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                                                                   EXHIBIT 10.21

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

                                    AGREEMENT

This agreement ("Agreement") is effective as of the 17th day of September, 2003
("Effective Date") between THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR
UNIVERSITY ("Stanford"), an institution of higher education having corporate
powers under the laws of the State of California, and Alnylam Pharmaceuticals,
Inc. ("Alnylam" or "Licensee"), a corporation having a principal place of
business at 790 Memorial Drive, Suite 202, Cambridge, MA 02139. Stanford and
Alnylam agree as follows:

1        BACKGROUND

1.1      Stanford has an assignment of "Efficient RNA Transfection to the Livers
         of Living Mice" from the laboratory of Mark Kay ("Invention"), as
         described in Stanford Docket S00-012 and any Licensed Patent, as
         defined below, which may issue to the Invention.

1.2      Stanford wants to have the Invention perfected and marketed as soon as
         possible so that resulting products may be available for public use and
         benefit.

1.3      Alnylam wants a license under the Invention, and Licensed Patent to
         develop, manufacture, use, and sell Licensed Product in the field of
         use of Delivery of synthesized siRNA molecules for research and
         therapeutic use.

1.4      The Technology and Invention were made in the course of research
         supported by the National Institutes of Health (NIH).

2        DEFINITIONS

2.1      "Licensed Patents" means all patent applications filed on the Invention
         and all patents issuing thereon including

         (A)      Stanford's U.S. Patent Application, Serial Number [**]
                  entitled [**],[**],

         (B)      Stanford's U.S. Patent Application, Serial Number [**]
                  entitled [**],

         (C)      [**]the Continuation-in-Part, Serial Number [**] entitled
                  [**], and

         (D)      any divisions, continuations and any foreign patent
                  application or equivalent corresponding thereto, and any
                  Letters patent or equivalent thereof issuing thereon or
                  reissue, reexamination or extension thereof.

         (E)      Continuation-in-part applications (CIPs) that are offered to
                  the other co-exclusive licensee will also be offered to
                  Alnylam for licensing in the Licensed Field of Use.

2.2      "Licensed Product" means any product or part in the Licensed Field of
         Use, the manufacture, use, or sale of which:

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         (A)      is covered by a valid claim of an issued, unexpired Licensed
                  Patent directed to the Invention in the country in which it is
                  made, used or sold. A claim of an issued, unexpired Licensed
                  Patent is presumed to be valid unless it has been held to be
                  invalid or unenforceable by a final judgment of a court of
                  competent jurisdiction from which no appeal can be or is
                  taken; rendered unenforceable through disclaimer or otherwise;
                  donated to the public; or lost through an interference
                  proceeding; or

         (B)      is covered by any claim being prosecuted in a pending
                  application of Licensed Patents in the country in which it is
                  made, used or sold unless such claim has been pending in such
                  application or an earlier application of Licensed Patents for
                  greater than [**] years.

2.3      "Net Sales" means the gross commercialization revenue derived by
         Alnylam and any sublicensee from Licensed Product, less the following
         items but only as they actually pertain to the disposition of Licensed
         Product by Alnylam and any sublicensee, are included in gross revenue,
         and are separately billed:

         (A)      import, export, excise and sales taxes, and custom duties;

         (B)      costs of insurance, packing, and transportation from the place
                  of manufacture to the customer's premises or point of
                  installation;

         (C)      costs of installation at the place of use; and

         (D)      credit for returns, allowances, or trades; and

         (E)      customary trade, quantity or cash discounts actually allowed
                  or taken.

         (F)      Where Licensed Products are not sold separately, but are sold
                  in combination with or as parts of other therapeutic products,
                  hereinafter such combinations referred to as a "Combination
                  Product" and the Licensed Product and each such other product
                  being referred to as a "Component Product", the Net Sales
                  price to be used for the purpose of calculating royalties
                  payable in respect of Combination Products must be determined
                  by multiplying the Net Sales price of the Combination Product
                  by the percentage value of the Licensed Product comprising a
                  Component Product contained in the Combination Product, such
                  percentage value being determined by dividing the current
                  market value of the Licensed Product comprising a Component
                  Product by a sum of the separate current market values of each
                  of the Component Products which are contained in the
                  Combination Product. The current market value of each of the
                  Component Products must be for a quantity comparable to that
                  contained in the Combination Product and of the same class,
                  purity and potency. When no current market value is available
                  for a Component Product, a reasonable hypothetical market
                  value for such Component Product based upon the allocation of
                  the same proportions of costs, reasonable overhead and profits
                  (all of which must be determined on the basis of generally
                  accepted accounting principles) as are or should be allocated
                  to similar Component Products and having an ascertainable
                  market value.

