Additional Study Information: The purpose of this study is to evaluate the safety and tolerability of study drug CCX168 when it is given to patients who are receiving the standard therapy for a certain type of vasculitis called ANCA-associated vasculitis (AAV). The study will also assess the effectiveness of the study drug, CCX168, in combination with the standard treatment of AAV. This study will also evaluate if CCX168 improves patients' symptoms, their kidney function (if they have kidney disease involvement) and their overall disease activity when compared to placebo (sugar pills) while they continue the standard treatment with cyclophosphamide or rituximab and prednisone.