<PAGE>

                                                                   EXHIBIT 10.23

          CONFIDENTIAL MATERIALS OMITTED AND FILED SEPARATELY WITH THE
         SECURITIES AND EXCHANGE COMMISSION. ASTERISKS DENOTE OMISSIONS.

                          SPONSORED RESEARCH AGREEMENT

         Effective as of 1 OCTOBER 2003, MAYO FOUNDATION FOR MEDICAL EDUCATION
AND RESEARCH, a Minnesota charitable corporation (MAYO), 200 First Street SW,
Rochester, MN 55905-0001 and MAYO CLINIC JACKSONVILLE, 4500 San Pablo Road,
Jacksonville, FL 32224 (collectively "MAYO") with Matthew J. Farrer, Ph.D., a
MAYO employee, as principal investigator (INVESTIGATOR) and Alnylam
Pharmaceuticals, Inc. (including its affiliated companies), a corporation having
its principal place of business at 790 Memorial Drive, Cambridge, MA 02139
(SPONSOR) agree as follows:

                           ARTICLE 1. PROJECT SUMMARY

         1.1 -- MAYO will undertake a research project ("Project") described in
the research plan attached hereto and incorporated herein as Exhibit A. Summary
data about the Project are forth as follows:

         (a)      TITLE:     Alpha-Synuclein as a Target for siRNA Therapy

         (b)      START DATE:     1 October 2003

         (c)      PROJECTED COMPLETION DATE:     [**]

         (d)      FUNDING AMOUNT:     $[**] pursuant to budget attached as
                                      Exhibit C

         (e)      PAYMENT PLAN: Quarterly in advance

         (f)      CHECKS PAYABLE TO:  Mayo Foundation for Medical Education and
                                      Research

         (g)      CHECKS MAILED TO:   Mayo Medical Ventures
                                      Office of Technology Commercialization
                                      200 First Street S.W.
                                      Rochester, Minnesota 55905
                                      Taxpayer ID No. 41-1506440

         (h)      MAYO ADMINISTRATIVE CONTACT:    Mayo Medical Ventures
                                                  Office of Technology
                                                  Commercialization
                                                  200 First Street S.W.
                                                  Rochester, Minnesota 55905

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                                 Execution Copy

                                                  507-284-8878
                                                  Attn: Susan L. Stoddard, Ph.D.
                                                  sstoddard@mayo.edu

         (i)      Sponsor ADMINISTRATIVE CONTACT: Nagesh Mahanthappa
                                                  Alnylam Pharmaceuticals, Inc.
                                                  790 Memorial Drive
                                                  Cambridge, MA 02139

         1.2 -- Anything contained in Exhibit A which is in conflict with
anything in this Agreement is superseded by this Agreement.

                ARTICLE 2. CONFIDENTIALITY AND PROPRIETARY DATA

         2.1 -- SPONSOR or a party on SPONSOR's behalf may provide MAYO and
INVESTIGATOR with proprietary information and materials ("Sponsor Information")
relevant to the work under this Agreement. MAYO and INVESTIGATOR understand that
any materials provided to it by or on behalf of SPONSOR ("Sponsor Materials")
remain the sole property of SPONSOR and are experimental materials intended
exclusively for investigative use only in laboratory animals and for in vitro
use and are not for use in humans. MAYO and INVESTIGATOR agree to use the
Sponsor Materials in compliance with all local laws and regulations, including
current guidelines of the National Institutes of Health of the United States.
SPONSOR agrees to furnish MAYO with sufficient information, to the extent that
it is in possession of such information, to identify precautions needed to help
protect the health and safety of personnel using the chemicals. MAYO's and
INVESTIGATOR's obligations with respect to such Sponsor Information (excluding
Sponsor Materials) shall be subject to the following:

         (a)      SPONSOR must mark or designate in writing any Sponsor
                  Information provided to MAYO or INVESTIGATOR which it deems to
                  be proprietary or confidential. Confidential information
                  disclosed orally must be identified as confidential or
                  proprietary at the time of disclosure and confirmed in writing
                  as confidential or proprietary within thirty (30) days of such
                  disclosure.

