Synthesis and evaluation of imidazolylmethylenetetrahydronaphthalenes and imidazolylmethyleneindanes: potent inhibitors of aldosterone synthase

Continuous flow-through steady state system for in vitro characterization of CYP11B2 inhibitors-Impact on enzyme kinetics of steroidogenesis

BACKGROUND

The homology of aldosterone- and cortisol-producing enzymes, aldosterone synthase (CYP11B2) and 11β-hydroxylase, complicates identification of selective CYP11B2 inhibitors required for antihypertensive treatment or for imaging approaches in patients with primary aldosteronism. To improve preclinical evaluation of novel CYP11B2-targeting compounds, we developed a flow-through cell culture system that provides insights into kinetics of steroidogenesis and inhibitory responses at CYP11B2 active sites.

METHODS

NCI-H295RA and HAC-15 cells were cultured in ibidi flow chambers under constant culture medium flow. Supernatants were collected hourly before and after treatment with (R)-1-[1-(4-iodophenyl)ethyl]-1H-imidazole-5-carboxylic acid azetidinylamide (IMAZA), a non-selective CYP11B1/B2 inhibitor, or the potential CYP11B2 inhibitors ID-69 and ID-191. Steroid profiles were analyzed by liquid chromatography-tandem mass spectrometry. Steady state approximation in steroidogenesis allowed mathematical modeling-based calculation of metabolic fluxes and relative rate constants of biocatalytic steps.

RESULTS

An optimized flow-through system is now available to characterize inhibitory responses at the three catalytic sites of CYP11B2 in two steroid-producing cell lines. IMAZA non-selectively inhibited CYP11B 11β-hydroxylase function, while ID-69 and ID-191 affected the CYP11B2-specific 18-hydroxylase active site with minor effects on catalytic activity of 11β-hydroxylase. ID-191 simultaneously impaired catalytic activity of cortisol production, whereas ID-69 was highly selective for CYP11B2 inhibition.

CONCLUSION

Our flow-through system provides insights into inhibitor-induced alterations of metabolic fluxes and enzymatic rate constants, and thus represents an improved preclinical model sytem for complex characterization of CYP11B2 inhibitors.

Emerging trends in small molecule inhibitors targeting aldosterone synthase: A new paradigm in cardiovascular disease treatment

Aldosterone synthase (CYP11B2) is the rate-limiting enzyme in aldosterone production. In recent years, CYP11B2 has become an appealing target for treating conditions associated with excess aldosterone, such as hypertension, heart failure, and cardiometabolic diseases. Several small-molecule inhibitors of CYP11B2 have demonstrated efficacy in both preclinical studies and clinical trials. Among them, the tetrahydroisoquinoline derivative Baxdrostat has entered clinical trial phases and demonstrated efficacy in treating patients with hypertension. However, the high homology (>93 %) between CYP11B2 and steroid-11β-hydroxylase (CYP11B1), which catalyzes cortisol production, implies that insufficient drug specificity can lead to severe side effects. Developing selective inhibitors for CYP11B2 remains a considerable challenge that requires ongoing attention. This review summarizes recent research progress on small-molecule inhibitors targeting CYP11B2, focusing on structure-activity relationships (SAR) and structural optimization. It discusses strategies for enhancing the specificity and inhibitory activity of inhibitors, while also exploring potential applications and future prospects for CYP11B2 inhibitors, providing a theoretical foundation for developing the new generation of CYP11B2-targeted medications.

Identification of Novel Scaffolds with Dual Role as Antiepileptic and Anti-Breast Cancer

Aromatase inhibitors with an $\mathrm{IC}_{50}$ IC 50 value ranging from 1.4 to 49.7 µM are known to act as antiepileptic drugs besides being potential breast cancer inhibitors. The aim of the present study is to identify novel antiepileptic aromatase inhibitors with higher activity exploiting the ligand-based pharmacophore approach utilizing the experimentally known inhibitors. The resultant Hypo1 consists of four features and was further validated by using three different strategies. Hypo1 was allowed to screen different databases to identify lead molecules and were further subjected to Lipinski's Rule of Five and ADMET to establish their drug-like properties. Consequently, the obtained 68-screened molecules were subjected to molecular docking by GOLD v5.2.2. Furthermore, the compounds with the highest dock scores were assessed for molecular interactions. Later, the MD simulation was applied to evaluate the protein backbone stabilities and binding energies adapting GROMACS v5.0.6 and MM/PBSA which was followed by the density functional theory (DFT), to analyze their orbital energies, and further the energy gap between them. Eventually, the number of Hit molecules was culled to three projecting Hit1, Hit2, and Hit3 as the potential lead compounds based on their highest dock scores, hydrogen bond interaction, lowest energy gap, and the least binding energies and stable MD results.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Inhibitors of Aldosterone Synthase

