Inclusion Criteria:  Diagnosis of MG with anti-AChRantibody. MGFA Clinical Classification Class II, III, or IV. MG-ADL score of 5 or greater at screening and at randomization with > 50% of this score attributed to non-ocular items. QMG score of 11 or greater.  Subjects must be on:  Cholinesterase inhibitor, with no dose increase within 4 weeks prior to randomization; Corticosteroids, with no dose increase within 4 weeks prior to randomization; or/and c. non-steroidal IST (including azathioprine, mycophenolate mofetil, tacrolimus, cyclosporine A), with continuous use for at least 6 months prior to randomization and no dose increase within 4 months prior to randomization.  Exclusion Criteria:  Participants had clinically relevant active infections (such as sepsis, pneumonia, or abscess) or severe infections (resulting in hospitalization or requiring antibiotic treatment) in the 4 weeks before randomization; Those with a history of high-risk tuberculosis infection, acquired tuberculosis infection, and chronic hepatitis; Human immunodeficiency virus (HIV) infection; Thymomas that have received thymectomy or planned thymectomy during RCP within 6 months before randomization, or require chemotherapy and/or radiotherapy at any time; Received rituximab treatment in the past 6 months before randomization; Received tocilizumab or eculizumab treatment within 3 months before randomization; Received IVIG or plasma exchange within 4 weeks before randomization; Unresected thymoma. History of other tumor diseases.