LY2603618 is a novel small molecular checkpoint kinase 1 (Chk1) inhibitor that has direct anti-tumour effect [1], as well as desensitizing tumour cell against DNA-damaging chemotherapy treatment [2].

Checkpoint kinase 1 (Chk1) is a type of kinase that coordinates damaged-DNA repair [1]. Some tumour cells have been found to possess over-regulated populations of Chk1 that desensitize the cell from DNA-targeting chemotherapy, promoting tumour proliferation [3].

LY2603618 inhibits Chk1 by competing with ATP molecules [2]. In A549 and H1299 non-small cancer cell lines, lethal concentration of LY2603618 (10 μM) not only resulted in cell proliferation arrest (increase population of cell at G2/M phase from 13% to 38%) but also directly DNA damage, the latter of which was indicated by the increasing occurrence of H2AX phosphorylation[1].

In vivo, experiment was carried out to determine the combining effect of LY2603618 with other chemotherapy[2] . In mice xenograft model that inculated with Calu-6 lung cancer cell, combining administration of injected gemcitabine 150 mg/kg and orally uptake LY2603618 (200 mg/kg) resulted in increased DNA damage of tumour, as was demonstrated by a 2-fold increase in Chk1 s345 phosphorylation in comparison with mice treated with gemcitabine alone[2].

References:
[1].? Wang F Z, Fei H R, Cui, Y J et al. The checkpoint 1 kinase inhibitor LY2603618 induces cell cycle arrest, DNA damage response and autophagy in cancer cells. Apoptosis, 2014,19:1389-1398.
[2].? King C, Diaz H, Barnard D et al.Characterization and preclinical development of LY2603618: a selective and potent Chk1 inhibitor. Invest New Drugs, 2014, 32: 213-26.
[3].? Zhang Y. & Hunter T. Roles of Chk1 in cell biology and cancer therapy. Int J Cancer, 2014. 134: 1013-23.