The CEllular Thermal Shift Assay (CETSA) allows a direct quantification of drug target engagement in living cells and tissues. The biophysical basis of the method enables a label free approach on the native endogenously expressed target in situ. Because of the generic format and the physiological relevance of CETSA, Pelago Bioscience has implemented multiple applications in Drug Discovery. Since the first publication of the CETSA method it has been used for orthogonal measures of drug occupancy adding real value to existing efficacy assays on more than 70 drug targets in multiple therapy areas. The examples of CETSA utility ranges from Target ID and validation, lead generation and drug candidate profiling to translational science and rational biomarker discovery.