Background {#s1}
==========

Majority of breast cancers diagnosed today are estrogen receptor (ER)-positive, where, estrogen binds to estrogen receptors on the surface of the cell [@R01]. According to the American Cancer Society, about 2 out of every 3 cases of breast cancer is hormone receptorpositive. However, in certain cases, progesterone receptor-positive (PR-positive) is also responsible for breast cancer [@R02]. Tumors that are ER/PR-positive are much more likely to respond to hormone therapy than tumors that are ER/PR-negative. ERa-positive breast cancer is more resistant to chemotherapy than ERa-negative cancer [@R03]. Estrogen- receptor status and outcomes of modern chemotherapy for patients with node-positive breast cancer is known. ERa plays an important role in determining the sensitivity of breast cancer cells to chemotherapeutic agents in vitro [@R04]. Down regulation of Aurora-A overrides estrogen-mediated growth and chemo resistance in breast cancer cells. Patients with ER-a-positive tumors have a slightly better survival rate than patients with ER-a- negative. However, both the ER and PR respond to the drug tamoxifen, designed to interfere the function of ER-a [@R05]. Tamoxifen decreases the incidence of invasive and non-invasive breast cancer. In spite of the tamoxifen administered side effects, its use as a breast cancer preventive agent is appropriate in many women at increased risk for the disease [@R06]. ER-a is thought to function as a ligand-activated transcription factor. Extracellular signals can also stimulate ER-a-mediated transcription in the absence of estrogen. Stimulated ER-a can influence gene expression by associating with other transcription factors without binding directly to DNA Estrogen receptor alpha rapidly activates the IGF-1 receptor pathway [@R07]-[@R08]. Specific binding sites for estrogen at the outer surfaces of isolated endometrial cells are known. Estrogens stimulate growth of many breast cancer cells. Reducing estrogen levels or blocking often leads to a clinical response in patients with receptor-positive disease. In premenopausal women, estrogen production is high and in postmenopausal women relatively small amounts of estrogens are produced. These low levels of estrogens can be inhibited either by blocking the estrogen receptor, or by inhibiting the peripheral conversion of androgens to estrogens [@R09]. The most widely accepted pharmacologic endocrine therapies for breast cancer are treatment with anti estrogens [@R10]. Tamoxifen has been shown to be effective in both premenopausal women as well as in postmenopausal women [@R11]. Tamoxifen is the most widely used and extensively studied anti estrogen and its role in the management of patients with breast cancer is well established [@R12]. However, extensive evaluation of tamoxifen treatment revealed significant side effects such as endometrial cancer, blood clots and the development of acquired resistance. Hence, there is a pressing need for the improvement and/or development of new antiestrogens for the prevention and treatment of breast cancer.

Methodology {#s2}
===========

A search for Estrogen Receptor alpha (ER-a) structure in Protein Data Bank (PDB) \[www.rcsb.org/pdb\] revealed several hits with bound ligands and drugs. In general, the selection of the receptor is based on highest possible resolution, no mutations or modified residues and the presence of bound ligand or drug [@R13] in particular. The resolution ensures that 3D structures utilized for docking were of a good quality and on the other hand, the structure should be devoid of any mutations, this is because mutations might have profound effects on the final confirmation of a protein [@R14] [@R15]. Moreover, a co-crystallized bound ligand represents better geometric orientation within the active site space of the protein. Therefore, the 3D structure of ERa bound with an antagonist, i.e. 4- hydroxytamoxifen (PDB ID: 3ERT), was selected as the preferred docking target protein.

Molecular Docking Analysis: {#s2a}
---------------------------

Molecular docking is a study of non-bonded, non-covalent interactions between a receptor or active site region of a protein and a drug or chemical molecule forming an intermolecular complex [@R16]. Docking is carried out to dock various conformations of small molecules to a receptor followed by evaluation of the molecules with respect to the geometrical orientation and complementarity in terms of shape and properties, such as electrostatics [@R17]. The outcome of a docking routine includes affinity prediction (scoring) for the molecules investigated, yielding a relative rank ordering of the docked compounds with respect to affinity, reported as kcal/mol [@R18].

Molegro Virtual Docker: {#s2b}
-----------------------

Molegro Virtual Docker is an integrated platform for predicting protein - ligand interactions [@R19]. All default options including preparation of the molecules to determination of the potential binding sites of the target protein, and prediction of the binding modes of the ligands were employed.

Ligand Drawing: {#s2c}
---------------

All ligands were drawn using ISIS-Draw (v. 2.3), which is a userfriendly drawing package that enables to draw chemical structures. ISIS/Draw is mainly a 2D drawing program with structure and reaction validation features and can calculate elementary properties such as formula and molecular weight [@R20] the 2-D structures are converted into 3-dimensional structures using ProDrug2 server [@R21].

Datasets: {#s2d}
---------

### Set-1: ERa ligands from literature {#s2d1}

Nearly 105 ligands reported as antagonists of ERa such as benzofurans [@R22], diphenyl amine analogs [@R23], sulfoximine-based acyclic triaryl olefins [@R24], isoxazole derivatives [@R25] thiazolidinone derivatives [@R26], tamoxifen mimics [@R27], pyrazolo\[1,5-a\]pyrimidine conjugates [@R28] chromen-2-one derivatives [@R29] etc. Many of those compounds are serving as anticancer agents [@R30] antifungal agents [@R31] and anti-inflammatory agents [@R32] etc. were selected for molecular docking analysis.

### Set-2: ERa Non-tested ligands from literature {#s2d2}

The method employed is to screen similar repertoire of inhibitors reported in various literature sources to identify new probable active compounds, which have not been tested for ERa inhibitory activity. Therefore search initiated for compounds containing pyrazole, bipyrazole, thiazole, thiadiazole etc scaffold analogs reported in Archives of organic chemistry journal www.arkat-usa.org. After preliminary docking investigations, bipyrazole classes of compounds were known to elicit inhibitory characteristics against ERa. Hence, a set of 34 bipyrazoles reported in literature www.arkat-usa.org was considered in the study [@R33]. Set-3: Drugs from Drug-Bank Database The rationale to choose Drug Bank database is due to the larger collection and unique resource of drugs with detailed information on each drug and drug target. The latest release of Drug-Bank (version 5.0.10, released 2017-11-14) contains 10,555 drug entries including 1,745 approved small molecule drugs, 877 approved biotech (protein/peptide) drugs, 107 nutraceuticals and over 5,031 experimental drugs. Additionally, 4,775 non-redundant protein (i.e. drug target/enzyme/transporter/carrier) sequences are linked to these drug entries [@R35]. In the present study, 2035 approved drugs were selected for analysis.

