e424b5

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-178489

CALCULATION OF REGISTRATION FEE

Proposed maximum

Amount of

Title of each class of

Amount to be

offering price

aggregate

registration

securities to be registered

registered⁽¹⁾

per security

offering price⁽¹⁾

fee⁽²⁾

Common Stock, $.001 par value

24,725,000

10.42

257,634,500

29,525


(1)	Includes shares of common stock that may be purchased by the underwriters pursuant to their over-allotment option to purchase additional shares of common stock.

(2)	This filing fee is calculated in accordance with Rule 457(r) and relates to the Registration Statement on Form S-3 (File No. 333-178489) filed by the Registrant on December 14, 2011.

Prospectus Supplement (to Prospectus dated December 14, 2011)

21,500,000 shares

Common stock

We are offering 21,500,000 shares of our common stock.

Our common stock is listed on The NASDAQ Global Market under the symbol “ARIA.” The last reported sale price on December 14, 2011 was $10.42 per share.



	Per share		Total



Public offering price	$	10.4200	$	224,030,000

Underwriting discounts and commissions	$	0.5731	$	12,321,650

Proceeds, before expenses, to us	$	9.8469	$	211,708,350

We have granted the underwriters an option for a period of up to 30 days from the date of this prospectus supplement to purchase up to 3,225,000 additional shares of our common stock at the public offering price less the underwriting discounts and commissions to cover over-allotments, if any.

Investing in our common stock involves risks. See “Risk Factors” on page S-4.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares on or about December 20, 2011.

Joint Book-Running Managers


J.P. Morgan	Cowen and Company	Jefferies

Co-Managers

BMO Capital Markets

Leerink Swann

Oppenheimer & Co.

Rodman & Renshaw, LLC

December 15, 2011

Table of contents


Prospectus supplement
About this prospectus supplement			S-ii
Prospectus supplement summary			S-1
Risk factors			S-4
Special note regarding forward-looking statements			S-5
Use of proceeds			S-6
Dilution			S-7
Price range of common stock			S-8
Dividend policy			S-8
Underwriting			S-9
Legal matters			S-14
Experts			S-14
Where you can find more information			S-14
Incorporation of certain information by reference			S-15
Prospectus
About this prospectus			1
About ARIAD Pharmaceuticals, Inc.			1
Where you can find more information			2
Incorporation of documents by reference			2
Risk factors			4
Special note regarding forward-looking statements			4
Ratio/Deficiency of earnings to fixed charges			5
Use of proceeds			5
Description of common stock			5
Description of preferred stock			6
Description of debt securities			7
Description of warrants			12
Description of units			13
Selling securityholders			14
Certain provisions of Delaware law and of the company’s certificate of incorporation and by-laws			14
Legal matters			15
Experts			15

About this prospectus supplement

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this common stock offering and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference herein. The second part, the accompanying prospectus, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying prospectus or any document incorporated by reference therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement; provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

You should rely only on the information contained in this prospectus supplement or the accompanying prospectus, or incorporated by reference herein. We have not authorized, and the underwriters have not authorized, anyone to provide you with information that is different. The information contained in this prospectus supplement or the accompanying prospectus, or incorporated by reference herein is accurate only as of the respective dates thereof, regardless of the time of delivery of this prospectus supplement and the accompanying prospectus or of any sale of our common stock. It is important for you to read and consider all information contained in this prospectus supplement and the accompanying prospectus, including the documents incorporated by reference herein and therein, in making your investment decision. You should also read and consider the information in the documents to which we have referred you in the sections entitled “Where you can find more information” and “Incorporation of certain information by reference” in this prospectus supplement and in the sections entitled “Where you can find more information” and “Incorporation of documents by reference” in the accompanying prospectus, respectively.

We are offering to sell, and seeking offers to buy, shares of our common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the accompanying prospectus and the offering of the common stock in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus supplement and the accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of the common stock and the distribution of this prospectus supplement and the accompanying prospectus outside the United States. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement and the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

S-ii

Prospectus supplement summary

This summary highlights information contained elsewhere or incorporated by reference in this prospectus supplement and the accompanying prospectus. This summary does not contain all of the information that you should consider before deciding to invest in our common stock. You should read this entire prospectus supplement and the accompanying prospectus carefully, including the “Risk factors” section contained in this prospectus supplement, our consolidated financial statements and the related notes thereto and the other documents and information incorporated by reference in this prospectus supplement and the accompanying prospectus and the information included in any free writing prospectus that we have authorized for use in connection with this offering.

ARIAD Pharmaceuticals, Inc.

Overview

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.

We are building a pipeline of product candidates that has the potential to expand and improve current treatment options for patients with cancer. Each of our product candidates—ponatinib, AP26113 and ridaforolimus—was discovered internally by our scientists based on our expertise in cell-signaling, cancer biology and structure-based drug design. We believe that our product candidates have the potential to treat multiple cancer indications and we anticipate pursuing broad development of each.

Ponatinib is an investigational pan BCR-ABL inhibitor that we believe has broad potential applications in various hematological cancers and solid tumors. In the third quarter of 2011, we completed enrollment of approximately 450 patients in a pivotal Phase 2 clinical trial of ponatinib in patients with chronic myeloid leukemia, or CML, or Philadelphia-positive acute lymphoblastic leukemia, or Ph+ ALL. Subject to further patient follow-up and data analysis in this trial, we expect to file for marketing approval of ponatinib in this indication in the middle of 2012. Subject to obtaining marketing approval, we intend to commercialize ponatinib in the United States, Europe and other markets around the world.

AP26113 is an investigational dual inhibitor of anaplastic lymphoma kinase, or ALK, and epidermal growth factor receptor, or EGFR—two clinically validated targets in non-small cell lung cancer, or NSCLC. In the third quarter of 2011 we commenced a Phase 1/2 clinical trial to determine the initial safety, tolerability, pharmacokinetic profile, recommended dose and preliminary anti-tumor activity of AP26113.

