Document:

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                                                                   EXHIBIT 10.35

                          SECURITIES PURCHASE AGREEMENT

        This Securities Purchase Agreement is entered into as of this 31 day of
January 1999 by and between Abbott Laboratories, an Illinois corporation
("Abbott") and SONUS Pharmaceuticals, Inc. a Delaware corporation ("SONUS").

                                    RECITALS

        A.     Concurrently herewith Abbott and SONUS are entering into a First
Amendment to that certain Agreement between Abbott and SONUS dated May 14, 1996
(as amended, the "U.S. Agreement") and a First Amendment to that certain
International License Agreement dated October 1, 1996 (as amended, the
"International Agreement") (the U.S. Agreement and the International Agreement
are collectively referred to herein as the "Agreements") whereby, among other
things, Abbott and SONUS have agreed that certain milestone payments shall be
made conditioned upon the achievement of specified milestones relating to a
Cardiology Indication (the "Cardiology Milestone Payments"), and that certain
milestone payments shall be conditioned upon the achievement of specified
milestones relating to a specified Radiology Indication (collectively, the
"Radiology Milestone Payments"), as more particularly specified on Appendix 2.3
of the U.S. Agreement and Appendix 5.2 and 5.3 of the International Agreement.

        B.     The Agreements provide that SONUS shall have the right to request
that Abbott prepay all or a portion of the Radiology Milestone Payments on or
after the Radiology Prepayment Date, as specified in Exhibit A attached hereto,
in consideration for the issuance by SONUS of shares of its Common Stock under
the terms and conditions provided herein.

        C.     Pursuant to Section 2.4 of the U. S. Agreement, and Article
2.2(A) of the International Agreement, Abbott may at its option elect to fund
certain expenditures for clinical research conducted by SONUS to support
research and development for ultrasound diagnostic applications for certain
specified indications for the Product, in which event SONUS shall become
obligated to reimburse Abbott fifty percent (50%) of such costs and expenses
funded by Abbott plus accrued interest (the "Additional Clinical Reimbursement
Amounts"). Such sections of the Agreements further provide that in the event
that the net tangible assets of SONUS shall at any time fall below an amount
equal to the current Nasdaq National Market listing requirement for net tangible
assets contained in paragraph 4450(a)(3) of the NASD Manual, plus $1,000,000,
SONUS at its option may repay the Additional Clinical Reimbursement Amounts by
delivering shares of Common Stock of SONUS pursuant to the terms and provisions
set forth herein.

        In consideration of the foregoing, and for other good and valuable
consideration, the receipt and adequacy of which is hereby acknowledged, the
parties hereby agree as follows:

        1.     Definitions. Capitalized terms used but not otherwise defined
herein shall have the meanings set forth in the Agreements, or a specific
Agreement as may be indicated herein or as may be applicable due to variations
in certain definitions between the Agreements.

<PAGE>

        2.     Purchase and Sale of Common Stock Upon Prepayment of Radiology
Milestone Payments and Payment of Repayment Amount.

                      2.1    Purchase and Sale Upon Prepayment of Radiology
Milestone Payments. In the event that SONUS desires that Abbott prepay all or
any portion of the Radiology Milestone Payment, SONUS shall give written notice
to Abbott of such prepayment request within one (1) year following the Radiology
Prepayment Date, which notice shall specify the amount of the prepayment (which
may not exceed the amount of the Radiology Milestone Payment). In such event,
pursuant to the terms and conditions set forth herein, SONUS shall issue to
Abbott and Abbott shall accept and purchase from SONUS a number of shares of
Common Stock equal to the amount of the prepayment divided by the "Fair Market
Value" per share of Common Stock. The "Fair Market Value" of the Common Stock
shall be determined as follows:

                             (a)    If the Common Stock is listed on a national
securities exchange or admitted to unlisted trading privileges on such an
exchange, or is listed on the Nasdaq National Market or Small Cap Market or any
comparable system, the current Fair Market Value shall be the average of the
daily closing prices of the Common Stock on such exchange or Nasdaq for the
twenty (20) trading days prior to the notice by SONUS to Abbott of the requested
prepayment; the closing price for any day shall be the last reported sale price
regular way or, if no such reported sale takes place on such day, the average of
the closing bid and asked prices regular way for such day, in each case (1) on
the principal national securities exchange on which the shares of Common Stock
are listed or to which such shares are admitted to trading or (2) if the Common
Stock is not listed or admitted to trading on a national securities exchange, in
the over-the-counter market as reported by Nasdaq or any comparable system; or

                             (b)    If the Common Stock is not so listed or
admitted to unlisted trading privileges or quoted on Nasdaq or any comparable
system, the current Fair Market Value shall be the average of the daily closing
prices for the twenty (20) trading days prior to the notice by SONUS to Abbott
of the requested repayment as furnished by two members of Nasdaq selected from
time to time in good faith by the Board of Directors of SONUS for that purpose;
or

                             (c)    In the absence of the foregoing valuation
methods in Section 2.1(a) or (b), or if for any other reason the Fair Market
Value per share cannot be determined pursuant to Section 2.1(a) or (b), the
current Fair Market Value shall be determined in good faith as promptly as
reasonably practicable by the Board of Directors of SONUS.

                             (d)    Anything herein to the contrary
notwithstanding, for the purpose of determining Fair Market Value under this
Section 2.1 (but not in Section 3.1), the Fair Market Value shall not exceed
$16.00 per share of Common Stock.

