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Executive Change-in-Control
Severance Plan

Chiron Corporation
January 2001

TIER II

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CONTENTS

Article 1.   Establishment, Term, and Purpose   1 Article 2.   Definitions   1
Article 3.   Participation   5 Article 4.   Severance Benefits   5 Article 5.  
Form and Timing of Severance Benefits   7 Article 6.   Excise Tax Equalization
Payment   7 Article 7.   The Company's Payment Obligation   8 Article 8.  
Arbitration   9 Article 9.   Successors and Assignment   9 Article 10.  
Miscellaneous   9

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Chiron Corporation
Executive Change-in-Control Severance Plan

Article 1. Establishment, Term, and Purpose

    1.1  Establishment of the Plan.  Chiron Corporation (hereinafter referred to
as the "Company") hereby establishes a change-in-control severance plan to be
known as the "Chiron Corporation Executive Change-in-Control Severance Plan"
(the "Plan").

    1.2  Term of the Plan.  This Plan will commence upon December 9, 2000 (the
"Effective Date") and shall continue in effect for two (2) full calendar years.
However, at the end of such two (2) year period and, if extended, at the end of
each additional year thereafter, the term of this Plan shall be extended
automatically for one (1) additional year, unless the Committee delivers written
notice six (6) months prior to the end of such term, or extended term, to each
Participant, that the Plan will not be extended. However, in the event a Change
in Control occurs during the original or any extended term, this Plan will
remain in effect, solely with respect to obligations relating to such Change in
Control, for the longer of: (i) two (2) years beyond the month in which such
Change in Control occurred; or (ii) until all obligations of the Company
hereunder have been fulfilled, and until all benefits required hereunder have
been paid to Participants.

    1.3.  Purpose of the Plan.  The purpose of the Plan is to provide certain
key employees of the Company with greater incentive to remain in the employ of
the Company, particularly in the event of any possible change or threatened
change in control of the Company.

Article 2. Definitions

    Whenever used in this Plan, the following terms shall have the meanings set
forth below and, when the meaning is intended, the initial letter of the word is
capitalized.

    2.1  "Base Salary"  as of any date means the annual rate of a Participant's
base salary, excluding amounts received under incentive or other bonus plans,
computed before any deferrals or pre-or post-tax payroll deductions.

    2.2  "Beneficial Owner"  shall have the meaning ascribed to such term in
Rule 13d-3 of the General Rules and Regulations under the Exchange Act.

    2.3  "Beneficiary"  means the persons or entities designated or deemed
designated by the Participant pursuant to Section 9.2 herein.

    2.4  "Board"  means the Board of Directors of the Company.

    2.5  "Cause"  means:

(a)The Participant's willful and continued failure to substantially perform
his/her duties with the Company (other than any such failure resulting from
Disability or occurring after issuance by the Participant of a Notice of
Termination for Good Reason), after a written demand for substantial performance
is delivered to the Participant that specifically identifies the manner in which
the Company believes that the Participant has willfully failed to substantially
perform his/her duties, and after the Participant has failed to resume
substantial performance of his/her duties on a continuous basis within thirty
(30) calendar days of receiving such demand;

(b)The Participant's material act of dishonesty, fraud or embezzlement against
the Company, unauthorized disclosure of confidential information or trade
secrets of the Company or an affiliate (whether or not in violation of any
confidentiality agreement) or other willful conduct (other than conduct covered
under (a) above) that is demonstrably injurious to the Company, monetarily or
otherwise; or

(c)The Participant's having been convicted of a felony.

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For purposes of this subparagraph, no act, or failure to act, on the
Participant's part shall be deemed "willful" unless done, or omitted to be done,
by the Participant not in good faith and without reasonable belief that the
action or omission was in the best interests of the Company.