Ridaforolimus is an investigational mTOR inhibitor that we discovered and licensed in 2010 to Merck & Co., Inc., or Merck. Merck is responsible for all activities related to the development, manufacturing and commercialization of ridaforolimus in oncology and funds 100 percent of all ridaforolimus costs. We intend to co-promote ridaforolimus in the United States, if approved. In the third quarter of 2011, Merck filed in both Europe and the United States for regulatory approval of ridaforolimus in patients with metastatic soft-tissue and bone sarcomas who had a favorable response to chemotherapy. Under the license agreement, Merck has agreed to pay us milestone payments based on specified regulatory submissions and approvals of ridaforolimus in multiple cancer indications and achievement of specified sales thresholds, as well as royalties upon commercialization of ridaforolimus.

S-1

The offering


Common stock offered by us in this offering		21,500,000 shares

Common stock to be outstanding after this offering		154,319,424 shares

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, preparation and submission of regulatory approval filings, product manufacturing, sales, marketing and distribution, including building our commercialization capabilities in the United States, Europe and other markets, 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.”

Risk factors		You should read the “Risk factors” section of this prospectus supplement on page S-4 for a discussion of factors to consider before deciding to purchase shares of our common stock.

Over-allotment option		We have granted the underwriters an option for a period of up to 30 days from the date of this prospectus supplement to purchase up to 3,225,000 additional shares of common stock at the public offering price less the underwriting discounts and commissions to cover over-allotments, if any.

NASDAQ Global Market symbol		ARIA

The number of shares of common stock to be outstanding after this offering is based on 132,819,424 shares outstanding as of September 30, 2011, and excludes as of such date:


•	6,920,610 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans, at a weighted average exercise price of $5.06;

•	2,776,684 shares of our common stock issuable upon vesting of restricted stock units outstanding under our stock plans;

•	3,935,842 shares of our common stock available for future grant or issuance pursuant to our employee stock purchase and stock plans; and

•	5,805,843 shares of our common stock issuable upon exercise of outstanding warrants, at an exercise price of $2.15 per share.

Unless we specifically state otherwise, all information in this prospectus supplement assumes that the underwriters do not exercise their option to purchase up to 3,225,000 additional shares of our common stock.

S-3

Risk factors

Investing in our common stock involves significant risks. In addition to the risk factors described below and the other information included or incorporated by reference in this prospectus supplement and the accompanying prospectus, you should carefully consider the risks described in Part I. Item 1A.—“Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2010, which we have filed with the Securities and Exchange Commission, or the SEC, and which is incorporated by reference herein, before making an investment decision. We caution you that the risks and uncertainties we have described, among others, could cause our actual results to differ materially from those expressed in forward-looking statements made by us or on our behalf in filings with the SEC, press releases, communications with investors and oral statements. Any or all such forward-looking statements we make may turn out to be wrong. They can be affected by inaccurate assumptions we might make or by known or unknown risks and uncertainties. Consequently, no results expressed by our forward-looking statements can be guaranteed. Actual future results may differ materially from those anticipated in forward-looking statements. We undertake no obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise. You are advised, however, to consult any further disclosure we make in our reports filed with the SEC.

Risks relating to this offering

Investors in this offering will pay a much higher price than the book value of our stock.

If you purchase common stock in this offering, you will incur an immediate and substantial dilution in net tangible book value of $8.92 per share, after giving effect to the sale by us of 21,500,000 shares in this offering at the public offering price of $10.42 per share. In addition, in the past, we have issued options and warrants to acquire common stock at prices significantly below the offering price. To the extent these outstanding options and warrants are ultimately exercised, you will incur additional dilution. See “Dilution” on page S-7 for more information about the dilution you will incur in this offering.

Our management will have broad discretion over the use of the net proceeds from this offering, and you may not agree with how we use the proceeds and the proceeds may not be invested successfully.

Our management will have broad discretion as to the use of the net proceeds from any offering by us and could use them for purposes other than those contemplated at the time of this offering. Accordingly, you may be relying on the judgment of our management with regard to the use of these net proceeds, and you will not have the opportunity, as part of your investment decision, to assess whether the proceeds are being used appropriately. It is possible that the proceeds will be invested in a way that does not yield a favorable, or any, return for ARIAD.

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

Sales of a substantial number of shares of our common stock in the public markets could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We, our directors and our executive officers have agreed not to sell, dispose of or hedge any common stock or securities convertible into or exchangeable for shares of common stock during the period from the date of this prospectus supplement continuing through and including the date 60 days after the date of this prospectus supplement, subject to certain exceptions. The underwriters may, in their discretion, release the restrictions on any such shares at any time without notice. We cannot predict the effect that future sales of our common stock would have on the market price of our common stock.

S-4

Special note regarding forward-looking statements

This prospectus supplement, the accompanying prospectus, the documents we have filed with the SEC that are incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering contain “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. These statements relate to future events or to our future operating or financial performance and involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements to be materially different from any future results, performances or achievements expressed or implied by the forward-looking statements. Forward-looking statements may include, but are not limited to, statements about:


•	the safety and efficacy of our product candidates;

•	the progress, timing and results of clinical trials and research and development efforts involving our product candidates, including the expected timing for filing for marketing approval of ponatinib;

•	the submission of applications for and receipt of regulatory clearances and approvals, including the timing thereof, of our product candidates, ponatinib and ridaforolimus;

•	our intention to commercialize ponatinib in the United States, Europe and other markets around the world, subject to obtaining marketing approval;

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

•	estimates of the potential markets for our product candidates;

•	our estimated expenditures and projected cash needs, including the sufficiency of cash resources to fund operations for at least the next two years;

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

•	the use of proceeds from this offering.

