receptor occupancy
Definition
Receptor occupancy refers to the proportion of receptors bound by a ligand (drug, hormone, or neurotransmitter) at a given concentration, typically expressed as a percentage. It is a fundamental pharmacodynamic parameter that describes the relationship between drug concentration and receptor binding, governed by the law of mass action. Receptor occupancy is determined by ligand concentration, receptor density, and binding affinity (Kd). While occupancy correlates with pharmacological response, the relationship is not always linear due to factors like receptor reserve, spare receptors, and signal amplification. Understanding receptor occupancy is critical for predicting drug efficacy, determining optimal dosing regimens, and explaining phenomena like partial agonism, where maximal response occurs at submaximal occupancy.
Visualize receptor occupancy in Nodes Bio
Researchers can use Nodes Bio to visualize receptor-ligand binding networks and map relationships between occupancy levels and downstream signaling cascades. Network graphs can illustrate how different occupancy thresholds activate distinct pathways, compare multiple ligands competing for the same receptor, and model dose-response relationships across receptor subtypes. This enables identification of optimal therapeutic windows and prediction of off-target effects through pathway crosstalk analysis.
Visualization Ideas:
- Dose-occupancy-response curves showing relationships between drug concentration, receptor binding, and pharmacological effects across multiple receptor subtypes
- Competitive binding networks illustrating multiple ligands competing for the same receptor with different affinities and resulting occupancy patterns
- Temporal occupancy dynamics networks mapping receptor binding kinetics, dissociation rates, and downstream signaling pathway activation over time
Example Use Case
A pharmaceutical team developing a dopamine D2 receptor antagonist for schizophrenia needs to determine the minimum receptor occupancy required for therapeutic efficacy while avoiding extrapyramidal side effects. Using PET imaging data and clinical outcomes, they discover that 60-80% D2 occupancy provides antipsychotic effects, but exceeding 80% causes motor symptoms. They map these occupancy thresholds against downstream signaling pathways to identify biomarkers predicting individual patient response and optimize dosing strategies for different patient populations.