The recent drug discovery process has been shifted from screening of natural and synthetic products for pharmacologically active materials to designing and synthesizing pharmacologically active materials based on the structure of a target molecule as a cause of relevant disease. To facilitate the drug discovery process, efficacy and possible side effects are simultaneously evaluated both in vitro and in vivo in the preclinical studies, and furthermore biomarkers or surrogate markers are identified and monitored to evaluate both efficacy and side effects in the Phase I clinical study. Pharmaco-pathological approaches at protein/glycoprotein and gene expression levels are often required for making a fair judgment on Go/No-Go decision of the project in the early stages of drug discovery research and development. 

For instance, the judgement of positive or false positive in cancer diagnosis solely depends on histological examination by pathologists. However, oncogene expression levels are often not considered during the pathological examination, which might mislead us into unfavorable results and conclusion. To achieve the accuracy of pathological judgment on the biopsy samples, pharmaco-pathological approaches are required. We will discuss current and future roles of pharmaco-pathologists in the drug discovery and development especially for cancer diagnosis and therapy.