UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

~~WASHINGTON~~Washington, D.C. 20549

FORM 8-K

CURRENT REPORT PURSUANT TO SECTION 13 OR 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

~~Pursuant~~Date toof ~~Section 13~~Report ~~or 15~~(d)Date of ~~the Securities~~earliest ~~Exchange~~event ~~Act~~reported): ofDecember 22, ~~1934~~2006

Date of Report (Date of earliest event reported): June 14, 2006

Sirna Therapeutics, Inc.

(Exact ~~Name~~name of ~~Registrant~~registrant as ~~Specified~~specified in its ~~Charter~~charter)

Delaware (State or ~~Other~~other ~~Jurisdiction~~jurisdiction of ~~Incorporation or Organization~~incorporation) 0-27914 (Commission File ~~Number~~No.) 34-1697351 (I.R.S. Employer Identification ~~No.~~Number)

~~185~~1700 ~~Berry~~Owens Street, ~~Suite~~4th ~~6504~~ Floor San Francisco, California 94158 (Address of ~~Principal~~principal ~~Executive~~executive ~~Offices~~offices) ~~94107 (Zip Code)~~

~~(415) 512-7200 (~~Registrant’s ~~Telephone~~telephone ~~Number~~number, ~~Including~~including ~~Area~~area ~~Code~~code: (415) 512-7200

~~Not~~185 ~~applicable~~Berry Street, Suite 6504 San Francisco, California 94107 (Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o Written communications pursuant to Rule 425 under the Securities Act (17 CFR ~~240~~230.425) o Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) o Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) o Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

~~o Soliciting~~ITEM ~~material~~8.01 ~~pursuant~~OTHER ~~to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)~~EVENTS

~~o Pre-commencement~~ On ~~communications~~December 22, ~~pursuant~~2006, toSirna ~~Rule 14d-2~~Therapeutics, Inc. (b“Sirna”) ~~under~~filed with the Securities and Exchange ~~Act~~Commission (17the ~~CFR~~“SEC”) definitive additional materials on Schedule 14A (the “Definitive ~~240~~Additional Materials”) that supplement Sirna’s Proxy Statement, mailed on or about November 29, 2006 to Sirna stockholders, in connection with the proposed acquisition of Sirna by Merck & Co, Inc.~~14d-2~~, a New Jersey corporation (b“Merck”), pursuant to a merger agreement (the “Merger Agreement”) by and among Merck, Spinnaker Acquisition Corp., a Delaware corporation and a wholly-owned subsidiary of Merck (“Merger Sub”) and Sirna. A copy of the Definitive Additional Materials is filed herewith as Exhibit 99.1 hereto and is incorporated herein by reference. A copy of Amendment No. 1 to Agreement and Plan of Merger entered into by and among Merck, Merger Sub and Sirna on December 21, 2006 that is described in the Definitive Additional Materials and filed therewith as Annex E is filed herewith as Exhibit 2.1 and is incorporated herein by reference.

~~o Pre~~Forward-~~commencement~~Looking ~~communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR~~Information ~~240.13e-4(c))~~

~~Item 1~~ Statements in this Form 8-K and the filings incorporated by reference which are not strictly historical are “forward-looking” statements which are subject to many risks and uncertainties.~~01 Entry~~ The settlement described in the Definitive Additional Materials and incorporated by reference into this Form 8-K may not result in a ~~Material~~written ~~Definitive~~settlement agreement, may not be approved by the court, and may be terminated for other reasons. Other risks and uncertainties include the failure to satisfy the closing conditions set forth in the Merger Agreement, as amended, the termination of the Merger Agreement, the failure of the proposed acquisition to close or a significant delay in the closing for any reason. Risk factors are identified in Sirna’s Securities and Exchange Commission filings, including Forms 10-K and 10-Q and in other SEC filings. Sirna undertakes no obligation to revise or update any forward-looking statements in order to reflect events or circumstances that may arise after the date of this Form 8-K.

