Guidance for Pharmacological Characterization of PPI Inhibitors

This technical note provides guidance on the pharmacological characterization of protein-protein interaction (PPI) inhibitors, focusing on the use of the Cheng-Prusoff equation for accurate determination of inhibitor affinities (Ki) and PPI affinities (Kd). The document outlines the importance of lead optimization in drug discovery and emphasizes that accurate pharmacological characterization is essential for effective therapeutic development. It presents various case studies demonstrating the application of HTRF® PPI reagents in determining Kd and Ki values across different assay formats. The note details the methodologies for calculating Kd using binding saturation curves and discusses limitations encountered in certain assay formats that prevent reliable Kd assessments. Additionally, it introduces a rearranged Cheng-Prusoff equation for scenarios where saturation binding curves cannot be obtained, supported by real-world case studies that validate this approach. Overall, the technical note serves as a comprehensive resource for researchers involved in the pharmacological assessment of PPI inhibitors.