Precision medicine approach has a potential to ensure optimum efficacy and safety of drugs at individual patient level. Physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) models could play a significant role in precision medicine by predicting interindividual variability in drug disposition and response. In order to develop robust PBPK/PD models, it is imperative that the critical physiological parameters affecting drug disposition and response are precisely characterized alongwith with their variability. Currently used PBPK/PD modeling software, e.g., Simcyp and Gastroplus, encompass information such as organ volumes, blood flows to organs, body fat composition, glomerular filtration rate, etc. However, the information on the interindividual variability of the majority of the proteins associated with PK and PD, e.g., drug metabolizing enzymes (DMEs), transporters and receptors, are not fully incorporated into these software. Such information is significant because the population factors (e.g., age, genotype, disease and gender), can affect abundance or activity of these proteins. To fill this critical knowledge gap, mass spectrometry (MS)-based quantitative proteomics has emerged as an important technique to characterize protein abundance of DMEs, transporters and receptors across the population. Integration of these quantitative proteomics data into in silico PBPK/PD modeling tools will be crucial toward precision medicine.