Ferric Citrate

Auryxia is a phosphate binder indicated for the control of serum phosphorus levels in adult patients with chronic kidney disease on dialysis. ( 1 ) Auryxia is an iron replacement product indicated for the treatment of iron deficiency anemia in adult patients with chronic kidney disease not on dialysis. ( 1 )

1.1 Hyperphosphatemia in Chronic Kidney Disease on Dialysis Auryxia is indicated for the control of serum phosphorus levels in adult patients with chronic kidney disease on dialysis.

1.2 Iron Deficiency Anemia in Chronic Kidney Disease Not on Dialysis Auryxia is indicated for the treatment of iron deficiency anemia in adult patients with chronic kidney disease not on dialysis.

Tablets: Auryxia 210 mg ferric iron, equivalent to 1 g ferric citrate, film-coated, peach-colored, and oval-shaped tablet debossed with “KX52.” Tablets: 210 mg ferric iron, equivalent to 1 g ferric citrate. ( 3 )

Auryxia is contraindicated in patients with iron overload syndromes (e.g., hemochromatosis) [see Warnings and Precautions ( 5.1 )] . Iron overload syndromes (e.g., hemochromatosis). ( 4 )

Iron overload: Monitor ferritin and TSAT. Patients may require a reduction in dose or discontinuation of intravenous iron. ( 5.1 ) Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children under 6 years of age. Keep this product out of reach of children. In case of accidental overdose, call a doctor or poison control center immediately. ( 5.2 )

5.1 Iron Overload Iron absorption from Auryxia may lead to excessive elevations in iron stores. Increases in serum ferritin and transferrin saturation (TSAT) levels were observed in clinical trials. In a 56-week safety and efficacy trial evaluating the control of serum phosphate levels in patients with chronic kidney disease on dialysis in which concomitant use of intravenous iron was permitted, 55 (19%) of patients treated with Auryxia had a ferritin level >1500 ng/mL as compared with 13 (9%) of patients treated with active control. Assess iron parameters (e.g., serum ferritin and TSAT) prior to initiating Auryxia and monitor iron parameters while on therapy [see Contraindications ( 4 ), Overdosage ( 10 ) and Clinical Pharmacology ( 12.2 )] . Patients receiving intravenous iron may require a reduction in dose or discontinuation of intravenous iron therapy.

5.2 Risk of Overdosage in Children Due to Accidental Ingestion Accidental ingestion and resulting overdose of iron-containing products is a leading cause of fatal poisoning in children under 6 years of age [see Overdosage ( 10 )] . Advise patients of the risks to children and to keep Auryxia out of the reach of children.

Most common adverse reactions (incidence ≥5%) are discolored feces, diarrhea, constipation, nausea, vomiting, cough, abdominal pain, and hyperkalemia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Keryx Biopharmaceuticals at 1-844-445-3799 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to adverse reaction rates in the clinical trials of another drug and may not reflect the rates observed in practice. Hyperphosphatemia in Chronic Kidney Disease on Dialysis A total of 289 patients were treated with Auryxia and 149 patients were treated with active control (sevelamer carbonate and/or calcium acetate) during the 52-week, randomized, open-label, active control phase of a trial in patients on dialysis. A total of 322 patients were treated with Auryxia for up to 28 days in three short-term trials. Across these trials, 557 unique patients were treated with Auryxia; dosage regimens in these trials ranged from 210 mg to 2,520 mg of ferric iron per day, equivalent to 1 to 12 tablets of Auryxia. Adverse reactions reported in more than 5% of patients treated with Auryxia in these trials included diarrhea (21%), discolored feces (19%), nausea (11%), constipation (8%), vomiting (7%), and cough (6%). During the 52-week, active-control period, 61 patients (21%) on Auryxia discontinued study drug because of an adverse reaction, as compared to 21 patients (14%) in the active control arm. Patients who were previously intolerant to any of the active control treatments (calcium acetate and sevelamer carbonate) were not eligible to enroll in the study. Gastrointestinal adverse reactions were the most common reason for discontinuing Auryxia (14%). Iron Deficiency Anemia in Chronic Kidney Disease Not on Dialysis Across two trials, 190 patients with CKD-NDD were treated with Auryxia. This included a study of 117 patients treated with Auryxia and 116 patients treated with placebo in a 16-week, randomized, double-blind period and a study of 75 patients treated with Auryxia and 73 treated with placebo in a 12-week randomized double-blind period. Dosage regimens in these trials ranged from 210 mg to 2,520 mg of ferric iron per day, equivalent to 1 to 12 tablets of Auryxia. Adverse reactions reported in at least 5% of patients treated with Auryxia in these trials are listed in Table 1. Table 1: Adverse Events Reported in Two Clinical Trials in at least 5% of patients receiving Auryxia Body System Adverse Reaction Auryxia % (N=190) Placebo % (N=188) Any Adverse Reaction 75 62 Metabolism and Nutrition Disorders Hyperkalemia 5 3 Gastrointestinal Disorders Discolored feces 22 0 Diarrhea 21 12 Constipation 18 10 Nausea 10 4 Abdominal Pain 5 2 During the 16-week, placebo-control trial, 12 patients (10%) on Auryxia discontinued study drug because of an adverse reaction, as compared to 10 patients (9%) in the placebo control arm. Diarrhea was the most common adverse reaction leading to discontinuation of Auryxia (2.6%).

