Potent New Agent Against Vancomycin-Resistant Bacteria

From the Interscience Conference on Antimicrobial Agents and Chemotherapy

SAN FRANCISCO—The investigational semisynthetic glycopeptide oritavancin (Targanta) offers a high level of activity against vancomycin-nonsusceptible enterococci, presenters said at the Interscience Conference on Antimicrobial Agents and Chemotherapy.

Researchers compared the in vitro potency of oritavancin with that of the other available glycopeptides—vancomycin and teicoplanin (the latter is not approved in the United States). All 3 agents showed comparable potency against vancomycin-susceptible bacteria, but only oritavancin maintained a high level of activity against vancomycin-resistant bacteria.

The relative potency of each agent was tested against hundreds of enterococcal clinical isolates, as well as against 2 strains of vancomycin-resis-tant Staphylococcus aureus. Oritavancin maintained superior efficacy compared with the other glycopeptides against the vancomycin-resistant enterococci and the 2 vancomycin-resistant S aureus strains studied.

“These findings demonstrate on a microbiological basis that oritavancin maintains high activity, even against those organisms that have developed resistance to sister compounds such as vancomycin or teicoplanin. This microbiology study indicates it is likely to maintain activity against those microorganisms that are resistant to closely related compounds,” coinvestigator Daniel Sahm, PhD, president of Focus Bio-Inova, Herndon, Va, told IMWR.

S aureus

Results of a separate study also presented at the meeting, in which oritavancin was tested against in both slow-growing and biofilm states, showed that oritavancin acted more rapidly and more completely than either vancomycin or teicoplanin in both situations.

“S aureus in particular has emerged as the number one gram-positive pathogen both in the hospitals and the community….It has also developed a lot of resistance to many of the antibiotics that are commonly used, and oritavancin brings a new strong selective choice for that key pathogen,” explained Dr Sahm.

The developer of oritavancin expects to file a new drug application with the FDA in 2007. In addition, clinical studies will be determining the efficacy of the agent against bacteremia and nosocomial pneumonia.