Keryx Biopharmaceuticals announced completion of patient enrollment in the long-term study component of its phase III registration program of Zerenex, the Company's ferric iron-based phosphate binder for the treatment of elevated serum phosphorus levels, or hyperphosphatemia, in patients with End-Stage Renal Disease (ESRD) on dialysis. The Zerenex phase III registration programme, which is being conducted pursuant to a Special Protocol Assessment (SPA) with the Food and Drug Administration (FDA), is comprised of an already successfully-completed phase III short-term study, and this ongoing phase III long-term study.

This phase III long-term study is a multi-centre, randomized, open-label, safety and efficacy clinical trial in over 400 ESRD patients on haemodialysis or peritoneal dialysis. The study consists of a 2-week washout period followed by a 52-week safety assessment in which patients are randomized 2:1 to receive either Zerenex or an active control. The 52-week safety assessment period is followed by a 4-week efficacy assessment. During the 4-week efficacy assessment, only those patients randomized to treatment with Zerenex during the safety assessment period will be randomized in a 1:1 ratio to either continue treatment with Zerenex or to be switched to placebo for a 4-week period.

Dr Julia Lewis, Professor of Medicine, Department of Nephrology, Vanderbilt University School of Medicine, and member of the Executive Committee of the Collaborative Study Group, is the Study Chair of the Zerenex phase III registration program. Dr Samuel S Blumenthal, Professor of Medicine at Medical College of Wisconsin, is the study's Co-Principal Investigator.

Ron Bentsur, CEO of Keryx, commented, “We are pleased to have completed patient enrollment into the Zerenex phase III long-term study, over-enrolling slightly to meet patient and physician interest in the study. We remain grateful to the investigators for their continued dedication and commitment to the clinical development of Zerenex.”

In April 2011, the Company reported the positive final dataset from the Zerenex phase III short-term study.

Keryx holds a worldwide license (except for certain Asian Pacific countries) to Zerenex (ferric citrate) from Panion and BF Biotech, Inc. The Japanese rights are sub-licensed by Keryx to Japan Tobacco Inc. and Torii Pharmaceutical Co., Ltd.

The SPA process is a procedure by which the FDA provides official evaluation and written guidance on the design and size of proposed protocols that are intended to form the basis for a new drug application.

Final marketing approval depends on the efficacy and safety results, including the adverse event profile, and an evaluation of the benefit/risk of treatment demonstrated in the phase III clinical programme. The SPA agreement may only be changed through a written agreement between the sponsor and the FDA, or if the FDA becomes aware of a substantial scientific issue essential to product efficacy or safety.

In the United States, according to data from the US Renal Data System, there are approximately 548,000 patients with end-stage renal disease, or ESRD, and the number of ESRD patients is projected to rise over 40% to approximately 785,000 by 2020. The majority of ESRD patients, over 375,000, require dialysis. Phosphate retention and the resulting hyperphosphatemia in patients with ESRD on dialysis are usually associated with secondary hyperparathyroidism, renal osteodystrophy, soft tissue mineralization and the progression of renal failure. ESRD patients usually require treatment with phosphate-binding agents to lower and maintain serum phosphorus at acceptable levels. The need for alternative phosphate-binding agents has long been recognized, especially given the increasing prevalence of ESRD as well as shortcomings with current therapies. Zerenex has the potential to be an effective and safe treatment in lowering and/or maintaining normal serum phosphorus levels in patients with ESRD and hyperphosphatemia.

The market for phosphate binders to treat hyperphosphatemia in ESRD patients in 2010 was approximately $750 million in the US and is approaching $1.5 billion worldwide.

Keryx Biopharmaceuticals is focused on the acquisition, development and commercialization of medically important pharmaceutical products for the treatment of cancer and renal disease.