Treatment of Axial Spondyloarthritis by Recombinant Human Tumor Necrosis Factor-α Receptor Ⅱ IgG Fc Fusion Protein

Inclusion Criteria:

* Fulfill the 2009 ASAS criteria for axial spondyloarthritis(SpA), and without bilateral more than grave 2 or unilateral more than grave 3 sacroilitis on X ray plan
* Active disease phase of SpA, defined as BASDAI≥4 or ASDAS≥2.1
* Inadequate response to NSAID≥4 week
* Application of NSAID with stable dose for no less than 2 weeks
* Stable dose of prenisone for at least four weeks at ≤10mg per day if used at screening, or stop use for at least 4 weeks.
* Stable dose of any DMARD for at least four weeks if used at screening, or stop use for at least 4 weeks
* Stop and receiving washing out for at least 4 week if receiving Chinese traditional drug for AS, physical treatment, vaccication or IVIG.
* The lab exam should achieve the criteria as below: Hb≥85g/L, 3.5×109/L≤WBC count≤10×109/L, PLT≥ lower limit of normal range, ALT≤2 fold of upper limit of normal range, serum creatine ≤upper limit of normal range.
* Negative pregnacy test for female patients. And promise to carry out contraception during the trial and 6 weeks after the trial is ended.
* Sign the informed consent.

Exclusion criteria:

* Previous application of any biologic agents.
* Allergic to any element of Yisaipu®
* Intolerance to NASID.
* History of active tubercolosis, or radiographic evidence of present or previous history of pulmonary tubercolosis, or close contact with patients with tubercolosis, or with high risk of infection of tubercolosis such as immune suppression status, or strong positive of PPD skin test with diameter ≥10mm.
* Presence of acute infection or acute onset of chronic infection at screen.
* Invasive fungal infection or conditional infection within 6 months prior to screen.
* Present or history of serious liver disease.
* History of infection on artifitial joints.
* Organ transplantation surgery within 6 months prior to screen.
* Presence of other autoimmune diseases, including IBD, psoriasis, uveitis, SLE, multiple sclerosis, etc.
* History of congestive heart failure.
* History of malignancies within 5 years prior to screen, excluding complete resection of squamous cell carcinoma, or basal cell carcinoma or cervical carcinoma in situ.
* AIDS or HIV infection.
* History of lymphoma or lymphoproliferative disorders.
* Presence of serious disorder of important organs or system.
* Presence of factors which may influence the compliance.