Investor Relations

WILMINGTON, Mass.--(BUSINESS WIRE)--April 7, 2003-- - Services to Speed Availability of Genetically-Modified Research Models -

Charles River Laboratories International, Inc. (NYSE:CRL), a leading provider of pre-clinical research products and services to biopharmaceutical and biotechnology companies, and Xenogen Biosciences, a wholly-owned subsidiary of Xenogen Corporation, today announced the formation of a marketing collaboration that seeks to speed the availability of genetically-modified research models to the pharmaceutical, biotechnology and academic research scientist.

In this two-year strategic collaboration, Charles River will market Xenogen Biosciences' genomic services to the clients of its Transgenic Services business. Xenogen Biosciences, located in Cranbury, New Jersey, holds intellectual property rights to multiple processes for the development of knock-out, knock-in and transgenic models, including the process of pronuclear microinjection, one of the most widespread techniques used to genetically engineer new research models.

"We have long known the importance of offering a services portfolio that includes the genomic manipulation of research models to make them more predictive of the human," said Bill Barbo, Executive Director, Charles River Transgenic Services. "With this collaboration, we will be able to market Xenogen's genomic technology as a seamless addition to our services, enabling us to further assist our clients in the more efficient pursuit of their research goals."

"We are pleased with the opportunity to offer our broad range of services in conjunction with Charles River, the acknowledged leader in our market," said Pamela Reilly Contag, Ph.D., President of Xenogen Corporation. "The combination of Xenogen Biosciences' genomic technology and Charles River's market share leadership in the Research Model and Transgenic Services arena makes this collaboration a win-win for the pharmaceutical, biotech and research communities."

Xenogen Biosciences offers a range of genomic services that can create a gene-specific research model. Charles River is recognized as the market leader in model development and breeding services associated with providing a continuing supply of genetically specific and virally clean research models for clients around the world. The strategic marketing agreement leverages the strengths of both companies to provide customers with more comprehensive outsourcing services to accelerate their drug discovery process.

About Charles River Laboratories, Inc.

Charles River Laboratories, based in Wilmington, Massachusetts, is a leading provider of critical research tools and integrated support services that enable innovative and efficient drug discovery and development. The Company is the global leader in providing the animal research models required in research and development for new drugs, devices and therapies. The Company also offers a broad and growing portfolio of biomedical products and services that enable customers to reduce cost, increase speed, and enhance productivity and effectiveness in drug discovery and development. Charles River's customer base spans over 50 countries, and includes all of the major pharmaceutical companies, biotechnology companies, and many leading hospitals and academic institutions. The Company operates 82 facilities in 16 countries worldwide. For more information, visit the Company's web site at www.criver.com.

About Xenogen Corporation

Xenogen Corporation, a privately held company based in Alameda, CA, is a leading biotechnology company focused on the development and commercialization of in vivo biophotonic imaging -- the real-time detection and recording of light emitted from sources within a living object. Xenogen's full complement of products and services includes imaging technologies as well as transgenic research model programs for pharmaceutical and biotechnology research and development.

Caution Concerning Forward-Looking Statements. This document includes "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements may be identified by the use of words such as "anticipate," "believe," "expect," "estimate," "plan," and "project" and other similar expressions that predict or indicate future events or trends or that are not statements of historical matters. These statements are based on management's current expectations, and involve a number of risks and uncertainties that could cause actual results to differ materially from those stated or implied by the forward-looking statements, and the company expressly does not undertake any duty to update forward-looking statements, which speak only as of the date of this document. Those risks and uncertainties include, but are not limited to: acquisition integration risks; special interest groups; contaminations; industry trends; new displacement technologies; outsourcing trends; USDA and FDA regulation; changes in law; continued availability of products and supplies; loss of key personnel; interest rate and foreign currency exchange rate fluctuations; changes in generally accepted accounting principles; and any changes in business, political, or economic conditions due to the threat of future terrorist activity in the U.S. and other parts of the world, and related U.S. military action overseas. A further description of these risks, uncertainties, and other matters can be found in the Risk Factors detailed in the Company's Annual Report on Form 10-K as filed on March 20, 2003, with the Securities and Exchange Commission.

CONTACT: CRL INVESTOR CONTACT
Charles River Laboratories, Inc.
Susan E. Hardy, 978/658-6000 ext.1616
shardy@criver.com
or
XENOGEN CONTACT
Xenogen Corporation
Michael J. Sterns, D.V.M., 510/291-6278
Michael.sterns@xenogen.com SOURCE: Charles River Laboratories International, Inc.