This clinical trial aims to evaluate the safety and efficacy of ripertamab in patients with neuromyelitis optica spectrum disorders (NMOSD). The key research objectives are as follows:

1. To assess the efficacy of ripertamab for the treatment of neuromyelitis optica spectrum disorders.
2. To assess the safety of ripertamab for the treatment of neuromyelitis optica spectrum disorders.

Study participants are required to:

Receive a single intravenous infusion of ripertamab. Attend follow-up examinations and laboratory tests at the study site at Week 1, Week 9, Week 17, Week 25, Week 33, Week 41, Week 49, Week 57, Week 65, Week 73, Week 81, Week 89, Week 97.

Maintain a daily symptom diary and record the number of rescue treatments.

Inclusion Criteria:

- 1. Age ≥ 18 and ≤ 75 years at screening. 2. Definite diagnosis of NMOSD. 3. Expanded Disability Status Scale (EDSS) score ≤ 7.0. 4. At least 1 NMOSD relapse requiring rescue treatment within 1 year prior to screening; or at least 2 NMOSD relapses requiring rescue treatment within 2 years prior to screening (including the initial episode).

5. Voluntarily sign the informed consent form. 6. Female patients of childbearing potential must have a negative pregnancy test (serum β-HCG). Effective contraception shall be used during the study period and for 6 months after treatment discontinuation.

Exclusion Criteria:

• 1. Any condition that, in the investigator's opinion, may interfere with the evaluation or administration of the study drug, assessment of patient safety, or interpretation of study results.

  2. Presence of any uncontrolled active infection or severe infection within 8 weeks prior to the screening period.

  3. Treatment with rituximab or any B-cell depleting agents within 6 months before screening (subjects with CD19+ or CD20+ B-cell counts above the lower limit of normal are eligible for enrollment).

  4. Use of tocilizumab, eculizumab, mitoxantrone, or alkylating agents such as cyclophosphamide within 3 months prior to the first dose administration.

  5. Use of immunosuppressants other than glucocorticoids within 1 month prior to the first dose administration, including but not limited to azathioprine, mycophenolate mofetil, tacrolimus, cyclosporine, methotrexate.

  6. Receipt of plasma exchange (PE), moderate-volume blood transfusion, or immunomodulatory agents such as interferon beta, interferon gamma, or intravenous immunoglobulin (IVIG) within 1 month prior to the first dose administration.

  7. Coexisting other chronic active immune system diseases requiring treatment with glucocorticoids, biologics or immunosuppressants (e.g., rheumatoid arthritis, scleroderma).

  8. Vaccination with live or attenuated vaccines within 1 month prior to the first dose administration.

  9. Prior history of bone marrow transplantation, hematopoietic stem cell transplantation, total lymphoid irradiation, or T-cell vaccine therapy.

  10. Participation in any clinical trial with investigational products within 28 days prior to the first dose or within 5 half-lives of the investigational product, whichever is shorter.

  11. Positive hepatitis B surface antigen (HBsAg) and/or hepatitis B core antibody (HBcAb) with HBV DNA exceeding the upper limit of normal; positive hepatitis C virus (HCV) antibody with HCV RNA exceeding the upper limit of normal; positive human immunodeficiency virus (HIV) serology; positive treponema pallidum antibody (TP-Ab).

  12. Known hypersensitivity to any component of ripeltumab. 13. History of malignant tumors including malignant thymoma, myeloproliferative or lymphoproliferative disorders, unless the disease is considered cured with adequate treatment and there is no evidence of relapse for ≥3 years before screening. Patients with completely resected non-melanoma skin cancer (e.g., basal cell carcinoma or squamous cell carcinoma) or carcinoma in situ of the cervix are allowed to be enrolled at any time.

  14. Patients with clinical evidence of other serious major illnesses or those who have recently undergone major surgery, which may confound trial results or expose patients to undue risks. This includes patients with severe renal or hepatic impairment.

  15. For male subjects without sterilization: refusal to use barrier contraception from screening until 6 months after the end of treatment, and refusal to ask their partners to adopt alternative contraceptive measures including oral contraceptives, intrauterine devices, barrier methods or spermicides.