The diversity of physiological functions mediated by the GPCR superfamily provides a rich source of molecular targets for drug discovery programs. Consequently, a variety of assays have been designed to identify lead molecules based on ligand binding or receptor function. In one of these, the binding of [(35)S]GTPgammaS, a nonhydrolyzable analogue of GTP, to receptor-activated G-protein alpha subunits represents a unique functional assay for GPCRs and is well suited for use with automated HTS. Here we compare [(35)S]GTPgammaS scintillation proximity binding assays for two different G(i)-coupled GPCRs, and describe their implementation with automated high-throughput systems.

Oral agents targeting Janus-associated kinases (JAKs) are promising new agents in clinical development. To better understand the relationship between JAK inhibition and biological outcome, compounds targeting JAKs were evaluated in peripheral human whole blood. To date, these analyses are low throughput and costly. Here, we developed a robust 384-well, high-throughput flow-based assay approach to screen small molecules for JAK/STAT signaling inhibition in human whole blood. This assay platform provides a highly sensitive analysis of signaling events in blood and facilitates measurement of target engagement. Further, the automation technologies and process optimizations developed here overcame sample integrity, handling, and multiparametric data analysis bottlenecks without affecting assay performance. Together these efforts dramatically increased sample throughput compared to conventional manual flow cytometric approaches and enabled development of novel JAK/STAT inhibitors.

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Tumor cell proliferation assays are widely used for oncology drug discovery, including target validation, lead compound identification, and optimization, as well as determination of compound off-target activities. Taking advantage of robotic systems to maintain cell culture and perform cell proliferation assays would greatly increase productivity and efficiency. Here we describe the establishment of automated systems for high-throughput cell proliferation assays in a panel of 13 human tumor cell lines. These cell lines were selected from various types of human tumors containing a broad range of well-characterized mutations in multiple cellular signaling pathways. Standard procedures for cell culture and assay performance were developed and optimized in each cell line. Moreover, in-house developed software (i.e., Toolset, Curvemaster, and Biobars) was applied to analyze the data and generate data reports. Using tool compounds, we have shown that results obtained through this panel exhibit high reproducibility over a long period. Furthermore, we have demonstrated that this panel can be used to identify sensitive and insensitive cell lines for specific cancer targets, to drive cellular structure-activity relationships, and to profile compound off-target activities. All those efforts are important for cancer drug discovery lead optimization.