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Poster
66

Evaluating tight binding small molecule inhibitors using the Morrison equation

Authors

E Godsman1; M Ferdinand1; C Pedder1
1 Cancer Research Horizons, UK

Discussion

Authors

E Godsman1; M Ferdinand1; C Pedder1
1 Cancer Research Horizons, UK

Discussion

Generating accurate potency data is crucial for driving structure-activity relationship (SAR) work in drug discovery. This project is focused on a NAD+-dependent EnzymeX. The current biochemical SAR is centred on determining compound IC50s, but issues with tight binding compounds have highlighted the Morrison equation as an alternative way to analyse concentration response (CR) data. This can provide a more appropriate potency indicator: a compound Kiapp value. The NADH-Glo Detection System was used to monitor the activity of EnzymeX, whilst publicly available tool compounds were used as a chemical starting point. These compounds were found to be highly potent, and it was difficult to differentiate their potencies at the bottom of the assay. In optimisation, it was possible to reduce the concentration of enzyme used from 500 nM to 100 nM: requiring protocol changes such as increasing the temperature and timescale the reaction was run at. Whilst this reduced the bottom of the assay, tight binding compounds were still an issue. Instead of practical optimisation, it was decided that altering the way data was analysed would be more beneficial, and so Kiapp values were determined using the Morrison equation. This was the first time Kiapp values had been generated in SAR screening in the group. Therefore, thorough testing was required to establish if the Morrison analysis would be useful for pushing forwards chemistry. This included comparing pIC50 and pKiapp data; optimising the screening format for compounds; and looking at the correlation between biochemical and cell biomarker data. Through our work, we have shown how Kiapp values can benefit SAR efforts and we will be implementing automated Morrison analysis for EnzymeX CR data, as well as future projects.