High Throughput Screen for Inhibitors of Rac1 GTPase by Flow Cytometry

High throughput (HT) screening is at the starting point for most drug discovery pro- grams. As the range of targets being pursued widens new technologies have to be deployed to enable assays built to measure the activity of proteins previously deemed challenging. Flow cytometry is a technology providing multi-parametric analysis of single cells or other particles in suspension, such as beads. High throughput (HT) flow cytometry has become a very attractive screening platform for drug discovery. In this chapter we describe a 1536 well format high throughput screen of 500,000 compounds to find inhibitors of Rac1 GTPase to prevent allergic airway hyper-responsiveness in asthma. We discuss the assay development, miniaturization and validation carried out prior to the full screening campaign. We then describe how we have automated our iQue ® HD screener instruments and how we proceed with the data analysis and explain why we chose to run this screen on a flow cytometer and how it enabled us to reduce cost and timelines for the project.