Edgar Filing: ARENA PHARMACEUTICALS INC

Rule 424(b)(5) - Prospectus Supplement

Filed pursuant to Rule 424(b)(5)
Registration No. 333-177826

PROSPECTUS SUPPLEMENT

To Prospectus dated November 21, 2011

9,953,250 Shares of Common Stock

9,953.25 Shares of Series D Convertible Preferred Stock

LOGO

Arena Pharmaceuticals, Inc.

Common Stock and Series D Convertible Preferred Stock

Pursuant to this prospectus supplement and the accompanying prospectus, we are offering an aggregate of 9,953,250 shares of our common stock and 9,953.25 shares of our Series D Convertible Preferred Stock (“Series D Preferred Stock”) to certain institutional investors pursuant to a securities purchase agreement, dated January 10, 2012, at a price of $1.65775 per share of common stock and $1,657.75 per share of Series D Preferred Stock. The aggregate purchase price for the shares of common stock and Series D Preferred Stock is approximately $33.0 million. We will receive net proceeds from the sale of these shares of approximately $32.9 million after deducting our estimated offering expenses.

Our common stock is quoted on The NASDAQ Global Select Market under the symbol “ARNA”. The last reported sale price of our common stock on The NASDAQ Global Select Market on January 10, 2012, was $1.75 per share. We are not listing our Series D Preferred Stock on an exchange or any trading system and we do not expect that a trading market for our Series D Preferred Stock will develop.

Each share of Series D Preferred Stock is convertible into 1,000 shares of our common stock at any time at the option of the holder, provided that the holder will be prohibited from converting Series D Preferred Stock into shares of our common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.98% of the total number of shares of our common stock then issued and outstanding. In the event of our liquidation, dissolution, or winding up, holders of our Series D Preferred Stock will receive a payment equal to $0.0001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of our common stock. Shares of Series D Preferred Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D Preferred Stock will be required to amend the terms of the Series D Preferred Stock.

Investing in our common stock and/or our Series D Preferred Stock involves a high degree of risk. Please read “Risk Factors” beginning on page S-5 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We currently anticipate that the closing of the offering will take place on or about January 13, 2012. On the closing date, we will issue the shares of common stock and Series D Preferred Stock to the investors and receive funds in the amount of the aggregate purchase price.

The date of this prospectus supplement is January 10, 2012.

TABLE OF CONTENTS


	Page
Prospectus Supplement
Prospectus Supplement Summary		S-1
Risk Factors		S-5
Special Note Regarding Forward-Looking Statements		S-7
Use of Proceeds		S-8
Dilution		S-9
Plan of Distribution		S-11
Description of Series D Convertible Preferred Stock		S-11
Legal Matters		S-12
Experts		S-12
Where You Can Find More Information		S-13
Incorporation of Certain Information by Reference		S-13

Prospectus
About this Prospectus		i
Summary		1
Risk Factors		6
Forward-Looking Statements		6
Financial Ratios		7
Use of Proceeds		7
Description of Capital Stock		8
Description of Debt Securities		13
Description of Warrants		20
Description of Units		22
Legal Ownership of Securities		24
Plan of Distribution		28
Legal Matters		30
Experts		30
Where You Can Find More Information		30
Incorporation of Certain Information by Reference		30

We provide information to you about this offering of shares of our common stock and Series D Preferred Stock in two separate documents that are bound together: (1) this prospectus supplement, which describes the specific details regarding this offering; and (2) the accompanying prospectus, which provides general information, some of which may not apply to this offering. Generally, when we refer to this “prospectus,” we are referring to both documents combined. If information in this prospectus supplement is inconsistent with the accompanying prospectus, you should rely on this prospectus supplement.

You should rely only on information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus. We have not authorized anyone to provide you with information that is different. We are offering to sell and seeking offers to buy shares of our common stock and Series D Preferred Stock only in jurisdictions where offers and sales are permitted. The information contained in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein are accurate only as of their respective dates, regardless of the time of delivery of this prospectus supplement or of any sale of our common stock and Series D Preferred Stock. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus, and the documents incorporated by reference in this prospectus supplement and the accompanying prospectus in their entirety before making an investment decision. You should also read and consider the information in the documents we have referred you to in the sections of this prospectus supplement entitled “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.”

Arena Pharmaceuticals^®, Arena^® and our corporate logo are registered service marks of Arena. CART™ and BRL Screening™ are unregistered service marks of Arena. “APD” is an abbreviation for Arena Pharmaceuticals Development. All other brand names or trademarks appearing in this prospectus supplement and the accompanying prospectus are the property of their respective holders. Unless otherwise specified or required by context, references in this prospectus supplement to “we,” “us,” “our” and “Arena” refer to Arena Pharmaceuticals, Inc., and its wholly owned subsidiaries on a consolidated basis.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and selected information contained elsewhere in or incorporated by reference into this prospectus supplement. This summary is not complete and does not contain all of the information that you should consider before deciding whether to invest in our common stock or Series D Preferred Stock. For a more complete understanding of our company and this offering, you should read and consider carefully the more detailed information in this prospectus supplement and the accompanying prospectus, including the information incorporated by reference in this prospectus supplement and the accompanying prospectus. If you invest in our common stock or Series D Preferred Stock, you are assuming a high degree of risk. See “Risk Factors” in this prospectus supplement beginning on page S-5 and in the documents incorporated by reference into this prospectus supplement.

Arena Pharmaceuticals, Inc.

We are a clinical-stage biopharmaceutical company focused on discovering, developing and commercializing oral drugs that target G protein-coupled receptors, or GPCRs, an important class of validated drug targets, in four major therapeutic areas: cardiovascular, central nervous system, inflammatory and metabolic diseases. Our most advanced drug candidate is lorcaserin hydrochloride, or lorcaserin, which is intended for weight management.

In December 2009, we submitted a New Drug Application, or NDA, to the US Food and Drug Administration, or FDA, for regulatory approval of lorcaserin. In October 2010, the FDA issued a Complete Response Letter, or CRL, with respect to the lorcaserin NDA. In the CRL, the FDA stated that it completed its review of the NDA and determined that it could not approve the application in its then present form. On December 27, 2011, we resubmitted the lorcaserin NDA, and the FDA has confirmed its acceptance of the resubmission for filing and review and assigned a new Prescription Drug User Fee Act target date of June 27, 2012.

We intend to focus our resources on seeking regulatory approval of lorcaserin in the United States, seeking regulatory approval of lorcaserin outside of the United States, and selectively advancing our earlier-stage research and development programs. We are also actively seeking collaborators or other licensing opportunities for our programs.

In addition to our lorcaserin-related activities, we completed in 2011 a Phase 1 clinical trial for APD811 (an internally discovered, orally available agonist of the prostacyclin receptor intended for the treatment of pulmonary arterial hypertension). We are also focused on advancing APD334 (an internally discovered, orally available agonist of the S1P1 receptor intended for the treatment of a number of conditions related to autoimmune diseases, including multiple sclerosis) toward clinical development and continuing development of our research programs on cannabinoid receptor 2, or CB2, agonists (intended for the treatment of osteoarthritis and pain) and GPR119 agonists (intended for the treatment of type 2 diabetes).

We also have other oral drug candidates that we have internally discovered, including APD597, APD791 and APD125. APD597, which targets the GPR119 receptor, is intended for the treatment of type 2 diabetes and has completed a Phase 1 clinical trial program under our former collaboration with Ortho-McNeil-Janssen Pharmaceuticals, Inc. APD791 is an inverse agonist of the serotonin 2A receptor intended for the treatment of arterial thrombosis and other related conditions and has completed Phase 1a and Phase 1b clinical trials. APD125 is a serotonin 2A receptor inverse agonist that we previously studied for insomnia, and has completed Phase 2a and Phase 2b clinical trials. We are not planning to conduct significant development

S-1

activities, including any additional clinical trials, for any of these drug candidates at this time. We may consider resuming development of these candidates in the future depending on the cost of further development and our available financial resources.

The headquarters of our operations outside of the United States is in Switzerland. Activities conducted at this location include manufacturing, quality control, quality assurance, development of manufacturing processes, qualifying suppliers and otherwise managing the global supply chain, regulatory compliance, distribution of finished products, and European strategic planning and development.

We have retained commercial rights for all of our programs and drug candidates, with the exception of Eisai’s right to commercialize lorcaserin in the United States. We have not received regulatory approval to market or sell any drugs or generated commercial revenues from selling any drugs, other than in connection with manufacturing drugs for Siegfried Ltd in our Swiss drug product manufacturing facility.

We incorporated in the state of Delaware in April 1997. Our corporate offices are located at 6166 Nancy Ridge Drive, San Diego, California 92121. Our telephone number is 858.453.7200. Our website address is www.arenapharm.com. Information contained in or accessible through our website does not constitute part of this prospectus.

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The Offering

Common Stock

Common Stock Offered By Us

9,953,250 shares

Common Stock To Be Outstanding Immediately After This Offering

156,046,069 shares

NASDAQ Global Select Market Listing

Our common stock is listed on The NASDAQ Global Select Market under the symbol “ARNA”.

Series D Convertible Preferred Stock

Series D Preferred Stock Offered By Us

9,953.25 shares

Conversion

Each share of our Series D Preferred Stock is convertible into 1,000 shares of our common stock at any time at the option of the holder, provided that the holder will be prohibited from converting Series D Preferred Stock into shares of our common stock if, as a result of such conversion, the holder, together with its affiliates, would own more than 9.98% of the total number of shares of our common stock then issued and outstanding.

Liquidation Preference

In the event of our liquidation, dissolution, or winding up, holders of our Series D Preferred Stock will receive a payment equal to $0.0001 per share of Series D Preferred Stock before any proceeds are distributed to the holders of our common stock.

Voting Rights

Shares of Series D Preferred Stock will generally have no voting rights, except as required by law and except that the consent of holders of a majority of the outstanding Series D Preferred Stock will be required to amend the terms of the Series D Preferred Stock.

Dividends

Shares of Series D Preferred Stock will not be entitled to receive any dividends, unless and until specifically declared by our board of directors.

Listing

We are not listing our Series D Preferred Stock on an exchange or any trading system and we do not expect that a trading market for our Series D Preferred Stock will develop.

Use of Proceeds

We estimate that our net proceeds from this offering, after deducting our estimated offering expenses, will be approximately $32.9 million. We will use $5.0 million of the proceeds of this offering for payment of loan principal under the Facility Agreement, dated June 17, 2009, as amended, by and between us and entities affiliated with Deerfield Management. We anticipate that we will use the remainder of the net proceeds from this offering for activities related to seeking regulatory approval of lorcaserin in the United States and outside of the United States, for preclinical and clinical development of our drug candidates, for discovery research for new drug candidates and for general corporate purposes, including working capital. See “Use of Proceeds” on page S-8 of this prospectus supplement.

Risk Factors

Investing in our common stock and Series D Preferred Stock involves a high degree of risk. See “Risk Factors” beginning on page S-5 of this prospectus supplement.

