Document:

Exhibit 4(f)

                          REGISTRATION RIGHTS AGREEMENT

            THIS REGISTRATION RIGHTS AGREEMENT, dated as of May 23, 2003 (this
"Agreement"), is made by and between SIGA TECHNOLOGIES, INC., a Delaware
corporation, having its principal place of business located at 420 Lexington
Avenue, Suite 620, New York, NY 10170 (the "Company"), and Plexus Vaccines Inc.,
a California corporation, having its principal place of business located at
11770 Bernardo Plaza Court, Suite 370-B, San Diego, CA 92128 (the "Initial
Investor").

                              W I T N E S S E T H:

            WHEREAS, upon the terms and subject to the conditions of the Asset
Purchase Agreement, dated as of May 14, 2003, between the Initial Investor and
the Company (the "Asset Purchase Agreement"), the Company has agreed to issue
and sell to the Initial Investor 1,950,000 shares of common stock, par value
$.0001 per share, of the Company (the "Shares"); and

            WHEREAS, to induce the Initial Investor to execute and deliver the
Asset Purchase Agreement, the Company has agreed to provide certain registration
rights under the Securities Act of 1933, as amended, and the rules and
regulations thereunder, or any similar successor statute (collectively, the
"Securities Act"), with respect to the Shares;

            NOW, THEREFORE, in consideration of the premises and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Initial Investor hereby agree as follows:

            1. Definitions. Terms not otherwise defined herein shall have the
meanings ascribed to them in the Asset Purchase Agreement. As used in this
Agreement, the following terms shall have the following meanings:

            (a) "Common Stock" means common stock, par value $.0001 per share,
of the Company.

            (b) "Investor" means the Initial Investor and any permitted
transferee or assignee who agrees to become bound by the provisions of this
Agreement in accordance with Section 9 hereof and who holds Registrable
Securities.

            (c) "Investor Group" means the Investor and each "Investor" (as such
term is defined in each registration rights agreement dated as of the date
hereof between the Company and each party identified on Schedule I attached
hereto and made a part hereof), as a group and not individually.

            (d) "Potential Material Event" means any of the following: (i) the
possession by the Company of material information not ripe for disclosure in a
registration statement, which shall be evidenced by a determination in good
faith by the Board of Directors of the Company

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that disclosure of such information in the registration statement would be
detrimental to the business and affairs of the Company or (ii) any material
engagement or activity by the Company which would, in the good faith
determination of the Board of Directors of the Company, be adversely affected by
disclosure in a registration statement at such time; in each case where such
determination shall be accompanied by a good faith determination by the Board of
Directors of the Company that the registration statement would be materially
misleading absent the inclusion of such information.

            (e) "Register," "Registered," and "Registration" refer to a
registration effected by preparing and filing a Registration Statement or
Statements in compliance with the Securities Act and pursuant to Rule 415 under
the Securities Act or any successor rule providing for offering securities on a
continuous basis ("Rule 415"), and the declaration or ordering of effectiveness
of such Registration Statement by the United States Securities and Exchange
Commission (the "SEC").

            (f) "Registrable Securities" means the Shares until the Shares are
eligible for resale pursuant to Rule 144 under the Securities Act.

            (g) "Registration Statement" means a registration statement of the
Company under the Securities Act covering Registrable Securities on Form S-3, if
the Company is then eligible to file using such form, and if not eligible, on
Form SB-2 or other appropriate form.

            (h) "Effective Date" means the date the SEC declares a Registration
Statement covering Registrable Securities and otherwise meeting the conditions
contemplated hereby to be effective.

            (i) "Restricted Sale Date" means the first date, other than during a
Permitted Suspension Period (as defined below), on which the Investor is
restricted from making sales of Registrable Securities covered by any previously
effective Registration Statement.

            2. Registration. The Company shall use its commercially reasonable
best efforts to prepare and file with the SEC, as soon as practicable after the
Closing Date, either a Registration Statement or an amendment to an existing
Registration Statement, in either event registering for resale by the Investor a
sufficient number of shares of Common Stock for the Initial Investor to sell the
Registrable Securities, but in no event less than the number of shares equal to
the Registrable Securities at the time of filing of such Registration Statement
(or such lesser number as may be required by the SEC). The Registration
Statement shall include only the Registrable Securities. The Company will use
its commercially reasonable best efforts to cause such Registration Statement to
be declared effective.

