Development of a Flow Cytometric Receptor Occupancy Assay for Clinical Analysis of Immune Checkpoint Inhibitor Therapeutics 

Flow cytometry is a powerful technique for assessing drug-target cell interactions, including receptor occupancy for molecules such as PD-1. Champions Oncology has developed a panel with an adrop-inchannel to measure PD-1 occupancy and other checkpoint markers for combination therapies. The assay was evaluated for sensitivity and reproducibility, and optimized for scalability and stability in fresh whole blood samples for up to 72 hours. This assay effectively measures drug-target interaction strength and PD-1 sensitivity, showcasing its flexibility and robustness.

• Pembrolizumab is widely applied in various cancer treatment. To further understand its pharmacokinetics and pharmacodynamics, Receptor Occupancy (RO) assay is a great tool to elucidate its therapeutic applications. This RO assay was designed to evaluate the fraction of free receptor using a competitive antibody for its sensitivity.

• Our flow-based RO assay provides an easy platform and consistent results in two models of cytometers, BD FACSymphony and the spectral Cytek Northern Lights. Two drop-in channels within the panel provides the flexible choices of add-on markers. The strength of this RO assay is suitable for both cryopreserved PBMC and whole blood samples with or without stimulation.