         2.2 -- MAYO and INVESTIGATOR agree to exercise their best efforts not
to publish or otherwise reveal or make available the Sponsor Information to
others outside Mayo without the prior written permission of the SPONSOR.
Additionally, MAYO and INVESTIGATOR agree:

         (a)      not to use Sponsor Information for any purpose other than as
                  advised or directed in writing by SPONSOR (which writing shall
                  include the research plan attached hereto as Exhibit A);

         (b)      to only disclose Sponsor Information to employees of MAYO
                  participating in the Project who have a need to receive such
                  Sponsor Information in the course of the performance of their
                  duties, and who are bound by the terms of this Agreement;

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         (c)      to not evaluate or analyze the Sponsor Materials for any
                  purpose other than as agreed to in the Project; and

         (d)      that the results of any evaluation or analysis of the Sponsor
                  Materials shall be treated as Sponsor Information, subject to
                  MAYO's publication rights under Article 4.

MAYO and INVESTIGATOR further agree that upon the termination of this Agreement,
completion of work performed under the Project or at the request of Sponsor,
MAYO and INVESTIGATOR will, at SPONSOR's option, either destroy or promptly
return, at SPONSOR's expense, to SPONSOR, all Sponsor Information and Sponsor
Material.

         2.3 -- Any data and materials generated solely or jointly by MAYO or
INVESTIGATOR pursuant to the Project will be made available to SPONSOR and are
collectively referred to as "Project Information." MAYO and INVESTIGATOR agree
that:

         (a)      they shall use Project Information only for internal,
                  non-commercial, non-commercially sponsored research purposes;

         (b)      they shall not disclose or make available any Project
                  Information to any third party, except in accordance with the
                  publication provisions of Section 4 below, without the prior
                  written consent of SPONSOR; and

         (c)      they shall disclose Project Information only to employees of
                  MAYO who are aware of the terms of this Agreement.

If one year following the expiration or termination of this Agreement, SPONSOR
is not commercially using Project Information, the obligations set forth in this
Section 2.3 shall no longer apply.

Sponsor Information and Project Information are collectively referred to as
"Information."

         2.4 -- Notwithstanding the above, the confidentiality obligation shall
not apply to Information which:

         (a)      at the time of receipt by MAYO or INVESTIGATOR is in the
                  public domain;

         (b)      comes into the public domain through no fault of MAYO or
                  INVESTIGATOR; or

         (c)      was known to MAYO or INVESTIGATOR before disclosure by SPONSOR
                  or was acquired from a source wholly independent from SPONSOR
                  who was not under an obligation of confidentiality to SPONSOR
                  with regard to such Information.

Additionally, MAYO or INVESTIGATOR may disclose to the appropriate legal
authority Information that is the subject of a valid subpoena or is otherwise
required by law to be disclosed, provided that advance notice is given to
SPONSOR of the requirement of such

<PAGE>

Sponsored Research Agreement and Option                             page 4 of 19
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disclosure to permit SPONSOR to oppose such disclosure by appropriate legal
action or to evaluate whether means can be taken to provide such disclosure on a
confidential basis.

         2.5 -- SPONSOR shall have the unrestricted right to use, disclose and
make available Project Information, subject to the following. Prior to any
disclosure of nonpublic Project Information, with the exception of disclosures
required by law or disclosures made under confidence, SPONSOR shall provide MAYO
and INVESTIGATOR with an advance copy of such disclosure. SPONSOR shall also not
submit a manuscript for publication in a peer-reviewed scientific journal
disclosing the research results without the prior agreement of MAYO; provided
that at the expiration of ninety (90) days following receipt of the proposed
manuscript by MAYO, SPONSOR shall have the right to submit such manuscript for
publication. Proper acknowledgement will be made for the contributions of each
party to the research results being published.

                 ARTICLE 3. INVENTIONS, DISCOVERIES AND PATENTS

         3.1 -- MAYO filed U.S. Provisional Patent Application No. [**] and U.S.
Provisional Patent Application No. [**] and is the owner of any and all rights
therein with respect to any MAYO employee, which together with all divisions,
continuations, continuations-in-part thereof, all patents issuing thereon, any
reexams, reissues or extensions thereof and any foreign counterparts thereon are
collectively referred to herein as "Background IP."

