Inhibition of CYP 17, a new strategy for the treatment of prostate cancer

Current Treatment Modalities Targeting Tumor Microenvironment in Castration-Resistant Prostate Cancer

Prostate cancer (PCa) is responsible for significant cancer-related morbidity and mortality following local treatment failure in men. The initial stages of PCa are typically managed with a combination of surgical resection and/or androgen deprivation therapy (ADT). Unfortunately, a significant proportion of PCa continues to progress despite being at castrate levels of testosterone (<50 ng/dl), at which point it is coined castration-resistant prostate cancer (CRPC). In recent years, many novel therapeutics and drug combinations have been created for CRPC patients. These include immune checkpoint inhibitors, chemokine receptor antagonists, steroidogenic enzyme inhibition, and novel tyrosine kinase inhibitors as well as combinations of drugs. The selection of the most appropriate therapy depends on several factors like stage of the disease, age of the patient, metastasis, functional status, and response towards previous therapies. Here, we review the current state of the literature regarding treatment modalities, focusing on the treatment recommendations per the American Urological Association (AUA), recent clinical trials, and their limitations. An accurate and reliable overview of the strengths and limitations of PCa therapeutics could also allow personalized therapeutic interventions against PCa.

A molecularly imprinted poly 2-aminophenol-gold nanoparticle-reduced graphene oxide composite for electrochemical determination of flutamide in environmental and biological samples

A selective and sensitive electrochemical sensor based on reduced graphene oxide, gold nanoparticles, and molecularly imprinted poly 2-aminophenol was developed for electrochemical determination of flutamide in environmental and biological samples. The composite fabrication was electrochemically carried out and the composite was characterized by Fourier transform infrared, proton and carbon nuclear magnetic resonance, field emission scanning electron microscopy, and energy-dispersive X-ray spectrometry. The spectroscopic results showed that polymerization of molecularly imprinted poly 2-aminophenol took place through a ladder structure system. After optimization of effective parameters on the response of the sensor, the obtained linear range, relative standard deviation (for a concentration of 50 μg L^-1 with five replicates) and limit of quantification for flutamide determination were determined to be 2-375 μg L^-1, 1.54% and 0.8 μg L^-1, respectively. The results showed that the application of poly 2-aminophenol in the structure of the proposed sensor using a molecular imprinting approach made the sensor highly selective toward flutamide, distinguishing it from similar nitro-containing compounds. The prepared sensor was successfully utilized to analyze environmental water and urine samples. The obtained results showed that the proposed method is in agreement with the HPLC method and can be used as a reliable alternative method for the analysis of flutamide.

Development of an in vitro screening assay for PIP5K1α lipid kinase and identification of potent inhibitors

The human phosphatidylinositol 4-phosphate 5-kinase type I α (hPIP5K1α) participates in the phosphoinositide-3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway. Despite the evidence that hPIP5K1α plays a role in the development of prostate cancer (PCa), only one inhibitor is known to date. With the aim of identifying new inhibitors, a nonradiometric assay for measurement of the hPIP5K1α enzyme activity was developed. The assay is based on the separation of the fluorescently labeled substrate phosphatidylinositol-4-phosphate (PI(4)P) and the resulting product phosphatidylinositol-4,5-bisphosphate (PIP₂ ) by capillary electrophoresis (CE). Furthermore, an inactive mutant K261A of hPIP5K1α was generated by site-directed mutagenesis and used as a control. Michaelis-Menten analysis revealed a K_m value of 21.6 µm and V_max of 0.65 pmol·min^-1 for the cosubstrate ATP. The average Z' value was determined to be 0.86, indicating a high reliability of the assay. An in silico screening of an in-house compound library was performed employing the crystal structure of zebrafish PIP5K1α. By applying this strategy, three compounds with a 2-amino-3-cyano-4H-pyranobenzoquinone scaffold were identified and tested using the CE-based assay. These compounds inhibited hPIP5K1α to > 90% at a concentration of 50 µm. Subsequently, the inhibitory activity of all compounds with a pyranobenzoquinone scaffold (29) was tested on hPIP5K1α. Compound 4-(2-amino-3-cyano-6-hydroxy-5,8-dioxo-7-undecyl-5,8-dihydro-4H-chromen-4-yl)benzoic acid appeared to be the most potent inhibitor of hPIP5K1α identified so far with an IC₅₀ value of 1.55 µm, exhibiting a substrate-competitive mode of action. The effects of this compound on cell viability and the induction of apoptosis were investigated in LNCaP, DU145, and PC3 PCa cells.

