Stephanie van Hoppe

31 ABCG2 & ABCB1 transport afatinib and restrict its oral availability and brain accumulation Figure 3. Brain and liver concentration ( A, D ), tissue-to-plasma ratio ( B, E ) and relative tissue accumulation ( C, F ) of afatinib in female WT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 24 h after oral administration of 10 mg/kg afatinib. Note the log scale used for the liver concentration in panel D . *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice, + , P < 0.05, ++ , P < 0.01, +++ , P < 0.001 compared to Abcg2;Abcb1a/1b -/- mice ; and # , P < 0.05, ## , P < 0.01, ### , P < 0.001 compared to Abcb1a/1b -/- mice. N.D., not detectable; LLOQ, lower limit of quantification 0.5 ng/ml. Data are presented as the mean ± SD. *** +++ +++ +++ N.D. (<LLOQ) # +++ *** +++ +++ ** WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0.015 0.5 1 1.5 2 2.5 0.050 Brainconcentration (µg/g) WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0 20 40 60 80 Brain toplasma ratio WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0.00 0.01 0.25 0.45 0.65 0.85 0.05 Brainaccumulation (hr -1 ) *** *** +++ +++ ### WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0.0 0.5 1.0 1.5 2.0 Liver accumulation (hr -1 ) WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0.001 0.01 0.1 1 10 Liver concentration (µg/g) *** *** +++ +++ WT Abcg2-/- Abcb1a/1b-/- Abcg2;Abcb1a/1b-/- 0 50 100 150 Liver toplasma ratio N.D. (<LLOQ) A B D C F E 24-hour experiment Figure 3 - Brain and liver concentration ( , D ), tissue-to-plas a ratio ( B, E ) and relative tissue accumulation ( C, F ) of afatinib in female WT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 24 h after oral administration of 10 mg/kg afatinib. Note the log scale used for the liver concentration in panel D . *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice, + , P < 0.05, ++ , P < 0.01, +++ , P < 0.001 compared to Abcg2;Abcb1a/1b -/- mice ; and # , P < 0.05, ## , P < 0.01, ### , P < 0.001 compared to Abcb1a/1b -/- mice. N.D., not detectable; LLOQ, lower limit of quantification 0.5 ng/ml. D ta are presented as the mean ± SD. by assessing an earlier time point (e.g., 2 h), where plasma concentration differences are much smaller (see below). The impact of transporter proteins on tissue accumulation of drugs is especially relevant around the time of maximum plasma concentrations. Mice were therefore sacrificed 2 h after oral administration of 10 mg/kg afatinib. Relative plasma concentrations between the strains up to 2 h were very similar to those seen during the 24 h experiment (Compare Figure 2A and B). Similar to the results at 24 h after administration, the brain concentration of afatinib in Abcb1a/1b;Abcg2 -/- mice showed a highly significant 72.4-fold increase (P < 0.001) compared to WT mice. In contrast, no significant differences were found for the single knockout strains compared toWT mice (Fig. 4A, Table 1). Correcting the afatinib brain concentrations for the corresponding plasma concentrations (Fig. 4B) or AUCs (Fig. 4C) yielded similar results. The brain accumulation showed a highly significant, 23.8-fold increase (P < 0.001) for Abcb1a/1b -