Background: Rituximab (RTX) achieved high remission-induction and sustained maintenance rates for patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). However, RTX is an expensive medication, which may potentially lead to serious side effects. Defining the best dose regimen for maintenance in AAV is still an unmet need. The aim is to compare the effects of ultra-low dose RTX (500 mg or 1000 mg once per year) to standard low dose RTX (500 or 1000 mg twice per year) as remission-maintenance therapy in AAV patients. Methods: We included AAV patients (classified as GPA and MPA) who successfully achieved disease remission (BVASv3=0) with conventional RTX regimen and have been subsequently treated with RTX for maintenance of remission. All patients received at least two maintenance infusions with 1000 mg or 500 mg, twice per year or once per year. After a period of 18 months, we assessed the effects of ultra-low dose RTX to standard low dose on disease activity (BVAS), damage (VDI), glucocorticoids intake, ANCA status, B-cells depletion, serum IgG levels. Results: From December 2014 to November 2021, 37 AAV patients (mean age 52, 56.8% female, 97.3% ANCA positive), 28 GPA and 9 MPA, achieved complete disease remission with conventional RTX induction regimen. After 8 [6-13] months, 51.3% patients started maintenance treatment with ultra-low dose RTX (once per year), while 49.7% patients with standard low dose (twice per year), for 18 months. No significant differences at baseline were noted between patients receiving ultra-low dose when compared to those treated with conventional low-dose. At the end of observation period (18 months of follow-up) all patients maintained disease remission (BVASv3=0). Comparing ultra-low dose regimen to low-dose, no differences were noted in negative ANCA rate (50% vs 37 %, p=0.42), ANCA titer (6.8 [0-48] vs 17 [0-47] UI/mL, p=0.55), B-cells depletion rate (88% vs 68%, p=0.15), mean serum IgG (909 vs 821 mg/dL, p=0.32), mean daily glucocorticoid dosage (2 vs 1.5 mg/d, p=0.53) and severe infections rate (11% vs 31%, p=0.28. Patients treated with ultra-low dose had significant lower VDI at the end of observation (4±1.8 vs 2±1.6, p=0.002). Conclusions: Reduced exposure to RTX was not associated with an impaired efficacy of maintenance therapy in patients with AAV. Remission maintenance with ultra-low dose RTX is safer and more cost-effective option. Disclosures: None