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BackgroundInflammatory myopathies are heterogeneous with variable clinical course and prognosis [1]. Despite conventional treatment, some patients are refractory [2].ObjectivesTo describe the efficacy and safety of JAK inhibitors (JAKi) in patients with refractory dermatomyositis (DM).MethodsRetrospective analysis of 6 patients with active DM, refractory to previous immunosuppressive treatment including methotrexate, rituximab, mycophenolate mofetil, cyclophosphamide and intravenous immunoglobulin. Demographical, clinical characteristics, outcomes and adverse events after JAKi administration were recorded.Results83.3% of the patients were women, with mean age 62.4±10.9 years. All patients had long-standing disease with mean disease duration 9±8.1 years. Three patients were seropositive: one with positive anti-MDA5 antibodies, one with association of anti-Jo1 and anti-Ro52 antibodies and the latter with positive anti-Ro52 antibodies. The most frequently used JAKi was upadacitinib (50%), followed by tofacitinib (33.3%) and baricitinib (16,6%). Mean daily dose of corticosteroids at baseline was 8. 5mg.Prior to treatment with JAKi, mean muscle strength was 108±35, with mean CPK levels of 997±2244. Four patients had active skin rash. After a mean follow-up period of 7.6 months, all four patients with persistent skin involvement had clinical response (MMT-8=127±30). Muscle strength was improved in 4 patients (66.6%). Of note, the two patients that did not respond to JAKi were seronegative with marked muscular atrophy. One patient discontinued treatment due to severe thrombocytopenia. No other adverse events were recorded.ConclusionIn this case series, JAKi treatment resulted in clinical improvement in seropositive patients with longstanding, refractory DM with acceptable safety profile. Prospective data are necessary to confirm these preliminary findings and define the subset of DM patients most likely to benefit from JAKi treatment.References[1]Lundberg, I.E., Fujimoto, M., Vencovsky, J. et al. Idiopathic inflammatory myopathies. Nat Rev Dis Primers 7, 86 (2021).[2]Oddis CV, Aggarwal R. Treatment in myositis. Nat Rev Rheumatol. 2018 May;14(5):279-289. doi: 10.1038/nrrheum.2018.42. Epub 2018 Mar 29. Erratum in: Nat Rev Rheumatol. 2018 Oct;14(10):619.Acknowledgements:NIL.Disclosure of InterestsNone Declared.