title: The Efficacy of the Wee1 Inhibitor MK-1775 Combined with Temozolomide Is Limited by Heterogeneous Distribution across the Blood-Brain Barrier in Glioblastoma.
abstract: OBJECTIVE
  Wee1 regulates key DNA damage checkpoints, and in this study, the efficacy of the Wee1 inhibitor MK-1775 was evaluated in glioblastoma multiforme (GBM) xenograft models alone and in combination with radiation and/or temozolomide.
  
  
  METHODS
  In vitro MK-1775 efficacy alone and in combination with temozolomide, and the impact on DNA damage, was analyzed by Western blotting and γH2AX foci formation. In vivo efficacy was evaluated in orthotopic and heterotopic xenografts. Drug distribution was assessed by conventional mass spectrometry (MS) and matrix-assisted laser desorption/ionization (MALDI)-MS imaging.
  
  
  RESULTS
  GBM22 (IC50 = 68 nmol/L) was significantly more sensitive to MK-1775 compared with five other GBM xenograft lines, including GBM6 (IC50 >300 nmol/L), and this was associated with a significant difference in pan-nuclear γH2AX staining between treated GBM22 (81% cells positive) and GBM6 (20% cells positive) cells. However, there was no sensitizing effect of MK-1775 when combined with temozolomide in vitro. In an orthotopic GBM22 model, MK-1775 was ineffective when combined with temozolomide, whereas in a flank model of GBM22, MK-1775 exhibited both single-agent and combinatorial activity with temozolomide. Consistent with limited drug delivery into orthotopic tumors, the normal brain to whole blood ratio following a single MK-1775 dose was 5%, and MALDI-MS imaging demonstrated heterogeneous and markedly lower MK-1775 distribution in orthotopic as compared with heterotopic GBM22 tumors.
  
  
  CONCLUSIONS
  Limited distribution to brain tumors may limit the efficacy of MK-1775 in GBM.
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Pokorny
authors.affiliation: Department of Neurosurgery, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
authors.forename: David
authors.initials: D
authors.lastname: Calligaris
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Shiv K
authors.initials: SK
authors.lastname: Gupta
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Dennis O
authors.initials: DO
authors.lastname: Iyekegbe
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Dustin
authors.initials: D
authors.lastname: Mueller
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Katrina K
authors.initials: KK
authors.lastname: Bakken
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Brett L
authors.initials: BL
authors.lastname: Carlson
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Schroeder
authors.affiliation: Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota.
authors.forename: Debra L
authors.initials: DL
authors.lastname: Evans
authors.affiliation: Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, Minnesota.
authors.forename: Zhenkun
authors.initials: Z
authors.lastname: Lou
authors.affiliation: Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Decker
authors.affiliation: Health Sciences Research, Mayo Clinic, Rochester, Minnesota.
authors.forename: Jeanette E
authors.initials: JE
authors.lastname: Eckel-Passow
authors.affiliation: Department of Pharmacokinetics, Pharmacodynamics and Drug Metabolism, Merck & Co., Boston, Massachusetts.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Pucci
authors.affiliation: Department of Pharmacokinetics, Pharmacodynamics and Drug Metabolism, Merck & Co., West Point, Pennsylvania.
authors.forename: Bennett
authors.initials: B
authors.lastname: Ma
authors.affiliation: Department of Oncology, Merck & Co., Boston, Massachusetts.
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Shumway
authors.affiliation: Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota.
authors.forename: William F
authors.initials: WF
authors.lastname: Elmquist
authors.affiliation: Department of Neurosurgery, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts. Department of Radiology, Brigham and Women's Hospital and Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.
authors.forename: Nathalie Y R
authors.initials: NY
authors.lastname: Agar
authors.affiliation: Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota. sarkaria.jann@mayo.edu.
authors.forename: Jann N
authors.initials: JN
authors.lastname: Sarkaria
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors; D004249:DNA Damage / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D004195:Disease Models, Animal; D005909:Glioblastoma / Q000188:drug therapy / Q000378:metabolism* / Q000401:mortality / Q000473:pathology*; D006801:Humans; D051379:Mice; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011720:Pyrazoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D011743:Pyrimidines / Q000493:pharmacokinetics / Q000494:pharmacology*; D011744:Pyrimidinones; D000077204:Temozolomide; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D011720:Pyrazoles; D011743:Pyrimidines; D011744:Pyrimidinones; D003606:Dacarbazine; D011505:Protein-Tyrosine Kinases; C499348:Wee1 protein, mouse; C549567:adavosertib; D000077204:Temozolomide