Consensus scoring for enrichment of drugs: {#s2e}
------------------------------------------

In general, docking routines have the capability to correctly predict protein-ligand complex structures with rational accuracy which is determined based on the RMSD of docked ligand within active site space of the target protein. The ability to forecast the possible geometric binding mode of the docked ligand to distinguish exact poses from incorrect ones is dependent on various scoring functions. Therefore, as is evidenced that both docking analysis and scoring functions play vital importance in drug design procedures, it was reported that the weakness of docking programs is their built-in scoring functions. The main scoring functions include the knowledge-based [@R36], Physics-based [@R37], and empirical [@R38] scoring functions. Therefore, combining various scoring functions would certainly minimize the errors that appear in single scoring programs and thereby enhance the chance of recognizing true hits [@R39]. Thus, it has been demonstrated that consensus scoring is generally more effective than single scoring for molecular docking [@R40] and represented an effective way in getting improved hit rates in various virtual database screening studies [@R41]. In this study, about five scoring functions were employed to evaluate consensus scoring patterns, they are: MolDock score of Molegro, Swiss Dock, mcule docking paradigm, Pose & Rank scoring, DSX scoring schemes respectively. Classes were generated based on the dock scores followed by ranking the best conformations.

Results and Discussion {#s3}
======================

The crystal structure of human estrogen receptor alpha ligand binding domain in complex with 4-hydroxytamoxifen (PDB ID: 3ERT) was used for the docking. A thorough analysis of the X-ray crystal structure of estrogen receptor revealed that the active site regions has flexible amino acid side chains and hence could accommodate different chemical scaffolds. The amino acid residues lining active site are: Phe404, Glu419, Leu428, Met343, Gly420, Met421, Leu525, Gly521, Thr347, Leu387, Asp351, Ala350, Glu353, Trp383, Arg394, Leu346, respectively. The protein was prepared using Molegro software. All bond orders and hybridization were assigned, hydrogen and other missing atoms were added to the residues and charges were assigned. The co-crystallized water molecules were excluded from docking. Cavities in the protein were evaluated by Cavity detection algorithm using Expanded Van der Waals molecular surface with default parameters such as minimum and maximum cavity volume set at 10 and 10000 Å, with 1.20 Å probe radius and grid resolution being 0.80 resulted in 5 cavities. A docking template was created using bound ligand, with a probe radius of 1.20 Å is used as template for docking external ligands within the active site space of protein. In this case, tamoxifen co-crystallized in ERa was set as ligand template and docking routine was performed using this template complexed in first cavity. 3ERT subjected to docking in triplicate in silico analysis using default parameters of Molegro resulted in RMSD less than 2 Å in all cases with average dock score -149.856 kcal/mol and RMSD 0.85 Å.

Set-1: ERa ligands from literature {#s3a}
----------------------------------

All 105 literature compounds ([Table 1](#T1){ref-type="table"}) converted into 3D formats are subjected to docking against ERa protein 3ERT using default parameters. Docking analysis resulted in varied dock scores, and compounds that exhibited better binding affinities than tamoxifen are given in [Table 2](#T2){ref-type="table"}. From [Table 2](#T2){ref-type="table"}, it is evidenced that nearly 31 compounds displayed better binding affinities than 3ERT bound tamoxifen (-149.856 kcal/mol). The maximum score obtained was - 175.282 kcal/mol for compound 11_6j. Interestingly, almost all compounds under 11 and 14 series displayed better affinities than tamoxifen. Compounds under 11 series represent pyrazolo\[1,5- a\]pyrimidine analogs whereas 3-aryl-4-anilino-2H-chromen-2-ones were reported under 14 series. The superimposed structures of top 3 compounds with tamoxifen are given in [Figure 1](#F1){ref-type="fig"} and the h-bond interactions are given in [Table 3](#T3){ref-type="table"}.

An electrostatic interaction was observed when the ligand interacted with oxygen atoms of Asp351. On the other hand, all other interacting amino acids displayed H-bond forces. Further, careful observations on the interacting amino acid residues revealed that pyrazolo\[1,5-a\]pyrimidine analogs under 11 series displayed major interactions with Thr347 whereas the 3-aryl-4- anilino-2H-chromen-2-ones reported under 14 series interacted majorly with His524 amino acid. The ERa bound tamoxifen displayed favourable interactions with Asp351 and Arg394, respectively. Similar interactions are observed with majority of the 14 series chromene derivatives.

Set-2: ERa Non-tested ligands from literature {#s3b}
---------------------------------------------

A thorough literature search was made on structural features of ligands that would fit into the active site region of ERa, which resulted in pyrazole, bipyrazole, thiazole, thiadiazoleetc scaffold analogs. Bipyrazoles are known to possess inhibitory properties against several classes of enzymes. Moreover, preliminary docking analysis revealed better inhibition of ERa with bipyrazoles. Other classes of compounds displayed reduced inhibition. Hence, bipyrazoles are considered for further analysis. Computational molecular docking and structural specificity of bipyrazoles as inhibitors of ERa Docking of all 34 bipyrazoles from literature was carried out to evaluate the best conformer based on the lowest docked energy (kcal/mol) ([Table 4](#T4){ref-type="table"}), in other words, it should possess highest affinity towards the binding site [@R42].From the bipyrazole Vs ERa docking analysis output, it is evidenced that the bipyrazoles are able to bind and fit into the geometrical space provided by the active site region of ERa. The binding orientations of all bipyrazoles were similar to the cocrystallized ligand, tamoxifen ([Figure 2](#F2){ref-type="fig"} ). The best compound 2 (ethyl 5-amino-1-(5-amino-3-anilino-4-ethoxycarbonyl-pyrazol-1-yl)-3- anilino-pyrazole-4-carboxylate) from Table-7 displayed a score of - 175.9 kcal per mol which is much better than the ERa bound ligand (- 149.8 kcal per mol). A favourable H-bond was formed with Thr347 ([Figure 3](#F3){ref-type="fig"} ) as observed with chromene derivatives. The next best compound 29 resulted in dock score (-167.1 kcal per mol), however two favourable H-bonds were found to interact with compound 29, via Thr347 ([Figure 4](#F4){ref-type="fig"} ).

Set-3: Drugs from DrugBank Database {#s3c}
-----------------------------------

Owing to the output from bipyrazole dataset, which showed better inhibitory than tamoxifen, the next step utilized was to search DrugBank database because it was observed that certain drugs which are specific against a particular disease were found to be effective against other disease conditions as well, for example, Pioglitazone, a drug used for type 2 diabetes, may prevent recurrent stroke and heart attacks in people with insulin resistance but without diabetes [@R43]-[@R44]. Several studies indicate that persons with type-2 diabetes are at higher risk of cancer of the pancreas, liver, endometrium, breast, colon, rectum and urinary bladder [@R45]. however, the use of metformin was associated with decreased risk of the occurrence of various types of cancers, especially of pancreas and colon and hepatocellular carcinoma [@R46] evidence suggested that metformin might reduce breast cancer incidence in postmenopausal women [@R47] In another study, by screening already approved drugs, researchers identified calcium channel blockers, which are used to treat hypertension, can efficiently stop cancer cell invasion in vitro [@R48]. Preliminary investigations revealed that Gleevec blocked the progression and development of rheumatoid arthritis in laboratory mice [@R49]. Therefore, in this context DrugBank database was accessed to select 2035 FDA approved drugs and subjected to molecular docking. Analysis resulted in 15 drugs, which showed better binding affinities than ERa bound tamoxifen, tabulated in [Table 5](#T5){ref-type="table"}.

