The With-No-Lysine (K) (WNK) kinases play a critical role in blood pressure regulation and body fluid and electrolyte homeostasis. Herein, we introduce the first orally bioavailable pan-WNK-kinase inhibitor, WNK463, that exploits unique structural features of the WNK kinases for both affinity and kinase selectivity. In rodent models of hypertension, WNK463 affects blood pressure and body fluid and electro-lyte homeostasis, consistent with WNK-kinase-associated physiology and pathophysiology.

BACKGROUND AND PURPOSEPreviously, a systems pharmacology model was developed characterizing drug effects on the interrelationship between mean arterial pressure (MAP), cardiac output (CO) and total peripheral resistance (TPR). The present investigation aims to (i) extend the previously developed model by parsing CO into heart rate (HR) and stroke volume (SV) and (ii) evaluate if the mechanism of action (MoA) of new compounds can be elucidated using only HR and MAP measurements. EXPERIMENTAL APPROACHCardiovascular effects of eight drugs with diverse MoAs (amiloride, amlodipine, atropine, enalapril, fasudil, hydrochlorothiazide, prazosin and propranolol) were characterized in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats following single administrations of a range of doses. Rats were instrumented with ascending aortic flow probes and aortic catheters/radiotransmitters for continuous recording of MAP, HR and CO throughout the experiments. Data were analysed in conjunction with independent information on the time course of the drug concentration following a mechanism-based pharmacokinetic-pharmacodynamic modelling approach. KEY RESULTSThe extended model, which quantified changes in TPR, HR and SV with negative feedback through MAP, adequately described the cardiovascular effects of the drugs while accounting for circadian variations and handling effects. CONCLUSIONS AND IMPLICATIONSA systems pharmacology model characterizing the interrelationship between MAP, CO, HR, SV and TPR was obtained in hypertensive and normotensive rats. This extended model can quantify dynamic changes in the CVS and elucidate the MoA for novel compounds, with one site of action, using only HR and MAP measurements. Whether the model can be applied for compounds with a more complex MoA remains to be established. Abbreviations amp, amplitude; BSL_CO, baseline value of cardiac output; BSL_HR, baseline value of heart rate; BSL_MAP, baseline value of mean arterial pressure; BSL_SV, baseline value of stroke volume; BSL_TPR, baseline value of total peripheral resistance; C, drug concentration in plasma; CO, cardiac output; Emax, maximum effect; FB, negative feedback of mean arterial pressure; FB0, feedback of a typical subject; FB0_MAP, exponent of the power relationship between FB and the individual BSL_MAP; HCTZ, hydrochlorothiazide; hor, horizontal displacement; HR, heart rate; Kin_HR, zero-order production rate constant of HR; Kin_SV, zero-order production rate constant of stroke volume; Kin_TPR, zero-order production rate constant of total peripheral resistance; kout_HR, first-order dissipation rate constant of HR; kout_SV, first-order dissipation rate constant of stroke volume; kout_TPR, first-order dissipation rate constant of total peripheral resistance; LVFT, left ventricular filling time; MAP, mean arterial pressure; MoA, mechanisms of action; MVOF, minimum value of the objective function;

BACKGROUND AND PURPOSEThe homeostatic control of arterial BP is well understood with changes in BP resulting from changes in cardiac output (CO) and/or total peripheral resistance (TPR). A mechanism-based and quantitative analysis of drug effects on this interrelationship could provide a basis for the prediction of drug effects on BP. Hence, we aimed to develop a mechanism-based pharmacokinetic-pharmacodynamic (PKPD) model in rats that could be used to characterize the effects of cardiovascular drugs with different mechanisms of action (MoA) on the interrelationship between BP, CO and TPR. EXPERIMENTAL APPROACHThe cardiovascular effects of six drugs with diverse MoA, (amlodipine, fasudil, enalapril, propranolol, hydrochlorothiazide and prazosin) were characterized in spontaneously hypertensive rats. The rats were chronically instrumented with ascending aortic flow probes and/or aortic catheters/radiotransmitters for continuous recording of CO and/or BP. Data were analysed in conjunction with independent information on the time course of drug concentration using a mechanism-based PKPD modelling approach. KEY RESULTSBy simultaneous analysis of the effects of six different compounds, the dynamics of the interrelationship between BP, CO and TPR were quantified. System-specific parameters could be distinguished from drug-specific parameters indicating that the model developed is drug-independent. CONCLUSIONS AND IMPLICATIONSA system-specific model characterizing the interrelationship between BP, CO and TPR was obtained, which can be used to quantify and predict the cardiovascular effects of a drug and to elucidate the MoA for novel compounds. Ultimately, the proposed PKPD model could be used to predict the effects of a particular drug on BP in humans based on preclinical data. AbbreviationsAmp, amplitude; BSL_CO, baseline value of cardiac output; BSL_MAP, baseline value of MAP; BSL_TPR, baseline value of total peripheral resistance; C, drug concentration in plasma; CO, cardiac output; Emax, maximum effect; FB1, negative feedback of mean arterial pressure on cardiac output; FB2, negative feedback of mean arterial pressure on total peripheral resistance; HCTZ, hydrochlorothiazide; HOR, horizontal displacement; IIV, inter-individual variability; Kin_CO, zero-order production rate constant of cardiac output; Kin_TPR, zero-order production rate constant of total peripheral resistance; kout_CO, first-order dissipation rate constant of cardiac output; kout_TPR, first-order dissipation rate constant of total peripheral resistance; MAP, mean arterial pressure; MC, methylcellulose; MoA, mechanisms of action; MVOF, minimum value of the objective function;

