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                                                                   EXHIBIT 10.11

                  ASSIGNMENT, ASSUMPTION AND LICENSE AGREEMENT

         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"). Capitalized terms used but not otherwise defined herein have the
meanings assigned to them in the Technology Agreements (as defined below).

                                    RECITALS

         A. Seller is engaged in the research and development of pharmaceutical
products. Among other assets, Seller owns certain patents and patent
applications in the field of ultrasound diagnostic imaging. Seller has
previously assigned and/or licensed certain of its patents and patent
applications to DuPont Pharmaceuticals Company ("DuPont") pursuant to the
Assignment and License Agreement dated October 23, 1995 and the License and
Marketing Agreement dated October 23, 1995, and amendments thereto (hereinafter
collectively referred to as the "Technology Agreements").

         B. DuPont has made an offer to acquire the stock of Seller, provided
that Seller divests itself of certain assets and liabilities. The parties
anticipate that Seller will be merged into a subsidiary of DuPont (the "Merger")
pursuant to an Agreement and Plan of Merger (the "Acquisition Agreement").

         C. Purchaser will assume all liabilities of Seller other than those
liabilities specifically retained by Seller and accepted by DuPont in the
Acquisition Agreement (the "Assumed Liabilities"). Purchaser wishes to acquire
certain assets of Seller (including the "Physical Assets and Receivables" and
the "Category III Assets") identified on Exhibit A. Seller wishes to license the
Category III Assets back from Purchaser for use within the field of contrast
enhancement of diagnostic ultrasound imaging, but specifically excluding
targeted and tissue specific diagnostic ultrasound products. This field of use
is referred to herein as "CEDUI."

         D. Purchaser wishes to license from Seller certain assets to be
acquired by DuPont in connection with the Acquisition Agreement (the "Category
II Assets") identified on Exhibit B for use outside of CEDUI.

         E. Seller wishes to secure from Purchaser a right of first negotiation
with respect to new products developed by Purchaser in the fields of thrombus
imaging and sonothrombolysis.

         F. The parties wish to agree on certain procedures and responsibilities
for addressing certain claims of infringement that may arise from Seller's
practice of its technology.

         G. The execution and delivery of this Agreement by Purchaser is a
condition to the obligations of Seller to consummate the transactions
contemplated by the Acquisition Agreement.

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                                    AGREEMENT

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

1.       Assignment of Assets.


         a.       Seller hereby grants, conveys, sells, transfers and assigns to
                  Purchaser, free and clear of all debts, obligations, liens and
                  encumbrances (other than the Assumed Liabilities, as that term
                  is defined below) all of the assets described on Exhibit A
                  hereto; provided, however, that the Category III Assets shall
                  not include any Assets to be acquired by DuPont in the Merger.

         b.       Seller hereby assigns to Purchaser its rights under the
                  Assigned Patents, as that term is defined in the Technology
                  Agreements, which rights are fully set forth and described in
                  Section 3 of the Assignment and License Agreement dated
                  October 23, 1995. Purchaser's license rights granted therein
                  will survive any termination, cancellation, or modification of
                  the Assignment and License Agreement by Seller.

2.       Assignment of Name. Effective as of the date of Closing pursuant to the
         Acquisition Agreement, Seller hereby assigns the name "ImaRx
         Pharmaceuticals" along with any variations thereof to Purchaser along
         with the goodwill associated with the Category III Assets. Seller will
         execute any additional documents necessary to transfer the name to
         Purchaser.

3.       Assumption of Liabilities. Seller hereby assigns to Purchaser, and
         Purchaser hereby assumes and agrees to pay, perform and discharge, and
         to indemnify Seller against and hold it harmless from all of the
         liabilities and obligations of Seller accrued or arising before the
         Closing (as that term is described in the Acquisition Agreement),
         including without limitation those Liabilities set forth on Exhibit D
         hereto (the "Assumed Liabilities"); provided, however, that the Assumed
         Liabilities shall not include any liabilities or obligations to be
         assumed by DuPont in the Merger as provided in the Acquisition
         Agreement.

