Multicenter double-blind, randomized, placebo-controlled trial of IDEC-C2B8 for the treatment of childhood-onset nephrotic syndrome(JSKDC10)

INTERVENTION: Intervention type:DRUG. Intervention1:IDEC‐C2B8, Dose form:INJECTION, Route of administration:INTRAVENOUS DRIP, intended dose regimen:375 mg/m2 (but, maximum 500 mg/body) of the study drug given 2 times at an interval of 7 +/‐ 2 days. Control intervention1:Placebo, Dose form:INJECTION, Route of administration:INTRAVENOUS DRIP, Intended dose regimen:375 mg/m2 (but, maximum 500 mg/body) of the study drug given 2 times at an interval of 7 +/‐ 2 days. CONDITION: Childhood onset idiopathic nephrotic syndrome showing frequent relapse or steroid dependence PRIMARY OUTCOME: 1. Efficacy outcome; Relapse‐free period; 2. Safety endpoint; Adverse event, Adverse drug reaction. Timepoint:1.Efficacy outcome; Time of randomization to the time of first relapse after starting the study treatment; 2. Safety endpoints ; Time of randomization to the end of observational period. SECONDARY OUTCOME: 1. Efficacy outcomes; (1) Time to treatment failure; (2) Total steroid dose; (3) Variation in B cell count during observational period; 1) Measurement of B cell count; 2) Duration of B‐cell depletion; 2. Other outcomes ; (1) Relapse‐free period in open‐label phase; (2) Serum IDEC‐C2B8 level; (3) Anti‐rituximab antibody (human anti‐chimeric antibody, HACA) in subject serum. Timepoint: 1.Efficacy outcomes; (1) Time to treatment failure; Time of randomization to the time of development of treatment failure; (2) Total Steroid dose; Time of randomization to the end of double‐blind phase observational period; (3) Duration of B‐cell depletion; Day1 in double‐blind period to the end of observational period; 2. Other outcomes ; (1) Relapse‐free period in open‐label phase; Time of enrollment to the time of first relapse during open‐label phase; (2) Serum IDEC‐C2B8 level; Day1 in open‐label period to the end of observational period; (3) Anti‐rituximab antibody (human anti‐chimeric antibody, HACA) in subject serum; Day1 in open‐label period to the end of observational period. INCLUSION CRITERIA: (1) Diagnosed as idiopathic nephrotic syndrome (INS) according to the ISKDC criteria. (2) First onset of INS is under 18 years of age. (3) Subjects who are diagnosed as frequent recurrence or steroid dependency with recurrence just before registration and who can confirm the date of recurrence as the basis for diagnosis. (4) Subjects who have not been treated with immunosuppressive treatment for INS. (5) Diagnosed as steroid‐sensitive relapse. (6) CD20 positive B‐cells >/= 5/mcL in the peripheral blood. (7) Subjects can be hospitalized for treatments. (8) Subjects have ability to provide written informed consent form. The written informed consent form of legal representative is also required for subjects less than 20 years of age.