Effectiveness and Continuation Rate of Half-dose Janus Kinase Inhibitors in Patients with Rheumatoid Arthritis

Objective: To assess the effectiveness and continuation rate of half-dose Janus kinase (JAK) inhibitors in patients with rheumatoid arthritis (RA). Methods: We conducted a retrospective cohort study of 212 patients who initiated JAK inhibitors at our hospital (standard-dose group: 142; half-dose group: 70). Among 141 patients who continued the same dose for more than 6 months (standard-dose: 99; half-dose: 42), propensity score matching was performed based on age, disease duration, sex, number of prior biologics/JAK inhibitors, baseline CRP, CDAI, glucocorticoid dose, methotrexate dose, and mHAQ score. Matched groups (37 per group) were compared for CRP, CDAI, and mHAQ at 6 months and for changes from baseline. Reasons for discontinuation were analysed in 71 patients who discontinued treatment within 6 months. Results: At 6 months, the half-dose group showed significantly higher CRP levels and less improvement in mHAQ scores than the standard-dose group. No significant differences were observed in CDAI or other parameters. Discontinuation due to insufficient effectiveness was significantly more frequent in the half-dose group, whereas discontinuation due to adverse events did not differ between groups. Conclusions: Compared with standard-dose therapy, half-dose JAK inhibitors are associated with reduced effectiveness and higher discontinuation rates owing to insufficient clinical response.