Inhibitors of Aldosterone Synthase

Identification of sulfonylpyrimidines as novel selective aldosterone synthase (CYP11B2) inhibitors

4-[(5-[2-Methyl-5-(methylsulfonyl)pentan-2-yl]sulfonylpyrimidin-4-yl)amino]benzonitrile 2 was identified as a novel potent aldosterone synthase inhibitor. Compound 2 was found to inhibit human CYP11B2 in the nanomolar range, and showed an aldosterone-lowering effect in a furosemide-treated cynomolgus monkey model. Although human CYP11B2 has the high homology sequence with human CYP11B1, compound 2 showed more than 80 times higher selectivity over human CYP11B1 in vitro.

Angiotensin receptor blocker-neprilysin inhibitor for heart failure with reduced ejection fraction

Heart failure with reduced ejection fraction (HFrEF) is a clinical syndrome characterized by volume overload, impaired exercise capacity, and recurrent hospital admissions. A major contributor to the pathophysiology and clinical presentation of heart failure is the activation of the renin-angiotensin-aldosterone system (RAAS). Normally, RAAS is responsible for the homeostatic regulation of blood pressure, extracellular fluid volume, and serum sodium concentration. In HFrEF, RAAS gets chronically activated in response to decreased cardiac output, further aggravating the congestion and cardiotoxic effects. Hence, inhibition of RAAS is a major approach in the pharmacologic treatment of those patients. The most recently introduced RAAS antagonizing medication class is angiotensin receptor blocker/ neprilysin inhibitor (ARNI). In this paper, we discuss ARNIs' superiority over traditional RAAS antagonizing agents in reducing heart failure hospitalization and mortality. We also tease out the evidence that shows ARNIs' renoprotective functions in heart failure patients including those with chronic or end stage kidney disease. We also discuss the evidence showing the added benefit resulting from combining ARNIs with a sodium-glucose cotransporter-2 (SGLT-2) inhibitor. Moreover, how ARNIs decrease the risk of arrhythmias and reverse cardiac remodeling, ultimately lowering the risk of cardiovascular death, is also discussed. We then present the positive outcome of ARNIs' use in patients with diabetes mellitus and those recovering from acute decompensated heart failure. ARNIs' side effects are also appreciated and discussed. Taken together, the provided insight and critical appraisal of the evidence justifies and supports the implementation of ARNIs in the guidelines for the treatment of HFrEF.

Mineralocorticoid receptor overactivation: targeting systemic impact with non-steroidal mineralocorticoid receptor antagonists

The overactivation of the mineralocorticoid receptor (MR) promotes pathophysiological processes related to multiple physiological systems, including the heart, vasculature, adipose tissue and kidneys. The inhibition of the MR with classical MR antagonists (MRA) has successfully improved outcomes most evidently in heart failure. However, real and perceived risk of side effects and limited tolerability associated with classical MRA have represented barriers to implementing MRA in settings where they have been already proven efficacious (heart failure with reduced ejection fraction) and studying their potential role in settings where they might be beneficial but where risk of safety events is perceived to be higher (renal disease). Novel non-steroidal MRA have distinct properties that might translate into favourable clinical effects and better safety profiles as compared with MRA currently used in clinical practice. Randomised trials have shown benefits of non-steroidal MRA in a range of clinical contexts, including diabetic kidney disease, hypertension and heart failure. This review provides an overview of the literature on the systemic impact of MR overactivation across organ systems. Moreover, we summarise the evidence from preclinical studies and clinical trials that have set the stage for a potential new paradigm of MR antagonism.

Treating Primary Aldosteronism-Induced Hypertension: Novel Approaches and Future Outlooks

Primary aldosteronism (PA) is the most common cause of secondary hypertension and is associated with increased morbidity and mortality when compared with blood pressure-matched cases of primary hypertension. Current limitations in patient care stem from delayed recognition of the condition, limited access to key diagnostic procedures, and lack of a definitive therapy option for nonsurgical candidates. However, several recent advances have the potential to address these barriers to optimal care. From a diagnostic perspective, machine-learning algorithms have shown promise in the prediction of PA subtypes, while the development of noninvasive alternatives to adrenal vein sampling (including molecular positron emission tomography imaging) has made accurate localization of functioning adrenal nodules possible. In parallel, more selective approaches to targeting the causative aldosterone-producing adrenal adenoma/nodule (APA/APN) have emerged with the advent of partial adrenalectomy or precision ablation. Additionally, the development of novel pharmacological agents may help to mitigate off-target effects of aldosterone and improve clinical efficacy and outcomes. Here, we consider how each of these innovations might change our approach to the patient with PA, to allow more tailored investigation and treatment plans, with corresponding improvement in clinical outcomes and resource utilization, for this highly prevalent disorder.

