Ahmed S. Abdelsamie

Part I: Synthesis, cancer chemopreventive activity and molecular docking study of novel quinoxaline derivatives

The reaction of o-phenylene diamine and ethyl oxamate is reinvestigated and led to 3-aminoquinoxalin-2(1H)-one rather than benzimidazole-2-carboxamide as was previously reported. The structure of the obtained quinoxaline has been confirmed by X-ray. The anti-tumor activity of synthesized quinoxalines 1-21 has been evaluated by studying their possible inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Among the studied compounds 1-21, compounds 12, 8, 13, 18, 17 and 19, respectively, demonstrated strong inhibitory effects on the EBV-EA activation without showing any cytotoxicity and their effects being stronger than that of a representative control, oleanolic acid. Furthermore, compound 12 exhibited a remarkable inhibitory effect on skin tumor promotion in an in vivo two-stage mouse skin carcinogenesis test using 7,12-dimethylbenz[a]anthracene (DMBA) as an initiator and TPA as a promoter. The result of the present investigation indicated that compound 12 might be valuable as a potent cancer chemopreventive agent. Moreover, the molecular docking into PTK (PDB: 1t46) has been done for lead optimization of the aforementioned compounds as potential PTK inhibitors.

Design, synthesis and molecular docking study of novel quinoxalin-2(1H)-ones as anti-tumor active agents with inhibition of tyrosine kinase receptor and studying their cyclooxygenase-2 activity

On continuation to our work, new quinoxalin-2(1H)-ones were synthesized to study their cytotoxic effect against HepG-2 and MCF-7 with their effect on the human tyrosine kinase (TRK). Compounds 12, 18, 15, 13, 11a, 20 and 16, respectively, were found to be more potent than cisplatin against HepG2 and selective to TRK. Also, compounds 12, 18, 20, 13, 14, and 22, respectively, exhibited decidedly activity against MCF-7 and selectivity against human TRK compared to cisplatin. A molecular docking study was also performed to gain comprehensive understanding into plausible binding modes and to conclude the structure activity relationships of the synthesized compounds. Moreover, anti-inflammatory activity was studied. Compounds 12, 15, 18 and 22 were found to be potent and selective against COX-2.

Design, synthesis and structure-activity relationship of novel quinoxaline derivatives as cancer chemopreventive agent by inhibition of tyrosine kinase receptor.

The cancer chemopreventive activity of quinoxaline derivatives 1-20 has been evaluated by studying the inhibitory effect on Epstein-Barr virus early antigen (EBV-EA) activation. The quinoxaline derivatives 1-20 showed inhibitory effect on EBV-EA activation without cytotoxicity on Raji cells. All compounds exhibited dose dependent inhibitory activities, most of them showed significant activity at 1000 mol ratio/12-O-tetradecanoylphorbol-13-acetate (TPA). Compounds 7 and 9 exhibited stronger inhibitory effects on the EBV-EA activation than that of the representative control, oleanolic acid, at the highest measured concentration. In addition, compounds 7-10 showed potent and selective inhibition of human tyrosine kinase (TRK) in liver cancer HepG2 and breast cancer MCF-7 cell lines similar to the positive control, doxorubicin.

First Dual Inhibitors of Steroid Sulfatase (STS) and 17β-Hydroxysteroid Dehydrogenase Type 1 (17β-HSD1): Designed Multiple Ligands as Novel Potential Therapeutics for Estrogen-Dependent Diseases

STS and 17β-HSD1 are attractive targets for the treatment of estrogen-dependent diseases like endometriosis and breast cancer. The simultaneous inhibition of both enzymes appears more promising than blockage of either protein alone. We describe a designed multiple ligand approach resulting in highly potent dual inhibitors. The most interesting compound 9 showed nanomolar IC50 values for both proteins, membrane permeability, and no interference with estrogen receptors. It efficiently reversed E1S- and E1-induced T47D cell proliferation.

Towards the evaluation in an animal disease model: Fluorinated 17β-HSD1 inhibitors showing strong activity towards both the human and the rat enzyme.

