-1 and GLP-1 receptor agonists on blood vessels and the kidney. The role of neprilysin in the metabolism of endogenous GLP-1 and long-acting GLP-1 analogues points to a range of potential pathophysiological effects that may be clinically relevant to patients with heart failure, with or without diabetes.

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.

Is Entresto good for the brain?

The main stay pharmacotherapy for heart failure (HF) is targeted towards rennin-angiotensin-aldosterone (RAAS) and neprilysin pathways (NP). Both therapeutic strategies decreases morbidity and mortality but also carry considerable adverse effects. This review of the literature highlights the new generation of HF drug, sacubitril-valsartan (SV), trade name Entresto (researched as LCZ696, Novartis) which simultaneously blocks RAAS and NP. This dual action of angiotensin receptors blocker and neprilysin inhibitor (NPi) has improved HF prognosis and it is an evolution in the management of HF. Although the initial follow-up of patients treated with SV has yielded promising results, there are concerns regarding potential side effects especially an increase in the risk of Alzheimer’s disease (AD) and young onset of AD. NPi interferes with the breakdown and clearing of beta-amyloid peptides, the plaques seen in AD, raising concern for AD in SV patients. On the other hand, hypertension and cardiovascular diseases are established risk factors for AD which can be decreased by SV therapy. It is therefore essential that SV treated patients are followed up over an extended period of time to detect any adverse cognitive changes.

Importance of endogenous compensatory vasoactive peptides in broadening the effects of inhibitors of the renin-angiotensin system for the treatment of heart failure

The magnitude of the clinical benefits produced by inhibitors of the renin-angiotensin system in heart failure has been modest, possibly because of the ability of renin-angiotensin activity to escape from suppression during long-term treatment. Efforts to intensify pharmacological blockade by use of dual inhibitors that interfere with the renin-angiotensin system at multiple sites have not yielded consistent incremental clinical benefits, but have been associated with serious adverse reactions. By contrast, potentiation of endogenous compensatory vasoactive peptides can act to enhance the survival effects of inhibitors of the renin-angiotensin system, as evidenced by trials that have compared angiotensin-converting enzyme inhibitors with drugs that inhibit both the renin-angiotensin system and neprilysin. Several endogenous vasoactive peptides act as adaptive mechanisms, and their augmentation could help to broaden the benefits of renin-angiotensin system inhibitors for patients with heart failure.

Current and emerging pharmacologic options for the management of patients with chronic and acute decompensated heart failure

INTRODUCTION

For many years heart failure (HF) was known as a fatal disease with an ominous prognosis. In the last decades better understanding of the pathophysiological mechanisms underlying HF has resulted in major breakthrough in the management and improvement in the natural history of this clinical syndrome. Areas covered: The review is focused on current and upcoming pharmacological therapies in patients with chronic and acute HF, starting with brief overview of drugs which improve the outcomes in patients with chronic HF with reduced ejection fraction (EF) including neurohormonal antagonists, angiotensin receptor neprilysin inhibitor and If- channel inhibitor, then presenting the summary of symptomatic treatment, the pharmacotherapy in chronic HF with preserved and mid-range EF and in acute HF. Finally, we report the emerging pharmacologic options and ongoing clinical trials and future directions in pharmacotherapy. Expert commentary: The guidelines-recommended therapies in HF with reduced EF need to be widely implemented into the everyday clinical practice. Better clinical characterization of HF with preserved, mid-range EF and acute HF, with better understanding of the underlying pathophysiological mechanisms may ultimately result in a development of effective strategies improving ominous outcomes in these patients.

Limitations of Sacubitril/Valsartan in the Management of Heart Failure

BACKGROUND

The PARADIGM-HF (Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and morbidity in Heart Failure) trial was a double-blind trial that randomized 8442 patients with heart failure (HF) with reduced ejection fraction (HFrEF) to receive twice daily dosing of either 200 mg of LCZ696 or 10 mg of enalapril in addition to standard medical therapy for HF.