~~The~~Participants ~~Board~~in ~~of Directors (~~the ~~“Board”)~~Solicitation ofand ~~Sirna~~Additional ~~Therapeutics, Inc. (the “Company”) has~~Information previously approved an amendment to the Sirna Therapeutics, Inc. 2005 Performance Incentive Plan (the “2005 Plan”) which would increase the number of shares of the Company’s common stock that may be delivered pursuant to awards granted under the 2005 Plan by an additional 2,000,000 shares. The proposed amendment would also increase the limit on the number of shares that may be delivered pursuant to “incentive stock options” by 2,000,000 shares. At the Company’s annual stockholders meeting held on June 14, 2006, the Company’s stockholders approved the 2005 Plan amendment.

~~The~~A ~~following~~special ~~summary~~meeting of ~~the~~Sirna ~~2005~~stockholders ~~Plan~~ is ~~qualified~~expected into ~~its~~be ~~entirety~~held byon ~~reference~~Thursday, December 28, 2006 to obtain stockholder approval for the ~~text~~merger. In connection with the proposed acquisition and ofrequired stockholder approval, Sirna filed with the ~~2005~~SEC ~~Plan~~a definitive proxy statement on November 27, ~~which~~2006. This proxy statement was ~~previously~~mailed to Sirna’s stockholders on or about November 29, 2006. Definitive Additional material has been filed aswith ~~Annex~~the ASEC toon December 14, 2006 and December 22, 2006. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE PROXY STATEMENT AND OTHER RELEVANT DOCUMENTS FILED WITH THE SEC BECAUSE THEY CONTAIN IMPORTANT INFORMATION ABOUT SIRNA AND THE PROPOSED ACQUISITION. Investors and security holders may obtain free copies of these documents and other documents filed with the ~~Company~~SEC at the SEC’s ~~revised~~website ~~proxy~~at ~~statement~~www.sec.gov or at Sirna’s website at ~~dated~~www.sirna.com. ~~May 25,~~Such ~~2006~~information is currently not available.

~~The~~Sirna ~~Board~~and orits ~~one~~directors orand ~~more~~executive ~~committees~~officers ~~appointed~~may bybe deemed to be participants in the solicitation ~~Board~~of ~~administers~~proxies from Sirna’s stockholders in connection with the ~~2005~~proposed ~~Plan~~acquisition. ~~The~~Such ~~Board~~individuals ~~has~~have ~~delegated~~interests ~~general~~in ~~administrative~~the ~~authority~~proposed acquisition, including as a result of holding options to purchase or shares of Sirna stock or affiliation with large stockholders of Sirna. Certain information regarding Sirna’s directors and executive officers and their interests in the solicitation is set forth in the proxy statement for Sirna’s 2006 annual meeting of stockholders filed with the ~~2005~~SEC ~~Plan~~on toMay 25, 2006 and is included in the ~~Compensation~~definitive proxy statement relating to ~~Committee~~the ofproposed acquisition filed with the ~~Board~~SEC on November 27, 2006.

~~The~~ITEM ~~administrator~~9.01 ofFINANCIAL ~~the~~STATEMENTS ~~2005~~AND ~~Plan has broad authority under the 2005 Plan to, among other~~EXHIBITS things, select participants and determine the type(s) of award(s) that they are to receive and determine the number of shares that are to be subject to awards and the terms and conditions of awards, including the price (if any) to be paid for the shares or the award.

~~Persons eligible to receive awards under the 2005 Plan include officers or employees of the~~(d) Exhibits ~~Company or any of its subsidiaries, directors of the Company or any of its subsidiaries, and certain consultants and advisors to the Company or any of its subsidiaries.~~

The maximum number of shares of the Company’s common stock that may be issued or transferred pursuant to awards under the 2005 Plan equals the sum of: (1) 5,749,745 shares (after giving effect to the 2005 Plan amendment), plus (2) the number of any shares subject to stock options granted under the Company’s 2001 Stock Option Plan (the “2001 Plan”) or the Company’s 1996 Stock Option Plan (the “1996 Plan”), which expire, or for any reason are cancelled or terminated, after June 14, 2005.

