2-(4-Chlorobenzyl)-6-arylimidazo[2,1-b][1,3,4]thiadiazoles: Synthesis, cytotoxic activity and mechanism of action

Synthesis and Characterization of Schiff Bases and Their Ag(I) Complexes Containing 2,5,6-Trisubstituted Imidazothiadiazole Derivatives: Molecular Docking and In Vitro Cytotoxic Effects Against Nonsmall Lung Cancer Cell Line

In this study, four novels 2,5,6-trisubstituted imidazothiadiazole derivative ligands and their Ag(I) complexes were synthesized and characterized using various spectroscopic analysis techniques. First, imidazo[2,1-b][1,3,4]thiadiazole derivative (3) was obtained from the reaction of 5-amino-1,3,4-thiadiazole-2-thiol with benzyl bromide in the presence of KOH in an ethanolic medium. In the next step, the resultant compound reacted sequentially with four substituted phenacyl bromide derivatives (4a-4d) under refluxed ethanol for 24 h to obtain substituted 2-(benzylthio)-6-phenylimidazo[2,1-b][1,3,4]thiadiazole derivatives (5-8). Compounds (9-12) were obtained by attaching a carbonyl group to carbon number 5 of the imidazothiadiazole group in these compounds with the help of Vilsmeier-Haack reagent. The resultant compounds were reacted in an ethanolic medium to synthesize the novel (13-16) ligands by adding ethylenediamine in a 1:2 molar ratio. The Ag(I) complexes of the resultant ligands were synthesized by mixing silver acetate with the ligands in a dimethyl sulfoxide medium to obtain (17-20) complexes. All the synthesized compounds were analyzed using FTIR, 1H NMR, 13C NMR, mass spectroscopy, magnetic susceptibility, ICP-OES, and thermogravimetric analysis techniques. The study also investigates the in vitro cytotoxic effect of the ligands and complexes on A549 (nonsmall cell lung cancer) cells using the MTT assay and shows that the 13, 15, and 16 ligands, together with their complexes, exhibit potent cytotoxicity. In addition, in silico molecular docking simulations were conducted both to support the in vitro cytotoxicity experiments and to ascertain the active binding sites and interactions of the ligands and complexes on the EGFR receptor. The result indicates that ligands and complexes may serve as promising candidates for further investigation as anticancer agents.

Synthesis, Molecular Docking and Preliminary Antileukemic Activity of 4-Methoxybenzyl Derivatives Bearing Imidazo[2,1-b][1,3,4]thiadiazole

In this study, we synthesized 22 compounds in a series with various substitution on imidazo[2,1-b][1,3,4]thiadiazole. The potential cytotoxic activity of these compounds investigated in leukemia cell lines by Differential Nuclear Staining (DNS). Our results identified two compounds, 2-(4-methoxybenzyl)-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl thiocyanate and 6-(4-chlorophenyl)-2-(4-methoxybenzyl)imidazo[2,1-b][1,3,4]thiadiazole-5-carbaldehyde, exhibited the most cytotoxic effect against murine leukemia cells (L1210), human T-lymphocyte cells (CEM) and human cervix carcinoma cells (HeLa) with IC50 values ranging between 0.79 and 1.6 μM. The results indicate that 2-(4-methoxybenzyl)-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl thiocyanate is inducing phosphatidylserine externalization and caspase-3 activation which are both a hallmark of apoptosis. Docking studies showed that 2-(4-methoxybenzyl)-6-(2-oxo-2H-chromen-3-yl)imidazo[2,1-b][1,3,4]thiadiazol-5-yl thiocyanate binds within the active sites of transforming growth factor beta (TGF-β) type I receptor kinase domain by strong hydrogen binding and hydrophobic interactions.

Cytotoxic Properties of 1,3,4-Thiadiazole Derivatives-A Review

During recent years, small molecules containing five-member heterocyclic moieties have become the subject of considerable growing interest for designing new antitumor agents. One of them is 1,3,4-thiadiazole. This study is an attempt to collect the 1,3,4-thiadiazole and its derivatives, which can be considered as potential anticancer agents, reported in the literature in the last ten years.