            3. Obligations of the Company. In connection with the registration
of the Registrable Securities, the Company shall do each of the following:

            (a) Use its commercially reasonable best efforts to prepare and file
with the SEC a Registration Statement with respect to not less than the number
of Registrable Securities provided in Section 2 above, and thereafter use its
commercially reasonable best efforts to cause such Registration Statement
relating to Registrable Securities to become effective and keep the Registration
Statement effective at all times during the period (the "Registration Period")

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continuing until the earlier of (i) the date that is two (2) years after the
last day of the calendar month following the month in which the Effective Date
occurs, or (ii) the date on which the Shares are no longer Registrable
Securities, which Registration Statement (including any amendments or
supplements thereto and prospectuses contained therein) shall not contain any
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein, in light of the
circumstances in which they were made, not misleading;

            (b) Use its commercially reasonable best efforts to prepare and file
with the SEC such amendments (including post-effective amendments) and
supplements to the Registration Statement and the prospectus used in connection
with the Registration Statement as may be necessary to keep the Registration
Statement effective at all times during the Registration Period, and, during the
Registration Period, comply with the provisions of the Securities Act with
respect to the disposition of all Registrable Securities of the Company covered
by the Registration Statement until such time as all of such Registrable
Securities have been disposed of in accordance with the intended methods of
disposition by the seller or sellers thereof as set forth in the Registration
Statement;

            (c) Permit one firm of counsel designated by the Investor Group to
review the Registration Statement and all amendments and supplements thereto a
reasonable period of time (but not less than two (2) business days and not more
than ten (10) days) prior to their filing with the SEC.

            (d) Notify each Investor promptly (and, in the case of (i)(A) below,
not less than two (2) business days prior to such filing) (i)(A) when a
prospectus or any prospectus supplement or post-effective amendment to the
Registration Statement is proposed to be filed; (B) whenever the SEC notifies
the Company whether there will be a "review" of such Registration Statement; (C)
whenever the Company receives (or a representative of the Company receives on
its behalf) any oral or written comments from the SEC in respect of a
Registration Statement (copies or, in the case of oral comments, summaries of
such comments shall be promptly furnished by the Company to the Investors); and
(D) with respect to the Registration Statement or any post-effective amendment,
when the same has become effective; (ii) of any request by the SEC or any other
Federal or state governmental authority for amendments or supplements to the
Registration Statement or prospectus or for additional information; (iii) of the
issuance by the SEC of any stop order suspending the effectiveness of the
Registration Statement covering any or all of the Registrable Securities or the
initiation of any proceedings for that purpose; (iv) of the receipt by the
Company of any notification with respect to the suspension of the qualification
or exemption from qualification of any of the Registrable Securities for sale in
any jurisdiction, or the initiation or threatening of any proceeding for such
purpose; and (v) of the occurrence of any event that to the best knowledge of
the Company makes any statement made in the Registration Statement or prospectus
or any document incorporated or deemed to be incorporated therein by reference
untrue in any material respect or that requires any revisions to the
Registration Statement, prospectus or other documents so that, in the case of
the Registration Statement or the prospectus, as the case may be, it will not
contain any untrue statement of a material fact or omit to state any material
fact required to be stated therein or necessary to make the statements therein,
in light of the circumstances under which they were made, not misleading;

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            (e) Furnish or make available to each Investor (i) promptly after
the same is prepared and publicly distributed, filed with the SEC, or received
by the Company, one (1) copy of the Registration Statement, each preliminary
prospectus and prospectus, and each amendment or supplement thereto, and (ii)
such number of copies of a prospectus, and all amendments and supplements
thereto and such other documents, as such Investor may reasonably request in
order to facilitate the disposition of the Registrable Securities owned by such
Investor;

            (f) As promptly as practicable after becoming aware thereof, notify
each Investor of the happening of any event of which the Company has knowledge,
as a result of which the prospectus included in the Registration Statement, as
then in effect, includes an untrue statement of a material fact or omits to
state a material fact required to be stated therein or necessary to make the
statements therein, in light of the circumstances under which they were made,
not misleading, and use its commercially reasonable efforts to promptly prepare
a supplement or amendment to the Registration Statement or other appropriate
filing with the SEC to correct such untrue statement or omission, and deliver or
make available a number of copies of such supplement or amendment to each
Investor as such Investor may reasonably request;

            (g) Notwithstanding the foregoing, if at any time or from time to
time after the date of effectiveness of the Registration Statement, the Company
notifies the Investors in writing of the existence of a Potential Material
Event, the Investor shall not offer or sell any Registrable Securities, or
engage in any other transaction involving or relating to the Registrable
Securities, from the time of the giving of notice with respect to a Potential
Material Event until such Investor receives written notice from the Company that
such Potential Material Event either has been disclosed to the public or no
longer constitutes a Potential Material Event; provided, however, that the
Company may not so suspend the right to such holders of Registrable Securities
during the periods the Registration Statement is required to be in effect other
than during a Permitted Suspension Period. The term "Permitted Suspension
Period" means one or more suspension periods during any consecutive 12-month
period which suspension periods, in the aggregate, do not exceed one hundred
eighty (180) days, provided, however, that no one such suspension period shall
either (i) be for more than forty-five (45) days or (ii) begin less than ten
(10) business days after the last day of the preceding suspension (whether or
not such last day was during or after a Permitted Suspension Period); provided,
further, that the Company shall, if lawful to do so, provide the Investor with
at least two (2) business days' notice of the existence (but not the substance
of) a Potential Material Event;

