Lacteal Secretion, Fetal and Maternal Tissue Distribution of Dasatinib in Rats

Dasatinib [ N -(2-chloro-6-methylphenyl)-2-[[6-[4-(2-hydroxyethyl)-1-piperazinyl]-2-methyl-4-pyrimidinyl]amino]-5-thiazolecarboxamide; BMS-354825] is a potent and broad-spectrum kinase inhibitor used for the treatment of chronic myeloid leukemia and Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia. Dasatinib exhibited extensive lacteal secretion in Sprague-Dawley rats following a single p.o. dose of [14C]dasatinib (10 mg/kg, 300 μCi/kg). Radioactivity was detected through 72 h postdose, with a milk/plasma area under concentration-time curve from 0 to infinity (AUC0-inf) ratio of approximately 25. The majority of the total radioactivity in milk was attributed to unchanged dasatinib. After a single dose of [14C]dasatinib to pregnant Sprague-Dawley rats at gestation day 18, radioactivity was extensively distributed in maternal tissues. The radioactivity detected by tissue excision or quantitative whole-body autoradiography was highest in adrenal gland, mammary tissue, lungs, kidneys, liver, and placenta. Compared with maternal tissues, a relatively low level of radioactivity was detected in fetal tissues. The concentrations of dasatinib-equivalents in fetal liver and kidneys were <13% of the respective maternal organs. The C max of dasatinib-equivalents in fetal blood was approximately 39% of that in maternal blood; however, the AUC values were comparable. Fetal brain/blood ratios of C max and AUC0-inf were approximately 1.58 and 1.48, respectively, which were much greater than the maternal ratios of 0.12 and 0.13. In summary, dasatinib was extensively distributed in maternal tissues and secreted into milk, but its penetration into the adult brain was limited. Transporters may be involved in mediating dasatinib distribution in the adult rat, whereas in the fetus, tissue and blood exposures were similar, suggesting that distribution in the fetus is predominantly mediated by diffusion.