         3.2 -- MAYO and INVESTIGATOR agree to promptly disclose to SPONSOR in
writing all inventions, innovations and discoveries and all modifications,
enhancements and improvements developed by MAYO or INVESTIGATOR during the term
of this Agreement and the term of any Option, as defined below and arising out
of or based upon the performance of research carried out under the provisions of
this Agreement (individually Discovery and collectively "Discoveries"). MAYO
shall own all of its Discoveries. Any inventions, innovations and discoveries
made solely by SPONSOR shall be the sole property of SPONSOR. Any inventions,
innovations and discoveries made jointly by one or more employees of MAYO and
one or more employees of SPONSOR arising out of or based upon the performance of
research carried out under the provisions of this Agreement shall be jointly
owned ("Joint Discovery").

         3.3 -- Other than as specified in Sections 2.1 and 2.2 hereto with
regard to performing research under this Agreement, MAYO and INVESTIGATOR
receive no right to a license, implied or otherwise, under any patent or other
right now or hereafter owned or controlled by SPONSOR.

         3.4 -- MAYO and INVESTIGATOR hereby grant to SPONSOR:

         (a)      a worldwide, sub licensable, paid-up, exclusive license under
                  their right, title and interest in and to Discoveries and
                  Joint Discoveries incorporating Sponsor Material(s) or
                  modifications to the Sponsor Material(s) ("Material
                  Discoveries");
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         (b)      a worldwide, non-sub licensable (except to entities with whom
                  SPONSOR is jointly researching, developing and/or
                  commercializing a product) paid-up, non-exclusive license
                  under their interest in and to all Joint Discoveries relating
                  to uses of Sponsor Material(s) or uses of modifications to the
                  Sponsor Materials including the right to make, have made, and
                  use such Joint Discoveries and have others use such Joint
                  Discoveries ;

         (c)      a worldwide, non-sub licensable, non-exclusive, paid-up
                  license solely for research purposes under their interest in
                  and to all Discoveries and Joint Discoveries other than those
                  set forth in 3.4(a) and (b) above ("Other Discoveries")
                  including the right to have others use such Other Discoveries
                  to perform direct services for SPONSOR; and

         (d)      an option ("Option") to acquire an exclusive, worldwide,
                  royalty bearing, sub licensable license to Background IP,
                  Joint Discoveries set forth in 3.4(b) above, and Other
                  Discoveries desired by SPONSOR on the terms set forth in
                  Exhibit B.

The Option set forth in 3.4(d) above shall extend for a period of [**] following
the completion of the Project or earlier termination of this Agreement. If
SPONSOR exercises the Option and a third party has any rights in the Background
IP, MAYO shall use reasonable efforts to negotiate in good faith with such third
party to obtain such third party's rights so that SPONSOR shall receive an
exclusive license to the Background IP.

         3.5 -- MAYO and the INVESTIGATOR shall provide SPONSOR with the
information SPONSOR reasonably needs to exercise its Option.

         3.6 -- If SPONSOR exercises its Option, then MAYO and SPONSOR shall
negotiate in good faith towards achieving a mutually agreeable license agreement
on the terms set forth in Exhibit B. Said negotiations must be concluded within
[**] from the date SPONSOR exercises its Option, unless the time period for
negotiations is extended in writing by mutual agreement.

         3.7 -- Upon the expiration of the unexercised Option or the license
agreement negotiation period (which did not result in an executed license
agreement), whichever event occurs later, MAYO shall have no further obligation
to SPONSOR with regard to the Discoveries and Project Information, other than
the licenses set forth in Section 3.3 hereto and obligations set forth in
Section 2.3.

         3.8 -- MAYO shall retain a royalty-free right to use any of its
Discoveries and Joint Discoveries in connection with its own internal,
non-commercial, non-commercially sponsored research, education and clinical
programs.

         3.9 -- MAYO warrants that all persons associated with the performance
of the Project have obligations to assign their ownership rights in any
Discoveries and Joint Discoveries to MAYO and to be bound by the confidentiality
provisions of this Agreement.

<PAGE>

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         3.10 -- At its option, SPONSOR shall have the right to obtain patent
protection in the United States and foreign countries for any Discoveries and
Joint Discoveries, at its expense. In such situation, SPONSOR shall keep MAYO
informed of the course of the patent prosecution and will give MAYO the right to
review and comment on all substantive filings and correspondence with patent
authorities and shall in good faith consider all comments of MAYO with respect
to such prosecution efforts. MAYO and INVESTIGATOR hereby undertake and agree to
execute such papers which are necessary at any time to permit the filing and
prosecution of applications for patent applications covering the Discoveries and
Joint Discoveries.

