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                                                                   Exhibit 10.20

    [CERTAIN MATERIAL (INDICATED BY A [*CON*]) HAS BEEN OMITTED FROM THIS
    DOCUMENT PURSUANT TO A REQUEST FOR CONFIDENTIAL TREATMENT. THE OMITTED
MATERIAL HAS BEEN FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION]


                             SERVICES AGREEMENT FOR
                               CHIRON CORPORATION

This Services Agreement ("AGREEMENT") is made effective as of February 7, 2000
("Effective Date") by and between Chiron Corporation ("CHIRON"), a Delaware
corporation with its principal place of business at 4560 Horton Street,
Emeryville, California 94608 and Mimotopes Pty. Ltd. ("MIMOTOPES"), an
Australian proprietary company with its principal place of business at 11
Duerdin Street, Clayton, Victoria 3168 Australia.

WHEREAS:

         By the terms of an Asset Purchase Agreement dated as of the Effective
Date of this Agreement ("PURCHASE AGREEMENT"), Chiron transferred certain of the
assets of its wholly owned subsidiary Chiron Technologies Pty. Ltd. ("CTPL") to
Mimotopes.

         Following such transfer, Chiron desires to have Mimotopes perform
certain services for Chiron.

THEREFORE,

         Chiron, hereby, contracts with Mimotopes to perform new services as
well as services formerly provided by CTPL to Chiron.

         1.       DESCRIPTION OF SERVICES

                  1.1      SERVICES. Mimotopes shall use reasonable commercial
efforts to provide at Chiron's request all services and technical assistance in
the synthesis and design of molecules in the support of Chiron's drug discovery
program for (a) projects involving discovery and development of (i) [ * CON * ]
and (ii) [ * CON * ]; and (b) other projects which may be mutually agreed to by
the parties as described below in this Section (the "SERVICES"). From time to
time, Chiron shall nominate such fields of research or specification of
compounds to be synthesized by submitting a written work order to Mimotopes, for
approval, which approval shall not be unreasonably withheld. The parties shall
mutually agree to a written research plan for each project outlining the
Services to be performed by Mimotopes for each such project. Mimotopes shall not
be required to provide Services that require staffing beyond the number of FTE's
set forth in Section 1.2 ("Employees"). The parties specifically agree that
Mimotopes is not responsible for any negligence, errors or omissions by CTPL in
CTPL's performance of the services prior to the Effective Date of this
Agreement.

                  1.2      EMPLOYEES. Mimotopes shall provide a minimum of
[ * CON * ] Full-Time Equivalents ("FTE's") to perform the Services (as defined
in Section 1.3 herein) during the first year of this Agreement, [ * CON * ]
FTE's to perform the Services during the second year of this Agreement and
[ * CON * ] FTE's to perform the Services during the third year of this
Agreement. Chiron reserves the right in its sole discretion to designate each of
the initial FTE's, further identified as the FTE Team and listed in ATTACHMENT
A. Subsequently, Chiron shall have the right to approve each additional or
replacement FTE on the basis of qualifications, with such approval not to be
unreasonably withheld.


                                       1
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                  1.3      TERM. The Services shall be provided for a term of
three (3) years commencing on the Effective Date ("TERM"), unless earlier
amended or extended in accordance with the terms and conditions of Article 9
("Amendment, Termination and Survival") herein.

         2.       WORK PRODUCT AND MATERIALS.

                  2.1      All data, reports, materials, inventions and
discoveries generated or created by Mimotopes arising from its conduct of the
Services which are conceived or reduced to practice during the Term of this
Agreement are hereafter collectively referred to as "WORK PRODUCT". Chiron shall
own all right, title and interest in the Work Product, except for any Process
Improvements (as defined below), which shall be the sole and exclusive property
of Mimotopes. A Process Improvements is any new, improved or modified technique,
process, method, instrument or equipment or similar know-how, including without
limitation new chemical processes, synthesis protocols, linker systems, cleavage
methods, or analytic techniques, developed or created by Mimotopes which is not
specific to Chiron Chemical Matter. Chiron will retain a non-exclusive,
royalty-free license to use any Process Improvements, with the right to
sublicense. Work Product will be deemed Confidential Information as defined in
Article 4 ("Confidentiality and Non-Use Obligation") herein. Subject to the
provisions of the Purchase Agreement, this Agreement (i) does not convey to
Mimotopes any right, title or interest to or in any patents, patent
applications, know-how (whether patentable or unpatentable) or other
intellectual property rights of Chiron; and (ii) does not convey to Chiron any
right, title or interest to or in any patents, patent applications, know-how
(whether patentable or unpatentable) or other intellectual property rights of
Mimotopes.