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

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

S-5

Use of proceeds

We estimate that the net proceeds we will receive from this offering, based on the public offering price of $10.42 per share, will be approximately $211.3 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, or approximately $243.1 million if the underwriters exercise their over-allotment option in full.

The net proceeds of this offering are expected to be used for:


•	preparation and submission of filings for regulatory approval of ponatinib in patients with CML and Ph+ALL with the U.S. Food and Drug Administration and the European Medicines Agency, which we would expect to file in mid-2012, subject to further patient follow-up and data analysis in the PACE clinical trial;

•	preparation for commercial launch of ponatinib in the United States and Europe, and if approved, our sales, marketing and distribution of ponatinib in these and other markets on our own, allowing us to retain ponatinib’s substantial potential commercial value;

•	additional clinical trials of ponatinib, including a Phase 3 trial in newly diagnosed CML patients and clinical trials of ponatinib in Japan;

•	expansion of development of ponatinib into other cancer indications;

•	completion of our current Phase 1/2 clinical trial of AP26113 and, depending on the results of the trial, conducting a pivotal trial in patients with non-small cell lung cancer and funding additional trials in the United States, Europe and Asia;

•	discovery research efforts to add to our pipeline of product candidates; and

•	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. The amounts and timing of these expenditures will depend on a number of factors, such as whether and when we receive any regulatory approvals for our product candidates, including ponatinib, the timing and progress of our research and development efforts, technological advances and the competitive environment for our product candidates. As a result, our management will have broad discretion to allocate the net proceeds from this offering. We have no current plans, commitments or agreements with respect to any acquisitions and may not make any acquisitions. 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.

Based on our current operating plans, the estimated net proceeds from this offering, together with existing cash and cash equivalents and the anticipated proceeds from the exercise of outstanding warrants, are expected to be sufficient to fund our operations for at least the next two years.

S-6

Dilution

The net tangible book value of our common stock on September 30, 2011 was $20.6 million, or $0.16 per share of common stock. Our net tangible book value per share is calculated by subtracting our total liabilities from our total tangible assets and dividing this amount by the number of shares of our common stock outstanding on September 30, 2011. After giving effect to the sale by us of all 21,500,000 shares of common stock that we are offering at the public offering price of $10.42 per share and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of September 30, 2011 would have been $231.9 million, or $1.50 per share of our common stock. This represents an immediate increase in net tangible book value of $1.34 per share to our existing stockholders and an immediate dilution in net tangible book value of $8.92 per share to new investors purchasing common stock in this offering. The following table illustrates this per share dilution:



Public offering price per share			$	10.42
Net tangible book value per share as of September 30, 2011	$	0.16
Increase per share attributable to new investors		1.34

As adjusted net tangible book value per share after the offering				1.50

Dilution per share to new investors			$	8.92

If the underwriters exercise in full their option to purchase 3,225,000 additional shares of common stock at the public offering price of $10.42 per share, the as adjusted net tangible book value after this offering would be $1.67 per share, representing an increase in net tangible book value of $1.51 per share to existing stockholders and immediate dilution in net tangible book value of $8.75 per share to new investors purchasing our common stock in this offering.

The information above does not include:


•	6,920,610 shares of our common stock issuable upon exercise of stock options outstanding under our stock plans as of September 30, 2011, at a weighted average exercise price of $5.06;

•	2,776,684 shares of our common stock issuable upon vesting of restricted stock units outstanding under our stock plans as of September 30, 2011;

•	3,935,842 shares of our common stock available as of September 30, 2011 for future grant or issuance pursuant to our employee stock purchase and stock plans; and

•	5,805,843 shares of our common stock issuable upon exercise of outstanding warrants as of September 30, 2011, at an exercise price of $2.15 per share.

To the extent options or warrants outstanding as of September 30, 2011 have been or may be exercised or other shares have been or are issued, there may be further dilution to new investors.

S-7

Price range of common stock

Our common stock is listed on The NASDAQ Global Market under the symbol “ARIA.” The last reported sale price for our common stock on December 14, 2011 was $10.42 per share. The table below sets forth high and low sale prices for our common stock during the periods indicated.



	High		Low


Fiscal Year ended December 31, 2009
First Quarter	$	2.95	$	0.83
Second Quarter		1.93		1.15
Third Quarter		3.48		1.46
Fourth Quarter		2.69		1.70
Fiscal Year ended December 31, 2010
First Quarter	$	3.92	$	2.06
Second Quarter		4.41		2.80
Third Quarter		3.85		2.57
Fourth Quarter		5.44		3.51
Fiscal Year ending December 31, 2011
First Quarter	$	7.69	$	5.04
Second Quarter		11.94		7.50
Third Quarter		13.50		7.55
Fourth Quarter (through December 14, 2011)		12.50		7.72

Dividend policy

We have not declared or paid dividends on our common stock in the past and do not intend to declare or pay such dividends in the foreseeable future. Our long-term debt agreement prohibits the payment of cash dividends.

S-8

Underwriting

We are offering the shares of common stock described in this prospectus through a number of underwriters. J.P. Morgan Securities LLC, Cowen and Company, LLC and Jefferies & Company, Inc. are acting as joint book-running managers of the offering. We have entered into an underwriting agreement with the underwriters. Subject to the terms and conditions of the underwriting agreement, we have agreed to sell to the underwriters, and each underwriter has severally agreed to purchase, at the public offering price less the underwriting discounts and commissions set forth on the cover page of this prospectus, the number of shares of common stock listed next to its name in the following table:



	Number of
Name	shares


J.P. Morgan Securities LLC		6,306,667
Cowen and Company, LLC		6,306,667
Jefferies & Company, Inc.		6,306,666
BMO Capital Markets Corp.		645,000
Leerink Swann LLC		645,000
Oppenheimer & Co. Inc.		645,000
Rodman & Renshaw, LLC		645,000

Total		21,500,000

The underwriters are committed to purchase all the common shares offered by us if they purchase any shares. The underwriting agreement also provides that if an underwriter defaults, the purchase commitments of non-defaulting underwriters may also be increased or the offering may be terminated.