2.4      "siRNA Molecule" means an agent that modulates expression of a target
         gene by an RNA interference mechanism.

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2.5      "Licensed Field of Use" means delivery of ex-vivo synthesized siRNA
         Molecules for research, development and therapeutic uses (including a
         diagnostic necessary for development, sale or reimbursement of a
         therapeutic Licensed Product). The Licensed Field of Use specifically
         excludes delivery of any system producing in vivo expressed siRNAs for
         therapeutic use, including but not limited to episomal and integrated
         vectors, and recombinant viruses.

2.6      "Licensed Territory" means worldwide.

2.7      "Co-Exclusive" means that, subject to Article 4, Stanford will only
         grant one further license in the Licensed Territory in the Licensed
         Field of Use.

2.8      "Affiliate" means any legal entity (such as a corporation, partnership,
         or limited liability company) that directly, or indirectly through one
         or more intermediaries, controls or is controlled by, or is under
         common control with Company and that is bound by the terms and
         conditions of this Agreement. For the purposes of this definition, the
         term "control" means (i) beneficial ownership of at least fifty percent
         (50%) of the voting securities of a corporation or other business
         organization with voting securities or (ii) a fifty percent (50%) or
         greater interest in the net assets or profits of a partnership or other
         business organization without voting securities. For purposes of this
         Agreement, the term Alnylam shall include its Affiliates, unless the
         context indicates otherwise.

3        GRANT

3.1      GRANT. Stanford grants and Alnylam accepts a license in the Licensed
         Field of Use to make, have made, use, have used, sell, have sold,
         import and have imported Licensed Product in the Licensed Territory.

3.2      CO-EXCLUSIVITY. The license is Co-Exclusive, including the right to
         sublicense pursuant to Article 13, in the Licensed Field of Use for a
         term beginning on the Effective Date, and ending, on a
         country-by-country basis, on the expiration of the last to expire of
         Licensed Patents.

3.3      RETAINED RIGHTS. Stanford may practice the Invention and use the
         Technology for its own bona fide research, including sponsored research
         and collaborations. Stanford has the right to publish any information
         included in Technology and Licensed Patent.

3.4      EXCLUSIVITY.

         (A)      If the other Co-Licensee discontinues licensing this Field of
                  Use, then the Field of Use will become exclusive for Alnylam.

         (B)      If the other Co-Licensee discontinues any other therapeutic
                  license under the Licensed Patents, Stanford shall so inform
                  Alnylam and Alnylam shall have the option to obtain an
                  exclusive, worldwide sublicensable license to such therapeutic
                  field. The terms of any such license shall be negotiated in
                  good faith by Stanford and Alnylam. This option may be
                  exercised by Alnylam by written notice to Stanford at any time
                  during a period of ninety (90) days after notification by
                  Stanford.

4        GOVERNMENT RIGHTS

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This Agreement is subject to all of the terms and conditions of Title 35 United
States Code Sections 200 through 204, including an obligation that Licensed
Product sold or produced in the United States be "manufactured substantially in
the United States." Alnylam will take all reasonable action necessary on its
part as licensee to enable Stanford to satisfy its obligations to the U.S.
Government under Title 35. If Alnylam reasonably desires an exception to the
government requirement of substantial manufacture in the United States then
Stanford shall reasonably cooperate with Alnylam in obtaining such exception.

5        DILIGENCE

5.1      MILESTONES. As an inducement to Stanford to enter into this Agreement,
         Alnylam will use all commercially reasonable efforts and diligence to
         develop, manufacture, and sell or lease Licensed Product and to
         diligently develop markets for the Licensed Product. In particular,
         Alnylam will meet the milestones shown in Appendix A, which shall
         satisfy Alnylam's diligence obligations. If Alnylam in good faith fails
         to meet a milestone set forth in Appendix A, then Alnylam shall have a
         [**] period of time to reestablish diligence towards its objectives,
         and if Alnylam reestablishes diligence towards its objectives during
         this [**] period, any prior lack of diligence will be deemed cured. If
         Alnylam does not reestablish diligence towards its objectives during
         this [**] period, Stanford may terminate this Agreement if Alnylam has
         not met the milestones. Stanford may terminate this Agreement if
         Alnylam or a sublicensee has not sold Licensed Product for any [**]
         period after Alnylam's or a sublicensee's first commercial sale of
         Licensed Product. Efforts by Alnylam's sublicensees or Affiliates shall
         be considered efforts of Alnylam under this section.

