Rib-X Raises $25M in Debt Financing, Reveals Final Results of Antibiotic Trial

1/26/09

Rib-X Pharmaceuticals has raked in $25 million in a debt financing to develop its pipeline of antibiotics for drug-resistant infections. The New Haven, CT-based biotech firm is expected this morning to reveal details of the financing and final results of a mid-stage clinical trial of its antibiotic delafloxacin.

Last time I spoke with Rib-X CEO Susan Froshauer, in September, she was on the hunt for a commercial partner to help fund further development of the firm’s lead antibiotics. The company has yet to land such a partner, but Froshauer was pleased that some previous equity backers—Warburg Pincus, ABS Ventures, Axiom Ventures, EuclidSR Partners, MedImmune Ventures, Oxford Bioscience Partners, SR  One, and Vox Equity Partners—opted to support her company in the debt round. Rib-X, founded in 2001, had previously raised $123 million in equity financing.

Rib-X says that delafloxacin showed positive results in the recent mid-stage clinical trial as a treatment for certain skin and tissue infections caused by bacteria such as the infamous antibiotic-resistant strain MRSA as well as bugs resistant to quinolone antibiotics. The 150-patient study showed that delafloxacin had efficacy comparable to that of the antibiotic tigecycline (Tygacil), marketed by Madison, NJ-based drug firm Wyeth, and better tolerability than the already-approved drug, according to Rib-X.

Rib-X has developed delafloxacin to treat the same types of bugs as South San Francisco-based Theravance’s (NASDAQ:THRX) telavancin and Cambridge, MA-based Targanta Therapeutics’ (NASDAQ:TARG) oritavancin. The FDA shot down Targanta’s bid to gain approval of oritavancin in late 2008, indicating that the company didn’t have enough data, particularly on the ability of oritavancin to treat MRSA. Froshauer notes that her firm’s recent delafloxacin study was completed last year with a higher percentage of MRSA patients than the oritavancin studies. She adds that delafloxacin is available in both intravenous infusions and oral pills, which enable patients to easily continue treatment after they leave the hospital. Oritavancin and other competing antibiotics are available in IV form only.

“We think of course that we’re in really good shape because we can look to those experiences and have a lot of take-home messages [from the FDA],” Froshauer says.

Still, Rib-X is considering additional uses of delafloxacin. Froshauer says that the company may decide to develop the antibiotic as a prophylactic treatment given to patients before surgeries to prevent infections. But the company is going to let its hoped-for development partner to weigh in on whether to develop delafloxacin for pre-surgical prophylaxis, she says, adding that its partner would also impact the design and timing of its next clinical trial of the drug.

Rib-X—which has a pipeline of other antibiotics discovered internally—licensed delafloxacin in 2006 from Japanese drug-maker Wakunaga Pharmaceutical Company. Froshauer says that health-care products giant Abbott Laboratories had previously developed delafloxacin in pill form for bronchitis and pneumonia, but opted to drop the program after two successful trials due to a change in strategy at the Abbott Park, IL-based firm. Rib-X developed the IV form of the antibiotic.

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