New steroidal oxazolines, benzoxazoles and benzimidazoles related to abiraterone and galeterone

Seven new oxazoline, benzoxazole and benzimidazole derivatives were synthesized from 3β-acetoxyandrosta-5,16-dien-17-carboxylic, 3β-acetoxyandrost-5-en-17β-carboxylic and 3β-acetoxypregn-5-en-21-oic acids. Docking to active site of human 17α-hydroxylase/17,20-lyase revealed that all oxazolines, as well as benzoxazoles and benzimidazoles comprising Δ¹⁶ could form stable complexes with enzyme, in which steroid moiety is positioned similarly to that of abiraterone and galeterone, and nitrogen atom coordinates heme iron, while 16,17-saturated benzoxazoles and benzimidazoles could only bind in a position where heterocycle is located nearly parallel to heme plane. Modeling of the interaction of new benzoxazole and benzimidazole derivatives with androgen receptor revealed the destabilization of helix 12, constituting activation function 2 (AF2) site, by mentioned compounds, similar to one induced by known antagonist galeterone. The synthesized compounds inhibited growth of prostate carcinoma LNCaP and PC-3 cells at 96 h incubation; the potency of 2'-(3β-hydroxyandrosta-5,16-dien-17-yl)-4',5'-dihydro-1',3'-oxazole and 2'-(3β-hydroxyandrosta-5,16-dien-17-yl)-benzimidazole was superior and could inspire further investigations of these compounds as potential anti-cancer agents.

Comparison of [17(20)E]-21-Norpregnene oxazolinyl and benzoxazolyl derivatives as inhibitors of CYP17A1 activity and prostate carcinoma cells growth

Four new 4,5-dihydro-1,3-oxazole, and four new benzo-[d]-oxazole derivatives of [17(20)E]-21-norpregnene, differing in the structure of steroid moiety, were synthesized and evaluated for their potency to inhibit 17α-hydroxylase/17,20-lyase (CYP17A1) activity. Among new compounds, the only oxazolinyl derivative comprising 5-oxo-4,5-seco-3-yn- moiety potently inhibited CYP17A1. Binding modes of the oxazolinyl derivatives of [17(20)E]-21-norpregnene were analyzed by molecular dynamics simulations, and model of alternate, water-bridged type II interaction was proposed for these compounds. Eight new compounds, together with two CYP17A1-inhibiting oxazolinyl derivatives synthesized earlier, abiraterone and galeterone were evaluated for their potency to inhibit prostate carcinoma PC-3 and LNCaP cells growth. Oxazolinyl and benzoxazolyl derivatives comprising 3β-hydroxy-5-ene moieties potently inhibited prostate carcinoma cell growth; inhibitory potencies of 3-oxo-4-en- and 5-oxo-4,5-seco-3-yn- derivatives were significantly lower.

Oxazolinyl derivatives of [17(20)E]-21-norpregnene differing in the structure of A and B rings. Facile synthesis and inhibition of CYP17A1 catalytic activity

Five 4,5-dihydro-1,3-oxazole derivatives of [17(20)E]-21-norpregnene, comprising 3β-hydroxy-5-ene (1), 3,6-dioxo-4-ene (2), 3-oxo-4-ene (3), 3α,5α-cyclo-6-oxo (4), 3β-hydroxy-6-oxo (5) fragments were synthesized. Synthesis was conducted with improved procedure, based on reaction of suitably protected [17(20)E]-pregnen-21-oic acids with ethanolamine in presence of triphenyl phosphine, carbon tetrachloride, and triethyl amine. Potency of the compounds 1-5 to inhibit 17α-hydroxylase/17,20-lyase (CYP17A1) activity was studied by highly sensitive electrochemical method, using the enzyme immobilization technique. Compounds 1 and 3 were found to be potent CYP17A1 inhibitors, compounds 2 and 5 were not active, compound 4 strongly and irreversibly suppressed the enzyme activity. Molecular docking of compounds 1-5 in the active site of CYP17A1 showed that positions of all compounds in the enzyme active site were similar.

New biaryl-chalcone derivatives of pregnenolone via Suzuki-Miyaura cross-coupling reaction. Synthesis, CYP17 hydroxylase inhibition activity, QSAR, and molecular docking study

A new class of steroids is being synthesized for its ability to prevent intratumoral androgen production by inhibiting the activity of CYP17 hydroxylase enzyme. The scheme involved the synthesis of chalcone derivative of pregnenolone 5 which was further modified to the corresponding biaryl-chalcone pregnenolone analogs 16-25 using Suzuki-Miyaura cross-coupling reaction. The synthesized compounds were tested for activity using human CYP17α hydroxylase expressed in Escherichia coli. Compounds 21 was the most active inhibitor in this series, with IC50 values of 0.61μM and selectivity profile of 88.7% inhibition of hydroxylase enzyme. Molecular docking study of 21 was performed and showed the hydrogen bonds and hydrophobic interaction with the amino acid residues of the active site of CYP17.