            (h) Use its commercially reasonable efforts to secure and maintain
the designation of all the Registrable Securities covered by the Registration
Statement on the "Nasdaq/Small Cap Market" of the National Association of
Securities Dealers Automated Quotations System ("NASDAQ") within the meaning of
Rule 11Aa2-1 of the SEC under the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), and the quotation of the Registrable Securities on The
Nasdaq/Small Cap Market;

            (i) Provide a transfer agent and registrar, which may be a single
entity, for the Registrable Securities not later than the initial Effective
Date.

            (j) Cooperate with the Investor who holds Registrable Securities
being offered to facilitate the timely preparation and delivery of certificates
for the Registrable

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Securities to be offered pursuant to the Registration Statement and enable such
certificates for the Registrable Securities to be in such denominations or
amounts as the case may be, as the Investor may reasonably request, and, within
five (5) business days after a Registration Statement which includes Registrable
Securities is ordered effective by the SEC, the Company shall deliver, and shall
cause legal counsel selected by the Company to deliver, to the transfer agent
for the Registrable Securities (with copies to the Investor whose Registrable
Securities are included in such Registration Statement) an appropriate
instruction and, if necessary, an opinion of such counsel; and

            (k) Take all other reasonable actions necessary to expedite and
facilitate disposition by the Investor of the Registrable Securities pursuant to
the Registration Statement.

            4. Obligations of the Investor. In connection with the registration
of the Registrable Securities, each Investor shall have the following
obligations:

            (a) It shall be a condition precedent to the obligations of the
Company to complete the registration pursuant to this Agreement with respect to
the Registrable Securities of a particular Investor that such Investor shall
furnish to the Company such information regarding itself, the Registrable
Securities held by it, and the intended method of disposition of the Registrable
Securities held by it, as shall be reasonably required to effect the
registration of such Registrable Securities and shall execute such documents in
connection with such registration as the Company may reasonably request. At
least ten (10) business days prior to the first anticipated filing date of the
Registration Statement, the Company shall notify each Investor of the
information the Company requires from each such Investor (the "Requested
Information") if such Investor has any Registrable Securities included in the
Registration Statement. If at least two (2) business days prior to the filing
date the Company has not received the Requested Information from an Investor (a
"Non-Responsive Investor"), then the Company may file the Registration Statement
without including Registrable Securities of such Non-Responsive Investor;

            (b) Each Investor, by such Investor's acceptance of the Registrable
Securities, agrees to cooperate with the Company as reasonably requested by the
Company in connection with the preparation and filing of the Registration
Statement hereunder, unless such Investor has notified the Company in writing of
such Investor's election to exclude all of such Investor's Registrable
Securities from the Registration Statement; and

            (c) Each Investor agrees that, upon receipt of any notice from the
Company of the happening of any event of the kind described in Section 3(f) or
3(g), above, such Investor will immediately discontinue disposition of
Registrable Securities pursuant to the Registration Statement covering such
Registrable Securities until such Investor's receipt of the copies of the
supplemented or amended prospectus contemplated by Section 3(f) or 3(g) or such
Investor is advised in writing by the Company that use of the applicable
prospectus may be resumed and, if so directed by the Company, such Investor
shall deliver to the Company (at the expense of the Company) or destroy (and
deliver to the Company a certificate of destruction) all copies in such
Investor's possession, of the prospectus covering such Registrable Securities
current at the time of receipt of such notice.

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            5. Expenses of Registration. All reasonable expenses (other than
underwriting discounts, commissions and fees of the Investor attributable to the
sale of the Registrable Securities or more than one counsel, any accountants and
other persons retained by the Investor Group in connection with the transactions
contemplated by this Agreement) incurred in connection with registrations,
filings or qualifications pursuant to Section 3, but including, without
limitation, all registration, listing, and qualifications fees, printers and
accounting fees, the fees and disbursements of counsel for the Company shall be
borne by the Company. In addition, a fee for one counsel for the Investor Group
up to $2,500 for the review of the Registration Statement and up to $1,500 for
each post-effective amendment to a Registration Statement, shall be borne by the
Company.