                             ARTICLE 4. PUBLICATION

         4.1 -- MAYO and INVESTIGATOR reserve the right to publish the results
of work completed under this Agreement. Review by SPONSOR of the proposed
publication prior to submission will be provided, but in the interest of free
exchange of scientific information, MAYO and INVESTIGATOR may publish after the
expiration of ninety (90) days following receipt of the proposed publication by
SPONSOR. Publication of the results will not include SPONSOR Information as
defined in Article 2 without the written permission of SPONSOR.

                             ARTICLE 5. USE OF NAME

         5.1 -- Except as required by law, SPONSOR and MAYO shall not use,
expressly or by implication,

         (a)      Any trademark, trade name, or any contraction, abbreviation,
                  simulation, or adaptation thereof of the other party; or

         (b)      The name of any of other party's staff;

in any news release, publicity, policy recommendation, advertising, product
promotion or any commercial communication without the express written approval
of the other party.

              ARTICLE 6. INDEMNIFICATION AND NEGATION OF WARRANTIES

         6.1 -- SPONSOR agrees to indemnify, defend and hold harmless MAYO, its
trustees, officers, employees and agents from any third party claims, loss,
damage, arising from SPONSOR'S use of the research performed under this
agreement. Notwithstanding the above, SPONSOR shall not be responsible for
indemnifying MAYO, its trustees, officers, employees or agents for any liability
to the extent due to MAYO's negligence, willful misconduct or research contrary
to the Project. In the event that SPONSOR defends MAYO and proof of the
foregoing is established, MAYO shall reimburse SPONSOR for all costs and
expenses incurred by SPONSOR in such defense. MAYO shall provide prompt written
notice to SPONSOR of any such claim or liability and SPONSOR shall control the
defense and/or settlement of any such claim or liability, provided that SPONSOR
agrees not to settle any such claim against MAYO without MAYO's consent where
such settlement would include any admission of liability on the part of MAYO or
MAYO would incur any financial liability; where the settlement would impose any
restriction on the conduct by MAYO of any of its activities, or where the
settlement would

<PAGE>

Sponsored Research Agreement and Option                             page 7 of 19
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                                 Execution Copy

not include an unconditional release of MAYO from all liability for claims that
are the subject matter of such claim.

Mayo agrees to be responsible for its acts of negligence or willful misconduct
in the performance of its duties and shall be financially and legally
responsible for all expenses, liabilities and attorneys fees resulting from or
attributable to any such negligence or willful misconduct. Mayo agrees to
maintain adequate insurance or a program of self-insurance to cover its
liabilities.

         6.2 -- Except as may be specifically stated in this Agreement, MAYO
makes no representations or warranties, expressed or implied, regarding the
intellectual property licensed hereunder or its performance under this
Agreement, including but not limited to, the marketability, use or fitness for
any particular purpose of the research results developed under this work, or
that such results do not infringe upon any third party property rights. Further,
neither party shall be liable under this Agreement for special, consequential,
or incidental damages.

              ARTICLE 7. CONDUCT OF PROJECT AND FISCAL MANAGEMENT

         7.1 -- MAYO and INVESTIGATOR shall perform those research activities as
described in Exhibit A for the Project. MAYO and INVESTIGATOR shall not make any
changes to the Project or deviate there from, without first consulting with
SPONSOR and receiving appropriate written authorization to implement the
modification. SPONSOR, in consultation with the INVESTIGATOR, may modify the
Project; provided that any modification requiring an increase in the payments to
be made hereunder shall not be effected, without the agreement of the parties in
writing. MAYO shall ensure that all employees of MAYO who are assigned to
perform research under this Agreement are made aware of the obligations
contained in this Agreement and are bound by such obligations. MAYO and
INVESTIGATOR shall not subcontract with any third party to perform any services
included in the Project without the express prior written consent of SPONSOR.
MAYO and INVESTIGATOR will provide status reports upon reasonable request and
shall provide a comprehensive, final written report upon conclusion of the
Project. Additionally, SPONSOR shall designate representatives to participate in
meetings to review performance of the research hereunder, which meetings shall
take place at least once each quarter, at the convenience of MAYO and the
INVESTIGATOR. SPONSOR's designated representatives shall have access at
reasonable times to observe the services in progress or review any and all
records generated as a result of MAYO and INVESTIGATOR's performance of
services. MAYO's relation to SPONSOR shall be that of an independent contractor
and neither this Agreement nor the research to be conducted hereunder shall for
any purpose whatsoever or in any way or manner create any employer employee
relationship between the parties. MAYO shall not be deemed an agent of SPONSOR
for any purpose and shall have no authority to bind SPONSOR.