               2.2    Purchase and Sale Upon Payment of Repayment Amount. In the
event SONUS has requested that Abbott prepay a Radiology Milestone Payment and
SONUS fails to achieve the milestone giving rise to the Radiology Milestone
Payment within five (5) years from the date of this Agreement, SONUS shall be
obligated to pay Abbott an amount equal to thirty percent (30%) of the amounts
prepaid (the "Repayment Amount") in cash, or by the issuance of shares of Common
Stock. In the event SONUS elects to pay the Repayment Amount in cash, such
repayment shall be made within ten (10) days following the expiration of the
five (5) year period. In the event SONUS elects to pay the Repayment Amount in
the form of the issuance of shares of Common Stock, SONUS shall issue to Abbott
and Abbott shall accept and purchase from SONUS that number

                                       2
<PAGE>

of shares of Common Stock of SONUS equal to the Repayment Amount divided by the
Fair Market Value per share (determined in accordance with Section 2.1 above for
the seventeen (17) trading days preceding the third trading day prior to the
closing date). The issuance of such shares of Common Stock shall constitute
payment in full of the Repayment Amount. Anything herein to the contrary
notwithstanding, in the event that SONUS elected to pay the Repayment Amount in
the form of issuance of shares of SONUS Common Stock and either (i) SONUS'
ability to issue some or all of the shares of Common Stock for such repayment to
Abbott is suspended pursuant to the terms of Section 2.4, or (ii) the conditions
to closing set forth in Section 6 have not been fulfilled within 180 days
following the expiration of the five (5) year period following the date hereof,
then in either such event SONUS shall pay to Abbott the portion of the Repayment
Amount (not paid in the form of Common Stock) in the form of cash or in another
form mutually agreed to by the parties.

               2.3    Closing. The closing for the purchase and sale of shares
of Common Stock shall occur at a mutually agreeable date and location, which
shall occur within the later of (i) (A) ten (10) days from the date of the
notice of exercise of prepayment by SONUS in the case of shares issued pursuant
to Section 2.1 above, or (B) within ten (10) days of expiration of the five (5)
year period following the date hereof in the case of shares issued pursuant to
Section 2.2 above, or (ii) five (5) days following the fulfillment of all of the
conditions set forth in Section 6 below. At the closing, SONUS shall deliver to
Abbott shares of Common Stock as provided in Section 2.1 or Section 2.2 above,
as applicable, against payment by Abbott to SONUS of the prepayment amount in
the case of Section 2.1 above. In addition, a duly authorized officer of each of
SONUS and Abbott shall deliver to the other a certificate confirming that their
respective representations and covenants set forth in Sections 4 and 5, as
applicable, are true and correct in all material respects as of the closing
date.

               2.4    Suspension of Right to Request Prepayment. Anything herein
to the contrary notwithstanding, SONUS shall not have the right to request that
Abbott make any prepayment of any Radiology Milestone Payment or accept payment
of any Repayment Amount in return for the issuance of shares of Common Stock as
provided in this Section 2 if the number of shares of Common Stock to be issued
to Abbott would result in Abbott beneficially owning shares of Common Stock of
SONUS following the issuance in an amount equal to 19.9% or more of the
outstanding Common Stock of SONUS in which event SONUS shall be obligated to pay
the appropriate Repayment Amount in cash as set forth in Section 5(E) of the
U.S. Agreement or Section 5.5 of the International Agreement, as applicable. The
shares of Common Stock of SONUS subject to any warrants or other rights to
acquire shares of Common Stock shall be included for the purpose of determining
the number of shares beneficially owned by Abbott, but warrants and other rights
to acquire Common Stock held by persons other than Abbott shall not be included
for the purpose of determining the total amount of outstanding Common Stock.
Furthermore, anything herein to the contrary notwithstanding, SONUS shall not
have the right to request that Abbott make any prepayment of any Radiology
Milestone Payment (a) with respect to the U.S. Agreement (i) relating to the
U.S. NDA approval milestone unless and until SONUS has received the first U.S.
FDA approval of the Product in the Field (as defined in the U.S. Agreement), and
(ii) relating to the U.S. first shipment of Product milestone unless and until
the U.S. first shipment of Product has occurred and (b) with respect to the
International Agreement (i) relating to the U.S. NDA approval milestone, unless
and until SONUS has received the first U.S. FDA approval of the Product in the
Field (as defined in the U.S. Agreement) and (ii) relating to the first shipment
date of the Product in Germany, France, Italy, Spain, Canada or the United
Kingdom milestone, unless and until the first shipment of Product has occurred
in any such country. SONUS shall not repurchase its shares of Common Stock if
such repurchases (including shares repurchased by SONUS from Abbott) would cause
Abbott to

                                       3
<PAGE>

beneficially own 19.9% or more of the outstanding Common Stock of SONUS,
calculated as set forth above.

        3.     and Sale of Common Stock Upon Exercise of Additional Clinical
               Research Reimbursement Option.

               3.1    Purchase and Sale. SONUS shall have the right at any time
after the amount of its net tangible assets is below an amount equal to the then
current Nasdaq National Market listing requirement for net tangible assets
contained in paragraph 4450(a)(3) of the NASD Manual, as such paragraph may be
amended from time to time, plus $1,000,000, to elect to fulfill its obligations
to repay Abbott for any or all of the outstanding Additional Clinical
Reimbursement Amounts payable to Abbott by the delivery to Abbott of shares of
Common Stock of SONUS. The amount of net tangible assets of SONUS shall be
determined as of the end of any month according to the unaudited balance sheet
of SONUS prepared in accordance with generally accepted accounting principles.
In the event SONUS desires to make such election, it shall notify Abbott in
writing of the election, specifying the amount of the Additional Clinical
Reimbursement Amount to be paid by delivery to Abbott of shares of Common Stock
and including a copy of the most recent monthly unaudited balance sheet.

               3.2    Closing. The closing of the purchase and sale of shares of
Common Stock in connection with any such election shall be a mutually agreeable
date and location, which shall be within the later of (i) ten (10) days from the
notice from SONUS, or (ii) five (5) days following the fulfillment of all of the
conditions set forth in Section 6 below. At the closing, SONUS shall deliver to
Abbott a number of shares of Common Stock of SONUS equal to the amount of the
Additional Clinical Reimbursement Amount to be so paid, divided by the Fair
Market Value per share of Common Stock of SONUS determined in accordance with
the provisions of Section 2.1 above (excluding paragraph 2.1(d), against a
receipt by Abbott acknowledging receipt of the shares of Common Stock and a
cancellation of the Additional Clinical Reimbursement Amount to be so paid. In
addition, a duly authorized officer of each of SONUS and Abbott shall deliver to
the other a certificate confirming that the respective representations,
warranties and covenants set forth in Section 4 and 5 as applicable, are true
and correct in all material respects as of the closing date.