                  2.2.     Mimotopes shall provide to Chiron a written report on
the current status of the Services, FTE's and Work Product, including but not
limited to a financial accounting and a project review. The report shall be made
within fifteen days of the close of each calendar quarter. Additionally,
Mimotopes shall send to Chiron, annually and at its expense, not more than
[ * CON * ] ([ * CON * ]) people-trips of lead scientists to participate in a
project meeting. If Chiron desires, and so requests, more people-trips within
any contract year, then either (i) Chiron will send its personnel to Mimotopes'
facility in Australia for such meeting; or (ii) Chiron will reimburse Mimotopes
for all out-of-pocket costs associated with such travel.

                  2.3      Mimotopes shall keep separate laboratory notebook
records, prepared and witnessed according to standard laboratory practices, of
all work performed under this Agreement. These notebooks and other records shall
be owned, properly maintained and stored by Mimotopes. Upon written request by
Chiron, Mimotopes shall (i) make such laboratory notebook records reasonably
available to Chiron for on-site inspection at Mimotopes; (ii) provide to Chiron
copies of the relevant portions of such laboratory notebook records as
reasonably needed by Chiron for routine patent protection (e.g., filing and
prosecution) or other purposes; and (iii) in the event Chiron needs the original
laboratory notebook records for litigation or patent interference purposes,
Mimotopes shall make such original records available to Chiron. Mimotopes shall
ordinarily bear the cost of the activities set forth in (i), (ii) and (iii);
provided, however, that in cases where Mimotopes in its reasonable discretion
determines that Chiron's requests become a significant burden in terms of time
and/or expense, then Mimotopes reserves the right to require Chiron to reimburse
Mimotopes for such activities.


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                  2.4      Mimotopes shall cooperate with Chiron and make its
scientists reasonably available for purposes of filing, prosecuting and
defending patent applications arising out of the Work Product. Mimotopes shall
ordinarily bear the cost of the activities set forth in this Section 2.4;
provided, however, that in cases where Mimotopes in its reasonable discretion
determines that Chiron's requests become a significant burden in terms of time
and/or expense, then Mimotopes reserves the right to request Chiron to reimburse
Mimotopes for such activities.

         3.       COMPENSATION. As compensation for Mimotopes' conduct of the
Services, Chiron shall pay Mimotopes in United States dollars at the rate of
[ * CON * ] dollars ($[ * CON * ]) per FTE per year. In any case, the payment
shall not exceed [ * CON * ] dollars ($[ * CON * ]) in the first year of this
Agreement, [ * CON * ] dollars ($[ * CON * ]) in the second year of this
Agreement and [ * CON * ] dollars ($[ * CON * ]) in the third year of this
Agreement. Chiron's first year payment shall be made within thirty (30) days
after the Effective Date of this Agreement. All other payments shall be made in
advance at the beginning of each subsequent year of the Term, that is, on the
first and second anniversary, of this Agreement.

         4.       CONFIDENTIALITY AND NON-USE OBLIGATIONS.

                  4.1      CONFIDENTIAL INFORMATION. During the course of
activities contemplated by this Agreement, either party, its employees, agents,
representatives and consultants (collectively, "Recipient") shall have access to
certain confidential and proprietary information ("Confidential Information") of
the other party ("Dislcoser"). Confidential Information shall include without
limitation Chiron's lead compounds (the "Chiron Chemical Matter") or either
party's proprietary materials and technologies, research and development data
and plans, business or research strategies, trade secrets and material
embodiments thereof, and manufacturing processes and technologies. Chiron and
Mimotopes each retains exclusive title to its Confidential Information.

