The main objective of this study is to explore the efficacy of avacopan in participants affected by AAV.
Male and female children and adolescents from 6 to < 18 years old of age.
Clinical diagnosis of Granulomatosis with Polyangiitis (GPA) or microscopic polyangiitis (MPA), consistent with Chapel-Hill Consensus Conference definitions (Jennette et al, 2013).
Positive anti-PR3(Anti-Proteinase 3) or anti-MPO(Anti-Myeloperoxidase) antibody documented at Screening or historically. Historical positivity is acceptable (even if Screening is negative) if supported by verifiable lab source documentation obtained during AAV diagnosis or disease course; use the most recent positive result.
At least 1 PVAS major item, at least 3 PVAS nonmajor items, or atleast the 2 renal items of proteinuria and hematuria.
Any other known multisystem autoimmune disease including and not limited to eosinophilic granulomatosis with polyangiitis (EGPA, previously, Churg-Strauss disease), systemic lupus erythematosus, IgA vasculitis / Henoch-Schönlein, Purpura, rheumatoid vasculitis, Sjögren's syndrome, anti-glomerular basement membrane disease, or cryoglobulinemic vasculitis.
Renal replacement therapy / plasmapheresis: subjects will be excluded who received, require, or initiate CRRT (continuous renal replacement therapy), hemodialysis, any renal dialysis, or plasmapheresis within 14 days prior to Screening or between Screening and Day 1.
History of kidney transplantation or is anticipated to require renal transplantation during the study.
Alveolar hemorrhage requiring invasive pulmonary ventilation support anticipated to last beyond the screening period of the study.