Design and synthesis of novel androgen receptor antagonists via molecular modeling

Several androgen receptor (AR) antagonists are clinically prescribed to treat prostate cancer. Unfortunately, many patients become resistant to the existing AR antagonists. To overcome this, a novel AR antagonist candidate called DIMN was discovered by our research group in 2013. In order to develop compounds with improved potency, we designed novel DIMN derivatives based on a docking study and substituted carbons with heteroatom moieties. Encouraging in vitro results for compounds 1b, 1c, 1e, 3c, and 4c proved that the new design was successful. Among the newly synthesized compounds, 1e exhibited the strongest inhibitory effect on LNCaP cell growth (IC₅₀ = 0.35 μM) and also acted as a competitive AR antagonist with selectivity over the estrogen receptor (ER) and the glucocorticoid receptor (GR). A docking study of compound 1e fully supported these biological results. Compound 1e is considered to be a novel, potent and AR-specific antagonist for treating prostate cancer. Thus, our study successfully applied molecular modeling and bioisosteric replacement for hit optimization. The methods here provide a guide for future development of drug candidates through structure-based drug discovery and chemical modifications.     

Design,synthesis, and biological evaluation of 3-aryl-3-hydroxy-1-phenylpyrrolidine derivatives as novel androgen receptor antagonists

We designed and synthesized a series of 3-aryl-3-hydroxy-1-phenylpyrrolidine derivatives D and evaluated their potential as novel androgen receptor (AR) antagonists therapeutically effective against castration-resistant prostate cancer (CRPC). Introduction of a methyl group at the 2-position (R²) of the pyrrolidine ring increased the AR binding affinity. The (2S,3R) configuration of the pyrrolidine ring was favorable for the AR antagonistic activity. It was found that introduction of an amide substituent (R¹) and a pyridin-3-yl group (Q) was effective for reducing the AR agonistic activity which appeared during the optimization of lead compound 6. Compound 54 showed potent antitumor effects against a CRPC model of LNCaP-hr cell line in a mouse xenograft, in which bicalutamide exhibited only partial suppression of tumor growth. Thus, the pyrrolidine derivatives such as 54 are novel AR antagonists, and their properties having efficacy against CRPC are distinct from those of a representative first-generation antagonist, bicalutamide.     

Design,synthesis and biological evaluation of novel 3-oxo-4-oxa-5α-androst-17β-amide derivatives as dual 5α-reductase inhibitors and androgen receptor antagonists

Prostate cancer (PCa) is the second leading cause of death in men. Recently, some researches have showed that 5α-reductase inhibitors were beneficial in PCa treatment as well. In this study, a series of novel 3-oxo-4-oxa-5α-androst-17β-amide derivatives have been designed and synthesized in a more simple and convenient method. Most of the synthesized compounds displayed good 5α-reductase inhibitory activities and androgen receptor binding affinities. Their anti-proliferation activities in PC-3 and LNCaP cell lines were also evaluated and the results indicated that most of the synthesized compounds exhibited potent anti-proliferative activities. It is obvious that the androgen-dependent cell line LNCaP was much more sensitive than the androgen-independent cell line PC-3. Among all the synthesized compounds, 11d and 11k displayed the best inhibition activity with 4-fold more sensitive toward LNCaP than PC-3, which was consistent with their high affinities observed in AR binding assay. Molecular modeling studies suggested that 11k could bind to AR in a manner similar to the binding of dihydrotestosterone to AR. Compared to the finasteride, 11k showed a longer plasma half-life (4 h) and a better bioavailability. Overall, based on biological activities data, compound 11d and 11k can be identified as potential dual 5α-reductase inhibitors and AR antagonists which might be of therapeutic importance for prostate cancer treatment.     

20-Aminosteroids as a novel class of selective and complete androgen receptor antagonists and inhibitors of prostate cancer cell growth

Here, the synthesis and the evaluation of novel 20-aminosteroids on androgen receptor (AR) activity is reported. Compounds 11 and 18 of the series inhibit both the wild type and the T877A mutant AR-mediated transactivation indicating AR antagonistic function. Interestingly, minor structural changes such as stereoisomers of the amino lactame moiety exhibit preferences for antagonism among wild type and mutant AR. Other tested nuclear receptors are only weakly or not affected. In line with this, the prostate cancer cell growth of androgen-dependent but not of cancer cells lacking expression of the AR is inhibited. Further, the expression of the prostate specific antigen used as a diagnostic marker is also repressed. Finally steroid 18 enhances cellular senescence that might explain in part the growth inhibition mediated by this derivative. Steroids 11 and 18 are the first steroids that act as complete AR antagonists and exhibit AR specificity.     

