FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person *   Flynn James E 2. Date of Event Requiring Statement (Month/Day/Year) 10/15/2007 3. Issuer Name and Ticker or Trading Symbol ARENA PHARMACEUTICALS INC [ARNA] (Last) (First) (Middle) 780 THIRD AVENUE, 37TH FLOOR 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) NEW YORK, NY 10017 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock (1) 1,870,860 I (2) Through Deerfield Partners, L.P Common Stock (1) 3,254,783 I (3) Through Deerfield International Limited

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Short Call Option (Obligation to Sell)	10/15/2007	01/19/2008	Common Stock	185,500	$ 17.5	I (2)	Through Deerfield Partners, L.P
Short Call Option (Obligation to Sell)	10/15/2007	01/19/2008	Common Stock	314,500	$ 17.5	I (3)	Through Deerfield International Limited
Short Put Option (Obligation to Buy)	10/15/2007	01/19/2008	Common Stock	283,500	$ 7.5	I (2)	Through Deerfield Partners, L.P
Short Put Option (Obligation to Buy)	10/15/2007	01/19/2008	Common Stock	466,500	$ 7.5	I (3)	Through Deerfield International Limited
Call Option (Right to Buy)	10/15/2007	04/19/2008	Common Stock	370,900	$ 12.5	I (2)	Through Deerfield Partners, L.P.
Call Option (Right to Buy)	10/15/2007	04/19/2008	Common Stock	629,100	$ 12.5	I (3)	Through Deerfield International Limited
Short Call Option (Obligation to Sell)	10/15/2007	04/19/2008	Common Stock	185,500	$ 20.4	I (2)	Through Deerfield Partners, L.P.
Short Call Option (Obligation to Sell)	10/15/2007	04/19/2008	Common Stock	314,500	$ 20.4	I (3)	Through Deerfield International Limited

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Flynn James E 780 THIRD AVENUE 37TH FLOOR NEW YORK, NY 10017	Â	  X	Â	Â
DEERFIELD CAPITAL LP 780 THIRD AVENUE 37TH FLOOR NEW YORK, NY 10017	Â	  X	Â	Â
DEERFIELD MANAGEMENT CO /NY 780 THIRD AVENUE, 37TH FLOOR NEW YORK, NY 10017	Â	  X	Â	Â
DEERFIELD INTERNATIONAL LTD Â	Â	  X	Â	Â
DEERFIELD PARTNERS, LP 780 THIRD AVENUE 37TH FLOOR NEW YORK, NY 10017	Â	  X	Â	Â

Signatures

/s/ Darren Levine		10/23/2007
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	This Form 3 is being filed by the undersigned s well as the entities listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons").
(2)	Deerfield Capital, L.P. is the general partner of Deerfield Partners, L.P. (the "Domestic Fund"). James E. Flynn is the managing member of the general partner of Deerfield Capital, L.P. In accordance with Instruction 5(b)(iv) to Form 3, the entire amount of the Issuer's securities held by the Domestic Fund is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.
(3)	Deerfield Management Company, L.P. is the investment manager of Deerfield International Limited (the "Offshore Fund"). James E. Flynn is the managing member of the general partner of Deerfield Management Company, L.P. In accordance with Instruction 5(b)(iv) to Form 3, the entire amount of the Issuer's securities held by the Offshore Fund is reported herein. For purposes of Section 16 of the Securities Exchange Act of 1934, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise.
  Remarks: Darren Levine, Attorney-In-Fact : Power of Attorney is attached hereto as Exhibit 24

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