A Phase 1/2A, (Part B, participant-, investigator-, and sponsor-blind) study; to investigate the safety, pharmacokinetics, and efficacy (Part B only) of UCB1381 in study participants with moderate to severe atopic dermatitis;(Part B)

This is an early study of a new drug called UCB1381. In the first part of the study, we are looking at increasing doses of the drug when compared to an inactive drug (placebo) when given to healthy participants. In the second part, we will look at the safety and effectiveness of one dose of UCB1381 compared to an inactive drug (placebo) when given to people who have moderate to severe Atopic Dermatitis.