Aldosterone synthase (CYP11B2) inhibitors (ASIs) represent an attractive therapeutic approach for mitigating the untoward effects of aldosterone. We characterized the pharmacokinetic/ pharmacodynamic relationships of a prototypical ASI, (ϩ)-(5R)-4-(5,6,7,8-tetrahydroimidazo[1,5-a]pyridin-5-yl]benzonitrile hydrochloride (CGS020286A, FAD286, FAD) and compared these profiles to those of the 11␤-hydroxylase inhibitor metyrapone (MET) in two rodent models of secondary hyperaldosteronism and corticosteronism. In chronically cannulated Sprague-Dawley rats, angiotensin II (ANG II) (300 ng/kg bolus ϩ 100 ng/kg/ min infusion) or adrenocorticotropin (100 ng/kg ϩ 30 ng/kg/ min) acutely elevated plasma aldosterone concentration (PAC) from ϳ0.26 nM to a sustained level of ϳ2.5 nM for 9 h. Adrenocorticotropin but not ANG II elicited a sustained increase in plasma corticosterone concentration (PCC) from ϳ300 to ϳ1340 nM. After 1 h of Ang II or adrenocorticotropin infusion, FAD (0.01-100 mg/kg p.o.) or MET (0.1-300 mg/kg p.o.) doseand drug plasma concentration-dependently reduced the elevated PACs over the ensuing 8 h. FAD was ϳ12 times more dose-potent than MET in reducing PAC but of similar or slightly greater potency on a plasma drug concentration basis. Both agents also decreased PCC in the adrenocorticotropin model at relatively higher doses and with similar dose potencies, whereas FAD was 6-fold weaker based on drug exposures. FAD was ϳ50-fold selective for reducing PAC versus PCC, whereas MET was only ϳ3-fold selective. We conclude that FAD is a potent, orally active, and relatively selective ASI in two rat models of hyperaldosteronism. MET is an order of magnitude less selective than FAD but is, nevertheless, more potent as an ASI than as an 11␤-hydroxylase inhibitor.

BackgroundAldosterone synthase inhibition provides the potential to attenuate both the mineralocorticoid receptor-dependent and independent actions of aldosterone. In vitro studies with recombinant human enzymes showed LCI699 to be a potent, reversible, competitive inhibitor of aldosterone synthase (Ki = 1.4 ± 0.2 nmol/L in humans) with relative selectivity over 11β-hydroxylase.MethodsHormonal effects of orally administered LCI699 were examined in rat and monkey in vivo models of adrenocorticotropic hormone (ACTH) and angiotensin-II-stimulated aldosterone release, and were compared with the mineralocorticoid receptor antagonist eplerenone in a randomized, placebo-controlled study conducted in 99 healthy human subjects. The effects of LCI699 and eplerenone on cardiac and renal sequelae of aldosterone excess were investigated in a double-transgenic rat (dTG rat) model overexpressing human renin and angiotensinogen.ResultsRat and monkey in vivo models of stimulated aldosterone release predicted human dose– and exposure–response relationships, but overestimated the selectivity of LCI699 in humans. In the dTG rat model, LCI699 dose-dependently blocked increases in aldosterone, prevented development of cardiac and renal functional abnormalities independent of blood pressure changes, and prolonged survival. Eplerenone prolonged survival to a similar extent, but was less effective in preventing cardiac and renal damage. In healthy human subjects, LCI699 0.5 mg selectively reduced plasma and 24 h urinary aldosterone by 49 ± 3% and 39 ± 6% respectively (Day 1, mean ± SEM; P < 0.001 vs placebo), which was associated with natriuresis and an increase in plasma renin activity. Doses of LCI699 greater than 1 mg inhibited basal and ACTH-stimulated cortisol. Eplerenone 100 mg increased plasma and 24 h urinary aldosterone while stimulating natriuresis and increasing renin activity. In contrast to eplerenone, LCI699 increased the aldosterone precursor 11-deoxycorticosterone and urinary potassium excretion.ConclusionsThese results provide new insights into the cardiac and renal effects of inhibiting aldosterone synthase in experimental models and translation of the hormonal effects to humans. Selective inhibition of aldosterone synthase appears to be a promising approach to treat diseases associated with aldosterone excess.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-014-0340-9) contains supplementary material, which is available to authorized users.

