Arth Res Ther 2020;22:115 doi.org/10.1186/s13075-020-02199-8This study aimed to characterize temporary interruptions of baricitinib and describe their impact on efficacy and safety. Brief interruptions during phase 3 baricitinib trials were associated with minor increases in symptoms which were resolved following treatment. In life-long, chronic conditions such as RA, interruption of therapy is common for various reasons, such as side effects, non-compliance, or because a patient requires surgery. Concerns have been raised that these treatment breaks could lead to symptom worsening or increase immunogenicity, yet to-date there have been few studies to examine the effect of DMARD interruption and re-treatment in this patient population.Using data from four Phase 3 clinical trials, timing, reason, and duration of investigator-initiated temporary interruptions were analysed alongside PROs from patient diaries. When documenting an interruption, investigators could choose one of four reasons: AE, abnormal laboratory values, suspected pregnancy, or investigator decision. Post hoc analyses investigated changes in symptom scores during interruption and resumption of treatment, and evaluated reoccurrence of AEs or laboratory abnormalities after re-treatment.In total, across the four studies there were 640 interruptions, with 84% subsequently able to restart the study drug. Treatment responses in patients with interruptions were generally similar to those in patients who never interrupted. Diary data suggested that brief interruptions of baricitinib was associated with minor increases in patient-reported symptoms, but these resolved following re-treatment. In patients receiving baricitinib, the most common AE leading to interruption was infection, but most were mild or moderate in severity. This analysis provides useful information for clinicians making treatment decisions in RA.