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

Abiraterone and Galeterone, Powerful Tools Against Prostate Cancer: Present and Perspective

Due to the high prostate cancer incidence worldwide, the development of different methods of treatment continues to be a hot research topic. Since its first clinical application at the beginning of the 2010s, abiraterone in the form of prodrug abiraterone acetate continues to be the most used hormone derivative in the treatment of castration-resistant prostate cancer. This is the reason behind the publication of many scientific results regarding its synthesis, biological activity, metabolism, novel designed steroid derivatives based on its structure, etc. A similar steroid compound with a heterocycle in the C17 position, called galeterone, also designed to treat prostate cancer, continues to be in clinical studies, which provides further proof of the importance of these steroid derivatives. Besides prostate cancer treatment, abiraterone showed indications for possible clinical application in the treatment of breast, ovarian, lung, kidney, salivary gland, and adrenocortical cancer, congenital adrenal hyperplasia, Cushing's syndrome, and COVID-19, while galeterone is investigated for its use against prostate, pancreatic, and breast cancer. Herein, we report a review comprising methods of synthesis, possible clinical applications, and mechanisms of action, as well as structures and bioactivities of derivatives of these two important steroids.

2-Chloro-3-cyano-4-nitrobenzyl pyridinium bromide as a potent anti-lung cancer molecule prepared using a single-step solvent-free method

Mono-/dimeric-substituted pyridinium and pyrazolium bromides were prepared under conventional and solvent-free silica-supported domestic microwave conditions. The atom economy, environmental product mass intensity and product mass intensity for solvent-free reactions showed significant importance for the synthesis of target molecules. 4-Nitrobenzyl-substituted pyridinium bromide showed potent anticancer properties compared with mono-/dimeric-substituted pyridinium and pyrazolium bromides against a lung cancer cell line (A-549). Molecular simulation studies were carried out for mono-/dimeric-substituted pyridinium and pyrazolium bromide against protein human CDK1/cyclinB1/CKS2 using the AutoDock program.

Toxic effects of environmental concentration Bisphenol AF exposure on the survival, growth and reproduction of adult male Oryzias curvinotus

Bisphenol AF (BPAF) is a novel environmental endocrine disruptor, and is widely detected in the aquatic environment, which is a potential threat to the health of fish. In this study, male Oryzias curvinotus were exposed to environmental concentrations (0.93 and 9.33 μg/L) of BPAF for 21 days. The effects of BPAF on survival, growth, reproduction, liver and testis histology, and gene transcriptional profiles of O. curvinotus were investigated. The results showed that the survival rate of male O. curvinotus slight decrease with increasing BPAF concentration, and there was no significant effect on body length, body weight, and K-factor. BPAF (9.33 μg/L) caused significant changes in testicular structure and reduced spermatid count in O. curvinotus. Changes in transcript levels of some antioxidant-related genes in gills and liver following BPAF exposure, imply an effect of BPAF on the immune system. After BPAF exposure, chgs and vtgs were up-regulated, validating the estrogenic effect of BPAF. In the hypothalamic - pituitary - gonadal axis (HPG) results, erα, erγ and cyp19a1b were all up-regulated in the brain, and the 0.93 μg/L BPAF group was more up-regulated than the 9.33 μg/L BPAF group. In testis, BPAF significantly up-regulated the mRNA expression level of cyp17a1 and cyp11b, while significantly down-regulated mRNA expression level of cyp11a, and cyp19a1 was significantly down-regulated only in the 0.93 μg/L BPAF group. In conclusion, environmental levels of BPAF have adverse effects on the survival and reproduction of O. curvinotus, and the potential toxic effects of environmental levels of BPAF cannot be ignored.

Description of Chemical Synthesis, Nuclear Magnetic Resonance Characterization and Biological Activity of Estrane-Based Inhibitors/Activators of Steroidogenesis

Steroid hormones play a crucial role in several aspects of human life, and steroidogenesis is the process by which hormones are produced from cholesterol using several enzymes that work in concert to obtain the appropriate levels of each hormone at the right time. Unfortunately, many diseases, such as cancer, endometriosis, and osteoporosis as examples, are caused by an increase in the production of certain hormones. For these diseases, the use of an inhibitor to block the activity of an enzyme and, in doing so, the production of a key hormone is a proven therapeutic strategy whose development continues. This account-type article focuses on seven inhibitors (compounds 1-7) and an activator (compound 8) of six enzymes involved in steroidogenesis, namely steroid sulfatase, aldo-keto reductase 1C3, types 1, 2, 3, and 12 of the 17β-hydroxysteroid dehydrogenases. For these steroid derivatives, three topics will be addressed: (1) Their chemical synthesis from the same starting material, estrone, (2) their structural characterization using nuclear magnetic resonance, and (3) their in vitro or in vivo biological activities. These bioactive molecules constitute potential therapeutic or mechanistic tools that could be used to better understand the role of certain hormones in steroidogenesis.

