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


                                  SCHEDULE 13G


                    Under the Securities Exchange Act of 1934
                              (Amendment No. __ )*


                           ISIS PHARMACEUTICALS, INC.
                           --------------------------
                                (Name of Issuer)


                    COMMON STOCK, PAR VALUE $0.001 PER SHARE
                    ----------------------------------------
                         (Title of Class of Securities)


                                    464330109
                                    ---------
                                 (CUSIP Number)


                               SEPTEMBER 27, 2007
                               ------------------
             (Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule
is filed:

        [_] Rule 13d-1(b)
        [X] Rule 13d-1(c)
        [_] Rule 13d-1(d)

*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 reminder 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).

                         (continued on following pages)

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CUSIP NO. 464330109 Schedule 13G Page 2 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Symphony Capital Partners, L.P. S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF 4,552,471 ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY -0- ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 4,552,471 ------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,552,471 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.1% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 3 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Symphony Capital GP, L.P. S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF 4,552,471 ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY -0- ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 4,552,471 ------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,552,471 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.1% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) PN - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 4 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Symphony GP, LLC S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF 4,552,471 ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY -0- ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 4,552,471 ------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,552,471 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.1% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) OO - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 5 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Symphony Strategic Partners, LLC S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION Delaware - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF 247,475 ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY -0- ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 247,475 ------------------------------------------- 8 SHARED DISPOSITIVE POWER -0- - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 247,475 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 0.3% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) OO - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 6 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Mark Kessel S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION United States - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF -0- ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY 4,799,946 ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON -0- ------------------------------------------- 8 SHARED DISPOSITIVE POWER 4,799,946 - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,799,946 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.4% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 7 of 18 --------- - -------------------------------------------------------------------------------- 1 NAMES OF REPORTING PERSON Harri V. Taranto S.S OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY) - -------------------------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a) [_] (b) [X] - -------------------------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION United States - -------------------------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF -0- ------------------------------------------- SHARES BENEFICIALLY 6 SHARED VOTING POWER OWNED BY 4,799,946 ------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON -0- ------------------------------------------- 8 SHARED DISPOSITIVE POWER 4,799,946 - -------------------------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 4,799,946 - -------------------------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS) [_] - -------------------------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9) 5.4% - -------------------------------------------------------------------------------- 12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS) IN - --------------------------------------------------------------------------------

CUSIP NO. 464330109 Schedule 13G Page 8 of 18 --------- Item 1. (a) NAME OF ISSUER Isis Pharmaceuticals, Inc. (the "Company"). (b) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES 1896 Rutherford Road, Carlsbad, California 92008. Item 2. (a) NAMES OF PERSONS FILING This Statement is being filed on behalf of each of the following persons (collectively, the "Reporting Persons") (i) Symphony Capital Partners, L.P. ("SCP") (ii) Symphony Capital GP, L.P. ("Symphony Capital GP") (iii) Symphony GP, LLC ("Symphony GP") (iv) Symphony Strategic Partners, LLC ("SSP") (v) Mark Kessel (vi) Harri V. Taranto

CUSIP NO. 464330109 Schedule 13G Page 9 of 18 --------- (b) ADDRESS OF PRINCIPAL BUSINESS OFFICE The address of the principal business offices of the Reporting Persons is 875 Third Avenue, 18th Floor, New York, NY 10022 (c) CITIZENSHIP (i) SCP - a Delaware limited partnership (ii) Symphony Capital GP - a Delaware limited partnership (iii) Symphony GP - a Delaware limited liability company (iv) SSP - a Delaware limited liability company (v) Mark Kessel - a citizen of the United States (vi) Harri V. Taranto - a citizen of the United States (d) TITLE OF CLASS OF SECURITIES Common Stock, par value $0.001 per share (the "Common Stock" or "Shares") (e) CUSIP NUMBER 464330109

