Aromatase inhibitors for the treatment of breast cancer: An overview (2019-2023).

Aromatase inhibition is considered a legitimate approach for the treatment of ER-positive (ER+) breast cancer as it accounts for more than 70% of breast cancer cases. Aromatase inhibitor therapy has been demonstrated to be highly effective in decreasing tumour size, increasing survival rates, and lowering the chance of cancer recurrence. The present review deliberates the pathophysiology and the role of aromatase in estrogen biosynthesis. Estrogen biosynthesis, various androgens, and their function in the human body have also been discussed. The salient aspects of the aromatase active site, its mode of action, and AIs, along with their intended interactions with presently FDA-approved inhibitors, have been briefly discussed. It has been detailed how different reported AIs were designed, their SAR investigations, in silico analysis, and biological evaluations. Various AIs from multiple origins, such as synthetic and semi-synthetic, have also been discussed.

Synthesis, In vitro and In silico Studies of Novel Bis-triazolopyridopyrimidines from Curcumin Analogues as Potential Aromatase Agents.

Breast cancer remains a major global health issue, particularly affecting women and contributing significantly to mortality rates. Current treatments for estrogen receptor-positive breast cancers, such as aromatase inhibitors, are effective but often come with side effects and resistance issues. This study addresses these gaps by targeting aromatase, an enzyme crucial for estrogen synthesis, which plays a pivotal role in breast cancer progression. The innovative approach involves synthesizing novel bis-triazolopyridopyrimidines, designed to leverage the combined pharmacological benefits of pyridopyrimidine and 1,2,4-triazole structures, known for their potent aromatase inhibition and anti-cancer properties. These compounds were synthesized and characterized using 1H-NMR, 13C-NMR, and MS spectral analyses, and their anticancer efficacy was evaluated through MTT assays against MCF-7 breast cancer cell lines in vitro. Molecular docking analyses revealed strong binding energies with aromatase, particularly for compounds 5 b, 5 c, 10 a, and 10 b, indicating their potential as effective aromatase inhibitors. The study highlights these compounds as promising candidates for further development as therapeutic agents against breast cancer.

New enantioenriched ß-indolyl ketones as aromatase inhibitors: Unraveling heme-ligand interactions by MD simulation and MMPBSA analysis.

A series of enantioenriched ß-indolyl ketones as aromatase inhibitors (AI) is synthesized through the Michael-type Friedel-Crafts alkylation of indole. A highly efficient bifunctionalized amino catalyst is developed to access structurally diverse ß-indolyl ketones in high yields (up to 91%) and excellent enantioselectivity (enantiomeric ratio up to 98:2). All the synthesized compounds demonstrated promising aromatase inhibitory potential, where ortho-substituted analogs (3c and 3e) were found most active with IC50 values of 0.68 and 0.90 µM, respectively. Both of these compounds exhibited significant cytotoxicity (IC50 = 0.34 and 0.37 µM) against the MCF-7 breast cancer cell line in the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) assay. Molecular docking studies of the synthesized compounds demonstrate favorable binding interactions with the estrogens controlling CYP19A1 (3EQM) and metabolizing CYP3A4 (5VCC) enzymes. Molecular dynamic (MD) simulation analysis revealed the essentiality of heme-ligand interactions to build a stable protein-ligand complex. An average root mean square deviation of 0.35 nm observed during a 100-ns MD simulation and binding free energy in the range of -190 to -227 kJ/mol calculated by g_mmpbsa analysis authenticated the stability of the 3c-3EQM complex. ADMET and drug-likeness parameters supported the suitability of these indole derivatives as the drug lead to develop potent inhibitors for estrogen-dependent breast cancer.

Switching from Aromatase Inhibitors to Dual Targeting Flavonoid-Based Compounds for Breast Cancer Treatment.

Despite the significant outcomes attained by scientific research, breast cancer (BC) still represents the second leading cause of death in women. Estrogen receptor-positive (ER+) BC accounts for the majority of diagnosed BCs, highlighting the disruption of estrogenic signalling as target for first-line treatment. This goal is presently pursued by inhibiting aromatase (AR) enzyme or by modulating Estrogen Receptor (ER) α. An appealing strategy for fighting BC and reducing side effects and resistance issues may lie in the design of multifunctional compounds able to simultaneously target AR and ER. In this paper, previously reported flavonoid-related potent AR inhibitors were suitably modified with the aim of also targeting ERα. As a result, homoisoflavone derivatives 3b and 4a emerged as well-balanced submicromolar dual acting compounds. An extensive computational study was then performed to gain insights into the interactions the best compounds established with the two targets. This study highlighted the feasibility of switching from single-target compounds to balanced dual-acting agents, confirming that a multi-target approach may represent a valid therapeutic option to counteract ER+ BC. The homoisoflavone core emerged as a valuable natural-inspired scaffold for the design of multifunctional compounds.

