title: Calibration of in vitro multidrug resistance protein 1 substrate and inhibition assays as a basis to support the prediction of clinically relevant interactions in vivo.
abstract: The multidrug resistance protein 1 (MDR1) is known to limit brain penetration of drugs and play a key role in drug-drug interactions (DDIs). Theoretical cut-offs from regulatory guidelines are used to extrapolate MDR1 interactions from in vitro to in vivo. However, these cut-offs do not account for interlaboratory variability. Our aim was to calibrate our experimental system to allow better in vivo predictions. We selected 166 central nervous system (CNS) and non-CNS drugs to calibrate the MDR1 transport screening assay using Lewis lung cancer porcine kidney 1 epithelial cells overexpressing MDR1 (L-MDR1). A threshold efflux ratio (ER) of 2 was established as one parameter to assess brain penetration in lead optimization. The inhibitory potential of 57 molecules was evaluated using IC50 values based on the digoxin ER-IC50(ER)-or apparent permeability-IC50(Papp)-in L-MDR1 cells. Published clinical data for 68 DDIs involving digoxin as the victim drug were collected. DDI risk assessments were based on intestinal concentrations ([I2]) as well as unbound [I1u] and total plasma [I1T] concentrations. A receiver operating characteristic analysis identified an [I2]/IC50(ER) of 6.5 as the best predictor of a potential interaction with digoxin in patients. The model was further evaluated with a test set of 11 digoxin DDIs and 16 nondigoxin DDIs, resulting in only one false negative for each test set, no false positives among the digoxin DDIs, and two among the nondigoxin DDIs. Future refinements might include using cerebrospinal fluid to unbound plasma concentration ratios rather than therapeutic class, better estimation of [I2], and dynamic modeling of MDR1-mediated DDIs.
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Agnès
authors.initials: A
authors.lastname: Poirier
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Cascais
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Bader
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Renée
authors.initials: R
authors.lastname: Portmann
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Marie-Elise
authors.initials: ME
authors.lastname: Brun
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Walter
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hillebrecht
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland.
authors.forename: Mohammed
authors.initials: M
authors.lastname: Ullah
authors.affiliation: Roche Pharmaceutical Research and Early Development, Roche Innovation Center, Basel, Switzerland christoph.funk@roche.com.
authors.forename: Christoph
authors.initials: C
authors.lastname: Funk
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D000818:Animals; D001681:Biological Assay / Q000379:methods; D001692:Biological Transport / Q000502:physiology; D002138:Calibration; D045744:Cell Line, Tumor; D002490:Central Nervous System / Q000187:drug effects / Q000378:metabolism; D004077:Digoxin / Q000378:metabolism; D004347:Drug Interactions / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques / Q000379:methods; D010539:Permeability; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D013552:Swine
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004364:Pharmaceutical Preparations; D004077:Digoxin