title: In situ intestinal perfusion in knockout mice demonstrates inhibition of intestinal p-glycoprotein by ritonavir causing increased darunavir absorption.
abstract: Darunavir is a second-generation protease inhibitor designed to have antiviral efficacy against HIV-1 with multiple resistance mutations to protease inhibitors. It is always coadministered with a subtherapeutic dose of ritonavir. It has been shown that darunavir and ritonavir are substrates of P-glycoprotein (P-gp). We explored the contribution of P-gp to the transport characteristics of darunavir (up to 100 muM) using Caco-2 monolayers and the recently developed in situ intestinal perfusion technique using wild-type and mdr1a/1b(-/-) mice. We observed that, in vitro, P-gp has a modulatory effect on the absorption of darunavir, even at a concentration of 100 muM (efflux ratio = 25). Simulated intestinal fluids partially inhibited P-gp functionality, which was further inhibited by adding the P-gp inhibitors verapamil, 6-[(2S,4R,6E)- 4-methyl-2-(methylamino)-3-oxo-6-octenoic acid]cyclosporine D (PSC833), N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl) ethyl]-phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxamide (GF120918), or ritonavir. Using the in situ intestinal perfusion technique, we demonstrated that coperfusion with ritonavir resulted in a similar apparent permeability coefficient to that observed using P-gp knockout mice, which was 2.7-fold higher than in control mice. We conclude that, in mice, even at a relevant intraluminal concentration of darunavir, P-gp has a modulatory effect on the absorption of darunavir. However, this P-gp-mediated darunavir transport is inhibited when it is combined with ritonavir.
authors.affiliation: Laboratory for Pharmacotechnology and Biopharmacy, K.U. Leuven, Gasthuisberg O&N 2, Herestraat 49, Leuven, Belgium.
authors.forename: Nico
authors.initials: N
authors.lastname: Holmstock
authors.forename: Raf
authors.initials: R
authors.lastname: Mols
authors.forename: Pieter
authors.initials: P
authors.lastname: Annaert
authors.forename: Patrick
authors.initials: P
authors.lastname: Augustijns
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics / Q000502:physiology; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D018938:Caco-2 Cells; D000069454:Darunavir; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D006801:Humans; D007408:Intestinal Absorption; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects*; D051379:Mice; D018345:Mice, Knockout; D019438:Ritonavir / Q000494:pharmacology*; D013449:Sulfonamides / Q000493:pharmacokinetics*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D017320:HIV Protease Inhibitors; D013449:Sulfonamides; C095122:multidrug resistance protein 3; D019438:Ritonavir; D000069454:Darunavir