How validated receptor occupancy flow cytometry assays can impact decisions and support drug development
Maxime Moulard1, Marie-Laure Ozoux2
1Biomarkers Department, BioCytex, Marseille, France.
Abstract:
Because of the pressure of significant attrition in drug development, demonstration of target engagement after drug administration enables dose and regimen optimization, patient selection, and stratification from the earliest stages of drug development. The determination of receptor occupancy (RO) can support these efforts. Flow cytometry is one of the preferred technologies to be used based on the important advances in the technology over the last years enabling the simultaneous determination on target cells, of multi intra or surface cell parameters with adequate precision in a regulated environment. Nevertheless, compared to other platforms using the same antigen-antibody binding concept, the flow cytometry approach has faced several challenges, not only due to the technology per se and the diversity of receptor occupancy approaches, but also related to the nature of the matrix where the determination is performed. To illustrate these points, three case studies (antibody-drug conjugate and naked antibody) are provided here to highlight the importance of the choice of the right antibody pair to measure both receptor density (RD) and occupancy by the drug on cancer cells in blood and in bone marrow and the possibility to circumvent the lack of a critical reagent with an innovative approach. In addition, the use of RO data to determine the minimum anticipated biological effect level (MABEL) with translational data from preclinical to human studies, selection of starting dose for the first in man study will be discussed.
Insights
Demonstrating target engagement using flow cytometry is crucial for optimizing drug development. This study highlights selecting the right antibody pairs to accurately measure receptor occupancy (RO) and receptor density (RD) in cancer cells.
Area of Science:
- Pharmacology
- Biotechnology
- Oncology
Background:
- Drug development faces high attrition rates, necessitating early-stage optimization.
- Target engagement, measured by receptor occupancy (RO), is key for dose optimization and patient stratification.
- Flow cytometry offers advanced capabilities for multi-parameter analysis of cell surface and intracellular targets.
Purpose of the Study:
- To emphasize the importance of selecting appropriate antibody pairs for accurate receptor occupancy (RO) and receptor density (RD) measurements.
- To illustrate challenges and innovative solutions in flow cytometry-based RO determination.
- To discuss the application of RO data in establishing the minimum anticipated biological effect level (MABEL) and guiding first-in-human dosing.
Main Methods:
- Utilized flow cytometry for simultaneous determination of multiple cell parameters.
- Employed three case studies involving antibody-drug conjugates and naked antibodies.
- Focused on measuring receptor density (RD) and drug-induced receptor occupancy (RO) on cancer cells in blood and bone marrow.
Main Results:
- Highlighted the critical role of antibody pair selection in accurately quantifying receptor density and occupancy.
- Demonstrated methods to overcome reagent limitations in flow cytometry assays.
- Showcased the utility of RO data in bridging preclinical and clinical studies for dose selection.
Conclusions:
- Accurate measurement of receptor occupancy (RO) via flow cytometry is vital for efficient drug development.
- Careful selection of antibody pairs and innovative approaches are essential for reliable RO and RD quantification.
- RO data provides a translational bridge for determining MABEL and optimizing first-in-human study designs.
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