            6. Indemnification. In the event any Registrable Securities are
included in a Registration Statement under this Agreement:

            (a) To the extent permitted by law, the Company will indemnify and
hold harmless each Investor who holds such Registrable Securities, the
directors, if any, of such Investor, the officers, if any, of such Investor,
each person, if any, who controls any Investor within the meaning of the
Securities Act or the Exchange Act (each, an "Indemnified Person" or
"Indemnified Party"), against any losses, claims, damages, liabilities or
expenses (joint or several) incurred (collectively, "Claims") to which any of
them may become subject under the Securities Act, the Exchange Act or otherwise,
insofar as such Claims (or actions or proceedings, whether commenced or
threatened, in respect thereof) arise out of or are based upon any of the
following statements, omissions or violations in the Registration Statement, or
any post-effective amendment thereof, or any prospectus included therein: (i)
any untrue statement or alleged untrue statement of a material fact contained in
the Registration Statement or any post-effective amendment thereof or the
omission or alleged omission to state therein a material fact required to be
stated therein or necessary to make the statements therein (in the case of a
prospectus, in light of the circumstances in which they were made) not
misleading, (ii) any untrue statement or alleged untrue statement of a material
fact contained in the final prospectus (as amended or supplemented, if the
Company files any amendment thereof or supplement thereto with the SEC) or the
omission or alleged omission to state therein any material fact necessary to
make the statements made therein, in light of the circumstances under which the
statements therein were made, not misleading or (iii) any violation or alleged
violation by the Company of the Securities Act, the Exchange Act, any state
securities law or any rule or regulation under the Securities Act, the Exchange
Act or any state securities law (the matters in the foregoing clauses (i)
through (iii) being, collectively, "Violations"). Subject to clause (c) of this
Section 6, the Company shall reimburse the Investors, promptly as such expenses
are incurred and are due and payable, for any legal fees or other reasonable
expenses incurred by them in connection with investigating or defending any such
Claim. Notwithstanding anything to the contrary contained herein, the
indemnification agreement contained in this Section 6(a) shall not (i) apply to
a Claim arising out of or based upon a Violation which occurs in reliance upon
and in conformity with information furnished in writing to the Company by or on
behalf of any Indemnified Person expressly for use in connection with the
preparation of the Registration Statement or any such amendment thereof or
supplement thereto, after such prospectus was made available by the Company
pursuant to Section 3(c) hereof; (ii) be available to the extent such Claim is
based on a failure of the Investor to deliver or cause to be delivered the
prospectus made available by the Company or the amendment or supplement thereto
made available by the Company; (iii) be available to the

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extent such Claim is based on the delivery of a prospectus by the Investor after
receiving notice from the Company under Section 3(f), (g) or (h) hereof (other
than a notice regarding the effectiveness of the Registration Statement or any
amendment or supplement thereto), (iv) be available if any untrue statement or
alleged untrue statement of a material fact contained in the final prospectus or
the omission or alleged omission to state therein any material fact necessary to
make the statements made therein, in light of the circumstances under which the
statements therein were made, not misleading is corrected in all material
respects in an amendment or supplement to the prospectus, or (v) apply to
amounts paid in settlement of any Claim if such settlement is effected without
the prior written consent of the Company, which consent shall not be
unreasonably withheld or delayed.

            (b) In connection with any registration in which any Investor is
participating, such Investor agrees to indemnify the Company, its directors and
officers who sign the Registration Statement, each person, if any, who controls
(within the meaning of either the Securities Act or of the Exchange Act) the
Company, each other Investor and any prospective underwriters, as the case may
be, and any of their respective affiliates, general partners, officers,
employees, agents and controlling persons (each, an "Indemnified Person" or
"Indemnified Party"), to the same extent as the foregoing indemnity from the
Company to such Investor, but only with respect to information relating to such
Investor furnished to the Company in writing by such Investor expressly for use
in the Registration Statement, the prospectus, any amendment or supplement
thereto, or any preliminary prospectus. Notwithstanding the foregoing, each
Investor shall not be liable for an amount in excess of the proceeds of sale of
such Investor's Registrable Securities (less applicable underwriting discounts
and commissions).

            (c) Promptly after receipt by an Indemnified Person or Indemnified
Party under this Section 6 of notice of the commencement of any action
(including any governmental action), such Indemnified Person or Indemnified
Party shall, if a Claim in respect thereof is to be made against any
indemnifying party under this Section 6, deliver to the indemnifying party a
written notice of the commencement thereof and the indemnifying party shall have
the right to participate in, and, to the extent the indemnifying party so
desires, jointly with any other indemnifying party similarly noticed, to assume
control of the defense thereof with counsel mutually satisfactory to the
indemnifying party and the Indemnified Person or the Indemnified Party, as the
case may be. In case any such action is brought against any Indemnified Person
or Indemnified Party, and it notifies the indemnifying party of the commencement
thereof, the indemnifying party will be entitled to participate in, and, to the
extent that it may wish, jointly with any other indemnifying party similarly
notified, assume the defense thereof, subject to the provisions herein stated
and after notice from the indemnifying party to such Indemnified Person or
Indemnified Party of its election so to assume the defense thereof, the
indemnifying party will not be liable to such Indemnified Person or Indemnified
Party under this Section 6 for any legal or other reasonable out-of-pocket
expenses subsequently incurred by such Indemnified Person or Indemnified Party
in connection with the defense thereof other than reasonable costs of
investigation, unless the indemnifying party shall not pursue the action to its
final conclusion. The Indemnified Person or Indemnified Party shall have the
right to employ separate counsel in any such action and to participate in the
defense thereof, but the fees and reasonable out-of-pocket expenses of such
counsel shall not be at the expense of the indemnifying party if the
indemnifying party has assumed the defense of the action with counsel reasonably
satisfactory to the Indemnified Person or Indemnified Party provided such
counsel is of the opinion that all