CUSIP NO. 464330109 Schedule 13G Page 10 of 18 --------- Item 3. This statement is not being filed pursuant to either Rule 13d-1(b) or 13d-2(b) or (c). Item 4. OWNERSHIP. (a) (i) Each of SCP, Symphony Capital GP and Symphony GP may be deemed to beneficially own an aggregate of 4,552,471 Shares (including 2,535,689 Shares issuable upon exercise of currently exercisable warrants). (ii) SSP may be deemed to beneficially own an aggregate of 247,475 Shares (including 137,842 Shares issuable upon exercise of currently exercisable warrants). (iii) Each of Mark Kessel and Harri V. Taranto may be deemed to beneficially own an aggregate of 4,799,946 Shares (including 2,673,531 Shares issuable upon exercise of currently exercisable warrants). (b) Based on calculations made in accordance with Rule 13d-3(d), and there being 86,174,309 Shares outstanding after giving effect to the issuance of 3,383,651 Shares on September 27, 2007, (i) each of SCP, Symphony Capital GP and Symphony GP may be deemed to own approximately 5.1% of the outstanding Common Stock, (ii) SSP may be deemed to own approximately 0.3% of the outstanding Common Stock, and (iii) each of Mark Kessel and Harri V. Taranto may be deemed to beneficially own approximately 5.4% of the outstanding Common Stock. (c) (i) Each of SCP, Symphony Capital GP, Symphony GP may be deemed to have sole power to direct the voting and disposition of 4,552,471 Shares (including 2,535,689 Shares issuable upon exercise of currently exercisable warrants). (ii) SSP may be deemed to have sole power to direct the voting and disposition of 247,475 Shares (including 137,842 Shares issuable upon exercise of currently exercisable warrants). (iii) Each of Mark Kessel and Harri V. Taranto may be deemed to have shared power to direct the voting and disposition of 4,799,946 Shares (including 2,673,531 Shares issuable upon exercise of currently exercisable warrants). Item 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS Not applicable.

CUSIP NO. 464330109 Schedule 13G Page 11 of 18 --------- Item 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON Not applicable. Item 7. IDENTIFICATION AND CLASSIFICATION OF 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 See Item 2. Item 9. NOTICE OF DISSOLUTION OF GROUP Not applicable. Item 10. CERTIFICATION By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect. [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]

CUSIP NO. 464330109 Schedule 13G Page 12 of 18 --------- SIGNATURES After reasonable inquiry and to the best of our knowledge and belief, the undersigned certify that the information set forth in this statement is true, complete and correct. Dated as of October 4, 2007 SYMPHONY CAPITAL PARTNERS, L.P. By: Symphony Capital GP, L.P. its general partner By: Symphony GP, LLC its general partner By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member SYMPHONY STRATEGIC PARTNERS, LLC By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member

CUSIP NO. 464330109 Schedule 13G Page 13 of 18 --------- SYMPHONY CAPITAL GP, L.P. By: Symphony GP, LLC its general partner By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member SYMPHONY GP, LLC By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member

CUSIP NO. 464330109 Schedule 13G Page 14 of 18 --------- MARK KESSEL By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member HARRI V. TARANTO By: /s/ Harri V. Tarranto -------------------------------- Name: Harri V. Taranto Title: Managing Member

EXHIBIT INDEX Exhibit 1. Joint Filing Agreement as required by Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended.

EXHIBIT 1 --------- JOINT FILING AGREEMENT PURSUANT TO RULE 13d-1(k)(1) The undersigned acknowledge and agree that the foregoing statement on Schedule 13G is filed on behalf of each of the undersigned and that all subsequent amendments to this statement on Schedule 13G shall be filed on behalf of each of the undersigned without the necessity of filing additional joint filing statements. The undersigned acknowledge that each shall be responsible for the timely filing of such amendments, and for the completeness and accuracy of the information concerning him, her or it contained herein, but shall not be responsible for the completeness and accuracy of the information concerning the other entities or persons, except to the extent that he, she or it knows or has reason to believe that such information is inaccurate. Dated as of October 4, 2007 SYMPHONY CAPITAL PARTNERS, L.P. By: Symphony Capital GP, L.P. its general partner By: Symphony GP, LLC its general partner By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member SYMPHONY STRATEGIC PARTNERS, LLC By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member

SYMPHONY CAPITAL GP, L.P. By: Symphony GP, LLC its general partner By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member SYMPHONY GP, LLC By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member

MARK KESSEL By: /s/ Mark Kessel -------------------------------- Name: Mark Kessel Title: Managing Member HARRI V. TARANTO By: /s/ Harri V. Tarranto -------------------------------- Name: Harri V. Taranto Title: Managing Member