China Bioanalysis Forum 2024 -- Drug-target engagement studies are essential to understand molecular pharmacology and pharmacokinetic/pharmacodynamic (PK/PD) relationships. The ability of drugs to penetrate the tumor and bind their target is critical for the successful treatment of solid tumors. Flow cytometry-based receptor occupancy (RO) assays are frequently used for measuring and quantifying the binding of a drug, which is regarded as a critical PD biomarker for the quantitative evaluation of PK/PD relationships and can provide useful information for initial dose range finding in early phases of clinical trials. RO assays are typically performed on fresh blood specimens. However, evaluating RO for the drugs that target receptors on solid tumor tissues (such as ADC drugs) is perceived to be very difficult if not impossible. In this study, we explored the feasibility of flow cytometry-based RO assay with solid tumor tissue samples in clinical trials through a CDX mouse model.

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