Sulfonamide-based ring-fused analogues for CAN508 as novel carbonic anhydrase inhibitors endowed with antitumor activity: Design, synthesis, and in vitro biological evaluation

In the present study, we report the design and synthesis of novel CAN508 sulfonamide-based analogues (4, 8a-e, 9a-h and 10a-e) as novel carbonic anhydrase (CA) inhibitors with potential CDK inhibitory activity. A bioisosteric replacement approach was adopted to replace the phenolic OH of CAN508 with a sulfamoyl group to afford compound 4. Thereafter, a ring-fusion approach was utilized to furnish the 5/5 fused imidazopyrazoles 8a-e which were subsequently expanded to 6/5 pyrazolopyrimidines 9a-h and 10a-e. All the synthesized analogues were evaluated for their inhibitory activity toward isoforms hCA I, II, IX and XII. The target tumor-associated isoforms hCA IX and XII were effectively inhibited with KIs ranges 6–67.6 and 10.1–88.6 nM, respectively. Furthermore, all compounds were evaluated for their potential CDK2 and 9 inhibitory activities. Pyrazolopyrimidines 9d, 9e and 10b displayed weak CDK2 inhibitory activity (IC50 = 6.4, 8.0 and 11.6 μM, respectively), along with abolished CDK9 inhibitory activity. This trend suggested that pyrazolopyrimidine derivatives merit further optimization to furnish more effective CDK2 inhibitor lead. On account of their excellent activity and selectivity towards hCA IX and XII, pyrazolopyrimidines 10 were evaluated for their anti-proliferative activity toward breast cancer MCF-7 and MDA-MB-468 cell lines under normoxic and hypoxic conditions. The most potent anti-proliferative agents 10a, 10c and 10d significantly increased cell percentage at sub-G1 and G2-M phases with concomitant decrease in the S phase population in MCF-7 treated cells. Finally, a docking study was undertaken to investigate the binding mode for the most selective hCA IX and XII inhibitors 10a-e, within hCA II, IX and XII active sites.