Filed Pursuant to Rule 424(b)(5)

Registration File No. 333-140333

PROSPECTUS SUPPLEMENT

(To Prospectus dated February 16, 2007)

ARIAD Pharmaceuticals, Inc.

14,378,698 Shares of Common Stock

Warrants to Purchase 10,784,024 Shares of Common Stock

We are offering up to 14,378,698 shares of our common stock and warrants to purchase up to 10,784,024 shares of our common stock (and the shares of common stock issuable from time to time upon exercise of these warrants). The common stock and the warrants will be sold in units, with each unit consisting of one share of common stock and a warrant to purchase 0.75 shares of common stock, at an exercise price of $2.15 per share of common stock. Each unit will be sold at a negotiated price of $1.69 per unit. Units will not be issued or certificated. The shares of common stock and warrants are immediately separable and will be issued separately. We refer to the shares of common stock issued or issuable hereunder upon exercise of the warrants, and the warrants to purchase common stock issued hereunder, collectively, as the securities.

Our common stock is listed on The NASDAQ Global Market under the symbol “ARIA.” On February 19, 2009, the last reported sale price of our common stock on The NASDAQ Global Market was $1.69 per share.

We are offering these shares of common stock and warrants to purchase common stock on a best efforts basis primarily to institutional investors. We have retained Lazard Capital Markets LLC to act as the exclusive placement agent in connection with this offering.

Investing in our securities involves significant risks. See “Risk Factors” beginning on page S-4 of this prospectus supplement and page 8 of the accompanying prospectus.

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		Maximum
	Unit		Offering Amount
Public offering price	$	1.69	$	24,300,000
Placement agent’s fees	$	0.0845	$	1,215,000
Proceeds, before expenses, to us	$	1.6055	$	23,085,000

We estimate the total expenses of this offering, excluding the placement agent’s fees, will be approximately $275,000. Because there is no minimum offering amount required as a condition to closing in this offering, the actual offering amount, the placement agent’s fees and net proceeds to us, if any, in this offering may be substantially less than the total maximum offering amounts set forth above. We are not required to sell any specific number or dollar amount of the units offered in this offering, but the placement agent will use its best efforts to arrange for the sale of all of the units offered. Pursuant to an escrow agreement among us, the placement agent and an escrow agent, some or all of the funds received in payment for the units sold in this offering will be wired to a non-interest bearing escrow account and held until we and the placement agent notify the escrow agent that this offering has closed, indicating the date on which the shares and warrants are to be delivered to the purchasers and the proceeds are to be delivered to us.

Lazard Capital Markets

Prospectus Supplement dated February 19, 2009

TABLE OF CONTENTS

	Page
Prospectus Supplement
Prospectus Supplement Summary		S-1
Risk Factors		S-4
Special Note Regarding Forward-Looking Statements		S-5
Use of Proceeds		S-5
Dividend Policy		S-5
Dilution		S-6
Description of the Securities We are Offering		S-7
Plan of Distribution		S-9
Legal Matters		S-10
Experts		S-10
Incorporation of Documents by Reference		S-10

Prospectus
About this Prospectus	1
Prospectus Summary	2
Risk Factors	8
Deficiency of Earnings to Fixed Charges	8
Special Note Regarding Forward-Looking Statements	8
Use of Proceeds	9
Plan of Distribution	9
Description of Common Stock	12
Description of Preferred Stock	13
Description of Debt Securities	14
Description of Warrants	20
Description of Units	21
Certain Provisions of Delaware Law and of the Company’s Certificate of Incorporation and By-Laws	21
Legal Matters	23
Experts	23
Where you can Find More Information	23
Incorporation of Documents by Reference	23

You should rely only on the information contained in this prospectus supplement, the accompanying prospectus, any free writing prospectus that we authorized to be distributed to you or information incorporated by reference herein. We have not, and the placement agent has not, authorized anyone else to provide you with different information. You should not assume that the information in this prospectus supplement or the accompanying prospectus is accurate as of any date other than the date on the front of those documents or that any document incorporated by reference is accurate as of any date other than its filing date. You should not consider this prospectus supplement or the accompanying prospectus to be an offer or solicitation relating to the securities in any jurisdiction in which such an offer or solicitation relating to the securities is not authorized. Furthermore, you should not consider this prospectus supplement or the accompanying prospectus to be an offer or solicitation relating to the securities if the person making the offer or solicitation is not qualified to do so, or if it is unlawful for you to receive such an offer or solicitation.

This prospectus supplement is part of a registration statement that we have filed with the Securities and Exchange Commission utilizing a “shelf” registration process. Under this shelf registration process, we are offering to sell the securities using this prospectus supplement and the accompanying prospectus. In this prospectus supplement, we provide you with specific information about the securities that we are selling in this offering. Both this prospectus supplement and the accompanying prospectus include important information about us, the securities being offered and other information you should know before investing. This prospectus supplement also adds, updates and changes information contained in the accompanying prospectus. You should read both this prospectus supplement and the accompanying prospectus as well as additional information described under “Incorporation of Documents by Reference” on page S-10 of this prospectus supplement and page 23 of the accompanying prospectus before investing in our securities

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and information appearing elsewhere in this prospectus supplement and in the accompanying prospectus and in the documents we incorporate by reference. This summary is not complete and does not contain all of the information that you should consider before investing. After you read this summary, to fully understand this offering and its consequences to you, you should read and consider carefully the more detailed information and financial statements and related notes that we include in and/or incorporate by reference into this prospectus supplement and the accompanying prospectus, especially the section entitled “Risk Factors.” If you invest in our securities, you are assuming a high degree of risk. Unless stated otherwise, references in this prospectus supplement and the accompanying prospectus to “we,” “us,” or “our” refer to ARIAD Pharmaceuticals, Inc., unless the context requires otherwise.

ARIAD Pharmaceuticals, Inc.

Our Business and Strategy

ARIAD’s 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. Our business strategy is to:

•           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, deforolimus (previously known as AP23573), is an internally discovered, potent inhibitor of the protein mTOR, a “master switch” in cancer cells. Blocking mTOR creates a starvation-like effect in cancer cells by interfering with cell growth, division, metabolism and angiogenesis. We are developing deforolimus in partnership with Merck & Co., Inc., or Merck, under a collaboration agreement signed in July 2007. Pursuant to a global development plan established by us and Merck, we are developing deforolimus in multiple cancer indications, both as a single agent and in combination with various targeted agents. In 2007, we initiated our first Phase 3 clinical trial of oral deforolimus in patients with metastatic soft-tissue and bone sarcomas and, in 2008, we initiated Phase 2 clinical trials of oral deforolimus in patients with endometrial, breast and prostate cancers, and Phase 1 studies of deforolimus in combination with other agents, all as part of our global development plan with Merck.

Deforolimus is also being developed pursuant to license agreements with medical device companies for use on drug-eluting stents to prevent restenosis, or reblockage, of injured vessels following interventions in which stents are used in conjunction with balloon angioplasty. We have entered into two such license

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agreements to date, one with Medinol Ltd., or Medinol, and another with ICON Medical Corp., or ICON, and have retained the right to enter into one additional non-exclusive agreement in this area.