    2.6  "Change in Control"  of the Company shall be deemed to have occurred as
of the first day during the term of this Plan that any one or more of the
following conditions is satisfied and regulatory approval has been granted if
necessary:

(a)The "beneficial ownership" (as defined in Rule 13d-3 under the Exchange Act)
of securities representing more than thirty percent (30%) of the combined voting
power of all securities of the Company is acquired, directly or indirectly, by a
Person (other than the Company, any trustee or other fiduciary holding
securities under an employee benefit plan of the Company or an affiliate
thereof, or any corporation owned, directly or indirectly, by the stockholders
of the Company in substantially the same proportions as their ownership of stock
of the Company); or

(b)During any period of two (2) consecutive years, individuals who at the
beginning of such period constitute the Board of Directors and any new director
(other than a director designated by a person who has entered into an agreement
with the Company to effect a transaction described in paragraph (a) or (b) of
this section) whose election by the Board of Directors or nomination for
election by the Company's stockholders was approved by a vote of at least
two-thirds of the directors then still in office who either were directors at
the beginning of the period or whose election or nomination for election was
previously so approved, cease for any reason to constitute a majority thereof;
or

(c)The stockholders of the Company approve a definitive agreement to sell or
otherwise dispose of all or substantially all of its assets, or adopt a plan for
liquidation, provided that such sale or liquidation has not been abandoned.

    Notwithstanding anything else contained herein to the contrary, in no event
shall a Change in Control be deemed to have occurred by reason of a purchase, or
series of purchases of Company stock by Novartis or its successor such that the
acquiring entity remains subject to the terms of that certain Governance
Agreement dated as of January 5, 1995, as amended through December 9, 2000,
provided the acquiring entity's Company stock holdings, direct or indirect, in
the aggregate, represent seventy-nine percent (79%) or less of the combined
voting power of all outstanding Company securities.

    However, in no event shall a Change in Control be deemed to have occurred,
with respect to the Participant, if the Participant is part of a purchasing
group that consummates the Change-in-Control transaction. The Participant shall
be deemed "part of a purchasing group" for purposes of the preceding sentence if
the Participant is an equity participant in the purchasing company or group
(except for: (i) passive ownership of less than three percent (3%) of the stock
or other equity of the purchasing company; or (ii) ownership of equity
participation in the purchasing company or group which is otherwise not
significant, as determined prior to the Change in Control by a majority of the
nonemployee continuing Directors).

    2.7  "Code"  means the United States Internal Revenue Code of 1986, as
amended, and any successors thereto.

    2.8  "Committee"  means the Compensation Committee of the Board or any other
committee appointed by the Board to perform the functions of the Compensation
Committee for purposes of administering this Plan.

    2.9  "Company"  means Chiron Corporation, a Delaware corporation, or any
successor thereto as provided in Article 9 herein.

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    2.10  "Disability"  means complete and permanent inability by reason of
illness or accident to perform the duties of the occupation at which the
Participant was employed when such disability commenced, where inability is
expected to last one year or longer.

    2.11  "Effective Date"  means the date of this Plan set forth above.

    2.12  "Effective Date of Termination"  means the date on which a Qualifying
Termination occurs which triggers the payment of Severance Benefits hereunder.

    2.13  "Exchange Act"  means the United States Securities Exchange Act of
1934, as amended.

    2.14  "Good Reason"  shall mean, without the Participant's express written
consent, the occurrence of any one or more of the following:

(a)The assignment of the Participant to duties materially inconsistent with the
Participant's authorities, duties, responsibilities as an employee of the
Company, or a material reduction in the nature or status of the Participant's
authorities, duties, or responsibilities than those in effect immediately
preceding the Change in Control;

(b)The Company's requiring the Participant to be based at a location which is at
least fifty (50) miles further from the Participant's current primary residence
than is such residence from the Company's current headquarters, except for
required travel on the Company's business to an extent substantially consistent
with the Participant's business obligations as of the Effective Date;

(c)A material reduction in the Participant's Base Salary or bonus opportunity as
in effect on the Effective Date or as the same shall be increased from time to
time;

(d)A material reduction in the Participant's level of participation in any of
the Company's short- and/or long-term incentive compensation plans, or employee
benefit or retirement plans, policies, practices, or arrangements in which the
Participant participates immediately preceding the Change in Control; provided,
however, that reductions in the levels of participation in any such plans shall
not be deemed to be "Good Reason" if the Participant's reduced level of
participation in each such program remains substantially consistent with the
average level of participation of other executives who have positions
commensurate with the Participant's position.

