Stephanie van Hoppe

105 Brain accumulation of ponatinib and its active metabolite is limited by ABCB1 and ABCG2 either t = 2 h or t = 24 h by the area under the plasma concentration-time curve from0–2 h (AUC0-2h) or 0-24 h (AUC0-24h), respectively. Ordinary one-way analysis of variance (ANOVA) was used to determine significant differences between groups. Post-hoc Tukey’s multiple comparisons were used to compare significant differences between individual groups. When variances were not homogeneously distributed, data were log- transformed before applying statistical tests. Differences were considered statistically significant when P < 0.05. Data are presented as mean ± SD with each experimental group containing 3-5 mice. R E S U LT S Pona t i n i b i s mode r a t e l y t r an s po r t ed by hABCB1 and mAb c g2 i n v i t r o We analyzed ponatinib (5 µM) transport across polarized monolayers of MDCKII cell lines stably transduced with hABCB1, mAbcg2, or hABCG2 cDNAs. The parental MDCKII cell line did not show apically directed transport (Figure 1A, r = 0.8) and addition of the potent ABCB1 inhibitor zosuquidar did not change this result (Figure 1B, r = 1.0). This indicates that endogenously present canine ABCB1 did not noticeably transport ponatinib in the parental cells. In the hABCB1 subclone, however, we observed modest apically directed transport of ponatinib (Figure 1C, r = 1.8), which was effectively inhibited by addition of zosuquidar (Figure 1D, r = 0.9). In MDCKII cells overexpressing mAbcg2 and hABCG2, we performed the transport assay in the presence of zosuquidar to exclude any transport contribution of endogenous canine ABCB1. We observed clear apically directed transport of ponatinib in mAbcg2 cells (r = 2.3), which was largely inhibited by the ABCG2 inhibitor Ko143 (Figure 1E and F). This indicates that ponatinib was moderately transported by mAbcg2. In the hABCG2 subclone we did not detect active transport of ponatinib and addition of Ko143 did not alter this profile (respective r = 0.9 and 1.0, Figure 1G and H). However, we note that the MDCKII-hABCG2 cell line consistently yields (much) lower transport rates for many drugs compared to the MDCKII-mAbcg2 line, which may relate to difficulty in expressing a high amount of hABCG2 in these cells [35, 36]. These data demonstrate that ponatinib is moderately transported by hABCB1 and mAbcg2. Therefore, both transporters might play a role in the oral availability and brain penetration of ponatinib.