e424b5

Filed Pursuant to Rule 424(b)(5)
Registration File No. 333-164283

Prospectus Supplement
(to Prospectus dated January 21, 2010)

16,000,000 Shares

Common Stock

We are offering 16,000,000 shares of our common stock. Our common stock is listed on The NASDAQ Global Market under the symbol “ARIA.” The last reported sale price of our common stock on The NASDAQ Global Market on October 25, 2010 was $4.10 per share.

Investing in our common stock involves a high degree of risk. Please read “Risk Factors” beginning on page S-4 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.


	Per Share		Total

Public Offering Price	$	3.70	$	59,200,000
Underwriting Discounts and Commissions	$	0.09	$	1,440,000
Proceeds to ARIAD (Before Expenses)	$	3.61	$	57,760,000

Delivery of the shares of common stock is expected to be made on or about October 29, 2010. We have granted the underwriters an option for a period of 30 days to purchase up to an additional 2,400,000 shares of our common stock solely to cover overallotments. If the underwriters exercise the option in full, the total underwriting discounts and commissions will be $1,656,000 and the total proceeds to us, before expenses, will be $66,424,000.

Joint Book-Running Managers


Jefferies & Company	Oppenheimer & Co.

Prospectus Supplement dated October 25, 2010

TABLE OF CONTENTS


	Page

Prospectus Supplement
About This Prospectus Supplement		ii
Prospectus Supplement Summary		S-1
Risk Factors		S-4
Special Note Regarding Forward-Looking Statements		S-5
Use of Proceeds		S-6
Dilution		S-7
Underwriting		S-8
Notice to Investors		S-11
Legal Matters		S-13
Where You Can Find More Information		S-13
Incorporation of Certain Information by Reference		S-13
Prospectus
About This Prospectus		ii
Prospectus Summary		1
Risk Factors		4
Deficiency of Earnings to Fixed Charges		4
Special Note Regarding Forward-Looking Statements		4
Use of Proceeds		5
Plan of Distribution		5
Description of Common Stock		7
Description of Preferred Stock		8
Description of Debt Securities		9
Description of Warrants		15
Description of Rights		16
Description of Purchase Contracts		17
Description of Units		18
Certain Provisions of Delaware Law and of the Company’s Certificate of Incorporation and By-Laws		19
Legal Matters		20
Experts		20
Where You Can Find More Information		21
Incorporation of Documents by Reference		21

You should rely only on the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus and in any free writing prospectus that we have authorized for use in connection with this offering. We have not, and the underwriters have not, authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and in any free writing prospectus that we have authorized for use in connection with this offering, is accurate only as of the date of those respective documents. Our business, financial condition, results of operations and prospects may have changed since those dates. You should read this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus supplement entitled “Where You Can Find More Information” and “Incorporation of Certain Information by Reference.”

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the terms of this offering of common stock and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part, the accompanying prospectus dated January 21, 2010, including the documents incorporated by reference therein, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or in any document incorporated by reference that was filed with the Securities and Exchange Commission, or SEC, before the date of this prospectus supplement, on the other hand, you should rely on the information in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date — for example, a document incorporated by reference in this prospectus supplement or the accompanying prospectus — the statement in the document having the later date modifies or supersedes the earlier statement.

You should rely only on the information contained, or incorporated by reference, in this prospectus supplement, the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering. We and the underwriters for this offering have not authorized anyone to provide you with different information. The common stock offered under this prospectus is not being offered in any state where the offer is not permitted. You should not assume that the information contained in this prospectus supplement or the accompanying prospectus is accurate as of any date other than the date on the front of this prospectus supplement or the accompanying prospectus, as applicable, or that any information incorporated by reference in this prospectus supplement or the accompanying prospectus is accurate as of any date other than the date of the document so incorporated by reference.

This prospectus supplement and the accompanying prospectus are part of a registration statement on Form S-3 (File No. 333-164283) we filed with the SEC using a “shelf” registration process. Under this “shelf” registration process, we may sell from time to time in one or more offerings up to $125,000,000 of our securities described in the accompanying prospectus.

All references in this prospectus supplement and the accompanying prospectus to “ARIAD,” the “Company,” “we,” “us,” “our,” or similar references refer to ARIAD Pharmaceuticals, Inc. and our subsidiaries, except where the context otherwise requires or as otherwise indicated.

This prospectus supplement, the accompanying prospectus, and the information incorporated herein and therein by reference, include trademarks, service marks and trade names owned by us or other companies. All trademarks, service marks and trade names included or incorporated by reference into this prospectus supplement or the accompanying prospectus are the property of their respective owners.

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 and the accompanying prospectus. 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. For a more complete understanding of our company and this offering, we encourage you to 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, and the information included in any free writing prospectus that we have authorized for use in connection with this offering, including the information referred to under the heading “Risk Factors” in this prospectus supplement beginning on page S-4.

Company Overview

Our vision is to transform the lives of cancer patients with breakthrough medicines. Our mission is to discover, develop and commercialize small-molecule drugs to treat cancer in patients with the greatest and most urgent unmet medical need — aggressive cancers where current therapies are inadequate. Our goal is to build a fully integrated oncology company focused on novel, molecularly targeted therapies to treat solid tumors and hematologic cancers, as well as the spread of primary tumors to distant sites.

Product Development and Discovery

Our lead cancer product candidate, ridaforolimus, previously known as deforolimus, is being studied in multiple clinical trials in patients with various types of cancers. In July 2007, we entered into a global collaboration agreement, or the Collaboration Agreement, with Merck & Co., Inc., or Merck, to jointly develop, manufacture and commercialize ridaforolimus for use in cancer, which agreement was amended and restated in May 2010 as discussed further below. We initiated patient enrollment in our initial Phase 3 clinical trial of ridaforolimus in patients with metastatic sarcoma in the third quarter of 2007. We completed patient enrollment in this Phase 3 clinical trial in the fourth quarter of 2009. We expect to obtain the results of the final analysis of progression-free survival, or PFS, the primary endpoint of the trial, in the first quarter of 2011. In addition, in 2008 and 2009 we and Merck initiated patient enrollment in Phase 2 clinical trials in patients with metastatic breast cancer, metastatic endometrial cancer, metastatic non-small-cell lung cancer and advanced prostate cancer, and Phase 1 clinical trials of ridaforolimus in combination with other agents, all as part of our joint global development plan with Merck. Clinical trials and other development activities for ridaforolimus continue at this time under Merck’s control and responsibilities pursuant to the amended and restated May 2010 agreement.

Our second product candidate, ponatinib, previously known as AP24534, is an investigational pan BCR-ABL inhibitor for which we initiated a Phase 1 clinical trial in the second quarter of 2008 in patients with chronic myeloid leukemia, or CML, acute myeloid leukemia, or AML, and other hematologic cancers, which is on-going at this time. In the third quarter of 2010, we initiated patient enrollment in a pivotal Phase 2 clinical trial of ponatinib in patients with resistant or intolerant CML and Philadelphia positive acute lymphoblastic leukemia, or Ph+ ALL. We expect to complete patient enrollment in this clinical trial by year-end 2011.

In 2009, we designated our third product candidate, AP26113, an investigational anaplastic lymphoma kinase, or ALK, inhibitor, as a development candidate. We have commenced preclinical testing and investigational new drug, or IND, enabling studies of this product candidate.

In addition to our lead development programs, we have a focused drug discovery program centered on small-molecule, molecularly targeted therapies and cell-signaling pathways implicated in cancer.

S-1

Our Collaboration and License Agreements with Merck

Under our Collaboration Agreement with Merck for the global development, manufacture and commercialization of ridaforolimus, we and Merck were conducting a broad-based development program in multiple potential indications. The Collaboration Agreement as in effect up to May 4, 2010 provided that each party would fund 50 percent of global development costs, except for certain specific costs to be funded 100 percent by Merck. The Collaboration Agreement established responsibilities for supply of the product for development and commercial purposes, promotion, distribution and sales of the product, governance of the collaboration, termination provisions and other matters.

In addition to cost-sharing provisions, the Collaboration Agreement as in effect up to May 4, 2010 provided for an up-front payment by Merck of $75 million, which was paid to us in July 2007, and provided up to $452 million in milestone payments based on the successful development of ridaforolimus in multiple potential cancer indications, of which $53.5 million had been paid to us through March 31, 2010, and up to $200 million in milestone payments based on achievement of specified product sales thresholds. The Collaboration Agreement provided that each party would receive 50 percent of the profit from the sales of ridaforolimus in the United States, and Merck would pay us tiered double-digit royalties on sales of ridaforolimus outside the United States.

In May 2010, we entered into an Amended and Restated Collaboration and Exclusive License Agreement, or the License Agreement, with Merck that replaces the Collaboration Agreement. Under the terms of the License Agreement, we have granted Merck an exclusive license to develop, manufacture and commercialize ridaforolimus in oncology, and Merck assumes responsibility for all activities related to the development, manufacture and commercialization of ridaforolimus and will fund 100 percent of all ridaforolimus costs effective as of January 1, 2010. If ridaforolimus receives regulatory approval, Merck will be responsible for selling ridaforolimus worldwide, will book global sales and will pay us tiered double-digit royalties on global net sales. We have an option to co-promote ridaforolimus with up to 20 percent of the sales effort in all indications in the United States and, in such case, we would be compensated by Merck for our sales efforts.

Under the License Agreement, Merck paid us an initial up-front fee of $50 million and has agreed to pay us up to $514 million in regulatory and sales milestone payments, based on the successful development of ridaforolimus in multiple potential cancer indications or upon achievement of specified product sales thresholds. These potential milestone payments include up to $65 million associated with the potential sarcoma indication, which currently is in Phase 3 clinical development, up to $249 million associated with potential regulatory filings and approvals for other cancer indications and up to $200 million based on achievement of certain sales thresholds.

The License Agreement provides that all ridaforolimus activities that had been our responsibility under the Collaboration Agreement will be transitioned to Merck, a process we estimate will be completed by year-end 2010. Merck will reimburse us for all costs we incur related to the transition.

Corporate Information

We were organized as a Delaware corporation in April 1991. Our principal executive offices are located at 26 Landsdowne Street, Cambridge, Massachusetts 02139-4234, and our telephone number is (617) 494-0400. We maintain an internet website at www.ariad.com. The information on our website or any other website is not incorporated by reference into this prospectus supplement and does not constitute a part of this prospectus supplement. Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K and all amendments to such reports are made available free of charge through the Investor Relations section of our website as soon as reasonably practicable after they have been filed or furnished with the SEC.

ARIAD and the ARIAD logo are our registered trademarks. ARGENT is our trademark. Other service marks, trademarks and trade names appearing in this prospectus supplement or the accompanying prospectus are the property of their respective owners.

