A Pilot Study to Assess the Efficacy of Rituximab Therapy in Treatment Resistant FSGS

Inclusion Criteria: * FSGS involving native kidneys with a diagnostic biopsy performed within the last 3 years * Patients \>6 years of age and \< 80 years of age * suPAR \> 3500 pg ml-1 * Treatment with an ACEI and/or ARB as tolerated for at least 3 months prior to enrollment to with a target a systolic blood pressure ≤ 140 mmHg and a diastolic pressure ≤ 90 mmHg in adults and blood pressure readings less than the 95th percentile for age, gender and height in children in at least 75% of readings * Proteinuria ≥ 3.0 grams as measured by 24-hour urine collection in adults and urine protein:creatinine ratio ≥ 1.0 in the first morning urine in children, despite ACE inhibitor / ARB treatment as tolerated and a minimum of 8 weeks of prednisone therapy at ≥ 1 mg/kg/day, a trial of calcineurin inhibitor for=\> 3 months or a contraindication/intolerance to such therapy (diabetes, osteoporosis/osteonecrosis, age \>60, BMI ≥35) * Negative serum pregnancy test (for women of child bearing age) * Men and women of reproductive potential must agree to use an acceptable method of birth control during treatment and for twelve months (1 year) after completion of the trial * Able and willing to give written informed consent and comply with study requirements Exclusion Criteria: * Estimated GFR \< 40 ml/min per1.73m2. The rationale is that patients with advanced renal failure may progress rapidly towards ESRD. * Collapsing variant of FSGS, as it is rare and has been associated with an aggressi…