SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549



                              AMENDED SCHEDULE 13D
                                 (Rule 13d-101)

  INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULE 13d-1(A) AND
               AMENDMENTS THERETO FILED PURSUANT TO RULE 13d-2(a)

                              (Amendment No. 4)(1)



                             SIGA Technologies, Inc.
                             -----------------------
                                (Name of Issuer)

                    Common Stock, par value $.0001 per share
                    ----------------------------------------
                         (Title of Class of Securities)

                                  82 6917-10-6
                                  -------------
                                 (CUSIP Number)

                                Donald G. Drapkin
                               35 East 62nd Street
                               New York, NY 10021
                                 (212) 872-0012

                                 with a copy to:

                       Kramer Levin Naftalis & Frankel LLP
                                919 Third Avenue
                               New York, NY 10022
                            Attn: Thomas E. Constance
                                 (212) 715-9100

   (Name, Address and Telephone Number of Person Authorized to Receive Notices
                               and Communications)

                               September 19, 2001
                               ------------------
             (Date of Event which Requires Filing of this Statement)

      If the filing person has previously filed a statement on Schedule 13G to
report the acquisition which is the subject of this Schedule 13D, and is filing
this schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the
following box [x]

      Note: Schedules filed in paper format shall include a signed original and
five copies of the schedule, including all exhibits. See Rule 13d-7 for other
parties to whom copies are to be sent.

                         (Continued on following pages)

                              (Page 1 of 14 pages)

---------------------

(1)  The remainder of this cover page shall be filled out for a reporting
person's initial filing on this form with respect to the subject class of
securities, and for any subsequent amendment containing information which would
alter disclosures provided in a prior cover page.

     The information required on the remainder of this cover page shall not be
deemed to be "filed" for the purpose of Section 18 of the Securities Exchange
Act of 1934 ("Act") or otherwise subject to the liabilities of that section of
the Act but shall be subject to all other provisions of the Act (however, see
the Notes).




--------------------------------------------------------------------------------
                                            13D              Page 2 of 14 pages
    CUSIP No. 82 6917-10-6
--------------------------------------------------------------------------------
    1    NAMES OF REPORTING PERSONS
         I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

         Donald G. Drapkin
--------------------------------------------------------------------------------
    2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*     (a) [ ]
                                                               (b) [x]
--------------------------------------------------------------------------------
    3     SEC USE ONLY

--------------------------------------------------------------------------------
    4    SOURCE OF FUNDS*

         PF, OO (see Item 3)
--------------------------------------------------------------------------------
    5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEM 2(d) or 2(e)
                                                                           [  ]
--------------------------------------------------------------------------------
    6    CITIZENSHIP OR PLACE OF ORGANIZATION
         United States
--------------------------------------------------------------------------------
         NUMBER OF               7     SOLE VOTING POWER
           SHARES                      2,824,558  ** ***
        BENEFICIALLY           -------------------------------------------------
       OWNED BY EACH             8     SHARED VOTING POWER
         REPORTING                     0 ***
        PERSON WITH            -------------------------------------------------
                                 9     SOLE DISPOSITIVE POWER
                                       1,918,926  ***
                               -------------------------------------------------
                                 10    SHARED DISPOSITIVE POWER
                                       0 ***
--------------------------------------------------------------------------------
   11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         2,824,558  ** ***
--------------------------------------------------------------------------------
   12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES* **

                                                                        [x]
--------------------------------------------------------------------------------
   13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

         27.46% ** ***
--------------------------------------------------------------------------------
   14    TYPE OF REPORTING PERSON*

         IN
--------------------------------------------------------------------------------
                      *SEE INSTRUCTIONS BEFORE FILLING OUT

**   Mr. Drapkin has entered into a Management Restructuring Agreement (see Item
4), pursuant to which  he will be granted proxies giving him voting power over
an aggregate of 905,632 shares of Common Stock.

***  Mr. Drapkin holds, inter alia, a warrant (an "Investor Warrant") to
purchase 347,826 shares of Common Stock and a warrant (the "Drapkin September
2001 Warrant") to purchase up to 30,500 shares of Common Stock. However, the
Investor Warrant and Drapkin September 2001 Warrant provide that, with certain
limited exceptions, they are not exercisable if, as a result of such exercise,
the number of shares of Common Stock beneficially owned by Mr. Drapkin and his
affiliates (other than shares of Common Stock which may be deemed beneficially
owned through the ownership of the unexercised portion of such Investor Warrant
and/or Drapkin September 2001 Warrant) would exceed 9.99% of the outstanding
shares of Common Stock. As a result of the restrictions described in the
immediately preceding sentence and the other securities which Mr. Drapkin may be
deemed beneficially to own, as of October 3, 2001, Mr. Drapkin's Investor
Warrant and Drapkin September 2001 Warrant are not presently exercisable. If not
for the 9.99% limit, Mr. Drapkin would be deemed beneficially to own 3,202,884
shares of common stock, or 30.0% of the outstanding shares of Common Stock.



--------------------------------------------------------------------------------
                                            13D               Page 4 of 14 pages
    CUSIP No. 82 6917-10-6
--------------------------------------------------------------------------------
    1    NAMES OF REPORTING PERSONS
         I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

         Gabriel M. Cerrone
--------------------------------------------------------------------------------
    2    CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*     (a) [ ]
                                                               (b) [x]
--------------------------------------------------------------------------------
    3    SEC USE ONLY

--------------------------------------------------------------------------------
    4    SOURCE OF FUNDS*

         PF, OO (see Item 3)
--------------------------------------------------------------------------------
    5    CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
         ITEM 2(d) or 2(e)
                                                                    [_]
--------------------------------------------------------------------------------
    6    CITIZENSHIP OR PLACE OF ORGANIZATION
         United States
--------------------------------------------------------------------------------
         NUMBER OF               7     SOLE VOTING POWER
           SHARES                      1,075,000 ***
        BENEFICIALLY           -------------------------------------------------
       OWNED BY EACH             8     SHARED VOTING POWER
          REPORTING                    202,584 ** ***
        PERSON WITH            -------------------------------------------------
                                 9     SOLE DISPOSITIVE POWER
                                       1,075,000 ***
                               -------------------------------------------------
                                 10    SHARED DISPOSITIVE POWER
                                       202,584 ** ***
--------------------------------------------------------------------------------
   11    AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

         1,277,584 ** ***
--------------------------------------------------------------------------------
   12    CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES*

                                                                      [_]
--------------------------------------------------------------------------------
   13    PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

         12.48% ** ***
--------------------------------------------------------------------------------
   14    TYPE OF REPORTING PERSON*

         IN
--------------------------------------------------------------------------------

                      *SEE INSTRUCTIONS BEFORE FILLING OUT

**   Mr. Cerrone, as the sole general partner of Panetta Partners Ltd., may be
deemed beneficially to own the securities held by Panetta.

***  Panetta holds, inter alia, a warrant (the "Distributor Warrant") to
purchase up to 210,000 shares of Common Stock, a warrant (the "Consulting
Warrant") to purchase up to 303,200 shares of Common Stock, two warrants (the
"Panetta May 2001 Warrants") to purchase an aggregate of up to 121,500 shares of
Common Stock and a warrant (the "Panetta September 2001 Warrant") to purchase up
to 14,688 shares of Common Stock. However, the Distributor Warrant, the
Consulting Warrant, the Panetta May 2001 Warrants and the Panetta September 2001
Warrant provide that, with certain limited exceptions, they are not exercisable
if, as a result of such exercise, the number of shares of Common Stock
beneficially owned by Panetta and its affiliates, including Mr. Cerrone, (other
than shares of Common Stock which may be deemed beneficially owned through the
ownership of the unexercised portion of such Consulting Warrant, Distributor
Warrant, Panetta May 2001 Warrant and/or Panetta September 2001 Warrant) would
exceed 9.99% of the outstanding shares of Common Stock. As a result of the
restrictions described in the immediately preceding sentence and the other
securities which Mr. Cerrone may be deemed beneficially to own, as of October 3,
2001, Panetta's Consulting Warrant, Distributor Warrant, Panetta May 2001
Warrants and Panetta September 2001 Warrant are not presently exercisable. If
not for the 9.99% limit, Mr. Cerrone would be deemed beneficially to own
1,926,972 shares of common stock, or 17.7% of the outstanding shares of Common
Stock.



--------------------------------------------------------------------------------
                                            13D               Page 5 of 14 pages
    CUSIP No. 82 6917-10-6
--------------------------------------------------------------------------------
    1     NAMES OF REPORTING PERSONS
          I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

          Panetta Partners Ltd.
--------------------------------------------------------------------------------
    2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*     (a) [  ]
                                                                (b) [x]
--------------------------------------------------------------------------------
    3     SEC USE ONLY

--------------------------------------------------------------------------------
    4     SOURCE OF FUNDS*

          OO (see Item 3)
--------------------------------------------------------------------------------
    5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEM 2(d) or 2(e)
                                                                      [  ]
--------------------------------------------------------------------------------
    6     CITIZENSHIP OR PLACE OF ORGANIZATION
          Colorado
--------------------------------------------------------------------------------
          NUMBER OF               7     SOLE VOTING POWER
            SHARES                      0
         BENEFICIALLY           -----------------------------------------------
        OWNED BY EACH             8     SHARED VOTING POWER
          REPORTING                     202,584 **
         PERSON WITH            -----------------------------------------------
                                  9     SOLE DISPOSITIVE POWER
                                        0
                                -----------------------------------------------
                                  10    SHARED DISPOSITIVE POWER
                                        202,584 **
--------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          202,584  **
--------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES*

                                                                      [  ]
--------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          2.21% **
--------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON*

          PN
--------------------------------------------------------------------------------

**   Panetta holds, inter alia, a warrant (the "Distributor Warrant") to
purchase up to 210,000 shares of Common Stock, a warrant (the "Consulting
Warrant") to purchase up to 303,200 shares of Common Stock, two additional
warrants (the "Panetta May 2001 Warrants") to purchase an aggregate of up to
121,500 shares of Common Stock and a warrant (the "Panetta September 2001
Warrant") to purchase up to 14,688 shares of Common Stock. However, the
Distributor Warrant, the Consulting Warrant, the Panetta May 2001 Warrants and
the Panetta September 2001 Warrant provide that, with certain limited
exceptions, they are not exercisable if, as a result of such exercise, the
number of shares of Common Stock beneficially owned by Panetta and its
affiliates, including Mr. Cerrone, (other than shares of Common Stock which may
be deemed beneficially owned through the ownership of the unexercised portion of
such Consulting Warrant, Distributor Warrant, Panetta May 2001 Warrant and/or
Panetta September 2001 Warrant) would exceed 9.99% of the outstanding shares of
Common Stock. As a result of the restrictions described in the immediately
preceding sentence and the other securities which Mr. Cerrone may be deemed
beneficially to own, as of October 3, 2001, Panetta's Consulting Warrant,
Distributor Warrant, Panetta May 2001 Warrants and Panetta September 2001
Warrant are not presently exercisable. If not for the 9.99% limit, Panetta would
be deemed beneficially to own 851,972 shares of common stock, or 8.7% of the
outstanding shares of Common Stock.



