The Real-World Effectiveness, Persistence, Adherence, and Safety of Janus Kinase Inhibitor Baricitinib in Rheumatoid Arthritis: A Long-Term Study.

: Baricitinib (BAR) is the first oral selective Janus kinase inhibitor approved in Europe for rheumatoid arthritis (RA). Real-world data are still needed to clarify its long-term benefits/risk profile. This study aimed to evaluate the effectiveness, persistence, adherence, and safety of BAR in a real-world setting. : An ambispective study was conducted between October 2017 and December 2021 in RA patients starting BAR. The effectiveness was evaluated, assessing changes from the baseline of the Disease Activity Score using 28-joint counts-C reactive protein (DAS28CRP), and the achievement of low disease activity/remission. Drug persistence was evaluated using Kaplan-Meier analysis. Adherence was estimated using the medication possession ratio (MPR) and the 5-item Compliance Questionnaire for Rheumatology. Safety was assessed determining global incidence proportion and adverse event adjusted incidence rates. : In total, 61/64 recruited patients were finally analyzed, 83.6% were female, 78.7% were seropositive, the mean age was 58.1 (15.4) years, and the disease duration was 13.9 (8.3) years. A total of 32.8% of patients were naïve to biologics and 16.4% received BAR as monotherapy. The median exposure to BAR was 12.4 (6.6-31.2) months (range 3.1-51.4). A significant change in DAS28CRP was observed after treatment (difference -1.2, = 0.000). 70.5% and 60.7% of patients achieved low disease activity or remission, respectively, and 50.8% (31/61) remained on BAR throughout the follow-up, with a median persistence of 31.2 (9.3-53.1) months. The average MPR was 0.96 (0.08) and all patients exhibited "good adherence" according to the questionnaire. In total, 21.3% of patients discontinued baricitinib due to toxicity. : In our real-world practice, BAR demonstrated effectiveness, large persistence, high adherence to treatment, and an acceptable safety profile.