The primary objectives of this trial are as follows:

• to compare the achievement of a partial remission (PR) or complete remission (CR) in urinary protein: creatinine ratio (Up/c ratio) in patients treated with fresolimumab versus placebo
• to compare the safety profile of patients treated with fresolimumab versus placebo

The secondary objectives are as follows:

• To compare the reduction in proteinuria in patients treated with fresolimumab versus placebo
• To evaluate fresolimumab dose-dependent reduction in proteinuria
• To compare the change in renal function (estimated glomerular filtration rate [eGFR]) in patients treated with fresolimumab versus placebo
• To evaluate the multiple-dose pharmacokinetics of fresolimumab

Inclusion Criteria:

• The patient's renal biopsy is consistent with the diagnosis of primary Focal Segmental Glomerulosclerosis (FSGS) including all histological subtypes.
• The patient has an eGFR ≥ 30 mL/min/1.73 m2
• The patient has a urinary total protein:creatinine ratio ≥ 3 mg protein/mg creatinine
• In the opinion of the Investigator, the patient has steroid-resistant FSGS. The patient must have been treated for FSGS with a course of high-dose steroid therapy for a minimum of 4 weeks
• The patient has been treated with an ACEi (angiotensin converting enzyme inhibitor) and/or ARB (angiotensin receptor blocker) at a stable dose for a minimum of 4 weeks prior to Visit 2 (treatment start)

Exclusion Criteria:

• The patient has FSGS which in the Investigator's opinion is secondary to another condition
• The patient has been taking prednisone at a dose > 10 mg/day (or equivalent dose of an alternative glucocorticoid) within 4 weeks prior to Visit 1 (Screening Visit).
• The patient has received any other systemically administered immunosuppressive drugs (other than glucocorticoids) within 8 weeks prior to Visit 1.
• The patient has received rituximab within 6 months prior to Visit 1.
• The patient has a history of organ transplantation.