A Clinical Sample Receptor Occupancy Assay Using Flow Cytometry

A global pharmaceutical company was conducting a European multi-site Phase I/IIa clinical study across several countries. One of the endpoints was assessment of changes in the amount of therapeutic drug bound to the target cell populations. Clinical protocol required assessment of changes from baseline; to allow correlation with the PK/PD endpoints. The project used a flow cytometry based receptor occupancy (RO) assay.

• As a secondary endpoint, it required a formal assay validation and the ability to monitor assay performance during the conduct of the clinical study.

• The dynamic nature of the RO endpoint required fresh whole blood samples were either be analyzed with 8 hours of collection, or stabilized to allow reliable analysis.

• The clinical protocol required study subjects to be enrolled individually and analyses conducted over several years.

• QA audited data were required on completion of each cohort as part of the dose escalation decision-making process.