Study to Evaluate the Efficacy and Safety of Oral Difelikefalin as Adjunct Therapy to a Topical Corticosteroid for Moderate to Severe Pruritus in Subjects With Atopic Dermatitis

Part A of this study includes a 12-week Double-blind Treatment Period and a 52-week Open-label Extension Period. Subjects will be randomized to receive oral difelikefalin 0.25 mg tablets BID plus TCS cream, difelikefalin 0.5 mg tablets BID plus TCS cream, placebo tablets BID plus TCS cream or placebo tablets BID plus vehicle cream. Part B of this study includes a 12-week Double-blind Treatment Period and 52-week Open-label Extension Period. Subjects will be randomized to receive oral difelikefalin 0.25 mg or 0.5 mg tablets BID plus TCS cream or oral placebo tablets BID plus TCS cream. Part A results at week 12 will inform Part B. Subjects who participated in Part A of the study may not participate in Part B. All subjects will sign an informed consent form (ICF) and undergo screening for study eligibility.