Study of Safety and Efficacy of AVB-S6-500 in Patients With IgA Nephropathy

Inclusion Criteria: * Diagnosis of biopsy-proven IgAN * Proteinuria ≥ 1g to 3g/24hr * Stable estimated glomerular filtration rate (eGFR) for at least 3 months prior to screening and ≥ 45 mL/min per 1.73 m2 using the Chronic Kidney Disease Epidemiology Collaboration formula * Systolic BP lesser than or equal to 150 mmHg and diastolic BP lesser than or equal to 100 mmHg * Patients who have been on a steady dose of ACE or ARB inhibitors for at least 3 months and throughout screening and who are not expected to have their dose adjusted during the study are allowed on study (patients who are not on ACEi/ARB due to inability to tolerate these therapies are also allowed) * If a sexually-active patient, must agree to use a reliable method of birth control from at least 4 weeks prior to first dose of study drug, during the study and for 1 month following completion of therapy. Exclusion Criteria: * Patients with chronic urinary tract infections (UTIs) or taking prophylactic antibiotics to prevent recurrent UTIs * Treatment with systemic immunosuppressants, including corticosteroids, within 8 weeks of the first dose of study drug * Rapidly progressing nephropathy defined as falling GFR (≥ 15%) over past 3 mos * Clinical or biological evidence of diabetes mellitus, systemic lupus erythematosus, IgA vasculitis (Henoch-Schonlein purpura), secondary IgAN, or other renal disease * Hemoglobin \< 9.0 g/dL * History or clinical evidence of cirrhosis, or liver disease with serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 3x upper limit of normal * Organ transplant recipient (including bone marrow) or a planned transplant during the study * Have a diagnosis of human immunodeficiency virus (HIV), hepatitis B, or hepatitis C infection, or positive serology at screening * Recent active infection requiring hospitalization or i.v. treatment within 30 days prior to the first dose of study drug * Received transfusion, plasmapheresis or plasma exchange, IV immunoglobulin (IVIg) within 90 days prior to screening * Malignancy within the past 5 years. Exceptions are squamous cell carcinoma of skin, basal cell carcinoma of skin, and cervical carcinoma in situ which have been excised and are considered cured * Females who are nursing, pregnant, or intending to become pregnant during the time of the study, or who have a positive pregnancy test at baseline * Exposure to an investigational drug or device within 90 days or 5 half-lives (whichever is longer) prior to the first dose of study drug * Known sensitivity to any of the products to be administered during dosing * Subject will not be available for follow-up assessment * Subject has any kind of disorder that compromises the ability of the subject to give written informed consent and/or to comply with study procedures * Prior exposure to AVB-S6-500