Aldosterone is a key signaling component of the renin-angiotensin-aldosterone system and as such has been shown to contribute to cardiovascular pathology such as hypertension and heart failure. Aldosterone synthase (CYP11B2) is responsible for the final three steps of aldosterone synthesis and thus is a viable therapeutic target. A series of imidazole derived inhibitors, including clinical candidate 7n, have been identified through design and structure−activity relationship studies both in vitro and in vivo. Compound 7n was also found to be a potent inhibitor of 11β-hydroxylase (CYP11B1), which is responsible for cortisol production. Inhibition of CYP11B1 is being evaluated in the clinic for potential treatment of hypercortisol diseases such as Cushing's syndrome. KEYWORDS: Inhibitor, CYP11B2, aldosterone synthase, aldosterone, hypertension, enzyme, CYP11B1, Cushing's syndrome, cortisol O ne of the primary functions of aldosterone through the mineralocorticoid receptor (MR) is to effect retention of sodium and excretion of potassium by the kidney.1 The elevation of aldosterone causes an increase in blood pressure as well as facilitating other cardiac, renal, and vascular damage. Activation of the renin-angiotensin system (RAS) induces aldosterone production. As such, MR antagonists have been used in the treatment of heart failure.2−4 While both RAS inhibitors and MR antagonists have been shown to reduce some of the pathological effects of aldosterone, there are noted drawbacks. In the case of RAS inhibition, a reduction of aldosterone is realized initially; however, this is not maintained. 5,6 Likewise, MR antagonists do not reduce the level of aldosterone, and in fact, they have been shown to induce aldosterone production.7 Thus, it was thought that there would be therapeutic benefit in directly inhibiting aldosterone production.Aldosterone is produced in the zona glomerulosa of the adrenal gland by the enzymatic action of aldosterone synthase (CYP11B2) on deoxycorticosterone. 8,9 Clinical observations suggested that the racemic aromatase (CYP19) inhibitor fadrazole affected aldosterone levels and subsequent preclinical studies demonstrated that the R-enantiomer (FAD286, Figure 1) was a potent inhibitor of CYP11B2.10 From this understanding we embarked on a program to investigate the structure−activity relationship of the FAD286 scaffold and to gain a more extensive understanding of the potential of aldosterone synthase inhibition to treat aldosterone-driven pathologies.Relatively little was known about the impact of substitution at R 1 , although we quickly realized that, as with FAD286, chirality at this point of attachment was important. The impact of altering the size of the saturated ring was not understood at the outset. Preliminary structure−activity relationships (SAR) around the phenyl ring indicated that R 2 would be a most promising site for optimization.In general the compounds from series I (n = 1), series II (n = 2), and series III (n = 3) were prepared as outlined in Scheme 1. Intermed...

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Human clinical studies conducted with LCI699 established aldosterone synthase (CYP11B2) inhibition as a promising novel mechanism to lower arterial blood pressure. However, LCI699's low CYP11B1/CYP11B2 selectivity resulted in blunting of adrenocorticotropic hormone-stimulated cortisol secretion. This property of LCI699 prompted its development in Cushing's disease, but limited more extensive clinical studies in hypertensive populations, and provided an impetus for the search for cortisol-sparing CYP11B2 inhibitors. This paper summarizes the discovery, pharmacokinetics, and pharmacodynamic data in preclinical species and human subjects of the selective CYP11B2 inhibitor 8.