Elacridar

To improve treatment outcome for unresectable metastatic colorectal cancer (mCRC), many small molecule kinase inhibitors (KIs) have been tested. Most fail in early-phase clinical trials due to intrinsic resistance. As ATP Binding Cassette transporters are known to cause treatment resistance in mCRC, as well as to obtain higher intracellular drug concentrations, we evaluated whether inhibition of these transporters could potentiate KI efficacy. In patient-derived tumour organoids (PDTOs) from mCRC biopsies, preincubation with potent transporter inhibitor elacridar significantly improved sunitinib efficacy. Contrasting expectations, this was accompanied by reduced intracellular sunitinib accumulation. Mechanistically, confocal fluorescence imaging revealed reduced lysosomal sequestration of sunitinib in cells preincubated with elacridar. Storage of drugs-that are lysosomotropic and substrates of ABC-transporters-in subcellular compartments reduces the active pool and potentially contributes to intrinsic drug resistance in mCRC. Combination strategies that target ABC-transporters or lysosomes might be considered to potentiate drug efficacy.

P-glycoprotein (P-gp) is one of the most studied drug transporters, as it enables the cellular efflux of 50 % of marketed drugs and plays a key role in many drug-drug interactions. While a high number of studies has investigated the use of drug probes to phenotype P-gp activity, identifying endogenous markers remain a not fulfilled challenge. A previous untargeted lipidomic study in healthy volunteers highlighted some sphingolipid species as putative endogenous substrates of P-gp. Based on an untargeted lipidomic analysis of Madin-darby canine kidney parental cells (MDCK-parental cells) and MDCK cells transfected with the MDR1 gene (MDCK-MDR1), the present study aimed to investigate the role of P-gp in intracellular sphingolipid transport and, more generally, to demonstrate the interest of metabolomics strategy in the study of in vitro drug transporters. Using an untargeted lipidomic approach based on liquid chromatography high resolution mass spectrometry, allowed us to detect 131 sphingolipid species within MDCK-parental cells and MDCK-MDR1. Among them, modifications of this sphingolipidome were observed because of MDR1 transfection, mainly involving glucosylceramides. Exposure to two P-gp inhibitors, GF120918 and clarithromycin, increased glucosylceramides, particularly in MDCK-parental cells, probably due to expression of endogenous canine P-gp in this cell line. These results support the hypotheses of a role for P-gp as well as glucosylceramide flippase within the Golgi apparatus of cells. It also provides a proof of concept for understanding pharmaco-metabolomic results in the study of drug transporters in humans.