                  4.2      CONFIDENTIALITY AND NON-USE. The Recipient shall
maintain the Discloser's Confidential Information in confidence. The Recipient
shall use the Discloser's Confidential Information solely for performing or
evaluating the Services unless otherwise mutually agreed in writing. Upon
request by the Discloser, the Recipient shall return all Confidential
Information, including all copies and extracts thereof, to the Discloser;
provided, however, that Mimotopes will be entitled to retain one copy of any
Work Product.

                  4.3      EXCLUSIONS. The Recipient's obligations of
confidentiality and non-use shall not apply to any information that: (i) is
shown by contemporaneous documentation of the Recipient to have been in its
rightful possession prior to receipt from the Discloser; (ii) is or becomes,
through no fault of the Recipient, publicly known; (iii) is furnished to the
Recipient by a third party without breach of a duty to the Discloser; (iv) the
Recipient is required to disclose such information by law, order or regulation
of a governmental agency or a court of competent jurisdiction or international
authority (after providing the Discloser with reasonable notice of such
requirement to divulge and with an opportunity to obtain a protective order; or
(v) was or is independently developed by the Recipient without reference to the
Discloser's Confidential Information.


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         5.       COMPLIANCE WITH LAW; STANDARD OF CARE. Mimotopes shall comply
with all applicable laws, ordinances, rules and regulations pertaining to its
performance of the Services. Mimotopes shall perform the Services in accordance
with the reasonable commercial standards of care and diligence practiced by
recognized firms in providing services of a similar nature and shall provide the
reasonable commercial skill and judgment of its employees in providing the
Services.

         6.       NOTICES. All notices and other official communications
hereunder shall be in writing and shall be deemed given if delivered personally
or by commercial delivery service, or within seventy-two (72) hours after being
mailed by registered or certified mail (return receipt requested) or sent via
facsimile (with confirmation of receipt) to the parties at the following
addresses (or at such other address for a party as shall be specified by like
notice):

                  In the case of Mimotopes:

                           Mimotopes Pty. Ltd.
                           11 Duerdin Street
                           Clayton, Victoria 3168 Australia
                           Attention:  Managing Director
                           Fax:     61-3-9565-1199
                           Tel:     61-3-9565-1111

                  with copies to:

                           MitoKor
                           11494 Sorrento Valley Road
                           San Diego, CA  92121
                           Attention:  Chief Executive Officer
                           Fax:     858-793-7805
                           Tel:     858-793-7800

                  In the case of Chiron:

                           Chiron Corporation
                           4560 Horton Street
                           Emeryville, California 94608
                           Attention:  Office of the General Counsel
                           Fax:     510-654-5360

                           cc: President, Chiron Technologies
                           Fax:     510-923-[ * CON * ]

                           cc: Dr. [ * CON * ]
                           Fax:     (510) 923-[ * CON * ]


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         7.       INDEMNIFICATION.

                  7.1      To the extent permitted by applicable law, and except
to the extent caused by the negligence or willful misconduct of Chiron, or its
employees, agents or representatives, Mimotopes shall indemnify, defend, protect
and hold Chiron, and its directors, officers, stockholders, employees, agents
and representatives, harmless from any and all liability, damages, causes of
action, loss, cost or expense (including but not limited to, reasonable
attorneys' fees) (collectively, "Losses") arising at any time out of Mimotopes'
negligence or willful misconduct performing under this Agreement. For the
avoidance of doubt, Chiron specifically agrees that Mimotopes' indemnification
does not, in any circumstances, extend to Losses arising out of Chiron's and/or
any third party's sale or use of any products which incorporate, or are produced
using, the Work Product or any derivative or modification thereof.