Our second product candidate, AP24534, is a novel multi-targeted kinase inhibitor that we believe has broad potential applications in cancer and is wholly owned by us. In preclinical studies, AP24534 demonstrated potent inhibition of a kinase that causes chronic myeloid leukemia, or CML, as well as mutants of this kinase, including a mutant that is resistant to all of the currently marketed therapies for CML. AP24534 also inhibits 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 multiple solid tumors. AP24534 has undergone extensive preclinical testing, including efficacy and safety assessment studies, which 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.

In 2009, we plan to initiate preclinical studies of our third, internally discovered drug candidate, an anaplastic lymphoma kinase, or ALK, inhibitor. We believe this product candidate has the potential to regulate multiple cancer pathways and to change the treatment of patients with non-small cell lung cancer, lymphoma and neuroblastoma.

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, hereinafter referred to as the ‘516 Patent. We permit broad use of our NF-κB intellectual property, at no cost, by investigators at academic and not-for-profit institutions to conduct non-commercial research. We have entered into two license agreements for use of our NF-κB cell-signaling technology for research and development purposes. The ‘516 Patent is the subject of two outstanding lawsuits and a proceeding before the United States Patent and Trademark Office, or PTO.

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. We distribute our ARGENT technologies at no cost to academic investigators in the form of our Regulation Kits to use in various research applications in an academic setting. In addition, we have licensed the ARGENT technology to several pharmaceutical and biotechnology companies for research and development and/or commercial purposes.

Corporate 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 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.

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The Offering

Common stock offered by us	14,378,698 shares
Common stock to be outstanding after this offering	86,357,681 shares
Warrants offered by us	Warrants to purchase 10,784,024 shares of common stock. The warrants will be exercisable during the period commencing six months after the date of original issuance and ending three years from the date of such issuance at an exercise price of $2.15 per share of common stock. This prospectus also relates to the offering of the shares of common stock issuable upon exercise of the warrants.
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, 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. See “Use of Proceeds” on page S-5.
Risk Factors	See “Risk Factors” beginning on page S-4 for a discussion of factors you should consider carefully when making an investment decision.
NASDAQ Global Market symbol	ARIA

The number of shares of our common stock to be outstanding immediately after this offering as shown above assumes that all of the units offered hereby are sold and is based on 71,978,983 shares of common stock outstanding as of February 19, 2009, and does not include 10,784,024 shares issuable upon the exercise of the warrants offered hereby and also excludes the following:

•           7,293,253 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans, at a weighted average exercise price of $5.00; and

•           441,000 shares of our common stock issuable upon the vesting of restricted stock units outstanding under our stock plans; and

•           2,453,056 shares of our common stock available for future grant or issuance pursuant to our employee stock purchase and stock plans.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before purchasing our securities, you should carefully consider the following risk factors as well as all other information contained in this prospectus supplement and the accompanying prospectus and incorporated by reference, including our consolidated financial statements and the related notes. The risks and uncertainties described below are not the only ones facing us. Additional risks and uncertainties that we are unaware of, or that we currently deem immaterial, also may become important factors that affect us. If any of the following risks occur, our business, financial condition or results of operations could be materially and adversely affected. In that case, the trading price of our common stock could decline, and you may lose some or all of your investment.

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.

Additional Risks Related to Our Business, Industry and an Investment in our Common Stock

For a discussion of additional risks associated with our business, our industry and an investment in our common stock, see the section entitled “Risk Factors” beginning on page 8 of the accompanying prospectus, as well as the disclosures contained in documents filed by us after the date of the accompanying prospectus pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, which are incorporated by reference into, and deemed to be a part of, the accompanying prospectus.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement and the accompanying prospectus and the documents we have filed with the SEC that are incorporated by reference into this prospectus supplement and the accompanying prospectus contain forward-looking statements, within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, that involve risk and uncertainties. Any statements contained, or incorporated by reference, in this prospectus supplement and the accompanying prospectus that are not statements of historical fact may be forward-looking statements. When we use the words “anticipates,” “plans,” “expects” and similar expressions, we are identifying forward-looking statements. Forward-looking statements involve risks and uncertainties which may cause our actual results, performance or achievements to be materially different from those expressed or implied by forward-looking statements. These factors include, among others, the uncertainties associated with product research and development, the risk that clinical trials by us or our collaborators will not be successful or commence or proceed as planned, the risks and uncertainties associated with dependence upon the actions of our collaborators and of government regulatory agencies, the risk that our intellectual property rights may be infringed or challenged by third parties, the uncertainty of future profitability and other factors set forth more fully in this prospectus supplement and the accompanying prospectus, including those described under “Risk Factors” beginning of page S-4 of this prospectus supplement and page 8 of the accompanying prospectus.

Although we believe that the expectations reflected in the forward-looking statements are reasonable, we cannot guarantee future results, levels of activity, performance or achievements. Except as may be required by law, we do not intend to update any of the forward-looking statements for any reason after the date of this prospectus supplement to conform such statements to actual results or if new information becomes available.

All forward-looking statements attributable to us, or to persons acting on our behalf, are expressly qualified in their entirety by these cautionary statements.

USE OF PROCEEDS

Assuming that all of the units offered hereby are sold, we estimate that the net proceeds to us will be approximately $22.8 million, after deducting the placement agent’s fee and estimated offering expenses (exclusive of proceeds, if any, from the exercise of warrants issued in this offering). 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, 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 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.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our common stock. We intend to retain any future earnings to finance the growth and development of our business and do not anticipate paying any cash dividends in the foreseeable future. In addition, the terms of our term loan place restrictions on our ability to pay dividends on our common stock.

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DILUTION

The pro forma net tangible book value of our common stock on September 30, 2008 was $(55.8) million, or $(0.78) per share of common stock. Our pro forma 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 September 30, 2008 after giving effect to the issuance of 2,252,128 shares of common stock by us after September 30, 2008 in connection with the merger of our majority-owned subsidiary, ARIAD Gene Therapeutics, Inc., with and into us.

Assuming the sale by us of all 14,378,698 units offered hereby at the offering price of $1.69 per unit (and assuming a value per share of common stock offered in each unit of $1.69 per share) and after deducting the placement agent’s fees and the estimated offering expenses, our pro forma as adjusted net tangible book value as of September 30, 2008 would have been $(33.0) million, or $(0.37) per share of our common stock. This represents an immediate increase in pro forma net tangible book value of $0.41 per share to our existing stockholders and an immediate decrease in the pro forma net tangible book value of $2.06 per share to investors participating in this offering. The following table illustrates this per share dilution:

Offering price per share included in each unit				$	1.69
Pro forma net tangible book value per share as of September 30, 2008	$	(0.78	)
Increase per share attributable to investors participating in this offering	$	0.41
Pro forma as adjusted net tangible book value per share after the offering					(0.37	)
Dilution per share to investors participating in this offering				$	2.06

The above discussion and table are based on 69,537,867 shares of our common stock outstanding as of September 30, 2008. The information above excludes the 10,784,024 shares of common stock issuable upon exercise of the warrants offered hereby and also excludes:

•   7,740,087 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans as of September 30, 2008, at a weighted average exercise price of $5.10;

•   489,000 shares of our common stock issuable upon the vesting of restricted stock units outstanding under our stock plans as of September 30, 2008; and

•   2,383,640 shares of our common stock available as of September 30, 2008 for future grant or issuance pursuant to our employee stock purchase and stock plans.

