title: Potent anti-tumor activity of a macrocycle-quinoxalinone class pan-Cdk inhibitor in vitro and in vivo.
abstract: Deregulation of cell-cycle control is a hallmark of cancer. Thus, cyclin-dependent kinases (Cdks) are an attractive target for the development of anti-cancer drugs. Here, we report the biological characterization of a highly potent pan-Cdk inhibitor with a macrocycle-quinoxalinone structure. Compound M inhibited Cdk1, 2, 4, 5, 6, and 9 with equal potency in the nM range and was selective against kinases other than Cdks. This compound inhibited multiple events in the cell cycle in vitro, including retinoblastoma protein (pRb) phosphorylation, E2F-dependent transcription, DNA replication (determined by bromodeoxyuridine incorporation), and mitosis completion (assayed by flow cytometry) in the 10 nM range. Moreover, this compound induced cell death, as determined by induction of the subG1 fraction, activated caspase-3, and anexin V. In vivo, Compound M showed anti-tumor efficacy at a tolerated dose. In a nude rat xenograft tumor model, an 8-h constant infusion of Compound M inhibited pRb phosphorylation and induced apoptosis in tumor cells at ~ 30 nM, which led to the inhibition of tumor growth. Immunosuppression was the only liability observed at this dose, but immune function returned to normal after 10 days. Suppression of pRb phosphorylation in tumor cells was clearly correlated with tumor cell growth inhibition and cell death in vitro and in vivo. In vivo, Compound M inhibited pRb phosphorylation in both tumor and gut crypt cells. Rb phosphorylation may be a suitable pharmacodynamic biomarker in both tumors and normal tissues for monitoring target engagement and predicting the efficacy of Compound M.
authors.affiliation: Department of Oncology, Banyu Tsukuba Research Institute, Merck Research Laboratories, Tsukuba, Ibaraki, 300-2611, Japan. Yrdyc661@yahoo.co.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirai
authors.forename: Ikuko
authors.initials: I
authors.lastname: Takahashi-Suziki
authors.forename: Toshiyasu
authors.initials: T
authors.lastname: Shimomura
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Fukasawa
authors.forename: Takumitsu
authors.initials: T
authors.lastname: Machida
authors.forename: Toru
authors.initials: T
authors.lastname: Takaki
authors.forename: Makiko
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Eguchi
authors.forename: Hiroko
authors.initials: H
authors.lastname: Oki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Arai
authors.forename: Koji
authors.initials: K
authors.lastname: Ichikawa
authors.forename: Shinichi
authors.initials: S
authors.lastname: Hasako
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kodera
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Kawanishi
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nakatsuru
authors.forename: Hidehito
authors.initials: H
authors.lastname: Kotani
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Iwasawa
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D001973:Bromodeoxyuridine / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D045325:HCT116 Cells; D006801:Humans; D007958:Leukocyte Count; D047028:Macrocyclic Compounds / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D011810:Quinoxalines / Q000009:adverse effects / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D011923:Rats, Nude; D013379:Substrate Specificity / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; D047028:Macrocyclic Compounds; D011810:Quinoxalines; D018844:Cyclin-Dependent Kinases; D001973:Bromodeoxyuridine