5.2      PROGRESS REPORT. Alnylam acknowledges that diligent development of
         Licensed Product is of utmost importance to Stanford. On or before
         September 30 of each year until Alnylam markets a Licensed Product,
         Alnylam will make a written annual report in confidence to Stanford
         covering the preceding year ending June 30, regarding the progress of
         Alnylam toward commercialization of Licensed Product. The report will
         include, as a minimum, information (e.g., summary of work completed,
         key scientific discoveries, summary of work in progress, current
         schedule of anticipated events or milestones and market plans for
         introduction of Licensed Product) sufficient to enable Stanford to
         satisfy reporting requirements of the U.S. Government and for Stanford
         to ascertain progress by Alnylam toward meeting the diligence
         requirements of this Article 5.

6        ROYALTIES

6.1      ISSUE ROYALTY. Alnylam will pay to Stanford a noncreditable,
         nonrefundable license issue royalty of $[**] on signing this Agreement.

6.2      MINIMUM ROYALTY. Beginning one year from the Effective Date, and each
         anniversary thereafter, Alnylam will pay to Stanford a yearly royalty
         of $[**]. Yearly royalty payments are nonrefundable, but they are
         creditable against earned royalties to the extent provided in Section
         6.4.

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6.3      EARNED ROYALTY. In addition, Alnylam will pay Stanford earned royalties
         on Net Sales as follows:

         (A)      [**]% of Net Sales for a Licensed Product subject to the
                  following;

         (B)      Such royalty payments shall be reduced up to [**]% (from [**]%
                  of Net Sales down to [**]% of Net Sales) by the amount of
                  royalty paid to access additional intellectual property
                  necessary in order to sell Licensed Products ("Additional
                  Earned Royalties").

         (C)      Such royalty payments shall be reduced as follows:

                  (1)      [**]% if Additional Earned Royalties are [**]% or
                           less.

                  (2)      [**]% if Additional Earned Royalties are greater than
                           [**]% but less than [**]%.

                  (3)      [**]% if Additional Earned Royalties are equal to or
                           greater than [**]% but less than [**]%.

                  (4)      [**]% if Additional Earned Royalties are equal to or
                           greater than [**]% but less than [**]%.

                  (5)      [**]% if Additional Earned Royalties are equal to or
                           higher than [**]%.

         (D)      Only one royalty is due on each Licensed Product sold by
                  Alnylam or its sublicensees regardless of whether its
                  manufacture, use, importation or sale are or shall be covered
                  by more than one patent or patent application included in
                  Licensed Patents under this Agreement, and no further
                  royalties will be due for use of such Licensed Product by
                  Alnylam or its sublicensee's customers.

6.4      CREDITABLE PAYMENTS. Creditable payments under this Agreement will be
         an offset to Alnylam against each earned royalty payment which Alnylam
         would be required to pay under Section 6.3 until the entire credit is
         exhausted.

6.5      MILESTONE PAYMENTS.

         (A)      For the first Licensed Product, Alnylam will make the
                  following payments for the filing of an IND, initiation of
                  Phase II trial, initiation of Phase III trial, and approval of
                  New Drug Application or equivalent in the U.S. ("Milestone
                  Payments"):

                  (1)      $[**] for filing of the first IND.

                  (2)      $[**] for initiation of the first Phase II trial.

                  (3)      $[**] for initiation of the first Phase III trial.

                  (4)      $[**] for approval of the first New Drug Application
                           or equivalent regulatory approval in the U.S.

         (B)      For the second Licensed Product, Alnylam will make the
                  following Milestone Payments:

                  (1)      $[**] for filing of the first IND.

                  (2)      $[**] for initiation of the first Phase II trial.

                  (3)      $[**] for initiation of the first Phase III trial.

                  (4)      $[**] for approval of the first New Drug Application
                           or equivalent regulatory approval in the U.S.

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         (C)      For the third and every subsequent Licensed Product, Alnylam
                  will make the following Milestone Payments:

                  (1)      $[**] for filing of the first IND.

                  (2)      $[**] for initiation of the first Phase II trial.

                  (3)      $[**] for initiation of the first Phase III trial.

                  (4)      $[**] for approval of the first New Drug Application
                           or equivalent regulatory approval in the U.S.

         (D)      Notwithstanding the above, at the time that Stanford receives
                  a Milestone Payment from Alnylam on behalf of a sublicensee
                  under Section 13.6, the corresponding Milestone Payment under
                  this Section 6.5 will not be due.