The mineralocorticoid aldosterone is an important regulator of blood pressure and electrolyte balance. However, excess aldosterone can be deleterious as a driver of inflammation, vascular remodeling and tissue fibrosis associated with cardiometabolic diseases. Mineralocorticoid receptor antagonists (MRA) and renin-angiotensin-aldosterone system (RAAS) antagonists are current clinical therapies used to antagonize deleterious effects of aldosterone in patients. MRAs compete with aldosterone for binding at its cognate receptor thereby limiting its effect while RAS antagonists reduce aldosterone levels indirectly by blocking the stimulatory effect of angiotensin. Both MRAs and RAS antagonists can result in incomplete inhibition of the harmful effects of excess aldosterone. Aldosterone synthase (AS) inhibitors (ASI) attenuate the production of aldosterone directly and have been proposed as an alternative to MRAs and RAS blockers. Cortisol synthase (CS) is an enzyme closely related to AS and responsible for generating the important glucocorticoid cortisol, required for maintaining critical metabolic and immune responses. The importance of selectivity against CS is shown by early examples of ASIs that were only modestly selective and as such, attenuated cortisol responses when evaluated in patients. Recently, next-generation, highly selective ASIs have been described and are presently being evaluated in the clinic as an alternative to angiotensin and MR antagonists for cardiometabolic disease. Herein we provide a brief review of the challenges associated with discovery of selective ASIs and the transition from the early compounds that paved the way toward the next-generation of highly selective ASIs currently under development.

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

Cortisol synthase (CYP11B1) is the main enzyme for the endogenous synthesis of cortisol and its inhibition is a potential way for the treatment of diseases associated with increased cortisol levels, such as Cushing's syndrome, metabolic diseases, and delayed wound healing. Aldosterone synthase (CYP11B2) is the key enzyme for aldosterone biosynthesis and its inhibition is a promising approach for the treatment of congestive heart failure, cardiac fibrosis, and certain forms of hypertension. Both CYP11B1 and CYP11B2 are structurally very similar and expressed in the adrenal cortex. To facilitate the identification of novel inhibitors of these enzymes, ligand-based pharmacophore models of CYP11B1 and CYP11B2 inhibition were developed. A virtual screening of the SPECS database was performed with our pharmacophore queries. Biological evaluation of the selected hits lead to the discovery of three potent novel inhibitors of both CYP11B1 and CYP11B2 in the submicromolar range (compounds 8–10), one selective CYP11B1 inhibitor (Compound 11, IC₅₀ = 2.5 μM), and one selective CYP11B2 inhibitor (compound 12, IC₅₀ = 1.1 μM), respectively. The overall success rate of this prospective virtual screening experiment is 20.8% indicating good predictive power of the pharmacophore models.

Noncanonical mechanisms to regulate nuclear receptor signaling

Nuclear receptor (NR)-targeted therapies comprise a large class of clinically employed drugs. A number of drugs currently being used against this protein class were designed as structural analogs of the endogenous ligand of these receptors. In recent years, there has been significant interest in developing newer strategies to target NRs, especially those that rely on mechanistic pathways of NR function. Prominent among these are noncanonical means of targeting NRs, which include selective NR modulation, NR coactivator interaction inhibition, inhibition of NR DNA binding, modulation of NR cellular localization, modulation of NR ligand biosynthesis and downregulation of NR levels in target tissues. This article reviews each of these promising emerging strategies for NR drug development and highlights some of most significant successes achieved in using them.

3-Pyridyl substituted aliphatic cycles as CYP11B2 inhibitors: aromaticity abolishment of the core significantly increased selectivity over CYP1A2

Aldosterone synthase (CYP11B2) is a promising therapeutic target for the treatment of cardiovascular diseases related to abnormally high aldosterone levels. On the basis of our previously identified lead compounds I–III, a series of 3-pyridinyl substituted aliphatic cycles were designed, synthesized and tested as CYP11B2 inhibitors. Aromaticity abolishment of the core was successfully applied to overcome the undesired CYP1A2 inhibition. This study resulted in a series of potent and selective CYP11B2 inhibitors, with compound 12 (IC₅₀ = 21 nM, SF = 50) as the most promising one, which shows no inhibition toward CYP1A2 at 2 µM. The design conception demonstrated in this study can be helpful in the optimization of CYP inhibitor drugs regarding CYP1A2 selectivity.

