Novel series of diphenyl-1H-pyrazoles (4a-g) and pyrazolo[3,4-b]pyridines (5a-g and 7a-i) were synthesized and evaluated for their antiproliferative activity against breast cancer cell line (MCF7) and Hepatocellular carcinoma cell line (HepG2). The highest MCF7 growth inhibition activity was attained via compounds 4f and 7e (IC = 1.29 and 0.93 μM, respectively), while compounds 5b and 7f were the most active ones against HepG2 (IC = 1.57 and 1.33 μM, respectively) compared to doxorubicin (IC = 1.88 and 7.30 μM, respectively). Cell cycle analysis showed arrest at S and G2-M phases in MCF7 cells treated with 4f and 7e, and at G2-M and G1/S phases in HepG2 cells treated with 5b and 7f, respectively. Apoptotic effect of compounds 4f, 5b, 7e, and 7f was indicated via their pre-G1 early and late apoptotic effects and augmented levels of caspase-9/MCF7 and caspase-3/HepG2. A worthy safety profile was assessed for compounds 4f and 7e on MCF10A and compounds 5b and 7f on THLE2 treated normal cells. Furthermore, compounds 4f, 5b and 7f displayed a promising selective profile for CDK2 inhibition vs. CDK1, CDK4, and CDK7 isoforms as proved from their selectivity index. Docking in CDK2 ATP binding site, co-crystallized with R-Roscovitine, demonstrated analogous interactions and comparable binding energy with the native ligand. 2D QSAR sighted the possible structural features governing the CDK2 inhibition activity elicited by the studied pyrazolo[3,4-b]pyridines. These findings present compounds 4f, 5b, and 7f as selective CDK2 inhibitors with promising antiproliferative activity against MCF7 and HepG2 cancer cells.
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