To the extent options outstanding as of September 30, 2008 have been or may be exercised or other shares have been or are issued, there may be further dilution to new investors.

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DESCRIPTION OF THE SECURITIES WE ARE OFFERING

In this offering, we are offering a maximum of 14,378,698 units, consisting of 14,378,698 shares of common stock and warrants to purchase an additional 10,784,024 shares of common stock. Each unit consists of one share of common stock and a warrant to purchase 0.75 of a share of common stock at an exercise price of $2.15 per share. Units will not be issued or certificated. The shares of common stock and warrants are immediately separable and will be issued separately. This prospectus also relates to the offering of shares of our common stock upon exercise, if any, of the warrants.

Common Stock

The material terms and provisions of our common stock are described under the caption “Description of Common Stock” starting on page 12 of the accompanying prospectus.

Warrants

The warrants offered in this offering will be issued pursuant to a subscription agreement between each of the purchasers and us. You should review a copy of the form of subscription agreement and the form of warrant, each of which will be filed by us as an exhibit to a Current Report on Form 8-K filed with the Securities and Exchange Commission in connection with this offering, for a complete description of the terms and conditions applicable to the warrants. The following is a brief summary of the material terms of the warrants and is subject in all respects to the provisions contained in the warrants.

Exercisability. Holders may exercise the warrants beginning on the date that is six months after the date of original issuance and at any time up to the date that is three years after such date of issuance. The warrants will be exercisable, at the option of each holder, in whole or in part by delivering to us a duly executed exercise notice accompanied by payment in full for the number of shares of our common stock purchased upon such exercise (except in the case of a cashless exercise as discussed below). Unless otherwise specified in the applicable warrant, except upon at least 61 days’ prior notice from the holder to us, the holder will not have the right to exercise any portion of the warrant if the holder (together with its affiliates) would beneficially own in excess of 9.9% of the number of shares of our common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the warrants.

Cashless Exercise. If at any time during the warrant exercisability period the holder is not permitted to sell shares of common stock issuable upon exercise of the warrant pursuant to the registration statement, and the fair market value of our common stock exceeds the exercise price of the warrants, the holder may elect to effect a cashless exercise of the warrants (in whole or in part) by surrendering the warrants to us together with delivery to us of a duly executed exercise notice, by canceling a portion of the warrant in payment of the purchase price payable in respect of the number of shares of our common stock purchased upon such exercise.

Exercise Price. The exercise price per share of common stock purchasable upon exercise of the warrants is $2.15 per share of common stock being purchased. The exercise price is subject to appropriate adjustment in the event of stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock.

Transferability. Subjects to applicable laws and the restriction on transfer set forth in the subscription agreements, the warrants may be transferred at the option of the holders upon surrender of the warrants to us together with the appropriate instruments of transfer.

Exchange Listing. We do not plan on making an application to list the warrants on The NASDAQ Global Market, any national securities exchange or other nationally recognized trading system.

Fundamental Transactions. In the event of any fundamental transaction, as described in the warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our common stock, then upon any subsequent exercise of a warrant, the holder shall have the right to receive as alternative consideration, for each share of our common

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stock that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction, the number of shares of common stock of the successor or acquiring corporation or of ARIAD, if it is the surviving corporation, and any additional consideration receivable upon or as a result of such transaction by a holder of the number of shares of our common stock for which the warrant is exercisable immediately prior to such event. In addition, in the event of a fundamental transaction in which the amount of the alternate consideration is less than the exercise price of the warrant, then we or any successor entity shall pay at the holder’s option, exercisable at any time concurrently with or within thirty (30) days after the consummation of the fundamental transaction, an amount of cash equal to the value of the warrant as determined in accordance with the Black Scholes option pricing model.

Rights as a Stockholder. Except as otherwise provided in the warrants or by virtue of such holder’s ownership of shares of our common stock, the holders of the warrants do not have the rights or privileges of holders of our common stock, including any voting rights, until they exercise their warrants.

Waivers and Amendments. Any term of the warrants may be amended or waived with our written consent and the written consent of the holders of warrants representing at least two-thirds of the number of shares of our common stock then subject to outstanding warrants, provided that such amendment or waiver applies to all warrants in the same fashion. However, in no event may the exercise price of or the number of shares of our common stock subject to any warrant be amended, nor may the right to exercise that warrant be waived, without the written consent of the holder of that warrant.

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PLAN OF DISTRIBUTION

We are offering the securities through a placement agent. Subject to the terms and conditions contained in the placement agent agreement, dated February 19, 2009, Lazard Capital Markets LLC has agreed to act as the placement agent for the sale of up to 14,378,698 units. The placement agent is not purchasing or selling any shares or warrants by this prospectus supplement or the accompanying prospectus, nor is it required to arrange for the purchase or sale of any specific number or dollar amount of units, but has agreed to use its best efforts to arrange for the sale of all units being offered hereby.

The placement agent agreement provides that the obligations of the placement agent and the investors are subject to certain conditions precedent, including the absence of any material adverse change in our business and the receipt of customary legal opinions, letters and certificates.

Confirmations and definitive prospectuses will be distributed to all investors who agree to purchase the units, informing investors of the closing date as to such units. We currently anticipate that closing of the sale of the units will take place on or about February 25, 2009. Investors will also be informed of the date and manner in which they must transmit the purchase price for their units.

On the scheduled closing date, the following will occur:

•           we will receive funds in the amount of the aggregate purchase price for the securities we sell; and

•           Lazard Capital Markets LLC will receive the placement agent’s fee in accordance with the terms of the placement agent agreement.

We will pay the placement agent an aggregate cash commission equal to 5.0% of the gross proceeds of the sale of units. We will also reimburse the placement agent for legal expenses incurred by it in connection with this offering, up to a maximum of $75,000. In no event will the total amount of compensation paid to the placement agent and other securities brokers and dealers upon completion of this offering exceed 8% of the gross proceeds of this offering. The estimated offering expenses payable by us, in addition to the placement agent’s fee of $1,215,000, are approximately $275,000 which includes legal, accounting and printing costs and various other fees associated with registering and listing the common stock. After deducting certain fees due to the placement agent and our estimated offering expenses, we expect the net proceeds from this offering to be approximately $22.8 million.

Lazard Frères & Co. LLC referred this transaction to Lazard Capital Markets LLC and will receive a referral fee from Lazard Capital Markets LLC in connection therewith.

We have agreed to indemnify the placement agent and Lazard Frères & Co. LLC against certain liabilities, including liabilities under the Securities Act of 1933, as amended, and liabilities arising from breaches of representations and warranties contained in the placement agent agreement. We have also agreed to contribute to payments the placement agent and Lazard Frères & Co. LLC may be required to make in respect of such liabilities.

