Introduction: Anti-neutrophil cytoplasm autoantibodies (ANCA)-associated 
vasculitides (AAVs) are a group of rare heterogeneous diseases characterized by 
blood vessel inflammation resulting in organ destruction and death. Although 
various treatment strategies have resulted in marked improvement in 
vasculitis-specific outcomes, many patients with AAV continue to suffer from 
complications related to the prolonged use of glucocorticoids (GC) such as 
infections, metabolic abnormalities, and increased cardiovascular morbidity. 
Recently, activation of the alternative complement pathway has been implicated 
in the augmentation of the damage caused by AAV via the complement C5a receptor 
(C5aR1, CD88). Specifically targeting this pathway may lead to improved outcomes 
in patients with AAV.Areas covered: In this article, we have summarized the 
rationale for targeting the complement pathway in AAV. The relevant 
pre-clinical, phase I, II and III findings with emphasis on the efficacy, and 
safety of avacopan, a new oral competitive inhibitor that interferes with the 
binding of C5a to C5aR1 (CD88), are reviewed.Expert opinion: These results are 
encouraging, may led to major changes in the treatment approach for AAV, and 
give rise to future studies utilizing complement inhibitors in AAV patients, and 
potentially in other immune mediated diseases.