Discovery and Development of a Potent, Selective, and Orally Bioavailable CHK1 Inhibitor Candidate: 5-((4-((3-Amino-3-methylbutyl)amino)-5-(trifluoromethyl)pyrimidin-2-yl)amino)picolinonitrile.

Checkpoint kinase 1 (CHK1) plays an important role in the DNA damage response pathway, being a potential anti-cancer drug target. In this study, we used a strategy for trifluoromethyl substitution to obtain orally bioavailable CHK1 inhibitors to overcome the limitations of lead compound , which can only be administered intravenously. After detailed investigation, we identified compound as an oral CHK1 inhibitor, which demonstrated a considerably higher plasma exposure in mice. Compound also showed good kinase selectivity. Moreover, it exhibited a significant antiproliferative effect in MV-4-11 cells singly and a synergistic effect in combination with gemcitabine in HT-29, A549, and RPMI-8226 cells. Additionally, compound could inhibit tumor growth in the MV-4-11 xenograft mouse model. The combination of and gemcitabine exhibited synergistic effect in the HT-29 xenograft mouse model. Thus, compound was found to be a selective and oral potential anticancer CHK1 inhibitor.