This is an open-label randomized controlled trial to evaluate the efficacy and safety of one dose versus two doses of ripertamab in children with frequent relapses or steroid-dependent nephrotic syndrome (FRNS/SDNS).

Inclusion Criteria:

1. 16 years old and above with FRNS/SDNS
2. Before enrollment, achieved complete remission (urine protein/creatinine ratio (morning urine or 24-hour urine) ≤ 20mg/mmol (0.2mg/mg) or < 100mg/m2/d, or test strip result negative or trace)
3. Within 2 months before enrollment, did not use levamisole, alkylating agents such as cyclophosphamide, calcineurin inhibitors such as cyclophosphamide and cyclosporine, or mycophenolate mofetil. Within 6 months before enrollment, did not use other CD20 monoclonal antibodies (such as ofatumumab, otuzumab, etc., excluding rituximab)
4. Glomerular filtration rate (eGFR) > 60ml/min/1.73m2
5. The patient or their guardian agrees to participate in this clinical trial and signs the informed consent form, indicating that they understand the purpose and procedures of this clinical trial and are willing to participate in the study

Exclusion Criteria:

1. Known causes (such as systemic lupus erythematosus, IgA nephropathy, other secondary nephrotic syndromes, amyloidosis, malignant tumors, etc.)
2. Known active chronic infections, including tuberculosis, HIV, HBV, HCV, etc.
3. Severe leukopenia (white blood cells < 3.0×109/L), severe anemia (hemoglobin < 8.9 g/dl), thrombocytopenia (platelets < 100×109/L), or liver dysfunction (alanine aminotransferase/aspartate aminotransferase > 2 times the upper limit of normal)
4. Received live vaccines within 1 month prior to screening
5. Currently participating in other drug clinical trials
6. Other conditions that the investigator deems make the patient unsuitable for this study