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Rib-X Reports Additional Positive Delafloxacin Data at ICAAC, Including Performance against New Objective Endpoints from FDA, from its Completed Phase 2b Study in Patients with Acute Bacterial Skin and Skin Structure Infections

Update: Baxdela (delafloxacin) Now FDA Approved - June 19, 2017

—Seven poster presentations and a symposium talk support delafloxacin development for use as a convenient and well-tolerated first-line antibiotic with broad-spectrum coverage as a monotherapy—

NEW HAVEN, Conn.--(BUSINESS WIRE)--Sep 11, 2012 - Rib-X Pharmaceuticals, Inc., today presented new efficacy and safety results from the Company's Phase 2b clinical trial of delafloxacin for the treatment of acute bacterial skin and skin structure infections (ABSSSI), including infections caused by methicillin- and quinolone- resistant Staphylococcus aureus (MRSA, QRSA). Results from the Phase 2b trial and other clinical and preclinical studies were presented in seven poster presentations and a symposium session at the 52nd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), taking place September 9-12, 2012 in San Francisco, CA.

Delafloxacin is being developed for use as an effective and convenient first-line antibiotic primarily in hospitals prior to the availability of a specific diagnosis. Delafloxacin has the potential to offer broad spectrum coverage as a monotherapy, including for MRSA, with both intravenous (IV) and oral formulations. With the exception of Zyvox, all other currently approved treatments for MRSA offer only IV delivery. In addition to strong Gram-positive potency, delafloxacin has shown excellent in vitro activity against susceptible Gram-negative bacteria.

“Delafloxacin has consistently demonstrated, with data from nearly 1,400 patients, its utility as a well-tolerated, broad spectrum antibiotic that effectively targets resistant pathogens,” said Scott Hopkins, M.D., Chief Medical Officer of Rib-X. “This latest Phase 2b study yielded statistically significant results for the primary endpoint. Furthermore, we accomplished our goal of gaining important validation of delafloxacin's efficacy and safety profile under the new objective endpoints issued by the FDA to guide the design of what we believe will be a de-risked Phase 3 program.”

As initially reported in December, 2011, Delafloxacin met or exceeded primary and secondary efficacy endpoints evaluated in comparison to Zyvox® (linezolid), with and without aztreonam, and vancomycin, with and without aztreonam, including endpoints based on the new draft guidance from the US Food and Drug Administration (FDA) in ABSSSI. Of note, for the primary endpoint of Investigators' Global Assessment of Cure, delafloxacin demonstrated statistical superiority in comparison to vancomycin (95% Confidence Interval -30.3%, -2.3%; p=0.031). This data was reported today in poster presentation L1-1663 titled, “Results of a Phase 2 Study of Delafloxacin (DLX) Compared to Vancomycin (VAN) and Linezolid (LNZ) in Acute Bacterial Skin and Skin Structure Infections (ABSSSI).”

Newly reported data including in the late breaking poster presentation L1-1667c, “Objective Measures of Clinical Efficacy in a Phase 2B Exploratory Study of Delafloxacin (DLX) Compared to Vancomycin (VAN) and Linezolid (LNZ) in Adults with Acute Bacterial Skin and Skin Structure Infections (ABSSSI),” showed that delafloxacin was equally as efficacious in the treatment of ABSSSI as linezolid and vancomycin when compared using the objective endpoint of cessation of lesion spread and absence or resolution of fever in the 48-72 hour timeframe. The time-point to achieve maximal benefit for all three compounds was 72 hours. When compared to linezolid and vancomycin using the objective endpoint of >20% or >30% reduction in lesion size in 48-72 hours, delafloxacin was shown to be numerically better and nearly statistically significant for >30%. Delafloxacin was shown to result in a greater percent reduction in the lesion size than either comparator by 72 hours.

Additional data from the delafloxacin Phase 2b trial and other studies are featured in the following posters and symposium talks:

Sunday, September 09, 2012

Poster Session 016: “In Vitro Activity of Fluoroquinolones,” 11:30am-1:30pm Pacific Time

E-208 “Characterization and In Vitro Activity of Delafloxacin (DLX) Against Isolates from a Phase 2 Study of Acute Bacterial Skin and Skin Structure Infections (ABSSSI)” – delafloxacin was greater than 32 fold more potent than levofloxacin and ciprofloxacin, more potent than vancomycin and linezolid, and equally potent to tigecycline against strains of Staphylococcus aureus isolated from this clinical study of ABSSSI. Delafloxacin was equally potent to ciprofloxacin against 17 strains if Gram-negative bacilli. These in vitro findings support the development of delafloxacin for the treatment of Gram-positive and Gram-negative infections, including those caused by strains resistant to currently available fluoroquinolones.

