UNITED STATES ~~SECURITIES AND EXCHANGE COMMISSION~~

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

Current Report Pursuant to Section 13 or 15(d) of ~~The Securities Exchange Act of 1934~~

The Securities Exchange Act of 1934

June 3, 2010

Date of Report (Date of earliest event reported)

OSI Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Delaware	0-15190	013-~~15190~~3159796	~~13-3159796~~
(State or other jurisdiction of		(Commission	(I.R.S. Employer
(State or other jurisdiction of incorporation)	(Commission File Number)	(I.R.S. Employer Identification No.)
incorporation)		File Number)	Identification No.)

420 Saw Mill River Road

Ardsley, NY 10502

(Address of principal executive offices)

(914) 231-8000

(Registrant’'s telephone number, including area code)

N/A

(Former name or former address,

if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) o¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) o¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) o¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

~~ITEM~~- 1~~.01~~ ~~Entry into a Material Definitive Agreement~~ -

~~Agreement~~ITEM ~~and~~2.04 ~~Plan~~Triggering ofEvents ~~Merger~~ That Accelerate or Increase a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement.

OnThe ~~May 16,~~consummation ~~2010,~~of ~~OSI~~the ~~Pharmaceuticals,~~Company ~~Inc.~~Change in Control (~~the~~as ~~“Company”~~defined below) ~~entered~~on ~~into~~June an3, ~~agreement~~2010 and ~~plan of~~the ~~merger~~consummation (of the “Merger ~~Agreement”)~~(as ~~with~~defined ~~Astellas~~below) ~~Pharma~~on ~~Inc.~~June 8, 2010 each constituted a ~~corporation~~"Fundamental ~~formed~~Change" under the ~~laws of~~Indentures ~~Japan~~ (~~“Astellas”~~the "Indentures"), ~~Astellas~~between USOSI ~~Holding~~Pharmaceuticals, Inc. (~~“Parent”~~the "Company"), aand ~~Delaware~~The ~~corporation~~Bank ~~and wholly-owned~~of ~~subsidiary~~New ofYork ~~Astellas~~Mellon ~~and~~relating ~~Ruby~~to ~~Acquisition,~~Company's ~~Inc.~~2% Convertible Senior Subordinated Notes Due 2025 (~~“Merger~~the ~~Sub”~~"2025 Notes"), aand ~~Delaware corporation~~3% ~~and~~Convertible ~~wholly-owned~~Senior ~~subsidiary~~Subordinated ofNotes ~~Parent,~~Due ~~pursuant~~2038 to(the ~~which~~"2038 Notes", ~~among~~and ~~other~~together ~~things,~~with ~~(i) Astellas~~the ~~will~~2025 ~~amend~~Notes, ~~its~~the ~~existing~~"Convertible ~~offer~~Notes"). As toa ~~purchase~~result, ~~all~~holders of the ~~issued~~Convertible ~~and~~Notes ~~outstanding~~have ~~shares~~the ofright (1) to require the Company’s ~~common~~to ~~stock,~~repurchase ~~par~~their ~~value~~Convertible ~~$.01~~Notes ~~per~~at ~~share~~their ~~(the~~principal ~~“Shares”),~~amount toplus ~~offer~~accrued ~~cash~~and ~~consideration~~unpaid ~~of $57.50~~interest ~~per~~on ~~Share~~a certain date (the ~~“Revised~~"Fundamental ~~Offer~~Change ~~Price”~~Purchase Date"), ~~without~~as ~~interest~~set ~~(the~~forth ~~“Revised~~in ~~Offer”)~~the ~~and~~Indentures or (ii2) ~~as promptly~~to asconvert ~~practicable~~their ~~following~~Convertible Notes pursuant to the ~~acceptance~~applicable Indenture for ~~payment~~cash ofat ~~any Shares~~the ~~tendered~~then ~~pursuant~~applicable toconversion rate, as may be adjusted under the ~~Revised~~applicable ~~Offer~~Indenture. The (Fundamental Change Purchase Date for the ~~“Acceptance Time”)~~Convertible Notes in connection with the Company Change in Control is July 16, ~~Merger~~2010. The ~~Sub~~Fundamental ~~will~~Change bePurchase ~~merged~~Date (for the ~~“Merger”)~~ Convertible Notes in connection with ~~and~~the ~~into~~Merger is July 21, 2010. Assuming that each holder of Convertible Senior Notes elected to convert its Convertible Notes, the Company ~~with~~would be obligated to make aggregate payments of approximately $408 million. On June 4 and June 9, 2010, the Company ~~surviving~~issued press releases announcing the ~~Merger~~Fundamental Changes under the Indenture governing the 2025 Notes, which press releases are attached hereto as aExhibits ~~wholly~~99.1 ~~owned subsidiary~~and of99.2, ~~Holding~~respectively.

