October 1, 2008

Affymetrix and Medical Prognosis Institute Collaborate to Develop Cancer Treatment Products

Affymetrix Inc. (Nasdaq:AFFX) and Medical Prognosis Institute A/S (MPI), a leading cancer diagnostic development company based in Denmark, today announced that they have signed a Powered by Affymetrix(TM) (PbA) agreement. With this agreement, MPI gains non-exclusive access to Affymetrix microarray technology to develop and commercialize drug sensitivity prediction and prognostic products for patients with cancer.

Of 179 new anti-cancer drugs tested in Phase I trials between 1976 and 1993, only 28 percent were considered effective in Phase III.(1) MPI believes the lack of effect is highly correlated to the response rate, and is now pursuing the opportunity to identify responders; for example, for failed Phase III cancer drugs. Based on Affymetrix microarray technology, MPI aims to market its own proprietary products targeted at individual cancer prognosis and prediction of anti-cancer treatment response.

"Our partnership with Affymetrix enables us to translate our discoveries into robust tools with broad clinical utility to greatly improve the prognosis and treatment of millions of people living with cancer. It also boosts the probability of successful anti-cancer drug development in partnership with drug companies," said Jesper Drejet, president and CEO of Medical Prognosis Institute. "We are confident of being able to obtain regulatory clearance and achieve commercialization within one to two years." (2)

"MPI's cancer prognosis tools have the potential to customize treatment schemes, revolutionize the control of this disease and the chances of recovery," said Kevin King, president of Affymetrix. "Agreements such as this continue to validate the need for microarrays for complex signatures for reproducibility and accuracy. We are proud to help MPI advance its ambitions to improve drug therapy choices and provide hope for those struggling with this destructive disease."

Affymetrix offers a continuous path to discover, develop and commercialize complex biomarker signatures. The company partners with leading diagnostic companies through its PbA program. The Affymetrix GeneChip(R) System 3000Dx is the only microarray instrumentation platform to receive regulatory clearance by the U.S. FDA and is CE marked in the European Union for in vitro diagnostic use.

The CLIA-certified Affymetrix Clinical Services Laboratory (ACSL) offers microarray-based molecular diagnostic development support and clinical trial testing services that enable customers to leverage Affymetrix' technology and experience to bring more effective molecular diagnostic tests to patients faster than ever before. There are currently more than 20 different molecular assay tests based on the Affymetrix platform under development by Affymetrix and its PbA partners.

(1) Sekine I., et al. Relationship between objective responses in phase I trials and potential efficacy of non-specific cytotoxic investigational new drugs. Annals of Oncology 13:1300 (2002).

(2) http://www.medical-prognosis.com/?id=6

About Medical Prognosis Institute

Headquartered in H0rsholm, Denmark, Medical Prognosis Institute's (MPI) mission is to improve cancer treatment with leading-edge technology based on DNA microarrays. MPI uses proprietary individualized genomic profiling of tumor tissue for prognostication of individual patients and for determining which cancer patients will benefit from which specific chemotherapy and/or radiation therapy. MPI is currently conducting clinical trials to validate its claims that its products and services will give cancer patients and oncologists necessary insight to help make better treatment decisions. In addition, MPI, also an Affymetrix Service Provider, recently began providing its fast turn-around, high-quality DNA microarray services on a fee-for-service basis to the academic and biopharmaceutical industry in the discovery phase. For more information, visit www.medical-prognosis.com, email [email protected] or call +45 40862156.

About Affymetrix

Affymetrix GeneChip(R) microarray technology is the industry-standard tool for analyzing complex genetic information. After inventing microarray technology in the late 1980s, Affymetrix scientists have been dedicated to developing innovative products that provide researchers with a more complete view of the genome. These products continue to accelerate genetic research and enable scientists to develop diagnostics and tailor treatments for individual patients by identifying and measuring the genetic information associated with complex diseases.

Today, Affymetrix technology is used by the world's top pharmaceutical, diagnostic and biotechnology companies, as well as leading academic, government and not-for-profit research institutes. More than 1,700 systems have been shipped around the world and more than 13,000 peer-reviewed papers have been published using the technology.

Affymetrix is headquartered in Santa Clara, Calif., and has manufacturing facilities in Sacramento, Calif., Cleveland, Ohio, and Singapore. The company has about 1,100 employees worldwide and maintains sales and distribution operations across Europe and Asia. For more information about Affymetrix, please visit the company's website at www.affymetrix.com.

Forward-looking Statements

All statements in this press release that are not historical are "forward-looking statements" within the meaning of Section 21E of the Securities Exchange Act as amended, including statements regarding Affymetrix' "expectations,""beliefs,""hopes,""intentions,""strategies" or the like. Such statements are subject to risks and uncertainties that could cause actual results to differ materially for Affymetrix from those projected, including, but not limited to: risks and uncertainties relating to commercial success of the agreement with Medical Prognosis Institute discussed in this press release; risks of the company's ability to achieve and sustain higher levels of revenue, higher gross margins and reduced operating expenses; uncertainties related to technological approaches, manufacturing and product development; personnel retention; uncertainties related to cost and pricing of Affymetrix products; dependence on collaborative partners; uncertainties related to sole-source suppliers; risks associated with past and future acquisitions; uncertainties relating to FDA and other regulatory approvals; competition; risks relating to intellectual property of others and the uncertainties of patent protection and litigation. These and other risk factors are discussed in Affymetrix' Form 10-K for the year ended December 31, 2007, and other SEC reports, including its Quarterly Reports on Form 10-Q for subsequent quarterly periods. Affymetrix expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in Affymetrix' expectations with regard thereto or any change in events, conditions or circumstances on which any such statements are based.

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