--------------------------------------------------------------------------------
                                            13D              Page 6 of 14 pages
    CUSIP No. 82 6917-10-6
--------------------------------------------------------------------------------
    1     NAMES OF REPORTING PERSONS
          I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

          Thomas E. Constance
--------------------------------------------------------------------------------
    2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*     (a) [ ]
                                                                (b) [x]
--------------------------------------------------------------------------------
    3     SEC USE ONLY

--------------------------------------------------------------------------------
    4     SOURCE OF FUNDS*

          N/A
--------------------------------------------------------------------------------
    5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEM 2(d) or 2(e)
                                                                       [  ]
--------------------------------------------------------------------------------
    6     CITIZENSHIP OR PLACE OF ORGANIZATION
          United States
--------------------------------------------------------------------------------
          NUMBER OF               7     SOLE VOTING POWER
            SHARES                      253,467
         BENEFICIALLY           ------------------------------------------------
        OWNED BY EACH             8     SHARED VOTING POWER
          REPORTING                     0
         PERSON WITH            ------------------------------------------------
                                  9     SOLE DISPOSITIVE POWER
                                        253,467
                                ------------------------------------------------
                                  10    SHARED DISPOSITIVE POWER
                                        0
--------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          253,467
--------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES*

                                                                       [  ]
--------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          2.70%
--------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON*

          IN
--------------------------------------------------------------------------------

                      *SEE INSTRUCTIONS BEFORE FILLING OUT



--------------------------------------------------------------------------------
                                            13D               Page 7 of 14 pages
    CUSIP No. 82 6917-10-6
--------------------------------------------------------------------------------
    1     NAMES OF REPORTING PERSONS
          I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY)

          Eric A. Rose, M.D.
--------------------------------------------------------------------------------
    2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*     (a) [ ]
                                                                (b) [x]
--------------------------------------------------------------------------------
    3     SEC USE ONLY

--------------------------------------------------------------------------------
    4     SOURCE OF FUNDS*

          PF
--------------------------------------------------------------------------------
    5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO
          ITEM 2(d) or 2(e)
                                                                       [  ]
--------------------------------------------------------------------------------
    6     CITIZENSHIP OR PLACE OF ORGANIZATION
          United States
--------------------------------------------------------------------------------
          NUMBER OF               7     SOLE VOTING POWER
            SHARES                      790,090
         BENEFICIALLY           ------------------------------------------------
        OWNED BY EACH             8     SHARED VOTING POWER
          REPORTING                     0
         PERSON WITH            ------------------------------------------------
                                  9     SOLE DISPOSITIVE POWER
                                        790,090
                                ------------------------------------------------
                                  10    SHARED DISPOSITIVE POWER
                                        0
--------------------------------------------------------------------------------
   11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

          790,090
--------------------------------------------------------------------------------
   12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW 11 EXCLUDES CERTAIN SHARES*

                                                                     [  ]
--------------------------------------------------------------------------------
   13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

          8.02%
--------------------------------------------------------------------------------
   14     TYPE OF REPORTING PERSON*

          IN
--------------------------------------------------------------------------------

                      *SEE INSTRUCTIONS BEFORE FILLING OUT



                                  SCHEDULE 13D

            This Amendment No. 4 amends and supplements  the Reporting  Persons'
            Statement on Schedule 13D,  dated March 30, 2001, as amended to date
            (the "Schedule"), in its entirety.

      Item 1.     Security and Issuer.

            This Statement on Schedule 13D (the "Statement") relates to the
            Common Stock, $.0001 par value per share, (the "Common Stock") of
            SIGA Technologies, Inc., a Delaware corporation (the "Issuer"). The
            principal executive offices of the Issuer are located at 420
            Lexington Avenue, Suite 620, New York, New York, 10170.

      Item 2.     Identity and Background.

            (a)   This  statement  is filed on  behalf  of  Donald  G.  Drapkin,
                  Gabriel M. Cerrone, Panetta Partners Ltd. ("Panetta"),  Thomas
                  E.  Constance  and  Eric  A.  Rose,  M.D.  (collectively,  the
                  "Reporting  Persons").  See attached Exhibit P which is a copy
                  of their  agreement in writing to file this statement  jointly
                  on behalf of each of them.  Each of the Reporting  Persons has
                  made, and will continue to make, its own investment  decisions
                  with  respect to  securities  of the  Issuer.  Each  Reporting
                  Person  expressly  disclaims  membership in a "group" with any
                  other  person  within the meaning of Rule  13d-5(b)(1)  of the
                  Securities Exchange Act of 1934, as amended.

            (b)   The  business  address of Mr.  Drapkin is 35 East 62nd Street,
                  New York, New York, 10021. The business address of each of Mr.
                  Cerrone and Panetta is 265 East 66th  Street,  Suite 16G,  New
                  York, New York,  10021.  The business address of Mr. Constance
                  is 919 Third Avenue,  41st Floor,  New York, New York,  10022.
                  The business address of Dr. Rose is 112 East 78th Street,  New
                  York, New York, 10021.

            (c)   Mr.  Drapkin is a Director and Vice  Chairman of  MacAndrews &
                  Forbes  Holdings  Inc.,  a  Delaware  corporation  having  its
                  address at 35 East 62nd Street, New York, New York, 10021. Mr.
                  Cerrone is an investment banker,  consultant and stock broker,
                  and the sole general  partner of Panetta,  a Colorado  limited
                  partnership  the  principal  business  of which is  delivering
                  consulting  services.  Mr.  Constance  is a Senior  Partner of
                  Kramer  Levin  Naftalis & Frankel  LLP, a law firm in New York
                  City.  Dr. Rose is Chairman of the  Department  of Surgery and
                  Surgeon-in-Chief  of the Columbia  Presbyterian  Center of New
                  York Presbyterian Hospital.

            (d)   The Reporting Persons and their respective managing members,
                  officers, directors, general partners, investment managers,
                  and trustees have not, during the five years prior to the date
                  hereof, been convicted in a criminal proceeding (excluding
                  traffic violations or similar misdemeanors).

            (e)   The Reporting  Persons and their respective  managing members,
                  officers,  directors, general partners and investment managers
                  have not, during the five years prior to the date hereof, been
                  party to a civil  proceeding  of a judicial or  administrative
                  body of  competent  jurisdiction,  as a result  of which  such
                  person was or is subject to a judgment,  decree or final order
                  enjoining  future  violations  of, or prohibiting or mandating
                  activities  subject to,  Federal or State  securities  laws or
                  finding any violation with respect to such laws.

            (f)   Mr.  Drapkin,  Mr.  Cerrone,  Mr.  Constance  and Dr. Rose are
                  citizens of the United States.

      Item 3.     Source and Amount of Funds or Other Consideration

            Pursuant to a Securities Purchase Agreement between Mr. Drapkin and
            the Issuer, dated as of January 31, 2000, (the "Purchase Agreement")
            a copy of which is filed as Exhibit B hereto, Mr. Drapkin purchased
            (i) $500,000 principal amount of 6% Convertible Debentures due
            January 31, 2002 of the Issuer ("Debentures"), a copy of which is
            filed as Exhibit C hereto, with $500,000 of his personal funds, and
            (ii) a warrant (an "Investor Warrant"), a copy of which is filed as
            Exhibit D hereto, to purchase up to 347,826 shares of Common Stock
            at an exercise price of $3.4059 per share, with $17,391.30 of his
            personal funds. The principal amount of, and accrued interest on,
            the Debentures were convertible into Common Stock at the option of
            the holder at any time prior to the maturity date, at a conversion
            price of $1.4375 per share. Pursuant to the Conversion Agreement (as
            defined below), Mr. Drapkin converted his Debentures into



            373,913  shares of Preferred  Stock (as defined below) of the Issuer
            (see  Item  4).  As  noted  below,  on July 16,  2001,  Mr.  Drapkin
            converted  his 373,913  shares of  Preferred  Stock,  together  with
            accrued dividends thereon, into 379,859 shares of Common Stock.

            Pursuant to a Distributor's Agreement between Fahnestock & Co. Inc.
            and the Issuer, dated as of January 27, 2000, and in connection with
            the Issuer's private placement of Debentures, Fahnestock designated
            Mr. Cerrone to receive, and he was issued, the Distributor Warrant,
            a copy of which is filed as Exhibit E hereto, to purchase up to
            210,000 shares of Common Stock at an exercise price of $1.45 per
            share. Mr. Cerrone then assigned the Distributor Warrant to Panetta.
            Pursuant to a Consulting Agreement between Fahnestock & Co. Inc. and
            the Issuer, dated as of October 31, 2000, Fahnestock & Co. Inc.
            designated Panetta to receive, and Panetta was issued the Consulting
            Warrant (together with the Investor Warrant and the Distributor
            Warrant, the "2000 Warrants") to purchase up to 303,200 shares of
            Common Stock at an exercise price of $2.00 per share, a copy of
            which is attached hereto as Exhibit F. The Consulting Warrant was
            issued to Panetta partially in consideration for the cancellation of
            a warrant to purchase 303,200 shares of Common Stock at an exercise
            price of $5.00 per share, a copy of which is filed as Exhibit G
            hereto, that had been issued to Mr. Cerrone in connection with the
            Issuer's March 2000 equity financing. The Distributor Warrant and
            the Consulting Warrant each contain provisions granting the holder
            certain registration rights.

            Each 2000 Warrant provides that, with certain limited exceptions, it
            is not exercisable if, as a result of such exercise, the number of
            shares of Common Stock beneficially owned by the holder thereof and
            its affiliates (other than shares of Common Stock which may be
            deemed beneficially owned through the ownership of the unexercised
            portion of such Warrant) would exceed 9.99% of the outstanding
            shares of Common Stock. As a result of the restrictions described in
            the immediately preceding sentence (the "9.99% Limit") and the other
            securities which Mr. Drapkin and Mr. Cerrone may be deemed
            beneficially to own, as of October 3, 2001, Mr. Drapkin's Investor
            Warrant and Drapkin September 2001 Warrant and Panetta's Consulting
            Warrant, Distributor Warrant, Panetta May 2001 Warrants and Panetta
            September 2001 Warrant are not presently exercisable. The Issuer may
            require the such warrants to be exercised (subject to the same 9.99%
            Limit) within five days if both (i) the registration statement with
            respect to the shares of Common Stock issuable thereupon is
            effective and (ii) the closing bid price for the Common Stock for
            each of any 15 consecutive trading days is at least 200% of the
            exercise price of the warrant at such time. Exceptions to the 9.99%
            Limit include the existence of a tender offer for the Issuer's
            common stock.

            Between June 26, 2000 and December 22, 2000, Mr. Drapkin engaged in
            open market transactions through which he acquired a net 373,400
            shares of Common Stock. Between February 9, 2000 and March 13, 2000,
            Mr. Cerrone purchased 61,500 shares of Common Stock on the open
            market. Mr. Cerrone then assigned such shares to Panetta. Mr.
            Drapkin and Mr. Cerrone used their respective general funds for such
            purchases.

            Mr. Drapkin made the following purchases:

               Date              No. of Shares   Purchase Price
               ----              -------------   --------------

               6/26/2000            31,500             $4.037
               6/27/2000             2,000             $3.977
               6/29/2000             5,000             $4.037
               7/6/2000              2,500             $4.54
               7/27/2000             4,000             $4.049
               8/2/2000             20,500             $3.947
               8/3/2000              1,600             $3.906
               8/4/2000              4,000             $3.747
               8/7/2000                500             $3.812
               8/8/2000              2,500             $3.581
               8/10/2000             5,000             $3.532
               8/11/2000             6,000             $4.122
               8/11/2000            50,000             $4.065
               8/14/2000            50,000             $4.399
               8/15/2000             1,100             $3.906
               8/16/2000             2,000             $3.967
               8/24/2000            12,500             $3.30
               8/25/2000            17,500             $3.406



               Date              No. of Shares   Purchase Price
               ----              -------------   --------------

               8/28/2000            11,000             $3.457
               8/29/2000             7,500             $3.195
               8/31/2000            10,000             $3.084
               9/14/2000             4,100             $3.004
               9/25/2000            20,500             $3.498
               9/27/2000               100             $2.906
               9/29/2000            40,000             $4.039
               11/3/2000             2,500             $4.175
               11/30/2000           20,500             $4.047
               12/1/2000             4,000             $3.852
               12/5/2000            40,000             $4.508
               12/22/2000           10,000             $3.026


            Mr. Drapkin made the following sale:

               Date              No. of Shares     Sales Price
               ----              -------------     -----------

               9/19/2000            15,000             $3.386


            Mr. Cerrone made the following purchases:

               Date              No. of Shares   Purchase Price
               ----              -------------   --------------

               2/9/2000             16,100             $4.589
               2/10/2000             3,900             $4.551
               2/11/2000            10,500             $4.560
               2/18/2000            12,100             $5.308
               2/22/2000             2,400             $5.369
               2/23/2000            12,500             $5.406
               3/2/2000              2,500             $5.986
               3/13/2000             1,500             $9.158


            In connection with the Management Restructuring Agreement (as
            defined in Item 4, below), each of Judson A. Cooper and Joshua D.
            Schein, Ph.D. agreed to grant an irrevocable proxy (collectively,
            the "Proxies") to Mr. Drapkin on the Effective Date (as defined in
            the Management Restructuring Agreement) giving Mr. Drapkin voting
            power over an aggregate of 905,632 shares of Common Stock owned by
            such parties (the "Proxy Shares") together with any shares of
            capital stock of the Issuer that such parties may acquire subsequent
            to the date of the Proxies (including, without limitation, upon the
            exercise of options held by Mr. Cooper and Mr. Schein, to purchase
            up to an aggregate of 1,400,002 shares of Common Stock).

