Continuous Soluble Ferric Pyrophosphate (SFP) Iron Delivery Via Dialysate in Hemodialysis Patients

Main Inclusion Criteria: 1. Male and female subjects ≥ 18 years of age. 2. End-stage renal disease undergoing maintenance hemodialysis 3 to 4 times a week for at least 4 months and expected to remain on this schedule and be able to complete the study. Subjects on a cadaveric transplant list need not be excluded for this reason unless there is an identified donor. 3. Mean Hgb in the range of ≥ 9.5 to ≤ 12.0 g/dL during screening. 4. The difference between the maximum and minimum Hgb values during screening does not exceed 1.0 g/dL. 5. Mean ferritin ≥ 200 to ≤ 1000 µg/L during screening. 6. Mean TSAT ≥ 15% to ≤ 40% during screening. 7. Any and all serum albumin measured during the 2 months preceding randomization must be ≥ 3.0 g/dL. 8. Prescribed ESA dosing remaining in the range of ≥ 4,000 to ≤ 45,000 U/week epoetin or ≥ 12.5 to ≤ 200 µg/week darbepoetin during the 6 weeks preceding randomization. 9. Required IV iron at any time in the 6 months preceding randomization. Main Exclusion Criteria: 1. Vascular access for dialysis is a catheter. 2. During the 6 months prior to randomization, infection of the vascular access to be used at the time of randomization. 3. Received a total of \> 600 mg IV iron during the 6 weeks prior to randomization. 4. Received any amount of IV or oral iron during the 2 weeks prior to randomization. 5. Change in prescribed ESA dose: 1. Any change in prescribed ESA dose within 4 weeks prior to randomization. 2. The prescribed ESA dose at the time of randomization is \> 25% higher or lower than the prescribed dose at 6 weeks prior to randomization. 3. Change in prescribed type of ESA (e.g., epoetin vs. darbepoetin) or route of administration within 6 weeks prior to randomization. 6. Actual ESA dosing missed or withheld for a cumulative total of ≥ 1 week for any reason during the 6 weeks prior to randomization. 7. Known cause of anemia other than anemia attributable to renal disease (e.g., sickle cell disease, thalassemia, pure red cell aplasia, hemolytic anemia, myelodysplastic syndrome, etc.) 8. Scheduled kidney transplant or a donor has been identified but the transplant has not been scheduled. 9. Known ongoing inflammatory disorder (other than Chronic Kidney Disease), such as systemic lupus erythematosus, rheumatoid arthritis, other collagen-vascular diseases, etc. 11\. Known active tuberculosis, fungal, viral, or parasitic infection requiring anti-microbial therapy or anticipated to require anti-microbial therapy during the patient's participation in this study. Subjects with hepatitis C, in the absence of cirrhosis, are not excluded from participation in the study if Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels are below 2 times the upper limit of normal on a consistent basis during the 2 months preceding randomization. 12\. Occult tuberculosis requiring prophylactic treatment with anti-tubercular drug(s) that overlaps with the patient's participation in this study. 13\. Cirrhosis of the liver based on histological criteria or clinical criteria (e.g., presence of ascites, esophageal varices, spider nevi, or history of hepatic encephalopathy).