Bismuth(iii)-catalyzed regioselective alkylation of tetrahydroquinolines and indolines towards the synthesis of bioactive core-biaryl oxindoles and CYP19 inhibitors.

Bismuth(iii)-catalyzed regioselective functionalization at the C-6 position of tetrahydroquinolines and the C-5 position of indolines has been demonstrated. For the first time, one pot symmetrical and unsymmetrical arylation of isatins with tetrahydroquinolines was accomplished giving a completely new product skeleton in good to excellent yields. Most importantly, this protocol leads to the formation of a highly strained quaternary carbon stereogenic center, which is a challenging task. Benzhydryl and 1-phenylethyl trichloroacetimidates have been used as the alkylating partners to functionalize the C-6 and C-5 positions of tetrahydroquinolines and indolines, respectively. The scope of the developed methodology has been extended for the synthesis of the bioactive CYP19-inhibitor and its analogue.

Design, synthesis, in vitro and in silico studies of some novel thiazole-dihydrofuran derivatives as aromatase inhibitors.

Aromatase inhibitors used against hormone-dependent breast cancer, especially in post-menopausal women, are very susceptible to the development of resistance due to their limited number and long-term use. In this study, it is aimed to obtain new aromatase inhibitors including thiazole and dihydrofuran ring systems. Synthesis of compounds (2a-2l) were performed according to literature methods. Their structures were elucidated by 1H NMR, 13C NMR and APCI-MS spectroscopic methods. MTT test was carried out to assess the cell proliferation effects of the different compounds on two different pulmonary cell lines (A549, CCD-19Lu) and mammary cell line (MCF7). According to MTT assay, it was observed that the calculated IC50 values of some compounds for the CCD-19Lu cell line were found higher than for the A549 and MCF7 cell lines. Considering the viability results, it was found that the selected compounds (2a, 2c, 2e, 2g, 2h, 2l) showed favourable safety profile and have anticancer activities. Apoptotic activities of the selected compounds were investigated by flow cytometry analysis. And were found that have apoptotic effects on cancerous cell lines. In the light of this information, the aromatase inhibition potentials of 2g and 2l compounds, which are the most active derivatives, were examined in vitro and it was determined that they showed a similar inhibition profile with letrazole. Interaction modes between aromatase enzyme and compounds 2g and 2l were investigated by docking studies. In conclusion, findings of these study indicate that compounds 2g and 2l possess significant anticancer activity.

New azolyl-derivatives as multitargeting agents against breast cancer and fungal infections: synthesis, biological evaluation and docking study.

Nonsteroidal aromatase inhibitors (NSAIs) are well-established drugs for the therapy of breast cancer. However, they display some serious side effects, and their efficacy can be compromised by the development of chemoresistance. Previously, we have reported different indazole-based carbamates and piperidine-sulphonamides as potent aromatase inhibitors. Starting from the most promising compounds, here we have synthesised new indazole and triazole derivatives and evaluated their biological activity as potential dual agents, targeting both the aromatase and the inducible nitric oxide synthase, being this last dysregulated in breast cancer. Furthermore, selected compounds were evaluated as antiproliferative and cytotoxic agents in the MCF-7 cell line. Moreover, considering the therapeutic diversity of azole-based compounds, all the synthesized compounds were also evaluated as antifungals on different Candida strains. A docking study, as well as molecular dynamics simulation, were carried out to shed light on the binding mode of the most interesting compound into the different target enzymes catalytic sites.

Novel 1,2,3-Triazole Derivatives as Mimics of Steroidal System-Synthesis, Crystal Structures Determination, Hirshfeld Surfaces Analysis and Molecular Docking.

Herein, we present the synthesis and crystal structures determination of five 4-(1-phenyl-1H-1,2,3-triazol-4-yl)phenol derivatives containing halogen atoms, 6a-e, which may be used as an excellent mimic of steroids in the drug development process. Good quality crystals obtained for all of the synthesized compounds allowed the analysis of their molecular structures. Subsequently, the determined crystal structures were used to calculate the Hirshfeld surfaces for each of the synthesized compounds. Furthermore, results of our docking studies indicated that synthesized derivatives are able to bind effectively to the active sites of selected enzymes and receptors involved in the hormone biosynthesis and signaling pathways, analogously to the native steroids.

