Theraclone Sciences Announces Initiation of Phase 2a Trial of TCN-202 for the Prevention of Human Cytomegalovirus Infection Seattle, WA

Theraclone Sciences Announces Initiation

of Phase 2a Trial of TCN-202 for the Prevention of Human Cytomegalovirus Infection

Seattle, WA - September 10, 2013

- Theraclone Sciences, Inc., a therapeutic antibody discovery and development company, today announced that it has dosed

the first patient in a Phase 2a clinical trial of TCN-202 for the prevention of human cytomegalovirus (CMV) infection in solid

organ transplant recipients. TCN-202 is a recombinant, fully human monoclonal antibody discovered using the Company's proprietary

"TCN-202 was chosen for its broad

activity against CMV infection and has demonstrated a favorable safety and pharmacokinetic profile in the Phase 1 study,"

said Eleanor Ramos, M.D., Chief Medical Officer, Theraclone. "We believe that this product candidate may provide a much needed

option for patients at risk for CMV infections, who face undesirable toxicities and the possibility of drug resistance with current

therapies, in both a preventative and therapeutic capacity."

The Phase 2a proof-of-concept study is

designed to evaluate the safety and efficacy of TCN-202 in solid organ (kidney) transplant recipients. In the study, up to twenty

renal transplant recipients will receive TCN-202 during the first ten weeks post-transplant. The primary objective of the study

is to evaluate the effect of TCN-202 on prevention of CMV infections during the first three months after transplant. Data from

the trial is expected in the second half of 2014.

TCN-202 is a recombinant fully human monoclonal

antibody for the treatment and prevention of CMV infections. In immune compromised individuals, such as solid organ or stem cell

transplant recipients, or those with leukemia or HIV infection,CMVinfection can cause serious life-threatening disease and may

significantly increase the risk of graft rejection. Additionally, each year approximately 30,000 children born in the United States

have congenital CMV infection and of these, approximately 150 die and over 5,000 have permanent hearing loss, intellectual disability,

psychomotor delay, speech and language disabilities, behavioral disorders or visual impairment.

Theraclone is a biopharmaceutical company

focused on the discovery and development of novel, monoclonal antibody therapeutics for diseases that are devastating for patients

and their families and which are a significant threat to human health. Theraclone leverages its proprietary antibody discovery

technology, I-STAR (In-Situ Therapeutic Antibody Rescue), to identify rare human antibodies that may be developed into antibody

product candidates that are potentially safer and more effective than current therapies. Theraclone has a portfolio of innovative

antibodies in clinical and preclinical development targeting serious medical conditions with a significant unmet medical need and

a primary focus on infectious disease and cancer, which include:

For more information about Theraclone,

please visit www.theraclone-sciences.com. On August 1, 2013, Theraclone Sciences and PharmAthene (NYSE

MKT: PIP) announced a definitive merger agreement.

PharmAthene is a leading biodefense company

engaged in the development and commercialization of next generation medical countermeasures against biological and chemical threats.

PharmAthene's current biodefense portfolio includes the following product candidates:

In addition, in May 2013, the Delaware

Supreme Court issued its ruling on the appeal in our litigation with SIGA Technologies, affirming the Court of Chancery's

finding that SIGA was liable for breach of contract, reversing its finding of promissory estoppel, and remanding the case back

to the Court of Chancery to reconsider the appropriate remedy and award of attorney's fees and expert witness costs in light of

the Supreme Court's opinion. For more information about PharmAthene, please visit www.PharmAthene.com.

