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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. )*

OSI PHARMACEUTICALS, INC.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

671040103

(CUSIP Number)

November 10, 2005

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

o Rule 13d-1 (b)

þ Rule 13d-1 (c)

o Rule 13d-1 (d)

*The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the notes).

Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

13G
CUSIP No. 671040103					Page 2 of 8
	1.	Name of Reporting Person: BB Biotech AG			I.R.S. Identification Nos. of above persons (entities only): N/A
	2.	Check the Appropriate Box if a Member of a Group:
		(a)	þ
		(b)	o
	3.	SEC Use Only:
	4.	Citizenship or Place of Organization: Switzerland
Number of Shares Beneficially Owned by Each Reporting Person With
			5.	Sole Voting Power: 0
			6.	Shared Voting Power: 3,787,7001
			7.	Sole Dispositive Power: 0
			8.	Shared Dispositive Power: 3,787,700
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person: 3,787,700
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares: o
	11.	Percent of Class Represented by Amount in Row (9): 7.3%
	12.	Type of Reporting Person: HC, CO

¹ Reflects ownership as of November 25, 2005.

13G
CUSIP No. 671040103					Page 3 of 8
	1.	Name of Reporting Person: Biotech Invest N.V.			I.R.S. Identification Nos. of above persons (entities only): N/A
	2.	Check the Appropriate Box if a Member of a Group:
		(a)	þ
		(b)	o
	3.	SEC Use Only:
	4.	Citizenship or Place of Organization: Netherlands Antilles
Number of Shares Beneficially Owned by Each Reporting Person With
			5.	Sole Voting Power: 0
			6.	Shared Voting Power: 3,787,700
			7.	Sole Dispositive Power: 0
			8.	Shared Dispositive Power: 3,787,700
	9.	Aggregate Amount Beneficially Owned by Each Reporting Person: 3,787,700
	10.	Check if the Aggregate Amount in Row (9) Excludes Certain Shares: o
	11.	Percent of Class Represented by Amount in Row (9): 7.3%
	12.	Type of Reporting Person: CO

Item 1

1(a)	Name of Issuer: OSI Pharmaceuticals, Inc.
1(b)	Address of Issuer’s Principal Executive Offices:
	58 South Service Road, Suite 110, Melville, NY, 11747

Item 2

2(a)	Name of Person Filing: BB Biotech AG (“BB Biotech”), on behalf of Biotech Invest N.V., its wholly-owned subsidiary and record owner of the securities.
2(b)	Address of Principal Business Office or, if none, Residence: BB Biotech AG: Vordergasse 3, CH-8200 Schaffhausen, Switzerland Biotech Invest N.V.: De Ruyterkade 62, Willemstad, Curacao, Netherlands Antilles

2(c)	Citizenship Switzerland
2(d)	Title of Class of Securities Common Stock
2(e)	CUSIP Number 671040103

Item 3

If this statement is filed pursuant to Rule 13d-1(b), or 13d-2(b) or (c), check whether the person filing is a:

a. o	Broker or Dealer registered under Section 15 of the Act.
b. o	Bank as defined in Section 3(a)(6) of the Act.
c. o	Insurance company as defined in Section 3(a)(19) of the Act.
d. o	Investment company registered under section 8 of the Investment Company Act of 1940.
e. o	An investment adviser in accordance with Rule 13d-1(b)(1)(ii)(E);
f. o	An employee benefit plan or endowment fund in accordance with Rule 13d-1(b)(1)(ii)(F);
g. o	A parent holding company or control person in accordance with Rule 13d-1(b)(1)(ii)(G);
h. o	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
i. o	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940;
j. o	Group, in accordance with Rule 13d-1(b)(1)(ii)(J).

Page 4 of 8

Item 4. Ownership

     Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

(a)	Amount beneficially owned: 3,787,700
(b)	Percent of class: 7.3%
(c)	Number of shares as to which the person has:

(i)	Sole power to vote or to direct the vote 0
(ii)	Shared power to vote or to direct the vote 3,787,700
(iii)	Sole power to dispose or to direct the disposition of 0
(iv)	Shared power to dispose or to direct the disposition of 3,787,700

Item 5. Ownership of Five Percent or Less of a Class

     If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following: o

Item 6. Ownership of More than Five Percent on Behalf of Another Person.

N/A

Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

     This statement is filed jointly by BB Biotech and Biotech Invest N.V. Biotech Invest N.V. is a wholly-owned subsidiary of BB Biotech.

Item 8. Identification and Classification of Members of the Group

N/A

Item 9. Notice of Dissolution of Group

N/A

Page 5 of 8

Item 10. Certification

     By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Page 6 of 8

SIGNATURES

     After reasonable inquiry and the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

	BB Biotech AG
Date: November 25, 2005	By:	/s/ Pascal Schmucki
		Signatory Authority
		Name: Title:	Pascal Schmucki Signatory Authority

Date: November 25, 2005	By:	/s/ Adrian Brüngger
		Signatory Authority
		Name: Title:	Adrian Brüngger Signatory Authority

	Biotech Invest N.V.
Date: November 25, 2005	By:	/s/ Pascal Schmucki
		Signatory Authority
		Name: Title:	Pascal Schmucki Signatory Authority

Date: November 25, 2005	By:	/s/ Adrian Brüngger
		Signatory Authority
		Name: Title:	Adrian Brüngger Signatory Authority

Page 7 of 8

Exhibit A

Joint Filing Statement

     Pursuant to Rule 13d-1(f)(1), we, the undersigned, hereby express our agreement that the attached Schedule 13G (including all amendments thereto) is filed on behalf of each of the undersigned.

	BB Biotech AG
Date: November 25, 2005	By:	/s/ Pascal Schmucki
		Signatory Authority
		Name: Title:	Pascal Schmucki Signatory Authority

Date: November 25, 2005	By:	/s/ Adrian Brüngger
		Signatory Authority
		Name: Title:	Adrian Brüngger Signatory Authority

	Biotech Invest N.V.
Date: November 25, 2005	By:	/s/ Pascal Schmucki
		Signatory Authority
		Name: Title:	Pascal Schmucki Signatory Authority

Date: November 25, 2005	By:	/s/ Adrian Brüngger
		Signatory Authority
		Name: Title:	Adrian Brüngger Signatory Authority

Page 8 of 8