We, along with our executive officers and directors, have agreed to certain lock-up provisions with regard to future sales of our common stock and other securities convertible into or exercisable or exchangeable for common stock for a period of ninety (90) days after the offering as set forth in the placement agent agreement.

The placement agent agreement is included as an exhibit to our Current Report on Form 8-K that we will file with the SEC in connection with the consummation of this offering.

The transfer agent for our common stock to be issued in this offering is Computershare Trust Company, N.A.

Our common stock is traded on the Nasdaq Global Market under the symbol “ARIA.”

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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 supplement. 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. Proskauer Rose LLP, New York, New York, is acting as counsel for the placement agent in connection with various matters related to the securities offered hereby.

EXPERTS

The financial statements incorporated in this prospectus supplement by reference 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 incorporated in this prospectus supplement by reference from the Company’s Annual Report on Form 10-K (which reports (1) express an unqualified opinion on the consolidated financial statements and includes an explanatory paragraph referring to the adoption of Statement of Financial Accounting Standards No. 123(R), Share- Based Payment, effective January 1, 2006), and (2) express an unqualified opinion on the effectiveness of internal control over financial reporting). Such financial statements have been so included in reliance upon the reports of such firm given upon their authority as experts in accounting and auditing.

INFORMATION INCORPORATED BY REFERENCE

We are “incorporating by reference” information into this prospectus supplement and the accompanying prospectus. This means that we are disclosing important information to you by referring you to another document that has been filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying prospectus, and information that we file later with the SEC will automatically update and supersede the information contained in documents filed earlier with the SEC or contained in this prospectus. We incorporate by reference into this prospectus supplement and the accompanying prospectus the documents listed below and any future filings made by us with the SEC under Section 13(a), 13(c), 14 and 15(d) of the Securities Exchange Act of 1934, which we refer to as the Exchange Act, after the initial filing of this registration statement that contains this prospectus supplement and prior to the time that we sell all of the securities offered by this prospectus supplement or the earlier termination of the offering (except in each case the information contained in such documents to the extent “furnished” and not “filed”):

•           Our annual report on Form 10-K for the fiscal year ended December 31, 2007, filed on March 17, 2008;

•           Our quarterly reports on Form 10-Q for the quarter ended March 31, 2008, filed on May 9, 2008; for the quarter ended June 30, 2008, filed on August 11, 2008; and for the quarter ended September 30, 2008, filed on November 10, 2008;

•           Our current reports on Form 8-K filed on January 10, 2008, February 8, 2008, February 14, 2008, March 27, 2008, April 15, 2008, May 7, 2008, May 20, 2008, May 22, 2008, June 30, 2008, July 30, 2008, August 7, 2008, August 7, 2008, September 17, 2008, September 22, 2008, September 23, 2008, October 6, 2008, October 7, 2008, October 15, 2008, October 20, 2008, October 21, 2008, October 23, 2008, October 27, 2008, November 5, 2008, November 6, 2008, December 5, 2008, December 12, 2008, January 16, 2009, February 12, 2009, and February 17, 2009; and

•           Our definitive Proxy Statement on Schedule 14A, filed on April 29, 2008.

In addition, all documents subsequently filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the date of this prospectus supplement and before the date

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our offering is terminated or completed are deemed to be incorporated by reference into, and to be a part of, this prospectus supplement.

Any statement contained in this prospectus or in a document incorporated or deemed to be incorporated by reference into this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or any other subsequently filed document that is deemed to be incorporated by reference into this prospectus supplement 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 supplement.

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.

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PROSPECTUS

ARIAD PHARMACEUTICALS, INC.

$100,000,000

COMMON STOCK
PREFERRED STOCK
DEBT SECURITIES
WARRANTS
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 $100,000,000 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 the debt securities, common stock upon conversion of the preferred stock, or common stock, preferred stock or debt securities upon the exercise of warrants. We will provide you with specific terms of any offering in one or more supplements to this prospectus. 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 common stock is listed on the NASDAQ Global Market under the symbol “ARIA.” On February 13, 2007, the last reported sale price of our common stock was $5.19 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 8 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.

     Our securities may be sold directly by us to investors, 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. If any underwriters are involved in the sale of our securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable 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.

     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 February 16, 2007.

TABLE OF CONTENTS

	Page
ABOUT THIS PROSPECTUS	1
PROSPECTUS SUMMARY	2
RISK FACTORS	8
DEFICIENCY OF EARNINGS TO FIXED CHARGES	8
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS	8
USE OF PROCEEDS	9
PLAN OF DISTRIBUTION	9
DESCRIPTION OF COMMON STOCK	12
DESCRIPTION OF PREFERRED STOCK	13
DESCRIPTION OF DEBT SECURITIES	14
DESCRIPTION OF WARRANTS	20
DESCRIPTION OF UNITS	21
CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF INCORPORATION AND BY-LAWS	21
LEGAL MATTERS	23
EXPERTS	23
WHERE YOU CAN FIND MORE INFORMATION	23
INCORPORATION OF DOCUMENTS BY REFERENCE	23

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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 to purchase any of such securities, either individually or in units, in one or more offerings, with a total value of up to $100,000,000. 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 this offering. 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 names refer to ARIAD Pharmaceuticals, Inc. and our subsidiaries, including ARIAD Gene Therapeutics, Inc., or AGTI, unless the context requires otherwise.

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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.

We are engaged in the discovery and development of breakthrough medicines to treat cancers by regulating cell signaling with small molecules. We are developing a comprehensive approach to patients with cancer that addresses the greatest medical need — aggressive and advanced-stage cancers for which current treatments 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.

Our Product Candidates

Human cells, both healthy and malignant, share an elaborate system of molecular pathways that carry signals back and forth from the cell surface to the nucleus and within the cell. Such signaling is essential to cell functioning and viability. When disrupted or over-stimulated, such pathways may trigger diseases such as cancer. For example, growth and proliferation of cancer cells are dependent on signals from external growth factors, as well as signals indicating the availability of sufficient nutrients and blood supply. These signals are conveyed along well defined pathways, several of which are regulated by a protein called the mammalian target of rapamycin, or mTOR.

Our lead cancer product candidate, AP23573, is an internally discovered, potent mTOR inhibitor. The protein, mTOR, serves as a “master switch” and appears to have a central function in cancer cells. Blocking mTOR creates a starvation-like effect in cancer cells by interfering with cell growth, division, metabolism and angiogenesis. We discovered AP23573 in a research and development program conducted by us on behalf of ARIAD Gene Therapeutics, Inc., or AGTI, our 80%-owned subsidiary.

As part of our global clinical development plan and registration strategy, AP23573 has been studied in multiple Phase 2 and 1b clinical trials in the U.S. and Europe as a single agent in patients with solid tumors, including sarcomas, hormone refractory prostate cancer and endometrial cancer. In addition, three multi-center Phase 1b trials of AP23573 in combination with other anti-cancer therapies are underway. These trials are focused primarily on patients with various types of solid tumors, especially breast, ovarian, non-small-cell lung and prostate cancers, as well as sarcomas. Further single agent and combination studies are planned. In addition, we have concluded enrollment in Phase 1b and Phase 2 clinical trials in patients with brain cancer and leukemias and lymphomas, respectively. Eleven clinical trials of AP23573 are ongoing or completed. Both intravenous and oral formulations of AP23573 have been studied in these trials.