               3.3    Suspension of Right to Issue Shares. Anything herein to
the contrary notwithstanding, SONUS shall not have the right to pay the
Additional Clinical Reimbursement Amounts in shares of Common Stock as provided
in this Section 3 if the number of shares of Common Stock to be issued to ABBOTT
would result in ABBOTT beneficially owning shares of Common Stock of SONUS
following the issuance in an amount equal to 19.9% or more of the outstanding
Common Stock of SONUS, in which event SONUS shall be obligated to pay the
Additional Clinical Reimbursement Amounts in cash as set forth in Section 2.4 of
the U.S. Agreement or Section 2.2A of the International Agreement, as
applicable. The shares of Common Stock of SONUS subject to any warrant or other
right to acquire shares of Common Stock held by Abbott shall be included for the
purpose of determining the number of shares beneficially owned by Abbott but
warrants and other rights to acquire Common Stock held by persons other than
Abbott shall not be included for the purpose of determining the total amount of
outstanding Common Stock.

                                       4
<PAGE>

        4.     Representations, Warranties and Covenants of SONUS. SONUS hereby
represents and warrants to, and covenants with, Abbott as of the date hereof as
follows:

               4.1    Authorization. SONUS has full power and authority to
execute, deliver and perform its obligations under this Agreement and to issue
and sell the Common Stock. All corporate action on the part of SONUS necessary
for the authorization, execution and delivery of this Agreement and the Common
Stock and the performance of all obligations of SONUS hereunder has been taken.
The execution and delivery of this Agreement and the Common Stock and the
performance of all obligations of SONUS hereunder have been duly authorized and
approved by the Board of Directors of SONUS and no further authorization is
necessary. This Agreement and the Common Stock are valid and legally binding
obligations of SONUS enforceable against it in accordance with their terms.

               4.2    No Conflict. The execution, delivery and performance of
this Agreement and the issuance and sale of the Common Stock and the
consummation of each of the transactions contemplated hereby and thereby do not
and will not (a) conflict with or result in a breach of the terms, conditions or
provisions of, (b) with or without notice or lapse of time or both, constitute a
default under, (c) result in the creation of any lien, security interest, charge
or encumbrance upon the capital stock or assets of SONUS pursuant to, (d) with
or without notice or lapse of time or both, give any third party the right to
accelerate, cancel or terminate any obligation under, (e) result in a violation
of, or (f) require any order, qualification, waiver, permit, authorization,
consent, approval, exemption or other action by or from, or any registration,
notice, declaration, application or filing to or with, any court or
administrative or governmental body or any other person or entity pursuant to
(i) the Certificate of Incorporation or Bylaws of SONUS, (ii) any agreement to
which SONUS is a party or is bound or to which its assets are subject, which
conflict, breach or default would have a material adverse effect on SONUS or the
ability of SONUS to perform its duties or obligations hereunder or (iii) any
law, statute, rule or regulation to which SONUS is subject; provided, however,
that with respect to clause (f) of this Section 4.2, no representation or
warranty is made as to any such requirements applicable to SONUS as a result of
the specific legal or regulatory status of Abbott (including without limitation
any agreements between Abbott or its affiliates) or as a result of any other
facts that specifically relate to Abbott, any business in which Abbott has
engaged or proposes to engage or any financing arrangements or transactions
entered into or proposed to be entered into by or on behalf of Abbott and
provided, further, that no representation or warranty is made with respect to
the application of the Hart-Scott-Rodino Antitrust Improvement Act of 1976, as
amended (the "HSR Act"), to the issuance of the Common Stock. In the event that
the HSR Act should apply to the issuance of any shares of Common Stock, upon the
request of Abbott, SONUS agrees to prepare and file, and to assist Abbott and
cooperate with Abbott in its preparation and filing of all necessary
notifications and the providing of all necessary information pursuant to the HSR
Act. The fees for any such HSR filing shall be paid fifty percent (50%) by SONUS
and fifty percent (50%) by Abbott.

               4.3    Valid Issuance of Common Stock. The Common Stock, when
issued, sold and delivered in accordance with the terms of this Agreement to
Abbott, will be duly authorized and validly issued and will be issued in
compliance in all material respects with all federal and state securities laws.
The shares of Common Stock have been duly and validly reserved for issuance and,
upon issuance in accordance with the terms hereof, will be duly authorized,
validly issued, fully paid and nonassessable and, assuming no distribution of
the Common Stock by Abbott, will be issued in compliance with all applicable
federal and state securities laws.

                                       5
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               4.4    Valid Existence and Capitalization. SONUS is duly
incorporated, validly existing and in good standing under the laws of the State
of Delaware and is qualified to do business as a foreign corporation in the
State of Washington. As of the date hereof, the description of the
capitalization of SONUS and its outstanding equity securities and rights to
acquire equity securities and the holders thereof is as set forth on Exhibit B.

               4.5    SEC Documents. As of their respective dates, all
registration statements and reports filed by SONUS with the Securities and
Exchange Commission under the Securities Act of 1933, as amended, and the
Securities Exchange Act of 1934, as amended, since January 1, 1998 complied in
all material respects with the requirements of such Acts and the rules and
regulations promulgated thereunder and did not contain any untrue statement of a
material fact or omit to state a material fact required to be stated therein or
necessary to make the statements therein not misleading.

        5.     and Covenants of Abbott. Abbott hereby represents and warrants
to, and covenants with, SONUS as of the date hereof as follows:

               5.1    Authorization. Abbott has full power and authority to
execute, deliver and perform its obligations under this Agreement. All corporate
action on the part of Abbott necessary for the authorization, execution and
delivery of this Agreement and the performance of all obligations of Abbott
hereunder has been taken. The execution and delivery of this Agreement and the
performance of all obligations of Abbott hereunder were duly authorized and
approved by Abbott, and no further authorization is necessary. This Agreement is
a valid and legally binding obligation of Abbott, enforceable against it in
accordance with its terms.