[Table 5](#T5){ref-type="table"} represented better inhibitory values of various drugs intended for specific disease conditions when compared to ERa bound tamoxifen. The top best compound obtained from analysis was Cobicistat with binding energy, -187.123 kcal per mol. All drugs displayed H-bond interactions except Lomitapide and Ritonavir, which displayed Van der Waals interactions with ERa.Superimposition of all drugs within the active space of ERa is given in [Figure 5](#F5){ref-type="fig"} where it is evidenced that all drugs occupied clearly within the geometric space of the protein. From the table, out of 15 drugs, only 11 are finalized to consider for further analysis. This is because the four drugs viz., Bazedoxifene, Lapatinib, Raloxifene and Dabrafenib found to be anti-cancer drugs and hence omitted from the list.

Consensus Scoring to enrich drugs active against ERa: {#s3d}
-----------------------------------------------------

It has been reported recently that consensus scoring, which combines multiple scoring functions, leads to higher hit-rates in virtual library screening studies [@R50] and presented an idealized computer experiment to explore how consensus scoring works based on the assumption that the error of a scoring function is a random number in a normal distribution. Many studies suggested that implementing consensus-scoring approaches enhances the performance by compensating for the deficiencies of the scoring functions with each other [@R51], [@R52], [@R53] The possibility that several scoring methods might have their own strengths and weaknesses and combined use of more than one method might increase the overall signal-noise ratio and might perform better than the average of the individual scoring functions [@R54] presented computer-aided analysis where they implemented an intersection-based consensus approach to group few scoring functions. Stahl and Rarey [@R55] reported the performance of four scoring functions on seven target proteins.

Screening analysis of DrugBank database drugs against ERa resulted in 11 drugs and all these drugs are subjected to consensus scoring using 5 scoring schemes such as MolDock score of Molegro, mcule, SwissDock, Pose & Rank and DSX respectively. Here, we chose the \'rank-by-number\' strategy to pool the output of multiple scoring functions. This is because, this strategy was reported to outperform the other techniques such as \'rank-by-rank\' and \'rank by- vote\' as the rank-by-number strategy summarized most of the information [@R56] Each scoring function was applied to generate three classes based on the obtained dock scores followed by ranking the best conformations. Classes were generated for all scoring functions and instead of taking an average, rank-bynumber technique [@R57] was employed to finalize best compounds. The ranks obtained from each of the scoring functions were added to give the rank-sum. The benefit of rank-by-number technique is that the each individual score involvement for a rank can certainly be split out for illustrative purposes [@R58]. The rank sums obtained for 11 drugs against five scoring functions were in the range 5 to 15, with 5 being low rank and 15 being first and best rank, respectively ([Table 6](#T6){ref-type="table"}). Therefore, finally from 11 drugs, the top five compounds with rank-sums 15 - 12 (Lomitapide, Itraconazole, Cobicistat, Azilsartanmedoxomil, and Zafirlukast) are finalized. Further work shall be carried out to study their affinity of binding and inhibitory characteristics against ERa in a breast cancer cell line MCF-7.

Conclusion {#s4}
==========

Molecular docking analysis carried out on a set of ERa inhibitors against 3ERT, complexed with 4-hydroxytamoxifen (-149.856 kcal/mol with RMSD 0.85 Å) resulted in better binding affinities than 3ERT bound tamoxifen for nearly 31 compounds with pyrazolo\[1,5-a\]pyrimidine and chromen-2-one derivatives. The best compound (-175.282 kcal/mol) was \[2-(4-Fluoro-phenylamino)- pyridin-3-yl\]-{4-\[2-phenyl-7-(3,4,5-trimethoxy-phenyl)-pyrazolo\[1,5- a\]pyrimidine-5-carbonyl\]-piperazin-1-yl}-methanone and favourable interactions were observed with Thr347. In our search to unearth entirely novel compounds, bipyrazole nucleus compounds were analyzed which resulted in with -175.9 kcal/mol binding affinity with the receptor and favourable H-bond interaction with Thr347. After realizing this novel inhibitor, 2035 FDA approved drugs from DrugBank database were screened to study their efficacy against ERa, resulted in 15 such drugs with binding affinities greater than tamoxifen ranging from -164.66 to -187.12 kcal per mol. After eliminating 4 anti-cancer drugs, the remaining 11 drugs are subjected to consensus scoring using MolDock score of Molegro, mcule, SwissDock, Pose & Rank and DSX. Consensus analysis resulted in top ranks for 5 drugs viz., Lomitapide, Itraconazole, Cobicistat, Azilsartanmedoxomil, and Zafirlukast, which were selected further to assess their experimental activity in an MCF-7 cell line.

Conflict of Interest {#s5}
====================

Authors declare no conflict of interest.

