The goal of this clinical study is to evaluate multiple dose levels of povetacicept in adults with immunoglobulin A (IgA) nephropathy (IgAN), primary membranous nephropathy (pMN), lupus-related kidney disease (lupus nephritis - LN), or anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV) to determine if povetacicept is safe and potentially beneficial in treating these diseases. During the study treatment period, participants will receive povetacicept approximately every 4 weeks for 6 months, with the possibility of participating in a 6-month treatment extension period and an optional 52-week treatment extension period. Participants with IgAN and pMN may also receive povetacicept for an additional 52 weeks, if eligible.