Design, microwave assisted synthesis, and molecular modeling study of some new 1,3,4-thiadiazole derivatives as potent anticancer agents and potential VEGFR-2 inhibitors

Recent advances and future directions on small molecule VEGFR inhibitors in oncological conditions

"A journey of mixed emotions" is a quote that best describes the progress chart of vascular endothelial growth factor receptor (VEGFR) inhibitors as cancer therapeutics in the last decade. Exhilarated with the Food and Drug Administration (FDA) approvals of numerous VEGFR inhibitors coupled with the annoyance of encountering the complications associated with their use, drug discovery enthusiasts are on their toes with an unswerving determination to enhance the rate of translation of VEGFR inhibitors from preclinical to clinical stage. The recently crafted armory of VEGFR inhibitors is a testament to their growing dominance over other antiangiogenic therapies for cancer treatment. This review perspicuously underscores the earnest attempts of the researchers to extract the antiproliferative potential of VEGFR inhibitors through the design of mechanistically diverse structural assemblages. Moreover, this review encompasses sections on structural/molecular properties and physiological functions of VEGFR, FDA-approved VEGFR inhibitors, and hurdles restricting the activity range/clinical applicability of VEGFR targeting antitumor agents. In addition, tactics to overcome the limitations of VEGFR inhibitors are discussed. A clear-cut viewpoint transmitted through this compilation can provide practical directions to push the cart of VEGFR inhibitors to advanced-stage clinical investigations in diverse malignancies.

Role of heterocycles in inhibition of VEGFR-2 - a recent update (2019-2022)

The literature reveals that oncogenic protein kinase inhibition has been proved to be a successful anticancer approach. The vascular endothelial growth factor receptor (VEGFR) kinase plays an important role in angiogenesis and metastasis. VEGFR-2 has an upper hand in the angiogenesis process. Vascular endothelial growth factor activates VEGFR-2 which initiates tumor angiogenesis. In addition, VEGFRs are associated with numerous other diseases. Hence, inhibition of VEGFRs is an attractive approach for cancer treatment. In view of this, researchers designed and discovered small molecular heterocycle-based VEGFR-2 inhibitors and some of them have been approved by the Food and Drug Administration (FDA). However, these VEGFR-2 inhibitors pose adverse side effects such as cardiovascular problems, diarrhea, and renal function impairment. Research indicates that combination of certain pharmacophores exhibits excellent VEGFR inhibitory activity. In particular, combination of heterocycles paved the way to efficient VEGFR inhibitors. In this review, the research focusing on VEGFR inhibitory activity has been discussed along with the structure-activity relationship. In addition to emphasizing the most potent molecule among the set of designed molecules, structural features responsible for such an activity are described. This review may aid in designing potent VEGFR inhibitors.

New pyrazolo[3,4-d]pyrimidine derivatives as EGFR-TK inhibitors: design, green synthesis, potential anti-proliferative activity and P-glycoprotein inhibition

In this study, four series of new pyrazolo[3,4-d]pyrimidine derivatives were designed and synthesized with both green and conventional methods. All the synthesized candidates were chemically confirmed using spectroscopic methods, and the DFT of the reaction mechanism was illustrated. The anti-proliferative activity of the synthesized compounds was evaluated against NCI 60 cancer cell lines. Two compounds (15 & 16) exhibited excellent broad-spectrum cytotoxic activity in NCI 5-log dose assays against the full 60-cell panel with GI50 values ranging from 0.018 to 9.98 μM. Moreover, the enzymatic assessment of the most active derivatives 4, 15, and 16 against EGFR tyrosine kinase showed significant inhibitory activities with IC50 of 0.054, 0.135, and 0.034 μM, respectively. The quantitative real-time PCR for the P-glycoprotein effect of compounds 15 and 16 was examined and illustrated the ability to inhibit the P-glycoprotein by 0.301 and 0.449 fold in comparison to the control. Mechanistic study using reversal activity in MDA-MB-468 cell line revealed the effect of both compounds 15 and 16 cytotoxicity against DOX/MDA-MB-468 with IC50 = 0.267 and 0.844 μM, respectively. Additionally, compound 16 was found to induce cell cycle arrest at the S phase with a subsequent increase in pre-G cell population in MDA-MB-468 cell line. It also increased the percentage of apoptotic cells in a time-dependent manner. Moreover, a molecular docking study was carried out to explain the target compounds' potent inhibitory activity within the EGFR binding site.

