The Selection and Assessment of a Low‐Efflux MDCK Cell Line for use in a High‐Throughput Permeability Screening Assay

Objectives To establish a low‐efflux Madin‐Darby canine kidney cell line for potential use in a high throughput permeability screening assay. Methods MDCK cells were subcloned by limiting dilution. Individual MDCK colonies were isolated and clones were expanded to cell culture plates and assessed for efflux potential. The permeability characteristics and corresponding efflux ratios were measured using a standard bidirectional permeability assay conducted using 96‐well permeable support plates. Results 72 clones were initially screened for efflux potential. 8 clones demonstrating the lowest level of efflux were further cultured for continued evaluation. The 8 clones were further reduced in number to 2 by comparison of efflux between clones, where clones demonstrating the lowest efflux were maintained. One clone, whose efflux did not increase with longitudinal culture time, was selected for use in a high‐throughput permeability screening assay. The final clone showed limited efflux of common P‐gp substrates: loperamide, quinidine, dipyridamole; BCRP substrates: prazosin, topotecan, imatinib; and an MRP‐2 substrate: valsartan. Despite the lack of transport of multiple probe substrates efflux was observed for some compounds such as vinblastine and saquinavir. The final clone was further tested using a diverse set of molecules. Conclusions A low efflux MDCK subclone (MDCK‐LE) was identified. The MDCK‐LE cells demonstrate low efflux for many representative substrates of efflux transporters, though the cells are not entirely a “no efflux” cell line as demonstrated by the efflux of vinblastine and saquinavir, they do delineate the permeability of structurally diverse molecules over a broad permeability range.