Rituximab induction and reinduction in granulomatosis with polyangiitis and microscopic polyangiitis: A retrospective multicenter study in Taiwan.

Objectives: This study aimed to investigate the clinical outcomes of granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) under rituximab induction and reinduction therapy in Taiwan. Methods: We performed a retrospective study in patients with GPA or MPA receiving rituximab therapy from August 2008 to July 2020 in seven medical centers in Taiwan. The clinical characteristics and outcomes of these patients were analyzed. Results: In total, 53 patients (18 with GPA and 35 with MPA) were included. Kidney involvement (82.9% vs. 22.2%, p <.001) and initial creatinine (3.25 ± 2.37 vs. 1.07 ± 0.82, p <.001) were significantly higher in MPA. Within 24 weeks after the first course of rituximab, there were seven deaths (five due to infection and two due to active disease) in patients with MPA (7/35, 20%) compared to 0 in patients with GPA. Of 33 patients receiving rituximab for kidney involvement, 23 survived and were free from renal replacement therapy at 24 weeks. Their chronic kidney disease (CKD) stages improved in 2 but progressed in 7, while 24 had stable CKD stages. Death or end‐stage renal disease (ESRD) was associated with infection and higher initial creatinine. Reinduction therapy for relapse was required in 18 (39.1%) of 46 survivors, which was associated with anti‐proteinase 3 (PR3) positive (odds ratio 3.667, p =.049) and younger age with a cutoff of 49.4 (AUC = 0.679, p =.030, sensitivity = 66.67%, specificity = 75%). Conclusion: Significant mortality occurred after rituximab induction, especially in patients with MPA. In survivors, age younger than 50 and anti‐PR3 positive were associated with the risk of relapse requiring reinduction. [ABSTRACT FROM AUTHOR]