SONUS PHARMACEUTICALS INC
8-K, 1999-10-14
IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES
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<PAGE>   1
                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM 8-K


                                 CURRENT REPORT


                       PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934


       Date of Report (Date of earliest event reported) September 28, 1999



                           SONUS PHARMACEUTICALS, INC.
             (Exact name of Registrant as specified in its charter)


                 Delaware                0-26866                95-4343413
     ----------------------------      ------------         ------------------
     (State or other jurisdiction      (Commission            (IRS Employer
            of incorporation)          File Number)         Identification No)


                22026 20th Avenue S.E., Bothell, Washington   98021
               -------------------------------------------- ---------
               (Address of principal executive offices)     (Zip Code)


        Registrant's telephone number, including area code (425) 487-9500


                                 Not Applicable
                                 --------------
          (Former name or former address, if changed since last report)


                                   Page 1 of 4
                             Exhibit Index on Page 4

<PAGE>   2
ITEMS 1 THROUGH 4, 6, 8 AND 9 ARE NOT APPLICABLE.

ITEM 5. ACQUISITION OR DISPOSITION OF ASSETS

             The license agreement between SONUS Pharmaceuticals, Inc. and
Nycomed Imaging AS dated August 31, 1999 became effective on September 28, 1999.
The text of which is attached hereto as Exhibit 10.36.

             Reference is made to the press release issued to the public by the
registrant on September 29, 1999, the text of which is attached hereto as
Exhibit 99.1, for a description of the events reported pursuant to this Form
8-K.

ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS

        (a)  Financial Statements

             Not Applicable

        (b)  Pro Forma Financial Information

             Not Applicable

        (c)  Exhibits


<TABLE>
<CAPTION>
         EXHIBIT NO.      DESCRIPTION
         -----------      -----------
<S>                       <C>
         10.36            License Agreement by and between Nycomed Amersham AS
                          and SONUS Pharmaceuticals, Inc. dated August 31, 1999.

         99.1             Press Release dated September 29, 1999.
</TABLE>



                                       2
<PAGE>   3
                                    SIGNATURE

             Pursuant to the requirements of the Securities Exchange Act of
1934, the Registrant has duly caused this report to be signed on its behalf by
the undersigned thereunto duly authorized.

                                       SONUS PHARMACEUTICALS, INC.



Date:  October 12, 1999                By: /s/ Gregory Sessler
                                           -------------------------------------
                                           Gregory Sessler
                                           Chief Financial Officer



                                       3
<PAGE>   4
                                  EXHIBIT INDEX



<TABLE>
<CAPTION>
EXHIBIT NO.           DESCRIPTION
- -----------           -----------
<S>                   <C>
10.36                 License Agreement by and between Nycomed Amersham AS and
                      SONUS Pharmaceuticals, Inc. dated August 31, 1999.

99.1                  Press Release dated September 29, 1999.
</TABLE>



                                       4

<PAGE>   1
                                                                   Exhibit 10.36


                                LICENSE AGREEMENT

          This License Agreement ("Agreement") dated as of August 31, 1999, is
entered into by and between Nycomed Imaging AS, a Norwegian corporation with
principal offices at Nycoveien 1-2, Oslo ("Nycomed") and Sonus Pharmaceuticals,
Inc., a Delaware corporation with principal offices at 22026 20th Avenue, S.E.,
Suite 102, Bothell, Washington 98021 ("Sonus").

                                    RECITALS

          WHEREAS, Nycomed has developed and holds patents and patent
applications on ultrasound contrast agents, and

          WHEREAS, Sonus has developed and holds patents and patent applications
on ultrasound contrast agents,

          WHEREAS, Nycomed desires to obtain the rights to manufacture, develop,
use, sell, offer to sell, and import Non-perfluoropentane Ultrasound Products
(such term subsequently defined) covered by any patents and applications held by
Sonus relating to ultrasound contrast agents, including the right to sublicense,
develop, have made, developed, used or sold such products, alone or in
combination with other products, with Third Parties (such term subsequently
defined), and

          WHEREAS, Sonus desires to obtain certain license rights under Nycomed
patents and applications on Perfluoropentane Ultrasound Products (such term
subsequently defined),

          NOW THEREFORE, in consideration of the premises and the faithful
performance of the mutual covenants hereinafter set forth, the parties hereto
hereby agree as follows:

1.    DEFINITIONS

      As used in this Agreement, the following defined terms shall have the
      respective meanings set forth below:



[*] Confidential portions omitted
and filed separately with Commission.



                                      -1-
<PAGE>   2
1.1   "Perfluoropentane Ultrasound Products" shall mean (i) an ultrasound
      contrast agent constituted as EchoGen(R) is presently constituted and
      described in the pending application for U.S. Food and Drug Administration
      approval of same, together with such modification thereto as may be made
      in connection with such application so long as any such modified product
      contains * (hereafter, "EchoGen"), (ii) an ultrasound contrast agent
      constituted as SonoGen (a/k/a QW 7437) is presently constituted, together
      with modifications thereto so long as any such modified product contains *
      (hereafter, "SonoGen"), and (iii) any ultrasound contrast agent developed
      by Sonus that contains *. Provided always that "Perfluoropentane
      Ultrasound Products" excludes any ultrasound contrast agent that contains
      any *. The current formulations of EchoGen and SonoGen shall be deemed
      Perfluoropentane Ultrasound Products notwithstanding the immediately
      preceding sentence.

1.2   "Non-perfluoropentane Ultrasound Products" shall mean all ultrasound
      contrast agents not within the definition of Perfluoropentane Ultrasound
      Products of paragraph 1.1 above. Provided always that
      "Non-perfluoropentane Ultrasound Products" excludes any ultrasound
      contrast agent that contains perfluoropentane.

1.3   "Sonus Patents" shall mean all patents owned or controlled by Sonus or its
      Current Affiliates pertaining to Non-perfluoropentane Ultrasound Products
      that (i) have issued on or before the day of the Closing, (ii) issue from
      any application that was filed before the day of the Closing, (iii) issue
      from any application that directly or through other applications claims
      priority from any application that was filed prior to the day of the
      Closing, and/or (iv) are listed in Appendix 1.3. "Sonus Patents" shall
      also include any patent application owned or controlled by Sonus or its
      Current Affiliates that (a) is published for opposition on or before the
      day of the Closing or after the day of the Closing and during the Term of
      this Agreement, and (b) would qualify as a Sonus Patent under clauses (i)
      through (iii) of this paragraph 1.3 above if it issued as a patent on the
      date it is published for opposition.

1.4   "Nycomed Patents" shall mean all patents owned or controlled by Nycomed or
      its Current Affiliates pertaining to Perfluoropentane Ultrasound Products
      that (i) have issued on or before the day of the Closing, (ii) issue from
      an application that was filed prior to the day of the Closing, (iii) issue
      from any application that directly or through other applications claims
      priority from any application that was filed prior to



[*] Confidential portions omitted
and filed separately with Commission.



                                      -2-
<PAGE>   3
      the day of the Closing, and/or (iv) are listed in Appendix 1.4. "Nycomed
      Patents" shall also include any patent application owned or controlled by
      Nycomed or its Current Affiliates that (a) is published for opposition on
      or before the day of the Closing or after the day of the Closing and
      during the Term of this Agreement, and (b) would qualify as a Nycomed
      Patent under clauses (i) through (iii) of this paragraph 1.4 above if it
      issued as a patent on the date it is published for opposition.

1.5   "Affiliate" means any entity which controls, is controlled by, or is under
      common control with another entity. An entity is deemed to be in control
      of another entity (controlled entity) if such company directly or
      indirectly owns 50% or more in nominal value of the issued equity share
      capital of such other company, or 50% or more of the shares entitled to
      vote upon the election of:

      (i)   the directors,

      (ii)  persons performing functions similar to those performed by directors
            or

      (iii) persons otherwise having the right to elect or appoint (a) directors
            having the majority vote of the Board of Directors, or (b) other
            persons having the majority vote of the highest and most
            authoritative directive body of such other company.

      Provided that Nihon MediPhysics shall not qualify as an Affiliate of
      Nycomed for purposes of this Agreement (but, if Nihon MediPhysics
      manufactures, uses, sells, offers for sale, or imports ultrasound contrast
      agents under license from Nycomed, it shall be treated as if it were an
      Affiliate of Nycomed for purposes of calculating any royalties due under
      this Agreement with respect to such ultrasound contrast agents). "Current
      Affiliates" shall mean those entities that are Affiliates of a party as of
      the day of the Closing for so long as such entities continue to satisfy
      the definition of "Affiliates" in this paragraph 1.5 above.

 1.6  "Pacific Rim Territory" shall mean Japan, Taiwan, China, South Korea,
      Hong Kong, Thailand, Indonesia, Singapore, Malaysia, and the
      Philippines.

1.7   "General Territory" shall mean all countries other than those in the
      Pacific Rim Territory.


[*] Confidential portions omitted
and filed separately with Commission.



                                      -3-
<PAGE>   4
1.8   "Net Sales" shall mean the gross revenues recognized by a party to this
      Agreement or its Affiliates (including revenues recognized from
      distributors, agents, or licensees), less sales, use, value-added or other
      similar taxes, returns, and actual discounts granted, on account of the
      sale or other disposition of any ultrasound contrast agents practicing any
      claim of the other party's Patents (as defined in paragraphs 1.3 and 1.4
      above), i.e., the Sonus Patents in the case of Nycomed and its Affiliates
      and the Nycomed Patents in the case of Sonus and its Affiliates. For
      purposes of calculating royalties payable to Sonus pursuant to paragraph
      5.5 below, "Net Sales" shall also include gross revenues recognized by
      Mallinckrodt or Molecular Biosystems and their Affiliates, less the
      foregoing taxes, returns, and discounts, on account of such sale or other
      disposition. For purposes of paragraph 26.3 below, "Net Sales" means gross
      revenues recognized by the Third Party, less the foregoing taxes, returns,
      and discounts, on account of such sale or other disposition. No unit of
      any product shall be subject to more than one sale or disposition that
      qualifies as a Net Sale, regardless of the number or form of sales or
      dispositions of such unit; the first sale or other disposition by Nycomed,
      Sonus, Mallinckrodt, Molecular Biosystems, or their respective Affiliates
      to an entity other than an entity which is controlled by or controls the
      entity making the sale or disposition shall be used to calculate Net
      Sales. When reference is made to Net Sales in a country or territory, such
      Net Sales shall be deemed to occur in the country or territory in which
      the product is to be used.

1.9   "Quarter" shall mean each three-month calendar quarter during the term of
      this Agreement, provided that the first Quarter shall include any
      remaining portion of the calendar quarter following the day of the Closing
      in addition to the calendar quarter following such portion.
      "Quarterly" shall mean per Quarter.

1.10  "Third Party" shall mean all persons and entities other than Nycomed,
      Sonus, and their respective Affiliates.

1.11  "Mallinckrodt Litigation" shall mean that certain action (and all
      claims made therein) pending in the U.S. District Court for the Western
      District of Washington captioned Sonus Pharmaceuticals, Inc. v.
      Molecular Biosystems, Inc. and Mallinckrodt Medical, Inc., Civil Action
      No. 97-1273R.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -4-
<PAGE>   5
1.12  "Sonus Patent Applications" shall mean all pending patent applications
      owned or controlled by Sonus or its current Affiliates pertaining to
      Non-perfluoropentane Ultrasound Products, including provisionals,
      divisions, continuations, continuations-in-part, extensions, renewals,
      reissues, or reexaminations of any such application, or supplemental
      protection certificate, including but not limited to all applications
      listed in Appendix 1.12.

1.13  "Abbott Agreements" shall mean the following agreements in the form
      attached to Sonus's U.S. Securities and Exchange Commission filings (i)
      that certain agreement dated May 14, 1996, between Sonus and Abbott
      Laboratories, as amended (plus Appendices 1.6 and 1.13, which appendices
      previously have been provided to Nycomed), and (ii) that certain
      International License Agreement dated October 1, 1996, between Sonus and
      Abbott International, Ltd., as amended (plus Appendices 1.7 and 1.16,
      which appendices previously have been provided to Nycomed).