S-2

The Offering


Common stock offered by us		16,000,000 shares

Common stock to be outstanding immediately after this offering		126,879,607 shares

Overallotment Option

We have granted the underwriters an option to purchase up to 2,400,000 additional shares of our common stock to cover overallotments, if any. This option is exercisable, in whole or in part, for a period of 30 days from the date of this prospectus supplement.

Use of Proceeds

We intend to use the net proceeds of this offering for our operations, including, but not limited to, research and development, clinical trials, product manufacturing, and working capital, and for other general corporate purposes, including, but not limited to, repayment or refinancing of existing indebtedness or other corporate borrowings, capital expenditures and possible acquisitions. Pending these uses, we may invest the net proceeds in short-term, investment grade, interest bearing securities. See “Use of Proceeds” on page S-6 of this prospectus supplement.

NASDAQ Global Market Listing

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

Risk Factors

Investing in our common stock involves a high degree of risk. See “Risk Factors” on page S-4 of this prospectus supplement.

Outstanding Shares

The number of shares of our common stock to be outstanding immediately after this offering is based on 110,879,607 shares of our common stock outstanding as of October 25, 2010, and excludes as of such date:


	•	7,283,678 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans, at a weighted average exercise price of $4.42 per share;

	•	2,782,300 shares of our common stock issuable upon vesting of restricted stock units outstanding under our stock plans;

	•	6,034,019 shares of our common stock available for future grant or issuance pursuant to our employee stock purchase and stock plans; and

	•	9,563,610 shares of our common stock issuable upon exercise of outstanding warrants, at an exercise price of $2.15 per share.

Except as otherwise indicated, all information in the prospectus supplement assumes no exercise by the underwriters of their overallotment option.

S-3

RISK FACTORS

An investment in our common stock involves a high degree of risk. Before deciding whether to invest in our common stock, you should consider carefully the risks described below and discussed under the section captioned “Risk Factors” contained in our Annual Report on Form 10-K for the year ended December 31, 2009, as filed with the SEC on March 16, 2010, and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2010, as filed with the SEC on August 9, 2010, which are incorporated by reference in this prospectus supplement and the accompanying prospectus in their entirety, together with other information in this prospectus supplement, the accompanying prospectus, the information and documents incorporated by reference, and in any free writing prospectus that we have authorized for use in connection with this offering. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our common stock to decline, resulting in a loss of all or part of your investment.

Additional Risks Related to This Offering

Management will have broad discretion as to the use of the proceeds from this offering.

We have not designated the amount of net proceeds we will receive from this offering for any particular purpose. Accordingly, our management will have broad discretion as to the application of these net proceeds and could use them for purposes other than those contemplated at the time of this offering. Our stockholders may not agree with the manner in which our management chooses to allocate and spend the net proceeds.

You will experience immediate dilution in the book value per share of the common stock you purchase. You may also experience dilution as a result of other equity issuances.

Because the price per share of our common stock being offered is higher than the net tangible book value per share of our common stock, you will suffer substantial dilution in the net tangible book value of the common stock you purchase in this offering. Based on a public offering price of $3.70 per share in this offering, if you purchase shares of common stock in this offering, you will suffer immediate and substantial dilution of $2.88 per share in the net tangible book value of the common stock. See “Dilution” on page S-7 of this prospectus supplement for a more detailed discussion of the dilution you will incur in this offering. In addition, we have a significant number of stock options, restricted stock units and warrants outstanding. If the holders of these securities exercise or become vested in them, as applicable, you may incur further dilution. You may also incur dilution upon the future grant of shares or exercise of options granted in the future pursuant to any of our employee stock option or benefit plans.

Sales of a significant number of shares of our common stock in the public markets, or the perception that such sales could occur, could depress the market price of our common stock.

Sales of a substantial number of shares of our common stock in the public markets could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We, our directors and our executive officers have agreed not to sell, dispose of or hedge any common stock or securities convertible into or exchangeable for shares of common stock during the period from the date of this prospectus supplement continuing through and including the date 90 days after the date of this prospectus supplement, subject to certain exceptions. The underwriters may, in their discretion, release the restrictions on any such shares at any time without notice. We cannot predict the effect that future sales of our common stock would have on the market price of our common stock.

S-4

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus, the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering 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 statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. Forward-looking statements may include, but are not limited to, statements about:


	•	the safety and efficacy of our product candidates;

	•	the progress, timing and results of clinical trials and research and development efforts involving our product candidates;

	•	the submission of applications for and receipt of regulatory clearances and approvals;

	•	our expecations with regard to our intellectual property position and our ability to successfully protect our intellectual property;

	•	our plans to conduct future clinical trials or research and development efforts;

	•	estimates of the potential markets for our product candidates;

	•	our estimated expenditures and projected cash needs;

	•	our expectations about partnering, acquisitions, licensing and marketing;

	•	the sufficiency of the net proceeds from the offering, together with existing cash and cash equivalents, to fund our operations into the second half of 2012; and

	•	the use of proceeds from this offering.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “could,” “would,” “expects,” “plans,” “anticipates,” “believes,” “estimates,” “projects,” “predicts,” “potential” and similar expressions intended to identify forward-looking statements. These statements reflect our current views with respect to future events and are based on assumptions and subject to risks and uncertainties. Given these uncertainties, you should not place undue reliance on these forward-looking statements. We discuss many of these risks in greater detail under the heading “Risk Factors” beginning on page S-4 of this prospectus supplement and in our SEC filings. Also, these forward-looking statements represent our estimates and assumptions only as of the date of the document containing the applicable statement.

You should read this prospectus supplement, the accompanying prospectus, the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in the foregoing documents by these cautionary statements. Unless required by law, we undertake no obligation to update or revise any forward-looking statements to reflect new information or future events or developments. Thus, you should not assume that our silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements.

S-5

USE OF PROCEEDS

We estimate that the net proceeds from the sale of the 16,000,000 shares of common stock that we are offering will be approximately $57.4 million, or approximately $66.1 million if the underwriters exercise in full their option to purchase 2,400,000 additional shares of common stock, based on the public offering price of $3.70 per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

The anticipated net proceeds from the offering, together with existing cash and cash equivalents, are expected to be sufficient to fund our operations into the second half of 2012, which does not include the effect of any payments relating to a potential collaboration agreement on ponatinib or any regulatory or sales milestone payments we may receive from Merck related to ridaforolimus. We intend to use the net proceeds of this offering for our operations, including, but not limited to, research and development, clinical trials, product manufacturing, and working capital, and for other general corporate purposes, including, but not limited to, repayment or refinancing of existing indebtedness or other corporate borrowings, capital expenditures and possible acquisitions. The funding is expected to enable us to complete enrollment in the ongoing pivotal Phase 2 clinical trial of ponatinib; to obtain at least six-months of follow-up response data; to complete analysis of the trial; and to prepare filings for marketing authorization of ponatinib. Depending on the results of this trial, ARIAD anticipates filing a new drug application for ponatinib in the second half of 2012.

We have not determined the amounts we plan to spend on any of the areas listed above or the timing of these expenditures. As a result, our management will have broad discretion to allocate the net proceeds from this offering for any purpose. Pending application of the net proceeds as described above, we may initially invest the net proceeds in short-term, investment-grade, interest-bearing securities or apply them to the reduction of short-term indebtedness.

S-6

DILUTION

The net tangible book value of our common stock on June 30, 2010 was $46.2 million, or $0.42 per share of common stock. Our net tangible book value per share is calculated by subtracting our total liabilities from our total tangible assets and dividing this amount by the number of shares of our common stock outstanding on June 30, 2010. Assuming the sale by us of all 16,000,000 shares of common stock that we are offering at the public offering price of $3.70 per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of June 30, 2010 would have been $103.6 million, or $0.82 per share of our common stock. This represents an immediate increase in net tangible book value of $0.40 per share to our existing stockholders and an immediate dilution in net tangible book value of $2.88 per share to new investors purchasing common stock in this offering. The following table illustrates this per share dilution:


Public offering price per share			$	3.70
Net tangible book value per share as of June 30, 2010	$	0.42
Increase per share attributable to new investors	$	0.40
As adjusted net tangible book value per share after the offering				0.82

Dilution per share to new investors			$	2.88

If the underwriters exercise in full their option to purchase 2,400,000 additional shares of common stock at the public offering price of $3.70 per share, the as adjusted net tangible book value after this offering would be $0.87 per share, representing an increase in net tangible book value of $0.45 per share to existing stockholders and immediate dilution in net tangible book value of $2.83 per share to new investors purchasing our common stock in this offering.

The information above does not include:


	•	7,600,623 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans as of June 30, 2010, at a weighted average exercise price of $4.39;

	•	2,825,400 shares of our common stock issuable upon vesting of restricted stock units outstanding under our stock plans as of June 30, 2010;

	•	5,851,964 shares of our common stock available as of June 30, 2010 for future grant or issuance pursuant to our employee stock purchase and stock plans; and

	•	9,563,610 shares of our common stock issuable upon exercise of outstanding warrants as of June 30, 2010, at an exercise price of $2.15 per share.

To the extent options or warrants outstanding as of June 30, 2010 have been or may be exercised or other shares have been or are issued, there may be further dilution to new investors.

S-7

UNDERWRITING

Under the terms and subject to the conditions contained in an underwriting agreement dated October 25, 2010 by and among us and the underwriters named below, the underwriters have agreed to purchase, and we have agreed to sell to them, the number of shares of common stock indicated in the table below:


Name	Number of Shares

Jefferies & Company, Inc.		8,000,000
Oppenheimer & Co. Inc.		8,000,000

Total		16,000,000

The underwriters are offering the common stock subject to their acceptance of the shares from us and subject to prior sale. The underwriting agreement provides that the obligations of the underwriters to pay for and accept delivery of the common stock offered by this prospectus supplement are subject to the approval of certain legal matters by their counsel and to certain other conditions. The underwriting agreement provides that the underwriters are obligated to take and pay for all of the common stock if any such shares are purchased, other than those shares covered by the overallotment option described below.

Commissions and Expenses

The underwriters have advised us that they propose to offer the shares to the public at the public offering price set forth on the cover page of this prospectus supplement and to certain dealers at that price less a concession not in excess of $0.05 per share. After the offering, the public offering price and concession to dealers may be reduced by the underwriters. No such reduction shall change the amount of proceeds to be received by us as set forth on the cover page of this prospectus supplement. The shares are offered by the underwriters as stated herein, subject to receipt and acceptance by them and subject to their right to reject any order in whole or in part.

The following table shows the per share and total public offering price, the underwriting discounts and commissions payable to the underwriters by us and the proceeds, before expenses, to us, assuming both no exercise and full exercise of the underwriters’ option to purchase additional shares, as discussed below.


