Remission induction therapies and long-term outcomes in granulomatosis with polyangiitis and microscopic polyangiitis: real-world data from a European cohort.

To explore disease characteristics, renal involvement and induction treatment strategies over the last decades and evaluate relapse rates and renal outcomes in ANCA-associated vasculitides (AAV). We retrospectively analyzed remission, relapse rates and the occurrence of the composite endpoint (comprising death and renal failure) in newly diagnosed AAV cases in four tertial referral centers in Germany and Switzerland diagnosed between 1999 and 2022. Hazard ratios were computed by Cox proportional hazard and Kaplan-Meier curves were plotted to compare therapeutic strategies after propensity-matching. In our cohort of 358 AAV patients, 203 (58.1%) were classified as granulomatosis with polyangiitis (GPA) based on the novel 2022 ACR/EULAR criteria, 139 (38.8%) as microscopic polyangiitis (MPA). The proportion of MPA cases among all AAV patients increased from 28.9% between 1999 and 2013 up to 46.7% thereafter. Cyclophosphamide (CYC) was chosen most frequently for remission induction (74.8% before 2013 and 57.3% thereafter), whereas the use of rituximab (RTX) increased from 5 to 26% within these periods. GPA patients had a higher relapse rate as compared to MPA patients (41.3% vs. 25.9%, p = 0.006). However, in AAV patients with renal involvement, renal events (i.e. end-stage kidney disease or a persistent drop in the estimated glomerular filtration rate (eGFR) below 15 ml/min/1.73 m²) occurred more frequently in MPA patients, particularly under RTX treatment as compared to matched CYC counterparts (11.8% vs. 7.5%, p = 0.011). In our cohort, GPA patients exhibited frequent relapses, advocating for a more intense and extended treatment. MPA patients had lower relapse rates, however, RTX was less effective to prevent renal endpoints in MPA as compared to CYC, highlighting the need to further investigate additional treatment strategies.