Impact of structural modifications at positions 13, 16 and 17 of 16β-(m-carbamoylbenzyl)-estradiol on 17β-hydroxysteroid dehydrogenase type 1 inhibition and estrogenic activity

C-Ring Oxidized Estrone Acetate Derivatives: Assessment of Antiproliferative Activities and Docking Studies

C-Ring oxidized estrone acetate derivatives as antiproliferative agents were prepared and tested against five cancer cell lines by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometry assays to evaluate cell viability and modifications in cell cycle phases and molecular docking research against estrogen receptor α, steroid sulfatase, and 17β-hydroxysteroid dehydrogenase type 1 were performed. 9α-Hydroxy,11β-nitrooxyestrone acetate was the most cytotoxic molecule against hormone-dependent cancer cells. Furthermore, flow cytometry experiments revealed that this 9α-hydroxy,11β-nitrooxy derivative markedly reduced HepaRG cells viability (~92%) after 24 h of treatment. However, 9α-hydroxyestrone acetate led to selective inhibition of HepaRG cells growth, inducing a G0/G1 cycle arrest, and did not originate a proliferation effect on T47-D cancer cells. Docking studies estimated a generally lower affinity of these compounds to estrogen receptor α than predicted for estrone and 17β-estradiol. Therefore, this structural modification can be of interest to develop new anticancer estrane derivatives devoid of estrogenic action.

N-Phenyl-1,2,3,4-tetrahydroisoquinoline: An Alternative Scaffold for the Design of 17β-Hydroxysteroid Dehydrogenase 1 Inhibitors

17β-Hydroxysteroid dehydrogenases catalyse interconversion at the C17 position between oxidized and reduced forms of steroidal nuclear receptor ligands. The type 1 enzyme, expressed in malignant cells, catalyses reduction of the less-active estrone to estradiol, and inhibitors have therapeutic potential in estrogen-dependent diseases such as breast and ovarian cancers and in endometriosis. Synthetic decoration of the nonsteroidal N-phenyl-1,2,3,4-tetrahydroisoquinoline (THIQ) template was pursued by using Pomeranz-Fritsch-Bobbitt, Pictet-Spengler and Bischler-Napieralski approaches to explore the viability of this scaffold as a steroid mimic. Derivatives were evaluated biologically in vitro as type 1 enzyme inhibitors in a bacterial cell homogenate as source of recombinant protein. Structure-activity relationships are discussed. THIQs possessing a 6-hydroxy group, lipophilic substitutions at the 1- or 4-positions in combination with N-4'-chlorophenyl substitution were most favourable for activity. Of these, one compound had an IC₅₀ of ca. 350 nM as a racemate, testifying to the applicability of this novel approach.

Application of Various Molecular Modelling Methods in the Study of Estrogens and Xenoestrogens

In this review, applications of various molecular modelling methods in the study of estrogens and xenoestrogens are summarized. Selected biomolecules that are the most commonly chosen as molecular modelling objects in this field are presented. In most of the reviewed works, ligand docking using solely force field methods was performed, employing various molecular targets involved in metabolism and action of estrogens. Other molecular modelling methods such as molecular dynamics and combined quantum mechanics with molecular mechanics have also been successfully used to predict the properties of estrogens and xenoestrogens. Among published works, a great number also focused on the application of different types of quantitative structure-activity relationship (QSAR) analyses to examine estrogen's structures and activities. Although the interactions between estrogens and xenoestrogens with various proteins are the most commonly studied, other aspects such as penetration of estrogens through lipid bilayers or their ability to adsorb on different materials are also explored using theoretical calculations. Apart from molecular mechanics and statistical methods, quantum mechanics calculations are also employed in the studies of estrogens and xenoestrogens. Their applications include computation of spectroscopic properties, both vibrational and Nuclear Magnetic Resonance (NMR), and also in quantum molecular dynamics simulations and crystal structure prediction. The main aim of this review is to present the great potential and versatility of various molecular modelling methods in the studies on estrogens and xenoestrogens.

3,20-Dihydroxy-13α-19-norpregna-1,3,5(10)-trienes. Synthesis, structures, and cytotoxic, estrogenic, and antiestrogenic effects

New 3,20-dihydroxy-13α-19-norpregna-1,3,5(10)-trienes were synthesized. The effects of these compounds on breast cancer cells and ERα activation were investigated. The scaffold of compounds containing the six-membered ring D' annulated at 16α,17α-positions was constructed via the Lewis acid catalyzed Diels-Alder reaction of butadiene with 3-methoxy-13α-19-norpregna-1,3,5(10),16-tetraen-20-one 5 under a pressure of 600 MPa. The hydrogenation of primary cyclohexene adduct 6 followed by the one-pot reduction-demethylation (DIBAH) gave target epimeric 3,20-dihydroxy steroids 8a and 8b. The Corey-Chaykovsky reaction of the same conjugated ketone 5 gave a 16α,17α-methylene-substituted compound. The reaction of the latter with DIBAH yielded 3,20(R,S)-dihydroxy-16α,17α-methyleno-13α-19-norpregna-1,3,5(10)-triene 10. The hydrogenation of the 16,17-double bond of compound 5 produced a mixture of 17α- and 17β-epimeric ketones, reduction-demethylation of which gave 3,20(S)-dihydroxy-13α,17α-19-norpregna-1,3,5(10)-triene 12a and 3,20(R)-dihydroxy-13α,17β-19-norpregna-1,3,5(10)-triene 12b. All compounds were fully characterized by 1D and 2D NMR, HRMS, and X-ray diffraction. All target compounds showed pronounced cytotoxic effect against MCF-7 breast cancer cells and NCI/ADR-RES doxorubicin-resistant cells at micromolar concentrations. The ERα-mediated luciferase reporter gene assay demonstrated that all compounds, except for compound 10, are ERα inhibitors, while cyclopropane compound 10 proved to be an ERα activator. Docking experiments showed that all compounds are well accommodated to LBD ERα but have some differences in the binding mode.