Novel 4-Azapregnene Derivatives as Potential Anticancer Agents: Synthesis, Antiproliferative Activity and Molecular Docking Studies

A series of novel 21E-arylidene-4-azapregn-5-ene steroids has been successfully designed, synthesized and structurally characterized, and their antiproliferative activity was evaluated in four different cell lines. Within this group, the 21E-(pyridin-3-yl)methylidene derivative exhibited significant cytotoxic activity in hormone-dependent cells LNCaP (IC₅₀ = 10.20 µM) and T47-D cells (IC₅₀ = 1.33 µM). In PC-3 androgen-independent cells, the steroid 21E-p-nitrophenylidene-4-azapregn-5-ene was the most potent of this series (IC₅₀ = 3.29 µM). Considering these results, the 21E-(pyridin-3-yl)methylidene derivative was chosen for further biological studies on T47-D and LNCaP cells, and it was shown that this azasteroid seems to lead T47-D cells to apoptotic death. Finally, molecular docking studies were performed to explore the affinity of these 4-azapregnene derivatives to several steroid targets, namely 5α-reductase type 2, estrogen receptor α, androgen receptor and CYP17A1. In general, compounds presented higher affinity to 5α-reductase type 2 and estrogen receptor α.

[The interactions of abiraterone and its pharmacologically active metabolite D4A with cytochrome P450 2C9 (CYP2C9)]

Interactions of cytochrome P450 2C9 (CYP2C9) were studied with the antitumor drug abiraterone and its pharmacologically active metabolite D4A, promising as an agent for prostate cancer treatment. It was shown by absorption spectroscopy, that both investigated compounds induced spectral changes of CYP2C9, indicating interactions of the pyridine nitrogen atom with the heme iron ion of the active site of the enzyme, but interactions of the ligands with the enzyme could be mediated by a water molecule bound to the heme iron ion. Based on the spectral changes, the values of dissociation constants (KS) for complexes of abiraterone and D4A with CYP2C9 were calculated as 1.73±0.14 μM and 3.95±0.16 μM. Both compounds inhibited O-demethylase activity of CYP2C9 towards its substrate. At 100 μM concentration of naproxen the concentrations of abiraterone, D4A and sulfaphenazole inhibiting CYP2C9 activity by 50% (IC50) were determined as 13.9 μM, 40 μM and 41 μM, respectively. The obtained results can be used for prognosis of drug-drug interactions at CYP2C9 level during administration of abiraterone or D4A as an antitumor agent for prostate cancer treatment in complex pharmacotherapy.

Discovery proteomics defines androgen-regulated glycoprotein networks in prostate cancer cells, as well as putative biomarkers of prostatic diseases

Supraphysiologic androgen (SPA) inhibits cell proliferation in prostate cancer (PCa) cells by transcriptional repression of DNA replication and cell-cycle genes. In this study, quantitative glycoprotein profiling identified androgen-regulated glycoprotein networks associated with SPA-mediated inhibition of PCa cell proliferation, and androgen-regulated glycoproteins in clinical prostate tissues. SPA-regulated glycoprotein networks were enriched for translation factors and ribosomal proteins, proteins that are known to be O-GlcNAcylated in response to various cellular stresses. Thus, androgen-regulated glycoproteins are likely to be targeted for O-GlcNAcylation. Comparative analysis of glycosylated proteins in PCa cells and clinical prostate tissue identified androgen-regulated glycoproteins that are differentially expressed prostate tissues at various stages of cancer. Notably, the enzyme ectonucleoside triphosphate diphosphohydrolase 5 was found to be an androgen-regulated glycoprotein in PCa cells, with higher expression in cancerous versus non-cancerous prostate tissue. Our glycoproteomics study provides an experimental framework for characterizing androgen-regulated proteins and glycoprotein networks, toward better understanding how this subproteome leads to physiologic and supraphysiologic proliferation responses in PCa cells, and their potential use as druggable biomarkers of dysregulated AR-dependent signaling in PCa cells.

