UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 2, 2010

OREXIGEN THERAPEUTICS, INC.

(Exact Name of Registrant as Specified in its Charter)

Registrant’s telephone number, including area code: (858) 875-8600

(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 (see General Instruction A.2. below):

On September 2, 2010, Orexigen Therapeutics, Inc. (the “Company”) issued a press release announcing that they entered into a Collaboration Agreement with Takeda Pharmaceutical Company Limited (“Takeda”) on September 1, 2010, to develop and commercialize Contrave^® in the United States, Canada and Mexico. The Company hosted a conference call on September 2, 2010 at 8:00 a.m., Eastern Time, to discuss the partnership.

A transcript of the above-referenced conference call is attached as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated in this Item 7.01 by reference. A replay of the webcast of the conference call will be available on the Company’s website at www.orexigen.com for approximately 14 days.

The information in this item, including Exhibit 99.1, is being furnished pursuant to Item 7.01 and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, and it shall not be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or under the Exchange Act, whether made before or after the date hereof, except as expressly set forth by specific reference in such filing to this item.

* * *

By filing this Current Report on Form 8-K and furnishing this information, the Company makes no admission as to the materiality of any information in this report. The information contained in this Current Report on Form 8-K is intended to be considered in the context of the Company’s filings with the SEC and other public announcements that the Company makes, by press release or otherwise, from time to time. The Company undertakes no duty or obligation to publicly update or revise the information contained in this report, although it may do so from time to time as its management believes is appropriate. Any such updating may be made through the filing of other reports or documents with the SEC, through press releases or through other public disclosure.

The Company cautions you that statements included in this report and the attached exhibit that are not a description of historical facts are forward-looking statements. Words such as “believes,” “anticipates,” “plans,” “expects,” “indicates,” “will,” “intends,” “potential,” “suggests,” “assuming,” “designed” and similar expressions are intended to identify forward-looking statements. These statements are based on the Company’s current beliefs and expectations. These forward-looking statements include statements regarding the potential for, and timing of, approval for Contrave, the Company’s belief that this product candidate may be an important therapeutic option in the treatment of obesity, the potential milestone and royalty payments under the agreement with Takeda and the potential strength of our market entry with Contrave, if approved. The inclusion of forward-looking statements should not be regarded as a representation by the Company that any of its plans will be achieved. Actual results may differ from those set forth in this release due to the risk and uncertainties inherent in the Orexigen business, including, without limitation: the Company’s dependence on Takeda for aspects of the development and commercialization of Contrave; the potential for the FDA to delay the scheduled PDUFA action date of January 31, 2011 due to the FDA’s internal resource constraints or other reasons; the uncertainty of the FDA approval process and other regulatory requirements; the FDA may not agree with the Company’s interpretation of efficacy and safety results; the FDA may require the Company to complete additional clinical, non-clinical or other requirements prior to the approval of the Contrave NDA; the therapeutic and commercial value of Contrave; reliance on third parties to assist with the development of Contrave and the regulatory submission related thereto; the potential for adverse safety findings relating to Contrave; and other risks described in the Company’s filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and the Company undertakes no obligation to revise or update this news release to reflect events or circumstances after the date hereof. Further information regarding these and other risks is included under the heading “Risk Factors” in the Company’s Quarterly Report on Form 10-Q, which was filed with the Securities Exchange Commission on August 6, 2010 and is available from the SEC’s website (www.sec.gov) and on the Company’s website (www.orexigen.com) under the heading “Investor Relations”. All forward-looking statements are qualified in their entirety by this cautionary statement. This caution is made under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995.

(d) Exhibits.

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 hereunto duly authorized.

EXHIBIT INDEX