It is usually beneficial to explore the sensitivity of a selection to the degree of bias chosen before making a final decision. Often, a significant degree of added diversity can be explored for a small decrease in the overall quality of the compounds selected. In this case, it is advisable to spread the risk across diverse compounds, provided synthetic resources permit. Conversely, in some cases, the selection of compounds will remain the same until a large bias toward diversity is selected. In this case, the selection of a diverse set may require an unacceptable decrease in the overall quality of the compounds. As a general rule, at the earlier stages of a project where little is known about the SAR of the target, it is advisable to bias a selection in favour of diversity. Typically a diversity:rank ratio of 80:20 will sample across the extremes of chemical diversity, whilst still ensuring that top scoring compounds are represented within the selection. As the project moves towards the candidate stage, it will become more important to bias the selection towards ‘good’ compounds. In this case a diversity:rank ratio of 20:80 may be more appropriate. Note that a diversity:rank ratio of 100:0 will select molecules on the basis of their structural diversity and the newly selected set will mirror the diversity of the original set (assuming a reasonable sample size of molecules has been selected). A diversity:rank ratio of 0:100 will select molecules entirely on their 'Rank' and the top molecules will be selected.




