To assess the long-term safety and effectiveness of Nephoxil® for the treatment of hyperphosphatemia in patients with ESRD undergoing dialysis.

This study is an open-label, prospective, long term, Phase IV study to assess the safety and efficacy of Nephoxil® in subjects with ESRD on dialysis.

Inclusion Criteria:

1. Is ≧ 18 years of age on the day of signing informed consent or other age required by local regulation
2. Willing and able to provide written informed consent
3. ESRD patients who is undergoing hemodialysis 3 times per week and is considered necessary to receive medication for hyperphosphatemia by his/her treating physician
4. Serum ferritin <1000 ng/mL and transferrin saturation (TSAT) < 50% at the Enrollment Visit
5. Women of child-bearing potential (WOCBP [defined as women ≤ 50 years of age with a history of amenorrhea for < 12 months prior to study entry]) who is willing to use an effective form of contraception during study participation

Exclusion Criteria:

1. Has any known contraindication to ferric citrate according to locally approved prescribing information, include but not limited to the following criteria:

   i. Is allergic to ferric citrate ii. Has hypophosphatemia iii. Has hemochromatosis or iron overload syndromes iv. Has active severe GI disorders

2. Has parathyroidectomy (PTx) or percutaneous ethanol injection therapy (PEIT) within 3 months prior to Enrollment Visit or serum calcium < 7 mg/dL at the Enrollment Visit

3. Has participated in another interventional study for any investigational agent or device within 30 days prior to enrollment

4. Is currently pregnant or breastfeeding

5. Other unstable medical condition or psychiatric conditions that is considered unsuitable for this study per Investigator's clinical judgment