Cyclophosphamide Therapy for Refractory Antibody-Mediated Rejection (AMR) in Kidney Transplants

Inclusion Criteria: * Patients with a living or deceased donor kidney transplant * Failed current standard of care for late antibody-mediated rejection * Persistent de novo donor specific antibody and a concurrent biopsy with histologic evidence of acute antibody-mediated inflammation * Adults with reproductive potential must agree to use approved methods of birth control while in the study Exclusion Criteria: * Leukopenia (WBC) \< 3.0 x 109/L * Creatinine Clearance less than or equal to 25 ml/min/1.73m2 * HCV or HBV positive * BKV or CMV viremia assessed by PCR * Any active infection * Use of other investigational drugs within 4 weeks of study * Pregnancy/breast feeding/unwilling or unable to take birth control * Active malignancy * de novo DSA occurring equal to or greater than15 years after kidney transplant * Screening biopsy with equal to or greater than cg2 on Banff criteria * Cumulative/lifetime dose of cyclophosphamide, including anticipated total study dose (calculated according to Creatinine Clearance and mg/kg/day) equal to or greater than 36 g. * Any condition that, in the opinion of the investigator, would pose risk to the subject's safe participation in the study