The interactions of a number of steroid-metabolizing cytochromes P450 with abiraterone D4A metabolite: spectral analysis and molecular docking

The interactions of pharmacologically active 3-keto-Δ4-metabolite of anticancer drug abiraterone (D4A) with steroid-metabolizing cytochromes P450 (CYP51A1, CYP11A1, CYP19A1) was studied by absorption spectroscopy and molecular docking. Both abiraterone and D4A induce type I spectral changes of CYP51A1, one of the enzymes of cholesterol biosynthesis. We have revealed that D4A did not induce spectral changes of CYP11A1, the key enzyme of pregnenolone biosynthesis, unlike abiraterone (type II ligand of CYP11A1). On the contrary, D4A interacts with the active site of CYP19A1, the key enzyme of estrogen biosynthesis, inducing type II spectral changes, while abiraterone does not. Spectral analysis allowed us to calculate spectral dissociation constant (K_S) for each complex of cytochrome P450 with respective ligands. The data were supported by molecular docking. The obtained results broaden understanding of interactions of D4A with some of the key steroid-metabolizing cytochromes P450 and allow one to predict possible disproportions of steroid metabolism.

Multistep Synthesis and In Vitro Anticancer Evaluation of 2-Pyrazolyl-Estradiol Derivatives, Pyrazolocoumarin-Estradiol Hybrids and Analogous Compounds

Although the hormone independent cytotoxic activity of several estradiol derivatives endowed with a simple substituent at C-2 has been reported so far, 2-heterocyclic and 2,3-condensed analogs are less investigated from both synthetic and pharmacological points of view. Therefore, novel A-ring-connected 2-pyrazoles of estradiol and, for comparison, their structurally simplified non-steroidal pairs were synthesized from estradiol 3-methyl ether and 6-methoxy-1,2,3,4-tetrahydronaphthalene. Friedel-Crafts acetylation of the protected phenolic compounds and subsequent O-demethylation led to ortho-substituted derivatives regioselectively, which were converted to arylhydrazones with phenylhydrazine, 4-tolylhydrazine and 4-chloro-phenylhydrazine, respectively, under microwave conditions. The hydrazones were subjected to cyclization with the Vilsmeier-Haack reagent immediately after preparation and the ring closure/formylation sequence resulted in steroidal and non-steroidal 4'-formylpyrazoles in moderate to good yields. During reductive transformations, 4-hydroxymethyl-pyrazoles were obtained, while oxidative lactonization of the 4-formylpyrazole moiety with the phenolic OH in the presence of the Jones reagent afforded A-ring-integrated pyrazolocoumarin hybrids and related analogs. Steroidal pyrazoles, which were produced as C-17 acetates due to acetylation of C-17 OH during the primary Friedel-Crafts reaction, underwent deacetylation in alkaline methanol to furnish 2-heterocyclic estradiol derivatives. Pharmacological studies revealed the overall and cancer cell-specific cytotoxicity of the derivatives and the half maximal inhibitory concentrations were obtained for the most promising compounds.

Estimation of the inhibiting impact of abiraterone D4A metabolite on human steroid 21-monooxygenase (CYP21A2)

Abiraterone D4A metabolite, the product of 3β-hydroxysteroid dehydrogenase activity toward abiraterone, may serve as a potential antitumor agent for the treatment of prostate cancer. The main adverse effect of abiraterone is the disruption of corticosteroid biosynthesis, and the more pharmacologically active abiraterone D4A metabolite may have the same issues. We therefore estimated the inhibiting impact of the abiraterone D4A metabolite on one of the key corticosteroidogenic enzymes - human steroid 21-monooxygenase (CYP21A2). Molecular docking of D4A into the active site of CYP21A2 has been predicted to be similar to abiraterone binding with the enzyme. Abiraterone D4A metabolite, similar to abiraterone, induces type II spectral changes of CYP21A2. The spectral dissociation constant for the abiraterone D4A metabolite-CYP21A2 complex was calculated as 3.4 ± 0.5 μM. Abiraterone D4A metabolite demonstrates competitive/mixed type CYP21A2 inhibition with an inhibitory constant of 1.8 ± 0.8 μM, as obtained by Dixon plot. These results make it possible to predict the adverse effects of the new perspective candidate compound for antitumor therapy.

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.