 1.14 "Optison" shall mean (i) an ultrasound contrast agent constituted as
      Optison(R) is presently constituted and described in the application for
      U.S. Food and Drug Administration approval of same, together with such
      modification thereto as may be made in connection with such application so
      long as any such modified product does not contain perfluoropentane, (ii)
      an ultrasound contrast agent constituted as Optison is presently
      constituted and described in any pending application for regulatory
      approval of same, together with such modification thereto as may be made
      in connection with such application so long as any such modified product
      does not contain perfluoropentane, and (iii) any ultrasound contrast agent
      developed and/or sold by Mallinckrodt Inc., Molecular Biosystems Inc., or
      their respective Affiliates to which Nycomed or its Affiliates acquires
      license, co-marketing, co-promotion, or other rights incident to a
      settlement of the Mallinckrodt Litigation under section 5 of this
      Agreement or to any other business relationship between Nycomed and
      Mallinckrodt, Molecular Biosystems, and their respective Affiliates, so
      long as any such product does not contain perfluoropentane.

1.15  "Closing" shall mean the closing of the transactions contemplated by this
      Agreement as provided in paragraph 31.3 of this Agreement.



[*] Confidential portions omitted
and filed separately with Commission.


                                      -5-
<PAGE>   6
2.    LICENSE GRANT

2.1   As of Closing, Sonus grants Nycomed and its Affiliates an exclusive
      license together with the right to sublicense under the Sonus Patents to
      develop, make, have made, use, sell, offer to sell, and import
      Non-perfluoropentane Ultrasound Products in the General Territory. This
      license shall be exclusive even as to Sonus.

2.2   As of Closing, Sonus grants Nycomed and its Affiliates a non-exclusive
      license under the Sonus Patents to develop, make, have made, use, sell,
      offer to sell, and import Non-perfluoropentane Ultrasound Products in the
      Pacific Rim Territory. (Products that Nycomed or its Affiliates develop,
      make, have made, use, sell, offer to sell, or import under the licenses of
      paragraph 2.1 and/or this paragraph 2.2 are referred to in this Agreement
      as "Nycomed Licensed Products.")

2.3   As of Closing, Nycomed grants Sonus and its Affiliates a non-exclusive
      license under the Nycomed Patents to develop, make, have made, use, sell,
      offer to sell, and import Perfluoropentane Ultrasound Products in the
      General Territory and Pacific Rim Territory. (Products that Sonus or its
      Affiliates develop, make, have made, use, sell, offer to sell, or import
      under the license of this paragraph 2.3 are referred to as "Sonus Licensed
      Products.") Sonus shall have the right to sublicense the Nycomed Patents
      as provided in paragraphs 4.3 and 4.4 below, but shall not otherwise have
      the right to sublicense the Nycomed Patents.

 2.4  Sonus warrants that (i) it will not grant, and (ii) with the possible
      exception of the Abbott Agreements it has not granted to any Third Party
      any license under the Sonus Patents to develop, make, have made, use,
      sell, import, or offer for sale Non-perfluoropentane Ultrasound Products
      in the General Territory.

2.5   Each party retains all rights in its patents and patent applications not
      granted to the other party in this Agreement. Notwithstanding anything to
      the contrary herein, the licenses and other rights granted to Nycomed in
      this Agreement under the Sonus Patents shall not detract from the scope of
      the licenses and other rights previously granted to Abbott Laboratories
      and Abbott International, Ltd. (collectively, "Abbott") under the Abbott
      Agreements.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -6-
<PAGE>   7
2.6   In the event that Sonus or its Affiliates develop and desire to make, use,
      sell, offer for sale, or import an ultrasound contrast agent that contains
      perfluoropentane but does not meet the definition of Perfluoropentane
      Ultrasound Products of paragraph 1.1 above (except any such agent that
      contains *), the parties will negotiate in good faith with respect to a
      possible license to Sonus or its Affiliates under the Sonus Patents and
      Nycomed Patents, provided that neither party shall have any obligation to
      enter into any such license if, in its sole and absolute discretion, entry
      into such a license would not be in the party's own business interests.

3.    UP-FRONT FEE AND ROYALTIES

3.1   On the business day following the execution of this Agreement, Nycomed
      shall pay into escrow a license fee of U.S. $10,000,000 to be disbursed to
      Sonus in accordance with the provisions of paragraph 31.2 below. Upon
      satisfaction of the escrow conditions, this payment shall be nonrefundable
      and shall not be creditable against any other amounts due Sonus under this
      Agreement.

3.2   In addition to the payment required under paragraph 3.1 above, Nycomed
      shall incur in favor of Sonus a royalty on Quarterly Net Sales, which
      royalty shall be the larger of:

      (i)   * said Quarterly Net Sales in each such country, provided that in no
            Quarter shall the amount incurred by Nycomed in favor of Sonus *
            that would be incurred by Sonus in favor of Nycomed in accordance
            with paragraph 3.3 below for that country in the Quarter if such
            paragraph 3.3 did not include a cap referring to this paragraph
            3.2(i), or

      (ii)  * of Quarterly Net Sales in the General Territory, * of Quarterly
            Net Sales in the General Territory, and * all additional Quarterly
            Net Sales in the General Territory (except in the Pacific Rim
            Territory, where the rate shall be * on all Net Sales in that
            territory).

      Provided always that the provisions of this paragraph 3.2 shall not apply
      to any sales of Optison in any territory, or any revenues received by
      Nycomed on account of any sales of Optison. Any royalties to which Sonus
      shall be entitled related to the sale of Optison shall be governed
      exclusively by the provisions of section 5 below.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -7-
<PAGE>   8
3.3   Sonus shall incur in favor of Nycomed a royalty on Quarterly Net Sales,
      which royalty for each country shall be * said Net Sales, provided that in
      no Quarter shall the amount incurred by Sonus in favor of Nycomed *
      incurred by Nycomed in favor of Sonus in accordance with paragraph 3.2
      above for that country in the Quarter.

3.4   The incurred royalties shall be calculated Quarterly on a
      country-by-country basis. No later than 30 days after the end of each
      Quarter, each party shall provide the other with a statement of Net Sales
      of its respective Licensed Products in each country, which statement shall
      report on a product-by-product and country-by-country basis showing the
      sales of each product in each country. The net royalty payment due Sonus
      by Nycomed shall then be made within 30 days of the exchange of said
      statements. Examples of the calculation of royalties are provided in
      Appendix 3.4 hereto.

3.5   All royalties for each Quarter shall be independent of royalties for any
      other Quarter and not subject to carry-over or set-off against royalties
      for any other Quarter.

3.6   Nycomed ultrasound contrast agents constituted as those products now
      designated (i) Sonazoid * are constituted shall be deemed Nycomed Licensed
      Products, and sales of such products shall be deemed royalty-bearing Net
      Sales for purposes of paragraph 3.2 under at least the patents listed in
      Appendix 3.6 hereto.

3.7   Sonus ultrasound contrast agents constituted as those products now
      designated (i) EchoGen and (ii) SonoGen are constituted shall be deemed
      Sonus Licensed Products, and sales of such products shall be deemed
      royalty-bearing Net Sales for purposes of paragraph 3.3 under at least the
      patents listed in Appendix 3.7 hereto.

4.    SUBLICENSES, RELEASES, AND PATENT ENFORCEMENT

4.1   For the General Territory, Nycomed shall have the right to sublicense one
      or more Third Parties under the Sonus Patents to make, have made, use,
      sell, import, or offer for sale Non-perfluoropentane Ultrasound Products.

      4.2 For each country of the Pacific Rim Territory, Nycomed shall have the
      right to sublicense one Third Party under the Sonus Patents to make, have
      made, use, sell, import, or offer for sale each Non-perfluoropentane



[*] Confidential portions omitted
and filed separately with Commission.



                                      -8-
<PAGE>   9
      Ultrasound Product. Nycomed may sublicense a different Third Party for
      each such product in each different country of the Pacific Rim Territory
      and substitute its Third Party sublicensees under this paragraph.

4.3   For each country of the Pacific Rim Territory, Sonus shall have the right
      to sublicense one Third Party under the Nycomed Patents to make, have
      made, use, sell, import, or offer for sale each Perfluoropentane
      Ultrasound Product. Sonus may sublicense a different Third Party for each
      such product in each different country of the Pacific Rim Territory and
      substitute its Third Party sublicensees under this paragraph.

4.4   In the General Territory, Sonus shall have the right to sublicense any
      Third Party to, under the Nycomed Patents, make, have made, use, sell,
      import, or offer for sale under license from Sonus of Perfluoropentane
      Ultrasound Products developed by Sonus. Sonus shall be limited to one such
      sublicense per commercial Perfluoropentane Ultrasound Product per country
      in the General Territory. Thus, by way of example only, Sonus may license
      one Third Party to manufacture EchoGen in the United States, another to
      manufacture and distribute SonoGen in the United States, and another to
      manufacture and distribute EchoGen in Brazil, but may not license one
      Third Party to manufacture EchoGen and SonoGen in the United States and
      another to manufacture and distribute SonoGen in the United States. Sonus
      shall provide Nycomed with written notice of any such sublicenses granted.

4.5   No sublicense granted by Nycomed under paragraph 4.1 or 4.2 above shall
      authorize the sublicensee to grant any sublicenses under the Sonus
      Patents. No sublicense granted by Sonus under paragraph 4.3 or 4.4 above
      shall authorize the sublicensee to grant any sublicenses under the Nycomed
      Patents.

4.6   If (i) Nycomed is engaged in negotiations for a license in the General
      Territory under patents or patent applications owned by a Third Party for
      Non-perfluoropentane Ultrasound Products in exchange (in whole or in part)
      for granting said Third Party a sublicense under the Sonus Patents (as
      permitted by paragraph 4.1) for sales in the General Territory, (ii) said
      Third Party *and (iii) said Third Party has the *, then Nycomed shall use
      *, in connection *. Nycomed shall have *, and Nycomed may *. Nycomed shall
      have *. Sonus shall *. Sonus, however, has *. Nycomed shall advise Sonus
      of any such negotiations and consult with Sonus as to the Third Party's
      patents and patent applications at issue. During the



[*] Confidential portions omitted
and filed separately with Commission.



                                      -9-
<PAGE>   10
      course of such negotiations between Nycomed and the Third Party, Sonus
      shall not contact or negotiate with the Third Party concerning licensing
      or sublicensing the Sonus Patents, Nycomed Patents, or the Third Party's
      patents or patent applications without the written consent of Nycomed,
      which Nycomed may grant, withhold, or condition in its sole and absolute
      discretion. The prohibition of the preceding sentence shall not apply to
      communications between Sonus and a Third Party related to litigation that
      is initiated or threatened by the Third Party against Sonus or its
      Affiliates.

4.7   Nycomed shall *, provided that, Nycomed *. If Nycomed receives payments
      from a Third Party in exchange for a sublicense pursuant to paragraph 4.1
      of any Sonus Patents or Nycomed Patents in the General Territory, Nycomed
      shall first deduct from such payments its reasonable and direct out of
      pocket expenses incurred after the day of the Closing to consummate its
      agreement with the Third Party, including any associated attorneys fees,
      and shall then pay Sonus * the balance. The only other benefit to which
      Sonus may be entitled as a result of any such transaction between Nycomed
      and such a Third Party is a license under that Third Party's patents as
      set forth in paragraph 4.6 above, which provisions may or may not apply to
      the transaction between Nycomed and the Third Party depending on the terms
      of said transaction. Sonus shall not be entitled to share in any other
      benefits or consideration realized by Nycomed, including but not limited
      to the value of a license or sublicense that Nycomed obtains under the
      Third Party's patents (including a royalty free cross-license in a
      transaction including licenses under the Sonus Patents), the value of
      marketing rights to the Third Party's products, or the value of any
      settlement of a dispute between Nycomed and the Third Party or their
      respective Affiliates. Sonus acknowledges that Nycomed may, in connection
      with licensing or sublicensing activities under this paragraph 4.7, enter
      into business arrangements with Third Parties in the field of ultrasound
      contrast agents or in other fields, which arrangements may include, by way
      of example and not limitation, co-marketing, co-promotion, joint ventures,
      or other cooperative relationships, or the settlement of other disputes
      between Nycomed and such Third Parties and their respective Affiliates.
      The exclusive consideration due Sonus shall be * the payments received by
      Nycomed (net Nycomed's reasonable and direct out of pocket expenses) as
      set forth above in this paragraph 4.7; Sonus shall be entitled to no other
      participation or consideration in, from, for, or on account of such a
      business relationship between Nycomed and any Third Party and their
      respective Affiliates. Sonus further acknowledges that



[*] Confidential portions omitted
and filed separately with Commission.



                                      -10-
<PAGE>   11
      Nycomed's freedom of action in this regard is paramount to this Agreement.
      Any dispute between Sonus and Nycomed concerning the parties' performance
      under this paragraph 4.7 shall be resolved as set forth in paragraph 26.3
      below. Except as provided by paragraph 26.3 below, Sonus irrevocably binds
      itself to never challenge the form or substance of any such transaction
      entered into by Nycomed and agrees to be bound for the purposes of this
      Agreement to any allocation and characterization of consideration flowing
      to Nycomed thereunder made between Nycomed and any Third Party.

