Keryx Biopharmaceuticals, Inc. has announced the initiation of a Phase 2 study of Zerenex (ferric citrate), an ferric iron-based phosphate binder drug candidate, in managing serum phosphorus and iron deficiency in anemic patients with Stage 3 to 5 non-dialysis dependent chronic kidney disease ("NDD-CKD").

In the United States alone, over one and a half million people suffering from Stages 3 to 5 NDD-CKD have iron deficiency anemia, however, there are currently no oral iron supplements with an FDA label in NDD-CKD. Also, there are currently no FDA approved phosphate binders in NDD-CKD.

It is estimated that approximately 10 to 15% of the U.S. adult population is affected by chronic kidney disease (CKD), a condition generally characterized by greater than 50% reduction of normal kidney function. In addition, elevated levels of serum phosphorus become more prevalent in Stages 3 to 5 non-dialysis dependent CKD (NDD-CKD) patients. Several studies have shown that higher serum phosphorus concentrations may be associated with increased mortality and morbidity in CKD, however, no phosphate binders are currently FDA approved for NDD-CKD.

Iron deficiency anemia, which develops early in the course of CKD and worsens with disease progression, is extremely prevalent in the NDD-CKD population and is associated with fatigue, lethargy, decreased quality of life and is also believed to be associated with cardiovascular complications, hospitalizations, and increased mortality. Based on data contained in a 2009 publication in the Journal of the American Society of Nephrology, it is estimated that over 1.5 million adults with NDD-CKD in the U.S. alone are also afflicted with iron deficiency anemia. To combat this anemia, iron replacement therapy is essential to increase iron stores, such as ferritin and TSAT levels, and raise hemoglobin levels.

Currently available oral iron supplements are associated with limited efficacy and dose-limiting tolerability issues. No oral iron agents are currently FDA approved to treat iron deficiency anemia in NDD-CKD. Erythropoiesis stimulating agents (ESAs) and intravenous (IV) iron are not frequently administered in NDD-CKD due to both the FDA warning label of potential cardiovascular risk for ESAs in NDD-CKD and logistical complications associated with administering IV medicines in office settings which lack the necessary facilities, such as emergency equipment and/or emergency medical access. Consequently, the NDD-CKD patient population remains underserved.

The Phase 2 study initiated today is a multicenter, randomized, safety and efficacy clinical trial designed to compare the ability of Zerenex to manage serum phosphorus and iron deficiency versus placebo in anemic patients with Stages 3 to 5 NDD-CKD. Eligible patients will be randomized 1:1 to receive either Zerenex or placebo for a 12-week treatment period. The primary endpoints of the study are to demonstrate changes in ferritin, TSAT and serum phosphorus levels over the 12-week treatment period. Secondary endpoints include changes in hemoglobin and FGF-23. The study plans to randomize approximately 150 patients from approximately 15 sites in the U.S. Patient enrollment is expected to take up to 6 months, with study completion expected in mid-2013.

Zerenex is currently also in a long-term Phase 3 study, under Special Protocol Assessment, as treatment for end-stage renal disease patients with hyperphosphatemia on dialysis. Top-line data from this Phase 3 study is expected to be announced by approximately year-end 2012, with the NDA filing expected in the first quarter of 2013 for this indication.