Prospective computational design and in vitro bio-analytical tests of new chemical entities as potential selective CYP17A1 lyase inhibitors

The development and advancement of prostate cancer (PCa) into stage 4, where it metastasize, is a major problem mostly in elder males. The growth of PCa cells is stirred up by androgens and androgen receptor (AR). Therefore, therapeutic strategies such as blocking androgens synthesis and inhibiting AR binding have been explored in recent years. However, recently approved drugs (or in clinical phase) failed in improving the expected survival rates for this metastatic-castration resistant prostate cancer (mCRPC) patients. The selective CYP17A1 inhibition of 17,20-lyase route has emerged as a novel strategy. Such inhibition blocks the production of androgens everywhere they are found in the body. In this work, a three dimensional-quantitative structure activity relationship (3D-QSAR) pharmacophore model is developed on a diverse set of non-steroidal inhibitors of CYP17A1 enzyme. Highly active compounds are selected to define a six-point pharmacophore hypothesis with a unique geometrical arrangement fitting the following description: two hydrogen bond acceptors (A), two hydrogen bond donors (D) and two aromatic rings (R). The QSAR model showed adequate predictive statistics. The 3D-QSAR model is further used for database virtual screening of potential inhibitory hit structures. Density functional theory (DFT) optimization provides the electronic properties explaining the reactivity of the hits. Docking simulations discovers hydrogen bonding and hydrophobic interactions as responsible for the binding affinities of hits to the CYP17A1 Protein Data Bank structure. 13 hits from the database search (including five derivatives) are then synthesized in the laboratory as different scaffolds. Ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) in vitro experiments reveals three new chemical entities (NCEs) with half maximal inhibitory concentration (IC₅₀) values against the lyase route at mid-micromolar range with favorable selectivity to the lyase over the hydroxylase route (one of them with null hydroxylase inhibition). Thus, prospective computational design has enabled the design of potential lead lyase-selective inhibitors for further studies.

Design, synthesis, and biological evaluation of novel androst-17β-amide structurally related compounds as dual 5α-reductase inhibitors and androgen receptor antagonists

Prostate cancer (PCa) is the second leading cause of death in men. Apart from androgen receptor, 5α-reductase has also been recognized as a potential target. In this study, a series of androst-17β-amide compounds have been designed and synthesized targeting both AR and 5α-reductase. Their anti-proliferation activities were evaluated in AR + cell line 22RV1 and AR - cell line PC-3. The results indicated that most of the synthesized compounds inhibited the testosterone-stimulated cell proliferation with good selectivity and safety. Among all the compounds, androst[3,2-c]pyrazole derivatives (9a-9d) displayed the best inhibition activity comparable with flutamide. Moreover, most of the synthesized compounds displayed good 5α-reductase inhibitory activities with IC₅₀ lower than 1 μM. The docking result of 9d-AR indicated that AR was forced to expands its binding cavity and maintain an antagonistic conformation since the steric hindrance of 9d impeded H12 transposition. Overall, compound 9d can be identified as a potential dual 5α-reductase inhibitor and AR antagonist, which might be of therapeutic importance for PCa treatment.

Microwave-assisted synthesis of biologically relevant steroidal 17-exo-pyrazol-5'-ones from a norpregnene precursor by a side-chain elongation/heterocyclization sequence

Multistep syntheses of novel 17β-pyrazol-5'-ones in the Δ⁵-androstane series were efficiently carried out from pregnenolone acetate. A steroidal 17-carboxylic acid was first synthesized as a norpregnene precursor by the bromoform reaction and subsequent acetylation. Its CDI-activated acylimidazole derivative was then converted to a β-ketoester containing a two carbon atom-elongated side chain than that of the starting material. A Knorr cyclization of the bifunctional 1,3-dicarbonyl compound with hydrazine and its monosubstituted derivatives in AcOH under microwave heating conditions led to the regioselective formation of 17-exo-heterocycles in good to excellent yields. The suppression of an acid-catalyzed thermal decarboxylation of the β-ketoester and thus a significant improvement in the yield of the desired heterocyclic products could be achieved by the preliminary liberation of the arylhydrazines from their hydrochloride salts in EtOH in the presence of NaOAc. The reaction rates were found to depend on the electronic character of the substituent present in the phenylhydrazine applied. The antiproliferative activities of the structurally related steroidal pyrazol-5'-ones and their deacetylated analogs were screened on three human adherent breast cancer cell lines (MCF7, T47D and MDA-MB-231): the microculture tetrazolium assay revealed that some of the presented derivatives exerted cell growth inhibitory effects on some of these cell lines comparable to those of the reference compound, cisplatin.