4.       License by Seller. Seller hereby grants to Purchaser an exclusive,
         transferable license to the Category II Assets, with right to
         sublicense, to make, have made, import, use, and sell product derived
         from the Category II Assets, worldwide, for every field of use outside
         of CEDUI. Seller also grants to Purchaser the right to file and
         prosecute divisional applications for patent claims relating solely to
         fields of use outside of CEDUI 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. Seller
         expressly retains all rights to the Category II Assets within CEDUI,
         including, without limitation, all rights relating to the product
         Definity(R), all related products (including, without limitation,
         MRX-421A1 and MRX-132), all back-up products, next-generation products,
         and improvements thereto.

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5.       License by Purchaser. Upon assignment of the Category III Assets,
         Purchaser grants to Seller an exclusive, transferable license to the
         Category III Assets, with right to sublicense, to make, have made,
         import, use, and sell products derived from the Category III Assets,
         worldwide, within CEDUI. Purchaser expressly retains all rights to the
         Category III Assets outside CEDUI.

6.       Seller's Right of First Negotiation to Purchaser's Products. If
         Purchaser develops products or technology in the area of thrombus
         imaging or sonothrombolysis, (collectively, "New Product"), Purchaser
         will offer to Seller an exclusive license to the New Product for
         development and commercialization before offering the New Product to
         any third party for license. In connection therewith, Purchaser will
         provide Seller with all relevant information requested by Seller and
         reasonably available to Purchaser concerning the New Product. Seller
         will then have ninety (90) days within which to make an offer for the
         New Product. If Seller makes such an offer, the parties will negotiate
         promptly and in good faith to arrive at an agreement. If the parties
         fail to reach such an agreement within a reasonable period, Purchaser
         may assign, license, or otherwise transfer rights in the New Product to
         a third party, but only on terms that are, on balance, not less
         favorable to Purchaser than the last written offer of Seller, as
         reasonably determined by Purchaser, or may pursue commercial
         development of the New Product on its own, at Purchaser's election.

7.       Representations and Warranties.

         a.       By Seller. Seller represents and warrants as follows:

                  (i)      Seller is the sole owner of the Category II Assets
                           and Category III Assets and, subject to any limited
                           rights that the U.S. government might have, has the
                           legal authority to assign the Category III Assets and
                           to license the Category II Assets to Purchaser and
                           otherwise to enter into and perform all of its
                           obligations set forth herein;

                  (ii)     all corporate and other formalities necessary to
                           authorize execution, delivery and performance of this
                           Agreement (and all other documents executed and
                           delivered in connection herewith) on behalf of Seller
                           have been taken; and

         Seller makes no other warranties, express or implied, except as
expressly set forth in this Agreement. In particular, and without limitation,
Seller makes no implied or express warranties of noninfringement or validity or
any other representation or warranty whatsoever regarding Patents or Product.

         b.       By Purchaser. Purchaser represents and warrants as follows:


                  (i)      Purchaser has the legal authority to accept the
                           assignment of Category III Assets and the license to
                           Category II Assets granted hereunder and otherwise to
                           perform all of its obligations set forth herein;

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                  (ii)     all LLC and other formalities necessary to authorize
                           execution, delivery and performance of this Agreement
                           (and all other documents executed and delivered in
                           connection herewith) on behalf of Purchaser have been
                           taken.

Purchaser makes no other warranties, express or implied, except as expressly set
forth in this Agreement. In particular, and without limitation, Purchaser makes
no implied or express warranties of noninfringement or validity or any other
representation or warranty whatsoever regarding Patents or Product.

