The tumultuous journey of nesiritide: past, present, and future

Exploring PKG signaling as a therapeutic avenue for pressure overload, ischemia, and HFpEF

INTRODUCTION

Heart failure (HF) is a complex and heterogeneous syndrome resulting from any diastolic or systolic dysfunction of the cardiac muscle. In addition to comorbid conditions, pressure overload, and myocardial ischemia are associated with cardiac remodeling which manifests as extracellular matrix (ECM) perturbations, impaired cellular responses, and subsequent ventricular dysfunction.

AREAS COVERED

The current review discusses the main aspects of the cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway (cGMP-PKG) pathway modulators and highlights the promising outcomes of its novel pharmacological boosters.

EXPERT OPINION

Among several signaling pathways involved in the pathogenesis of pressure overload, ischemia and HF with preserved ejection fraction (HFpEF) is cGMP-PKG pathway. This pathway plays a pivotal role in the regulation of cardiac contractility, and modulation of cGMP-PKG signaling, contributing to the development of the diseases. Ventricular cardiomyocytes of HF patients and animal models are known to exhibit reduced cGMP levels and disturbed cGMP signaling including hypophosphorylation of PKG downstream targets. However, restoration of cGMP-PKG signaling improves cardiomyocyte function and promotes cardioprotective effects.

Endocrine functions of the heart: from bench to bedside

Heart has a recognized endocrine function as it produces several biologically active substances with hormonal properties. Among these hormones, the natriuretic peptide (NP) system has been extensively characterized and represents a prominent expression of the endocrine function of the heart. Over the years, knowledge about the mechanisms governing their synthesis, secretion, processing, and receptors interaction of NPs has been intensively investigated. Their main physiological endocrine and paracrine effects on cardiovascular and renal systems are mostly mediated through guanylate cyclase-A coupled receptors. The potential role of NPs in the pathophysiology of heart failure and particularly their counterbalancing action opposing the overactivation of renin-angiotensin-aldosterone and sympathetic nervous systems has been described. In addition, NPs are used today as key biomarkers in cardiovascular diseases with both diagnostic and prognostic significance. On these premises, multiple therapeutic strategies based on the biological properties of NPs have been attempted to develop new cardiovascular therapies. Apart from the introduction of the class of angiotensin receptor/neprilysin inhibitors in the current management of heart failure, novel promising molecules, including M-atrial natriuretic peptide (a novel atrial NP-based compound), have been tested for the treatment of human hypertension. The development of new drugs is currently underway, and we are probably only at the dawn of novel NPs-based therapeutic strategies. The present article also provides an updated overview of the regulation of NPs synthesis and secretion by microRNAs and epigenetics as well as interactions of cardiac hormones with other endocrine systems.

Natriuretic peptide pathways in heart failure: further therapeutic possibilities

The discovery of the heart as an endocrine organ resulted in a remarkable recognition of the natriuretic peptide system (NPS). Specifically, research has established the production of atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) from the heart, which exert pleiotropic cardiovascular, endocrine, renal, and metabolic actions via the particulate guanylyl cyclase A receptor (GC-A) and the second messenger, cGMP. C-type natriuretic peptide (CNP) is produced in the endothelium and kidney and mediates important protective auto/paracrine actions via GC-B and cGMP. These actions, in part, participate in the efficacy of sacubitril/valsartan in heart failure (HF) due to the augmentation of the NPS. Here, we will review important insights into the biology of the NPS, the role of precision medicine, and focus on the phenotypes of human genetic variants of ANP and BNP in the general population and the relevance to HF. We will also provide an update of the existence of NP deficiency states, including in HF, which provide the rationale for further therapeutics for the NPS. Finally, we will review the field of peptide engineering and the development of novel designer NPs for the treatment of HF. Notably, the recent discovery of a first-in-class small molecule GC-A enhancer, which is orally deliverable, will be highlighted. These innovative designer NPs and small molecule possess enhanced and novel properties for the treatment of HF and cardiovascular diseases.

The diuresis clinic: a new paradigm for the treatment of mild decompensated heart failure

BACKGROUND

Heart failure results in approximately 1 million hospital admissions annually in the United States and is the leading cause of 30-day readmissions.

METHODS

This study explores the impact of a diuresis clinic on heart failure outcomes and cost. Data were collected prospectively on all consecutive patients who received intravenous diuretics and multidisciplinary care in the clinic from its establishment from October 2011 to December 2012, as well as a comparison cohort of patients with heart failure who were admitted to the hospital for <48 hours. The percentage of hospitalized days was calculated for both cohorts 180 days before and 180 days after each patient's index visit.

