Stephanie van Hoppe

81 ABCB1 restricts brain penetration of the BTK inhibitor ibrutinib while CYP3A limits its oral bioavailability CYP3A is thought to primarily mediate the oxidation of ibrutinib to ibrutinib-DiOH, and we therefore also investigated the extent and tissue specificity of the impact of CYP3A in WT, Cyp3a -/- , Cyp3aXA, Cyp3aXV, and Cyp3aXAV mice. Cyp3a -/- mice lack all mouse Cyp3a proteins, whereas the “humanized” Cyp3aXA, Cyp3aXV, and Cyp3aXAV strains express human CYP3A4 in, respectively, the liver (XA), the intestine (XV), or in both liver and intestine (XAV) of the Cyp3a -/- mice. We first performed a pilot study with oral ibrutinib at 10 mg/kg in WT, Cyp3a -/- , and Cyp3aXAV mice, analyzing the ibrutinib and ibrutinib-DiOH plasma concentrations over 8 h.We found that the absence of Cyp3a led to highly increased ibrutinib concentrations in the plasma compared to WT mice, resulting in a 9.7-fold increased AUC 0-8 h , whereas the T max was not substantially altered (Figure 5A, Table 2). Conversely, the formation of ibrutinib-DiOH was dramatically decreased in Cyp3a -/- mice, resulting in only 6.7% of the ibrutinib-DiOH AUC 0-8 h in WT mice (Figure 5C, Supplemental Table 2). These data indicate that the mouse Cyp3a Figure 5. Plasma concentration−time curves of ibrutinib ( A, B ) and ibrutinib-DiOH (DiOH) ( C, D ) in female WT (black circles), Cyp3a −/− (blue squares), Cyp3aXA (peach triangles), Cyp3aXV (red circles) and Cyp3aXAV (maroon triangles) mice over 8 h ( A & C ) or 20 minutes ( B & D ) after oral administration of 10 mg/kg ibrutinib. Insets: semi-log plots of the data. When the 8 h data were below the lower limit of quantification, data were only plotted up till 3 h. Note the different concentration scales in panels A and C as well as panels B and D . Data are given as mean ± SD. n = 5−6 mice per group. 0 2 4 6 8 0 500 1000 1500 2000 Time (hours) DiOH (ng/m)l WildType Cyp3a-/- Cyp3aXAV 0 2 4 6 8 1 10 100 1000 10000 0 2 4 6 8 0 1000 2000 3000 4000 5000 Time (hours) Ibrutinib (ng/m)l WildType Cyp3a-/- Cyp3aXAV 0 2 4 6 8 1 10 100 1000 10000 C 0 5 10 15 20 25 0 2000 4000 6000 Time (minutes) Ibrutinib (ng/m)l Wild Type Cyp3a -/- Cyp3aXA Cyp3aXV Cyp3aXAV 0 5 10 15 20 25 0 500 1000 1500 Time (minutes) DiOH (ng/m)l Wild Type Cyp3a -/- Cyp3aXA Cyp3aXV Cyp3aXAV B E A Figure 5 - Plasm con e tra ion−time cur i rutinib ( A, B ) and ibrutin b-DiOH (DiOH ( C, D ) in female WT (bl ircles), Cyp3a −/− (blue squares), Cyp3aXA (peach triangles), Cyp3aXV (red circles) and Cyp3aXAV (maroon triangles) mice over 8 h ( A & C ) or 20 minutes ( B & D ) af er oral administration of 10 mg/kg ibrutinib. Insets: semi-log plots of t e d ta. Wh n the 8 h data were below the lower limit of quantification, data were only plott d up till 3 h. Note the different concentration scale in panels A and C s well as panels B and D . Data ar given as mean ± SD. n = 5−6 mice per group.