               5.2    No Conflict. The execution, delivery and performance of
this Agreement and the consummation of each of the transactions contemplated
hereby do not and will not (a) conflict with or result in a breach of the terms,
conditions or provisions of, (b) with or without notice or lapse of time or
both, constitute a default under, (c) result in the creation of any lien,
security interest, charge or encumbrance upon Abbott's capital stock or assets
pursuant to, (d) with or without notice or lapse of time or both, give any third
party the right to accelerate, cancel or terminate any obligation under, (e)
result in a violation of, or (f) require any order, qualification, waiver,
permit, authorization, consent, approval, exemption or other action by or from,
or any registration, notice, declaration, application or filing to or with, any
court or administrative or governmental body or any other person or entity
pursuant to (i) the Certificate of Incorporation or Bylaws of Abbott, (ii) any
material agreement to which Abbott is a party or is bound or to which its assets
are subject or (iii) any law, statute, rule or regulation to which Abbott is
subject; provided, however, that with respect to clause (f) of this Section 5.2,
no representation or warranty is made as to any such requirements applicable to
Abbott as a result of the specific legal or regulatory status of SONUS
(including without limitation any agreements between SONUS or its affiliates) or
as a result of any other facts that specifically relate to SONUS, any business
in which SONUS has engaged or proposes to engage or any financing arrangements
or transactions entered into or proposed to be entered into by or on behalf of
SONUS and provided, further, that no representation or warranty is made with
respect to the application of the HSR Act to the issuance of the Common Stock.
Upon the request of SONUS, Abbott agrees to prepare and file, and to assist
SONUS and cooperate with SONUS in its preparation and filing of all necessary
notifications and the providing of all necessary information pursuant to the HSR
Act. The fees for any such HSR filing shall be paid fifty percent (50%) by
Abbott and fifty percent (50%) by SONUS.

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<PAGE>

               5.3    Accredited Investor Status. Abbott is an "accredited
investor" within the meaning of Regulation D promulgated under the Securities
Act of 1933, as amended (the "Securities Act").

               5.4    Restricted Securities. Abbott understands that the shares
of Common Stock to be issued hereunder are restricted securities and may not be
sold, transferred or otherwise disposed of without registration under the
Securities Act or the availability of an exemption therefrom, and that in the
absence of an effective registration statement covering such securities or an
exemption from registration, the Common Stock must be held indefinitely. In the
absence of an effective registration statement under the Securities Act with
respect to the Common Stock, Abbott shall notify the Company of any proposed
disposition by Abbott of the Common Stock, shall furnish SONUS with a statement
of the circumstances surrounding the proposed disposition and, if reasonably
requested by SONUS, shall furnish SONUS with an opinion of counsel, reasonably
satisfactory to SONUS, that such disposition will not require the registration
of such Common Stock under the Securities Act; provided, however, that a notice
and an opinion of counsel will not be required for routine sales under Rule 144
under the Securities Act.

        6.     Conditions. The closing of the purchase by Abbott of Common Stock
of SONUS under Sections 2.3 and 3.2 shall be conditioned upon receipt of the
officer's certificates referenced in Sections 2.3 and 3.2, and upon the
following conditions any or all of which may be waived by Abbott in its sole
discretion:

               6.1    Agreements in Effect. The amendments to the Agreements
referred to in Recital A above shall have been executed and delivered by the
parties thereto, and the Agreements shall be in full force and effect and SONUS
shall not be in breach, after all applicable cure periods, in any material
respect of its obligations thereunder.

               6.2    No Material Adverse Change. Since the end of the last
fiscal quarter of SONUS, there shall have been no material adverse change in the
business, management, results of operations or financial condition of SONUS
which has not been publicly disclosed by SONUS.

               6.3    Hart-Scott-Rodino. If the HSR Act shall apply, all waiting
periods under the HSR Act shall have expired or been earlier terminated without
action by the Justice Department or the Federal Trade Commission to prevent or
materially alter the consummation of the transactions contemplated by this
Agreement.

               6.4    Actions or Proceedings. No action or proceeding by any
court or other governmental authority or other person or entity shall have been
instituted or threatened which could enjoin or prohibit any provision of this
Agreement or the consummation of the transactions contemplated hereby.

                                       7
<PAGE>

        7.     Miscellaneous.

               7.1    Governing Law. This Agreement shall be governed by, and
construed in accordance with the laws of the State of Delaware, without regard
to the conflicts of law rules of such state.

               7.2    Successors and Assigns. Neither this Agreement nor any of
the rights, interests or obligations hereunder shall be assigned by SONUS or
Abbott without the prior written consent of Abbott or SONUS, respectively;
provided, however, that either party may assign this Agreement to any of its
Affiliates, or to any successor by merger or sale of substantially all of its
business unit to which this Agreement relates without the consent of the other
party. Any assignment or delegation in contravention of this Agreement shall be
void and shall not relieve the assigning or delegating party of any obligation
hereunder. Except as set forth in the preceding sentences, this Agreement shall
inure to the benefit of and be binding upon the parties hereto and their
respective successors and permitted assigns.

               7.3    No Third Party Beneficiaries. Nothing in this Agreement,
whether express or implied, shall be construed to give any person, other than
the parties hereto, any legal or equitable right, remedy or claim under or in
respect of this Agreement.

               7.4    Counterparts. This Agreement may be executed in any number
of counterparts with the same effect as if all parties hereto had signed the
same document. Each counterpart shall be enforceable against the parties
actually executing such counterpart, and all counterparts shall be construed
together and shall constitute one instrument.

               7.5    Severability. If one or more provisions of this Agreement
are held to be unenforceable under applicable law, such provision shall be
excluded from this Agreement and the balance of the Agreement shall be
interpreted as if such provision were so excluded and shall be enforceable in
accordance with its terms.