Evaluation of A-ring fused pyridine d-modified androstane derivatives for antiproliferative and aldo-keto reductase 1C3 inhibitory activity

New A-ring pyridine fused androstanes in 17a-homo-17-oxa (d-homo lactone), 17α-picolyl or 17(E)-picolinylidene series were synthesized and validated by X-ray crystallography, HRMS, IR and NMR spectroscopy. Novel compounds 3, 5, 8 and 12 were prepared by treatment of 4-en-3-one or 4-ene-3,6-dione d-modified androstane derivatives with propargylamine catalyzed by Cu(ii), and evaluated for potential anticancer activity in vitro using human cancer cell lines and recombinant targets of steroidal anti-cancer drugs. Pyridine fusion to position 3,4 of the A-ring may dramatically enhance affinity of 17α-picolyl compounds for CYP17 while conferring selective antiproliferative activity against PC-3 cells. Similarly, pyridine fusion to the A-ring of steroidal d-homo lactones led to identification of new inhibitors of aldo-keto reductase 1C3, an enzyme targeted in acute myeloid leukemia, breast and prostate cancers. One A-pyridine d-lactone steroid 5 also has selective submicromolar antiproliferative activity against HT-29 colon cancer cells. None of the new derivatives have affinity for estrogen or androgen receptors in a yeast screen, suggesting negligible estrogenicity and androgenicity. Combined, our results suggest that A-ring pyridine fusions have potential in modulating the anticancer activity of steroidal compounds.

Multicomponent access to androstano-arylpyrimidines under microwave conditions and evaluation of their anti-cancer activity in vitro

Novel ring D- and A-fused pyrimidines in the androstane series were efficiently synthesized within 10-15min in polar protic solvents under microwave irradiation via two kinds of multicomponent heterocyclization reactions followed by spontaneous or promoted oxidation. The rates of the one-pot catalyst-free transformations of steroidal β-ketoaldehydes, ammonium acetate and substituted benzaldehydes in EtOH were found to be affected slightly by the steric and electronic feature of the substituents on the aromatic ring of the arylaldehyde component and the different reactivities of rings D and A of the sterane core. At the same time, the acid-catalyzed Biginelli-type reaction of dihydrotestosterone acetate, urea and arylaldehydes, and subsequent Jones oxidation of the primarily formed dihydropyrimidinones led to the corresponding ring A-fused 1H-pyrimidin-2-ones in moderate yields independently of the substituents on the aromatic moiety. The synthesized compounds were tested in vitro on human cancer cell lines as well as on non-cancerous fibroblast cells by the MTT assay in order to investigate their biological effects. As a result of the pharmacological screen, a remarkable structure-function relationship has been observed as the acetylated Biginelli products exhibited higher toxicity compared to the deacetylated version of each compound. Furthermore, in case of three 2'-arylpyrimidine derivatives a strong prostate cancer cell specific activity has been identified.

Development and validation of a novel LC-MS/MS method for simultaneous determination of abiraterone and its seven steroidal metabolites in human serum: Innovation in separation of diastereoisomers without use of a chiral column

Abiraterone acetate (AA), the prodrug of abiraterone, is FDA-approved for the treatment of castration-resistant prostate cancer. Abiraterone is metabolized in patients to a more potent analogue, D4A. However, we have recently reported that this analogue is further metabolized to additional metabolites in patients treated with AA. Here, we present a liquid chromatography-tandem mass spectrometry method developed to resolve and detect abiraterone and its seven metabolites in human serum using an AB Sciex Qtrap 5500 mass analyzer coupled with a Shimadzu Nexera UPLC station. Analytes and the internal standard (abiraterone-d4) were extracted from human serum using the liquid-liquid extraction procedure. The analytes were separated using a Zorbax Eclipse Plus C18 150×2.1mm, 3.5μm column at 40°C and an isocratic mobile phase 35% A (0.1% formic acid in water), 65% B (0.1% formic acid in methanol:acetonitrile; 60:40). Electrospray ionization in positive mode was applied with multiple reaction monitoring in a total run time of 13min. Abiraterone detection was linear in the range 2-400ng/mL and all metabolites from 0.1-20ng/mL. The method was validated following US FDA guidelines for bioanalytical method validation, and all the metabolite results were within the acceptance limits. Despite the similarity in structure and mass transition between the metabolites, the validated method separated all the metabolites, including diastereomers, to allow accurate identification and quantitation of each compound.

Isoxazolidine: A Privileged Scaffold for Organic and Medicinal Chemistry

The isoxazolidine ring represents one of the privileged structures in medicinal chemistry, and there have been an increasing number of studies on isoxazolidine and isoxazolidine-containing compounds. Optimization of the 1,3-dipolar cycloaddition (1,3-DC), original methods including electrophilic or palladium-mediated cyclization of unsaturated hydroxylamine, has been developed to obtain isoxazolidines. Novel reactions involving the isoxazolidine ring have been highlighted to accomplish total synthesis or to obtain bioactive compounds, one of the most significant examples being probably the thermic ring contraction applied to the total synthesis of (±)-Gelsemoxonine. The unique isoxazolidine scaffold also exhibits an impressive potential as a mimic of nucleosides, carbohydrates, PNA, amino acids, and steroid analogs. This review aims to be a comprehensive and general summary of the different isoxazolidine syntheses, their use as starting building blocks for the preparation of natural compounds, and their main biological activities.

