This study consists of Screening Period, Observation Period, In-patient Period, and Follow-up Period. Screening assessments will be performed within 28 to 2 days before starting the study treatment, and Observation Period assessments will be performed on a day before starting the study treatment to confirm the eligibility of study subjects. The eligible subjects will be randomized into either E6011 arm or placebo arm using the drug allocation list prepared by the random code statistician. Each subjects dosing interval will be at least a 30-minutes.