Safety Study of IgAN, LN, MN, & C3 Glomerulopathy Including Dense Deposit Disease Treated With OMS721

Inclusion Criteria:

• At least 18 years of age at screening and competent to provide informed consent; ForCohort 4 only, participants are of Asian descent

• Have a diagnosis of one of the following:

1. IgAN on kidney biopsy

2. LN, MN and C3 Glomerulopathy including Dense Deposit Disease on kidney biopsy and 24-hour Urine Protein Excretion (UPE) > 1000 mg/24 hours (for Cohort 1 only)

3. IgAN diagnosis is confirmed by biopsy within 8 years of screening for Asiandescent (for Cohort 4 only)

• For Cohort 4 only: subjects with IgAN of Asian descent, documented history of 24-hourUPE > 1 g within 6 months prior to Screening or Urine Protein-Creatinine Ratio (uPCR) > 0.75 by spot urine at screening

• Screening Estimated Glomerular Filtration Rate (eGFR) >= 30 mL/min/1.73 m^2

• Are on physician-directed, stable, optimized treatment with angiotensin convertingenzyme inhibitors (ACEI) and/or angiotensin receptor blockers (ARB) and have asystolic blood pressure of < 150 mmHg and a diastolic blood pressure of < 90 mmHg atrest

Exclusion Criteria:

• Have a hemoglobin less than 9.0 g/dL

• Have a platelet count =less than 100,000/mm^3

• Have an absolute neutrophil count <500 cells/mm^3

• Have an Alanine aminotransferase (ALT) or Aspartate Aminotransferase (AST) greaterthan 5.0 x the upper limit of normal (ULN)

• Have systemic manifestations of Henoch-Schonlein purpura within 2 years prior toScreening

• Have used: belimumab, eculizumab, or rituximab within 6 months prior to Screening

• Have a history of renal transplant

• History of human immunodeficiency virus (HIV), evidence of immune suppression, activehepatitis C virus (HCV) infection (subjects with positive anti-HCV antibody

• Have a malignancy except for adequately treated and cured basal or squamous cell skincancer, curatively treated in situ disease, or other cancer from which the patient hasbeen disease-free for 5 years or more