New indole-based chalconoids as tubulin-targeting antiproliferative agents

Tubulin-targeting compounds have a broad anticancer spectrum and are an important class of chemotherapeutic agents. Due to the importance of 3-bromo-3,5-dimethoxyphenyl scaffold in the anticancer activity of microtubule inhibitors such as crolibulin (EPC2407), we introduced this functionality into the indole-derived chalcones. Thus, we describe here the synthesis and biological evaluation of new indole-based chalconoids as tubulin-targeting antiproliferative agents. The best result was obtained by compound 9b against A549 cell with IC₅₀ of 4.3 µg/mL, being more potent than the reference drug etoposide. Further biological evaluations revealed that compound 9b can inhibit tubulin polymerization and decrease the mitochondrial thiol content, resulting the induction of apoptosis in cancer cells. Docking studies with tubulin indicated that compound 9b could bind to the colchicine binding site.     

Structure-based virtual screening of novel tubulin inhibitors and their characterization as anti-mitotic agents

Microtubule cytoskeletons are involved in many essential functions throughout the life cycle of cells, including transport of materials into cells, cell movement, and proper progression of cell division. Small compounds that can bind at the colchicine site of tubulin have drawn great attention because these agents can suppress or inhibit microtubule dynamics and tubulin polymerization. To find novel tubulin polymerization inhibitors as anti-mitotic agents, we performed a virtual screening study of the colchicine binding site on tubulin. Novel tubulin inhibitors were identified and characterized by their inhibitory activities on tubulin polymerization in vitro. The structural basis for the interaction of novel inhibitors with tubulin was investigated by molecular modeling, and we have proposed binding models for these hit compounds with tubulin. The proposed docking models were very similar to the binding pattern of colchicine or podophyllotoxin with tubulin. These new hit compound derivatives exerted growth inhibitory effects on the HL60 cell lines tested and exhibited strong cell cycle arrest at G2/M phase. Furthermore, these compounds induced apoptosis after cell cycle arrest. In this study, we show that the validated derivatives of compound 11 could serve as potent lead compounds for designing novel anti-cancer agents that target microtubules.     

Rational design and synthesis of 2-anilinopyridinyl-benzothiazole Schiff bases as antimitotic agents

Based on our previous results and literature precedence, a series of 2-anilinopyridinyl-benzothiazole Schiff bases were rationally designed by performing molecular modeling experiments on some selected molecules. The binding energies of the docked molecules were better than the E7010, and the Schiff base with trimethoxy group on benzothiazole moiety, 4y was the best. This was followed by the synthesis of a series of the designed molecules by a convenient synthetic route and evaluation of their anticancer potential. Most of the compounds have shown significant growth inhibition against the tested cell lines and the compound 4y exhibited good antiproliferative activity with a GI₅₀ value of 3.8 µM specifically against the cell line DU145. In agreement with the docking results, 4y exerted cytotoxicity by the disruption of the microtubule dynamics by inhibiting tubulin polymerization via effective binding into colchicine domain, comparable to E7010. Detailed binding modes of 4y with colchicine binding site of tubulin were studied by molecular docking. Furthermore, 4y induced apoptosis as evidenced by biological studies like mitochondrial membrane potential, caspase-3, and Annexin V-FITC assays.     

Synthesis of 2-anilinopyridine dimers as microtubule targeting and apoptosis inducing agents

A series of 2-anilinopyridine dimers have been synthesized and evaluated for their anticancer potential. Most of the compounds have showed significant growth inhibition of the cell lines tested and compound 4d was most effective amongst the series displaying a GI₅₀ of 0.99 μM specifically against the prostate cancer cell line (DU145). Studies to understand the mechanism of action of 4d indicates that it disrupts microtubule dynamics by inhibiting tubulin polymerization thereby arresting the cell cycle in G2/M phase. Competitive colchicine binding assay suggests that 4d binds into colchicine binding site of the tubulin. Further from some detailed biological studies like mitochondrial membrane potential, caspase-3 assay, DNA fragmentation analysis and Annexin V-FITC assay it is evident that 4d induces apoptosis. Molecular modeling studies provide an insight into the binding modes of 4d with colchicine binding site of tubulin and the data obtained correlates with the antiproliferative activity.     

