Quantitative Target Engagement of RIPK1 in Human Whole Blood Via the Cellular Thermal Shift Assay for Potential Pre-Clinical and Clinical Applications

The cellular thermal shift assay (CETSA (R)) is a target engagement method widely used for preclinical characterization of small molecule compounds. CETSA (R) has been used for semi -quantitative readouts in whole blood with PBMC isolation, and quantitative, plate -based readouts using cell lines. However, there has been no quantitative evaluation of CETSA (R) in unprocessed human whole blood, which is preferred for clinical applications. Here we report two separate assay formats - Alpha CETSA (R) and MSD CETSA (R) - that require less than 100 mu L of whole blood per sample without PBMC isolation. We chose RIPK1 as a proof -of -concept target and, by measuring engagement of seven different inhibitors, demonstrate high assay sensitivity and robustness. These quantitative CETSA (R) platforms enable possible applications in preclinical pharmacokinetic-pharmacodynamic studies, and direct target engagement with small molecules in clinical trials.