New Haven, Connecticut and Osaka, Japan, June 1, 2006 - Rib-X Pharmaceuticals, Inc. and Wakunaga Pharmaceutical Company, Ltd. announced today that they have entered into an agreement to develop and commercialize WQ-3034, a broad spectrum quinolone antibiotic. WQ-3034 was originally identified by Wakunaga scientists and has been shown to be safe and effective in Phase II human clinical testing.

Under the terms of the agreement, Rib-X receives an exclusive worldwide license to WQ-3034 and all formulations of the compound for all uses with the right to sublicense. Wakunaga has received an upfront fee and will receive additional payments based upon certain development and commercialization milestones and royalty payment on the eventual sale of products containing the compound.

"WQ-3034 is a very exciting quinolone antibiotic distinguished by its excellent activity against methicillin-resistant Staphylococcus aureus (MRSA) and penicillin-resistant Streptococcus pneumoniae (PRSP), including strains resistant to currently available fluoroquinolones, and a clinical package showing us that it is a very safe and effective antibiotic," said Susan Froshauer, PhD, President and CEO of Rib-X. "WQ-3034 is a broad spectrum antibiotic that has the potential to be used in a range of distinct market sectors," continued Dr. Froshauer. "Rib-X is committed to the development of a broad portfolio of antibiotics that are active against the ever increasing numbers of resistant bacteria, and we are excited by the addition of WQ-3034 to our growing pipeline of novel internally discovered antibiotics."

"Rib-X is a developing leader in antibiotic therapies, and we are thrilled to have them as our partner in the development of WQ-3034," said Akira Yazaki, PhD, Distinguished Scientist of the Institute of Medical Research of Wakunaga. "Rib-X benefits from the data from seven Phase I and two Phase II studies involving more than 900 patients."

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.

Wakunaga Background

Wakunaga Pharmaceutical Company, established in 1955, and its US affiliate, Wakunaga of America (http://www.kyolic.com) have been playing an important role in promoting public health worldwide through the research, development, manufacturing and marketing of high quality medicinal herb products. In addition, the Company has an active and innovative research venture focused on the discovery of novel small-molecule candidates for prescription drugs. One area of focused interest is the discovery of next generation quinolone antibiotics. The company's basic strategy for the development and commercialization of prescription drugs is to out-license drug candidates at an early stage of discovery or development. Wakunaga has been highly successful with this strategy and has implemented productive relationships with a number of pharmaceutical companies. Wakunaga is a pioneer in the area of biotechnology research in Japan and currently develops and markets DNA diagnostics and other products.

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