Intermediate levels were observed in the skeletal muscles, spleen, thymus and placenta, whereas minimal levels (<0.25 fold of blood levels) were in brain, spinal cord and fetus. Thus, Ticagrelor was deemed effectively excluded from the brain and spinal tissues by the blood brain barrier. Ticagrelor and its metabolite (main
circulating metabolite of Ticagrelor and active Baf-A1 nmr at the P2Y12 receptor) were evaluated for activity at more than 300 secondary targets using in vitro radioligand binding, enzyme, and electrophysiological assays. When tested at a single concentration of 10 μM, neither Ticagrelor nor metabolite caused inhibition of radioligand binding at the D1, D2L and D4.2 receptors. Ticagrelor displaced [125I] Iometopane (RTI-55) from the human dopamine transporter recombinantly expressed in chinese hamster ovary (CHO) cells, with a pKi value of 6.79 ± 0.05 (0.202 μM, mean ± standard deviation, n = 4 separate experiments; Figure 4A). The rat free systemic exposure maximal concentration (Cmax) in the high dose group of 0.502 μM (based on 99.0%
protein binding) was above the Ticagrelor IC50 of DAT, but rat free systemic exposure in the mid and low dose group Cmax values of 0.157 and 0.043 μM were below the Ticagrelor IC50 of DAT. The human GSK1120212 cell line free systemic Cmax in clinical studies of 0.012 μM (based on 99.2% protein binding) was more than one log below the
Ticagrelor IC50 of DAT. The metabolite inhibited radioligand binding at the dopamine transporter with a pKi value of 6.12 ± 0.08 (0.8 μM, mean ± standard deviation, n = 4; Figure 4B). The rat and human free systemic Cmax values were more than one log below the metabolite IC50 of DAT. Ticagrelor treated ovariectomized rats were treated for four days with Ticagrelor and then stimulated with estradiol on Day 4 of treatment. Exposure of Ticagrelor and metabolite on Day 1 of dosing were similar to Day 1 and Week 26 exposure in the carcinogenicity bioassay (Table 5). Vehicle control treated rats with estradiol-stimulation IMP dehydrogenase had increased prolactin plasma levels between 3 and 4.5 hours post vehicle treatment and an AUC of 25.24 ± 18.62 (mean ± standard deviation) (Figure 5). At 180 mg/kg/day the peripherally-restricted Ticagrelor all but completely blocked the estradiol-induced prolactin release, with an AUC of 9.7 ± 5.53, which was significantly different from the control group (p < 0.01). Based upon these findings, Ticagrelor was deemed an inhibitor of estrogen-stimulated prolactin release in the female rat, at the dosage tested.