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Kidney Week

Abstract: TH-PO514

Ferric Citrate Lowered Serum Phosphate Only When Elevated in Patients with Nondialysis-Dependent (NDD) CKD and Iron Deficiency Anemia (IDA)

Session Information

Category: Chronic Kidney Disease (Non-Dialysis)

  • 305 CKD: Clinical Trials and Tubulointerstitial Disorders


  • Block, Geoffrey A., Denver Nephrology, Denver, Colorado, United States
  • Pergola, Pablo E., Renal Associates PA, San Antonio, Texas, United States
  • Uhlig, Katrin, Keryx Biopharmaceuticals, Boston, Massachusetts, United States
  • Neylan, John F., Keryx Biopharmaceuticals, Boston, Massachusetts, United States
  • Fishbane, Steven, Hofstra Northwell Health, Great Neck, New York, United States
  • Chertow, Glenn Matthew, Stanford University School of Medicine, Palo Alto, California, United States

Ferric citrate (FC), an oral iron-based phosphate (P) binder approved for control of serum P in patients (pts) with CKD on dialysis, has also shown improvement in hemoglobin (Hb) and iron parameters in pts with NDD-CKD with IDA. Here, in a post-hoc analysis of a phase 3 study, we examine effects of FC on serum P in pts by different baseline (BL) P levels and stages of CKD.


233 pts with NDD-CKD and IDA were randomized 1:1 to receive FC (n=117) or placebo (n=116) for 16 weeks. FC was initiated at 3 1-g tablets/day and titrated to achieve a Hb increase ≥1 g/dL from BL (max 12 g/day). FC effects on P were examined by BL strata of P, CKD stage (per eGFR), and FGF23 (grouped by BL quartile [Q]).


Decreases in P with FC treatment were greater in pts with higher BL P levels. P remained stable in pts in the lowest BL P group even with increased FC dose. Likewise, P decrease was greatest in pts with lower BL eGFR (which correlated to higher BL P) [Figure]. Similar results were seen when pts were stratified by BL FGF23 [Table]. At 16 wks, the FC dose was similar across sub-groups, suggesting BL P did not affect dosing for treatment of IDA. Multivariate linear regression analysis confirmed BL P as a strong independent predictor of change in P (p<0.0001) after adjusting for treatment, BL eGFR and BL albumin.


In NDD-CKD pts with IDA, the effect of FC on P reduction is dependent on the BL P, with the greatest reduction in pts with the highest serum P. These results support the use of FC in NDD-CKD pts with IDA regardless of BL P.

Mean Serum P (mg/dL) Levels Stratified by BL FGF23
i-FGF23 (pg/mL)Q1
(87 – <134.8)
(134.8 – <211.3)
BL±SE (n)3.87±0.13 (28)3.96±0.09 (31)4.20±0.13 (25)4.83±.21 (33)
16 wks±SE (n)3.68±0.13 (22)3.58±0.11 (26)3.86±0.19 (16)3.84±0.10 (22)
Mean Δ (SE)-0.24 (0.13)-0.37 (0.16)-0.33 (0.13)-0.92 (0.26)


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