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defenses available to the Indemnified Party can be maintained without
prejudicing the rights of the indemnifying party. The failure to deliver written
notice to the indemnifying party within a reasonable time of the commencement of
any such action shall not relieve such indemnifying party of any liability to
the Indemnified Person or Indemnified Party under this Section 6, except to the
extent that the indemnifying party is prejudiced in its ability to defend such
action. The indemnification required by this Section 6 shall be made by periodic
payments of the amount thereof during the course of the investigation or
defense, as such expense, loss, damage or liability is incurred and is due and
payable.

            7. Contribution. To the extent any indemnification by an
indemnifying party is prohibited or limited by law, the indemnifying party
agrees to make the maximum contribution with respect to any amounts for which it
would otherwise be liable under Section 6 to the fullest extent permitted by
law; provided, however, that (a) no contribution shall be made under
circumstances where the maker would not have been liable for indemnification
under the fault standards set forth in Section 6; (b) no seller of Registrable
Securities guilty of fraudulent misrepresentation (within the meaning of Section
11(f) of the Securities Act) shall be entitled to contribution from any seller
of Registrable Securities who was not guilty of such fraudulent
misrepresentation; and (c) except where the seller has committed fraud or
intentional misconduct, contribution by any seller of Registrable Securities
shall be limited in amount to the net amount of proceeds received by such seller
from the sale of such Registrable Securities.

            8. Reports under Securities Act and Exchange Act. With a view to
making available to Investor the benefits of Rule 144 promulgated under the
Securities Act or any other similar rule or regulation of the SEC that may at
any time permit Investor to sell securities of the Company to the public without
Registration ("Rule 144"), the Company agrees to:

            (a) make and keep public information available, as those terms are
understood and defined in Rule 144; and

            (b) file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and the Exchange Act.

            9. Assignment of the Registration Rights. The rights to have the
Company register Registrable Securities pursuant to this Agreement shall be
automatically assigned by the Investors to any transferee of the Registrable
Securities only if: (a) the Investor agrees in writing with the transferee or
assignee to assign such rights, and a copy of such agreement is furnished to the
Company within a reasonable time after such assignment, (b) the Company is,
within a reasonable time after such transfer or assignment, furnished with
written notice of (i) the name and address of such transferee or assignee and
(ii) the securities with respect to which such registration rights are being
transferred or assigned, (c) immediately following such transfer or assignment
the further disposition of such securities by the transferee or assignee is
restricted under the Securities Act and applicable state securities laws, (d) at
or before the time the Company received the written notice contemplated by
clause (b) of this sentence the transferee or assignee agrees in writing with
the Company to be bound by all of the provisions contained herein, and (e) such
transfer of Registrable Securities is completed and disclosed to the Company
prior to the initial Effective Date. In the event of any delay in filing or
effectiveness of the

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Registration Statement as a result of such assignment, the Company shall not be
liable for any damages arising from such delay.

            10. Amendment of Registration Rights. Any provision of this
Agreement may be amended and the observance thereof may be waived (either
generally or in a particular instance and either retroactively or
prospectively), only with the written consent of the Company and Investors who
hold a fifty-one percent (51%) interest of the Registrable Securities. Any
amendment or waiver effected in accordance with this Section 10 shall be binding
upon each Investor and the Company.

            11. Miscellaneous.

            (a) A person or entity is deemed to be a holder of Registrable
Securities whenever such person or entity owns of record such Registrable
Securities. If the Company receives conflicting instructions, notices or
elections from two or more persons or entities with respect to the same
Registrable Securities, the Company shall act upon the basis of instructions,
notice or election received from the registered owner of such Registrable
Securities.

            (b) Notices required or permitted to be given hereunder shall be
given in the manner contemplated by the Asset Purchase Agreement, (i) if to the
Company or to the Initial Investor, to their respective address contemplated by
the Asset Purchase Agreement, and (ii) if to any other Investor, at such address
as such Investor shall have provided in writing to the Company, or at such other
address as each such party furnishes by notice given in accordance with this
Section 11(b).

            (c) This Agreement is intended for the benefit of the parties hereto
and their respective permitted successors and assigns and is not for the benefit
of, nor may any provision hereof be enforced by, any other person.

            (d) Failure of any party to exercise any right or remedy under this
Agreement or otherwise, or delay by a party in exercising such right or remedy,
shall not operate as a waiver thereof.