In clinical trials to date, AP23573 has been well tolerated at the fixed doses administered, and adverse events were generally mild to moderate in severity and readily reversible. The most common treatment-related adverse events experienced by patients in the trials were mouth sores, rash, fatigue, nausea and lipid abnormalities.

In June 2006, at the annual meeting of the American Society of Clinical Oncology, or ASCO, we announced that single agent AP23573 demonstrated efficacy and was well tolerated when administered intravenously in a multi-center Phase 2 clinical trial in metastatic and/or unresectable soft-tissue and bone

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sarcomas involving 212 patients, at least 90% of whom had progressive disease. The primary endpoint of the trial, evidenced by clinical-benefit response, or CBR, rates, was achieved in the three most prevalent types of sarcoma, namely, bone sarcoma (CBR rate of 30%), leiomyosarcoma (33%) and liposarcoma (30%). In addition, the progression-free survival, or PFS, rate at six months for the patients in this trial was 24%, and the median PFS was 15 weeks. As it relates to both the CBR rate and the PFS rate, there was no statistical difference between the four sub-groups of patients in this trial, indicating that AP23573 demonstrated activity and clinical benefit across all four sub-groups of sarcomas. The adverse events experienced by patients in the trial were generally mild to moderate in severity and readily reversible.

Based on our ongoing interactions with the U.S. Food and Drug Administration, or FDA, and the European Medicines Agency, or EMEA, we plan to conduct a randomized, worldwide Phase 3 clinical trial of an oral dosage form of AP23573 in patients with advanced sarcomas. The FDA and the EMEA have designated AP23573 as an orphan drug for treatment of soft-tissue and bone sarcomas. The FDA has also designated AP23573 as a fast-track product for the same indications.

The oral dosage form of AP23573 is also being studied in a multi-center Phase 1b clinical trial of patients with various solid tumors. Initial results from this trial indicate that the oral dosage form can be administered safely, using several daily and intermittent dosing schedules, and achieves blood levels over time and mTOR inhibition generally consistent with those observed with intravenous administration.

As an mTOR inhibitor, AP23573 has also been shown to potently block the growth, proliferation and migration of vascular smooth muscle cells, the primary cause of narrowing and blockage of injured vessels. In 2005, we entered into a partnership with Medinol Ltd., a leading cardiovascular medical device company, to develop and commercialize stents and other medical devices to deliver AP23573 in order to prevent reblockage of injured vessels following stent-assisted angioplasty, a common non-surgical procedure for dilating or opening narrowed arteries.

Inhibition of the mTOR pathway may be useful for additional indications beyond oncology and drug-delivery stents, and we are evaluating such opportunities as part of the broader clinical development plan for AP23573.

Our second product candidate, AP24534, is an orally active oncogenic kinase inhibitor, which is in preclinical development for the treatment of chronic myeloid leukemia, or CML. CML is a slowly progressing cancer in which too many white blood cells are made in the bone marrow. In most cases, a genetic abnormality involving a protein known as Bcr-Abl results in constantly activated growth of cancer cells. Treatment with existing molecularly targeted drugs inhibits the Bcr-Abl protein but results in mutations of the Bcr-Abl gene, which creates substantial drug resistance over time. One of the clinically relevant mutations, T315I, is estimated to account for 25 percent of overall drug resistance in CML. In preclinical studies, AP24534 has demonstrated potent inhibition of the Bcr-Abl-T315I mutant as well as the major clinically relevant variants of Bcr-Abl and the naturally occurring unmutated form of the protein. In addition, AP24534 has demonstrated dose-dependent tumor shrinkage and increased survival in animal models. These findings support broad potential applicability of AP24534 in the treatment of CML, particularly in the refractory forms of CML.

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. In addition to our oncogenic kinase inhibitor program (including AP24534), our preclinical pipeline includes single compounds that target multiple cancer pathways (e.g., cell survival, metastases and angiogenesis).

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-kB cell-signaling activity, hereinafter referred to as the ‘516 Patent, awarded to a team of inventors from The Whitehead Institute for Biomedical Research, Massachusetts Institute of Technology and Harvard University. NF-kB is a protein that can be generally thought of as a “biological switch” that can be turned off using these treatment methods to

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treat disorders such as inflammation, cancer, sepsis and osteoporosis. We permit broad use of our NF-kB intellectual property, at no cost, by investigators at academic and not-for-profit institutions to conduct non-commercial research. Our goal is to license our NF-kB technology to pharmaceutical and biotechnology companies that are conducting research to discover and develop drugs that modulate NF-kB cell signaling and/or that are marketing such drugs. We have entered into two license agreements for use of our NF-kB cell-signaling technology for research and development purposes. However, the ‘516 Patent is the subject of two outstanding lawsuits and a proceeding before the United States Patent and Trademark Office, or PTO. See the section entitled “Legal Proceedings” set forth in our most recent annual report on Form 10-K filed with the SEC, and a description of the related risks in the section entitled “Risk Factors” contained in such annual report, in each case as revised or supplemented by our most recent quarterly report on Form 10-Q.

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. We distribute our ARGENT technologies at no cost to academic investigators in the form of our Regulation Kits to use in various research applications in an academic setting. We have entered into more than 1,200 material transfer agreements with 474 different institutions in 33 countries for the use of this technology in diverse areas of research, and more than 300 scientific papers describing its use have been published. In addition, we have licensed the ARGENT technology to several pharmaceutical and biotechnology companies for research and development and/or commercial purposes.

All of our product candidates and technology platforms are covered by claims of our owned or licensed patents and patent applications. As of January 30, 2007, we had 93 patents and patent applications in the United States, with foreign counterparts, of which 26 are owned, co-owned or exclusively licensed by us and 67 are owned, co-owned or exclusively licensed by AGTI. Approximately two-thirds of the United States patent applications we have filed since inception have already issued as patents.

Our Relationship with ARIAD Gene Therapeutics, Inc.

ARIAD Gene Therapeutics, Inc., or AGTI, is our 80%-owned subsidiary. Minority stockholders of AGTI, including Harvey J. Berger, M.D., our Chairman and Chief Executive Officer, Jay R. LaMarche, our former Chief Financial Officer and a member of our Board of Directors, several of our scientific advisors, Harvard University, and Stanford University, own the other 20% of AGTI. AGTI owns or licenses from others the intellectual property related to the ARGENT technology and know-how, as well as the product candidates developed from the application of this technology, including mTOR inhibitors. The mTOR inhibitor program, encompassing our lead product candidate, AP23573, and other compounds, was made possible by the creation of intellectual property, technology, and know-how related to inhibition of mTOR and the development of analogs of rapamycin as part of AGTI’s research and development program.