RESULTS

In the diuresis clinic group, 106 patients (mean age, 68.2 ± 13 years; 48% were women) were treated over 328 visits (1-22 visits per person), with a mean intravenous furosemide dose of 100 mg, average urine output of 1460 ± 730 mL, and weight loss of 2.3 ± 1.8 kg. Days hospitalized decreased from 38.3 to 31.2 per 1000 patient-days after the index diuresis clinic visit (P < .01). In the comparison group, 143 patients (mean age, 69 ± 16 years; 54% were women) were admitted for <48 hours. Days hospitalized increased from 14.4 to 21.0 per 1000 patient-days after index admission (P < .01). On multivariate analysis, the diuresis clinic was associated with 3 fewer days in the hospital per 180 days per patient, with an estimated annual savings of $12,113 per patient.

CONCLUSIONS

Compared with a brief hospital stay, treatment of mild decompensated heart failure in a diuresis clinic resulted in a substantial and cost-effective decline in the rate of subsequent hospitalization.

Impaired sinoatrial node function and increased susceptibility to atrial fibrillation in mice lacking natriuretic peptide receptor C

Natriuretic peptides (NPs) are critical regulators of the cardiovascular system that are currently viewed as possible therapeutic targets for the treatment of heart disease. Recent work demonstrates potent NP effects on cardiac electrophysiology, including in the sinoatrial node (SAN) and atria. NPs elicit their effects via three NP receptors (NPR-A, NPR-B and NPR-C). Among these receptors, NPR-C is poorly understood. Accordingly, the goal of this study was to determine the effects of NPR-C ablation on cardiac structure and arrhythmogenesis. Cardiac structure and function were assessed in wild-type (NPR-C(+/+)) and NPR-C knockout (NPR-C(-/-)) mice using echocardiography, intracardiac programmed stimulation, patch clamping, high-resolution optical mapping, quantitative polymerase chain reaction and histology. These studies demonstrate that NPR-C(-/-) mice display SAN dysfunction, as indicated by a prolongation (30%) of corrected SAN recovery time, as well as an increased susceptibility to atrial fibrillation (6% in NPR-C(+/+) vs. 47% in NPR-C(-/-)). There were no differences in SAN or atrial action potential morphology in NPR-C(-/-) mice; however, increased atrial arrhythmogenesis in NPR-C(-/-) mice was associated with reductions in SAN (20%) and atrial (15%) conduction velocity, as well as increases in expression and deposition of collagen in the atrial myocardium. No differences were seen in ventricular arrhythmogenesis or fibrosis in NPR-C(-/-) mice. This study demonstrates that loss of NPR-C results in SAN dysfunction and increased susceptibility to atrial arrhythmias in association with structural remodelling and fibrosis in the atrial myocardium. These findings indicate a critical protective role for NPR-C in the heart.

Rationale and design of a randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy of B-type natriuretic peptide for the preservation of left ventricular function after anterior myocardial infarction

BACKGROUND

B-type natriuretic peptide (BNP) is a hormone with pleiotropic cardioprotective properties. Previously in our non-placebo-controlled non-blinded pilot study (BELIEVE) in human ST-segment-elevation anterior acute myocardial infarction (AMI), a 72-hour intravenous (IV) infusion of recombinant human BNP (nesiritide) at a dose of 0.006 μg kg(-1) min(-1) suppressed plasma aldosterone, reduced cardiac dilatation, and improved left ventricular (LV) ejection fraction (LVEF) at 1 month compared with baseline.

METHODS AND DESIGN

The BELIEVE II study is a phase II, randomized, double-blind, placebo-controlled, single-center clinical trial to assess the efficacy of 72-hour IV infusion of nesiritide therapy (0.006 μg kg(-1) min(-1)) in humans with first-time ST-segment-elevation anterior AMI and successful reperfusion, in preventing adverse LV remodeling and preserving LV function. A total of 60 patients will be randomized to placebo or nesiritide therapy. The primary efficacy end point is LV end-systolic and end-diastolic dimensions determined by multiple gated acquisition scan between placebo and nesiritide groups at 30 days; secondary end points include 30-day LVEF, diastolic function, infarct size, LV mass, and combined total mortality and heart failure hospitalization.

CONCLUSIONS

This will be the first randomized, double-blind, placebo-controlled clinical trial to assess the clinical efficacy of nesiritide in human ST-segment-elevation anterior AMI.

CD-NP: an innovative designer natriuretic peptide activator of particulate guanylyl cyclase receptors for cardiorenal disease

The natriuretic peptide (NP) family consists of structurally similar, although physiologically distinct, peptides that play an important role in cardiorenal homeostasis. CD-NP is a novel chimeric natriuretic peptide developed by the Mayo Clinic, in which the 15-amino acid COOH-terminus of dendroaspis NP is fused to C-type NP. CD-NP is a dual activator of NP receptors A and B, and therefore, possesses the strong antiproliferative and antifibrotic properties of C-type NP with the potent natriuretic, diuretic, and aldosterone-inhibiting properties of dendroaspis NP. CD-NP has favorable cardiorenal properties when compared to recombinant B-type NP (nesiritide), including preservation of glomerular filtration rate with minimal blood pressure-lowering effects. Thus, CD-NP has emerged as an appealing novel therapeutic strategy for heart failure. The endogenous NP system, the development rationale for CD-NP, as well as in vitro, animal, and human studies and future directions will be reviewed.

