Document:

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                                                                   EXHIBIT 10.12

            AMENDMENT TO ASSIGNMENT, ASSUMPTION AND LICENSE AGREEMENT

THIS AMENDMENT to the Assignment, Assumption and License Agreement dated as of
October 7, 1999 (the "Agreement") by and between IMARX, LLC, an Arizona limited
liability company ("Purchaser") and IMARX PHARMACEUTICAL CORP., an Arizona
corporation ("Seller") is entered into and effective this 31 day of July, 2000
by and between IMARX THERAPEUTICS, INC., successor in interest to Purchaser
("ImaRx") and DuPont Contrast Imaging, Inc. ("DuPont"), successor in interest to
Seller. Capitalized terms used but not otherwise defined herein have the
meanings assigned to them in the Agreement.

                                    RECITALS

         A. Purchaser and Seller entered into the Agreement as of October 7,
1999. Thereafter, Seller was merged into DuPont.

         B. Exhibit A and Exhibit B to the Agreement were incomplete. The
parties now wish to correct this error by amending Exhibit A and Exhibit B to
conform to the parties' original understanding.

         NOW, THEREFORE, in consideration of the foregoing premises and of the
agreements and covenants set forth in the Agreement, the parties agree as
follows:

                                    AGREEMENT

1.       Assignment of Assets. Attached hereto is Exhibit E. Exhibit E sets
         forth additional Category III Assets that were intended to be and
         hereby are included in Exhibit A, effective as of the date of the
         Agreement. DuPont will execute any other or further documents
         reasonably deemed necessary to reflect the transfer of the assets set
         forth in Exhibit E to ImaRx in accordance with the terms of the
         Agreement.

2.       License of Assets. Attached hereto is Exhibit F. Exhibit F sets forth
         additional Category II Assets that were intended to be and hereby are
         included in Exhibit B, effective as of the date of the Agreement. The
         Assets set forth in Exhibit F are subject to the license terms of
         Paragraph 4 of the Agreement, effective as of the date of the
         Agreement.

3.       No Warranty. DuPont believes that it has not assigned, conveyed,
         licensed or otherwise transferred any interest in any asset listed on
         Exhibit E to any other person or entity. DuPont believes that it has
         not licensed or otherwise transferred any interest in any asset listed
         on Exhibit F that would conflict with or be contrary to the exclusive
         license to ImaRx as provided in Paragraph 4 of the Agreement.
         Notwithstanding anything to the contrary, DuPont makes no warranty,
         express or implied, regarding the assets listed on Exhibit E and
         specifically disclaims any responsibility for any action or inaction
         with respect to the assets, including action or inaction with regard to
         the prosecution of any patents or any other protection of any
         intellectual property embodied or reflected in Exhibit E and Exhibit F
         during the period from the date of the Agreement to the date of this
         Amendment.

                                      -1-

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4.       Continued Effect. Except as amended hereby, the Agreement remains in
         full force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be duly
executed as of 31 the day and year first above written.

DUPONT CONTRAST IMAGING INC,            IMARX THERAPEUTICS, INC.,
a Delaware general partnership          an Arizona corporation

By:  /s/ Nicholas L. Teti               By:   /s/ Evan C. Unger
     -------------------------                ------------------
      Nicholas L. Teti                        Dr. Evan Unger
Its:                                    Its:  President
     -------------------------                ------------------

                                      -2-<PAGE>
                                                                   Exhibit 10.13

        SECOND AMENDMENT TO ASSIGNMENT, ASSUMPTION AND LICENSE AGREEMENT

      THIS AMENDMENT to the Assignment, Assumption and License Agreement dated
as of October 7, 1999 (as amended by the amendment dated July 31, 2000,
hereinafter collectively the "Agreement") by and between IMARX, LLC, an Arizona
limited liability company ("Purchaser") and IMARX PHARMACEUTICAL CORP., an
Arizona corporation ("Seller") is entered into and effective April 1, 2002 by
and between IMARX THERAPEUTICS, INC., successor in interest to Purchaser
("ImaRx") and Bristol-Myers Squibb Medical Imaging, Inc. ("BMS"), successor in
interest to Seller. Capitalized terms used but not otherwise defined herein have
the meanings assigned to them in the Agreement.

                                    RECITALS

      A. Purchaser and Seller entered into the Agreement as of October 7, 1999.
Thereafter, Seller was merged into DuPont Contrast Imaging, Inc.

      B. DuPont Contrast Imaging, Inc. was acquired by Bristol-Myers Squibb
Company on October 1, 2001 and the name of DuPont Contrast Imaging, Inc. was
changed to Bristol-Myers Squibb Medical Imaging, Inc.

      C. The parties now wish to amend Exhibit A and Exhibit B of the Agreement
to delete certain Category II Assets and to provide for additional Category III
Assets.

      NOW, THEREFORE, in consideration of the foregoing premises and of the
agreements and covenants set forth in the Agreement, the parties agree as
follows.

                                    AGREEMENT

      1. Assignment of Assets. Attached hereto is Attachment A. The parties
agree that the assets set forth in Attachment A are Category III Assets, and
Exhibit A is hereby amended to include the assets set forth in Attachment A. BMS
will execute any other or further documents reasonably deemed necessary to
reflect the transfer and assignment of the assets set forth in Attachment A to
ImaRx in accordance with the terms of the Agreement. Exhibit B is hereby amended
to delete the assets set forth in Attachment A.