S-3

The number of shares of common stock to be outstanding immediately after this offering as reflected above is based on the actual number of shares outstanding as of December 31, 2011, which was 146,092,819, and does not include, as of that date:

•

9,953,250 shares of common stock issuable upon the conversion of the Series D Preferred Stock offered pursuant to this prospectus;

•

1,831,410 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $3.45 per share (which as a result of this offering will be canceled and of no further force or effect);

•

11,800,000 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $5.42 per share (which as a result of this offering will become warrants to purchase 8,631,410 shares of common stock at an exercise price of $1.745 per share);

•

14,368,590 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $1.68 per share;

•

1,640,368 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $5.20 per share (which as a result of this offering will become warrants to purchase 1,846,301 shares of common stock at an exercise price of $4.62 per share);

•

1,227,743 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $10.47 per share (which as a result of this offering will become warrants to purchase 1,379,235 shares of common stock at an exercise price of $9.32 per share);

•

10,309,972 shares of common stock issuable upon the exercise of outstanding options at a weighted-average exercise price of $5.63 per share;

•

1,171,250 performance-based restricted stock unit awards outstanding under our 2006 Long-Term Incentive Plan, as amended;

•

4,144,008 shares of common stock available for future issuance under our 2009 Long-Term Incentive Plan;

•

554,633 shares of common stock available for future issuance under our 2009 Employee Stock Purchase Plan; and

•

79,169 shares of common stock available for future issuance under our Deferred Compensation Plan.

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RISK FACTORS

An investment in our common stock and Series D Preferred Stock involves a high degree of risk. Before you make a decision to invest in our common stock and Series D Preferred Stock, you should consider carefully the risks described below, together with other information in this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein. If any of the following events actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our common stock and/or the value of our Series D Preferred Stock to decline and you may lose all or part of your investment. These risks are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business operations.

Risks Related to This Offering

We will have broad discretion as to the use of a portion of the proceeds from this offering, and we may not use the proceeds effectively.

Apart from the use of $5.0 million of the proceeds from this offering to repay a portion of our outstanding indebtedness, our management will have broad discretion in the application of the net proceeds from this offering and could spend the proceeds in ways that do not improve our results of operations or enhance the value of our common stock. Our failure to apply these funds effectively could have a material adverse effect on our business or the development of our product candidates and cause the price of our common stock to decline.

Our Series D Convertible Preferred Stock has never been publicly traded and an active trading market for such stock is not expected to develop.

Prior to this offering, there has been no public market for our Series D Preferred Stock. We are not listing our Series D Preferred Stock on an exchange or any trading system and we do not expect that a trading market for our Series D Preferred Stock will develop.

You will experience immediate and substantial dilution in the net tangible book value per share of the stock you purchase.

Since the price per share of our common stock and Series D Preferred Stock being offered is substantially higher than the net tangible book value per share of our stock, you will suffer substantial dilution in the net tangible book value of the stock you purchase in this offering. Based on the public offering price of $1.65775 per share, assuming the conversion of 9,953.25 shares of our Series D Preferred Stock being offered in this offering into 9,953,250 shares of our common stock, if you purchase stock in this offering, you will suffer immediate and substantial dilution of $1.32 per share in net tangible book value. See the section entitled “Dilution” in this prospectus supplement for a more detailed discussion of the dilution you will incur if you purchase stock in this offering.

You may experience future dilution as a result of future equity offerings or other equity issuances.

To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock. The terms of the Series D Preferred Stock do not restrict our ability to offer additional shares of common stock or a new series of preferred stock that is senior to, on parity with or junior in rank to the Series D Preferred Stock. Our board of directors has the authority to establish the designation of additional shares of preferred stock that may be convertible into common stock without any action by our stockholders, and to fix the rights, preferences, privileges and restrictions, including voting rights, of such shares. Any such additional shares of preferred stock may have rights, preferences and privileges senior to those of outstanding common stock and the Series D Preferred Stock, and the issuance and

S-5

conversion of any such preferred stock would further dilute the percentage ownership of our stockholders. We cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal to or greater than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock or other securities convertible into or exchangeable for our common stock in future transactions may be higher or lower than the price per share in this offering.

Our Series D Convertible Preferred Stock will rank junior to all our liabilities to third party creditors in the event of a bankruptcy, liquidation or winding up of our assets.

In the event of bankruptcy, liquidation or winding up, our assets will be available to pay obligations on our Series D Preferred Stock only after all our liabilities have been paid. Our Series D Preferred Stock will effectively rank junior to all existing and future liabilities held by third party creditors. The terms of our Series D Preferred Stock do not restrict our ability to raise additional capital in the future through the issuance of debt. In the event of bankruptcy, liquidation or winding up, there may not be sufficient assets remaining, after paying our liabilities, to pay amounts due on any or all of our Series D Preferred Stock then outstanding.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus, including the documents that we incorporate by reference herein and therein, contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These forward-looking statements can generally be identified as such because the context of the statement will include words such as “may,” “will,” “intends,” “plans,” “believes,” “anticipates,” “expects,” “estimates,” “predicts,” “potential,” “continue,” “likely,” “unlikely” or “opportunity,” the negative of these words or words of similar import. Similarly, statements that describe our future plans, strategies, intentions, expectations, objectives, goals or prospects are also forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in the “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections incorporated by reference from our most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q, as well as any amendments thereto reflected in subsequent filings with the SEC. These forward-looking statements are based largely on our expectations and projections about future events and future trends affecting our business, and are subject to risks and uncertainties that could cause actual results to differ materially from those anticipated in the forward-looking statements. The risks and uncertainties include, among others, those noted in the sections entitled “Risk Factors” in this prospectus supplement and included in the documents that we incorporate by reference herein.

In addition, past financial and/or operating performance is not necessarily a reliable indicator of future performance and you should not use our historical performance to anticipate results or future period trends. We can give no assurances that any of the events anticipated by the forward-looking statements will occur or, if any of them do, what impact they will have on our results of operations and financial condition. Except as required by law, we undertake no obligation to publicly revise our forward-looking statements to reflect events or circumstances that arise after the filing of this prospectus supplement or the filing of the accompanying prospectus or documents incorporated by reference herein and therein that include forward-looking statements.

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USE OF PROCEEDS

We estimate the net proceeds from the sale of 9,953,250 shares of our common stock and 9,953.25 shares of our Series D Preferred Stock that we are offering will be approximately $32.9 million, based on the offering price of $1.65775 per share of common stock and $1,657.75 per share of Series D Preferred Stock and after deducting our estimated offering expenses of $0.1 million.

We will use $5 million of the proceeds of this offering for payment of loan principal under the Facility Agreement, dated June 17, 2009, as amended, by and between us and entities affiliated with Deerfield Management. We anticipate that we will use the remainder of the net proceeds from this offering for activities related to seeking regulatory approval of lorcaserin in the United States and outside of the United States, for preclinical and clinical development of our drug candidates, for discovery research for new drug candidates and for general corporate purposes, including working capital. In addition, we may use a portion of the proceeds to acquire drugs or drug candidates, technologies, businesses or other assets that complement our own, although we have no current plans, commitments or agreements to do so as of the date of this prospectus supplement. The timing and amount of our actual expenditures will be based on many factors, including the timing and success of our preclinical and clinical trials, whether we partner any of our internal programs, whether we choose to curtail some of our research activities and whether we achieve regulatory approval of lorcaserin. We will retain broad discretion in determining how we will allocate the net proceeds from this offering.

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DILUTION

Our unaudited net tangible book value as of September 30, 2011 was approximately $23.5 million, or $0.16 per share. “Net tangible book value” is total assets minus the sum of liabilities and intangible assets. “Net tangible book value per share” is net tangible book value divided by the total number of shares outstanding.

After giving effect to the sale of 9,953,250 shares of common stock offered and 9,953.25 shares of Series D Preferred Stock by us in this offering, and assuming the conversion of 9,953.25 shares of our Series D Preferred Stock into 9,953,250 shares of our common stock, our as adjusted net tangible book value as of September 30, 2011 would have been approximately $56.4 million, or $0.34 per share. The adjustments made to determine as adjusted net tangible book value per share are the following:

•

an increase in total assets to reflect the net proceeds of the offering as described under “Use of Proceeds”;

•

the addition of 9,953,250 shares of our common stock offered by this prospectus supplement to the number of shares outstanding; and

•

the addition of 9,953,250 shares of our common stock issuable upon conversion of the 9,953.25 shares of our Series D Preferred Stock offered by this prospectus supplement to the number of shares outstanding.

The following table illustrates the as adjusted net tangible book value of $0.34 per share and the dilution (the difference between the offering price per share and net tangible book value per share) to new investors:


Offering price per share of our common stock			$	1.65775
Offering price per share of our Series D Preferred Stock			$	1,657.75
Net tangible book value per share as of September 30, 2011	$	0.16
Increase in net tangible book value per share attributable to the offering	$	0.18
As adjusted net tangible book value per share as of September 30, 2011, after giving effect to the offering			$	0.34
Dilution per share to new investors in the offering			$	1.32

The above discussion and tables are based on the actual number of shares outstanding as of September 30, 2011, which was 146,024,830, and does not include, as of that date:

•

14,368,590 shares of common stock issuable upon the exercise of outstanding warrants at an exercise price of $1.68 per share;

•

S-9

•

10,518,829 shares of common stock issuable upon the exercise of outstanding options at a weighted-average exercise price of $5.69 per share;

•

1,180,850 performance-based restricted stock unit awards outstanding under our 2006 Long-Term Incentive Plan, as amended;

•

3,922,671 shares of common stock available for future issuance under our 2009 Long-Term Incentive Plan;

•

622,622 shares of common stock available for future issuance under our 2009 Employee Stock Purchase Plan; and

•

79,169 shares of common stock available for future issuance under our Deferred Compensation Plan.

To the extent that outstanding options or warrants are exercised, investors purchasing our common stock or Series D Preferred Stock in this offering will experience further dilution. In addition, we may choose to raise additional capital due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. To the extent that additional capital is raised through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

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PLAN OF DISTRIBUTION

We are selling 9,953,250 shares of our common stock and 9,953.25 shares of our Series D Preferred Stock under this prospectus supplement and the accompanying prospectus directly to certain institutional investors at a price of $1.65775 per share of common stock and $1,657.75 per share of Series D Preferred Stock pursuant to a securities purchase agreement. We have agreed, subject to certain exceptions, to refrain from selling any of our common stock or stock or securities directly or indirectly convertible into or exercisable or exchangeable for our common stock, and to refrain from selling any rights, warrants or options to subscribe for or purchase our common stock (or stock or securities directly or indirectly convertible into or exercisable or exchangeable for our common stock) for a period of 30 days following the date of the closing of this offering. We currently anticipate that the closing of the sale of such shares under this agreement will take place on or about January 13, 2012. On the closing date, we will issue the shares of our common stock and Series D Preferred Stock to the investors and receive funds in the amount of the aggregate purchase price.

DESCRIPTION OF SERIES D CONVERTIBLE PREFERRED STOCK

The description in this prospectus supplement of the terms of our Series D Preferred Stock is only a summary. The terms of our Series D Preferred Stock are contained in a certificate of designations that will amend our amended and restated certificate of incorporation, as amended. We have previously filed with the SEC copies of our amended and restated certificate of incorporation, as amended. See “Where You Can Find More Information.” The certificate of designations will be filed as an exhibit to a Current Report on Form 8-K that will be filed with the SEC in connection with the consummation of this offering.

General

Our certificate of incorporation authorizes our board of directors to issue up to 7,500,000 shares of our preferred stock, par value $.0001 per share. Our board of directors has designated 350,000 of the 7,500,000 authorized shares of preferred stock as Series A Junior Participating Preferred Stock, which series is described in greater detail in the accompanying prospectus.