         7.2 -- MAYO and INVESTIGATOR shall devote their reasonable efforts and
ability to the performance of the research hereunder, devoting an amount of time
as mutually agreed. MAYO hereby represents that it has the experience,
capability and resources, including but not limited to sufficient personnel and
supervisors, to efficiently and expeditiously perform the research to be
conducted under the Project hereunder in a professional and competent manner.

<PAGE>

Sponsored Research Agreement and Option                             page 8 of 19
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MAYO further represents that it will at all times devote the necessary personnel
and supervisors to perform such research hereunder in such a manner. MAYO and
INVESTIGATOR shall perform all services under the Project hereunder in
accordance with the current state of the art and this Agreement. All information
provided to SPONSOR pursuant to this Agreement shall be accurate in accordance
with scientifically accepted standards. MAYO and INVESTIGATOR shall also comply
with all current government regulatory requirements as appropriate to such
research and all other applicable federal, state and local laws and regulations.
To the best of their knowledge, without the obligation to inquire, MAYO and
INVESTIGATOR warrant and represent that no trade secrets or other confidential
information of any other person, firm, corporation, institution or other entity
will be wrongfully disclosed by them to SPONSOR in connection with any of the
research services called for hereunder. MAYO and INVESTIGATOR further warrant
and represent that none of the provisions of this Agreement, nor the services
which will be performed by MAYO and INVESTIGATOR hereunder, contravenes or is in
conflict with any agreement of MAYO or INVESTIGATOR with, or obligation to, any
other person, firm, corporation, institution or other entity including, without
limiting the generality of the foregoing, employment agreements, consulting
agreements, service agreements, disclosure agreements or agreements for
assignment of inventions.

         7.3 -- In consideration for the completion of the Project by MAYO and
INVESTIGATOR, and as detailed in the budget that is part of Exhibit A, SPONSOR
shall pay MAYO [**] (US $[**]) such amount to be paid in quarterly payments of
[**] (US $[**]), the first payment to be made within thirty (30) days of the
execution of this Agreement and the initiation of the Project. Such amount shall
include all costs associated with the Project.

         7.4 -- MAYO shall maintain complete and accurate accounting records in
accordance with accepted accounting practices. These records shall be available
for inspection, review and audit at reasonable times by SPONSOR, or its duly
authorized representative, at SPONSOR's expense, for three (3) years following
the end of the calendar year in which such costs are incurred. This section
shall survive termination of this Agreement.

         7.5 -- MAYO shall retain title to equipment and all other items
purchased with funds provided by SPONSOR.

         7.6 -- In consideration for the option grant set forth in Article 3,
SPONSOR shall pay MAYO [**] DOLLARS (US $[**]), such payment to be made within
thirty (30) days of the execution of this Agreement.

                             ARTICLE 8. TERMINATION

         8.1 -- If for any reason INVESTIGATOR becomes unavailable to direct the
performance of the work under this Agreement, MAYO shall notify SPONSOR. If the
parties are unable to identify a mutually acceptable successor, this Agreement
may be terminated by either party upon ten (10) days written notice.

         8.2 -- Either party may terminate this Agreement in the event of a
breach of a material obligation of the other if such breach remains uncured
after thirty (30) days notice.

<PAGE>

Sponsored Research Agreement and Option                             page 9 of 19
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         8.3 -- This Agreement may be terminated by either party giving to the
other a minimum of sixty (60) days prior written notice provided, however, that
MAYO shall not terminate the Agreement until the Project is completed. MAYO and
INVESTIGATOR will take all reasonable efforts to minimize further costs upon
issuing or receiving such notice.

         8.4 -- In the event of any notice of termination of this Agreement by
SPONSOR, MAYO shall immediately terminate work and use its best efforts to
reduce costs to SPONSOR, and, if MAYO is not in default by having breached a
material obligation of the Agreement, SPONSOR shall pay MAYO upon receipt of
MAYO's invoice, all of its reasonable costs incurred under the Project including
applicable indirect costs and agreed-upon noncancellable obligations made before
receipt of notice of termination, reduced by all prior payments made by SPONSOR,
which shall in no event exceed on a pro rata basis the agreed-upon price for
performance of the research as stated in Section 7.3 hereof.

