Rib-X Pharmaceuticals, Inc. Appoints Dr. Russell Greig to Board of Directors

NEW HAVEN, Conn., June 30 /PRNewswire/ -- Rib-X Pharmaceuticals, Inc., a
development stage company focused on the discovery and development of novel
antibiotics for the treatment of antibiotic resistant infections, announced
today that Russell Greig, Ph.D., of SR One venture capital, has been appointed
to the Company's Board of Directors. Rib-X's board now consists of eleven
members.

"We are extremely pleased that Russell Greig has joined the Rib-X Board of
Directors," said Dr. Susan Froshauer, President and Chief Executive Officer,
Rib-X. "Russell brings an impressive mix of both R&D and business development
experience that will be crucial as the Company grows and continues to move
products through the development pipeline."

Russell Greig is President of SR One, the venture capital arm of
GlaxoSmithKline (GSK). Prior to joining SR One, he served as President of
GSK's Pharmaceuticals International from 2003 to 2008, and also served on the
GSK Corporate Executive Team. Dr. Greig originally joined GSK (then
SmithKline & French) in 1980 in the Departments of Tumor and Cell Biology. In
1991, following the merger with Beecham, he was appointed Vice President,
Project Management. From 1993 to 1996, he served as Vice President and
Director of Advanced Technologies in Genetics with special responsibility for
managing collaborations with The Institute of Genomic Research and Human
Genome Sciences. In 1996 Dr. Greig joined SmithKline Beecham's European
Pharmaceutical Operations as Vice President and Director of European Market
Development, and was later appointed Managing Director and General Manager of
SmithKline Beecham's UK Pharmaceuticals. Following the merger of SmithKline
Beecham with Glaxo Wellcome in 2000, he returned to the United States as
Senior Vice President for Worldwide Business Development.

Dr. Greig also serves on the boards of Genocea Biosciences and the Edinburgh
BioQuarter Commercialisation Advisory Group, and is a member of the Imperial
College Innovations Healthcare Advisory Board and a board observer for
Anaphore, Inc. He holds a Ph.D. in Biochemistry from the University of
Manchester, England and is a former Fulbright Scholar.

About Rib-X Pharmaceuticals, Inc.
Rib-X Pharmaceuticals, Inc. is a product-driven small molecule drug discovery
and development company focused on the structure-based design of new classes
of antibiotics. NDAs for Rib-X's most advanced compounds, delafloxacin and
radezolid, are anticipated in the 2011/2012 timeframe. The Company's
underlying drug discovery engine capitalizes on its proprietary
high-resolution crystal structure of the ribosome, which performs an essential
role in protein synthesis. Many known, commercially valuable antibiotics exert
their effects by binding to the bacterial ribosome. The Company's integrated
research strategy, which combines state-of-the-art, proprietary computational
analysis, X-ray crystallography, medicinal chemistry, microbiology and
biochemistry, allows it to rapidly synthesize new agents designed to avoid
typical antibiotic resistance mechanisms. Rib-X's iterative intelligent engine
has yielded several distinctive new antibiotics that can be used for the
treatment of either community- or hospital-acquired infections. The Company
has recently completed Phase 2 trials in complicated skin and skin structure
infections with the IV form of delafloxacin (RX-3341), and is currently in
Phase 2 trials with radezolid (RX-1741), an oxazolidinone that was discovered
at Rib-X, as an oral/IV agent for treatment of serious Gram-positive
infections and community or hospital acquired pneumonias. The Rx-04 discovery
program is developing novel classes of antibiotics active against multi-drug
resistant Gram-negative bacteria and the Rx-02 discovery program is focused on
developing an IV/oral macrolide active against methicillin-resistant S.
aureus, multidrug-resistant Streptococcus pneumoniae and S. pyogenes.

For more information on the Rib-X mission and the pipeline, please visit the
Company website at www.rib-x.com.

For further information please contact:
Media:
Irma Gomez-Dib
FD Life Sciences
Tel: 212-850-5761
irma.gomez-dib@fd.com

Investors:
John Capodanno
FD Life Sciences
Tel: 212-850-5705
John.capodanno@fd.com

SOURCE Rib-X Pharmaceuticals, Inc.

Media: Irma Gomez-Dib, +1-212-850-5761, irma.gomez-dib@fd.com, or Investors:
John Capodanno, +1-212-850-5705, John.capodanno@fd.com, both of FD Life
Sciences