Pharmacokinetics Of Emulsified Avacopan Applied By NG Tube

Inclusion Criteria * Fulfillment of the definitions of the Second Chapel Hill Consensus Conference for ANCA-associated vasculitis (either granulomatosis with polyangiitis (GPA) or microscopic polyangiitis MPA). * Positivity for ANCA, directed against PR3 or MPO. * Diffuse alveolar hemorrhage. * Respiratory failure requiring mechanical ventilation. * Severe newly diagnosed disease or severe relapsing disease. Severe new or relapsing disease is defined as at least one major BVAS/WG item or a score ≥ 3 and the investigator deems standard treatment for severe disease is necessary. * Minimum BVAS-WG of 3. * Requirement of standard-of-care remission induction therapy for active severe ANCA-associated vasculitis (GPA or MPA). Exclusion Criteria * Diagnosis with eosinophilic granulomatosis with polyangiitis (EGPA, formally Churg-Strauss syndrome) as defined by the Chapel Hill consensus conference. * Allergies: History of severe allergic reaction to avacopan * History of documented anti-glomerular basement membrane disease (anti-GBM disease) * Previous administration of avacopan within the last 5 days. * Concomitant use of a strong CYP3A4 inhibitor. * Aspartate aminotransferase \[AST\], alanine amino transferase \[ALT\], alkaline phosphatase, or total bilirubin elevation \>2.5 times the upper limit of normal (unless attributed to vasculitis) on routine liver function testing obtained within 3 days prior to anticipated treatment with avacopan. * Evidence of prior active or current Hepatitis B virus (HBV), hepatitis C virus (HCV), or human immunodeficiency (HIV) infection. * Active serious infection, including localized infection. * Pregnancy and breastfeeding