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Exhibit 10.520

CHIRON CORPORATION FINANCE COMMITTEE CHARTER

ROLE

        The Finance Committee (the "Committee") of the Board of Directors (the
"Board") of Chiron Corporation ("Chiron") assists the Board in fulfilling its
responsibility for oversight with respect to Chiron's capital structure,
financing and investment strategies and financial management.

        The chairperson of the Committee, acting in consultation with all
committee members that are not otherwise affected by the issue or interest under
consideration, and in consultation with such other directors, representatives of
management, counsel or other advisors as the chairperson may deem appropriate,
may determine from time to time the scope of the Committee's authority under
this charter.

MEMBERSHIP AND STRUCTURE

        The Committee shall consist of at least three directors. At least a
majority of the members of the Committee shall not be officers or employees of
Chiron and shall be free of any relationship that, in the determination of the
Board, would interfere with his or her individual exercise of independent
judgment.

        Subject to the requirements described above with respect to Committee
membership, members of the Committee shall be appointed by the Board in
accordance with the Governance Agreement, dated as of November 20, 1994, between
Chiron and Novartis AG, as amended (as it may be further amended from time to
time, the "Governance Agreement"). Committee members shall serve at the pleasure
of the Board. The chairperson shall be appointed by the full Board.

        The Committee shall meet in person or telephonically at least two times
a year or more frequently when deemed necessary or desirable by the Committee or
its chairperson, at such times and places as the Committee determines.

COMMUNICATIONS/REPORTING

        The Committee may invite such members of management to its meetings as
it may deem desirable. The Committee shall perform or cause to be performed and
approved by the Committee annually an evaluation of the performance of the
Committee of its role under this charter, including the duties and
responsibilities set forth below in Annex A. The evaluation shall include
consideration of possible amendments to this charter, including the duties and
responsibilities set forth in Annex A. The performance evaluation may be
conducted in such manner as the Committee deems appropriate, and the result and
recommendations shall be reported to the Board by the chairperson or any other
member of the Committee. The chairperson shall report in a timely manner on
Committee activities to the full Board.

EDUCATION

        Chiron is responsible for providing the Committee with educational
resources related to its role and duties and responsibilities, including those
with respect to capitalization, financings, investment strategies and any other
material as may be requested by the Committee.

AUTHORITY

        In discharging its oversight role, duties and responsibilities, the
Committee is empowered to cause and direct the investigation of any matter
within its role, with full power to cause independent counsel or other experts
or advisors to be retained for this purpose. The Committee may require any
officer or employee of Chiron or Chiron's outside lawyers to attend a meeting of
the Committee or to meet with any member of or consultants to the Committee and
to provide any information requested by the

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Committee or its member or consultants. The Committee shall have the full
authority of the Board to discharge its duties and responsibilities, including
the authority to select, retain, terminate and approve the compensation and
other terms of engagement of independent consultants, counsel, accountants or
other experts or advisors as the Committee deems appropriate in its discretion,
without seeking approval of the Board or management. The Committee may, in its
discretion, delegate all or a portion of its duties and responsibilities to a
subcommittee of the Committee. The Committee shall also have the resources that
it deems necessary to discharge its duties and responsibilities.

KEY DUTIES AND RESPONSIBILITIES

        The key duties and responsibilities of the Committee in carrying out its
role are delineated in Annex A to the Finance Committee Charter. Annex A will be
reviewed annually, and updated if necessary, to reflect changes in regulatory
requirements, authoritative guidance and evolving oversight practices. As the
compendium of Committee duties and responsibilities, Annex A will be considered
to be incorporated in, and a part of, this charter.

        The Committee may rely on the expertise and knowledge of management,
consultants, counsel, advisors and experts in carrying out its oversight
responsibilities.

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ANNEX A

The following are the key duties and responsibilities of the Committee:

1.To review and make recommendations to the Board about policies and strategies
related to Chiron's capital structure, capital formation and capital needs,
including but not limited to: (i) total capitalization and relative levels of
debt and equity; (ii) the need for capital raising transactions (including both
debt, equity, and hybrid securities); (iii) stock repurchases and redemptions or
repayments of debt; (iv) pricing related to the issuance or retirement of debt,
equity and hybrid securities; and (v) the impact of capital structure on debt
ratings, including the relations and positioning with debt rating agencies (i.e.
Moody's and Standard & Poor's).

2.To review and make recommendations to the Board concerning Chiron's dividend
policy.

3.To review and make recommendations to the Board concerning the advisability of
stock splits, reverse splits or similar transactions.

4.To review and make recommendations to the Board about Chiron's short- and
long-term financing strategy, including but not limited to anticipated sources
and uses of cash in light of, among other things, capital expenditures and
mergers, acquisitions and divestiture activities, and its needs for guaranties
and credit supports.

5.To review and make recommendations to the Board about financial metrics and
measurement options and its effect on capital allocation decisions.

6.To approve deviations to the approved annual capital budget of up to 5% in the
aggregate, for projects not representing a strategic change of direction. To
authorize the Chair of the Committee to approve cost increases or deviations of
up to 10% for individual board-approved capital projects on an urgent or
as-needed basis.

7.To review and make recommendations to the Board about borrowings or issuance
of debt guarantees by Chiron or any of its subsidiaries outside of existing
Board-approved levels; and to review and make recommendations to the Board about
pricing of any new issuance of debt or equity securities by Chiron outside of
previously-approved programs or guidelines.

8.To review and make recommendations to the Board about Chiron's cash investment
strategy, including policy and control procedures and oversight of investment
managers and to approve the specific terms and conditions of any investments by
Chiron or any of its subsidiaries of cash or cash equivalents outside of
approved Investment Policy guidelines.

9.To review and make recommendations to the Board about Chiron's financial risk
management policies, including but not limited to: (i) the adequacy of
insurance; (ii) policies concerning interest rate risk, foreign exchange risk
and the use of derivatives and other hedges; (iii) policies concerning liquidity
management; and (iv) policies concerning counterparty risk.

10.To review and make recommendations to the Board about Chiron's tax planning
strategies.

11.To review and make recommendations to the Board about Chiron's Investor
Relations program.

12.To review and report to the Board on Chiron's compliance with any of the
foregoing policies and practices.

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QuickLinks

Exhibit 10.520

CHIRON CORPORATION FINANCE COMMITTEE CHARTER
ROLE
MEMBERSHIP AND STRUCTURE
COMMUNICATIONS/REPORTING
EDUCATION
AUTHORITY
KEY DUTIES AND RESPONSIBILITIES

ANNEX A