                  7.2      To the extent permitted by applicable law, and except
to the extent caused by the negligence or willful misconduct of Mimotopes, or
its employees, agents or representatives, Chiron shall indemnify, defend,
protect and hold Mimotopes, and its directors, officers, stockholders,
employees, agents and representatives, harmless from any and all Losses arising
at any time out of (i) Chiron's negligence or willful misconduct in performing
under this Agreement; or (ii) Chiron's and/or any third party's sale or use of
any products which incorporate, or are produced using, the Work Product or any
derivative or modification thereof.

                  7.3      The party seeking indemnification under Section 7.1
or 7.2 (the "Indemnified Party") agrees to give prompt notice to the party
against whom indemnity is sought (the "Indemnifying Party") of the assertion of
any claim, or the commencement of any suit, action or proceeding in respect of
which indemnity may be sought under such section. The Indemnifying Party may,
and at the request of the Indemnified Party shall, participate in and control
the defense of any such third party suit, action or proceeding at its own
expense. The Indemnifying Party shall not be liable under Section 7.1 or 7.2 for
any settlement effected without its consent of any claim, litigation, or
proceeding in respect of which indemnity may be sought hereunder.

         8.       INDEPENDENT CONTRACTOR. Mimotopes is an independent contractor
engaged by Chiron to perform the Services in accordance with the provisions of
this Agreement, and the relationship hereby created is specifically governed by,
limited to, and subject to all of the terms and conditions contained in this
Agreement. The parties further agree that Chiron does not have the authority to
hire or fire employees of Mimotopes, nor does Chiron determine the rate or
method of pay of such employees. Additionally, nothing contained in this
Agreement shall entitle either party to the right or authority to make any
representation on behalf of or bind the other party to others in any manner,
except as may be specifically authorized in writing by the other party. Neither
party may make any representations or commitments on the other's behalf, nor may
either party use the other party's name or trademarks in any public disclosure,
without the named party's prior written consent.

         9.       AMENDMENT, TERMINATION AND SURVIVAL.

                  9.1.     This Agreement may be amended or renewed only with
the written agreement of both parties.


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                  9.2      Either party may terminate this Agreement if such
party provides written notice of Material Breach to the breaching party and such
Material Breach has not been remedied within thirty (30) days after the date of
such notice. In the case of Mimotopes, a Material Breach of this Agreement shall
be defined as a substantial failure by Mimotopes to meet any material mutually
agreed upon written performance criteria or a failure of Mimotopes to provide
the required number of FTE's. In the case of Chiron, a Material Breach of this
Agreement shall be defined as the failure to make any required payment. Upon
early termination of this Agreement under this Section by either party, (i) if
Chiron has made payment for Services which have not yet been performed, then
Chiron shall be entitled, as damages, to a pro-rated return of the compensation
it has paid under Section 3 ("Compensation") of this Agreement; or (ii) if
Mimotopes has not yet been paid for Services which it has performed, then
Mimotopes shall be entitled to a pro-rated payment of such compensation for the
period in which the Services were performed.

                  9.3      Those terms and obligations which by their nature
should continue shall survive any termination or expiration of this Agreement,
including without limitation the terms and obligations of Articles 1.1
("Services"), 2 ("Work Product and Materials"), 4 ("Confidentiality and
Non-Use"), 7 ("Indemnification"), 8 ("Independent Contractor") and 13 ("Warranty
Disclaimer; Consequential Damages").

         10.      WAIVER AND SEVERABILITY. No waiver of any of the provisions of
this Agreement shall be deemed, or shall constitute, a waiver of any other
provision, whether or not similar, nor shall any waiver constitute a continuing
waiver. No waiver shall be binding unless executed in writing by the party
making the waiver. This Agreement shall be interpreted as a whole and neither
for or against either party, in accordance with their common meaning, but taking
into account the nature of the Services to be rendered by Mimotopes.

         11.      ASSIGNMENT. This Agreement and any rights under it may be
assigned by Chiron with the prior written consent of Mimotopes, which shall not
be unreasonably withheld. This Agreement and any rights under is may not be
assigned by Mimotopes, except that either party may assign its rights and
obligations under this Agreement, in whole or in part, to a successor in
interest, in whole or in part, of the business to which this Agreement relates.
Such assignment shall be binding upon and inure to the benefit of the parties,
their successors and permissible assigns.

