We named this clinical trial “Efficacy and safety of selective JAK1 inhibitor Filgotinib in active rheumatoid arthritis patients with inadequate response to methotrexate: Comparative study with Filgotinib and Tocilizumab examined by clinical index as well as musculoskeletal ultrasound assessment (TRANSFORM study).” Herein we describe the final study protocol (version 1.4; October 27, 2021). Here, JAK1 is linked to rheumatoid arthritis.