Is the human model RPTEC/TERT1 a relevant model for assessing renal drug efflux?

Active tubular secretion plays a major role in renal excretion of drugs thanks to the presence of many membrane transporters such as ABC transporters. These proteins facilitate drug transfer into the urine and could be a source of pharmacokinetic variabilities. Up to now, several human in vitro models of proximal tubule have been proposed but few of them have been characterized for predicting drugs renal efflux. The aim of this study was to determine whether the human model RPTEC/TERT1 meets all the criteria expected of a good model to assess renal drug transport. First, in vitro barrier properties were investigated. Then, the expression of several ABC transporters was assessed by immunofluorescence and relative quantification by liquid chromatography-high-resolution mass spectrometry (LC-HRMS) in comparison to the MDCK model. Finally, bidirectional transport studies were performed to evaluate the functionality of transporters and the abilities of model to discriminate several drugs. The RPTEC/TERT1 model formed a tight structure (192 Ω.cm² ) that was confirmed by paracellular permeability assays. Proteomic analysis and immunofluorescence staining showed the expression of several ABC transporters. Then, only the functionality of P-gp was confirmed by the active efflux of apixaban in this study. In addition, the RPTEC/TERT1 model presents the key criteria of a renal barrier and expresses several ABC transporters. Nevertheless, the BCRP and MRP's functionality was not confirmed and further investigations are required to valid this model as in vitro model for assessing renal drug efflux.