         8.5 -- In the event of termination of the Project or the Agreement
itself, MAYO and INVESTIGATOR agree to provide SPONSOR with all reports,
materials or other deliverable items, in whatever state of completion, as of the
date of termination. The provisions of Articles 2,3,4,5,6,8 and 9 shall survive
termination or expiration of this Agreement.

                               ARTICLE 9. GENERAL

         9.1 -- This document sets forth the entire Agreement between the
parties hereto with respect to the subject matter hereof and will supersede all
prior and contemporaneous negotiations, agreements, representations,
understandings and commitments with respect thereto. This Agreement shall not be
changed or modified in any manner except by an instrument signed by the duly
authorized officers of each of the parties hereto, and specifically referencing
this Agreement.

         9.2 -- This Agreement and any interest herein may not be assigned by
MAYO or SPONSOR without the prior written consent of the other, which shall not
be unreasonably withheld or delayed; provided, however, that SPONSOR may assign
this Agreement to an affiliated company or to any entity with which SPONSOR may
merge or consolidate or to which SPONSOR may assign substantially all of its
assets or that portion of its business to which this Agreement pertains (as long
as the reputation of such entity would not negatively impact MAYO's reputation
as a health care institution), without obtaining the agreement of MAYO.

         9.3 -- The captions and headings used in this Agreement are for
convenience and reference only and are not a part of this Agreement.

         9.4 -- All notices shall be in writing and shall be effective upon
receipt. Notices should be sent to the respective administrative contacts set
forth in Section 1.1 of this Agreement.

         9.5 -- Either party's failure to require the other party to comply with
any provision of this Agreement shall not be deemed a waiver of such provision
or any other provision of this Agreement.

<PAGE>

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         9.6 -- If any clause, section or paragraph of this Agreement is
determined by a court of competent jurisdiction to be illegal, invalid or
unenforceable, it will be deemed severed from the remainder of this Agreement
and will have no effect on the legality, validity or enforceability of the
remaining provisions of this Agreement provided that a party's rights under this
Agreement are not materially affected. The parties hereto covenant and agree to
renegotiate any such provision in good faith in order to provide a reasonably
acceptable alternative to such provision, it being the intent of the parties
that the basic purposes of this Agreement are to be effectuated.

MAYO FOUNDATION FOR MEDICAL                     MAYO CLINIC JACKSONVILLE
EDUCATION AND RESEARCH

/s/ Rick F. Colvin                              /s/ Jeff Schultz
--------------------------------                --------------------------------
RICK F. COLVIN                                  NAME:
ASSISTANT TREASURER                             TITLE:

9/29/03                                         10/2/03
--------------------------------                --------------------------------
DATE                                            DATE

         READ AND UNDERSTOOD:

/s/ DEMETRIUS M. MARAGANORE                     /s/ MATTHEW J. FARRER
--------------------------------                --------------------------------
DEMETRIUS M. MARAGANORE, M.D.                   MATTHEW J. FARRER, PH.D.

ALNYLAM PHARMACEUTICALS, INC.
/s/ John G. Conley
--------------------------------
NAME:  John G. Conley
TITLE: CFO

10/6/03
--------------------------------
DATE

<PAGE>

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                                 Execution Copy

                                    EXHIBIT A

                                  RESEARCH PLAN

                  ALPHA-SYNUCLEIN AS A TARGET FOR SIRNA THERAPY

Technical aspects of starting plan:

         [**]:

         (1)      [**] to initially be performed [**] from Matt Farrer lab with
                  [**]. Dr. Basir will provide protocol from Alnylam.

         (2)      [**] will be performed [**], in conditions identical to those
                  provided by the company.

         (3)      Alnylam estimates that [**] will be sufficient [**], this may
                  be as many as [**]. [**] at an initial [**] will be [**].

         (4)      Expected results [**] will be [**]y.

         (5)      [**] will be [**].

         [**]:

         (1)      [**] will then be [**] and/or [**].

         (2)      [**] will be initially [**] which Alnylam will provide. This
                  will help us [**].[**] may be used [**], as needed. Based on
                  the [**], it may not be necessary [**].