We do not have a license agreement with AGTI that provides us with rights to commercialize product candidates based on the ARGENT cell-signaling regulation technology or mTOR inhibitors derived from AGTI’s programs, solely for our benefit, as opposed to the benefit of AGTI. All of the research and development activities of AGTI, including the development of AP23573, have been conducted by us on behalf of AGTI pursuant to a research and development agreement. As of September 30, 2006, we have accrued an inter-company receivable of approximately $172 million representing funds we have advanced to AGTI for costs associated with AGTI’s research and development programs, of which approximately $99 million has been accrued since January 1, 2003, as clinical development of AP23573 has progressed. Other than a fee of 10% of the accrued costs advanced by us to fund the research and development activities of AGTI, we are not entitled to receive from AGTI any rights or other remuneration under the research and development agreement. Accordingly, our future economic benefit from the commercialization of such products on behalf of AGTI will only be in the form of dividends or other payments received in respect of our 80% ownership interest in AGTI, unless we acquire the equity interests of the minority stockholders, license rights to AP23573 from AGTI, or enter into a different arrangement with AGTI and/or its minority stockholders.

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Consequently, as the inter-company receivable has increased to fund the development of AP23573, in order to maximize the value of ARIAD for our stockholders and to mitigate or eliminate the conflicts of interest which currently exist between ARIAD and AGTI, the independent members of our Board of Directors (all of ARIAD’s Board members other than Dr. Berger and Mr. LaMarche) are currently engaged in evaluating a variety of strategic alternatives with respect to acquiring the 20% minority interest of AGTI that we do not own and have hired independent legal counsel and financial consultants to assist them in their evaluation. Dr. Berger and Mr. LaMarche have also hired independent legal counsel to assist them in evaluating any proposal that may be proffered by the independent members of our Board of Directors for the acquisition of the minority interest in AGTI, and they are currently negotiating with the independent directors the terms under which ARIAD may agree to reimburse or advance their expenses for their legal counsel and their financial advisors to be selected in connection with such evaluation. While this evaluation is currently ongoing, there can be no assurance that ARIAD will, at any time, enter into a transaction with AGTI as a result of this evaluation. If any of these strategic alternatives is pursued as a result of the evaluation by ARIAD’s independent and disinterested directors, there can be no assurance as to the timing of any such transaction, the form of such transaction, the particular transaction terms, such as the form, amount or timing of payment of consideration offered or provided by ARIAD to the minority stockholders of AGTI, ARIAD’s ability to effectuate any such transaction, or the consequences of any such proposed or completed transaction to ARIAD or the minority stockholders of AGTI. See a description of the risk factors related to our relationship with AGTI in the section entitled “Risk Factors” set forth in our most recent annual report on Form 10-K filed with the SEC, as revised or supplemented by our most recent quarterly report on Form 10-Q, which includes a description of such risks, the existing conflicts of interest between ARIAD and AGTI, and the key terms of the research and development agreement and associated financial accounting.

Our Corporate Strategy

Our current business strategy is to:

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

establish a U.S. commercial platform;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 outside the U.S.;broadly develop our lead oncology product candidates, AP23573 and AP24534, and build a pipeline of innovative follow-on product candidates;license our NF-kB and ARGENT cell-signaling regulation technologies to pharmaceutical and biotechnology companies; anddevelop and commercialize AP23573, in collaboration with up to three medical device companies, in drug-delivery stents and other medical devices to decrease reblockage of injured vessels following stent-assisted angioplasty.

Additional 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 http://www.ariad.com. The information on our website or 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 to purchase any of such securities, either individually or in units, with a total value of up to $100,000,000, 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

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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 prices, if any; andimportant 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; andthe net proceeds to us.

Common Stock

We may issue shares of our common stock from time to time. The holders of common stock are entitled to one vote per share on all matters to be voted upon by stockholders. Subject to preferences that may be applicable to any outstanding preferred stock, the holders of common stock are entitled to receive ratably any dividends that may be declared from time to time by our board of directors out of funds legally available for that purpose. In the event of our liquidation, dissolution or winding up, the holders of common stock are entitled to share ratably in all assets remaining after payment of liabilities, subject to prior distribution rights of preferred stock then outstanding.

Preferred Stock

We may issue shares of our preferred stock from time to time, in one or more series. Our board of directors may determine the rights, preferences, privileges and restrictions of the preferred stock, including dividend rights, conversion rights, preemptive rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series. Convertible preferred stock will be convertible into our common stock. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

If we sell any series of preferred stock under this prospectus and applicable prospectus supplements, we will fix the rights, preferences, privileges, qualifications and restrictions of the preferred stock of such series in the certificate of designation relating to that series. We will file as an exhibit to the registration statement of which this prospectus is a part, or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of any certificate of designation that describes the terms of the series of preferred stock we are offering before the issuance of the related series of preferred stock. We urge you to read the prospectus supplements related to the series of preferred stock being offered, as well as the complete certificate of designation that contains the terms of the applicable series of preferred stock.

Debt Securities

We may offer debt securities from time to time, in one or more series, as either senior or subordinated debt or as senior or subordinated convertible debt. The senior debt securities will rank equally with any other unsecured and unsubordinated debt. The subordinated debt securities will be subordinate and junior in priority of payment to certain of our other indebtedness to the extent described in a prospectus supplement. Convertible debt securities will be convertible into or exchangeable for our common stock or our other securities. Conversion may be mandatory or at your option and would be at prescribed conversion rates.

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The debt securities will be issued under one or more documents called indentures, which are contracts between us and a national banking association or other eligible party, as trustee. In this prospectus, we have summarized certain general features of the debt securities. We urge you, however, to read the prospectus supplements related to the series of debt securities being offered, as well as the complete indentures that contain the terms of the debt securities. Forms of indentures have been filed as exhibits to the registration statement of which this prospectus is a part, and supplemental indentures and forms of debt securities containing the terms of the debt securities being offered will be filed as exhibits to the registration statement of which this prospectus is a part or will be incorporated by reference from a current report on Form 8-K that we file with the SEC.

Warrants

We may issue warrants for the purchase of common stock, preferred stock and/or debt securities, in one or more series. We may issue warrants independently or together with common stock, preferred stock and/or debt securities, and the warrants may be attached to or separate from these securities. In this prospectus, we have summarized certain general features of the warrants. We urge you, however, to read the prospectus supplements related to the particular series of warrants being offered, as well as the warrant agreements and warrant certificates that contain the terms of the warrants. Forms of the warrant agreements and forms of warrant certificates containing the terms of the warrants being offered will be incorporated by reference into the registration statement of which this prospectus is a part from a current report on Form 8-K that we file with the SEC.

We will evidence each series of warrants by warrant certificates that we will issue under a separate agreement. We will enter into the warrant agreements with a warrant agent. Each warrant agent will be a bank or trust company that we select. We will indicate the name and address of the warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

Units

We may issue units consisting of common stock, preferred stock, debt securities and/or warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. In this prospectus, we have summarized certain general features of the units. We urge you, however, to read the prospectus supplements related to the series of units being offered, as well as the unit agreements that contain the terms of the units. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of unit agreement and any supplemental agreements that describe the terms of the series of units we are offering before the issuance of the related series of units.

