This study is to evaluate the efficacy and safety of different doses of JAK1 inhibitor SHR0302 in subjects with moderate to severe active rheumatoid arthritis who had inadequate response to conventional synthetic DMARDs.

Inclusion Criteria:

• Provide signed informed consent.
• RA diagnosis consistent with the 2010 ACR/EULAR criteria;
• Moderate to severe RA defined by 6 or more tender joints, 6 or more swollen joints (68- or 66-joint count), and an ESR of 28 mm/h or greater or a CRP level greater than 5mg/L.
• Subjects were required to have an inadequate response to treatment with csDMARDs before baseline.
• If subjects are taking permitted csDMARDs or low-dose corticosteroid orally at baseline , the stable doses should have lasted for more than 4 weeks already.
• BMI ≥18 kg/m2

Exclusion Criteria:

• Pregnant women or refuse to receive contraception during the study.
• Lab abnormality within 4 weeks of randomization as follows: WBC count <3.0×10^9/L；neutrophil count<1.5×10^9/L;hemoglobin level<90.0 g/L ; platelet count <100×10^9/L; AST or ALT levels greater than the upper limit of normal; HBsAg or HCV or HIV antibody positivity.
• History of another autoimmune rheumatic disease ; history of cancer or infection including tuberculosis and hepatitis; history of important cardiovascular events or thrombotic diseases.
• Previous treatment with JAK inhibitor or cytotoxic drugs; bDMARDs within 6 months of randomization; other strong immunosuppressants within 3 months of randomization.