Efficacy and Safety Study of Jaktinib in Subjects With Active Ankylosing Spondylitis(AS)

Inclusion Criteria: * Participants must be able to understand the study and signed the informed consent. * 18-65 years, male or female. * Participants with a clinical diagnosis of ankylosing spondylitis (AS), and radiologic evidence (x-ray) fulfilling the Modified New York criteria for AS(1984). * Participants must have baseline disease activity as defined by having a Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score ≥ 4 and a Patient's Assessment of Total Back Pain score ≥ 4 based on a 0 - 10 Numeric Rating Scale (NRS) at the Screening and Baseline Visits. * Participants may be receiving the following Disease-Modifying Anti-Rheumatic Drugs(DMARDs) at the time of the screening visit. These medications should be continued throughout the entire study and doses should remain unchanged. * Participants has had an inadequate response to at least two Nonsteroidal Anti-inflammatory Drugs (NSAIDs) over an at least 4-week period in total at maximum recommended or tolerated doses, or participant has an intolerance to or contraindication for NSAIDs. * Participants who are regularly taking NSAIDs (including COX-1 or COX-2 inhibitors) as part of their AS therapy are required to be on a stable dose for at least 2 weeks before randomisation. * Participants receiving non-prohibited concomitant medications for any reason must be willing to stay on a stable regimen as defined in the protocol. Exclusion Criteria: * History of known or suspected complete ankylosis of the spine.…