4.8   Nycomed shall have the exclusive right, exclusive even as to Sonus, to sue
      any Third Party for direct infringement, contributory infringement, or
      inducement of infringement of the Sonus Patents, when the Third Party's
      direct infringement, contributory infringement, or inducement of
      infringement relates to the manufacture, use, sale, importation, or offer
      for sale in the General Territory of any ultrasound contrast agent that
      does not contain perfluoropentane. Nycomed shall have sole and absolute
      discretion over whether to bring any claims and complete control of any
      suits or counterclaims it asserts. Nycomed will bear all costs and
      expenses associated with the prosecution of such claims. Sonus agrees to
      cooperate reasonably with Nycomed in connection with such suits or
      counterclaims and will, if requested by Nycomed, join as a co-party to
      Nycomed in any suit or counterclaims Nycomed asserts pursuant to this
      paragraph provided that Nycomed promptly reimburses Sonus for its
      reasonable and direct out of pocket expenses (including attorneys fees)
      that Sonus incurs to undertake such aspects of cooperation as requested by
      Nycomed. Immediately following the Closing, Sonus will provide Nycomed
      with full access to all files, records, and other documents relating to
      the Sonus Patents, giving due protection to privileged information. Any
      proceeds that Nycomed receives from a suit or counterclaim brought under
      this paragraph for infringement of a Sonus Patent shall be divided between
      Nycomed and Sonus as follows: (x) first, Nycomed shall recover its full
      out of pocket expenses incurred after the day of the Closing for that suit
      or counterclaim (including attorneys fees and any reimbursements made to
      Sonus), and (y) second, from any remaining proceeds, Nycomed shall provide
      Sonus with * such excess.

4.9   If Sonus, its Affiliates or their licensees are sued for alleged direct
      infringement, contributory infringement, or inducement of infringement of
      a patent owned by a Third Party, and the alleged infringement involves



[*] Confidential portions omitted
and filed separately with Commission.



                                      -11-
<PAGE>   12
      the manufacture, use, sale, importation, or offering to sell by Sonus, its
      Affiliates or their licensees of Perfluoropentane Ultrasound Products,
      Sonus may request in writing that Nycomed file a claim for infringement of
      the Sonus Patents against that Third Party pursuant to paragraph 4.8
      above, which request shall include (i) identification of the infringing
      products and/or conduct, (ii) identification of the infringed claims of
      the Sonus Patents, and (iii) a full explanation of Sonus's bases for
      concluding that the Third Party is infringing claims of the Sonus Patents.
      Nycomed shall * to evaluate same, during which period Sonus *. If Nycomed
      notifies Sonus in writing that *. Nycomed may *. If Nycomed *. If Nycomed
      declines to pursue a claim for infringement of the Sonus Patents against
      the Third Party *, Sonus shall have the right to sue said Third Party for
      direct infringement, contributory infringement, or inducement of
      infringement of the Sonus Patents, by way of counterclaim or independent
      action. Nycomed agrees to provide Sonus with reasonable cooperation in
      connection with any such infringement suit brought by Sonus, including
      joining as co-plaintiff if requested, provided that Sonus promptly
      reimburses Nycomed for its reasonable and direct out of pocket expenses
      (including attorneys fees) that Nycomed incurs to undertake such aspects
      of cooperation as requested by Sonus. In any suit brought by Sonus against
      a Third Party under the provisions of this paragraph 4.9, Sonus shall
      control the suit, shall bear all costs and expenses associated with the
      prosecution of such suit, and any proceeds that Sonus receives for
      infringement of the Sonus Patents shall be retained by Sonus.

4.10  If Sonus, its Affiliates or their licensees are sued or threatened with
      suit by a Third Party in a lawsuit alleging that Sonus, its Affiliates or
      their licensees are infringing a patent owned by that Third Party by
      developing, making, using, selling, importing, or offering for sale
      Perfluoropentane Ultrasound Products in the General Territory, Sonus may
      *. If Sonus makes such a request to Nycomed, *. If the Third Party agrees
      to *, provided that Nycomed may *. If Nycomed *.

4.11  Nycomed's authority under this Agreement to license or sublicense Third
      Parties under the Sonus Patents (as permitted in paragraphs 4.1 and 4.2)
      also includes the authority to release Third Parties from back damages
      under the Sonus Patents for activities within the scope for which Nycomed
      may grant licenses or sublicenses under the Sonus Patents, regardless of
      whether such back damages accrued from activities before or after the day
      of the Closing. If Nycomed receives any



[*] Confidential portions omitted
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                                      -12-
<PAGE>   13
      payments or royalties from Third Parties for such a release, they shall,
      except as otherwise provided herein, be divided * Nycomed and * Sonus.

4.12  Sonus shall have the exclusive right, exclusive even as to Nycomed, to sue
      any Third Party for direct infringement, contributory infringement, or
      inducement of infringement of the Sonus Patents, when the Third Party's
      direct infringement, contributory infringement, or inducement of
      infringement relates to the manufacture, use, sale, importation, or offer
      for sale of Perfluoropentane Ultrasound Products. Sonus shall have sole
      and absolute discretion over whether to bring any claims and complete
      control of any suits or counterclaims it asserts. Sonus will bear all
      costs and expenses associated with the prosecution of such claims, and
      shall retain any proceeds it receives. Nycomed agrees to cooperate
      reasonably with Sonus in connection with such suits or counterclaims and
      will, if requested by Sonus, join as a co-party to Sonus in any suit or
      counterclaims Sonus asserts pursuant to this paragraph provided that Sonus
      promptly reimburses Nycomed for its reasonable and direct out of pocket
      expenses (including attorneys fees) that Nycomed incurs to undertake such
      aspects of cooperation as requested by Sonus.

4.13  Each party shall have the rights as set forth in this paragraph 4.13 to
      sue any Third Party on account of the manufacture, use, sale, importation,
      or offer for sale of an ultrasound contrast agent that contains
      perfluoropentane but does not meet the definition of Perfluoropentane
      Ultrasound Products in paragraph 1.1 above. Sonus shall have *, and
      Nycomed shall have *.

      (1)   In a case brought by Nycomed under this paragraph 4.13, Nycomed
            shall *. Nycomed *. Sonus agrees to *.

      (2)   In a case brought by Sonus under this paragraph 4.13, Sonus shall *.
            Sonus *. Nycomed agrees to *.

4.14  The provisions of this section 4 (specifically including but not limited
      to paragraph 4.7 above) shall not apply to matters concerning the
      Mallinckrodt Litigation or settlement thereof (including any licenses,
      sublicenses, releases, or transactions incident to or associated with such
      settlement), which matters are and shall be governed exclusively by
      section 5 below.

5.    MALLINCKRODT LITIGATION



[*] Confidential portions omitted
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                                      -13-
<PAGE>   14
5.1   * the Closing and subject to the provisions of this section 5, Nycomed
      shall have sole authority to settle (within the scope of the rights
      granted to Nycomed elsewhere in this Agreement) the Mallinckrodt
      Litigation on its own behalf and on behalf of Sonus at any time, including
      after entry of judgment and on appeal. Sonus acknowledges that such a
      settlement may include, by way of example and not limitation, *. Sonus
      shall subscribe or cause its attorneys to subscribe all papers, pleadings,
      and agreements necessary or desirable to effectuate any such settlement of
      the Mallinckrodt Litigation, including but not limited to *. Subject to
      the below provisions concerning the compensation due Sonus for settlement
      of the Mallinckrodt Litigation and the release of the counterclaims
      asserted against Sonus, Nycomed shall have sole and absolute discretion
      to settle or refrain from settling the Mallinckrodt Litigation and over
      the terms, conditions, and timing of any settlement.

5.2   Absent Sonus's written consent, Nycomed shall not settle the Mallinckrodt
      Litigation without also settling the counterclaims asserted against Sonus
      and obtaining a release of such claims, provided that, Nycomed may, *.

5.3   Absent Sonus's prior written consent, no settlement of the Mallinckrodt
      Litigation shall bind Sonus to make a payment to any party.

5.4   Sonus acknowledges that Nycomed may, in connection with settlement of the
      Mallinckrodt Litigation, enter into business arrangements with
      Mallinckrodt and/or Molecular Biosystems and their respective Affiliates,
      licensees, and sublicensees for Optison or otherwise, which arrangements
      may include, by way of example and not limitation, co-marketing,
      co-promotion, joint ventures, or other cooperative relationships, and
      settlement of other disputes between Nycomed and Mallinckrodt and/or
      Molecular Biosystems and their respective Affiliates, licensees, and
      sublicensees (including but not limited to settlement and release of all
      claims asserted against Nycomed in those certain actions styled
      Mallinckrodt Medical, Inc. and Molecular Biosystems, Inc. v.



[*] Confidential portions omitted
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                                      -14-
<PAGE>   15
      Nycomed Imaging AS, Civil Action No. 97-1732 (PLF/DAR) pending in the U.S.
      District Court for the District of Columbia and Nycomed Inc. v.
      Mallinckrodt Medical, Inc., Civil Action No. 98-1833 (GEB) pending in the
      U.S. District Court for the District of New Jersey). Sonus further
      acknowledges that, incident to or as a result of a settlement of the
      Mallinckrodt Litigation, Nycomed may use its rights under the Sonus
      Patents to reach agreements with Third Parties for licenses or other
      arrangements to secure for itself, Mallinckrodt, and/or Molecular
      Biosystems the freedom to make, use, sell, offer to sell, and import
      Optison in the General Territory, provided that no such settlements or
      other agreements shall confer rights in the Pacific Rim Territory under
      the Sonus Patents to Mallinckrodt, Molecular Biosystems or any Third Party
      except as permitted in, and subject to the limitations of, paragraph 4.2
      above.

5.5   Sonus's consideration for any settlement of the Mallinckrodt Litigation by
      Nycomed (however accomplished, including by dismissal, covenant not to
      sue, and/or license), which settlement may include but is not limited to a
      complete release of all claims asserted by Sonus against Mallinckrodt and
      Molecular Biosystems and the grant of a sublicense under the Sonus Patents
      to Mallinckrodt and Molecular Biosystems for the manufacture, use, sale,
      offer for sale, and importation of Optison in the General Territory, shall
      * wherein Sonus Patents claiming direct or indirect priority from the
      applications for U.S. Patents 5,558,094 or 5,573,751 have issued or been
      published for opposition and are unexpired, (ii) dismissal with prejudice
      of all counterclaims asserted by Molecular Biosystems or Mallinckrodt in
      the Mallinckrodt Litigation, without payment by Sonus or admission of
      liability, and (iii) a grant to Sonus of a royalty-free license or
      covenant not to sue under the patents listed in Appendix 5.5 that are
      owned or controlled by Molecular Biosystems, Mallinckrodt, or their
      Current Affiliates sufficient to provide Sonus, its Affiliates and
      licensees the freedom to make, use, sell, offer to sell, and import
      EchoGen and SonoGen in the General Territory (clauses (i), (ii), and
      (iii), collectively, the "Consideration"). No settlement of the
      Mallinckrodt Litigation or grant of a sublicense under the Sonus Patents
      to Mallinckrodt, Molecular Biosystems or their Affiliates shall be
      concluded unless Sonus receives the Consideration. Other than the
      Consideration, no other or further compensation shall be due Sonus on
      account of the Mallinckrodt Litigation, Nycomed's settlement thereof, any
      business relationship between Nycomed and Mallinckrodt and/or Molecular
      Biosystems and their respective Affiliates, and the grant of



[*] Confidential portions omitted
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                                      -15-
<PAGE>   16
      licenses under the Sonus Patents. Sonus shall be entitled to no other
      participation or consideration in, from, for, or on account of any
      business relationship between Nycomed and Mallinckrodt and/or Molecular
      Biosystems and their respective Affiliates that is entered into as part
      of, incident to, or following settlement of the Mallinckrodt Litigation.
      Provided that it receives the Consideration, Sonus irrevocably binds
      itself to never challenge the form or substance of any agreement of
      settlement of the Mallinckrodt Litigation and agrees to be bound for the
      purposes of this Agreement to any allocation and characterization of
      consideration flowing to Nycomed thereunder.

