Abstract C82: Role of influx and efflux transporters on gut absorption of selected tyrosine kinase inhibitors in a polarized gut epithelium model system.
Authors: Honeywell Richard J. , Fatmawati Christien , Boeddha Marita , Hitzerd Sarina , Kathmann Ietje , Giovannetti Elisa , Peters Godefridus J. 
Published: August 2014

Abstract
Tyrosine kinase inhibitors (TKI) are a family of small molecules which inhibit the ATP driven phosphorylation of signaling proteins that normally activate transduction cascades. Aberrations in signal cascades have been linked to the development of tumors and their survival pathways. TKIs tend to be alkali in nature with a correspondingly high pKa (5-8) while absorption properties have been linked to both ABC and Organic Cation Transporters (OCT). Because of their poor solubility, TKI are administered orally but available pharmacokinetic data indicate that in most cases bioavailability is relatively low (∼60% or lower). Despite a molecular weight in a similar range, doses vary significantly: Sunitinib (Sun) - 50 mg/d, Dasatinib (Das) - 150 mg/d, Erlotinib (Erl) - 150 mg/d, Gefitinib (Gef) - 250 mg/d, Crizotinib (Cri) - 250 mg BID and Sorafenib (Sor) - 400 mg BID. Steady state plasma levels vary from 0.13 (Sun), 0.21 (Das), 0.29 (Gef), 0.7 (Cri), 2.54 (Erl) to 12.1 µM (Sor). Variations in intestinal absorption may seriously affect plasma concentrations, tumour exposure and antitumor effect. To investigate the mechanisms behind these differences a well-established model for intestinal transport was used: the human colon cell line, CaCo2, when grown in special coated transwell plates forms a confluent differentiated polarised monolayer resembling gut epithelium. This model was used to determine the permeability of Gef, Erl, Sun, Cri, Sor, and Das, using LC-MS-MS to determine drug concentrations. Absorption from the gut given as the transfer rates from Apical to Basolateral (A/B) sides using 20 µM TKI at the apical side was determined over a 3 hour period. Transfer was linear in this period. Transfer rates varied from about 30 for Cri, 43 for Sun, 209 for Das, 180 for Gef, 223 for Sor, to 479 pmol/hr for Erl. In order to determine the role of ABC pumps, we depleted ATP with azide, which partially reduced transfer of Gef, Sun and Sor, but did not affect Erl. Ko143, a specific ABCG2 inhibitor decreased transfer of Gef and Sor but unexpectedly increased Sun. Remarkably, permeability transfer rates from the basolateral (blood) side to gut (B/A) were much higher (252 for Gef, 621 for Sor, 685 for Sun, 1623 for Erl and 4630 pmol/hr for Das) than A/B transfer. Verapamil, an inhibitor of P-glycoprotein and to some extend OCT1 increased A/B transfer of Sor and Das, but did not affect the transfer of the other compounds. Desipramine, a general OCT inhibitor, did not affect transfer of Erl, increased that of Gef and Cri about 2-fold and that of Sun 1.5-fold, but hardly affected that of Sor and Das. In conclusion, absorption of TKI from the apical side (gut epithelium) is relatively poor, while there was a relatively high negative flow (B/A); this is in line with the low bioavailability of most TKI. Some ABC transporters and OCTs play a role in the absorption, in line with their substrate specificity.
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):C82.
Citation Format: Richard J. Honeywell, Christien Fatmawati, Marita Boeddha, Sarina Hitzerd, Ietje Kathmann, Elisa Giovannetti, Godefridus J. Peters. Role of influx and efflux transporters on gut absorption of selected tyrosine kinase inhibitors in a polarized gut epithelium model system. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr C82.