               7.6    Notices. Unless otherwise provided, any notice required or
permitted under this Agreement shall be given as follows:

                                       8
<PAGE>

                      To Abbott:

               (1)    Abbott Laboratories
                      100 Abbott Park Road
                      Abbott Park, Illinois 60064-3500
                      Attn: President - Hospital Products Division

                      With a copy to:

                      Abbott Laboratories
                      100 Abbott Park Road
                      Abbott Park, Illinois 60064-3500
                      Attn: Divisional Vice President
                            Domestic Legal Affairs
                            D-322/AP6D

              and (2) Abbott International, Ltd.
                      200 Abbott Park Road
                      Abbott Park, Illinois 60064-3537
                      Attn: President - Abbott International

                      With a copy to:

                      Abbott International, Ltd.
                      100 Abbott Park Road
                      Abbott Park, Illinois 60064-3500
                      Attn: Divisional Vice President
                            International Legal Operations
                            D-323/AP6D

                      To SONUS:

                      SONUS Pharmaceuticals, Inc.
                      22026 20th Avenue, S.E., Suite 201
                      Bothell, Washington 98021
                      Attn: Chief Executive Officer

               7.7    Public Announcements. Any press release or other public
statement issued by any party relating to this Agreement or the transactions
contemplated hereby shall be governed by Section 22 of the U.S. Agreement.

               7.8    Entire Agreement. This Agreement constitutes the entire
agreement between the parties concerning the subject matter hereof. This
Agreement may be amended, modified or waived only by a written instrument
executed by duly authorized representatives or both parties.

               7.9    Alternative Dispute Resolution. The Parties agree that any
dispute that arises in connection with this Agreement shall be determined
according to the Alternative Dispute Resolution provisions set forth in Section
21 of the U.S. Agreement.

                                       9
<PAGE>

        IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first above written.

                               SONUS PHARMACEUTICALS, INC.

                               By: /s/ Michael A. Martino
                                   ---------------------------------------------
                                   Name: Michael A. Martino
                                   Title:   President

                               ABBOTT LABORATORIES

                               By: /s/ Richard A. Gonzalez
                                   ---------------------------------------------
                                   Name: Richard A. Gonzalez
                                   Title: President - Hospital Products Division

Attachments:

Exhibit A - Radiology Milestone Dates
Exhibit B - Capitalization of SONUS

                                       10
<PAGE>

                                    EXHIBIT A

U.S. AGREEMENT

<TABLE>
<CAPTION>
-----------------------------------------------------------------------
                                 RADIOLOGY             RADIOLOGY
        MILESTONE             PREPAYMENT DATE      MILESTONE PAYMENT
<S>                           <C>                  <C>
-----------------------------------------------------------------------
         U.S. NDA                 6/1/99*               $2.0 Million
         Approval
-----------------------------------------------------------------------
        U.S. First                7/1/99**              $2.0 Million
   Shipment of Product
-----------------------------------------------------------------------
                                                 Total: $4.0 Million
-----------------------------------------------------------------------
</TABLE>

INTERNATIONAL AGREEMENT

<TABLE>
<CAPTION>
-----------------------------------------------------------------------
                                 RADIOLOGY             RADIOLOGY
        MILESTONE             PREPAYMENT DATE      MILESTONE PAYMENT
-----------------------------------------------------------------------
<S>                           <C>                  <C>
         U.S. NDA                 6/1/99*                $1,500,000
 Approval Within 15 Days
-----------------------------------------------------------------------
        European Community
     Authorization Granted
          Within 105 days:         2/1/99                  $850,000
          Within 195 days:         2/1/99                  $850,000
          Within 265 days:         5/1/99                  $350,000
-----------------------------------------------------------------------
    First Shipment Date of
          Product for Sale
      (to Germany, France,
  Italy, Spain, Canada, or
       the United Kingdom)
           Within 15 days:       6/1/99***               $1,500,000
          Within 105 days:       9/1/99***                 $500,000
-----------------------------------------------------------------------
                                                  Total: $5,550,000
-----------------------------------------------------------------------
</TABLE>

* Anything herein to the contrary notwithstanding, the Radiology Prepayment Date
shall be the later of (i) the date referenced, or (ii) the first U.S. FDA
approval for the Product in the Field (as defined in the U.S. Agreement).

** Anything herein to the contrary notwithstanding, the Radiology Prepayment
Date shall be the later of (i) the date referenced, or (ii) the U.S. first
shipment of Product.

*** Anything herein to the contrary notwithstanding, the Radiology Prepayment
Date shall be the later of (i) the date referenced, or (ii) the first shipment
date of Product in Germany, France, Italy, Spain, Canada or United Kingdom.

                                       1
<PAGE>

                                    EXHIBIT B

                             CAPITALIZATION OF SONUS

Common Stock:

      Authorized:         20,000,000 shares of Common Stock; 5,000,000 shares of
                          Preferred Stock

      Outstanding as of
      December 31, 1998:  8,632,225 shares of Common Stock
                          No shares of Preferred Stock

Options:

      Authorized:         2,022,137
      Outstanding as of
      December 31, 1998:  1,311,091

Warrants:

      Outstanding as of
      December 31, 1998:  785,161

------
Note: SONUS also has in place a Stockholders Rights Plan which provides for the
issuance of Convertible Preferred Stock under certain circumstances.

                                       2<PAGE>
                                                                   EXHIBIT 10.50

                           FOURTH AMENDMENT TO LEASE
                                    RENEWAL

This FOURTH AMENDMENT TO LEASE (this "Fourth Amendment") is made this 29th day
of November, 2001 (the "Reference Date"), by and between TEACHERS INSURANCE &
ANNUITY ASSOCIATION OF AMERICA, INC., a New York corporation ("Landlord") and
SONUS PHARMACEUTICALS, INC., a New York corporation ("Landlord") and SONUS
PHARMACEUTICALS, INC., a Delaware corporation ("Tenant").