5.6   Nycomed shall use *. For a period *, Nycomed and Sonus shall *, and
      Nycomed shall *.

5.7   If Nycomed does not settle the Mallinckrodt Litigation * from the day of
      the Closing, Nycomed shall assume sole control over the Mallinckrodt
      Litigation including responsibility for the costs and expenses of the
      litigation incurred thereafter, provided that Sonus shall retain sole
      control (at its own expense) over the defense of the Tort Counterclaims
      (as hereafter defined). "Tort Counterclaims" are all counterclaims
      asserted by Mallinckrodt and Molecular Biosystems in the Mallinckrodt
      Litigation other than the counterclaims seeking declaratory judgment of
      non-infringement, invalidity, and/or unenforceability of the patents
      asserted by Sonus in that litigation. Sonus shall cooperate with Nycomed
      in transferring control of the Mallinckrodt Litigation (other than the
      Tort Counterclaims) to Nycomed, and shall subscribe and execute all papers
      and pleadings necessary or desirable to join or substitute Nycomed as
      plaintiff therein. The provisions of paragraphs 5.1, 5.2, 5.3, 5.4, and
      5.5 above shall continue to apply to any settlement of the Mallinckrodt
      Litigation reached after the * period. The parties agree to cooperate and
      consult with one another in connection with their respective roles in the
      Mallinckrodt Litigation.

5.8   If Nycomed does not settle the Mallinckrodt Litigation (as provided
      above), it may litigate the case (other than the Tort Counterclaims as
      provided in paragraph 5.7 above) and any proceeds that Nycomed recovers
      from the Mallinckrodt Litigation as plaintiff shall be divided between
      Sonus and Nycomed as follows: (a) first, Nycomed shall recover its full
      out of pocket expenses incurred after the day of the Closing for the
      Mallinckrodt Litigation, including attorneys fees, and (b) second, any
      remaining proceeds * between Sonus and Nycomed.



[*] Confidential portions omitted
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                                      -16-
<PAGE>   17
5.9   The provisions of this section 5 shall apply to matters concerning the
      Mallinckrodt Litigation and/or the settlement thereof notwithstanding any
      different or conflicting provisions of this Agreement (specifically
      including but not limited to section 4 above), and shall take precedence
      over same. In all events any sublicense or other rights under the Sonus
      Patents granted to Mallinckrodt or Molecular Biosystems pursuant to this
      section 5 shall be limited to Non-perfluoropentane Ultrasound Products.

6.    SONUS PATENTS AND SONUS PATENT APPLICATIONS

6.1   Sonus shall be responsible for and shall diligently carry out and shall
      bear all costs (including attorney fees) for the preparation, filing,
      prosecution, maintenance, and extensions, if any, of all Sonus Patents and
      Sonus Patent Applications, including the prosecution of any reissue
      application, reexamination proceeding, and interference proceeding. Sonus
      shall send Nycomed Quarterly reports on the status of all Sonus Patents
      and Patent Applications.

6.2   Sonus shall be responsible for the selection and retention of counsel
      subject to Nycomed's approval, such approval not to be unreasonably
      withheld. It shall not be unreasonable for Nycomed to withhold or withdraw
      consent as to any counsel that is, becomes, or threatens to become
      directly adverse to Nycomed or an Affiliate in any inter partes judicial
      or administrative proceeding.

6.3   Sonus shall promptly provide Nycomed with a copy of all correspondence,
      filings and notices of action between Sonus and the pertinent official
      patent office concerning the Sonus Patents and Sonus Patent Applications.
      Sonus shall provide Nycomed with a reasonable opportunity to review and
      advise Sonus on the written or oral response to any official patent office
      action or correspondence or written submission by a Third Party to any
      official patent office concerning the Sonus Patents or Sonus Patent
      Applications. Sonus *. In the case *, Sonus shall *.

6.4   If Sonus and Abbott (to the extent Abbott is entitled to assume
      prosecution as provided in the Abbott Agreements) decide to discontinue
      the prosecution or maintenance of any Sonus Patent or Sonus Patent
      Application (which Sonus may do in its sole and absolute discretion),



[*] Confidential portions omitted
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                                      -17-
<PAGE>   18
      Sonus shall promptly notify Nycomed, supply Nycomed with copies of all
      written communications with the pertinent official patent office, and
      fully cooperate with Nycomed to transfer control of the patent or
      application to Nycomed, including subscribing all papers necessary or
      desirable to effectuate same. In such event, Nycomed may, but does not
      have the obligation to, file or continue prosecution of such application
      or maintain such patent without any liability to Sonus for any acts or
      omissions related thereto. In the case of filing or continuing prosecution
      of an application (including maintenance fees for any patents issuing
      therefrom), such actions shall be at Nycomed's sole expense. Sonus shall
      bear the cost of paying official maintenance fees for those Sonus Patents
      that have issued or been published for opposition as of the day of the
      Closing, and shall promptly reimburse Nycomed for all such costs upon
      notice by Nycomed, and Nycomed shall have the right to set-off
      reimbursements due it from Sonus against any amounts owed by Nycomed to
      Sonus under sections 3, 4, and/or 5 of this Agreement.

6.5   Nycomed may request that Sonus act under paragraph 6.4 above with respect
      to any Sonus Patent Application that Nycomed desires to prosecute itself
      (which request Sonus may honor or reject in its sole discretion, except as
      provided in the following sentence). If Nycomed makes such a request as to
      a Sonus Patent Application that concerns only Non-perfluoropentane
      Ultrasound Products, Sonus shall not unreasonably withhold approval of
      Nycomed's request, and Nycomed shall upon approval of its request by Sonus
      assume all further costs and expenses associated with the prosecution of
      such application.

6.6   If any Sonus Patent Application *, Nycomed shall *. Any agreement between
      Sonus and any entity (other than Abbott) *.

6.7   The handling of the enforcement of the Sonus Patents is governed by
      sections 4 and 5 of this Agreement.

6.8   Sonus hereby agrees that prior to electing to discontinue prosecution of
      any Sonus Patent Application or claims that concern only
      Non-perfluoropentane Ultrasound Products, it shall first consult with
      Nycomed. If Nycomed so requests, Sonus shall continue prosecution of such
      application or claims at Nycomed's expense (including reimbursement of
      Sonus's attorneys fees).



[*] Confidential portions omitted
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                                      -18-
<PAGE>   19
7.    PATENT MARKING

7.1   If requested by any party, insofar as practical, the other party (and any
      sublicensees) shall place, or shall cause the manufacturer to place,
      appropriate patent and/or patent pending markings on an exposed surface of
      each Licensed Product made or sold hereunder or on the packaging for such
      Licensed Product. The content, form, size, location and language used in
      such markings shall be in accordance with the laws and practices of the
      country where such markings are required.

7.2   To the extent permitted by law, Nycomed shall include, in any submission
      to the U.S. Food and Drug Administration for a Nycomed Product which
      includes a listing of Nycomed Patents that cover such product, a listing
      of the appropriate Sonus Patents that also cover such product.

7.3   To the extent permitted by law, Sonus shall include, in any submission to
      the U.S. Food and Drug Administration for a Sonus Product which includes a
      listing of Sonus Patents that cover such product, a listing of the
      appropriate Nycomed Patents that also cover such product.

8.    ASSIGNMENT

8.1   This Agreement may not be assigned or transferred by either party
      without written consent of the other party, such consent not to be
      unreasonably withheld, except that either party may assign this
      Agreement to any successor by merger, consolidation, or sale of
      substantially all of its business unit (or assets relating to that
      business unit) to which this Agreement relates without the consent of
      the other party.  Any attempted delegation or assignment not in
      accordance with this Article shall be of no force or effect.

8.2   This Agreement shall inure to the benefit of and be binding upon the
      parties hereto and their successors and permitted assigns.

8.3   Notwithstanding the provisions of paragraph 8.1 above, either party may
      upon written notice assign this Agreement to an Affiliate, provided that
      no such assignment shall relieve the assigning party of its duties and
      responsibilities under this Agreement.



[*] Confidential portions omitted
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                                      -19-
<PAGE>   20
9.    RIGHT OF FIRST REFUSAL AS TO *

      In the event Sonus receives an offer to buy * Nycomed shall have a right
      of first refusal with respect to *. If Sonus desires to solicit any such
      offer from Third Parties or desires to file for bankruptcy protection,
      Sonus shall promptly give written notice to Nycomed, which shall be at
      least 30 days prior to any such solicitation and as soon as possible prior
      to any such bankruptcy filing. Within 30 days of such notice, Nycomed
      shall indicate whether or not it is interested in making the purchase. If
      Nycomed is interested, Sonus and Nycomed shall negotiate in good faith for
      a maximum of 60 days to mutually determine the material terms of a
      definitive agreement. If Nycomed and Sonus do not reach such agreement,
      but during the negotiation period, Nycomed offered in writing economic
      terms which were rejected by Sonus, and during the term of this Agreement
      Sonus subsequently solicits and receives a bona fide Third Party offer on
      the same or less favorable economic terms considered as a whole than those
      offered by Nycomed, then Sonus shall promptly notify Nycomed in writing.
      Nycomed then may offer to meet such terms within 45 days from such notice.
      If Nycomed does not offer to meet such terms within such 45 day period,
      then Nycomed shall have no further rights under this Section with respect
      to such bona fide Third Party offer for *. The provisions of this
      paragraph 9 shall not apply where, *.

10.   CONFIDENTIALITY

      Each party agrees that the terms of this Agreement and any information
      provided by either party to the other hereunder (including information
      provided under paragraphs 6.3-6.6 and section 20) shall remain
      confidential throughout the term of this Agreement and shall not be
      disclosed to any person or entity, except to a party's professional
      advisor, Abbott, for purposes of obtaining its consent, and the escrow
      agent pursuant to section 31, without advance written permission of the
      other party, provided that, either party in negotiation or business with a
      Third Party concerning the sublicensing of patent rights pursuant to this
      Agreement may disclose to such Third Party, under a written
      confidentiality agreement, such terms of this Agreement as are reasonably
      necessary in order to engage in such negotiations or business, and further
      provided that either party may make any filings of this Agreement, subject
      to confidential treatment, required by law in any country. Each party
      further agrees that it will not issue any press



[*] Confidential portions omitted
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                                      -20-
<PAGE>   21
      release or publicity in regard to this Agreement without the advance
      written permission of the other party. Advance written permission will not
      be required when a party is ordered to disclose information concerning the
      Agreement by a competent tribunal, such disclosures are required by law,
      or disclosure is to be made to the tribunal in arbitration proceedings
      under section 26 below. Each party agrees that to the extent that
      information subject to claims of attorney-client privilege, work product,
      or any similar privilege or immunity is disclosed to the other pursuant to
      performance of this Agreement, such disclosure is intended to further the
      parties' common legal interests and/or joint defense and shall remain
      subject to such privilege or immunity to the maximum extent permitted by
      law.

11.   TERM

      This Agreement is effective as of Closing. Unless earlier terminated as
      provided in section 13 or paragraph 31.2 of this Agreement, it shall
      continue in effect until the expiration of the last to expire patent among
      the Nycomed Patents and the Sonus Patents. As used in this Agreement, the
      "expiration" of a patent includes (i) irrevocable lapse for failure to pay
      maintenance fees or the like, (ii) final revocation of the applicable
      claims by a national patent office and the exhaustion or expiration of all
      appeals of such revocation, and (iii) final adjudication by a court of
      competent jurisdiction that the applicable claims of the patent are
      invalid or unenforceable and the exhaustion or expiration of all appeals
      from said adjudication.

 12.  STANDSTILL

      Nycomed shall not directly or indirectly, for the Term of this Agreement,
      absent prior written of consent of Sonus which may be withheld in its sole
      discretion, purchase, acquire, or obtain the right to vote or control the
      voting of any voting securities of Sonus, or seek or propose to influence
      or control the management or policies of Sonus except in the exercise of
      Nycomed's rights under this Agreement.

13.   DEFAULT AND TERMINATION

13.1  If either party breaches any of the material terms or conditions of this
      Agreement, the party claiming such breach may serve the alleged breaching
      party with a notice of breach specifying the acts or omissions



[*] Confidential portions omitted
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                                      -21-
<PAGE>   22
      creating such alleged breach. If the alleged breaching party fails to
      remedy said breach within 60 days of receipt of said notice, the other
      party may terminate this Agreement by serving a notice of termination.

13.2  Any notice of termination pursuant to paragraph 13.1 above shall be
      effective 30 days after receipt of such notice by the non-terminating
      party, unless before the expiration of said 30 day period, the
      non-terminating party requests or shall have requested mediation pursuant
      to paragraph 26.2 of this Agreement, in which event this Agreement shall
      not terminate until after the conclusion of (i) such mediation, and (ii)
      any arbitration under paragraph 26.1 commenced by either party within 30
      days of service by either party of a request for mediation under paragraph
      26.2, and then only if and to the extent not inconsistent with any award
      rendered in such arbitration.

