a 24-week phase 3, multi-center clinical trial, comprised of a 16-week, randomized, double-blind, placebo-controlled period ("Randomized Period"), followed by an 8-week open-label safety extension period, where all subjects receive KRX-0502 (ferric citrate) ("Extension Period").

a 24-week phase 3, multi-center clinical trial, comprised of a 16-week, randomized, double-blind, placebo-controlled period ("Randomized Period"), followed by an 8-week open-label safety extension period, where all subjects receive KRX-0502 (ferric citrate) ("Extension Period"). The study will consist of 14 clinic visits over a period of 24 weeks. There will be a screening period of up to 14 days; Approximately 230 subjects will be randomized into the Randomized Period in a 1:1 ratio to receive either KRX-0502 or matching placebo, at baseline

Inclusion Criteria:

1. Men and non-lactating women with negative serum pregnancy test (for women of child-bearing potential) at Screening
2. Age ≥18 years
3. CKD with Estimated Glomerular Filtration Rate (eGFR) <60 mL/min at Screening using the 4-variable Modification of Diet in Renal Disease (MDRD) equation (with a limit of up to 20% of the target randomization of 230 subjects with eGFR <15 mL/min)
4. Patients who were intolerant of or have had an inadequate therapeutic response to oral iron supplements (in the opinion of the investigator)
5. Hgb ≥ 9.0 g/dL and ≤11.5 g/dL at Screening
6. Serum ferritin ≤200 ng/mL and Transferrin Saturation (TSAT) ≤25% at Screening
7. Serum Intact Parathyroid Hormone (iPTH) ≤600 pg/mL at Screening
8. Must consume a minimum of 2 meals per day
9. Willing and able to give written informed consent

Exclusion Criteria:

1. Serum phosphate <3.5 mg/dL at Screening
2. Liver enzymes (ALT/AST) >X3 times upper limit of normal at Screening
3. Symptomatic gastrointestinal bleeding or inflammatory bowel disease within 12 weeks prior to Screening
4. Evidence of acute kidney injury or requirement for dialysis within 12 weeks prior to Screening
5. Scheduled kidney transplant or initiation of dialysis planned within 24 weeks of Screening
6. IV iron administered within 4 weeks prior to Screening
7. Erythropoiesis-stimulating agent (ESA) administered within 4 weeks prior to Screening
8. Blood transfusion within 4 weeks prior to Screening
9. Receipt of any investigational drug within 4 weeks prior to Screening
10. Cause of anemia other than iron deficiency or chronic kidney disease
11. Malignancy (except non-melanoma skin cancer or disease-free for ≥2 years after curative therapy)
12. History of hemochromatosis
13. Active drug or alcohol dependence or abuse (excluding tobacco use or medicinal marijuana) within the 12 months prior to Screening or evidence of such abuse (in the opinion of the PI)
14. Subjects with known allergic reaction to previous oral iron therapy
15. Previous intolerance to oral ferric citrate
16. Psychiatric disorder that interferes with the subject's ability to comply with the study protocol
17. Planned surgery or hospitalization (anticipated to last >72 hours) during the randomized period of the trial other than dialysis access related surgery.
18. Any other medical condition that, in the opinion of the PI, renders the subject unable to or unlikely to complete the trial or that would interfere with optimal participation in the trial or produce significant risk to the subject
19. Inability to cooperate with study personnel