A new pregnenolone analogues as privileged scaffolds in inhibition of CYP17 hydroxylase enzyme. Synthesis and in silico molecular docking study

A new series of 17-(N-(arylimino)-5-pregnen-3β-ol derivatives 19-32 as well as carboxylate and acrylate analogues of pregnenolone 37-40 were synthesized and evaluated for their inhibitory activity against human CYP17 hydroxylase expressed in Escherichia coli. Compounds 32 and 37 were the most potent analogues in this series, showing inhibition activity with IC50 = 2.11 and 1.29 μM, respectively. However, the analogue 37 revealed a better selectivity profile (83.21% inhibition of hydroxylase), which is a leading candidate for further development. Molecular docking study of 37 showed binding with the amino acid residues of CYP17 through hydrogen bonds and hydrophobic interaction.

Novel oxazolinyl derivatives of pregna-5,17(20)-diene as 17α-hydroxylase/17,20-lyase (CYP17A1) inhibitors

New oxazolinyl derivatives of [17(20)E]-pregna-5,17(20)-diene: 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',5'-dihydro-1',3'-oxazole 1 and 2'-{[(E)-3β-hydroxyandrost-5-en-17-ylidene]methyl}-4',4'-dimethyl-4',5'-dihydro-1',3'-oxazole 2 were evaluated as potential CYP17A1 inhibitors in comparison with 17-(pyridin-3-yl)androsta-5,16-dien-3β-ol 3 (abiraterone). Differential absorption spectra of human recombinant CYP17A1 in the presence of compound 1 (λmax=422 nm, λmin=386 nm) and compound 2 (λmax=416 nm) indicated significant differences in enzyme/inhibitors complexes. CYP17A1 activity was measured using electrochemical methods. Inhibitory activity of compound 1 was comparable with abiraterone 3 (IC50=0.9±0.1 μM, and IC50=1.3±0.1 μM, for compounds 1 and 3, respectively), while compound 2 was found to be weaker inhibitor (IC50=13±1 μM). Docking of aforementioned compounds to CYP17A1 revealed that steroid fragments of compound 1 and abiraterone 3 occupied close positions; oxazoline cycle of compound 1 was coordinated with heme iron similarly to pyridine cycle of abiraterone 3. Configuration of substituents at 17(20) double bond in preferred docked position corresponded to Z-isomers of compounds 1 and 2. Presence of 4'-substituents in oxazoline ring of compound 2 prevents coordination of oxazoline nitrogen with heme iron and worsens its docking score in comparison with compound 1. These data indicate that oxazolinyl derivative of [17(20)E]-pregna-5,17(20)-diene 1 (rather than 4',4'-dimethyl derivative 2) may be considered as potential CYP17A1 inhibitor and template for development of new compounds affecting growth and proliferation of prostate cancer cells.

Steroidal 5α-reductase and 17α-hydroxylase/17,20-lyase (CYP17) inhibitors useful in the treatment of prostatic diseases

The role of steroidal inhibitors of androgen biosynthesis as potential weapons in the treatment of prostatic diseases, such as benign prostatic hyperplasia and prostatic cancer will be reviewed. Two enzymes have been targeted in the development of inhibitors that potentially could be useful in the management of such conditions. 5α-Reductase is primarily of interest in benign prostatic disease, though some role in the chemoprevention of prostatic carcinoma have been considered, whereas the 17α-hydroxylase/17,20-lyase (CYP17) enzyme is of interest in the treatment of malignant disease. An overview of the main achievements obtained during the past years will be presented, however special focus will be made on steroidal molecules that reached clinical trials or have been commercially launched. Relevant examples of such drugs are finasteride, dutasteride, abiraterone acetate and galeterone (TOK-001, formerly known as VN/124-1). This article is part of a Special Issue entitled "Synthesis and biological testing of steroid derivatives as inhibitors".

Management of castration-resistant prostate cancer: a global approach

Treatment options for castration-resistant prostate cancer (crpc) have evolved since the start of the 2000s, with most of the new effective therapies appearing since 2010. In 2004, docetaxel was the first chemotherapeutic agent to improve survival in crpc, but little else was available once patients recurred. Since 2010, four new options have been shown to improve survival in patients with refractory or recurring disease after docetaxel. In the management of bone metastases, two bone-targeted therapies have been shown to reduce the risk of bone complications, and they are part of the overall management strategy in crpc patients. Therapeutic options before chemotherapy have shown promising results and may soon become available in Canada. The present article reviews the treatment options that have shown to be effective in crpc and also some of the ongoing work in the field.

