Tyrosine kinase inhibitors (TKI) are effective in treating malignant disorders and were suggested to also have an impact on non-malignant diseases. However, in some inflammatory diseases like rheumatoid arthritis (RA) their in vivo effect seemed to be rather moderate. To exert their effect hydrophilic TKI are actively accumulated in target cells by membrane transporters, a process which is known to govern drug efficiency. This study aims to evaluate the importance of this process for TKI delivery in inflammatory diseases and its pathology induced regulation at the example of the treatment of RA with Imatinib mesylates. Imatinib transport was investigated in transporter-transfected HEK293 cells and human RA synovial fibroblasts (hRASF). Transporter expression was quantified by qRT-PCR. Moreover, the expression of the multidrug and toxin extrusion transporter 1 (hMATE1) was investigated in hRASF by immunofluorescence. Imatinib transport was quantified by HPLC. hRASF specifically accumulate Imatinib via hMATE1, the transporter with the highest apparent affinity for Imatinib among other organic cation transporters (OCT1 to 3 and OCTN1). This uptake was significantly reduced by an acidic extracellular pH according to hMATE1 transport properties and under incubation with the pro-inflammatory cytokines TGFß, IL-1ß and IL-6 by down-regulation of hMATE1 mRNA and protein expression. The regulation of Imatinib uptake in hRASF via hMATE1 can explain moderate in vivo effects on RA. These results implicate that investigating transporter mediated drug processing under normal and pathological conditions is important for developing drugs used in inflammatory diseases (supported by IMF of the Medical Faculty Münster, BE12009).