Comparison of Oral Administration of a JAK Inhibitor in Rheumatoid Arthritis

Inclusion Criteria: * Patient aged over 18 years * Patient with Rheumatoid Arthritis according to the 2010 ACR/EULAR criteria * Patient meeting the criteria for initiation of a JAK inhibitor according to the marketing authorization and international recommendations * Patient capable of providing informed, written, dated, and signed consent before the start of any trial-related procedure. Exclusion Criteria: * No contraindication to a bDMARD * Not stable dose of corticosteroids in the 4 weeks preceding enrollment * Not stable dose of maintenance therapy (methotrexate, leflunomide, hydroxychloroquine, cyclosporine, gold salts) in the 4 weeks preceding enrollment * Prior treatment with a JAK inhibitor * Patient unable to be followed-up in the study during 6 months * Minors or adults under guardianship or curatorship, or deprived of their liberty * Pregnant or breastfeeding patient * Patient refusing to use an effective method of contraception for the duration of the study * Person not affiliated with a social security scheme.