      2. ImaRx shall have no obligation to prosecute or maintain any asset in
Attachment A either within CEDUI or outside CEDUI, provided however, that prior
to abandoning any asset in Attachment A, ImaRx shall give BMS at least 15
business days written notice of its intention to do so. Upon notice by BMS that
it wishes to acquire any such asset from ImaRx, ImaRx will assign the asset to
BMS, transfer any files or other documents relating to the asset to BMS, and BMS
will thereafter be solely responsible for prosecution or maintenance of the
asset, including

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BMS-ImaRx                             -2-
Second Amendment to Assignment, Assumption and License Agreement

all costs associated therewith. Any such asset assigned to BMS shall be a
Category II Asset subject to the license set forth in Section 4 of the
Agreement, and BMS shall only have rights under such asset within the CEDUI
field of use.

      3. The second sentence of Section 4 of the Agreement is hereby deleted and
replaced by the following:

   Seller also grants to Purchaser the right to file and prosecute divisional,
   continuation and continuation-in-part applications for patent claims relating
   solely to fields of use outside of the CEDUI field of use arising from patent
   applications included within Category II Assets, provided that Purchaser will
   be solely responsible for all costs and expenses incurred in connection with
   such filing and prosecution and further provided that Purchaser will have no
   right to practice, transfer, license, or otherwise exploit any patents
   issuing from such applications within CEDUI. Purchaser shall provide notice
   to the Seller of the filing of any such patent application, the filing date
   and the Category II patent(s) or patent application(s) to which such patent
   application claims priority and identify the assignee of such patent
   application. Where possible, Purchaser shall be the assignee of such patent
   applications (and patents issuing thereon), unless such assignment will
   adversely effect the patent rights involved (for example, in the case of a
   terminal disclaimer). Where Purchaser is the assignee, such patent
   applications (and patents issuing thereon) shall be Category III Assets,
   subject to the license set forth in Section 5. Where Seller is the assignee,
   such patent applications (and patents issuing thereon) shall be Category II
   Assets, subject to the foregoing provisions of this Section 4.

      4. All applications for patents filed by ImaRx as of the date of this
Amendment pursuant to Section 4 of the Agreement which are Category III assets
are identified in Attachment C hereof.

      5. No Warranty. BMS believes that it has not assigned, conveyed, licensed
or otherwise transferred any interest in any asset listed on Attachment A to any
other person or entity. Notwithstanding anything to the contrary, BMS makes no
warranty, express or implied, regarding the assets listed on Attachment A and
specifically disclaims any responsibility for any action or inaction regarding
the prosecution of any patents or any other protection of any intellectual
property embodied or reflected in Attachment A during the period from the date
of the Agreement to the date of this Amendment.

      6. Attachment B. Attached hereto is Attachment B. The assets set forth in
Attachment B are Category II assets. ImaRx agrees to be responsible for the
prosecution and maintenance of the patents and patent applications set forth in
Attachment B, including all costs associated therewith. In the event that ImaRx
wants to abandon any patent or patent application set forth in Attachment B,
ImaRx shall provide BMS at least 15 business days prior written notice of its
intention to do so. BMS shall then have the right to assume responsibility for
the prosecution and maintenance of such patent or patent application and the
costs associated therewith. Upon request

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BMS-ImaRx                             -3-
Second Amendment to Assignment, Assumption and License Agreement

by BMS, ImaRx will transfer any files or other documents relating to such patent
or patent application and otherwise cooperate with BMS to enable BMS to assume
responsibility for such patent or patent application.

      7. Section 5. The following is hereby added to the end of Section 5 of the
Agreement:

   Purchaser also grants to Seller the right to file and prosecute divisional,
   continuation and continuation-in-part applications for patent claims relating
   solely to the CEDUI field of use arising from patent applications included
   within Category III Assets, provided that Seller will be solely responsible
   for all costs and expenses incurred in connection with such filing and
   prosecution and further provided that Seller will have no right to practice,
   transfer, license, or otherwise exploit any patents issuing from such
   applications outside of the CEDUI field of use. Seller shall provide notice
   to the Purchaser of the filing of any such patent application, the filing
   date and the Category III patent(s) or patent application(s) to which such
   patent application claims priority and identify the assignee of such patent
   application. Where possible, Seller shall be the assignee of such patent
   applications (and patents issuing thereon), unless such assignment will
   adversely effect the patent rights involved (for example, in the case of a
   terminal disclaimer). Where Seller is the assignee, such patent applications
   (and patents issuing thereon) shall be Category II Assets, subject to the
   license set forth in Section 4. Where Purchaser is the assignee, such patent
   applications (and patents issuing thereon) shall be Category III Assets,
   subject to the foregoing provisions of this Section 5.

      8. Continued Effect. Except as amended hereby, the Agreement remains in
full force and effect.

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

BRISTOL-MYERS SQUIBB                    IMARX THERAPEUTICS, INC.
MEDICAL IMAGING, INC.

By:   /s/ illegible                     By:   /s/ illegible
      -----------------------------           ----------------------------------

Its:  President                         Its:  Sr. Director, Business Development
      -----------------------------           ----------------------------------

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