The purpose of this study is to compare the effect of blisibimod plus standard of care versus placebo plus standard of care alone on the proportion of subjects achieving improvement in renal disease parameters.

Inclusion Criteria:

• 18 years of age or older.
• Biopsy-proven IgA nephropathy
• Proteinuria ≥ 2g/24hr or equivalent
• Receiving physician-directed optimized standard of care that includes ACEI and/or ARB.
• Estimated glomerular filtration rate (eGFR) >40mL/min/1.73m2

Exclusion Criteria:

• Clinical or histologic evidence of non-IgA-related glomerulonephritis
• IgA nephropathy with greater than 50% glomerulosclerosis or cortical scarring
• Meets eGFR criteria
• Malignancy within past 5 years
• Known to be positive for HIV and/or positive at the screening visit for hepatitis B, or hepatitis C
• Liver disease
• Neutropenia
• Active infection requiring hospitalization or treatment with parenteral antibiotics within the past 60 days or history of repeated herpetic viral infections
• History of active tuberculosis or a history of tuberculosis infection
• Pregnant or nursing