            Pursuant to separate Common Stock and Warrant Purchase Agreements
            between the Issuer and each of Panetta and Dr. Rose, dated as of May
            8, 2001, (the "May 2001 Purchase Agreements") the form of which is
            Exhibit K hereto: (i) Panetta purchased, with $180,000 of its
            general funds, 90,000 shares of Common Stock and a warrant (a "May
            2001 Investor Warrant"), the form of which is Exhibit L hereto, to
            purchase up to 90,000 shares of Common Stock; and Dr. Rose
            purchased, with $100,000 of his personal funds, 50,000 shares of
            Common Stock and a May 2001 Investor Warrant to purchase up to
            50,000 shares of Common Stock. The May 2001 Investor Warrants are
            exercisable for a period of seven years at an exercise price of
            $2.94 per share and contain provisions analogous to the 9.99% Limit
            described above.

            On May 31, 2001, the Issuer consummated another closing of its
            private placement pursuant to May 2001 Purchase Agreements in which
            closing Panetta purchased, with $63,000 of its general funds, 31,500
            shares of Common Stock and a May 2001 Investor Warrant to purchase
            up to 31,500 shares of Common Stock.

            Pursuant to separate Common Stock and Warrant Purchase Agreements
            between the Issuer and each Panetta, Mr. Drapkin, Mr. Constance and
            Dr. Rose, dated as of August 31, 2001, as amended in September 2001
            (the "September 2001 Purchase Agreements"), the form of which is
            Exhibit Q hereto: (i) Panetta purchased, with $60,000 of its general
            funds, 19,584 shares of Common Stock and a warrant (a "September
            2001 Investor Warrant"), the form of which is Exhibit R hereto, to
            purchase up to 14,688 shares of Common Stock; Mr. Drapkin



            purchased, with $125,000 of his personal funds, 40,667 shares of
            Common Stock and a September 2001 Investor Warrant to purchase up to
            30,500 shares of common Stock; Mr. Constance purchased, with $50,000
            of his personal funds, 16,267 shares of Common Stock and a September
            2001 Investor Warrant to purchase up to 12,200 shares of Common
            Stock, and Dr. Rose purchased, with $150,000 of his personal funds,
            51,480 shares of Common Stock and a September 2001 Investor Warrant
            to purchase up to 38,610 shares of Common Stock. The September 2001
            Investor Warrants are exercisable for a period of seven years at an
            exercise price of $3.552 per share and contain provisions analogous
            to the 9.99% Limit described above.

            On May 3, 2001, the Issuer's Board of Directors made grants (the
            "Conditional Grants") of options to certain officers, directors and
            advisors of the Issuer, subject to approval of an Amendment and
            Restatement of the Issuer's Amended and Restated 1996 Incentive and
            Non-Qualified Stock Option Plan (the "Plan"). Mr. Drapkin, Dr. Rose,
            Mr. Constance and Mr. Cerrone received Conditional Grants of options
            to purchase up to 1,125,000, 600,000, 225,000 and 1,075,000 shares
            of Common Stock, respectively. The Conditional Grants were made
            subject to stockholder approval, and such approval was granted when
            the Issuer's stockholders approved the Amendment and Restatement of
            the Plan at the Issuer's 2001 Annual Meeting, held on August 15,
            2001. The shares of Common Stock subject to the Conditional Grant
            options were exercisable immediately upon such stockholder approval
            at an exercise price of $2.50 per share, and the options granted to
            the Reporting Persons under the Conditional Grants are included in
            the beneficial ownership figures reported in this Schedule 13D.

            Each Reporting Person disclaims beneficial ownership of all the
            Common Stock except Common Stock held by such Reporting Person that
            were purchased on the open market or pursuant to the May 2001
            Purchase Agreements or the September 2001 Purchase Agreements
            (collectively, the "Purchased Common"). Each Reporting Person
            disclaims beneficial ownership of the securities held by any other
            party.

      Item 4.     Purpose of Transaction.

            Each Reporting Person which acquired securities of the Issuer did so
            as an investment in the Issuer. Except as indicated in this Schedule
            13D, no Reporting Person currently has any plans or proposals that
            relate to, or would result in, any of the matters described in
            subparagraphs (a) through (j) of Item 4 of Schedule 13D.

            In connection with the Purchase Agreement, Mr. Drapkin entered into
            a Registration Rights Agreement with the Issuer, dated as of January
            31, 2000, ("Registration Rights Agreement"), a copy of which is
            filed as Exhibit H hereto. Pursuant to the Registration Rights
            Agreement, the Issuer agreed: (i) to file no later than 30 days
            after the Closing Date (as used in the Purchase Agreement), a
            Registration Statement under the Securities Act of 1933, as amended,
            (the "Required Registration Statement") covering the resale of the
            shares of Common Stock issuable upon conversion of principal and
            interest of the Debentures and upon exercise of the Warrant; and
            (ii) to use its reasonable best efforts to cause such Registration
            Statement to be declared effective no later than the earlier of (x)
            five days after notice by the Securities and Exchange Commission
            that it may be declared effective and (y) 90 days after the Closing
            Date. On May 10, 2000, the Issuer filed the Required Registration
            Statement and, on May 24, 2000, it was declared effective. The
            shares of Common Stock issuable upon exercise of the Distributor
            Warrant were also included in the Required Registration Statement.

            Pursuant to a letter agreement, dated as of March 30, 2001, among
            Mr. Drapkin, the Issuer, Mr. Cerrone, Mr. Constance, Dr. Rose,
            Judson A. Cooper and Joshua D. Schein, Ph.D. (the "Management
            Restructuring Agreement"), a copy of which is filed as Exhibit I
            hereto, Mr. Drapkin had the right to be and to have his designees
            elected to the Board of Directors of the Issuer (the "Board") on the
            Effective Date. The Management Restructuring Agreement also provides
            that the members of the Board at such time would be caused to resign
            from the Board and from any and all offices held with the Issuer.
            Pursuant to the Management Restructuring Agreement, Judson A. Cooper
            and Joshua D. Schein have agreed to resign from the Board of the
            Issuer, and from all other offices held with the Issuer, effective
            as of the Effective Date. Mr. Drapkin has designated Mr. Cerrone,
            Mr. Constance and Dr. Rose for election to the Board in accordance
            with the Management Restructuring Agreement. As of April 19, 2001,
            Mr. Drapkin, Mr. Cerrone, Mr. Constance and Dr. Rose were appointed
            to the Board and each of the Issuer's remaining other directors
            resigned from the Board as contemplated by the Management
            Restructuring Agreement. Thereafter, the Board filled the vacancies
            on the Board that resulted from such resignations.



            In connection with the May 2001 Purchase Agreement, Panetta and Dr.
            Rose each entered into a Registration Rights Agreement with the
            Issuer, dated as of May 8, 2001, (the "May 2001 Registration Rights
            Agreements"), the form of which is Exhibit M hereto. Pursuant to the
            May 2001 Registration Rights Agreement, the Issuer agreed: (i) to
            file no later than 60 days after the Closing Date (as defined in the
            May 2001 Purchase Agreement), a Registration Statement under the
            Securities Act of 1933, as amended, (the "2001 Required Registration
            Statement") covering the resale of the shares of Common Stock issued
            pursuant to the May 2001 Purchase Agreements and the shares of
            Common Stock issuable upon exercise of the May 2001 Investor
            Warrants; and (ii) to use its reasonable best efforts to cause such
            Registration Statement to be declared effective no later than the
            earlier of (x) five days after notice by the Securities and Exchange
            Commission that it may be declared effective and (y) 180 days after
            the Closing Date.

            Pursuant to a Conversion Agreement among the Issuer and holders of
            Debentures (the "Conversion Agreement"), the form of which is
            attached hereto as Exhibit N, Mr. Drapkin agreed to convert the
            outstanding principal and accrued interest on his Debentures, into
            373,913 shares of Series A Convertible Preferred Stock of the Issuer
            (the "Preferred Stock"), the form of the Certificate of Designations
            for which is attached hereto as Exhibit O, representing at a
            conversion price of $1.4375 per share of Preferred Stock. The
            Preferred Stock has a cumulative dividend of 6% per annum payable in
            cash or additional shares of Preferred Stock at the Issuer's
            discretion. The Preferred Stock is convertible into Common Stock an
            initial conversion rate of one-to-one, and each holder of Preferred
            Stock is entitled to the number of votes equal to the number of
            whole shares of Common Stock into which the shares of Preferred
            Stock held by such holder are then convertible. The Preferred Stock
            is not subject to the 9.99% Limit. On July 16, 2001, Mr. Drapkin
            converted his 373,913 shares of Preferred Stock, together with
            accrued dividends thereon, into 379,859 shares of Common Stock.

            Each Reporting Person may from time to time acquire, or dispose of,
            Common Stock and/or other securities of the Issuer if and when it
            deems it appropriate. Each Reporting Person may formulate other
            purposes, plans or proposals relating to any securities of the
            Issuer to the extent deemed advisable in light of market conditions,
            investment policies and other factors.

      Item 5.     Interest in Securities of Issuer.

            (a)   As of October 3, 2001: Mr. Drapkin, as the holder of
                  securities of the Issuer and as proxyholder under the Proxies
                  may be deemed beneficially to own 2,824,558 shares of Common
                  Stock or 27.5% of the outstanding shares, and, if not for the
                  9.99% Limit, Mr. Drapkin could be deemed to beneficially own
                  3,202,884 shares of Common Stock or 30.0% of the outstanding
                  shares; Mr. Cerrone, in his own name and as the sole general
                  partner of Panetta, may be deemed beneficially to own an
                  aggregate of 1,277,584 shares of Common Stock or 12.5% of the
                  outstanding shares, and, if not for the 9.99% Limit, Mr.
                  Cerrone could be deemed beneficially to own an aggregate of
                  1,926,972 shares of Common Stock or 17.7% of the outstanding
                  shares; Panetta may be deemed beneficially to own 202,584
                  shares of Common Stock or 2.2% of the outstanding shares, and,
                  if not for the 9.99% Limit, Panetta could be deemed
                  beneficially to own an aggregate of 851,972 shares of Common
                  Stock or 8.7% of the outstanding shares; and each of Mr.
                  Constance and Dr. Rose may be deemed beneficially to own the
                  respective numbers of shares of Common Stock (representing the
                  respective percentages of Common Stock outstanding) set forth
                  below:

                  Mr. Constance        253,467          2.7%
                  Dr. Rose             790,090          8.0%


                  Pursuant to Rule 13d-4 promulgated under the Securities
                  Exchange Act of 1934, as amended, each Reporting Person
                  disclaims beneficial ownership of all the Common Stock except
                  the Purchased Common Stock, if any, held by such Reporting
                  Person. Pursuant to Rule 13d-4 promulgated under the
                  Securities Exchange Act of 1934, as amended, each Reporting
                  Person disclaims beneficial ownership of the securities held
                  by any other person.

            (b)   Mr. Drapkin has the sole power to vote or to direct the vote
                  and to dispose or to direct the disposition of the shares that
                  he owns. Mr. Drapkin has the sole power to vote or to direct
                  the vote of the Proxy Shares. Mr. Cerrone has sole power to
                  vote or direct the vote and to dispose or to direct the



                  disposition of the shares issuable upon exercise of the
                  options which he owns, and Mr. Cerrone and Panetta share the
                  power to vote or to direct the vote and to dispose or to
                  direct the disposition of the shares owned by Panetta. Mr.
                  Constance has the sole power to vote or to direct the vote and
                  to dispose or to direct the disposition of the shares that he
                  owns. Dr. Rose has the sole power to vote or to direct the
                  vote and to dispose or to direct the disposition of the shares
                  that he owns.

            (c)   Other than the receipt of options upon the stockholder
                  approval of the Conditional Grants, Mr. Drapkin's conversion
                  of Preferred Stock into shares of Common Stock (to the extent
                  that any of the above may be deemed a transaction in the
                  Common Stock) and the Reporting Persons' purchasing Common
                  Stock pursuant to the September 2001 Purchase Agreements, no
                  Reporting Person has engaged in any transactions in the Common
                  Stock of the Issuer in the past 60 days.

            (d) & (e)   Not applicable.

      Item 6.     Contracts, Arrangements, Understandings or Relationships With
                  Respect to Securities of the Issuer.

                  Pursuant to the Proxies, Mr. Drapkin was appointed proxyholder
                  with respect to certain securities held by Mr. Cooper and Mr.
                  Schein (see Item 3). A form of the Proxies is attached to the
                  Management Restructuring Agreement that is filed as Exhibit I
                  hereto. The Management Restructuring Agreement includes
                  provisions restricting the abilities of the parties thereto to
                  transfer their respective securities of the Issuer.
                  Additionally, Mr. Drapkin has entered into a Lock-Up Agreement
                  with Vincent Fischetti, a copy of which is filed as Exhibit J
                  hereto, pursuant to which Mr. Fischetti is restricted in
                  transferring his securities of the Issuer without Mr.
                  Drapkin's prior written consent.

