INTRODUCTION: Farnesoid X receptor (FXR) is an ascending target for metabolic 
and inflammatory diseases. As a nuclear receptor, FXR exhibits many 
physiological effects in transcription control of several genes. Therefore, the 
development of synthetic FXR ligands requires elaborate in vitro test systems to 
characterize novel ligands and to estimate their in vivo activities.
AREAS COVERED: This work gathers and describes published in vitro test systems 
for FXR ligands including cell-based functional assays as well as binding 
assays. It also evaluates the information which can be provided by these assays.
EXPERT OPINION: In vitro screening of FXR ligands widely relies on reporter gene 
assays. Additionally, some co-activator re-cruitment assays are described and 
for the characterization of potent compounds the pattern of affected target 
genes is evaluated by qPCR. Compared to other nuclear receptors such as PPARs 
the variety of test systems is quite low for FXR and might eventually not be 
enough to sufficiently characterize FXR targeting drug candidates.