**Edited by P Kangueane**

**Citation:**Tilak Vijay *et al.* Bioinformation 15(5): 321-332 (2019)

###### Physico-chemical properties and related information of 105 literature compound data

  T1                       SMILES                                                                                       MW        HBA   HBD   logP     RB
  ------------------------ -------------------------------------------------------------------------------------------- --------- ----- ----- -------- ----
  1_4d.mol                 Oc1ccc(cc1)N(CC1CC1)c1ccc(cc1)O                                                              255.34    2     2     3.6614   4
  6_12.mol                 O=C1CS\[C\@H\](N1c1ccccc1)c1ccccc1                                                           255.35    1     0     3.2436   2
  estradiol.mol            O\[C@\@H\]1CC\[C@\@H\]2\[C@\@H\]1CC\[C@\@H\]1\[C@\@H\]2CCc2cc(ccc21)O                        258.39    2     2     3.5024   0
  diethylstilbestrol.mol   CC/C(/c1ccc(cc1)O)=C(/CC)\\c1ccc(cc1)O                                                       268.38    2     2     4.794    5
  1_4e.mol                 CC(C)CCN(c1ccc(cc1)O)c1ccc(cc1)O                                                             271.39    2     2     4.4894   5
  1_4m.mol                 Oc1ccc(cc1)N(c1ccccc1)c1ccc(cc1)O                                                            277.34    2     2     4.6332   3
  6_1.mol                  Oc1ccc(cc1)\[C@\@H\]1SCC(=O)N1c1ccc(cc1)O                                                    287.35    3     2     2.6748   2
  1_4j.mol                 Oc1ccc(cc1)N(Cc1ccccc1)c1ccc(cc1)O                                                           291.37    2     2     4.7281   4
  5_2.mol                  COc1cc2occ(c2cc1O)C(=O)/C=C/c1ccccc1                                                         294.32    4     1     3.0895   5
  1_4g.mol                 Oc1ccc(cc1)N(CC1CCCCC1)c1ccc(cc1)O                                                           297.43    2     2     4.8503   4
  1_4l.mol                 Oc1ccc(cc1)N(CC1CCCCC1)c1ccc(cc1)O                                                           297.43    2     2     4.8503   4
  6_4.mol                  Oc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1ccc(c(c1)O)O                                                 303.35    4     3     2.3904   2
  6_5.mol                  Oc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1cc(cc(c1)O)O                                                 303.35    4     3     2.3904   2
  6_6.mol                  Oc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1ccc(cc1O)O                                                   303.35    4     3     2.3904   2
  6_11.mol                 Cc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1ccc(cc1)Cl                                                   303.82    1     0     4.2288   2
  6_10.mol                 Oc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1ccc(cc1)Cl                                                   305.79    2     1     3.4772   2
  1_4k.mol                 Oc1ccc(cc1)CN(c1ccc(cc1)O)c1ccc(cc1)O                                                        307.37    3     3     4.4437   4
  1_4h.mol                 Oc1ccc(cc1)N(CCC1CCCCC1)c1ccc(cc1)O                                                          311.46    2     2     5.1743   5
  5_5.mol                  COc1ccc(cc1)\\C=C\\C(=O)c1coc2cc(c(cc21)O)F                                                  312.31    4     1     3.229    5
  3_vioxx.mol              CS(=O)(=O)c1ccc(cc1)C1=C(C(=O)OC1)c1ccccc1                                                   314.37    4     0     2.2409   3
  5_4.mol                  Oc1cc2c(occ2C(=O)/C=C/c2cccc(c2)Cl)cc1F                                                      316.72    3     1     3.9997   4
  6_13.mol                 Cc1ccc(cc1)N1\[C@\@H\](SCC1=O)c1cccc2ccccc21                                                 319.44    1     0     4.713    2
  5_1.mol                  COc1cc2occ(c2cc1O)C(=O)c1cccc(c1)NC(C)=O                                                     325.34    5     2     1.5304   4
  5_3.mol                  COc1cc2occ(c2cc1O)C(=O)/C=C/c1cccc(c1)Cl                                                     328.76    4     1     3.6075   5
  8_11d.mol                Oc1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                               330.35    4     1     2.793    2
  6_7.mol                  COc1ccc(c(c1)OC)\[C@\@H\]1SCC(=O)N1c1ccc(cc1)O                                               331.41    4     1     2.4538   4
  6_9.mol                  COc1ccc(cc1OC)\[C@\@H\]1SCC(=O)N1c1ccc(cc1)O                                                 331.41    4     1     2.4538   4
  8_11b.mol                Fc1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                               332.34    3     0     3.2169   2
  4_4m.mol                 CC(C)(C)\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                               335.43    4     2     5.6743   5
  5_7.mol                  COc1cc2occ(c2cc1O)C(=O)/C=C/c1ccc2c(c1)OCO2                                                  338.33    6     1     2.424    5
  8_11l.mol                O=C1C=CC2(OC(=O)C(=C2c2ccccc2)c2ccc(cc2)C\#N)C=C1                                            339.36    4     0     2.9424   2
  8_11f.mol                COc1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                              344.38    4     0     2.8247   3
  8_11g.mol                OCc1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                              344.38    4     1     2.5421   3
  8_11n.mol                O=Cc1sc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                              348.38    4     0     1.8088   3
  3_9b.mol                 CC(c1ccc(cc1)S(C)(N)=O)=C(c1ccccc1)c1ccccc1                                                  348.51    2     1              5
  8_11c.mol                O=C1OC2(C=CC(=O)C=C2)C(=C1c1oc2ccccc2c1)c1ccccc1                                             354.37    4     0     2.7922   2
  4_4a.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1ccccc1)c1ccc(cc1)O                                                 355.41    4     2     5.7315   5
  8_11k.mol                O=C1C=CC2(OC(=O)C(=C2c2ccccc2)c2ccc3c(c2)OCO3)C=C1                                           358.36    5     0     2.4119   2
  8_11m.mol                OC(=O)c1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                          358.36    5     1     2.7758   3
  8_11e.mol                \[O-\]\[N+\](=O)c1ccc(cc1)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                359.35    5     0     3.031    2
  6_14.mol                 COc1cc(cc(c1OC)OC)\[C@\@H\]1SCC(=O)N1c1ccc(cc1)C                                             359.47    4     0     2.9527   5
  6_8.mol                  COc1cc(cc(c1OC)OC)\[C@\@H\]1SCC(=O)N1c1ccc(cc1)O                                             361.44    5     1     2.2011   5
  8_11i.mol                COc1ccc(cc1C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2)F                                             362.37    4     0     2.9642   3
  4_4c.mol                 Cc1ccc(cc1)\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                            369.44    4     2     6.1987   5
  1_3.mol                  Oc1ccc(cc1)C(c1ccc(cc1)O)=C(CC(F)(F)F)c1ccccc1                                               370.39    2     2     5.8763   5
  5_6.mol                  COc1cc2occ(c2cc1O)C(=O)/C=C/c1ccc(cc1)c1ccccc1                                               370.42    4     1     4.7739   6
  8_11a.mol                O=C1OC2(C=CC(=O)C=C2)C(=C1c1sc2ccccc2c1)c1ccccc1                                             370.43    3     0     3.1355   2
  4_4h.mol                 Oc1ccc(cc1)\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                            371.41    5     3     5.4471   5
  4_4i.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1cccc(c1)O)c1ccc(cc1)O                                              371.41    5     3     5.4471   5
  4_4d.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1ccc(cc1)F)c1ccc(cc1)O                                              373.4     4     2     5.871    5