Discovery of orteronel (TAK-700), a naphthylmethylimidazole derivative, as a highly selective 17,20-lyase inhibitor with potential utility in the treatment of prostate cancer

A novel naphthylmethylimidazole derivative 1 and its related compounds were identified as 17,20-lyase inhibitors. Based on the structure-activity relationship around the naphthalene scaffold and the results of a docking study of 1a in the homology model of 17,20-lyase, the 6,7-dihydro-5H-pyrrolo[1,2-c]imidazole derivative (+)-3c was synthesized and identified as a potent and highly selective 17,20-lyase inhibitor. Biological evaluation of (+)-3c at a dose of 1mg/kg in a male monkey model revealed marked reductions in both serum testosterone and dehydroepiandrosterone concentrations. Therefore, (+)-3c (termed orteronel [TAK-700]) was selected as a candidate for clinical evaluation and is currently in phase III clinical trials for the treatment of castration-resistant prostate cancer.

Current management of castrate-resistant prostate cancer

Prostate cancer (PCa) is the most frequently diagnosed cancer in North America. Castrate-resistant PCa presents a spectrum of disease ranging from rising PSA levels in the absence of metastases or symptoms and despite androgen-deprivation therapy, to metastases and significant debilitation from cancer symptoms. Castrate-resistant PCa is usually suspected in patients with new symptoms on androgen deprivation therapy, with a rising PSA, or with new evidence of disease on bone scans or computed tomography scans. Institution of treatment and the choice of systemic or local therapy depend on a number of factors. This review discusses the various currently available treatments for patients with castrate-resistant PCa, from secondary hormonal manipulations to options for post-docetaxel systemic therapy.

CYP17 inhibitors for prostate cancer therapy

Prostate cancer (PC) is now the second most prevalent cause of death in men in the USA and Europe. At present, the major treatment options include surgical or medical castration. These strategies cause ablation of the production of testosterone (T), dihydrotestosterone (DHT) and related androgens by the testes. However, because these procedures do not affect adrenal, prostate and other tissues' androgen production, they are often combined with androgen receptor antagonists to block their action. Indeed, recent studies have unequivocally established that in castration-resistant prostate cancer (CRPC) many androgen-regulated genes become re-expressed and tissue androgen levels increase despite low serum levels. Clearly, inhibition of the key enzyme which catalyzes the biosynthesis of androgens from pregnane precursors, 17α-hydroxy/17,20-lyase (hereafter referred to as CYP17) could prevent androgen production from all sources. Thus, total ablation of androgen production by potent CYP17 inhibitors may provide effective treatment of prostate cancer patients. This review highlights the role of androgen biosynthesis in the progression of prostate cancer and the impact of CYP17 inhibitors, such as ketoconazole, abiraterone acetate, VN/124-1 (TOK-001) and TAK-700 in the clinic and in clinical development. Article from the special issue on Targeted Inhibitors.

Molecular modeling on inhibitor complexes and active-site dynamics of cytochrome P450 C17, a target for prostate cancer therapy

A molecular model for the P450 enzyme cytochrome P450 C17 (CYP17) is presented based on sequence alignments of multiple template structures and homology modeling. This enzyme plays a central role in the biosynthesis of testosterone and is emerging as a major target in prostate cancer, with the recently developed inhibitor abiraterone currently in advanced clinical trials. The model is described in detail, together with its validation, by providing structural explanations to available site-directed mutagenesis data. The CYP17 molecule in this model is in the form of a triangular prism, with an edge of approximately 55 A and a thickness of approximately 37 A. It is predominantly helical, comprising 13 alpha helices interspersed by six 3(10) helices and 11 beta-sheets. Multinanosecond molecular dynamics simulations in explicit solvent have been carried out, and principal components analysis has been used to reveal the details of dynamics around the active site. Coarse-grained methods have also been used to verify low-frequency motions, which have been correlated with active-site gating. The work also describes the results of docking synthetic inhibitors, including the drug abiraterone and the natural substrate pregnenolone, in the CYP17 active site together with molecular dynamics simulations on the complexes.

The Coffey Lecture: steroidogenic enzyme inhibitors and hormone dependent cancer

OBJECTIVES

To improve treatment for patients with breast and prostate cancer.

METHODS

A number of novel inhibitors of steroidogenic enzymes have been developed. Their biological effects have been evaluated in a variety of preclinical models. Aromatase (estrogen synthetase) inhibitors have now been extensively tested in clinical trials in breast cancer patients. Inhibitors of 17alpha-hydroxylase/lyase have also been studied in preclinical models and are beginning trials in prostate cancer patients.

