In concert with clinical trial data granting drug approval, a new study finds that hyperphosphatemia and anemia biomarker levels improved in a small group of real-world patients taking ferric citrate.

Pablo E. Pergola, MD, PhD, of Renal Associates PA in San Antonio, and colleagues reviewed the medical charts of 67 hemodialysis (HD) and 25 peritoneal dialysis (PD) patients from 7 clinical practices in the United States who received ferric citrate at a starting dose of 6 tablets daily. Of the 92 patients, 21 were previously binder-naïve, 62 were treated with sevelamer and/or calcium-based binders, and 9 received other phosphate binders. For 17 patients, ferric citrate therapy was added to their current binder.

Before taking ferric citrate, just 22% had serum phosphorus levels in the target range of 5.5 mg/dL or below. At 6 months after treatment, 65% of patients were within the target range. Average serum phosphorus declined from 6.55 to 5.4 mg/dL. PD patients responded better than HD patients after the first 2 months. No changes in serum calcium or intact parathyroid hormone levels occurred.

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Although ferric citrate is not indicated for iron maintenance, anemia biomarkers also improved. Average hemoglobin rose from 10.6 g/dL within 3 months and reached 11.1 g/dL at 6 months. Ferritin and transferrin saturation increased from 734 ng/mL and 27.1%, respectively, to 947 ng/mL and 37% at 6 months.

By study’s end, HD and PD patients had comparable iron results, except for average ferritin, which was higher in the HD group. Binder-naïve and binder-experienced patients likewise responded similarly. A third or more patients received intravenous (IV) iron and some erythropoiesis-stimulating agents.

“In conclusion, real-world data from this analysis have demonstrated that ferric citrate is an effective phosphate binder with 65% of the patients within the target phosphorus range and overall increased iron stores and maintenance of Hgb levels following 6 months of treatment,” Dr Pergola and colleagues concluded in Clinical Nephrology.

According to the investigators, the real-world efficacy of ferric citrate appears similar to the efficacy observed in phase III trial results reported on the drug label. The findings also are in line with DOPPS (Dialysis Outcomes and Practice Patterns Study) data.

No drug-related adverse events were reported or suspected.

Among possible reasons for switching to ferric citrate, the previous binder may have been ineffective, causing side effects, or difficult to take due to the number of pills.

Study limitations included the relatively small sample size and exclusion of patients who could not tolerate ferric citrate or otherwise discontinued treatment.

The study was funded by Keryx Biopharmaceuticals, which manufactures ferric citrate (Auryxia). Various authors disclosed fees from the company.

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Hain DJ, Marinaro M, Koeper DW, et al. Ferric citrate controls serum phosphorus in dialysis patients: retrospective data. Clin Nephrol. 2017 Jul;88(1):12–18. doi: 10.5414/CN109057