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. 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...

Discovery of new 7-substituted-4-imidazolylmethyl coumarins and 4′-substituted-2-imidazolyl acetophenones open analogues as potent and selective inhibitors of steroid-11β-hydroxylase

“…Despite these objective drawbacks, careful evaluation of the structure-activity and structureselectivity relationships (SAR and SSR, respectively) allowed the discovery of potent and highly selective CYP11B2 [22][23][24][25][26] and potent but slightly selective CYP11B1 inhibitors. [7][8][9][10] Two of the best compounds discovered in recent studies (e.g., A [8] and B [14] in Chart2) displayed very good to moderately potent CYP11B1 inhibition (IC 50 = 2 and 107 nM, respectively) and moderate selectivity indices (SIB= 13.3 and 16.5, respectively; SIB= IC 50 CYP11B2/IC 50 CYP11B1) but greater than that observed for metyrapone (SIB= 4.8). [14] To discover novel and more potent CYP11B1 inhibitors, with a higher selectivity over CYP11B2, and CYP17 and CYP19 as well, a new research project was conceived stemming from 7-substituted-4-imidazolylmethyl coumarins recently reported by us as potent CYP19 inhibitors with high selectivity over CYP17.…”

“…Aromatase (CYP 19) [3][4][5] and 17β-hydroxylase/17,20-lyase (CYP17) [6] inhibitors are well known examples of CYPs inhibitors largely used in breast and prostate cancer, respectively (Chart 1). More recently, two additional CYP enzymes, namely, steroid 11β-hydroxylase (CYP11B1) [7][8][9][10] and aldosterone synthase (CYP11B2), [11][12][13] both involved in the biosynthesis of corticosteroid hormones, have been exploited as possible druggable targets. CYP11B1 catalyzes the last step of cortisol biosynthesis, that is the hydroxylation of 11-deoxycortisol to cortisol, whereas CYP11B2 catalyzes the conversion of 11-deoxycorticosterone to corticosterone, 18-hydroxycorticosterone and finally to aldosterone (Scheme 1).…”

Targeting Steroidogenic Cytochromes P450 (CYPs) with 6‐Substituted 1‐Imidazolylmethylxanthones

“…Despite this drawback, variousp otent and selectivei nhibitors have been developed [10][11][12][13] that bear nitrogen-containing heterocyclic functions (pyridine or imidazole), which are able to interact with the heme iron of the cytochromeand are thus considered to be key features forefficient inhibition. They catalyze key steps in the biosynthesis of cortisola nd aldosterone, respectively,a nd, as expected, they are mainly localized in the adrenalc ortex.…”

“…These isoformss how ah igh degree of sequenceh omology (up to 93 %), making it difficult to recognize specific features that would allow the design of specifica nd selectivei nhibitors. Despite this drawback, variousp otent and selectivei nhibitors have been developed [10][11][12][13] that bear nitrogen-containing heterocyclic functions (pyridine or imidazole), which are able to interact with the heme iron of the cytochromeand are thus considered to be key features forefficient inhibition.…”

Discovery of Spirocyclic Aldosterone Synthase Inhibitors as Potential Treatments for Resistant Hypertension

“…12 In the clinic, LCI-699 produced an undesired impairment of the stress response, an adverse effect presumed to be caused by inhibition of CYP11B1. Given the physiological importance of cortisol in glucose metabolism and stress response, selectivity for inhibition of CYP11B2 over CYP11B1 is required in a clinically viable candidate.…”