JAK inhibitors in the treatment of adult patients with juvenile idiopathic arthritis: a retrospective monocentric experience

Objective This study aims to evaluate the efficacy and safety of JAK inhibitors (JAKi) in a monocentric cohort of adult patients with juvenile idiopathic arthritis (JIA). Methods Patients attending a rheumatology transition clinic were retrospectively included in case of: i) JIA diagnosis according to current classification criteria (1); ii) age ≥18 years and iii) treatment with JAKi for at least 3 months. Results Seventeen adult patients with JIA were treated with JAKi (as first JAKi, 9 patients (52.9%) received tofacitinib and 8 (47.1%) baricitinib). At 3 months after JAKi initiation, 8 patients (47%) achieved a response and 4 patients (23.5%) achieved disease remission (3 patients with baricitinib and 1 with tofacitinib, 37.5% vs. 16.7%, p=0.294). None of those with systemic JIA and enthesitis-related arthritis obtained remission; the remission rate at 3 months was higher, although not significantly, in the oligoarticular subset compared to the polyarticular subset (37.5% vs.20%). Patients with ≤1 active joint involvement at JAKi start had a higher remission rate (50% vs.22.2%). Subjects who achieved remission on JAKi had a significantly lower pre-treatment DAS28-CRP compared to those with still active disease (p=0.010, Mann-Whitney U=4). A pre-treatment DAS28-CRP <3.76 predicted response to JAKi with 100% sensitivity and 84.6% specificity (p=0.023). The remission rate was lower among patients who had been treated with ≥2 biological drugs before JAKi start (9% vs. 66.7%; p=0.05). One patient in concomitant treatment with leflunomide developed severe arterial hypertension. Conclusion JAKi may represent an effective and safe treatment option for adult JIA patients with low/moderate disease activity, particularly in case of oligoarticular involvement.