Study to Evaluate the Safety, Tolerability of BCX9930 in Participants With Either Complement 3 Glomerulopathy (C3G), Immunoglobulin A Nephropathy (IgAN), or Primary Membranous Nephropathy (PMN)

Inclusion Criteria: * Body weight ≥ 40 kilograms (kg) * Primary diagnosis of C3G, IgAN, or PMN confirmed by central pathology review * An estimated glomerular filtration rate (eGFR) ≥ 50 milliter per minute per 1.73 meter square (mL/min/1.73 m\^2) (or ≥ 30 mL/min/1.73 m\^2 after Data Monitoring Committee \[DMC\] recommendation) * Receiving treatment with a stable, maximum recommended or maximum tolerated dose of an angiotensin-converting enzyme inhibitor (ACEi) or angiotensin receptor blocker (ARB) for at least 60 days prior to the Day 1 Visit * Documentation of current vaccinations against Neisseria meningitidis and Streptococcus pneumoniae or willingness to start vaccination series Exclusion Criteria: * Known congenital deficiency of C1s, C1r, C1q, C2, or C4 * History of hematopoietic cell transplant or solid organ transplant or anticipated candidate for transplantation * Myocardial infarction or cerebrovascular accident within 30 days prior to screening, or current and uncontrolled clinically significant cardiovascular or cerebrovascular condition * History of malignancy within 5 years prior to the screening visit * Active serious bacterial, viral, or fungal infection or any other serious infection within 14 days of screening * Treatment with any systemic immunosuppressive or immunomodulatory therapy within 90 days OR anti-CD20 antibody therapies (eg, rituximab) within 180 days prior to the screening visit * Treatment with renin inhibitors (eg, aliskiren) or sodium-gluc…