			Total Without Exercise of		Total With Full Exercise of
	Per Share		Overallotment Option		Overallotment Option

Public offering price	$	3.70	$	59,200,000	$	68,080,000
Underwriting discounts and commissions	$	0.09	$	1,440,000	$	1,656,000
Proceeds to ARIAD (before expenses)	$	3.61	$	57,760,000	$	66,424,000

We estimate expenses payable by us in connection with the offering of common stock, other than the underwriting discounts and commissions referred to above, will be approximately $350,000.

Option to Purchase Additional Shares

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase up to an aggregate of 2,400,000 additional shares at the same price they are paying for the shares shown in the table above. The underwriters may exercise this option at any time and from time to time, in whole or in part, within 30 days after the date of this prospectus supplement. If the underwriters exercise the option in full, the total underwriting discounts and commissions payable by us and the total proceeds to us, before expenses, will be as shown in the table above.

Indemnification

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act. We have also agreed to contribute to payments that the underwriters may be required to make in respect of those liabilities.

S-8

Lock-up Agreements

Our executive officers and directors have agreed, subject to specified exceptions, not to directly or indirectly, (1) offer, sell, assign, transfer, pledge, contract or grant an option to sell, or otherwise dispose of or agree to dispose of, any shares of our common stock or securities convertible into or exercisable or exchangeable for our common stock (including, without limitation, shares of our common stock or any such securities which may be deemed to be beneficially owned by such person in accordance with the rules and regulations promulgated under the Securities Act), (2) enter into any swap, hedge or other agreement or arrangement that transfers in whole or in part, the economic risk of ownership of any shares of our common stock or securities convertible into or exercisable or exchangeable for our common stock, (3) engage in any short selling of any shares of our common stock or securities convertible into or exercisable or exchangeable for our common stock or (4) publicly announce an intention to effect a transaction specified in clauses (1), (2) or (3) above. We have also agreed, subject to specified exceptions, not to issue, sell or register with the SEC, or otherwise dispose of, directly or indirectly, any of our equity securities or any securities convertible into, exercisable for or exchangeable for equity securities.

These restrictions terminate after the close of trading of the shares on and including the 90th day after the date of this prospectus supplement. The underwriters may, in their sole discretion and at any time or from time to time before the termination of the 90-day period, without notice, release all or any portion of the securities subject to lock-up agreements. However, subject to specified exceptions, if (a) during the last 17 days of the 90-day period, ARIAD issues an earnings release or material news or a material event relating to ARIAD occurs or (b) prior to the expiration of the 90-day period, ARIAD announces that it will release earnings results during the 16-day period beginning on the last day of the 90-day period, then in each case the 90-day period will be extended until the expiration of the 18-day period beginning on the date of the issuance of the earnings release or the occurrence of the material news or material event, as applicable, unless the underwriters waive, in writing, such extension.

Electronic Distribution

This prospectus supplement and the accompanying prospectus in electronic format may be made available on websites or through other online services maintained by the underwriters of the offering, or by their affiliates. Other than the prospectus in electronic format, the information on the underwriters’ websites and any information contained in any other website maintained by the underwriters or any of their affiliates is not part of the prospectus or the registration statement of which this prospectus supplement forms a part, has not been approved and/or endorsed by us or the underwriters in their capacity as underwriters and should not be relied upon by investors.

Price Stabilization, Short Positions and Penalty Bids

Until the distribution of the shares of common stock is completed, SEC rules may limit the underwriters from bidding for and purchasing shares of our common stock.

In connection with this offering, the underwriters may engage in transactions that stabilize, maintain or make short sales of our common stock and may purchase our common stock on the open market to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater number of shares than they are required to purchase in this offering. The underwriters may close out any short position by purchasing shares in the open market or by exercising their overallotment option.

An underwriter also may impose a penalty bid, whereby the underwriter may reclaim selling concessions allowed to other broker-dealers in respect of the common stock sold in the offering for their account if the underwriter repurchases the shares in stabilizing or covering transactions. These activities may stabilize, maintain or otherwise affect the market price of our common stock, which may be higher than the price that might otherwise prevail in the open market. The imposition of a penalty bid may also affect the price of the shares of our common stock in that it discourages resales of those shares of our common stock.

S-9

A short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the shares in the open market after pricing that could adversely affect investors who purchase in this offering. A “stabilizing bid” is a bid for or the purchase of common stock on behalf of the underwriters in the open market prior to the completion of this offering for the purpose of fixing or maintaining the price of the shares of common stock. A “syndicate covering transaction” is the bid for or purchase of common stock on behalf of the underwriters to reduce a short position incurred by the underwriters in connection with the offering.

Similar to other purchase transactions, the underwriters’ purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our shares or preventing or retarding a decline in the market price of our shares. As a result, the price of our shares may be higher than the price that might otherwise exist in the open market.

In connection with this offering, the underwriters may also engage in passive market making transactions in our common stock on The NASDAQ Global Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of shares of our common stock in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker’s bid, that bid must then be lowered when specified purchase limits are exceeded.

Neither we nor the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our common stock. In addition, neither we nor the underwriters make any representation that the underwriters will engage in these transactions or that any transaction, if commenced, will not be discontinued without notice.

Affiliations

In the future, the underwriters and their affiliates may provide various investment banking, commercial banking, financial advisory and other services to us and our affiliates for which services they have received, and may in the future receive, customary fees. In the course of their businesses, the underwriters and their affiliates may actively trade our securities or loans for their own accounts or for the accounts of customers, and, accordingly, the underwriters and their affiliates may at any time hold long or short positions in such securities or loans.

S-10

NOTICE TO INVESTORS

European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (as defined below) (each, a Relevant Member State), with effect from and including the date on which the Prospectus Directive is implemented in that Relevant Member State, or the Relevant Implementation Date, an offer of our common stock to the public may not be made in that Relevant Member State prior to the publication of a prospectus in relation to our common stock which has been approved by the competent authority in that Relevant Member State or, where appropriate, approved in another Relevant Member State and notified to the competent authority in that Relevant Member State, all in accordance with the Prospectus Directive, except that an offer to the public in that Relevant Member State of any shares of our common stock may be made at any time under the following exemptions under the Prospectus Directive if they have been implemented in the Relevant Member State:


	(a)	to legal entities which are authorized or regulated to operate in the financial markets or, if not so authorized or regulated, whose corporate purpose is solely to invest in securities;


	(b)	to any legal entity which has two or more of (1) an average of at least 250 employees during the last financial year; (2) a total balance sheet of more than €43,000,000 and (3) an annual net turnover of more than €50,000,000, as shown in its last annual or consolidated accounts;


	(c)	to fewer than 100 natural or legal persons per Relevant Member State (other than qualified investors as defined in the Prospectus Directive); or


	(d)	in any other circumstances falling within Article 3(2) of the Prospectus Directive,

provided that no such offer of our common stock shall result in a requirement for the publication by us or any underwriter of a prospectus pursuant to Article 3 of the Prospectus Directive.

For the purposes of this provision, the expression an “offer of our common stock to the public” in relation to any shares of our common stock in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and our common stock to be offered so as to enable an investor to decide to purchase or subscribe our common stock, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State and the expression “Prospectus Directive” means Directive 2003/71/EC and includes any relevant implementing measure in each Relevant Member State.

United Kingdom

Shares of our common stock may not be offered or sold and will not be offered or sold to any persons in the United Kingdom other than to persons whose ordinary activities involve them in acquiring, holding, managing or disposing of investments (as principal or as agent) for the purposes of their businesses or otherwise in circumstances which have not resulted or will not result in an offer to the public in the United Kingdom within the meaning of the Financial Services and Markets Act 2000, or the FSMA.

In addition, any invitation or inducement to engage in investment activity (within the meaning of section 21 of the FSMA) in connection with the issue or sale of shares of our common stock may only be communicated or caused to be communicated in circumstances in which Section 21(1) of the FSMA does not apply to us. Without limitation to the other restrictions referred to herein, this prospectus supplement is directed only at (1) persons outside the United Kingdom or (2) persons who:


	(a)	are qualified investors as defined in section 86(7) of FSMA, being persons falling within the meaning of article 2.1(e)(i), (ii) or (iii) of the Prospectus Directive; and


	(b)	are either persons who fall within article 19(1) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005, as amended, or Order, or are persons who fall within article 49(2)(a) to (d) (“high net worth companies, unincorporated associations, etc.”) of the Order; or

S-11


	(c)	to whom it may otherwise lawfully be communicated in circumstances in which Section 21(1) of the FSMA does not apply.

Without limitation to the other restrictions referred to herein, any investment or investment activity to which this offering circular relates is available only to, and will be engaged in only with, such persons, and persons within the United Kingdom who receive this communication (other than persons who fall within (2) above) should not rely or act upon this communication.

Germany

Any offer or solicitation of securities within Germany must be in full compliance with the German Securities Prospectus Act (Wertpapierprospektgesetz — WpPG). The offer and solicitation of securities to the public in Germany requires the publication of a prospectus that has to be filed with and approved by the German Federal Financial Services Supervisory Authority (Bundesanstalt für Finanzdienstleistungsaufsicht — BaFin). This prospectus supplement has not been and will not be submitted for filing and approval to the BaFin and, consequently, will not be published. Therefore, this prospectus supplement does not constitute a public offer under the German Securities Prospectus Act (Wertpapierprospektgesetz). This prospectus supplement and any other document relating to our common stock, as well as any information contained therein, must therefore not be supplied to the public in Germany or used in connection with any offer for subscription of our common stock to the public in Germany, any public marketing of our common stock or any public solicitation for offers to subscribe for or otherwise acquire our common stock. This prospectus supplement and other offering materials relating to the offer of our common stock are strictly confidential and may not be distributed to any person or entity other than the designated recipients hereof.

France

This prospectus supplement has not been, and will not be, submitted to the clearance procedures of the Autorité des marchés financiers (the “AMF”) in France and may not be directly or indirectly released, issued, or distributed to the public in France, or used in connection with any offer for subscription or sale of our common stock to the public in France, in each case within the meaning of Article L. 411-1 of the French Code monétaire et financier (the “French Financial and Monetary Code”).

The securities have not been, and will not be, offered or sold to the public in France, directly or indirectly, and will only be offered or sold in France (i) to qualified investors (investisseurs qualifiés) investing for their own account, in accordance with all applicable rules and regulations, and in particular in accordance with Articles L. 411-2 and D. 411-2 of the French Financial and Monetary Code; (ii) to investment services providers authorized to engage in portfolio investment on behalf of third parties, in accordance with Article L.411-2 of the French Financial and Monetary Code; or (iii) in a transaction that, in accordance with all applicable rules and regulations, does not otherwise constitute an offer to the public (“appel public à l’épargne”) in France within the meaning of Article L.411-1 of the French Financial and Monetary Code.

This prospectus supplement is not to be further distributed or reproduced (in whole or in part) in France by any recipient, and this prospectus supplement has been distributed to the recipient on the understanding that such recipient is a qualified investor or otherwise meets the requirements set forth above, and will only participate in the issue or sale of the securities for their own account, and undertakes not to transfer, directly or indirectly, the securities to the public in France, other than in compliance with all applicable laws and regulations and in particular with Articles L.411-1, L.411-2, D.411-1 and D.411-2 of the French Financial and Monetary Code.