    For purposes of this Plan, long-term incentive plans shall mean the Chiron
Executive Long-Term Incentive Plan, the 1991 Stock Option Plan, and any other
similar plans instituted by the Company;

(e)The failure of the Company to obtain a satisfactory agreement from any
successor to the Company to assume and agree to perform this Agreement, as
contemplated in Article 10 herein; or

(f)Any termination of Participant's employment by the Company that is not
effected pursuant to a Notice of Termination.

    The existence of Good Reason shall not be affected by the Participant's
temporary incapacity due to physical or mental illness not constituting a
Disability. However, the occurrence of an event set forth in (a) through(f)
above shall not constitute Good Reason if the Company has cured such event
within fifteen (15) days of receipt of written notice from the Participant that
such event has occurred and constitutes Good Reason.

    2.15  "Notice of Termination"  shall mean a written notice which shall
indicate the specific termination provision in this Plan relied upon, and shall
set forth in reasonable detail the facts and circumstances claimed to provide a
basis for termination of the Participant's employment under the provision so
indicated.

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    2.16  "Participant"  means an employee of the Company who fulfills the
eligibility and participation requirements, as provided in Article 3 herein.

    2.16  "Person"  shall have the meaning ascribed to such term in
Section 3(a)(9) of the Exchange Act and used in Sections 13(d) and 14(d)
thereof, including a "group" as provided in Section 13(d).

    2.17  "Qualifying Termination"  means any of the events described in
Section 4.2 herein.

    2.18  "Severance Benefits"  means the payment of severance compensation as
provided in Section 4.3 herein.

    2.19  "Target Bonus"  shall mean the target bonus amount established under
the Company's annual incentive plan.

Article 3. Participation

    3.1  Eligible Employees.  Individuals eligible to participate in the Plan
shall include all key employees of the Company, as determined by the Committee
in its sole discretion.

    3.2  Participation.  Subject to the terms of the Plan, the Committee may,
from time to time, select from all eligible employees those who shall
participate in the Plan.

Article 4. Severance Benefits

    4.1  Right to Severance Benefits.  A Participant shall be entitled to
receive from the Company Severance Benefits, as described in Section 4.3 herein,
if (i) there has been a Change in Control of the Company, (ii) within
twenty-four (24) calendar months following the Change in Control, a Qualifying
Termination of the Participant has occurred, and (iii) Participant has executed
a Release, as described in Section 4.8 herein. The benefits provided under this
Plan shall be reduced to the extent similar benefits are provided under the
Chiron Corporation Executive Officer Severance Plan or any other severance
protection arrangements provided by the Company either as a plan or in the form
of individual agreement or contract.

    The Participant shall not be entitled to receive Severance Benefits if
he/she is terminated for Cause, or if his/her employment with the Company ends
due to death or Disability or due to a voluntary termination of employment by
the Participant without Good Reason.

    4.2  Qualifying Termination.  The term Qualifying Termination means any of
the following events:

(a)An involuntary termination of the Participant's employment by the Company for
reasons other than Cause, death or Disability pursuant to a Notice of
Termination delivered to the Participant by the Company;

(b)A voluntary termination by the Participant for Good Reason pursuant to a
Notice of Termination delivered to the Company by the Participant; provided
that, if upon receiving such Notice of Termination, the Company requests that
the Participant remain an employee for a period ending no later than six
(6) months following the date of the Change in Control (the "Transition
Employment Period") with compensation and benefits equal to or greater than the
Participant's compensation and benefits immediately before the Qualifying
Termination (or, if more favorable to the Participant, immediately before the
Change in Control), the Participant will not be deemed to have a Qualifying
Termination unless he or she remains employed throughout the Transition
Employment Period or Executive's employment earlier terminates due to death,
Disability or involuntary termination by the Company for reason other than
Cause.