8.       Intellectual Property Protection.

         a.       Claim of Infringement. If Purchaser discovers that a third
                  party claims that practice of the Category II Assets infringes
                  a patent or other intellectual property right of such third
                  party, then Purchaser will promptly so notify Seller and
                  Seller shall have sole authority to defend against or settle
                  any such claim of infringement, provided that no settlement
                  will impair Purchaser's license granted by Section 4 above. If
                  Seller discovers that a third party claims that practice of
                  the Category III Assets infringes a patent or other
                  intellectual property right of such third party, then Seller
                  will promptly so notify Purchaser and Purchaser shall have
                  sole authority to defend against or settle any such claim of
                  infringement, provided that no settlement will impair Seller's
                  license granted by Section 5 above.

         b.       Infringement of Patents. If either party becomes aware that a
                  third party is or may be infringing the Patents, it shall
                  promptly so notify the other party. If the infringement
                  related to Category II Assets, Seller shall have authority to
                  pursue a claim for infringement. If Seller fails to resolve
                  such infringement or institute an infringement action against
                  the third party within one hundred twenty (120) days after
                  Seller becomes aware of the infringement, Seller will assign
                  its rights to pursue the infringement to Purchaser. If there
                  is infringement related to Category III Assets, Purchaser
                  shall have authority to pursue a claim for infringement. If
                  Purchaser fails to resolve such infringement or institute an
                  infringement action against the third party within one hundred
                  twenty (120) days after Purchaser becomes aware of the
                  infringement, then Purchaser shall assign its rights to pursue
                  the infringement to Seller.

9.       Claim of Infringement of Sonus Patents. Notwithstanding anything to the
         contrary contained in Section 8 above, the provisions of this Section 9
         will apply to and govern any claim asserted (whether by litigation or
         otherwise) by Sonus Pharmaceuticals, Inc. and/or its licensees or
         assignees (collectively, "Sonus") within five years of the date of this
         Agreement that Seller's manufacture or sale of the product known as
         Definity(R) infringes a patent or other intellectual property right of
         Sonus (a "Sonus infringement claim"). If Seller receives a Sonus
         infringement claim, it will promptly so notify Purchaser, and the
         parties will proceed as follows:

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         a.       Seller will keep Purchaser informed of developments relevant
                  to the Sonus claim and will consider Purchaser's
                  recommendations for proceeding, although Seller will have the
                  final authority;

         b.       Seller will use all commercially reasonable efforts to defeat
                  or resolve a Sonus claim, including but not limited to cross
                  licensing its diagnostic technology to Sonus;

         c.       Purchaser will use all commercially reasonable efforts in
                  cooperation with Seller and in support of Seller's efforts,
                  including the commitment of all reasonable amounts of Dr. Evan
                  Unger's time, subject to reimbursement by Seller of
                  Purchaser's out of pocket costs (which will not include the
                  value of Dr. Unger's time);

         d.       At Seller's election, if these commercially reasonable efforts
                  fail to resolve the Sonus claim and Seller believes it is at
                  substantial risk of losing the ability to manufacture or sell
                  Definity(R) in a commercially significant geographic market,
                  Purchaser will grant to Seller a transferable covenant not to
                  sue Sonus for infringement of Purchaser's Category III assets
                  to the extent necessary to allow Sonus to manufacture and sell
                  its therapeutic products, provided that Seller receives a
                  reciprocal covenant from Sonus, which Seller will then
                  transfer to Purchaser;

         e.       The covenant referenced in Paragraph 9.d above will be drawn
                  as narrowly as possible to allow Sonus to manufacture and sell
                  Sonus's therapeutic products, and will not be construed as a
                  license to allow Sonus to manufacture or sell products
                  developed by Purchaser or to grant Sonus and rights in any
                  safety or efficacy data developed by Purchaser relating to
                  those products; and

         f.       If Seller directs Purchaser to provide a covenant pursuant to
                  Paragraph 9.d, Seller will pay Purchaser the sum of $1.5
                  million in partial compensation for Purchaser's delivery of
                  the covenant.

