Oritavancin

Oritavancin (INN, also known as LY333328) is a novel semi-synthetic glycopeptide antibiotic being developed for the treatment of serious Gram-positive infections. Originally discovered and developed by Eli Lilly, oritavancin was acquired by InterMune in 2001 and then by Targanta Therapeutics in late 2005^[1].

In Vitro Activity

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Oritavancin shares certain properties with other members of the glycopeptide class of antibiotics, which includes vancomycin, the current standard of care for serious Gram-positive infections in the United States and Europe^[2]. Data presented at the 47th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in September 2007 demonstrated that oritavancin possesses potent and rapid bactericidal activity in vitro against a broad spectrum of both resistant and susceptible Gram positive bacteria, including Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Enterococci, and Streptococci^[3]. Two posters presented at the meeting also demonstrated that oritavancin was more active than either metronidazole or vancomycin against strains of Clostridium difficile tested^[4]. In addition, research was conducted in partnership with the U.S. Army Medical Research Institute of Infectious Diseases (USAMRIID) and presented at the American Society for Microbiology (ASM) 107th Annual General Meeting in May 2007, suggesting oritavancin’s potential utility as a therapy for exposure to Bacillus anthracis, the bacterium that causes anthrax, having demonstrated efficacy in a mouse model both pre- and post-exposure to the bacterium^[5]

Clinical Progress

Results have been presented but not yet published from two pivotal Phase 3 clinical trials testing the efficacy of oritavancin for the treatment of complicated skin and skin-structure infections (cSSSI) caused by Gram-positive bacteria. The primary endpoints of both studies were successfully met, with oritavancin achieving efficacy with fewer days of therapy than the comparator agents (vancomycin followed by cephalexin). In addition, oritavancin showed a significantly improved safety profile with a 19.2 percent relative reduction in the overall incidence of adverse events versus vancomycin/cephalexin (p<0.001) in the second and larger pivotal trial^[6].

A Phase 2 clinical study is currently ongoing entitled “Single or Infrequent Doses for the Treatment of Complicated Skin and Skin Structure Infections (SIMPLIFI),” evaluating the efficacy and safety of either a single dose of oritavancin or an infrequent dose of oritavancin compared to the previously studied dosing regimen of 200mg oritavancin given once daily for 3 to 7 days^[7].

References

1. ^ Targanta Revives Oritavancin: Next Weapon Against cSSSI? BioWorld Today, November 26, 2007
2. ^ Scheinfeld, N (2007). "A comparison of available and investigational antibiotics for complicated skin infections and treatment-resistant Staphylococcus aureus and enterococcus". J Drugs Dermatol. 6 (4): 97–103. PMID 17373167.
3. ^ 2007 ICAAC Posters: E-1612 “In Vitro Activity Profile of Oritavancin against a Broad Spectrum of Aerobic and Anaerobic Bacterial Pathogens”/E -1613 “In Vitro Activity Profile of Oritavancin (ORI) Against Organisms Demonstrating Key Resistance Profiles to Other Antimicrobial Agents”/E-1614 “In vitro Time Kill Studies of Oritavancin against Drug-resistant Isolates of Staphylococcus aureus and Enterococci”/E-1615 “Anti-Enterococcal Activity Profile of Oritavancin, a Potent Lipoglycopeptide under Development for Use Against Gram-Positive Infections”/E-1616 “Anti-Streptococcal Activity Profile of Oritavancin, a Potent Lipoglycopeptide under Development for Use Against Gram-Positive Infections”/E-1617 “In Vitro Activity Profile of Oritavancin (ORI) Against Resistant Staphylococcal Populations From a Recent Surveillance Initiative”/E-1620 “Pharmacokinetic Concentrations of Oritavancin Kill Stationary-Phase and Biofilm Staphylococcus aureus In Vitro.” / Targanta Press Release September 19, 2007
4. ^ ICAAC 2007 Posters: “In Vitro Susceptibility of Genotypically Distinct Clostridium difficile Strains to Oritavancin” and “Activity of Metronidazole, Vancomycin and Oritavancin Against Epidemic Clostridium difficile Spores” / Targanta Press Release September 19, 2007
5. ^ ASM 2007 Poster: “Efficacy of Oritavancin in a Murine Model of Bacillus anthracis Spore Inhalation Anthrax” / Targanta Press Release May 24, 2007
6. ^ ICAAC 2003 Late-breaker poster: "Phase III Trial Comparing 3-7 days of Oritavancin vs. 10-14 days of Vancomycin/Cephalexin in the Treatment of Patients with Complicated Skin and Skin Structure Infections (cSSSI)" / InterMune Press Release September 15, 2003
7. ^ ClinicalTrials.gov