SAN DIEGO, CA - (August 11, 1999) - Quest Diagnostics Incorporated (NYSE: DGX) and privately-held Structural Bioinformatics Inc. (SBI) today announced a strategic alliance regarding the application of structural pharmacogenomics to clinical testing and pharmaceutical research.

Increasingly, physicians are becoming aware of the relevance of genetics to patient-specific differences in response to drug treatment. New correlations between gene sequence and treatment outcomes continue to be sought through empirical observation. In many clinical situations (e.g., AIDS, hypertension, depression, etc.), lack of such information may lead to several weeks to months of ineffective treatment with potentially severe impact on a patient's health.

Structural pharmacogenomics is the analysis of structural variations of drug targets resulting from genetic variations within a population. The structural variant data can be used for the development of new drugs as well as for preclinical selection of drug candidates for advancement into clinical trials. SBI will extend existing and generate new proprietary target-specific Structural Variant database (SVdBase^TM) modules for a number of therapeutic targets based on Quest Diagnostics' clinical sequence databases. Such modules will permit highly accurate modeling of structurally variant proteins to facilitate design and identification of best-in-class drug compounds. These databases will be jointly offered under the QSVdBase^TM name by Quest Diagnostics and SBI for licensing to the pharmaceutical industry within the year.

"The collaboration between Quest Diagnostics and SBI represents a novel approach in an exciting new field," said Dr. Dean Goddette, Vice President of Marketing and Sales at SBI. "We see this as the first application of protein modeling to influence clinical practice and patient health management directly. Structural pharmacogenomics holds great promise for increasing the success rate of drugs in the clinical trial process, for the selection of new drugs effective in the broadest population of patients, and for combating drug resistance by linking clinical data to pharmaceutical drug discovery and therapeutic drug selection."

"We are very excited that this strategic alliance presents an important new avenue to develop new market opportunities," said Dr. Patrick Hess, Director of Biotechnology Affairs at Quest Diagnostics' Nichols Institute. "The structural variant databases (SVdBases^TM) generated from our genotyping databases should provide a fertile new source of information helpful in the design of new antiviral compounds using the structure-based drug discovery approach pioneered by SBI." Dr. Bernard L. Kasten, Quest Diagnostics' Chief Laboratory Officer said, "It is possible that structure-based modeling may have important new applications for clinical testing and test reporting for the care of individual patients. For this and other reasons, we are looking forward to a long and fruitful relationship with SBI."

Quest Diagnostics is one of the nation's leading providers of diagnostic testing, information and services to physicians, hospitals, managed care organizations, employers and government agencies. The wide variety of tests performed on human tissue and fluids help doctors and hospitals diagnose, treat and monitor disease. Its Nichols Institute unit conducts research, specializes in esoteric testing using genetic screening and other advanced technologies, performs clinical studies testing, and manufactures and distributes diagnostic test kits and instruments. Quest Informatics collects and analyzes laboratory, pharmaceutical and other data to help large health care customers better manage the health of their patients. QuestNet is an innovative new product offering that provides network management services to large buyers of health care services. Additional information about the company can be found on the Internet at: www.questdiagnostics.com.

Structural Bioinformatics Inc. accelerates lead discovery by closing the gap from gene sequence to lead discovery and is a world leader in computer-based protein structure generation and analysis. The company has developed advanced algorithms to calculate and refine the dynamic 3-D structure of proteins from sequence information using comparative modeling highly augmented with energy-based methods. SBI enables pharmaceutical companies to access rapidly the full range of molecular diversity available through combinatorial chemistry and the full range of protein targets revealed from worldwide human genome sequencing efforts by translating this data into structural information for use in rational drug design, molecular biology, molecular pharmacology and structural pharmacogenomics.

Statements in this press release may constitute forward-looking statements and are subject to numerous risks and uncertainties. Certain of these risks and uncertainties are listed in the Quest Diagnostics Incorporated 1998 Form 10-K and subsequent filings. Accordingly, actual results may differ materially from those contained in this press release. The companies disclaim any obligation to update any statements in this press release.

QuestNet® is a registered trademark of Quest Diagnostics Incorporated.