Stephanie van Hoppe

111 Brain accumulation of ponatinib and its active metabolite is limited by ABCB1 and ABCG2 Although the Cyp3a deficiency resulted in a modest increase in the ponatinib plasma AUC (Figure 2A, Table 1), the plasma concentration at 24 h was not significantly different from that in WT mice. The brain concentration and accumulation were also not significantly altered in Cyp3a -/- mice (Figure 3A-C). The same applied to the liver concentration and accumulation (Figure 3D-F). Collectively, these data suggest that Cyp3a did not impact brain (or liver) accumulation of ponatinib independent of its effect on the plasma concentration. In general, the impact of transporter proteins on tissue accumulation of drugs is especially relevant when plasma concentrations are high. Mice were therefore also sacrificed 2 h after oral administration of 10 mg/kg ponatinib. Similar to the 24 h experiment, the brain concentration of ponatinib in Abcb1a/1b;Abcg2 -/- mice showed a highly significant 11-fold increase (P < 0.001) compared to WT mice. No significant differences were found for the single knockout strains compared to WT mice (Figure 4A, Table 2). Correcting the ponatinib brain concentrations for the corresponding plasma AUCs (Figure 4C) showed a more pronounced difference of the single knockout Figure 4. Brain and liver concentration ( A, D ), tissue-to-plasma ratio ( B, E ) and relative tissue accumulation ( C, F ) of ponatinib in female WT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 2 h after oral administration of 10 mg/kg ponatinib. *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice. Data are given as mean ± SD. n = 3-5 mice per group. A B C D E F 2 hours after oral administration Brain concentration (ng/g) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 1000 2000 3000 4000 11-fold *** 1-fold 0.5-fold Liver concentration (ng/g) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 5000 10000 15000 20000 25000 * Brain to plasma ratio Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 5 10 15 20 25 ** 17-fold 1.9-fold 1-fold *** -1 ) Brain accumulation (h Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 5 10 15 20 *** ** 18-fold 1.5-fold 1.9-fold Liver to plasma ratio Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 50 100 150 Liver accumulation (h -1 ) Wild-type Abcg2-/- Abcb1a/1b-/- Abcb1a/1b;Abcg2-/- 0 50 100 150 Figure 4 - Brain and liver concentration ( A, D ), tissue-to-plasma ratio ( B, E ) and relative tissue accumulation ( C, F ) of ponatinib in femaleWT, Abcg2 -/- , Abcb1a/1b -/- and Abcg2;Abcb1a/1b -/- mice 2 h after oral administration of 10 mg/kg ponatinib. *, P < 0.05; **, P< 0.01; ***, P < 0.001 compared to WT mice. Data are given as mean ± SD. n = 3-5 mice per group.