Abstract 354: Physiologically relevant target engagement using CETSA

Abstract

Abstract Targeted therapies are dependent on adequate occupancy and target engagement to reach their efficacy measure. Yet, more than half of novel candidate drugs entering clinical trial stage fail before proof of concept is achieved. Inadequate target engagement is often at the root cause of these failures. Therefore we have developed a versatile label-free method to quantify the target engagement of drugs on their native physiological relevant targets. The method is validated in multiple sample matrices from bench to bedside: in living cells and tissue from rodents and man. CETSA is a patented biophysical method measuring the thermal stability of drug target proteins and the shift induced by their ligands. By quantifying the melting temperature and shift induced by the ligand we can quantify the potency of target engagement. This potency determination then allows filtering of candidate drugs by their ability to engage the target in its physiologically relevant form, in relevant sample formats such as intact cells or tissue. We present a number of applications and readouts of the CETSA method quantifying target engagement of drugs used in the clinic and in development. Furthermore, we show that the target engagement of cyclin dependent kinase inhibitors correlated both to viability and to a dose dependent decrease of a cell cycle activity marker in cellular sample matrices. The biomarker, thymidine kinase activity, was analyzed with the commercially available test DiviTum®. By combining CETSA with DiviTum® in the same samples, it was thus possible to correlate CETSA outcomes to pharmacodynamic effects of a drug. The utility and value of the CETSA method enabling preclinical development of novel drugs is substantiated by the examples included here. Combining quantifications of efficacy with the molecular target engagement of the drug yields an orthogonal dataset, which has a potential to validate the target-mediated efficacy. Such datasets can be generated from early in vitro systems to clinical studies and may reduce the high failure rate in drug development by facilitating the discovery, development and evaluation of novel drugs. Citation Format: Jakob Karén, Catrine Sioberg, Pawel Niekrasz, Magnus Neumuller, Daniel Martinez Molina. Physiologically relevant target engagement using CETSA. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 354.