PRINCETON, N.J. and ANNAPOLIS, Md., Oct. 28 /PRNewswire-FirstCall/ --
Medarex, Inc. (Nasdaq: MEDX), a leading monoclonal antibody company, and
PharmAthene, Inc. (NYSE: PIP), 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(R)
(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(R) 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).
About Anthrax
According to the Centers for Disease Control and Prevention, anthrax is an
acute infectious disease caused by the spore-forming bacterium Bacillus
anthracis. Anthrax most commonly occurs in hoofed mammals and can also infect
humans. Symptoms of disease vary depending on how the disease is contracted,
but usually occur within seven days after exposure. The serious forms of human
anthrax are inhalation anthrax, cutaneous anthrax, and intestinal anthrax.
Initial symptoms of inhalation anthrax infection may resemble a common cold.
After several days, the symptoms may progress to severe breathing problems and
shock. Inhalation anthrax is often fatal, even if treated by antibiotics.
Currently, antibiotics are the only drugs available for therapeutic or
prophylactic use for inhalation anthrax, and post-exposure prophylaxis is the
only FDA-approved indication for such products. However, antibiotic therapy,
while useful, is believed to be associated with a number of limitations,
including: (1) lack of activity against the toxins produced by the B.
anthracis bacteria (2) need for long-term dosing to achieve full protection,
complicated by side effects and non-compliance (3) lack of efficacy when
administered late in the anthrax disease cycle, and (4) lack of effectiveness
against multi-drug resistant or genetically engineered strains of anthrax.
About Medarex
Medarex is a biopharmaceutical company focused on the discovery,
development and potential commercialization of fully human antibody-based
therapeutics to treat life-threatening and debilitating diseases, including
cancer, inflammation, autoimmune disorders and infectious diseases. Medarex
applies its UltiMAb(R) technology and product development and clinical
manufacturing experience to generate, support and potentially commercialize a
broad range of fully human antibody product candidates for itself and its
partners. Over forty of these therapeutic product candidates derived from
Medarex technology are in human clinical testing or have had INDs submitted
for such trials, with the most advanced product candidates currently in Phase
3 clinical trials or the subject of regulatory applications for marketing
authorization. Medarex is committed to building value by developing a diverse
pipeline of antibody products to address the world's unmet healthcare needs.
For more information about Medarex, visit its website at www.medarex.com.
About PharmAthene, Inc.
PharmAthene was formed to meet the critical needs of the United States and
its allies by developing and commercializing medical countermeasures against
biological and chemical weapons. PharmAthene's lead product development
programs include:
-- SparVax(TM) - a second generation recombinant protective antigen (rPA)
anthrax vaccine
-- Third generation rPA anthrax vaccine
-- Valortim(R) - a fully human monoclonal antibody for the prevention and
treatment of anthrax infection
-- Protexia(R) - a novel bioscavenger for the prevention and treatment of
morbidity and mortality associated with exposure to chemical nerve agents
-- RypVax(TM) - a recombinant dual antigen vaccine for plague
For more information about PharmAthene, please visit www.PharmAthene.com.
Statement on Cautionary Factors for Medarex
Except for the historical information presented herein, matters discussed
herein may constitute forward-looking statements within the meaning of the
Private Securities Litigation Reform Act of 1995 that are subject to certain
risks and uncertainties that could cause actual results to differ materially
from any future results, performance or achievements expressed or implied by
such statements. Statements that are not historical facts, including
statements preceded by, followed by, or that include the words "potential";
"believe"; "suggest"; "may"; or similar statements are forward-looking
statements. Medarex disclaims, however, any intent or obligation to update
these forward-looking statements, except as required by law. Risks and
uncertainties include risks associated with the reliability of animal
modelling, unforeseen safety issues resulting from the handling of Bacillus
anthracis, unforeseen safety issues resulting from the administration of
Valortim(R) (MDX-1303) in human subjects, uncertainties related to product
manufacturing as well as risks detailed from time to time in Medarex's public
disclosure filings with the U.S. Securities and Exchange Commission (SEC),
including its Annual Report on Form 10-K for the fiscal year ended December
31, 2007 and its quarterly reports on Form 10-Q. Copies of Medarex's public
disclosure filings are available from its investor relations department.
Statement on Cautionary Factors for PharmAthene
Except for the historical information presented herein, matters discussed
may constitute forward-looking statements within the meaning of the Private
Securities Litigation Reform Act of 1995 that are subject to certain risks and
uncertainties that could cause actual results to differ materially from any
future results, performance or achievements expressed or implied by such
statements. Statements that are not historical facts, including statements
preceded by, followed by, or that include the words "potential"; "believe";
"anticipate"; "intend"; "plan"; "expect"; "estimate"; "could"; "may";
"should"; or similar statements are forward-looking statements. PharmAthene
disclaims, however, any intent or obligation to update these forward-looking
statements. Risks and uncertainties include risk associated with the
reliability of the results of the studies relating to human safety and
possible adverse effects resulting from the administration of the Company's
product candidates, unexpected funding delays and/or reductions or elimination
of U.S. government funding for one or more of the Company's development
programs, the award of government contracts to our competitors, unforeseen
safety issues, unexpected determinations that these product candidates prove
not to be effective and/or capable of being marketed as products, as well as
risks detailed from time to time in PharmAthene's Form 10-K under the caption
"Risk Factors" and in its other reports filed with the U.S. Securities and
Exchange Commission (the "SEC"). In particular, the study described above
constitutes non-clinical animal studies. Significant additional non-clinical
animal studies, human clinical trials, and manufacturing development work
remain to be completed. At this point there can be no assurance that
Valortim(R) will be shown to be safe and effective and approved by regulatory
authorities for use in humans. Copies of PharmAthene's public disclosure
filings are available from its investor relations department and our website
under the investor relations tab at www.PharmAthene.com.
Medarex(R), the Medarex logo and UltiMAb(R) are registered trademarks of
Medarex, Inc. All rights are reserved. Valortim(R) is a trademark of
PharmAthene, Inc. All rights are reserved.