         12.      ENTIRE AGREEMENT. This Agreement contains all the
representations and the entire agreement between the parties with respect to the
Services identified herein. The terms and conditions of the Purchase Agreement
shall continue to apply to all other aspects of the relationship between the
parties not specifically addressed in this Agreement.

         13.      WARRANTY DISCLAIMER; CONSEQUENTIAL DAMAGES. ANY WORK PRODUCT
IS PROVIDED WITHOUT WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE OR ANY OTHER WARRANTY, EXPRESS OR IMPLIED. MIMOTOPES MAKES NO
REPRESENTATION OR WARRANTY THAT THE WORK PRODUCT WILL NOT INFRINGE ANY PATENT OR
OTHER PROPRIETARY RIGHTS. IN NO EVENT WILL EITHER PARTY BE LIABLE FOR ANY
INCIDENTAL, SPECIAL OR CONSEQUENTIAL DAMAGES ARISING FROM THIS AGREEMENT.


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         14.      COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original as against any party
whose signature appears on such counterpart and all of which shall be considered
on and the same agreement and shall become effective when one or more
counterparts have been signed by each of the parties and delivered to the other
party, it being understood that each party need not sign the same counterpart.
This Agreement may be executed by facsimile signature as long as the party so
executing commits to deliver an original signature within twenty (20) days.

         15.      GOVERNING LAW; VENUE AND JURISDICTION. This Agreement shall be
governed and construed in accordance with the laws of the State of California
without regard to any applicable conflicts of laws principles. Any legal action
arising under this Agreement shall be resolved in the courts located in San
Diego, California if brought by Chiron and in San Francisco, California if
brought by Mimotopes.

         16.      THIRD PARTY BENEFICIARIES. Nothing contained in this Agreement
is intended to confer upon any person other than the parties hereto and their
respective successors and permitted assigns, any rights, remedies or obligations
under, or by reason of this Agreement.


[Remainder of this page intentionally left blank]


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         This Agreement is executed by the parties to be effective as of the
Effective Date.


CHIRON CORPORATION                       MIMOTOPES PTY. LTD.

By:                                      By:
       ------------------------------             ------------------------------

Name:                                    Name:
       ------------------------------             ------------------------------

Title:                                   Title:
       ------------------------------             ------------------------------


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                                  ATTACHMENT A
                          FTE TEAM FOR CHIRON PROJECTS

The following FTE's will work 100% of their time on Chiron projects and the
entire team shall not be changed without Chiron's written approval.

[ * CON * ]


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October 3, 2000

Walter H. Moos, Ph.D.
Chairman
Mimotopes Pty. Ltd.
11494 Sorrento Valley Road
San Diego, CA 92121

Dear Dr. Moos:

In response to your request, and pursuant to the Services Agreement entered into
by Mimotopes Pty. Ltd. and Chiron Corp. effective February 7, 2000 and the Asset
Purchase Agreement executed concurrently by the parties, the parties hereby
agree to amend such services specifically relating to Mimotopes' employee
staffing allocations during the term of that agreement.

Specifically, the parties agree that Section 1.2 of the Services Agreement is
hereby amended in entirety as follows:

1.2 EMPLOYEES. Mimotopes shall provide a minimum of [ * CON * ] Full-Time
Equivalents ("FTE's") to perform the Services (as defined in Section 1.3 herein)
during each full year of this Agreement. Chiron reserves the right in its sole
discretion to designate each of the initial FTE's, further identified as the FTE
Team and listed in Attachment A. Subsequently, Chiron shall have the right to
approve each additional or replacement FTE on the basis of qualifications, with
such approval not to be unreasonably withheld.

If you agree to this modification, please indicate your approval by signing
below.

Sincerely,



Sean O'Connell
Chiron Corporation


I agree:


- ------------------------------                       ------------
Walter H. Moos, PhD.                                 Date
Chairman of the Board of Directors
Mimotopes Pty. Ltd.