                                    RECITALS

     Landlord is the landlord and Tenant is the tenant under that certain Lease
dated January 14, 1994 (the "Initial Lease"), for premises located at 22026
20th Avenue SE, Bothell, Washington 98021, Building L, Unit 102 (the "Initial
Premises"), as modified by First Amendment to Lease dated for reference
purposes August 26, 1996 (the "First Amendment"), by the Second Amendment dated
for reference purposes October 28, 1997 (the "Second Amendment"), and by the
Third Amendment dated for reference purposes October 15, 1998 (the "Third
Amendment"). As used herein the "Amended Lease shall mean the Initial Lease as
modified by the First Amendment, Second Amendment and Third Amendment; and the
"Lease" shall mean the Amended Lease as further amended by this Fourth
Amendment.

     The parties desire to further amend the Amended Lease and effective on the
Reference Date stated above the portions of the Lease as numbered below shall
be amended to read as follows:

     Except as otherwise specifically defined herein all capitalized terms shall
have the meanings assigned in the Amended Lease.

1.g. EXTENDED TERM OF THE LEASE: The Lease Expiration Date shall be July 31,
2007.

1.h. RENT ADJUSTMENT: Additional Base Monthly Rent Adjustments shall be as
follows:

     Effective Date of Rent        New Base Monthly Rent
     Increase
     May 1, 2002                   $0.00
     June 1, 2002                  $45,750.00
     October 1, 2002               $0.00
     November 1, 2002              $45,750.00
     October 1, 2003               $0.00
     November 1, 2003              $45,750.00
     August 1, 2004                $48,500.00
     August 1, 2006                $51,500.00

1k.  SECURITY DEPOSIT: On May 1, 2002, the Security Deposit shall be increased
to $51,500.00 of which $18,039.00 has previously been deposited with Landlord.

15.  RELEASE AND INDEMNITY.
a.   Indemnity. Tenant shall indemnify, defend (using legal counsel reasonably
acceptable to Landlord) and save Landlord and its property manager harmless
from all claims, suits, losses, damages, fines, penalties, liabilities and
expenses (including Landlord's personnel and overhead costs and attorneys fees
and other costs incurred in connection with claims, regardless of whether such
claims involve litigation, but excluding consequential damages such as lost
profits) resulting from any actual or alleged injury (including death) of any
person or from any actual or alleged loss of or damage to, any property arising
out of or in connection with (i) Tenant's occupation, use or improvement of the
Premises, or that of its employees, agents or contractors, (ii) Tenant's breach
of its obligations hereunder, or (iii) any act or omission  of Tenant or any
subtenant, licensee, assignee or concessionaire of Tenant, or of any officer,
agent, employee, guest or invitee of Tenant, or of any such entity in or about
the Premises, provided that this indemnity shall not apply to claims to the
extent caused by Landlord's gross negligence or willful misconduct. Tenant
agrees that the foregoing indemnity specifically covers actions brought by its
own employees. This indemnity with respect to acts or omissions during the term
of this Lease shall survive termination or expiration of this Lease. The
foregoing indemnity is specifically and expressly intended to,

<PAGE>
constitute a waiver of Tenant's immunity under Washington's Industrial
Insurance Act, RCW Title 51, to the extent necessary to provide Landlord with a
full and complete indemnity from claims made by Tenant and its employees, to
the extent provided herein. Tenant shall promptly notify Landlord of casualties
or accidents occurring in or about the Premises. LANDLORD AND TENANT
ACKNOWLEDGE THAT THE INDEMNIFICATION PROVISIONS OF SECTION 8 AND THIS SECTION
15 WERE SPECIFICALLY NEGOTIATED AND AGREED UPON BY THEM.

b.   LANDLORD INDEMNITY. Except as otherwise provided in this Section 15,
Landlord shall indemnify, defend (using legal counsel reasonably acceptable to
Tenant) and save Tenant harmless from all claims, suits, losses, fines,
penalties, liabilities and expenses (including Tenant's personnel and overhead
costs and attorneys' fees and other costs incurred in connection with claims,
regardless of whether such claims involve litigation, but excluding
consequential damages such as lost profits) resulting from any actual or
alleged injury (including death) of any person or from any actual or alleged
loss of or damage to, any property to the extent caused by the intentional
misconduct or gross negligence of Landlord or of any employee or agent of
Landlord in the Common Areas. Landlord agrees that the foregoing indemnity
specifically covers actions brought by its own employees. This indemnity with
respect to actions or omissions during the term of this Lease shall survive
termination or expiration of this Lease. The foregoing indemnity is
specifically and expressly intended to constitute a waiver of Landlord's
immunity under Washington's Industrial Insurance Act, RCW Title 51, to the
extent necessary to provide Tenant with a full and complete indemnity from all
claims made by Landlord and its employees to the extent provided herein.
LANDLORD AND TENANT ACKNOWLEDGE THAT THE INDEMNIFICATION PROVISIONS OF SECTION
15 WERE SPECIFICALLY NEGOTIATED AND AGREED UPON BY THEM.

c.   RELEASE. Tenant hereby fully and completely releases all claims against
Landlord for any losses or other damages sustained by Tenant or any person
claiming through Tenant resulting from any accident or occurrence in or upon
the Premises, including but not limited to: any defect in or failure of Project
equipment; any failure to make repairs; any defect, failure, surge in, or
interruption of Project facilities or services; any defect in or failure of
Common Areas; broken glass; water leakage; the collapse of any Building
component; or any act, omission or negligence of co-tenants, licensees or any
other persons or occupants of the Building, provided only that the release
contained in this Section 15(b) shall not apply to claims for actual damage to
persons or property (excluding consequential damages such as lost profits) to
the extent caused by Landlord's gross negligence or willful misconduct or
breach of its express obligations under this Lease which Landlord has not cured
within a reasonable time after receipt of written notice of such breach from
Tenant. Notwithstanding any other provision of this Lease, and to the fullest
extent permitted by law, Tenant hereby agrees that Landlord shall not be liable
for injury to Tenant's business or any loss of income therefrom, whether such
injury or loss results from conditions arising upon the Premises or the
Project, or from other sources or places including, without limitation, any
interruption of services and utilities or any casualty, or from any cause
whatsoever, including Landlord's negligence, and regardless of whether the
cause of such injury or loss or the means of repairing the same is inaccessible
to Landlord or Tenant. Tenant may elect, at its sole cost and expense, to
obtain business interruption insurance with respect to such potential injury
and loss.

