Rib-X Pharmaceuticals Receives Award from NIAID to Develop Antibiotic Treatment for...

Rib-X Pharmaceuticals Receives Award from NIAID to Develop Antibiotic
Treatment for Gonorrhea
-- Government to Fund Clinical Development of Lead Compound, Delafloxacin, in
Treatment of Resistant Gonococcal Infections --

NEW HAVEN, Conn., Sept. 14 /PRNewswire/ -- Rib-X Pharmaceuticals, Inc., a
company focused on the discovery, development and commercialization of novel
drugs for the treatment of multi-antibiotic resistant infections, today
announced that it intends to enter into a Clinical Trials Agreement with the
U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of
the National Institutes of Health (NIH), an agency of the United States
Department of Health and Human Services. The purpose of this agreement is to
advance the clinical development of an oral formulation of Rib-X's novel
fluoroquinolone delafloxacin, in the treatment of Neisseria gonorrhoeae.

N. gonorrhoeae, a gram-negative bacteria, is the cause of the sexually
transmitted disease gonorrhea which affects more than 700,000 people in the
United States annually. Currently, N. gonorrhoeae has become resistant to a
number of antibiotics, including penicillin and other quinolones. Delafloxacin
is a next-generation fluoroquinolone that has been shown to be very active
against gram-positive organisms, including methicillin-resistant
Staphylococcus aureus (MRSA) and a broad range of gram-negatives. In addition
to work under this agreement, Rib-X is preparing to progress delafloxacin to
Phase 3 clinical trials for multiple indications.

This agreement with the NIAID will further support the broad clinical
potential for our lead compound, delafloxacin, which has already demonstrated
potent activity against a variety of resistant bacteria and has successfully
completed three Phase 2 trials," said Susan Froshauer, PhD, President and CEO
of Rib-X Pharmaceuticals. "In recent years, gonococcal infections have become
increasingly resistant to available antibiotic treatments and we look forward
to collaborating with the team at NIAID in the coming months to evaluate
possible alternative therapeutic options for such infections."

About Delafloxacin
Delafloxacin, a novel, broad spectrum, next-generation fluoroquinolone, has
demonstrated better activity than other quinolones against Gram-positive
bacteria, including isolates of MRSA that are quinolone-resistant. Recently,
Rib-X has announced positive results from a Phase 2 trial utilizing the IV
formulation of delafloxacin in complicated skin and skin structure infections
(cSSSI). Delafloxacin successfully completed two previous Phase 2 trials with
the oral formulation. In microbiological tests of large numbers of
contemporary clinical isolates, the compound has been shown to be at least
32-fold more potent than levofloxacin, ciprofloxacin, gatifloxacin and
moxifloxacin against quinolone-resistant MRSA (MIC90 of = 0.5 ug/ml for
delafloxacin compared to > 16 ug/ml for all other quinolones) and twice as
potent as daptomycin against MRSA. Additionally, delafloxacin was shown to
more potent than ciprofloxacin against N. gonorrhoeae (MIC90 of = 0.06 ug/ml
for delafloxacin compared to > 16 ug/ml for ciprofloxacin). Delafloxacin has
also been shown to be more potent than existing quinolones against a range of
Gram-positive, anaerobic and Gram-negative organisms. Rib-X is currently
developing both IV and oral formulations of delafloxacin for use in surgical
prophylaxis and other therapeutic arenas within the over $9.9 billion hospital
antibiotic market.

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. 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. In addition to delafloxacin, Rib-X has completed two 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.
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 MRSA,
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 for Rib-X Pharmaceuticals, Inc.