Abstract
BACKGROUND: This study aimed to compare the efficacy and safety of baricitinib in patients with rheumatoid arthritis (RA) receiving different doses based on renal function. METHODS: We conducted a retrospective study within the JAK Study Group, involving 23 facilities in Fukuoka Prefecture, examining patients treated with baricitinib for RA. Patients were categorized into two dose groups: 4 mg with normal/mild renal dysfunction and 2 mg with moderate renal dysfunction. Baricitinib's efficacy, retention rate, and safety were compared between the groups after propensity score matching. RESULTS: After propensity score matching, disease duration, methotrexate dosage, and anti-cyclic citrullinated peptide antibody positivity rate were balanced across 33 patients in both groups. No significant differences were observed between the groups in tender/swollen joint counts, changes in evaluator/patient global assessments, achievement rate of low disease activity, remission rate on clinical/simplified disease activity indices, or retention rate. Additionally, the incidence of adverse events aligned with previous reports, indicating similar drug safety profiles. CONCLUSIONS: Baricitinib 2 mg in RA patients with moderate renal dysfunction showed comparable efficacy and retention rate to 4 mg in patients with normal/mild renal dysfunction. The incidence and types of adverse events were consistent with previous studies, indicating the safety of the drug at these dosages.