title: Decreased affinity for efflux transporters increases brain penetrance and molecular targeting of a PI3K/mTOR inhibitor in a mouse model of glioblastoma.
abstract: BACKGROUND
  Targeting drug delivery to invasive glioma cells is a particularly difficult challenge because these cells lie behind an intact blood-brain barrier (BBB) that can be observed using multimodality imaging. BBB-associated efflux transporters such as P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) influence drug distribution to these cells and may negatively impact efficacy. To test the hypothesis that efflux transporters influence brain pharmacokinetics/pharmacodynamics of molecularly targeted agents in glioma treatment, we assessed region-specific penetrance and molecular-targeting capacity for a PI3K/mTOR kinase inhibitor that has high substrate affinity for efflux transporters (GDC-0980) and an analog (GNE-317) that was purposely designed to have reduced efflux.
  
  
  METHODS
  Brain tumor penetrance of GDC-0980 and GNE-317 was compared between FVB/n wild-type mice and Mdr1a/b(-/-)Bcrp(-/-) triple-knockout mice lacking P-gp and BCRP. C57B6/J mice bearing intracranial GL261 tumors were treated with GDC-0980, GNE-317, or vehicle to assess the targeted pharmacokinetic/pharmacodynamic effects in a glioblastoma model.
  
  
  RESULTS
  Animals treated with GNE-317 demonstrated 3-fold greater penetrance in tumor core, rim, and normal brain compared with animals dosed with GDC-0980. Increased brain penetrance correlated with decreased staining of activated p-Akt, p-S6, and p-4EBP1 effector proteins downstream of PI3K and mTOR.
  
  
  CONCLUSIONS
  GDC-0980 is subject to active efflux by P-gp and BCRP at the BBB, while brain penetrance of GNE-317 is independent of efflux, which translates into enhanced inhibition of PI3K/mTOR signaling. These data show that BBB efflux by P-gp and BCRP is therefore an important determinant in both brain penetrance and molecular targeting efficacy in the treatment of invasive glioma cells.
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Chani M
authors.initials: CM
authors.lastname: Becker
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Rajneet K
authors.initials: RK
authors.lastname: Oberoi
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Stephan J
authors.initials: SJ
authors.lastname: McFarren
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Muldoon
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Deanna H
authors.initials: DH
authors.lastname: Pafundi
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Jenny L
authors.initials: JL
authors.lastname: Pokorny
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Debra H
authors.initials: DH
authors.lastname: Brinkmann
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: John R
authors.initials: JR
authors.lastname: Ohlfest
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: Jann N
authors.initials: JN
authors.lastname: Sarkaria
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: David A
authors.initials: DA
authors.lastname: Largaespada
authors.affiliation: Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota (C.M.B., S.J.M., D.M.M., J.R.O., W.F.E); Brain Tumor Program, University of Minnesota, Minneapolis, Minnesota (C.M.B., R.K.O., S.J.M., D.M.M., J.R.O., D.A.L., W.F.E); Department of Pharmaceutics, University of Minnesota, Minneapolis, Minnesota (R.K.O., W.F.E); Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota (J.R.O., D.A.L); Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota (D.H.P., J.L.P., D.H.B., J.N.S); Brain Barriers Research Center, University of Minnesota, Minneapolis, Minnesota 
authors.forename: William F
authors.initials: WF
authors.lastname: Elmquist
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors* / Q000235:genetics; D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics*; D001812:Blood-Brain Barrier / Q000378:metabolism; D001921:Brain / Q000187:drug effects; D001932:Brain Neoplasms / Q000378:metabolism* / Q000517:prevention & control; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000493:pharmacokinetics*; D016503:Drug Delivery Systems; D005909:Glioblastoma / Q000378:metabolism* / Q000517:prevention & control; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011743:Pyrimidines / Q000493:pharmacokinetics*; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D013876:Thiophenes / Q000493:pharmacokinetics*
chemical_list: C569670:1-(4-((2-(2-aminopyrimidin-5-yl)-7-methyl-4-morpholinothieno(3,2-d)pyrimidin-6-yl)methyl)piperazin-1-yl)-2-hydroxypropan-1-one; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; C501412:Abcg2 protein, mouse; D000970:Antineoplastic Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; C580635:GNE-317; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011743:Pyrimidines; D013876:Thiophenes; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases
keywords: blood-brain barrier; brain tumors; efflux transport; molecularly targeted agents; p-glycoprotein