A Study to Assess the Efficacy and Safety of PG-011 Gel in Adolescents and Adults With Atopic Dermatitis

This is a Multicenter, Randomized, Double-blind, Placebo-controlled seamless and adaptive-designed phase IIb/III study to Assess the Efficacy and Safety of topical use of PG-011 Gel in adolescents and Adults With Atopic Dermatitis. It consists of phase IIb and phase III parts, phase IIb is a dose-ranging part and has been done, and phase III is a pivotal study part which is registered this time. The goal of this phase III clinical trial is to learn if PG-011gel works to treat mild to moderate Atopic Dermatitis in adolescents and adults by topical use. It will also learn about the safety of PG-011gel. Investigators will compare PG-011gel to a placebo (a look-alike substance that contains no drug) to see if PG-011gel works to treat mild to moderate Atopic Dermatitis. Participants will: * Use PG-011gel or a placebo twice daily for initial 8 weeks, and followed by using PG-011 gel for all of the participants till 52-week. * Visit the clinic at weeks 1, 2, 4 and 8 for checkups and tests, and followed by visiting the clinic every 4 weeks till 52-week. * Keep a diary of their symptoms.