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Exhibit 10.727

AMENDMENT TO GOVERNANCE AGREEMENT

        AMENDMENT TO GOVERNANCE AGREEMENT dated as of March 11, 2003 (this
"Amendment") to the Governance Agreement dated as of November 20, 1994, as
amended (the "Agreement"), by and between Chiron Corporation, a Delaware
corporation ("Chiron"), and Novartis AG as successor in interest to Ciba-Geigy
Limited ("Novartis").

        WHEREAS, Section 2.03 of the Agreement provides for, among other things,
a Nominating Committee and specifies the number of members on the Nominating
Committee who are to be "Investor Directors," "Independent Directors" and
"Management Directors" (as each such term is defined in the Agreement) and the
parties now desire to amend the Agreement to clarify that the Nominating
Committee shall consist of only Investor Directors and Independent Directors.

        NOW, THEREFORE, in consideration of the promises and mutual covenants
herein contained, and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, it is mutually agreed by the
parties as follows:

        1.    Amendment to Section 2.03(b)(ii).    Section 2.03(b)(ii) of the
Agreement is hereby amended by deleting such clause in its entirety and
replacing it with the following language:

        (ii)  a Nominating Committee, responsible, among other things, for
recommending the nomination of Directors, all pursuant to Section 2.01, and
comprised and conducting itself as follows:

        (A)  if Ciba's Percentage Interest is less than 40%, the Nominating
Committee shall be comprised of three Independent Directors and one Investor
Director;

        (B)  so long as Ciba's Percentage Interest is at least 40%, the
Nominating Committee shall be composed of three Independent Directors and two
Investor Directors;

        (C)  a majority of the Independent Directors shall designate the
Independent Directors that serve on the Nominating Committee and a majority of
the Investor Directors shall designate the Investor Directors that serve on the
Nominating Committee;

        (D)  a quorum of the Nominating Committee required for any action
thereby shall require the attendance of at least two Independent Directors and
both Investor Director members thereof; and

        (E)  the Nominating Committee shall act by majority vote of the entire
Nominating Committee; provided, however, that (1) so long as Ciba's Percentage
Interest is at least 40%, no action may be taken by the Nominating Committee
that is opposed by both of the Investor Directors; and (2) in addition on and
after the eleventh anniversary of the Effectiveness of this Agreement, so long
as Ciba's Percentage Interest is at least 49%, the Investor Director members
shall have a deciding vote (meaning that, with respect to any motion before the
committee, if the two Investor Director members vote one way, the vote of the
Investor Directors will control regardless of the vote of the Independent
Directors);

        2.    No Further Changes.    Except as otherwise provided herein, the
Agreement shall remain in full force and effect.

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

 
   
   
    CHIRON CORPORATION
 
 
By:
 
/s/  WILLIAM G. GREEN      

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    Name:   William G. Green     Title:   Sr. Vice President, General Counsel
and Secretary
 
 
NOVARTIS AG
 
 
By:
 
/s/  P. RUPPRECHT      

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    Name:   Peter Rupprecht     Title:   authorized signatory
 
 
By:
 
/s/  BREU      

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    Name:   [Raymund Breu]     Title:   CFO

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Exhibit 10.727

AMENDMENT TO GOVERNANCE AGREEMENT