In the open-label, non-randomized trial, patients with chronic kidney disease (CKD), who had anti-erythropoietin antibody-mediated PRCA and who were anemic, generally experienced increases in hemoglobin above 11 g/dL following once monthly injections of Hematide.

PRCA is a rare, serious and debilitating autoimmune disorder, which can occur when the body produces neutralizing antibodies against the currently marketed recombinant human erythropoietins, such as epoetin alfa or beta and darbepoetin alfa, thus suppressing the production of red blood cells by the bone marrow. While PRCA is a rare disorder, it remains a concern among physicians and patients as it can significantly limit treatment options for anemia in patients with CKD and requires these patients to receive regular blood transfusions. Hematide is under development for the treatment of anemia associated with chronic renal failure, including patients on chronic dialysis and not on dialysis. Hematide is a novel investigational synthetic, PEGylated peptide-based erythropoietin (EPO) receptor agonist with no sequence homology with human EPO, and hence is not expected to induce PRCA.

"These data suggest that Hematide may be a promising anemia treatment alternative for patients in this population, with a different immunogenicity profile than other erythropoiesis-stimulating agents," said Iain C. Macdougall, M.D., consultant nephrologist in the Department of Renal Medicine at King`s College Hospital in London, Hematide clinical investigator and lead author of the New England Journal of Medicine article. "Hematide stimulated red blood cell production in most patients with antibody-mediated PRCA and thereby diminished these patients` dependence on blood transfusions. Additionally, following the start of treatment with Hematide, most patients experienced a decline in their levels of neutralizing anti-EPO antibodies associated with the underlying PRCA condition."

The purpose of this study was to test whether Hematide given subcutaneously can stimulate red blood cell production in patients with anti-EPO antibodies, who otherwise had a compromised ability to generate red blood cells. Fourteen patients were treated with Hematide for a median of 28 months (range 3-36). Thirteen of the 14 patients (93%) achieved the primary endpoint of an increase in hemoglobin to a level greater than 11 g/dL without the need for regular blood transfusions. While the number of patients tested is small, the beneficial effect was consistent and sustained for up to 156 weeks. Further, in six of 14 patients, titers of anti-erythropoietin antibodies fell below the detection limit following treatment with Hematide.

Overall, adverse events were generally mild or moderate in severity. Adverse events that were possibly related to Hematide were hypertension, bone pain and injection site hematoma. Two serious adverse events were considered possibly related to Hematide (severe anemia and lack of response) and both occurred in a patient who developed anti-Hematide antibodies. This patient initially responded to Hematide, but later had a diminished clinical response despite increasing doses of the drug.

"We are encouraged by these findings, which suggest fundamental differences with Hematide compared to commercially available ESAs," said Anne-Marie Duliege, M.D., M.S., chief medical officer of Affymax. "If approved, we believe that Hematide could represent a significant new treatment option for providers caring for patients with chronic renal failure."

About Hematide

Hematide is a synthetic, peptidic erythropoiesis stimulating agent (ESA) linked to polyethylene glycol (PEG) that is being developed for the treatment of anemia associated with chronic renal failure.

Affymax and Takeda are collaborating on the development of Hematide and plan to co-commercialize the product once approved in the United States. Phase 3 clinical trials are being conducted to investigate the potential for Hematide to treat anemia associated with chronic renal failure.

About PRCA

Dialysis and non-dialysis patients with CKD frequently develop anemia because of a reduction in native EPO production by dysfunctional kidneys. Since the late 1980s, recombinant EPO has been used successfully to treat anemia-associated EPO deficiency. A small number of CKD patients develop antibody-mediated PRCA, a type of anemia that develops when patients mount a neutralizing antibody response against recombinant EPO used to treat the anemia associated with CKD. These antibodies neutralize not only the recombinant EPO but also cross-neutralize natural EPO produced by the patients, leading to a state of EPO resistance and transfusion dependence. While the incidence of PRCA is low, there continues to be sporadic reports of antibody-mediated PRCA associated with commercially available EPO products. Concern over PRCA prompted the addition of warnings in the prescribing information of all EPO-based products marketed in the U.S. In April 2009, currently marketed ESA manufacturers warned healthcare professionals of the potential for antibody-mediated PRCA when the drugs are used to treat anemia associated with interferon or Pegylated interferon and ribavirin therapy in patients with HCV infection.

About Takeda Pharmaceuticals North America, Inc.and Takeda Global Research & Development Center, Inc.

Based in Deerfield, Ill., Takeda Pharmaceuticals North America, Inc. and Takeda Global Research & Development Center, Inc. are subsidiaries of Takeda Pharmaceutical Company Limited, the largest pharmaceutical company in Japan. The respective companies currently market oral diabetes, insomnia, rheumatology and gastroenterology treatments and seek to bring innovative products to patients through a pipeline that includes compounds in development for diabetes, cardiovascular disease, gastroenterology, neurology and other conditions. To learn more about these Takeda companies, visit www.tpna.com.

About Affymax, Inc.

Affymax, Inc. is a biopharmaceutical company committed to developing novel drugs to improve the treatment of serious and often life-threatening conditions. Affymax`s product candidate, Hematide, is currently in Phase 3 clinical trial stage for the treatment of anemia associated with chronic renal failure. For additional information, please visit www.affymax.com.

This release contains forward-looking statements, including statements regarding the success of the collaboration, timing, design and results of the Companies` clinical trials and drug development program and the timing and likelihood of the commercialization of Hematide. The Companies` actual results may differ materially from those indicated in these forward-looking statements due to risks and uncertainties, including risks relating to the continued safety and efficacy of Hematide in clinical development, the potential for once per month dosing and room temperature stability, the cardiovascular event rate in the Phase 3 program, the timing of patient accrual in ongoing and planned clinical studies, regulatory requirements and approvals, research and development efforts, industry and competitive environment, intellectual property rights and disputes and other matters that are described in Affymax's quarterly report on Form 10-Q filed with the Securities and Exchange Commission. Investors are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this release. The Companies undertake no obligation to update any forward-looking statement in this press release.

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Affymax, Inc. Paul B. Cleveland, EVP Corporate Development, 650-812-8717 or Takeda Global Research & Development Center, Inc. Julia Ellwanger, Corporate Communications, 224-554-7681 or WeissComm Partners Carolyn Wang, Director, 415-946-1065

Copyright Business Wire 2009