Medarex And PharmAthene Announce New Therapeutic Data for Anthrax Anti-Toxin, Valortim(R)
Tuesday October 28, 8:00 am ET
- Data Presentation at 48th ICAAC / IDSA 46th Annual Meeting -
PRINCETON, N.J. and ANNAPOLIS, Md., Oct. 28 /PRNewswire-FirstCall/ -- Medarex, Inc. (Nasdaq: MEDX - News), a leading monoclonal antibody company, and PharmAthene, Inc. (NYSE: PIP - News), a biodefense company developing medical countermeasures against biological and chemical threats, today announced results from a pilot study showing that the anthrax anti-toxin, Valortim® (MDX-1303), enhanced survival as compared to a control group in a therapeutic animal model known as the New Zealand White (NZW) rabbit model. Valortim is a fully human monoclonal antibody generated by Medarex's UltiMAb® technology that is being co-developed by the two companies for potential use as an anti- toxin therapeutic to prevent and treat inhalation anthrax.
The data were presented in an oral presentation entitled "Therapeutic Efficacy of MDX-1303, an Anti-toxin Monoclonal Antibody, for Inhalation Anthrax in the New Zealand White (NZW) Rabbit Model" at the 48th ICAAC/ IDSA 46th Annual Meeting by Israel Lowy, M.D., Ph.D., Senior Director of Clinical Science and Infectious Diseases at Medarex.
David P. Wright, President & Chief Executive Officer of PharmAthene, commented, "Mounting evidence from a number of animal studies suggests that Valortim may be efficacious as both a prophylactic and therapeutic for inhalation anthrax infection. Based on these results, we believe that Valortim is ideally positioned for procurement consideration in the Strategic National Stockpile, and we look forward to working collaboratively with the Department of Health and Human Services to fulfill a critical need in the Nation's arsenal to combat the threat of anthrax."
"We are pleased to have been able to refine this model for therapeutic intervention in anthrax infection, further defining the potential efficacy of Valortim in anthrax disease," commented Dr. Lowy. "Animal modeling for therapeutic intervention in anthrax infection (in contrast to post-exposure prophylaxis) has been challenging because of the variability in onset time to disease after exposure and the rapidity of disease progression once symptoms are manifest. We used a rapid approach to identify animals with active disease, and our results showed that the animals designated for treatment proved to have bacteria circulating in their blood, supporting the accuracy of the approach and that Valortim had impressive activity in this setting. This study, along with others being conducted by our partner PharmAthene, may help to define an optimal and reproducible approach to evaluate therapeutic agents for anthrax disease in general, as well as Valortim in particular."
Details of the study
The pilot study, funded by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health (NIH), was designed to attempt to refine the New Zealand White (NZW) rabbit model as a predictive therapeutic model for anthrax inhalation disease, and to assess the efficacy of Valortim in this model. In the study, 32 adult NZW rabbits were exposed by aerosol to Ames anthrax spores. Beginning 12 hours post-exposure, animals were evaluated hourly for changes in temperature, and every 6 hours blood samples were collected to assess bacteremia and protective antigen in blood. Samples were analyzed for protective antigen via a rapid electrochemiluminescent immunoassay (ECL), and bacteremia was evaluated by 24- hour culture. A significant increase in body temperature and/or a positive ECL were used to identify an active infection that required therapeutic intervention, and animals were then treated with either Valortim or saline (control).
In this study, 94 percent (30/32) of the animals were subsequently shown to be bacteremic at the time of treatment. Twelve of the NZW rabbits were treated with an intravenous (IV) 10 mg/kg dose of Valortim, 8 were treated with a 20 mg/kg IV dose of Valortim, and 12 were treated with IV saline in the control group. Study findings showed that 100 percent (8/8) of the 20 mg/kg Valortim-treated animals survived compared to 83 percent (10/12) in the 10 mg/kg Valortim-treated group and 8 percent (1/12) in the control group.
About Valortim
Valortim (MDX-1303) is a fully human monoclonal antibody designed to protect against and treat anthrax infection, including inhalation anthrax, the most lethal form of illness in humans caused by the Bacillus anthracis bacterium. The investigational antibody is designed to target a protein component known as the anthrax protective antigen (PA) of the lethal toxin complex produced by the bacterium. The anthrax protective antigen is believed to initiate the onset of the illness by attaching to cells in the infected person, and then is believed to facilitate the entry of additional destructive toxins into the cells. Valortim is designed to target anthrax protective antigen and protect the cells from damage by the anthrax toxins.
As previously presented, Valortim has been administered intravenously and intramuscularly to healthy human volunteers in a completed Phase 1 study, was well tolerated at doses as high as 20 mg/kg (IV), and was not immunogenic. Pharmacokinetic analysis suggested that doses as low as 1 mg/kg resulted in circulating levels of antibody after a month, with a similar potency for neutralizing anthrax toxin in vitro as was seen with serum obtained from subjects who had been vaccinated with anthrax vaccine.
Preclinical studies suggest that Valortim has the potential to provide significant protection against anthrax infection when administered prophylactically post-exposure (prior to the emergence of symptoms of anthrax infection) and also may increase survival when administered therapeutically (once symptoms become evident). |