d.   LIMITATION ON INDEMNITY. In compliance with RCW 4.24.115 as in effect on
the date of this Lease, all provisions of this Lease pursuant to which Landlord
or Tenant (the "Indemnitor") agrees to indemnify the other (the "Indemnitee")
against liability for damages arising out of bodily injury to Persons or damage
to property relative to the construction, alteration, repair, addition to,
subtraction from, improvement to, or maintenance of, any building, road, or
other structure, project, development, or improvement attached to real estate,
including the Premises, (i) shall not apply to damages caused by or resulting
from the sole negligence of the Indemnitee, its agents or employees, and (ii)
to the extent caused by or resulting from the concurrent negligence of (a) the
Indemnitee or the Indemnitee's agents or employees, and (b) the Indemnitor or
the Indemnitor's agents or employees, shall apply only to the extent of the
Indemnitor's negligence; PROVIDED, HOWEVER, the limitations on indemnity set
forth in this Section shall automatically and without further act by either
Landlord or Tenant be deemed amended so as to remove any of the restrictions
contained in this Section no longer required by then applicable law.

c.   DEFINITIONS. As used in any Section establishing indemnity or release of
Landlord, "Landlord" shall include Landlord, its partners, officers, agents,
employees and contractors, and "Tenant" shall include Tenant and any person or
entity claiming through Tenant.

<PAGE>
16.  INSURANCE: Tenant shall, throughout the term of this Lease and any renewal
hereof, at its own expense, keep and maintain in full force and effect, a policy
of commercial general liability (occurrence form) insurance, including
contractual liability (including Tenant's indemnification obligations under this
Lease) insuring Tenant's activities upon, in or about the Premises or the
Project, against claims of bodily injury or death or property damage or loss
with a combined single limit of not less than One Million Dollars ($1,000,000)
per occurrence and an excess/umbrella liability insurance policy with minimum
limits of not less than Five Million Dollars ($5,000,000), with such increases
in limits as Landlord may from time to time require consistent with insurance
requirements of institutional landlords in similar projects in the area, if such
increased limits are available at commercially reasonable terms. If Tenant
manufactures on the Premises consumer goods using any materials supplied by
Landlord (including but not limited to water supplied as part of utilities to
the Premises), Tenant's insurance shall include products liability insurance, on
a claims made basis, in the amounts specified for the commercial general
liability insurance.

Tenant shall further, throughout the term of this Lease and any renewal
thereof, at its own expense, keep and maintain in full force and effect,
property insurance for what is commonly referred to as "Special Cause of Loss"
or "Special" coverage insurance (excluding earthquake and flood) on tenant's
leasehold improvements in an amount equal to one hundred percent (100%) of the
replacement value thereof with a coinsurance waiver. Tenant shall use the
proceeds from any such policy for the restoration of Tenant's improvements or
alterations, unless restoration is not an available option. As used in this
Lease, "tenant's leasehold improvements" shall mean any alterations, additions
or improvements installed in or about the Premises by or with Landlord's
permission or otherwise permitted by this Lease, whether or not the cost
thereof was paid for by Tenant.

All insurance required to be provided by Tenant under this Lease: (a) shall be
issued by Insurance companies authorized to do business in the state in which
the premises are located with a financial rating of at least an A VIII status
as rated in the most recent edition of Best's insurance Reports; (b) shall be
issued as a primary policy, or umbrella policy where appropriate (in which case
there shall be a per location endorsement making the limits available at each
location); shall be on an occurrence basis, except with respect to products
liability; (c) name Landlord and Landlord's property manager as additional
insured; and (d) shall contain an endorsement requiring at least 30 days prior
written notice of cancellation to Landlord and Landlord's lender, before
cancellation or change in coverage, scope or amount of any policy. Tenant shall
deliver a certificate or copy of such policy together with evidence of payment
of all current premiums to Landlord within 30 days of execution of this Lease
and at the time of all renewals thereof. If Tenant fails at any time to
maintain the insurance required by this Lease, and fails to cure such default
within ten (10) business days of written notice from Landlord then, in addition
to all other remedies available under this Lease and applicable law, Landlord
may purchase such insurance on Tenant's behalf and the cost of such insurance
shall be Additional Rent due within ten (10) days of written invoice from
Landlord to Tenant.

Landlord and Tenant release and relieve the other, and waive their entire right
of recovery for loss or damage to property located within or constituting a
part or all of the Building or the Development to the extent that the loss or
damage is covered by (a) the injured party's insurance, or (b) the insurance
the injured party is required to carry under this Article 16, whichever is
greater. This waiver applies whether or not the loss is due to the negligent
acts or omissions of Landlord or Tenant, or their respective officers,
directors, employees, agents, contractors, or invitees. Each of Landlord and
Tenant shall have their respective property insurers endorse the applicable
insurance policies to reflect the foregoing waiver of claims, provided however,
that the endorsement shall not be required if the applicable policy of
insurance permits the named insured to waive rights of subrogation on a blanket
basis, in which case the blanket waiver shall be acceptable.

30.  TENANT IMPROVEMENT ALLOWANCE: Landlord shall make up to One Hundred Sixty
Thousand Six Hundred Eighty Dollars ($160,680) (the "Fourth Amendment Tenant
Improvement Allowance") available to Tenant after January 1, 2002 but before
October 1, 2003 to reimburse Tenant for actual out-of-pocket costs paid to
third parties for designing and constructing tenant improvements to the
Premises pursuant to plans reasonably approved by Landlord and otherwise
subject to the provisions of Section 14. Landlord shall pay the Fourth
Amendment Tenant Improvement Allowance within thirty (30) days of invoice
submitted after the improvements have been inspected and accepted by Tenant
(less minor punch list items). Landlord
<PAGE>
may require lien releases as a condition of payment. Tenant confirms that
Landlord's obligations under any previous tenant improvement allowances have
been satisfied.