The underwriters propose to offer the common shares directly to the public at the public offering price set forth on the cover page of this prospectus and to certain dealers at that price less a concession not in excess of $0.34386 per share. After the public offering of the shares, the offering price and other selling terms may be changed by the underwriters. Sales of shares made outside of the United States may be made by affiliates of the underwriters.

The underwriters have an option to buy up to 3,225,000 additional shares of common stock from us to cover sales of shares by the underwriters which exceed the number of shares specified in the table above. The underwriters have 30 days from the date of this prospectus to exercise this over-allotment option. If any shares are purchased with this over-allotment option, the underwriters will purchase shares in approximately the same proportion as shown in the table above. If any additional shares of common stock are purchased, the underwriters will offer the additional shares on the same terms as those on which the shares are being offered.

The underwriting fee is equal to the public offering price per share of common stock less the amount paid by the underwriters to us per share of common stock. The underwriting fee is $0.5731 per share. The following table shows the per share and total underwriting discounts and commissions to be paid

S-9

to the underwriters assuming both no exercise and full exercise of the underwriters’ option to purchase additional shares.



	Without		With full
	over-allotment		over-allotment
	exercise		exercise


Per Share	$	0.5731	$	0.5731
Total	$	12,321,650	$	14,169,898

We estimate that the total expenses of this offering, including registration, filing and listing fees, printing fees and legal and accounting expenses, but excluding the underwriting discounts and commissions, will be approximately $400,000. The aggregate value of all compensation received or to be received by the participating FINRA members does not exceed 8% of the offering proceeds.

A prospectus in electronic format may be made available on the web sites maintained by one or more underwriters, or selling group members, if any, participating in the offering. The underwriters may agree to allocate a number of shares to underwriters and selling group members for sale to their online brokerage account holders. Internet distributions will be allocated by the underwriters to selling group members that may make Internet distributions on the same basis as other allocations.

We have agreed that we will not (i) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise transfer or dispose of, directly or indirectly, or file with the Securities and Exchange Commission, or SEC, a registration statement under the Securities Act of 1933, as amended, or the Securities Act, relating to, any shares of our common stock or securities convertible into or exchangeable or exercisable for any shares of our common stock, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing, or (ii) enter into any swap or other arrangement that transfers, in whole or in part, any of the economic consequences associated with the ownership of any shares of common stock or any such other securities (regardless of whether any of these transactions are to be settled by the delivery of shares of common stock or such other securities, in cash or otherwise), in each case without the prior written consent of J.P. Morgan Securities LLC on behalf of the underwriters for a period of 60 days after the date of this prospectus. Notwithstanding the foregoing, if (1) during the last 17 days of the 60-day restricted period, we issue an earnings release or material news or a material event relating to our company occurs; or (2) prior to the expiration of the 60-day restricted period, we announce that we will release earnings results during the 16-day period beginning on the last day of the 60-day period, the restrictions described above shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.

The restrictions described in the immediately preceding paragraph do not apply, subject to certain conditions, to the following:


•	the sale of shares of common stock pursuant to the underwriting agreement;

•	the issuance of shares of our common stock upon pursuant to our stock plans and our employee stock purchase plan;

•	the issuance of shares of our common stock upon the exercise of warrants outstanding on the date hereof;

•	the filing by us of any Registration Statement on Form S-8 or a successor form thereto; or

S-10

•

the issuance of shares of common stock or securities convertible into or exercisable or exchangeable for shares of common stock representing in the aggregate no more than 5% of our issued and outstanding shares of common stock as of the date of the underwriting agreement, which may be sold only to collaborators, vendors, manufacturers, distributors, customers or other similar parties pursuant to a collaboration, licensing agreement, strategic alliance, manufacturing or distribution arrangement or similar transaction, so long as the recipients of such securities shall sign and deliver a lock-up agreement.

Our directors and executive officers have entered into lock-up agreements with the underwriters prior to the commencement of this offering pursuant to which each of these persons or entities, with limited exceptions, for a period of 60 days after the date of this prospectus, may not, without the prior written consent of J.P. Morgan Securities LLC on behalf of the underwriters, (i) offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, or otherwise transfer or dispose of, directly or indirectly, any shares of our common stock or any securities convertible into or exercisable or exchangeable for our common stock (including, without limitation, common stock or such other securities which may be deemed to be beneficially owned by such persons or entities in accordance with the rules and regulations of the SEC and securities which may be issued upon exercise of a stock option or warrant) or (ii) enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of the common stock or such other securities (regardless of whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of common stock or such other securities, in cash or otherwise), or (iii) make any demand for or exercise any right with respect to the registration of any shares of our common stock or any securities convertible into or exercisable or exchangeable for our common stock. Notwithstanding the foregoing, if (1) during the last 17 days of the 60-day restricted period, we issue an earnings release or material news or a material event relating to our company occurs; or (2) prior to the expiration of the 60-day restricted period, we announce that we will release earnings results during the 16-day period beginning on the last day of the 60-day period, the restrictions described above shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.

The restrictions described in the immediately preceding paragraph do not apply, subject to certain conditions, to the following:


•	the transfer of shares of our common stock as a bona fide gift or gifts;

•	the transfer to any trust for the direct or indirect benefit of the individual executing the lock-up agreement or a member of his or her immediate family in a transaction not involving a disposition for value;

•	the transfer by will, other testamentary document or intestate succession to the legal representative, heir, beneficiary or a member of the immediate family of the individual executing the lock-up agreement;

•	the exercise of options to purchase shares of common stock granted under our stock plans;

•	the establishment of a trading plan pursuant to Rule 10b5-1 under the Securities Exchange Act of 1934, as amended, for the transfer of common stock; or

•	the transfer, sale or disposal of shares of common stock held by the individual executing the lock-up agreement pursuant to a trading plan existing on the date of the underwriting agreement.

