A Single-ascending Dose (Part A) and Repeat-dose (Part B) Study to Investigate the Safety, Pharmacokinetics and Efficacy (Part B Only) of UCB1381 in Healthy Study Participants (Part A) and in Study Participants With Moderate to Severe Atopic Dermatitis (Part B)

A Phase 1/2A, Randomized, Placebo-Controlled, Single-Ascending Dose (Part A, Participant- and Investigator-Blind) and Repeat-Dose (Part B, Participant-, Investigator-, and Sponsor-Blind) Study to Investigate the Safety, Pharmacokinetics, and Efficacy (Part B Only) of UCB1381 in Healthy Study Participants (Part A) and in Study Participants With Moderate to Severe Atopic Dermatitis (Part B)