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Exhibit 10.320

 
   
CONFIDENTIAL   REDACTED VERSION

[**] CERTAIN INFORMATION IN THIS EXHIBIT HAS BEEN
OMITTED AND FILED SEPARATELY WITH THE COMMISSION.
CONFIDENTIAL TREATMENT HAS BEEN REQUESTED WITH
RESPECT TO THE OMITTED PORTIONS.

AMENDMENT NO. 4 TO
AGREEMENT

        This Amendment No. 4 ("Amendment No. 4") is entered effective March 5,
2003 (the "Amendment Effective Date") pursuant to and amending that certain
Agreement between Gen-Probe Incorporated, a Delaware corporation ("Gen-Probe")
and Chiron Corporation, a Delaware corporation ("Chiron"). Capitalized terms
used but not defined herein shall have the meanings set forth in the Agreement.

Recitals

        A.    The parties entered into the Agreement as of June 11, 1998
pursuant to which, among other things, the parties described their respective
rights and obligations with respect to the development, manufacture, marketing
and distribution of Products in the Blood Screening and Clinical Diagnostic
Fields. The Agreement was amended by the following: (i) June 11, 1998
Collaboration Agreement, (ii) June 11, 1998 Supplemental letter agreement,
(iii) June 26, 1998 Addendum to Collaboration Agreement, (iv) June 30, 1998
Supplemental letter agreement, (v) June 30, 1998 Consent, (vi) December 1, 1998
letter agreement re American Red Cross revenues, (vii) December 7, 1999
Amendment, (viii) February 1, 2000 Second Amendment, (ix) June 7, 2001
Supplemental Agreement No. 1 (Customer training and Support), (x) October 30,
2001 Confidentiality and Joint Interest Agreement, (xi) April 4, 2001 Agreement
re Arbitration and (xii) April 1, 2002 Amendment No. 3 (warehousing and
shipping). In addition, the parties submitted a number of disputes under the
Agreement to arbitration pursuant to Section 13 of the Agreement, and in
resolution of those disputes, executed a Definitive Written Settlement
Agreement, dated December 5, 2001, and a Short Form Agreement, dated
November 16, 2001.

        B.    The parties have previously revised Article 14 of the Agreement,
memorialized in that certain December 7, 1999 Amendment. The parties have
discussed a further revision to and clarification of their respective rights and
obligations with respect to Article 14, and have agreed to make certain
additional changes to the Agreement in connection therewith, in accordance with
the provisions of this Amendment No. 4.

Agreement

        NOW, THEREFORE, for and in consideration of the mutual covenants and
agreements set forth in this Amendment No. 4, the parties agree as follows:

        1.    Ultrio on Tigris.    Article 14 of the Agreement shall be and is
hereby amended to read as follows:

        "In consideration for the rights originally granted to Chiron by this
Agreement with respect to TMA and HPA, Chiron shall pay to Gen-Probe, or shall
cause Bayer Corporation to pay to Gen-Probe, the following nonrefundable amounts
upon the occurrence of each event set forth below:

        (1)  [**]

        (2)  [**]

        (3)  [**]

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        (4)  [**]

        2.    No Other Amendment.    Except as is expressly set forth in this
Amendment No. 4, all other terms and conditions of the Agreement shall continue
in full force and effect.

        3.    Counterparts.    This Amendment No. 4 may be executed in
counterparts, each of which shall be an original, and all of which together
shall constitute one and the same instrument.

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        IN WITNESS WHEREOF, the parties have caused this Amendment No. 4 to be
executed and the persons signing below warrant that they are duly authorized to
sign for and on behalf of the respective parties.

Gen-Probe:   Chiron:
GEN-PROBE INCORPORATED,
a Delaware corporation
 
CHIRON CORPORATION,
a Delaware corporation
By: /s/ Henry L. Nordhoff
Its: President & Chief Executive Officer
Date: March 5, 2003
 
By: /s/ Jack Goldstein
Its: President, Chiron Blood Testing
Date: March 18, 2003

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Exhibit 10.320

AMENDMENT NO. 4 TO AGREEMENT