We have agreed to indemnify the underwriters against certain liabilities, including liabilities under the Securities Act.

S-11

In connection with this offering, the underwriters may engage in stabilizing transactions, which involve making bids for, purchasing and selling shares of common stock in the open market for the purpose of preventing or retarding a decline in the market price of the common stock while this offering is in progress. These stabilizing transactions may include making short sales of the common stock, which involves the sale by the underwriters of a greater number of shares of common stock than they are required to purchase in this offering, and purchasing shares of common stock on the open market to cover positions created by short sales. Short sales may be “covered” shorts, which are short positions in an amount not greater than the underwriters’ over-allotment option referred to above, or may be “naked” shorts, which are short positions in excess of that amount. The underwriters may close out any covered short position either by exercising their over-allotment option, in whole or in part, or by purchasing shares in the open market. In making this determination, the underwriters will consider, among other things, the price of shares available for purchase in the open market compared to the price at which the underwriters may purchase shares through the over-allotment option. A naked short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market that could adversely affect investors who purchase in this offering. To the extent that the underwriters create a naked short position, they will purchase shares in the open market to cover the position.

The underwriters have advised us that, pursuant to Regulation M of the Securities Act, they may also engage in other activities that stabilize, maintain or otherwise affect the price of the common stock, including the imposition of penalty bids. This means that if the representatives of the underwriters purchase common stock in the open market in stabilizing transactions or to cover short sales, the representatives can require the underwriters that sold those shares as part of this offering to repay the underwriting discount received by them.

These activities may have the effect of raising or maintaining the market price of the common stock or preventing or retarding a decline in the market price of the common stock, and, as a result, the price of the common stock may be higher than the price that otherwise might exist in the open market. If the underwriters commence these activities, they may discontinue them at any time. The underwriters may carry out these transactions on The NASDAQ Global Market, in the over-the-counter market or otherwise.

In addition, in connection with this offering certain of the underwriters (and selling group members) may engage in passive market making transactions in our common stock on The NASDAQ Global Market prior to the pricing and completion of this offering. Passive market making consists of displaying bids on The NASDAQ Global Market no higher than the bid prices of independent market makers and making purchases at prices no higher than these independent bids and effected in response to order flow. Net purchases by a passive market maker on each day are generally limited to a specified percentage of the passive market maker’s average daily trading volume in the common stock during a specified period and must be discontinued when such limit is reached. Passive market making may cause the price of our common stock to be higher than the price that otherwise would exist in the open market in the absence of these transactions. If passive market making is commenced, it may be discontinued at any time.

Other than in the United States, no action has been taken by us or the underwriters that would permit a public offering of the securities offered by this prospectus in any jurisdiction where action for that purpose is required. The securities offered by this prospectus may not be offered or sold, directly or indirectly, nor may this prospectus or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution

S-12

of this prospectus. This prospectus does not constitute an offer to sell or a solicitation of an offer to buy any securities offered by this prospectus in any jurisdiction in which such an offer or a solicitation is unlawful.

This document is only being distributed to and is only directed at (i) persons who are outside the United Kingdom or (ii) to investment professionals falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (the “Order”) or (iii) high net worth entities, and other persons to whom it may lawfully be communicated, falling with Article 49(2)(a) to (d) of the Order (all such persons together being referred to as “relevant persons”). The securities are only available to, and any invitation, offer or agreement to subscribe, purchase or otherwise acquire such securities will be engaged in only with, relevant persons. Any person who is not a relevant person should not act or rely on this document or any of its contents.

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a “Relevant Member State”), from and including the date on which the European Union Prospectus Directive (the “EU Prospectus Directive”) is implemented in that Relevant Member State (the “Relevant Implementation Date”) an offer of securities described in this prospectus may not be made to the public in that Relevant Member State prior to the publication of a prospectus in relation to the shares which has been approved by the competent authority in that Relevant Member State or, where appropriate, approved in another Relevant Member State and notified to the competent authority in that Relevant Member State, all in accordance with the EU Prospectus Directive, except that it may, with effect from and including the Relevant Implementation Date, make an offer of shares to the public in that Relevant Member State at any time:


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

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

•	to fewer than 100 natural or legal persons (other than qualified investors as defined in the EU Prospectus Directive) subject to obtaining the prior consent of the book-running managers for any such offer; or

•	in any other circumstances which do not require the publication by the Issuer of a prospectus pursuant to Article 3 of the Prospectus Directive.

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

Certain of the underwriters and their affiliates have provided in the past to us and our affiliates and may provide from time to time in the future certain commercial banking, financial advisory, investment banking and other services for us and such affiliates in the ordinary course of their business, for which they have received and may continue to receive customary fees and commissions. In addition, from time to time, certain of the underwriters and their affiliates may effect transactions for their own account or the account of customers, and hold on behalf of themselves or their customers, long or short positions in our debt or equity securities or loans, and may do so in the future.

S-13

Legal matters

The validity of the shares of common stock offered hereby will be passed upon for us by Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston, Massachusetts. Members of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C. and certain members of their families and trusts for their benefit own an aggregate of approximately 5,000 shares of our common stock. Latham & Watkins LLP, San Diego, California, will act as counsel to the underwriters in connection with this offering.

Experts

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

Where you can find more information

We are subject to the reporting requirements of the Securities Exchange Act of 1934, as amended, and file annual, quarterly and current reports, proxy statements and other information with the SEC. You may read and copy these reports, proxy statements and other information at the SEC’s public reference facilities at 100 F Street, N.E., Room 1580, Washington, D.C. 20549. You can request copies of these documents by writing to the SEC and paying a fee for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information about the operation of the public reference facilities. SEC filings are also available at the SEC’s web site at http://www.sec.gov. Our common stock is listed on The NASDAQ Global Market, and you can read and inspect our filings at the offices of the Financial Industry Regulatory Authority at 1735 K Street, Washington, D.C. 20006.

