This is a randomized, double-blind, placebo-controlled, parallel-group comparison study in subjects with mild to moderate AD. Following a 2-week screening period, subjects will be randomly assigned into one of four treatment arms. Placebo or HL-009 study treatments will be administrated to subjects twice daily for 8 consecutive weeks. After the randomization at Week 0 (Visit 2), subjects will visit their respective trial sites at Weeks 0.5, 1, 2, 4, 6, 8, and 10 (Visits 3, 4, 5, 6, 7, 8, and 9). All study drugs will be in identical laminated tubes to preserve double-blinding of the study.