January 8, 2004

FOR IMMEDIATE RELEASE

World Renowned Ribosome Expert Dr. Venki Ramakrishnan Joins Rib-X Pharmaceuticals' Scientific Advisory Board

NEW HAVEN, Conn., Jan. 8 /PRNewswire/ -- 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 appointment of another world-renowned ribosome scientist Venki Ramakrishnan, Ph.D., to the Rib-X Scientific Advisory Board (SAB).

Dr. Ramakrishnan joins the Company founder team of advisors who are also ribosome structure experts. This team includes Drs. Thomas Steitz and Peter Moore of Yale University and Dr. Harry Noller of University of California, Santa Cruz, and Dr. John Abelson of the California Institute of Technology. This appointment brings the total number of SAB members to eight.

"One of our greatest accomplishments at Rib-X has been the success we have had in bringing the best possible people onto our team," said Dr. Susan Froshauer, President and Chief Executive Officer of Rib-X. "Venki is a world leader in research focused on the structure and function of the ribosome, having received international recognition for his determination of the atomic structure of the 30S subunit of the ribosome, and we are very fortunate to have him join our Scientific Advisory Board."

Dr. Ramakrishnan is currently a Group Leader in the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, England. He has published approximately 50 research papers pertaining to ribosomal studies. Internationally recognized for his achievement in determining the atomic structure of the 30S ribosomal subunit and its complexes with several antibiotics, he mapped the arrangement of proteins in the 30S subunit by neutron diffraction and solved X-ray structures of individual components and their RNA complexes early in his career. Dr. Ramakrishnan earned his Bachelor of Science degree in physics from Baroda University in India and his Ph.D. in Physics from Ohio University. He pursued further post-graduate studies at The University of California, San Diego. Recently, Dr. Ramakrishnan received the high honor of election to the Royal Society.

"It is a pleasure to be invited to work along side people who share my level of commitment to the study and utilization of the ribosome as a drug discovery target," said Dr. Ramakrishnan. "Rib-X has made remarkable strides in the relatively short life of the company and I am confident their extraordinary technology will serve an instrumental role in our collective quest for a new class of antibiotics."

About Rib-X 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 to which many known antibiotics bind. 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 is optimizing leads to create new classes of antibiotics.

Contacts Rx Communications Group Rhonda Chiger (investors) 917-322-2569 rchiger@rxir.com

Pete Holmberg (media) 917-322-2164 pholmberg@rxir.com

About Warburg Pincus Warburg Pincus is a global private equity firm and a leading investor in healthcare, biotechnology and specialty pharmaceuticals. Since 1971, Warburg Pincus has sponsored ten private equity investment funds with committed capital in excess of $19 billion. The firm is currently investing its eighth global fund, Warburg Pincus Private Equity VIII, which had a final closing in April 2002 at $5.3 billion. Warburg Pincus has invested more than $800 million in the biotechnology industry and helped to build more than 40 biotechnology and biopharmaceutical companies spanning a broad range of technologies and stages of development. For more information, please visit our website at www.warburgpincus.com.