Pharmacodynamics of a novel designer natriuretic peptide, CD-NP, in a first-in-human clinical trial in healthy subjects

CD-NP is a novel chimeric natriuretic peptide (NP) consisting of the 22-amino-acid (AA) human C-type natriuretic peptide (CNP), a venodilating peptide with limited renal actions and minimal effects on blood pressure, and the 15-AA C-terminus of Dendroaspis NP (DNP). The rationale for the design of CD-NP was to enhance the renal actions of CNP, the ligand for natriuretic peptide receptor-B, but without inducing excessive hypotension. Here we report the first-in-human studies for CD-NP, which represent the first successful clinical testing of a chimeric NP demonstrating in normal human volunteers that CD-NP possesses cyclic guanosine monophosphate-activating, natriuretic, and aldosterone-suppressing properties without inducing excessive hypotension, laying the foundation for additional studies on this first-in-class new cardiovascular therapeutic in human heart failure, which are now underway worldwide.

Designer natriuretic peptides

Designer natriuretic peptides (NPs) are novel hybrid peptides that are engineered from the native NPs through addition, deletion, or substitution of amino acid(s) with a goal toward optimization of pharmacological actions while minimizing undesirable effects. In this article, selected peptides that were designed in our laboratory are reviewed, and future directions for research and development of designer NPs are discussed.

Designer natriuretic peptides

Designer natriuretic peptides (NPs) are novel hybrid peptides that are engineered from the native NPs through addition, deletion, or substitution of amino acid(s) with a goal toward optimization of pharmacological actions while minimizing undesirable effects. In this article, selected peptides that were designed in our laboratory are reviewed, and future directions for research and development of designer NPs are discussed.

Modulation of cGMP in heart failure: a new therapeutic paradigm

Heart failure (HF) is a common disease that continues to be associated with high morbidity and mortality warranting novel therapeutic strategies. Cyclic guanosine monophosphate (cGMP) is the second messenger of several important signaling pathways based on distinct guanylate cyclases (GCs) in the cardiovascular system. Both the nitric oxide/soluble GC (NO/sGC) as well as the natriuretic peptide/GC-A (NP/GC-A) systems are disordered in HF, providing a rationale for their therapeutic augmentation. Soluble GC activation with conventional nitrovasodilators has been used for more than a century but is associated with cGMP-independent actions and the development of tolerance, actions which novel NO-independent sGC activators now in clinical development lack. Activation of GC-A by administration of naturally occurring or designer natriuretic peptides is an emerging field, as is the inhibition of enzymes that degrade endogenous NPs. Finally, inhibition of cGMP-degrading phosphodiesterases, particularly phosphodiesterase 5 provides an additional strategy to augment cGMP-signaling.

Insights into natriuretic peptides in heart failure: an update

Natriuretic peptides (NPs) secreted by the heart in response to volume overload are pleiotropic molecules with vasodilating, diuretic, natriuretic, antiproliferative, and antifibrotic actions. Functioning of the NP system is altered in congestive heart failure (CHF), suggesting that support of the NP system might be beneficial in treatment of acute and chronic CHF. Several approaches alone or in combination with other pharmacologic therapies have been shown to enhance function of the NP system: direct administration of native and designer NPs, inhibition of degradation of NPs and their second messenger (cyclic guanosine monophosphate ), and stimulation of cGMP generation. Despite increasing numbers of studies using NPs in therapy of acute and chronic CHF, several controversies regarding safety, efficacy, and dosing of NPs need to be addressed. Moreover, further research is warranted to identify the stages and etiologies of CHF that may profit from NP therapy.

Nesiritide in acute decompensated heart failure: current status and future perspectives

Acute decompensated heart failure (ADHF) is a growing public health problem with high mortality and costs. ADHF often, if not usually, occurs in the setting of cardiovascular and noncardiovascular comorbidities as well as advanced age. New insights provide support for the concept of heart failure as a state of deficiency of and/or resistance to endogenous B-type natriuretic peptide. The primary goals of ADHF therapy are to relieve symptoms and optimize volume status with minimal side effects. Few therapies are proven to effectively do so. Nesiritide is a balanced vasodilator with favorable neurohumoral effects and is superior to placebo in providing rapid symptom relief and to nitroglycerin in reducing filling pressures. Recent trials confirm a lack of renal toxicity at recommended doses. An adequately powered multinational mortality trial is underway. Nesiritide represents a proven therapy for normotensive/hypertensive ADHF patients with severe symptoms at rest.