            (e) This Agreement shall be governed by and interpreted in
accordance with the laws of the State of New York for contracts to be wholly
performed in such state and without giving effect to the principles thereof
regarding the conflict of laws. Each of the parties consents to the jurisdiction
of the federal courts whose districts encompass any part of the City of New York
or the state courts of the State of New York sitting in the City of New York in
connection with any dispute arising under this Agreement and hereby waives, to
the maximum extent permitted by law, any objection, including any objection
based on forum non coveniens, to the bringing of any such proceeding in such
jurisdictions. To the extent determined by such court, either party hereto shall
reimburse the other party for any reasonable legal fees and disbursements
incurred by such party in enforcement of or protection of any of its rights
under this Agreement.

            (f) If any provision of this Agreement shall be invalid or
unenforceable in any jurisdiction, such invalidity or unenforceability shall not
affect the validity or enforceability of the remainder of this Agreement or the
validity or enforceability of

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this Agreement in any other jurisdiction.

            (g) Subject to the requirements of Section 9 hereof, this Agreement
shall inure to the benefit of and be binding upon the successors and assigns of
each of the parties hereto.

            (h) All pronouns and any variations thereof refer to the masculine,
feminine or neuter, singular or plural, as the context may require.

            (i) The headings in this Agreement are for convenience of reference
only and shall not limit or otherwise affect the meaning thereof.

            (j) This Agreement may be executed in one or more counterparts, each
of which shall be deemed an original but all of which shall constitute one and
the same agreement. This Agreement, once executed by a party, may be delivered
to the other party hereto by telephone line facsimile transmission of a copy of
this Agreement bearing the signature of the party so delivering this Agreement.

            (k) The Company acknowledges that any failure by the Company to
perform its obligations under Section 3(a) hereof, or any delay in such
performance could result in loss to the Investors, and the Company agrees that,
in addition to any other liability the Company may have by reason of such
failure or delay, the Company shall be liable for all direct damages caused by
any such failure or delay, unless the same is the result of force majeure.
Neither party shall be liable for consequential damages.

            (l) This Agreement constitutes the entire agreement among the
parties hereto with respect to the subject matter hereof. There are no
restrictions, promises, warranties or undertakings, other than those set forth
or referred to herein. This Agreement supersedes all prior agreements and
understandings among the parties hereto with respect to the subject matter
hereof. This Agreement may be amended only by an instrument in writing signed by
the party to be charged with enforcement thereof.

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      IN WITNESS WHEREOF, the parties have caused this Agreement to be duly
executed by their respective officers thereunto duly authorized as of the day
and year first above written.

                                        COMPANY:

                                        SIGA TECHNOLOGIES, INC.

                                        By: /s/ Thomas N. Konatich
                                            ------------------------------------

                                        Name:  Thomas N. Konatich
                                        Title: Acting Chief Executive Officer
                                               and Chief Financial Officer

                                        INITIAL INVESTOR:

                                        PLEXUS VACCINE INC.

                                        By: /s/ Susan K. Burgess
                                            ------------------------------------

                                        Name:  Susan K. Burgess
                                        Title: President and Chief Executive
                                               Officer

                                       11Exhibit 4(g)

                             SIGA TECHNOLOGIES, INC.

                      Non-Qualified Stock Option Agreement

                                                     Granting Date: May 23, 2003

To: ______________________

            We are pleased to notify you that, pursuant to the SIGA
Technologies, Inc. Amended and Restated 1996 Incentive and Non-Qualified Stock
Option Plan (the "Plan"), SIGA TECHNOLOGIES, INC., a Delaware corporation (the
"Company") has granted to you (the "Holder") a Non-Qualified stock option (the
"Option") to purchase all or any part of an aggregate of ____________ shares of
Common Stock of the Company (the "Optioned Shares"), subject to the terms and
conditions of this Agreement and the Plan. All terms, conditions and
restrictions of the Plan are incorporated herein and made part hereof as if
stated herein. If there is any conflict between the terms and conditions of the
Plan and this Agreement, the terms and conditions of the Plan, as interpreted by
the Committee, shall govern. Except as otherwise provided herein, all
capitalized terms (and any other terms defined in the Plan) used herein shall
have the meaning given to such terms in the Plan.

            1. Term and Exercise of Option. Subject to the provisions of this
Agreement, this Option may be exercised for up to the number of Optioned Shares
(subject to adjustment as provided in Section hereof) by you on or prior to May
23, 2013 ("Last Exercise Date") at an initial exercise price (the "Exercise
Price") of $1.69 per share (subject to adjustment as provided in Section 7
hereof) and all as subject to the Plan and this Agreement. The Holder may
exercise this Option at any time after the date of this Agreement. Any portion
of the Option that you do not exercise shall accumulate and can be exercised by
you any time prior to the Last Exercise Date. You may not exercise your Option
to purchase a fractional share or fewer than 100 shares, and you may only
exercise your Option by purchasing shares in increments of 100 shares unless the
remaining shares purchasable are less than 100 shares.

