The purpose of this study is to evaluate the efficacy and safety of iptacopan compared to standard of care (SOC) to induce and maintain remission in study participants with active granulomatosis with polyangiitis (GPA) or microscopic polyangiitis (MPA), when used in combination with rituximab (RTX) induction. The trial will also assess the impact of iptacopan on disease relapses, evolution of renal function and proteinuria, GC side effects, patients' immune status, and QoL.