6.6      OBLIGATION TO PAY ROYALTIES. If this Agreement is not terminated in
         accordance with other provisions, Alnylam will be obligated to pay
         royalties on all Licensed Product that is either sold or produced under
         the license granted in Article 3, whether or not the Licensed Product
         is produced before the Effective Date of this Agreement or sold after
         the Licensed Patent has expired.

6.7      CURRENCY. The royalty on sales in currencies other than U.S. Dollars
         will be calculated using the appropriate foreign exchange rate for the
         currency quoted by the Bank of America (San Francisco) foreign exchange
         desk, on the close of business on the last banking day of each calendar
         quarter. Royalty payments to Stanford will be in U.S. Dollars. All
         non-U.S. taxes related to royalty payments will be paid by Alnylam and
         are not deductible from the payments due Stanford. Stanford shall
         assist Alnylam as reasonably requested by Alnylam and at Alnylam's
         expense, in recovering such taxes to the extent possible under
         applicable tax laws and treaties.

6.8      PATENT COSTS. Within thirty days after receiving a statement from
         Stanford during the Co-Exclusive period, Alnylam will reimburse
         Stanford:

         (A)      [**] of the Licensed Patent patenting expenses incurred by
                  Stanford before the Effective Date; and

         (B)      $[**] per year for Licensed Patent patenting expenses incurred
                  by Stanford after the Effective Date.

         (C)      If the Field of Use covered in this license becomes Exclusive
                  for Alnylam, Stanford and Alnylam will negotiate coverage of
                  patent expenses in good faith.

6.9      PATENT PROSECUTION.

         (A)      Stanford will be responsible for the filing, prosecution and
                  maintenance of the Licensed Patents. Alnylam shall be kept
                  informed of and shall receive copies of all documentation and
                  substantive actions pertaining to the filing, prosecution and
                  maintenance of Licensed Patents. Alnylam shall have reasonable
                  opportunities to participate in decision making and Stanford
                  will use diligent efforts to incorporate Alnylam's reasonable
                  suggestion.

         (B)      Throughout the term of this agreement, Alnylam will retain
                  rights to any claims that have support in the Licensed Patents
                  (defined in Section 2.1), whether or not they are in a CIP.

         (C)      If Stanford elects not to continue to seek or maintain patent
                  prosecution on any Licensed Patent in any country during the
                  co-exclusive term of the license despite

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                  Alnylam's willingness to pay its share of the prosecution
                  costs, Alnylam shall have the right, at its expense, to
                  procure, maintain and enforce in any country such Licensed
                  Patent.

6.10     MOST FAVORED LICENSEE Stanford warrants and represents that it has not
         granted a license in the Field of Use to another party and shall not do
         so in the future on terms that are more favorable than those hereby
         granted to Alnylam.

7        ROYALTY REPORTS, PAYMENTS, AND ACCOUNTING

7.1      QUARTERLY EARNED ROYALTY PAYMENT AND REPORT. Beginning with the first
         sale of a Licensed Product, Alnylam will make written reports (even if
         there are no sales) and earned royalty payments to Stanford within
         thirty days after the end of each calendar quarter. This report will be
         in the form of the report of Appendix B and will state the number,
         description, and aggregate Net Sales of Licensed Product during the
         completed calendar quarter, and resulting calculation pursuant to
         Section 6.3 of earned royalty payment due Stanford for the completed
         calendar quarter. With each report, Alnylam will include payment due
         Stanford of royalties for the completed calendar quarter.

7.2      TERMINATION REPORT. Alnylam will make a written report to Stanford
         within ninety days after the license expires under Section 3.2. Alnylam
         will continue to make reports after the license has expired, until all
         Licensed Product produced under the license have been sold or
         destroyed. Concurrent with the submittal of each post-termination
         report, Alnylam will pay Stanford all applicable royalties.

7.3      ACCOUNTING. Alnylam will keep and maintain records for a period of
         three years showing the manufacture, sale, use, and other disposition
         of products sold or otherwise disposed of under the license. Records
         will include general-ledger records showing cash receipts and expenses,
         and records that include production records, customers, serial numbers,
         and related information in sufficient detail to enable Alnylam to
         determine the royalties payable under this Agreement.

7.4      AUDIT BY STANFORD. Alnylam will permit an independent certified public
         accountant selected by Stanford and acceptable to Alnylam to examine
         Alnylam's books and records from time to time (but no more than one
         time a year) to the extent necessary to verify reports provided for in
         Sections 7.1 and 7.2. Stanford will pay for the cost of such audit,
         unless the results of the audit reveal an underreporting of royalties
         due Stanford of five percent or more, in which case, Alnylam will pay
         the audit costs.

