Safety and Efficacy of Allogeneic Bone Marrow MSCs in Ankylosing Spondylitis

The goal of this clinical trial is to learn if allogeneic human bone marrow-derived mesenchymal stem cells (CG-BM1) are safe and show preliminary efficacy in treating patients with ankylosing spondylitis (AS). It will also explore the appropriate dose of CG-BM1. The main questions it aims to answer are: What medical problems (adverse events) do participants have when taking CG-BM1? (Safety and tolerability) Does CG-BM1 improve disease activity, pain, and function in patients with AS? (Preliminary efficacy) Researchers will compare CG-BM1 to a placebo (an inactive substance that looks like CG-BM1) in the second phase of the study to see if CG-BM1 works for AS. This study has two phases: Phase 1 (dose-escalation): Open-label, single-arm. Participants will receive one of three escalating doses of CG-BM1 weekly for 4 weeks. Phase 2 (dose-expansion): Randomized, double-blind, placebo-controlled. Participants will receive either the recommended dose of CG-BM1 or a placebo weekly for 4 weeks, in addition to standard background therapy (celecoxib). Participants will: Receive CG-BM1 or placebo via intravenous infusion once a week for 4 weeks Visit the clinic for follow-up assessments at Week 1, 4, 8, 12, and 24 after the first infusion Undergo physical exams, laboratory tests (blood and urine), and complete questionnaires about disease activity, pain, and function (e.g., BASDAI, VAS, ASAS response criteria)