The purpose of this study is to assess the safety, tolerability, PK, PD, immunogenicity, and preliminary clinical activity of Cizutamig in patients with Generalized Myasthenia Gravis.

This is a Phase 1b, open-label, multicenter study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity, and preliminary clinical activity of cizutamig in patients with Generalized Myasthenia Gravis.

Inclusion Criteria:

1. At least 18 years old at the time of signing the Informed Consent Form (ICF);
2. Diagnosed with MG, classified as MGFA Class II-IVa, and judged by the investigator as unlikely to require respiratory support during the study;
3. At screening, the Myasthenia Gravis Activities of Daily Living (MG-ADL) score ≥ 5, with non-ocular items accounting for ≥ 50% of the total score, and GMG ≥ 11;
4. Inadequate response to conventional therapies or lack of effective treatment options, defined as disease recurrence or progression despite treatment with corticosteroids, immunosuppressants (e.g., azathioprine, mycophenolate mofetil, tacrolimus, cyclosporine A, methotrexate), or biologics (e.g., rituximab), and/or lack of effective treatment methods.

Exclusion Criteria:

1. Any history of CAR-T or TCE therapy targeting any antigen or BCMA-targeted therapy;

2. Use of any approved immunosuppressive drugs not listed here within 12 weeks or 5 half-lives (whichever is longer) before screening, unless approved by the medical monitor;

3. Participation in any investigational trial involving non-biological agents within 4 weeks or 5 half-lives (whichever is longer) of the investigational product (IP) before screening;

4. Participation in any investigational trial involving biological agents within 12 weeks or 5 half-lives (whichever is longer) of the IP before screening;

5. Administration of live vaccines within 4 weeks before screening;

6. History of progressive multifocal leukoencephalopathy;

7. History of primary immunodeficiency (e.g., hypogammaglobulinemia) or hereditary complement deficiency;

8. Presence of one or more significant concurrent diseases, as judged by the investigator, including but not limited to:

   1. Poorly controlled diabetes
   2. Chronic kidney disease stages IIIb, IV, or V
   3. Severe chronic pulmonary disease (e.g., requiring supplemental oxygen) or respiratory failure

9. Any severe medical condition or clinically significant laboratory abnormality that, in the judgment of the investigator or medical monitor, would compromise the patient's safe participation and completion of the study or may affect protocol compliance or interpretation of study results.