This study aims to explore the clinical characteristics and mechanism of inhibitors of janus kinase in the treatment of idiopathic inflammatory myopathies

The investigators designed a single center, open-label, prospective study. Adults with active idiopathic inflammatory myopathies will be enrolled, meeting the Bohan & Peter Dermatomyositis/Polymyositis(DM/PM) or Rheumatology(ACR) & European allance of associations for rheumatology(EULAR)(2017) diagnostic criteria. Inhibitors of janus kinase including tofacitinib 5 mg once a day or twice a day and baricitinib 2mg once a day or 4mg once a day was administered for 6 months to explore its efficacy and safety, which could help to evaluate inhibitors of janus kinase's clinical characteristics and mechanism. Patients would be evaluated the improvement of clinical and laboratory indexes. Changes of symptoms, immune cell subsets and cytokines were monitored. Symptoms were evaluated by Visual Analogue Scale (VAS) of patient global and physician global, manual muscle testing(MMT-8), the Health Assessment Questionnaire(HAQ), Creatine kinase, Myositis Disease Activity Assessment Tool(MDAAT).

Inclusion Criteria:

• Adults between 18 years and 75 years of age.
• Adults with active idiopathic inflammatory myopathies will be enrolled, meeting the Bohan & Peter DM/PM or American College of Rheumatology(ACR) & European allance of associations for rheumatology(EULAR)(2017) diagnostic criteria.
• Written informed consent should be obtained from each study subject.
• Concomitant immunosuppressive agents or glucocorticoids were allowed, but subjects should have been on these therapies at least 4 weeks and on a stable dose for ≥4 weeks(glucocorticoid doses are lower than <0.5mg/kg/d).
• Consent to use effective contraception during the study (women of childbearing age).

Exclusion Criteria:

Any subject meeting either of the following criteria should be excluded:

• Laboratory abnormality: Hb<8 g/dl or platelet<60*10^9/L, or combined with severe hepatic, renal and cardiac insufficiency;
• Myositis in overlap with another systemic autoimmune rheumatic disorder, cancer-associated myositis, inclusion body myositis or any other non-immune mediated myopathy.
• Biologics such as rituximab are not allowed in the 3-month before enrollment.
• Patients with malignancy within 3 years of screening.
• Patients with hypersensitivity to study drug.
• Active infections(including but not limited to hepatitis, HIV).
• Uncontrolled mental or emotional disorders.