RESULTS

The enzyme aromatase (CYP19) has proven to be an important therapeutic target. Inhibitors of aromatase (AIs) are showing greater benefit than antiestrogens in the treatment of breast cancer. Although effective in other conditions in both women and men, AIs have not been useful in benign prostatic hypertrophy or prostate cancer. However inhibitors of 17alphahydroxylase/lyase (CYP17) to block synthesis of androgens may be effective for prostate cancer. Recent clinical trials with abiraterone and preclinical studies with other novel CYP17 inhibitors, which also interact with the androgen receptor and cause its down-regulation, could provide a new approach for treating this disease. In further studies, we optimized treatment with aromatase inhibitors and antiestrogens utilizing an intratumoral aromatase xenograft model. AIs were more effective and sustained growth inhibition was longer than antiestrogens. However, inevitably tumors eventually began to grow despite continued treatment. Analysis of breast tumors from mice treated with letrozole revealed up-regulation of HER-2 and MAP Kinase signaling proteins and down-regulation of the estrogen receptor. Our studies showed that tumors adapt to AI treatment by activating alternate signaling pathways, thus enabling them to proliferate in the absence of estrogen. When mice bearing resistant tumors were treated with trastuzumab, the anti-HER-2 antibody (herceptin), HER-2 was decreased in the tumor but the estrogen receptor and aromatase were restored. Tumor growth was significantly inhibited by treatment with trastuzumab in addition to letrozole.

CONCLUSIONS

Aromatase inhibitors are proving to be an effective new class of agents for the treatment of breast cancer. Compounds inhibiting 17alphahydroxylase/lyase have potential for the treatment of prostate cancer. Our results suggest that strategies to overcome resistance to these types of agents can restore sensitivity of the tumors to hormone therapy.

CYP17 inhibitors. Annulations of additional rings in methylene imidazole substituted biphenyls: synthesis, biological evaluation and molecular modelling

Twenty-one novel compounds originating from two classes of annulated biphenyls were synthesized as mimetics of the steroidal A- and C-rings and examined for their potency as inhibitors of human CYP17. Selected compounds were tested for inhibition of the hepatic CYP enzyme 3A4. Potent CYP17 inhibitors were found for each class, compound 9 (17 and 71% at 0.2 and 2 microM, respectively) and 21 (591 nM). Compound 21 showed only weak inhibition of CYP3A4 (32 and 64% at 2 and 10 microM, respectively). Both compounds, however, exhibited moderate to strong inhibition of the glucocorticoid-forming enzyme CYP11B1. The most interesting compounds were docked into our protein model. They bound into one of the modes which we have previously published. New interaction regions were identified.

Synthesis of novel C17 steroidal carbamates. Studies on CYP17 action, androgen receptor binding and function, and prostate cancer cell growth

We have exploited the reaction of 1,1'-carbonylbis(2-methylimidazole) (CBMI) with several 17beta-hydroxy androstanes to synthesize a series of novel C17 steroidal carbamates. Structural elucidation features have been provided for the final compounds based on 1D and 2D NMR techniques, IR spectroscopy, and related literature. The new compounds were tested for inhibition of human cytochrome 17alpha-hydroxylase-C17,20-lyase (CYP17) and androgen receptor (AR) binding and function effects. Their inhibitory potential against PC-3 cell proliferation was also evaluated. Compounds 11 and 23 were found to inhibit CYP17 with IC50 values of 17.1 and 11.5 microM, respectively. The carbamate moiety at C17 allowed tight binding of the synthesized compounds to both wild-type (wt-) and mutated AR. When bound to the mutated AR, the compounds were found to have a dual effect, stimulating transcription at low concentrations while almost fully blocking it at the higher concentrations tested, in the presence of the natural androgen dihydrotestosterone (DHT). Compounds 8 and 12 were the most active against PC-3 cell proliferation with EC50 values of 2.2 and 0.2 microM, respectively.

Androgen receptor inactivation contributes to antitumor efficacy of 17{alpha}-hydroxylase/17,20-lyase inhibitor 3beta-hydroxy-17-(1H-benzimidazole-1-yl)androsta-5,16-diene in prostate cancer