AREAS OF UNCERTAINTY

Limitations of this trial include (1) sacubitril has not been tested by itself in the treatment of HFrEF; (2) the maximum recommended dose of valsartan for the treatment of HFrEF was used in this trial, but the maximum recommended dose of enalapril for the treatment of HFrEF was not used; (3) a run-in phase was used in this trial to test the tolerability of LCZ696, and patients who had adverse effects in this period were excluded from randomization; (4) the percent of blacks enrolled in this trial was only 5%; (5) LCZ696 caused a 14% incidence of hypotension; (6) neprilysin inhibition might favor the development of Alzheimer dementia, which was not assessed in the PARADIGM-HF trial; (7) patients with severe symptomatic HF were underrepresented in this trial; (8) major exclusions from this trial included an acute coronary event in the last 3 months, severe pulmonary disease, hepatic impairment, and an estimated glomerular filtration rate <30 mL per minute per 1.73 m.

DATA SOURCES

Review of the PARADIGM-HF trial.

RESULTS

At 27-month follow-up, the PARADIGM-HF trial showed that compared with enalapril, LCZ696 reduced the composite of cardiovascular death or hospitalization for HF 20% (absolute risk reduction 4.7%, P < 0.001).

CONCLUSIONS

The numerous limitations discussed under the areas of uncertainty should be considered when prescribing LCZ696 for the treatment of HFrEF.

The Effects of LCZ696 in Patients With Hypertension Compared With Angiotensin Receptor Blockers

LCZ696, a first-in-class angiotensin receptor neprilysin inhibitor, has been demonstrated to have greater advantages in the treatment of heart failure compared with angiotensin-converting enzyme inhibitors, enalapril, or angiotensin receptor blockers (ARBs). However, studies that compared the efficacy and safety of LCZ696 against valsartan in patients with hypertension are limited. To provide further evidence for the benefits of LCZ696 and to make this assessment, a meta-analysis of randomized controlled trials (RCTs) was performed. The Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE, MEDLINE, PubMed, and ClinicalTrials.gov were searched for RCTs. Twelve studies involving 3816 patients were eligible for inclusion. Seven studies compared LCZ696 with valsartan, and 5 studies compared LCZ696 with olmesartan. LCZ696 showed a significantly greater reduction in systolic blood pressure (BP; mean difference [MD] = −5.43 mm Hg; 95% confidence interval [CI]: −6.36 to −4.49 mm Hg; P < .001), diastolic BP (MD = −2.34 mm Hg; 95% CI: −2.67 to −2.01 mm Hg; P < .001), 24-hour ambulatory systolic BP (MD = −3.57 mm Hg, 95% CI: −4.29 to −2.85 mm Hg; P < .001), and 24-hour ambulatory diastolic BP (MD = −1.32 mm Hg, 95% CI: −1.77 to −0.78 mm Hg; P < .001) from the baseline than ARBs. LCZ696 was more effective in reducing BP (odds ratio [OR] = 5.34; 95% CI: 4.49-6.36; P < .01) and had a higher rate of BP control compared with ARBs (OR = 1.52; 95% CI: 1.37-1.69; P < .01). LCZ696 had no difference in the incidence of adverse events (OR = 1.05; 95% CI: 0.94-1.18; P = .38) or serious adverse events (OR = 0.80; 95% CI: 0.51-1.24; P = .31) compared to ARBs. This meta-analysis revealed that LCZ696 has a greater antihypertensive efficacy and an equal tolerability profile.

Angiotensin receptor neprilysin inhibitor LCZ696: pharmacology, pharmacokinetics and clinical development

Heart failure still has a significant disease burden with poor outcomes worldwide despite advances in therapy. The standard therapies have been focused on blockade of renin–angiotensin–aldosterone system with angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and mineralocorticoid antagonists and the sympathetic nervous system with β-blockers. The natriuretic peptide system is a potential counter-regulatory system that promotes vasodilatation and natriuresis. Angiotensin receptor neprilysin inhibitors are a new class drug capable of blocking the renin–angiotensin–aldosterone system and enhancing the natriuretic peptide system to improve neurohormonal balance. The success of the PARADIGM-HF trial with LCZ696 and its approval for heart failure treatment is likely to generate a paradigm shift. This review summarises the current knowledge of LCZ696 with a focus on pharmacology, pharmacokinetics and pharmacodynamics, mechanisms of action, clinical efficacy and safety.

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.

