In drug discovery, clinical candidate compounds are generated through a long process from target discovery to IND-enabling studies for clinical trials. However, the success rate is very low. Therefore, translational research using biomarkers is becoming essential because the biomarkers including pharmacodynamics (PD) markers play important roles in drug development such as target engagement of drug candidates, selection of right patients, selection of right doses, and detection of efficacy. In this seminar, I will introduce the importance of PK/PD/Efficacy and PD evaluation.