We previously reported that our novel compound 3beta-hydroxy-17-(1H-benzimidazole-1-yl)androsta-5,16-diene (VN/124-1) is a potent 17alpha-hydroxylase/17,20-lyase (CYP17) inhibitor/antiandrogen and strongly inhibits the formation and proliferation of human prostate cancer LAPC4 tumor xenografts in severe combined immunodeficient mice. In this study, we report that VN/124-1 and other novel CYP17 inhibitors also cause down-regulation of androgen receptor (AR) protein expression in vitro and in vivo. This mechanism of action seems to contribute to their antitumor efficacy. We compared the in vivo antitumor efficacy of VN/124-1 with that of castration and a clinically used antiandrogen, Casodex, and show that VN/124-1 is more potent than castration in the LAPC4 xenograft model. Treatment with VN/124-1 (0.13 mmol/kg twice daily) was also very effective in preventing the formation of LAPC4 tumors (6.94 versus 2410.28 mm(3) in control group). VN/124-1 (0.13 mmol/kg twice daily) and VN/124-1 (0.13 mmol/kg twice daily) + castration induced regression of LAPC4 tumor xenografts by 26.55% and 60.67%, respectively. Treatments with Casodex (0.13 mmol/kg twice daily) or castration caused significant tumor suppression compared with control. Furthermore, treatment with VN/124-1 caused marked down-regulation of AR protein expression, in contrast to treatments with Casodex or castration that caused significant up-regulation of AR protein expression. The results suggest that VN/124-1 acts by several mechanisms (CYP17 inhibition, competitive inhibition, and down-regulation of the AR). These actions contribute to inhibition of the formation of LAPC4 tumors and cause regression of growth of established tumors. VN/124-1 is more efficacious than castration in the LAPC4 xenograft model, suggesting that the compound has potential for the treatment of prostate cancer.

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.

A fission yeast-based test system for the determination of IC50values of anti-prostate tumor drugs acting on CYP21

Human steroid 21-hydroxylase (CYP21) and steroid 17alpha-hydroxylase/17,20-lyase (CYP17) are two closely related cytochrome P450 enzymes involved in the steroidogenesis of glucocorticoids, mineralocorticoids, and sex hormones, respectively. Compounds that inhibit CYP17 activity are of pharmacological interest as they could be used for the treatment of prostate cancer. However, in many cases little is known about a possible co-inhibition of CYP21 activity by CYP17 inhibitors, which would greatly reduce their pharmacological value. We have previously shown that fission yeast strains expressing mammalian cytochrome P450 steroid hydroxylases are suitable systems for whole-cell conversion of steroids and may be used for biotechnological applications or for screening of inhibitors. In this study, we developed a very simple and fast method for the determination of enzyme inhibition using Schizosaccharomyces pombe strains that functionally express either human CYP17 or CYP21. Using this system we tested several compounds of different structural classes with known CYP17 inhibitory potency (i.e. Sa 40, YZ5ay, BW33, and ketoconazole) and determined IC50 values that were about one order of magnitude higher in comparison to data previously reported using human testes microsomes. One compound, YZ5ay, was found to be a moderate CYP21 inhibitor with an IC50 value of 15 microM, which is about eight-fold higher than the value determined for CYP17 inhibition (1.8 microM) in fission yeast. We conclude that, in principle, co-inhibition of CYP21 by CYP17 inhibitors cannot be ruled out.

Synthesis of Hydroxy Derivatives of Highly Potent Non-steroidal CYP 17 Inhibitors as Potential Metabolites and Evaluation of their Activity by a Non Cellular Assay using Recombinant Human Enzyme

Inhibition of CYP 17 is a promising strategy for the treatment of prostate cancer. Recently two non-steroidal compounds with high in vitro activity were synthesized in our group (BW19 and BW95). However, after a few hours they showed in vivo a strong decrease in their activity. This might be due to a fast biodegradation. Potential hydroxy and epoxy metabolites were synthesized and their inhibitory activities were tested by a new non-cellular assay using recombinant enzyme. As source, membrane fractions of E. coli pJL17/OR coexpressing human CYP 17 and rat NADPH-P450-reductase were, used. Showing a high and constant CYP 17 activity and a fast and easy isolation procedure the new method was advantageous compared with the microsomal assay. Interestingly, all the new synthesized hydroxy and epoxy compounds except one showed a lower inhibition of CYP 17 than the parent compounds. Thus, the loss of in vivo activity may be partly explained.

Synthesis, biological evaluation, and molecular modeling of abiraterone analogues: novel CYP17 inhibitors for the treatment of prostate cancer

Abiraterone, a steroidal cytochrome P450 17alpha-hydroxylase-17,20-lyase inhibitor (CYP17), is currently undergoing phase II clinical trials as a potential drug for the treatment of androgen-dependent prostate cancer. Since steroidal compounds often show side effects attributable to their structure, we have tried to replace the sterane scaffold by nonsteroidal core structures. The design and synthesis of 20 new abiraterone mimetics are described. Their activities have been tested with recombinant human CYP17 expressed in E. coli. Promising compounds were further evaluated for selectivity against CYP11B1, CYP11B2, and the hepatic CYP3A4. Compounds 19 and 20 showed comparable activity to abiraterone (IC50 values of 144 and 64 nM vs 72 nM) and similar or even better selectivity against the other CYP enzymes. Selected compounds were also docked into our homology model, and the same binding modes as for abiraterone were found.

