Over the past decade, Creative Biolabs has supported a diverse range of antibody function assay studies and provides receptor occupancy (RO) assay services to facilitate your project success.
Receptor occupancy (RO) assays are commonly used to quantify the binding of therapeutic drugs to their cell surface targets. The RO data can provide some reference for pharmacodynamic (PD) biomarker data; meanwhile, it can establish PK/PD relationships when combined with the pharmacokinetic (PK) profile.
Commonly, receptor occupancy (RO) assays are measured by flow cytometry. As quantitative assays, flow cytometry-based RO assays could evaluate both the receptor binding and other pharmacodynamic characteristics of experimental therapies. Under different research scenarios, receptor occupancy (RO) assays can be designed to be relatively simple to measure the number of receptors for the binding drug, as well as more complex experiments to evaluate the internalization of receptors after the binding drug.
These are three basic formats that have been used as PD measurements in drug development.
Fig.1 The three basic RO assay formats. (Liang, 2016)
The first format is a critical measurement when evaluating the cell specificity and therapeutic dose of an antibody. In this format measurement, the proportion of unbound or unoccupied receptors by using a fluorescence-labeled detection reagent to the receptor.
For the second RO assay format measuring drug-occupied receptors, a fluorescence-labeled anti-drug antibody (ADA) is generally used for detection based on non-competing with drug binding, and the proportion of receptors bound by the drug is determined by the measurement of the bound drug.
The total receptor assay is commonly employed for biotherapeutic drugs with a mechanism of ADCC action. For the third format including both free and drug-occupied receptors, the detection reagent is usually an anti-receptor antibody that binds to an epitope distinct from that of the drug (i.e., a non-competing antibody).
To ensure reliable and high-quality results of RO assays, our technical team is dedicated to providing custom assay design, key reagent characterization, data normalization/reporting, and thorough planning for implementation.
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Reference
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