Table 2: Oral drugs that can be administered concomitantly with Auryxia Amlodipine Aspirin Atorvastatin Calcitriol Clopidogrel Digoxin Diltiazem Doxercalciferol Enalapril Fluvastatin Glimepiride Levofloxacin Losartan Metoprolol Pravastatin Propranolol Sitagliptin Warfarin Oral drugs that have to be separated from Auryxia and meals Dosing Recommendations Doxycycline Take at least 1 hour before Auryxia Ciprofloxacin Take at least 2 hours before or after Auryxia Oral medications not listed in Table 2 There are no empirical data on avoiding drug interactions between Auryxia and most concomitant oral drugs. For oral medications where a reduction in the bioavailability of that medication would have a clinically significant effect on its safety or efficacy, consider separation of the timing of the administration of the two drugs. The duration of separation depends upon the absorption characteristics of the medication concomitantly administered, such as the time to reach peak systemic levels and whether the drug is an immediate release or an extended release product. Consider monitoring clinical responses or blood levels of concomitant medications that have a narrow therapeutic range. When clinically significant drug interactions are expected, consider separation of the timing of administration. Consider monitoring clinical responses or blood levels of the concomitant medication. ( 7 )

8.1 Pregnancy Risk Summary There are no available data on Auryxia use in pregnant women to inform a drug-associated risk of major birth defects and miscarriage. Animal reproduction studies have not been conducted using Auryxia. Skeletal and encephalic malformation was observed in neonatal mice when ferric gluconate was administered intraperitoneally to gravid dams on gestation days 7-9. However, oral administration of other ferric or ferrous compounds to gravid CD1-mice and Wistar-rats caused no fetal malformation. An overdose of iron in pregnant women may carry a risk for spontaneous abortion, gestational diabetes and fetal malformation. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. Adverse outcomes in pregnancy occur regardless of the health of the mother or the use of medications. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2 to 4% and 15 to 20%, respectively. Clinical Considerations The effect of Auryxia on the absorption of vitamins and other nutrients has not been studied in pregnant women. Requirements for vitamins and other nutrients are increased in pregnancy.

8.2 Lactation Risk Summary There are no human data regarding the effect of Auryxia in human milk, the effects on the breastfed child, or the effects on milk production. Data from rat studies have shown the transfer of iron into milk by divalent metal transporter-1 (DMT-1) and ferroportin-1 (FPN-1). Hence, there is a possibility of infant exposure when Auryxia is administered to a nursing woman. The development and health benefits of breastfeeding should be considered along with the mother’s clinical need for Auryxia and any potential adverse effects on the breastfed child from Auryxia or from the underlying maternal condition.

8.4 Pediatric Use The safety and efficacy of Auryxia have not been established in pediatric patients. Juvenile Animal Toxicity Data In animal studies, greater gastrointestinal toxicity was observed when ferric citrate was administered by gavage as compared to administration with solid food. Because Auryxia is recommended to be taken with meals and patients under 6 months of age are unlikely to be eating solid food, they may be at greater risk of gastrointestinal toxicity.

8.5 Geriatric Use Clinical studies of Auryxia included 292 subjects aged 65 years and older (104 subjects aged 75 years and older). Overall, the clinical study experience has not identified any obvious differences in responses between the elderly and younger patients in the tolerability or efficacy of Auryxia.

Hyperphosphatemia in Chronic Kidney Disease on Dialysis Ferric iron binds dietary phosphate in the GI tract and precipitates as ferric phosphate. This compound is insoluble and is excreted in the stool. By binding phosphate in the GI tract and decreasing absorption, ferric citrate lowers the phosphate concentration in the serum. Iron Deficiency Anemia in Chronic Kidney Disease Not on Dialysis Ferric iron is reduced from the ferric to the ferrous form by ferric reductase in the GI tract. After transport through the enterocytes into the blood, oxidized ferric iron circulates bound to the plasma protein transferrin, and can be incorporated into hemoglobin.