Caco-2 (an immortal human colon carcinoma cell line) is the most well known cell model for assessing in vitro permeability within drug discovery. The Caco-2 assay models the epithelial cell layer permeability barrier in the small intestine. Caco-2 cells develop microvilli on their apical surface that resemble the morphology of GI epithelial cells that line the intestinal villi. They also express cell membrane transporters on the apical surface, such as P-glycoprotein, BCRP and MRP2. Deliverables: apparent permeability Papp, identify if efflux is present, and identify whether P-gp or BCRP are involved in transport.