PharmAthene Presents New Anthrax Anti-Toxin Data at the ASM Biodefense and Emerging Diseases Research Meeting

ANNAPOLIS, Md., Feb. 8, 2011 /PRNewswire/ -- PharmAthene, Inc. (NYSE Amex: PIP), a biodefense company developing medical countermeasures against biological and chemical threats, announced today that new pharmacokinetic data from the Company's Valortim® anthrax anti-toxin program were presented at the 9th Annual ASM Biodefense and Emerging Diseases Research Meeting, held in Washington, DC, February 6-9, 2011.  The data were presented by Dr. Elizabeth Leffel, Director of Non-Clinical Sciences for PharmAthene, in a poster presentation entitled, "Pharmacokinetics of a Monoclonal Anthrax Anti-Toxin Antibody in Healthy and Infected Cynomolgus Macaques."

Valortim® is a fully human anti-toxin monoclonal antibody being developed by PharmAthene for the prevention and treatment of inhalational anthrax.  Valortim® was licensed from Medarex, which was acquired by Bristol-Myers Squibb in 2009.  Nonclinical animal studies suggest that Valortim® has the potential to provide protection against anthrax infection when administered prophylactically (prior to the emergence of symptoms of anthrax infection) and also may increase survival when administered therapeutically (once symptoms become evident).

"Anti-toxins such as Valortim® are an important part of our nation's biodefense armamentarium against anthrax," commented Dr. Thomas Fuerst, Executive Vice President and Chief Scientific Officer.  "The accumulating data suggest that Valortim® possesses important characteristics that may make it a strong choice for procurement in the Strategic National Stockpile, including: demonstrated efficacy in animal models as both a prophylactic and therapeutic for inhalational anthrax, efficacy at low doses, and a mechanism of action with unique properties that make it an attractive candidate.  We look forward to continuing to work collaboratively with the U.S. Government to develop innovative new biodefense countermeasures like Valortim® to protect our nation's citizens both at home and on the battlefield."

Valortim® Findings Reported

The objective of the study was to compare the pharmacokinetics (PK) of Valortim® following a single intravenous injection in non-challenged cynomolgus macaques (cynos) to that in cynos infected with Bacillus anthracis.  

In this study, 30 healthy non-challenged cynos were given 1, 5, 10, 20, or 40 mg/kg of Valortim® on Day 1.  Separately, 48 cynos were challenged with Bacillus anthracis spores and subsequently given 5, 10, 20, or 40 mg/kg of Valortim® at the time they were determined to be antigenemic (evidence of bacterial infection in the bloodstream).

Serum was collected over 56 days in the non-challenged animals and over 5 days in challenged animals for pharmacokinetics as measured by ELISA.  Non-compartmental analysis was conducted on the concentration-time profiles in all cynos.

The results indicated that healthy animals had approximately a 45-fold increase in Cmax for a 40-fold increase in dose between 1 and 40 mg/kg and an approximately 34-fold increase in area under the curve (AUC). Dose normalized Cmax, AUC values, mean clearance, volume of distribution, and half-life were generally similar across doses of 1 to 40 mg/kg.  Infected animals had approximately a 10-fold increase in Cmax for an 8-fold increase in dose, and an approximately 8- to 9-fold increase in partial AUC for an 8-fold increase in dose between 5 and 40 mg/kg groups.  Due to limited numbers of measurable observations in the terminal phase for cynos in all dose groups, other pharmacokinetic parameters were not calculated.

"Our results demonstrated that the pharmacokinetic parameters in non-challenged cynos were similar to those observed in anthrax-challenged cynos treated with Valortim®," commented Dr. Leffel.   "This is an encouraging finding which could have important implications for translation to a human dose for Valortim®."

Funding for these studies was provided by federal funds from the Biomedical Advanced Research and Development Authority (BARDA), Department of Health and Human Services (HHS), and the National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), under Contract No. HHSN272200800040C.

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 Valortim®. At this point there can be no assurance that Valortim® 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.