<PAGE>

                                                                  Exhibit 10.602

                        SUPPLEMENTAL BENEFITS AGREEMENT

         This Agreement entered into this 21 day of July 1989, between Chiron
Corporation, a Delaware Corporation (the "Company"), and Dr. William J.
Rutter ("Executive").

                                   WITNESSETH

         WHEREAS, Executive has at the request of the Company agreed to
become an employee of Chiron and, to facilitate such employment, has ceased
to be a full time member of the faculty of the University of California
("University");

         WHEREAS, Executive will suffer a loss of benefits under the
University's retirement program, as a result of his change of status with the
University and the Company wishes to compensate the Executive for such loss
of benefits;

         NOW, THEREFORE, in consideration of the foregoing, it is agreed as
follows:

    I.   RETIREMENT AND SURVIVOR BENEFITS

         1.1 The Company agrees to pay Executive a supplemental retirement
benefit (including survivor and co-annuitant benefits) equal to the benefit
that Executive would have been entitled to receive under the University of
California Retirement System ("UCRS") had he remained a full-time faculty
member of the University throughout his period of employment with the
Company ("Projected UCRS Benefit"), less the benefit that Executive actually
becomes entitled to receive under UCRS based on service rendered prior to his
termination of employment with the Company ("Actual UCRS Benefit").

         1.2 For purposes of determining Executive's Projected and Actual
UCRS Benefits under Section 1.1, Executive will be assumed to have made the
maximum employee contributions that he would be eligible to make, including
any contributions required upon reimbursement with the University to
reinstate benefits previously refunded or forfeited under UCRS.

         1.3 Executive's Projected UCRS Benefit will be computed in accordance
with the terms of UCRS as in effect on the date of this agreement, including
any amendments subsequently adopted to comply with the Tax Reform Act of 1986
and related technical correction legislation. For purposes of computing his
Projected UCRS Benefit, Executive's highest average permissible compensation
under UCRS shall be determined as if Executive continued to receive a full
time rate of pay from the University

                                    1.

<PAGE>

through the date of his termination of employment with the Company equal to
the most recent rate he was paid as a full-time member of the faculty of the
University prior to the date of this Agreement increased by 6% per year from
the date of this Agreement.

         1.4 Notwithstanding anything to the contrary herein, the maximum
payments hereunder by the Company in any twelve month period shall not exceed
$10,000.

    II.  PAYMENTS OF BENEFITS

         Any benefit payable pursuant to Article I of this Agreement shall be
paid at the same time and in the same form and manner as payments are made to
Executive (or to his spouse or his co-annuitant) under UCRS.

    III. OFFSET

         Any benefit payable to Executive under Article I of this Agreement
shall be reduced by the actuarial equivalent of any benefits payable to the
Executive under any other retirement or supplemental retirement plan or
program established by the Company (other than the Salary Deferral Plan and
Trust of Chiron Corporation). For purposes of the preceding sentence, any
benefit which is payable to an estranged or former spouse of Executive
pursuant to an interlocutory or final decree of dissolution of marriage or
other order of any court arising out of an action for dissolution shall be
deemed payable to Executive.

    IV.  GENERAL PROVISIONS

         4.1  NO ASSIGNMENT

              No interest created by this Agreement may be sold, assigned,
transferred, conveyed, hypothecated, encumbered, anticipated or otherwise
disposed of and such interest shall not be subject to any liability or
obligation of Executive or his spouse or joint annuitant, nor to attachment,
garnishment, execution, or other legal process for payment of any claim
against any such person or his property.

         4.2  NO EMPLOYMENT CONTRACT

              This Agreement is not an employment contract and nothing
contained herein shall prohibit the adjustment from time to time of the terms
of employment of Executive, including his current compensation and fringe
benefits to which he may otherwise be entitled (except that no amendment may
be made to this Agreement other than as provided in Section 4.5, below). No

                                       2.


<PAGE>

provision in this Agreement shall be construed to guarantee continued
employment to Executive.

         4.3  INTERPRETATION

              The interpretation, performance, and enforcement of this
Agreement shall be governed by the laws of the State of California. Any
disputes concerning this Agreement shall be subject to resolution in state or
federal courts in San Francisco, California, and all expenses shall be paid
by the party against whom or which a final judgement is entered.

         4.4  NO FUNDING OBLIGATION

              This Agreement shall not be construed to require the Company to
fund any of the benefits payable under this Agreement nor to require the
establishment of a trust and Executive's rights to benefits hereunder shall
be as a general unsecured creditor of the Company. The Company, in its sole
discretion, may make such arrangements as it desires to provide for the
payment of benefits hereunder, and no person shall have any claim against a
particular fund or asset owned by the Company or in which it has an interest
to secure the payment of the Company's obligations hereunder.

         4.5  AMENDMENT

              This Agreement and any provision hereof may not be changed,
waived, discharged or terminated except by an instrument in writing signed by
the party against whom enforcement of the change, waiver, discharge or
termination is sought.

         4.6  ENTIRE AGREEMENT

              This Agreement definitively restates the entire understandings
and representations between the parties hereto, whether written or oral, with
respect to the subject matter contained herein. There are no representations,
agreements, arrangements, or understandings, oral or written, between the
parties relating to the subject matter of this Agreement which are not fully
expressed herein.

         4.7  HEADINGS

              All headings herein are for convenience only and shall be
disregarded in construing the substance of the provisions of this Agreement.

                                      3.

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement
as of July 21, 1989, at Emeryville, California.

                                       CHIRON CORPORATION

                                       By /s/ Greg Lawless
                                          -------------------------------------
                                          President and Chief Operating Officer

                                          /s/ William J. Rutter
                                          -------------------------------------
                                          Dr. William J. Rutter



                                       4.