A Study Evaluating APG777 in Atopic Dermatitis

Inclusion Criteria: * Have a diagnosis of AD that has been present for \>=1 year prior to the Screening visit * Moderate-to-severe AD at Screening and Baseline visits * History of inadequate response to treatment with topical medications, or medical determination that topical therapies are inadvisable * Applied a stable dose of non-medicated over-the-counter emollient/moisturizer of their choice on their skin for \>=14 days prior to Baseline visit and agrees to continue using the same moisturizer throughout the study except the day of the study visits. * Have completed itch questionnaires in the electronic diary for \>=4 of 7 days prior to Baseline visit Exclusion Criteria: * Participation in a prior study with APG777. * Prior treatment with protocol-specified monoclonal antibodies (mAbs) * Has used any AD-related topical medications within 7 days prior to Baseline visit. * Has used systemic treatments (other than biologics) and/or phototherapies and/or laser therapy that could affect AD within 4 weeks prior to Baseline visit Note: Other protocol defined inclusion/exclusion criteria may apply.