Design,synthesis and biological evaluation of ring A modified 11-keto-boswellic acid derivatives as Pin1 inhibitors with remarkable anti-prostate cancer activity

Pin1 (Protein interaction with never in mitosis A1) is a validated molecular target for anticancer drug discovery. Herein, we reported the design, synthesis, and structure-activity relationship study of novel ring A modified AKBA (3-acetyl-11-keto-boswellic acid) derivatives as Pin1 inhibitors. Most compounds showed superior Pin1 inhibitory activities to AKBA. One of the most promising compounds, 10a, potently inhibited Pin1 with IC₅₀ value of 0.46?μM, while it displayed excellent anti-proliferative effect against prostate cancer cells PC-3 with GI₅₀ value of 1.82?μM. Structure-activity relationship indicated that reasonable structural modifications in ring A had significant impact on improving activity. Further mechanism research revealed that 10a decreased the level of Cyclin D1 and caused cell cycle arrest at G0/G1 phase in PC-3 cancer cells. Thus, compound 10a may serve as potential anti-prostate cancer agent for further investigation through Pin1 inhibition.     

Marine spongian sesquiterpene phenols,dictyoceratin-C and smenospondiol,display hypoxia-selective growth inhibition against cancer cells

In the course of our search for hypoxia-selective growth inhibitors against cancer cells, a sesquiterpene phenol, dictyoceratin-C (1), was isolated from the Indonesian marine sponge of Dactylospongia elegans under the guidance of the constructed bioassay. Dictyoceratin-C (1) inhibited proliferation of human prostate cancer DU145 cells selectively under hypoxic condition in a dose-dependent manner at the concentrations ranging from 1.0 to 10 μM. The subsequent structure–activity relationship study using nine sesquiterpene phenol/quinones (2–10), which were isolated from marine sponge, was executed. We found that smenospondiol (2) also exhibited the similar hypoxia-selective growth inhibitory activity against DU145 cells, and the para-hydroxybenzoyl ester moiety would be important for hypoxia-selective growth inhibitory activity of 1. In addition, the mechanistic analysis of dictyoceratin-C (1) revealed that the 10 μM of 1 inhibited accumulation of Hypoxia-Inducible Factor-1α under hypoxic condition.     

Effect of dehydroepiandrosterone derivatives on the activity of 5α-reductase isoenzymes and on cancer cell line PC-3

It is well known that testosterone (T) under the influence of 5α-reductase enzyme is converted to dihydrotestosterone (DHT), which causes androgen-dependent diseases. The aim of this study was to synthesize new dehydroepiandrosterone derivatives (3a–e, 4a–i, 6 and 7) having potential inhibitory activity against the 5α-reductase enzyme. This paper also reports the in vivo pharmacological effect of these steroidal molecules. The results from this study showed that all compounds exhibited low inhibitory activity for 5α-reductase type 1 and 2 enzymes and they failed to bind to the androgen receptor. Furthermore, in the in vivo experiment, steroids 3b, 4f, and 4g showed comparable antiandrogenic activity to that of finasteride; only derivatives 4d and 7 produced a considerable decrease in the weight of the prostate gland of gonadectomized hamsters treated with (T). On the other hand, compounds 4a, f and h showed 100% inhibition of the growth of prostate cancer cell line PC-3, with compound 4g having a 98.2% antiproliferative effect at 50 μM. The overall data indicated that these steroidal molecules, having an aromatic ester moiety at C-3 (4f–h), could have anticancer properties.     

New pyrimidine-benzoxazole/benzimidazole hybrids: Synthesis,antioxidant, cytotoxic activity,in vitro cyclooxygenase and phospholipase A2-V inhibition

To enhance the cytotoxicity of benzimidazole and/or benzoxazole core, the benzimidazole/benzoxazole azo-pyrimidine were synthesized through diazo-coupling of 3-aminophenybenzimidazole (6a) or 3-aminophenylbenzoxazole (6b) with diethyl malonate. The new azo-molanates 6a&b mixed with urea in sodium ethoxide to afford the benzimidazolo/benzoxazolopyrimidine 7a&b. The structure elucidation of new synthesized targets was proved using spectroscopic techniques NMR, IR and elemental analysis. The cytoxicity screening had been carried out against five cancer cell lines: prostate cancer (PC-3), lung cancer (A-549), breast cancer (MCF-7), pancreas cancer (PaCa-2) and colon cancer (HT-29). Furthermore, the antioxidant activity, phospholipase A2-V and cyclooxygenases inhibitory activities of the target compounds 7a&b were evaluated and the new compounds showed potent activity (cytotoxicity IC₅₀ range from 4.3 to 9.2 µm, antioxidant activity from 40% to 80%, COXs or LOX inhibitory activity from 1.92 µM to 8.21 µM). The docking of 7a&b was made to confirm the mechanism of action.     

