UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 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): February 1, 2012

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

6166 Nancy Ridge Drive, San Diego, California 92121

(Address of principal executive offices) (Zip Code)

858.453.7200

(Registrant’s telephone number, including area code)

N/A

(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:

In this report, “Arena Pharmaceuticals,” “Arena,” “Company,” “we,” “us” and “our” refer to Arena Pharmaceuticals, Inc., unless the context otherwise provides.

Item 8.01 Other Events.

On February 1, 2012, we and Eisai Inc. announced that the US Food and Drug Administration, or FDA, has notified us that an Endocrinologic and Metabolic Drugs Advisory Committee meeting to discuss the lorcaserin New Drug Application, or NDA, resubmission will be held in the second quarter of 2012. Confirmation and details of the meeting will be published in the Federal Register. Lorcaserin is an investigational drug candidate intended for weight management, including weight loss and maintenance of weight loss, in patients who are obese (BMI >30) or patients who are overweight (BMI >27) and have at least one weight-related co-morbid condition.

Forward-Looking Statements

Certain statements in this Form 8-K are forward-looking statements that involve a number of risks and uncertainties. Such forward-looking statements include statements about the advancement, therapeutic indication and use, safety, efficacy, and potential of lorcaserin; the FDA advisory committee meeting and the discussion on the lorcaserin NDA resubmission; and availability of information in the Federal Register. For such statements, we claim the protection of the Private Securities Litigation Reform Act of 1995. Actual events or results may differ materially from our expectations. Factors that could cause actual results to differ materially from the forward-looking statements include, but are not limited to, the following: the timing of regulatory review and approval is uncertain, and the FDA may not complete its review of the resubmission of the lorcaserin NDA by the PDUFA date; the FDA advisory committee meeting for lorcaserin may not be held as expected; nonclinical and clinical data is voluminous and detailed, and regulatory agencies may interpret or weigh the importance of data differently and reach different conclusions than we or others, request additional information, have additional recommendations or change their guidance or requirements before or after approval; data and other information related to lorcaserin and our other research and development programs may not meet safety or efficacy requirements or otherwise be sufficient for regulatory review or approval; unexpected or unfavorable new data; risks related to commercializing new products; our ability to obtain and defend our patents; results of clinical trials and other studies are subject to different interpretations and may not be predictive of future results; having adequate funds; risks related to relying on collaborative agreements; and satisfactory resolution of pending and any future litigation or other disagreements with others. Additional factors that could cause actual results to differ materially from those stated or implied by our forward-looking statements are disclosed in our filings with the Securities and Exchange Commission. These forward-looking statements represent our judgment as of the time of the filing of this Form 8-K. We disclaim any intent or obligation to update these forward-looking statements, other than as may be required under applicable law.

SIGNATURE

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.