SANTA CLARA, Calif — Affymetrix, Inc., (NASDAQ:AFFX) and eBioscience, Inc., a privately-held San Diego, CA-based company with an industry-leading position in flow cytometry and immunoassay reagents for immunology and oncology research and diagnostics, today announced they have amended their existing definitive agreement dated November 29, 2011 under which Affymetrix will acquire eBioscience. Under the terms of the amended agreement, Affymetrix will acquire eBioscience for $315 million in cash subject to usual adjustments. The transaction remains subject to customary closing conditions and is now expected to close late in the quarter ending June 30, 2012.

As previously announced, Affymetrix expects the acquisition of eBioscience to:

• Create significant new commercial opportunities in the key post-genomic applications of immunology, oncology, cell biology, stem cell biology, and diagnostics

• Diversify the Company’s revenues and complement its genomics franchise

• Augment the Company’s growing business in diagnostics

• Expand the Company’s product portfolio to include multicolor flow cytometry reagents and a broad spectrum of reagents for the analysis of cytokines, growth factors and other soluble proteins

• Enhance the operational and new product opportunities for Panomics RNA and protein analysis products

• Leverage the commercial capabilities of both companies to generate new opportunities for growth

“The feedback from our customers, shareholders and partners has been consistently positive since we announced our original agreement with eBioscience last November,” said Dr. Frank Witney, president and chief executive officer of Affymetrix. “By amending the transaction, we are now able to realize the benefits of combining with eBioscience with significantly less senior secured debt than under the original agreement. With eBioscience, Affymetrix will expand its addressable markets by adding an industry-leading portfolio of cell-based and immunoassays. These new products are a critical part of our customers’ workflow in our key target markets of translational medicine, oncology, and immunology. We believe that these markets represent a nearly $3 billion annual opportunity, which will put Affymetrix on a solid path to sustained growth and profitability. We look forward to welcoming the eBioscience team to the Affymetrix family.”

The amended agreement contemplates funding the acquisition using a combination of cash-on-hand, a senior secured financing of $75 million and additional financing options available to the Company. The senior secured financing, which includes an additional $15 million revolving credit facility, is being provided by a group of lenders led by administrative agent GE Healthcare Financial Services Inc. and Silicon Valley Bank.

“We expect that adding eBioscience to Affymetrix will accelerate our growth,” said Tim Barabe, executive vice president and chief financial officer of Affymetrix. “With 2011 revenues of $71 million, gross margins in excess of 70% and EBITDA margin of in excess of 30%, eBioscience makes Affymetrix a much stronger company, both operationally and financially. The revised purchase price represents approximately 4.5 times 2011 revenue and 13.5 times 2011 EBITDA, and the transaction is expected to be accretive to Affymetrix’s cash earnings per share.”

As previously announced, Affymetrix, which is headquartered in Santa Clara, expects to maintain eBioscience’s management team and operations in San Diego.

Houlihan Lokey, Inc. is acting as exclusive financial advisor to Affymetrix and Davis Polk & Wardwell LLP is acting as legal counsel to Affymetrix in the transaction. Jefferies & Company, Inc. is acting as exclusive financial advisor to eBioscience and DLA Piper LLP is acting as eBioscience’s legal counsel in the transaction.

Affymetrix’s management team will host a conference call on May 4, 2012 at 5:30a.m. PT to discuss the amended transaction with eBioscience. A live webcast can be accessed by visiting the Investor Relations section of the Company’s website at https://www.affymetrix.com. In addition, investors and other interested parties can listen by dialing domestic: (877) 407-8291, international: (201) 689-8345.

A replay of this call will be available from 5:00 p.m. PT on May 4, 2012 until 8:00 p.m. PT on May 11, 2012 at the following numbers: domestic: (877) 660-6853, international: (201) 612-7415. The passcode for both replays is 394110. An archived webcast of the conference call will be available under the Investor Relations section of the Company’s website.

About Affymetrix

Affymetrix technology is used by the world’s top pharmaceutical, diagnostic, and biotechnology companies, as well as leading academic, government, and nonprofit research institutes. More than 2,200 systems have been shipped around the world and almost 25,000 peer-reviewed papers have been published using the technology. Affymetrix is headquartered in Santa Clara, California, and has manufacturing facilities in Cleveland, Ohio, and Singapore. The Company has about 900 employees worldwide and maintains sales and distribution operations across Europe, Asia and Latin America.