Synthesis,characterization and anti-tumor activity of novel thymoquinone analogs against pancreatic cancer

Thymoquinone (TQ), isolated from the seeds of Nigella sativa, show moderate efficacy against pancreatic cancer. In the present work we report synthesis and characterization of novel TQ analogs appended with gallate and fluorogallate pharmacophores and evaluation of their effects against pancreatic cancer cell lines for cell viability and induction of apoptosis. The efficacy of the analogs alone or in combination with Gemcitabine was assessed in vitro. LC–MS spectra of ATQTHB and ATQTFB showed major peaks corresponding to expected M+1 fragment at 316.34 and 322.34 respectively. Molecular docking studies revealed good fit for these analogs in the COX-2 protein cavity with better binding energies compared to parent TQ compound. Present TQ analogs exhibit superior anti-proliferative activity, excellent chemo-sensitizing activity against pancreatic cancer in vitro and in combination with Gemcitabine.     

Synthesis,biological evaluation and molecular docking studies of aminochalcone derivatives as potential anticancer agents by targeting tubulin colchicine binding site

A series of aminochalcone derivatives have been synthesized, characterized by HRMS, ¹H NMR and ¹³C NMR and evaluated for their antiproliferative activity against HepG2 and HCT116 human cancer cell lines. The most of new synthesized compounds displayed moderate to potent antiproliferative activity against test cancer cell lines. Among the derivatives, compound 4 displayed potent inhibitory activity with IC₅₀ values ranged from 0.018 to 5.33 μM against all tested cancer cell lines including drug resistant HCT-8/T. Furthermore, this compound showed low cytotoxicity on normal human cell lines (LO2). The in vitro tubulin polymerization assay showed that compound 4 inhibited tubulin assembly in a concentration-dependent manner with IC₅₀ value of 7.1 μM, when compared to standard colchicine (IC₅₀ = 9.0 μM). Further biological evaluations revealed that compound 4 was able to arrest the cell cycle in G2/M phase. Molecular docking study demonstrated the interaction of compound 4 at the colchicine binding site of tubulin. All the results indicated that compound 4 is a promising inhibitor of tubulin polymerization for the treatment of cancer.     

Synthesis and biological evaluation of a series of podophyllotoxins derivatives as a class of potent antitubulin agents

A series of eight novel podophyllotoxin derivatives were designed, synthesized and evaluated for biological activities. The antiproliferative activities were tested against a panel of human cancer cell lines (K562, SGC, Hela and HepG) and the inhibition of tubulin polymerization was also evaluated. Compound 8e displayed significant antiproliferative activities for all four cell lines and strong levels of tubulin polymerization inhibition effect. Combined with cell apoptosis and cell cycle analysis, it demonstrated that compound 3e that effectively interfere with tubulin dynamics prevent mitosis in cancer cells, leading to cell cycle arrest and, eventually dose dependent apoptosis. All experimental measurements were also supported by molecular docking simulations of colchicine binding site, which revealed the governing forces for the binding behavior and a good relationship with anti-tubulin activity and antiproliferative activities. The synthesis and biological studies provided an interesting new class of antitubulin agents for development of lead compounds and also a direction for further structure modification to obtain more potent anti-cancer drugs.     

A novel tetrazole analogue of resveratrol is a potent anticancer agent

A series of novel tetrazole analogues of resveratrol were synthesized and evaluated for their anti-leukemic activity against an extensive panel of human cancer cell lines and against the MV4-11 AML cell line. These molecules were designed as drug-like derivatives of the resveratrol analogue DMU-212 and its cyano derivatives. Four compounds 8g, 8h, 10a and 10b exhibited LD₅₀ values of 4.60?µM, 0.02?µM, 1.46?µM, and 1.08?µM, respectively, against MV4-11 leukemia cells. The most potent compounds, 8h and 10b, were also found to be active against an extensive panel of human hematological and solid tumor cell lines; compound 8h was the most potent compound with GI₅₀ values <10?nM against more than 90% of the human cancer cell lines in the 60-cell panel. Analogues 8g, 8h, 10a and 10b were also tested for their ability to inhibit the polymerization of tubulin, and compound 8h was found to be the most potent analogue. Molecular modeling studies demonstrated that 8h binds to the colchicine binding site on tubulin. Thus, compound 8h is considered to be a lead druglike molecule from this tetrazole series of compounds.     