Subject to the limitations prescribed by our certificate of incorporation, our board of directors is authorized to establish the number of shares constituting each series of preferred stock and to fix the designations, powers, preferences and rights of the shares of each of those series and the qualifications, limitations and restrictions of each of those series, all without any further vote or action by our stockholders. Our Series D Preferred Stock is a series of preferred stock. When issued, the shares of Series D Preferred Stock will be validly issued, fully paid and non-assessable.

Rank

The Series D Preferred Stock will rank

•

senior to all of our common stock;

•

senior to any class or series of our capital stock hereafter created specifically ranking by its terms junior to the Series D Preferred Stock;

•

on parity with any class or series of our capital stock hereafter created specifically ranking by its terms on parity with the Series D Preferred Stock; and

•

junior to any class or series of our capital stock hereafter created specifically ranking by its terms senior to the Series D Preferred Stock,

in each case, as to distributions of assets upon our liquidation, dissolution or winding up whether voluntarily or involuntarily.

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Conversion

Liquidation Preference

Voting Rights

Dividends

Shares of Series D Preferred Stock will not be entitled to receive any dividends, unless and until specifically declared by our board of directors.

Redemption

We are not obligated to redeem or repurchase any shares of Series D Preferred Stock. Shares of Series D Preferred Stock are not otherwise entitled to any redemption rights, or mandatory sinking fund or analogous fund provisions.

The foregoing description of the principal terms of our Series D Convertible Preferred Stock and related Securities Purchase Agreement and Certificate of Designations are a summary only. The complete text of each of the agreements will be filed as exhibits to a Current Report on Form 8-K on or about the date of this prospectus supplement.

LEGAL MATTERS

Selected legal matters with respect to the validity of the common stock and Series D Preferred Stock offered by this prospectus supplement will be passed upon for us by Steven W. Spector, our Senior Vice President, General Counsel and Secretary.

EXPERTS

Our consolidated financial statements, as of and for the year ended December 31, 2010, and management’s assessment of the effectiveness of internal control over financial reporting as of December 31, 2010, have been incorporated by reference herein and in the registration statement in reliance upon the reports of KPMG LLP, independent registered public accounting firm, incorporated by reference herein, and upon the authority of said firm as experts in accounting and auditing. The audit report covering the December 31, 2010 financial statements refers to a change in our method of accounting for certain warrants due to the adoption of a new accounting pronouncement in 2009.

Ernst & Young LLP, independent registered public accounting firm, has audited our consolidated financial statements at December 31, 2009 and for the years ended December 31, 2009 and 2008 included in our Annual Report on Form 10-K for the year ended December 31, 2010, as set forth in their report, which is incorporated by reference in this prospectus and elsewhere in the registration statement. Our financial statements are incorporated by reference in reliance on Ernst & Young LLP’s report, given on their authority as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of common stock we are offering under this prospectus supplement. This prospectus supplement and the accompanying prospectus do not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities we are offering under this prospectus supplement, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement. We also file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy the registration statement, as well as any other material we file with the SEC, at the SEC’s Public Reference Room at 100 F Street, NE, Washington, D.C. 20549. Please call the SEC at 1.800.SEC.0330 for more information on the Public Reference Room. The SEC maintains an Internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, including Arena. The SEC’s Internet site can be found at http://www.sec.gov.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” into this prospectus supplement the information we file with it, which means that we can disclose important information to you by referring you to those documents. Information incorporated by reference is part of this prospectus supplement. Later information filed with the SEC will update and supersede this information. The SEC’s Internet site can be found at http://www.sec.gov.

We incorporate by reference the documents listed below and any future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act until this offering is completed:

•

our Annual Report on Form 10-K for the year ended December 31, 2010 filed with the SEC on March 15, 2011;

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our Quarterly Reports on Form 10-Q for the periods ended March 31, 2011 (filed with the SEC on May 10, 2011), June 30, 2011 (filed with the SEC on August 9, 2011) and September 30, 2011 (filed with the SEC on November 9, 2011);

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our Current Reports on Form 8-K (other than information furnished rather than filed) filed with the SEC on January 25, 2011, January 28, 2011, February 11, 2011, March 4, 2011, March 29, 2011, May 26, 2011, June 14, 2011, June 24, 2011, July 13, 2011, August 2, 2011, August 11, 2011, August 12, 2011, September 13, 2011, October 3, 2011, October 24, 2011, November 8, 2011, December 21, 2011, January 3, 2012 and January 10, 2012;

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the description of our Rights Agreement contained in our registration statement on Form 8-A filed with the SEC on November 5, 2002, as amended on December 30, 2003 and November 16, 2006, including any amendments or reports filed for the purposes of updating this description; and

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the description of our common stock contained in our registration statement on Form 8-A filed with the SEC on July 26, 2000, including any amendments or reports filed for the purposes of updating this description.

You may request a copy of these filings, at no cost, by contacting us at:

Arena Pharmaceuticals, Inc.

Attention: Investor Relations

6166 Nancy Ridge Drive

San Diego, CA 92121

Telephone number: 858.453.7200

In accordance with Section 412 of the Exchange Act, any statement contained in a document incorporated by reference herein shall be deemed modified or superseded to the extent that a statement contained herein or in any other subsequently filed document which also is or is deemed to be incorporated by reference herein modifies or supersedes such statement.

S-13

PROSPECTUS

$50,000,000

LOGO

Arena Pharmaceuticals, Inc.

Common Stock

Preferred Stock

Debt Securities

Warrants

Units

We may, from time to time, offer to sell up to $50,000,000 of any combination of our common stock, preferred stock, debt securities or warrants described in this prospectus, either individually or in units, at prices and on terms described in one or more supplements to this prospectus. We may also offer common stock or preferred stock upon conversion of debt securities, common stock upon conversion of preferred stock, or common stock, preferred stock or debt securities upon the exercise of warrants. We may also authorize one or more free writing prospectus to be provided to you in connection with these offerings.

This prospectus describes some of the general terms that may apply to an offering of our securities. The specific terms and any other information relating to a specific offering will be set forth in a post-effective amendment to the registration statement of which this prospectus is a part, in a supplement to this prospectus, or in a free writing prospectus or may be set forth in one or more documents incorporated by reference in this prospectus. You should read this prospectus, the information incorporated by reference in this prospectus and any applicable prospectus supplement or free writing prospectus carefully before you invest.

Securities may be sold by us to or through underwriters or dealers, directly to purchasers or through agents designated from time to time. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus and in the applicable prospectus supplement. If any underwriters are involved in the sale of any securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable discounts or commissions and over-allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds we expect to receive from such sale will also be set forth in a prospectus supplement.

Our common stock is listed on the NASDAQ Global Select Market under the symbol “ARNA.” On November 21, 2011, the last reported sale price of our common stock on the NASDAQ Global Select Market was $1.34 per share.

Investing in our securities involves a high degree of risk. See “Risk Factors” on page 6 of this prospectus and as updated in our future filings made with the Securities and Exchange Commission that are incorporated by reference into this prospectus.

This prospectus may not be used to offer or sell any securities unless accompanied by a prospectus supplement.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is November 21, 2011.

TABLE OF CONTENTS


	Page
About this Prospectus		i
Summary		1
Risk Factors		6
Forward-Looking Statements		6
Financial Ratios		7
Use of Proceeds		7
Description of Capital Stock		8
Description of Debt Securities		13
Description of Warrants		20
Description of Units		22
Legal Ownership of Securities		24
Plan of Distribution		28
Legal Matters		30
Experts		30
Where You Can Find More Information		30
Incorporation of Certain Information by Reference		30

You should rely only on the information contained in or incorporated by reference into this prospectus or any applicable prospectus supplement or free writing prospectus. We have not authorized anyone to provide you with different information. We are not making an offer to sell or seeking an offer to buy securities under this prospectus or any applicable prospectus supplement or free writing prospectus in any jurisdiction where the offer or sale is not permitted. The information contained in this prospectus, any applicable prospectus supplement or free writing prospectus and the documents incorporated by reference herein and therein are accurate only as of their respective dates, regardless of the time of delivery of this prospectus or any sale of a security.

About this Prospectus

This prospectus is part of a registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or SEC, using a “shelf” registration process. Under this shelf registration statement, we may sell from time to time in one or more offerings up to a total dollar amount of $50,000,000 of common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in units as described in this prospectus. Each time we sell any type or series of securities under this prospectus, we will provide a prospectus supplement that will contain more specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. We may also add, update or change in a prospectus supplement or free writing prospectus any of the information contained in this prospectus or in documents we have incorporated by reference into this prospectus. This prospectus, together with any applicable prospectus supplement or free writing prospectus and the documents incorporated by reference into this prospectus, include all material information relating to this offering. You should carefully read both this prospectus and any applicable prospectus supplement and any related free writing prospectus together with the additional information described under “Where You Can Find More Information” before buying securities in this offering.

Arena Pharmaceuticals^®, Arena^® and our corporate logo are registered service marks of Arena. All other brand names or trademarks appearing in this prospectus are the property of their respective holders. Unless otherwise specified or required by context, references in this prospectus to “Arena Pharmaceuticals,” “Arena,” “we,” “us” and “our” refer to Arena Pharmaceuticals, Inc., and its wholly owned subsidiaries on a consolidated basis.

Summary

The following summary highlights information contained elsewhere in this prospectus or incorporated by reference herein and does not contain all the information that may be important to purchasers of our securities. Prospective purchasers of our securities should review this entire prospectus carefully, including the risks of investing discussed under “Risk Factors” on page 4, the financial statements and related notes, and the information to which we refer you and the information incorporated into this prospectus by reference, for a complete understanding of our business and this offering.

Arena Pharmaceuticals

In December 2009, we submitted a New Drug Application, or NDA, to the US Food and Drug Administration, or FDA, for regulatory approval of lorcaserin. In October 2010, the FDA issued a Complete Response Letter, or CRL, with respect to the lorcaserin NDA. In the CRL, the FDA stated that it completed its review of the NDA and determined that it could not approve the application in its then present form. Our primary focus is working to submit our response to the lorcaserin CRL, and we expect to make such submission around the end of 2011. However, such submission may take longer, depending on the timing and results of our ongoing and planned activities, guidance and feedback from the FDA and the need for any additional activities.

Our wholly owned subsidiary, Arena Pharmaceuticals GmbH, or Arena GmbH, has granted Eisai Inc., or Eisai, exclusive rights to commercialize lorcaserin in the United States and its territories and possessions subject to FDA approval of the lorcaserin NDA, and we are working with Eisai with regard to our studies and other activities in support of our response to the lorcaserin CRL.

We intend to focus our resources on working with Eisai to obtain regulatory approval of lorcaserin in the United States, seeking approval of lorcaserin outside of the United States, and selectively advancing our earlier-stage research and development programs. We are also actively seeking collaborators or other licensing opportunities for our programs.

