In vitro testing of receptor occupancy allows the study of drug binding affinity prior to testing in animals, giving a representation of how strong the drug’s affinity is for its receptor. This can provide additional data about the safety of the ligand being studied prior to starting human drug trials. By doing this, dosing can be fine tuned to be safer and more effective.
Testing receptor occupancy in vivo is more difficult. A concentration response curve must be obtained, however this depends on the species being studied. In vivo testing of a drug in animal models will give different receptor occupancy data to studies conducted in humans, and so therefore this data is not likely to be useful.
In vitro receptor occupancy studies are generally preferred and are becoming more common after issues experienced during the TGN1412 clinical trial. Biological drugs can react in different ways, and it is important to understand the affinity they have to their target receptor prior to starting work in animals (especially humans), and so in vitro receptor occupancy studies are becoming more common.