17β-Estradiol (E2), the most potent human estrogen, is known to be involved in the etiology of estrogen-dependent diseases (EDD) like breast cancer and endometriosis. 17β-Hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyses the last step of E2 biosynthesis and is thus a promising target for the treatment of EDD. The previously described bicyclic substituted hydroxyphenylmethanones (BSHs) display high inhibitory potency towards human 17β-HSD1, but marginal activity towards rodent 17β-HSD1, precluding a proof of principle study in an animal endometriosis model. The aim of this work was to perform structural optimizations in the BSHs class to enhance inhibitory activity against rodent (mouse and rat) 17β-HSD1 while maintaining activity against the human enzyme. The introduction of fluorine atoms on the benzoyl moiety resulted in compounds with the desired properties. Molecular docking and homology modeling were applied to elucidate the binding mode and interspecies differences in activity. Compound 33 is the most potent inhibitor of both human and rat 17β-HSD1 up to date (IC₅₀ = 2 nM and 97 nM, respectively).

Inhibition of 17β-HSD1: SAR of bicyclic substituted hydroxyphenylmethanones and discovery of new potent inhibitors with thioether linker.

Estradiol is the most potent estrogen in humans. It is known to be involved in the development and proliferation of estrogen dependent diseases such as breast cancer and endometriosis. The last step of its biosynthesis is catalyzed by 17β-hydroxysteroid dehydrogenase type 1 (17β- HSD1) which consequently is a promising target for the treatment of these diseases. Recently, we reported on bicyclic substituted hydroxyphenylmethanones as potent inhibitors of 17β-HSD1. The present study focuses on rational structural modifications in this compound class with the aim of gaining more insight into its structure-activity relationship (SAR). (4-Hydroxyphenyl)-(5-(3-hydroxyphenylsulfanyl)-thiophen-2-yl)methanone (25) was discovered as a member of a novel potent class of human 17β-HSD1 inhibitors. Computational methods were used to elucidate its interactions with the target protein. The compound showed activity also towards the murine 17β-HSD1 enzyme and thus is a starting point for the design of compounds suitable for evaluation in an animal disease model.

Treatment of estrogen-dependent diseases: Design, synthesis and profiling of a selective 17β-HSD1 inhibitor with sub-nanomolar IC50 for a proof-of-principle study

Current endocrine therapeutics for the estrogen-dependent disease endometriosis often lead to considerable side-effects as they act by reducing estrogen action systemically. A more recent approach takes advantage of the fact that the weak estrogen estrone (E1) which is abundant in the plasma, is activated in the target cell to the highly estrogenic estradiol (E2) by 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1). 17β-HSD1 is overexpressed in endometriosis and thus a promising target for the treatment of this disease, with the prospect of less target-associated side-effects. Potent inhibitors from the class of bicyclic substituted hydroxyphenylmethanones with sulfonamide moiety recently described by us suffered from high molecular weight and low selectivity over 17βHSD2, the physiological adversary of 17β-HSD1. We describe the structural optimizations leading to the discovery of (5-(3,5-dichloro-4-methoxyphenyl)thiophen-2-yl)(2,6-difluoro-3-hydroxyphenyl)methanone 20, which displayed a sub-nanomolar IC50 towards 17β-HSD1 as well as high selectivity over the type 2 enzyme, the estrogen receptors α and β and a range of hepatic CYP enzymes. The compound did neither show cellular toxicity, nor PXR activation nor mutagenicity in the AMES II assay. Additional favourable pharmacokinetic properties (rat) make 20 a suitable candidate for proof-of-principle studies using xenotransplanted immunodeficient rats.

Inhibitors of 17β-hydroxysteroid dehydrogenase type 1, 2 and 14: Structures, biological activities and future challenges

During the past 25 years, the modulation of estrogen action by inhibition of 17β-hydroxysteroid dehydrogenase types 1 and 2 (17β-HSD1 and 17β-HSD2), respectively, has been pursued intensively. In the search for novel treatment options for estrogen-dependent diseases (EDD) and in order to explore estrogenic signaling pathways, a large number of steroidal and nonsteroidal inhibitors of these enzymes has been described in the literature. The present review gives a survey on the development of inhibitor classes as well as the structural formulas and biological properties of their most interesting representatives. In addition, rationally designed dual inhibitors of both 17β-HSD1 and steroid sulfatase (STS) as well as the first inhibitors of 17β-HSD14 are covered.