Synthesis of (1,3,4-thiadiazol-2-yl)-acrylamide derivatives as potential antitumor agents against acute leukemia cells

A lead compound with the (1,3,4-thiadiazol-2-yl)-acrylamide scaffold was discovered to have significant cytotoxicity on several tumor cell lines in an in-house cell-based screening. A total of 60 derivative compounds were then synthesized and tested in a CCK-8 cell viability assay. Some of them exhibited improved cytotoxic activities. The most potent compounds had IC₅₀ values of 1-5 μM on two acute leukemia tumor cell lines, i.e. RS4;11 and HL-60. Flow cytometry analysis of several active compounds and detection of caspase activation indicated that they induced caspase-dependent apoptosis. It was also encouraging to observe that these compounds did not have obvious cytotoxicity on normal cells, i.e. IC₅₀ > 50 μM on HEK-293T cells. Although the molecular targets of this class of compound are yet to be revealed, our current results suggest that this class of compound represents a new possibility for developing drug candidates against acute leukemia.

Imidazo[2,1-b] [1,3,4]thiadiazoles with antiproliferative activity against primary and gemcitabine-resistant pancreatic cancer cells

A new series of eighteen imidazo [2,1-b] [1,3,4]thiadiazole derivatives was efficiently synthesized and screened for antiproliferative activity against the National Cancer Institute (NCI-60) cell lines panel. Two out of eighteen derivatives, compounds 12a and 12h, showed remarkably cytotoxic activity with the half maximal inhibitory concentration values (IC50) ranging from 0.23 to 11.4 μM, and 0.29-12.2 μM, respectively. However, two additional compounds, 12b and 13g, displayed remarkable in vitro antiproliferative activity against pancreatic ductal adenocarcinoma (PDAC) cell lines, including immortalized (SUIT-2, Capan-1, Panc-1), primary (PDAC-3) and gemcitabine-resistant (Panc-1R), eliciting IC50 values ranging from micromolar to sub-micromolar level, associated with significant reduction of cell-migration and spheroid shrinkage. These remarkable results might be explained by modulation of key regulators of epithelial-to-mesenchymal transition (EMT), including E-cadherin and vimentin, and inhibition of metalloproteinase-2/-9. High-throughput arrays revealed a significant inhibition of the phosphorylation of 45 tyrosine kinases substrates, whose visualization on Cytoscape highlighted PTK2/FAK as an important hub. Inhibition of phosphorylation of PTK2/FAK was validated as one of the possible mechanisms of action, using a specific ELISA. In conclusion, novel imidazothiadiazoles show potent antiproliferative activity, mediated by modulation of EMT and PTK2/FAK.

3-(6-Phenylimidazo [2,1-b][1,3,4]thiadiazol-2-yl)-1H-Indole Derivatives as New Anticancer Agents in the Treatment of Pancreatic Ductal Adenocarcinoma

A new series of imidazo[2,1-b][1,3,4]thiadiazole derivatives was efficiently synthesized and screened for their in vitro antiproliferative activity on a panel of pancreatic ductal adenocarcinoma (PDAC) cells, including SUIT-2, Capan-1 and Panc-1. Compounds 9c and 9l, showed relevant in vitro antiproliferative activity on all three pre-clinical models with half maximal inhibitory concentration (IC50) ranging from 5.11 to 10.8 µM, while the compounds 9e and 9n were active in at least one cell line. In addition, compound 9c significantly inhibited the migration rate of SUIT-2 and Capan-1 cells in the scratch wound-healing assay. In conclusion, our results will support further studies to increase the library of imidazo [2,1-b][1,3,4] thiadiazole derivatives for deeper understanding of the relationship between biological activity of the compounds and their structures in the development of new antitumor compounds against pancreatic diseases.

A Benzothiazole Derivative (5g) Induces DNA Damage And Potent G2/M Arrest In Cancer Cells

Chemically synthesized small molecules play important role in anticancer therapy. Several chemical compounds have been reported to damage the DNA, either directly or indirectly slowing down the cancer cell progression by causing a cell cycle arrest. Direct or indirect reactive oxygen species formation causes DNA damage leading to cell cycle arrest and subsequent cell death. Therefore, identification of chemically synthesized compounds with anticancer potential is important. Here we investigate the effect of benzothiazole derivative (5g) for its ability to inhibit cell proliferation in different cancer models. Interestingly, 5g interfered with cell proliferation in both, cell lines and tumor cells leading to significant G2/M arrest. 5g treatment resulted in elevated levels of ROS and subsequently, DNA double-strand breaks (DSBs) explaining observed G2/M arrest. Consistently, we observed deregulation of many cell cycle associated proteins such as CDK1, BCL2 and their phosphorylated form, CyclinB1, CDC25c etc. Besides, 5g treatment led to decreased levels of mitochondrial membrane potential and activation of apoptosis. Interestingly, 5g administration inhibited tumor growth in mice without significant side effects. Thus, our study identifies 5g as a potent biochemical inhibitor to induce G2/M phase arrest of the cell cycle, and demonstrates its anticancer properties both ex vivo and in vivo.

