SAN DIEGO, CA - (January 11, 2000) - Privately-held Structural Bioinformatics Inc., a world leader in protein modeling, and Quest Diagnostics Incorporated (NYSE: DGX), the nation's leading provider of diagnostic testing, information and services, announced today the availability of two structural pharmacogenomic databases targeted at HIV-Protease and HIV-Reverse Transcriptase, two critical drug targets in the fight against AIDS. The databases, QSVdBase-HIV/PR^TM and QSVdBase-HIV/RT^TM respectively, are available in February 2000.

Each QSVdBase^TM database module is composed of a large-scale collection of high-quality protein structures generated from the genetic sequence variants (polymorphisms) of a single drug target derived from many individuals. These structure data provide a definitive key to understanding differences in interactions between a drug or potential drug and the structural variations of its intended target, which is critical to optimal drug design and the selection of the optimal drug candidate for initiation of human trials.

Each QSVdBase^TM module converts sequence information into statistically relevant three-dimensional structural information. The HIV-RT and HIV-PR modules contain more than 15,000 unique structures (in aggregate) derived from individual patient samples, along with drug resistance data and structures for all currently approved drugs docked into the active site.

The QSVdBase^TM interface provides query tools and is SQL-compatible for more complex queries. The large sample size provides a representative spectrum of HIV mutations for meaningful statistics and provides trend data for changes in mutational frequencies over a period of two years. Sampling is current and ongoing with the addition of approximately 1,000 sequences/structures per month. The sequence data is generated by Quest Diagnostics' CAP and ISO9001 certified procedures.

"HIV drug resistance is a critical factor that needs to be accounted for in the development of new drugs," said Dr. Edward Maggio, President and CEO of SBI. "The information contained in QSVdBase^TM will allow pharmaceutical companies to make better choices of candidate compounds before tens of millions of dollars are spent on clinical trials."

"Researchers and physicians may be familiar with so-called mutation lookup tables, which list amino acid positions and known mutations which correlate with resistance," Dr. Bernard L. Kasten, Quest Diagnostics' Chief Medical Officer said. "The QSVdBase^TM is deeper, richer and more accessible than public HIV mutation tables and adds structural, temporal and patient-specific information that is not available elsewhere."

Quest Diagnostics is the nation's leading provider of diagnostic testing, information and services to physicians, hospitals, managed care organizations, employers and government agencies with annualized revenues of more than $3 billion. 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, and manufactures and distributes diagnostic test kits and instruments. Quest Diagnostics is one of the leading providers of testing to support clinical trials of new pharmaceuticals worldwide. 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 company information can be found on the Internet at: www.questdiagnostics.com.

Structural Bioinformatics is a world leader in computational proteomics--the large-scale generation and use of protein structure and protein structural properties. The Company has developed advanced and proprietary computational technologies to generate highly refined three-dimensional structural models of proteins from primary gene sequence data that compare well to crystal structures, and to perform primary drug-discovery screening in silico on millions of compounds present in SBI's scaffold-specific virtual combinatorial libraries (CombiLib^TM modules) or our clients' in-house compound collections. SBI offers two subscription database products. The first, SBdBase^TM, which is composed of thousands of structural models of proteins from more than 150 distinct families, promises to accelerate lead discovery and optimization and to enable broad rational experimental design across multiple disciplines within the pharmaceutical and life sciences. The second is SVdBase^TM, a growing series of database modules each containing structural models generated from genetic variations in a single, medically important gene. SBI also employs its technologies in collaborative R&D programs. Current partners include BioChem Pharma Inc., Yamanouchi Pharmaceutical Co., Ltd. and DuPont Pharmaceuticals Company.