         (3)      [**] will be performed [**].

TIMELINE:

[**]:                      [**]
Months [**]:               [**]
Months [**]:               [**]
Months [**]                [**]
<PAGE>

Sponsored Research Agreement and Option                            page 12 of 19
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                           control mice

Months [**]:               [**]

<PAGE>

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                              BUDGET JUSTIFICATION

                     REFER TO EXHIBIT C FOR DETAILED BUDGET

SALARIES AND FRINGE BENEFITS ($[**]):

Technician=$[**]

Post-doctoral fellow=$[**]

MOUSE COSTS ($[**]):

Importation and Quarantine of mice: $[**]

Breeders at 0M and 6M: $[**]

Breeding cages: $[**] (based on [**] breeding cages maintained for app. [**] at
$[**]/day)

         --       This should allow [**] at any one time for both [**] purposes

Weaning and Aging: approximately $[**]

MANY ANIMALS WILL [**] AND FOR SHORT TERM STUDIES. MUCH OF THIS COST COVERS
[**].[**]MOLECULAR BIOLOGY AND BIOCHEMISTRY ($[**])

Genotyping supplies ($[**]):

         Tail prep: $[**]

         PCR supplies (Taq, plates, sealers, primers, film, etc.): $[**]Avid
         Chips: $[**]

Expression supplies:

         RNA (RT-PCR, primers, Taqman, etc.): $[**]

         Westerns (gels, antibodies, film, ECL, etc.): $[**]

IMMUNOHISTOCHEMISTRY/TISSUE STAINING ($[**])

Antibodies, slides, sectioning, etc.

CELL CULTURE AND INFUSION SUPPLIES ($[**])

Cell Culture ($[**]) could vary depending [**]. This should allow adequate
supplies for [**] of cell/neuronal/embryo culture.

Infusion pumps/Hamiltons/drill bits, etc. ($[**])

Infusion pumps run $[**]/mouse and will have to be replaced in trials longer
than app. 2 weeks

1.       DIRECT COSTS:                   $[**]

INDIRECT COSTS:                          $[**] (INDIRECTS ONLY ON NON-PERSONNEL)
TOTAL COSTS:                             $[**]

<PAGE>

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                                    EXHIBIT B

I.       IAn exclusive, worldwide, sub licensable license under desired
Background IP, Joint Discoveries set forth in Section 3.4(b) above and Other
Discoveries to make, have made, use, have used, market, sell, import and offer
products or methods in all fields until the expiration of all patents covering
such Background IP, Joint Discoveries and Other Discoveries ("Licensed
Patents"). In return for such license, SPONSOR will make the following payments
to MAYO:

II.      For the indications stated below, the following clinical milestones
will be paid for product covered by an issued, unexpired claim of Licensed
Patents ("Licensed Product").

<TABLE>
<CAPTION>
MILESTONE                 PD [**]     PD [**]     EACH ADDITIONAL [**]
----------------------------------------------------------------------
<S>                       <C>         <C>         <C>
   Filing of first IND     $[**]        [**]             $[**]
----------------------------------------------------------------------
   Phase II initiation     $[**]       $[**]             $[**]
----------------------------------------------------------------------
   NDA Filing, or
   equivalent, in the US
   or EU                   $[**]       $[**]             $[**]
----------------------------------------------------------------------
   Market approval in
   the US or EU            $[**]       $[**]             $[**]
----------------------------------------------------------------------
</TABLE>

In addition, upon first issuance of a valid claim of the Licensed Patents that
covers an Alnylam Licensed Product -- $[**]

III.     For a Licensed Product that is marketed by SPONSOR or its Sub
licensees, a royalty of:

         [**]% of Net Sales < or = $[**]

         [**]% of Net Sales > $[**]

Such royalty payments shall be reduced up to [**]% by amounts paid to access
additional intellectual property believed to be necessary in order to sell
Licensed Products.

IV.      An annual license maintenance fee of $[**] per year (creditable to
milestones and royalties).

V.       SPONSOR will be responsible for and will incur the cost for future
patent filings and prosecution. SPONSOR will inform MAYO of all substantive
activities. In the event that SPONSOR exercises its Option for an exclusive
license, SPONSOR shall reimburse MAYO for the past costs of filing and
prosecution for Licensed Patents.

VI.      Both parties can terminate for material breach upon written notice and
a 90 day cure period. Alnylam can terminate upon 30 days notice.