In silico molecular docking and in vitro antioxidant activity studies of novel α-aminophosphonates bearing 6-amino-1,3-dimethyl uracil.

In the present study, a new series of α-Aminophosphonates bearing 6-amino-1,3-dimethyluracil was synthesized in good to excellent yields (78-95%) by one-pot, three-component reaction of 6-amino-1,3-dimethyluracil, aromatic aldehydes and diethylphosphite via Kabachnik-Fields reaction by using an eco-friendly Eaton's reagent. All the compounds were screened for in vitro antioxidant studies by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) methods. Among the synthesized bioactive molecules, 4a, 4d, 4g, and 4h exhibited promising antioxidant activity compared with the standard drug Ascorbic acid. Furthermore, in order to support the biological results of the compounds, molecular docking studies were performed against Aromatase enzyme for four compounds which revealed that the compounds 4a, 4d, 4g, and 4h have significant binding modes, with docking scores of -8.6, -8.4, -8.1 and -8.1 respectively and the compound 4b specifically has equal dock score of -8.0 when compared with the standard drug Exemestane.

2-Anilinopyrimidine derivatives: Design, synthesis, in vitro anti-proliferative activity, EGFR and ARO inhibitory activity, cell cycle analysis and molecular docking study.

Novel anti-proliferative agents possessing pyrimidine scaffolds were designed, synthesized and evaluated for their IC50 values using MTT assay. Most compounds displayed good to excellent activity against the two tested breast cancer lines (MCF-7 and MDA-MB-231) as compared to 5-FU. The observed IC50 values for active compounds ranged from 0.27 to 10.57 µM in MCF-7 compared to the reference drug 5-FU (IC50 = 10.80 µM) and from 0.73 to 29.07 µM in MDA-MB-231 (IC50 for 5-FU = 11.40 µM). SAR analysis indicated that compounds 2c, 3b with hydrazone functionalities and compound 12 possessing pyrazolone ring exhibited superior activities. The most promising compounds were evaluated for their inhibitory activity against epidermal growth factor receptor (EGFR) and aromatase (ARO) enzymes and were further tested for caspase-9 activation, apoptosis and Annexin V/PI staining. Results of enzyme-based experiments indicated that the tested compounds 2c and 12 exert their activities through EGFR inhibition while compound 3b exhibited remarkable ARO inhibition activity. Furthermore, they remarkably induce caspase-9 activation and showed pre G1 apoptosis and cell cycle arrest at G2/M phase. In addition, docked compounds displayed good binding affinities to the target enzymes. Binding interaction details for the most promising inhibitors with the active site of the target enzymes EGFR and ARO utilizing MOE-dock method are also reported.

Synthesis and docking study of benzimidazole-triazolothiadiazine hybrids as aromatase inhibitors.

Aromatase is involved in the biosynthesis of estrogen and thus is a critical target for breast cancer. In this study, to identify new aromatase enzyme inhibitors, seven 3-[4-(5-methyl-1H-benzo[d]imidazol-2-yl)phenyl]-6-(substituted phenyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine derivatives were synthesized. First, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to determine the inhibitory activity of the synthesized compounds on the MCF-7 cell line. The aromatase inhibitory activity was determined for the active compounds 5b, 5c, 5e, and 5g on the MCF-7 cell line. Compound 5g showed significant aromatase inhibitory activity (IC50 = 0.037 ± 0.001 µM). Interestingly, this compound, which bears a difluoro substituent at positions 2 and 4 of the phenyl ring, displayed the most potent aromatase inhibitory activity without significant cytotoxicity to a normal healthy cell line (NIH3T3). Furthermore, the interactions between the best active compounds and the active site of the enzyme were analyzed through a docking study. The results of this study determined that benzimidazole-triazolothiadiazine derivatives are promising compounds that should be further developed as a novel class of aromatase inhibitors.

Synthesis, Docking Studies and Biological Activity of New Benzimidazole- Triazolothiadiazine Derivatives as Aromatase Inhibitor.

In the last step of estrogen biosynthesis, aromatase enzyme catalyzes the conversion of androgens to estrogens. Aromatase inhibition is an important way to control estrogen-related diseases and estrogen levels. In this study, sixteen of benzimidazole-triazolothiadiazine derivatives have been synthesized and studied as potent aromatase inhibitors. First, these compounds were tested for their anti-cancer properties against human breast cancer cell line (MCF-7). The most active compounds 5c, 5e, 5k, and 5m on MCF-7 cell line were subject to further in vitro aromatase enzyme inhibition assays to determine the possible mechanisms of action underlying their activity. Compound 5e showed slight less potent aromatase inhibitory activity than that of letrozole with IC50 = 0.032 ± 0.042 µM, compared to IC50 = 0.024 ± 0.001 µM for letrozole. Furthermore, compound 5e and reference drug letrozole were docked into human placental aromatase enzyme to predict their possible binding modes with the enzyme. Finally, ADME parameters (absorption, distribution, metabolism, and excretion) of synthesized compounds (5a-5p) were calculated by QikProp 4.8 software.