                  Except as indicated in this Schedule 13D and the exhibits
                  hereto, there is no contract, arrangement, understanding or
                  relationship between the Reporting Person and any other
                  person, with respect to any securities of the Issuer.


      Item 7.     Material to be Filed as Exhibits. (2)

            Exhibit A:  Agreement of Joint Filing of Schedule 13D, dated as
                        of April 6, 2001.

            Exhibit B:  Securities Purchase Agreement between Mr.
                        Drapkin and the Issuer, dated as of January 31,
                        2000.

            Exhibit C:  6% Convertible Debenture due January 31, 2002 of the
                        Issuer in the principal amount of $500,000 issued to Mr.
                        Drapkin, dated as of January 31, 2000.

            Exhibit D:  Common Stock Purchase Warrant to purchase 347,826
                        shares of Common Stock issued to Mr. Drapkin, dated as
                        of January 31, 2000.

            Exhibit E:  Common Stock Purchase Warrant to purchase 210,000
                        shares of Common Stock issued to Mr. Cerrone, dated as
                        of January 31, 2000.

            Exhibit F:  Common Stock Purchase Warrant to purchase 303,200
                        shares of Common Stock, issued to Panetta, dated as of
                        November 10, 2000.

            Exhibit G:  Cancelled Common Stock Purchase Warrant to purchase
                        303,200 shares of Common Stock, issued to Mr. Cerrone,
                        dated as of May 1, 2000.

            Exhibit H:  Registration Rights Agreement between the
                        Issuer and Mr. Drapkin dated as of January 31,
                        2000.

            Exhibit I:  Letter Agreement, dated as of March 30, 2001,
                        among Mr. Drapkin, the Issuer, Mr. Cerrone, Mr.
                        Constance, Dr. Rose, Judson A. Cooper and
                        Joshua D. Schein, Ph.D.

-----------------------

(2)  Except as otherwise indicated, all exhibits have been previously filed with
     the original Schedule 13D or prior Amendments thereto.



            Exhibit J:  Lock-Up Agreement between Mr. Drapkin and
                        Vincent Fischetti.

            Exhibit K:  Form of Common Stock and Warrant Purchase Agreements
                        between the Issuer and each Buyer (as defined therein),
                        dated as of May 8, 2001.

            Exhibit L:  Form of Common Stock Purchase Warrants to purchase
                        shares of Common Stock issued to each Buyer, dated as of
                        May 8, 2001.

            Exhibit M:  Form of Registration Rights Agreements between the
                        Issuer and each Buyer, dated as of May 8, 2001.

            Exhibit N:  Form of Conversion Agreement among the Issuer and
                        holders of Debentures.

            Exhibit O:  Form of Certificate of Designation of Series A
                        Convertible Preferred Stock of the Issuer.

            Exhibit P:  Agreement of Joint Filing of Schedule 13D,
                        dated as of October 1, 2001. (filed herewith)

            Exhibit Q:  Form of Common Stock and Warrant Purchase
                        Agreements between the Issuer and each Buyer
                        (as defined therein).  (filed herewith)

            Exhibit R:  Form of Common Stock Purchase Warrants to
                        purchase shares of Common Stock issued to each
                        Buyer. (filed herewith)



                                   SIGNATURES

      After reasonable inquiry and to the best knowledge and belief of each of
the undersigned, each of the undersigned certifies that the information set
forth in this statement with respect to such undersigned is true, complete and
correct.



Dated:   October 1, 2001            /s/ Donald G. Drapkin
                                    ------------------------------
                                    Donald G. Drapkin



Dated:   October 1, 2001            /s/ Gabriel M. Cerrone
                                    ------------------------------
                                    Gabriel M. Cerrone



                                    PANETTA PARTNERS LTD.



Dated:   October 1, 2001             By  /s/ Gabriel M. Cerrone
                                       ---------------------------
                                       Name:  Gabriel M. Cerrone
                                       Title:  General Partner



Dated:   October 1, 2001            /s/ Thomas E. Constance
                                    ------------------------------
                                    Thomas E. Constance



Dated:   October 1, 2001            /s/ Eric A. Rose, M.D.
                                    ------------------------------
                                    Eric A. Rose, M.D.



                                                                       Exhibit P

                                  AGREEMENT OF

                          JOINT FILING OF SCHEDULE 13D


      The undersigned hereby agree jointly to prepare and file with regulatory
authorities Amendment 4 to the Schedule 13D and any subsequent amendments
thereto reporting each of the undersigned's ownership of securities of SIGA
Technologies, Inc. and hereby affirm that such Schedule 13D is being filed on
behalf of each of the undersigned.



Dated:   October 1, 2001            /s/ Donald G. Drapkin
                                    ------------------------------
                                    Donald G. Drapkin



Dated:   October 1, 2001            /s/ Gabriel M. Cerrone
                                    ------------------------------
                                    Gabriel M. Cerrone


                                    PANETTA PARTNERS LTD.



Dated:   October 1, 2001            By /s/ Gabriel M. Cerrone
                                       ----------------------------
                                       Name:  Gabriel M. Cerrone
                                       Title: General Partner



Dated:   October 1, 2001            /s/ Thomas E. Constance
                                    -------------------------------
                                    Thomas E. Constance



Dated:   October 1, 2001            /s/ Eric A. Rose, M.D.
                                    -------------------------------
                                    Eric A. Rose, M.D.



                                                                       Exhibit Q


                   COMMON STOCK AND WARRANT PURCHASE AGREEMENT

            COMMON   STOCK  AND  WARRANT   PURCHASE   AGREEMENT,   dated  as  of
____________, 2001 (this "Agreement"), 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"),  each entity
named on a signature page hereto (each, a "Buyer") (each  agreement with a Buyer
being deemed a separate and independent  agreement  between the Company and such
Buyer, except that each Buyer acknowledges and consents to the rights granted to
each other Buyer under such agreement and the Transaction Agreements, as defined
below, referred to therein).


                               W I T N E S S E T H

            WHEREAS,  the Company wishes to sell to the Buyer,  and the Buyer is
willing to buy from the Company,  subject to the terns and  conditions set forth
herein,  the number of shares of Common  Stock,  par value $.0001 per share (the
"Common Stock"),  of the Company,  determined as provided  herein,  based on the
Purchase Price specified on the Buyer's  signature page (the "Purchase  Price"),
out of the Total Purchase Price (as defined below); and

            WHEREAS,  in  connection  with the purchase of such shares of Common
Stock,  the Company  will issue to the Buyer  warrants  to  purchase  additional
shares of Common Stock,  as  contemplated  by the terms of this  Agreement  (the
"Warrants");

            NOW,  THEREFORE,  for and in  consideration  of the premises and the
mutual agreement contained herein and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree as follows:

      1.    PURCHASE AND SALE; MUTUAL DELIVERIES.

            (a)   Upon  the following terms  and  conditions, the  Company shall
issue and sell to the Buyer and the Buyer shall  purchase  from the Company that
number of shares of Common Stock equal to (i) the Purchase Price divided by (ii)
the Per Share Price. Such shares (the "Purchased Shares") shall be issued to the
Buyer on the Closing Date  against  receipt of the  Purchase  Price.  The shares
shall be  evidenced  by one or more  certificates  representing  such  Purchased
Shares  issued in the name of the Buyer,  bearing  substantially  the  following
legend:

            THE SECURITIES REPRESENTED HEREBY (THE "SECURITIES ")
            HAVE NOT BEEN REGISTERED  UNDER THE SECURITIES ACT OF
            1933,  AS  AMENDED  (THE  "SECURITIES  ACT"),  OR THE
            SECURITIES  LAWS OF ANY  STATE AND MAY NOT BE SOLD OR
            OFFERED  FOR  SALE  IN THE  ABSENCE  OF AN  EFFECTIVE
            REGISTRATION  STATEMENT  FOR  THE  SECURITIES  OR  AN
            OPINION OF COUNSEL OR OTHER  EVIDENCE  ACCEPTABLE  TO
            THE  CORPORATION   THAT  SUCH   REGISTRATION  IS  NOT
            REQUIRED.




            (b)   As  used herein, each  of the following  terms has the meaning
set forth below, unless the context otherwise requiem:

                  (i)    "Affiliate" means, with  respect to a  specific  Person
referred to in the relevant  provision,  another Person who or which controls or
is controlled by or is under common control with such specified Person.

                  (ii)   "Certificates" means the certificates  representing the
Purchased Shares and the Warrants,  each duly executed by the Company and issued
on the Closing Date in the name of the Buyer.

                  (iii)  "Closing  Bid Price" means the closing bid price during
regular  trading  hours of the Common Stock (in U.S.  Dollars) on the  Principal
Trading Market, as reported by the Reporting Service.

                  (iv)   "Closing  Date"  means  the date of the  closing of the
purchase and sale of the Purchased Shares, as provided herein.

                  (v)    "Escrow Agent" means the escrow agent identified in the
Joint  Escrow  Instructions  attached  hereto  as  Annex II (the  "Joint  Escrow
Instructions").

                  (vi)   "Escrow Funds"  means  the Purchase Price  delivered to
the Escrow Agent as contemplated by Section 1(c) hereof.

                  (vii)  "Escrow  Property"  means  the  Escrow  Funds  and  the
Certificates  delivered  to the Escrow  Agent as  contemplated  by Section  1(c)
hereof.

                  (viii) "Per Share Price" means $2.75.

                  (ix)   "Person"  means any living  person or  any entity, such
as, but not necessarily limited to, a corporation, partnership or trust.

                  (x)    "Principal Trading Market"  means The  Nasdaq  SmallCap
Market.

                  (xi)   "Registrable  Shares"  means the  aggregate  of (A) the
Purchased  Shares  and (B) the  Warrant  Shares  then  head by the Buyer or then
subject to issuance upon, exercise of any outstanding Warrant.

                  (xii)  "Registration  Rights Agreement" means the Registration
Rights Agreement between the Company and the Buyer, substantially in the form of
Annex III attached hereto, being executed simultaneously herewith.

                  (xiii) "Reporting  Service"  means  Bloomberg  LP or  if  that
service is not then  reporting  the relevant  information  regarding  the Common
Stock, a comparable  reporting  service of national  reputation  selected by the
Buyers  subscribing  for a majority of the Total  Purchase  Price and reasonably
acceptable to the Company.


                                      -2-



                  (xiv)  "Securities"  means the Purchased Shares,  the Warrants
and the Warrant Shares.

                  (xv)   "Total  Purchase  Price"  means the  aggregate Purchase
Prices for all Buyers,  which shall not be less than  $500,000 and not more than
$2,000,000.

                  (xvi)  "Transaction  Agreements"  means  this  Agreement,  the
Joint Escrow  Instructions,  the Registration  Rights Agreement and the Warrants
and includes all ancillary documents referred to in those agreements.

            (c)   The  following  provisions  shall  apply to the payment of the
Purchase Price and the delivery of the Certificates.

                  (i)   The Buyer shall pay the Purchase Price for the Purchased
Shares by delivering  immediately  available good finds in United States Dollars
to the Escrow  Agent no later than the date prior to the Closing  Date.  Payment
into escrow of the Purchase Price shall be made by wire transfer of funds to:

                        Bank of New York
                        350 Fifth Avenue
                        New York, New York 10001

                        ABA# 021000018
                        For credit to the account of Krieger & Prager LLP
                        Account No.: [To be provided to the Buyer by
                                      Krieger & Prager LLP]
                        Re:  Siga August 2001 Transaction

                  (ii)  On the  Closing  Date, the  Company  shall  deliver  the
Certificates, each duly executed on behalf of the Company and issued in the name
of the Buyer, to the Escrow Agent.

                  (iii) By  signing  this  Agreement,  each of the Buyer and the
Company,  subject to acceptance by the Escrow Agent,  agrees to all of the terms
and conditions of, and becomes a party to, the Joint Escrow Instructions, all of
the  provisions  of which are  incorporated  herein by this  reference as if set
forth in full.

