Rib-X Pharmaceuticals, Inc. an antibiotics company with a broad development-stage pipeline,  announced the publication of positive preclinical data for delafloxacin highlighting the candidate’s superior infection-site potency against Gram-positive pathogens when compared to moxifloxacin, a leading approved antibiotic in the fluoroquinolone class.

The data were published in an online pre-publication of Antimicrobial Agents and Chemotherapy. Delafloxacin is a novel fluoroquinolone antibiotic candidate that offers both IV and oral versatility and has successfully completed three phase II clinical studies in approximately 1,000 subjects.

According to details from the publication as well as from studies presented at the 50th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), delafloxacin’s chemical structure and molecular properties lead to an increase in potency at acidic pHs, such as those found in sites of bacterial infection, by enhancing the candidate’s ability to permeate both the bacterial and the cellular membranes. It is believed that this increased potency may translate to an enhanced clinical benefit with regard to both improved efficacy and an improved resistance profile when compared to traditional quinolone compounds. The paper entitled, “Contrasting effect of acidic pH on the extracellular and intracellular activity of anti Gram-positive fluoroquinolones (moxifloxacin and delafloxacin) against Staphylococcus aureus” was authored by Sandrine Lemaire, Paul M. Tulkens and Françoise Van Bambeke, Pharmacologie cellulaire et moléculaire & Louvain Drug Research Institute, Université catholique de Louvain, Brussels, Belgium.

“These properties should translate to both improved efficacy and to reduced resistance development in the clinical setting. The results of these studies support a superior profile for delafloxacin in the fluoroquinolone class and as compared to other antibiotics for resistant infections. Delafloxacin is a well-tolerated, broad-spectrum antibiotic candidate that effectively targets key resistant pathogens, such as methicillin resistant Staphylococcus aureus (MRSA) that cause life-threatening hospital-treated infections,” said Mark Leuchtenberger, president and chief executive officer at Rib-X.

“We will be initiating multiple clinical studies for delafloxacin in 2011 to further strengthen the clinical profile for this candidate. This winter, we will initiate a phase II b study to evaluate objective endpoints for the treatment of complicated skin infections and later in the year, we plan to initiate a phase I study to assess a new oral formulation” he added.

Rib-X Pharmaceuticals is developing broad spectrum antibiotics with superior coverage, safety and convenience to deliver new standards of care for patients with serious infections. The Company’s Nobel Prize winning platform enables a unique understanding of how antibiotics combat infection and has generated an industry leading pipeline spanning all phases of research and clinical development.