New Potent 5α- Reductase and Aromatase Inhibitors Derived from 1,2,3-Triazole Derivative.

This work describes the utility of pyrazole-4-carbaldehyde 1 as starting material for the synthesis of a novel potent series of 5α-reductase and aromatase inhibitors derived from 1,2,3-triazole derivative. Condensation of 1 with active methylene and different amino pyrazoles produced the respective Schiff bases 2-4, 8 and 9. On the other hand, 1 was reacted with ethyl cyanoacetate and thiourea in one-pot reaction to afford the pyrazolo-6- thioxopyridin-2-[3H]-one (10). Moreover, α-ß unsaturated chalcone derivative 11 was prepared via the reaction of compound 1 with P-methoxy acetophenone, which in turn reacted with each of ethyl cyanoacetate, malononitrile, hydrazine hydrate, and thiosemicarbazide to afford the corresponding pyridine and pyrazole derivatives 13, 14, 17, and 20. The structure of newly synthesized compounds was characterized by analytical and spectroscopic data (IR, MS and NMR). All new compounds were evaluated against 5α-reductase and aromatase inhibitors and the results showed that many of these compounds inhibit 5α-reductase and aromatase activity; compound 13 was found to be the highest potency among the tested samples comparing with the reference drugs.

Synthesis of α-methylstilbenes using an aqueous Wittig methodology and application toward the development of potent human aromatase inhibitors.

The development of aqueous Wittig methodology for the synthesis of α-methylstilbenes using tripropylphosphine-derived phosphonium salts is described. The Wittig olefination reaction was high yielding and allowed isolation of stilbenes by simple filtration and washing with water. The novel phosphonium salts employed were accessed via a highly efficient, regioselective addition of hydrogen bromide to styrenes. Application of the α-methylstilbenes toward the synthesis of a collection of stilbenoid-triazoles is reported and their inhibition of CYP450 19A1 (aromatase) investigated. The overall structure-activity profile provided additional evidence on the aryl halide-ketone bioisostere hypothesis and identified 6c as a potent inhibitor of aromatase in vitro (Ki = 8 nM).

Synthesis, molecular docking, and QSAR study of bis-sulfonamide derivatives as potential aromatase inhibitors.

A library of bis-sulfonamides (9-26) were synthesized and tested for their aromatase inhibitory activities. Interestingly, all bis-sulfonamide derivatives inhibited the aromatase with IC50 range of 0.05-11.6 µM except for compound 23. The analogs 15 and 16 bearing hydrophobic chloro and bromo groups exhibited the potent aromatase inhibitory activity in sub-micromolar IC50 values (i.e., 50 and 60 nM, respectively) with high safety index. Molecular docking revealed that the chloro and bromo benzenesulfonamides (15 and 16) may play role in the hydrophobic interaction with Leu477 of the aromatase to mimic steroidal backbone of the natural substrate, androstenedione. QSAR study also revealed that the most potent activity of compounds was governed by van der Waals volume (GATS6v) and mass (Mor03m) descriptors. Finally, the two compounds (15 and 16) were highlighted as promising compounds to be further developed as novel aromatase inhibitors.

Novel triazole-tetrahydroisoquinoline hybrids as human aromatase inhibitors.

Novel thirteen triazole-tetrahydroisoquinoline derivatives (2a-m) were synthesized and evaluated for their aromatase inhibitory activities. Seven triazoles showed significant aromatase inhibitory activity (IC50 = 0.07-1.9 µM). Interestingly, the analog bearing naphthalenyloxymethyl substituent at position 4 of the triazole ring (2i) displayed the most potent aromatase inhibitory activity (IC50 = 70 nM) without significant cytotoxicity to a normal cell. Molecular docking also suggested that the direct H-bonding interaction with residue Thr310 may be responsible for a striking inhibitory effect of the most potent compound 2i.

Synthesis, Biological Evaluation and Docking Studies of 13-Epimeric 10-fluoro- and 10-Chloroestra-1,4-dien-3-ones as Potential Aromatase Inhibitors.