Advances in the Pathogenesis and Treatment of Resistant Hypertension

Hypertension is a prevalent chronic disease associated with an increased risk of cardiovascular (CV) premature death, and its severe form manifests as resistant hypertension (RH). The accurate prevalence of resistant hypertension is difficult to determine due to the discrepancy in data from various populations, but according to recent publications, it ranges from 6% to 18% in hypertensive patients. However, a comprehensive understanding of the pathogenesis and treatment of RH is essential. This review emphasizes the importance of identifying the causes of treatment resistance in antihypertensive therapy and highlights the utilization of appropriate diagnostic methods. We discussed innovative therapies such as autonomic neuromodulation techniques like renal denervation (RDN) and carotid baroreceptor stimulation, along with invasive interventions such as arteriovenous anastomosis as potential approaches to support patients with inadequate medical treatment and enhance outcomes in RH.

Non-Haemodynamic Mechanisms Underlying Hypertension-Associated Damage in Target Kidney Components

Arterial hypertension (AH) is a global challenge that greatly impacts cardiovascular morbidity and mortality worldwide. AH is a major risk factor for the development and progression of kidney disease. Several antihypertensive treatment options are already available to counteract the progression of kidney disease. Despite the implementation of the clinical use of renin-angiotensin aldosterone system (RAAS) inhibitors, gliflozins, endothelin receptor antagonists, and their combination, the kidney damage associated with AH is far from being resolved. Fortunately, recent studies on the molecular mechanisms of AH-induced kidney damage have identified novel potential therapeutic targets. Several pathophysiologic pathways have been shown to play a key role in AH-induced kidney damage, including inappropriate tissue activation of the RAAS and immunity system, leading to oxidative stress and inflammation. Moreover, the intracellular effects of increased uric acid and cell phenotype transition showed their link with changes in kidney structure in the early phase of AH. Emerging therapies targeting novel disease mechanisms could provide powerful approaches for hypertensive nephropathy management in the future. In this review, we would like to focus on the interactions of pathways linking the molecular consequences of AH to kidney damage, suggesting how old and new therapies could aim to protect the kidney.

Aldosterone: Renal Action and Physiological Effects

Aldosterone exerts profound effects on renal and cardiovascular physiology. In the kidney, aldosterone acts to preserve electrolyte and acid-base balance in response to changes in dietary sodium (Na+ ) or potassium (K+ ) intake. These physiological actions, principally through activation of mineralocorticoid receptors (MRs), have important effects particularly in patients with renal and cardiovascular disease as demonstrated by multiple clinical trials. Multiple factors, be they genetic, humoral, dietary, or otherwise, can play a role in influencing the rate of aldosterone synthesis and secretion from the adrenal cortex. Normally, aldosterone secretion and action respond to dietary Na+ intake. In the kidney, the distal nephron and collecting duct are the main targets of aldosterone and MR action, which stimulates Na+ absorption in part via the epithelial Na+ channel (ENaC), the principal channel responsible for the fine-tuning of Na+ balance. Our understanding of the regulatory factors that allow aldosterone, via multiple signaling pathways, to function properly clearly implicates this hormone as central to many pathophysiological effects that become dysfunctional in disease states. Numerous pathologies that affect blood pressure (BP), electrolyte balance, and overall cardiovascular health are due to abnormal secretion of aldosterone, mutations in MR, ENaC, or effectors and modulators of their action. Study of the mechanisms of these pathologies has allowed researchers and clinicians to create novel dietary and pharmacological targets to improve human health. This article covers the regulation of aldosterone synthesis and secretion, receptors, effector molecules, and signaling pathways that modulate its action in the kidney. We also consider the role of aldosterone in disease and the benefit of mineralocorticoid antagonists. © 2023 American Physiological Society. Compr Physiol 13:4409-4491, 2023.

Post-myocardial infarction fibrosis: Pathophysiology, examination, and intervention

Cardiac fibrosis plays an indispensable role in cardiac tissue homeostasis and repair after myocardial infarction (MI). The cardiac fibroblast-to-myofibroblast differentiation and extracellular matrix collagen deposition are the hallmarks of cardiac fibrosis, which are modulated by multiple signaling pathways and various types of cells in time-dependent manners. Our understanding of the development of cardiac fibrosis after MI has evolved in basic and clinical researches, and the regulation of fibrotic remodeling may facilitate novel diagnostic and therapeutic strategies, and finally improve outcomes. Here, we aim to elaborate pathophysiology, examination and intervention of cardiac fibrosis after MI.