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RISK FACTORS

Investing in our securities involves 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 subsequent quarterly reports on Form 10-Q or 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, 2001, 2002, 2003, 2004 or 2005 or for the nine-month period ended September 30, 2006. 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 and an estimate of the interest portion of rent expenses. 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
											Ended
	Year Ended December 31,										September 30,
	2001		2002		2003		2004		2005		2006
	(In thousands)
Coverage deficiency	$	19,759	$	27,843	$	19,726	$	35,573	$	55,510	$	47,561

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.

Words such as “may,” “anticipate,” “estimate,” “expects,” “projects,” “intends,” “plans,” “believes” and words and terms of similar substance used in connection with any discussion of future operating or financial performance, identify forward-looking statements. Forward-looking statements represent management’s present judgment regarding future events and are subject to a number of risks and uncertainties that could cause actual results to differ materially from those described in the forward-looking statements. These risks include, but are not limited to, risks and uncertainties regarding our preclinical studies, our ability to conduct clinical trials of our product candidates and the results of such trials, as well as risks and uncertainties relating to litigation, government regulation and third-party reimbursement, economic conditions, markets, products, competition, intellectual property, services and prices, key employees, future capital needs, dependence on our collaborators and other factors. Please also see 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 subsequent quarterly reports on Form 10-Q or current reports on Form 8-K, as well as any amendments thereto, as filed with the SEC and which are incorporated herein by reference.

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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 and for other general corporate purposes, including, but not limited to, repayment or refinancing of existing indebtedness or other corporate borrowings, working capital, intellectual property protection and enforcement, capital expenditures, investments, acquisitions and repurchases and redemption of our securities. 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;

market prices prevailing at the time of sale;prices related to the prevailing market prices; ornegotiated 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. Shares of our

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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. 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.

Equity Financing Commitment

On February 14, 2007, we entered into what is sometimes termed an equity line of credit arrangement with Azimuth Opportunity Ltd., or Azimuth. Specifically, we entered into a Common Stock Purchase Agreement, or the Purchase Agreement, with Azimuth, which provides that, upon the terms and subject to the conditions set forth therein, Azimuth is committed to purchase up to the lesser of (a) $50,000,000 of our common stock, or (b) the number of shares of our common stock that is one share less than 20% of the issued and outstanding shares of our common stock as of February 14, 2007, over the 18-month term of the Purchase Agreement. From time to time over the term of the Purchase Agreement, and at our sole discretion, we may present Azimuth with draw down notices requiring Azimuth to purchase a specified dollar amount of shares of our common stock, subject to certain limitations and so long as specified conditions are met. The price per share at which the shares will be sold, and therefore the number of shares to be sold pursuant to the draw down notice, is determined over a ten consecutive trading day pricing period, or such other period as is mutually agreed between us and Azimuth. We are able to present Azimuth with up to 24 draw down notices during the 18-month term of the Purchase Agreement, with a minimum of three trading days elapsing between each draw down pricing period. One draw down is allowed in each draw down pricing period, unless otherwise mutually agreed upon by us and Azimuth. Each draw down is limited in size, unless otherwise mutually agreed upon by us and Azimuth, to the lesser of (i) $12,000,000, or (ii) 2.5% of our market capitalization as defined in the Purchase Agreement.

Once presented with a draw down notice, Azimuth is required to purchase a pro rata portion of the dollar amount of shares specified in the notice for each trading day during the pricing period on which the daily volume weighted average price for our common stock exceeds a threshold price specified by us in the draw down notice. The per share purchase price for the shares sold on any particular trading day during the pricing period will equal the daily volume weighted average price of our common stock for that day, less a discount ranging from 3.5% to 5.5%. The amount of the discount varies based on the threshold price specified by us. If the daily volume weighted average price of our common stock falls below the threshold price on any trading day during a draw down period, the Purchase Agreement provides that Azimuth will not be required to purchase the pro rata portion of shares of common stock allocated to that day. However, at its election, Azimuth may buy the pro rata portion of shares allocated to that day at the threshold price less the discount described above. The total number of shares sold to Azimuth during each draw down will be the sum of the number of shares required and/or elected to be purchased on each day of the pricing period. The Purchase Agreement also provides that, from time to time and at our sole discretion, we may grant Azimuth the option to purchase additional shares of our common stock up to an aggregate amount specified by us during each draw down pricing period. Upon Azimuth’s exercise of the option, we would sell to Azimuth the shares of our

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common stock subject to the option at a price equal to the greater of the daily volume weighted average price of our common stock on the day Azimuth notifies us of its election to exercise its option or the threshold price for the option determined by us, less a discount calculated in the same manner as for the fixed amount of the draw down notices.

Any sale of shares of our common stock to Azimuth will be registered on our registration statement of which this prospectus is a part, which also covers the sale of those shares from time to time by Azimuth to the public. Azimuth is an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act.

Azimuth has informed us that, unless it notifies us that it will use a different broker-dealer and we have filed a prospectus supplement, Azimuth will use an unaffiliated broker-dealer to effectuate all sales, if any, of the common stock that it may purchase from us pursuant to the Purchase Agreement. Such sales will be made on the NASDAQ Global Market at prices and at terms then prevailing or at prices related to the then current market price. Each such unaffiliated broker-dealer will be an underwriter within the meaning of Section 2(a)(11) of the Securities Act. Azimuth has informed us that each such broker-dealer will receive commissions from Azimuth that will not exceed customary brokerage commissions. Azimuth also will pay other expenses associated with the sale of our common stock it acquires pursuant to the Purchase Agreement.

The shares of our common stock may be sold in one or more of the following manners:

ordinary brokerage transactions and transactions in which the broker solicits purchasers; ora block trade in which the broker or dealer so engaged will attempt to sell the shares as agent, but may position and resell a portion of the block as principal to facilitate the transaction.

Azimuth has agreed that during the 18-month term of and for a period of 90 days after the termination of the Purchase Agreement, neither Azimuth nor any of its affiliates will, directly or indirectly, sell any of our securities except the shares that it owns or has the right to purchase pursuant to the provisions of a draw down notice. Azimuth has agreed that during the periods listed above it will not enter into a short position with respect to shares of our common stock, except that Azimuth may sell shares that it is obligated to purchase under a pending draw down notice but has not yet taken possession of so long as Azimuth covers any such sales with the shares purchased pursuant to such draw down notice. Azimuth has further agreed that during the periods listed above it will not grant any option to purchase or acquire any right to dispose or otherwise dispose for value any shares of our common stock or any securities convertible into, or exchangeable for, or warrants to purchase, any shares of our common stock, or enter into any swap, hedge or other agreement that transfers, in whole or in part, the economic risk of ownership of our common stock, except for the sales permitted by the prior two sentences.

In addition, Azimuth and any unaffiliated broker-dealer will be subject to liability under the federal securities laws and must comply with the requirements of the Securities Act and the Securities Exchange Act of 1934, as amended, including without limitation, Rule 10b-5 and Regulation M under the Exchange Act. These rules and regulations may limit the timing of purchases and sales of shares of our common stock by Azimuth or any unaffiliated broker-dealer. Under these rules and regulations, Azimuth and any unaffiliated broker-dealer:

may not engage in any stabilization activity in connection with our securities;must furnish each broker which offers shares of our common stock covered by this prospectus with the number of copies of this prospectus and any prospectus supplement that are required by each broker; andmay not bid for or purchase any of our securities or attempt to induce any person to purchase any of our securities other than as permitted under the Exchange Act.

