Clinical Characteristics and Mechanism Research of Inhibitors of Janus Kinase in the Idiopathic Inflammatory Myopathies

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.