Drug retention rate of Janus kinase inhibitors in patients with rheumatoid arthritis: the KEIO-RA cohort study

This study aimed to investigate the effectiveness and safety of Janus kinase inhibitors (JAKis) in patients with rheumatoid arthritis (RA) in the real world. All consecutive patients with RA from the KEIO-RA cohort who had received a JAKi from July 2013 to June 2023 were included. We assessed drug retention rates, factors associated with retention, disease activity, and adverse events. In total, 294 treatment courses in 201 patients were analyzed. The mean drug continuation duration was 17.2 ± 17.4 months. Full-dose JAKi use and concomitant methotrexate (MTX) use were associated with higher retention rates (<i>p</i> < 0.001 and <i>p</i> = 0.03, respectively). Combination therapy with full-dose JAKi and MTX showed a significantly lower discontinuation rate due to lack of efficacy (<i>p</i> = 0.02), with no increase in safety issues. This pattern was observed across age groups and difficult-to-treat status, though residual confounding cannot be excluded. When comparing retention across five JAKi formulations among patients receiving full-dose JAKi with concomitant MTX, upadacitinib and filgotinib showed significantly lower discontinuation rates due to lack of efficacy (<i>p</i> = 0.04), whereas baricitinib had a lower discontinuation rate due to safety issues (<i>p</i> = 0.01). In conclusion, combination therapy with full-dose JAKi and MTX showed higher retention in this cohort.