ARENA PHARMACEUTICALS, INC.

May 15, 2009

Dear Arena Stockholder:

You are cordially invited to attend the 2009 Annual Meeting of Stockholders of Arena Pharmaceuticals, Inc., a Delaware corporation. The Annual Meeting will be held on Thursday, June 25, 2009, at 9:00 a.m. (Pacific Time), at our offices located at 6154 Nancy Ridge Drive, San Diego, California 92121. I look forward to meeting with as many of our stockholders as possible.

At the Annual Meeting, we will discuss each item of business described in the Notice of Annual Meeting and proxy statement and report on Arena’s business. You will also have an opportunity to ask questions.

If you would like directions to our offices, please visit our website at www.arenapharm.com, where you will find directions and a map locator under “Contact Us.” For further information about the Annual Meeting, please call 858.453.7200 and ask for Investor Relations.

On behalf of our employees and Board of Directors, I would like to express our appreciation for your continued interest in Arena.

6166 Nancy Ridge Drive, San Diego, California 92121

Table of Contents

ARENA PHARMACEUTICALS, INC.

ALIGN="center">TABLE OF CONTENTS

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Table of Contents

ARENA PHARMACEUTICALS, INC.

ARENA PHARMACEUTICALS, INC.

ARENA PHARMACEUTICALS, INC.

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

ARENA PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

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 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))

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

ARENA PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

ARENA PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Arena Pharmaceuticals, Inc.

			Electronic Voting Instructions
			You can vote by Internet or telephone! Available 24 hours a day, 7 days a week!
			Instead of mailing your proxy, you may choose one of the two voting methods outlined below to vote your proxy.
			VALIDATION DETAILS ARE LOCATED BELOW IN THE TITLE BAR.
			Proxies submitted by the Internet or telephone must be received by 11:00 p.m. Pacific Time on June 10, 2008.
					Vote by Internet
					•	Log on to the Internet and go to www.investorvote.com/ARNA
					•	Follow the steps outlined on the secured website.
					Vote by telephone
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