13.3  In the event that either party files a petition in bankruptcy, is
      adjudicated a bankrupt or files a petition or otherwise seeks relief under
      or pursuant to any bankruptcy, insolvency or reorganization statute or
      proceeding, or if a petition in bankruptcy is filed against it or it
      becomes insolvent or makes an assignment for the benefit of its creditors
      or a custodian, receiver or trustee is appointed for it or a substantial
      portion of its business or assets, the other party shall have the right to
      terminate this Agreement forthwith upon written notice, which notice shall
      be effective upon dispatch.

13.4  No debtor-in-possession, assignee for the benefit of creditors, custodian,
      receiver, trustee in bankruptcy, sheriff or any other officer of the court
      or official charged with taking over custody of a party's assets or
      business shall have any right to continue this Agreement if this Agreement
      terminates pursuant to paragraph 13.3 hereof.

13.5  In the event that, notwithstanding the provisions of paragraph 13.4
      hereof, pursuant to the U.S. Bankruptcy Code or any amendment or successor
      thereto (the "Code"), a trustee in bankruptcy of a party to this
      Agreement, or a party to this Agreement as debtor-in-possession, is
      permitted to assume this Agreement and does so and, thereafter, desires to
      assign this Agreement to a third party, which assignment satisfies the
      requirements of the Code, the trustee or debtor-in-possession, as the case
      may be, shall notify the other party to this Agreement (the "Nonbankrupt
      Party") of same in writing. Said notice shall set forth the name and
      address of the proposed assignee, the proposed consideration



[*] Confidential portions omitted
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                                      -22-
<PAGE>   23
      for the assignment and all other relevant details thereof. The giving of
      such notice shall be deemed to constitute the grant to the Nonbankrupt
      Party of an option to have this Agreement assigned to it or to its
      designee for such consideration, or its equivalent in money, and upon such
      terms as are specified in the notice. The aforesaid option may be
      exercised only by written notice by the Nonbankrupt Party to the trustee
      or debtor-inpossession, as the case may be, within 15 days of receipt of
      the notice of the proposed transaction. If the Nonbankrupt Party fails to
      accept the terms within the said exercise period, the party giving notice
      may complete the assignment referred to in its notice, but only if such
      assignment is to the entity named in said notice and for the consideration
      and upon the terms specified therein.

13.6  Nothing contained herein shall be deemed to preclude or impair any rights
      that the Nonbankrupt party may have as a creditor in any bankruptcy
      proceeding.

14.   CHOICE OF LAW; CHOICE OF FORUM

      This Agreement shall be construed and interpreted in accordance with the
      laws of the State of Delaware without reference to its choice of law
      principles. As provided in section 26 of this Agreement, any dispute
      between the parties related to or arising out of this Agreement, the
      parties' relationship created hereby, and/or the negotiations for and
      entry into this Agreement including any dispute concerning its conclusion,
      binding effect, amendment, coverage, or termination, shall be submitted to
      and resolved by arbitration. If, however, any such dispute is not subject
      to arbitration under section 26 of this Agreement, the state and federal
      courts located in New York County, New York shall have exclusive
      jurisdiction of such dispute. Said courts shall also have exclusive
      jurisdiction of any action to compel arbitration under this Agreement,
      incident to arbitration under this Agreement, or to enter or set aside an
      arbitration award. The parties expressly submit to the personal
      jurisdiction of such courts for any action described in this paragraph 14,
      agree that such courts provide a convenient forum for any such action, and
      waive any objections or challenges to venue.

15.   ENTIRE AGREEMENT; NO ORAL MODIFICATIONS; WAIVER

15.1  This Agreement contains the entire understanding and agreement between
      Nycomed and Sonus with respect to the subject matter hereof,



[*] Confidential portions omitted
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                                      -23-
<PAGE>   24
      and supersedes all prior oral or written understandings and agreements
      relating thereto. Neither party shall be bound by any conditions,
      definitions, warranties, understandings, or representations concerning the
      subject matter hereof except as are (i) provided in this Agreement, (ii)
      contained in any prior existing written agreement between the parties, or
      (iii) duly set forth on or after the day of the Closing of this Agreement
      in a written instrument subscribed by an authorized representative of the
      party to be bound thereby.

15.2  Each party has relied solely on its own evaluation of the subject matter
      in deciding to enter into this Agreement, and has not been induced to
      enter into this Agreement by any statements, promises, or representations
      of the other party, nor has it relied on any such statements, promises, or
      representations.

15.3  No waiver by either party, whether express or implied, of any provision of
      this Agreement, or of any breach or default thereof, shall constitute a
      continuing waiver of such provision or of any other provision of this
      Agreement. Either party's acceptance of payments by the other under this
      Agreement shall not be deemed a waiver of any violation of or default
      under any of the provisions of this Agreement.

16.   RELATIONSHIP OF THE PARTIES

      Nothing herein contained shall be construed to constitute the parties
      hereto as partners or as joint venturers, or either as agent or employee
      of the other. Neither party shall take any action that purports to bind
      the other.

17.   SEVERABILITY

      If any provision or any portion of any provision of this Agreement shall
      be held to be void or unenforceable (or a formal indication to that effect
      is communicated by any competent authority), the parties shall in good
      faith negotiate valid substitute provisions which reflect, as closely as
      reasonably practicable, their commercial intentions as set out herein.
      Subject thereto, the remaining provisions of this Agreement and the
      remaining portion of any provision held void or unenforceable in part
      shall continue in full force and effect.



[*] Confidential portions omitted
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                                      -24-
<PAGE>   25
18.   CONSTRUCTION

      This Agreement shall be construed without regard to any presumption or
      other rule requiring construction against the party causing this Agreement
      to be drafted. If any words or phrases in this Agreement shall have been
      stricken out or otherwise eliminated, whether or not any other words or
      phrases have been added, this Agreement shall be construed as if those
      words or phrases were never included in this Agreement, and no implication
      or inference shall be drawn from the fact that the words or phrases were
      so stricken out or otherwise eliminated.

19.   HEADINGS

      The captions and paragraph headings appearing in this Agreement are
      inserted for convenience and reference only and in no way define, limit or
      describe the scope or intent of this Agreement or any of the provisions
      thereof.

20.   BOOKS AND RECORDS; AUDITS

20.1  Each party shall prepare and maintain, in accordance with generally
      accepted accounting principles, complete and accurate books of account and
      records covering all sales, receipts, payments, and other transactions
      relating to this Agreement. Each party may appoint an independant
      certified public accountant, recognized nationally in the United States
      and approved by the other party (such approval not to be unreasonably
      withheld), to inspect and audit such books and records with respect to the
      subject matter and terms of this Agreement. Such audits shall be conducted
      during regular business hours (no more than once per year and no more than
      three years after termination of this Agreement) at the expense of the
      party requesting the audit (except as provided in paragraph 20.2 below).
      The auditors may inspect and copy all such books of account and records in
      the possession or under the control of the party being audited, but shall
      maintain such information in confidence, provided that the auditor may
      report its findings (but not the underlying data) to the party requesting
      the audit. All such books of account, records, and documents shall be kept
      available by each party for at least three years after the end of the
      quarter to which they relate.

20.2  If as a result of any audit of books and records it is shown that payments
      under this Agreement were less than the amount that should have been



[*] Confidential portions omitted
and filed separately with Commission.



                                      -25-
<PAGE>   26
      paid, all payments required to be made to eliminate such underpayment
      shall be made promptly upon the auditing party's demand therefor. If the
      discrepancy is in an amount equal to five percent (5%) or more of the
      amount actually paid, the audited party shall also reimburse the auditing
      party for the reasonable costs of such audit. No claim of underpayment may
      be made more than three years after the Quarter in which the payments in
      question were initially due.

21.   TAXES

      Each party shall bear all taxes resulting from royalties under this
      Agreement, that party's granting or receipt of licenses or sublicenses
      under this Agreement, or that party's other activities under this
      Agreement. The payments to be made to Sonus as provided in paragraphs
      3.2-3.7 and sections 4 and 5 above shall be net of any withholding taxes
      or duties (there shall be no withholding in connection the payment to be
      made under paragraph 3.1).

22.   IMMUNITY UNDER OTHER PATENTS

22.1  During the term of this Agreement, Nycomed hereby grants to Sonus, its
      Affiliates and their licensees, with respect to and only with respect to
      Sonus Licensed Products for which royalties are incurred under the Nycomed
      Patents pursuant to paragraph 3.3 above, a royalty-free immunity from suit
      under all other patents or patent applications presently owned or
      controlled by Nycomed or its Current Affiliates.

22.2  During the term of this Agreement, Sonus hereby grants to Nycomed, its
      Affiliates and their licensees, with respect to and only with respect to
      (i) Nycomed Licensed Products for which royalties are incurred under the
      Sonus Patents pursuant to paragraph 3.2 above and (ii) Optison if a
      royalty is incurred under the Sonus Patent pursuant to paragraph 5.5
      above, a royalty-free immunity from suit under all other patents or patent
      applications presently owned or controlled by Sonus or its Current
      Affiliates.

22.3  Each party shall promptly discontinue, and refrain from initiating or
      pursuing, any patent office opposition proceedings (worldwide) against the
      other's licensed patents and applications. Neither this paragraph 22.3 nor
      any other provisions of this Agreement shall affect any interference
      proceedings currently pending in the U.S. Patent and



[*] Confidential portions omitted
and filed separately with Commission.



                                      -26-
<PAGE>   27
      Trademark Office between Sonus and Nycomed involving patents or
      applications licensed under this Agreement.

23.   REPRESENTATIONS AND WARRANTIES OF SONUS

      Sonus hereby represents and warrants that:

23.1  Sonus has the full right, power, and corporate authority to enter into
      this Agreement and to make the promises and grant the licenses set forth
      herein.

23.2  Sonus is the owner of all right, title, and interest in and to the Sonus
      Patents and Sonus Patent Applications (subject to the Abbott Agreements).
      Sonus has no license agreements or other agreements or obligations with or
      to third parties or any other binding commitments, obligations, liens,
      mortgages, or encumbrances of any kind or nature that diminish, limit, or
      impair (i) the rights granted by Sonus to Nycomed in this Agreement or
      (ii) the ability of Sonus to perform its covenants and obligations under
      this Agreement.

23.3  Sonus will not divest itself of any rights now or hereafter possessed when
      the effect of doing so may diminish limit, or impair (i) the rights
      granted by Sonus to Nycomed in this Agreement or (ii) the ability of Sonus
      to perform its covenants and obligations under this Agreement. In no event
      shall Sonus's exercise of rights that it is accorded under this Agreement
      constitute a breach of Sonus's obligations under this paragraph 23.3.

23.4  The Abbott Agreements are the only agreements between Sonus and Abbott
      Laboratories or Abbott International, Ltd. and their respective Affiliates
      conferring license rights under the Sonus Patents.

23.5  Sonus has obtained the consent of Abbott Laboratories and Abbott
      International, Ltd., to enter into this Agreement, and Abbott Laboratories
      and Abbott International, Ltd., have each executed a form of Statement of
      Consent as provided in Appendix 23.5 hereto.

23.6  Sonus is not party to any other agreement the terms of which (i) conflict
      with the covenants and obligations of Sonus under this Agreement or the
      rights granted by Sonus to Nycomed under this Agreement or (ii) diminish
      limit, or impair the rights granted by Sonus to Nycomed in this



[*] Confidential portions omitted
and filed separately with Commission.



                                      -27-
<PAGE>   28
      Agreement or the ability of Sonus to perform its covenants and obligations
      under this Agreement.

23.7  Sonus is not in default in its payment of legal fees associated with the
      Mallinckrodt Litigation. No attorney will assert a retaining lien on or
      other interest in the pleadings and papers for the Mallinckrodt Litigation
      that would interfere with their transfer to Nycomed or require payment of
      a fee to cause their release. No attorney will assert a lien on or other
      interest in any proceeds of the Mallinckrodt Litigation, nor is any
      attorney entitled to compensation that is contingent on the outcome of the
      Mallinckrodt Litigation.

23.8  With the exception of claims for infringement of the Sonus Patents or
      Sonus PatentApplications and claims asserted in the Mallinckrodt
      Litigation, Sonus has no claims against any Third Party in the business of
      researching, developing, manufacturing, or marketing ultrasound contrast
      agents.

23.9 Sonus is party to an enforceable agreement with * under which *.

24.   REPRESENTATIONS AND WARRANTIES OF NYCOMED

      Nycomed hereby represents and warrants that:

24.1  Nycomed has the full right, power, and corporate authority to enter into
      this Agreement and to make the promises and grant the licenses set forth
      herein.

