Design, Synthesis, and Biological Evaluation of 2-Aminothiazole Derivatives as Novel Checkpoint Kinase 1 (CHK1) Inhibitors.

A series of 2-aminothiazole derivatives were designed, synthesized on the basis of bioisosterism strategy and evaluated for their CHK1 inhibitory activity. Most of them exhibited potent CHK1 inhibition, and excellent antiproliferative activity against MV-4-11 and Z-138 cell lines. Systematic structure-activity relationship (SAR) efforts led to the discovery of a promising compound 8 n, which showed potent CHK1 inhibitory activity with IC 50 value of 4.25±0.10 nM, excellent antiproliferative activity against MV-4-11 and Z-138 cells with IC 50 value of 42.10±5.77 nM and 24.16±6.67 nM, respectively, as well as moderate oral exposure (AUC (0-t) =1076.25 h ⋅ ng/mL) in mice. Additionally, treatment of MV-4-11 cells with compound 8 n for 2 h led to robust inhibition of CHK1 autophosphorylation on serine 296. Furthermore, kinase selectivity assay revealed that 8 n displayed acceptable selectivity toward 15 kinases. These results demonstrated that compound 8 n may be a promising potential anticancer agent for further development.