Synthesis,antiproliferative activity and molecular docking of thiocolchicine urethanes

A number of naturally occurring compounds such as paclitaxel, vinblastine, combretastatin, and colchicine exert their therapeutic effect by changing the dynamics of tubulin and its polymer form, microtubules. The identification of tubulin as a potential target for anticancer drugs has led to extensive research followed by clinical development of numerous compounds from several families. In this paper we report on the design, synthesis and in vitro evaluation of a group of thiocolchicine derivatives, modified at ring-B, labelled here compounds 4–14. These compounds have been obtained in a simple reaction of 7-deacetyl-10-thiocolchicine 3 with eleven different alcohols in the presence of triphosgene. These novel agents have been checked for anti-proliferative activity against four human cancer cell lines and their mode of action has been confirmed as colchicine binding site inhibition (CBSI) using molecular docking. Molecular simulations provided rational tubulin binding models for the tested compounds. On the basis of in vitro tests, derivatives 4–8 and 14 demonstrated the highest potency against MCF-7, LoVo and A549 tumor cell lines (IC₅₀ values = 0.009–0.014 μM). They were more potent and characterized by a higher selectivity index than several standard chemotherapeutics including cisplatin and doxorubicin as well as unmodified colchicine. Further, studies revealed that colchicine and its several derivatives arrested MCF-7 cells in mitosis, while its selected derivatives caused microtubule depolymerization.     

Synthesis and evaluation of diaryl sulfides and diaryl selenide compounds for antitubulin and cytotoxic activity

We have devised a procedure for the synthesis of analogs of combretastatin A-4 (CA-4) containing sulfur and selenium atoms as spacer groups between the aromatic rings. CA-4 is well known for its potent activity as an inhibitor of tubulin polymerization, and its prodrugs combretastatin A-4 phosphate (CA-4P) and combretastatin A-1 phosphate (CA-1P) are being investigated as antitumor agents that cause tumor vascular collapse in addition to their activity as cytotoxic compounds. Here we report the preparation of two sulfur analogs and one selenium analog of CA-4. All synthesized compounds, as well as several synthetic intermediates, were evaluated for inhibition of tubulin polymerization and for cytotoxic activity in human cancer cells. Compounds 3 and 4 were active at nM concentration against MCF-7 breast cancer cells. As inhibitors of tubulin polymerization, both 3 and 4 were more active than CA-4 itself. In addition, 4 was the most active of these agents against 786, HT-29 and PC-3 cancer cells. Molecular modeling binding studies are also reported for compounds 1, 3, 4 and CA-4 to tubulin within the colchicine site.     

Design and synthesis of silicon-containing tubulin polymerization inhibitors: Replacement of the ethylene moiety of combretastatin A-4 with a silicon linker

Silicon-containing combretastatin analogs were designed, synthesized and evaluated for stability and biological activities. Among them, compound 31 exhibited strong tubulin polymerization-inhibitory activity and very potent tumor cell growth-inhibitory activity (IC₅₀ = 0.007 μM) in MCF-7 cell proliferation assay. This compound also potently inhibited [³H]colchicine binding (90.7% inhibition at 3 μM). These activities were comparable to those of combretastatin A-4 (CA-4) (1). In addition, compound 31 was physico-chemically more stable than 1. These results suggest that a silicon linker can act as a bioisoster of a cis carbon–carbon double bond.     

Design,synthesis, cytotoxic evaluation and tubulin inhibitory activity of 4-aryl-5-(3,4,5-trimethoxyphenyl)-2-alkylthio-1H-imidazole derivatives

A new series of 4-aryl-5-(3,4,5-trimethoxyphenyl)-2-alkylthio-1H-imidazoles were synthesized and their cytotoxic activities in vitro against four different cell lines (HT-29, MCF-7, NIH-3T3, AGS) were evaluated. Compound 6g bearing 3,4,5-trimethoxyphenyl moiety on ring A and 4-methoxy substituent on ring B displayed potent cytotoxic activity against all cell lines. Flow cytometry analysis and microtubule polymerization assay confirmed that cytotoxic activities of this compound were related to inhibitory effect against microtubules polymerization. Molecular modeling studies revealed that compound 6g could strongly bind to the colchicine binding site of α,β-tubulin through hydrogen bond interactions with Thrα179 and Cysβ241.     