  4_4j.mol                 CCCCCCC\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                                377.52    4     2     6.8921   10
  hydroxytamoxifen.mol     CC\\C(\\c1ccccc1)=C(/c1ccc(cc1)O)\\c1ccc(cc1)OCCN(C)C                                        387.56    3     1     5.6257   9
  4_4e.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1ccc(cc1)Cl)c1ccc(cc1)O                                             389.85    4     2     6.2495   5
  3_2.mol                  CCCCC(c1ccc(cc1)S(C)(=O)=O)=C(c1ccccc1)c1ccccc1                                              390.57    2     0     6.1213   8
  3_9a.mol                 CCCCC(c1ccc(cc1)S(C)(N)=O)=C(c1ccccc1)c1ccccc1                                               390.6     2     1              8
  4_4k.mol                 CCCCCCCC\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                               391.55    4     2     7.2884   11
  8_11h.mol                COc1cc(cc(c1OC)OC)C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2                                        404.44    6     0     2.3193   5
  4_4l.mol                 CCCCCCCCC\\C=C\\c1c(onc1c1ccc(cc1)O)c1ccc(cc1)O                                              405.58    4     2     7.6847   12
  3_8a.mol                 CCCCC(c1ccc(cc1)S(C)(=O)NC\#N)=C(c1ccccc1)c1ccccc1                                           415.61    3     1              9
  4_4f.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1ccc(cc1)C(F)(F)F)c1ccc(cc1)O                                       423.41    4     2     6.6143   5
  4_4g.mol                 Oc1ccc(cc1)c1onc(c1/C=C/c1cccc(c1)C(F)(F)F)c1ccc(cc1)O                                       423.41    4     2     6.6143   5
  1_4i.mol                 Oc1ccc(cc1)N(C\[C@@\]12C\[C@\@H\]3C\[C@\@H\](C\[C@@\](Br)(C3)C1)C2)c1ccc(cc1)O               428.4     2     2     5.3113   4
  14_15a.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN(C)C)c2ccccc2OC1=O                                           430.54    5     1     3.1602   8
  8_11j.mol                COc1c(cc(cc1C1=C(c2ccccc2)C2(OC1=O)C=CC(=O)C=C2)C)Br                                         437.3     4     0     4.0837   3
  14_18a.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN(C)C)c2ccc(cc2OC1=O)O                                        446.54    6     2     2.8758   8
  14_15c.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCC2)c2ccccc2OC1=O                                         456.58    5     1     3.4858   8
  14_15b.mol               CCN(CC)CCOc1ccc(cc1)NC1=C(C(=O)Oc2ccccc21)c1ccc(cc1)OC                                       458.6     5     1     3.8452   10
  14_16a.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN(C)C)c2ccc(cc2OC1=O)OC                                       460.57    6     1     2.9075   9
  14_15d.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCCC2)c2ccccc2OC1=O                                        470.61    5     1     3.8821   8
  14_15e.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCOCC2)c2ccccc2OC1=O                                        472.58    6     1     2.8176   8
  14_18c.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCC2)c2ccc(cc2OC1=O)O                                      472.58    6     2     3.2014   8
  14_18b.mol               CCN(CC)CCOc1ccc(cc1)NC1=C(C(=O)Oc2cc(ccc21)O)c1ccc(cc1)OC                                    474.6     6     2     3.5608   10
  14_15f.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCN(C)CC2)c2ccccc2OC1=O                                     485.63    6     1     2.9615   8
  14_16c.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCC2)c2ccc(cc2OC1=O)OC                                     486.61    6     1     3.2331   9
  14_18d.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCCC2)c2ccc(cc2OC1=O)O                                     486.61    6     2     3.5977   8
  14_18e.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCOCC2)c2ccc(cc2OC1=O)O                                     488.58    7     2     2.5332   8
  14_16b.mol               CCN(CC)CCOc1ccc(cc1)NC1=C(C(=O)Oc2cc(ccc21)OC)c1ccc(cc1)OC                                   488.63    6     1     3.5925   11
  14_16d.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCCCC2)c2ccc(cc2OC1=O)OC                                    500.64    6     1     3.6294   9
  14_18f.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCN(C)CC2)c2ccc(cc2OC1=O)O                                  501.63    7     2     2.6771   8
  14_16e.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCOCC2)c2ccc(cc2OC1=O)OC                                    502.61    7     1     2.5649   9
  14_16f.mol               COc1ccc(cc1)C1=C(Nc2ccc(cc2)OCCN2CCN(C)CC2)c2ccc(cc2OC1=O)OC                                 515.66    7     1     2.7088   9
  11_6a.mol                Fc1ccc(cc1)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccccc1                  597.7     5     1     4.5686   6
  11_6c.mol                COc1ccc(cc1)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccccc1                 609.74    6     1     4.1764   7
  11_6f.mol                Fc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(cc1)F)c1ccccc1               615.69    5     1     4.7081   6
  11_6h.mol                COc1ccc(cc1)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccc(cc1)F              627.73    6     1     4.3159   7
  11_6k.mol                COc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(cc1)F)c1ccccc1              627.73    6     1     4.3159   7
  11_6d.mol                COc1ccc(cc1OC)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccccc1               639.771   7     1     3.9237   8
  11_6m.mol                COc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(cc1)OC)c1ccccc1             639.771   7     1     3.9237   8
  11_6b.mol                Clc1ccc(cc1Cl)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccccc1               648.59    5     1     5.4651   6
  11_6i.mol                COc1ccc(cc1OC)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccc(cc1)F            657.76    7     1     4.0632   8
  11_6p.mol                COc1ccc(cc1OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(cc1)F)c1ccccc1            657.76    7     1     4.0632   8
  11_6g.mol                Fc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)Cl)Cl)c1ccccc1          666.58    5     1     5.6046   6
  11_6e.mol                COc1cc(cc(c1OC)OC)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccccc1           669.801   8     1     3.671    9
  11_6n.mol                COc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)OC)OC)c1ccccc1         669.801   8     1     3.671    9
  11_6r.mol                COc1ccc(cc1)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccc(c(c1)OC)OC         669.801   8     1     3.671    9
  11_6l.mol                COc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)Cl)Cl)c1ccccc1         678.62    6     1     5.2124   7
  11_6j.mol                COc1cc(cc(c1OC)OC)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1ccc(cc1)F        687.791   8     1     3.8105   9
  11_6u.mol                COc1cc(cc(c1OC)OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(cc1)F)c1ccccc1        687.791   8     1     3.8105   9
  11_6o.mol                COc1ccc(cc1)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1cc(c(c(c1)OC)OC)OC)c1ccccc1     699.831   9     1     3.4183   10
  11_6s.mol                COc1ccc(cc1OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)OC)OC)c1ccccc1       699.831   9     1     3.4183   10
  11_6w.mol                COc1ccc(cc1)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1cc(c(c(c1)OC)OC)OC     699.831   9     1     3.4183   10
  11_6q.mol                COc1ccc(cc1OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)Cl)Cl)c1ccccc1       708.651   7     1     4.9597   8
  11_6t.mol                COc1ccc(cc1OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1cc(c(c(c1)OC)OC)OC)c1ccccc1   729.861   10    1     3.1656   11
  11_6x.mol                COc1ccc(cc1OC)C1=CC(=Nc2cc(nn21)c1ccccc1)C(=O)N1CCN(CC1)C(=O)c1cccnc1Nc1cc(c(c(c1)OC)OC)OC   729.861   10    1     3.1656   11
  11_6v.mol                COc1cc(cc(c1OC)OC)Nc1ncccc1C(=O)N1CCN(CC1)C(=O)C1=Nc2cc(nn2C(=C1)c1ccc(c(c1)Cl)Cl)c1ccccc1   738.681   8     1     4.7079   