Sweden

This is not a prospectus under, and has not been prepared in accordance with the prospectus requirements provided for in, the Swedish Financial Instruments Trading Act [lagen (1991:980) om handel med finasiella instrument] nor any other Swedish enactment. Neither the Swedish Financial Supervisory Authority nor any other Swedish public body has examined, approved, or registered this document.

S-12

LEGAL MATTERS

Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts, will pass upon the validity of the issuance of the common stock offered by this prospectus supplement and the accompanying prospectus. Members of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. and certain members of their families and trusts for their benefit own an aggregate of approximately 5,000 shares of our common stock. Latham & Watkins LLP, San Diego, California, is counsel for the underwriters in connection with this offering.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the reporting requirements of the Exchange Act, and file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy these reports, proxy statements and other information at the SEC’s public reference facilities at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference facilities. SEC filings are also available at the SEC’s web site at http://www.sec.gov. Copies of information filed by us with the SEC are also available on our website at http://www.ariad.com under the heading “Investors/News.”

Our common stock is listed on The NASDAQ Global Market, and you can read and inspect our filings at the offices of the Financial Industry Regulatory Authority at 1735 K Street, Washington, D.C. 20006.

This prospectus supplement and the accompanying prospectus are only part of a registration statement on Form S-3 that we have filed with the SEC under the Securities Act, and therefore omits certain information contained in the registration statement. We have also filed exhibits and schedules with the registration statement that are excluded from this prospectus supplement and the accompanying prospectus, and you should refer to the applicable exhibit or schedule for a complete description of any statement referring to any contract or other document. You may inspect a copy of the registration statement, including the exhibits and schedules, without charge, at the public reference room or obtain a copy from the SEC upon payment of the fees prescribed by the SEC.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE


	•	our annual report on Form 10-K for the fiscal year ended December 31, 2009, filed on March 16, 2010;

	•	our quarterly reports on Form 10-Q for the quarters ended March 31, 2010 and June 30, 2010 filed on May 10, 2010 and August 9, 2010, respectively;

	•	our current reports on Form 8-K filed on January 22, 2010, March 1, 2010, March 16, 2010 (Item 8.01 only), March 23, 2010, April 15, 2010, May 3, 2010, May 6, 2010 (Item 1.01 only), May 10, 2010 (Item 8.01 only), May 20, 2010, May 25, 2010, June 7, 2010, June 25, 2010, August 4, 2010 (Item 8.01 only), September 13, 2010 and October 25, 2010;

	•	the portions of our Definitive Proxy Statement on Schedule 14A that are deemed “filed” with the SEC under the Securities Exchange Act of 1934, as amended, filed on April 30, 2009;

	•	the description of our common stock contained in our registration statement on Form 10/A filed on June 25, 1993, including any amendment or report filed for the purpose of updating such description; and

S-13


	•	the description of our preferred share purchase rights contained in our registration statement on Form 8-A filed on June 19, 2000, including any amendment or report filed for the purpose of updating such description.

In addition, all reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended, after the date of this prospectus supplement and prior to the termination or completion of the offering of securities under this prospectus supplement and the accompanying prospectus shall be deemed to be incorporated by reference in this prospectus supplement and to be a part hereof from the date of filing such reports and other documents.

Any statement contained in this prospectus supplement, the accompanying prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus supplement or the accompanying prospectus will be deemed to be modified or superseded to the extent that a statement contained in this prospectus, the accompanying prospectus or any other subsequently filed document that is deemed to be incorporated by reference modifies or supersedes the statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus or the accompanying prospectus.

You may request, orally or in writing, a copy of any or all of the documents incorporated herein by reference. These documents will be provided to you at no cost, by contacting: Investor Relations, ARIAD Pharmaceuticals, Inc., 26 Landsdowne Street, Cambridge, Massachusetts 02139-4234. Our telephone number is (617) 494-0400.

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 different from that contained in this prospectus supplement and the accompanying prospectus or incorporated by reference in this prospectus supplement and the accompanying prospectus. We are not making offers to sell the securities in any jurisdiction in which such an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such offer or solicitation.

S-14

PROSPECTUS

ARIAD PHARMACEUTICALS, INC.

$125,000,000

COMMON STOCK
PREFERRED STOCK
DEBT SECURITIES
WARRANTS
RIGHTS
PURCHASE CONTRACTS
UNITS

This prospectus will allow us to issue, from time to time at prices and on terms to be determined at or prior to the time of the offering, up to $125,000,000 of any combination of the securities described in this prospectus, either individually or in units. We may also offer common stock or preferred stock upon conversion of or exchange for the debt securities; common stock upon conversion of or exchange for the preferred stock; common stock, preferred stock or debt securities upon the exercise of warrants, rights or performance of purchase contracts; or any combination of these securities upon the performance of purchase contracts.

This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. We will provide you with specific terms of any offering in one or more supplements to this prospectus. The prospectus supplements will also describe the specific manner in which these securities will be offered and may also supplement, update or amend information contained in this document. You should read this prospectus and any prospectus supplement, as well as any documents incorporated by reference into this prospectus or any prospectus supplement, carefully before you invest.

Our securities may be sold directly by us to you, through agents designated from time to time or to or through underwriters or dealers. 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 or agents are involved in the sale of our securities with respect to which this prospectus is being delivered, the names of such underwriters or agents and any applicable fees, commissions or discounts and over-allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds that 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 Market under the symbol “ARIA.” On January 8, 2010, the last reported sale price of our common stock was $2.45 per share. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on The NASDAQ Global Market or any securities market or other securities exchange of the securities covered by the prospectus supplement. Prospective purchasers of our securities are urged to obtain current information as to the market prices of our securities, where applicable.

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks that we have described on page 4 of this prospectus under the caption “Risk Factors”. We may include specific risk factors in supplements to this prospectus under the caption “Risk Factors”. This prospectus may not be used to offer or sell our 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 January 21, 2010.

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission, or SEC, utilizing a “shelf” registration process. Under this shelf registration process, we may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants, rights or purchase contracts to purchase any of such securities, either individually or in units, in one or more offerings, with a total value of up to $125,000,000. 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 contain specific information about the terms of that offering.

This prospectus does not contain all of the information included in the registration statement. For a more complete understanding of the offering of the securities, you should refer to the registration statement, including its exhibits. The prospectus supplement may also add, update or change information contained or incorporated by reference in this prospectus. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness. This prospectus, together with the applicable prospectus supplements and the documents incorporated by reference into this prospectus, includes all material information relating to the offering of securities under this prospectus. You should carefully read this prospectus, the applicable prospectus supplement, the information and documents incorporated herein by reference and the additional information under the heading “Where You Can Find More Information” before making an investment decision.

You should rely only on the information we have provided or incorporated by reference in this prospectus or any prospectus supplement. We have not authorized anyone to provide you with information different from that contained or incorporated by reference in this prospectus. No dealer, salesperson or other person is authorized to give any information or to represent anything not contained or incorporated by reference in this prospectus. You must not rely on any unauthorized information or representation. This prospectus is an offer to sell only the securities offered hereby, but only under circumstances and in jurisdictions where it is lawful to do so. You should assume that the information in this prospectus or any prospectus supplement is accurate only as of the date on the front of the document and that any information we have incorporated herein by reference is accurate only as of the date of the document incorporated by reference, regardless of the time of delivery of this prospectus or any sale of a security.

This prospectus may not be used to consummate sales of our securities, unless it is accompanied by a prospectus supplement. To the extent there are inconsistencies between any prospectus supplement, this prospectus and any documents incorporated by reference, the document with the most recent date will control.

Unless the context otherwise requires, “ARIAD,” “the Company,” “we,” “us,” “our” and similar terms refer to ARIAD Pharmaceuticals, Inc. and our subsidiaries, unless the context requires otherwise.

PROSPECTUS SUMMARY

The following is a summary of what we believe to be the most important aspects of our business and the offering of our securities under this prospectus. We urge you to read this entire prospectus, including the more detailed consolidated financial statements, notes to the consolidated financial statements and other information incorporated by reference from our other filings with the SEC or included in any applicable prospectus supplement. Investing in our securities involves risks. Therefore, carefully consider the risk factors in any prospectus supplements and in our most recent annual and quarterly filings with the SEC, as well as other information in this prospectus and any prospectus supplements and the documents incorporated by reference herein or therein, before purchasing our securities. Each of the risk factors could adversely affect our business, operating results and financial condition, as well as adversely affect the value of an investment in our securities.

About ARIAD Pharmaceuticals, Inc.

Our Business and Strategy


	•	build a fully integrated oncology company and become a leader in the discovery, development and commercialization of molecularly targeted oncology therapies;

	•	broadly develop our lead oncology product candidates and build a pipeline of innovative follow-on product candidates;

	•	enter into partnerships with major pharmaceutical or biotechnology companies, after obtaining definitive clinical data, to assist in developing our cancer product candidates and commercializing them in selected markets;

	•	license our NF-κB and ARGENT cell-signaling regulation technologies to pharmaceutical and biotechnology companies; and

	•	leverage the market potential of our product candidates by licensing them to other companies for development and commercialization in non-oncology indications or non-core applications.

Our Product Candidates

Our lead cancer product candidate, ridaforolimus, previously known as deforolimus, is being studied in multiple clinical trials in patients with various types of cancers. In July 2007, we entered into a global collaboration with Merck & Co., Inc., or Merck, to jointly develop and commercialize ridaforolimus for use in cancer. We initiated patient enrollment in our initial Phase 3 clinical trial of ridaforolimus in patients with metastatic sarcoma in the third quarter of 2007. We completed patient enrollment in this Phase 3 clinical trial during December 2009. We also expect to obtain the results of the second interim analysis of the primary endpoint of this trial, progression-free survival or PFS, in the first half of 2010 and the final analysis of PFS in the second half of 2010. In addition, in 2008 and 2009, we and Merck initiated patient enrollment in Phase 2 clinical trials in patients with metastatic breast cancer, metastatic endometrial cancer, metastatic non-small-cell lung cancer and advanced prostate cancer, and Phase 1 clinical trials of ridaforolimus in combination with other agents, all as part of our joint global development plan with Merck. These various trials are ongoing at this time.

Our collaboration with Merck for the global development and commercialization of ridaforolimus anticipates that we together with Merck will conduct a broad-based development program in multiple potential indications. The collaboration agreement provides that each party will fund 50 percent of global development

costs, except for certain specific costs to be funded 100 percent by Merck. The collaboration agreement establishes responsibilities for supply of the product for development and commercial purposes, promotion, distribution and sales of the product, governance of the collaboration, termination provisions and other matters.

