New thienopyrimidine-based derivatives: Design, synthesis, and biological evaluation as potent anticancer agents and VEGFR-2 inhibitors

A series of new thienopyrimidine (TP)-based derivatives were designed and synthesized in accordance with the structure-activity relationship (SAR) studies of VEGFR-2 inhibitors. The synthesized TP derivatives were inspected for their anti-proliferative activity on a panel of 60 different human cancer cell lines (NCI, USA). This preliminary in vitro anticancer screening revealed that three scaffolds 5a, 5g, and 5h were the most promising growth inhibitors at a dose of 10 µM therefore, they were further assessed at five dose concentrations. The GI₅₀, TGI, and LC₅₀ results were promising for the three scaffolds against the leukemia HL‐60 (TB) cell line. Therefore, their cytotoxic activity was examined against a normal blood cell line (Lymphocytes PCS-800-017), where compounds 5a, 5g, and 5h exhibited IC₅₀ values of 0.221, 0.386, and 0.269 µM, respectively against VEGFR-2 enzyme. They exerted their cytotoxic effect by proliferation inhibition of leukemia HL-60 (TB) cells in the G0-G1 phase. Furthermore, they significantly increased the total apoptotic ratio by 16.59, 11.01, and 13.05 folds, respectively. An increase in caspase-3 levels accompanied this apoptotic activity, where compound 5a demonstrated apoptotic caspase-3 levels of 4.99 folds, which was higher than that of Sorafenib (4.43 folds); while compounds 5g and 5h showed caspase-3 levels that were comparable to that of Sorafenib. Additionally, anti-angiogenic activity against human umbilical vascular endothelial cells (HUVECs) was performed using the wound healing migration assay. The wound closure percentage and migratory potential of HUVEC cells were significantly reduced after exposure to TPs 5a, 5g, and 5h for 72 h. These results were further explained by molecular docking studies using the crystal structure of VEGFR-2 receptor (PDB ID: 4ASD) which revealed the ability of TP derivatives to form a network of key interactions, known to be essential for VEGFR-2 inhibitors.