These restrictions may affect the marketability of the shares of our common stock by Azimuth and any unaffiliated broker-dealer.

We have agreed to indemnify and hold harmless Azimuth, any unaffiliated broker-dealer and each person who controls Azimuth or any unaffiliated broker-dealer against certain liabilities, including liabilities under the Securities Act. We have agreed to pay up to $35,000 of Azimuth’s reasonable attorneys’ fees and expenses (exclusive of disbursements and out-of-pocket expenses) incurred by Azimuth in connection with the preparation, negotiation, execution and delivery of the Purchase Agreement. We have also agreed to pay up to $12,500 per quarter, during the 18-month term of the Purchase Agreement, for any quarter during which Azimuth does not purchase shares of our common stock, to cover the reasonable fees and expenses incurred by Azimuth in connection with any amendments, modifications or waivers of the Purchase Agreement and

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ongoing due diligence. Further, we have agreed that if we issue a draw down notice and fail to deliver the shares to Azimuth on the applicable settlement date, and such failure continues for ten trading days, we will pay Azimuth liquidated damages in cash or, at Azimuth’s election, unregistered shares of our common stock. Azimuth has agreed to indemnify and hold harmless us and each of our directors, officers and persons who control us against certain liabilities, including liabilities under the Securities Act.

Upon each sale of our common stock to Azimuth under the Purchase Agreement, we have also agreed to pay Reedland Capital Partners, an Institutional Division of Financial West Group, member NASD/SIPC, a placement fee equal to 1.0% of the aggregate dollar amount of common stock purchased by Azimuth. We have agreed to indemnify and hold harmless Reedland Capital Partners against certain liabilities, including liabilities under the Securities Act.

DESCRIPTION OF COMMON STOCK

We are authorized to issue 145,000,000 shares of common stock, par value $0.001 per share. On January 30, 2007, we had 65,435,269 shares of common stock outstanding and approximately 472 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 by-laws, both of which are included as exhibits to the registration statement we have filed with the SEC in connection with this offering. 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 by-laws 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 of common stock that we may offer pursuant to this prospectus, will be fully-paid and nonassessable.

Rights Agreement

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

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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 we have filed with the SEC in connection with this offering.

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 February 13, 2007, the last reported sale price of our common stock was $5.19 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 January 30, 2007, 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 by-laws, both of which are included as exhibits to the registration statement we have filed with the SEC in connection with this offering. 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;

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•      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 is Computershare Trust Company, N.A.

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, which includes this prospectus. 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.

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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;

•      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

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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

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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

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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 a 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.

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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 indicate otherwise in the applicable prospectus supplement, on any interest payment date, we will pay the interest on any debt securities to the person in whose name such 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

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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

Our obligations 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

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;

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•      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 UNITS

We may issue units consisting of common stock, preferred stock, debt securities and/or warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. In this prospectus, we have summarized certain general features of the units. We urge you, however, to read the prospectus supplements related to the series of units being offered, as well as the unit agreements that contain the terms of the units. We will file as exhibits to the registration statement of which this prospectus is a part, or will incorporate by reference from a current report on Form 8-K that we file with the SEC, the form of unit agreement and any supplemental agreements that describe the terms of the series of units we are offering before the issuance of the related series of units.

We will evidence each series of units by unit certificates that we will issue under a separate agreement. We will enter into the unit agreements with a unit agent. Each unit agent will be a bank or trust company that we select. We will indicate the name and address of the unit agent in the applicable prospectus supplement relating to a particular series of units.

CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF
INCORPORATION AND BY-LAWS

Anti-Takeover Provisions of our Certificate of Incorporation and By-laws

In addition to the board of directors’ ability to issue shares of preferred stock, our certificate of incorporation and by-laws 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.

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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 by-laws provide that, except as otherwise required by law, special meetings of our stockholders can only be called by a majority of our board of directors or by our chief executive officer or 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 by-laws 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. 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. Although our by-laws 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 by-laws 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%

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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 provides that we will indemnify them to the fullest extent permitted by such law. We have also entered into indemnification agreements with our current and former directors and certain of our officers and key employees and expect to enter into a similar agreement with any new directors, and certain new 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 and management’s report on the effectiveness of internal controls over financial reporting incorporated in this prospectus by reference from our Annual Report on Form 10-K have been audited by Deloitte & Touche LLP, an independent registered public accounting firm, as stated in their reports, which are incorporated herein by reference, and have been so incorporated in reliance upon the reports 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. Our common stock is listed on the NASDAQ Global Market, and you can read and inspect our filings at the offices of the National Association of Securities Dealers, Inc. at 1735 K Street, Washington, D.C. 20006.

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

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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:

(a)        Our Annual Report on Form 10-K for the fiscal year ended December 31, 2005, filed on March 16, 2006 (File No. 000-21696);

(b)        Our Quarterly Reports on Form 10-Q for the three-month periods ended March 31, 2006, June 30, 2006 and September 30, 2006, filed on May 10, 2006, August 8, 2006 and November 9, 2006, respectively (File Nos. 000-21696);

(c)        Our Current Reports on Form 8-K filed on April 7, 2006 (Item 8.01), May 4, 2006 (Items 8.01 and 9.01), May 9, 2006 (Item 8.01 and portions of Item 9.01), June 5, 2006 (Items 8.01 and 9.01), July 31, 2006 (Items 1.01 and 9.01), August 8, 2006 (Item 8.01 and portions of Item 9.01), August 15, 2006 (Items 8.01 and 9.01), October 11, 2006 (Items 8.01 and 9.01), October 20, 2006 (Items 8.01 and 9.01), November 2, 2006 (Item 8.01 and portions of Item 9.01), November 2, 2006 (Items 8.01 and 9.01), December 11, 2006 (Items 8.01 and 9.01), January 18, 2007 (Item 5.02), February 12, 2007 (Items 8.01 and 9.01) and February 15, 2007 (Items 1.01, 2.02, 8.01 and 9.01) (File Nos. 000-21696);

(d)        The portions of our Definitive Proxy Statement on Schedule 14A that are deemed “filed” with the SEC under the Securities Exchange Act, as amended, on April 28, 2006 (File No. 000-21696);

(e)        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 (File No. 000-21696);

(f)        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 (File No. 000-21696); and

(g)        All of the filings pursuant to the Securities Exchange Act of 1934, as amended, after the date of the filing of the original Registration Statement and prior to the effectiveness of the Registration Statement.

In addition, all documents subsequently filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, before the date our offering is terminated or completed are deemed to be incorporated by reference into, and to be a part of, this prospectus.

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 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 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.

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14,378,698 Shares of Common Stock

Warrants to Purchase 10,784,024 Shares of Common Stock

PROSPECTUS SUPPLEMENT

Lazard Capital Markets

February 19, 2009