###### Compounds which exhibited better binding affinities than bound tamoxifen

  S. No   Ligand       MolDock Score
  ------- ------------ ---------------
  1       11_6j.mol    -175.282
  2       11_6o.mol    -172.882
  3       14_16c.mol   -171.234
  4       11_6h.mol    -169.719
  5       14_15e.mol   -168.139
  6       11_6e.mol    -167.14
  7       14_16d.mol   -165.673
  8       11_6g.mol    -165.019
  9       14_15c.mol   -164.805
  10      11_6k.mol    -164.018
  11      14_18e.mol   -162.91
  12      11_6d.mol    -162.147
  13      11_6t.mol    -161.625
  14      14_18f.mol   -160.374
  15      14_18d.mol   -159.463
  16      11_6n.mol    -158.725
  17      11_6i.mol    -158.478
  18      14_18a.mol   -157.811
  19      11_6a.mol    -156.748
  20      11_6c.mol    -156.4
  21      11_6s.mol    -156.129
  22      11_6q.mol    -156.068
  23      11_6p.mol    -155.936
  24      11_6f.mol    -155.614
  25      11_6b.mol    -154.125
  26      14_15a.mol   -154.078
  27      11_6x.mol    -153.768
  28      11_6l.mol    -153.718
  29      14_18b.mol   -153.633
  30      11_6m.mol    -153.504
  31      14_16a.mol   -152.413
  32      Tamoxifen    -149.856

###### H-bond interactions of top 31 compounds

  S. No   Ligand       MolDock Score   H-bond interacting amino acid residues   H-bond energy (kcal/mol)
  ------- ------------ --------------- ---------------------------------------- --------------------------
  1       11_6j.mol    -175.282        Cys530, Thr347                           -4.617
  2       11_6o.mol    -172.882        Cys530, Thr347                           -5
  3       14_16c.mol   -171.234        Arg394, Glu353, His524                   -5.644
  4       11_6h.mol    -169.719        Thr347                                   -0.2
  5       14_15e.mol   -168.139        Arg394, Glu353, His524                   -5.336
  6       11_6e.mol    -167.14         Thr347, Asp351                           -3.02
  7       14_16d.mol   -165.673        Arg394, His524                           -3.141
  8       11_6g.mol    -165.019        Thr347                                   -2.455
  9       14_15c.mol   -164.805        His524                                   -1.214
  10      11_6k.mol    -164.018        Thr347                                   -2.059
  11      14_18e.mol   -162.91         Arg394, Glu353, His524                   -5.729
  12      11_6d.mol    -162.147        Cys530, Thr347                           -2.789
  13      11_6t.mol    -161.625        Leu536, Thr347, His524                   -4.251
  14      14_18f.mol   -160.374        Arg394, Glu353, His524                   -5.331
  15      14_18d.mol   -159.463        Arg394, His524                           -3.6
  16      11_6n.mol    -158.725        Thr347                                   -2.333
  17      11_6i.mol    -158.478        Thr347                                   -2.388
  18      14_18a.mol   -157.811        Arg394, Glu353, His524, Leu387, Asp351   -6.595
  19      11_6a.mol    -156.748        Thr347                                   -2.5
  20      11_6c.mol    -156.4          Thr347                                   -2.369
  21      11_6s.mol    -156.129        Thr347, Cys530                           -3.623
  22      11_6q.mol    -156.068        Thr347                                   -2.227
  23      11_6p.mol    -155.936        Thr347                                   -1.414
  24      11_6f.mol    -155.614        Thr347                                   -2.5
  25      11_6b.mol    -154.125        Thr347                                   -1.064
  26      14_15a.mol   -154.078        Asp351, His524                           -1.176
  27      11_6x.mol    -153.768        Arg394                                   -1.237
  28      11_6l.mol    -153.718        Thr347, Cys530                           -2.682
  29      14_18b.mol   -153.633        Glu353, Arg394, His524                   -5.869
  30      11_6m.mol    -153.504        Thr347                                   -2.073
  31      14_16a.mol   -152.413        Asp351, Arg394, His524                   -3.214
  32      Tamoxifen    -149.856        Asp351, Arg394                           -2.5

