Stephanie van Hoppe

29 ABCG2 & ABCB1 transport afatinib and restrict its oral availability and brain accumulation Table I - Pharmacokinetic parameters of afatinib after oral administration of 10 mg/kg to female wild-type, Abcg2 -/- , Abcb1a/1b -/- , and Abcb1a/1b;Abcg2 -/- mice (n = 5 - 6). Parameter Genotype Time (h) WT Abcg2 -/- Abcb1a/1b -/- Abcb1a/1b;Abcg2 -/- AUC 0-2 (ng∙h/ml) 2 145 ± 33 254 ± 30 **,+ 239 ± 70 *,++ 441 ± 86 *** C plasma (ng/ml) 120 ± 40 180 ± 26 +++ 192 ± 41 *,+++ 312 ± 48 *** C brain (ng/g) 51 ± 12 65 ± 16 +++ 130 ± 66 +++ 3658 ± 689 *** P brain (h -1 ) 0.35 ± 0.06 0.25 ± 0.04 +++ 0.51 ± 0.15 +++ 8.34 ± 0.99 *** Fold change 1 0.72 1.5 23.8 C liver (µg/g) 10.0 ± 2.9 19.6 ± 4.1 * 15.0 ± 6.1 + 28.7 ± 10.5 *** P liver (h -1 ) 70.7 ± 19 76.7 ± 8.8 63.3 ± 17.2 64.9 ± 20.9 Fold change 1 1.1 0.9 0.9 AUC 0-24 (ng∙h/ml) 24 434 ± 184 1831 ± 651 *** 1061 ± 253 **,++ 3020 ± 590 *** C max (ng/ml) 73.2 ± 31.5 167 ± 39.4 * 131 ± 28.3 + 227 ± 57.3 *** T max (h) 2.8 ± 1.1 4.5 ± 2.5 2 4 C brain (ng/g) 1.7 ± 0.2 7.8 ± 3.7 ***,+++ 5.5 ± 1.0 ***,+++ 2054 ± 299 *** P brain (h -1 ) 4.3 ± 2.4 4.1 ± 0.9 +++ 5.4 ± 1.6 +++ 688 ± 80.1 *** Fold change 1 0.95 1.2 160 C liver (ng/g) 12.6 ± 4.8 371 ± 176 ***,+++ 22.5 ± 5.1 +++ 3598 ± 1192 *** P liver (*10 -3 h -1 ) 31.9 ± 15.6 207 ± 110 ***,+++,### 21.4 ± 3.6 +++ 1214 ± 429 *** Fold change 1 6.5 0.67 38 AUC, area under the plasma concentration-time curve; C max maximum drug concentration in plasma; T max , the time after drug administration needed to reach maximum plasma concentration; C brain , brain concentration; P brain , brain accumulation (C brain divided by plasma AUC); C liver , liver concentration; P liver , liver accumulation (C liver divided by plasma AUC). Note: C liver at 2 hours is shown in µg/g and P liver at 24 hours is shown in *10 -3 h -1 . * , P < 0.05; ** , P < 0.01; *** , P < 0.001 compared to WT mice and + , P < 0.05; ++ , P < 0.01, +++ , P < 0.001 compared to Abcb1a/1b -/- ;Abcg2 -/- mice and ### , P < 0.001 compared to Abcb1a/b -/- mice. Data are given as mean ± SD. Similar results were obtained when measuring the afatinib plasma AUC 0-2 in an independent 2-hour experiment, with 1.6- and 1.8-fold increased values in Abcg2 -/- mice and Abcb1a/1b -/- mice, respectively (P < 0.01 and P < 0.05), and a 3-fold increase in the combination knockout strain (P < 0.001) compared to the WT mice (Table I). Like for the 24-h experiment, the contribution of each of the individual transporters yielded significant differences in the AUC 0-2 with the combination knockout strain, further supporting that Abcb1 and Abcg2 can each restrict the oral availability of afatinib. Interestingly, a semi-log plot of the plasma concentrations in the 24-hour experiment indicated that, from 8 h on, the plasma clearance in Abcg2 -/- mice, but especially also in the combination knockout mice, was substantially reduced compared to that inWT and