The question whether compounds should be screened individually or in mixtures is present since the beginning of HTS and is still of current interest. Despite of the high importance of the question there are very few publications on the pros and cons of both approaches, especially regarding those taking into account the major changes in screening of the last years (homogeneous assays, uHTS, miniaturization). We have made an in depth cost-benefit-evaluation of pool 10 and single compound screening. For several assays representing the most important target families and HTS assay technologies a diversity selected set of 150.000 was screened in parallel in pool 10 and single compound mode. In the pool 10 mode compounds were tested twice in the presence of 9 different compounds (= orthogonal pooling) whereas in the single compound mode a compound was tested only once. A quantitative analysis of the data will be presented.

Over the past 10 years at Berlex, 10 GPCR projects have been implemented leading to the identification of small molecules GPCR antagonists that achieved clinical development. These successes validate the technologies used for HTS: radioligand receptor binding screens. Considerable effort was dedicated to further characterization of hits by secondary assays: calcium flux, cAMP, microphysiometry, platelet aggregation and chemotaxis. These various assays have been performed in whole cells naturally expressing the receptor of interest, or transfected with and overexpressing the receptor human whole blood or human washed platelets. Specific results in these projects have taught us that not all GPCRs are created equal. For example, one GPCR target was not amenable to HTS using receptor binding. We have identified both antagonists and agonists by primary receptor binding assays as well as by functional assays. Examples will be given of successful and unsuccessful assay development and lessons learned in the process.

Expanding corporate compound files have defined our approach to HTS, driving the introduction of large-scale automated systems for primary screening and reagent production. Ideas of industrialization of R&D have raised the expectation of using standardized processes to shorten timelines and increase productivity. Although, applying a set of standard technologies has decreased the cycle time from assay development to screening, massive parallelization and 'industrialization' of processes is often hampered by the needs of highly specific projects. Biological performance is key to success, and targets requiring technologies not amenable to 1536 well formats still present problems. As a consequence of these bottlenecks and aided by the introduction of reliable benchtop equipment, we have seen a renaissance of workstation approaches. This presentation will cover strategies to enable resource, time and cost effective HTS, compare requirements for biochemical and cell-based HTS, and summarize the practical implementation of the different concepts at Pfizer, Sandwich.

Fast, efficient and robust HTS with high quality and data content is a key prerequisite for keeping pace with the demands of modern drug discovery and with recent trends towards high quality / high content approaches for industrialized lead finding.

Novartis is addressing these issues with high flexibility in assay readout techniques and target portfolio on the NanoScreening platform. Within the same screening platform, confocal single molecule detection as well as more 'classical' assay readouts is applied according to particular demands of each biological target. Throughout several years of productive use we could achieve a significant experience with these technologies in order to strengthen the conscious application of either one of these different technologies. The most appropriate assay setup has to fulfill a number of criteria. The crucial criteria are stability of the assay readout in miniaturized format in terms of maximum sensitivit