~~The~~ITEM Merger Agreement contains representations and warranties of the parties customary for transactions of this type, and which, in the case of the Company’s representations and warranties, are qualified by disclosures contained in the Company’s disclosure letter delivered by the Company to the other parties to the Merger Agreement in connection with the Merger Agreement3.01 ~~The~~Notice ~~Company has agreed to various customary covenants and agreements, including, among others, (i) to conduct its business in the ordinary course during the interim period between the execution~~ of ~~the~~Delisting ~~Merger Agreement and the earlier of (A) the date of election~~ or ~~appointment~~Failure ~~of Parent’s designees~~ to ~~the Company’s~~Satisfy Board of Directors (the “Board”) in accordance with the Merger Agreement and (B) the effective time of the Merger, (ii) not to engage in certain kinds of transactions during such period, (iii) to convene and hold a ~~meeting~~Continued ofListing ~~its~~Rule ~~stockholders to consider and vote upon the Merger, if required by the General Corporation Law~~ of ~~the~~Standard; ~~State~~Transfer of Delaware, and (iv) not to (A) knowingly solicit or initiate any alternative proposal to acquire the Company, or (B) subject to certain exceptions, engage in any discussions or negotiations regarding or provide any non-public information in connection with, any such proposalListing. The Merger Agreement also contains certain termination provisions for the Company and Astellas and provides that, in connection with the termination of the Merger Agreement under specified circumstances, including, subject to the terms of the Merger Agreement, if the Company’s Board determines to accept an unsolicited “Superior Proposal” (as that term is defined in the Merger Agreement), the Company will be required to pay Astellas a termination fee of $125 million.

~~Astellas~~In ~~has~~connection ~~agreed~~with ~~that~~the completion of the Merger, ~~Sub~~on ~~will~~June ~~amend~~8, ~~its~~2010, ~~initial~~the ~~offer~~Company asnotified ~~promptly~~The asNASDAQ ~~practicable after~~Stock ~~the~~Market ~~date~~("NASDAQ") ofthat the Merger ~~Agreement~~had been completed and ~~will~~requested ~~keep~~that NASDAQ file a delisting notification on Form 25 with the ~~Revised~~Securities ~~Offer~~and ~~open~~Exchange ~~for~~Commission 10(the ~~business~~"SEC") ~~days~~to delist the Company's common stock, ~~subject~~ topar ~~extension~~value $.01 per share (the "Common Stock") and terminate the registration of the Common Stock under Section 12(b) of the Securities Exchange Act of 1934, as ~~permitted~~amended, ~~pursuant~~which toNASDAQ filed with the ~~Merger~~SEC ~~Agreement~~on June 8, 2010. Trading ~~Merger~~of ~~Sub~~the ~~may~~Common ~~also~~Stock ~~elect~~on ~~to provide~~The ~~for~~NASDAQ ~~one~~Global orSelect ~~more~~Market ~~subsequent~~was ~~offering~~suspended ~~periods~~following ~~after~~the close of the ~~Acceptance~~ ~~Time. During~~NASDAQ ~~any~~trading ~~subsequent~~session ~~offering~~on ~~period~~June 8, 2010.

ITEM 3.03 Material Modification to Rights of Security Holders.

The disclosure contained in Items 2.04 and 5.01 of this Report is incorporated by reference into this Item 3.03.

ITEM 5.01 Changes in Control of Registrant.