Our research and development programs also include APD597, APD791 and APD125. All of these candidates are oral drug candidates that we internally discovered. APD597, which targets the GPR119 receptor, is intended for the treatment of type 2 diabetes and has completed a Phase 1 clinical trial program under our former collaboration with Ortho-McNeil-Janssen Pharmaceuticals, Inc. APD791 is an inverse agonist of the serotonin 2A receptor intended for the treatment of arterial thrombosis and other related conditions and has completed Phase 1a and Phase 1b clinical trials. APD125 is a serotonin 2A receptor inverse agonist that we previously studied for insomnia, and has completed Phase 2a and Phase 2b clinical trials. We are not planning to conduct significant development activities, including any additional clinical trials, for any of these programs at this time. We may consider resuming development of such drug candidates in the future depending on the cost of further development, our financial condition and our assessment of their potential.

The Securities We May Offer

We may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants to purchase any of such securities, either individually or in units, with a total value of up to $50,000,000 from time to time under this prospectus at prices and on terms to be determined at the time of any offering. This prospectus provides you with a general description of the securities we may offer. Each time we offer a type or series of securities under this prospectus, we will provide a prospectus supplement that will describe the specific amounts, prices and other important terms of the securities, including, to the extent applicable:

•

designation or classification;

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aggregate principal amount or aggregate offering price;

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maturity;

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original issue discount;

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rates and times of payment of interest or dividends;

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redemption, conversion, exercise, exchange or sinking fund terms;

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ranking;

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restrictive covenants;

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voting or other rights;

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conversion or exchange prices or rates and, if applicable, any provisions for changes to or adjustments in the conversion or exchange prices or rates and in the securities or other property receivable upon conversion or exchange; and

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a discussion of material United States federal income tax considerations.

The prospectus supplement and any related free writing prospectus that we may authorize to be provided to you may also add, update or change information contained in this prospectus or in documents we have incorporated by reference. However, no prospectus supplement or free writing prospectus will offer a security that is not registered and described in this prospectus at the time of the effectiveness of the registration statement of which this prospectus is a part.

This prospectus may not be used to offer or sell securities unless it is accompanied by a prospectus supplement.

We may sell the securities directly to investors or to or through agents, underwriters or dealers. We, and our agents, underwriters or dealers reserve the right to accept or reject all or part of any proposed purchase of securities. If we do offer securities to or through agents, underwriters or dealers, we will include in the applicable prospectus supplement:

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the names of those agents, underwriters or dealers;

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applicable fees, discounts and commissions to be paid to them;

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details regarding over-allotment options, if any; and

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the net proceeds to us.

Common Stock. We may issue shares of our common stock from time to time. Common stockholders are entitled to one vote per share for the election of directors and on all other matters that require common stockholder approval. Holders of our common stock are entitled to share in an equal amount per share in any dividends declared by our board of directors on the common stock and paid out of legally available assets.

Subject to any preferential rights of any outstanding preferred stock, in the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in the assets remaining after payment of liabilities and the liquidation preferences of any outstanding preferred stock. Our common stock does not carry any preemptive rights enabling a holder to subscribe for, or receive shares of, any class of our common stock or any other securities convertible into shares of any class of our common stock, or any redemption rights.

Preferred Stock. We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors will determine the designations, voting powers, preferences and rights of the preferred stock, as well as the qualifications, limitations or restrictions thereof, including dividend rights, conversion rights, preemptive rights, terms of redemption or repurchase, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our common stock or exchangeable for other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we sell any series of preferred stock under this prospectus, we will fix the designations, voting powers, preferences and rights of such series of preferred stock, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock that we are offering before the issuance of the related series of preferred stock. We urge you to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities. We may issue debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in right of payment, to the extent and in the manner described in the instrument governing the debt, to all of our senior indebtedness. Convertible debt securities will be convertible into or exchangeable for our common stock or other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

Any debt securities issued under this prospectus will be issued under one or more documents called indentures, which are contracts between us and a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities. We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of debt securities being offered, as well as the complete indentures that contain the terms of the debt securities. Forms of indentures have been filed as exhibits to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

Warrants. We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. In this prospectus, we have summarized certain general features of the warrants. We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of warrants being offered, as well as any warrant agreements and warrant certificates that contain the terms of the warrants. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, any forms of warrant agreements and forms of warrant certificates containing the terms of the warrants being offered, and any supplemental warrant agreements and forms of warrant certificates containing the terms of the warrants being offered.

Any warrants issued under this prospectus may be evidenced by warrant certificates. Warrants also may be issued under an applicable warrant agreement that we enter into with a warrant agent. We will indicate the name and address of the warrant agent, if applicable, in the prospectus supplement relating to the particular series of warrants being offered.

Units. We may issue, in one or more series, units consisting of common stock, preferred stock, debt securities and/or warrants for the purchase of common stock, preferred stock and/or debt securities in any combination. In this prospectus, we have summarized certain general features of the units. We urge you, however, to read the applicable prospectus supplement (and any free writing prospectus that we may authorize to be provided to you) related to the series of units being offered, as well as any unit agreement that contains the terms of the units. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, any form of unit agreement and any supplemental agreements that describe the terms of the series of units we are offering before the issuance of the related series of units.

Any units issued under this prospectus may be evidenced by unit certificates. Units also may be issued under an applicable unit agreement that we enter into with a unit agent. We will indicate the name and address of the unit agent, if applicable, in the prospectus supplement relating to the particular series of units being offered.

Risk Factors

An investment in our securities involves a high degree of risk. Before you make a decision to invest in our securities, you should consider carefully the risks described in the section entitled “Risk Factors” contained in our quarterly report for the period ended June 30, 2011, as filed with the SEC on August 9, 2011, which is incorporated herein by reference in its entirety, as well as any amendment or update thereto reflected in our subsequent filings with the SEC. If any of these risks actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our common stock, or, if applicable, other securities, to decline and you may lose part or all of your investment. Moreover, the risks described are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business, operating results, prospects or financial condition.

Forward-Looking Statements

This prospectus, including the documents that we incorporate by reference herein, contains, and any applicable prospectus supplement or free writing prospectus including the documents we incorporate by reference therein may contain, “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or Exchange Act. These forward-looking statements can generally be identified as such because the context of the statements will include words such as “may,” “will,” “intend,” “plan,” “believe,” “anticipate,” “expect,” “estimate,” “predict,” “potential,” “continue,” “likely,” or “opportunity,” the negative of these words or similar words. Similarly, statements that describe our future plans, strategies, intentions, expectations, objectives, goals or prospects are also forward-looking statements. Discussions containing these forward-looking statements may be found, among other places, in the “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections incorporated by reference from our most recent annual report on Form 10-K and our quarterly reports on Form 10-Q for the quarters ended subsequent to our filing of such annual report on Form 10-K with the SEC, as well as any amendments thereto reflected in subsequent filings with the SEC. These forward-looking statements are or will be, as applicable, based largely on our expectations, beliefs and projections about future events and future trends affecting our business, and so are or will be, as applicable, subject to risks and uncertainties that could cause actual results to differ materially from those anticipated in the forward-looking statements. The risks and uncertainties include, among others, those referenced in “Risk Factors” above and in any applicable prospectus supplement or free writing prospectus and any documents incorporated by reference herein or therein.

In addition, past financial or operating performance is not necessarily a reliable indicator of future performance and you should not use our historical performance to anticipate results or future period trends. We can give no assurances that any of the events anticipated by the forward-looking statements will occur or, if any of them do, what impact they will have on our results of operations and financial condition. Except as required by law, we undertake no obligation to publicly update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.

Financial Ratios

The following table sets forth, for the periods presented, our ratio of earnings to fixed charges and our ratio of earnings to combined fixed charges and preferred stock dividends. The ratios are prepared on a consolidated basis.

For purposes of computing the ratio of earnings to fixed charges and the ratio of earnings to combined fixed charges and preferred stock dividends, “earnings” consist of loss from continuing operations before income taxes plus fixed charges and amortization of capitalized interest, reduced by interest capitalized during the period. Fixed charges consist of interest expense and an estimate of the interest component of rent expense. In each of the periods presented, earnings were insufficient to cover fixed charges and combined fixed charges and preferred stock dividends.


	Year Ended December 31,															Six Months Ended June 30, 2011
	2006			2007			2008			2009			2010			Six Months Ended June 30, 2011
	(in thousands)
Ratio of earnings to fixed charges		—			—			—			—			—			—
Deficiency of earnings available to cover fixed charges		$ (86,248	)		$ (143,166	)		$ (238,147	)		$ (153,856	)		$ (124,491	)		$ (62,785	)
Ratio of earnings to combined fixed charges and preferred stock dividends		—			—			—			—			—			—
Deficiency of earnings available to cover combined fixed charges and preferred stock dividends		$ (88,279	)		$ (145,280	)		$ (240,059	)		$ (153,856	)		$ (124,491	)		$ (65,045	)

Use of Proceeds

Except as described in any prospectus supplement, we currently intend to use the net proceeds from the sale of securities under this prospectus for the clinical and preclinical development of drug candidates, for discovery research for new drug candidates, for general corporate purposes, including working capital, capital expenditures and debt repayment, and potentially for the commercialization of any approved drugs. In addition, we may use a portion of the net proceeds to acquire drugs or drug candidates, technologies, businesses or other assets that complement our own, although we have no current plans, commitments or agreements to do so as of the date of this prospectus. The timing and amount of our actual expenditures will be based on many factors, including the timing and success of our preclinical and clinical trials, whether we partner any of our internal programs, whether we choose to curtail some of our research activities and whether we achieve regulatory approval of lorcaserin. We will retain broad discretion in determining how we will allocate the net proceeds from the sale of securities under this prospectus.

Description of Capital Stock

As of the date of this prospectus, our amended and restated certificate of incorporation, as amended, authorizes us to issue 242,500,000 shares of common stock, par value $.0001 per share, and 7,500,000 shares of preferred stock, par value $.0001 per share. As of November 4, 2011, 146,024,830 shares of common stock were outstanding. Currently, our board of directors has designated 350,000 of the authorized shares of preferred stock as Series A Junior Participating Preferred Stock (the “Series A Preferred Stock”), which series is described in greater detail below under “Share Purchase Rights Agreement.” As of November 4, 2011, no shares of Series A Preferred Stock were outstanding.

The following summary describes the material terms of our capital stock and stockholder rights plan. The description of capital stock and stockholder rights plan is qualified by reference to our amended and restated certificate of incorporation, our Bylaws, the certificate of designations of our Series A Preferred Stock, and our stockholder rights plan, which are incorporated by reference as exhibits into the registration statement of which this prospectus is a part.

Common Stock

Voting. Common stockholders are entitled to one vote per share for the election of directors and on all other matters that require common stockholder approval.

Dividends and Other Distributions. Holders of our common stock are entitled to share in an equal amount per share in any dividends declared by our board of directors on the common stock and paid out of legally available assets.

Distribution on Dissolution. Subject to any preferential rights of any outstanding preferred stock, in the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in the assets remaining after payment of liabilities and the liquidation preferences of any outstanding preferred stock.

Other Rights. Our common stock does not carry any preemptive rights enabling a holder to subscribe for, or receive shares of, any class of our common stock or any other securities convertible into shares of any class of our common stock, or any redemption rights.

Preferred Stock

Under our amended and restated certificate of incorporation, as amended, our board of directors has the authority, without further action by stockholders, to designate up to 7,500,000 shares of preferred stock in one or more series and to fix the rights, preferences, privileges, qualifications and restrictions granted to or imposed upon the preferred stock, including dividend rights, conversion rights, voting rights, rights and terms of redemption, liquidation preference and sinking fund terms, any or all of which may be greater than the rights of our common stock.