Human aldosterone synthase: recombinant expression in E. coli and purification enables a detailed biochemical analysis of the protein on the molecular level

Aldosterone, the most important human mineralocorticoid, is involved in the regulation of the blood pressure and has been reported to play a key role in the formation of arterial hypertension, heart failure and myocardial fibrosis. Aldosterone synthase (CYP11B2) catalyzes the biosynthesis of aldosterone by successive 11β- and 18-hydroxylation followed by an 18-oxidation of 11-deoxycorticosterone and thus comprises an important drug target. For more than 20 years, all attempts to purify recombinant human CYP11B2 in significant amounts for detailed analysis failed due to its hydrophobic nature as a membrane protein. Here, we present the successful expression of the protein in E. coli yielding approx. 90 nmol/l culture, its purification and detailed enzymatic characterization. Biochemical analyses have been performed using in vitro conversion assays which revelead a V(max) of 238±8 nmol products/nmol hCYP11B2/min and a K(m) of 103±8 μM 11-deoxycorticosterone. Furthermore, binding analyses indicated a very loose binding of the first intermediate of the reaction, corticosterone with a K(d) value of 115±6 μM whereas for 11-deoxycorticosterone a K(d) of 1.34±0.13 μM was estimated. Upon substrate conversion of 11-deoxycorticosterone, new intermediates have been identified as 19- and 18-hydroxylated products not described before for the human enzyme. To understand the differences in substrate conversion, we constructed a new homology model based on the 3D structure of CYP11A1, performed docking studies and calculated the activation energy for hydrogen abstraction of the different ligands. The data demonstrated that the 11β-hydroxylation requires much less abstraction energy than hydroxylation at C18 and C19. However, the C18 and C19 hydroxylated products might be of clinical importance. Finally, purified CYP11B2 represents a suitable tool for the investigation of potential inhibitors of this protein for the development of novel drugs against hypertension and heart failure as was shown using ketoconazole.

Optimization of the First Selective Steroid-11β-hydroxylase (CYP11B1) Inhibitors for the Treatment of Cortisol Dependent Diseases

CYP11B1 is the key enzyme in cortisol biosynthesis, and its inhibition with selective compounds is a promising strategy for the treatment of diseases associated with elevated cortisol levels, such as Cushing's syndrome or metabolic disease. Expanding on a previous study from our group resulting in the first potent and rather selective inhibitor described so far (1, IC50 = 152 nM), we herein describe further optimizations of the imidazolylmethyl pyridine core. Five compounds among the 42 substances synthesized showed IC50 values below 50 nM. Most interesting was the naphth-1-yl compound 23 (IC50 = 42 nM), showing a 49-fold selectivity toward the highly homologous CYP11B2 (1: 18-fold) as well as selectivity toward the androgen and estrogen forming enzymes CYP17 and CYP19, respectively.

The development of a whole-cell based medium throughput screening system for the discovery of human aldosterone synthase (CYP11B2) inhibitors: old drugs disclose new applications for the therapy of congestive heart failure, myocardial fibrosis and hypertension

Cytochrome P450 enzymes play an important role in steroid hormone biosynthesis of the human adrenal gland, e.g., the production of cortisol and aldosterone. Aldosterone, the most important human mineralocorticoid, is involved in the regulation of the salt and water homeostasis of the body and thus in the regulation of blood pressure, whereas cortisol is the most important glucocorticoid of the human body. CYP11B-dependent steroid hydroxylases are drug development targets, and since they are very closely related enzymes, the discovery of selective inhibitors has been subject to intense investigations for several years. Here we report the development of a whole-cell medium throughput screening technology for the discovery of CYP11B2 inhibitors. The new screening system displayed high reproducibility and was applied to investigate a library of pharmacologically active compounds. 1268 compounds were investigated during this study which revealed 5 selective inhibitors of CYP11B2 (after validation against CYP11B1). The new inhibitors of CYP11B2 are already existing drugs that could be used either in the treatment of hyperaldosteronism-related diseases or as lead compounds that could further be optimised to achieve safer and selective inhibitors of aldosterone synthase. Article from the Special issue on 'Targeted Inhibitors'.

