(2010) were used, with the endocardial variant of O’Hara et al. (2011) (as this model was primarily parameterised with endocardial data). PyCML was used to convert the CellML format into C++ code (Cooper, Corrias, Gavaghan, & Noble, 2011). The CellML files were tagged with metadata denoting the conductances of interest (Cooper, Mirams, & Niederer, 2011), which results in check details auto-generated methods for changing the channel conductances in the resulting C++ code. The equations were solved using the adaptive time-stepping CVODE solver (Hindmarsh et al., 2005), with relative and absolute tolerances of 10–6 and 10–8 respectively, and a maximum

time step of less than the stimulus duration. Adaptive time-stepping solvers offer significant speed and accuracy improvements over ‘traditional’ fixed time step solvers for numerically stiff systems such as cardiac action potential models. The software is a custom-made program based on the open-source Chaste library (Mirams et al., 2013) and its ApPredict (action potential prediction) module. For the interested reader we have made the following resources

MG-132 available: the IC50 datasets, the action potential simulation software; and the scripts for generating the figures presented in this article. These can be downloaded as a ‘bolt-on project’ for Chaste (written to work with version 3.2) from http://www.cs.ox.ac.uk/chaste/download. Further instructions on downloading and using the code can be found in Supplementary Material S1.3. Calculated free plasma concentrations during the TQT study are given Megestrol Acetate in a separate spreadsheet (Supplementary Material S2), based on data gathered for the Gintant (2011) study. The spreadsheet implements the necessary calculations for calculating molar free plasma estimates from maximum plasma concentration (‘Cmax’), percent plasma binding, and molecular weight. The equations used for calculations are given in Supplementary Material S1.4. The change in QT that was used for comparison

with simulation predictions is the mean change in QTc, at the highest dose tested in the TQT study, as reported in Gintant (2011). In this section we present the results of the ion channel screening, followed by the simulations based upon those screens, and then analyse their predictions of TQT results. Table 1 shows the pIC50 values (–log10 of IC50 values in Molar) fitted to the concentration effect points from each ion channel screen. We also display the manual hERG patch clamp values taken from Gintant (2011), which were collated from regulatory submission document GLP studies (ICH, 2005). Note that an IC50 > 106 μM (or equivalently pIC50 < 0) would indicate a very weak (or no) compound effect on an ion current. When this was the case, we have ‘rounded’ and we show this in Table 1 as pIC50 = 0 for clarity. N.B. using pIC50 = 0 corresponds to just 0.