Indole derivatives targeting colchicine binding site as potential anticancer agents

Microtubules are appealing as intracellular targets for anticancer activity due to their importance in cell division. Three important binding sites are present on the tubulin protein: taxane, vinca, and colchicine binding sites (CBS). Many USFDA-approved drugs such as paclitaxel, ixabepilone, vinblastine, and combretastatin act by altering the dynamics of the microtubules. Additionally, a large number of compounds have been synthesized by medicinal chemists around the globe that target different tubulin binding sites. Although CBS inhibitors have proved their cytotoxic potential, no CBS-targeting drug had been able to reach the market. Several studies have reported design, synthesis, and biological evaluation of indole derivatives as potential anticancer agents. These compounds have been shown to inhibit cancer cell proliferation, induce apoptosis, and disrupt microtubule formation. Moreover, the binding affinity of these compounds to the CBS has been demonstrated using molecular docking studies and competitive binding assays. The present work has reviewed indole derivatives as potential colchicine-binding site inhibitors. The structure-activity relationship studies have revealed the crucial pharmacophoric features required for the potent and selective binding of indole derivatives to the CBS. The development of these compounds with improved efficacy and reduced toxicity could potentially lead to the development of novel and effective cancer therapies.

Synthesis and Anti-Breast Cancer Potency of Mono- and Bis-(pyrazolyl[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine) Derivatives as EGFR/CDK-2 Target Inhibitors

The target mono- and bis-(6-pyrazolyltriazolo-thiadiazine) derivatives 4a-c and 6a-d were synthesized using a straightforward protocol via reaction of 3-bromoacetylpyrazole 2 with 4-amino-s-triazole-3-thiols 3a-c and bis(4-amino-5-mercapto-s-triazol-3-yl)alkanes 5a-d, respectively. The bis(6-pyrazolyl-s-triazolo[3,4-b][1,3,4]thiadiazine) derivatives 8a,b and 10 were also constructed by reaction of the triazolo[3,4-b][1,3,4]thiadiazine-3-thiol 4c with the proper dibromo compounds 7a,b and 9, respectively. Structures of the new substances were determined by spectroscopic and analytical data. Compounds 4b, 4c, and 6a showed potent cytotoxicity against MCF-7 (IC50 = 3.16, 2.74, and 0.39 μM, respectively) and were safe against the MCF-10A cells. Compounds 4b, 4c, and 6a also showed promising dual EGFR and CDK-2 inhibition activities, particularly 6a was the most effective (IC50 = 19.6 and 87.9 nM, respectively), better than Erlotinib and Roscovitine. Compound 6a treatment induced EGFR and CDK-2 enzyme inhibition by 97.18% and 94.11%, respectively, at 10 μM (the highest concentration). Compound 6a notably induced cell apoptosis in MCF-7 cells, increasing the cell population by total apoptosis 43.3% compared to 1.29% for the untreated control group, increasing the cell population at the S-phase by 39.2% compared to 18.6% (control).

Discovery of novel 6-p-tolyl-3-(3,4,5-trimethoxybenzyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine derivative as a potent tubulin inhibitor with promising in vivo antitumor activity

Building on our prior research, a novel series of trimethoxyphenoxymethyl- and trimethoxybenzyl-substituted triazolothiadiazine compounds has been designed and achieved successfully via a direct ring-closing strategy. Initial biological evaluation illustrated that the most active derivative B₅ exhibited significant cell growth inhibitory activity toward HeLa, HT-29, and A549 giving the IC₅₀ values of 0.046, 0.57, and 0.96 μM, respectively, which are greater or similar with CA-4. The mechanism study revealed that B₅ caused the G₂/M phase arrest, induced cell apoptosis in HeLa cells in a concentration-dependent manner, and also showed potent tubulin polymerization inhibitory effect. Meanwhile, B₅ exerted significant antivascular activity in the wound-healing and tube formation assays. Most importantly, B₅ remarkably inhibited tumor growth without obvious signs of toxicity in A549-xenograft mice model. These observations indicate that 6-p-tolyl-3-(3,4,5-trimethoxybenzyl)-7H-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazine might be considered as the potential lead compound to develop highly efficient anticancer agents with potent selectivity over normal human cells.