Synthesis, biochemical evaluation and rationalisation of the inhibitory activity of a range of 4-hydroxyphenyl ketones as potent and specific inhibitors of the type 3 of 17beta-hydroxysteroid dehydrogenase (17beta-HSD3)

We report the synthesis and biochemical evaluation of a number of 4-hydroxyphenyl ketones as potential inhibitors of the enzyme 17beta-hydroxysteroid dehydrogenase (17beta-HSD). In particular, we evaluated compounds against the catalysis of the conversion of androstenedione (AD) to testosterone (T) [17beta-HSD type 3 (17beta-HSD3)], furthermore, in an effort to determine the specificity of our compounds, we evaluated the ability of the compounds to inhibit the catalysis of the conversion of estrone (E1) to estradiol (E2) [17beta-HSD type 1 (17beta-HSD1)] as well as the conversion of dehydroepiandrosterone (DHEA) to AD [by 3beta-hydroxysteroid dehydrogenase (3beta-HSD)]. The results of our study suggest that the synthesised compounds are, in general, able to inhibit 17beta-HSD3 whilst being weak inhibitors of 17beta-HSD1. Against 3beta-HSD, we discovered that all of the synthesised compounds were weak inhibitors (all were found to possess less than 50% inhibition at [I]=500 microM). More specifically, we discovered that 1-(4-hydroxy-phenyl)-nonan-1-one (15) was the most potent against 17beta-HSD3 (IC(50)=2.9 microM) whilst possessing poor inhibitory activity against 17beta-HSD1 ( approximately 36% inhibitory activity against this reaction at [I]=100 microM) and less than 10% inhibition for the conversion of DHEA to AD. We have therefore provided good lead compounds in the design and synthesis of novel non-steroidal inhibitors of 17beta-HSD3.

Pharmacophore mapping of flavone derivatives for aromatase inhibition

Aromatase, which catalyses the final step in the steroidogenesis pathway of estrogen, has been target for the design of inhibitor in the treatment of hormone dependent breast cancer for postmenopausal women. The extensive SAR studies performed in the last 30 years to search for potent, selective and less toxic compounds, have led to the development of second and third generation of non-steroidal aromatase inhibitors (AI). Besides the development of synthetic compounds, several naturally occurring and synthetic flavonoids, which are ubiquitous natural phenolic compounds and mediate the host of biological activities, are found to demonstrate inhibitory effects on aromatase. The present study explores the pharmacophores, i.e., the structural requirements of flavones (Fig. 1) for inhibition of aromatase activity, using quantitative structure activity relationship (QSAR) and space modeling approaches. The classical QSAR studies generate the model (R (2) = 0.924, Q (2) = 0.895, s = 0.233) that shows the importance of aromatic rings A and C, along with substitutional requirements in meta and para positions of ring C for the activity. 3D QSAR of Comparative Molecular Field Analysis (CoMFA, R (2) = 0.996, R(2)(cv) = 0.791) and Comparative Molecular Similarity Analysis (CoMSIA, R (2) = 0.992, R(2)(cv) = 0.806) studies show contour maps of steric and hydrophobic properties and contribution of acceptor and donor of the molecule, suggesting the presence of steric hindrance due to ring C and R''-substituent, bulky hydrophobic substitution in ring A, along with acceptors at positions 11, and alpha and gamma of imidazole ring, and donor in ring C favor the inhibitory activity. Further space modeling (CATALYST) study (R = 0.941, Delta( cost ) = 96.96, rmsd = 0.876) adjudge the presence of hydrogen bond acceptor (keto functional group), hydrophobic (ring A) and aromatic rings (steric hindrance) along with critical distance among features are important for the inhibitory activity.

Synthesis and evaluation of novel 17-indazole androstene derivatives designed as CYP17 inhibitors

A series of novel 1H- and 2H-indazole derivatives of the commercially available dehydroepiandrosterone acetate have been synthesized and tested for inhibition of human cytochrome 17alpha-hydroxylase-C(17,20)-lyase (CYP17), androgen receptor (AR) binding affinity, and cytotoxic potential against three prostate cancer (PC) cell lines.