            This Option may be exercised by delivering to the Secretary of the
Company (i) a written Notice of Intention to Exercise in the form attached
hereto as Exhibit A signed by you and specifying the number of Optioned Shares
you desire to purchase, (ii) payment, in full, of the Exercise Price for all
such Optioned Shares in cash, certified check, surrender of shares of Common
Stock of the Company having a value equal to the exercise price of the Optioned
Shares as to which you are exercising this Option, provided that such
surrendered shares, if previously acquired by exercise of a Company stock
option, have been held by you at least six months prior to their surrender, or
by means of a brokered cashless exercise. As a holder of an option, you shall
have the rights of a shareholder with respect to the Optioned Shares only after
they shall have been issued to you upon the exercise of this Option. Subject to
the terms and provisions of this Agreement and the Plan, the Company shall use
its best efforts to cause the Optioned Shares to be issued as promptly as
practicable after receipt of your Notice of Intention to Exercise.

            2. Non-transferability of Option. This Option shall not be
transferable and may be exercised during your lifetime only by you. Any
purported transfer or assignment of this Option shall be void and of no effect,
and shall give the Company the right to terminate this Option as of the date of
such purported transfer or assignment. No transfer of an Option by will or by
the laws of descent and distribution shall be effective unless the Company shall
have been furnished with written notice thereof, and such other evidence as the
Company may deem necessary to establish the validity of the transfer and
conditions of the Option, and to establish compliance with any laws or
regulations pertaining thereto.

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            3. Certain Rights and Restrictions With Respect to Common Stock. The
Optioned Shares which you may acquire upon the exercise of this Option will not
be registered under the Securities Act of 1933, as amended, or under state
securities laws and the resale by you of such Optioned Shares will, therefore,
be restricted. You will be unable to transfer such Optioned Shares without
either registration under such Act and compliance with applicable state
securities laws or the availability of an exemption therefrom. Accordingly, you
represent and warrant to the Company that all shares of Common Stock you may
acquire upon the exercise of this Option will be acquired by you for your own
account for investment and that you will not sell or otherwise dispose of any
such shares except in compliance with all applicable federal and state
securities laws. The Company may place a legend to such effect upon each
certificate representing Optioned Shares acquired by you upon the exercise of
this Option.

            4. Disputes. Any dispute which may arise under or as a result of or
pursuant to this Agreement shall be finally and conclusively determined in good
faith by the Board of Directors of the Company in its sole discretion, and such
determination shall be binding upon all parties.

            5. Termination of Status.

            (a) This Option is a separate incentive and not in lieu of salary or
other compensation. The Optioned Shares do not vest you with any right to
employment with the Company, nor is the Company's right to terminate your
employment in any way restricted by this Agreement. Subject to the following
provisions of this Section 5, the Option will terminate upon and will not be
exercisable after termination of your employment with the Company ("Employment
Termination Date"). If your employment with the Company is terminated for any
reason other than death or disability, this Option may not be exercised after
the earlier of (i) ninety (90) days from the Employment Termination Date or (ii)
the Expiration Date, and may not be exercised for more than the number of
Optioned Shares purchasable under Section 1 on the Employment Termination Date.

            (b) If you die while this Option is exercisable, or within a period
of three months after the Employment Termination Date, the Option may be
exercised by the duly authorized executor of your last will or by the duly
authorized administrator of your estate, but may not be exercised after the
earlier of (i) one year from the date of your death or (ii) the Expiration Date,
and may not be exercised for more than the number of Optioned Shares purchasable
under Section 1 on the date of your death.

            (c) If your employment is terminated as a result of your permanent
disability, this Option may not be exercised after the earlier of (i) one year
from the Employment Termination Date, or (ii) the Expiration Date, and may not
be exercised for more than the number of Optioned Shares purchasable under
Section 1 on the Employment Termination Date. If you die after the date your
employment is terminated under the provisions of this Section 5(c) but before
the Expiration Date, the provisions of Section 5(b) above shall apply.

            Permanent disability shall mean a disability described in Section
422(c)(6) of the Code. The existence of a Disability shall be determined by the
Committee in its absolute discretion.

            6. Adjustments to Exercise Price and Number of Securities. If the
Company shall at any time subdivide or combine the outstanding shares of Common
Stock, or similar corporate events the Exercise Price and the number of shares
subject to the Option shall be appropriately adjusted.