24.2  Nycomed is the owner of all right, title, and interest in and to the
      Nycomed Patents. Nycomed has no license agreements or other agreements or
      obligations with or to third parties or any other binding commitments,
      obligations, liens, mortgages, or encumbrances of any kind or nature that
      diminish, limit, or impair (i) the rights granted by Nycomed to Sonus in
      this Agreement or (ii) the ability of Nycomed to perform its covenants and
      obligations under this Agreement.

24.3  Nycomed will not divest itself of any rights now or hereafter possessed
      when the effect of doing so may diminish limit, or impair (i) the rights
      granted by Nycomed to Sonus in this Agreement or (ii) the ability of
      Nycomed to perform its covenants and obligations under this Agreement. In
      no event shall Nycomed's exercise of rights that it is accorded under



[*] Confidential portions omitted
and filed separately with Commission.



                                      -28-
<PAGE>   29
      this Agreement constitute a breach of Nycomed's obligations under this
      paragraph 24.3.

24.4  Nycomed is not party to any other agreement the terms of which (i)
      conflict with the covenants and obligations of Nycomed under this
      Agreement or the rights granted by Nycomed to Sonus under this Agreement
      or (ii) diminish limit, or impair the rights granted by Nycomed to Sonus
      in this Agreement or the ability of Nycomed to perform its covenants and
      obligations under this Agreement.

24.5  Nycomed AS is a wholly owned subsidiary of Nycomed Amersham plc

25.   RECORDING

      Neither party shall record this Agreement or any abstract hereof in any
      patent office or public recording office. Provided that each party shall
      be permitted to record abstracts or short forms of its licenses under the
      other's licensed patents in the European Patent Office, U.S. Patent and
      Trademark Office, and any other national patent office. Each party shall
      execute and deliver to the other any documents required for such
      recording.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -29-
<PAGE>   30
26.   ARBITRATION

26.1  Subject to the mediation requirements of paragraph 26.2 below and the
      limitation on any award of paragraph 26.3 below, all disputes between the
      parties related to or arising out of this Agreement, the parties'
      relationship created hereby, and/or the negotiations for and entry into
      this Agreement, including any dispute concerning its conclusion, binding
      effect, amendment, coverage, or termination, shall be resolved, to the
      exclusion of the ordinary courts, by a three-person arbitral tribunal
      composed of one arbitrator appointed by each party and a third arbitrator,
      who shall be a retired judge of a U.S. federal or state trial or appeal
      court of record, selected by the arbitrators appointed by the parties.
      Arbitration shall proceed in accordance with the CPR Rules for
      Non-Administered Arbitration of Patent and Trade Secret Disputes in effect
      on the day of the Closing of this Agreement. In no case shall the arbitral
      tribunal make any award that is inconsistent with the limitations set
      forth in paragraph 26.3 below, and the arbitral tribunal shall have no
      jurisdiction to make any such inconsistent award. The decision of the
      arbitral tribunal shall be final, and the parties waive all challenge of
      the award. The venue of any such proceeding shall be New York County, New
      York. All proceedings shall be conducted in the English language.

26.2  If either party desires to commence arbitration pursuant to paragraph 26.1
      above, prior to doing so it shall so notify the other party in writing and
      simultaneously request an internal mediation proceeding between the
      parties ("Mediation Request"). The Mediation Request shall not constitute
      a notice of arbitration, nor serve to commence arbitration proceedings
      under paragraph 26.1 above. Within 7 business days of service of the
      Mediation Request, each party shall (i) designate a senior member of its
      management, at the level of at least executive vice president or division
      chief executive, and with authority to settle the dispute (subject to
      approval of a settlement by the party's board if necessary), to
      participate in the mediation as its management representative, and (ii)
      submit to the other party a confidential summary of its position, in
      letter form not to exceed 5 pages in length, which shall be provided to
      that other party's management representative. Within 14 business days
      thereafter, the management representatives shall meet with each other in
      person to attempt in good faith to resolve the dispute. If a party desires
      to have counsel also attend such meeting, it shall notify the other party
      at least 5 business days in advance. The meeting shall be held in London,
      England, if the Mediation Request is served by Sonus, and in Seattle,
      Washington, if the Mediation Request is served by



[*] Confidential portions omitted
and filed separately with Commission.



                                      -30-
<PAGE>   31
      Nycomed. If the parties are unable to resolve the dispute within 7
      business days following the meeting, either party may commence arbitration
      under paragraph 26.1 above. A party that refuses or fails to participate
      in the mediation process shall not initiate arbitration proceedings until
      such time as it so participates, but the other party shall be free to
      initiate arbitration proceedings (and the non-participating party shall
      respond to the commencement of arbitration in accordance with the
      arbitration rules specified in paragraph 26.1).

26.3  Any dispute arising under paragraph 4.7 concerning the compensation due
      Sonus incident to any transaction between Nycomed and a Third Party
      thereunder shall be subject to mediation and arbitration under paragraphs
      26.2 and 26.1 above and the additional provisions of this paragraph 26.3.
      If the only consideration that Nycomed receives from a transaction with a
      Third Party under paragraph 4.7 consists of payments that are shared with
      Sonus thereunder, Sonus shall not be permitted to challenge the
      transaction. If Nycomed receives other consideration in any such
      transaction that is not shared with Sonus, and if Sonus contends that
      consideration for the grant of licenses or sublicenses has been
      unreasonably allocated to such other forms of consideration, Sonus must so
      notify Nycomed within 30 days after it is informed of the terms of such
      transaction by Nycomed. If Sonus does not so notify Nycomed within such
      30-day period, it shall not be permitted to challenge the transaction. In
      any challenge of the allocation of consideration by Sonus, Sonus shall be
      obligated to demonstrate by clear and convincing evidence that the
      allocation was unreasonable or made in bad faith. In any such challenge by
      Sonus, the maximum award to which Sonus would be entitled upon such
      showing is *. At any time during such dispute, including during mediation
      or arbitration, Nycomed may conclusively resolve all claims brought by
      Sonus by agreeing to pay or have paid to Sonus *, and in no dispute
      concerning Sonus's entitlement pursuant to paragraph 4.7 to share in
      consideration received by Nycomed shall the arbitral tribunal be permitted
      to make an award to Sonus that is *. The provisions of this paragraph 26.3
      constitute Sonus's exclusive right and remedy to challenge the allocation
      of consideration flowing to Nycomed in any such transaction. In no case
      shall Sonus pursue or assert any claim against the Third Party to any such
      transaction, or attempt to set-aside, modify, void, annul, or terminate
      the transaction between Nycomed and the Third Party.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -31-
<PAGE>   32
27.   NOTICES

      All reports, approvals, requests, demands and notices required or
      permitted by this Agreement to be given to a party (hereafter "Notices")
      shall be in writing. Notices shall be hand delivered, sent by certified or
      registered mail, return receipt requested, or sent via a reputable private
      express service which requires the addressee to acknowledge receipt
      thereof. Notices may also be transmitted by fax, provided that a
      confirmation copy is also sent by one of the above methods. Except as
      otherwise provided in this Agreement, notices shall be effective upon
      dispatch unless sent by mail, in which case they shall be effective five
      days after mailing. Notices shall be sent to the party concerned as
      follows (or at such other address as a party may specify by notice to the
      other):

      As to Nycomed:

            Nycomed Amersham Imaging
            Amersham Place
            Little Chalfont
            Buckinghamshire HP7 9LL
            ENGLAND
            Telefax: +44 1494 542242

            Attn: Group Legal Advisor and Corporate Secretary

            -with a copy to-

            Richard L. DeLucia, Esq.
            Kenyon & Kenyon
            1 Broadway
            New York, NY 10004-1050
            Telefax: (212) 425-5288

      As to Sonus:

            Sonus Pharmaceuticals, Inc.
            22026 20th Avenue, S.E., Suite 102
            Bothell, Washington 98021
            Telefax:  (206) 489-0626



[*] Confidential portions omitted
and filed separately with Commission.



                                      -32-
<PAGE>   33
            Attention: President

            -with a copy to-

            Gary N. Frischling, Esq.
            Irell & Manella LLP
            1800 Avenue of the Stars, Suite 900
            Los Angeles, CA 90067-4276
            Telefax:  (310) 203-7199

28.   APPENDICES AND EXHIBITS

      All Appendices and Exhibits referenced herein are hereby made a part of
      this Agreement.

29.  PAYMENTS; PARTIAL PAYMENTS; INTEREST; CURRENCY

29.1  Each party may accept partial payments from the other of any amount due
      under this Agreement without prejudice to any claim for the balance owed.
      The acceptance of any payments or checks marked "Payment in Full" or
      otherwise shall be without prejudice and such notations shall be of no
      effect.

29.2  Any payments not made when due shall bear interest from the due date until
      the date of payment at the rate which is the lower of (i) two percentage
      points above the one-month London Interbank Offering Rate in effect on the
      due date or (ii) the highest rate permitted by applicable law.

29.3  All payments required by this Agreement shall be made by wire transfer to
      the institution and account designated in writing for receipt of such
      payments by each party.

29.4  All payments required by this Agreement shall be made in U.S. dollars.
      When conversion of currency is required to render a statement under
      paragraph 3.4 of this Agreement, the conversion shall be made at the rate
      in effect on the last business day of the Quarter to which such statement
      relates. The conversion rates shall be the New York foreign exchange
      mid-range rates published in the Wall Street Journal.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -33-
<PAGE>   34
30.   COEXISTENCE OF SONAZOID AND SONOGEN TRADEMARKS

      The parties have determined and agree that there is no likelihood that
      consumers will be confused by the use and registration of the trademark
      "Sonazoid" adopted by Nycomed and the trademark "SonoGen" adopted by
      Sonus.
31.   CONDITIONS OF CLOSING; HART-SCOTT-RODINO FILING; ESCROW

31.1  As soon as practicable after the execution of this Agreement, but in no
      event later than two business days thereafter, Sonus and Nycomed shall
      cause to be filed any notices, reports and other documents required to be
      filed under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
      amended (the "HSR Act"). Each party shall respond as promptly as
      practicable, and in a manner deemed advisable by that party as most likely
      to further the attainment of any necessary governmental approvals or the
      avoidance of any order impeding the consummation of the transactions
      contemplated by this Agreement, to (i) any inquiries or requests received
      from the Federal Trade Commission or the Department of Justice for
      additional information or documentation and (ii) any inquiries or requests
      received from any state attorney general or other governmental body in
      connection with antitrust or related matters. Each of the parties shall
      (a) give the other party prompt notice of the commencement of any action,
      suit, litigation, arbitration, preceding or investigation ("Legal
      Proceeding") by or before any governmental body with respect to the
      transactions contemplated by this Agreement, (b) keep the other party
      informed as to the status of any such Legal Proceeding, and (c) promptly
      inform the other party of any communication to or from the Federal Trade
      Commission, the Department of Justice or any other governmental body
      regarding the proposed licensing arrangements between Nycomed and Sonus
      contemplated by this Agreement. Nycomed shall pay the fee associated with
      any filing of the notification form under the HSR Act.

31.2  Concurrent with execution of this Agreement, the parties shall establish
      an escrow in substantially the form provided in Appendix 31.2 hereto, with
      a mutually agreeable financially responsible escrow agent. Nycomed shall
      pay the license fee called for under paragraph 3.1 above into escrow
      within one business day after execution of this Agreement. The escrow
      terms shall provide that (x) $5,000,000 be disbursed by the escrow holder
      to Sonus on the satisfaction of the conditions set forth in 31.3(i) and
      31.3(ii) below, and (y) if the Closing has occurred, the balance be
      disbursed to Sonus on October 1, 1999 (or on the day of Closing if the
      Closing occurs after October 1, 1999). The escrow terms shall further
      provide that, in the event that conditions (i) and (ii) set forth in
      paragraph 31.3 below are not satisfied on or before October 31, 1999,
      either party shall have the right to terminate this Agreement and all
      obligations, rights, and licenses hereunder (except that the provisions of
      sections 10, 14, and 26 shall survive such termination), in which event
      all funds contained in the escrow account shall be released to Nycomed.
      All interest on the funds in escrow shall follow the amount paid into
      escrow



[*] Confidential portions omitted
and filed separately with Commission.



                                      -34-
<PAGE>   35
      and shall be disbursed to the party to whom the payment is made, which
      party shall also bear any fees and costs charged by the escrow agent.