Pharmacophore Modeling and in Silico Screening for New P450 19 (Aromatase) Inhibitors

Cytochrome P450 19 (P450 19, aromatase) constitutes a successful target for the treatment of breast cancer. This study analyzes chemical features common to P450 19 inhibitors to develop ligand-based, selective pharmacophore models for this enzyme. The HipHop and HypoRefine algorithms implemented in the Catalyst software package were employed to create both common feature and quantitative models. The common feature model for P450 19 includes two ring aromatic features in its core and two hydrogen bond acceptors at the ends. The models were used as database search queries to identify active compounds from the NCI database.

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.

Design, synthesis, and 3D QSAR of novel potent and selective aromatase inhibitors

The design, synthesis, and biological evaluation of a series of new aromatase inhibitors bearing an imidazole or triazole ring linked to a fluorene (A), indenodiazine (B), or coumarin scaffold (C) are reported. Properly substituted coumarin derivatives displayed the highest aromatase inhibitory potency and selectivity over 17-alpha-hydroxylase/17-20 lyase. The modeling of the aromatase inhibition data by Comparative Molecular Field Analysis (CoMFA/GOLPE 3D QSAR approach) led to the development of a PLS model with good fitting and predictive powers (n = 22, ONC = 3, r(2) = 0.949, s = 0.216, and q(2) = 0.715). The relationship between aromatase inhibition and the steric and electrostatic fields generated by the examined azole inhibitors enables a clear understanding of the nature and spatial location of the main interactions modulating the aromatase inhibitory potency.

Effects of novel 17alpha-hydroxylase/C17, 20-lyase (P450 17, CYP 17) inhibitors on androgen biosynthesis in vitro and in vivo

Aiming at the development of new drugs for the treatment of prostate cancer, the effects of steroidal compounds and one non-steroidal substance on androgen biosynthesis were evaluated in vitro and in vivo. Sa 40 [17-(5-pyrimidyl)androsta-5,16-diene-3beta-ol], its 3-acetyl derivate Sa 41 and BW 19 [3,4-dihydro-2-(4-imidazolylmethyl)-6-methoxy-1-methyl-naphthalene] are compounds from our group, which have been developed as inhibitors of CYP 17 (17alpha-hydroxylase-C17, 20-lyase, the key enzyme in androgen biosynthesis). They have been compared with CB 7598 [abiraterone: 17-(3-pyridyl)androsta-5,16-diene-3beta-ol], its 3-acetyl compound CB 7630 and ketoconazole, compounds which already have been used clinically. The most potent compound toward human CYP 17 (testicular microsomes) was Sa 40 (IC(50) value of 24 nM), followed by Sa 41, CB 7598, BW 19, CB 7630 and ketoconazole. Sa 40 shows a type II difference spectrum and a non-competitive type of inhibition (K(i) value of 16 nM). No recovery of enzyme activity was observed after preincubation of CYP 17 with Sa 40 and subsequent charcoal treatment. In Escherichia coli cells coexpressing human CYP 17 and NADPH-P450 reductase, Sa 40 was more active than CB 7598 and BW 19, whereas the acetyl compounds were not active. The latter three compounds were equally active towards rat CYP 17. Male Sprague-Dawley (SD) rats were administered daily for 14 days BW 19 and the acetyl derivatives Sa 41 and CB 7630 as prodrugs (0.1 mmol/kg intraperitoneally). The test compounds strongly reduced plasma testosterone concentration, as well as prostate and seminal vesicles weights. They showed moderate inhibitory effects on the weights of levator ani, bulbocavernosus and testes, whereas they led to an increase in adrenal and pituitary weights. The only exception was BW 19 which did not change pituitary weights. Based on its superiority on the human enzyme, it was concluded that Sa 40 in its 3beta-acetate form (Sa 41) could be a promising candidate for clinical evaluation.

Discovery of selective CYP11B2 (aldosterone synthase) inhibitors for the therapy of congestive heart failure and myocardial fibrosis

An increased aldosterone concentration due to congestive heart failure leads to a further progression of the disease as well as to myocardial fibrosis. To interfere with these fatal processes selective inhibition of aldosterone synthase (CYP11B2) is required. CYP11B1, a key enzyme in glucocorticoid biosynthesis showing a high homology to the target enzyme (>93%), must not be inhibited. Screening of our P450 inhibitor library for inhibition of bovine aldosterone synthase resulted in a high number of compounds showing reasonable inhibition. In the next step substances were tested for oral absorption using two artificial membrane assays. The inhibition of human CYP11B2 was evaluated using assays in fission yeast and V79MZ cells stably expressing the active human target enzyme. For selectivity, inhibition of CYP11B1, CYP11A1, CYP17, CYP19 and CYP5 was determined. Rather potent and selective compounds obtained in this way were structurally further optimised, finally leading to inhibitors showing IC(50) values within the low nanomolar range.