Pos0771 jak inhibitors as treatment of adult patients with pediatric-onset juvenile idiopathic arthritis: a monocentric experience

Background JAK inhibitors (JAKi), small molecules that inhibit the Janus kinase enzymes, are increasingly used to treat children with rheumatologic diseases. Clinical experience of JAKi in the management of adult patients with pediatric-onset rheumatic conditions is still scarce. Objectives The aim of this study consists in evaluating efficacy and safety of JAKi in a monocentric cohort of adult patients with juvenile idiopathic arthritis (JIA). Methods Clinical records of patients attending the rheumatology transition clinic at our centre were retrospectively reviewed; patients were 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 17 patients that met the inclusion criteria were included in this study. Their demographics and clinical features are detailed in Table 1 . 9 patients were treated with tofacitinib (52.9%) and 8 subjects (47.1%) received baricitinib. At 3 months, 4 patients (23.5%) achieved disease remission on JAKi: 3 patients achieving remission were treated with baricitinib and 1 with tofacitinib (37.5 vs. 16.7%, p=0.29). None of the patients 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%; p=1.0). Disease duration, age at onset and at JAKi start were similar between patients achieving remission and those with active disease (p=0.94, p=0.58 and p=0.72, respectively). Patients with ≤1 active joint involvement at JAKi start had higher remission rate (50 vs. 22.2%; p=0.58). Subjects who achieved remission on JAKi had a significantly lower pre-treatment DAS28 compared to those with still active disease (median DAS28 (IQR) 2.17 (1.9-2.4) and 4.54 (3.8-4.9), respectively; p=0.01, Mann-Whitney U=4). A pre-treatment DAS28 <3.76 predicted response to JAKi with 100% sensitivity and 84.6% specificity (AUC 0.88, p=0.02, 95%CI 0.71-1.05). Concomitant treatment with methotrexate did not significantly affect the remission rate (16.7 vs. 37.5%; p=1.0). This was lower among patients who had been treated with ≥2 biological drugs before JAKi start (9 vs. 66.7%; p=0.05). None of the patients developed side effects during JAKi treatment. Conclusion JAKi could represent an effective and safe treatment option for adult JIA patients with low/moderate disease activity, particularly in case of oligoarticular involvement. Reference [1]Petty RE, International League of Associations for Rheumatology classification of juvenile idiopathic arthritis: second revision, Edmonton, 2001. J Rheumatol 2004;31:390–2. Table 1. Demographics and clinical features of enrolled JIA subjects. O-JIA (n=8) P-JIA (n=5) ERA (n=2) S-JIA (n=2) Total cohort (n=17) Age at JIA onset, median (IQR) 4.5 (9) 13 (6) 15 (1) 10 (6) 10 (13) Age at JIA diagnosis, median (IQR) 4.5 (10) 14 (8) 15 (1) 10 (6) 11 (13) Age at starting treatment with JAKi, median (IQR) 28.8 (6.7) 26 (12) 40.8 (1.8) 37 (10) 31 (13.6) Gender (F, %) 75% (6) 100% (5) 100% (2) 50% (1) 83.4% (14) ANA positivity, % (n) 75% (6) 60% (3) 50% (1) 0% (0) 58.8% (10) Disease duration at JAKi start in years, median (IQR) 27.1 (11.2) 18 (3) 26.25 (1.2) 28 (4) 25 (11.3) DAS28 at starting treatment with JAKi, median (IQR) 3.76 (1.07) 5 (1) 4.86 (0.25) 3.0 (1) 4 (1.57) Iridocyclitis, % (n) 50% (4) 20% (1) 0.0 (0) 0.0 (0) 29.4 (5) N of pre-JAKi sDMARDs, median (IQR) 2 (1.0) 2.0 (1.0) 3.0 (2.0) 4.5 (0.5) 3 (2.0) Ongoing MTX, % (n) Median dose (IQR) 12.5% (1) 15mg/wk 60%(3) 10 mg/wk 50%(1) 7,5 mg/wk 50%(1) 7.5 mg/wk 35.2 (6) 15mg/wk Ongoing LEF, % (n) Median dose (IQR) 25%(2) 20%(1) 20mg die 0% (0) 0% (0) 17.6% (3) Ongoing oral steroids, % (n) Median dose (IQR) 0% (0) 40%(2) 10mg die 0%(0) 0% (0) 11.7% (2) N of pre-JAKi bDMARDs, median (IQR) 2.5 (2.25) 3 (2) 5 (1) 2 (2) 2 (2) N of involved joints at JAKi discontinuation, median (IQR) 0.5(0) 1 (2) 4 (1) 1 (1) 1 (2) Days of duration of treatment with JAKi, median (IQR) 324.5 (345) 297(149) 95 (5) 574.5 (513.5) 297 (315) Acknowledgements: NIL. Disclosure of Interests None Declared.