8        NEGATION OF WARRANTIES

8.1      To the best of Stanford's OTL knowledge, Stanford is the sole owner of
         Licensed Patent and has the right to enter into this Agreement and to
         grant the rights and licenses set forth herein.

8.2      NEGATION OF WARRANTIES. Nothing in this Agreement is construed as:

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         (A)      Stanford's warranty or representation as to the validity or
                  scope of any Licensed Patent;

         (B)      A warranty or representation that anything made, used, sold,
                  or otherwise disposed of under any license granted in this
                  Agreement is or will be free from infringement of patents,
                  copyrights, and other rights of third parties;

         (C)      An obligation to bring suit against third parties for
                  infringement, except as described in Article 12;

         (D)      Granting by implication, estoppel, or otherwise any licenses
                  or rights under patents or other rights of Stanford or other
                  persons other than Licensed Patent, regardless of whether the
                  patents or other rights are dominant or subordinate to any
                  Licensed Patent; or

         (E)      An obligation to furnish any technology or technological
                  information.

8.3      NO WARRANTIES. Except as expressly set forth in this Agreement,
         Stanford makes no representations and extends no warranties of any
         kind, either express or implied. There are no express or implied
         warranties of merchantability or fitness for a particular purpose, or
         that Licensed Product will not infringe any patent, copyright,
         trademark, or other rights, or any other express or implied warranties.

8.4      SPECIFIC EXCLUSION. Nothing in this Agreement grants Alnylam any
         express or implied license or right under or to U.S. Patent 4,656,134
         entitled "Amplification of Eucaryotic Genes" or any patent application
         corresponding thereto.

9        INDEMNITY

9.1      INDEMNIFICATION. Alnylam will indemnify, hold harmless, and defend
         Stanford and Stanford Hospitals and Clinics, and their respective
         trustees, officers, employees, students, and agents against all claims
         for death, illness, personal injury, property damage, and improper
         business practices arising out of the manufacture, use, sale, or other
         disposition of Invention, Licensed Patent, Licensed Product, by Alnylam
         or any sublicensee, or their customers except to the extent such claims
         are due to the gross negligence or willful misconduct of Stanford.
         Stanford agreed to promptly notify Alnylam in writing of any such claim
         and Alnylam shall manage and control, at its own expense, the defense
         of such claim and its settlement. Alnylam agrees not to settle any such
         claim against Stanford without Stanford's written consent where such
         settlement would include any admission of liability on the part of
         Stanford, where the settlement would impose any restriction on the
         conduct by Stanford of any of its activities, or where the settlement
         would not include an unconditional release of Stanford from all
         liability for claims that are the subject matter of such claim.

9.2      NO LIABILITY. Subject to Section 9.1, neither party will be liable to
         each other for any loss profit, expectation, punitive or other
         indirect, special, consequential, or other damages whatsoever, in
         connection with any claim arising out of or related to this Agreement
         whether grounded in tort (including negligence), strict liability,
         contract, or otherwise.

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9.3      WORKERS' COMPENSATION. Alnylam will at all times comply, through
         insurance or self-insurance, with all statutory workers' compensation
         and employers' liability requirements covering all employees with
         respect to activities performed under this Agreement.

9.4      INSURANCE. Alnylam will maintain, during the term of this Agreement,
         Comprehensive General Liability Insurance, including Product Liability
         Insurance prior to commercialization, with a reputable and financially
         secure insurance carrier to cover the activities of Alnylam and its
         sublicensees. Upon initiation of human clinical trials of Licensed
         Product, such insurance will provide minimum limits of liability of
         Five Million Dollars and will include Stanford and Stanford Hospitals
         and Clinics, and their respective trustees, directors, officers,
         employees, students, and agents as additional insureds. Insurance will
         be written to cover claims incurred, discovered, manifested, or made
         during or after the expiration of this Agreement and must be placed
         with carriers with ratings of at least A- as rated by A.M. Best.
         Alnylam will furnish a Certificate of Insurance evidencing primary
         coverage and additional insured requirements and requiring thirty (30)
         days prior written notice of cancellation or material change to
         Stanford. Alnylam will advise Stanford, in writing, that it maintains
         excess liability coverage (following form) over primary insurance for
         at least the minimum limits set forth above. All insurance of Alnylam
         will be primary coverage; insurance of Stanford and Stanford Hospitals
         and Clinics will be excess and noncontributory.

10       MARKING

Before the issuance of Licensed Patents, Alnylam will mark Licensed Product (or
their containers or labels) made, sold, or otherwise disposed of by it under the
license granted in this Agreement with the words "Patent Pending," and following
the issuance of one or more patents, with the numbers of the Licensed Patent.