QSAR models of antiproliferative activity of imidazo[2,1-b][1,3,4]thiadiazoles in various cancer cell lines

Imidazo[2,1-b][1,3,4]thiadiazoles have been recognized to possess antiproliferative potency towards a wide spectrum of cancer cell lines. QSAR investigations on a set of 42 di(tri)substituted imidazo[2,1-b][1,3,4]thiadiazoles were carried out to find the descriptors determining their biological potency. Three-variable equations were obtained by combinatorial protocols in multiple linear regression (CP MLR) for all three studied cancer cell lines. They showed that lipophilicity, electronic, and steric factors are decisive for the antiproliferative potency of compounds and indicate the important role of nitrogen atoms of imidazothiadiazole ring in the interactions with the molecular target. The best models gave high r squared values in the range from 0.887 to 0.924. They also have good predictive accuracy confirmed by the high value LOO cross-validation coefficient [Formula: see text] (from 0.842 to 0.904) and by the external validation quantities.

The crystal structure of 6-(4-chloro-phen-yl)-2-(4-methyl-benz-yl)imidazo[2,1-b][1,3,4]thia-diazole-5-carbaldehyde

In the title imidazo[2,1-b][1,3,4]thia-diazole derivative, C19H14ClN3OS, the 4-methyl-benzyl and chloro-phenyl rings are inclined to the planar imidazo[2,1-b][1,3,4]thia-diazole moiety (r.m.s. deviation = 0.012 Å) by 64.5 (1) and 3.7 (1)°, respectively. The mol-ecular structure is primarily stabilized by a strong intra-molecular C-H⋯O hydrogen bond, leading to the formation of a pseudo-seven-membered S(7) ring motif, and a short intra-molecular C-H⋯N contact forming an S(5) ring motif. In the crystal, mol-ecules are linked by pairs of C-H⋯S hydrogen bonds, forming inversion dimers. The dimers are linked by C-H⋯O and C-H⋯π inter-actions, forming chains propagating along [110].

Design, synthesis and antiproliferative activity of novel heterobivalent hybrids based on imidazo[2,1-b][1,3,4]thiadiazole and imidazo[2,1-b][1,3]thiazole scaffolds

Heterobivalent ligands constituted by two different pharmacophores that bind to different molecular targets or to two distinct sites on the same molecular target could be one of the methods used for the treatment of cancer. In view of the importance of imidazo[1,2-b][1,3]thiazole and imidazo[1,2-b][1,3,4]thiadiazole as privileged structures for the preparation of novel anticancer agents, we decided to explore the synthesis and biological evaluation of molecular conjugates comprising these fused bicyclic systems tethered at their C-6 position by a meta-(α-bromoacryloylamido)phenyl moiety. We found that most of the hybrid compounds displayed high antiproliferative activity toward a wide panel of cancer cell lines, with one-digit micromolar to submicromolar 50% inhibitory concentrations (IC50). We have observed that selected compounds 7d, 7e, 7n and 8c induced apoptosis, which was associated with the release of cytochrome c and cleavage of multiple caspases. Overexpression of the protective mitochondrial protein Bcl-2 did not confer protection to cell death induced by these compounds.

Synthesis and evaluation of the biological activity of N′-[2-oxo-1,2 dihydro-3H-indol-3-ylidene] benzohydrazides as potential anticancer agents

New N′-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]benzohydrazide derivatives were synthesized and evaluated for their cytotoxic properties against murine leukemia, L1210, human leukemia, REH, K562 and CEM and human cervix carcinoma, HeLa cells.

A novel benzimidazole derivative binds to the DNA minor groove and induces apoptosis in leukemic cells

In the present study, we have synthesized various benzimidazole derivatives, evaluated their potential to act as DNA minor groove binder and tested their chemotherapeutic efficacy.