We will fix the designations, voting powers, preferences and rights of the preferred stock of each series we issue under this prospectus, as well as the qualifications, limitations or restrictions thereof, in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering. We will describe in the applicable prospectus supplement the terms of the series of preferred stock being offered, including, to the extent applicable:

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the title and stated value;

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the number of shares we are offering;

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the liquidation preference per share;

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the purchase price;

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the dividend rate, period and payment date and method of calculation for dividends;

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whether dividends will be cumulative or non-cumulative and, if cumulative, the date from which dividends will accumulate;

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the procedures for any auction and remarketing;

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the provisions for a sinking fund;

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the provisions for redemption or repurchase, if applicable, and any restrictions on our ability to exercise those redemption and repurchase rights;

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any listing of the preferred stock on any securities exchange or market;

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whether the preferred stock will be convertible into our common stock, and, if applicable, the conversion price, or how it will be calculated, and the conversion period;

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whether the preferred stock will be exchangeable into debt securities, and, if applicable, the exchange price, or how it will be calculated, and the exchange period;

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voting rights of the preferred stock;

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preemptive rights;

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restrictions on transfer, sale or other assignment;

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whether interests in the preferred stock will be represented by depositary shares;

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a discussion of material United States federal income tax considerations applicable to the preferred stock;

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the relative ranking and preferences of the preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs;

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any limitations on the issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights if we liquidate, dissolve or wind up our affairs; and

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any other specific terms, preferences, rights or limitations of, or restrictions on, the preferred stock.

If we issue shares of preferred stock under this prospectus, the shares will be fully paid and non-assessable.

The issuance of preferred stock could adversely affect the voting power of holders of common stock and reduce the likelihood that common stockholders will receive dividend payments and payments upon liquidation. The issuance could have the effect of decreasing the market price of the common stock. The issuance of preferred stock also could have the effect of delaying, deterring or preventing a change in control of us.

Share Purchase Rights Agreement. Each outstanding share of our common stock has attached to it one preferred share purchase right, which we refer to as a Right. Each Right entitles the registered holder to purchase from us one one-hundredth of a share of Series A Preferred Stock at a price of $36 (the “Purchase Price”), subject to adjustment. The description and terms of the Rights are set forth in a Rights Agreement dated as of October 30, 2002, as amended, between us and Computershare Trust Company, Inc. as Rights Agent, which is incorporated by reference as an exhibit into the registration statement of which this prospectus is a part.

Until the earlier to occur of (i) 10 days following a public announcement that a person or group of affiliated or associated persons (an “Acquiring Person”) have acquired beneficial ownership of 15% or more of our outstanding common stock or (ii) 10 business days (or such later date as may be determined by action of our board of directors prior to such time as any person or group of affiliated persons becomes an Acquiring Person)

following the commencement of, or announcement of an intention to make, a tender offer or exchange offer the consummation of which would result in the beneficial ownership by a person or group of 15% or more of our outstanding common stock (the earlier of such dates being called the “Distribution Date”), the Rights will be evidenced, with respect to any of our common stock certificates outstanding as of November 13, 2002, by such common stock certificate with a copy of the Summary of Rights in the form attached as Exhibit C to the Rights Agreement.

The Rights Agreement provides that none of our directors or officers shall be deemed to beneficially own any of our common stock owned by any other director or officer by virtue of such persons acting in their capacities as such, including, without limitation, in connection with any formulation and publication of our board of directors’ recommendation of its position, and any actions taken in furtherance thereof, with respect to any acquisition proposal relating to Arena, a tender or exchange offer for any of our common stock or any solicitation of proxies with respect to any of our common stock.

The Rights Agreement provides that, until the Distribution Date (or earlier redemption or expiration of the Rights), the Rights will be transferred with and only with our common stock. Until the Distribution Date (or earlier redemption or expiration of the Rights), new common stock certificates issued after November 13, 2002, upon transfer or new issuance of our common stock will contain a notation incorporating the Rights Agreement by reference. Until the Distribution Date (or earlier redemption or expiration of the Rights), the surrender for transfer of any certificates for our common stock outstanding as of November 13, 2002, even without such notation or a copy of the Summary of Rights attached thereto, will also constitute the transfer of the Rights associated with our common stock represented by such certificate. As soon as practicable following the Distribution Date, separate certificates evidencing the Rights (“Right Certificates”) will be mailed to holders of record of our common stock as of the close of business on the Distribution Date and such separate Right Certificates alone will evidence the Rights.

The Rights are not exercisable until the Distribution Date. The Rights will expire on October 30, 2012, (the “Final Expiration Date”), unless the Final Expiration Date is extended or the Rights are earlier redeemed or exchanged by us, in each case, as described below.

The Purchase Price payable, and the number of shares of the Series A Preferred Stock or other securities or property issuable, upon exercise of the Rights are subject to adjustment from time to time to prevent dilution (i) in the event of a stock dividend on, or a subdivision, combination or reclassification of, the Series A Preferred Stock, (ii) upon the grant to holders of the Series A Preferred Stock of certain rights or warrants to subscribe for or purchase Series A Preferred Stock at a price, or securities convertible into Series A Preferred Stock with a conversion price, less than the then current market price of the Series A Preferred Stock or (iii) upon the distribution to holders of the Series A Preferred Stock of evidences of indebtedness or assets (excluding regular periodic cash dividends paid out of earnings or retained earnings or dividends payable in Series A Preferred Stock) or of subscription rights or warrants (other than those referred to above).

The number of outstanding Rights and the number of one one-hundredths of a share of Series A Preferred Stock issuable upon exercise of each Right are also subject to adjustment in the event of a stock split of our common stock or a stock dividend on our common stock payable in our common stock or subdivisions, consolidations or combinations of our common stock occurring, in any such case, prior to the Distribution Date. Series A Preferred Stock purchasable upon exercise of the Rights will not be redeemable. Once issued upon exercise of Rights, each share of Series A Preferred Stock will be entitled to a minimum preferential quarterly dividend payment of $1 per share but will be entitled to an aggregate dividend of 100 times the dividend declared per share of our common stock. In the event of liquidation, the holders of outstanding shares of Series A Preferred Stock will be entitled to a minimum preferential liquidation payment of $100 per share but will be entitled to an aggregate payment of 100 times the payment made per share of our common stock. Each outstanding share of Series A Preferred Stock will have 100 votes, voting together with our common stock. Finally, in the event of any merger, consolidation or other transaction in which our common stock is exchanged, each outstanding share of Series A Preferred Stock will be entitled to receive 100 times the amount received per share of our common stock. These rights are protected by customary antidilution provisions.

Because of the nature of the Series A Preferred Stock’s dividend, liquidation and voting rights, the value of the one one-hundredth interest in a share of Series A Preferred Stock purchasable upon exercise of each Right should approximate the value of one share of our common stock.

In the event that any person or group of affiliated or associated persons becomes an Acquiring Person, the Rights Agreement provides that proper provision shall be made so that each holder of a Right, other than Rights beneficially owned by the Acquiring Person (which will thereafter be void), will thereafter have the right to receive (subject to adjustment) upon exercise thereof at the then current Purchase Price, that number of shares of our common stock having a market value of two times the Purchase Price. At any time after any person or group becomes an Acquiring Person and prior to the acquisition by such person or group of 50% or more of our outstanding common stock, our board of directors may exchange the Rights (other than Rights owned by such person or group, which will have become void), in whole or in part, at an exchange ratio of one share of our common stock, or one one-hundredth of a share of Series A Preferred Stock (or of a share of a class or series of our preferred stock having equivalent rights, preferences and privileges), per Right (subject to adjustment).

In the event that we are acquired in a merger or other business combination transaction or 50% or more of our consolidated assets or earning power are sold after a person or group has become an Acquiring Person, proper provision will be made so that each holder of a Right will thereafter have the right to receive, upon the exercise thereof at the then current Purchase Price, that number of shares of common stock of the acquiring company which at the time of such transaction will have a market value of two times the Purchase Price.

With certain exceptions, no adjustment in the Purchase Price will be required until cumulative adjustments require an adjustment of at least 1% in the Purchase Price. No fractional shares of Series A Preferred Stock will be issued (other than fractions which are integral multiples of one one-hundredth of a share of Series A Preferred Stock, which may, at our election, be evidenced by depositary receipts) and in lieu thereof, an adjustment in cash will be made based on the market price of the Series A Preferred Stock on the last trading day prior to the date of exercise.

At any time prior to the acquisition by a person or group of affiliated or associated persons of beneficial ownership of 15% or more of our outstanding common stock, our board of directors may redeem the Rights in whole, but not in part, at a price of $.01 per Right (the “Redemption Price”). The redemption of the Rights may be made effective at such time on such basis with such conditions as our board of directors in its sole discretion may establish.

The terms of the Rights may be amended by our board of directors without the consent of the holders of the Rights, including an amendment to (i) fix a Final Expiration Date later than October 30, 2012, (ii) reduce the Redemption Price or (iii) increase the Purchase Price, except that from and after such time as any person or group of affiliated or associated persons becomes an Acquiring Person no such amendment may adversely affect the interests of the holders of the Rights (other than the Acquiring Person and its affiliates and associates).

Until a Right is exercised, the holder thereof, as such, will have no rights as a stockholder of Arena, including, without limitation, the right to vote or to receive dividends.

Anti-Takeover Provisions

Delaware Law. We are governed by the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a publicly held Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years after the date of the transaction in which the person became an interested stockholder, unless (i) before the date that the person became an “interested stockholder,” our board of directors approved either the “business combination” or the transaction which makes the person an “interested stockholder,” (ii) the “interested stockholder” owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the number of shares outstanding (a) shares owned by persons who are directors and also officers and (b) shares owned by employee stock plans in which employee participants do not have the right

to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer, or (iii) after the date that the person became an “interested stockholder,” the business combination is approved by our board of directors and the vote of at least 66 2/3% of our outstanding voting stock that is not owned by the “interested stockholder.” Generally, a “business combination” includes (A) any merger or consolidation involving the corporation and the interested stockholder, (B) any sale, transfer, pledge or other disposition involving the interested stockholder of 10% or more of the assets of the corporation; (C) subject to exceptions, any transaction that results in the issuance or transfer by the corporation of any stock of the corporation to the interested stockholder; (D) any transaction involving the corporation that has the effect of increasing the proportionate share of its stock owned by the interested stockholder; or (E) the receipt by the interested stockholder of the benefit of any loans, advances, guarantees, pledges or other financial benefits provided by or through the corporation. An “interested stockholder” is a person who either owns 15% or more of our outstanding voting stock or, together with affiliates and associates, owns or, within three prior years, did own, 15% or more of our outstanding voting stock. The statute could have the effect of delaying, deferring or preventing a change in our control.

Bylaw and Certificate of Incorporation Provisions. Our bylaws provide that special meetings of our stockholders may be called by our board of directors or President. Our amended and restated certificate of incorporation (i) specifies that the authorized number of directors shall be fixed by our board of directors in the manner provided by our bylaws, which provide that the number of directors constituting our board of directors shall be fixed from time to time by resolution passed by a majority of our board of directors and (ii) does not include a provision for cumulative voting for directors. Under cumulative voting, a minority stockholder holding a sufficient percentage of a class of shares may be able to ensure the election of one or more directors. These and other provisions contained in our amended and restated certificate of incorporation and bylaws could delay or discourage transactions involving an actual or potential change in control of us or our management, including transactions in which stockholders might otherwise receive a premium for their shares over then current prices. Such provisions could also limit the ability of stockholders to remove current management or approve transactions that stockholders may deem to be in their best interests and could adversely affect the price of our common stock or, if applicable, other securities.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Computershare Trust Company, N.A.