This prospectus supplement is only part of a registration statement on Form S-3 that we have filed with the SEC under the Securities Act and therefore omits certain information contained in the registration statement. We have also filed exhibits and schedules with the registration statement that are excluded from this prospectus supplement, and 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.

We also maintain a website at www.ariad.com, through which you can access our SEC filings. The information set forth on our website is not part of this prospectus.

S-14

Incorporation of certain information 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. Statements in this prospectus regarding the provisions of certain documents filed with, or incorporated by reference in, the registration statement are not necessarily complete and each statement is qualified in all respects by that reference. Copies of all or any part of the registration statement, including the documents incorporated by reference or the exhibits, may be obtained upon payment of the prescribed rates at the offices of the SEC listed above in “Where You Can Find More Information.” The documents we are incorporating by reference are:


•	our annual report on Form 10-K for the fiscal year ended December 31, 2010 filed on March 15, 2011;

•	our quarterly report on Form 10-Q for the fiscal quarter ended March 31, 2011 filed on May 10, 2011;

•	our quarterly report on Form 10-Q for the fiscal quarter ended June 30, 2011 filed on August 9, 2011;

•	our quarterly report on Form 10-Q for the fiscal quarter ended September 30, 2011 filed on November 7, 2011;

•	our current reports on Form 8-K filed on January 12, 2011, January 19, 2011, February 17, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), March 18, 2011, March 28, 2011, April 21, 2011, May 2, 2011, May 6, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), June 3, 2011, June 6, 2011, June 23, 2011, August 1, 2011, August 2, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), August 18, 2009, September 6, 2011, September 21, 2011, September 23, 2011, September 27, 2011, October 6, 2011 and November 3, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), and December 12, 2011;

•	the portions of our definitive proxy statement on Schedule 14A that are deemed “filed” with the SEC under the Securities Exchange Act of 1934, as amended, filed on May 2, 2011;

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

•	all documents filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, on or after the date of this prospectus and before the termination of offerings under this prospectus are deemed to be incorporated by reference into, and to be a part of, this prospectus, except in each case for information contained in any such filing where we indicate that such information is being furnished and is not considered “filed” under the Securities Exchange Act of 1934, as amended.

The SEC file number for each of the documents listed above is 000-21696.

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.

S-15

We will provide without charge to each person, including any beneficial owner, to whom a copy of this prospectus is delivered, upon the request of any such person, a copy of any or all of the information incorporated herein by reference (exclusive of exhibits to such documents unless such exhibits are specifically incorporated by reference herein). Requests, whether written or oral, for such copies should be directed to: 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 an offer or solicitation is not qualified to do so or to anyone to whom it is unlawful to make such an offer or solicitation.

S-16

PROSPECTUS

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, 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. In addition, this prospectus may be used to offer securities for the account of persons other than us. We will provide you with specific terms of any offering in one or more supplements to this prospectus. This prospectus may not be used to offer or sell our securities unless accompanied by a prospectus supplement. 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 December 13, 2011, the last reported sale price of our common stock was $11.01 per share. Prospective purchasers of our securities are urged to obtain current information as to the market prices of our securities, where applicable.

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks that we have described on page 4 of this prospectus under the caption “Risk Factors.” We may include specific risk factors in supplements to this prospectus under the caption “Risk Factors.”

Our securities may be sold directly to investors, through agents designated from time to time or to or through underwriters or dealers. 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 December 14, 2011.

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 process, we may sell any combination of the securities described in this prospectus in one or more offerings. Each time securities are offered 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. You should read both this prospectus and the applicable prospectus supplement together with additional information under the headings “Where You Can Find More Information” and “Incorporation by Reference.” 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.

The information contained in this prospectus is accurate only as of the date on the front cover of this prospectus and information we have incorporated by reference in this prospectus is accurate only as of the date of the document incorporated by reference. You should not assume that the information contained in, or incorporated by reference into, this prospectus is accurate as of any other date.

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

ABOUT ARIAD PHARMACEUTICALS, INC.

Overview

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.

We are building a pipeline of product candidates that has the potential to expand and improve current treatment options for patients with cancer. Each of our product candidates — ponatinib, AP26113 and ridaforolimus — was discovered internally by our scientists based on our expertise in cell-signaling, cancer biology and structure-based drug design. We believe that our product candidates have the potential to treat multiple cancer indications, and we anticipate pursuing broad development of each.

In the third quarter of 2011, we commenced a Phase 1/2 clinical trial to determine the initial safety, tolerability, pharmacokinetic profile, recommended dose and preliminary anti-tumor activity of AP26113.

Our goal is to build a fully integrated oncology company. We are focused on building a commercial organization to market, distribute and sell our products upon regulatory approval in the United States, Europe and in other markets around the world.

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 and any other website is not incorporated by reference into this prospectus or any accompanying prospectus supplement and does not constitute a part of this prospectus or any accompanying prospectus supplement. Our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K and all amendments to such reports are made available free of charge through the Investor Relations section of our website as soon as reasonably practicable after they have been filed or furnished with the SEC.

WHERE YOU CAN FIND MORE INFORMATION

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.

We also maintain a website at www.ariad.com, through which you can access our SEC filings. The information set forth on our website is not part of this prospectus.

