Attenuation of intestinal absorption by major efflux transporters: quantitative tools and strategies using a Caco-2 model.
Efflux transporters expressed in the apical membrane of intestinal enterocytes have been implicated in drug oral absorption. The current study presents a strategy and tools to quantitatively predict the impact of efflux on oral absorption for new chemical entities (NCEs) in early drug discovery. Sixty-three marketed drugs with human absorption data were evaluated in the Caco-2 bidirectional permeability assay and subjected to specific transporter inhibition. A four-zone graphical model was developed from apparent permeability and efflux ratios to quickly identify compounds whose efflux activity may distinctly influence human absorption. NCEs in "zone 4" will probably have efflux as a barrier for oral absorption and further mechanistic studies are required. To interpret mechanistic results, we introduced a new quantitative substrate classification parameter, transporter substrate index (TSI). TSI allowed more flexibility and considered both in vitro and in vivo outcomes. Its application ranged from addressing the challenge of overlapping substrate specificity to projecting the role of transporter(s) on exposure or potential drug-drug interaction risk. The potential impact of efflux transporters associated with physicochemical properties on drug absorption is discussed in the context of TSI and also the previously reported absorption quotient. In this way, the chemistry strategy may be differentially focused on passive permeability or efflux activity or both.
Metabolism and Pharmacokinetics, Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA.
Xuena
X
Lin
Suzanne
S
Skolnik
Xiaohui
X
Chen
Jianling
J
Wang
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000502:physiology*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000502:physiology*; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002853:Chromatography, Liquid; D003986:Dibenzocycloheptenes / Q000494:pharmacology; D054659:Diketopiperazines; D055808:Drug Discovery / Q000379:methods; D006576:Heterocyclic Compounds, 4 or More Rings; D006801:Humans; D007408:Intestinal Absorption / Q000187:drug effects / Q000502:physiology*; D013058:Mass Spectrometry; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D011237:Predictive Value of Tests; D011422:Propionates / Q000494:pharmacology; D011804:Quinolines / Q000494:pharmacology; D013379:Substrate Specificity; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000241:Adenosine; D003986:Dibenzocycloheptenes; D054659:Diketopiperazines; D006576:Heterocyclic Compounds, 4 or More Rings; D009363:Neoplasm Proteins; D004364:Pharmaceutical Preparations; D011422:Propionates; D011804:Quinolines; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C541506:3-(6-isobutyl-9-methoxy-1,4-dioxo-1,2,3,4,6,7,12,12a-octahydropyrazino(1',2'-1,6)pyrido(3,4-b)indol-3-yl)propionic acid tert-butyl ester; C116614:ABCG2 protein, human; C059141:verlukast; C095179:zosuquidar trihydrochloride