10.      Indemnification.

         a.       Seller shall indemnify, defend, and hold Purchaser harmless
                  from any and all claims, demands, lawsuits, and associated
                  costs and expenses, including reasonable attorneys' fees and
                  cost of settlement, arising out of Seller's manufacture,
                  promotion, marketing, and sale of products derived from or
                  based on Category III Assets; provided, however, that Seller
                  shall not be obligated to indemnify, defend, and hold
                  Purchaser harmless where the claim, demand, lawsuit, and
                  associated costs and expenses, including reasonable attorneys'
                  fees and cost of settlement arises out of the breach of this
                  Agreement by Purchaser and further provided that Purchaser
                  promptly notifies Seller upon becoming aware of any such
                  claims. Seller shall have the right to conduct the defense of
                  any such claim but if Seller fails after reasonable notice
                  from Purchaser to conduct such defense, Purchaser shall have
                  the right to do so and Seller will reimburse

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                  Purchaser for all reasonable costs and expenses of defending
                  the action, including attorneys' fees and costs of settlement.

         b.       Purchaser shall indemnify, defend, and hold Seller harmless
                  from any and all claims, demands, lawsuits, and associated
                  costs and expenses, including reasonable attorneys' fees and
                  cost of settlement, arising out of Purchaser's manufacture,
                  promotion, marketing, and sale of products derived from or
                  based on Category II Assets; provided however, that Purchaser
                  shall not be obligated to indemnify, defend, and hold Seller
                  harmless where the claim, demand, lawsuit, and associated
                  costs and expenses, including reasonable attorneys' fees and
                  cost of settlement arises out of the breach of this Agreement
                  by Seller and further provided that Seller promptly notifies
                  Purchaser upon becoming aware of any such claims. Purchaser
                  shall have the right to conduct the defense of any such claim
                  but if Purchaser fails after reasonable notice from Seller to
                  conduct such defense, Seller shall have the right to do so and
                  Purchaser will reimburse Seller for all reasonable costs and
                  expenses of defending the action, including attorneys' fees
                  and costs of settlement.

11.      Rights to Improvements in Product or Manufacturing. All assignments and
         licenses hereunder include such rights to improvements as Seller has
         received or is entitled to receive from DuPont pursuant to Section 5 of
         the Assignment and License Agreement dated October 23, 1995, through
         the date of the Closing of the Acquisition Agreement, to the extent
         that such improvements apply outside the field of CEDUI.

12.      Maintenance and Prosecution of Patents

         a.       Seller may elect not to prosecute or maintain a patent within
                  the Category II Assets if it reasonably concludes that such
                  patent has no significant value to Seller within the field of
                  CEDUI. In that event, it will so notify Purchaser. Purchaser
                  will, within ninety (90) days of receipt of such notice,
                  notify Seller whether it wishes to acquire the patent from
                  Seller. During this ninety (90) day period, Seller will take
                  any action necessary to continue to prosecute or maintain the
                  patent. Purchaser will reimburse Seller for its out-of-pocket
                  costs incurred in such actions. Upon notice by Purchaser that
                  it wishes to acquire the patent from Seller, Seller will
                  assign the patent to Purchaser, transfer any files or other
                  documents relating to the patent to Purchaser, and Purchaser
                  will thereafter be solely responsible for prosecution or
                  maintenance of the Patent, including all costs associated
                  therewith. Seller agrees to execute any additional documents
                  necessary to perfect Purchaser's rights to the patent.
                  Purchaser agrees that,

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

<TABLE>
<CAPTION>
<S>                                                          <C>
IMARX PHARMACEUTICAL CORP.,                                  IMARX LLC,
an Arizona corporation                                       an Arizona limited liability company
By:  /s/ Evan Unger                                          By:     /s/ Evan Unger
     -------------------------------------                        -------------------------------------
Dr. Evan Unger                                               Dr. Evan Unger
Its:    President                                            Its:    Manager
     -------------------------------------                        -------------------------------------
</TABLE>

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