If low quality data were censored, inequality signs of the standard relation were reversed (Supplementary Table ) unless expressing an approximation with a tilde, in which case the data were dropped. Standard values of low quality data with unassigned pChEMBL values were only considered if they had case insensitive standard type of either GI50, Ki, Kd, IC50, EC50 or XC50 and if standard units denoted molar or mass concentrations. Scaling factors were appropriately applied to standard activity values (Supplementary Table ), mass concentrations were transformed to molar concentrations and log-scale transformation applied to all concentrations. Only exceptions to data with unassigned pChEMBL values were records with derivatives of the following standard types: pKi, pKd, pIC50, pEC50 or pXC50 (Supplementary Table ). For those records, no transformations were applied. Finally, data were flagged on whether activities were derived from IC50, EC50, Ki, Kd or any other data. The preprocessed ChEMBL29 high quality data consisted of 1,097,673 activity values, 549,140 compounds and 4,644 targets, the medium quality data of 489,315 activity values, 263,824 compounds and 2,886 targets, and low quality data of 1,510,494 activity values, 514,302 compounds and 4,711 targets.