INCORPORATION OF DOCUMENTS BY REFERENCE

the provisions of certain documents filed with, or incorporated by reference in, the registration statement are not necessarily complete and each statement is qualified in all respects by that reference. Copies of all or any part of the registration statement, including the documents incorporated by reference or the exhibits, may be obtained upon payment of the prescribed rates at the offices of the SEC listed above in “Where You Can Find More Information.” The documents we are incorporating by reference are:


	•	our annual report on Form 10-K for the fiscal year ended December 31, 2010 filed on March 15, 2011;

	•	our quarterly report on Form 10-Q for the fiscal quarter ended March 31, 2011 filed on May 10, 2011;

	•	our quarterly report on Form 10-Q for the fiscal quarter ended June 30, 2011 filed on August 9, 2011;

	•	our quarterly report on Form 10-Q for the fiscal quarter ended September 30, 2011 filed on November 7, 2011;

	•	our current reports on Form 8-K filed on January 12, 2011, January 19, 2011, February 17, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), March 18, 2011, March 28, 2011, April 21, 2011, May 2, 2011, May 6, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), June 3, 2011, June 6, 2011, June 23, 2011, August 1, 2011, August 2, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”), August 18, 2009, September 6, 2011, September 21, 2011 and September 23, 2011 September 27, 2011, October 6, 2011, November 3, 2011 (only the portions of Items 8.01 and 9.01 deemed to be “filed”) and December 12, 2011;

	•	the portions of our definitive proxy statement on Schedule 14A that are deemed “filed” with the SEC under the Securities Exchange Act of 1934, as amended, filed on May 2, 2011;

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

	•	all documents filed by us pursuant to Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, on or after the date of this prospectus and before the termination of offerings under this prospectus are deemed to be incorporated by reference into, and to be a part of, this prospectus, except in each case for information contained in any such filing where we indicate that such information is being furnished and is not considered “filed” under the Securities Exchange Act of 1934, as amended.

The SEC file number for each of the documents listed above is 000-21696.

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 us. 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, which is on file with the SEC and is 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. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations.

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

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

Such statements in connection with any discussion of future operations or financial performance are identified by the use of words such as “may,” “anticipate,” “estimate,” “expect,” “project,” “intend,” “plan,” “believe,” and other words and terms of similar meaning. Such statements are based on management’s expectations and are subject to certain factors, risks and uncertainties that may cause actual results, outcome of events, timing and performance to differ materially from those expressed or implied by such statements. These risks and uncertainties include, but are not limited to, the costs associated with our research, development, manufacturing and other activities, the conduct and results of pre-clinical and clinical studies of our product candidates, difficulties or delays in obtaining regulatory approvals to market products resulting from our development efforts, our reliance on strategic partners and licensees and other key parties for the successful development, manufacturing and commercialization of products, the adequacy of our capital resources and the availability of additional funding, including with respect to commercialization for our product candidates, if approved, patent protection and third-party intellectual property claims relating to our and any partner’s product candidates, the timing, scope, cost and outcome of legal proceedings, future capital needs, risks related to key employees, markets, economic conditions, prices, reimbursement rates, competition and other factors detailed under the heading “Risk Factors” in this prospectus as updated and supplemented by the discussion of risks and uncertainties under “Risk Factors” contained in any supplements to this prospectus and in our most recent annual report on Form 10-K, as revised or supplemented by our most recent quarterly report on Form 10-Q or our current reports on Form 8-K, as well as any amendments thereto, as filed with the SEC and which are incorporated herein by reference. The information contained in this document is believed to be current as of the date of this document. We do not intend to update any of the forward-looking statements after the date of this document to conform these statements to actual results or to changes in our expectations, except as required by law.

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

RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES

The following table sets forth, for each of the periods presented, our ratio of earnings to fixed charges. You should read this table in conjunction with the consolidated financial statements and notes incorporated by reference in this prospectus.

Year Ended

Nine Months Ended

December 31,

September 30, 2011

2010

2009

2008

2007

2006

Ratio of earnings to fixed charges

N/A

251

N/A

We did not have earnings for the years ended December 31, 2009, 2008, 2007 and 2006 or for the nine months ended September 30, 2011. Accordingly, our earnings were insufficient to cover fixed charges for such periods and we are unable to disclose a ratio of earnings to fixed charges for such periods. The dollar amount of the deficiency in earnings available for fixed charges for the years ended December 31, 2009, 2008, 2007 and 2006 was approximately $80.0 million, $71.1 million, $58.5 million and $61.9 million, respectively, and for the nine months ended September 30, 2011 was $71.8 million.

This information 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.

USE OF PROCEEDS

Except as provided in the applicable prospectus supplement, we intend to use the net proceeds from the sale of the securities by us through this prospectus for general corporate purposes. Except as provided in the applicable prospectus supplement, we will not receive any proceeds in the event that securities are sold by a selling securityholder. Additional information on the use of net proceeds from the sale of securities covered by this prospectus may be set forth in the prospectus supplement relating to the specific offering.

DESCRIPTION OF COMMON STOCK

We are authorized to issue 240,000,000 shares of common stock, par value $0.001 per share. On December 1, 2011, we had 132,860,819 shares of common stock outstanding and approximately 402 stockholders of record.

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

General

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

Transfer Agent and Registrar

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

The NASDAQ Global Market

Our common stock is listed for quotation on The NASDAQ Global Market under the symbol “ARIA.” On December 13, 2011, the last reported sale price of our common stock was $11.01 per share.

DESCRIPTION OF PREFERRED STOCK

We are authorized to issue 10,000,000 shares of preferred stock, par value $0.01 per share, of which 500,000 shares have been designated Series A Preferred Stock. As of December 1, 2011, no shares of our preferred stock were outstanding. The following summary of certain provisions of our preferred stock does not purport to be complete. You should refer to our certificate of incorporation, as amended, and our restated bylaws, both of which are included as exhibits to the registration statement of which this prospectus is a part. The summary below is also qualified by provisions of applicable law.

General

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

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


	•	the title and stated value;

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

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

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

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

	•	the provisions for a sinking fund, if any;

	•	the provisions for redemption, if applicable;

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

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

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


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

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

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

	•	any material limitations on issuance of any class or series of preferred stock ranking senior to or on a parity with the series of preferred stock as to dividend rights and rights upon liquidation, dissolution or winding up of ARIAD.

