Discovery of Triazole CYP11B2 Inhibitors with in Vivo Activity in Rhesus Monkeys

Abstract

Hit-to-lead efforts resulted in the discovery of compound 19, a potent CYP11B2 inhibitor that displays high selectivity vs related CYPs, good pharmacokinetic properties in rat and rhesus, and lead-like physical properties. In a rhesus pharmacodynamic model, compound 19 displays robust, dose-dependent aldosterone lowering efficacy, with no apparent effect on cortisol levels. KEYWORDS:Aldosterone synthase, CYP11B2, hit-to-lead, hypertension A ldosterone is a steroid hormone produced in the adrenal zona glomerulosa, and is one of several endogenous ligands that bind the mineralocorticoid receptor (MR). 1,2 Binding of aldosterone to MR yields a complex that can activate gene transcription, ultimately leading to the production of proteins such as ENaC, the epithelial sodium channel responsible for reabsorption of sodium in the kidney. Classically, this sodium reabsorption and its attendant water retention and blood volume increase were thought to drive aldosterone's known ability to increase blood pressure. However, more recent studies indicate that aldosterone raises blood pressure primarily by promoting vasoconstriction, and by acting in the CNS to increase central sympathetic drive. 3 In addition to its effects on blood pressure (BP), aldosterone is also known to produce BPindependent organ damage via inflammatory and pro-fibrotic pathways, and to play a role in insulin resistance. 4 Aldosterone synthase (CYP11B2) is a mitochondrial cytochrome P450 (CYP) enzyme that catalyzes the final three steps of aldosterone biosynthesis. Compounds that inhibit CYP11B2 should thus inhibit the formation of aldosterone, and may be useful as treatments for hypertension, heart failure, and diabetes. Small molecule CYP11B2 inhibitors have been reported in the literature, and one, LCI-699, has recently been shown to lower blood pressure in the clinic, thus providing validation for the use of CYP11B2 inhibitors as treatments for hypertension. 5−10 Steroid-11β-hydroxylase (CYP11B1) is a related enzyme that catalyzes the formation of glucocorticoids such as cortisol, an important regulator of glucose metabolism. Human CYP11B2 and CYP11B1 are >93% homologous, and given the physiological importance of cortisol, selectivity for inhibition of CYP11B2 vs 11B1 is required. LCI-699 displays only ∼4-fold selectivity for inhibition of human CYP11B2 vs 11B1 in cellbased in vitro assays. 7 In the clinic, doses of LCI-699 higher than 0.5 mg elicited suppression of cortisol levels, presumably as a result of CYP11B1 inhibition. Selectivity greater than that exhibited by LCI-699 would thus be desired to derisk the potential for adverse effects resulting from cortisol suppression.Related CYPs 17 and 19, though less homologous to CYP11B2, play important roles in the conversion of steroidal precursors such as pregnenelone and progesterone to end products such as estrone and testosterone. Selectivity with regard to these CYPs as well as the major hepatic CYPs involved in drug metabolism is also required.Our goal is to discover selective CYP1...

Pharmacophore Modeling and in Silico/in Vitro Screening for Human Cytochrome P450 11B1 and Cytochrome P450 11B2 Inhibitors

“…The heterocyclic nitrogen part has a crucial role in forming an iron-binding interaction with heme of these CYP enzymes and was mapped by the HBA-1 and AR-1 features of the pharmacophores. This type of interaction inhibited the catalytic process of the target enzymes and has been reported earlier (Denner et al, 1995a , b ; Hartmann et al, 2003 ; Bureik et al, 2004 ; Ulmschneider et al, 2005b ; Hoyt et al, 2015 ).…”

Human cytochrome P450 11B2 produces aldosterone by a processive mechanism due to the lactol form of the intermediate 18-hydroxycorticosterone

“…Several aspects of the mechanism were still unclear following the published studies (11, 12, 20), including the rate-limiting step(s) and the extent of processivity. Searches for pharmacological inhibitors have been done primarily using simple aldosterone end-point assays (in cells) (15,22,(32)(33)(34)(35)(36), but a better understanding of the kinetics of the individual steps of the enzyme could have practical applications as well as yield insight into the more general mechanisms of P450 catalysis.…”

Development of Highly Selective Pyrimidine-Based Aldosterone Synthase (CYP11B2) Inhibitors

“…Indeed, the development of the first CYP11B2 inhibitor to reach the clinic, LCI699, suffered from poor selectivity against CYP11B1 and was eventually discontinued for the treatment of hypertension for this reason. , Given the high homology between the two enzymes (93%) it is not surprising this challenge exists . However, several recent reports detail significant progress in the development of selective inhibitors, − including the identification of highly selective clinical candidates LFF269 and RO-6836191. , …”