Design, synthesis, and biological evaluation of imidazolyl derivatives of 4,7-disubstituted coumarins as aromatase inhibitors selective over 17-α-hydroxylase/C17-20 lyase

The design, synthesis, and biological evaluation of a series of new aromatase (AR, CYP19) inhibitors bearing an imidazole ring linked to a 7-substituted coumarin scaffold at position 4 (or 3) are reported. Many compounds exhibited an aromatase inhibitory potency in the nanomolar range along with a high selectivity over 17-α-hydroxylase/C17-20 lyase (CYP17). The most potent AR inhibitor was the 7-(3,4-difluorophenoxy)-4-imidazolylmethyl coumarin 24 endowed with an IC(50) = 47 nM. Docking simulations on a selected number of coumarin derivatives allowed the identification of the most important interactions driving the binding and clearly indicated the allowed and disallowed regions for appropriate structural modifications of coumarins and closely related heterocyclic molecular scaffolds.

First Selective CYP11B1 Inhibitors for the Treatment of Cortisol-Dependent Diseases

Outgoing from an etomidate-based design concept, we succeeded in the development of a series of highly active and selective inhibitors of CYP11B1, the key enzyme of cortisol biosynthesis, as potential drugs for the treatment of Cushing's syndrome and related diseases. Thus, compound 33 (IC50 = 152 nM) is the first CYP11B1 inhibitor showing a rather good selectivity toward the most important steroidogenic CYP enzymes aldosterone synthase (CYP11B2), the androgen-forming CYP17, and aromatase (estrogen synthase, CYP19).

Synthesis, biological evaluation, and molecular modeling of 1-benzyl-1H-imidazoles as selective inhibitors of aldosterone synthase (CYP11B2)

Reducing aldosterone action is beneficial in various major diseases such as heart failure. Currently, this is achieved with mineralocorticoid receptor antagonists, however, aldosterone synthase (CYP11B2) inhibitors may offer a promising alternative. In this study, we used three-dimensional modeling of CYP11B2 to model the binding modes of the natural substrate 18-hydroxycorticosterone and the recently published CYP11B2 inhibitor R-fadrozole as a rational guide to design 44 structurally simple and achiral 1-benzyl-1H-imidazoles. Their syntheses, in vitro inhibitor potencies, and in silico docking are described. Some promising CYP11B2 inhibitors were identified, with our novel lead MOERAS115 (4-((5-phenyl-1H-imidazol-1-yl)methyl)benzonitrile) displaying an IC(50) for CYP11B2 of 1.7 nM, and a CYP11B2 (versus CYP11B1) selectivity of 16.5, comparable to R-fadrozole (IC(50) for CYP11B2 6.0 nM, selectivity 19.8). Molecular docking of the inhibitors in the models enabled us to generate posthoc hypotheses on their binding modes, providing a valuable basis for future studies and further design of CYP11B2 inhibitors.

Selective aldosterone synthase inhibitors reduce aldosterone formation in vitro and in vivo

Aldosterone plays a crucial role in salt and water homeostasis but in case of pathologically increased plasma aldosterone levels it is also involved in the development and the progression of severe cardiovascular diseases like heart failure and myocardial fibrosis. For the treatment of these diseases we propose inhibition of the aldosterone forming enzyme CYP11B2 as a new pharmacological strategy. We recently developed in vitro highly potent and selective inhibitors of human CYP11B2, but the evidence of their in vivo activity is still missing. For this purpose, rat aldosterone synthase gene was cloned and expressed in V79MZ cells to establish a new screening assay for the identification of "rat-active" substances. Compound 7 from the class of heteroaryl substituted 3,4-dihydro-1H-quinolin-2-ones showed a moderate inhibitory effect (65% at 2 microM) on rat CYP11B2 in vitro. Furthermore, it diminished the conversion of deoxycorticosterone to aldosterone in rat adrenals and significantly reduced plasma aldosterone levels in vivo.

