ObjectivesObesity is associated with lower treatment response in patients with rheumatoid arthritis (RA). In patients with obesity, abatacept was suggested as a preferable option to tumour necrosis factor-alpha inhibitors. We aimed to assess the comparative effectiveness of etanercept, infliximab and abatacept, compared with adalimumab, in patients with RA with obesity. Secondarily, we also investigated this in patients with overweight and normal weight for completeness.DesignObservational cohort study.SettingSwiss Clinical Quality Management in Rheumatic Diseases (SCQM) registry (1997–2019).ParticipantsAdult patients with RA from the SCQM registry who received etanercept, infliximab, abatacept or adalimumab as their first biological or targeted synthetic disease-modifying antirheumatic drug were classified based on their body mass index (BMI) at the start of that treatment in three cohorts: obese, overweight, normal weight. They were followed for a maximum of 1 year.ExposureThe study exposure of interest was the patients’ first biological, particularly: etanercept, infliximab and abatacept, compared with adalimumab.Primary and secondary outcome measuresThe primary study outcome was remission within 12 months, defined as 28-joint Disease Activity Score (DAS28) <2.6. Missingness was addressed using confounder-adjusted response rate with attrition correction. Logistic regression was used to compare the effectiveness of etanercept, infliximab and abatacept versus adalimumab. Each BMI cohort was addressed and analysed separately.ResultsThe study included 443 obese, 829 overweight and 1243 normal weight patients with RA. There were no statistically significant differences in the odds of DAS28-remission at ≤12 months for etanercept, infliximab and abatacept, compared with adalimumab, in any of the BMI cohorts.ConclusionsNo differences in DAS28-remission were found between the study drugs and adalimumab as first biologic in patients with RA, independently of the BMI cohort. We did not find evidence that treatment with abatacept increased the likelihood of remission compared with adalimumab among obese patients with RA.