Inclusion Criteria: 

• A diagnosis of GPA or MPA according to the Chapel-Hill Consensus Conference definitions (Jennette et al, 2013) and ACR/EULAR 2022 criteria (Robson et al, 2022; Suppiah et al, 2022)

• Evidence of active GPA/MPA (new, relapsing, persistent, or worsening signs/symptoms) resulting in life- or organ-threatening disease or at near term risk of progression to life- or organ-threatening disease. Manifestations of severe active GPA/MPA may include but are not limited to:

  • Any kidney involvement

  • Gangrene • Scleritis

  • Retinal exudate/hemorrhage

  • Sensorineural deafness

  • Mesenteric ischemic

  • Alveolar hemorrhage

  • Respiratory failure

  • Any nervous system involvement

  • Sinonasal disease with bony and/or cartilage damage

  • Subglottic stenosis

  • Cutaneous ulceration

  • Retro-orbital disease

  • Evidence of active GPA/MPA in > 3 different organ systems

• Receiving standard therapy for the treatment of GPA or MPA

• Initiating avacopan for clinical purposes within +/- 14 days of consent. Those who do not initiate avacopan within 14 days of consent, can re-screen for participation within 14 days of avacopan initiation.

• With an intended course of avacopan use of at least 6 months

• At least 18 years of age at the time of consent

• Willing and able to give written Informed Consent and to comply with the requirements of the study protocol

• Judged by the investigator to be otherwise fit for the study, based on medical history, physical examination, and clinical laboratory assessment.

Exclusion Criteria:

• A diagnosis of EGPA

• Patients with alveolar hemorrhage requiring invasive pulmonary ventilation anticipated to last beyond screening or patients requiring avacopan to be administered by methods other than oral capsule form.

• Known pregnancy or breast-feeding

• Interstitial lung disease as the primary manifestation of GPA/MPA

• Any other known autoimmune disease (excluding Hashimoto’s thyroiditis) that could confound the assessment of the study outcomes due to the disease manifestations or the treatment that may be required (e.g., glucocorticoids and/or immunosuppression)

• Malignancy receiving immunosuppressive treatment (e.g., chemotherapy) or immunotherapy (e.g., check point inhibitors)

• Known untreated hepatitis C virus infection

• Known active or latent hepatitis B virus infection

• Known human immunodeficiency virus infection

• Known active or untreated latent tuberculosis infection

• Liver function test abnormalities (AST, ALT, alkaline phosphatase, or bilirubin >3 times the upper limit of normal before start of avacopan)

• History or presence of any medical condition or disease which, in the opinion of the Investigator, may place the patient at unacceptable risk for study participation

• Currently involved in an interventional study and/or concurrently using experimental agents/medications

• Has previously received avacopan for treatment of GPA/MPA (including relapse) for at least 30 days.

• Prior discontinuation of avacopan because of an adverse event or lack of response.

• History of cocaine/levamisole use

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 08/11/2026. Questions regarding updates should be directed to the study team contact.