Listing on the NASDAQ Global Select Market

Our common stock is listed on the NASDAQ Global Select Market under the symbol “ARNA.”

Description of Debt Securities

We may issue debt securities, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. While the terms we have summarized below will apply generally to any debt securities that we may offer under this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. The terms of any debt securities offered under a prospectus supplement may differ from the terms described below. Unless the context requires otherwise, whenever we refer to the indentures, we also are referring to any supplemental indentures that specify the terms of a particular series of debt securities.

If we issue debt securities under this prospectus, we will issue the senior debt securities under the senior indenture that we will enter into with the trustee named in the senior indenture, and we will issue the subordinated debt securities under the subordinated indenture that we will enter into with the trustee named in the subordinated indenture. The indentures will be qualified under the Trust Indenture Act of 1939. We use the term “debenture trustee” to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable. We have filed forms of indentures to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from reports that we file with the SEC.

The following summaries of material provisions of the senior debt securities, the subordinated debt securities and the indentures are subject to, and qualified in their entirety by reference to, all of the provisions of the indenture applicable to a particular series of debt securities. We urge you to read the applicable prospectus supplements and any related free writing prospectuses related to the debt securities that we may offer under this prospectus, as well as the complete indentures that contain the terms of the debt securities. Except as we may otherwise indicate, the terms of the senior indenture and the subordinated indenture are identical.

General

We will describe in the applicable prospectus supplement the terms of the series of debt securities being offered, including, to the extent applicable:

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the title;

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the principal amount being offered, and if a series, the total amount authorized and the total amount outstanding;

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any limit on the amount that may be issued;

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whether or not we will issue the series of debt securities in global form, the terms and who the depositary will be;

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the maturity date;

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whether and under what circumstances we will pay additional amounts on any debt securities held by a person who is not a United States person for tax purposes, and whether we can redeem the debt securities if we have to pay such additional amounts;

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the annual interest rate, which may be fixed or variable, or the method for determining the rate and the date interest will begin to accrue, the dates interest will be payable and the regular record dates for interest payment dates or the method for determining such dates;

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whether or not the debt securities will be secured or unsecured, and the terms of any secured debt;

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the terms of the subordination of any series of subordinated debt;

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the place where payments will be payable;

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restrictions on transfer, sale or other assignment;

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our right to defer payment of interest and the maximum length of any such deferral period;

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the date after which, and the price at which, we may, at our option, redeem the series of debt securities pursuant to any optional or provisional redemption provisions and the terms of those redemption provisions;

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the date on which, and the price at which we are obligated, pursuant to any mandatory sinking fund or analogous fund provisions or otherwise, to redeem, or at the holder’s option to purchase, the series of debt securities and the currency or currency unit in which the debt securities are payable;

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whether the indenture will restrict our ability and/or the ability of our subsidiaries to:

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incur additional indebtedness;

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issue additional securities;

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create liens;

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pay dividends and make distributions in respect of our capital stock and the capital stock of our subsidiaries;

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redeem capital stock;

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place restrictions on our subsidiaries’ ability to pay dividends, make distributions or transfer assets;

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make investments or other restricted payments;

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sell or otherwise dispose of assets;

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enter into sale-leaseback transactions;

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engage in transactions with stockholders and affiliates;

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issue or sell stock of our subsidiaries; or

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effect a consolidation or merger;

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whether the indenture will require us to maintain any interest coverage, fixed charge, cash flow-based, asset-based or other financial ratios;

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a discussion of material United States federal income tax considerations applicable to the debt securities;

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information describing any book-entry features;

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provisions for a sinking fund purchase or other analogous fund;

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the applicability of the provisions in the indenture on discharge;

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whether the debt securities are to be offered at a price such that they will be deemed to be offered at an “original issue discount” as defined in paragraph (a) of Section 1273 of the Internal Revenue Code;

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the denominations in which we will issue the series of debt securities, if other than denominations of $1,000 and any integral multiple thereof;

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the currency of payment of debt securities if other than U.S. dollars and the manner of determining the equivalent amount in U.S. dollars; and

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any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities, including any additional events of default or covenants provided with respect to the debt securities, and any terms that may be required by us or advisable under applicable laws or regulations.

Conversion or Exchange Rights

We will set forth in the prospectus supplement the terms on which a series of debt securities may be convertible into or exchangeable for our common stock or our other securities, if applicable. We will include provisions as to whether conversion or exchange is mandatory, at the option of the holder or at our option. We may include provisions pursuant to which the number of shares of our common stock or our other securities that the holders of the series of debt securities receive would be subject to adjustment.

Consolidation, Merger or Sale

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the indentures will not contain any covenant that restricts our ability to merge or consolidate, or sell, convey, transfer or otherwise dispose of all or substantially all of our assets. However, any successor to or acquirer of such assets must assume all of our obligations under the indentures or the debt securities, as appropriate. If the debt securities are convertible into or exchangeable for our other securities or securities of other entities, the person with whom we consolidate or merge or to whom we sell all of our property must make provisions for the conversion of the debt securities into securities that the holders of the debt securities would have received if they had converted the debt securities before the consolidation, merger or sale.

Events of Default Under the Indenture

Unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, the following are events of default under the indentures with respect to any series of debt securities that we may issue:

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if we fail to pay interest when due and payable and our failure continues for 90 days and the time for payment has not been extended or deferred;

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if we fail to pay the principal, premium or sinking fund payment, if any, when due and payable and the time for payment has not been extended or delayed;

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if we fail to observe or perform any other covenant contained in the debt securities or the indentures, other than a covenant specifically relating to another series of debt securities, and our failure continues for 90 days after we receive notice from the debenture trustee or holders of at least a majority in aggregate principal amount of the outstanding debt securities of the applicable series; and

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if specified events of bankruptcy, insolvency or reorganization occur.

If an event of default with respect to debt securities of any series occurs and is continuing, other than an event of default specified in the last bullet point above, the debenture trustee or the holders of at least a majority in aggregate principal amount of the outstanding debt securities of that series, by notice to us in writing, and to the debenture trustee if notice is given by such holders, may declare the unpaid principal of, premium, if any, and accrued interest, if any, due and payable immediately. If an event of default specified in the last bullet point above occurs with respect to us, the principal amount of and accrued interest, if any, of each issue of debt securities then outstanding shall be due and payable without any notice or other action on the part of the debenture trustee or any holder.

The holders of a majority in principal amount of the outstanding debt securities of an affected series may waive any default or event of default with respect to the series and its consequences, except defaults or events of default regarding payment of principal, premium, if any, or interest, unless we have cured the default or event of default in accordance with the indenture. Any waiver shall cure the default or event of default.

Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the debenture trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such

holders have offered the debenture trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the debenture trustee, or exercising any trust or power conferred on the debenture trustee, with respect to the debt securities of that series, provided that:

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the direction so given by the holder is not in conflict with any law or the applicable indenture; and

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subject to its duties under the Trust Indenture Act of 1939, the debenture trustee need not take any action that might involve it in personal liability or might be unduly prejudicial to the holders not involved in the proceeding.

A holder of the debt securities of any series will have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies only if:

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the holder has given written notice to the debenture trustee of a continuing event of default with respect to that series;

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the holders of at least a majority in aggregate principal amount of the outstanding debt securities of that series have made written request, and such holders have offered reasonable indemnity to the debenture trustee to institute the proceeding as trustee; and

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the debenture trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series other conflicting directions within 90 days after the notice, request and offer.

These limitations do not apply to a suit instituted by a holder of debt securities if we default in the payment of the principal, premium, if any, or interest on, the debt securities.

We will periodically file statements with the debenture trustee regarding our compliance with specified covenants in the indentures.

Modification of Indenture; Waiver

We and the debenture trustee may change an indenture without the consent of any holders with respect to specific matters:

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to fix any ambiguity, defect or inconsistency in the indenture;

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to comply with the provisions described above under “Description of Debt Securities—Consolidation, Merger or Sale”;

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to comply with any requirements of the SEC in connection with the qualification of any indenture under the Trust Indenture Act of 1939;

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to add to, delete from or revise the conditions, limitations, and restrictions on the authorized amount, terms, or purposes of issue, authentication and delivery of debt securities, as set forth in the indenture;

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to provide for the issuance of and establish the form and terms and conditions of the debt securities of any series as provided under “Description of Debt Securities—General” to establish the form of any certifications required to be furnished pursuant to the terms of the indenture or any series of debt securities, or to add to the rights of the holders of any series of debt securities;

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to evidence and provide for the acceptance of appointment hereunder by a successor trustee;

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to provide for uncertificated debt securities in addition to or in place of certificated debt securities and to make all appropriate changes for such purpose;

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to add to our covenants such new covenants, restrictions, conditions or provisions for the protection of the holders, and to make the occurrence, or the occurrence and the continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default; or

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to change anything that does not materially adversely affect the interests of any holder of debt securities of any series.

In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series that is affected. However, unless we provide otherwise in the prospectus supplement applicable to a particular series of debt securities, we and the debenture trustee may make the following changes only with the consent of each holder of any outstanding debt securities affected:

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extending the fixed maturity of the series of debt securities;

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reducing the principal amount, reducing the rate of or extending the time of payment of interest, or reducing any premium payable upon the redemption of any debt securities; or

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reducing the percentage of debt securities, the holders of which are required to consent to any amendment, supplement, modification or waiver.

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities. Notwithstanding the foregoing, we cannot be discharged from certain specified obligations, including obligations to:

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replace stolen, lost or mutilated debt securities of the series;

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maintain paying agencies;

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hold monies for payment in trust;

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recover excess money held by the debenture trustee;

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compensate and indemnify the debenture trustee; and

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appoint any successor trustee.

In order to exercise our rights to be discharged, we must deposit with the debenture trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange and Transfer

We will issue each series of debt securities only in fully registered form without coupons and, unless we provide otherwise in the applicable prospectus supplement, in denominations of $1,000 and any integral multiple thereof. The indentures provide that we may issue debt securities of a series in temporary or permanent global form and as book-entry securities that will be deposited with, or on behalf of, The Depository Trust Company, or DTC, or another depositary named by us and identified in a prospectus supplement with respect to that series. See “Legal Ownership of Securities” for a further description of the terms relating to any book-entry securities.

At the option of the holder, subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, the holder of the debt securities of any series can exchange the debt securities for other debt securities of the same series, in any authorized denomination and of like tenor and aggregate principal amount.

Subject to the terms of the indentures and the limitations applicable to global securities described in the applicable prospectus supplement, holders of the debt securities may present the debt securities for exchange or for registration of transfer, duly endorsed or with the form of transfer endorsed thereon duly executed if so required by us or the security registrar, at the office of the security registrar or at the office of any transfer agent designated by us for this purpose. Unless otherwise provided in the debt securities that the holder presents for transfer or exchange, we will impose no service charge for any registration of transfer or exchange, but we may require payment of any taxes or other governmental charges.

