2.4. Calculation of IC50

The relative half-maximal inhibitory concentrations (IC₅₀) for single and combined BRAFi/MEKi treatment regimens were calculated from the normalized MUH proliferation data using GraphPad Prism 7. For this, the curve-fitting function “non-linear regression” and the option “log(inhibitor) vs. response—Variable slope (four parameters)” were selected, constraining the bottom plateau to be a constant equal to the maximal inhibition value achieved by one of the inhibitor combinations. The highest concentration from all single and combined dabrafenib treatment regimens was omitted, to exclude the “off-target” effects of dabrafenib from the IC₅₀ calculations. Resulting IC₅₀ curves were plotted onto mean values ± SD of normalized MUH proliferation data using GraphPad Prism 7 software. Significance was defined as p < 0.05 based on a two-tailed non-paired t-test.