Safe Effective Therapy With Low-Dose Glucocorticoid in ANCA-Associated Vasculitis (SAFE-LOW)

* New diagnosis of, or relapse of, granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), consistent with Chapel-Hill consensus definitions - Positive ELISA test for anti-meyloperoxidase (MPO) or anti-proteinase 3 (PR3) - Severe kidney involvement from active AAV, characterised by both of the following: - eGFR \< 40ml/min/1.73m2 (Patients known to have a stable eGFR \<40 ml/min/1.73m2 for \>3 months prior to enrollment are NOT eligible) - Biopsy proven at least focal necrotizing/crescentic glomerulonephritis OR active urinary sediment by microscopy (greater than or equal to 10 red blood cells \[RBC\]/high power field with erythrocyte casts or greater than or equal to 20% dysmorphic RBCs or greater than or equal to 5% acanthocytes without an alternative cause. Exclusion Criteria (any of the following) - A diagnosis of vasculitis other than GPA or MPA (including eosinophilic granulomatosis with polyangiitis, IgA vasculitis, cryoglobulinemic vasculitis, rheumatoid vasculitis) - Positive anti-glomerular basement membrane antibody test or renal biopsy demonstrating linear glomerular immunoglobulin deposition - A diagnosis of systemic lupus erythematosus or Sjögren's syndrome - Receipt of dialysis for \>21 days immediately prior to randomization or prior renal transplant - Age \<18 - Pregnant at time of screening - Treatment with \>1 IV dose of CYC and/or \>14 days PO CYC and/or \>14 days of prednisone/prednisone (less than or equal to 30mg/day) and/or \>1 dose of RTX within the 28 days immediately prior to randomization - Chronic viral infection: HIV. HBV or HCV - Untreated latent mycobacterium tuberculosis infection - Active infection at time of presentation - A comorbidity or condition that, in the opinion of the investigator, precludes the use of GC, CYC or RTX Always talk to your doctor about whether this trial is right for you.