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Background Sequential rituximab (RTX) administration has emerged as an important strategy to sustain remission of disease in patients with difficult-to-treat nephrotic syndrome. Methods We report the efficacy and safety of sequential therapy with two or more courses of intravenous RTX in 250 patients with difficult-to-treat steroid dependence (n  = 127) and calcineurin inhibitor (CNI)-dependent or CNI-refractory steroid resistance (n  = 123) managed at one center during 2015–2021. Subsets of patients were cross-sectionally tested for hypogammaglobulinemia, seroprotection against and hyporesponsiveness to vaccines for hepatitis B and tetanus, BK/JC viruria and human antichimeric antibodies (HACAs). Results Sequential RTX therapy, initiated at a median of 10 years [interquartile range (IQR) 7.3–14.4], was administered for 1.8 courses/person-year [95% confidence interval (CI) 1.7–2.0] over 2.0 years (95% CI 1.2–3.0). Therapy was associated with postponement of relapses by a median of 3 years in patients with steroid-sensitive disease and 2 years in those with steroid resistance. Relapses were reduced by a mean of 2.0 relapses/person-year (95% CI 1.8–2.2), enabling a reduction in prednisolone dose to 0.04 mg/kg/day (95% CI 0.01–0.11) and withdrawal of additional immunosuppression in 154 (62%) patients. RTX-associated adverse events, occurring at 0.20 events/person-year (95% CI 0.17–0.23), were chiefly comprised of infusion reactions (n  = 108) and infections (n  = 46); serious adverse events were observed in 10.8% patients, at 0.03 events/person-year (95% CI 0.02–0.05). Hypogammaglobulinemia was observed in 35% of 177 patients and was moderate to severe in 8.5% of cases. Rates of seroprotection at baseline and response following vaccination were lower for hepatitis B [1.9% and 29.4% (n  = 52)] than tetanus [65.5% and 34.5% (n  = 58)]. BK/JC viruria, without viremia, was observed in 7.3% of 109 cases. A total of 19 of 107 patients (17.8%) had HACAs, which were associated with B cell nondepletion and serum sickness. Age at therapy of <9–10 years was associated with a risk of early relapse, treatment failure and hypogammaglobulinemia following RTX therapy. Conclusions Sequential therapy with RTX effectively reduces relapses in patients with difficult-to-treat steroid- and/or CNI-dependent or CNI-refractory nephrotic syndrome. Therapy is associated with high rates of hypogammaglobulinemia and infusion reactions. [ABSTRACT FROM AUTHOR]