Inclusion Criteria:

• Age ≥6 years and <18 years, with body weight ≥20 kg
• Meets the 2019 European League Against Rheumatism (EULAR) and American College of Rheumatology (ACR) classification criteria for Systemic Lupus Erythematosus (SLE)
• Renal biopsy confirming Lupus Nephritis class III, IV, III+V, or IV+V according to the International Society of Nephrology / Renal Pathology Society (ISN/RPS) classification
• At screening: 24-hour urinary protein ≥1.0 g (or ≥25 mg/kg), or urine protein-to-creatinine ratio (UPCR) ≥1.0 g/g
• White blood cell count ≥3.0 × 10⁹/L and lymphocyte count ≥1.0 × 10⁹/L
• No prior intravenous methylprednisolone pulse therapy before enrollment, and glucocorticoid exposure ≤2 weeks before enrollment, with a maximum prednisone-equivalent dose ≤30 mg/day (or ≤1 mg/kg/day)
• Written informed consent obtained and good treatment compliance expected

Exclusion Criteria:

• Uncertain diagnosis of SLE, genetically confirmed monogenic lupus, or a history of immunodeficiency
• Severe infection, including hepatitis C, active hepatitis B, HIV infection, tuberculosis infection, severe fungal infection, etc.
• Severe neuropsychiatric lupus
• Peripheral blood hemoglobin <60 g/L, platelet count <10 × 10⁹/L, or concomitant aplastic anemia
• Severe cardiac insufficiency (NYHA functional class ≥ II)
• Severe pulmonary involvement, including pulmonary hemorrhage, respiratory failure, pulmonary embolism, or other conditions requiring respiratory support
• Estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m²
• Severe gastrointestinal bleeding, pancreatitis, or hepatic lesions
• Patients deemed by the investigator to be unsuitable for participation in this trial