Impaired Kidney Function Associated with Increased Risk of Side Effects in Patients with Small Vessel Vasculitis Treated with Rituximab as an Induction Therapy

Rituximab (RTX), a monoclonal antibody against the CD20 molecule, is used as an induction therapy in the treatment of small vessel vasculitis (SVV). The aim of the study was to evaluate the efficacy and safety of RTX induction therapy for refractory SVV. A retrospective analysis of 20 patients treated with RTX for active SVV (BVAS/WG ≥ 3) was performed to assess the remission rate and the drug-related severe adverse events 6 months after therapy. The mean age of the studied population was 49 ± 13 years (50% female), 90% of which were PR3-ANCA positive. Complete remission was achieved in 85% of patients, and partial remission was achieved in a further 10% within 6 months after RTX infusions. The remission rate was not influenced by kidney function. Adverse events such as infections (25%), a late onset of neutropenia (10%) and severe hypogammaglobulinemia (5%) were noted. The patients who developed adverse events were older (42 ± 11 vs. 57 ± 12 years; p = 0.014) and had a higher serum creatinine level (1.3 mg/dL vs. 3.35 mg/dL; p = 0.044). Patients with a glomerular filtration rate (eGFR) lower than 30 mL/min/1.73 m² had a nine-fold higher risk of side effects (OR 9.0, 95%CI: 1.14-71.0). In conclusion, RTX was highly effective as an induction therapy in patients with SVV. Advanced kidney failure with an eGFR lower than 30 mL/min/1.73 m² was one of the risk factors for the occurrence of side effects.