Coexpression of CYP11B2 or CYP11B1 with adrenodoxin and adrenodoxin reductase for assessing the potency and selectivity of aldosterone synthase inhibitors

Excessive production of aldosterone has been implicated in the pathogenesis of hypertension and heart failure. One approach to ameliorate the deleterious effects of aldosterone is to suppress its biosynthesis. The enzyme aldosterone synthase (CYP11B2) is responsible for the final step of aldosterone synthesis. It requires electron transfer from the adrenodoxin/adrenodoxin reductase system to catalyze the production of aldosterone. A stable cell line simultaneously overexpressing recombinant human CYP11B2 as well as human adrenodoxin and adrenodoxin reductase was established to help maximize the enzyme activity. The homogenate of these cells was used to develop an in vitro CYP11B2 assay using 11-deoxycorticosterone as a substrate. By the same strategy, another stable cell line simultaneously overexpressing human 11beta-hydroxylase (CYP11B1), an enzyme responsible for the final step of cortisol biosynthesis, and the two electron transfer proteins was also established, and an in vitro CYP11B1 assay using 11-deoxycortisol as a substrate was likewise developed to assess the selectivity of CYP11B2 inhibitors. FAD286, a reference CYP11B2 inhibitor, inhibited CYP11B2 and CYP11B1 activities with IC(50) values of 1.6+/-0.1 and 9.9+/-0.9 nM (mean+/-SEM, n=3-6), respectively. Kinetics studies revealed that the compound inhibited the activity of both enzymes competitively with respective K(i) values of 0.8+/-0.04 and 2.2+/-0.2 nM (n=3-4). These assays can be used for assessing the potency and selectivity of CYP11B2 inhibitors for the treatment of hypertension and heart failure.

Inhibition of Cytochromes P450: Existing and New Promising Therapeutic Targets

Mammalian cytochromes P450 have been shown to play highly important roles in the metabolism of drugs and xenobiotics as well as in the biosynthesis of a variety of endogenous compounds, many of them displaying hormonal function. The role of P450s as therapeutic targets is still inadequately recognized although several P450 inhibitors became efficient drugs that even reached blockbuster status. Here, we try to give a comprehensive overview on cytochromes P450s, which are already well-established targets - particularly focussing on the treatment of infectious diseases, metabolic disorders and cancer - and on those, which have a high potential to become successful targets. In addition, the design of inhibitors of cytochromes P450 will be discussed.

Construction of 3D models of the CYP11B family as a tool to predict ligand binding characteristics

Aldosterone is synthesised by aldosterone synthase (CYP11B2). CYP11B2 has a highly homologous isoform, steroid 11beta-hydroxylase (CYP11B1), which is responsible for the biosynthesis of aldosterone precursors and glucocorticoids. To investigate aldosterone biosynthesis and facilitate the search for selective CYP11B2 inhibitors, we constructed three-dimensional models for CYP11B1 and CYP11B2 for both human and rat. The models were constructed based on the crystal structure of Pseudomonas Putida CYP101 and Oryctolagus Cuniculus CYP2C5. Small steric active site differences between the isoforms were found to be the most important determinants for the regioselective steroid synthesis. A possible explanation for these steric differences for the selective synthesis of aldosterone by CYP11B2 is presented. The activities of the known CYP11B inhibitors metyrapone, R-etomidate, R-fadrazole and S-fadrazole were determined using assays of V79MZ cells that express human CYP11B1 and CYP11B2, respectively. By investigating the inhibitors in the human CYP11B models using molecular docking and molecular dynamics simulations we were able to predict a similar trend in potency for the inhibitors as found in the in vitro assays. Importantly, based on the docking and dynamics simulations it is possible to understand the enantioselectivity of the human enzymes for the inhibitor fadrazole, the R-enantiomer being selective for CYP11B2 and the S-enantiomer being selective for CYP11B1.

Can the dextroenantiomer of the aromatase inhibitor fadrozole be useful for clinical investigation of aldosterone-synthase inhibition?

The beneficial effects of spironolactone, eplerenone, amiloride and potassium in preventing cardiovascular damage in various experimental models of salt-induced hypertension can be dissociated from blood pressure effects, and have drawn attention to the direct genomic and non-genomic actions of aldosterone at the level of the vessels, the heart and the kidneys. Exposure to endogenous aldosterone could be decreased by direct and specific aldosterone-synthase inhibition. FAD 286A, the dextroenantiomer of the aromatase inhibitor fadrozole, might be a first candidate to investigate in humans, the physiological impact and therapeutic properties of aldosterone-synthase inhibition, especially in various forms of primary aldosteronism.