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    4.3  Description of Severance Benefits.  In the event the Participant
becomes entitled to receive Severance Benefits, as provided in Sections 4.1 and
4.2 herein, the Company shall pay to the Participant and provide him/her with
the following:

(a)An amount equal to two (2) times the highest rate of the Participant's
annualized Base Salary in effect immediately preceding the Change in Control.

(b)An amount equal to two (2) times the Participant's highest target bonus
established for the year immediately preceding the Change in Control.

(c)An amount equal to the Participant's unpaid Base Salary, any unpaid bonus
earned before the year in which the termination occurs, a pro rata amount of the
Participant's Target Bonus for the year in which the termination occurs, and
accrued but unused paid time off in accordance with company policy through the
Effective Date of Termination.

(d)A continuation of the welfare benefits of life and accidental death and
dismemberment, and disability insurance coverage for two (2) full years after
the Effective Date of Termination. These benefits shall be provided to the
Participant at the same premium cost, and at the same coverage level, as in
effect as of the Participant's Effective Date of Termination. However, in the
event the premium cost and/or level of coverage shall change for all employees
of the Company, or for management employees with respect to supplemental
benefits, the cost and/or coverage level, likewise, shall change for the
Participant in a corresponding manner. The Company may satisfy its obligation to
provide a continuation of health care benefits by paying that portion of the
Participant's premiums required under Consolidated Omnibus Budget Reconciliation
Act ("COBRA") that exceed the amount of premiums that the Participant would have
been required to pay for continuing coverage had he or she continued in
employment. If the Company is not reasonably able to continue these benefits
under the Company's plans, the Company may provide similar coverage under other
vehicles or may, in lieu thereof, pay the Participant an amount equal to the
value of these benefits.

The continuation of these welfare benefits shall be discontinued prior to the
end of the two (2) year period in the event the Participant has available
substantially similar benefits at a comparable cost from a subsequent employer,
as determined by the Committee.

(e)All long-term incentive awards will vest in accordance with the terms of the
plan or program under which they were granted.

    The aggregate vested benefits accrued by the Participant as of the Effective
Date of Termination under all other savings and retirement plans sponsored by
the Company shall be distributed pursuant to the terms of the applicable plans.

    4.4  Termination for Disability.  Following a Change in Control of the
Company, if a Participant's employment is terminated due to Disability, the
Participant shall receive his/her Base Salary through the Effective Date of
Termination, at which point in time the Participant's benefits shall be
determined in accordance with the Company's disability, retirement, insurance,
and other applicable plans and programs then in effect.

    4.5  Termination for Death.  Following a Change in Control of the Company,
if the Participant's employment is terminated by reason of his/her death, the
Participant's benefits shall be determined in accordance with the Company's
survivor's benefits, insurance, and other applicable programs of the Company
then in effect.

    4.6  Termination for Cause or Other Than for Good Reason.  Following a
Change in Control of the Company, if the Participant's employment is terminated
either: (a) by the Company for Cause; or (b) by the Participant (other than for
Good Reason under circumstances giving rise to a Qualifying Termination
described in Section 4.2(b) herein), the Company shall pay the Participant
his/her full Base

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Salary and accrued but unused paid time off in accordance with company policy
through the Effective Date of Termination, at the rate then in effect, plus all
other amounts to which the Participant is entitled under any compensation plans
of the Company, at the time such payments are due.

    4.7  Notice of Termination.  Any termination of employment by the Company or
by the Participant for Good Reason shall be communicated by a Notice of
Termination.

