PHARMATHENE, INC. (NYSEMKT:PIP) Files An 8-K Regulation FD Disclosure

Item 7.01. Regulation FD Disclosure.

On April 26, 2017, PharmAthene, Inc. (PharmAthene) and Altimmune,
Inc. (Altimmune), issued a joint press release announcing that,
pending the approval of the merger between the two companies by
PharmAthenes stockholders and the subsequent completion of the
merger, the common stock of the combined company has been
approved for listing on the The Nasdaq Global Select Market by
The NASDAQ Stock Market LLC under the symbol ALT. If the merger
is approved by PharmAthenes stockholders and subsequently
completed, trading on the Nasdaq Global Market is expected to
commence on May 5, 2017, the day after the anticipated completion
of the merger. PharmAthenes common stock will continue to trade
on the NYSE MKT until the completion of the merger, and, if the
merger is not completed, PharmAthenes common stock will continue
to trade on the NYSE MKT. A copy of the joint press release of
PharmAthene and Altimmune dated April 26, 2017, is attached
hereto as Exhibit 99.1.

On September 9, 2014, PharmAthene entered into an incrementally
funded contract with the National Institutes of Allergy and
Infectious Diseases (NIAID) for the development of a next
generation lyophilized anthrax vaccine (SparVax-L) which provided
for potential aggregate funding of up to approximately $28.1
million, if all technical milestones were met and all eight
contract options were exercised by NIAID. NIAID has exercised
four options under this agreement providing for performance
through December 31, 2017. PharmAthene has been informed by NIAID
that it will exercise only one of the additional remaining
options under the contract to provide funding for a non-human
primate challenge study which PharmAthene believes may be used to
support an advanced development funding proposal to Biomedical
Advanced Research and Development Authority (BARDA). Work under
all exercised options will continue bringing total committed and
final funding under the NAIAD contract to $15.1 million.

In accordance with General Instruction B.2. of Form 8-K, the
information in this Item 7.01, including Exhibit 99.1, shall not
be deemed filed for the purposes of Section 18 of the Securities
Exchange Act of 1934, as amended, or otherwise subject to the
liabilities of that section. The information in this Item 7.01,
including Exhibit 99.1, shall not be incorporated by reference
into any filing or other document to the Securities Act of 1933,
as amended, except as shall be expressly set forth by specific
reference in such filing or document.

Item 9.01. Financial Statements and Exhibits.

(d) Exhibits

Important Additional Information about the Proposed
Merger Transaction

In connection with a proposed merger transaction involving
Altimmune, Inc. and PharmAthene, Inc., PharmAthene has filed a
registration statement on Form S-4 (File No. 333-215891) (the
Registration Statement) with the U.S. Securities and Exchange
Commission (the SEC), which contains a proxy
statement/prospectus/consent solicitation and other relevant
materials. The proxy statement/prospectus/consent solicitation
contains information about PharmAthene, Altimmune, the proposed
merger 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, AS THEY
CONTAIN IMPORTANT INFORMATION THAT STOCKHOLDERS SHOULD CONSIDER
BEFORE MAKING A DECISION ABOUT THE MERGER TRANSACTION 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 SECs website (http://www.sec.gov) or, without charge, by
directing a written request to: PharmAthene, Inc., One Park
Place, Suite 450, Annapolis, Maryland 21401, Attention: Investor
Relations.

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 transaction or otherwise, nor shall
there be any sale, issuance or transfer of securities in any
jurisdiction in contravention of applicable law.

Participants in Solicitation

PharmAthene and its executive officers and directors may be
deemed to be participants in the solicitation of proxies from
PharmAthenes stockholders with respect to the matters relating to
the proposed merger transaction. Altimmune and its officers and
directors may also be deemed a participant in such solicitation.
Information regarding PharmAthenes executive officers and
directors is available in PharmAthenes Annual Report on Form 10-K
filed with the SEC on March 14, 2017. Information regarding any
interest that PharmAthene, Altimmune or any of the executive
officers or directors of PharmAthene or Altimmune may have in the
transaction with Altimmune is set forth in the proxy
statement/prospectus/ consent solicitation. Stockholders can
obtain this information by reading the proxy
statement/prospectus/consent solicitation filed with the SEC.

Forward-Looking Statements

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
will; potential; believe; anticipate; intend; plan; expect;
estimate; could; may; should; or similar statements are
forward-looking statements. Such statements include, but are not
limited to those referring to the potential for growth and the
expected completion and outcome of the merger transaction and the
transactions contemplated by the Merger Agreement and related
agreements. PharmAthene disclaims 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 transaction with Altimmune 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 Altimmune 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 companys 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
companys product candidates; unexpected funding delays and/or
reductions or elimination of U.S. government funding for one or
more of the combined companys development programs; the award of
government contracts to 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 PharmAthenes Form
10-K under the caption Risk Factors and in its other reports
filed with the SEC. Copies of PharmAthenes public disclosure
filings are available from its investor relations department and
its website under the investor relations tab at
http://www.pharmathene.com.

About PHARMATHENE, INC. (NYSEMKT:PIP)

Pharmathene, Inc. (Pharmathene) is a biodefense company. The Company is focused on the development of medical counter measures against biological and chemical threats. The Company is involved in the development of two next generation anthrax vaccines. The Company’s anthrax vaccines use recombinant protective antigen (rPA) manufacturing processes. The Company’s product portfolio includes recombinant butyrylcholinesterase (rBChE) bioscavenger, which is used in prevention and treatment of nerve agent poisoning. The Company has developed a recombinant form of human butyrylcholinesterase for pre- and post-exposure therapy to patients with nerve agent attacks. Its rBChE bioscavenger acts with mechanism, which includes reversal of the acute toxicity associated with organophosphate poisoning agents used in chemical warfare (cholinergic crisis). Its development program also includes Valortim for monoclonal human antibody treatment.

PHARMATHENE, INC. (NYSEMKT:PIP) Recent Trading Information

PHARMATHENE, INC. (NYSEMKT:PIP) closed its last trading session up +0.030 at 0.725 with 679,940 shares trading hands.