The study will be a randomized, open-label trial in children with the initial episode of SSNS and whose state of complete remission after received standard prednisolone, to determine whether rituximab (a single intravenous infusion of 375 mg/m2) would be noninferior to corticosteroid alone in maintaining complete disease remission during 12-month of follow-up.

The 12-month relapse-free survival rate is less than 30% in steroid-sensitive nephrotic syndrome (SSNS) children after the standard corticosteroid therapy, with approximately half becoming frequent relapsers or steroid dependent and necessitating the need for alternative immunosuppressive agents. The first relapse of SSNS most occurs within 6-12 months of onset, and contemporary cohorts suggest up to 16-42% of children with SSNS continue to have relapses in adulthood. Rituximab and rituximab biosimilar appear effective in reducing the relapse in children with frequent relapse or steroid dependent nephrotic syndrome. Accordingly, we hypothesize in paediatric SSNS, rituximab added to guideline-recommended corticosteroid therapy is noninferior to corticosteroid alone for maintaining remission for the first year of onset, expected to improve long-term outcomes.

An open-label, single-arm, multicentre trial was performed at eight centers in China with a 12-month follow-up (NCT04783675). The study found that in children with the initial episode of SSNS, rituximab appears to be an effective and safe treatment for maintaining disease remission.

The goal of this prospective study is to determine whether rituximab (a single intravenous infusion of 375 mg/m2) would be noninferior to corticosteroid alone in maintaining complete disease remission during 12-month of follow-up. The study will be a randomized, open-label, parallel group, in a 1:1 ratio, active controlled, multicenter trial.

Inclusion Criteria:

1. Children between 1 and 18 years with Steroid-Sensitive Nephrotic Syndrome (nephrotic-range proteinuria and either hypoalbuminemia or edema when albumin level is not available)
2. Estimated glomerular filtration rate (eGFR) ≥90 ml/min per 1.73 m2 at study entry
3. Remission at study entry
4. the cluster of differentiation antigen 20 (CD20) positive cells in peripheral blood ≥1% total lymphocytes
5. No immunosuppressive agents have been used within 3 months of enrolment, except for the use of corticosteroid to treat nephrotic syndrome
6. Provision of consent by a legal representative using a document approved by the institutional review board after receiving an adequate explanation of this clinical trial. For children ages 8-18, written assent is required using age-appropriate and background-appropriate documents

Exclusion Criteria:

1. Diagnosis of secondary NS
2. Patients showing one of the following abnormal clinical laboratories
3. values: leukopenia (white blood cell count ≤3.0*109/L); moderate and severe anemia (hemoglobin <9.0g/dL); thrombocytopenia (platelet count <100*1012/ L); positivity of autoimmunity tests (ANA, Anti DNA antibody, ANCA) or reduced C3 levels; Alanine aminotransferase or aspartate aminotransferase > 2.5× upper limit of normal value
4. Presence of severe or chronic infections within 6 months before assignment: tuberculosis or in whom tuberculosis is suspected; Epstein-Barr virus or cytomegalovirus; hepatitis B or hepatitis C or hepatitis B virus carrier, human immunodeficiency virus or other active viral infections
5. Live vaccination within last month
6. Patients with poorly controlled hypertension
7. Patients with severe brain, heart, liver, and other important organs, as well as blood and endocrine system diseases
8. Presence or history of autoimmune diseases, primary immunodeficiency, or tumor
9. Patients with a known allergy to Rituximab and its excipients
10. Assessed to be unfit for participation by the investigators (patients highly likely to be lost to follow-up or provide inaccurate data, for example, patients with alcohol or other substance misuse disorders, and patients with psychological disorders)

Data will be available to researchers with a clear research plan and hypothesis, with the appropriate team in place to undertake the work.

When the article has been published with no end date

Requests for access to data from the RTXFIRPedINS2 trial should be addressed to the corresponding author at hxu@shmu.edu.cn. The individual participant data collected during the trial (including the data dictionary) will be available, after de-identification. All proposals requesting data access will need to have a research plan and specify how the data will be used, and all proposals will need the approval of the trial coinvestigator team (or individual(s) subsequently delegated this responsibility) before data release