    4.8  Release.  The Severance Benefits are in consideration of Participant's
release of all claims against the Company and its employees and agents, in the
form provided by the Company and in substantially the form as attached hereto as
Exhibit A (the "Release"). If Participant does not properly execute the Release
or if the Participant effectively revokes it, he or she will not be entitled to
any Severance Benefits.

Article 5. Form and Timing of Severance Benefits

    5.1  Form and Timing of Cash Severance Benefits.  The Severance Benefits
described in Sections 4.3(a), 4.3(b), and 4.3(c) herein shall be paid in cash to
the Participant in a single lump sum as soon as practicable following the latest
of (i) the Effective Date of Termination or (ii) the date that the Participant
executes the Release or (iii) the last day following Participant's execution of
the Release that the Participant may, by its terms, revoke such Release, but in
no event beyond thirty (30) days from such date.

    5.2  Withholding of Taxes.  The Company shall be entitled to withhold from
any amounts payable under this Plan all taxes as legally shall be required
(including, without limitation, any United States federal taxes and any other
state, city, or local taxes).

Article 6. Excise Tax Equalization Payment

    6.1  Excise Tax Equalization Payment.  In the event that the Participant
becomes entitled to Severance Benefits or any other payment or benefit under
this Plan, or under any other agreement with or plan of the Company (in the
aggregate, the "Total Payments"), if all or any part of the Total Payments will
be subject to the tax (the "Excise Tax") imposed by Section 4999 of the Code (or
any similar tax that may hereafter be imposed), the Company shall pay to the
Participant in cash an additional amount (the "Gross-Up Payment") such that the
net amount retained by the Participant from the Total Payments and the Gross-Up
Payment after deduction of any Excise Tax upon the Total Payments and any
federal, state, and local income and employment tax, penalties, interest, and
Excise Tax upon the Gross-Up Payment provided for by this Section 5.1 (including
FICA), shall be equal to the Total Payments. Such payment shall be made by the
Company to the Participant as soon as practicable following the latest of
(i) the Effective Date of Termination or (ii) the date that the Participant
executes the Release or (iii) the last day following Participant's execution of
the Release that the Participant may, by its terms, revoke such Release, but in
no event beyond thirty (30) days from such date.

    6.2  Tax Computation.  For purposes of determining whether any of the Total
Payments will be subject to the Excise Tax and the amounts of such Excise Tax:

(a)Any other payments or benefits in the nature of compensation received or to
be received by the Participant in connection with a Change in Control of the
Company or the Participant's termination of employment (whether pursuant to the
terms of this Plan or any other plan, arrangement, or agreement with the Company
or otherwise) shall be treated as "parachute payments" within the meaning of
Section 280G(b)(2) of the Code, and all "excess parachute payments" within the
meaning of Section 280G(b)(1) shall be treated as subject to the Excise Tax,
unless in the opinion of tax counsel as supported by the Company's independent
auditors and acceptable to the Participant, such other payments or benefits (in
whole or in part) do not

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constitute parachute payments, or unless such excess parachute payments (in
whole or in part) represent reasonable compensation for services actually
rendered within the meaning of Section 280G(b)(4) of the Code in excess of the
base amount within the meaning of Section 280G(b)(3) of the Code, or are
otherwise not subject to the Excise Tax;

(b)The amount of the Total Payments which shall be treated as subject to the
Excise Tax shall be equal to the lesser of: (i) the total amount of the Total
Payments; or (ii) the amount of excess parachute payments within the meaning of
Section 280G(b)(1) (after applying clause (a) above); and

(c)The value of any noncash benefits or any deferred payment or benefit shall be
determined by the Company's independent auditors in accordance with the
principles of Sections 280G(d)(3) and (4) of the Code.

    For purposes of determining the amount of the Gross-Up Payment, the
Participant shall be deemed to pay federal income taxes at the highest marginal
rate of federal income taxation (including the effects of applicable phase-outs
of deductions and other benefits) in the calendar year in which the Gross-Up
Payment is to be made, and state and local income taxes at the highest marginal
rate of taxation in the state and locality of the Participant's residence on the
Effective Date of Termination.

