Long-term effectiveness and safety of baricitinib treatment on refractory or severe juvenile dermatomyositis

Objective The objective of this study was to evaluate the long-term effectiveness and safety of baricitinib (BAR) add-on therapy for refractory or severe juvenile dermatomyositis (rsJDM) in a practical, real-world setting. Methods In this single-centre retrospective study, 27 children with rsJDM and poor response to corticosteroids (CS) and immunosuppressants were treated with BAR. Disease activity was assessed via physician global assessment of overall disease activity (PhyGloVAS), the childhood myositis assessment scale (CMAS), manual muscle testing-8 (MMT-8), and the disease activity score (DAS). Disease response was determined according to the PRINTO criteria at 0, 6, 12, 24, and 36 months after the initiation of BAR treatment. Results Over an average follow-up period of 25.1 months (ranging from 12 to 58 months), 77% of patients (21 out of 27) experienced improvement in skin rashes, with complete resolution in 62% of patients. Analysis of the median values revealed a significant decrease in the DAS of the skin at 12 months (6.0 vs 0.8, p< 0.01). Furthermore, the CMAS score significantly increased at 12 months (40.5 [30.8, 45.0] vs 52.0 [50.0, 52.0], p< 0.05), and the MMT-8 score also notably increased at 12 months (66.0 [47.8, 72.3] vs 79.0 [79.0, 80.0], p= 0.004) Last observation for the three patients who did not respond was carried forward for their month 12 data. Over the course of the 36-month follow-up, a total of 70% of patients (19 out of 27) achieved inactive disease inactive disease (ID), with a reduction in CS dosage from baseline (0.50 [0.34, 0.89] mg/kg/d) to (0 [0, 0.10] mg/kg/d) at 36 months (p< 0.001). One-third of patients (9 out of 27) discontinued CS treatment. The percentage of patients who achieved ID was 48.1% (13/27), 70.8% (17/24), 90.0% (18/20), and 92.3% (12/13) at the 6-, 12-, 24-, and 36-month observation points, respectively. Radiographic analysis revealed an improvement in calcinosis in one patient, while stabilization was observed in two others. Interstitial lung disease improved in three patients and stabilized in three others. Macrophage activation syndrome was resolved in two patients. One patient required hospitalization and temporary cessation of BAR due to herpes zoster virus infection. There were no deaths or anyone who had to permanently discontinue baricitinib due to an adverse event. Conclusions We demonstrated the general long-term effectiveness and safety of BAR treatment in patients with rsJDM over a follow-up period of 36 months.