As previously disclosed, on May 16, 2010, the Company entered into an agreement and plan of merger with Astellas Pharma Inc., a corporation formed under the

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~~Shares~~laws ~~not~~of ~~tendered~~Japan ("Astellas"), Astellas US Holding, Inc. ("Parent"), a Delaware corporation and ~~purchased~~wholly-owned ~~prior~~subsidiary of Astellas and Ruby Acquisition, Inc. ("Merger Sub"), a Delaware corporation and wholly-owned subsidiary of Parent (as amended by the First Amendment to the ~~expiration~~Agreement and Plan of ~~the~~Merger, ~~Revised~~dated ~~Offer~~June ~~may~~3, be2010, ~~tendered~~by to and among Astellas, Holding, Merger Sub ~~for~~and the ~~Revised~~Company, the "Merger Agreement"), pursuant to which, among other things, Astellas amended its existing offer to purchase all of the issued and outstanding shares of the Company's Common Stock, including the associated rights to purchase shares of Series SRP Junior Participating Preferred Stock, par value $0.01 (the "Rights", and together with the Common Stock, the "Shares"), to offer cash consideration of $57.50 per Share (the "Offer Price"), without interest (as amended, the "Offer").

~~The~~On ~~obligation~~June of3, ~~Merger~~2010, ~~Sub~~Astellas toannounced ~~accept~~that ~~for~~the ~~payment~~initial offering period had expired at midnight, New York City time, on June 2, 2010 and ~~pay~~that it had commenced a subsequent offering period for all remaining untendered Shares, inwhich ~~the~~expired ~~Revised~~at midnight, New York City time, on June 7, 2010. The depositary for the Offer ~~is subject~~advised toAstellas that a ~~number~~total of ~~conditions~~48, ~~including~~415,727 ~~among~~Shares ~~other~~were ~~things:~~validly ~~(1) more~~tendered ~~than~~and ~~50%~~not withdrawn prior to the expiration of the ~~outstanding~~ ~~shares~~initial ~~(on~~offering aperiod ~~fully~~and ~~diluted~~4,190,714 ~~basis)~~Shares ~~being~~were tendered inthrough ~~the~~guaranteed ~~Revised~~delivery ~~Offer~~procedures, ~~(2) there~~representing ~~not having~~an ~~been~~aggregate aof “52,606,441 Shares or approximately 86% of the Company's ~~Material~~issued ~~Adverse~~and ~~Effect”~~outstanding ~~(as~~Shares. All ~~defined~~Shares that were validly tendered in the ~~Merger~~initial ~~Agreement)~~offering ~~since~~period and not withdrawn were accepted for payment by Merger Sub. Upon the ~~date~~ acceptance of Shares for payment pursuant to the ~~Merger~~Offer ~~Agreement~~on ~~and~~June (3, 2010 (the "Acceptance Time") , a change of control of the Company ~~has~~occurred ~~not~~(the ~~sold,~~"Company ~~licensed~~Change orin ~~otherwise~~Control"). ~~transferred~~The ~~any rights~~depositary ~~relating~~for the Offer advised Astellas that an additional 4,625,916 Shares were validly tendered prior to ~~any~~the ~~product~~expiration ~~containing~~of ~~erlotinib~~the subsequent offering period, ~~except~~which, together with the Shares tendered in ~~connection~~the ~~with~~initial ~~sales~~offering ofperiod, ~~inventory~~ represented approximately 93% of ~~such~~the ~~product~~Company's issued and outstanding Shares. All Shares that were validly tendered in the ~~ordinary~~subsequent ~~course~~offering orperiod aswere ~~contractually~~immediately ~~required~~accepted for payment by Merger Sub.

