PharmAthene Anthrax Protection Data Presented at ASM Biodefense Disease Meeting

PhaRmAthene Presents Data for SparVax™ and Valortim®, A NOVEL VACCINE AND ANTI-TOXIN FOR THE PREVENTION AND TREATMENT OF ANTHRAX INFECTION aT thE 7th ANNUAL ASM BIODEFENSE Meeting

ANNAPOLIS, MD – February 24, 2009 – PharmAthene, Inc. (NYSE Alternext US: PIP), a biodefense company developing medical countermeasures against biological and chemical threats, announced today that results from a Phase II study of SparVax™ and pharmacokinetic (PK) data for Valortim® were presented at the 7th Annual ASM Biodefense and Emerging Diseases Research Meeting, being held in Baltimore, MD, February 22-25, 2009. David P. Wright, President and Chief Executive Officer of PharmAthene commented, “The ASM conference is among the leading industry meetings of the year for biodefense and we are pleased to be able to showcase advancements in each of our SparVax™ and Valortim® programs to key policy makers at this important meeting.”

“PharmAthene has received tremendous support from a variety of government funding partners, including, the Department of Defense, the Department of Health and Human Services, and the National Institute of Allergy and Infectious Diseases. This unprecedented collaborative effort will help to ensure the development of urgently needed medical countermeasures to meet the biosecurity needs of our Nation and Allies.”

SparVax™ is a novel second generation recombinant protective antigen (rPA) anthrax vaccine that is being developed for pre and post exposure protection against anthrax infection. Valortim®, in co-development with Medarex, Inc. (Nasdaq:MEDX), is a fully human monoclonal antibody designed to protect against and treat inhalational anthrax, the most lethal form of illness in humans caused by anthrax.

SparVax™ Phase II Clinical Data Results from a Phase II clinical trial of SparVax™ were presented during a poster session by Dr. Matthew Duchars, Chief Scientific Officer for PharmAthene. The Phase II trial was designed to evaluate the safety, tolerability and immunogenicity of two different dose levels and dosing schedules of SparVax™. A total of 415 healthy volunteers were enrolled in the Phase II trial.

Subjects were assigned to one of four groups in the priming phase of the study and two, three-dose schedules were examined at two different dose levels. At day 182, subjects were re-randomized to receive a challenge dose of SparVax™ at the original dose level, on either day 182 or 364.

Results from the Phase II trial showed that, overall, SparVax™ was safe and well tolerated. The immunogenicity data confirm that SparVax™ was immunogenic for both doses as well as each dosing schedule evaluated. Further, data from the challenge dose suggest that SparVax™ promotes good immunological recall.

In the study, geometric mean (GM) anti-rPA antibody concentrations were measured by ELISA on day 14 after the third dose. The data showed that the titers were significantly higher on one regimen (by almost x5) than those on the other regimen. No significant differences in GM titers were observed between groups that received different dose levels. An antigenic challenge dose was given at either day 182 or day 365. A significant response was seen in all groups that received an antigenic challenge, but no significant difference in the level of that response was seen across these groups.

These results suggest that SparVax™ may be a promising second generation rPA anthrax vaccine candidate for civilian defense against anthrax infection.

The SparVax™ Phase II clinical trial has been funded in whole or in part with Federal funds from the National Institute of Allergy and Infectious Disease, National Institutes of Health.

Valortim® PK Findings Reported

Pharmacokinetic data for Valortim® were presented by Dr. Matthew Meldorf, M.D., Senior Program Director for Valortim®, during an oral presentation on February 23, 2009.

Inhalational anthrax in certain primates such as African Green Monkeys (AGMs) and cynomolgus monkeys (cynos) is believed to follow a similar disease course as in humans. Valortim®, a fully human monoclonal antibody that binds to a distinct epitope on protective antigen, has demonstrated preliminary efficacy in the post-exposure prophylaxis and therapeutic settings in these animal models. PharmAthene and its collaborators are working to demonstrate that doses effective in these models may be translated into potentially efficacious human doses through PK modeling.

In separate PK studies reported at the ASM meeting, cynos and AGMs (n=6 per dosing group) were administered IV Valortim® at doses that included 1 mg/kg and 10 mg/kg.

Valortim® PK results for the two different species were comparable, including Cmax and AUCinf values. The half-life for Valortim® was slightly longer in the AGMs at 18-21 days compared to 15-17 days in the cynos. In both studies, Valortim® was well-tolerated without any clinical signs or changes in body weight noted in the animals.

These data indicate that Valortim® PK parameters are similar in both the cyno and AGM models. Evaluation of additional doses and further PK analyses of both challenged and non-challenged animals will be necessary to confirm these findings and may better refine the ability to select an efficacious human dose using PK data from these animal models. Additional PK testing of Valortim® is currently ongoing.

The cynomolgus PK project was funded in whole or in part with Federal funds from the National Institutes of Health. Funding for the AGM PK study was provided by the Department of Defense.

About SparVax™ SparVax™ is a novel second generation recombinant protective (rPA) anthrax vaccine being developed for pre and post exposure protection against anthrax infection. SparVax™ is a highly purified, well characterized, sub unit vaccine comprised of a single protein (recombinant PA) manufactured in E.coli. Phase I and Phase II clinical trials involving 770 healthy human subjects have been completed and showed that SparVax™ appears to be well tolerated and immunogenic in humans. These studies suggest that three doses of SparVax™, administered several weeks apart, should be sufficient to induce protective immunity. In preclinical studies SparVax™ has also demonstrated the capability to protect rabbits and non-human primates against a lethal aerosol spore challenge of the anthrax Ames strain.

About Valortim® Valortim® is a fully human monoclonal antibody designed to protect against and treat anthrax infection, including inhalational 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. Preclinical studies suggest that Valortim® has the potential to provide significant protection against anthrax infection when administered prophylactically post-exposure (i.e., prior to the emergence of symptoms of anthrax infection) and also may increase survival when administered therapeutically (i.e., once symptoms become evident).

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.

Anti-toxins such as Valortim® are a key element in combating and treating anthrax infection, in addition to vaccines and antibiotics. The Department of Health and Human Services has issued a requirement for up to 200,000 anthrax anti-toxin treatments to be included in the Strategic National Stockpile and PharmAthene believes that Valortim® is well positioned to address this need.

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 the ASM Biodefense and Emerging Diseases Research Meeting The 7th Annual ASM Biodefense and Emerging Diseases Research Meeting held in Baltimore, Maryland, is intended to bring together individuals who are carrying out research to defend against the growing threat of bioterrorism, and decision makers shaping the future biodefense research agenda, recognizing that emerging infectious diseases serve as a paradigm for handling the public threat of bioterrorism.

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™ - a second generation recombinant protective antigen (rPA) anthrax vaccine * Third generation rPA anthrax vaccine * Valortim® - a fully human monoclonal antibody for the prevention and treatment of anthrax infection * Protexia® - a novel bioscavenger for the prevention and treatment of morbidity and mortality associated with exposure to chemical nerve agents * RypVax™ - a recombinant dual antigen vaccine for plague

For more information about PharmAthene, please visit www.PharmAthene.com.

Statement on Cautionary Factors 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.


 

Posted: February 2009

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