Direct semi-synthesis of the anticancer lead-drug protoapigenone from apigenin, and synthesis of further new cytotoxic protoflavone derivatives

Protoapigenone, a natural flavonoid possessing an unusual p-quinol moiety on its B-ring, is a novel prospective anticancer agent with low toxicity that is currently in development. The first economical, one-step synthesis of protoapigenone from apigenin is described on up to gram scale. 13 new 1'-O-alkylflavone analogs were also synthesized, either from apigenin or β-naphthoflavone. The in vitro cytotoxic activity of each compound was tested on six human cancer cell lines (HepG2, Hep3B, Ca9-22, A549, MCF-7 and MDA-MB-231). In the case of 1'-O-alkyl-protoapigenone derivatives, structure-activity relationships were found depending on the side-chain, and protoapigenone 1'-O-butyl ether was found to exert significantly stronger activity against three of the cell lines (Hep3B, MCF-7 and MDA-MB-231) than its non-substituted analog, protoapigenone itself. In contrast to this, all β-naphthoflavone derivatives bearing the same pharmacophore on their B-ring showed decreased cytotoxic activities when substituted with an O-alkyl side-chain at position 1', comparing to that of the non-substituted compound.     

Synthesis and mechanism of action of novel pyrimidinyl pyrazole derivatives possessing antiproliferative activity

Pyrimidinyl pyrazole derivatives 1-4, prepared as a new scaffold of an anti-tumor agent, showed antiproliferative activity against human lung cancer cell lines and inhibited tubulin polymerization. Furthermore, it was found that compound 2 bound at the colchicine site on tubulin, but the tubulin binding pattern was different from that of colchicine. Here, we describe the synthesis of the derivatives and the differences of the action mechanism on tubulin polymerization inhibition between compound 2 and colchicine.     

Synthesis,biological evaluation and molecular docking studies of bis-chalcone derivatives as xanthine oxidase inhibitors and anticancer agents

In this study, a series of B-ring fluoro substituted bis-chalcone derivatives were synthesized by Claisen-Schmidt condensation reactions and evaluated for their ability to inhibit xanthine oxidase (XO) and growth inhibitory activity against MCF-7 and Caco-2 human cancer cell lines, in vitro. According to the results obtained, the bis-chalcone with fluoro group at the 2 (4b) or 2,5-position (4g) of B-ring were found to be potent inhibitors of the enzyme with IC₅₀ values in the low micromolar range. The effects of these compounds were about 7 fold higher than allopurinol. The binding modes of the bis-chalcone derivatives in the active site of xanthine oxidase were explained using molecular docking calculations. Also, compound 4g and 4h showed in vitro growth inhibitory activity against a panel of two human cancer cell lines 1.9 and 6.8 μM of IC₅₀ values, respectively.     

From a novel HTS hit to potent,selective, and orally bioavailable KDM5 inhibitors

A high-throughput screening (HTS) of the Genentech/Roche library identified a novel, uncharged scaffold as a KDM5A inhibitor. Lacking insight into the binding mode, initial attempts to improve inhibitor potency failed to improve potency, and synthesis of analogs was further hampered by the presence of a C–C bond between the pyrrolidine and pyridine. Replacing this with a C–N bond significantly simplified synthesis, yielding pyrazole analog 35, of which we obtained a co-crystal structure with KDM5A. Using structure-based design approach, we identified 50 with improved biochemical, cell potency and reduced MW and lower lipophilicity (Log D) compared with the original hit. Furthermore, 50 showed lower clearance than 9 in mice. In combination with its remarkably low plasma protein binding (PPB) in mice (40%), oral dosing of 50 at 5 mg/kg resulted in unbound C_max ～2-fold of its cell potency (PC9 H3K4Me3 0.96 μM), meeting our criteria for an in vivo tool compound from a new scaffold.     