If Tenant utilizes the entire Fourth Amendment Tenant Improvement Allowance,
Landlord shall make available to Tenant after January 1, 2002 but before
October 1, 2003 up to an additional Two Hundred Seventy-Five Thousand Dollars
($275,000) as a supplemental Tenant Improvement Allowance (the "Fourth
Amendment Supplemental Tenant Improvement Allowance") to be expended for the
same purposes, subject to the same approvals, and with the same disbursement
provisions as the Fourth Amendment Tenant Improvement Allowance. If Tenant
utilizes all or some of the Fourth Amendment Supplemental Tenant Improvement
Allowance, then commencing with the first payment of Base Monthly Rent due
after payment of the Fourth Amendment Supplemental Tenant Improvement
Allowance, Tenant shall pay monthly, as additional Base Monthly Rent, an amount
sufficient to amortize the Fourth Amendment Supplemental Tenant Improvement
Allowance on an equal payments basis over the then remaining term of this Lease
(excluding any renewal terms) with interest at ten percent (10%) per annum
(which payments shall include amortization of interest accrued from date of
disbursement to the first amortization payment).

35.  OPTION TO RENEW. Tenant is granted the right to extend the term of this
Lease beyond the expiration date of the initial Lease Term for one (1)
successive period of thirty-six (36) months (the "Extended Term"). This
replaces any prior Options to Renew. If Tenant has materially defaulted in its
obligations under this Lease, and failed to cure such defaults within any
applicable cure period, then Tenant's right to extend the Lease for the
Extended Term shall automatically terminate. Tenant's right to extend the Lease
for the Extended Term is personal to Tenant and may not be exercised by any
subtenant. Tenant's extension rights shall apply to all of the Property under
lease to Tenant at the time. From and after the commencement of the Extended
Term, all of the terms, covenants, and conditions of the Lease shall continue
in full force and effect as written, except that Base Rent for the Extended
Term shall be at the then prevailing market rate (the "Fair Market Rent") for
similar space in the Project but not less than that paid in the last month of
the initial term. Tenant shall provide Landlord one hundred eighty (180) days
written notice of its intent to renew the Lease.

If Landlord and Tenant are not able to agree on the Fair Market Rent for the
Extended Term within thirty days after Tenant's notice of election to renew,
then such Fair Market Rent shall be determined as follows. Landlord and Tenant
shall each select an appraiser with at least ten years experience in the
office/high-tech industrial market in the eastside area. If the two appraisers
are unable to agree within ten days after their selection, they shall select a
similarly qualified third appraiser (the "Neutral Appraiser"). Within twenty
days after selection of the Neutral Appraiser, the three appraisers shall
simultaneously exchange determinations of Fair Market Rent. If the lowest
appraisal is not less than ninety percent (90%) of the highest appraisal, then
the three appraisals shall be averaged and the result shall be the Fair Market
Rent. If the lowest appraisal is less than ninety percent (90%) of the highest
appraisal, then the Fair Market Rent shall be deemed the rent set forth in the
appraisal that is closest in dollar amount to the appraisal submitted by the
Neutral Appraiser.

All other terms and conditions of the above described Lease shall remain in full
force and effect.

Landlord: Teachers Insurance & Annuity
          Association of America, Inc.
          ----------------------------

      By: /s/ JAMES P. GAROFALO
          ----------------------------
              James P. Garofalo

     Its: Assistant Secretary
          ----------------------------

  Tenant: Sonus Pharmaceuticals, Inc.
          ----------------------------

      By: /s/ RICHARD J. KLEIN
          ----------------------------
              Richard J. Klein

     Its: CFO
          ----------------------------
<PAGE>
STATE OF New York       )
                        )ss.
COUNTY OF New York      )

        I certify that I know or have satisfactory evidence that James P.
Garofalo is the person who appeared before me, and said person acknowledged
that he signed this instrument, on oath stated that he was authorized to
execute the instrument and acknowledged it as the Assistant Secretary of
Teachers Insurance & Annuity Association of America, Inc. to be the free and
voluntary act of such party for the uses and purposes mentioned in the
instrument.

                                             Date: November 30, 2001
                                             ---------------------------

                [SEAL OF HARRIET L. ROSENTHAL, NOTARY PUBLIC, STATE OF NEW YORK]

                                             /s/ HARRIET L. ROSENTHAL
                                             --------------------------------
                                             (Signature)

                                             Harriet L. Rosenthal
                                             --------------------------------
                                             (Print Name)

                                             Notary Public, in and for the State
                                             of New York, residing at New York,
                                             N.Y.

                                             My Commission Expires 8/17/02

                                                    HARRIET L. ROSENTHAL
                                              Notary Public, State of New York
                                                       No. 01RO6011725
                                                 Qualified in Suffolk County
                                             Commission Expires August 17, 2002

STATE OF Washington     )
                        )ss.
COUNTY OF King          )

        I certify that I know or have satisfactory evidence that Richard J.
Klein is the person who appeared before me, and said person acknowledged that
he/she signed this instrument, on oath stated that he/she was authorized to
execute the instrument and acknowledged it as the CFO of Sonus Pharmaceuticals,
Inc. to be the free and voluntary act of such party for the uses and purposes
mentioned in the instrument.

                                             Dated: November 29, 2001
                                                   --------------------------

             [SEAL OF CONSTANCE E. ANDERSON, NOTARY PUBLIC, STATE OF WASHINGTON]

                                             /s/ CONSTANCE E. ANDERSON
                                             --------------------------------
                                             (Signature)

                                             Constance E. Anderson
                                             --------------------------------
                                             (Print Name)

                                             Notary Public, in and for the State
                                             of Washington, residing at
                                             Newcastle

                                             My Commission Expires 4/2/04

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