We will name in the applicable prospectus supplement the security registrar, and any transfer agent in addition to the security registrar, that we initially designate for any debt securities. We may at any time designate additional transfer agents or rescind the designation of any transfer agent or approve a change in the office through which any transfer agent acts, except that we will be required to maintain a transfer agent in each place of payment for the debt securities of each series.

If we elect to redeem the debt securities of any series, we will not be required to:

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issue, register the transfer of, or exchange any debt securities of that series during a period beginning at the opening of business 15 days before the day of mailing of a notice of redemption of any debt securities that may be selected for redemption and ending at the close of business on the day of the mailing; or

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register the transfer of or exchange any debt securities so selected for redemption, in whole or in part, except the unredeemed portion of any debt securities we are redeeming in part.

Information Concerning the Debenture Trustee

The debenture trustee, other than during the occurrence and continuance of an event of default under an indenture, undertakes to perform only those duties as are specifically set forth in the applicable indenture. Upon an event of default under an indenture, the debenture trustee must use the same degree of care as a prudent person would exercise or use in the conduct of his or her own affairs. Subject to this provision, the debenture trustee is under no obligation to exercise any of the powers given it by the indentures at the request of any holder of debt securities unless it is offered reasonable security and indemnity against the costs, expenses and liabilities that it might incur.

Payment and Paying Agents

Unless we otherwise indicate in the applicable prospectus supplement, we will make payment of the interest on any debt securities on any interest payment date to the person in whose name the debt securities, or one or more predecessor securities, are registered at the close of business on the regular record date for the interest.

We will pay principal of and any premium and interest on the debt securities of a particular series at the office of the paying agents designated by us, except that unless we otherwise indicate in the applicable prospectus supplement, we will make interest payments by check that we will mail to the holder or by wire transfer to certain holders. Unless we otherwise indicate in the applicable prospectus supplement, we will designate the corporate trust office of the debenture trustee in the City of New York as our sole paying agent for payments with respect to debt securities of each series. We will name in the applicable prospectus supplement any other paying agents that we initially designate for the debt securities of a particular series. We will maintain a paying agent in each place of payment for the debt securities of a particular series.

All money we pay to a paying agent or the debenture trustee for the payment of the principal of or any premium or interest on any debt securities that remains unclaimed at the end of two years after such principal, premium or interest has become due and payable will be repaid to us, and the holder of the debt security thereafter may look only to us for payment thereof.

Governing Law

The indentures and the debt securities will be governed by and construed in accordance with the laws of the State of New York, except to the extent that the Trust Indenture Act of 1939 is applicable.

Subordination of Subordinated Debt Securities

The subordinated debt securities will be unsecured and will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. The subordinated indenture does not limit the amount of subordinated debt securities that we may issue, nor does it limit us from issuing any other secured or unsecured debt.

Description of Warrants

We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. While the terms summarized below will apply generally to any warrants that we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. The terms of any warrants offered under a prospectus supplement may differ from the terms described below.

Warrants issued under this prospectus may be issued under warrant agreements which we will enter into with a warrant agent to be selected by us. We use the term “warrant agreement” to refer to any of these warrant agreements. We use the term “warrant agent” to refer to the warrant agent under any of these warrant agreements. The warrant agent will act solely as an agent of ours in connection with the warrants and will not act as an agent for the holders or beneficial owners of the warrants.

The following summaries of material provisions of the warrants and the warrant agreements are subject to, and qualified in their entirety by reference to, all the provisions of the warrant agreement applicable to a particular series of warrants. We urge you to read the applicable prospectus supplements or free writing prospectus related to the warrants that we sell under this prospectus, as well as the complete warrant agreements that contain the terms of the warrants.

General

We will describe in the applicable prospectus supplement the terms of the series of warrants being offered, including, to the extent applicable:

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the offering price and aggregate number of warrants offered;

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the currency for which the warrants may be purchased;

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the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;

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the date on and after which the warrants and the related securities will be separately transferable;

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in the case of warrants to purchase debt securities, the principal amount of debt securities purchasable upon exercise of one warrant and the price at, and currency in which, this principal amount of debt securities may be purchased upon such exercise;

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in the case of warrants to purchase common stock or preferred stock, the number of shares of common stock or preferred stock, as the case may be, purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;

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the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreements and the warrants;

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the terms of any rights to redeem or call the warrants;

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any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;

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the dates on which the right to exercise the warrants will commence and expire;

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the manner in which the warrant agreements and warrants may be modified;

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a discussion of material United States federal income tax consequences of holding or exercising the warrants;

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the terms of the securities issuable upon exercise of the warrants; and

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any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

Before exercising their warrants, holders of warrants will not have any of the rights of holders of the securities purchasable upon such exercise, including:

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in the case of warrants to purchase debt securities, the right to receive payments of principal of, or premium, if any, or interest on, the debt securities purchasable upon exercise or to enforce covenants in the applicable indenture; or

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in the case of warrants to purchase common stock or preferred stock, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Exercise of Warrants

Each warrant will entitle the holder to purchase the securities that we specify in the applicable prospectus supplement at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to the specified time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Holders of the warrants may exercise the warrants by delivering the warrant or warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent, if applicable, in immediately available funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of any warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to any warrant agent.

Upon receipt of the required payment and any warrant certificate properly completed and duly executed at the corporate trust office of any warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the securities purchasable upon such exercise. If fewer than all of the warrants represented by a warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Governing Law

Unless we provide otherwise in the applicable prospectus supplement, the warrants and warrant agreements will be governed by and construed in accordance with the laws of the State of New York.

Enforceability of Rights by Holders of Warrants

Any warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of any related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

Description of Units

We may issue, in one more series, units consisting of common stock, preferred stock, debt securities and/or warrants for the purchase of common stock, preferred stock and/or debt securities in any combination. While the terms we have summarized below will apply generally to any units that we may offer under this prospectus, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement. The terms of any units offered under a prospectus supplement may differ from the terms described below.

We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from reports that we file with the SEC, any form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements. The following summaries of material terms and provisions of the units are subject to, and qualified in their entirety by reference to, all the provisions of any unit agreement and any supplemental agreements applicable to a particular series of units. We urge you to read the applicable prospectus supplements related to the particular series of units that we may offer under this prospectus, as well as any related free writing prospectuses and any unit agreement and any supplemental agreements that contain the terms of the units.

General

Each unit will be issued so that the holder of the unit is also the holder of each security included in the unit. Thus, the holder of a unit will have the rights and obligations of a holder of each included security. Any unit agreement under which a unit is issued may provide that the securities included in the unit may not be held or transferred separately, at any time or at any time before a specified date.

We will describe in the applicable prospectus supplement the terms of the series of units being offered, including, to the extent applicable:

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the designation and terms of the units and of the securities comprising the units, including whether and under what circumstances those securities may be held or transferred separately;

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any provisions of the governing unit agreement that differ from those described below; and

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any provisions for the issuance, payment, settlement, transfer or exchange of the units or of the securities comprising the units.

The provisions described in this section, as well as those described under “Description of Capital Stock,” “Description of Debt Securities” and “Description of Warrants” will apply to each unit and to any common stock, preferred stock, debt security or warrant included in each unit, respectively.

Issuance in Series

We may issue units in such amounts and in such numerous distinct series as we determine.

Enforceability of Rights by Holders of Units

Any unit agent will act solely as our agent under the applicable unit agreement and will not assume any obligation or relationship of agency or trust with any holder of any unit. A single bank or trust company may act as unit agent for more than one series of units. A unit agent will have no duty or responsibility in case of any default by us under the applicable unit agreement or unit, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a unit may, without the consent of any related unit agent or the holder of any other unit, enforce by appropriate legal action its rights as holder under any security included in the unit.

Title

We, and any unit agent and any of their agents, may treat the registered holder of any unit certificate as an absolute owner of the units evidenced by that certificate for any purpose and as the person entitled to exercise the rights attaching to the units so requested, despite any notice to the contrary. See “Legal Ownership of Securities” below.

Legal Ownership of Securities

We can issue securities in registered form or in the form of one or more global securities. We describe global securities in greater detail below. We refer to those persons who have securities registered in their own names on the books that we or any applicable trustee, depositary or warrant agent maintain for this purpose as the “holders” of those securities. These persons are the legal holders of the securities. We refer to those persons who, indirectly through others, own beneficial interests in securities that are not registered in their own names, as “indirect holders” of those securities. As we discuss below, indirect holders are not legal holders, and investors in securities issued in book-entry form or in street name will be indirect holders.

Book-Entry Holders

We may issue securities in book-entry form only, as we will specify in the applicable prospectus supplement. This means securities may be represented by one or more global securities registered in the name of a financial institution that holds them as depositary on behalf of other financial institutions that participate in the depositary’s book-entry system. These participating institutions, which are referred to as participants, in turn, hold beneficial interests in the securities on behalf of themselves or their customers.

Only the person in whose name a security is registered is recognized as the holder of that security. Securities issued in global form will be registered in the name of the depositary or its participants. Consequently, for securities issued in global form, we will recognize only the depositary as the holder of the securities, and we will make all payments on the securities to the depositary. The depositary passes along the payments it receives to its participants, which in turn pass the payments along to their customers who are the beneficial owners. The depositary and its participants do so under agreements they have made with one another or with their customers; they are not obligated to do so under the terms of the securities.

As a result, investors in a book-entry security will not own securities directly. Instead, they will own beneficial interests in a global security, through a bank, broker or other financial institution that participates in the depositary’s book-entry system or holds an interest through a participant. As long as the securities are issued in global form, investors will be indirect holders, and not holders, of the securities.

Street Name Holders

We may terminate a global security or issue securities in non-global form. In these cases, investors may choose to hold their securities in their own names or in “street name.” Securities held by an investor in street name would be registered in the name of a bank, broker or other financial institution that the investor chooses, and the investor would hold only a beneficial interest in those securities through an account he or she maintains at that institution.

For securities held in street name, we will recognize only the intermediary banks, brokers and other financial institutions in whose names the securities are registered as the holders of those securities, and we will make all payments on those securities to them. These institutions pass along the payments they receive to their customers who are the beneficial owners, but only because they agree to do so in their customer agreements or because they are legally required to do so. Investors who hold securities in street name will be indirect holders, not holders, of those securities.

Legal Holders

Our obligations, as well as the obligations of any applicable trustee and of any third parties employed by us or a trustee, run only to the legal holders of the securities. We do not have obligations to investors who hold beneficial interests in global securities, in street name or by any other indirect means. This will be the case whether an investor chooses to be an indirect holder of a security or has no choice because we are issuing the securities only in global form.

For example, once we make a payment or give a notice to the holder, we have no further responsibility for the payment or notice even if that holder is required, under agreements with depositary participants or

customers or by law, to pass it along to the indirect holders but does not do so. Similarly, we may want to obtain the approval of the holders to amend an indenture, to relieve us of the consequences of a default or of our obligation to comply with a particular provision of the indenture or for other purposes. In such an event, we would seek approval only from the holders, and not the indirect holders, of the securities. Whether and how the holders contact the indirect holders is up to the holders.