Important Additional Information about

This communication is being made in respect

of the proposed merger involving Theraclone and PharmAthene. On August 1, 2013, PharmAthene filed with the Securities and Exchange

Commission (the "SEC") a current report on Form 8-K, which includes the merger agreement and related documents. On

September 9, 2013, PharmAthenefiled a registration statement on Form S-4 with the SEC, which contains a preliminary proxy statement/prospectus/consent

solicitation and other relevant materials, and plans to file with the SEC other documents regarding the proposed transaction. Once

the registration statement has been declared effective, the final proxy statement/prospectus/consent solicitation will be sent

to the stockholders of PharmAthene and Theraclone in connection with the stockholder votes on matters relating to the proposed

transaction. The proxy statement/prospectus/consent solicitation contains information about PharmAthene, Theraclone, the proposed

transaction, and related matters. STOCKHOLDERS ARE URGED TO READ THE PROXY STATEMENT/PROSPECTUS/CONSENT SOLICITATION (INCLUDING

ANY AMENDMENTS OR SUPPLEMENTS THERETO) AND OTHER DOCUMENTS FILED WITH THE SEC CAREFULLY IN THEIR ENTIRETY WHEN THEY BECOME AVAILABLE,

AS THEY WILL CONTAIN IMPORTANT INFORMATION THAT STOCKHOLDERS SHOULD CONSIDER BEFORE MAKING A DECISION ABOUT THE MERGER AND RELATED

MATTERS. In addition to receiving the proxy statement/prospectus/consent solicitation and proxy card by mail, stockholders

will also be able to obtain the proxy statement/prospectus/consent solicitation, as well as other filings containing information

about PharmAthene, without charge, from the SEC's website (http://www.sec.gov) or, without charge, by contacting Stacey Jurchison

at PharmAthene at (410) 269-2610.

No Offer or Solicitation

This communication is not intended to and

does not constitute an offer to sell or the solicitation of an offer to subscribe for or buy or an invitation to purchase or subscribe

for any securities or the solicitation of any vote or approval in any jurisdiction in connection with the merger or otherwise,

nor shall there be any sale, issuance or transfer of securities in any jurisdiction in contravention of applicable law. No offer

of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933,

Participants in Solicitation

PharmAthene and its executive officers

and directors may be deemed to be participants in the solicitation of proxies from PharmAthene's stockholders with respect

to the matters relating to the proposed merger. Theraclone may also be deemed a participant in such solicitation. Information regarding

PharmAthene's executive officers and directors is available in Amendment No. 1 to PharmAthene's proxy statement on

Schedule 14A, filed with the SEC on May 9, 2013. Information regarding any interest that PharmAthene, Theraclone or any of the

executive officers or directors of PharmAthene or Theraclone may have in the transaction will be set forth in the proxy statement/prospectus/consent

solicitation that PharmAthene will file in connection with the stockholder votes on matters relating to the proposed transaction.

Stockholders will be able to obtain this information by reading the proxy statement/prospectus/consent solicitation when it becomes

Forward-Looking Statements

Except for the historical information presented

herein and in the exhibit thereto, 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 "will," "hopeful,"

"designed," "expect,""objective" or similar statements are forward-looking statements. Such

statements include, but are not limited to those referring to Theraclone's clinical development activities and the expected

benefits of TCN-202 and TCN-032, the expected completion and outcome of the merger and the transactions contemplated by the merger

agreement and related agreements. PharmAthene and Theraclone disclaim any intent or obligation to update these forward-looking

statements. Risks and uncertainties include, among others, failure to obtain necessary stockholder approval for the proposed merger

and the matters related thereto; failure of either party to meet the conditions to closing of the transaction; delays in completing

the transaction and the risk that the transaction may not be completed at all; failure to realize the anticipated benefits from

the transaction or delay in realization thereof; the businesses of PharmAthene and Theraclone may not be combined successfully,

or such combination may take longer, be more difficult, time-consuming or costly to accomplish than expected; operating costs and

business disruption during the pendency of and following the transaction, including adverse effects on employee retention and on

business relationships with third parties; the combined company's need for and ability to obtain additional financing; 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 combined company's product candidates; unexpected funding delays and/or reductions or elimination

of U.S. government funding for one or more of the combined company's development programs; the award of government contracts to

competitors; unforeseen safety issues; unexpected determinations that these product candidates prove not to be effective or capable

of being marketed as products; as well as risks detailed from time to time in PharmAthene's annual report on Form 10-K and

quarterly reports on Form 10-Q under the caption "Risk Factors" and in its other reports filed with the SEC. 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.

Theraclone Media Contact:

MacDougall Biomedical Communications

Doug MacDougall or Michelle Avery