SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO 13d-2(b) ARENA PHARMACEUTICALS, INC. -------------------------------------------------------------------------------- (Name of Issuer) COMMON STOCK -------------------------------------------------------------------------------- (Title of Class of Securities) 040047 10 2 -------------------------------------------------------------------------------- (CUSIP Number) December 31, 2001 -------------------------------------------------------------------------------- (Date of Event which Requires Filing of this Statement) Check the appropriate box to designate the one pursuant to which this Schedule is filed: [ ] Rule 13d-1(b) [ ] Rule 13d-1(c) [X] Rule 13d-1(d) /1/ The remainder of this cover page shall be filled out for a reporting person's initial filing on this 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 (the "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 13G Page 2 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM Capital L.P. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 3 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person BB BioVentures L.P. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 4 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person BAB BioVentures L.P. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 5 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM BioVentures Parallel Fund, L.P. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 6 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person BAB BioVentures, N.V. -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Netherlands Antilles -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* CO -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 7 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM BioVentures I, LP -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* PN -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 8 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM BioVentures I, LLC -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* OO -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- -------------------- CUSIP NO. 040047 10 2 13G Page 9 of 15 Pages --------------------- -------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM Asset Management LLC -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* OO -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- --------------------- CUSIP NO. 040047 10 2 13G Page 10 of 15 Pages --------------------- --------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person Medical Portfolio Management, LLC -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* OO -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! --------------------- --------------------- CUSIP NO. 040047 10 2 13G Page 11 of 15 Pages --------------------- --------------------- -------------------------------------------------------------------------------- 1 NAME OF REPORTING PERSON S.S. or I.R.S. Identification No. Of Above Person MPM Asset Management Investors 1998 LLC -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [X] -------------------------------------------------------------------------------- 3 SEC USE ONLY -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware -------------------------------------------------------------------------------- NUMBER OF 5 SOLE VOTING POWER SHARES BENEFICIALLY OWNED BY 2,074,792 (1) EACH REPORTING PERSON ----------------------------------------------- WITH 6 SHARED VOTING POWER None ----------------------------------------------- 7 SOLE DISPOSITIVE POWER 2,074,792 (1) ----------------------------------------------- 8 SHARED DISPOSITIVE POWER None -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 2,074,792 (1) -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9 7.52% -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* OO -------------------------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! STATEMENT ON SCHEDULE 13G Item 1(a). Name of Issuer: -------------- Arena Pharmaceuticals, Inc. Item 1(b). Address of Issuer's Principal Executive Offices: ----------------------------------------------- 6166 Nancy Ridge Drive, San Diego, CA 92121 Item 2(a). Names of Person Filing: ---------------------- MPM Capital L.P. BB BioVentures L.P. BAB BioVentures L.P. MPM BioVentures Parallel Fund, L.P. BAB BioVentures, N.V. MPM BioVentures I L.P. MPM BioVentures I LLC MPM Asset Management, LLC Medical Portfolio Management LLC MPM Asset Management 1998 LLC Item 2(b). Business Mailing Address for the Person Filing: ---------------------------------------------- c/o MPM Capital L.P. 111 Huntington Avenue, 31st floor Boston, MA 02199 Item 2(c). Citizenship: ----------- All entities were organized in Delaware, except BAB BioVentures, N.V., which was organized in the Netherlands Antilles. Item 2(d). Title of Class of Securities: ---------------------------- Common Stock Item 2(e). CUSIP Number: ------------ 040047 10 2 Item 3. If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b), check whether the person filing is a: ---------------------------------------------- Not Applicable Item 4. Ownership: --------- (a) Amount Beneficially Owned: 2,074,792 (1) (b) Percent of Class Owned: 7.52% (c) Number of shares as to which such person has: (i) sole power to vote or to direct the vote: 2,074,792 shares of Common Stock (1) (ii) shared power to vote or to direct the vote: None (iii) sole power to dispose or to direct the disposition of: 2,074,792 shares of Common Stock (1) (iv) shared power to dispose or to direct the disposition of: None Item 5. Ownership of Five Percent or Less of a Class: -------------------------------------------- Not Applicable Item 6. Ownership of More than Five Percent on Behalf of Another Person: --------------------------------------------------------------- Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares to which this statement relates. No one person's interest in such shares is more than five percent of the total outstanding stock of the Issuer. Item 7. Identification and Classification of the Subsidiary Which Acquired the ---------------------------------------------------------------------- Security Being Reported on By the Parent Holding Company: -------------------------------------------------------- Not Applicable Item 8. Identification and Classification of Members of the Group: --------------------------------------------------------- Not Applicable Item 9. Notice of Dissolution of Group: ------------------------------ Not Applicable Item 10. Certification: ------------- Not Applicable /1/ Includes shares held through interests in MPM Capital L.P. ("MPM Capital") and in entities directly or indirectly controlled by it. MPM Capital is a direct or indirect parent and or a control person of MPM Asset Management LLC and funds managed or advised by it and the general partners of such funds. Also includes shares held through interests in Medical Portfolio Management LLC, the general partner of MPM Capital. Among the shares included, 1,796,035 shares are held by BB BioVentures L.P.; 257,172 shares are held by MPM BioVentures Parallel Fund, L.P.; and 21,585 shares are held by MPM Asset Management Investors 1998 LLC. Each reporting person herein disclaims beneficial ownership of shares not directly held by such reporting person. 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: February 13, 2002 MPM CAPITAL L.P. BB BIOVENTURES L.P. By: Medical Portfolio Management LLC, By: BAB BioVentures L.P., its General Partner its General Partner By: BAB BioVentures N.V., its General Partner By: /s/ Michael Steinmetz ------------------------- Name: Michael Steinmetz Title: Manager By: /s/ Michael Steinmetz ------------------------------ Name: Michael Steinmetz Title: Manager BAB BIOVENTURES L.P. MPM BIOVENTURES PARALLEL FUND, L.P. By: BAB BioVentures, N.V., By: MPM BioVentures I LP, its General Partner its General Partner By: MPM BioVentures I LLC, By: /s/ Michael Steinmetz its General Partner ------------------------- Name: Michael Steinmetz Title: Manager By: /s/ Michael Steinmetz ------------------------------- Name: Michael Steinmetz Title: Manager BAB BIOVENTURES, N.V. MPM BIOVENTURES I LP By: MPM BioVentures I LLC, its General Partner By: /s/ Michael Steinmetz ----------------------- Name: Michael Steinmetz Title: Manager By: /s/ Michael Steinmetz ------------------------------- Name: Michael Steinmetz Title: Manager MPM BIOVENTURES I LLC MPM ASSET MANAGEMENT LLC By: /s/ Michael Steinmetz By: /s/ Michael Steinmetz ---------------------------- ------------------------------- Name: Michael Steinmetz Name: Michael Steinmetz Title: Manager Title: Manager MEDICAL PORTFOLIO MANAGEMENT, LLC MPM ASSET MANAGEMENT 1998 LLC By: /s/ Michael Steinmetz By: /s/ Michael Steinmetz ------------------------------- ------------------------------- Name: Michael Steinmetz Name: Michael Steinmetz Title: Manager Title: Manager