31.3  The Closing shall take effect automatically upon the satisfaction (or
      waiver by both Parties) of the following conditions: (i) the waiting
      period applicable to this Agreement under the HSR Act shall have
      expired or early termination of the HSR Act waiting period shall have
      been granted by the applicable government agency; (ii) no court or
      governmental entity of competent jurisdiction shall have enacted,
      issued, promulgated, enforced or entered any statute, rule, regulation,
      judgment, decree, injunction or other order which is in effect and
      prohibits the consummation of the Closing or threatened any action that
      if successful would have the effect of prohibiting the consummation of
      the Closing, and (iii) Sonus shall have received payment from the
      escrow agent of the amounts to which it is entitled under paragraph
      31.2(x) above.  Notwithstanding the foregoing, paragraphs and sections
      3.1, 10, 13.1, 13.2, 14, 15.1, 15.3, 16, 17, 18, 19, 21, 26, 27, 29,
      and 31 of this Agreement shall take effect upon execution of this
      Agreement.

      IN WITNESS WHEREOF, each of the parties has caused this Agreement to be
executed by its duly authorized representative as of the day and year first
above written.


NYCOMED IMAGING AS                     SONUS PHARMACEUTICALS, INC.


By: /s/Ase Aulie Michelet              By: /s/ Michael A. Martino
    ----------------------------           -------------------------------------



[*] Confidential portions omitted
and filed separately with Commission.



                                      -35-
<PAGE>   36
                                  APPENDIX 1.3
                                 (SONUS PATENTS)

                                      *



And foreign equivalents of the above, which foreign equivalents have issued or
are published for opposition.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -37-
<PAGE>   37
                                  APPENDIX 1.4
                                (NYCOMED PATENTS)

                                      *

                                      *

And foreign equivalents of the above, which foreign equivalents have issued or
are published for opposition.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -38-
<PAGE>   38
                                  APPENDIX 1.12
                           (SONUS PATENT APPLICATIONS)


                                      *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -39-
<PAGE>   39
                       APPENDIX 3.4 TO LICENSE AGREEMENT
                   (Exemplification of royalty calculations)

Example 1

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -40-
<PAGE>   40
      Example 2


                                      *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -41-
<PAGE>   41
Example 3

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -42-
<PAGE>   42
Example 4

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -43-
<PAGE>   43
Example 5

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -44-
<PAGE>   44
Example 6

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -45-
<PAGE>   45
Example 7

Net Sales in Quarter are as follows:


                                         *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -46-
<PAGE>   46
                                  APPENDIX 3.6
                             (CERTAIN SONUS PATENTS)

                                      *


And foreign equivalents of the above, which foreign equivalents have issued or
are published for opposition.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -47-
<PAGE>   47
                                  APPENDIX 3.7
                            (CERTAIN NYCOMED PATENTS)


                                        *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -48-
<PAGE>   48
                                      *


And foreign equivalents, which foreign equivalents have issued or are published
for opposition.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -49-
<PAGE>   49
                                  Appendix 5.5
(Certain Molecular Biosystems and Mallinckrodt Medical patents and applications)


                                         *


and all patents or patent applications (worldwide) claiming priority, directly
or indirectly, from the above applications and/or the applications resulting in
the above patents.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -50-
<PAGE>   50
                                  Appendix 23.5


                               Abbott Laboratories
                           Abbott International, Ltd.


                                          August        , 1999

Nycomed Imaging AS
Nycoveien 1-2
Oslo, Norway

Sonus Pharmaceuticals, Inc.
22026 20th Avenue, S.E., Suite 102
Bothell, Washington 98021

      Re:   License Agreement between Nycomed Imaging AS ("Nycomed") and
            Sonus Pharmaceuticals, Inc.
            ("Sonus")

Gentlemen:

At the request of Sonus, we have reviewed the proposed License Agreement between
Sonus and Nycomed that is attached to this letter.

Abbott Laboratories and Abbott International, Ltd. (collectively, "Abbott")
hereby give their consent to Sonus's entry into the proposed License Agreement.
Such consent is given notwithstanding sections 9 and 10.1(D) of the Abbott
International, Ltd. agreement and sections 10 and 11.1(D) of the Abbott
Laboratories agreement to the extent of Sonus's grant of rights to Nycomed
relating to Non-perfluoropentane Ultrasound Products.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -51-
<PAGE>   51
                                       Very truly yours,

ABBOTT LABORATORIES                    ABBOTT INTERNATIONAL, LTD.


By: /s/ Richard A. Gonzales            By:  /s/ William J. Dempsey
    ---------------------------             -----------------------------------

Its:  President                        Its:  President
      -------------------------              -----------------------------------



[*] Confidential portions omitted
and filed separately with Commission.



                                      -52-
<PAGE>   52
                       APPENDIX 31.2 TO LICENSE AGREEMENT


                                ESCROW AGREEMENT

      This Escrow Agreement dated as of August 31, 1999, is entered into by and
between Nycomed Imaging AS, a Norwegian corporation with principal offices at
Nycoveien 1-2, Oslo ("Nycomed"), Sonus Pharmaceuticals, Inc., a Delaware
corporation with principal offices at 22026 20th Avenue, S.E., Suite 102,
Bothell, Washington 98021 ("Sonus"), and Summit Bank ("Escrow Agent"), a New
Jersey corporation having offices at 210 Main Street, Hackensack, NJ 07601.

      WHEREAS Nycomed and Sonus desire to establish an escrow account ("Escrow
Account") in connection with an intended transaction between them, the terms of
which are set forth in that certain proposed License Agreement attached hereto
in draft form; and

      WHEREAS Nycomed and Sonus desire to appoint the Escrow Agent to carry out
the escrow functions defined in the License Agreement, more particularly
paragraph 31.2 thereof; and

      WHEREAS the Escrow Agent desires to accept such appointment in accordance
with the terms set forth in this Escrow Agreement,

      NOW THEREFORE, the parties agree as follows:

1.    Nycomed and Sonus hereby appoint the Escrow Agent to act as the escrow
      agent and to carry out the functions of the escrow agent as set forth in
      this Escrow Agreement, and the Escrow Agent accepts such appointment.

2.    Following execution of the License Agreement, Nycomed will provide a
      copy of the executed License Agreement to the Escrow Agent, which shall
      attach such executed copy to this Escrow Agreement, and the executed
      copy of the License Agreement shall then govern over the terms of the
      draft License Agreement.  The executed copy of the License Agreement
      may be supplied to the Escrow Agent without the exhibits that are
      referred to and made part of the License Agreement, such exhibits not
      having any effect on the Escrow Agent's performance of its duties
      hereunder.

3.    Nycomed shall deposit with the Escrow Agent the amount of $10,000,000, as
      provided in paragraph 3.1 of the License Agreement. Those funds, together
      with interest thereon (the "Escrowed Funds") shall be held by the Escrow
      Agent in the Escrow Account. The Escrow Agent shall disburse funds from
      the Escrow Account as follows:

      (a)   $5,000,000 shall be disbursed by the Escrow Agent to Sonus on the
            satisfaction of the following conditions: (i) the waiting period
            applicable to the License Agreement under the Hart-Scott-Rodino Act



[*] Confidential portions omitted
and filed separately with Commission.



                                      -53-
<PAGE>   53
            shall have expired or early termination of the Hart-Scott-Rodino Act
            waiting period shall have been granted by the applicable government
            agency; and (ii) no court or governmental entity of competent
            jurisdiction shall have enacted, issued, promulgated, enforced or
            entered any statute, rule, regulation, judgment, decree, injunction
            or other order which is in effect and prohibits the consummation of
            the Closing (as defined in the License Agreement) or threatened any
            action that if successful would have the effect of prohibiting the
            consummation of the Closing.

      (b)   If the Closing (as defined in the License Agreement) occurs on or
            before October 1, 1999, the balance of the Escrowed Funds (including
            interest) shall be disbursed to Sonus on October 1, 1999. If the
            Closing occurs after October 1, 1999, the balance (including
            interest) shall be disbursed to Sonus on the day of the Closing.

      (c)   As set forth in section 31.2 of the License Agreement, Sonus and
            Nycomed shall each have the right to terminate the License
            Agreement as set forth in that paragraph in the event that
            conditions a(i) and a(ii) above are not satisfied on or before
            October 31, 1999.  Such termination must be by written notice
            from the terminating party to the other party and the Escrow
            Agent, and shall be effective upon receipt.  In the event of
            termination under this paragraph 3(c), the Escrowed Funds shall
            be released to Nycomed.

      (d)   The parties shall provide the Escrow Agent with notice of the
            occurrence of any of the events specified in (a)-(c) above, and the
            Escrow Agent shall be authorized to act on such notice as provided
            in this Escrow Agreement.

      (e)   All interest on the Escrowed Funds shall follow the amounts paid
            into escrow and shall be disbursed to the party to whom the payment
            is made, which party shall also bear the fees charged by the Escrow
            Agent as provided in paragraph 16 below. Funds shall be disbursed by
            wire transfer in accordance with written instructions to be provided
            by the party receiving the funds. In the case of Sonus, wire
            transfer instructions are as follows:

                  Wells Fargo Bank
                  ABA:        121000248
                  *



[*] Confidential portions omitted
and filed separately with Commission.



                                      -54-
<PAGE>   54
                  Name of:    SONUS Pharmaceuticals, Inc.
                  Attn:       Mora Andrews
                  Phone:      415-396-7188

4.    The Escrow Agent is authorized to act on written instructions of Nycomed's
      attorneys (such attorneys being Kenyon & Kenyon) as if such instructions
      were received directly from Nycomed, and on written instructions of
      Sonus's attorneys (such attorneys being Irell & Manella LLP) as if such
      instructions were received directly from Sonus.

5.    Notices to the parties shall be made as follows:

            As to Nycomed:

                  Nycomed Amersham Imaging
                  Amersham Place
                  Little Chalfont
                  Buckinghamshire HP7 9LL
                  ENGLAND
                  Telefax: +44 1494 542242

                  Attn: Robert Allnutt,
                        Group Legal Advisor and Corporate Secretary

                -with a copy to-

                  Richard L. DeLucia, Esq.
                  Kenyon & Kenyon
                  1 Broadway
                  New York, NY 10004-1050
                  Telefax: (212) 425-5288

            As to Sonus:
                  Sonus Pharmaceuticals, Inc.
                  22026 20th Avenue, S.E., Suite 102
                  Bothell, Washington 98021
                  Telefax:  (206) 489-0626

                  Attn: Michael Martino
                        President

                -with a copy to-



[*] Confidential portions omitted
and filed separately with Commission.



                                      -55-
<PAGE>   55
                  Gary N. Frischling, Esq.
                  Irell & Manella LLP
                  1800 Avenue of the Stars, Suite 900
                  Los Angeles, CA 90067-4276
                  Telefax:  (310) 203-7199

            As to the Escrow Agent:

                  Corporate Trust Department
                  Summit Bank
                  210 Main Street, 6th floor
                  Hackensack, NJ 07601
                  Telefax:   (201) 646-0087

6.    Any dispute between Nycomed and Sonus concerning this Escrow Agreement
      shall be subject to the arbitration provisions of paragraph 26 of the
      License Agreement. The Escrow Agent shall not be made a party to any such
      arbitration proceedings.

7.    The Escrowed Funds shall be invested by the Escrow Agent in accordance
      with the signed, written instructions of Nycomed and Sonus.  In the
      absence of written instructions from the above-named parties, the
      Escrow Agent shall invest the Escrowed Funds in the money market mutual
      funds customarily utilized by the Escrow Agent's corporate trust
      department in the ordinary course of its corporate trust and escrow
      agent duties.  Such money market mutual fund is the U.S. Treasury
      Securities portfolio of The Pillar Funds(R) managed by the Investment
      Management Division of the Escrow Agent.  The Investment Management
      Division of the Escrow Agent derives a fee for managing the Funds and
      acting as its Custodian.

      In investing the Escrowed Funds, the Escrow Agent shall rely upon the
      written instructions of Nycomed and Sonus and the Escrow Agent shall be
      and hereby is relieved of all liability with respect to making, holding,
      redeeming or selling such investments in accordance with such
      instructions. In the absence of the written investment instructions
      contemplated herein, for any reasons whatsoever, the Escrow Agent shall be
      and hereby is relieved of all liability with respect to making, holding,
      redeeming or selling investments made in accordance with the preceding
      paragraph which prescribes the permissible investment vehicles for the
      Escrowed Funds absent written instructions from Nycomed and Sonus.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -56-
<PAGE>   56
      Escrow Agent is and shall be under not duty to enforce the obligation of
      Nycomed and Sonus to furnish written investment instructions nor shall the
      Escrow Agent be liable to any person, firm or corporation, including any
      of the parties hereto, for the investments made, held, redeemed or sold as
      directed herein in the event that written investment instructions from
      Nycomed and Sonus are not furnished to the Escrow Agent.

