WHITEHOUSE STATION, N.J. and REDWOOD CITY, Calif., Jun. 21- Merck and Codexis, Inc. (NASDAQ:CDXS) today announced that they have jointly been awarded the annual Presidential Green Chemistry Challenge Award from the U.S. Environmental Protection Agency (EPA) for the development of a novel biocatalytic method for the synthesis of sitagliptin. In addition, a paper co-authored by Merck and Codexis scientists and published online June 17 in the peer-reviewed journal Science, details how an enzyme was systematically customized using Codexis technology to perform the key chemical step in the sitagliptin synthesis process. This process showed improved efficiency and significantly decreased chemical waste byproducts.

"Merck has a longstanding commitment to environmental sustainability," said Richard Tillyer, Ph.D, head of Drug Discovery and Preclinical Sciences, Merck Research Laboratories. "This award and the recent publication underscore the strength of the innovative science and the productive collaboration with our colleagues at Codexis."

The publication in Science outlines how Merck and Codexis collaborated to create a custom enzyme, or biocatalyst, that can allow for commercial-scale manufacturing of sitagliptin. No natural enzyme able to produce this compound was found. Enzymes are biodegradable, renewable and are generally believed to provide a more sustainable means of chemical synthesis than many currently employed methods used for the manufacture of pharmaceuticals. Evidence suggests that the new process may offer a 10-13 percent overall increase in yield of sitagliptin over the current process and a significant reduction in waste byproducts.

"Codexis is honored to receive one of the U.S. government's highest awards for environmental protection with Merck," said Alan Shaw, Ph.D., Codexis President and CEO. "Our proven technology platform is in use around the world, enabling creation of cleaner, more efficient pharmaceutical manufacturing processes. We are committed, with our colleagues at Merck, to leveraging the power of green chemistry for a sustainable environment."

About Presidential Green Chemistry Challenge Awards Program
The Presidential Green Chemistry Challenge Awards are presented annually by the Environmental Protection Agency to recognize new technologies that help prevent pollution by reducing or eliminating hazardous waste in industrial production. It provides recognition of outstanding chemical technologies that incorporate the principles of green chemistry into chemical design, manufacture, and use, and that have been or can be utilized by industry in achieving their pollution prevention goals. The award was launched in 1995 in partnership with the chemical industry, the American Chemical Society, the National Academies and other stakeholders. Both Merck and Codexis won awards individually in 2006.

About Merck
Today's Merck is a global healthcare leader working to help the world be well. Merck is known as MSD outside the United States and Canada. Through our prescription medicines, vaccines, biologic therapies, and consumer care and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to healthcare through far-reaching policies, programs and partnerships. Merck. Be well. For more information, visit www.merck.com.

About Codexis
Codexis, Inc. is a leading provider of optimized biocatalysts that make existing industrial processes faster, cleaner and more efficient than current methods and have the potential to make new industrial processes possible at commercial scale. Codexis has commercialized its biocatalysts in the pharmaceutical industry and is developing biocatalysts for use in producing advanced biofuels under a multi-year research and development collaboration. The company is also using its technology platform to pursue biocatalyst-enabled solutions in other bioindustrial markets, including carbon management, water treatment and chemicals. For more information, visit www.codexis.com.

Merck Forward-Looking Statement
This news release includes "forward-looking statements" within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. Such statements may include, but are not limited to, statements about the benefits of the merger between Merck and Schering-Plough, including future financial and operating results, the combined company's plans, objectives, expectations and intentions and other statements that are not historical facts. Such statements are based upon the current beliefs and expectations of Merck's management and are subject to significant risks and uncertainties. Actual results may differ from those set forth in the forward-looking statements.

The following factors, among others, could cause actual results to differ from those set forth in the forward-looking statements: the possibility that the expected synergies from the merger of Merck and Schering-Plough will not be realized, or will not be realized within the expected time period; the impact of pharmaceutical industry regulation and health care legislation; the risk that the businesses will not be integrated successfully; disruption from the merger making it more difficult to maintain business and operational relationships; Merck's ability to accurately predict future market conditions; dependence on the effectiveness of Merck's patents and other protections for innovative products; the risk of new and changing regulation and health policies in the U.S. and internationally and the exposure to litigation and/or regulatory actions.

Merck undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in Merck's 2009 Annual Report on Form 10-K and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site (www.sec.gov).

Codexis Forward-Looking Statement

This press release contains forward-looking statements relating to the benefits of the novel biocatalytic method for the synthesis of sitagliptin and the future environmental benefits of green chemistry as discussed in this press release. You should not place undue reliance on these forward-looking statements because they involve known and unknown risks, uncertainties and other factors that are, in some cases, beyond our control and that could materially affect actual results. Factors that could materially affect actual results can be found in Codexis' Quarterly Report on Form 10-Q dated May 28, 2010 including under the caption "Risk Factors." Codexis expressly disclaims any intent or obligation to update these forward-looking statements, except as required by law.

Contacts

Lyn Christenson

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(650) 421-8144
Codexis Media Contact

Derick Sutton

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(650) 421-8130
Codexis Investor Contact