title: In vitro cytotoxicity, pharmacokinetics, tissue distribution, and metabolism of small-molecule protein kinase D inhibitors, kb-NB142-70 and kb-NB165-09, in mice bearing human cancer xenografts.
abstract: OBJECTIVE
  Protein kinase D (PKD) mediates diverse biological responses including cell growth and survival. Therefore, PKD inhibitors may have therapeutic potential. We evaluated the in vitro cytotoxicity of two PKD inhibitors, kb-NB142-70 and its methoxy analogue, kb-NB165-09, and examined their in vivo efficacy and pharmacokinetics.
  
  
  METHODS
  The in vitro cytotoxicities of kb-NB142-70 and kb-NB165-09 were evaluated by MTT assay against PC-3, androgen-independent prostate cancer cells, and CFPAC-1 and PANC-1, pancreatic cancer cells. Efficacy studies were conducted in mice bearing either PC-3 or CPFAC-1 xenografts. Tumor-bearing mice were euthanized between 5 and 1,440 min after iv dosing, and plasma and tissue concentrations were measured by HPLC-UV. Metabolites were characterized by LC-MS/MS.
  
  
  RESULTS
  kb-NB142-70 and kb-NB165-09 inhibited cellular growth in the low-mid μM range. The compounds were inactive when administered to tumor-bearing mice. In mice treated with kb-NB142-70, the plasma C (max) was 36.9 nmol/mL, and the PC-3 tumor C (max) was 11.8 nmol/g. In mice dosed with kb-NB165-09, the plasma C (max) was 61.9 nmol/mL, while the PANC-1 tumor C (max) was 8.0 nmol/g. The plasma half-lives of kb-NB142-70 and kb-NB165-09 were 6 and 14 min, respectively. Both compounds underwent oxidation and glucuronidation.
  
  
  CONCLUSIONS
  kb-NB142-70 and kb-NB165-09 were rapidly metabolized, and concentrations in tumor were lower than those required for in vitro cytotoxicity. Replacement of the phenolic hydroxyl group with a methoxy group increased the plasma half-life of kb-NB165-09 2.3-fold over that of kb-NB142-70. Rapid metabolism in mice suggests that next-generation compounds will require further structural modifications to increase potency and/or metabolic stability.
authors.affiliation: Molecular Therapeutics and Drug Discovery, The University of Pittsburgh Cancer Institute, Hillman Cancer Center, 5117 Centre Ave, Room G27b, Pittsburgh, PA 15213, USA.
authors.forename: Jianxia
authors.initials: J
authors.lastname: Guo
authors.forename: Dana M
authors.initials: DM
authors.lastname: Clausen
authors.forename: Jan H
authors.initials: JH
authors.lastname: Beumer
authors.forename: Robert A
authors.initials: RA
authors.lastname: Parise
authors.forename: Merrill J
authors.initials: MJ
authors.lastname: Egorin
authors.forename: Karla
authors.initials: K
authors.lastname: Bravo-Altamirano
authors.forename: Peter
authors.initials: P
authors.lastname: Wipf
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Sharlow
authors.forename: Qiming Jane
authors.initials: QJ
authors.lastname: Wang
authors.forename: Julie L
authors.initials: JL
authors.lastname: Eiseman
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006575:Heterocyclic Compounds, 3-Ring / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D051379:Mice; D016513:Mice, SCID; D011485:Protein Binding; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D053719:Tandem Mass Spectrometry; D013841:Thiazepines / Q000378:metabolism / Q000494:pharmacology*; D014018:Tissue Distribution; D023041:Xenograft Model Antitumor Assays
chemical_list: D006575:Heterocyclic Compounds, 3-Ring; D047428:Protein Kinase Inhibitors; D013841:Thiazepines; C579279:kb-NB142-70; C579280:kb-NB165-09; C089212:protein kinase D; D011493:Protein Kinase C