-------------------------------------------------------------------------------- SEC 1745 Potential persons who are to respond to the collection of information (02-02) contained in this form are not required to respond unless the form displays a currently valid OMB control number. -------------------------------------------------------------------------------- OMB APPROVAL OMB Number: 3235-0145 Expires: December 31, 2005 Estimated average burden hours per response..11.0 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. ___________)* Alnylam Pharmaceuticals, Inc. ------------------------------------------------------------------------ (Name of Issuer) Common Stock, $0.0001 par value ------------------------------------------------------------------------ (Title of Class of Securities) 02043Q107 --------------------------------------------------------------- (CUSIP Number) December 30, 2004 ------------------------------------------------------------------------ (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant to which this Schedule is filed: [ ] Rule 13d-1(b) [x] Rule 13d-1(c) [ ] Rule 13d-1(d) Page 1 of 5 *The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page. The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes). CUSIP No. 02043Q107 --------------- ------------------------------------------------------------------------ 1. Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only). Merck & Co., Inc. ------------------------------------------------------------------------ 2. Check the Appropriate Box if a Member of a Group (See Instructions) (a) [ ] (b) [ ] ------------------------------------------------------------------------ 3. SEC Use Only ------------------------------------------------------------------------ 4. Citizenship or Place of Organization New Jersey ------------------------------------------------------------------------ 5. Sole Voting Power Number of 1,236,588 Shares --------------------------------------------------------- Beneficially 6. Shared Voting Power Owned by Each --------------------------------------------------------- Reporting 7. Sole Dispositive Power Person 1,236,588 --------------------------------------------------------- 8. Shared Dispositive Power ------------------------------------------------------------------------ 9. Aggregate Amount Beneficially Owned by Each Reporting Person 1,236,588 ------------------------------------------------------------------------ 10. Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] ------------------------------------------------------------------------ 11. Percent of Class Represented by Amount in Row (9) 5.9% ------------------------------------------------------------------------ 12. Type of Reporting Person (See Instructions) CO ------------------------------------------------------------------------ Item 1. (a) Name of Issuer Alnylam Pharmaceuticals, Inc. (b) Address of Issuer's Principal Executive Offices 300 Third Street, Cambridge, MA 02142 Item 2. (a) Name of Person Filing Merck & Co., Inc. (b) Address of Principal Business Office or, if none, Residence One Merck Drive, Whitehouse Station, NJ 08889 (c) Citizenship NJ (d) Title of Class of Securities Common Stock, par value $0.0001 (e) CUSIP Number 02043Q107 Item 3. Not applicable as this Schedule is filed pursuant to Rule 13d-1 (c). Item 4. Ownership. Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1. (a) Amount beneficially owned: 1,236,588 -------------------------. (b) Percent of class: 5.9% -------------------------. (c) Number of shares as to which the person has: (i) Sole power to vote or to direct the vote 1,236,588 ------------------ (ii) Shared power to vote or to direct the vote -------------------------. (iii) Sole power to dispose or to direct the disposition of 1,236,588 -----------------------------. (iv) Shared power to dispose or to direct the disposition of -------------------------. Item 5. Ownership of Five Percent or Less of a Class Not Applicable. Item 6. Ownership of More than Five Percent on Behalf of Another Person. Not Applicable. Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person Not Applicable. Item 8. Identification and Classification of Members of the Group Not Applicable. Item 9. Notice of Dissolution of Group Not Applicable. Item 10. Certification By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. April 15, 2005 ----------------------------------- Date /s/ Celia A. Colbert ----------------------------------- Signature Celia A. Colbert Vice President, Secretary and Assistant General Counsel ----------------------------------- Name/Title The original statement shall be signed by each person on whose behalf the statement is filed or his authorized representative. If the statement is signed on behalf of a person by his authorized representative other than an executive officer or general partner of the filing person, evidence of the representative's authority to sign on behalf of such person shall be filed with the statement; provided, however, that a power of attorney for this purpose which is already on file with the Commission may be incorporated by reference. The name and any title of each person who signs the statement shall be typed or printed beneath his signature. NOTE: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See Section 240.13d-7 for other parties for whom copies are to be sent. ATTENTION: INTENTIONAL MISSTATEMENTS OR OMISSIONS OF FACT CONSTITUTE FEDERAL CRIMINAL VIOLATIONS (SEE 18 U.S.C. 1001)