###### IUPAC names, SMILES notation and molecular dock scores in kcal/mol of 34 bipyrazole class of compounds

  ID   IUPAC Name                                                                                                                                       SMILES                                                                                                          Dock Score (kcal/mol)
  ---- ------------------------------------------------------------------------------------------------------------------------------------------------ --------------------------------------------------------------------------------------------------------------- -----------------------
  1    ethyl 5-amino-3-anilino-1H-pyrazole-4-carboxylate                                                                                                CCOC(=O)c1c(N)\[nH\]nc1Nc2ccccc2                                                                                -105.689
  2    ethyl 5-amino-1-(5-amino-3-anilino-4-ethoxycarbonyl-pyrazol-1-yl)-3-anilino-pyrazole-4-carboxylate                                               CCOC(=O)c1c(N)n(nc1Nc2ccccc2)n3nc (Nc4ccccc4)c(C(=O)OCC)c3N                                                     -175.937
  3    ethyl 5-amino-1-(4-chloro-4-ethoxycarbonyl-5-oxo-1H-pyrazol-3-yl)-3-ethoxy-pyrazole-4-carboxylate                                                CCOC(=O)c1c(N)n(nc1OCC)C2=NNC(=O) C2(Cl)C(=O)OCC                                                                -137.361
  4    5-(4-chlorophenyl)-4-(4-cyanopyrazol-1-yl)-N-(4-phenylphenyl)-3,4-dihydropyrazole-2-carboxamide                                                  Clc1ccc(cc1)C2=NN(CC2n3cc(cn3)C\#N)C(=O) Nc4ccc(cc4)c5ccccc5                                                    -139.765
  5    1-(1,5-diphenylpyrazol-4-yl)-3,5-dimethyl-pyrazole                                                                                               Cc1cc(C)n(n1)c2cnn(c3ccccc3)c2c4ccccc4                                                                          -131.507
  6    methyl 4-(3,5-dimethylpyrazol-1-yl)-5-phenyl-pyrazole-1-carboxylate                                                                              COC(=O)n1ncc(c1c2ccccc2)n3nc(C)cc3C                                                                             -120.717
  7    1-tert-butyl-4-(3,5-dimethylpyrazol-1-yl)-5-phenyl-pyrazole                                                                                      Cc1cc(C)n(n1)c2cnn(c2c3ccccc3)C(C)(C)C                                                                          -117.359
  8    bis(2-adamantyl)-\[2-\[1-(4-methoxyphenyl)-3,5-diphenyl-pyrazol-4-yl\]pyrazol-3-yl\]phosphane                                                    COc1ccc(cc1)n2nc(c3ccccc3)c(c2c4ccccc4)n5nccc5P(C6C7CC8CC(CC6C8)C7) C9C%10CC%11CC(CC9C%11) C%10                 -146.054
  9    dicyclohexyl-\[2-\[1-(4-methoxyphenyl)-3,5-diphenyl-pyrazol-4-yl\]pyrazol-3-yl\]phosphane                                                        COc1ccc(cc1)n2nc(c3ccccc3)c(c2c4ccccc4)n5nccc5P (C6CCCCC6)C7CCCCC7                                              -148.556
  10   ditert-butyl-\[2-\[1-(4-methoxyphenyl)-3,5-diphenyl-pyrazol-4-yl\]pyrazol-3-yl\]phosphane                                                        COc1ccc(cc1)n2nc(c3ccccc3)c(c2c4ccccc4)n5nccc5P(C(C)(C)C)C(C)(C)C                                               -147.159
  11   4-chloro-1-(3,5-dinitro-1H-pyrazol-4-yl)-5-nitro-pyrazole                                                                                        \[O-\]\[N+\](=O)c1n\[nH\]c(c1n2ncc(Cl)c2\[N+\](=O)\[O-\])\[N+\](=O)\[O-\]                                       -110.157
  12   1-(3,5-dinitro-1H-pyrazol-4-yl)-4,5-dinitro-pyrazole                                                                                             \[O-\]\[N+\](=O)c1cnn(c1\[N+\](=O)\[O-\])c2c(n\[nH\]c2\[N+\](=O)\[O-\])\[N+\](=O)\[O-\]                         -117.658
  13   1-methyl-3,4-dinitro-5-(3-nitropyrazol-1-yl)pyrazole                                                                                             Cn1nc(c(c1n2ccc(n2)\[N+\](=O)\[O-\])\[N+\](=O)\[O-\])\[N+\](=O)\[O-\]                                           -109.876
  14   1-methyl-3,4-dinitro-5-(4-nitropyrazol-1-yl)pyrazole                                                                                             Cn1nc(c(c1n2cc(cn2)\[N+\](=O)\[O-\])\[N+\](=O)\[O-\])\[N+\](=O)\[O-\]                                           -107.758
  15   N-\[1-(4-methoxyphenyl)-3-methyl-5-pyrazol-1-yl-pyrazol-4-yl\]methanesulfonamide                                                                 COc1ccc(cc1)n2nc(C)c(NS(=O)(=O)C)c2n3cccn3                                                                      -125.453
  16   N-\[1-(4-bromophenyl)-3-methyl-5-pyrazol-1-yl-pyrazol-4-yl\]methanesulfonamide                                                                   Cc1nn(c2ccc(Br)cc2)c(c1NS(=O)(=O)C)n3cccn3                                                                      -120.706
  17   N-\[1-(4-chlorophenyl)-3-methyl-5-pyrazol-1-yl-pyrazol-4-yl\]methanesulfonamide                                                                  Cc1nn(c2ccc(Cl)cc2)c(c1NS(=O)(=O)C)n3cccn3                                                                      -118.696
  18   N-\[1-(4-fluorophenyl)-3-methyl-5-pyrazol-1-yl-pyrazol-4-yl\]methanesulfonamide                                                                  Cc1nn(c2ccc(F)cc2)c(c1NS(=O)(=O)C)n3cccn3                                                                       -123.955
  19   N-\[3-methyl-1-(4-nitrophenyl)-5-pyrazol-1-yl-pyrazol-4-yl\]methanesulfonamide                                                                   Cc1nn(c2ccc(cc2)\[N+\](=O)\[O-\])c(c1NS(=O)(=O)C) n3cccn3                                                       -121.433
  20   ethyl 5-amino-1-(5-methyl-4-nitro-2-phenyl-pyrazol-3-yl)pyrazole-4-carboxylate                                                                   CCOC(=O)c1cnn(c1N)c2c(c(C)nn2c3ccccc3)\[N+\] (=O)\[O-\]                                                         -133.582
  21   3-acetyl-1-(4-bromo-3-phenyl-1H-pyrazol-5-yl)-5-phenyl-pyrazole-4-carbonitrile                                                                   CC(=O)c1nn(c(c2ccccc2)c1C\#N)c3\[nH\]nc(c3Br) c4ccccc4                                                          -148.595
  22   ethyl 3-acetyl-5-amino-1-(4-bromo-3-phenyl-1H-pyrazol-5-yl)pyrazole-4-carboxylate                                                                CCOC(=O)c1c(N)n(nc1C(=O)C)c2\[nH\]nc(c2Br) c3ccccc3                                                             -113.874
  23   1-(4-nitrophenyl)-3-\[1-(4-nitrophenyl)-5-propyl-pyrazol-3-yl\]-5-propyl-pyrazole                                                                CCCc1cc(nn1c2ccc(cc2)\[N+\](=O)\[O-\])c3cc(CCC)n (n3)c4ccc(cc4)\[N+\](=O)\[O-\]                                 -154.386
  24   5-isopropyl-3-\[5-isopropyl-1-(4-nitrophenyl)pyrazol-3-yl\]-1-(4-nitrophenyl)pyrazole                                                            CC(C)c1cc(nn1c2ccc(cc2)\[N+\](=O)\[O-\])c3cc(C(C)C)n(n3)c4ccc(cc4)\[N+\](=O)\[O-\]                              -154.361
  25   5-\[5-carbamoyl-1-(2,4-dichlorophenyl)-4H-pyrazol-3-yl\]-2-(2,4-dichlorophenyl)pyrazole-3-carboxamide                                            NC(=O)C1=\[N\](N=C(C1)c2cc(C(=O)N)n(n2)c3ccc(Cl)cc3Cl) c4ccc(Cl)cc4Cl                                           -130.783
  26   2-\[5-\[5-(1,3-benzothiazol-2-yl)-1,4-bis(4-chlorophenyl)pyrazol-3-yl\]-2,4-bis(4-chlorophenyl)-4H-pyrazol-3-yl\]-1,3-benzothiazole              Clc1ccc(cc1)C2C(=N\[N\](=C2c3nc4ccccc4s3)c5ccc(Cl)cc5)c6nn(c7ccc(Cl)cc7)c (c8nc9cccc c9s8) c6c%10ccc(Cl)cc%10   -138.603
  27   \[2-(4-chlorophenyl)-5-\[1-(4-chlorophenyl)-5-(2-hydroxybenzoyl)-4-phenyl-4H-pyrazol-3-yl\]-4-phenyl-pyrazol-3-yl\]-(2-hydroxyphenyl)methanone   Oc1ccccc1C(=O)C2=\[N\](N=C(C2c3ccccc3)c4nn(c5ccc(Cl)cc5)c(C(=O)c6ccccc6O)c4c7ccccc7)c8ccc(Cl)cc8                -140.477
  28   1-(4-chlorophenyl)-5-phenyl-3-(1H-pyrazol-3-yl)pyrazole-4-carbohydrazide                                                                         NNC(=O)c1c(nn(c2ccc(Cl)cc2)c1c3ccccc3)c4cc\[nH\]n4                                                              -137.395
  29   4-\[(4Z)-5-amino-4-\[(4-bromophenyl)methylene\]pyrazol-3-yl\]-1,5-dimethyl-2-phenyl-pyrazol-3-one                                                CN1N(C(=O)C(=C1C)C2=NN=C(N)/C/2=C\\c3ccc(Br)cc3)c4ccccc4                                                        -167.179
  30   (E)-3-(2-hydroxyphenyl)-1-\[1-phenyl-3-(2-thienyl)pyrazol-4-yl\]prop-2-en-1-one                                                                  Oc1ccccc1\\C=C\\C(=O)c2cn(nc2c3cccs3)c4ccccc4                                                                   -98.6882
  31   5-methyl-4-\[5-(4-oxochromen-3-yl)-4,5-dihydro-1H-pyrazol-3-yl\]-1,2-dihydropyrazol-3-one                                                        CC1=C(C(=O)NN1)C2=NNC(C2)C3=COc4ccccc4C3=O                                                                      -138.46
  32   5-amino-N-(1,3-benzothiazol-2-yl)-3-(1,3-diphenylpyrazol-4-yl)-1H-pyrazole-4-carboxamide                                                         Nc1\[nH\]nc(c2cn(nc2c3ccccc3)c4ccccc4)c1C(=O)Nc5nc6ccccc6s5                                                     -145.914
  33   3-(5-hydroxy-3-methyl-1-phenyl-pyrazol-4-yl)-1H-pyrazole-5-carbohydrazide                                                                        Cc1nn(c(O)c1c2cc(\[nH\]n2)C(=O)NN)c3ccccc3                                                                      -117.006
  34   diethyl 2-(4-bromophenyl)-5-(4-cyano-5-methyl-2-phenyl-pyrazol-3-yl)pyrazole-3,4-dicarboxylate                                                   CCOC(=O)c1c(nn(c2ccc(Br)cc2)c1C(=O)OCC)c3c(C\#N)c(C)nn3c4ccccc4                                                 -121.309

