PharmAthene Presents New Anthrax Data at the 5th Annual PHEMCE Stakeholders Workshop and BARDA Industry Day

ANNAPOLIS, Md., Jan. 13, 2011 /PRNewswire/ -- PharmAthene, Inc. (NYSE Amex: PIP), a biodefense company developing medical countermeasures against biological and chemical threats, announced today that the Company recently presented new data from its anthrax anti-toxin and recombinant Protective Antigen (rPA) anthrax vaccine programs at the HHS Public Health Emergency Medical Countermeasures Enterprise (PHEMCE) Stakeholders Workshop and the Biomedical Advanced Research and Development Authority (BARDA) Industry Day, held January 11 – 13, 2011 in Washington, DC.

"BARDA continues to move forward to work closely with industry in the development and procurement of new medical countermeasures," commented Dr. Thomas Fuerst, Executive Vice President and Chief Scientific Officer of PharmAthene.  "We are delighted to present new data from our biodefense programs, which demonstrate progress towards our shared goal of enhancing biodefense national security initiatives.  As the data illustrate, PharmAthene continues to advance its pipeline and further its leadership position in biodefense."

Valortim® Anthrax Anti-Toxin Findings Reported

In an oral presentation entitled, "Comparison of Functional Activity and Pharmacokinetic Data from Nonclinical Valortim® Efficacy Studies: Implications for the Animal Rule" Dr. James Bourdage, Director of Bioanalytical Assay Development, at PharmAthene presented a biostatistical analysis of pharmacokinetic and toxin neutralization assay results for multiple Valortim® doses in three separate animal species – the African Green Monkey, New Zealand White Rabbit and Cynomolgus Monkey.

In these studies, animals were exposed to anthrax spores and subsequently treated with various doses of Valortim® upon detection of antigenemia (evidence of bacterial infection in the bloodstream) and/or significant increases in body temperature (in the case of New Zealand White rabbits).  Pharmacokinetic (PK) analysis of serum samples was conducted utilizing a capture ELISA assay and a toxin neutralization assay (TNA).

Comparisons of the pharmacokinetic and toxin neutralization results for multiple Valortim® doses across the three separate species indicated that the TNA/PK ratios were relatively consistent within individual animals across various time points ranging from five minutes to five days for doses ranging from 2.5 to 40 mg/kg.  While the absolute ratios differed slightly for some animals, the consistency of these ratios across time, regardless of dose, species, or animal outcome, suggests the suitability of these assays in providing reliable data to support the Food and Drug Administration's use of the 'The Animal Rule' to approve new drugs or biological products when human efficacy studies are not ethical or feasible.

Dr. Bourdage commented, "Despite the presence of potentially interfering substances in animals with active disease, we're very encouraged that two separate assays evaluating Valortim® concentration and functional activity demonstrated comparable results.  In our opinion, this suggests the utility of these assays in providing data to support use of the Animal Rule for the approval of novel medical countermeasures, and thus represents a potentially important advance in the development of monoclonal antibody-based anthrax anti-toxins."

Funding for these studies was provided by the National Institute of Allergy and Infectious Diseases (NIAID) and the Biomedical Advanced Research and Development Authority (BARDA) under contract HHSN27220070033C and by the Department of Defense under contract WB81XWH-07-2-0036.

rPA-Based Anthrax Vaccine Findings Reported

In an poster presentation entitled, "Development of a Thermostable Recombinant Protective Antigen (rPA) Anthrax Vaccine: Product Characterization, Stability and Immunogenicity in the New Zealand White Rabbit" Dr. Elizabeth Leffel, Director of Non-Clinical Sciences at PharmAthene, presented new stability and immunogenicity data for the Company's rPA-based lyophilized anthrax vaccine program.  

The objective of the current study was to demonstrate the stability of rPA-based anthrax vaccine at elevated temperatures and to evaluate the immunogenicity of lyophilized rPA anthrax vaccine in comparison to a pre-formulated liquid vaccine.  In this study, lyophilized rPA was manufactured using a robust lyophilization cycle and its immunogenic potential was evaluated at 55 degrees centigrade and 70 degrees centigrade.  Immunogenicity was determined using New Zealand White rabbits receiving 1.0 micrograms/dose intramuscularly on days 1 and 29 of either pre-formulated liquid rPA or lyophilized rPA reconstituted in Alhydrogel-diluent and administered within 2 hours of reconstitution or at 1, 2, or 3 days after reconstitution.  Anti-rPA activity was determined by TNA and anti-PA IgG ELISA on days 15, 29, and 43.

Previous data have demonstrated that PharmAthene's lyophilized rPA anthrax vaccine was structurally stable and potent after 16 months at various temperatures up to and including 55 degrees centigrade. These new findings provide further evidence that lyophilized rPA-based anthrax vaccine continued to retain its native structural integrity when stored for prolonged time periods at elevated temperatures (55 degrees centigrade and 70 degrees centigrade) or room temperature (25 degrees centigrade) for periods of 18 and 29 months, respectively.   In addition, at present, PharmAthene has previously reported that it has demonstrated the stability of rPA bulk drug substance at 56 months using a well characterized mouse challenge potency assay, with stability testing ongoing.

In addition, the study results showed that reconstituted lyophilized rPA vaccine was immunogenic in a mouse challenge assay with a robust immune response from two doses that was at least as effective as a pre-formulated liquid vaccine.  Further, reconstituted rPA vaccine remained stable and potent for at least three days following reconstitution, suggesting potential flexibility of use in the field or in an emergency setting.

Dr. Leffel commented, "These data provide additional supportive evidence of the potential benefits of lyophilized rPA vaccine including enhanced stability and ease of deployment in a non-refrigerated environment, as well as an improved product shelf life to optimize product life-cycle management costs.  We're excited about these data and continue to work in close partnership with our counterparts at BARDA to evaluate this promising next generation vaccine approach."

Funding for these studies was provided under a Challenge grant (UC1 AI067223) from the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.  

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
• Valortim®  – a fully human monoclonal antibody for the prevention and treatment of anthrax infection
• rBChE (recombinant butyrylcholinesterase) – a medical countermeasure for nerve agent poisoning by organophosphate compounds, including nerve gases and pesticides

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.  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 risks 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, challenges related to the development, scale-up, and/or process validation of manufacturing processes for our product candidates, 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 and 10-Q under the caption "Risk Factors" and in its other reports filed with the U.S. Securities and Exchange Commission (the "SEC").  In particular, significant additional non-clinical animal studies, human clinical trials, and manufacturing development work remain to be completed for both our anthrax anti-toxin, Valortim® and our lyophilized rPA anthrax vaccine candidate. At this point there can be no assurance that either Valortim® or the Company's liquid or lyophilized rPA-based anthrax vaccine product candidates 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.

SOURCE PharmAthene, Inc.