Redox partner adrenodoxin alters cytochrome P450 11B1 ligand binding and inhibition

Human cytochrome P450 11B1 (CYP11B1) generation of the major glucocorticoid cortisol requires two electrons delivered sequentially by the iron‑sulfur protein adrenodoxin. While the expected adrenodoxin binding site is on the opposite side of the heme and 15-20 Å away, evidence is provided that adrenodoxin allosterically impacts CYP11B1 ligand binding and catalysis. The presence of adrenodoxin both decreases the dissociation constant (Kd) for substrate binding and increases the proportion of substrate that is bound at saturation. Adrenodoxin additionally decreases the Michaelis-Menten constant for the native substrate. Similar studies with several inhibitors also demonstrate the ability of adrenodoxin to modulate inhibition (IC50 values). Somewhat similar allosterism has recently been observed for the closely related CYP11B2/aldosterone synthase, but there are several marked differences in adrenodoxin effects on the two CYP11B enzymes. Comparison of the sequences and structures of these two CYP11B enzymes helps identify regions likely responsible for the functional differences. The allosteric effects of adrenodoxin on CYP11B enzymes underscore the importance of considering P450/redox partner interactions when evaluating new inhibitors.

The Type of Fat in the Diet Influences Regulatory Aminopeptidases of the Renin-Angiotensin System and Stress in the Hypothalamic-Pituitary-Adrenal Axis in Adult Wistar Rats

(1) Background: Prolonged feeding with a high-fat diet (HFD) acts as a stressor by activating the functions of the hypothalamic-pituitary-adrenal gland (HPA) stress axis, accompanied of hypertension by inducing the renin-angiotensin-aldosterone system. Angiotensinases enzymes are regulatory aminopeptidases of angiotensin metabolism, which together with the dipeptidyl peptidase IV (DPP-IV), pyroglutamyl- and tyrosyl-aminopeptidase (pGluAP, TyrAP), participate in cognitive, stress, metabolic and cardiovascular functions. These functions appear to be modulated by the type of fat used in the diet. (2) Methods: To analyze a possible coordinated response of aminopeptidases, their activities were simultaneously determined in the hypothalamus, adenohypophysis and adrenal gland of adult male rats fed diets enriched with monounsaturated (standard diet (S diet) supplemented with 20% virgin olive oil; VOO diet) or saturated fatty acids (diet S supplemented with 20% butter and 0.1% cholesterol; Bch diet). Aminopeptidase activities were measured by fluorimetry using 2-Naphthylamine as substrates. (3) Results: the hypothalamus did not show differences in any of the experimental diets. In the pituitary, the Bch diet stimulated the renin-angiotensin system (RAS) by increasing certain angiotensinase activities (alanyl-, arginyl- and cystinyl-aminopeptidase) with respect to the S and VOO diets. DPP-IV activity was increased with the Bch diet, and TyrAP activity decrease with the VOO diet, having both a crucial role on stress and eating behavior. In the adrenal gland, both HFDs showed an increase in angiotensinase aspartyl-aminopeptidase. The interrelation of angiotensinases activities in the tissues were depending on the type of diet. In addition, correlations were shown between angiotensinases and aminopeptidases that regulate stress and eating behavior. (4) Conclusions: Taken together, these results support that the source of fat in the diet affects several peptidases activities in the HPA axis, which could be related to alterations in RAS, stress and feeding behavior.

Nonsteroidal mineralocorticoid receptor antagonism for cardiovascular and renal disorders - New perspectives for combination therapy

During the recent 30 years, there has been a dramatic increase in knowledge about the role of aldosterone and the mineralocorticoid receptor (MR) in the pathophysiology of cardiovascular (CV) and kidney diseases. The scientific perspective on the aldosterone/MR ensemble extended from a previously renal epithelial-centered focus on sodium-potassium exchange to a broader view as systemic modulators of extracellular matrix, inflammation and fibrosis. Spironolactone was launched as the first antagonist of aldosterone 27 years before the MR was cloned. It was classified as a potassium-sparing diuretic, based on its initial clinical characterization as a diuretic and its preferred activity to compensate for the potassium loss induced by loop diuretics when used in combination. The second steroidal MR antagonist was eplerenone which was discovered at a time when the role of aldosterone and MR in cardiac fibrosis was rediscovered. The constraint of developing potentially life-threatening hyperkalaemia when used in combination with other inhibitors of the renin-angiotensin-system (RAS) in patients with reduced kidney function initiated extensive research and development activities with the goal to identify novel nonsteroidal MR antagonists with an improved benefit-risk ratio. Here we summarize major current clinical trials with MRAs in different CV and renal diseases. Addition of the nonsteroidal MRA finerenone to optimal RAS blockade recently reduced CV and kidney outcomes in two large phase III trials in patients with chronic kidney disease (CKD) and type 2 diabetes (T2D). We provide an outlook on further opportunities for combination therapy of nonsteroidal MRA finerenone with RAS inhibitors and sodium-glucose cotransporter-2 inhibitors (SGLT2i).