11       STANFORD NAMES AND MARKS

Alnylam will not identify Stanford in any promotional advertising or other
promotional materials to be disseminated to the public or to use the name of any
Stanford faculty member, employee, or student, or any trademark, service mark,
trade name, or symbol of Stanford or Stanford Hospitals and Clinics, or any that
is associated with any of them, without Stanford's prior written consent, except
as may be required by law. Any use of Stanford's name will be limited to
statements of fact, e.g., that Stanford has co-exclusively licensed Licensed
Patents to Alnylam, and will not imply endorsement of Alnylam's products or
services.

12       INFRINGEMENT BY OTHERS: PROTECTION OF PATENTS

12.1     INFRINGEMENT ACTION.

         (A)      The parties will promptly inform each other of any suspected
                  infringement of any Licensed Patent by a third party.

         (B)      Stanford, Licensee and the other Co-Exclusive licensee will
                  meet to discuss the matter during the Co-Exclusive period of
                  this Agreement.

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         (C)      If the Field-of-Use becomes Exclusive for Licensee, Stanford
                  and Licensee will meet to discuss the matter during the
                  Exclusive period of this Agreement.

         (D)      If Stanford does not choose to institute suit against said
                  third party within sixty days of notification, then the suit
                  may be brought in both Licensee's and the other Co-Exclusive
                  licensee's names, and Stanford's name if necessary and the
                  out-of-pocket costs thereof shall be borne equally by Licensee
                  and the other Co-Exclusive licensee and any recovery or
                  settlement shall be shared equally between Licensee and the
                  other Co-Exclusive licensee. In such situation, Licensee and
                  the other Co-Exclusive licensee shall agree to the manner in
                  which they exercise control over such action and if either
                  party desires to also be represented by separate counsel of
                  its own selection, the fees for such counsel shall be paid by
                  such party.

         (E)      If both, Stanford and the other Co-Exclusive licensee, or
                  Stanford if there is no other Co-Exclusive Licensee, choose
                  not to institute suit against said third party within sixty
                  days of notification, then Licensee shall have the right to
                  institute suit in its own name or if necessary, in Stanford's
                  name, to enjoin such infringement. Licensee shall bear the
                  entire cost of such litigation and shall be entitled to retain
                  the entire amount of any recovery or settlement. However, any
                  recovery in excess of litigation/settlement costs will be
                  considered Net Sales and Licensee will pay Stanford royalties
                  as indicated in Article 6 hereof. Stanford shall provide
                  reasonable assistance to Licensee in the prosecution of any
                  such suit brought by Licensee, at Licensee's expense.

13       SUBLICENSING

13.1     PERMITTED SUBLICENSING FOR LICENSED CO-EXCLUSIVE FIELD OF USE. Alnylam
         may grant sublicenses in the Co-exclusive Licensed Field of Use during
         the Co-Exclusive period:

         (A)      only in conjunction with intellectual property under Alnylam's
                  control; and

         (B)      only if Alnylam is developing or selling Licensed Products in
                  the Co-Exclusive Licensed Field of Use.

13.2     REQUIRED SUBLICENSING FOR LICENSED CO-EXCLUSIVE FIELD OF USE.

         (A)      If Alnylam or its sublicensee(s) is unable or unwilling to
                  serve or develop a potential market or market territory for
                  which there is a willing sublicensee, Alnylam will, at
                  Stanford's request, negotiate in good faith a sublicense under
                  the Licensed Patents, provided that the same request has been
                  made of the other Co-Exclusive licensee.

         (B)      Bona fide business concerns of Alnylam will be considered in
                  any good faith negotiations for a sublicense under this
                  Agreement and Alnylam shall not be required to
                  license/sublicense any other intellectual property to such
                  sublicensee.

         (C)      If the other Co-Exclusive licensee itself or through its
                  sublicensees is already developing a product in the market or
                  market territory for which there is a willing sublicensee,
                  Alnylam will not be required to sublicense to such party.

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         (D)      In case that any other issue arises in the context of Required
                  Sublicensing, Stanford will discuss and try to resolve such
                  issue with Alnylam in good faith.

13.3     SUBLICENSE REQUIREMENTS. Any sublicense granted by Alnylam under this
         Agreement will be subject and subordinate to terms and conditions of
         this Agreement, except:

         (A)      Sublicense terms and conditions will reflect that any
                  sublicensee will not further sublicense, with the exception
                  that sublicensee may further sublicense rights under Licensed
                  Patents only as needed or implied in the course of
                  distribution or performance of service as required for the
                  sale to an end user of Licensed Products; and

         (B)      The earned royalty rate specified in the sublicense may be at
                  different rates than the rates in this Agreement.