      2.    REPRESENTATIONS  AND   WARRANTIES  Of  THE  COMPANY.   The   Company
represents  and  warrants  to the Buyer  that,  except as  provided  in Annex IV
attached hereto:

            (a)   The  Company has  the corporate power  and authority to  enter
into this Agreement and to perform its obligations hereunder.  The execution and
delivery by the Company of tins Agreement and the consummation by the Company of
the transactions  contemplated hereby have been duly authorized by all necessary
corporate  action  on the part of the  Company.  This  Agreement  has been  duly
executed  and  delivered  by the  Company and  constitute  the valid and binding
obligation of the Company  enforceable  against it in accordance with its terms,
subject to the effects of any applicable bankruptcy, insolvency, reorganization,


                                      -3-



moratorium or similar laws affecting  creditors' rights generally and to general
equitable principles,

            (b)   The  authorized capital stock of the  Company  consists of (1)
50,000,000  shares of Common Stock,  $,0001 par value per share, of which, as of
August 23, 2001, 8,750,386 shares are outstanding, and (ii) 10,000,000 shares of
Preferred Stock,  $.0001 par share, of which, as of August 23, 2001, 394,266 are
outstanding.  All issued and  outstanding  shares of Common Stock have been duly
authorized and validly issued and are filly paid and nonassessable.  The Company
has  sufficient  authorized  and  unissued  shares  of  Common  Stock  as may be
necessary to effect the issuance of the Purchased  Shares.  The Purchased Shares
have been duly  authorized  and, when issued,  will be duly and validly  issued,
fully  paid and  non-assessable  and will not  subject  the  holder  thereof  to
personal liability by reason of being such holder.

            (c)   There  are  no  preemptive  rights of any  shareholder  of the
Company, as such, to acquire the Purchased Shares or the Warrants.  No party has
a currently  exercisable right of first refusal which would be applicable to any
or all of the transactions contemplated by the Transaction Agreements.

            (d)   Except  as set forth  in the  SEC  Documents  (as  hereinafter
defined),  there is no pending, or to the knowledge of the Company,  threatened,
judicial,   administrative  or  arbitral  action,  claim,  suit,  proceeding  or
investigation  which  might  affect  the  validity  or  enforceability  of  this
Agreement or which involves the Company and which if adversely determined, could
reasonably be expected to have a material  adverse effect on the Company and its
subsidiaries taken as a whole.

            (e)   No  consent or  approval of, or exemption  by, or filing with,
any party or  governmental or public body or authority is required in connection
with the execution,  delivery and performance under this Agreement or any of the
other Transaction  Agreements or the taking of any action contemplated hereunder
or thereunder, except such authorizations, approvals and consents that have been
obtained.

            (f)   The Company has been duly organized and is validly existing as
a  corporation  in good  standing  under  the  laws of the  jurisdiction  of its
incorporation.

            (g)   The execution, delivery and  performance of this Agreement and
each of the other  Transaction  Agreements  by the Company,  the issuance of the
Securities,  and the consummation of the transactions contemplated hereby and by
the other  Transaction  Agreements,  will not (i) violate may  provision  of the
Company's articles of incorporation or bylaws, each as currently in effect, (ii)
violate,  conflict  with or result in the breach of any of the terms of, or give
any other  contracting  party the right to  terminate,  or  constitute  (or with
notice  or lapse of time or bath  constitute)  a  default  under,  any  material
contract  or other  agreement  to which the Company is a party or by or to which
the  Company  or any of the  Company's  assets  or  properties  may be  bound or
subject, (iii) violate any order, judgment,  injunction,  award or decree of any
court,  arbitrator or governmental  or regulatory body by which the Company,  or
the  assets or  properties  of the  Company  are  bound,  (iv) to the  Company's
knowledge,  violate any statute,  law or regulation  applicable to the Company's
business.


                                      -4-



            (h)   Each of the other Transaction Agreements, and the transactions
contemplated  thereby, have been duly and validly authorized by the Company, and
the  Warrants  and  each  of the  other  Transaction  Agreements  (assuming  due
execution,  to the extent relevant, by the other party or parties thereto), when
executed and delivered by the Company,  will be, valid and binding agreements of
the Company  enforceable in accordance with, their respective terms,  subject as
to enforceability to general principles of equity and to bankruptcy, insolvency,
moratorium,  and other  similar laws  affecting  the  enforcement  of creditors'
rights generally.

            (i)   None of the SEC  Documents contained,  at the time  they  were
filed,  any untrue statement of a material fact or omitted to state any material
fact  required to be stated  therein or  necessary to make the  statements  made
therein  in,  light  of the  circumstances  under  which  they  were  made,  not
misleading. Since May 1, 2000, the Company has timely filed all requisite forms,
reports and exhibits thereto required to be filed by the Company with the SEC.

            (j)   Since  December 31, 2000 (the "Last Audited  Date"), there has
been no material  adverse change and no material adverse effect on the business,
operations,  financial condition or results of operations of the Company and its
subsidiaries taken as a whole,  except as disclosed in the SEC Documents.  Since
the Last Audited Date,  except as provided in the Company's SEC  Documents,  the
Company  has not (i)  incurred  or become  subject to any  material  liabilities
(absolute or contingent) except  liabilities  incurred in the ordinary course of
business  consistent  with past  practices;  (ii)  discharged  or satisfied  any
material  lien or  encumbrance  or paid any  material  obligation  or  liability
(absolute or contingent),  other than current  liabilities  paid in the ordinary
course of, business  consistent with past practices;  (iii) declared or made any
payment or distribution  of cash or other property to shareholders  with respect
to its capital  stock,  or  purchased  or redeemed,  or made any  agreements  to
purchase or redeem,  any shares of its  capital  stock;  (iv) sold,  assigned or
transferred any other tangible assets,  or canceled any debts or claims,  except
in the ordinary course of business consistent with past practices;  (v) suffered
any substantial losses or waived any rights of material value, whether or not in
the ordinary course of business,  or suffered the loss of any material amount of
existing business; (vi) made any changes in employee compensation, except in the
ordinary  course  of  business   consistent  with,  past  practices;   or  (vii)
experienced  any material  problems with labor or management in connection  with
the terms and conditions of their employment.

            (k)   There  is no fact  known to the  Company (other  than  general
economic  conditions  known to the public  generally  or as disclosed in the SEC
Documents) that has not been disclosed in writing to the Buyer (which disclosure
may have been made subject to the Buyer's execution of a written confidentiality
agreement)  that (i) would  reasonably  be expected  to have a material  adverse
effect on the business, operations, financial condition or results of operations
of the Company and its subsidiaries  taken as a whole,  (ii) would reasonably be
expected  to  materially  and  adversely  affect the  ability of the  Company to
perform its obligations pursuant to any of the Transaction Agreements,  or (iii)
would reasonably be expected to materially and adversely affect the value of the
rights granted to the Buyer in the Transaction Agreements.

            (l)   There is no action, suit, proceeding, inquiry or investigation
before or by any court, public board or body pending or, to the knowledge of the
Company,  threatened  against or affecting the Company,  wherein an  unfavorable
decision,  ruling  or  finding  would  have a


                                      -5-



material  adverse  effect on the business,  operations,  financial  condition or
results of  operations of the Company and its  subsidiaries  taken as a whole or
the  transactions  contemplated  by any of the  Transaction  Agreements or which
would adversely  affect the validity or  enforceability  of, or the authority or
ability of the Company to perform its obligations  under, any of the Transaction
Agreements.

            (m)   Except as  set forth in  Section 2(g), no Event of Default (or
its  equivalent  term),  as defined  in the  respective  agreement  to which the
Company is a party, and no event which, with the giving of notice or the passage
of time or both,  would become an Event of Default (or its equivalent  term) (as
so defined in such agreement), has occurred and is continuing,  which would have
a material adverse effect on the business,  operations,  financial  condition or
results of operations of the Company and its subsidiaries taken as a whole.

            (n)   The Company has no liabilities or obligations other than those
disclosed in the  Transaction  Agreements or the SEC Documents or those incurred
in the ordinary course of the Company's business since the Last Audited Date, or
which  individually  or in the  aggregate,  do not or would not have a  material
adverse effect on the business,  operations,  financial  condition or results of
operations  of the Company and its  subsidiaries  taken as a whole.  No event or
circumstances  has  occurred  or  exists  with  respect  to the  Company  or its
properties, business, operations, condition (financial or otherwise), or results
of operations, which, under applicable law, rule or regulation,  requires public
disclosure or announcement prior to the date hereof by the Company but which has
not been so publicly  announced or disclosed.  There are no proposals  currently
under  consideration or currently  anticipated to be under  consideration by the
Board of Directors or the executive officers of the Company which proposal would
(x) change the certificate of incorporation or other charter document or by-laws
of the  Company,  each as  currently  in  effect,  with or  without  shareholder
approval, which change would reduce or otherwise adversely affect the rights and
powers  of  the   shareholders   of  the  Common  Stock  or  (y)  materially  or
substantially change the business,  assets or capital of the Company,  including
its interests in subsidiaries.

      3.    REPRESENTATIONS  AND  WARRANTIES  OF  THE  BUYER.  The Buyer  hereby
represents and warrants to the Company that:

            (a)   If not an  individual, (i) the Buyer has the  corporate  power
and  authority  to enter  into this  Agreement  and to perform  its  obligations
hereunder,  and (ii) the execution and delivery by the Buyer of this  Agreement,
and the consummation by the Buyer of the transactions  contemplated hereby, have
been duly authorized by all necessary corporate action on the part of the Buyer.
This Agreement bas been duly executed and delivered by the Buyer and constitutes
the valid and binding obligation of the Buyer,  enforceable against the Buyer in
accordance with its terms, subject to the effects of any applicable  bankruptcy,
insolvency,  reorganization.,  moratorium or similar laws  affecting  creditors'
rights generally and to general equitable principles.

            (b)   The  execution, delivery and performance  by the Buyer of this
Agreement, and the consummation of the transactions  contemplated hereby, do not
and will not  breach  or  constitute  a  default  under  any  applicable  law or
regulation or of any  agreement,  judgment,  order,  decree or other  instrument
binding on the Buyer.


                                      -6-



            (c)   The Buyer has such  knowledge and prior substantial investment
experience in financial and business matters, including investment in non-listed
and  non-registered  securities,  and,  either  has read the SEC  Documents  and
evaluated the merits and risks of investment in the Company and the  Securities,
or has had the  opportunity  to engage the  services of an  investment  advisor,
attorney or  accountant  to read such SEC  Documents and to evaluate such merits
and risks.

            (d)   The  Buyer is an "accredited investor" as that term is defined
in Rule 501(a) of Regulation D promulgated  under the Securities Act of 1933, as
amended (the "Securities Act").

            (e)   The  Buyer and its  advisors, if any, have been furnished with
all materials  relating to the business,  finances and operations of the Company
and materials  relating to the offer and sale of the Purchased Shares which have
been, requested by the Buyer,  including those set forth on Annex IV hereto. The
Buyer and its  advisors,  if any,  have been  afforded  the  opportunity  to ask
questions of the Company and have received complete and satisfactory  answers to
any such inquiries.  Without limiting the generality of the foregoing, the Buyer
has  also  had the  opportunity  to  obtain  and to  review  the SEC  Documents,
including,  but not limited to, (1) Annual  Report on Form 10-KSB for the fiscal
year ended December 31, 2000, (2) Quarterly  Reports on Form 10-QSB, as amended,
for the fiscal  quarters  ended March 31, 2001 and June 30, 2001,  respectively,
(3) Schedule SC 14f-1  Statement of Change in Control  filed April 9, 2001,  (4)
Definitive  Proxy  Statement,  as  filed  on July  31,  2001,  (5)  Registration
Statement  on Form S-8,  as filed on February  26,  2001,  and (6)  Registration
Statement on Form S-3, as filed on July 2, 2001 and amended on July 6, 2001.

            (f)   The Buyer is acquiring  the Purchased Shares, the Warrants and
the Warrant  Shares  solely for the Buyer's own account for  investment  and not
with a view  to or for  sale in  connection  with a  distribution  of any of the
Securities.

            (g)   The  Buyer does  not  have a  present intention  to  sell  the
Securities,  nor a present  arrangement or /intention to effect any distribution
of any of the  Securities  to or through  any person or entity for  purposes  of
selling, offering, distributing or otherwise disposing of any of the Securities.

            (h)   The  Buyer may be  required  to bear the economic  risk of the
investment indefinitely because none of the Securities may be sold, hypothecated
or otherwise disposed of unless subsequently registered under the Securities Act
and  applicable  state  securities  laws or an exemption  from  registration  is
available.  Any resale of any of the Securities can be made only pursuant to (i)
a registration statement under the Securities Act which is effective and current
at the  time  of  sale  or  (ii) a  specific  exemption  from  the  registration
requirements of the Securities  Act. In claiming any such  exemption,  the Buyer
will,  prior to any offer or sale or distribution  of any Securities  advise the
Company and, if requested,  provide the Company with a favorable written opinion
of counsel, in form and substance  satisfactory to counsel to the Company, as to
the applicability of such exemption to the proposed sale or distribution.

