RadarScreen is an in vitro genotoxicity screening assay that uses a yeast strain with a RAD54-LacZ reporter construct to detect agents that affect genomic DNA integrity. Compounds are supplied to yeast cells in microplates in the presence or absence of hepatic enzymes, allowing detection of reactive metabolites. Reporter activity is measured by luminescence within 8 hours. The assay has proven sensitive (80%) and specific (77%) for detecting clastogenic and aneuploidy compounds. Combining it with another test leads to 96% sensitivity for mutagenicity and 84% for genotoxicity. RadarScreen is a high-throughput, cost-effective, and user-friendly method to identify genotoxic liabilities

1. reMYND NV, Bio-incubator, Leuven Arenberg Research Park , Gaston Geenslaan 1, B-3001 Heverlee, Belgium, Annick.lauwers@remynd.be; Stefaan.Wera@remynd.be RadarScreen A valuable assay for in vitro genotoxicity screening

2. Lack of specificity and predictivity of the current battery of genotoxicity tests is a major hurdle for pharmaceutical product development. Drug development shows a low overall success rate, mainly related to toxicity issues. Clearly, more predictive in vitro tests for in vivo genotoxicity would significantly reduce the number of animal studies and the cost of preclinical development. Commonly used in vitro genotoxicity screens have serious limitations contributing to high failure rates. For instance, most cell types used have compromised metabolism systems for xenobiotics and are incompatible for using exogenous metabolic activation systems. The high compound concentrations required for most tests also contributes to false positives and thus may not be informative for human risk assessment. Furthermore, many methods measure permanent DNA damage as an endpoint, either in the form of misrepaired DNA, unrepaired damage or fragmented DNA. However, permanent DNA damage only occurs if the conditions are so severe that repair mechanisms have been saturated. To address these issues reMYND has constructed a yeast strain bearing a RAD54 -LacZ reporter construct which is responsive to agents that affect integrity of genomic DNA. Minute amounts of compound are supplied to the yeast cells in a microplate format in the presence or absence of hepatic P450 enzyme-containing microsomal S9 fraction, thus allowing detection of reactive metabolites. After incubation, reporter activity is measured by luminescence. Introduction

3. Luciferase Luciferine + galactose D-luciferin-o- β- galactopyranoside Beta-galactosidase Principle

4. This fully validated screen has proven to detect a broad range of DNA-damaging compounds. Addition of rat liver S9 allows identification of compounds that require metabolic activation. With a sensitivity of 80% and a specificity of 77% for clastogenicity and aneuploidy, RadarScreen is an excellent method for detecting these classes of compounds. Combination of Vitotox and RadarScreen leads to a sensitivity of 96% for mutagenicity and 84% for genotoxicity with a compound selection of the recommended EVCAM list for the validation of new genotoxicity tests. Together with a high throughput set-up, RadarScreen is a user-friendly and cost-effective method for identifying genotox liabilities early on in the drug discovery process. Properties of RadarScreen Highly sensitive and specific Compatible with S9 metabolic activation No quenching of the luminescent signal with the S9 fraction Detection of clastogenic compounds HTS compatible (96/384 well plates) No interference of the compound with the read-out Results within 8 hours Low cost materials and growth media Discussion