title: LY2603618, a selective CHK1 inhibitor, enhances the anti-tumor effect of gemcitabine in xenograft tumor models.
abstract: Pharmacological inhibition of CHK1 in the absence of p53 functionality leads to abrogation of the S and G2/M DNA damage checkpoints. We report the preclinical therapeutic activity of LY2603618 (CHK1 inhibitor) at inhibiting CHK1 activation by gemcitabine and enhancing in vivo efficacy. The in vivo biochemical effects of CHK1 inhibition in the absence or presence of DNA damage were measured in human tumor xenograft models. Colon, lung and pancreatic xenografts models were treated with gemcitabine, LY2603618, or gemcitabine plus LY2603618. Gemcitabine treatment alone induced a significant increase in CHK1 autophosphorylation over untreated tumors. Co-administration of LY2603618 with gemcitabine showed a clear inhibition of CHK1 autophosphorylation for at least 24 h. Combining LY2603618 with gemcitabine resulted in an increase in H2AX serine 139 phosphorylation, indicating a corresponding increase in damaged DNA in the tumors. LY2603618 abrogated the S-phase DNA damage checkpoint in Calu-6 xenograft tumors treated with gemcitabine but did not significantly alter the G2/M checkpoint. Combining gemcitabine with LY2603618 resulted in a significant increase in tumor growth inhibition in Calu-6, HT-29 and PAXF 1869 xenografts over gemcitabine treatment alone. The best combination efficacy occurred when LY2603618 was given 24 h following dosing with gemcitabine. LY2603618 worked effectively to remove the S-phase DNA damage checkpoint and increase the DNA damage and the antitumor activity of gemcitabine treatment.
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Darlene
authors.initials: D
authors.lastname: Barnard
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: H Bruce
authors.initials: HB
authors.lastname: Diaz
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Teresa
authors.initials: T
authors.lastname: Burke
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Gregory
authors.initials: G
authors.lastname: Donoho
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Beckmann
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Bonita
authors.initials: B
authors.lastname: Jones
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: David
authors.initials: D
authors.lastname: Barda
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA.
authors.forename: Constance
authors.initials: C
authors.lastname: King
authors.affiliation: Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, IN, 46285, USA. mmarshall@lilly.com.
authors.forename: Mark
authors.initials: M
authors.lastname: Marshall
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology*; D000071877:Checkpoint Kinase 1; D003110:Colonic Neoplasms / Q000188:drug therapy; D004249:DNA Damage / Q000187:drug effects; D003841:Deoxycytidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D010190:Pancreatic Neoplasms / Q000188:drug therapy / Q000473:pathology; D010671:Phenylurea Compounds / Q000008:administration & dosage / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D011494:Protein Kinases / Q000187:drug effects*; D011719:Pyrazines / Q000008:administration & dosage / Q000494:pharmacology*; D023041:Xenograft Model Antitumor Assays; D000093542:Gemcitabine
chemical_list: C582547:LY2603618; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011719:Pyrazines; D003841:Deoxycytidine; D011494:Protein Kinases; D000071877:Checkpoint Kinase 1; D000093542:Gemcitabine
keywords: CHK1; DNA-damage; Gemcitabine; LY2603618; Xenograft