PF-0477736

Antagonizing the Chk1-mediated cell cycle checkpoints has emerged as an attractive target for anticancer therapy. If Chk1 activity is blocked, DNA-damaged or spindle-disrupted cells would exit cell cycle arrest before full repair and subsequently undergo mitotic catastrophe or cell death. Chk1 inhibitors consequently increase the therapeutic index of DNA-damaging or antimitotic agents as well. PF-0477736 is a selective, potent ATP-competitive Chk1 inhibitor, derived from PF-0394691, inhibits Chk1 (Ki, 0.49nM) and Chk2 (Ki, 47nM) in vitro. In tests, PF-0477736 was identified as a potent, selective ATP-competitive small-molecule inhibitor that inhibits Chk1 with a Ki of 0.49nM. PF-0477736 abrogates cell cycle arrest induced by DNA damage and enhances cytotoxicity of clinically important chemotherapeutic agents, including gemcitabine and carboplatin. In xenografts, PF-0477736 enhanced the antitumor activity of gemcitabine in a dose-dependent manner. PF-0477736 combinations were well tolerated with no exacerbation of side effects commonly associated with cytotoxic agents.