            7. Reservation and Listing of Securities. The Company shall at all
times reserve and keep available out of its authorized shares of Common Stock,
solely for the purpose of issuance upon the exercise of this Option, such number
of shares of Common Stock or other securities, properties or rights as shall be
issuable upon the exercise thereof. The Company covenants and agrees that, upon
exercise of

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this Option and payment of the Exercise Price therefor, all shares of Common
Stock and other securities issuable upon such exercise shall be duly and validly
issued, fully paid, non-assessable and not subject to the preemptive rights of
any stockholder. As long as this Option shall be outstanding, the Company shall
use its best efforts to cause all shares of Common Stock issuable upon the
exercise of the Option to be listed (subject to official notice of issuance) on
all securities exchanges on which the Common Stock may then be listed and/or
quoted on NASDAQ.

            8. Forfeiture of Option Gains. If at any time within one year after
the exercise of all or any portion of the Option the Committee determines that
the Company has been materially harmed by you, which harm either (a) results in
your being terminated for Cause or (b) results from your engaging in any
activity determined by the Committee, in its sole discretion, to be in
competition with any activity of the Company, or otherwise inimical, contrary or
harmful to the interests of the Company (including, but not limited to,
violating any non-competition or similar agreements entered into with the
Company or otherwise accepting employment with or serving as a consultant,
adviser or in any other capacity to an entity that is in competition with or
acting against the interests of the Company), then upon notice from the Company
to you any gain ("Gain") realized by you upon exercising such Option shall be
paid by you to the Company. For purposes of this Section 9, such Gain shall be
the excess of the Fair Market Value of the shares of Company Stock obtained
through such exercise as of the date of option exercise over the purchase price
of such shares. The Company shall have the right to offset such Gain against any
amounts otherwise owed to you by the Company (including, but not limited to
wages, vacation pay, or pursuant to any benefit plan or other compensatory
arrangement).

            9. Notices.

            All notices, requests, consents and other communications hereunder
shall be in writing and shall be deemed to have been duly made and sent when
delivered, or mailed by registered or certified mail, return receipt requested:

            (a) If to the registered Holder of this Option, to the address of
the Holder as shown on the books of the Company; or

            (b) If to the Company, to 420 Lexington Avenue, Suite 620, New York,
NY 10017, or to such other address as the Company may designate by notice to the
Holders.

            10. Supplements and Amendments. The Company and the Holder may from
time to time supplement or amend this Agreement in any respect, provided,
however, that no amendment may adversely affect your rights hereunder without
your written consent.

            11. Successors. All the covenants and provisions of this Agreement
shall be binding upon and inure to the benefit of the Company, the Holder and
their respective successors and assigns hereunder.

            12. Governing Law. This Agreement shall be deemed to be a contract
made under the laws of the State of New York and for all purposes shall be
construed in accordance with the laws of the State of New York without giving
effect to the rules of the State of New York governing the conflicts of laws.

            13. Entire Agreement; Modification. This Agreement contains the
entire understanding between the parties hereto with respect to the subject
matter hereof.

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            14. Severabilitv. If any provision of this Agreement shall be held
to be invalid or unenforceable, such invalidity or unenforceability shall not
affect any other provision of this Agreement.

            15. Captions. The caption headings of the Sections of this Agreement
are for convenience of reference only and are not intended, nor should they be
construed as, a part of this Agreement and shall be given no substantive effect.

            16. Benefits of this Agreement. Nothing in this Agreement shall be
construed to give to any person or corporation other than the Company and the
registered Holder of this Option any legal or equitable right, remedy or claim
under this Agreement; and this Agreement shall be for the sole and exclusive
benefit of the Company and the Holder.

            17. Counterparts. This Agreement may be executed in any number of
counterparts and each of such counterparts shall for all purposes be deemed to
be an original, and such counterparts shall together constitute but one and the
same instrument.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

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            IN WITNESS WHEREOF, the parties hereto have caused this Agreement to
be dully executed, as of the day and year first written.

                                        SIGA TECHNOLOGIES, INC.

                                        By: ____________________________________
                                            Thomas N. Konatich
                                            Acting Chief Executive Officer
                                            Chief Financial Officer

                                        ________________________________________
                                        Signature of Holder

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                                   Appendix A

                  NOTICE OF INTENTION TO EXERCISE STOCK OPTIONS

The undersigned grantee of a SIGA Technologies, Inc. Stock Option Agreement
dated as of ______________________ to purchase _________ shares of SIGA
Technologies, Inc. common stock hereby gives notice of his or her intention to
exercise the Stock Option (or a portion thereof) and elects to purchase shares
of SIGA Technologies, Inc. common stock.

Shares should be issued in the name of the undersigned and should be sent to the
undersigned at:

______________________________
______________________________
______________________________
______________________________

Dated this _____ day of ____________________.

Social Security Number: ____________________

Name: _________________________________

_______________________________________
Signature

INSTRUCTIONS: The exercise of these Stock Options is effective on the date the
Company has received all of (1) this Notice of Intention to Exercise Stock
Options, and (2) payment in full in cash of the exercise price for all shares
being purchased pursuant to this Notice.

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