Development of pyrolo[2,3-c]pyrazole, pyrolo[2,3-d]pyrimidine and their bioisosteres as novel CDK2 inhibitors with potent in vitro apoptotic anti-proliferative activity: Synthesis, biological evaluation and molecular dynamics investigations.

Inhibiting the CDK2/cyclin A2 enzyme has been validated in multiple clinical manifestations related to multiple types of cancer. Herein, novel series of pyrolo[2,3-c]pyrazole, pyrolo[2,3-c]isoaxazole and pyrolo[2,3-d]pyrimidine, pyrolo[3,2-c]pyridine & indole based analogs were designed, synthesized and biologically evaluated for their in vitro antiproliferative activity where the obtained results revealed that most of the newly synthesized compounds showed significant cytotoxic activity towards MCF-7 (breast cancer cell lines) and HepG-2 (hepatocellular carcinoma) with IC50 ranging from 3.20 µM to 10.05 µM & from 2.18 µM to 13.49 µM, respectively, compared to that of Sorafenib (IC50 9.76 & 13.19 µM, respectively). The in vitro inhibitory profile of the most promising compounds (9, 11, 14, 15, 16, 17 and 20) towards CDK2/CyclinA2 was evaluated. Compounds 14 & 15 exhibited potent inhibitory profile against CDK2 with (IC50 0.11 and 0.262 µM, respectively comparable to Sorafenib IC50 0.184 µM. Western blotting of 14 & 15 at MCF-7 cell line confirmed the diminishing activity on CDK2. Furthermore, both compounds exserted a significant cell cycle arrest and apoptosis. Moreover, the normal cell line cytotoxicity for both compounds revealed low cytotoxic results in normal cells rather than cancer cells. Molecular docking and dynamic simulation validated the potentiality of the newly synthesized compounds to have high binding affinity within CDK2 binding pocket. 3DQSAR pharmacophore, in-silico ADME/TOPKAT studies and drug-likeness showed proper pharmacokinetic properties and helped in structure requirements prediction. The obtained model and pattern of substitution could be used for further development of CDK2 inhibitors.