Target-based anticancer indole derivatives and insight into structure‒activity relationship: A mechanistic review update (2018‒2021)

Cancer, which is the uncontrolled growth of cells, is the second leading cause of death after heart disease. Targeting drugs, especially to specific genes and proteins involved in growth and survival of cancer cells, is the prime need of research world-wide. Indole moiety, which is a combination of aromatic-heterocyclic compounds, is a constructive scaffold for the development of novel leads. Owing to its bioavailability, high unique chemical properties and significant pharmacological behaviours, indole is considered as the most inquisitive scaffold for anticancer drug research. This is illustrated by the fact that the U.S. Food and Drug Administration (FDA) has recently approved several indole-based anticancer agents such as panobinostat, alectinib, sunitinib, osimertinib, anlotinib and nintedanib for clinical use. Furthermore, hundreds of studies on the synthesis and activity of the indole ring have been published in the last three years. Taking into account the facts stated above, we have presented the most recent advances in medicinal chemistry of indole derivatives, encompassing hot articles published between 2018 and 2021 in anticancer drug research. The recent advances made towards the synthesis of promising indole-based anticancer compounds that may act via various targets such as topoisomerase, tubulin, apoptosis, aromatase, kinases, etc., have been discussed. This review also summarizes some of the recent efficient green chemical synthesis for indole rings using various catalysts for the period during 2018–2021. The review also covers the synthesis, structure‒activity relationship, and mechanism by which these leads have demonstrated improved and promising anticancer activity. Indole molecules under clinical and preclinical stages are classified into groups based on their cancer targets and presented in tabular form, along with their mechanism of action. The goal of this review article is to point the way for medicinal chemists to design and develop effective indole-based anticancer agents.

Design and synthesis of new bis(1,2,4-triazolo[3,4-b][1,3,4]thiadiazines) and bis((quinoxalin-2-yl)phenoxy)alkanes as anti-breast cancer agents through dual PARP-1 and EGFR targets inhibition

A number of new 1,ω-bis((acetylphenoxy)acetamide)alkanes 5a–f were prepared then their bromination using NBS furnished the novel bis(2-bromoacetyl)phenoxy)acetamides 6a–f. Reaction of 6a–f with 4-amino-5-substituted-4H-1,2,4-triazole-3-thiol 7a–d and with o-phenylenediamine derivatives 9a and b afforded the corresponding bis(1,2,4-triazolo[3,4-b][1,3,4]thiadiazine) derivatives 8a–l and bis(quinoxaline) derivatives 10a–e in good yields. The cytotoxicity of the synthesized compounds as well as apoptosis induction through PARP-1 and EGFR as molecular targets was evaluated. Three compounds, 8d, 8i and 8l, exhibited much better cytotoxic activities against MDA-MB-231 than the drug Erlotinib. Interestingly, compound 8i induced apoptosis in MDA-MB-231 cells by 38-fold compared to the control arresting the cell cycle at the G2/M phase, and its treatment upregulated P53, Bax, caspase-3, caspase-8, and caspase-9 gene levels, while it downregulated the Bcl2 level. Compound 8i exhibited promising dual enzyme inhibition of PARP-1 (IC₅₀ = 1.37 nM) compared to Olaparib (IC₅₀ = 1.49 nM), and EGFR (IC₅₀ = 64.65 nM) compared to Erlotinib (IC₅₀ = 80 nM). These results agreed with the molecular docking studies that highlighted the binding disposition of compound 8i inside the PARP-1 and EGFR protein active sites. Hence, compound 8i may serve as a potential anti-breast cancer agent.

A series of bis(triazolothiadiazines) and bis(quinoxalines) were synthesized and tested for their cytotoxicity and apoptosis-induction through PARP-1 and EGFR as molecular targets. Compound 8i exhibited high cytotoxic activity and promising dual enzyme inhibition.