This study is designed to assess the long-term safety and efficacy of avacopan as adjunctive treatment for AAV. This will be evaluated in a randomized, double-blind, placebo-controlled, 5-year clinical trial in participants with severe, active, newly diagnosed, or relapsed AAV (granulomatosis with polyangiitis [GPA] or microscopic polyangiitis [MPA]) where induction treatment with cyclophosphamide or rituximab is needed. Approximately 300 participants across an estimated 200 sites will be enrolled, with 100 participants in each treatment group. Eligible participants will be randomized into 1 of 3 groups. Group 1 will receive 30mg avacopan twice daily for 5 years with standard of care background immunosuppressive therapy. Group 2 will receive 30mg avacopan twice daily for 1 year, followed by placebo twice daily for 4 years and standard of care background immunosuppressive therapy. Group 3 will receive placebo twice daily for 5 years along with standard of care background immunosuppressive therapy.

Who can Participate

1. 18 years or above adults with newly diagnosed or relapse of granulomatosis with polyangiitis or microscopic polyangiitis, consistent with Chapel-Hill Consensus Conference definitions (Jennette et al, 2013), where induction treatment with cyclophosphamide or rituximab is needed. 2. Any other known multisystem autoimmune disease including eosinophilic granulomatosis with polyangiitis (GPA [Churg-Strauss]), systemic lupus erythematosus, immunoglobulin (Ig) A vasculitis (Henoch-Schönlein), rheumatoid vasculitis, Sjogren's syndrome, anti-glomerular basement membrane disease, or cryoglobulinemic vasculitis is excluded. 3. Cyclophosphamide (CYC) within 12 weeks before signing the informed consent is an exclusion; if on azathioprine (AZA), mycophenolate, or methotrexate at the time of screening, these drugs must be withdrawn before receiving the CYC or rituximab (RTX). Inclusion Criteria: Participants has provided informed consent before initiation of any study-specific activities/procedures. Newly diagnosed or relapse of granulomatosis with polyangiitis or microscopic polyangiitis, consistent with Chapel-Hill Consensus Conference definitions (Jennette et al, 2013), where induction treatment with cyclophosphamide or rituximab is needed. Age >/= 18 years (or >/= legal age within the country if it is older than 18 years). Positive test for anti-positive antiproteinase 3 or antimyeloperoxidase (current or historic) antibodies. At least 1 Birmingham Vasculitis Activity Score (BVAS) major item, or at least 3 BVAS nonmajor items, or at least the 2 renal items of proteinuria and hematuria. eGFR >/= 15 mL/min/1.73 m^2 (using Chronic Kidney Disease Epidemiology Collaboration equations). Exclusion Criteria: Alveolar hemorrhage requiring invasive pulmonary ventilation support anticipated to last beyond the screening period of the study. Any other known multisystem autoimmune disease including eosinophilic granulomatosis with polyangiitis (GPA [Churg-Strauss]), systemic lupus erythematosus, immunoglobulin (Ig) A vasculitis (Henoch-Schönlein), rheumatoid vasculitis, Sjogren's syndrome, anti-glomerular basement membrane disease, or cryoglobulinemic vasculitis. Any medical condition requiring or expected to require continued use of immunosuppressive therapies, including corticosteroids that may cause confoundment with study assessments and study conclusions. Received dialysis or plasma exchange within 12 weeks before signing of the informed consent. Have had a kidney transplant. Malignancy (except curatively treated nonmelanoma skin cancers, curatively treated cervical carcinoma in situ, or breast ductal carcinoma in situ within the last 5 years before signing the informed consent). Acute or chronic, active hepatitis B virus or hepatitis C virus, or human immunodeficiency virus infection during screening. Positive test for active or latent tuberculosis during screening. White blood cell count < 3500/µL, neutrophil count < 1500/µL, or lymphocyte count < 500/µl. Note: Complete Blood Count can be repeated once in the screening period per investigator discretion. In this case, eligibility will be determined based on the repeat complete blood count. Evidence of clinically significant hepatic disease including prior diagnosis of cirrhosis. Aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase (ALP) >2.0 times the upper limit of normal (ULN). Total bilirubin > 1.5 times the ULN. A participant with documented Gilbert's syndrome with total bilirubin < 2 x ULN may be eligible. Active infection and/or infection requiring oral or intravenous (IV) anti-infective agents within 4 weeks before signing of the informed consent or completion of oral anti-infective agents within 2 weeks prior to signing informed consent. History of any clinically significant cardiovascular disease, such as symptomatic congestive heart failure, unstable angina, myocardial infarction or stroke, within 12 weeks before signing of the informed consent. Received cyclophosphamide (CYC) within 12 weeks before signing the informed consent; if on azathioprine (AZA), mycophenolate, or methotrexate at the time of screening, these drugs must be withdrawn before receiving the CYC or rituximab (RTX). Note: If induction therapy with cyclophosphamide was started within 1 week before signing the informed consent for the current episode of newly diagnosed or relapse of GPA or MPA, the participant may be eligible, provided no cyclophosphamide was received within 12 weeks before the start of the current induction therapy and if on AZA, mycophenolate, or MTX, these were withdrawn prior to receiving the current induction therapy with cyclophosphamide. Have been taking an oral daily dose of a glucocorticoid of more than 10 mg prednisone equivalent for more than 6 weeks continuously before si

Study ID