Study to Evaluate the Safety and Tolerability of KRX-0502 (Ferric Citrate) in Children With Iron Deficiency Anemia Associated With Non-Dialysis Dependent Chronic Kidney Disease

Inclusion Criteria: * Age 6 years to \<18 years at Screening * Body Weight ≥12 kilograms (kg) at Screening * Chronic kidney disease (CKD) stage 3 to 5, not on dialysis, with estimated glomerular filtration rate (eGFR) \<60 milliliters per minute (mL/min)/1.73 meters squared (m\^2) utilizing the "Bedside Schwartz" equation * Hemoglobin (Hgb) ≥8.5 and ≤11.5 grams per deciliter (g/dL) at Screening * Transferrin saturation (TSAT) ≤25% at Screening * Ferritin ≤200 nanograms per milliliter (ng/mL) at Screening Exclusion Criteria: * Serum phosphorus level at Screening: * 6 to \<13 years: ≤4.0 milligrams per deciliter (mg/dL); * 13 to \<18 years: ≤2.7 mg/dL * Liver transaminases (aspartate aminotransferase \[AST\] and/or alanine aminotransferase \[ALT\]) ˃3× the upper limit of normal at Screening * Active significant gastrointestinal (GI) disorder, including overt gastrointestinal (GI) bleeding or active inflammatory bowel disease * Unable to swallow pills * Anemia due to causes other than iron deficiency anemia (IDA) of CKD * Intravenous iron therapy or blood transfusion within 4 weeks before the Screening visit * Participants with a functioning organ transplant * Receipt of any investigational drug within 4 weeks before Screening * Phosphate binder use during the Screening period