###### Screening result of DrugBank database against ERa showing binding affinities (kcal/mol).

  DrugBank ID   Binding affinity (kcal/mol)   Drug Name             Interaction Type   Interacting Residues                     Drug Indication, disease and related information
  ------------- ----------------------------- --------------------- ------------------ ---------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------
  DB09065       -187.123                      Cobicistat            H-bonding          Arg394, Cys530                           Cobicistat is a CYP3A inhibitor
  DB08827       -185.233                      Lomitapide            Van der Waals      No interactions                          Used in homozygous familial hypercholesterolemia (HoFH) patients
  DB01167       -180.646                      Itraconazole          H-bonding          Thr347, Cys530                           For the treatment of the fungal infections
  DB06809       -178.689                      Plerixafor            H-bonding          Glu353                                   Used in combination with granulocyte-colony stimulating factor (G-CSF, filgrastim) in patients with non-Hodgkin�s lymphoma (NHL) and multiple myeloma (MM).
  DB08822       -173.473                      Azilsartanmedoxomil   H-bonding          Thr347, His524                           Treatment of hypertension (alone or as an adjunct).
  DB00549       -172.426                      Zafirlukast           H-bonding          Thr347                                   For the prophylaxis and chronic treatment of asthma.
  DB06401       -170.261                      Bazedoxifene          H-bonding          Gly420, His524, Leu387, Arg394           Bazedoxifene is a third generation selectiveestrogen receptor modulator (SERM).
  DB01259       -169.171                      Lapatinib�            H-bonding          Thr347, Asp351                           Indicated in combination with capecitabine for the treatment of patients with advanced or metastatic breast cancer
  DB00430       -166.876                      Cefpiramide           H-bonding          Thr347, Asp351, Leu525                   For treatment of severe infections caused by susceptible bacteria such as P. aeruginosa.
  DB01264       -165.672                      Darunavir             H-bonding          Leu346, Thr347                           Darunavir, co-administered with ritonavir is indicated for the treatment of HIV infection
  DB00503       -165.18                       Ritonavir             Van der Waals      No interactions                          Indicated in combination with other antiretroviral agents for the treatment of HIV-1 infection.
  DB01263       -164.662                      Posaconazole          H-bonding          Glu353, Leu387, Cys530                   For prophylaxis of invasive Aspergillus and Candida infections
  DB00481       -163.664                      Raloxifene            H-bonding          Arg394, Glu353, Gly521, Gly420, His524   A second generation selective estrogen receptor modulator (SERM), for the prevention and treatment of osteoporosis in post-menopausal women
  DB08912       -163.634                      Dabrafenib            H-bonding          Gly521                                   Indicated for the treatment of patients with unresectable or metastatic melanoma.
  DB06590       -163.214                      Ceftarolinefosamil    H-bonding          Met343, Thr347, Cys530                   Ceftarolinefosamil is a cephalosporin antibacterial.

###### DrugBank drugs and corresponding scores of five scoring functions with rank-sum technique

  Drug Name             DrugBank ID   DSX online   Rank   Pose & Rank   Rank   MolDock    Rank   mcule   Rank   Swiss    Rank   Rank-Sum
  --------------------- ------------- ------------ ------ ------------- ------ ---------- ------ ------- ------ -------- ------ ----------
  Cobicistat            DB09065       -124         2      -52.01        3      -187.123   3      -8      1      -10.08   3      12
  Lomitapide            DB08827       -166         3      -49.06        3      -185.233   3      -10.3   3      -9.77    3      15
  Itraconazole          DB01167       -125         2      -44.55        3      -180.646   3      -10.4   3      -9.52    3      14
  Plerixafor            DB06809       -105         1      -25.77        1      -178.689   2      -9.6    3      -9.87    3      10
  Azilsartanmedoxomil   DB08822       -107         2      -42.56        2      -173.473   2      -9.7    3      -9.06    3      12
  Zafirlukast           DB00549       -137         3      -46.05        3      -172.426   2      -9.3    2      -8.36    2      12
  Cefpiramide           DB00430       -96          1      -31.8         1      -166.876   1      -8.2    1      -6.83    1      5
  Darunavir             DB01264       -119         2      -42.25        2      -165.672   1      -8.1    1      -7.82    1      7
  Ritonavir             DB00503       -74          1      -26.46        1      -165.18    1      -7.6    1      -7.17    1      5
  Posaconazole          DB01263       -116         2      -26.43        1      -164.662   1      -7.9    1      -7.4     1      6
  Ceftarolinefosamil    DB06590       -102         1      -25.22        1      -163.214   1      -7.2    1      -7.72    1      5

![Structural superimposition of top 3 literature compounds Vstamoxifen (ball and stick model).](97320630015321F1){#F1}

![Overlap image of bipyrazole compound 2 (dock score - 175.937 kcal per mol) with ERa bound tamoxifen.](97320630015321F2){#F2}

![Bipyrazole compound 2 showing H-bond interaction with Thr347](97320630015321F3){#F3}

![Bipyrazole compound 29 (dock score -167.1 kcal/mol) showing two H-bond interactions with Thr347](97320630015321F4){#F4}

![All 15 drugs superimposed within the active site of ERa](97320630015321F5){#F5}