Monday, September 10, 2012

Symposium Session 078: “50 Years of Fluoroquinolones: Past, Present and Future,” 11:15am-12:45pm Pacific Time

David C. Hooper, M.D., Professor, Harvard Medical School, “New Quinolones: What's on the Horizon”

Tuesday, September 11, 2012

Poster Session 189: “Novel Agents and Insights in Skin and Soft Tissue Infections,” 11:15am-1:15pm Pacific Time

L1-1667b late breaking abstract “Effect of a Single Prior Dose Short Acting Antibiotic on Clinical Efficacy in a Phase 2B Exploratory Study of Delafloxacin (DLX) Compared to Vancomycin (VAN) and Linezolid (LNZ) in Adults with Acute Bacterial Skin and Skin Structure Infections (ABSSSI)” – Neither the primary end point, Investigators' Global Assessment of Cure, nor the assessment of the objective end point, cessation of lesion spread and absence or resolution of fever as measured at 48-72 hours, was affected by the prior use of a single dose of a short-acting antibiotic.

Wednesday, September 12, 2012

Poster Session 241: “Toxicokinetics and PK/PD of New and Old Fluoroquinolones,” 9:15am-11:15am Pacific Time

A-1956 “Metabolism and Mass Balance of Delafloxacin in Healthy Human Volunteers Following Intravenous Administration” – Good recovery of radioactivity was obtained, with excretion predominantly via the urine. Radioactivity was rapidly distributed and eliminated from plasma. In addition to Delafloxacin, one major circulating metabolite (a glucuronide) was identified in man.

A-1957 “Pharmacokinetics (PK) of Delafloxacin (DLX), Vancomycin (VAN) and Linezolid (LNZ) in a Phase 2 Exploratory Study in Subjects with Acute Bacterial Skin and Skin Structure Infections (ABSSSI)” –The exposures of DLX, LNZ and VAN were determined after multiple intravenous infusions in subjects in a Phase 2 study on the treatment of ABSSSI. Exposures to each drug were in the expected range. DDLX exposures were similar to those observed in previous clinical experience with this dosing regimen, which was shown to be efficacious and support 300 mg twice daily as a dose for Phase 3 studies.

A-1958 “A Thorough Phase 1 QTc Study of Delafloxacin (DLX) Compared with Placebo and Moxifloxacin (MXF)” – DLX at therapeutic and supratherapeutic doses showed no effect on cardiac repolarization using QTcF, PR or QRS interval durations, while MXF demonstrated predicted effects on QTc duration.

Additional Information about Delafloxacin:

Delafloxacin has been in four Phase 2 trials where it has shown promising results for the treatment of lung infections, including pneumonia and bronchitis, and skin infections. Rib-X is developing both IV and oral formulations of delafloxacin to enable patients who begin IV treatment in the hospital setting to transition to oral dosing for home-based care, offering the potential to increase patient convenience, lower the overall cost of treatment and reduce the length of hospital stays. These attributes, combined with delafloxacin's safety profile and reduced probability of resistance, demonstrate the potential of delafloxacin to become a new standard of care for first-line treatment of serious infections and thereby reduce the need to switch to second-line, narrow spectrum antibiotics.

About Rib-X:

Rib-X Pharmaceuticals, Inc. is a biopharmaceutical company developing new antibiotics to provide superior coverage, safety and convenience for the treatment of serious and life-threatening infections. The Company's proprietary drug discovery platform provides an atomic-level, three-dimensional understanding of interactions between drug candidates and their bacterial targets and enables design of antibiotics with enhanced characteristics. Rib-X has two antibiotic candidates in clinical development. Delafloxacin is an enhanced spectrum IV/oral antibiotic intended for use as first-line monotherapy primarily in hospitals and recently completed a Phase 2b clinical trial for the treatment of acute bacterial skin and skin structure infections. Radezolid is a next-generation IV/oral oxazolidinone designed to be a potent antibiotic with a safety profile permitting long-term treatment of resistant infections. The Company's pipeline also includes its preclinical RX-04 program, partnered with Sanofi, S.A., and other discovery stage anti-infective programs.

Contact: Company
Rib-X Pharmaceuticals, Inc.
Bob Conerly, 203-624-5606
Media Relations
For Rib-X Pharmaceuticals, Inc.
Kari Watson, 781-235-3060


Posted: September 2012