Fermagate

Phosphate excess is associated with increased mortality in patients with chronic kidney disease (CKD) and has recently been linked to accelerated aging. Oral phosphate binders are prescribed to patients with CKD to prevent absorption of dietary phosphate. Currently available binders have been associated with impaired outcomes (calcium-based binders) or are expensive (non-calcium-based binders). Iron-based phosphate binders represent a new class of phosphate binders. Four iron-based phosphate binders have undergone testing in clinical trials. The development of fermagate and SBR759 is currently on hold due to suboptimal and adverse effect profiles in at least some clinical trials. Ferric citrate and sucroferric oxyhydroxide (PA21) are at different stages of application for regulatory approval after being found safe and efficacious in decreasing serum phosphate. Iron from ferric citrate is more readily absorbed than that from sucroferric oxyhydroxide. Sucroferric oxyhydroxide was launched in the USA in 2014 for the treatment of hyperphosphatemia in adult dialysis patients. Ferric citrate may be more suited for chronic treatment of hyperphosphatemia in CKD patients requiring iron supplements but its use may have to be limited in time because of potential for iron overload in patients not needing iron or not receiving erythropoiesis-stimulating agents. In contrast, sucroferric oxyhydroxide may be more suited for hyperphosphatemic CKD patients not requiring iron supplements.

This phase II study tested the safety and efficacy of fermagate, a calcium-free iron and magnesium hydroxycarbonate binder, for treating hyperphosphatemia in hemodialysis patients.

A randomized, double-blind, three-arm, parallel-group study compared two doses of fermagate (1 g three times daily or 2 g three times daily with placebo). Sixty-three patients who had been on a stable hemodialysis regimen for > or =3 mo were randomized to the treatment phase. Study medication was administered three times daily just before meals for 21 d. The primary endpoint was reduction in serum phosphate over this period.

In the intention-to-treat analysis, mean baseline serum phosphate was 2.16 mmol/L. The fermagate 1- and 2-g three-times-daily treatment arms were associated with statistical reductions in mean serum phosphate to 1.71 and 1.47 mmol/L, respectively. Adverse event (AE) incidence in the 1-g fermagate arm was statistically comparable to the placebo group. The 2-g arm was associated with a statistically higher number of patients reporting AEs than the 1-g arm, particularly gastrointestinal AEs, as well as a higher number of discontinuations, complicating interpretation of this dose's efficacy. Both doses were associated with elevations of prehemodialysis serum magnesium levels.

The efficacy and tolerability of fermagate were dose dependent. Fermagate showed promising efficacy in the treatment of hyperphosphatemia in chronic hemodialysis patients as compared with placebo in this initial phase II study. The optimal balance between efficacy and tolerability needs to be determined from future dose-titration studies, or fixed-dose comparisons of more doses.