Special Considerations For Indirect Holders

If you hold securities through a bank, broker or other financial institution, either in book-entry form or in street name, you should check with your own institution to find out:

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how it handles securities payments and notices;

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whether it imposes fees or charges;

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how it would handle a request for the holders’ consent, if ever required;

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whether and how you can instruct it to send you securities registered in your own name so you can be a holder, if that is permitted in the future;

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how it would exercise rights under the securities if there were a default or other event triggering the need for holders to act to protect their interests; and

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if the securities are in book-entry form, how the depositary’s rules and procedures will affect these matters.

Global Securities

A global security is a security that represents one or any other number of individual securities held by a depositary. Generally, all securities represented by the same global securities will have the same terms.

Each security issued in book-entry form will be represented by a global security that we deposit with and register in the name of a financial institution or its nominee that we select. The financial institution that we select for this purpose is called the depositary. Unless we specify otherwise in the applicable prospectus supplement, DTC will be the depositary for all securities issued in book-entry form.

A global security may not be transferred to or registered in the name of anyone other than the depositary, its nominee or a successor depositary, unless special termination situations arise. We describe those situations below under “Special Situations When a Global Security Will Be Terminated.” As a result of these arrangements, the depositary, or its nominee, will be the sole registered owner and holder of all securities represented by a global security, and investors will be permitted to own only beneficial interests in a global security. Beneficial interests must be held by means of an account with a broker, bank or other financial institution that in turn has an account with the depositary or with another institution that does. Thus, an investor whose security is represented by a global security will not be a holder of the security, but only an indirect holder of a beneficial interest in the global security.

If the prospectus supplement for a particular security indicates that the security will be issued in global form only, then the security will be represented by a global security at all times unless and until the global security is terminated. If termination occurs, we may issue the securities through another book-entry clearing system or decide that the securities may no longer be held through any book-entry clearing system.

Special Considerations For Global Securities

The rights of an indirect holder relating to a global security will be governed by the account rules of the investor’s financial institution and of the depositary, as well as general laws relating to securities transfers. We do not recognize an indirect holder as a holder of securities and instead deal only with the depositary that holds the global security.

If securities are issued only in the form of a global security, an investor should be aware of the following:

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an investor cannot cause the securities to be registered in his or her name, and cannot obtain non-global certificates for his or her interest in the securities, except in the special situations we describe below;

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an investor will be an indirect holder and must look to his or her own bank, broker or other financial institution for payments on the securities and protection of his or her legal rights relating to the securities, as we describe above;

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an investor may not be able to sell interests in the securities to some insurance companies and to other institutions that are required by law to own their securities in non-book-entry form;

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an investor may not be able to pledge his or her interest in a global security in circumstances where certificates representing the securities must be delivered to the lender or other beneficiary of the pledge in order for the pledge to be effective;

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the depositary’s policies, which may change from time to time, will govern payments, transfers, exchanges and other matters relating to an investor’s interest in a global security;

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we and any applicable trustee have no responsibility for any aspect of the depositary’s actions or for its records of ownership interests in a global security, nor do we or any applicable trustee supervise the depositary in any way;

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the depositary may, and we understand that DTC will, require that those who purchase and sell interests in a global security within its book-entry system use immediately available funds, and your bank, broker or other financial institution may require you to do so as well; and

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financial institutions that participate in the depositary’s book-entry system, and through which an investor holds its interest in a global security, may also have their own policies affecting payments, notices and other matters relating to the securities.

There may be more than one financial intermediary in the chain of ownership for an investor. We do not monitor and are not responsible for the actions of any of those intermediaries.

Special Situations When a Global Security Will Be Terminated

In a few special situations described below, the global security will terminate and interests in it will be exchanged for physical certificates representing those interests. After that exchange, the choice of whether to hold securities directly or in street name will be up to the investor. Investors must consult their own banks, brokers or other financial institutions to find out how to have their interests in securities transferred to their own name, so that they will be direct holders. We have described the rights of holders and street name investors above.

Unless we provide otherwise in the applicable prospectus supplement, the global security will terminate when the following special situations occur:

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if the depositary notifies us that it is unwilling, unable or no longer qualified to continue as depositary for that global security and we do not appoint another institution to act as depositary within 90 days;

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if we notify any applicable trustee that we wish to terminate that global security; or

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if an event of default has occurred with regard to securities represented by that global security and has not been cured or waived.

The prospectus supplement may also list additional situations for terminating a global security that would apply only to the particular series of securities covered by the applicable prospectus supplement. When a global security terminates, the depositary, and not we or any applicable trustee, is responsible for deciding the names of the institutions that will be the initial direct holders.

Plan of Distribution

We may sell our securities covered by this prospectus in any of three ways (or in any combination):

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to or through underwriters or dealers;

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directly to one or more purchasers; or

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through agents.

We may distribute the securities:

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from time to time in one or more transactions at a fixed price or prices, which may be changed from time to time;

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at market prices prevailing at the time of sale;

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at prices related to the prevailing market prices; or

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at negotiated prices.

Each time we offer and sell securities covered by this prospectus, we will provide a prospectus supplement or supplements that will describe the method of distribution and set forth the terms of the offering, including:

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the name or names of any underwriters, dealers or agents;

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the amounts of securities underwritten or purchased by each of them;

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the purchase price of securities and the proceeds we will receive from the sale;

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any over-allotment options under which underwriters may purchase additional securities from us;

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any underwriting discounts or commissions or agency fees and other items constituting underwriters’ or agents’ compensation;

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the public offering price of the securities;

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any discounts, commissions or concessions allowed or reallowed or paid to dealers; and

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any securities exchange or market on which the securities may be listed.

Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may be changed from time to time. We may determine the price or other terms of the securities offered under this prospectus by use of an electronic auction. We will describe how any auction will determine the price or any other terms, how potential investors may participate in the auction and the nature of the obligations of the underwriter, dealer or agent in the applicable prospectus supplement.

Underwriters or dealers may offer and sell the offered securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. If underwriters or dealers are used in the sale of any securities, the securities will be acquired by the underwriters or dealers for their own account and may be resold from time to time in one or more transactions described above. The securities may be either offered to the public through underwriting syndicates represented by managing underwriters, or directly by underwriters or dealers. Generally, the underwriters’ or dealers’ obligations to purchase the securities will be subject to certain conditions precedent. The underwriters or dealers will be obligated to purchase all of the securities if they purchase any of the securities, unless otherwise specified in the prospectus supplement. We may use underwriters with whom we have a material relationship. We will describe the nature of any such relationship in the prospectus supplement, naming the underwriter.

We may sell the securities through agents from time to time. The prospectus supplement will name any agent involved in the offer or sale of the securities and any commissions we pay to them. Generally, any agent will be acting on a best efforts basis for the period of its appointment. We may authorize underwriters, dealers or

agents to solicit offers by certain purchasers to purchase the securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. The contracts will be subject only to those conditions set forth in the prospectus supplement, and the prospectus supplement will set forth any commissions we pay for solicitation of these contracts.

Agents, dealers and underwriters may be entitled to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, or to contribution with respect to payments which the agents, dealers or underwriters may be required to make in respect thereof. Agents, dealers and underwriters may be customers of, engage in transactions with, or perform services for us in the ordinary course of business.

All securities we may offer, other than common stock, will be new issues of securities with no established trading market. Any underwriters may make a market in these securities, but will not be obligated to do so and may discontinue any market making at any time without notice. We cannot guarantee the liquidity of the trading markets for any securities.

Any underwriter may engage in overallotment, stabilizing transactions, short covering transactions and penalty bids in accordance with Regulation M under the Exchange Act. Overallotment involves sales in excess of the offering size, which create a short position. This short sales position may involve either “covered” short sales or “naked” short sales. Covered short sales are short sales made in an amount not greater than the underwriters’ over-allotment option to purchase additional securities in this offering described above. The underwriters may close out any covered short position either by exercising their over-allotment option or by purchasing securities in the open market. To determine how they will close the covered short position, the underwriters will consider, among other things, the price of securities available for purchase in the open market, as compared to the price at which they may purchase securities through the over-allotment option. Naked short sales are short sales in excess of the over-allotment option. The underwriters must close out any naked short position by purchasing securities in the open market. A naked short position is more likely to be created if the underwriters are concerned that, in the open market after pricing, there may be downward pressure on the price of the securities that could adversely affect investors who purchase securities in this offering. Stabilizing transactions permit bids to purchase the underlying security for the purpose of fixing the price of the security so long as the stabilizing bids do not exceed a specified maximum. Penalty bids permit the underwriters to reclaim a selling concession from a dealer when the securities originally sold by the dealer are purchased in a covering transaction to cover short positions.

Any underwriters who are qualified market makers on the Nasdaq Global Select Market may engage in passive market making transactions in our common stock, preferred stock, warrants and debt securities, as applicable, on the Nasdaq Global Select Market in accordance with Rule 103 of Regulation M, during the business day prior to the pricing of the offering, before the commencement of offers or sales of the securities. Passive market makers must comply with applicable volume and price limitations and must be identified as passive market makers. In general, a passive market maker must display its bid at a price not in excess of the highest independent bid for such security; if all independent bids are lowered below the passive market maker’s bid, however, the passive market maker’s bid must then be lowered when certain purchase limits are exceeded.

In compliance with guidelines of the Financial Industry Regulatory Authority, or FINRA, the maximum consideration or discount to be received by any FINRA member or independent broker dealer may not exceed 8% of the aggregate amount of the securities offered pursuant to this prospectus and any applicable prospectus supplement.

Similar to other purchase transactions, an underwriter’s purchase to cover the syndicate short sales or to stabilize the market price of our securities may have the effect of raising or maintaining the market price of our securities or preventing or mitigating a decline in the market price of our securities. As a result, the price of our securities may be higher than the price that might otherwise exist in the open market. The imposition of a penalty bid might also have an effect on the price of the securities if it discourages resales of the securities.

Neither we nor the underwriters makes any representation or prediction as to the effect that the transactions described above may have on the price of the securities. If such transactions are commenced, they may be discontinued without notice at any time.

Legal Matters

The validity of the securities being offered hereby will be passed upon for us by Steven W. Spector, our Senior Vice President, General Counsel and Secretary.

Experts

Where You Can Find More Information

We file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy any document we file with the SEC at the SEC’s public reference room at 100 F Street, N.E., Washington, D.C., 20549. Please call the SEC at 1.800.SEC.0330 for further information on the operation of the public reference room. Our SEC filings are also available to the public at the SEC’s website at http://www.sec.gov.

Incorporation of Certain Information by Reference

The SEC allows us to “incorporate by reference” the information we file with it, which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future filings we will make with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act after the date of this prospectus until the termination of the offering of the shares covered by this prospectus (other than information furnished under Item 2.02 or Item 7.01 of Form 8-K):

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our Annual Report on Form 10-K for the year ended December 31, 2010, filed with the SEC on March 15, 2011;

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You can request a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

Arena Pharmaceuticals, Inc.

Attn: General Counsel

6166 Nancy Ridge Drive

San Diego, California 92121

Telephone number: 858.453.7200

This prospectus is part of a registration statement we filed with the SEC. That registration statement and the exhibits filed along with the registration statement contain more information about us and the shares in this offering. Because information about documents referred to in this prospectus is not always complete, you should read the full documents which are filed as exhibits to the registration statement. You may read and copy the full registration statement and its exhibits at the SEC’s public reference rooms or their website.

9,953,250 Shares of Common Stock

9,953.25 Shares of Series D Convertible Preferred Stock

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Prospectus Supplement

January 10, 2012