The purpose of this study is to evaluate the safety and tolerability of FG-3019 administered over 8 weeks to adolescent and adult subjects with steroid-resistant focal segmental glomerulosclerosis (FSGS).

Inclusion Criteria:

1. Age 12-64 years, inclusive, and girls age 10-11 years, inclusive if Tanner stage 3 or greater
2. Biopsy diagnosis of primary FSGS with biopsy confirmed centrally
3. Age less than or equal to 2 years old at onset of proteinuria
4. First morning urine protein/creatinine ratio (U p/c) >1 gm/gm
5. Estimated glomerular filtration rate greater than or equal to 40 mL/min/1.73 m2

Exclusion Criteria:

1. Non-FSGS renal disease other than benign cyst; or secondary FSGS
2. History of organ transplantation
3. History of allergic or anaphylactic reaction to human, humanized, chimeric or murine monoclonal antibodies
4. History of malignancy, cardiovascular disease, diabetes mellitus, sickle cell disease, multiple sclerosis, systemic lupus erythematosus, or active or recurrent serious infections (including but not limited to Hepatitis B, Hepatitis C, or HIV)
5. Participation in studies of investigational drugs within 6 weeks prior to Day 0 or receipt of an investigational drug within 12 weeks prior to Day 0
6. Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 2.5 times the upper limit of normal
7. Hematocrit < 30%