Contemporary agents in the management of metastatic castration-resistant prostate cancer

Docetaxel-based chemotherapy has been the standard of care for metastatic castration-resistant prostate cancer (mCRPC) since 2004. Over the past few years, there has been a significant paradigm shift in the treatment landscape of this disease. A deeper understanding of prostate cancer biology, along with the development of novel agents has created hope towards treating chemotherapy-naïve and resistant disease. Following the implementation of docetaxel as the first-line therapy for mCRPC, five novel therapies have demonstrated survival benefit in mCRPC. Cabazitaxel, abiraterone acetate, and enzalutamide are three agents recently approved for the treatment of mCRPC, having shown overall survival benefit in patients previously treated with docetaxel, while both abiraterone acetate and enzalutamide have also shown promise in the pre-docetaxel setting. Sipuleucel-T has shown overall survival benefit in asymptomatic mCRPC, while radium-223 provides survival benefit to patients with mCRPC who are symptomatic from their skeletal metastases in both docetaxel-naïve patients and post-docetaxel patients. Denosumab, an anti-RANKL antibody, has been approved for the prevention of skeletal-related events in patients with prostate cancer bone metastases. This review examines the phase 3 trials supporting the use of theses novel agents in the treatment of mCRPC. While these agents provide incremental increases in patient survival, further study to determine the best choice, combination, and/or sequencing of administration is still necessary.

Serum androgens and prostate cancer risk: results from the placebo arm of the Prostate Cancer Prevention Trial

BACKGROUND

Compelling and long-standing data suggest that androgens play an important role in the development of both normal prostate epithelium and prostate cancer. Although testosterone administration can induce prostate cancer (PCA) in laboratory animals, serum-based epidemiologic studies examining androgens in humans have not consistently supported a role for androgens in prostate carcinogenesis. We examined whether pre-diagnostic serum androgens were associated with PCA risk in the placebo arm of the Prostate Cancer Prevention Trial.

METHODS

In this nested case-control study, cases (n = 1,032) were primarily local-stage, biopsy-detected cancers, and controls (n = 1,025) were biopsy-confirmed to be PCA-free. Pre-diagnostic serum androgens (total testosterone, 3α-androstanediol glucuronide, free testosterone), estrogen-to-testosterone ratio, and sex hormone-binding globulin (SHBG) concentrations were measured in pooled (baseline and year 3) blood samples.

RESULTS

We found no significant associations between serum androgens, estrogen-to-testosterone ratios, or SHBG and risk of total, low (Gleason <7) or high-grade (Gleason 7-10) PCA.

CONCLUSION

Much remains to be learned about the role of androgens in prostate carcinogenesis. Further research is needed to evaluate the role of androgens, timing of exposure, genetic modulators of androgen metabolism, or environmental exposures that may affect androgen influence on prostate carcinogenesis.

The post-translational regulation of 17,20 lyase activity

A single enzyme, microsomal P450c17, catalyzes the 17α-hydroxylase activity needed to make cortisol and the subsequent 17,20 lyase activity needed to produce the 19-carbon precursors of sex steroids. The biochemical decision concerning whether P450c17 stops after 17α-hydroxylation or proceeds to 17,20 lyase activity is largely dependent on three post-translational factors. First, 17,20 lyase activity is especially sensitive to the molar abundance of the electron-transfer protein P450 oxidoreductase (POR). Second, cytochrome b5 strongly promotes 17,20 lyase activity, principally by acting as an allosteric factor promoting the interaction of P450c17 with POR, although a minor role as an alternative electron-transfer protein has not been wholly excluded. Third, the serine/threonine phosphorylation of P450c17 itself promotes 17,20 lyase activity, again apparently by promoting the interaction of P450c17 with POR. The principal kinase that phosphorylates P450c17 to confer 17,20 lyase activity appears to be p38α (MAPK14), which increases the maximum velocity of the 17,20 lyase reaction, while having no effect on the Michaelis constant for 17,20 lyase or any detectable effect on the 17α-hydroxylase reaction. Other kinases can also phosphorylate P450c17, but only p38α has been shown to affect its enzymology. Understanding the mechanisms regulating 17,20 lyase activity is essential for the understanding of hyperandrogenic disorders such as premature, exaggerated adrenarche and the polycystic ovary syndrome, and also for the design of selective 17,20 lyase inhibitors for use in hyperandrogenic states and in sex-steroid dependent cancers.

