BSEPcyte® is a fully-validated assay platform for measuring BSEP (Bile salt export pump) inhibition and it uses metabolically competent primary hepatocytes in suspension. The assay involves incubation of hepatocytes with exogenous bile acids that allows for bypassing the de novo rate limiting step of bile acid synthesis to form bile salts, followed by specific LC-MS/MS quantification of the amounts of bile salts exported into extracellular medium by BSEP.