6-K

FORM 6-K

SECURITIES AND EXCHANGE COMMISSION

450, 5th Street

Washington, D.C. 20549

REPORT OF FOREIGN PRIVATE ISSUER

Pursuant to Rule 13a-16 or 15d-16 of

the Securities Exchange Act of 1934

For the month of March, 2006

Daiichi Sankyo Company, Limited

(Translation of registrant’s name into English)

5-1, Nihonbashi 3-chome

Chuo-ku, Tokyo 103-8426

Japan

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover Form 20-F or Form 40-F.

Form 20-F  þ            Form 40-F  ¨

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1):

Yes  ¨            No  þ

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7):

Yes  ¨            No  þ

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes  ¨            No  þ

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b): N/A

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	DAIICHI SANKYO COMPANY, LIMITED
DATE: March 23, 2006	By:	/s/ Takashi Shoda
	Name:	Takashi Shoda
	Title:	President and Representative Director

EXHIBIT INDEX

Exhibit Number		Description of Exhibit
99.1	—	Press Release: “Sankyo and Exelixis Sign Joint Research Agreement”

EX-99.1

Exhibit 99.1

For Immediate Release

Company name: DAIICHI SANKYO COMPANY, LIMITED

Representative: Takashi Shoda, President and Representative Director

(Code no.: 4568, First Section, Tokyo, Osaka and Nagoya Stock Exchanges)

Please address inquiries to Toshio Takahashi, Corporate Officer in Charge,

Corporate Communications Department

Telephone: +81-3-6225-1126

Sankyo and Exelixis Sign Joint Research Agreement

Tokyo, March 23, 2006 – DAIICHI SANKYO COMPANY, LIMITED has announced today that its subsidiary, Sankyo Co., Ltd. (President: Yasuhiro Ikegami), has entered into a joint research agreement with Exelixis, Inc. (California, U.S.A).

The two companies will collaborate in developing modulators targeting the mineralocorticoid receptor – a nuclear hormone receptor implicated in various cardiovascular diseases such as hypertension and congestive heart failure. Their goal is to develop drugs which are superior to existing aldosterone antagonists in terms of safety and effectiveness. After the joint research term, Sankyo will be responsible for all further development, regulatory, manufacturing and commercialization activities for the compounds.

Under the terms of this agreement, Sankyo will pay Exelixis an upfront payment of $20 million upon signing the agreement.

* Please refer to the appendix for company information about Exelixis, Inc.

<Appendix>

About Exelixis

1. President and CEO: George A. Scangos, Ph.D.

2. Company headquarters: South San Francisco, California

3. Sales: Approx. $76 million (2005)

4. Target therapeutic area: Cancer and metabolic diseases, among others

5. Web site: http://www.exelixis.com