Screening period is defined as the interval between the day of obtaining informed consent and the day of the baseline visit (0-30 days). The investigator performs a screening examination after obtaining informed consent from the subject's legal guardian (and, if possible, after obtaining consent from the subject).~Assessment period (treatment period) is defined as the period between the day of baseline visit and the end of Week 4 visit (or the end of withdrawal visit). Subjects who meet the inclusion criteria and do not meet the exclusion criteria at the baseline visit will be assigned to receive 0.3% or 1% OPA-15406 ointment or comparator (vehicle [Placebo]). The allocated IMP will be administered to the treatment area from the day of baseline visit twice-daily for 4 weeks. After the baseline visit, examinations will be performed at Weeks 1, 2, and 4. If a subject discontinues the IMP administration between the day of baseline visit and the day of the Week 4 visit, a withdrawal visit will be performed for that subject~Trial period The trial period for an individual subject is the period from the day of obtaining the written informed consent from the subject's legal guardian to the day of the Week 4 visit or withdrawal visit. For subjects who miss the Week 4 visit or withdrawal visit, the termination date, will be the date, as determined by the investigator, when the subject is withdrawn from the trial. The trial period does not include a follow-up period for AE.
A multicenter, randomized, double-blind, vehicle-controlled, parallel group trial to demonstrate the superiority of 0.3% and 1% OPA-15406 ointment to vehicle in pediatric subjects with AD. This trial consists of the 0.3% OPA-15406 group, the 1% OPA-15406 group, and the vehicle group.