Differential Roles of P-Glycoprotein, Multidrug Resistance-Associated Protein 2, and CYP3A on Saquinavir Oral Absorption in Sprague-Dawley Rats

Abstract

ABSTRACT:The objective of this investigation was to differentiate the roles of P-glycoprotein (Pgp), multidrug resistance-associated protein 2 (Mrp2), and CYP3A on saquinavir ( -(((3-(2-(7-chloro-2-quinolinyl)-(E)-ethenyl)phenyl) ((3-(dimethylamino-3-oxopropyl)thio)methyl)-thio) propanoic acid (MK571)], and/or CYP3A (midazolam). Plasma concentrations of SQV and related metabolites were analyzed by liquid chromatography-tandem mass spectrometry. When given alone, SQV absorption was extremely low both in situ (F a ‫؍‬ 0.07%) and in vivo [C max ‫؍‬ 0.068 g/ml; area under the curve (AUC) ‫؍‬ 6.8 g ⅐ min/ml]. Coadministration of GF120918 boosted SQV absorption by more than 20-fold with decreased variation in AUCs (percent coefficient of variation ‫؍‬ 30% versus 100%). In contrast, coadministration of MK571 or midazolam increased SQV absorption only 2-to 3-fold without improving the variation in AUCs. SQV oral absorption was not further improved when it was given with GF120918 and midazolam or with GF120918 and MK571. The current results provide, for the first time, direct and explicit evidence that the low oral absorption of SQV is controlled by a secretory transporter, Pgp, and not by limited passive diffusion owing to its poor physicochemical properties. Pgp-mediated transport is also responsible for the highly variable oral bioavailability of SQV. In contrast, intestinal Mrp2 and intestinal CYP3A appear to play minor roles in SQV oral bioavailability. Given the differential and complex roles of Pgp and CYP3A in SQV oral absorption, the optimization of AIDS boosting regimens requires careful consideration to avoid therapylimiting drug-drug transporter and enzyme interactions.

Evidence for Time-Dependent Interactions between Ritonavir and Lopinavir/Ritonavir Plasma Levels Following P-Glycoprotein Inhibition in Sprague-Dawley Rats

“…After acute treatment with verapamil (day 1), a statistically significant increase in the plasma concentrations of ritonavir (monotherapy) (pϽ 0.005) and lopinavir (LPV/r) (pϽ0.005) was observed, with a non-significant change in ritonavir (LPV/r) plasma concentrations. Since earlier studies have confirmed that doses of verapamil used in this study inhibit P-gp in rats, 22) our results concur with previously published data that the inhibitory effect of verapamil does indeed have a rapid onset. 29) Data from the literature, regarding the acute effect of P-gp inhibitors, is contradictory and little data on the sustained effect of P-gp inhibition after chronic treatment could be found.…”

“…A number of studies in the literature have investigated the possibility that variation in P-gp expression may have an impact on treatment outcomes of highly active antiretroviral therapy (HAART). 20,21) To further illustrate the important contribution of P-gp to treatment response, an earlier study in rats by Usansky et al 22) found that the absorption of saquinavir was increased 20-fold when the expression of P-gp was inhibited. Furthermore, the authors also found that the inter-individual variability of saquinavir decreased following the inhibition of P-gp.…”

First-Pass Metabolism Changes After Long-Term Garlic Supplementation

“…We reported previously that activities of Pgp and Mrp-2 significantly changed owing to allosteric modulations exerted in the presence of AGE components (Berginc et al, 2009;Berginc et al, 2010c). The impact of Pgp on the absorption of HIV-PIs was found to exceed that of Mrp-2, which has also been corroborated by Usansky (Usansky et al, 2008) in their in vivo study with Sprague-Dawley rats and Saq. In the case of Dar, mixed reports can be found regarding MRP-2/Mrp-2 importance in Dar absorption (Berginc et al, 2010c;Kakuda&Kiser, 2006).…”

“…In the case of Dar, mixed reports can be found regarding MRP-2/Mrp-2 importance in Dar absorption (Berginc et al, 2010c;Kakuda&Kiser, 2006). Based on this and the Mrp-2 expression pattern along GIT tract in rats (Mrp-2 expression decreases in more distal parts of rats small intestine) (Berginc et al, 2010c;Usansky et al, 2008), the participation of Mrp-2 in HIV-PIs intestinal absorption is minor and the observed short-term effects in our studies were predominately caused by modified Pgps activity. The noted short-term activity changes of the studied ABC transporters in our previous studies were explained by multiple binding sites in these transporters (four in Pgp and two in MRP-2) (Martin et al, 2000), which allow simultaneous binding of more substrates leading to allosteric modifications.…”

Multiple Efflux Pumps Are Involved in the Transepithelial Transport of Colchicine: Combined Effect of P-Glycoprotein and Multidrug Resistance-Associated Protein 2 Leads to Decreased Intestinal Absorption Throughout the Entire Small Intestine

“…Because of the overlapping substrate specificities, multiple efflux pumps might be involved in limiting the membrane permeability of a drug molecule. Drug substances that have been shown to be cosubstrates for several efflux pumps include atorvastatin (Lau et al, 2006), rosuvastatin (Kitamura et al, 2008), cyclosporine (Mannermaa et al, 2006), sulfasalazine (Dahan and Amidon, 2009c), saquinavir (Usansky et al, 2008), and fexofenadine (Matsushima et al, 2008). It is necessary to determine the contribution of each transporter to the overall efflux process, because such information could allow one to predict changes in membrane permeability when the functions of transporters are altered, e.g., by genetic polymorphism, disease state, or drug-drug interactions.…”