1.Combination drug scheduling defines a "window of opportunity" for chemopotentiation of gemcitabine by an orally bioavailable, selective ChK1 inhibitor, GNE-900.
Blackwood E1, Epler J, Yen I, Flagella M, O'Brien T, Evangelista M, Schmidt S, Xiao Y, Choi J, Kowanetz K, Ramiscal J, Wong K, Jakubiak D, Yee S, Cain G, Gazzard L, Williams K, Halladay J, Jackson PK, Malek S. Mol Cancer Ther. 2013 Oct;12(10):1968-80. doi: 10.1158/1535-7163.MCT-12-1218. Epub 2013 Jul 19.
Checkpoint kinase 1 (ChK1) is a serine/threonine kinase that functions as a central mediator of the intra-S and G2-M cell-cycle checkpoints. Following DNA damage or replication stress, ChK1-mediated phosphorylation of downstream effectors delays cell-cycle progression so that the damaged genome can be repaired. As a therapeutic strategy, inhibition of ChK1 should potentiate the antitumor effect of chemotherapeutic agents by inactivating the postreplication checkpoint, causing premature entry into mitosis with damaged DNA resulting in mitotic catastrophe. Here, we describe the characterization of GNE-900, an ATP-competitive, selective, and orally bioavailable ChK1 inhibitor. In combination with chemotherapeutic agents, GNE-900 sustains ATR/ATM signaling, enhances DNA damage, and induces apoptotic cell death. The kinetics of checkpoint abrogation seems to be more rapid in p53-mutant cells, resulting in premature mitotic entry and/or accelerated cell death.