Synthesis,biological evaluation and molecular docking of 4-Amino-2H-benzo[h]chromen-2-one (ABO) analogs containing the piperazine moiety

Prostate cancer (PCa) is a major cause of cancer-related male death in worldwide. To develop of potential anti-prostate cancer agents, 22 kinds of 4-Amino-2H-benzo[h]chromen-2-one analogs were designed and synthesized as potent androgen receptor (AR) antagonist through rational drug modification leading to the discovery of a series of novel antiproliferative compounds. Analogs (3, 4, 5, 7, 8, 10, 11, 12, 16, 18, 21, 23, and 24) exhibited potent antagonistic potency against AR (inhibition >50%), and exhibited potent AR binding affinities as well as displayed the higher activities than finasteride toward LNCaP cells (AR-rich) versus PC-3 cells (AR-deficient). Moreover, the docking study suggested that the most potent antagonist 23 mainly bind to AR ligand binding pocket (LBP) site through Van der Waals’ force interactions. The structure-activity relationship (SAR) of these designed 4-Amino-2H-benzo[h]chromen-2-one analogs was rationally explored and discussed. Collectively, this work provides a potential lead compound for anticancer agent development related to prostate cancer therapy, and took a step forward towards the development of novel and improved AR antagonists.     

新型四氢苯并噻唑化合物作为雄激素受体调节剂的合成与构效关系

前列腺癌是男性最常被诊断出的癌症之一,而雄激素受体（androgen receptor, AR）是前列腺癌治疗的重要靶标。现有的AR拮抗剂在长期使用后通常由于多种原因而失效。因此,新型AR拮抗剂的开发仍具有重要的意义。一系列四氢苯并噻唑类化合物,通过 α,β-环氧环己酮与适当的硫脲的缩合反应被合成。其中,多个化合物在酵母双杂交系统中表现出强于或相当于氟他胺的雄激素受体拮抗活性（IC50≤2.48 mmol/L）。进一步的细胞活力试验表明,这些活性化合物有效地抑制了雄激素敏感的LNCaP细胞的增殖（IC50值17.1~41.4 mmol/L）。分子对接研究提供了化合物与受体相互作用的可能模型,较好地符合了初步的构效关系研究。总之,本文的研究证明,四氢苯并噻唑可以作为有效的AR调节剂,可能代表了一种有前景的先导化合物,有助于进一步开发出新型的更加强效的雄激素受体拮抗剂。     

Novel C-6 substituted and unsubstituted pregnane derivatives as 5α-reductase inhibitors and their effect on hamster flank organs diameter size

The present study is addressed to ascertain the inhibitory effect of several progesterone derivatives having a chlorine substituent at C-6 (12a–12d), 15 with a bromine substituent at C-6 and 14a–14d, without any halogen atom at C-6 all having an ester side chain at C-17 (benzoate ester bearing a Cl, F and a Br atom at C-4 position of the phenyl ring) on the 5α-reductase enzyme activity present in human prostate. In addition, it was also of interest to investigate the pharmacological effect on hamster flank organs diameter size.In order to study the structure–activity relationships of steroids 12a–12d, 14a–14d and 15 we determined the concentration of these steroids that inhibited 50% of the activity of human prostate 5α-reductase enzyme (IC₅₀), as well as the in vivo effect of these compounds in the hamster flank organs diameter size. We also ascertained, the capacity of these steroids to bind to the androgen receptors present in the rat prostate cytosol using labeled mibolerone (MIB) for monitoring the binding to the androgen receptor.The results from this study indicated that compounds 12a–12d (having a chlorine substituent at C-6), 14a–14d (lacking a halogen atom at C-6), 13 and 15 (having a bromine atom at C-6) showed an increased antiandrogenic effect (lower value for the diameter of the flank organs) as compared to the flank organs from testosterone-treated hamsters. On the other hand, the series of compounds containing a chlorine substituent at C-6 compounds (12a–12d) showed a higher antiandrogenic activity as compared to the compounds lacking a halogen atom at C-6 (14a, 14b and 14d). Although compounds 13 and 15 decreased the flank organs diameter size, however, this increase was not statistically significant as compared to that of the commercially available product finasteride. The steroidal derivatives 13, 14a–14d (lacking the chlorine substituent at C-6) and 15 (having a bromine atom at C-6) exhibited a higher 5α-reductase inhibitory activity (lower IC₅₀ values) as compared to the series of compounds 12a–12d having the halogen substituent at C-6.Finasteride reduced the diameter size of the flank organs. The effect of this steroid and compounds 12a–12d, 13, 14a–14d and 15 on hamster flank organs can be explained by the fact that these steroids did not bind to the androgens receptor, which indicates that its mechanism of action is an inhibiting for the 5α-reductase activity. This enzyme is present in the hamster flank organs and was inhibited by the novel steroids in the human prostate homogenates.     