A patent review of aldosterone synthase inhibitors (2014-present)

INTRODUCTION

Aldosterone synthase (AS) is a key enzyme involved in the final three rate-limiting steps of the biosynthesis pathway of aldosterone, and its inhibition has been considered as an effective strategy to treat hypertension, heart failure, and related cardio-metabolic diseases.

AREA COVERED

This review provides an update on the discovery and development of aldosterone synthase inhibitors by means of patents published between January 2014 and March 2021. The molecules are classified by pharmaceutical company with progress that has been made in clinical trials being highlighted.

EXPERT OPINION

Mineralocorticoid receptor antagonists (MRAs) and aldosterone synthase inhibitors (ASI) represent two of the main approaches for the blockade of aldosterone. Clinical success, as well as foreseen side effects of steroidal MRAs, prompted the discovery and development of ASI. Since the observation of decreased cortisol levels in clinical trials for LCI699, subsequent efforts have been largely focused on improving its selectivity over hCYP11B1. Candidates with improved potency and selectivity are under investigation across a wide range of indications. Whether ASI will provide an additional therapeutic advantage over current safe and selective non-steroidal MRAs is highly anticipated.

Development of [18F]AldoView as the First Highly Selective Aldosterone Synthase PET Tracer for Imaging of Primary Hyperaldosteronism

The purpose of this study was to synthesize a fluorine-18 labeled, highly selective aldosterone synthase (hCYP11B2) inhibitor, [¹⁸F]AldoView, and to assess its potential for the detection of aldosterone-producing adenomas (APAs) with positron emission tomography in patients with primary hyperaldosteronism (PHA). Using dibenzothiophene sulfonium salt chemistry, [¹⁸F]AldoView was obtained in high radiochemical yield in one step from [¹⁸F]fluoride. In mice, the tracer showed a favorable pharmacokinetic profile, including rapid distribution and clearance. Imaging in the adrenal tissue from patients with PHA revealed diffuse binding patterns in the adrenal cortex, avid binding in some adenomas, and "hot spots" consistent with aldosterone-producing cell clusters. The binding pattern was in good visual agreement with the antibody staining of hCYP11B2 and distinguished areas with normal and excessive hCYP11B2 expression. Taken together, [¹⁸F]AldoView is a promising tracer for the detection of APAs in patients with PHA.

Mitigating risk of aldosterone in diabetic kidney disease

PURPOSE OF REVIEW

Diabetic kidney disease is a growing problem leading to end-stage kidney disease but also atherosclerotic cardiovascular disease and heart failure. Aldosterone is a key risk factor promoting inflammation and fibrosis causing cardio-renal failure. Current options and challenges with mitigating the risk of aldosterone are reviewed.

RECENT FINDINGS

More aggressive renin-angiotensin-aldosterone system (RAAS) blockade can be maintained in individuals with hyperkalemia if new potassium binders are added. Aldosterone synthase inhibitors may lower aldosterone without causing hyperkalemia. Novel nonsteroidal mineralocorticoid receptor antagonists (MRA) are able to lower proteinuria and markers of heart failure, with limited potassium problems and without renal impairment. Ongoing clinical trials are evaluating the safety and potential benefits of nonsteroidal MRAs on progression of renal disease and development of cardiovascular outcomes in type 2 diabetes and kidney disease.

SUMMARY

Aldosterone is an important driver of inflammation and fibrosis leading to renal and cardiovascular complications. MRA lower albuminuria but data showing prevention of end-stage kidney disease are lacking. Side effects including hyperkalemia have previously prevented long-term studies in diabetic kidney disease but new treatment strategies with potassium binders, aldosterone synthase inhibitors and nonsteroidal MRA have been developed for clinical testing.

The role of aldosterone inhibitors in cardiac ischemia-reperfusion injury

Myocardial ischaemia-reperfusion (I/R) injury is a well-known term for exacerbation of cellular destruction and dysfunction after the restoration of blood flow to a previously ischaemic heart. A vast number of studies that have demonstrated that the role of mineralocorticoids in cardiovascular diseases is based on the use of pharmacological mineralocorticoid receptor (MR) antagonists. This review paper aimed to summarize current knowledge on the effects of MR antagonists on myocardial I/R injury as well as postinfarction remodeling. Animal models, predominantly the Langendorff technique and left anterior descending coronary artery occlusion, have confirmed the potency of MR antagonists as preconditioning and postconditioning agents in limiting infarct size and postinfarction remodeling. Several preclinical studies in rodents have established and proved possible mechanisms of cardioprotection by MR antagonists, such as reduction of oxidative stress, reduction of inflammation, and apoptosis, therefore limiting the infarct zone. However, the results of some clinical trials are inconsistent, since they reported no benefit of MR antagonists in acute myocardial infarction. Due to this, further studies and the results of ongoing clinical trials regarding MR antagonist administration in patients with acute myocardial infarction are being awaited with great interest.