Functional interaction of nitrogenous organic bases with cytochrome P450: A critical assessment and update of substrate features and predicted key active-site elements steering the access, binding, and orientation of amines

The widespread use of nitrogenous organic bases as environmental chemicals, food additives, and clinically important drugs necessitates precise knowledge about the molecular principles governing biotransformation of this category of substrates. In this regard, analysis of the topological background of complex formation between amines and P450s, acting as major catalysts in C- and N-oxidative attack, is of paramount importance. Thus, progress in collaborative investigations, combining physico-chemical techniques with chemical-modification as well as genetic engineering experiments, enables substantiation of hypothetical work resulting from the design of pharmacophores or homology modelling of P450s. Based on a general, CYP2D6-related construct, the majority of prospective amine-docking residues was found to cluster near the distal heme face in the six known SRSs, made up by the highly variant helices B', F and G as well as the N-terminal portion of helix C and certain beta-structures. Most of the contact sites examined show a frequency of conservation < 20%, hinting at the requirement of some degree of conformational versatility, while a limited number of amino acids exhibiting a higher level of conservation reside close to the heme core. Some key determinants may have a dual role in amine binding and/or maintenance of protein integrity. Importantly, a series of non-SRS elements are likely to be operative via long-range effects. While hydrophobic mechanisms appear to dominate orientation of the nitrogenous compounds toward the iron-oxene species, polar residues seem to foster binding events through H-bonding or salt-bridge formation. Careful uncovering of structure-function relationships in amine-enzyme association together with recently developed unsupervised machine learning approaches will be helpful in both tailoring of novel amine-type drugs and early elimination of potentially toxic or mutagenic candidates. Also, chimeragenesis might serve in the construction of more efficient P450s for activation of amine drugs and/or bioremediation.

CYP17- and CYP11B-dependent steroid hydroxylases as drug development targets

Steroid hormone biosynthesis is catalyzed by the action of a series of cytochrome P450 enzymes as well as reductases. Defects in steroid hydroxylating P450s are the cause of several severe defects such as the adrenogenital syndrome (AGS), corticosterone methyl oxidase (CMO) I or II deficiencies, or pseudohermaphroditism. In contrast, overproduction of steroid hormones can be involved in breast or prostate cancer, in hypertension, and heart fibrosis. Besides inhibiting the action of the steroid hormones on the level of steroid hormone receptors by using antihormones, which often is connected with severe side effects, more recently the steroid hydroxylases themselves turned out to be promising new targets for drug development. Since the 3-dimensional structures of steroid hydroxylases are not yet available, computer models of the corresponding CYPs may help to develop new inhibitors of these enzymes. During the past years, the necessary test systems have been developed and new compounds have been synthesized, which displayed selective and specific inhibition of CYP17, CYP11B2, and CYP11B1. With some of these potential new drugs, clinical trials are under way. It can be expected that in the near future some of these compounds will contribute to our arsenal of new and selective drugs.

Development and evaluation of a pharmacophore model for inhibitors of aldosterone synthase (CYP11B2)

Recently, we proposed inhibition of aldosterone synthase (CYP11B2) as a novel strategy for the treatment of congestive heart failure and myocardial fibrosis and synthesized a large number of inhibitors. In this work, a pharmacophore model for CYP11B2 inhibitors was developed by superimposition of active and non-active compounds. This model was confirmed by the synthesis of two pyridyl substituted acenaphthene derivatives (A,B). This new class of compounds as well as the pharmacophore could be helpful for the discovery of novel inhibitors.

The adrenocortical tumor cell line NCI-H295R as an in vitro screening system for the evaluation of CYP11B2 (aldosterone synthase) and CYP11B1 (steroid-11beta-hydroxylase) inhibitors

Aldosterone plays a key role in salt and water homeostasis but is also involved in the development and progression of congestive heart failure and myocardial fibrosis. As a new pharmacological strategy for the treatment of these diseases, we propose the inhibition of the key enzyme of mineralcorticoid formation, CYP11B2 (aldosterone synthase). For studies of the effects of CYP11B2 inhibitors on the adrenal cortex, we selected the NCI-H295R cell line which expresses most of the key enzymes necessary for steroidogenesis. To evaluate this cell line as a test system for effects and side effects of CYP inhibitors, we established assays using radiolabeled substrates of CYP11B2 and CYP11B1 and subsequently tested a series of CYP11B2 inhibitors including the CYP19 inhibitor fadrozole. Fadrozole and compounds 6, 9 and 10 were more potent towards CYP11B2 compared to CYP11B1 with IC(50) values in the nanomolar range. To analyze their overall effect, the formation of steroids in the cell culture supernatant was monitored. All compounds led to a concentration-dependent reduction of the aldosterone secretion but also reduced the formation of cortisol and androgens. In conclusion, the H295R cell line is a suitable tool for the prediction of overall side effects of CYP11B2 inhibitors on steroidogenesis.