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 Three different formats of Receptor Occupancy (RO) assays.1
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).
Creative Biolabs has developed state-of-the-art, GMP-compliant platforms that integrate the latest technologies and equipment for scientific research. Our team of Ph. Ph.D.-level scientists brings a wealth of expertise and experience to the table, ensuring meticulous custom assay design, rigorous reagent characterization, precise data normalization/reporting, and comprehensive implementation planning. This enables us to deliver reliable, high-quality RO assay results with a quick turnaround time, meeting the needs of our global customers.
This research report examines two independent flow cytometry techniques for determining CCR5 receptor occupancy (RO) using the anti-CCR5 antibody. Findings indicate that both methods yielded similar CCR5 RO values, exhibited minimal background in untreated CCR5+CD4+ T cells, and enabled sensitive occupancy assessments on both blood-derived and tissue-resident CD4+ T cells. These measurements demonstrated a longitudinal correlation with plasma concentrations in the anti-CCR5 antibody-treated macaques.
Fig.2 CCR5 receptor occupancy.2
Fig.3 RO test for CCR5 in human samples.2
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References
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