X0202 4 2004-07-07 1 0001080709 ARENA PHARMACEUTICALS INC ARNA 0001055947 BVF PARTNERS L P/IL 227 WEST MONROE STREET, SUITE 4800 CHICAGO IL 60606 0 0 1 1 Indirect Beneficial Owner 0000918923 BIOTECHNOLOGY VALUE FUND L P 227 W MONROE STREET, SUITE 4800 CHICAGO IL 60606 0 0 0 1 Direct Beneficial Owner 0001102444 BIOTECHNOLOGY VALUE FUND II LP 227 WEST MONROE STREET, SUITE 4800 CHICAGO IL 60606 0 0 0 1 Direct Beneficial Owner 0001132245 BVF INVESTMENTS LLC 227 WEST MONROE STREET, SUITE 4800 CHICAGO IL 60606 0 0 0 1 Direct Beneficial Owner 0001056807 BVF INC/IL ONE SANSOME STREET, 31ST FLOOR SAN FRANCISCO CA 94104 0 0 1 1 Indirect Beneficial Owner Common Stock 2004-07-07 4 S 0 232500 5.10 D 584977 I See footnotes Common Stock 2004-07-07 4 S 0 147000 5.10 D 379884 I See footnotes Common Stock 2004-07-07 4 S 0 356500 5.10 D 1038851 I See footnotes Common Stock 2004-07-07 4 S 0 8288 5.2031 D 576689 I See footnotes Common Stock 2004-07-07 4 S 0 5000 5.2031 D 374884 I See footnotes Common Stock 2004-07-07 4 S 0 12000 5.2031 D 1026851 I See footnotes Common Stock 2004-07-08 4 S 0 21800 5.00 D 554889 I See footnotes Common Stock 2004-07-08 4 S 0 13000 5.00 D 361884 I See footnotes Common Stock 2004-07-08 4 S 0 32000 5.00 D 994851 I See footnotes The shares reported in this response are beneficially owned by Biotechnology Value Fund, L.P., a Delaware limitedpartnership ("BVF, L.P.") (554,889 shares ); Biotechnology Value Fund II, L.P., a Delaware limited partnership("BVF2, L.P.") (361,884 shares); BVF Investments, L.L.C., a Delaware limited liability company ("Investments")(994,851 shares); and by BVF Partners L.P., a Delaware limited partnership ("Partners"), and by its generalpartner BVF Inc., a Delaware corporation ("BVF Inc."), which is also an investment advisor to Partners. Partnersis the general partner of BVF, L.P. and BVF2, L.P. and is the manager of Investments. Pursuant to the operatingagreement of Investment 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 beneficiallyowned by Investments. Mark N. Lampert is the sole shareholder and sole director of BVF Inc., and is an officer of BVF Inc. This jointfiling on Form 4 shall not be deemed an admission that Mark N. Lampert is, for purposes of Section 16 of theSecurities Exchange Act of 1934, as amended, or otherwise, the beneficial owner of any equity securitiescovered by this joint filing. Mr. Lampert disclaims beneficial ownership of shares reported in this response,except to the extent that he has a pecuniary interest therein. Shares beneficailly owned by BVF, L.P. Shares beneficailly owned by BVF2, L.P. Shares beneficailly owned by Investments By: /s/ BVF Partners L.P., By: BVF Inc., its GP, By: /s/ Mark N. Lampert 2004-07-09 By: /s/ BIOTECHNOLOGY VALUE FUND, L.P. By BVF Partners L.P., its GP, By: BVF Inc., By: /s/ Mark N. Lampert 2004-07-09 By: /s/ BIOTECHNOLOGY VALUE FUND II, L.P. By BVF Partners L.P., its GP, By: BVF Inc., By: /s/ Mark N. Lampert 2004-07-09 By: /s/ BVF INVESTMENTS, L.L.C, By: BVF Partners L.P., its Manager, By: BVF Inc., By: /s/ Mark N. Lampert 2004-07-09 By: /s/ BVF INC., By: /s/ Mark N. Lampert 2004-07-09