Phase 3 Long-Term Study of Zerenex for Hyperphosphatemia in ESRD

Keryx Biopharmaceuticals announced top-line results from the long-term Phase 3 study of Zerenex (ferric citrate), for the treatment of elevated serum phosphorus levels, or hyperphosphatemia, in patients with end-stage renal disease (ESRD) on dialysis.

This long-term study was a multicenter, randomized, open-label, safety and efficacy clinical trial in 441 ESRD patients on hemodialysis or peritoneal dialysis. The study consisted of a two week washout period followed by a 52-week Safety Assessment Period in which patients were randomized 2:1 to receive wither Zerenex or an active control (Renvela[sevelamer carbonate; Genzyme] and/or Phoslo[calcium acetate; Fresenius Medical Care]). This was followed by a 4-week Efficacy Assessment Period, in which only those subjects randomized to treatment with Zerenex during the Safety Assessment Period were randomized in a 1:1 ratio to either continue treatment with Zerenex or switch to placebo for a 4-week treatment period. Subjects were titrated during the study to achieve serum phosphorus levels that ranged between 3.5 to 5.5 mg/dL. The primary endpoint of the study was the mean change in serum phosphorus from baseline (Week 52) to end of the four-week Efficacy Assessment Period (Week 56) vs. placebo in the intent-to-treat group.

The study met its primary endpoint, resulting in a highly statistically significant change in serum phosphorus vs. placebo over the four-week Efficacy Assessment Period of the study (P<0.0001).

Zerenex is an oral, ferric iron-based compound that has the capacity to bind to phosphate and form non-absorbable complexes.

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