Inclusion Criteria:  Demographic and general characteristics:  Adult male or female patients, at least 18 years of age. Able and willing to give written informed consent. Have sufficient knowledge of the Dutch language to be able to comply with the requirements of the study protocol.  Inclusion criteria:  Diagnosis of adult-onset RA as defined by the 2010 ACR/ EULAR Rheumatoid arthritis classification criteria; Diagnosis of RA for ≥ three months; Are being treated ≥ three months with ≥ 1 csDMARD therapy; Have had an inadequate response or intolerance to at least 1 csDMARD; Have moderately to severely active RA to the discretion of the rheumatologist or defined as a DAS28 ≥ 3.2 at screening and baseline visits; Subjects must have been on a stable dose of csDMARD therapy (restricted to methotrexate, chloroquine, hydroxychloroquine, sulfasalazine, or leflunomide) for ≥ 4 weeks prior to the baseline visit.  Exclusion Criteria:  Previous treatment with any biological DMARD or targeted synthetic DMARD/JAKi; Inflammatory rheumatic disease other than RA, except for secondary Sjögren's syndrome. Having a contraindication for either TNFi or filgotinib; Latent or active tuberculosis; Active or recurrent infections; History of any malignancy within 5 years except for successfully treated NMSC or localized carcinoma in situ of the cervix; ≥ 3x upper limit of normal ALT, AST; eGFR ≤ 30 ml/min; planned or actual pregnancy or planning to father a child.