Discovery of novel pyrazolo[3,4-d]pyrimidine-6-amine derivatives as potent polo-like kinase 2 inhibitors.

Polo-like kinase 2 (PLK2), a serine/threonine kinase involved in cell cycle regulation, has emerged as a promising therapeutic target in cancer due to its role in tumor cell proliferation and survival. In this study, we report the design and synthesis of novel PLK2 inhibitors, featuring pyrazolo[3,4-d]pyrimidine derivatives. Among them, compounds 8 and 11 exhibited potent PLK2 inhibitory activity, with IC50 values of 0.36 μM and 0.78 μM, respectively (ON1231320, IC50 = 0.10 μM). In colorectal cancer cell lines SW480 and HT29, compounds 8 and 11 suppressed cell proliferation in a dose-dependent manner, induced apoptosis, caused cell cycle arrest, and inhibited anchorage-independent growth. Notably, compound 11 showed significant in vivo tumor growth efficacy in a xenograft mouse model (TGI = 69.37%), markedly superior to ON1231320 (TGI = 8.36%) with favorable pharmacokinetic parameters. These findings establish pyrazolo[3,4-d]pyrimidine derivatives as promising PLK2 inhibitors with strong therapeutic potential for colorectal cancer.