Efficient access to novel androsteno-17-(1',3',4')-oxadiazoles and 17β-(1',3',4')-thiadiazoles via N-substituted hydrazone and N,N'-disubstituted hydrazine intermediates, and their pharmacological evaluation in vitro

A series of novel 17-exo-oxadiazoles and -thiadiazoles in the Δ(5) androstene series were efficiently synthesized from pregnenolone acetate and pregnadienolone acetate via multistep pathways. 17β-(1',3',4')-Oxadiazoles were obtained in high yields by the phenyliodonium diacetate-induced oxidative ring closure of semicarbazone and N-acylhydrazones derived from 3β-acetoxy- and 3β-hydroxyandrost-5-ene-17β-carbaldehydes. For the synthesis of analogous Δ(16)-17-oxadiazolyl derivatives, N,N'-disubstituted hydrazine intermediates were prepared from 3β-acetoxyandrosta-5,16-diene-17-carboxylic acid, which then underwent cyclodehydration in the presence of POCl3. The cyclization of steroidal N,N'-diacylhydrazines containing a saturated ring D with the Lawesson reagent afforded 17β-(1',3',4')-thiadiazoles in good yields. Most of the products were subjected to deacetylation in basic media in order to enlarge the compound library available for pharmacological studies. All of these derivatives were screened in vitro for their antiproliferative effects against four malignant human adherent cell lines (HeLa, A2780, MCF7 and A431) by means of the MTT assay. The 3β-hydroxy derivatives of the newly-synthesized 17-exo-heterocycles were tested in vitro to investigate their inhibitory effects on rat testicular C17,20-lyase. One of the 1,3,4-oxadiazolyl derivatives proved to exert noteworthy enzyme-inhibitory action, with an IC50 (0.065 μM) of the same order of magnitude as that of abiraterone.

Generation of comparative pharmacophoric model for steroidal 5α-reductase I and II inhibitors: A 3D-QSAR study on 6-azasteroids

Steroidal 5α-reductase, a key enzyme involved in the transformation of testosterone to dihydrotestosterone, is unstable during the purification leading to loss of the activity. Therefore, due to unstable nature, the crystal structure of the 5α-reductase is unknown. In the present study, we have generated a comparative pharmacophoric model for both isoforms of steroidal 5α-reductase using 6-azasteroids. The steric and electrostatic maps generated for both isoforms provides structure framework for designing of new inhibitors. Further, 3D-maps are also helpful in understanding variability in the activity of the compounds. Statistical measures generated for both enzymes showed good internal and external prediction. Overall, the analyses of models provides structural requirement of dual and selective steroidal 5α-reductase inhibitors in an interactive fashion.

A click approach to novel D-ring-substituted 16α-triazolylestrone derivatives and characterization of their antiproliferative properties

A simple and efficient synthesis of novel, D-ring substituted estrone derivatives containing a 16α-triazolyl moiety is described. Two epimeric azido alcohols (16α-azido-17α-hydroxy and 16α-azido-17β-hydroxy) of estra-1,3,5(10)-triene-3-methyl ether were prepared, followed by copper(I)-catalyzed azide-alkyne cycloaddition with various terminal alkynes. The steroidal triazoles were obtained in high yields and their activities against three human cancer cell lines (HeLa, MCF7 and A431) were screened. The most effective analogs were submitted to additional experiments in order to characterize their antiproliferative properties. As evidenced by flow cytometry, the selected steroids induced a disturbance in the HeLa cell cycle in a concentration- and exposure-dependent manner, through an increase of the hypodiploid population (subG1) and a cell cycle arrest in the G2/M phase. A noncancerous human fibroblast cell line (MRC5) was used to determine the selectivities of these compounds. Fluorescent microscopy after Hoechst 33258 - propidium iodide (HOPI) double staining revealed nuclear condensation and disturbed cell membrane integrity. The enhanced activities of caspase-3 and caspase-9 without activation of caspase-8 in the treated cells indicated the activation of the intrinsic pathway of apoptosis. The levels of cell cycle regulators (CDK1, cyclin B1/B2 and cdc25B) were decreased and the ratio Bax/Bcl-2 was increased 24 h after the treatment of HeLa cells (determined at an mRNA level by means of an RT-PCR technique). Under the same conditions, two agents elicited substantially increased degrees of phosphorylation of stathmin, as evidenced by Western blotting. The presented results demonstrate that these steroids can be regarded as appropriate structural scaffolds for the design and synthesis of further steroid analogs as innovative drug candidates with good efficacy.

