Affymax® Reports Phase 2 Clinical Trial Data Supporting Hemoglobin Increases with Once-Per-Month Hematide™ Regardless of Patient Baseline Renal Function

PALO ALTO, Calif., May 26, 2009 (BUSINESS WIRE) -- Affymax, Inc. (Nasdaq:AFFY) today announced data from a post hoc analysis of 120 patients in a Phase 2 clinical trial of Hematide™ in non-dialysis chronic kidney disease (CKD) patients. The data suggest that there is no major impact of baseline renal function as measured by Estimated Glomerular Filtration Rate (eGFR)on the monthly Hematide dose required to increase and maintain hemoglobin (Hgb) values within target range in non-dialysis CKD patients. The data were presented by Iain C. Macdougall, M.D. at the World Congress of Nephrology meeting being held in Milan, Italy.

"As Hematide is partially excreted by the kidneys, it was imperative to evaluate whether renal function affected the product's ability to achieve hemoglobin target ranges," said Dr. Macdougall, consultant nephrologist in the Department of Renal Medicine at King's College Hospital in London. "These data suggest that Hematide results in appropriate management of hemoglobin levels in a broad spectrum of patients with CKD, regardless of baseline renal function. Anemia is a pervasive problem in the chronic kidney disease patient population. Being able to manage and control anemia allows treating physicians to focus attention on management of the patient's underlying renal disease."

The post-hoc analysis included data from an open-label Phase 2 study of 120 patients with stage 3, 4 or 5 CKD. The analysis suggests that mean Hgb increased approximately 2 g/dL by three months (from approximately 10 g/dL to approximately 12 g/dL) and remained stable for five months across all CKD groups, regardless of baseline eGFR. In addition, Hematide doses were similar across all CKD groups regardless of baseline eGFR. Twelve patients (10%) reported an adverse event considered possibly related to treatment. Adverse events occurring in more than one patient included arthritis (2), headache (2), and hypertension (7). One serious adverse event, an embolic cerebral infarction, was considered possibly related to study drug. The study was not specifically designed to evaluate the effect of renal function on Hematide dose and therefore caution should be exercised in the interpretation of results.

Anne-Marie Duliege, M.D., chief medical officer for Affymax added, "This is an encouraging post hoc analysis that warrants further evaluation. Hematide's ability to increase hemoglobin in a broad spectrum of chronic renal failure patients is the subject of our ongoing Phase 3 clinical trials. We will continue to generate data which we believe will assist physicians in optimizing anemia management in their patients."

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 in the United States. The product, upon approval, will be commercialized in the European Union by Takeda. Affymax is conducting Phase 3 clinical trials for Hematide to treat anemia associated with chronic renal failure.

About Affymax, Inc.
Affymax, Inc. is a biopharmaceutical company developing novel drugs to improve the treatment of serious and often life-threatening conditions. Affymax's lead 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 Company's clinical trials and drug development program and the timing and likelihood of the commercialization of Hematide. The Company's 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, 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 Company undertakes no obligation to update any forward-looking statement in this press release.

Source
Affymax, Inc.
Sylvia Wheeler, 650-812-8861
Executive Director, Corporate Communications