Sec Form 4 Filing - LAMPERT MARK N @ ARENA PHARMACEUTICALS INC - 2003-10-17

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP 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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1. Name and Address of Reporting Person LAMPERT MARK N 2. Issuer Name and Ticker or Trading Symbol ARENA PHARMACEUTICALS INC [ ARNA] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) ONE SANSOME STREET, 31ST FLOOR 3. Date of Earliest Transaction (MM/DD/YY) 10/17/2003 (Street) SAN FRANCISCO, CA94104 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 10/17/2003 S 2,911,000 D $ 7.69 4,520,212( 2 ) I See Footnotes( 1 )( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other LAMPERT MARK N ONE SANSOME STREET, 31ST FLOOR SAN FRANCISCO, CA94104 X X Signatures Mark N. Lampert 10/21/2003 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The shares reported in this response are beneficially owned by Biotechnology Value Fund, L.P., a Delaware limited partnership ("BVF, L.P.") (1,376,977 shares); Biotechnology Value Fund II, L.P., a Delaware limited partnership ("BVF2, L.P.") (883,884 shares); BVF Investments, L.L.C., a Delaware limited liability company ("Investments") (2,259,351 shares); and by BVF Partners L.P., a Delaware limited partnership ("Partners"), and by its general partner BVF Inc., a Delaware corporation ("BVF Inc."), which is also an investment advisor to Partners. Partners is the general partner of BVF, L.P. and BVF2, L.P. and is the manager of Investments. Pursuant to the operating agreement of Investments, Partners is authorized, among other things, to invest the funds of Ziff Asset Management, L.P., the majority member of Investments, in the shares of common stock described herein as being beneficially owned by Investments. ( 2 )Mark N. Lampert is the sole shareholder and sole director of BVF Inc., and is an officer of BVF Inc. Mr. Lampert disclaims beneficial ownership of shares reported in this response, except to the extent that he has a pecuniary interest therein. Mr. Lampert is currently a director of Arena Pharmaceuticals, Inc.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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