Bioengineering in Cell and Tissue Research

Chapter 1 Reporter Genes in Cell Based ultra High Throughput Screening (p. 3-4)

Stefan Golz

Bayer Healthcare AG, Institute for Target Research, 42096Wuppertal, Germany, stefan.golz@bayerhealthcare.com

Abstract Pharma research in most organizations is organized in discrete phases together building a "value chain" along which discovery programs process to fi- nally drug candidates for clinical testing. The process envisioned to identify targetspecific modulators lacking several side effects. Following a technical assessment of the targets "drugability", the probability to identify small molecule modulators, and technical feasibility target-specific assays are developed to probe the corporate compound collection for meanful leads. "High-Throughput-Screening" (HTS) started roughly one decade ago with the introduction of laboratory automation to handle the different assay steps typically performed in microtiter plates. Today a large arsenal of screening technologies is available for researchers in industry and academia to set up uHTS or HTS assays. Here the use of reporter genes offer an alternative for following signal transduction pathways from receptors at the cell surface to nuclear gene transcription in living cells.

1.1 Introduction

The modern drug research process has reversed the classical pharmacological strategy. Today, research programs are initiated based on biological evidence suggesting a particular gene or gene product to be a meaningful target for small molecule drugs useful for therapies. The process envisioned to identify target-specific modulators lacking several side effects. Also, it allows setting up a linear drug discovery process starting from target identification to finally delivering molecules for clinical development. One central element is lead discovery through high-throughput screening of comprehensive corporate compound collections. Pharma research in most organizations is organized in discrete phases together building a "value chain" along which discovery programs process to finally drug candidated for clinical testing (Hüser et al. 2006).

This pipeline is fueled by targets suggested from external or in-house generated data suggesting a gene or gene product to be disease relevant. Today a large arsenal of technologies is available for researchers in industry and academia to generate data in support of a functional link between a given gene and a disease state.

1.2 From Gene to Target

Following a technical assessment of the targets "drugability" (Hopkins and Groom, 2002), the probability to identify small molecule modulators, and technical feasibility target-specific assays are developed to probe the corporate compound collection for meanful leads. Lead discovery in the pharmaceutical industry today still depends largely on experimental screening of compound collections. To this end, the industry has invested heavily in expanding their compound files and established appropiate screening capabilities to handle large numbers of compounds within a reasonable period of time. "High-Troughput-Screening" (HTS) started roughly one decade ago with the introduction of laboratory automation to handle the different assay steps typically performed in microtiter plates. HTS technologies during the last decade have witnessed remarkable developments. Assay technologies have advanced to provide a large variety of various cell-based and biochemical test formats for a large spectrum of disease relevant target classes (Walters and Namchuk, 2003). In parallel, further miniaturization of assays volumes and parallelization of processing have further increased the test throughput. The ultra-high-throughput is required to fully exploit big compound files of >,1million compounds and is performed entirely in 1536-well plates with assay volumes between 5 – 10 ìl. This assay carrier together with fully-automated robotic systems allow for testing in excess of 200,000 compounds per day. The comprehensive substance collection, together with sophisticated screening technologies, have resulted in a clear advantages in lead discovery especially for poorly druggable targets with a poor track record in the past.