	UNITED STATES
	SECURITIES AND EXCHANGE COMMISSION
	Washington, D.C. 20549
	SCHEDULE 13D

Under the Securities Exchange Act of 1934
(Amendment No. 11)(1)

Arena Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

040047 10 2

(CUSIP Number)

Hope Flack
BVF Partners L.P.
227 West Monroe Street, Suite 4800
Chicago, Illinois 60606
(312) 263-7777

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

August 2, 2004

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. o

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

(1) 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 disclosures provided in a prior cover page.

The information required on 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 (“Act”) 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).

CUSIP No. 040047 10 2

	1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) Biotechnology Value Fund, L.P.

	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)			ý
		(b)			o

	3.	SEC Use Only

	4.	Source of Funds (See Instructions) WC

	5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) o

	6.	Citizenship or Place of Organization Delaware

Number of Shares Beneficially Owned by Each Reporting Person With			7.	Sole Voting Power 0

			8.	Shared Voting Power 0

			9.	Sole Dispositive Power 0

			10.	Shared Dispositive Power 0

	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0

	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) o

	13.	Percent of Class Represented by Amount in Row (11) 0%

	14.	Type of Reporting Person (See Instructions) PN

	1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) Biotechnology Value Fund II, L.P.

	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)			ý
		(b)			o

	3.	SEC Use Only

	4.	Source of Funds (See Instructions) WC

	5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) o

	6.	Citizenship or Place of Organization Delaware

Number of Shares Beneficially Owned by Each Reporting Person With			7.	Sole Voting Power 0

			8.	Shared Voting Power 0

			9.	Sole Dispositive Power 0

			10.	Shared Dispositive Power 0

	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0

	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) o

	13.	Percent of Class Represented by Amount in Row (11) 0%

	14.	Type of Reporting Person (See Instructions) PN

	1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) BVF Investments, L.L.C.

	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)			ý
		(b)			o

	3.	SEC Use Only

	4.	Source of Funds (See Instructions) WC

	5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) o

	6.	Citizenship or Place of Organization Delaware

Number of Shares Beneficially Owned by Each Reporting Person With			7.	Sole Voting Power 0

			8.	Shared Voting Power 0

			9.	Sole Dispositive Power 0

			10.	Shared Dispositive Power 0

	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0

	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) o

	13.	Percent of Class Represented by Amount in Row (11) 0%

	14.	Type of Reporting Person (See Instructions) OO

	1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) BVF Partners L.P.

	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)			ý
		(b)			o

	3.	SEC Use Only

	4.	Source of Funds (See Instructions) OO

	5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) o

	6.	Citizenship or Place of Organization Delaware

Number of Shares Beneficially Owned by Each Reporting Person With			7.	Sole Voting Power 0

			8.	Shared Voting Power 0

			9.	Sole Dispositive Power 0

			10.	Shared Dispositive Power 0

	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0

	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) o

	13.	Percent of Class Represented by Amount in Row (11) 0%

	14.	Type of Reporting Person (See Instructions) PN

	1.	Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only) BVF Inc.

	2.	Check the Appropriate Box if a Member of a Group (See Instructions)
		(a)			ý
		(b)			o

	3.	SEC Use Only

	4.	Source of Funds (See Instructions) OO

	5.	Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) o

	6.	Citizenship or Place of Organization Delaware

Number of Shares Beneficially Owned by Each Reporting Person With			7.	Sole Voting Power 0

			8.	Shared Voting Power 0

			9.	Sole Dispositive Power 0

			10.	Shared Dispositive Power 0

	11.	Aggregate Amount Beneficially Owned by Each Reporting Person 0

	12.	Check if the Aggregate Amount in Row (11) Excludes Certain Shares (See Instructions) o

	13.	Percent of Class Represented by Amount in Row (11) 0%

	14.	Type of Reporting Person (See Instructions) IA, CO

This Amendment No. 11 to the Statement on Schedule 13D (this “Amendment”) is being filed with the Securities and Exchange Commission on behalf of the Biotechnology Value Fund, L.P., a Delaware limited partnership (“BVF”), Biotechnology Value Fund II, L.P., a Delaware limited partnership (“BVF2”), BVF Investments L.L.C., a Delaware limited liability company (“Investments”), BVF Partners L.P., a Delaware limited partnership (“Partners”) and BVF Inc., a Delaware corporation (“BVF Inc.” and, together with BVF, BVF2, Investments, and Partners, the “Reporting Persons”) with respect to the Common Stock, par value $0.0001 per share (the “Stock”), of Arena Pharmaceuticals, Inc., a Delaware corporation (“Arena”). The principal executive office of Arena is located at 6166 Nancy Ridge Road, San Diego, California 92121.

Item 5 is hereby amended to read in its entirety as follows:

Item 5.	Interest in Securities of the Issuer
(a) No shares of Arena’s Stock are beneficially owned by the Reporting Persons.
(b) No shares of Arena’s Stock are beneficially owned by the Reporting Persons..
(c) On August 2, 2004, BVF sold 554,889 shares of the Stock, BVF2 sold 361,884 shares of the Stock and Investments sold 994,851 shares of the Stock. Each such sale was made on the open market at a price of $4.05 per share.
(d) No shares of Arena’s Stock are beneficially owned by the Reporting Persons.
(e) On August 2, 2004, the Reporting Persons sold all of their remaining shares of the Stock. Accordingly, the Reporting Persons no longer beneficially own any shares of the Stock.

Item 7.	Material to Be Filed as Exhibits
Exhibit 1 – Agreement Regarding Joint Filing

Signature

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

Dated:	August 5, 2004

	BIOTECHNOLOGY VALUE FUND, L.P.

	By:	BVF Partners L.P., its general partner

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BIOTECHNOLOGY VALUE FUND II, L.P.

	By:	BVF Partners L.P., its general partner

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BVF INVESTMENTS, L.L.C.

	By:	BVF Partners L.P., its manager

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BVF PARTNERS L.P.

	By:	BVF Inc., its general partner

		By:	/s/ Mark N. Lampert
			Mark N. Lampert
			President

	BVF INC.


	By:	/s/ Mark N. Lampert
		Mark N. Lampert
		President

Dated: August 5, 2004

	BIOTECHNOLOGY VALUE FUND, L.P.

	By:	BVF Partners L.P., its general partner

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BIOTECHNOLOGY VALUE FUND II, L.P.

	By:	BVF Partners L.P., its general partner

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BVF INVESTMENTS, L.L.C.

	By:	BVF Partners L.P., its manager

		By:	BVF Inc., its general partner

			By:	/s/ Mark N. Lampert
				Mark N. Lampert
				President

	BVF PARTNERS L.P.

	By:	BVF Inc., its general partner

		By:	/s/ Mark N. Lampert
			Mark N. Lampert
			President

	BVF INC.

	By:	/s/ Mark N. Lampert
		Mark N. Lampert
		President

Under the Securities Exchange Act of 1934 (Amendment No. 11)(1)

Signature

Under the Securities Exchange Act of 1934
(Amendment No. 11)(1)