~~Pursuant~~On June 8, 2010, pursuant to the terms of the Merger Agreement, ~~the~~and ~~Company~~in ~~granted~~accordance ~~Astellas~~with ~~and~~Section ~~Merger~~253 ~~Sub~~of anthe ~~irrevocable option~~General (Corporation Law of the ~~“Top~~State Upof ~~Option”~~Delaware (the "DGCL"), ~~exercisable~~Merger atSub orwas ~~following~~merged ~~the~~by ~~Acceptance~~way ~~Time~~of ~~and~~a ~~upon~~"short-form" merger (the ~~terms~~"Merger") with and ~~subject~~into to the ~~conditions~~Company ~~set~~with ~~forth~~the inCompany surviving the Merger ~~Agreement,~~as ~~to purchase~~a atwholly ~~the~~owned ~~Revised~~subsidiary ~~Offer~~of ~~Price~~Holding anwithout ~~aggregate~~a ~~number~~vote of ~~Shares~~the ~~that,~~Company's ~~when~~stockholders. At ~~added to~~ the ~~number~~effective time of ~~Shares~~ ~~held~~the ofMerger ~~record~~(the by"Effective ~~Astellas~~Time"), ~~Holding~~each Share issued and ~~Merger~~outstanding ~~Sub~~immediately atprior to the ~~time~~Effective ofTime ~~such~~(other ~~exercise~~than Shares held by the Company, ~~constitute one~~Astellas, ~~Share~~Holding, ~~more~~Merger ~~than~~Sub ~~90%~~or ofstockholders ~~the~~who ~~Shares~~are ~~then~~entitled ~~outstanding,~~to ~~but~~demand ~~which~~and ~~number~~properly ofperfect ~~Shares~~appraisal ~~cannot~~rights ~~exceed~~ under the ~~number~~DGCL) ofwas ~~authorized~~converted ~~but~~into ~~unissued~~the ~~Shares~~right ~~under~~to receive the ~~Company’s~~Offer ~~Restated~~Price, ~~Certificate~~without ~~of Incorporation~~interest.

The ~~foregoing~~total ~~description~~amount of ~~the~~funds ~~Merger~~necessary ~~Agreement~~to iscomplete ~~qualified in its entirety by reference to~~ the ~~full~~Offer ~~text~~and of the Merger ~~Agreement,~~was aapproximately ~~copy~~$4 ~~of which is attached as Exhibit 2~~billion.1 Certain toof ~~this~~the ~~Current Report~~expenses onincurred ~~Form~~in ~~8-K~~connection ~~(“Report”) and is incorporated herein by reference. The Merger Agreement has been attached as an exhibit to provide investors and security holders~~ with ~~information regarding its terms. It is not intended to provide any other financial information about~~ the ~~Company,~~Offer ~~or its respective subsidiaries~~ and ~~affiliates. The representations, warranties and covenants contained in the~~ Merger ~~Agreement~~ were ~~made~~paid ~~only for purposes of that agreement and as of specific dates, are solely for the benefit of the parties to the Merger Agreement, may be subject to limitations agreed upon~~ by the ~~parties,~~Company ~~including~~using ~~being qualified by confidential disclosures made for~~ the ~~purposes~~Company's ~~of allocating~~available ~~contractual~~cash ~~risk~~on ~~between~~hand ~~the parties to the Merger Agreement instead of establishing these matters as facts,~~ and ~~may~~Astellas beprovided ~~subject to standards of materiality applicable to~~ the ~~contracting~~ ~~parties~~remaining ~~that~~funds ~~differ~~required ~~from those applicable~~ to ~~investors.~~consummate ~~Investors should not rely on~~ the ~~representations,~~Offer ~~warranties~~ and ~~covenants or any description thereof as characterizations of~~ the ~~actual~~Merger ~~state~~to ofMerger ~~facts~~Sub orfrom ~~condition of the Company, or any of~~ its ~~subsidiaries~~available orcash ~~affiliates. Moreover,~~on information concerning the subject matter of the representations, warranties and covenants may change after the date of the Merger Agreement, which subsequent information may or may not be fully reflected in public disclosures by the Companyhand.

