title: In vitro and in vivo activity of R547: a potent and selective cyclin-dependent kinase inhibitor currently in phase I clinical trials.
abstract: The cyclin-dependent protein kinases are key regulators of cell cycle progression. Aberrant expression or altered activity of distinct cyclin-dependent kinase (CDK) complexes results in escape of cells from cell cycle control, leading to unrestricted cell proliferation. CDK inhibitors have the potential to induce cell cycle arrest and apoptosis in cancer cells, and identifying small-molecule CDK inhibitors has been a major focus in cancer research. Several CDK inhibitors are entering the clinic, the most recent being selective CDK2 and CDK4 inhibitors. We have identified a diaminopyrimidine compound, R547, which is a potent and selective ATP-competitive CDK inhibitor. In cell-free assays, R547 effectively inhibited CDK1/cyclin B, CDK2/cyclin E, and CDK4/cyclin D1 (K(i) = 1-3 nmol/L) and was inactive (K(i) > 5,000 nmol/L) against a panel of >120 unrelated kinases. In vitro, R547 effectively inhibited the proliferation of tumor cell lines independent of multidrug resistant status, histologic type, retinoblastoma protein, or p53 status, with IC(50)s </= 0.60 mumol/L. The growth-inhibitory activity is characterized by a cell cycle block at G(1) and G(2) phases and induction of apoptosis. R547 reduced phosphorylation of the cellular retinoblastoma protein at specific CDK phosphorylation sites at the same concentrations that induced cell cycle arrest, suggesting a potential pharmacodynamic marker for clinical use. In vivo, R547 showed antitumor activity in all of the models tested to date, including six human tumor xenografts and an orthotopic syngeneic rat model. R547 was efficacious with daily oral dosing as well as with once weekly i.v. dosing in established human tumor models and at the targeted efficacious exposures inhibited phosphorylation of the retinoblastoma protein in the tumors. The selective kinase inhibition profile and the preclinical antitumor activity of R547 suggest that it may be promising for development for use in the treatment of solid tumors. R547 is currently being evaluated in phase I clinical trials.
authors.affiliation: Discovery Oncology, Hoffmann-La Roche, Inc., 340 Kingsland Street, Nutley, NJ 07110, USA. wanda.depinto@roche.com
authors.forename: Wanda
authors.initials: W
authors.lastname: DePinto
authors.forename: Xin-Jie
authors.initials: XJ
authors.lastname: Chu
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Yin
authors.forename: Melissa
authors.initials: M
authors.lastname: Smith
authors.forename: Kathryn
authors.initials: K
authors.lastname: Packman
authors.forename: Petra
authors.initials: P
authors.lastname: Goelzer
authors.forename: Allen
authors.initials: A
authors.lastname: Lovey
authors.forename: Yingsi
authors.initials: Y
authors.lastname: Chen
authors.forename: Hong
authors.initials: H
authors.lastname: Qian
authors.forename: Rachid
authors.initials: R
authors.lastname: Hamid
authors.forename: Qing
authors.initials: Q
authors.lastname: Xiang
authors.forename: Christian
authors.initials: C
authors.lastname: Tovar
authors.forename: Roger
authors.initials: R
authors.lastname: Blain
authors.forename: Tom
authors.initials: T
authors.lastname: Nevins
authors.forename: Brian
authors.initials: B
authors.lastname: Higgins
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Luistro
authors.forename: Kenneth
authors.initials: K
authors.lastname: Kolinsky
authors.forename: Bernardo
authors.initials: B
authors.lastname: Felix
authors.forename: Sazzad
authors.initials: S
authors.lastname: Hussain
authors.forename: David
authors.initials: D
authors.lastname: Heimbrook
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D017321:Clinical Trials, Phase I as Topic; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D005260:Female; D016193:G1 Phase / Q000187:drug effects; D016195:G2 Phase / Q000187:drug effects; D019450:Genes, MDR / Q000187:drug effects; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D010766:Phosphorylation / Q000187:drug effects; D011743:Pyrimidines / Q000493:pharmacokinetics / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D011916:Rats, Inbred F344; D012175:Retinoblastoma / Q000188:drug therapy / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C515235:(4-amino-2-(1-methanesulfonylpiperidin-4-ylamino)pyrimidin-5-yl)(2,3-difluoro-6-methoxyphenyl)methanone; D000970:Antineoplastic Agents; D011743:Pyrimidines; D016159:Tumor Suppressor Protein p53; D018844:Cyclin-Dependent Kinases