Simultaneous pharmacokinetic and pharmacodynamic analysis of 5α-reductase inhibitors and androgens by liquid chromatography tandem mass spectrometry

Benign prostatic hyperplasia and prostate cancer can be treated with the 5α-reductase inhibitors, finasteride and dutasteride, when pharmacodynamic biomarkers are useful in assessing response. A novel method was developed to measure the substrates and products of 5α-reductases (testosterone, 5α-dihydrotestosterone (DHT), androstenedione) and finasteride and dutasteride simultaneously by liquid chromatography tandem mass spectrometry, using an ABSciex QTRAP(®) 5500, with a Waters Acquity™ UPLC. Analytes were extracted from serum (500 µL) via solid-phase extraction (Oasis(®) HLB), with (13)C3-labelled androgens and d9-finasteride included as internal standards. Analytes were separated on a Kinetex C18 column (150 × 3 mm, 2.6 µm), using a gradient run of 19 min. Temporal resolution of analytes from naturally occurring isomers and mass +2 isotopomers was ensured. Protonated molecular ions were detected in atmospheric pressure chemical ionisation mode and source conditions optimised for DHT, the least abundant analyte. Multiple reaction monitoring was performed as follows: testosterone (m/z 289 → 97), DHT (m/z 291 → 255), androstenedione (m/z 287 → 97), dutasteride (m/z 529 → 461), finasteride (m/z 373 → 317). Validation parameters (intra- and inter-assay precision and accuracy, linearity, limits of quantitation) were within acceptable ranges and biological extracts were stable for 28 days. Finally the method was employed in men treated with finasteride or dutasteride; levels of DHT were lowered by both drugs and furthermore the substrate concentrations increased.

Steroidal pyrazolines and pyrazoles as potential 5α-reductase inhibitors: synthesis and biological evaluation

Taking pregnenolone as the starting material, two series of pyrazolinyl and pyrazolyl pregnenolones were synthesized through different routes. The synthesis of the analogs of both series is multistep and proceeds in good overall yields. While the key step in the synthesis of pyrazolinyl pregnenolones is the heterocyclization of benzylidine derivatives (3) in presence of hydrazine hydrate, it is the condensation of 3β-hydroxy-21-hydroxymethylidenepregn-5-en-3β-ol-20-one (5) with phenylhydrazine in the synthesis of pyrazolyl derivatives. Compounds of both the series were tested for their 5α-reductase inhibitory activities. Amongst all the compounds screened for their 5α-reductase inhibitory activities, compound 4b, 4c and 6b were found to be the most active.

Challenges in the sequencing of therapies for the management of metastatic castration-resistant prostate cancer

Prior to 2010, docetaxel was the standard option for chemotherapy in men with metastatic castration-resistant prostate cancer (mCRPC). Today, the picture is vastly different: several additional therapies have each demonstrated a survival benefit such that we now have chemotherapy (cabazitaxel), androgen suppressive agents (abiraterone acetate and enzalutamide), a cellular vaccine (sipuleucel-T) and radium-233 (for symptomatic bone metastases). With several other agents in the pipeline for late-stage disease, the future looks promising for mCRPC. As the available data are not able to inform as to the optimum sequencing of therapy, this remains a challenge. This paper draws on insights from published and ongoing clinical studies to provide a practical patient-focused approach to maximize the benefits of the current therapeutic armamentarium. Preliminary sequencing suggestions are made based on clinical trial criteria. But until more data become available, clinical gestalt, experience, cost and individual patient preferences will continue to drive choices.

A facile access to novel steroidal 17-2'-(1',3',4')-oxadiazoles, and an evaluation of their cytotoxic activities in vitro

Novel types of 17-exo-heterocycles in the Δ(5) androstene series carrying an 1,3,4-oxadiazole moiety were efficiently synthesized via aldehyde N-acylhydrazone intermediates, obtained from the microwave-assisted condensation of 3β-hydroxy- or 3β-acetoxyandrost-5-ene-17β-carbaldehyde with different acylhydrazides. The subsequent phenyl iodonium diacetate-induced oxidative cyclization proceeded under mild conditions. The synthesized compounds were subjected to in vitro pharmacological studies to investigate their antiproliferative activities on four malignant adherent cell lines (HeLa, MCF7, A2780 and A431), and exhibited the highest potency against HeLa cells, some of them revealing action comparable to that of the reference agent cisplatin.