2.1		Amendment No. 1 to Agreement and Plan of Merger, dated as of December 21, 2006, by and among Merck, Spinnaker Acquisition Corp. and Sirna

99.1		Definitive Additional Materials on Schedule 14A, as filed with the SEC on December 22, 2006

~~To the extent that an award is settled in cash or a form other than shares, the shares that~~SIGNATURES would have been delivered had there been no such cash or other settlement will not be counted against the shares available for issuance under the 2005 Plan. In the event that shares are delivered in respect of a dividend equivalent right, stock appreciation right, or other award, only the actual number of shares delivered with respect to the award will be counted against the share limits of the 2005 Plan. Shares that are subject to or underlie awards which expire or for any reason are cancelled or terminated, are forfeited, fail to vest, or for any other reason are not paid or delivered under the 2005 Plan will again be available for subsequent awards under the 2005 Plan. Shares that are exchanged by a participant or withheld by the Company as full or partial payment in connection with any award under the 2005 Plan, the 2001 Plan or the 1996 Plan (with respect to such payment in connection with any award under the 2001 Plan or the 1996 Plan, only to the extent such transaction occurred after June 14, 2005), as well as any shares exchanged by a participant or withheld by the Company or one of its subsidiaries to satisfy the tax withholding obligations related to any award under the 2005 Plan, the 2001 Plan or the 1996 Plan (with respect to such exchange or withholding in connection with any award under the 2001 Plan or the 1996 Plan, only to the extent such transaction occurs after the June 14, 2005), will be available for subsequent awards under the 2005 Plan. In addition, the 2005 Plan generally provides that shares issued in connection with awards that are granted by or become obligations of the Company through the assumption of awards (or in substitution for awards) in connection with an acquisition of another company will not count against the shares available for issuance under the 2005 Plan.

~~The~~Pursuant ~~types~~to ofthe ~~awards~~requirements ~~that~~of ~~may be granted under~~ the ~~2005~~Securities ~~Plan~~Exchange ~~include~~Act ~~stock~~of ~~options~~1934, ~~stock appreciation~~as ~~rights~~amended, ~~restricted~~the Registrant ~~stock,~~has ~~stock~~duly ~~bonuses~~caused ~~and~~this ~~other~~report ~~forms~~to ofbe ~~awards~~signed ~~granted~~on ~~or denominated~~its inbehalf ~~the~~by ~~Company’s common stock or units of~~ the ~~Company’s~~undersigned ~~common~~hereunto ~~stock, as well as~~duly ~~certain cash bonus awards~~authorized.

AsDate: ~~is customary in incentive plans of this nature~~December 22, ~~each share limit and the number and kind of~~2006 shares available under the 2005 Plan and any outstanding awards, as well as the exercise or purchase prices of awards, and performance targets under certain types of performance-based awards, are subject to adjustment in the event of certain reorganizations, mergers, combinations, recapitalizations, stock splits, stock dividends, or other similar events that change the number or kind of shares outstanding, and extraordinary dividends or distributions of property to the stockholders.

2SIRNA THERAPEUTICS, INC.

~~SIGNATURE~~ (Registrant)

~~Pursuant~~By: to/s/ ~~the~~Howard ~~requirements~~W. ofRobin ~~the~~Name: ~~Securities~~Howard ~~Exchange~~W. ~~Act~~Robin ofTitle: ~~1934,~~President ~~the~~and ~~Registrant~~Chief ~~has~~Executive ~~duly caused~~Officer ~~this~~(Principal ~~report~~Executive ~~to be signed on its behalf by the undersigned, thereunto duly authorized.~~ Officer)

	Sirna Therapeutics, Inc. (Registrant)
Date: June 20, 2006	By:	/s/ Gregory L. Weaver
		Gregory L. Weaver
		Senior Vice President and Chief Financial Officer

Exhibit Index


Exhibit No.		Description of Exhibit

2.1		Amendment No. 1 to Agreement and Plan of Merger, dated as of December 21, 2006, by and among Merck, Spinnaker Acquisition Corp. and Sirna

99.1		Definitive Additional Materials on Schedule 14A, as filed with the SEC on December 22, 2006

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