In addition to cost-sharing provisions, the collaboration agreement provides for an up-front payment by Merck of $75 million, which was paid to us in July 2007, up to $452 million in milestone payments based on the successful development of ridaforolimus in multiple potential cancer indications, of which $53.5 million has been paid to us through September 30, 2009, and up to $200 million in milestone payments based on achievement of specified product sales thresholds. The upfront payment and milestone payments, when earned by us and paid by Merck, are non-refundable. Merck has also agreed to provide us with up to $200 million in interest-bearing, repayable, development cost advances to cover a portion of our share of global development costs, after we have paid $150 million in global development costs and have obtained regulatory approval to market ridaforolimus from the Food and Drug Administration, or FDA, in the United States or similar regulatory authorities in Europe or Japan. The collaboration agreement provides that each party will receive 50 percent of the profit from the sales of ridaforolimus in the United States, and Merck will pay us tiered double-digit royalties on sales of ridaforolimus outside the United States.

Our second product candidate, AP24534, is an investigational, multi-targeted kinase inhibitor that we believe has potential applications in various hematological cancers and solid tumors and is wholly owned by us. Kinases are a large family of cell-signaling proteins that control many aspects of cell behavior and are often inappropriately activated in cancer cells. In preclinical studies, AP24534 demonstrated potent inhibition of Bcr-Abl, a kinase that, when activated, causes chronic myeloid leukemia, or CML, as well as mutants of this kinase, including the T315I mutant that is resistant to all of the currently marketed therapies for CML. In additional preclinical studies, AP24534 was also shown to inhibit Flt3, a kinase involved in acute myeloid leukemia, or AML, as well as kinases that control angiogenesis, or new blood vessel formation, a process important in the progression of many solid tumors. AP24534 has undergone extensive preclinical testing, including efficacy models and safety-assessment studies, which we believe indicate that it should be well tolerated at anticipated therapeutic dose levels in cancer patients. In 2008, we initiated a Phase 1 clinical trial of AP24534 in patients with refractory CML, AML and other hematological malignancies. Initial data from this trial were presented at a medical meeting in December 2009 and demonstrated hematologic, cytogenetic, and molecular responses in heavily pretreated patients with refractory CML. Pending further analysis of the results of this trial and discussions with regulatory authorities, we believe that we will be able to proceed to a registration trial of this product candidate in 2010.

In the second quarter of 2009, we designated our third product candidate, AP26113, an investigational anaplastic lymphoma kinase, or ALK, inhibitor, as a development candidate, and we have commenced preclinical testing and investigational new drug, or IND, enabling studies of this product candidate. We believe this product candidate has the potential to regulate multiple cancer pathways and to be used in the treatment of certain patients with various cancers, including non-small cell lung cancer, lymphoma and neuroblastoma. In addition to our lead development programs, we have a focused drug discovery program centered on small-molecule, molecularly targeted therapies and cell-signaling pathways implicated in cancer. Our drug discovery program builds on our expertise in cell signaling, cancer biology, structure-based drug design and computational chemistry in designing and characterizing small-molecule drug candidates, such as ridaforolimus, AP24534 and AP26113, to treat disease.

Our Technologies

We are the exclusive licensee of a family of patents, three in the U.S. and one in Europe, including a pioneering U.S. patent covering methods of treating human disease by regulating NF-κB cell-signaling activity. Additionally, we have also developed a proprietary portfolio of cell-signaling regulation technologies, our ARGENT technology, to control intracellular processes with small molecules, which may be useful in the development of therapeutic vaccines and gene and cell therapy products and which provide versatile tools for applications in cell biology, functional genomics and drug discovery research.

Additional Information

We were organized as a Delaware corporation in April 1991. Our corporate headquarters are located at 26 Landsdowne Street, Cambridge, Massachusetts 02139-4234, and our telephone number is (617) 494-0400. We maintain an internet website at www.ariad.com. The information on our website and any other website is not incorporated by reference into this prospectus or any accompanying prospectus supplement and does not constitute a part of this prospectus or any accompanying prospectus supplement. Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K and all amendments to such reports are made available free of charge through the Investor Relations section of our website as soon as reasonably practicable after they have been filed or furnished with the SEC.

ARIAD and the ARIAD logo are our registered trademarks. ARGENT is our trademark. Other service marks, trademarks and trade names appearing in this prospectus are the property of their respective owners.

Offerings Under This Prospectus

Under this prospectus, we may offer shares of our common stock and preferred stock, various series of debt securities and/or warrants, rights or purchase contracts to purchase any of such securities, either individually or in units, with a total value of up to $125,000,000, from time to time at prices and on terms to be determined by market conditions at the time of 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;

	•	aggregate principal amount or aggregate offering price;

	•	maturity, if applicable;

	•	rates and times of payment of interest or dividends, if any;

	•	redemption, conversion or sinking fund terms, if any;

	•	voting or other rights, if any;

	•	conversion or exercise prices, if any; and

	•	important United States federal income tax considerations.

The prospectus supplement also may add, update or change information contained in this prospectus or in documents we have incorporated by reference into this prospectus. However, no prospectus supplement will fundamentally change the terms that are set forth in this prospectus or offer a security that is not registered and described in this prospectus at the time of its effectiveness.

This prospectus may not be used to consummate a sale of any 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 or underwriters, reserve the right to accept or reject all or part of any proposed purchase of securities. If we offer securities through agents or underwriters, we will include in the applicable prospectus supplement:


	•	the names of those agents or underwriters;

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

	•	details regarding over-allotment options, if any; and

	•	the net proceeds to us.

RISK FACTORS

Investing in our securities involves significant risk. The prospectus supplement applicable to each offering of our securities will contain a discussion of the risks applicable to an investment in ARIAD. Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading “Risk Factors” in the applicable prospectus supplement, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus. You should also consider the risks, uncertainties and assumptions discussed under the heading “Risk Factors” included in our most recent annual report on Form 10-K, as revised or supplemented by our most recent quarterly report on Form 10-Q or our current reports on Form 8-K, each of which are on file with the SEC and are incorporated herein by reference, and which may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future.

DEFICIENCY OF EARNINGS TO FIXED CHARGES

We did not record earnings for any of the years ended December 31, 2004, 2005, 2006, 2007 or 2008 or for the nine-month period ended September 30, 2009. Accordingly, our earnings were insufficient to cover our fixed charges in such periods and we are unable to disclose a ratio of earnings to fixed charges. The following table sets forth, for each of the periods presented, the dollar amount of the deficiency of earnings available to cover fixed charges. For purposes of computing the deficiency of earnings available to cover fixed charges, fixed charges represent interest expensed and capitalized. This table is qualified by the more detailed information appearing in the computation table found in Exhibit 12.1 to the registration statement of which this prospectus is a part. We have not included a ratio of combined fixed charges and preferred stock dividends to earnings because we do not have any preferred stock outstanding.


											Nine
											Months
	Year Ended December 31,										Ended
	2004		2005		2006		2007		2008		September 30, 2009
	(In thousands)

Coverage deficiency	$	35,573	$	55,510	$	61,914	$	58,508	$	71,052		$	62,000

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

The SEC encourages companies to disclose forward-looking information so that investors can better understand a company’s future prospects and make informed investment decisions. This prospectus and the documents we have filed with the SEC that are incorporated herein by reference contain such “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995.

Such statements in connection with any discussion of future operations or financial performance are identified by the use of words such as “may,” “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” and other words and terms of similar meaning. Such statements are based on management’s expectations and are subject to certain factors, risks and uncertainties that may cause actual results, outcome of events, timing and performance to differ materially from those expressed or implied by such statements. These risks and uncertainties include, but are not limited to, the costs associated with our research, development, manufacturing and other activities, the conduct and results of pre-clinical and clinical studies of our product candidates, difficulties or delays in obtaining regulatory approvals to market products resulting from our development efforts, our reliance on strategic partners and licensees and other key parties for the successful development, manufacturing and commercialization of products, the adequacy of our capital resources and the availability of additional funding, patent protection and third-party intellectual property claims relating to our and any partner’s product candidates, the timing, scope, cost and outcome of legal proceedings, future capital needs, risks related to key employees, markets, economic conditions, prices, reimbursement rates, competition and other factors detailed under the heading “Risk Factors” in this prospectus as updated and supplemented by the discussion of risks and uncertainties under “Risk Factors” contained in any supplements to this prospectus and in our most recent annual report on Form 10-K, as revised or

supplemented by our most recent quarterly report on Form 10-Q or our current reports on Form 8-K, as well as any amendments thereto, as filed with the SEC and which are incorporated herein by reference. The information contained in this document is believed to be current as of the date of this document. We do not intend to update any of the forward-looking statements after the date of this document to conform these statements to actual results or to changes in our expectations, except as required by law.

In light of these assumptions, risks and uncertainties, the results and events discussed in the forward-looking statements contained in this prospectus or in any document incorporated herein by reference might not occur. Investors are cautioned not to place undue reliance on the forward-looking statements, which speak only as of the date of this prospectus or the date of the document incorporated by reference in this prospectus. We are not under any obligation, and we expressly disclaim any obligation, to update or alter any forward-looking statements, whether as a result of new information, future events or otherwise. All subsequent forward-looking statements attributable to us or to any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section.

USE OF PROCEEDS

We cannot assure you that we will receive any proceeds in connection with securities offered pursuant to this prospectus. Unless otherwise indicated in the applicable prospectus supplement, we intend to use any net proceeds from the sale of securities under this prospectus for our operations, including, but not limited to, research and development, clinical trials, product manufacturing, intellectual property protection and enforcement, and working capital, and for other general corporate purposes, including, but not limited to, repayment or refinancing of existing indebtedness or other corporate borrowings, capital expenditures and possible acquisitions. We have not determined the amounts we plan to spend on any of the areas listed above or the timing of these expenditures. As a result, our management will have broad discretion to allocate the net proceeds, if any, we receive in connection with securities offered pursuant to this prospectus for any purpose. Pending application of the net proceeds as described above, we may initially invest the net proceeds in short-term, investment-grade, interest-bearing securities or apply them to the reduction of short-term indebtedness.

PLAN OF DISTRIBUTION

We may offer securities under this prospectus from time to time pursuant to underwritten public offerings, negotiated transactions, block trades or a combination of these methods. We may sell the securities (1) through underwriters or dealers, (2) through agents or (3) directly to one or more purchasers, or through a combination of such methods. We may distribute the securities from time to time in one or more transactions at:


	•	a fixed price or prices, which may be changed from time to time;

	•	market prices prevailing at the time of sale;

	•	prices related to the prevailing market prices; or

	•	negotiated prices.

We may directly solicit offers to purchase the securities being offered by this prospectus. We may also designate agents to solicit offers to purchase the securities from time to time. We will name in a prospectus supplement any underwriter or agent involved in the offer or sale of the securities.

