A Study to Evaluate ABT-494 (Upadacitinib) in Adults With Moderate to Severe Atopic Dermatitis

* Atopic dermatitis with a diagnosis confirmed by a dermatologist (according to the Hanifin and Rajka criteria) and onset of symptoms at least 1 year prior to Baseline. * Moderate to severe atopic dermatitis defined by an Eczema Area and Severity Index (EASI) ≥ 16, body surface area (BSA) ≥ 10% and an Investigators Global Assessment (IGA) score ≥ 3 at the Baseline visit. * Documented history (within 1 year prior to the screening visit) of inadequate response to treatment with topical corticosteroids (TCS), or topical calcineurin inhibitors (TCI), or for whom topical treatments are otherwise medically inadvisable (e.g., because of important side effects or safety risks). * Twice daily use of an additive-free, bland emollient for at least 7 days prior to Baseline.

* Prior exposure to any systemic or topical Janus kinase (JAK) inhibitor (including but not limited to tofacitinib, baricitinib, ruxolitinib, and filgotinib). * Treatment with topical corticosteroids (TCS), topical calcineurin inhibitors (TCI), prescription moisturizers or moisturizers containing additives such as ceramide, hyaluronic acid, urea, or filaggrin within 10 days prior to the Baseline visit. * Prior exposure to dupilumab or exposure to systemic therapies for AD including corticosteroids, methotrexate, cyclosporine, azathioprine, phosphodiesterase type 4 (PDE4)-inhibitors and mycophenolate mofetil within 4 weeks prior to Baseline. * Prior exposure to any investigational systemic treatment within 30 days or 5 half-lives (whichever is longer) of the Baseline visit or is currently enrolled in another clinical study.