Biochemistry, Therapeutics, and Biomarker Implications of Neprilysin in Cardiorenal Disease

BACKGROUND

Neprilysin (NEP) is a membrane-bound neutral endopeptidase that degrades a variety of bioactive peptides. The substrates include natriuretic peptides (NPs), which are important regulating mediators for cardiovascular and renal biology. Inhibition of NEP activity and exogenous NP administration thus have emerged as potential therapeutic strategies for treating cardiorenal diseases. More recently, B-type natriuretic peptide (BNP) or N-terminal-proBNP (NT-proBNP), 3'-5' cyclic guanosine monophosphate (cGMP), and soluble NEP as biomarkers have also been investigated in heart failure (HF) trials and their predictive value are beginning to be recognized.

CONTENT

The biological functions of NEP and NPs are discussed. Enhancing NPs through NEP inhibition combined with renin-angiotensin-aldosterone system (RAAS) antagonism has proved to be successful in HF treatment, although future surveillance studies will be required. Direct NP enhancement through peptide delivery may have fewer potentially hazardous effects compared to NEP inhibition. Strategies of combined inhibition on NEP with other cardiorenal pathophysiological pathways are promising. Finally, monitoring BNP/NT-proBNP/cGMP concentrations during NEP inhibition treatment may provide supplemental benefits to conventional biomarkers, and the identification of soluble NEP as a novel biomarker for HF needs further investigation.

SUMMARY

In this review, the biology of NEP is summarized, with a focus on NP regulation. The degradation of NPs by NEP provides the rationale for NEP inhibition as a strategy for cardiorenal disease treatment. We also describe the current therapeutic strategies of NEP inhibition and NP therapeutics in cardiorenal diseases. Moreover, the discovery of its circulating form, soluble NEP, as a biomarker is also discussed.

Neprilysin inhibition: A brief review of past pharmacological strategies for heart failure treatment and future directions

Heart failure (HF) is a manifestation of aberrant vascular responses and remains a public health concern with a worldwide prevalence of around 23 million and a 5-year mortality numerically equivalent to many cancers. Over the last two decades, mortality from HF reached a plateau with current pharmaceutical agents and mechanical cardiac support. In the last several years, various "novel" pharmaceutical agents have been tested in clinical trials and ultimately met with disappointment, showing only incremental benefit in the treatment of HF. Designing a HF drug with enhanced efficacy over existing agents seemed like a Sisyphean task. Yet again, pharmaceutical chemists have demonstrated their prowess in lateral thinking by developing a vasoactive agent which is a co-crystallized compound of valsartan and sacubitril in a one-to-one molar ratio; the former molecule belongs to a family of agents that are the current standard of care for HF and the latter molecule is a novel agent which inhibits neprilysin - a neutral endopeptidase found in human plasma which alters neurohumoral responses. In July of 2015, a drug which is a combination of valsartan and sacubitril was formally licensed by the United States Food and Drug Administration for the treatment of HF. This review describes the evolution of HF medications focusing on rational drug design with the first HF medication, the beta-adrenergic receptor antagonist. We then discuss the biochemical and physiological properties of sacubitril/valsartan which likely lead to its dramatic ability to ameliorate HF mortality.

Kicking the tyres of a heart failure trial: physician response to the approval of sacubitril/valsartan in the USA

Angiotensin receptor-neprilysin inhibition has been shown to be superior to target doses of an ACE inhibitor in reducing the risk of cardiovascular death and clinical disease progression in patients with chronic heart failure and a reduced EF. Nevertheless, although sacubitril/valsartan has been available in the USA for a year, uptake of the drug by practitioners has been slow, in part because of misconceptions about the pivotal trial that demonstrated its efficacy in heart failure (PARADIGM-HF). This review addresses questions that have been raised in the USA about the design of the trial as well as the patients who were studied, the replicability and applicability of the results, and the safety of neprilysin inhibition. The totality of evidence indicates that the PARADIGM-HF trial used an appropriate comparator; enrolled patients typical of those seen in the community with mild to moderate symptoms; yielded highly persuasive and replicable results; and demonstrated benefits that are applicable to patients taking subtarget doses of ACE inhibitors and ARBs. Regulatory review in the USA concluded that the established advantages of sacubitril/valsartan on cardiovascular death and disease progression outweighed hypothetical uncertainties about the long-term effects of neprilysin inhibition in patients who might not have survived without the drug. Accordingly, both the new US and European Society of Cardiology heart failure guidelines recommend sacubitril/valsartan as the preferred approach to inhibiting the renin-angiotensin system in patients with chronic heart failure who are currently receiving an ACE inhibitor or ARB.