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                                                                   Exhibit 10.53

                               FIRST AMENDMENT TO
                                SUPPLY AGREEMENT

         This First Amendment to Supply Agreement (the "Amendment") is made as
of this day of March 31, 2003, by and between Sonus Pharmaceuticals, Inc., a
Delaware corporation ("Sonus"), and Indena SpA, a company organized and existing
under the laws of Italy ("Indena").

                                    RECITALS:

         A.       Indena and Sonus are parties to that certain Supply Agreement
dated January 22, 2002 (the "Agreement"), pursuant to which Indena has agreed to
supply Sonus with medical grade paclitaxel.

         B.       The Agreement sets forth the date on which Indena will begin
regular supplies of the Product.

         C.       Pursuant to Section 5.3 of the Agreement, Sonus and Indena
desire to revise the date for the beginning of regular supplies of the Product.

         NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties agree as follows:

         1.       INITIAL SUPPLIES. Section 3 of the Agreement is hereby amended
and restated to read in full as follows:

                  "3.1     Until such time as Supplier begins the Further
Supplies in accordance with Section 4, Supplier undertakes to supply and
Purchaser undertakes to purchase up to 2000 grams of Product per calendar year,
prorated for any portion of a year, to be used by Purchaser to manufacture the
Finished Product (the "Initial Supplies"). Notwithstanding the foregoing, in the
event that Purchaser's clinical trials require additional Product, upon thirty
(30) days advance written notice, Supplier undertakes to increase the Initial
Supplies and supply such additional Product as Purchaser may request, provided,
that if the aggregate amounts requested exceed 1,000 grams during any calendar
quarter, Supplier shall use commercial reasonable efforts to supply such excess
amounts, but shall not be obligated to fulfill such requests with respect to
such excess.

                  3.2      Orders for each lot of Initial Supplies shall be
placed with Supplier at least 90 days before the requested date of supply."

         2.       REGULAR SUPPLIES. Section 4 of the Agreement is hereby amended
and restated to read in full as follows:

                  "Regular supplies of Product (the "Further Supplies") shall
begin within thirty (30) days after the date on which Sonus receives
unconditional FDA Approval, or such other date as the parties may agree in
writing, as provided in Section 5 of the Agreement."

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         3.       FORECASTS AND ORDERS.

                  3.1      The first paragraph of Section 5.1 of the Agreement
is hereby amended and restated to read in full as follows:

                  "5.1     Promptly following receipt of unconditional FDA
Approval, Purchaser shall submit to Supplier an estimated forecast of the
quantities of Product that Purchaser expects to order during the remainder of
the calendar year in which unconditional FDA Approval was obtained (the "Partial
Year"). By October 31 of each year during the term hereof, starting with the
year in which unconditional FDA Approval is obtained, Purchaser shall submit to
Supplier an estimated rolling forecast of the quantities of Product that
Purchaser expects to order during the two following years, provided, that if
unconditional FDA Approval is obtained after October 31 of such year, the
estimated rolling forecast shall be delivered as soon as practicable following
unconditional FDA Approval, but in no event later than thirty days following
unconditional FDA Approval. The forecast for the Partial Year shall be binding
and considered a firm purchase commitment.

                  3.2      Section 5.2 of the Agreement is hereby amended and
restated to read in full as follows:

                  "5.2     By no later than two weeks following submission by
Purchaser of a firm purchase order for Product, Supplier will confirm in writing
to Purchaser the receipt and acceptance of such firm order. Failure to confirm
such firm order in writing within such time period or full or partial shipment
of any such order shall be deemed acceptance of such firm order in full."

                  3.3      Section 5.3 of the Agreement is hereby amended and
restated to read in full as follows:

                  "In the event that the parties agree on a date other than a
date within thirty (30) days following FDA Approval for the beginning of regular
supplies, the dates set out in the preceding Sections may be revised by mutual
agreement."

         4.       DEFINITIONS. Unless otherwise defined herein, capitalized
terms used in this Amendment shall have the same meanings ascribed to them in
the Agreement.

         5.       ENTIRE AGREEMENT. The Agreement, as amended by this Amendment,
constitutes the full and complete agreement between the parties hereto regarding
the subject matter of the Agreement and shall supersede all prior understanding
or agreements, if any, whether written or oral, concerning the subject matter of
the Agreement, as amended.

         6.       FORCE AND EFFECT. Except as modified by this Amendment, the
terms and provisions of the Agreement are hereby ratified and confirmed and are
and shall remain in full force and effect.

         7.       COUNTERPARTS. This Amendment may be executed in one or more
counterparts, all of which together shall constitute one instrument.

         8.       EXECUTION. This Amendment may be executed by facsimile
signatures and such signature will be deemed binding for all purposes of this
Amendment, without delivery of an original signature being required.

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         IN WITNESS WHEREOF, the undersigned have executed this Amendment as of
the date first written above.

                                SONUS PHARMACEUTICALS, INC.

                                By: /s/ Michael A. Martino
                                    --------------------------------------
                                Name: Michael A. Martino
                                Title: President and Chief Executive Officer

                                INDENA, SpA

                                By: /s/ G.P. Forni
                                        ------------------------------------
                                Name:   G.P. Forni
                                Title:  Sr. Vice President Mktg and Business
                                Development

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