[Latest findings from the RABBIT register].

Since 2001 rheumatologists throughout Germany have been recruiting patients with rheumatoid arthritis into the biologics register (rheumatoid arthritis: observation of biologics treatment, RABBIT) to investigate the long-term safety and efficacy of modern antirheumatic treatment. Over the past 20 years more than 20,000 patients have been enrolled in the prospective cohort study. This article summarizes the research findings published in 2020/2021, focusing on safety aspects, factors influencing treatment efficacy and patient-reported outcomes. With herpes zoster, facial nerve palsy and psoriasis, several adverse events were investigated that were either reported as a safety signal from clinical trials or through the EudraVigilance database or occurred as a paradoxical reaction under drug treatment. For these events, the influence of biological disease-modifying antirheumatic drug (DMARD) treatment was analyzed. In the publication on herpes zoster, we also considered drug treatment with Janus kinase inhibitors. Severe overweight can influence the success of treatment. There are gender-specific differences and the mode of action of a treatment also determines whether obesity reduces the response to treatment. The majority of patients observed in RABBIT were satisfied with the treatment they have received after 1 year. We were able to show which factors either favor or negatively influence satisfaction with the effectiveness and safety of the treatment. This review article shows that long-term observational studies such as the RABBIT register contribute to the understanding of treatment risks and can identify factors that influence the effects of treatment even after two decades of data collection.