13.4     SUBLICENSES REVERT TO STANFORD. Any sublicense will expressly include
         the provisions of Articles 7, 8, and 9 for the benefit of Stanford. If
         a sublicensee desires that its sublicense survive the termination of
         this agreement, Stanford agrees that the sublicense will revert to
         Stanford subject to the transfer of all obligations, including the
         payment of royalties specified in the sublicense, to Stanford or its
         designee, if this Agreement is terminated.

13.5     COPY OF SUBLICENSES. Alnylam will provide Stanford in confidence a copy
         of all relevant portions of any sublicenses granted pursuant to this
         Article 13.

13.6     SHARING OF SUBLICENSING INCOME. In addition to the earned royalties
         defined in Article 6, Alnylam will pay Stanford [**] percent ([**]%) of
         the amount received by Alnylam, that is specifically attributable to
         the Licensed Patents, from a sublicensee in

         (A)      up-front license fees, and

         (B)      clinical Milestone Payments as defined in Article 6.5.

13.7     ROYALTY-FREE SUBLICENSES. Alnylam may grant royalty-free or noncash
         sublicenses or cross-licenses if Alnylam pays all royalties due
         Stanford from sublicensee's Net Sales.

14       TERMINATION

14.1     TERMINATION BY ALNYLAM - Alnylam may terminate this Agreement by giving
         Stanford notice in writing at least thirty days in advance of the
         effective date of termination selected by Alnylam.

14.2     TERMINATION BY STANFORD - Stanford may terminate this Agreement if:

         (A)      Alnylam is:

                  (1)      delinquent on any royalty payment or report;

                  (2)      not diligently developing and commercializing
                           Licensed Product in accordance with Article 5 hereof;

                  (3)      in breach of any material provision; or

                  (4)      provides any false report; and

         (B)      Alnylam fails to remedy the breach within sixty days after
                  written notice by Stanford.

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14.3     SURVIVING PROVISIONS - Surviving any termination or expiration are:

         (A)      Alnylam's obligation to pay royalties accrued or accruable
                  based on Licensed Product made, used or sold during the term
                  of this Agreement;

         (B)      Any cause of action or claim of Alnylam or Stanford, accrued
                  or to accrue, because of any breach or default by the other
                  party; and

         (C)      The provisions of Articles 6, 7, 8, and 9, 18.8and any other
                  provisions that by their nature are intended to survive.

15       ASSIGNMENT

15.1     ASSIGNMENT BY ALNYLAM - Alnylam may assign this Agreement to an
         Affiliate or, subject to Section 15.2 as part of:

         (A)      A sale or other transfer of Alnylam's entire business; or

         (B)      Sale or other transfer of that part of Alnylam's business to
                  which the license granted hereby relates.

15.2     CONDITIONS OF ASSIGNMENT - Prior to any assignment,

         (A)      Alnylam must give Stanford written notice of the assignment,
                  including the new assignee's contact information and;

         (B)      The new assignee must agree in writing to Stanford to be bound
                  by this Agreement.

         (C)      If the new assignee is a pharmaceutical or biotechnology
                  company having aggregate annual sales revenues of at least 3
                  times higher than the aggregate annual sales revenues of
                  Alnylam, Stanford must have received a $40,000 assignment fee.

15.3     AFTER THE ASSIGNMENT - Upon assignment of this Agreement, Alnylam will
         be released of liability under this Agreement and the term "Alnylam" as
         used in this Agreement will mean the new assignee.

16       ARBITRATION

16.1     DISPUTE RESOLUTION BY ARBITRATION. Any controversy arising under or
         related to this Agreement, and any disputed claim by either party
         against the other under this Agreement excluding any dispute relating
         to patent validity or infringement arising under this Agreement, will
         be settled by arbitration in accordance with the Licensing Agreement
         Arbitration Rules of the American Arbitration Association.

16.2     REQUEST FOR ARBITRATION. Either party may request arbitration. Stanford
         and Alnylam will mutually agree in writing on a third party arbitrator
         within thirty days of the arbitration request. The arbitrator's
         decision will be final and nonappealable and may be entered in any
         court having jurisdiction.

                                                                  Page: 12 of 16
<PAGE>

16.3     DISCOVERY. The parties will be entitled to discovery as if the
         arbitration were a civil suit in the California Superior Court. The
         arbitrator may limit the scope, time, and issues involved in discovery.

16.4     PLACE OF ARBITRATION. The parties will mutually agree in writing to a
         place where arbitration will be held.