If we utilize a dealer in the sale of the securities being offered by this prospectus, we will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

If we utilize an underwriter in the sale of the securities being offered by this prospectus, we will execute an underwriting agreement with the underwriter at the time of sale, and we will provide the name of any underwriter in the prospectus supplement which the underwriter will use to make resales of the securities to the public. In connection with the sale of the securities, we, or the purchasers of the securities for whom the underwriter may act as agent, may compensate the underwriter in the form of underwriting discounts or

commissions. The underwriter may sell the securities to or through dealers, and the underwriter may compensate those dealers in the form of discounts, concessions or commissions.

With respect to underwritten public offerings, negotiated transactions and block trades, we will provide in the applicable prospectus supplement any compensation we pay to underwriters, dealers or agents in connection with the offering of the securities, and any discounts, concessions or commissions allowed by underwriters to participating dealers. Underwriters, dealers and agents participating in the distribution of the securities may be deemed to be underwriters within the meaning of the Securities Act of 1933, as amended, or the Securities Act, and any discounts and commissions received by them and any profit realized by them on resale of the securities may be deemed to be underwriting discounts and commissions. We may enter into agreements to indemnify underwriters, dealers and agents against civil liabilities, including liabilities under the Securities Act, or to contribute to payments they may be required to make in respect thereof.

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in the prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in the prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:


	•	the purchase by an institution of the securities covered under that contract shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that institution is subject; and

	•	if the securities are also being sold to underwriters acting as principals for their own account, the underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

Shares of our common stock sold pursuant to the registration statement of which this prospectus is a part will be authorized for quotation and trading on The NASDAQ Global Market. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on The NASDAQ Global Market or any securities market or other securities exchange of the securities covered by the prospectus supplement. We can make no assurance as to the liquidity of or the existence of trading markets for any of the securities.

In order to facilitate the offering of the securities, certain persons participating in the offering may engage in transactions that stabilize, maintain or otherwise affect the price of the securities. This may include over-allotments or short sales of the securities, which involve the sale by persons participating in the offering of more securities than we sold to them. In these circumstances, these persons would cover such over-allotments or short positions by making purchases in the open market or by exercising their over-allotment option. In addition, these persons may stabilize or maintain the price of the securities by bidding for or purchasing the applicable security in the open market or by imposing penalty bids, whereby selling concessions allowed to dealers participating in the offering may be reclaimed if the securities sold by them are repurchased in connection with stabilization transactions. The effect of these transactions may be to stabilize or maintain the market price of the securities at a level above that which might otherwise prevail in the open market. These transactions may be discontinued at any time.

The underwriters, dealers and agents may engage in other transactions with us, or perform other services for us, in the ordinary course of their business.

DESCRIPTION OF COMMON STOCK

We are authorized to issue 145,000,000 shares of common stock, par value $0.001 per share. On December 31, 2009, we had 109,042,782 shares of common stock outstanding and approximately 480 stockholders of record.

The following summary of certain provisions of our common stock does not purport to be complete. You should refer to our certificate of incorporation, as amended, and our restated bylaws, both of which are included as exhibits to the registration statement of which this prospectus is a part. The summary below is also qualified by provisions of applicable law.

General

Holders of common stock are entitled to one vote per share on matters on which our stockholders vote. There are no cumulative voting rights. Our bylaws require that one-third of the issued and outstanding shares of common stock be represented in person or by proxy to constitute a quorum and transact business at a stockholder meeting. Holders of common stock are entitled to receive dividends, if declared by our board of directors, out of funds that we may legally use to pay dividends. If we liquidate or dissolve, holders of common stock are entitled to share ratably in our assets once our debts and any liquidation preference owed to any then-outstanding preferred stockholders are paid. Our certificate of incorporation does not provide the common stock with any redemption, conversion, preferential or preemptive rights. All shares of common stock that are outstanding as of the date of this prospectus and, upon issuance and sale, all shares being sold under this prospectus, will be fully-paid and nonassessable.

Shareholder Rights Plan

On June 8, 2000, we entered into a Rights Agreement with State Street Bank and Trust Company, as rights agent, and approved the declaration of a dividend distribution of one preferred share purchase right on each outstanding share of our common stock. Each right entitles the registered holder to purchase from us one one-thousandth of a share of our Series A Preferred Stock at a price of $65.00 per one one-thousandth of a share of Series A Preferred Stock, subject to adjustment. Because of the nature of the preferred stock’s dividend, liquidation and voting rights, the value of the one one-thousandth 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. The rights are protected by customary anti-dilution provisions.

In general, the rights become exercisable if a person or group acquires or announces a tender offer to acquire 15% or more of our common stock. Our board of directors will, in general, be entitled to redeem the rights at one cent per right at any time before any such person acquires 15% or more of our outstanding common stock. Rights held by the person acquiring 15% or more will become void. If we are acquired in a merger or other business combination transaction after a person acquires 15% or more of our common stock, each right will entitle its holder to purchase, at the right’s then-current exercise price, a number of shares of the acquiring company’s common stock having a market value at that time of twice the right’s exercise price. The dividend distribution of the preferred share purchase rights was payable on July 19, 2000 to stockholders of record on June 19, 2000. The rights will expire on June 19, 2010. The rights distribution is not taxable to stockholders.

The above summary of the Rights Agreement does not purport to be complete. You should refer to the Rights Agreement, as amended, which is included as an exhibit to the registration statement of which this prospectus is a part.

Transfer Agent and Registrar

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

NASDAQ Global Market

Our common stock is listed for quotation on The NASDAQ Global Market under the symbol “ARIA.” On January 8, 2010, the last reported sale price of our common stock was $2.45 per share.

DESCRIPTION OF PREFERRED STOCK

We are authorized to issue 10,000,000 shares of preferred stock, par value $0.01 per share, of which 500,000 shares have been designated Series A Preferred Stock. As of December 31, 2009, no shares of our preferred stock were outstanding. The following summary of certain provisions of our preferred stock does not purport to be complete. You should refer to our certificate of incorporation, as amended, and our restated bylaws, both of which are included as exhibits to the registration statement of which this prospectus is a part. The summary below is also qualified by provisions of applicable law.

General

Our board of directors may, without further action by our stockholders, from time to time, direct the issuance of shares of preferred stock in series and may, at the time of issuance, determine the rights, preferences and limitations of each series, including voting rights, dividend rights and redemption and liquidation preferences. Satisfaction of any dividend preferences of outstanding shares of preferred stock would reduce the amount of funds available for the payment of dividends on shares of our common stock. Holders of shares of preferred stock may be entitled to receive a preference payment in the event of any liquidation, dissolution or winding-up of our company before any payment is made to the holders of shares of our common stock. In some circumstances, the issuance of shares of preferred stock may render more difficult or tend to discourage a merger, tender offer or proxy contest, the assumption of control by a holder of a large block of our securities or the removal of incumbent management. Upon the affirmative vote of our board of directors, without stockholder approval, we may issue shares of preferred stock with voting and conversion rights which could adversely affect the holders of shares of our common stock.

If we offer a specific series of preferred stock under this prospectus, we will describe the terms of the preferred stock in the prospectus supplement for such offering and will file a copy of the certificate establishing the terms of the preferred stock with the SEC. To the extent required, this description will include:


	•	the title and stated value;

	•	the number of shares offered, the liquidation preference per share and the purchase price;

	•	the dividend rate(s), period(s) and/or payment date(s), or method(s) of calculation for such dividends;

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

	•	the procedures for any auction and remarketing, if any;

	•	the provisions for a sinking fund, if any;

	•	the provisions for redemption, if applicable;

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

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

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

	•	voting rights, if any, of the preferred stock;

	•	a discussion of any material and/or special U.S. federal income tax considerations applicable to the preferred stock;

	•	the relative ranking and preferences of the preferred stock as to dividend rights and rights upon liquidation, dissolution or winding up of the affairs of ARIAD; and

	•	any material limitations on 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 upon liquidation, dissolution or winding up of ARIAD.

Transfer Agent and Registrar

The transfer agent and registrar for our preferred stock will be set forth in the applicable prospectus supplement.

DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any future debt securities we may offer pursuant to this prospectus, we will describe the particular terms of any debt securities that we may offer in more detail in the applicable prospectus supplement. If we indicate in a prospectus supplement, the terms of any debt securities we offer under that prospectus supplement may differ from the terms we describe below.

We may sell from time to time, in one or more offerings under this prospectus, debt securities, which may be senior or subordinated. We will issue any such senior debt securities under a senior indenture that we will enter into with a trustee to be named in the senior indenture. We will issue any such subordinated debt securities under a subordinated indenture, which we will enter into with a trustee to be named in the subordinated indenture. We have filed forms of these documents as exhibits to the registration statement of which this prospectus is a part. We use the term “indentures” to refer to both the senior indenture and the subordinated indenture. The indentures will be qualified under the Trust Indenture Act of 1939, as in effect on the date of the indenture. We use the term “debenture trustee” to refer to either the trustee or under the senior indenture or the trustee under the subordinated indenture, as applicable.

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 the provisions of the indenture applicable to a particular series of debt securities.

We conduct some of our operations through our subsidiaries. Our rights and the rights of our creditors, including holders of debt securities, to the assets of any subsidiary of ours upon that subsidiary’s liquidation or reorganization or otherwise would be subject to the prior claims of that subsidiary’s creditors, except to the extent that we may be a creditor with recognized claims against the subsidiary. Our subsidiaries’ creditors would include trade creditors, debt holders, secured creditors and taxing authorities. Except as we may provide in a prospectus supplement, neither the debt securities nor the indentures restrict us or any of our subsidiaries from incurring indebtedness or from imposing restrictions on the ability of our subsidiaries to pay dividends to us or others. Under this caption, the phrase “the Company” refers solely to ARIAD Pharmaceuticals, Inc.

General

Each indenture provides that debt securities may be issued from time to time in one or more series and may be denominated and payable in foreign currencies or units based on or relating to foreign currencies, including European Currency Units. Neither indenture limits the amount of debt securities that may be issued thereunder, and each indenture provides that the specific terms of any series of debt securities shall be set forth in, or determined pursuant to, an authorizing resolution and/or a supplemental indenture, if any, relating to such series.

We will describe in each prospectus supplement the following terms relating to a series of debt securities:


	•	the title or designation;

	•	the aggregate principal amount and any limit on the amount that may be issued;

	•	the currency or units based on or relating to currencies in which debt securities of such series are denominated and the currency or units in which principal or interest or both will or may be payable;

	•	whether we will issue the series of debt securities in global form, the terms of any global securities and who the depositary will be;


	•	the maturity date and the date or dates on which principal will be payable;

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

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

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

	•	the place or places where payments will be payable;

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

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

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

	•	whether the indenture will restrict our ability to pay dividends, or will require us to maintain any asset ratios or reserves;

	•	whether we will be restricted from incurring any additional indebtedness;

	•	a discussion on any material or special United States federal income tax considerations applicable to a series of debt securities;

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

	•	any other specific terms, preferences, rights or limitations of, or restrictions on, the debt securities.

