New Haven, Connecticut, Oct 30, 2003 -- Rib-X Pharmaceuticals, Inc., a privately held biotechnology company focused on the design and development of the next generation of antibiotics to fight multidrug-resistant bacteria, announced today the issuance of a US Patent describing the Company's proprietary technology on the high-resolution crystal structure of the 50S subunit of the ribosome. The 50S is the target for many clinically important classes of antibiotics, including those used to treat both community-acquired and hospital pathogens.

"The antibiotic market, at some $25 billion worldwide, is huge," said Dr. Susan Froshauer, President and Chief Executive Officer of Rib-X. "The patent protects a core component of the Company's structure-based drug discovery approach and helps to ensure the Rib-X advantage in the global hunt for more effective antibiotics."

The 50S subunit is a large drug target, which performs an essential role in the fundamental process of protein synthesis. Having what amounts to a map of the 50S provides the Company an advantage in the design of new classes of antibiotics.

"With the problem of antibiotic resistance on the rise in both hospital and community settings, securing our hold on this proprietary technology will enable us to build faster, efficient and more informed routes to the design of better anti-infective agents," continued Froshauer. "Our goal is a strong and growing pipeline comprising multiple new classes of antibiotic agents, and we are committed to building a substantial patent portfolio to support these efforts."

US Patent number 6,638,908, which relates to the 50S high resolution crystal structure subunit from Haloarcula marismortui and for which Rib-X holds the exclusive, world-wide license, derives from the research of two of the founders of Rib-X, Thomas Steitz, PhD and Peter Moore, PhD, both of Yale University.

About Rib-X Pharmaceuticals

Rib-X Pharmaceuticals is a small molecule drug discovery company focused on the structure-based design of new classes of anti-infective agents. The Company's drug discovery strategy is focused on the exploitation of its proprietary high-resolution crystal structure of the 50S subunit of the ribosome, which performs an essential role in the fundamental process of protein synthesis, and to which many known antibiotics bind. The 50S is the target for many clinically important classes of antibiotics, including those used to treat both community-acquired and hospital pathogens. The Company's integrated research approach combines state of the art, proprietary computational analysis, X-ray crystallography, medicinal chemistry, microbiology and biochemistry, allowing for the rapid synthesis of new agents, which avoid typical antibiotic resistance mechanisms. Utilizing these tools, Rib-X has what amounts to a map of the 50S subunit of the ribosome. The Company is utilizing this advantage in the optimization of leads and the creation of new classes of antibiotics.

For more information on the Rib-X mission, please visit the Company website.

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