(E)-N-Aryl-2-oxo-2-(3,4,5-trimethoxyphenyl)acetohydrazonoyl cyanides as tubulin polymerization inhibitors: Structure-based bioisosterism design,synthesis, biological evaluation,molecular docking and in silico ADME prediction

A series of (E)-N-Aryl-2-oxo-2-(3,4,5-trimethoxyphenyl)acetohydrazonoyl cyanides have been synthesized and evaluated for their anticancer activity in human hepatocellular liver carcinoma HepG2 and breast adenocarcinoma MCF-7?cell lines. Among all the tested compounds, compound 3a, 3e and 3n displayed more activity than lead compound with IC₅₀ value of 0.26–0.61?μM. Meanwhile, these compounds (3a, 3e and 3n) showed potent antiproliferative activity against a panel of cancer cells and the HCT-8/T multidrug resistant cell line with IC₅₀ values in the range of 0.077– 7.44?μM. Flow cytometric analyses revealed that compound 3n induced cell cycle arrest in G2/M phases in a dose dependent manner. The compound 3n also displayed potent tubulin polymerization inhibition with an IC₅₀ value of 0.9?µM, with ten folds more active than colchicine (IC₅₀?=?9?μM). Molecular docking studies revealed that compound 3n efficiently interacted with the colchicine binding site of tubulin through hydrophobic, cation-π and hydrogen bond interaction. Furthermore, in silico pharmacokinetic prediction shown that these compounds have a good ADME-related physicochemical parameters. These results demonstrate that 3n exhibits potent cytotoxicity in cancer cells by targeting the colchicine binding site of tubulin and potentially acts as a therapeutic lead compound for the development of anticancer drugs.     

Discovery of structurally simplified analogs of colchicine as an immunosuppressant

We have discovered a new class of colchicine-derived therapeutic agents for immune diseases including rejection of organ-transplantation and autoimmune disease. Compound 2, which had been developed to overcome poor pharmacokinetic properties of compound 1, a first-generation colchicine analog, turned out to show toxicity such as intestinal toxicity and loss of weight during in vivo tests. The deletion of 7-carboxamide group and middle ring-truncation in colchicine allowed us to have structurally simplified analogs with strong immunosuppressive activity. Herein, we report non-alkaloid tricyclic compound 7 and 12 as immunosuppressants which exhibited a strong immunosuppressive in vivo efficacy on the T-dependent antibody response, the Zymosan A-induced arthritis model and the Carrageenan-induced edema model. Compound 7 and 12 revealed less toxicity than the previous lead compound 2, and their minimum lethal doses (MLD) were proved to exceed 100 mg/kg.     

3-Ketone-4,6-diene ceramide analogs exclusively induce apoptosis in chemo-resistant cancer cells

Multidrug-resistance is a major cause of cancer chemotherapy failure in clinical treatment. Evidence shows that multidrug-resistant cancer cells are as sensitive as corresponding regular cancer cells under the exposure to anticancer ceramide analogs. In this work we designed five new ceramide analogs with different backbones, in order to test the hypothesis that extending the conjugated system in ceramide analogs would lead to an increase of their anticancer activity and selectivity towards resistant cancer cells. The analogs with the 3-ketone-4,6-diene backbone show the highest apoptosis-inducing efficacy. The most potent compound, analog 406, possesses higher pro-apoptotic activity in chemo-resistant cell lines MCF-7TN-R and NCI/ADR-RES than the corresponding chemo-sensitive cell lines MCF-7 and OVCAR-8, respectively. However, this compound shows the same potency in inhibiting the growth of another pair of chemo-sensitive and chemo-resistant cancer cells, MCF-7 and MCF-7/Dox. Mechanism investigations indicate that analog 406 can induce apoptosis in chemo-resistant cancer cells through the mitochondrial pathway. Cellular glucosylceramide synthase assay shows that analog 406 does not interrupt glucosylceramide synthase in chemo-resistant cancer cell NCI/ADR-RES. These findings suggest that due to certain intrinsic properties, ceramide analogs’ pro-apoptotic activity is not disrupted by the normal drug-resistance mechanisms, leading to their potential use for overcoming cancer multidrug-resistance.     

Discovery of nonbenzamidine factor VIIa inhibitors using a biaryl acid scaffold

In this Letter, we describe the synthesis of several nonamidine analogs of biaryl acid factor VIIa inhibitor 1 containing weakly basic or nonbasic P1 groups. 2-Aminoisoquinoline was found to be an excellent surrogate for the benzamidine group (compound 2) wherein potent inhibition of factor VIIa is maintained relative to most other related serine proteases. In an unanticipated result, the m-benzamide P1 (compounds 21a and 21b) proved to be a viable benzamidine replacement, albeit with a 20–40 fold loss in potency against factor VIIa.