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 may be offered under this prospectus. While the terms we have summarized below will apply generally to any future debt securities that may be offered pursuant to this prospectus, we will describe the particular terms of any debt securities that may be offered in more detail in the applicable prospectus supplement. If we so indicate in a prospectus supplement, the terms of any debt securities offered under that prospectus supplement may differ from the terms we describe below, and to the extent the terms set forth in a prospectus supplement differ from the terms described below, the terms set forth in the prospectus supplement shall control.

Under this prospectus, debt securities, which may be senior or subordinated, may be sold from time to time, in one or more offerings. 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, or the Trust Indenture Act. We use the term “debenture trustee” to refer to either the trustee under the senior indenture or the trustee under the subordinated indenture, as applicable.

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.

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 United States dollars or foreign currencies or units based on or relating to United States dollars or foreign currencies, including euros. Neither indenture limits the amount of debt securities that may be issued thereunder, and each indenture provides that the specific terms of any series of debt securities shall be set forth in, or determined pursuant to, an authorizing resolution and/or a supplemental indenture, if any, relating to such series.

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


	•	the title or designation;

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

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

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

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


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

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

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

	•	the place or places where payments will be payable;

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

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

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

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

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

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

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

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

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

Conversion or Exchange Rights

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

Consolidation, Merger or Sale; No Protection in Event of a Change of Control or Highly Leveraged Transaction

The indentures may 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 will be required to 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 will be events of default under the indentures with respect to any series of debt securities that we may issue:


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

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

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

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

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

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

Subject to the terms of the indentures, if an event of default under an indenture shall occur and be continuing, the debenture trustee will be under no obligation to exercise any of its rights or powers under such indenture at the request or direction of any of the holders of the applicable series of debt securities, unless such holders have offered the debenture trustee reasonable indemnity. The holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the debenture trustee or exercising any trust or power conferred on the debenture trustee, with respect to the debt securities of that series, provided that:


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

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

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


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

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

	•	the debenture trustee does not institute the proceeding, and does not receive from the holders of a majority in aggregate principal amount of the outstanding debt securities of that series (or at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) other conflicting directions within 60 days after the notice, request and offer.

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

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

Modification of Indenture; Waiver

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


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

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

In addition, under the indentures, the rights of holders of a series of debt securities may be changed by us and the debenture trustee with the written consent of the holders of at least a majority in aggregate principal amount of the outstanding debt securities of each series (or, at a meeting of holders of such series at which a quorum is present, the holders of a majority in principal amount of the debt securities of such series represented at such meeting) that is affected. However, the debenture trustee and we may make the following changes only with the consent of each holder of any outstanding debt securities affected:


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

	•	reducing the principal amount, reducing the rate of or extending the time of payment of interest, or 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 will provide 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 will have to deposit with the trustee money or government obligations sufficient to pay all the principal of, any premium, if any, and interest on, the debt securities of the series on the dates payments are due.

Form, Exchange, and Transfer

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

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

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

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

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


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


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

Information Concerning the Debenture Trustee

The debenture trustee, other than during the occurrence and continuance of an event of default under the applicable indenture, will undertake 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 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

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 may be offered, as described in the applicable prospectus supplement. Below is a description of certain general terms and provisions of the warrants that may be offered. Particular terms of the warrants will be described in the warrant agreements and the prospectus supplement 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 the warrants will be issued;


	•	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 United States federal income tax consequences;

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

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

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

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

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

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

	•	any redemption or call provisions;

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

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

DESCRIPTION OF UNITS

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 any combination, may be offered. 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 an amendment 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, as applicable, the form of unit agreement and any supplemental agreements that describe the terms of the series of units being offered before the issuance of the related series of units.

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

SELLING SECURITYHOLDERS

Selling securityholders are persons or entities that, directly or indirectly, have acquired or will from time to time acquire, securities in various private or other transactions. Such selling securityholders may be parties to registration rights agreements with us, or we otherwise may have agreed or will agree to register their securities for resale. The purchasers of our securities, as well as their transferees, pledgees, donees or successors, all of whom we refer to as “selling securityholders,” may from time to time offer and sell the securities pursuant to this prospectus and any applicable prospectus supplement. The applicable prospectus supplement will set forth the name of each of the selling securityholders and the number of shares of our common stock or other relevant securities beneficially owned by such selling securityholders that are covered by such prospectus supplement.

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

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

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

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

Classified Board

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

Advanced Notice Procedures for Stockholder Proposals

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

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

Provisions of Delaware Law Governing Business Combinations

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


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

	•	upon consummation of the transaction which resulted in the stockholder becoming an “interested stockholder,” the “interested stockholder” owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, excluding for purposes of determining the voting stock outstanding (but not the outstanding voting stock owned by the “interested stockholder”) those shares owned by (a) persons who are directors and also officers and (b) employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the plan will be tendered in a tender or exchange offer; or

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

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

Limitations on Liability and Indemnification of Officers and Directors

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

LEGAL MATTERS

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

EXPERTS

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


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ABOUT THIS PROSPECTUS		1
ABOUT ARIAD PHARAMCEUTICALS, INC.		1
WHERE YOU CAN FIND MORE INFORMATION		2
INCORPORATION OF DOCUMENTS BY REFERENCE		2
RISK FACTORS		4
SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS		4
RATIO/DEFICIENCY OF EARNINGS TO FIXED CHARGES		5
USE OF PROCEEDS		5
DESCRIPTION OF COMMON STOCK		5
DESCRIPTION OF PREFERRED STOCK		6
DESCRIPTION OF DEBT SECURITIES		7
DESCRIPTION OF WARRANTS		12
DESCRIPTION OF UNITS		13
SELLING SECURITYHOLDERS		14
CERTAIN PROVISIONS OF DELAWARE LAW AND OF THE COMPANY’S CERTIFICATE OF INCORPORATION AND BY-LAWS		14
LEGAL MATTERS		15
EXPERTS		15