Pharmacokinetic profile of PBRM in rodents, a first selective covalent inhibitor of 17β-HSD1 for breast cancer and endometriosis treatments

The development of a covalent inhibitor of 17β-hydroxysteroid dehydrogenase type 1 (17β-HSD1) is a promising approach for the treatment of hormone-dependent breast cancer and endometriosis. After reporting the steroid derivative PBRM as a first potent covalent inhibitor of 17β-HSD1 without estrogenic activity, we are now interested in studying its pharmaceutical behavior. The metabolism study in a human liver microsomal preparation showed a gradual transformation of PBRM into PBRM-O, an oxidized ketonic form of PBRM at position C17. Interestingly, PBRM-O also inhibits 17β-HSD1 and is not estrogenic in estrogen-sensitive T-47D cells. However, when PBRM was injected subcutaneously (sc) in mice, a very small proportion of PBRM-O was measured in a 24 h-time course experiment. A pharmacokinetic study in mice revealed suitable values for half-life (T_1/2 = 3.4 h), clearance (CL = 2088 mL/h kg), distribution volume (Vz = 10.3 L/kg) and absolute bioavailability (F = 65%) when PBRM was injected sc at 14.7 mg/kg. A good F value of 33% was also obtained when PBRM was given orally. A tritiated version of PBRM, ³H-PBRM, was synthesized and used for an in vivo biodistribution study that showed its gradual accumulation in various mouse tissues (peak at 6 h) followed by elimination until complete disappearance after 72 h. Elimination was found to occur in feces (93%) and urine (7%) as revealed by a mass balance experiment. PBRM was also evaluated for its toxicity in mice and it was found to be very well tolerated after weekly sc administration (30-405 mg/kg for 8 weeks) or by po administration (300-900 mg/kg for 4 weeks). Overall, these experiments represent important steps in the preclinical characterization of the pharmaceutical behavior of PBRM, as well as for its translation to clinical trials.

Impact of androstane A- and D-ring inversion on 17β-hydroxysteroid dehydrogenase type 3 inhibitory activity, androgenic effect and metabolic stability

17β-Hydroxysteroid dehydrogenase type 3 (17β-HSD3) is a major player in human endocrinology, being one of the most important enzymes involved in testosterone production. To capitalize on the discovery of RM-532-105, a steroidal 17β-HSD3 inhibitor, we explored the effect of its backbone configuration on inhibitory activity, androgenic profile, and metabolic stability. Two modifications that greatly alter the natural shape of steroids, i.e. inversion of the methyl on carbon 13 (13α-CH₃ instead of 13β-CH₃) and inversion of the hydrogen on carbon 5 (5β-H instead of 5α-H), were tested after the syntheses in 6 steps of 2 isomeric forms (5α/13α-RM-532-105 (6a) and 5β/13β-RM-532-105 (6b), respectively) of the 17β-HSD3 inhibitor RM-532-105 (5α/13β-configurations). For compound 6b, a cis/trans junction of the A/B rings did not significantly alter the inhibitory activity on 17β-HSD3 (IC₅₀=0.15μM) as well as the liver microsomal stability (16.6% of 6b remaining after 1h incubation) compared to RM-532-105 (IC₅₀=0.11μM and 14.1% remaining). In contrast, a trans/cis junction of C/D rings reduced the inhibitory activity on 17β-HSD3 (IC₅₀=1.09μM) but increased the metabolic stability with 29.4% of compound 6a remaining after incubation. The structural modifications represented by compounds 6a and 6b did not change the non-androgenicity profile of an androsterone derivative such as RM-532-105, but slightly increased its cytotoxic activity.

Comparative investigation of the in vitro inhibitory potencies of 13-epimeric estrones and D-secoestrones towards 17β-hydroxysteroid dehydrogenase type 1

The inhibitory effects of 13-epimeric estrones, D-secooxime and D-secoalcohol estrone compounds on human placental 17β-hydroxysteroid dehydrogenase type 1 isozyme (17β-HSD1) were investigated. The transformation of estrone to 17β-estradiol was studied by an in vitro radiosubstrate incubation method. 13α-Estrone inhibited the enzyme activity effectively with an IC₅₀ value of 1.2 μM, which indicates that enzyme affinity is similar to that of the natural estrone substrate. The 13β derivatives and the compounds bearing a 3-hydroxy group generally exerted stronger inhibition than the 13α and 3-ether counterparts. The 3-hydroxy-13β-D-secoalcohol and the 3-hydroxy-13α-D-secooxime displayed an outstanding cofactor dependence, i.e. more efficient inhibition in the presence of NADH than NADPH. The 3-hydroxy-13β-D-secooxime has an IC₅₀ value of 0.070 μM and is one of the most effective 17β-HSD1 inhibitors reported to date in the literature.