Background In the randomized, phase III, global SELECT-COMPARE study, upadacitinib 15 mg demonstrated efficacy at week 12 versus placebo and adalimumab with methotrexate (MTX) in patients with rheumatoid arthritis and inadequate response to MTX, which was maintained over 48 weeks. This post hoc analysis of SELECT-COMPARE reports the efficacy and safety of upadacitinib in Central and Eastern European (CEE) patients. Methods Patients were randomized 2:2:1 to upadacitinib 15 mg once daily, placebo, or adalimumab 40 mg every other week, and continued MTX. Efficacy and safety were assessed through 48 weeks. Primary endpoints were the achievement of ≥20% improvement in American College of Rheumatology response criteria and Disease Activity Score in 28 joints with C-reactive protein