            (i)   The Buyer understands  that the exemption afforded by Rule 144
promulgated by the Securities and Exchange  Commission  under the Securities Act
("Rule  144")


                                      -7-



will not become available for at least one year from the date of payment for the
Securities and any sales in reliance on Rule 144, if them available, can be made
only in accordance with the terms and conditions of that rule, including,  among
other things, a requirement that the Company then be subject to, and current, in
its periodic filing  requirements under the Securities  Exchange Act of 1934, as
amended (the  "Exchange  Act"),  and,  among other  things,  a limitation on the
amount of shares of Common Stock that may be sold in specified  time periods and
the manner in which the sale can be made; that, while the Company's Common Stock
is registered under the Exchange Act and the Company is presently subject to the
periodic  reporting  requirements of the Exchange Act, there can be no assurance
that the Company will remain subject to such reporting obligations or current in
its  filing  obligations;  and  that,  in case Rule 144 is not  applicable  to a
disposition of the Securities,  compliance with the  registration  provisions of
the Securities Act or some other  exemption  from such  registration  provisions
will be required.

            (j)   The  Buyer understands  that legends  shall be  placed  on the
certificates  evidencing the  Securities to the effect that the Securities  have
not been registered under the Securities Act or applicable state securities laws
and  appropriate  notations  thereof will be made in the Company's  stock books.
Stop  transfer  instructions  will be  placed  with  the  transfer  agent of the
securities constituting the Common Stock.

      4.    COVENANTS OF THE COMPANY.  The Company hereby  further represents to
or covenants and agrees with the Buyer as follows:

            (a)   The company has furnished  or made available to the Buyer true
and  correct  copies of all  registration  statements,  reports  and  documents,
including proxy statements (other than preliminary proxy statements), filed with
the  Securities  and Exchange  Commission  (the "SEC") by or with respect to the
Company  since  December  31,  1999 and  prior  to the  date of this  Agreement,
pursuant to the  Securities  Act or the  Exchange  Act  (collectively,  the "SEC
Documents").  The SEC  Documents  are the only filings made by the Company since
December 31, 2000 pursuant to Sections 13(a), 13(c) 14 and 15(d) of the Exchange
Act or  pursuant to the  Securities  Act.  The  Company  has filed all  reports,
schedules,  forms,  statements  and other  documents  required to be filed by it
under Sections 13(a),  13(c), 14 and 15(d) of the Exchange Act since May 1, 2000
and prior to the date of this  Agreement.  The  Company  meets  the  "Registrant
Requirement"  for  eligibility to use Form S-3 under the Securities Act in order
to register the Company's Common Stock for resales.

            (b)   The  Company has  not  provided to the  Buyer any  information
which  according  to  applicable  law,  rule or  regulation,  should  have  been
disclosed  publicly  prior to the date  hereof by the  Company but which has not
been so disclosed. As of their respective dates, the SEC Documents complied, and
all similar documents filed with the SEC prior to the Closing Date will comply.,
in all material  respects with the  requirements  of the  Securities  Act or the
Exchange  Act,  as the  case  may  be,  and  rules  and  regulations  of the SEC
promulgated  thereunder  and other  federal,  state and  local  laws,  rules and
regulations applicable to such SEC Documents, and no document similar to the SEC
Documents  filed by the  Company  with the SEC  prior to the  Closing  Date will
contain, any untrue statement of a material fact or omitted to state a material,
fact required to be stated  therein or necessary in order to make the statements
therein,  in  light  of the  circumstances  under  which  they  were  made,  not
misleading.  The  financial  statements  of the  Company  included  in  the  SEC
Documents,  as of the dates thereof,  complied,  and all similar


                                      -8-



documents  filed with the SEC prior to the Closing Date will comply,  as to form
in all  material  respects  with  applicable  accounting  requirements  and  the
published  riles  and  regulations  of the SEC and  other  applicable  rules and
regulations  with respect  thereto.  Such  financial  statement were prepared in
accordance with generally accepted accounting principles applied on a consistent
basis during the periods involved  (except (i) as may be otherwise  indicated in
such financial  statements or the notes thereto or (ii) in the case of unaudited
interim  statements,  to the extent  they may not  include  footnotes  or may be
condensed or summary statements as permitted by Form 10-Q of the SEC) and fairly
present in all material  respects the financial  position of the Company and its
consolidated  subsidiaries as of the dates thereof and the consolidated  results
of operations and cash flows for the periods then ended (subject, in the case of
unaudited statements, to normal year-end audit adjustments).

            (c)   The  Company  will  issue  to the Buyer  on the Closing  Date,
transferable divisible Warrants to purchase up to the number of shares of Common
Stock equal to seventy-five percent (75%) of the Purchased Shares. Such Warrants
shall  bear an  exercise  price per share of Common  Stock  equal to 120% of the
average  Closing Bid Prices of a share of Common  Stock for the five (5) trading
days ending on the  trading  day  immediately  preceding  the Closing  Date_ The
Warrants shall be exercisable immediately upon issuance and thereafter until the
last day of the month in which  the  seventh  anniversary  of the  Closing  Date
occurs and shall otherwise be substantially in the form attached hereto as Annex
I.

            (d)   (i)    The  Company shall enter  into the Registration  Rights
Agreement with the Buyer.

                  (ii)    Except  for  periods  during  which  the  Registration
Statement  contemplated  by the  Registration  Rights  Agreement is effective or
subject to a Permitted  Suspension Period (as defined in the Registration Rights
Agreement),  during the period from the Closing  Date  through the date when all
Purchased  Shares have been sold and either the Warrants  have expired or all of
the Warrants have been  exercised and all of the Warrant  Shares have been sold,
the  Buyer  shall  have  piggy-back  registration  rights  with  respect  to the
Registrable  Shares,  subject to the conditions set forth below.  If at any time
during that period, the Company  participates  (whether voluntarily or by reason
of an  obligation  to a third  party) in the  registration  of any shares of the
Company's  stock  (other  than a  registration  on Form S-4 or Forth  S-8),  the
Company shall give written  notice thereof to the Buyer and the Buyer shall have
the right,  exercisable  within  ten (10)  business  days after  receipt of such
notice,  to demand  inclusion  of all or a portion  of the  Buyer's  Registrable
Shares in such registration statement. If the Buyer exercises such election, the
Registrable Shares so designated shall be included in the registration statement
at no cost or expense to the Buyer  (other than any  commissions  payable to the
broker effecting the sale, which would be borne by the Buyer). If, in connection
with any  underwritten  offering  for the account of the  Company  the  managing
underwriter or underwriters  thereof  (collectively,  the  "Underwriter")  shall
impose a  limitation  on the  number  of shares  of  Common  Stock  which may be
included in the registration statement because, in the Underwriter's  judgement,
such  limitation  its  necessary  to effect an orderly  public  distribution  of
securities  covered thereby,  then, the Company shall be obligated to include in
such registration only such limited portion of the Registrable  Shares for which
such Buyer has requested  inclusion  hereunder as the Underwriter  shall permit.
Any  exclusion  of  Registrable  Shares  shall be made pro rata among the Buyers
seeking  to  include   Registrable  Shares,  in  proportion  to  the  number  of


                                      -9-


Registrable  Shares  sought to be included by such holders;  provided,  however,
that the Company shall not exclude any Registrable Shares unless the Company has
first excluded all outstanding  securities the holders of which are not entitled
by right to inclusion of securities in such registration statement; and provided
further,  however,  that,  after  giving  effect  to the  immediately  preceding
proviso, any exclusion of Registrable Shares shall be made pro rata with holders
of  other  securities  having  the  right to  include  such  securities  in such
registration  statement.  The Buyer's piggy-back  registration rights under this
Section  4(c)  shall  expire  at such  time as the  Buyer  can  sell  all of the
Registrable Shares under Rule 144 without volume or other restrictions or limit.

            (e)   If (i) the Buyer, other than by reason of its gross negligence
or  willful  misconduct,  becomes  involved  in  any  capacity  in  any  action,
proceeding  or  investigation  brought by any  stockholder  of the  Company,  in
connection  with  or  as a  result  of  the  consummation  of  the  transactions
contemplated by thus  Agreement,  or if such Buyer impleaded in any such action,
proceeding  or  investigation  by any Person,  or (ii) the Buyer,  other than by
reason of its gross negligence or willful misconduct or by reason of its trading
of the Common  Stock in a manner that is illegal  under the  federal  securities
laws  or  other  actions,  becomes  involved  in any  capacity  in  any  action,
proceeding or investigation  brought by the Commission  against or involving the
Company  or in  connection  with  or as a  result  of  the  consummation  of the
transactions contemplated by this Agreement, or if the Buyer is impleaded in any
such action, proceeding or investigation,  by any Person, then in any such case,
the Company will reimburse the Buyer for its reasonable legal and other expenses
(including the cost of any investigation and preparation) incurred in connection
therewith,  as such expenses are incurred. In addition,  other than with respect
to any such matter in which the Buyer is a named party, the Company will pay the
Buyer the charges,  as reasonably  determined by the Buyer,  for the time of any
officers or employees of the Buyer,  if any,  devoted to appearing and preparing
to appear  as  witnesses,  assisting  in  preparation  for  hearings,  trials or
pretrial matters, or otherwise with respect to inquiries,  hearing,  trials, and
other  proceedings  relating  to the  subject  matter  of  this  Agreement.  The
reimbursement  obligations  of the  Company  under  this  paragraph  shall be in
addition to any  liability  which the Company may otherwise  have,  shall extend
upon the same  terms and  conditions  to any  Affiliates  of the  Buyers who are
actually  named in such  action,  proceeding  or  investigation,  and  partners,
directors,  agents,  employees and controlling persons (if any), as the case may
be, of the Buyers and any such Affiliate, and shall be binding upon and inure to
the benefit of any successors,  assigns,  heirs and personal  representatives of
the Company,  the Buyers and any such Affiliate and any such Person. The Company
also agrees that neither the Buyer nor any such Affiliate,  partners, directors,
agents, employees or controlling persons shall have any liability to the Company
or any  person  asserting  claims  on behalf  of or in right of the  Company  in
connection with or as a result of the consummation of the Transaction Agreements
except to the extent that any losses, claims,  damages,  liabilities or expenses
incurred by the Company result from the gross  negligence or willful  misconduct
of the Buyer or any such Affiliate.

      5.    CLOSING DATE.

            (a)   The  Closing  Date shall occur on, the date which is the first
NYSE trading day after each of the conditions  contemplated  by Sections 6 and 7
hereof  shall have  either been  satisfied  or been waived by the party in whose
favor such conditions run.


                                      -10-



            (b)  The closing of the purchase  and issuance of  Purchased  Shares
shall  occur on the Closing  Date at the  offices of the Escrow  Agent and shall
take place no later than 3:00 P.M. New York time, on such day or such other time
as is mutually agreed upon by the Company and the Buyer.

            (c)   Notwithstanding anything to the contrary contained herein, the
Escrow Agent will be  authorized  to release the Escrow Funds to the Company and
to others and to release the other Escrow Property on the relevant  Closing Date
upon  satisfaction of the conditions set forth in Sections 6 and 7 hereof and as
provided in the Joint Escrow Instructions.

      6.    CONDITIONS   TO  THE  COMPANY'S   OBLIGATION  TO  SELL.   The  Buyer
understands  that the Company's  obligation to sell the  Securities to the Buyer
pursuant to this Agreement on the Closing Date is conditioned upon:

            (a)   Delivery  by the  Buyer to the Escrow  Agent of good  funds as
payment  in full of an amount  equal to the  Purchase  Price  for the  Purchased
Shares in accordance with this Agreement;

            (b)   The  accuracy on such Closing Date of the  representations and
warranties  of the Buyer  contained in this  Agreement,  each as if made on such
date,  and the  performance by the Buyer on or before such date of all covenants
and agreements of the Buyer required to be performed on or before such date; and

            (c)   There  shall  not be in  effect  any  law, rule or  regulation
prohibiting or restricting the transactions  contemplated  hereby,  or requiring
any consent or approval which shall not have been obtained.