<PAGE>

Sponsored Research Agreement and Option                            page 15 of 19
Farrer / Alnylam                                                       9/29/2003

                                 Execution Copy

                                    EXHIBIT C
                                     BUDGET

                     BUDGET IS ON THE FOLLOWING THREE PAGES.

<PAGE>

Sponsored Research Agreement and Option                            page 16 of 19
Farrer / Alnylam                                                       9/29/2003

                                 Execution Copy

Principal Investigator:   FARRER, M .J. PhD
Funding Source:           Alnylam Pharmaceuticals
External Grant Id:
Title:                    a-Synuclein as a Target for siRNA Therapy

<TABLE>
<CAPTION>
                                                             09/01/2003
                                            %          Base  08/31/2004    Total
                                         Effort       Salary   Amount     Amount
<S>                                   <C>             <C>    <C>          <C>
PERSONNEL

FARRER, M.J. PHD
Principal Investigator
LEWIS, J. PHD
Principal Investigator
TO BE NAMED
Technician                                 100%
TO BE NAMED
Postdoctoral Fellow                        100%
                                                               ------     ------
Total PERSONNEL                                                $ [**]     $ [**]
Benefits                                                       $ [**]     $ [**]
                                                               ------     ------
Total PERSONNEL (including benefits)                           $ [**]     $ [**]
                                                               ------     ------
SUPPLIES

[**]                                                             [**]       [**]
[**]                                                             [**]       [**]
[**]                                                             [**]       [**]
                                                               ------     ------
Total SUPPLIES                                                 $ [**]     $ [**]

OTHER EXPENSES

[**]                                                             [**]       [**]
[**]                                                             [**]       [**]
                                                               ------     ------
Total OTHER EXPENSES                                           $ [**]     $ [**]

TOTAL DIRECT COST                                              $ [**]     $ [**]

INDIRECT COST                         [**]% of MTDC            $ [**]     $ [**]
                                                               ------     ------
TOTAL COST                                                     $ [**]     $ [**]
                                                               ======     ======
</TABLE>

<TABLE>
<S>                                   <C>
Budget Id:                            19306

Grant Id:                             0
Administrator Name:                   SCHEFFEL, J.G.
Finance Specialist:                   TETZLAFF, L.M.
Grant Specialist:
Printed On:                           08/20/2003
Last Modified:                        08/20/2003
</TABLE>

<PAGE>

Sponsored Research Agreement and Option                            page 17 of 19
Farrer / Alnylam                                                       9/29/2003

                                 Execution Copy

FOOT NOTE:

<PAGE>

Sponsored Research Agreement and Option                            page 18 of 19
Farrer / Alnylam                                                       9/29/2003

                                 Execution Copy

Principal Investigator:   FARRER, M .J. PhD
Funding Source:           Alnylam Pharmaceuticals
External Grant Id:
Title:                    a-Synuclein as a Target for siRNA Therapy

<TABLE>
<CAPTION>
                                         09/01/2003
                                         08/31/2004                Total
                                            Amount                Amount
<S>                                 <C>                           <C>
PERSONNEL EFFORT BY PERIOD

FARRER, M.J. PhD                    Principal Investigator

     Salary

     EOE                                      0.00

     FB Rate

     FB

LEWIS, J. PhD                       Principal Investigator

     Salary

     EOE                                      0.00

     FB Rate

     FB

TO BE NAMED                               Technician

     Salary

     EOE                                    100.00

     FB Rate

     FB

TO BE NAMED                          Postdoctoral Fellow

     Salary

     EOE                                    100.00

     FB Rate

     FB
------------------------------------------------------------------------
Total FB                                       [**]
</TABLE>

<PAGE>

Sponsored Research Agreement and Option                            page 19 of 19
Farrer / Alnylam                                                       9/29/2003

                                 Execution Copy

Principal Investigator:   FARRER, M .J. PhD
Funding Source:           Alnylam Pharmaceuticals
External Grant Id:
Title:                    a-Synuclein as a Target for siRNA Therapy

<TABLE>
<CAPTION>
                                         09/01/2003
                                         08/31/2004                Total
                                            Amount                Amount
<S>                                      <C>                      <C>
Rate

Frequency

Patients #

Cost

------------------------------------------------------------------------
Total Cost
</TABLE>