Design, synthesis, and biological evaluation of dibromotyrosine analogues inspired by marine natural products as inhibitors of human prostate cancer proliferation, invasion, and migration

Bioactive secondary metabolites originating from dibromotyrosine are common in marine sponges, such as sponges of the Aplysina species. Verongiaquinol (1), 3,5-dibromo-1-hydroxy-4-oxocyclohexa-2,5-diene-1-acetamide, and aeroplysinin-1 are examples of such bioactive metabolites. Previous studies have shown the potent antimicrobial as well as cytotoxic properties of verongiaquinol and the anti-angiogenic activity of aeroplysinin-1. The work presented herein shows the design and synthesis of dibromotyrosine-inspired phenolic ester and ether analogues with anti-angiogenic, anti-proliferative and anti-migratory properties and negligible cytotoxicity. Several analogues were synthesized based on docking experiments in the ATP binding site of VEGFR2 and their anti-angiogenic potential and ability to inhibit angiogenesis and prostate cancer proliferation, migration and invasion were evaluated using the chick chorioallantoic membrane (CAM) assay, MTT, wound-healing, and Cultrex® BME cell invasion assay models, respectively. Analogues with high docking scores showed promising anti-angiogenic activity in the CAM assay. In general, ester analogues (5, 6, and 8–10) proved to be of higher anti-migratory activity whereas ether analogues (11–14) showed better anti-proliferative activity. These results demonstrate the potential of dibromotyrosines as promising inhibitory scaffolds for the control of metastatic prostate cancer proliferation and migration.     

Synthesis and biological evaluation of histone deacetylase and DNA topoisomerase II-Targeted inhibitors

HDAC inhibitors enable histones to maintain a high degree of acetylation. The resulting looser state of chromatin DNA may increase the accessibility of DNA drug targets and consequently improve the efficiency of anticancer drugs targeting DNA, such as Topo II inhibitors. A novel class of nucleoside-SAHA derivatives has been designed and synthesized based on the synergistic antitumor effects of topoisomerase II and histone deacetylase inhibitors. Their inhibitory activities toward histone deacetylases and Topo II, and their cytotoxicities in cancer cell lines, were evaluated. Among the synthesized hybrid compounds, compound 16b showed the potent HDAC inhibitory activity at a low nanomolar level and exhibited antiproliferative activity toward cancer cell lines including MCF-7 (breast), HCT-116 (colon), and DU-145 (prostate) cancer cells at a low micromolar level. Moreover, compound 16a showed HDAC6-selectivity 20-fold over HDAC1.     

Replacing alkyl sulfonamide with aromatic sulfonamide in sulfonamide-type RXR agonists favors switch towards antagonist activity

Retinoid X receptor (RXR) ligands are attractive candidates for clinical application because of their activity against tamoxifen-resistant breast cancer, taxol-resistant lung cancer, metabolic syndrome, and allergy. Though several RXR ligands, especially RXR antagonists, have been reported, the rational molecular design of such compounds is not well advanced. 4-[N-Methanesulfonyl-N-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-2-naphthyl)amino]nicotinic acid (5a) is a moderately RXRα-preferential agonist, and we examined the feasibility of replacing the methyl group on the sulfonamide with a longer alkyl chain or an aromatic ring as an approach to produce new RXR antagonists. Several of the resulting benzenesulfonanilide-type compounds showed RXR antagonist activity. This design strategy should be a useful approach for addressing the lack of structure diversity of RXR antagonists.     

