Safety, Tolerability and PK of SHR1314 in axSpA

Inclusion Criteria: 1. Diagnosis of axial spondyloarthritis (axSpA) and fulfilling the 2009 ASAS classification criteria. 2. Have a history of back pain ≥3 months with age at onset \<45 years. 3. Have active axSpA defined as BASDAI ≥4 at screening and baseline. 4. Have objective signs of inflammation by presence of elevated ESR and/or presence of elevated CRP. 5. In the past had an inadequate response to at least 1 or 2 non-steroidal anti-inflammatory drugs (NSAIDS) for duration of 4 weeks or cannot tolerate NSAIDS. 6. If taking NSAIDS be on stable dose for at least 2 weeks prior to randomization. Exclusion Criteria: 1. History of ongoing, chronic or recurrent infectious disease or evidence of tuberculosis infection. 2. Previous exposure to other biologic drug directly targeting Interleukin (IL)-17 or Interleukin (IL)-17 receptor. 3. Total ankylosis of the spine. 4. Have recently received biologics, tumor necrosis factor inhibitors or other immunomodulatory agents within 12 weeks. 5. Have either a current diagnosis or a recent history of malignant disease. 6. Are pregnant or breastfeeding.