Rights Agreement Amendment

In connection with the Merger Agreement, on May 16, 2010, the Company entered into Amendment No. 1 (the “Rights Agreement Amendment”) to the Rights

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~~Agreement, dated as of September~~ ~~27, 2000, by and between the Company and~~ The ~~Bank~~foregoing description of ~~New~~certain ~~York Mellon~~provisions ~~(the “Rights Agreement”). The Rights Agreement Amendment provides, among other things, that neither the execution~~ of the Merger Agreement, ~~nor~~is ~~the~~qualified ~~consummation~~in ofits ~~the~~entirety ~~Revised Offer,~~by ~~the~~reference ~~Merger,~~to or the ~~other transactions contemplated by the~~ Merger Agreement, ~~will~~a ~~trigger~~copy ~~the exercise~~ of ~~the~~which ~~stockholder~~was ~~rights~~filed ~~under~~as ~~the~~Exhibit ~~Rights Agreement~~2.1 ~~The~~to ~~Rights Agreement Amendment also provides that none of Astellas, Holding or Merger Sub or any of their affiliates or associates will be deemed an “Acquiring Person” under~~ the ~~Rights~~Form ~~Agreement~~8-K ~~and~~filed ~~no “Distribution Date” will be deemed to occur, in each case, solely~~ by ~~virtue of~~ the ~~approval,~~Company ~~execution,~~with ~~delivery or adoption of~~ the ~~Merger~~SEC ~~Agreement,~~on orMay ~~the consummation of the Revised Offer~~17, ~~the Merger or any other transactions contemplated by the Merger Agreement~~2010.

~~The~~ITEM ~~foregoing~~5.02 ~~description~~Departure of ~~the~~Directors ~~Rights~~or ~~Agreement~~Certain ~~Amendment~~Officers; isElection ~~qualified~~of inDirectors; ~~its~~Appointment ~~entirety by reference to the full text~~ of ~~the~~Certain ~~Rights~~Officers; ~~Agreement~~Compensatory ~~Amendment,~~Arrangements ~~a copy~~ of ~~which~~Certain ~~is attached as Exhibit 4~~Officers.~~1 to this Report and is incorporated herein by reference.~~

~~ITEM~~Pursuant to the terms of the Merger Agreement, following the Acceptance Time, each of Colin Goddard, Santo J. Costa, Joseph Klein, III, Kenneth B. Lee, Jr., David W. Niemiec, Herbert M. Pinedo and John P. White resigned from the Board of Directors of the Company (the "Board"), effective June 3, 2010.03 Pursuant ~~Material~~to ~~Modification~~the Merger Agreement, and effective as of June 3, 2010, designees of Astellas, William Fitzsimmons, Linda Friedman, Stephen Knowles and Patrick Shea, were appointed to ~~Rights~~the Board. Each of ~~Security~~Astellas' ~~Holders~~ designees are officers of Astellas or one of its subsidiaries. Additional information about Astellas' designees was previously disclosed in the Information Statement comprising Annex C to Amendment No. 6 to the Company's Solicitation/Recommendation Statement on Schedule 14D-9 filed with the SEC on May 20, 2010 and is incorporated herein by reference. Effective on June 3, 2010, Robert A. Ingram also resigned from the Board. In addition, pursuant to the employment agreement, as amended, between the Company and Dr. Colin Goddard, the Company's Chief Executive Officer, Dr. Goddard gave notice on June 3, 2010 of his election to terminate his employment for "good reason" based on the Company Change in Control, which shall become effective on July 2, 2010 unless otherwise agreed to by the relevant parties.

~~The~~Pursuant ~~disclosure~~to ~~regarding~~the terms of the ~~Rights~~Merger Agreement, ~~Amendment~~at ~~set~~the ~~forth~~Effective ~~under~~Time, ~~Item 1.01~~the directors of ~~this Report~~the isCompany ~~incorporated~~were byremoved ~~reference~~and ~~into~~Linda ~~this~~Friedman, ~~Item 3~~Seigo Kashii and Stephen Knowles, the directors of Merger Sub immediately prior to the Effective Time, became the initial directors of the surviving corporation.~~03.~~

ITEM 85.0103 ~~Other~~Amendments ~~Events~~ to Articles of Incorporation or Bylaws; Change in Fiscal Year.