17       NOTICES

All notices under this Agreement will be sent by first class mail, registered or
certified with return receipt requested, by reputable overnight courier or
delivered personally and shall be deemed to have been fully given upon receipt:

All general notices to Alnylam will be sent to:

                                    John Maraganore, Ph.D.
                                    President and Chief Executive Officer
                                    Alnylam Pharmaceuticals, Inc.
                                    790 Memorial Drive, Suite 202
                                    Cambridge, MA 02139

All financial invoices to Alnylam (i.e., accounting contact) will be sent in
writing to:

                                    Mary Trueblood
                                    Controller
                                    Alnylam Pharmaceuticals, Inc.
                                    790 Memorial Drive, Suite 202
                                    Cambridge, MA 02139

                                                                  Page: 13 of 16
<PAGE>

All progress report invoices to Alnylam (i.e., technical contact) will be sent
in writing to:

                                    Nagesh Mahanthappa, Ph.D., M.BA.
                                    Director, Corporate Development
                                    Alnylam Pharmaceuticals, Inc.
                                    790 Memorial Drive, Suite 202
                                    Cambridge, MA 02139

All general notices to Stanford will be e-mailed or mailed to:

                                    Office of Technology Licensing
                                    900 Welch Road, Suite 350
                                    Palo Alto, CA 94304-1080
                                    info@otlmail.Stanford.edu

All payments to Stanford will be mailed to:

                                    Stanford University
                                    Office of Technology Licensing
                                    Department #44439
                                    P.O. Box 44000
                                    San Francisco, CA 94144-4439

All progress reports to Stanford will be e-mailed or mailed to:

                                    Office of Technology Licensing
                                    1705 El Camino Real
                                    Palo Alto, CA 94306-1106
                                    info@otlmail.Stanford.edu

Either party may change its address with written notice to the other party.

18       MISCELLANEOUS

18.1     WAIVER AND AMENDMENT. This Agreement may be amended, supplemented or
         otherwise modified only by means of a written instrument signed by both
         parties. None of the terms of this Agreement can be waived except by
         the written consent of the party waiving compliance.

18.2     CHOICE OF LAW. This Agreement will be governed by the laws of the State
         of California applicable to agreements negotiated, executed, and
         performed within California.

18.3     HEADINGS. The headings in this Agreement are for convenience of
         reference only and do not constitute a part of it. The headings do not
         affect its interpretation.

                                                                  Page: 14 of 16
<PAGE>

18.4     FORCE MAJEURE. Neither party will be responsible for delays resulting
         from causes beyond the reasonable control of such party, including
         without limitation fire, explosion, flood, war, strike, or riot,
         provided that the nonperforming party uses commercially reasonable
         efforts to avoid or remove such causes of nonperformance and continues
         performance under this Agreement with reasonable dispatch whenever such
         causes are removed.

18.5     BINDING EFFECT. This Agreement shall be binding upon and inure to the
         benefit of the parties and their respective permitted successors and
         assigns.

18.6     SEVERABILITY In the event that any provision of this Agreement shall be
         held invalid or unenforceable for any reason, such invalidity or
         unenforceability shall not affect any other provision of this
         Agreement, and the parties shall negotiate in good faith to modify the
         Agreement to preserve (to the extent possible) their original intent.

18.7     ENTIRE AGREEMENT This Agreement constitutes the entire agreement
         between the parties with respect to its subject matter and supercedes
         all prior agreements or understandings between the parties relating to
         its subject matter.

18.8     CONFIDENTIALITY. Stanford agrees that diligent efforts shall be used to
         maintain the confidentiality of reports or documents received from
         Alnylam or its Affiliate or sublicensees pursuant to this Agreement.

The parties execute this Agreement in duplicate originals by their duly
authorized officers or representatives.

                           THE BOARD OF TRUSTEES OF THE LELAND

                           STANFORD JUNIOR UNIVERSITY

                                              /s/ Katharine Ku
                                    Signature __________________________________

                                             Katharine Ku
                                    Name    ____________________________________

                                             Director, Technology Licensing
                                    Title   ____________________________________

                                             Sept. 17, 2003
                                    Date    ____________________________________

                           LICENSEE

                                    Signature /s/John Maraganore

                                              _________________________________

                                    Name John Maraganore

                                    Title President and CEO

                                             September 19, 2003
                                    Date    ____________________________________

                                                                  Page: 15 of 16
<PAGE>

                             APPENDIX A: MILESTONES

1.       By the end of the year [**], Alnylam will [**].

2.       By the end of the year [**], Alnylam will [**].

3.       By the end of the year [**], Alnylam will [**].

                                                                  Page: 16 of 16