The purpose of this study is to evaluate the safety and tolerability of OMS721 in subjects with IgA Nephropathy (IgAN), Lupus Nephritis (LN), Membranous Nephropathy (MN), and C3 Glomerulopathy (C3G), including Dense Deposit Disease. The study will also evaluate Pharmacokinetics (PK), Pharmacodynamics (PD), anti-drug antibody response (ADA), and neutralizing antibodies (Nab).