We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

Conversion or Exchange Rights

We will set forth in the prospectus supplement the terms, if any, on which a series of debt securities may be convertible into or exchangeable for our common stock or our other securities. 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; No Protection in Event of a Change of Control or Highly Leveraged Transaction

The indentures do 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.

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions that may afford holders of the debt securities protection in the event we have a change of control or in the event of a highly leveraged transaction (whether or not such transaction results in a change of control), which could adversely affect holders of debt securities.

Events of Default Under the Indenture

The following are events of default under the indentures with respect to any series of debt securities that we may issue:


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

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

	•	if we fail to observe or perform any other covenant relating to such series contained in the debt securities of such series or the applicable indentures, other than a covenant specifically relating to and for the benefit of holders of another series of debt securities, and our failure continues for 90 days after we receive written notice from the debenture trustee or holders of not less than a majority in aggregate principal amount of the outstanding debt securities of the applicable series; and

	•	if specified events of bankruptcy, insolvency or reorganization occur as to us.

No event of default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an event of default with respect to any other series of debt securities. The occurrence of an event of default may constitute an event of default under any bank credit agreements we may have in existence from time to time. In addition, the occurrence of certain events of default or an acceleration under the indenture may constitute an event of default under certain of our other indebtedness outstanding from time to time.

If an event of default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than a majority in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the debenture trustee if given by the holders), declare to be due and payable immediately the principal (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) of and premium and accrued and unpaid interest, if any, on all debt securities of that series. Before a judgment or decree for payment of the money due has been obtained with respect to debt securities of any series, the holders of a majority in principal amount of the outstanding debt securities of that series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) may rescind and annul the acceleration if all events of default, other than the non-payment of accelerated principal, premium, if any, and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the applicable indenture (including payments or deposits in respect of principal, premium or interest that had become due other than as a result of such acceleration). We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an 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:


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

	•	subject to its duties under the Trust Indenture Act, 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 only have the right to institute a proceeding under the indentures or to appoint a receiver or trustee, or to seek other remedies if:


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

	•	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

	•	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 (or at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) other conflicting directions within 60 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 applicable debenture trustee regarding our compliance with specified covenants in the applicable indenture.

Modification of Indenture; Waiver

The debenture trustee and we may change the applicable indenture without the consent of any holders with respect to specific matters, including:


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

	•	to change anything that does not materially adversely affect the interests of any holder of debt securities of any series issued pursuant to such indenture.

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 (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) that is affected. However, the debenture trustee and we may make the following changes only with the consent of each holder of any outstanding debt securities affected:


	•	extending the fixed maturity of the series of debt securities;

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

	•	reducing the principal amount of discount securities payable upon acceleration of maturity;

	•	making the principal of or premium or interest on any debt security payable in currency other than that stated in the debt security; or

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

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on any debt security of that series or in respect of a covenant or provision, which

cannot be modified or amended without the consent of the holder of each outstanding debt security of the series affected; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration.

Discharge

Each indenture provides that we can elect to be discharged from our obligations with respect to one or more series of debt securities, except for obligations to:


	•	register the transfer or exchange of debt securities of the series;

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

	•	maintain paying agencies;

	•	hold monies for payment in trust;

	•	compensate and indemnify the trustee; and

	•	appoint any successor trustee.

In order to exercise our rights to be discharged with respect to a series, we must deposit with the trustee money or government obligations sufficient to pay all the principal of, the 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 the debt securities of each series only in fully registered form without coupons and, unless we otherwise specify 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 another depositary named by us and identified in a prospectus supplement with respect to that series.

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 set forth 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 or in the applicable indenture, we will make 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:


	•	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


	•	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 the applicable 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 under such indenture 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, will we make interest payments by check which we will mail to the holder. Unless we otherwise indicate in a 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 which 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 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 is applicable.

Subordination of Subordinated Debt Securities

The obligations of the Company pursuant to any 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 senior indebtedness we may incur. It also does not limit us from issuing any other secured or unsecured debt.

DESCRIPTION OF WARRANTS

General

We may issue warrants to purchase shares of our common stock, preferred stock and/or debt securities in one or more series together with other securities or separately, as described in the applicable prospectus supplement. Below is a description of certain general terms and provisions of the warrants that we may offer. Particular terms of the warrants will be described in the warrant agreements and the prospectus supplement relating to the warrants.

The applicable prospectus supplement will contain, where applicable, the following terms of and other information relating to the warrants:


	•	the specific designation and aggregate number of, and the price at which we will issue, the warrants;

	•	the currency or currency units in which the offering price, if any, and the exercise price are payable;

	•	the designation, amount and terms of the securities purchasable upon exercise of the warrants;

	•	if applicable, the exercise price for shares of our common stock and the number of shares of common stock to be received upon exercise of the warrants;

	•	if applicable, the exercise price for shares of our preferred stock, the number of shares of preferred stock to be received upon exercise, and a description of that series of our preferred stock;

	•	if applicable, the exercise price for our debt securities, the amount of debt securities to be received upon exercise, and a description of that series of debt securities;

	•	the date on which the right to exercise the warrants will begin and the date on which that right will expire or, if you may not continuously exercise the warrants throughout that period, the specific date or dates on which you may exercise the warrants;

	•	whether the warrants will be issued in fully registered form or bearer form, in definitive or global form or in any combination of these forms, although, in any case, the form of a warrant included in a unit will correspond to the form of the unit and of any security included in that unit;

	•	any applicable material U.S. federal income tax consequences;

	•	the identity of the warrant agent for the warrants and of any other depositaries, execution or paying agents, transfer agents, registrars or other agents;

	•	the proposed listing, if any, of the warrants or any securities purchasable upon exercise of the warrants on any securities exchange;

	•	if applicable, the date from and after which the warrants and the common stock, preferred stock and/or debt securities will be separately transferable;

	•	if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

	•	information with respect to book-entry procedures, if any;

	•	the anti-dilution provisions of the warrants, if any;

	•	any redemption or call provisions;

	•	whether the warrants are to be sold separately or with other securities as parts of units; and

	•	any additional terms of the warrants, including terms, procedures and limitations relating to the exchange and exercise of the warrants.

Transfer Agent and Registrar

The transfer agent and registrar for any warrants will be set forth in the applicable prospectus supplement.

DESCRIPTION OF RIGHTS

General

We may issue rights to our stockholders to purchase shares of our common stock, preferred stock or the other securities described in this prospectus. We may offer rights separately or together with one or more additional rights, debt securities, preferred stock, common stock, warrants or purchase contracts, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. Each series of rights will be issued under a separate rights agreement to be entered into between us and a bank or trust company, as rights agent. The rights agent will act solely as our agent in connection with the certificates relating to the rights of the series of certificates and will not assume any obligation or relationship of agency or trust for or with any holders of rights certificates or beneficial owners of rights. The following description sets forth certain general terms and provisions of the rights to which any prospectus supplement may relate. The particular terms of the rights to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the rights so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the rights, rights agreement or rights certificates described in a prospectus supplement differ from any of the terms described below, then the terms described below will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable rights agreement and rights certificate for additional information before you decide whether to purchase any of our rights.

We will provide in a prospectus supplement the following terms of the rights being issued:


	•	the date of determining the stockholders entitled to the rights distribution;

	•	the aggregate number of shares of common stock, preferred stock or other securities purchasable upon exercise of the rights;

	•	the exercise price;

	•	the aggregate number of rights issued;

	•	the date, if any, on and after which the rights will be separately transferable;

	•	the date on which the right to exercise the rights will commence, and the date on which the right to exercise the rights will expire;

	•	the method by which holders of rights will be entitled to exercise;

	•	the conditions to the completion of the offering, if any;

	•	the withdrawal, termination and cancellation rights, if any;

	•	whether the rights are transferrable;

	•	whether there are any backstop or standby purchaser or purchasers and the terms of their commitment, if any;

	•	whether stockholders are entitled to oversubscription rights, if any;

	•	any applicable federal income tax considerations; and

	•	any other terms of the rights, including terms, procedures and limitations relating to the distribution, exchange and exercise of the rights, as applicable.

Each right will entitle the holder of rights to purchase for cash the principal amount of shares of common stock, preferred stock or other securities at the exercise price provided in the applicable prospectus supplement. Rights may be exercised at any time up to the close of business on the expiration date for the rights provided in the applicable prospectus supplement.

Holders may exercise rights as described in the applicable prospectus supplement. Upon receipt of payment and the rights certificate properly completed and duly executed at the corporate trust office of the

rights agent or any other office indicated in the prospectus supplement, we will, as soon as practicable, forward the shares of common stock, preferred stock or other securities, as applicable, purchasable upon exercise of the rights. If less than all of the rights issued in any rights offering are exercised, we may offer any unsubscribed securities directly to persons other than stockholders, to or through agents, underwriters or dealers or through a combination of such methods, including pursuant to standby arrangements, as described in the applicable prospectus supplement.

Rights Agent

The rights agent for any rights we offer will be set forth in the applicable prospectus supplement.

DESCRIPTION OF PURCHASE CONTRACTS

We may issue purchase contracts, including contracts obligating holders to purchase from us, and for us to sell to holders, a specific or variable number of our debt securities, shares of common stock, preferred stock, warrants or rights, or securities of an entity unaffiliated with us, or any combination of the above, at a future date or dates. Alternatively, the purchase contracts may obligate us to purchase from holders, and obligate holders to sell to us, a specific or variable number of our debt securities, shares of common stock, preferred stock, warrants, rights or other property, or any combination of the above. The price of the securities or other property subject to the purchase contracts may be fixed at the time the purchase contracts are issued or may be determined by reference to a specific formula described in the purchase contracts. We may issue purchase contracts separately or as a part of units each consisting of a purchase contract and one or more of our other securities described in this prospectus or securities of third parties, including U.S. Treasury securities, securing the holder’s obligations under the purchase contract. The purchase contracts may require us to make periodic payments to holders or vice versa and the payments may be unsecured or pre-funded on some basis. The purchase contracts may require holders to secure the holder’s obligations in a manner specified in the applicable prospectus supplement.

The applicable prospectus supplement will describe the terms of any purchase contracts in respect of which this prospectus is being delivered, including, to the extent applicable, the following:


	•	whether the purchase contracts obligate the holder or us to purchase or sell, or both purchase and sell, the securities subject to purchase under the purchase contract, and the nature and amount of each of those securities, or the method of determining those amounts;

	•	whether the purchase contracts are to be prepaid;

	•	whether the purchase contracts are to be settled by delivery, or by reference or linkage to the value, performance or level of the securities subject to purchase under the purchase contract;

	•	any acceleration, cancellation, termination or other provisions relating to the settlement of the purchase contracts;

	•	any applicable federal income tax considerations; and

	•	whether the purchase contracts will be issued in fully registered or global form.