    6.3  Subsequent Recalculation.  In the event the Participant ultimately owes
more Excise Tax on the Total Payments and the Gross-Up Payments than computed by
the Company under Section 6.1 herein, the Gross-Up Payment shall be recalculated
based on the actual Excise Tax.

Article 7. The Company's Payment Obligation

    The Company's obligation to make the payments and the benefits provided for
herein, to the extent that the Participant qualifies for such payments and
benefits under the terms of this Plan, shall be absolute and unconditional, and
shall not be affected by any circumstances, including, without limitation, any
offset, counterclaim, recoupment, defense, or other right which the Company may
have against the Participant or anyone else.

    The Participant shall not be obligated to seek other employment in
mitigation of the amounts payable or arrangements made under any provision of
this Plan, and the obtaining of any such other employment shall in no event
effect any reduction of the Company's obligations to make the payments and
arrangements required to be made under this Plan, except to the extent provided
in Section 4.3(d) herein.

Article 8. Arbitration

    Any dispute or controversy arising under or in connection with this Plan
shall be settled by arbitration, conducted before a panel of three (3)
arbitrators sitting in a location selected by the Participant within fifty (50)
miles from the location of his/her employment with the Company, in accordance
with the rules of the American Arbitration Association then in effect.

    Judgment may be entered on the award of the arbitrator in any court having
proper jurisdiction. All expenses of such arbitration, including the fees and
expenses of the counsel for the Participant, shall be borne by the Company.

Article 9. Successors and Assignment

    9.1  Successors to the Company.  The Company will require any successor
(whether direct or indirect, by purchase, merger, consolidation, or otherwise)
of all or substantially all of the business and/or assets of the Company or of
any division or subsidiary thereof to expressly assume and agree to

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perform the Company's obligations under this Plan in the same manner and to the
same extent that the Company would be required to perform them if no such
succession had taken place.

    9.2  Assignment by the Participant.  This Plan shall inure to the benefit of
and be enforceable by the Participant's personal or legal representatives,
executors, administrators, successors, heirs, distributees, devisees, and
legatees. If the Participant dies while any amount would still be payable to
him/her hereunder had he/she continued to live, all such amounts, unless
otherwise provided herein, shall be paid in accordance with the terms of this
Plan to the Participant's Beneficiary. If the Participant has not named a
Beneficiary, then such amounts shall be paid to the Participant's devisee,
legatee, or other designee, or if there is no such designee, to the
Participant's estate.

Article 10. Miscellaneous

    10.1  Employment Status.  Except as may be provided under any other
agreement between the Participant and the Company, the employment of the
Participant by the Company is "at will," and may be terminated by either the
Participant or the Company at any time and for any or no reason, subject to
applicable law.

    10.2  Beneficiaries.  The Participant may designate one or more persons or
entities as the primary and/or contingent Beneficiaries of any Severance
Benefits owing to the Participant under this Plan. Such designation must be in
the form of a signed writing acceptable to the Committee. The Participant may
make or change such designations at any time.

    10.3  Severability.  In the event any provision of this Plan shall be held
illegal or invalid for any reason, the illegality or invalidity shall not affect
the remaining parts of the Plan, and the Plan shall be construed and enforced as
if the illegal or invalid provision had not been included. Further, the captions
of this Plan are not part of the provisions hereof and shall have no force and
effect.

    10.4  Modification.  No provision of this Plan may be modified, waived, or
discharged unless such modification, waiver, or discharge is agreed to in
writing and signed by the Participant and by an authorized member of the
Committee, or by the respective parties' legal representatives and successors.

    10.5  Applicable Law.  To the extent not preempted by the laws of the United
States, the substantive laws of the state of California, without regard to
conflict of law principles, shall be the controlling law in all matters relating
to this Plan. [End of Plan]

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Executive Change-in-Control Severance Plan
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Chiron Corporation Executive Change-in-Control Severance Plan