Solute carrier (SLC) transporters present as the loci of important drug–drug interactions (DDIs). Therefore, sponsors generate in vitro half‐maximal inhibitory concentration (IC50) data and apply regulatory agency‐guided “static” methods to assess DDI risk and the need for a formal clinical DDI study. Because such methods are conservative and high false‐positive rates are likely (e.g., DDI study triggered when liver SLC R value ≥ 1.04 and renal SLC maximal unbound plasma (Cmax,u)/IC50 ratio ≥ 0.02), investigators have attempted to deploy plasma‐ and urine‐based SLC biomarkers in phase I studies to de‐risk DDI and obviate the need for drug probe‐based studies. In this regard, it was possible to generate in‐house in vitro SLC IC50 data for various clinically (biomarker)‐qualified perpetrator drugs, under standard assay conditions, and then estimate “% inhibition” for each SLC and relate it empirically to published clinical biomarker data (area under the plasma concentration vs. time curve (AUC) ratio (AUCR, AUCinhibitor/AUCreference) and % decrease in renal clearance (ΔCLrenal)). After such a “calibration” exercise, it was determined that only compounds with high R values (> 1.5) and Cmax,u/IC50 ratios (> 0.5) are likely to significantly modulate liver (AUCR > 1.25) and renal (ΔCLrenal > 25%) biomarkers and evoke DDI risk. The % inhibition approach supports integration of liver and renal SLC data and allows one to generate pan‐SLC inhibition signatures for different test perpetrators (e.g., SLC % inhibition ranking). In turn, such signatures can guide the selection of the most appropriate individual (or combinations of) biomarkers for testing in phase I studies.