The preceding description sets forth certain general terms and provisions of the purchase contracts to which any prospectus supplement may relate. The particular terms of the purchase contracts to which any prospectus supplement may relate and the extent, if any, to which the general provisions may apply to the purchase contracts so offered will be described in the applicable prospectus supplement. To the extent that any particular terms of the purchase contracts described in a prospectus supplement differ from any of the terms described above, then the terms described above will be deemed to have been superseded by that prospectus supplement. We encourage you to read the applicable purchase contract for additional information before you decide whether to purchase any of our purchase contracts.

DESCRIPTION OF UNITS

The following description, together with the additional information that we include in any applicable prospectus supplements summarizes the material terms and provisions of the units that we may offer under this prospectus. 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, the form of unit agreement that describes the terms of the series of units we are offering, and any supplemental agreements, before the issuance of the related series of units. 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 the 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 the complete unit agreement and any supplemental agreements that contain the terms of the units.

General

We may issue units consisting of common stock, preferred stock, one or more debt securities, warrants, rights or purchase contacts for the purchase of common stock, preferred stock and/or debt securities in one or more series, in any combination. 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. The 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:


	•	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

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

	•	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 Common Stock,” “Description of Preferred Stock,” “Description of Debt Securities,” “Description of Warrants,” “Description of Rights” and “Description of Purchase Contracts” will apply to each unit, as applicable, and to any common stock, preferred stock, debt security, warrant, right or purchase contract included in each unit, as applicable.

Unit Agent

The name and address of the unit agent for any units we offer will be set forth in the applicable prospectus supplement.

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

Each 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 the 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.

CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF INCORPORATION AND BYLAWS

Anti-Takeover Provisions of our Delaware Certificate of Incorporation and Bylaws

In addition to the board of directors’ ability to issue shares of preferred stock, our certificate of incorporation and bylaws contain other provisions that are intended to enhance the likelihood of continuity and stability in the composition of the board of directors and which may have the effect of delaying, deferring or preventing a future takeover or change in control of our company unless such takeover or change in control is approved by our board of directors.

These provisions, summarized below, are expected to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our board of directors. We believe that the benefits of increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us outweigh the disadvantages of discouraging these proposals because negotiation of these proposals could result in an improvement of their terms.

Classified Board

Our certificate of incorporation provides for our board of directors to be divided into three classes, as nearly equal in number as possible, serving staggered terms. Approximately one-third of our board will be elected each year. Under the Delaware General Corporation Law, unless the certificate of incorporation otherwise provides, directors serving on a classified board can only be removed by the stockholders for cause. The provision for a classified board could prevent a party who acquires control of a majority of our outstanding common stock from obtaining control of our board of directors until our second annual stockholders meeting following the date the acquirer obtains the controlling stock interest. The classified board provision could have the effect of discouraging a potential acquirer from making a tender offer or otherwise attempting to obtain control of us and could increase the likelihood that incumbent directors will retain their positions.

Elimination of the Ability to Call Special Meeting

Our bylaws provide that, except as otherwise required by law, special meetings of our stockholders can only be called by our board of directors, our chief executive officer or upon the direction of either of the foregoing, our secretary. Stockholders are not permitted to call a special meeting or to require our board to call a special meeting.

Advanced Notice Procedures for Stockholder Proposals

Our bylaws establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to our board, as well as procedures for including proposed nominations at special meetings at which directors are to be elected. Stockholders at our annual meeting may only consider proposals or nominations specified in the notice of meeting or brought before the meeting by or at the direction of our board or by a stockholder who was a stockholder of record on the record date for the meeting, who is entitled to vote at the meeting and who has given to our secretary timely written notice, in proper form, of the stockholder’s intention to bring that business before the meeting, and who has complied with the procedures and requirements set forth in the bylaws. Although our bylaws do not give our board the power to approve or disapprove stockholder

nominations of candidates or proposals regarding other business to be conducted at a special or annual meeting, our bylaws may have the effect of precluding the conduct of some business at a meeting if the proper procedures are not followed or may discourage or defer a potential acquirer from conducting a solicitation of proxies to elect its own slate of directors or otherwise attempting to obtain control of us.

Provisions of Delaware Law Governing Business Combinations

We are subject to the “business combination” provisions of Section 203 of the Delaware General Corporation Law. In general, such provisions prohibit a publicly held Delaware corporation from engaging in any “business combination” transactions with any “interested stockholder” for a period of three years after the date on which the person became an “interested stockholder,” unless:


	•	prior to such date, the board of directors approved either the “business combination” or the transaction which resulted in the “interested stockholder” obtaining such status;

	•	upon consummation of the transaction which resulted in the stockholder becoming an “interested stockholder,” 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 voting stock outstanding (but not the outstanding voting stock owned by the “interested stockholder”) those shares owned by (a) persons who are directors and also officers and (b) 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

	•	at or subsequent to such time the “business combination” is approved by the board of directors and authorized at an annual or special meeting of stockholders, and not by written consent, by the affirmative vote of at least 662/3% of the outstanding voting stock which is not owned by the “interested stockholder.”

A “business combination” is defined to include mergers, asset sales and other transactions resulting in financial benefit to a stockholder. In general, an “interested stockholder” is a person who, together with affiliates and associates, owns 15% or more of a corporation’s voting stock or within three years did own 15% or more of a corporation’s voting stock. The statute could prohibit or delay mergers or other takeover or change in control attempts with respect to us and, accordingly, may discourage attempts to acquire us.

Limitations on Liability and Indemnification of Officers and Directors

Our certificate of incorporation limits the liability of our officers and directors to the fullest extent permitted by the Delaware General Corporation Law, and our certificate of incorporation and bylaws provide that we will indemnify them to the fullest extent permitted by such law. We have also entered into indemnification agreements with our directors and certain of our officers and key employees and expect to enter into a similar agreement with any new directors, officers or key employees.

LEGAL MATTERS

Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts, will pass upon the validity of the issuance of the securities offered by this prospectus. Members of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. and certain members of their families and trusts for their benefit own an aggregate of approximately 5,000 shares of our common stock.

EXPERTS

The financial statements incorporated in this prospectus by reference from the Company’s Annual Report on Form 10-K and the effectiveness of ARIAD Pharmaceuticals, Inc.’s internal control over financial reporting have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports which are incorporated herein by reference. Such financial statements have been so incorporated in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, and file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy these reports, proxy statements and other information at the SEC’s public reference facilities at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference facilities. SEC filings are also available at the SEC’s web site at http://www.sec.gov. Copies of information filed by us with the SEC are also available on our website at http://www.ariad.com under the heading “Investors/News.”

This prospectus is only part of a registration statement on Form S-3 that we have filed with the SEC under the Securities Act of 1933, as amended, and therefore omits certain information contained in the registration statement. We have also filed exhibits and schedules with the registration statement that are excluded from this prospectus, and you should refer to the applicable exhibit or schedule for a complete description of any statement referring to any contract or other document. You may inspect a copy of the registration statement, including the exhibits and schedules, without charge, at the public reference room or obtain a copy from the SEC upon payment of the fees prescribed by the SEC.

INCORPORATION OF DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information that we file with them. Incorporation by reference allows us to disclose important information to you by referring you to those other documents. The information incorporated by reference is an important part of this prospectus, and information that we file later with the SEC will automatically update and supersede this information. We filed a registration statement on Form S-3 under the Securities Act of 1933, as amended, with the SEC with respect to the securities being offered pursuant to this prospectus. This prospectus omits certain information contained in the registration statement, as permitted by the SEC. You should refer to the registration statement, including the exhibits, for further information about us and the securities being offered pursuant to this prospectus. Statements in this prospectus regarding the provisions of certain documents filed with, or incorporated by reference in, the registration statement are not necessarily complete and each statement is qualified in all respects by that reference. Copies of all or any part of the registration statement, including the documents incorporated by reference or the exhibits, may be obtained upon payment of the prescribed rates at the offices of the SEC listed above in “Where You Can Find More Information.” The documents we are incorporating by reference are (unless otherwise noted, the SEC file number for each of the documents listed below is 000-21696):


	•	Our annual report on Form 10-K for the fiscal year ended December 31, 2008, filed on March 16, 2009;

	•	Our quarterly reports on Form 10-Q for the quarters ended March 31, 2009, June 30, 2009 and September 30, 2009 filed on May 11, 2009, August 10, 2009 and November 9, 2009, respectively;

	•	Our current reports on Form 8-K filed on January 16, 2009 (Items 8.01 and 9.01), February 12, 2009 (Items 2.02 and 9.01), February 17, 2009 (Item 8.01), February 20, 2009 (Items 1.01 and 9.01), March 16, 2009 (Item 5.02), April 8, 2009 (Items 8.01 and 9.01), April 8, 2009 (Items 5.02 and 9.01), April 20, 2009 (Items 8.01 and 9.01), April 21, 2009 (Items 8.01 and 9.01), May 8, 2009 (Items 8.01 and 9.01), June 25, 2009 (Items 5.02 and 9.01), July 28, 2009 (Items 8.01 and 9.01), July 30, 2009 (Items 2.02, 7.01 and 9.01), August 3, 2009 (Items 8.01 and 9.01), August 4, 2009 (Items 1.01, 8.01 and 9.01), August 27, 2009 (Items 5.03 and 9.01), September 23, 2009 (Items 8.01 and 9.01), November 5, 2009 (Items 2.02, 7.01 and 9.01), December 7, 2009 (Items 8.01 and 9.01), December 15, 2009 (Items 8.01 and 9.01), and December 17, 2009 (Items 8.01 and 9.01).


	•	The portions of our Definitive Proxy Statement on Schedule 14A that are deemed “filed” with the SEC under the Securities Exchange Act of 1934, as amended, filed on April 30, 2009;

	•	The description of our common stock contained in our registration statement on Form 10/A filed on June 25, 1993, including any amendment or report filed for the purpose of updating such description;

	•	The description of our preferred share purchase rights contained in our registration statement on Form 8-A filed on June 19, 2000, including any amendment or report filed for the purpose of updating such description; and

	•	all reports and other documents subsequently filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, as amended, after the date of this prospectus and prior to the termination or completion of the offering of securities under this prospectus shall be deemed to be incorporated by reference in this prospectus and to be a part hereof from the date of filing such reports and other documents.

Any statement contained in this prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or any other subsequently filed document that is deemed to be incorporated by reference into this prospectus modifies or supersedes the statement. Any statement so modified or superseded will not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

You should rely only on information contained in, or incorporated by reference into, this prospectus and any prospectus supplement. We have not authorized anyone to provide you with information different from that contained in this prospectus or incorporated by reference in this prospectus. We are not making offers to sell the securities in any jurisdiction in which such an offer or solicitation is not authorized or in which the person making such offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such offer or solicitation.