New 1,3,4-thiadiazoles as potential anticancer agents: pro-apoptotic, cell cycle arrest, molecular modelling, and ADMET profile

A series of novel 1,3,4-thiadiazoles was synthesized via the reaction of N-(5-(2-cyanoacetamido)-1,3,4-thiadiazol-2-yl)benzamide (3) with different carbon electrophiles and evaluated as potential anticancer agents. The chemical structures of these derivatives were fully elucidated using various spectral and elemental analyses. Out of 24 new thiadiazoles, derivatives 4, 6b, 7a, 7d, and 19 have significant antiproliferative activity. However, derivatives 4, 7a, and 7d were toxic to the normal fibroblasts, and therefore were excluded from further investigations. Derivatives 6b and 19 with IC50 at less than 10 μM and with high selectivity were selected for further studies in breast cells (MCF-7). Derivative 19 arrested the breast cells at G2/M probably through inhibition of CDK1, while 6b significantly increased the sub-G1 percent of cells probably through induction of necrosis. These results were confirmed by the annexin V-PI assay where 6b did not induce apoptosis and increased the necrotic cells to 12.5%, and compound 19 significantly increased the early apoptosis to 15% and increased the necrotic cells to 15%. Molecular docking showed that compound 19 was like FB8, an inhibitor of CDK1, in binding the CDK1 pocket. Therefore, compound 19 could be a potential CDK1 inhibitor. Derivatives 6b and 19 did not violate Lipinski's rule of five. In silico studies showed that these derivatives have a low blood-brain barrier penetration capability and high intestinal absorption. Taken together, derivatives 6b and 19 could serve as potential anticancer agents and merit further investigations.

The Reformatsky analogous reaction for the synthesis of novel β-thioxoesters via using aroyl isothiocyanates under solvent-free ball milling and conventional conditions

The classical Reformatsky reaction, initially described in 1887, is considered one of the most useful ways of forming C-C bonds. The target of this work includes improving the Reformatsky reaction between aroyl isothiocyanates and α-haloesters using metallic zinc to form β-thioxoesters (3-11). In this procedure, a new metal-mediated carbon-carbon linkage is formed with the formation of an organozinc halide and decomposition due to the presence of dilute acid, affording a good yield of the desired product via conventional techniques and ball milling. The Reformatsky reaction requires no solvent and no inert gases.

Monoamine oxidase A and B inhibitory activities of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives

Monoamine oxidase (EC 1.4.3.4, MAO) is a flavin adenine dinucleotide-containing flavoenzyme located on the outer mitochondrial membrane and catalyzes the oxidative deamination of monoaminergic neurotransmitters and dietary amines. MAO exists in humans as two isoenzymes, hMAO-A and hMAO-B, which are distinguished by their tertiary structures, preferred substrates and inhibitors, and selective inhibition of these isoenzymes are used in the treatment of different diseases such as Alzheimer's, Parkinson's and depression. In the present study, we report the design, synthesis and characterization of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives as novel and selective inhibitors of hMAO-B. Twenty one compounds (38, 39a-h, 41a-d, 42a-h) were screened for their inhibitory activity against hMAO-A and hMAO-B by using in vitro Amplex Red® reagent based fluorometric method and all compounds were found to be as selective h-MAO-B inhibitors to a different degree. The compound 42e and 42h displayed the highest inhibitory activity against hMAO-B with IC₅₀ values of 2.51 and 2.81 µM, respectively, and more than 25-fold selectivity towards inhibition of hMAO-B. A further kinetic evaluation of the most potent derivative (42e) was also performed and a mixed mode of inhibition of hMAO-B by the compound 42e was determined (K_i = 0,26 µM). According to our findings the [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole emerged as a promising scaffold for the development of novel and selective hMAO-B inhibitors.