OnPursuant ~~May 16,~~to ~~2010~~the terms of the Merger Agreement, ~~Astellas~~at ~~and~~the Effective Time, the Company's ~~issued~~Certificate aof ~~joint~~Incorporation ~~press~~was ~~release~~amended ~~announcing~~and ~~the execution~~restated in its entirety. A copy of the ~~Merger~~Company's ~~Agreement~~certificate of incorporation, aas ~~copy~~amended ofand ~~which~~restated pursuant to the Merger, is attached hereto as Exhibit 99 3.1 ~~to this Report~~ and is incorporated herein by reference.

~~ITEM~~Pursuant 9to the terms of the Merger Agreement, at the Effective Time, the Company's bylaws were amended and restated in their entirety.01 A ~~Financial~~copy ~~Statements~~of the Company's bylaws, as amended and ~~Exhibits~~ restated pursuant to the Merger, is attached hereto as Exhibit 3.2 and incorporated herein by reference.

ITEM 9.01 Financial Statements and Exhibits.

(d)

Exhibits.

See Exhibit Index.

Additional Information

This communication does not constitute an offer to sell or the solicitation of an offer to buy any securities of any stockholder of OSI Pharmaceuticals, Inc. (“OSI”).

In connection with the tender offer commenced by Astellas, OSI has filed a Solicitation/Recommendation Statement on Schedule 14D-9 with the SEC (as amended, the “Schedule 14D-9”). STOCKHOLDERS OF OSI ARE URGED TO READ THE SCHEDULE 14D-9 AND OTHER DOCUMENTS FILED WITH THE SEC CAREFULLY IN THEIR ENTIRETY BECAUSE THEY CONTAIN IMPORTANT INFORMATION. Stockholders may obtain a free copy of the Schedule 14D-9 and other documents filed by OSI with the SEC through the website maintained by the SEC at http://www.sec.gov. Stockholders may also obtain, without charge, a copy of

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the Schedule 14D-9 from MacKenzie Partners, Inc., OSI’s information agent, by calling 800-322-2885 toll free or by calling 212-929-5500 or by emailing osipharma@mackenziepartners.com.

Forward Looking Statements

This report contains forward-looking statements that do not convey historical information, but relate to predicted or potential future events, such as statements of our plans, strategies and intentions, or our future performance or goals for our product development programs. These statements can often be identified by the use of forward-looking terminology such as “believe,” “expect,” “intend,” “may,” “will,” “should,” or “anticipate” or similar terminology. The statements involve risks and uncertainties and are based on various assumptions. Stockholders and prospective stockholders are cautioned that these statements are only projections. In addition, any forward-looking statement that we make is intended to speak only as of the date on which we made the statement. Except for our ongoing obligations to disclose material information under the federal securities laws, we will not update any forward-looking statement to reflect events or circumstances that occur after the date on which the statement is made. The following risks and uncertainties, among others, may cause our actual results to differ materially from those described in forward-looking statements made in this report or presented elsewhere by management from time to time.

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SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: May 17, 2010	OSI Pharmaceuticals, Inc.
	By:	/s/ Barbara A. Wood
		Barbara A. Wood
		Senior Vice President, GeneralCounsel and Secretary

Date: June 9, 2010

-OSI 6Pharmaceuticals, - Inc. By: /s/ Barbara A. Wood Barbara A. Wood Senior Vice President, General Counsel and Secretary

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EXHIBIT INDEX

Exhibit No.	Description	~~Description~~
2.1		Agreement and Plan of Merger, dated as of May 16, 2010, among OSI Pharmaceuticals, Inc., Astellas Pharma Inc., Astellas US Holding, Inc. and Ruby Acquisition, Inc.
3.1	Amended and Restated Certificate of Incorporation of OSI Pharmaceuticals, Inc.
4.1		Amendment No. 1 to the Rights Agreement, dated May 16, 2010, by and among OSI Pharmaceuticals, Inc. and The Bank of New York Mellon
3.2	Bylaws of the Surviving Corporation
99.1	Press Release of OSI Pharmaceuticals, dated June 4, 2010	~~Joint Press Release, issued by OSI Pharmaceuticals, Inc. and Astellas Pharma Inc. on May 16, 2010~~
99.2	Press Release of OSI Pharmaceuticals, dated June 9, 2010

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