During the study period, a subject may be hospitalized to facilitate the collection of blood samples for pharmacokinetic (PK)/pharmacodynamic (PD) analysis. Hospitalization itself will not be considered as a serious adverse event if no adverse event occurs. PK/PD analysis and safety assessments will be conducted for each cohort. The Data Safety Monitoring Board (DSMB) and Data Monitoring Committee (DMC) will be operated after the end of Cohorts 1 to 4. These committees will monitor the PK/PD and safety data from each cohort to determine the continuation of next cohort (Cohorts 2 to 5), target dose, and blood sampling period for PK/PD (including timing of collection). Additional subjects may be enrolled in all cohorts or cohorts may be canceled depending on the results of PK/PD analysis.