Design,synthesis and biological evaluation of 2,5-dimethylfuran-3-carboxylic acid derivatives as potential IDO1 inhibitors

Indoleamine 2,3-dioxygenase 1 (IDO1) plays a vital role in tumor immune escape and has emerged as a promising target for cancer immunotherapy. In this study, a novel series of 2,5-dimethylfuran-3-carboxylic acid derivatives were designed, synthesized and evaluated for inhibitory activities against IDO1, and their structure-activity relationship was investigated. Among these, compound 19a exhibited excellent IDO1 inhibitory activity (HeLa cellular IC₅₀?=?4.0?nM, THP-1 cellular IC₅₀?=?4.6?nM). Further molecular docking studies revealed that the compound 19a formed a coordinate bond with the heme iron through the carboxylic acid moiety. These results indicate that compound 19a is a potential IDO1 inhibitor for further investigation.     

Design and synthesis of peptide conjugates of phosphoramide mustard as prodrugs activated by prostate-specific antigen

A series of Glutaryl-Hyp-Ala-Ser-Chg-Gln-4-aminobenzyl phosphoramide mustard conjugates (1a–e) was designed and synthesized as potential prodrugs for site-specific activation by PSA in prostate cancer cells. All conjugates were found to be substrates of PSA with cleavage occurring between Gln and the para-aminobenzyl (PAB) linker. Structure–activity relationship studies on these conjugates indicated that introduction of electron-withdrawing fluorine(s) on the phenyl ring in the PAB linker uniformly improved the chemical stability of the conjugates while the position of substitution affected differently the self-immolative process of conjugates upon proteolysis. Introduction of a fluorine at ortho position to benzylic phosphoramide as in 1b results in better stability of the conjugate prior to activation while maintaining its antiproliferative activity upon activation by PSA. The conjugate 1b with 2-fluoro substitution was identified as a promising lead for further evaluation and optimization in the development of prostate cancer-targeted prodrugs.     

Synthesis of novel ageladine A analogs showing more potent matrix metalloproteinase (MMP)-12 inhibitory activity than the natural product

By employing a previously established synthetic scheme, the synthesis described in the title was carried out in order to explore the substituent effects in the pyrrole ring of ageladine A on MMP-12 inhibitory activity. It became evident that a halogen atom (Br or Cl) at the 2-position and an additional bromine atom at the 4-position are highly effective for improving the inhibitory activity. These studies led us to discover three novel ageladine A analogs (4a, c, o) showing more potent MMP-12 inhibitory activity than the natural product.     

Design,synthesis and evaluation of 2-(indolylmethylidene)-2,3-dihydro-1-benzofuran-3-one and 2-(indolyl)-4H-chromen-4-one derivatives as novel monoamine oxidases inhibitors

A series of 2-(indolylmethylidene)-2,3-dihydro-1-benzofuran-3-ones (aurone-indole hybrids) and 2-(indolyl)-4H-chromen-4-ones (flavone-indole hybrids) were designed, synthesized, and their monoamine oxidase (MAO) A and B inhibitory activities were evaluated. Compounds 5b and 11b showed potent inhibitory activities against MAO-A, comparable to that of pargyline used as a positive control, and most of the compounds, except for 2a and 10b, showed potent inhibitory activities against MAO-B. Compound 9a was the most potent and highly selective inhibitor of MAO-B (IC₅₀ value for MAO-B: 0.0026 μM, and MAO-A: >100 μM). Comparison of the inhibitory activities of 1a vs. 9a vs. 13a and 1b vs. 7b vs. 11b suggested that methoxy substitution at R¹ on the A-rings of flavonoids increases MAO-A inhibition whereas methoxy substitution at R² increased MAO-B inhibition. Comparison of 4a vs. 10a, 6a vs. 11a, 3b vs. 8b and 4b vs. 9b showed incremental increases in MAO-B inhibitory activity by R² substitution on the A ring. Comparison of the MAO-B inhibitory effects of the flavone-indole hybrids and aurone-indole hybrids showed that most of the aurone-indole hybrids were stronger inhibitors than the corresponding flavone-indole hybrids. Molecular docking analysis of compounds 1a and 9a with MAO-B further supported the above structural effects of these compounds on MAO-B inhibitory activity.This is the first report identifying aurone-indole hybrids as potent MAO-B inhibitors. The results reported here suggest that 2-(1H-indol-1-ylmethylene)-6-methoxy-3(2H)-benzofuranone (9a) might be a useful lead for the design and development of novel MAO-B inhibitors