      7.    CONDITIONS  TO  THE  BUYER'S  OBLIGATION  TO  PURCHASE.  The Company
understands  that the Buyer's  obligation  to  purchase  the  Securities  on the
Closing Date is conditioned upon:

            (a)   The  execution  and delivery  of this  Agreement and the other
Transaction Agreements by the Company;

            (b)   Delivery   by  the   Company  to  the   Escrow  Agent  of  the
Certificates in accordance with this Agreement;

            (c)   On the Closing Date, the Buyer shall have received an opinion
of  counsel  for the  Company,  dated  such  Closing  Date,  in form,  scope and
substance reasonably satisfactory to the Buyer,  substantially to the effect set
forth in Annex V attached hereto;

            (d)   The  accuracy in all  material  respects on such Closing Date
of  the  representations  and  warranties  of  the  Company  contained  in  this
Agreement,  each as if made on such date, and the  performance by the Company on
or before such date of all covenants and  agreements of the Company  required to
be performed on or before such date;


                                      -11-



            (e)    There  shall  not be in effect  any  law, rule or  regulation
prohibiting or restricting the transactions  contemplated  hereby,  or requiring
any consent or approval which shall not have been obtained; and

            (f)   From and after the date hereof to and  including  such Closing
Date,  trading in securities  generally an the New York Stock Exchange shall not
have been  suspended  or  limited,  nor shall  there be any  major  outbreak  or
escalation of hostilities involving the United States that in either case in the
reasonable  judgment  of the  Buyer  makes  it  impracticable  to  purchase  the
Securities.

     8.    NOTICES. Any notice required or permitted hereunder shall be given in
writing  (unless  otherwise  specified  herein) and shall be deemed  effectively
given on the earliest of

            (a)   the  date  delivered, if  delivered  by  personal  delivery as
against written receipt therefor or by confirmed facsimile transmission,

            (b)   the  seventh business day  after deposit, postage  prepaid, in
the United States Postal Service by registered or certified mail, or

            (c)   the  third  business   day  after   mailing  by   domestic  or
international express courier, with delivery costs and fees prepaid,

in each case,  addressed to each of the other parties thereunto  entitled at the
following  addresses (or at such other  addresses as such party may designate by
ten (10)  days'  advance  written  notice  similarly  given to each of the other
parties hereto):

COMPANY:          SIGA TECHNOLOGIES, INC.
                  420 Lexington Avenue, Suite 620
                  New York, NY 10170
                  ATTN: Thomas Konatich
                  Telephone No.: (212) 672-9100
                  Facsimile No.: (212) 697-3130

                  with a copy to:

                  Akin, Gump, Strauss, Hauer & Feld, L.L.P.
                  590 Madison Avenue
                  New York, New York 10022
                  ATTN: Jeffrey J. Fessler, Esq.
                  Telephone No.: (212) 872-1000
                  Facsimile No.: (212) 872-1002


                                      -12-



BUYER:            At the address set forth on the signature page
                  of this Agreement.

                  with a copy to:

                  Krieger & Prager, LLP
                  39 Broadway, Suite 1440
                  New York, New York 10006
                  ATTN: Ronald Nussbaum, Esq.
                  Telephone No.: (212) 363-2900
                  Facsimile No.: (212) 363-2999

ESCROW AGENT:     Krieger & Prager LLP
                  39 Broadway
                  Suite 1440
                  New York, NY 10006
                  Attn: Samuel Krieger, Esq.
                  New York, New York 10016
                  Telephone No.:  (212) 363-2900
                  Telecopier No.: (212) 363-2999

      9.    GOVERNING LAW; MISCELLANEOUS.

            (a)   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 exclusive
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  conveniens,  to the  bringing  of any such,
proceeding in such  jurisdictions.  To the extent  determined by such court, the
Company  shall   reimburse  the  Buyer  for  any   reasonable   legal  fees  and
disbursements  incurred by the Buyer in  enforcement  of or protection of any of
its rights under any of the Transaction Agreements.

            (b)   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.

            (c)   This  Agreement  shall inure  to the benefit of and be binding
upon the successors and assigns of each of the parties hereto.

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

            (e)   A  facsimile  transmission  of  this signed Agreement shall be
legal and binding on all parties hereto.


                                      -13-



            (f)   This Agreement may be signed in one or more counterparts, each
of which shall be deemed an original.

            (g)   The   headings  of  this  Agreement  are  for  convenience  of
reference  and shall not form part of, or affect  the  interpretation  of,  this
Agreement.

            (h)   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 this Agreement in any other jurisdiction.

            (i)   Thus Agreement may be amended only by an instrument in writing
signed by the party to be charged with enforcement thereof.

            (j)   This   Agreement   supersedes   all   prior   agreements   and
understandings  among the  parties  hereto with  respect to the  subject  matter
hereof.

10. SURVIVAL OF  REPRESENTATIONS  AND WARRANTIES.  The Company's and the Buyer's
representations  and warranties  herein shall survive the execution and delivery
of this  Agreement and the delivery of the  Certificates  and the payment of the
Purchase Price,  and shall inure to the benefit of the Buyer and the Company and
their respective successors and assigns.



                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]






                                      -14-




            IN WITNESS  WHEREOF,  this  Agreement  has been duly executed by the
Buyer (if an entity, by one of its officers thereunto duly authorized) as of the
date set forth below.


PURCHASE PRICE OF BUYER



----------------------------------------    ------------------------------------
Address                                     (Printed Name of Buyer)

----------------------------------------    By:
Telecopier No.                              (Signature of Authorized Person)
                 -----------------------
                 Printed Name and Title


Jurisdiction of Incorporation
or Organization

As of the date set forth below,  the  undersigned  hereby accepts this Agreement
and  represents  that the foregoing  statements are true and correct and that it
has caused this Securities Agreement to be duly executed on its behalf.

SIGA TECHNOLOGIES, INC.


By:

Title:
Date:  _______________________, 2001







                                      -15-




ANNEX I           FORM OF WARRANT

ANNEX II          JOINT ESCROW INSTRUCTIONS

ANNEX III         REGISTRATION RIGHTS AGREEMENT

ANNEX IV          COMPANY DISCLOSURE MATERIALS

ANNEX V           FORM OF OPINION



                                                                      Exhibit R

                                 FORM OF WARRANT

            THESE  SECURITIES HAVE NOT BEEN REGISTERED  UNDER THE
            SECURITIES ACT OF 1933, AS AMENDED, OR THE SECURITIES
            LAWS OF ANY STATE AND MAY NOT BE SOLD OR OFFERED  FOR
            SALE  IN THE  ABSENCE  OF AN  EFFECTIVE  REGISTRATION
            STATEMENT FOR THE SECURITIES OR AN OPINION OF COUNSEL
            OR OTHER EVIDENCE ACCEPTABLE TO THE COMPANY THAT SUCH
            REGISTRATION IS NOT REQUIRED.



                             SIGA TECHNOLOGIES, INC.

                          COMMON STOCK PURCHASE WARRANT

            1.    Issuance;  Certain   Definitions.  In  consideration  of  good
and valuable consideration,  the receipt of which is hereby acknowledged by SIGA
TECHNOLOGIES,     INC.,    a    Delaware     corporation     (the     "Company")
_________________________________ or registered assigns (the "Holder") is hereby
granted the right to  purchase at any time until 5:00 P.M.,  New York City time,
on  _________________,  20081 (the "Expiration Date"),  ______________  Thousand
(_________)2  a fully  paid and  nonassessable  shares of the  Company's  Common
Stock,  $.0001 par value per share (the "Common Stock"),  at as initial exercise
price per share (the "Exercise  Price") of $____3 per share,  subject to further
adjustment  as set forth  herein.  This Warrant is being issued  pursuant to the
terms of that certain Common Stock and Warrant Purchase  Agreement,  dated as of
August  _____,  2001 (the  "Agreement"),  to which the  Company  and  Holder (or
Holder's  predecessor in interest) are parties.  Capitalized terms not otherwise
defined herein shall have the meanings ascribed to them in the Agreement.


            2.    Exercise of Warrants.

                  2.1 General.  This Warrant is  exercisable in whole or in part
at any time and  from  time to time.  Such  exercise  shall be  effectuated,  by
submitting  to the Company  (either by  delivery to the Company or by  facsimile
transmission  as  provided in Section 8 hereof) a  completed  and duly  executed
Notice  of  Exercise  (substantially  in  the  form  attached  to  this  Warrant
Certificate) as provided in this paragraph.  The date such Notice of Exercise is
faxed to the  Company  shall be the  "Exercise  Date,"  provided  that,  if this
Warrant  has been fully  exercised,  the  Holder of this  Warrant  tenders  this
Warrant Certificate to the Company within five (5) business days thereafter. The
Notice of Exercise  shall be  executed  by the Holder of this


----------
1     Insert  date which is last day of month in which  seventh  anniversary  of
      Closing Date occurs.

2     Insert number equal to 75% of Buyer's Purchased Shares.

3     Insert amount equal to 120% of the average Closing Bid Price of the Common
      Stock  for the 5  trading  days  ending  on the  trading  day  immediately
      receding the Closing Date.




Warrant and shall indicate the number of shares then,  being purchased  pursuant
to such exercise. Upon surrender of this Warrant Certificate, if relevant, with,
together with appropriate payment of the Exercise Price for the shares of Common
Stock  purchased,  the Holder  shall be  entitled  to receive a  certificate  or
certificates for the shares of Common Stock so purchased. The Exercise Price per
share of Common  Stock for the shares then being  exercised  shall be payable in
cash or by certified or official bank check or wire  transfer.  The Holder shall
be deemed to be the holder of the shares  issuable to it in accordance  with the
provisions of this Section 2.1 on the Exercise Date.

                  2.2   Limitation on  Exercise.  Notwithstanding the provisions
of this Warrant,  the Agreement or of the other  Transaction  Agreements,  in no
event  (except (i) as  specifically  provided in this Warrant as an exception to
this provision, (ii) while there is outstanding a tender offer for any or all of
the shares of the Company's Common Stock, or (iii) at the Holder's option, on at
least  sixty-five  (65) days' advance  written notice from the Holder) shall the
Holder be entitled  to  exercise  this  Warrant,  or shall the Company  have the
obligation  to issue  shares  upon such  exercise  of all or any portion of this
Warrant  (and the  Company  shall  not have the  right to  require  a  Mandatory
Exercise,  as defined below), to the extent that, after such exercise the sum of
(1) the number of shares of Common  Stock  beneficially  owned by the Holder and
its  affiliates  (other  than  shares  of  Common  Stock  which  may  be  deemed
beneficially  owned  through the  ownership  of the  unexercised  portion of the
Warrants),  and (2) the  number  of shares of  Common  Stock  issuable  upon the
exercise of the Warrants with respect to which the determination of this proviso
is being  made,  would  result in  beneficial  ownership  by the  Holder and its
affiliates of more than 9.99% of the  outstanding  shares of Common Stock (after
taking into  account the shares to be issued to the Holder upon such  exercise).
For purposes of the proviso to the immediately  preceding  sentence,  beneficial
ownership shall be determined in accordance with Section 13(d) of the Securities
Exchange Act of 1934, as amended (the "1934 Act"),  except as otherwise provided
in clause (1) of such sentence.  The Holder,  by its acceptance of this Warrant,
further agrees that if the Holder  transfers or assigns any of the Warrants to a
party who or which would not be considered  such an affiliate,  such  assignment
shall be made subject to the transferee's or assignee's specific agreement to be
bound by the  provisions  of this Section 2.2 as if such  transferee or assignee
were the original Holder hereof.

                  2.3   Mandatory Exercise.

            (a)   Company's Right to Issue Mandatory  Exercise  Notice.  Subject
to the terms of this  Section  2.3, at its option,  the Company  may, by written
notice (a  "Mandatory  Exercise  Notice")  given to the Holder,  accelerate  the
Expiration Date for all or a portion of the then  unexercised  shames covered by
this  Warrant  to a date (the  "Mandatory  Expiration  Date")  which is at least
fifteen  (15)  business  days after the date the  Mandatory  Exercise  Notice is
given. The exercise of the Warrant contemplated by the Mandatory Exercise Notice
is referred to as the "Mandatory  Exercise." The numbest of shares  specified in
the Mandatory Exercise Notice is referred to as the "Mandatory Exercise Shares."
The Company may issue a  Mandatory  Exercise  Notice if, and only if, all of the
following requirements are met:

                  (i)   Registration    Statement    Available.    The
      Registration  Statement  must have been  effective and available
      for the  resale of all of the  shares of Common  Stock  issuable
      upon the  Mandatory  Exercise  at all times  during the ten (10)
      consecutive  trading days ending on the trading day  immediately
      before the Company issues a Mandatory  Exercise Notice (such ten
      trading days, the "Mandatory  Period") and at all times from the
      issuance of the Mandatory  Exercise Notice through and including
      the Mandatory Expiration Date.

                  (ii) Required Common Stock Market Price. The Closing
      Bid  Price  of the  Common  Stock  for each  trading  day of the
      Mandatory  Period shall be at least $5.25 (adjusted to take into
      account any stock split effected after the Closing Date).

                  (iii)  Required  Common  Stock  Volume.  The average
      trading  volume of the Common Stock during the Mandatory  Period
      shall be at least  100,000  shares per trading day  (adjusted to
      take into  account  any stock split  effected  after the Closing
      Date,  except that with respect to a reverse  stock  split,  the
      adjustment shall not be greater than a ratio of 1:4).