Fluorination of 13-epimeric estrones and their 17-deoxy counterparts was performed with Selectfluor as the reagent. In acetonitrile or trifluoroacetic acid (TFA), 10ß-fluoroestra-1,4-dien-3-ones were formed exclusively. Mechanistic investigations suggest that fluorinations occurred via SET in acetonitrile, but another mechanism was operative in TFA. Simultaneous application of N-chlorosuccinimide (NCS) and Selectfluor in TFA led to a 1.3:1 mixture of 10ß-fluoroestra-1,4-dien-3-one and 10ß-chloroestra-1,4-dien-3-one as the main products. The potential inhibitory action of the 10-fluoro- or 10-chloroestra-1,4-dien-3-one products on human aromatase was investigated via in vitro radiosubstrate incubation. The classical estrane conformation with trans ring anellations and a 13ß-methyl group seems to be crucial for the inhibition of the enzyme, while test compounds bearing the 13ß-methyl group exclusively displayed potent inhibitory action with submicromolar or micromolar IC50 values. Concerning molecular level explanation of biological activity or inactivity, computational simulations were performed. Docking studies reinforced that besides the well-known Met374 H-bond connection, the stereocenter in the 13 position has an important role in the binding affinity. The configuration inversion at C-13 results in weaker binding of 13α-estrone derivatives to the aromatase enzyme.

Synthesis and molecular docking of N,N'-disubstituted thiourea derivatives as novel aromatase inhibitors.

A three series of thioureas, monothiourea type I (4a-g), 1,4-bisthiourea type II (5a-h) and 1,3-bisthiourea type III (6a-h) were synthesized. Their aromatase inhibitory activities have been evaluated. Interestingly, eight thiourea derivatives (4e, 5f-h, 6d, 6f-h) exhibited the aromatase inhibitory activities with IC50 range of 0.6-10.2 µM. The meta-bisthiourea bearing 4-NO2 group (6f) and 3,5-diCF3 groups (6h) were shown to be the most potent compounds with sub-micromolar IC50 values of 0.8 and 0.6 µM, respectively. Molecular docking also revealed that one of the thiourea moieties of these two compounds could mimic steroidal backbone of the natural androstenedione (ASD) via hydrophobic interactions with enzyme residues (Val370, Leu477, Thr310, and Phe221 for 6f, Val370, Leu477, Ser478, and Ile133 for 6h). This is the first time that the bisthioureas have been reported for their potential to be developed as aromatase inhibitors, in which the 4-NO2 and 3,5-diCF3 analogs have been highlighted as promising candidates.

Pyridine-substituted thiazolylphenol derivatives: Synthesis, modeling studies, aromatase inhibition, and antiproliferative activity evaluation.

Drugs used in breast cancer treatments target the suppression of estrogen biosynthesis. During this suppression, the main goal is to inhibit the aromatase enzyme that is responsible for the cyclization and structuring of estrogens either with steroid or non-steroidal-type inhibitors. Non-steroidal derivatives generally have a planar aromatic structure attached to the triazole ring system in their structures, which inhibits hydroxylation reactions during aromatization by coordinating the heme group. Bioisosteric replacement of the triazole ring system and development of aromatic/cyclic structures of the side chain can increase the selectivity for aromatase enzyme inhibition. In this study, pyridine-substituted thiazolylphenol derivatives, which are non-steroidal triazole bioisosteres, were synthesized using the Hantzsch method, and physical analysis and structural determination studies were performed. The IC50 values of the compounds were determined by a fluorescence-based aromatase inhibition assay. Then, their antiproliferative activities on the MCF7 and HEK 293 cell lines were evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Furthermore, the crystal structure of human placental aromatase was subjected to a series of docking experiments to identify the possible interactions between the most active structure and the active site. Lastly, an in silico technique was performed to analyze and predict the drug-likeness, molecular and ADME properties of the synthesized molecules.

Evaluation of synthesized coumarin derivatives on aromatase inhibitory activity.

In women across the world, the most common type of cancer is breast cancer. Among medical treatments, endocrine therapy based on aromatase inhibitors (AI) is expected to be effective against not only post-menopausal but also pre-menopausal breast cancer. In this study, we examined the structure-activity relationship between the aromatase inhibitory effects of 7-diethylaminocoumarin derivatives with a substituent at position 3 and coumarin derivatives with a substituent at position 7. Consequently, we found that 7-(pyridin-3-yl)coumarin (IC50 values 30.3nM) and 7,7'-diethylamino-3,3'-biscoumarin (28.7nM) are the most potent inhibitors of aromatase. These inhibitors were found to be comparable to the existing CYP19 inhibitor exemestane (42.5nM).