Synergistic stimulation of aldosterone production in human adrenocortical carcinoma NCI-H295R cells by endothelin-1 and angiotensin II.

Aldosterone has recently been implicated in the pathogenesis of heart failure. The purpose of the present study was to determine the effect of endothelin-1 (ET-1) and angiotensin II (Ang II), two potent vasoconstrictors that are also involved in heart failure, on aldosterone secretion by human adrenocortical carcinoma NCIH295R cells grown in 96-well plates. Ang II stimulated the production of aldosterone dose-dependently in serum-free medium, and the presence of serum drastically decreased aldosterone secretion. In contrast, ET-1-stimulated aldosterone production absolutely required serum. Under optimal conditions, ET-1 was more effective than Ang II as an aldosterone secretagogue. In a suboptimal condition of 2.5% serum, ET-1 and Ang II at 1 microM produced 63 and 76 pmol aldosterone/mg protein, respectively, while 230 pmol aldosterone/mg protein was generated upon coincubation with ET-1 and Ang II. The effect of ET-1 was inhibited dose-dependently by the selective ETA receptor antagonist BQ-123 with an IC50 of 23 nM, but the selective ETB receptor antagonist RES-701 had no effect up to 10 microM. These results suggest that ET-1 and Ang II stimulated aldosterone secretion synergistically in NCIH295R cells and that the effect of ET-1 was mediated via the ETA receptor subtype

Pharmacodynamic and pharmacokinetic characterization of the aldosterone synthase inhibitor FAD286 in two rodent models of hyperaldosteronism: comparison with the 11{beta}-hydroxylase inhibitor metyrapone

Aldosterone synthase (CYP11B2) inhibitors (ASI) represent an attractive therapeutic approach for mitigating the untoward effects of aldosterone. We characterized the pharmacokinetic/pharmacodynamic relationships of a prototypical ASI FAD286 (FAD) and compared these profiles to the "11beta-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 + 100 ng/kg/min infusion) or adrenocorticotropic hormone (ACTH, 100 ng/kg + 30 ng/kg/min) acutely elevated plasma aldosterone concentration (PAC) from ~0.26 nM to a sustained level of ~2.5 nM for 9 h. ACTH but not ANG II elicited a sustained increase in plasma corticosterone concentration (PCC) from ~300 nM to ~1340 nM. After 1 h of Ang II or ACTH infusion, FAD (0.01-100 mg/kg p.o.) or MET (0.1-300 mg/kg p.o.) dose- and drug-plasma-concentration-dependently reduced the elevated PACs over the ensuing 8 h. FAD was ~12 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 ACTH model at relatively higher doses and with similar dose potencies whereas FAD was 6-fold weaker based on drug exposures. FAD was ~50-fold selective for reducing PAC vs. PCC whereas MET was only ~3-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 11beta-hydroxylase inhibitor

Structure-Activity Relationships, Pharmacokinetics and In Vivo Activity of CYP11B2 and CYP11B1 Inhibitors

CYP11B2, the aldosterone synthase, and CYP11B1, the cortisol synthase, are two highly homologous enzymes implicated in a range of cardiovascular and metabolic diseases. We have previously reported the discovery of LCI699, a dual CYP11B2 and CYP11B1 inhibitor which has provided clinical validation for the lowering of plasma aldosterone as a viable approach to modulate blood pressure in humans, as well normalization of urinary cortisol in Cushing’s disease patients. We now report novel series of aldosterone synthase inhibitors with single-digit nanomolar cellular potency and excellent physico-chemical properties. Structure-activity relationships and optimization of their oral bioavailability are presented. An illustration of the impact of the age of pre-clinical models on pharmacokinetic properties is also highlighted. Similar biochemical potency was generally observed against for CYP11B2 and CYP11B1, although emerging structure-selectivity relationships were noted leading to more CYP11B1-selective analogs

Aldosterone synthase inhibition: cardiorenal protection in animal disease models and translation of hormonal effects to human subjects.

International audienceBackgroundAldosterone 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 (K i¿=¿1.4¿±¿0.2 nmol/L in humans) with relative selectivity over 11ß-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 (dTGR) 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 dTGR 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

Discovery and in vivo evaluation of potent dual CYP11B2 (aldosterone synthase) and CYP11B1 inhibitors

ABSTRACT: 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

Discovery of LFF269, a Cortisol-Sparing CYP11B2 Inhibitor that Lowers Aldosterone in Human Subjects

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 pharmacodynamics data in pre-clinical species and human subjects of the selective CYP11B2 inhibitor LFF269 (8)