                  (iv)  Conversion  Limitation.  Neither the Mandatory
      Exercise Shares nor the exercise of the Warrant  contemplated by
      the Mandatory  Exercise  Notice shall be  inconsistent  with the
      provisions of Section 2.2 hereof,  which  provisions shall apply
      to mandatory Exercise. If the Mandatory Exercise Notice provides
      for a number of  Mandatory  Exercise  Shares  which  exceeds the
      number  contemplated  by Section 2.2,  such  Mandatory  Exercise
      Notice  shall be deemed  automatically  adjusted  and revised to
      refer only to the maximum number of shares  contemplated by said
      Section 2.2.

            (b)   Holder's  Exercise.  Upon the  proper issuance of a  Mandatory
Exercise  Notice,  the Holder may, on or before the Mandatory  Expiration  Date,
exercise  this Warrant for all or any of the  Mandatory  Exercise  Shares at the
Exercise  Price.  The Mandatory  Exercise Shares as to which the Holder does not
exercise this Warrant on or before the Mandatory Expiration Date are referred to
as the  "Unexercised  Shares." To the extent the Holder does not  exercise  this
Warrant with respect to any Unexercised  Shares,  the Holder's rights under this
Warrant with respect to the  Unexercised  Shares shall expire as of the close of
business on the Mandatory Expiration Date.

            3.    Reservation  of Shares. The Company hereby  agrees that at all
times during the term of this Warrant  there shall be reserved for issuance upon
exercise of this  Warrant  such number of shares of its Common Stock as shall be
required, for issuance upon exercise of this Warrant (the "Warrant Shares").

            4.    Mutilation or Loss of Warrant. Upon  receipt by the Company of
evidence  satisfactory  to it of the loss,  theft,  destruction or mutilation of
this  Warrant,  and (in the  case of  loss,  theft or  destruction)  receipt  of
reasonably  satisfactory  indemnification,  and (in the case of mutilation) upon
surrender and cancellation of this Warrant, the Company will execute and deliver
a new  Warrant of like tenor and date and any such lost,  stolen,  destroyed  or
mutilated Warrant shall thereupon become void.




            5.    Rights of the Holder.  The Holder shall not, by virtue hereof,
be  entitled to any rights of a  stockholder  in the  Company,  either at law or
equity,  and the  rights of the Holder are  limited to those  expressed  in this
Warrant and are not  enforceable  against  the Company  except to the extent set
forth herein.

            6.    Protection Against Dilution and Other Adjustments.

                  6.1  Adjustment  Mechanism.  If an  adjustment of the Exercise
Price is required  pursuant to this  Section 6, the Holder  shall be entitled to
purchase such number of additional  shares of Common Stock as will cause (i) the
total number of shares of Common  Stock Holder is entitled to purchase  pursuant
to this Warrant,  multiplied by (ii) the adjusted  Exercise Price per share,  to
equal  (iii) the  dollar  amount of the total  number of shares of Common  Stock
Holder  is  entitled  to  purchase  before  adjustment  multiplied  by the total
Exercise Price before adjustment.

                  6.2  Capital Adjustment. In case of any stock split or reverse
stock   split,   stock   dividend,   reclassification   of  the  Common   Stock,
recapitalization,  merger or consolidation, or like capital adjustment affecting
the Common  Stock of the  Company,  the  provisions  of this  Section 6 shall be
applied as if such capital  adjustment event had occurred  immediately  prior to
the date of this  Warrant  and the  original  Exercise  Price  had  been  fairly
allocated  to the stock  resulting  from such capital  adjustment;  and in other
respects the  provisions of thus Section  shall be applied in a fair,  equitable
and reasonable manner so as to give effect, as nearly as may be, to the purposes
hereof.  A rights offering to  stockholders  shall be deemed a stock dividend to
the extent of the bargain purchase element of the rights.

                  6.3  Adjustment for Spin Off. If, for any reason, prior to the
exercise of this Warrant in full,  the Company  spins off or  otherwise  divests
itself of a part of its business or  operations  or disposes all or of a part of
its assets in a  transaction  (the  "Spin  Off") in which the  Company  does not
receive  compensation  for such  business,  operations  or  assets,  but  causes
securities  of  another  entity  (the  "Spin  Off  Securities")  to be issued to
security holders of the Company, then

            (a)   the Company shall cause (i) to be reserved Spin Off Securities
      equal to the number thereof which would have been issued to the Holder had
      all of the Holder's  unexercised  Warrants  outstanding on the record date
      (the  "Record  Date")  for  determining  the amount and number of Spin Off
      Securities  to  be  issued  to  security   holders  of  the  Company  (the
      "Outstanding  Warrants") been exercised as of the close of business on the
      trading day  immediately  before the Record Date (the  "Reserved  Spin Off
      Shares"),  and (ii) to be issued to the Holder on the  exercise  of all or
      any of the  Outstanding  Warrants,  such amount of the  Reserved  Spin Off
      Shares  equal to (x) the  Reserved  Spin Off  Shares  multiplied  by (y) a
      fraction,  of which (I) the  numerator  is the  amount of the  Outstanding
      Warrants then being  exercised,  and (II) the denominator is the amount of
      the Outstanding Warrants; and

            (b)   the  Exercise  Price  on  the  Outstanding  Warrants  shall be
      adjusted immediately after consummation of the Spin Off by multiplying the
      Exercise  Price by a fraction (if, but only if, such fraction is less than
      1.0),  the  numerator  of which is the





      average  Closing  Bid Price of the Common  Stock far the five (5)  trading
      days  immediately  following  the fifth trading day after the Record Date,
      and the  denominator  of which is the  average  Closing  Bid  Price of the
      Common Stock on the five (5) trading days immediately preceding the Record
      Date; and such adjusted  Exercise Price shall be deemed to be the Exercise
      Price with respect to the Outstanding Warrants after the Record Date.

            7.    Transfer to Comply with the Securities Act;
                  Registration Rights.

                  7.1  Transfer. This Warrant has not been registered  under the
Securities  Act of 1933,  as  amended,  (the  "Act") and has been  issued to the
Holder  for  investment  and not with a view to the  distribution  of either the
Warrant or the  Warrant  Shares.  Neither  this  Warrant  nor any of the Warrant
Shares or any other  security  issued or issuable  upon exercise of this Warrant
may be  sold,  transferred,  pledged  or  hypothecated  rut  the  absence  of an
effective  registration  statement under the Act relating to such security or an
opinion of counsel satisfactory to the Company that registration is not required
under the Act.  Each  certificate  for the Warrant,  the Warrant  Shares and any
other security  issued or issuable upon exercise of this Warrant shall contain a
legend on the face thereof,  in form and substance  satisfactory  to counsel for
the  Company,  setting  forth the  restrictions  on transfer  contained  in this
Section.

                  7.2  Registration   Rights.  (a)  Reference  is  made  to  the
Registration Rights Agreement.  The Company's obligations under the Registration
Rights Agreement and the other terms and conditions  thereof with respect to the
Warrant  Shares,  including,  but not  necessarily  limited  to,  the  Company's
commitment to file a registration  statement  including the Warrant  Shares,  to
have the  registration  of the Warrant Shares  completed and  effective,  and to
maintain such registration, are incorporated herein by reference.

            (b)   Reference  is made to Section 4(d) of the  Agreement regarding
piggy-back registration rights covering, among other things, the Warrant Shares.
The  terms  and  conditions  of said  Section  4(d) are  incorporated  herein by
reference.

            8.    Notices.   Any  notice  or  other  communication  required  or
permitted  hereunder  shall be in  writing  and shall be  delivered  personally,
telegraphed,  telexed,  sent by  facsimile  transmission  or sent by  certified,
registered or express mail,  postage  pre-paid.  Any such notice shall be deemed
given when so delivered  personally,  telegraphed,  telexed or sent by facsimile
transmission,  or, if  mailed,  two days after the date of deposit in the United
States mails, as follows:




                  (i)   if to the Company, to;

                        SIGA TECHNOLOGIES, INC.
                        420 Lexington Avenue, Suite 620
                        New York, NY 10170
                        ATTN: Thomas Konatich
                        Telephone No.: (212) 672-9100
                        Facsimile No.: (212) 697-3130

                  with a copy to:

                        Akin, Gump, Strauss, Hauer & Feld, L.L.P.
                        590 Madison Avenue
                        New York, New York 10022
                        ATTN: Jeffrey J. Fessler, Esq.
                        Telephone No.: (212) 872-1000
                        Facsimile No.: (212) 872-1002

                  (ii)  if to the Holder, to:



                        Attn:
                        Telephone No.: ( )
                        Telecopier No.: ( )


                  with a copy to:

                        Krieger & Prager LLP, Esqs.
                        39 Broadway
                        Suite 1440
                        New York, NY 10006
                        Attn: Ronald Nussbaum, Esq.
                        Telephone No.:  (212) 363-2900
                        Telecopier No.: (212) 363-2999

Any party may be  notice  given in  accordance  with this  Section  to the other
parties designate another address or person for receipt of notices hereunder.

            9.    Supplements and  Amendments; Whole Agreement. This Warrant may
be amended  or  supplemented  only by an  instrument  in  waiting  signed by the
parties  hereto.  This Warrant  contains the full  understanding  of the parties
hereto with  respect to the subject  matter  hereof and thereof and there are no
representations,  warranties,  agreements or understandings other than expressly
contained herein and therein.




           10.    Governing Law. This  Warrant shall  be deemed to be a contract
made  under  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 o(pound)
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  Warrant  and hereby
waives,  to the maximum extent  permitted by law, any  objection,  including any
objection based on forum non conveniens,  to the bringing of any such proceeding
in such jurisdictions. To the extent determined by such court, the Company shall
reimburse the Holder for any reasonable legal fees and disbursements incurred by
the Buyer in  enforcement of or protection of any of its rights under any of the
Transaction Agreements.

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

           12.    Descriptive  Headings.  Descriptive  headings  of  the several
Sections of this Warrant are inserted for convenience only and shall not control
or affect the meaning or construction of any of the provisions hereof.

      IN WITNESS  WHEREOF,  the parties  hereto have executed this Warrant as of
the ___th day of ___________________, 2001.


                                    SIGA TECHNOLOGIES, INC.




                                    By:
                                        -------------------------------
                                        (Print Name)




                                        -------------------------------
                                        (Title)





                          NOTICE OF EXERCISE OF WARRANT

      The  undersigned   hereby   irrevocably  elects  to  exercise  the  right,
represented by the Warrant  Certificate dated as of  _________________,  ___, to
purchase  ___________  shares of the Common  Stock,  $.0001  par value,  of SIGA
TECHNOLOGIES,  INC. and tenders herewith payment in accordance with Section 1 of
said Common Stock Purchase Warrant.

      It is the intention of the Holder to comply with the provisions of Section
2.2 of the Warrant  regarding  certain  limits on the Holder's right to exercise
thereunder. Based on the analysis on the attached Worksheet Schedule, the Holder
believe  this  exercise  complies  with  the  provisions  of said  Section  2.2.
Nonetheless,  to the extent that,  pursuant to the exercise effected hereby, the
Holder  would have more shares than  permitted  under said  Section  this notice
should be amended and revised,  ab initio,  to refer to the exercise which would
result in the issuance of shares  consistent with such  provision.  Any exercise
above such amount is hereby deemed void and revoked.

      Please deliver the stock certificate to:



Dated:
      --------------------------




--------------------------------
[Name of Holder]

By:
   -----------------------------

|_|   CASH:                                     $
                                                 -----------------------





                          NOTICE OF EXERCISE OF WARRANT


                               WORKSHEET SCHEDULE



1.    Current Common Stock holdings of Holder and Affiliates
                                                                      ----------

2.    Shares to be issued on current exercise
                                                                      ----------

3.    Other shares eligible to be acquired without restriction
                                                                      ----------

4.    Total [sum of Lines 1 through 3]
                                                                      ----------

5.    Outstanding shares of Common Stock
                                                                      ----------

6.    Adjustments to Outstanding
                                                                      ----------
        a.  Shares from Line 1 not included in Line 5
                                                        ----------
        b.  Shares to be issued per Line 2
                                                        ----------
        c.  Total Adjustments [Lines 6a and 6b]
                                                        ----------
7.    Total Adjusted Outstanding [Lines 5 plus 6c]
                                                                      ----------
8.    Holder's Percentage (Line 4 divided by Line 7]                          %
                                                                      ----------


[Note: Line 8 not to be above 9.99%]