Exhibit 10.726

NOVARTIS AG    WRITTEN CONSENT AND APPROVAL    Effective as of February 21, 2003

CHANGES IN THE NAME AND COMPOSITION OF THE NOMINATING COMMITTEE; AMENDMENT TO GOVERNANCE AGREEMENT

WHEREAS, Section 2.04 (a)(iv) of that certain Governance Agreement dated as of November 20, 1994, as amended (the "Governance Agreement"),
between Chiron Corporation ("Chiron" or the "Company") and Novartis AG ("Novartis") as successor-in-interest to Ciba-Geigy Limited, requires the approval of
Novartis of any change in the size or composition of any committee of the Board of Directors of Chiron;

WHEREAS,
the Company has established a Nominating Committee (the "Committee") of the Board of Directors of Chiron;

WHEREAS,
at the February 21, 2003 meeting of the independent directors, the non-management directors recommended that it would be in the best interests of the Company
to: (i) amend Section 2.03(b)(ii) of the Governance Agreement to eliminate the requirement that the Committee include a Management Director (as defined in the Governance
Agreement) and to include an additional Independent Director (as defined in the Governance Agreement) instead; and (ii) approve a change in the name of the committee from "Nominating Committee"
to "Nominating and Corporate Governance Committee" in light of the proposed changes to the corporate governance rules of The Nasdaq Stock Market and the New York Stock Exchange;

WHEREAS,
the proposed changes would require the consent of Novartis under Section 2.04(a)(iv) and (vi) of the Governance Agreement and Novartis has determined to
enter into an Amendment to Governance Agreement with Chiron to effect that change;

NOW,
THEREFORE, BE IT RESOLVED, that Novartis hereby consents to the proposed changes in the composition of the Nominating Committee contemplated by the form of Amendment to the
Governance Agreement in substantially the form attached hereto asAddendum 1, and the change in the name of the committee to "Nominating and Corporate
Governance Committee", effective as of February 21, 2003.

| |  | NOVARTIS AG
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| |  | By:        
| |  | Its:       
| |  |            
| |  | By:        
| |  | Its:       
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ADDENDUM 1AMENDMENT TO GOVERNANCE AGREEMENT

AMENDMENT
TO GOVERNANCE AGREEMENT dated as of                        , 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:



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

2

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

| |  |                    |  | 
| |  | ------------------ |  | 
| |  | CHIRON CORPORATION
| |  | By:                |  | 
| |  |                    |  | 
| |  | Name:
Title:      
| |  | NOVARTIS AG       
| |  | By:                |  | 
| |  |                    |  | 
| |  | Name:
Title:      
| |  | By:                |  | 
| |  |                    |  | 
| |  | Name:
Title:      

3

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