8.    The Escrow Agent shall not be responsible for or be required to enforce
      any of the terms or conditions of the License Agreement or any other
      agreement between Nycomed and Sonus.

      The Escrow Agent shall not be responsible or liable in any manner
      whatsoever for the performance of or by Nycomed and Sonus of their
      respective obligations under this Escrow Agreement nor shall the Escrow
      Agent be responsible or liable in any manner whatsoever for the failure of
      the other parties to the Escrow Agreement or of any third party to honor
      any of the provisions of this Escrow Agreement.

9.    The parties hereto represent to the Escrow Agent that they are authorized
      to enter into the Escrow Agreement by their duly authorized
      representatives and that the Escrow Agent is entitled to rely on this
      representation without the need to confirm the authority of the
      representatives.

10.   The duties and obligations of the Escrow Agent shall be limited to and
      determined solely by the express provisions of the Escrow Agreement and
      no implied duties or obligations shall be read into this Escrow
      Agreement against the Escrow Agent.  The Escrow Agent is not bound by
      and is under no duty to inquire into the terms or validity of any other
      agreements or documents, including any agreements or documents which
      may be related to, referred to in or deposited with the Escrow Agent in
      connection with this Escrow Agreement.

11.   The Escrow Agent shall be entitled to rely upon and shall be protected in
      acting in reliance upon any instruction, notice, information, certificate,
      instrument or other document which is submitted to it in connection with
      its duties under this Escrow Agreement and which the Escrow Agent in good
      faith believes to have been signed or presented by the proper party or
      parties. The Escrow Agent shall have no liability with respect to the
      form, execution, validity or authenticity thereof.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -57-
<PAGE>   57
12.   The Escrow Agent shall not be liable for any act which the Escrow Agent
      may do or omit to do hereunder, or for any mistake of fact or law, or for
      any error of judgment, or for the misconduct of any employee, agent or
      attorney appointed by it, while acting in good faith, unless caused by or
      arising from its own gross negligence or willful misconduct.

13.   The Escrow Agent shall be entitled to consult with counsel of its own
      selection and the opinion of such counsel shall be full and complete
      authorization and protection to the Escrow Agent in respect of any action
      taken or omitted by the Escrow Agent hereunder in good faith and in
      accordance with the opinion of such counsel.

14.   The Escrow Agent shall have the right at any time to resign for any
      reason and be discharged of its duties as Escrow Agent hereunder by
      giving written notice of its resignation to the parties hereto at least
      thirty days prior to the date specified for such resignation to take
      effect.  All obligations of the Escrow Agent hereunder shall cease and
      terminate on the effective date of its resignation and its sole
      responsibility thereafter shall be to hold the Escrowed Funds for a
      period of thirty days following the effective date of resignation, at
      which time,

      (a)   if a successor escrow agent shall have been appointed and written
            notice thereof shall have been given to the resigning Escrow Agent
            by parties hereto and the successor escrow agent, then the resigning
            Escrow Agent shall deliver the Escrowed Funds to the successor
            escrow agent; or

      (b)   if a successor escrow agent shall not have been appointed, for any
            reason whatsoever, the resigning Escrow Agent shall deliver the
            Escrowed Funds to a court of competent jurisdiction and give written
            notice of the same to the parties hereto.

      The resigning Escrow Agent shall be entitled to be reimbursed from the
      Escrowed Funds for any expenses incurred in connection with its
      resignation and transfer of the Escrowed Funds pursuant to and in
      accordance with the provisions of this section.

15.   The Escrow Agent shall be entitled to receive its fee of $1,500.00 per
      year for its services hereunder and a one time document review fee of
      $500.00. The fees shall be deducted by the Escrow Agent from the Escrowed
      Funds. Any fee that is not so paid shall become a charge upon the Escrowed
      Funds.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -58-
<PAGE>   58
16.   Nycomed and Sonus jointly and severally agree to indemnify and hold the
      Escrow Agent harmless from and against any and all liabilities, causes of
      action, claims, demands, judgments, damages, costs and expenses (including
      reasonable attorneys fees and expenses) that may arise out of or in
      connection with the Escrow Agent's good faith acceptance of or performance
      of its duties and obligations under this Escrow Agreement.

      The Escrow Agent shall be under no duty to institute any suit, or to take
      any remedial procedures under this Escrow Agreement, or to enter any
      appearance or in any way defend any suit in which it may be made a
      defendant hereunder until it shall be indemnified as provided above.

17.   In the event that the Escrow Agent shall be uncertain as to its duties
      or rights hereunder or shall receive instructions with respect to the
      Escrow Account which, in its sole discretion, are in conflict either
      with other instructions received by it or with any provision of this
      Agreement, the Escrow Agent shall have the absolute right to suspend
      all further performance under this Escrow Agreement (except for the
      safekeeping of the Escrowed Fund) until the resolution of such
      uncertainty or conflicting instructions to the Escrow Agent's sole
      satisfaction by final judgment of a court of competent jurisdiction,
      joint written instructions from all of the other parties hereto, or
      otherwise.

18.   In the event that any controversy arises between one or more of the
      parties hereto or any other party with respect to this Escrow Agreement
      or the Escrow Account, the Escrow Agent shall not be required to
      determine the proper disposition of such controversy or the proper
      disposition of the Escrow Account and shall have the absolute right, in
      its sole discretion, to deposit the Escrow Account with the Clerk of a
      court of competent jurisdiction, file a suit in interpleader and obtain
      an order from the court requiring all parties involved to litigate in
      such court their respective claims arising out of or in connection with
      the Escrow Account.  Upon the deposit by the Escrow Agent of the Escrow
      Account with the Clerk of a court of competent jurisdiction in
      accordance with this provision, the Escrow Agent shall be relieved of
      all further obligations and released from all liability hereunder.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -59-
<PAGE>   59
19.   It is understood that all checks received by the Escrow Agent hereunder
      are subject to clearance time and the funds represented thereby cannot
      be drawn upon or disbursed until such time as the same constitute good
      and collected funds.  If any checks are returned to the Escrow Agent as
      uncollectible, the Escrow Agent shall notify the other parties hereto
      and redeposit such check for collection upon the verbal instructions of
      the party tendering such check.  Notwithstanding the foregoing, if for
      any reason any check or instrument entered for collection by the Escrow
      Agent hereunder is uncollectible after payment of the funds represented
      thereby has been made pursuant to the terms hereof, the party tendering
      such check shall immediately reimburse the Escrow Agent and the Escrow
      Agent shall deliver the returned check or instrument to the party
      tendering such check.

20.   Nycomed and Sonus hereby indemnify and hold the Escrow Agent harmless
      from any possible violations of any Environmental Laws including any
      local, state or federal law, rule or regulation pertaining to
      environmental matters, as now or hereafter enacted or amended,
      including without limitation, the Federal Comprehensive Environmental
      Response; Compensation and Liability Act of 1980; the Federal Resource
      Conservation and Recovery Act; the Federal Superfund Amendments and
      Reauthorization Act of 1986; the Federal Toxic Substance Control Act;
      the Federal Hazardous Material Transportation Act; the Federal Clean
      Air Act; the Federal Water Pollution Control Act; the Industrial Site
      Recovery Act; the New Jersey Spill Act; the Underground Storage Tank
      Act; together with any other federal, state or local superlien, or
      other statutes, rules or regulations, as now or hereafter amended in
      any way pertaining to clean-up, disclosure, water pollution control,
      air pollution control, regulation of solid waste, hazardous waste
      management, storage tanks, regulation of environmentally sensitive
      areas, use of ground water, surface waters and wetlands, hazardous and
      toxic substance reporting and any other laws including case law, which
      might be deemed or referred to as environmental common law.

      Neither this Escrow Agreement, the License Agreement or any other
      agreement between Nycomed and Sonus and the Escrow Agent shall be deemed
      to create a joint venture between the Escrow Agent and Nycomed or Sonus.
      Nor shall the Escrow Agent be considered the alter ego of Nycomed or Sonus
      by virtue of this Agreement, or any other agreement.



[*] Confidential portions omitted
and filed separately with Commission.



                                      -60-
<PAGE>   60
NYCOMED IMAGING AS                     SONUS PHARMACEUTICALS, INC.


By: /s/ Ase Aulie Michelet             By: /s/ Michael A. Martino
    --------------------------             -------------------------------------



SUMMIT BANK


By:________________________



[*] Confidential portions omitted
and filed separately with Commission.



                                      -61-

<PAGE>   1
                                                                    Exhibit 99.1


         NEWS RELEASE


         SONUS PHARMACEUTICALS ANNOUNCES ULTRASOUND CONTRAST AGREEMENT
                             WITH NYCOMED AMERSHAM


        REPRESENTS FIRST SUCH ARRANGEMENT IN ULTRASOUND CONTRAST INDUSTRY


BOTHELL, WASHINGTON, SEPTEMBER 29, 1999 - SONUS Pharmaceuticals, Inc.
(Nasdaq:SNUS) announced today that it has entered into an agreement with Nycomed
Amersham plc (NYSE:NYE; LSE:NAM) for the broad cross-licensing of patents in the
field of ultrasound contrast agents.

Under the terms of the agreement, Nycomed Amersham will pay SONUS an up-front
license fee of $10 million, of which SONUS will receive $5 million in the third
quarter of 1999 and $5 million in the fourth quarter of 1999. In addition, both
companies have agreed to pay each other royalties on future sales of their
ultrasound contrast agents.

The agreement provides Nycomed Amersham with an exclusive license to SONUS'
ultrasound contrast patents except as related to perfluoropentane, which is the
perfluorocarbon gas used by SONUS in its contrast products. Under its exclusive
license to the patents, Nycomed Amersham also has the right to freely sublicense
to other companies with a portion of any sublicense fees to be paid to SONUS.
Nycomed Amersham's exclusive license covers all territories of the world except
for ten Pacific Rim countries where its license is non-exclusive.

Also under the agreement, SONUS has a worldwide, non-exclusive license to
Nycomed Amersham's ultrasound contrast agent patents related to
perfluoropentane. SONUS also has the right to sublicense these patents to its
collaborative partners, such as Abbott Laboratories.

"We are pleased for the opportunity to partner the complementary patent
portfolios of SONUS and Nycomed Amersham, and we believe that the combination of
these two portfolios represents the strongest patent estate in the industry,"
said Michael A. Martino, President and Chief Executive Officer of SONUS. "By
leveraging the value of our patents, the arrangement provides necessary
operating capital to SONUS without any dilution to our shareholders and enables
us to avoid the cost and distraction of future intellectual property disputes."

SONUS Pharmaceuticals, Inc., with headquarters in Bothell, Washington, is
engaged in the research and development of proprietary ultrasound contrast
agents and drug delivery systems. The Company's products are being investigated
for use in the diagnosis and treatment of heart disease, cancer and other
debilitating conditions. News releases and other corporate information are
available on SONUS' web site at www.sonuspharma.com. News releases may also be
obtained via fax by calling 800-758-5804, Ext. 108377.



                                       1
<PAGE>   2

Based in Amersham, England, Nycomed Amersham plc is a world leader in in-vivo
diagnostic imaging and in life sciences. The company has annual sales of Pound
Sterling1.1 billion and approximately 8,500 employees worldwide.


Contacts: Gregory Sessler or Pamela Dull, SONUS Pharmaceuticals, (425) 487-9500
          Tracy Cheung, Nycomed Amersham, (44) 1494 542051
          Corinne Daniels, Brunswick Group Limited, (44) 171 404 5959

Certain of the statements made in this news release are forward-looking such as
those, among others, relating to the value and strength of SONUS' patents and
the receipt of royalties and sublicense fees. As discussed in the Company's
annual report on Form 10-K filed March 25, 1999, actual results could differ
materially from those projected in the forward-looking statements as a result of
the following factors, among others: there can be no assurance that any or all
of SONUS' patents will survive any legal challenges or will be ultimately
enforceable or that any royalties will be received on licenses to the Company's
patents. In addition, there can be no assurance that third parties will not be
able to develop competitive products or processes that do not infringe any valid
patents held by SONUS, or that any patents will issue from pending or future
patent applications of the Company; SONUS' ultrasound contrast products will
require regulatory approval by the FDA and other regulatory agencies, which
approvals may never occur or may be subject to certain regulatory requirements;
and market acceptance of the Company's products will depend upon a number of
factors, including safety, efficacy, ease of administration, the presence of
competitive imaging products or technologies and the availability of
reimbursement by third party payors.



                                       ###



                                       2


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