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                                                                EXHIBIT 10.280

                  AMENDMENT NUMBER 1 TO THE OPTION AGREEMENT
                                   BETWEEN
               INVESTORS TRUST & CUSTODIAL SERVICES (IRELAND) LTD.,
               SOLELY IN ITS CAPACITY AS TRUSTEE FOR ROYALTY PHARMA,
                          ROYALTY PHARMA FINANCE TRUST
                                     AND
                       LIGAND PHARMACEUTICALS INCORPORATED

        THIS AMENDMENT TO OPTION AGREEMENT (the "Amendment") is made and entered
into on this 5th day of November, 2004, among Ligand Pharmaceuticals
Incorporated ("Seller"), Royalty Pharma Finance Trust, a Delaware Business Trust
("Buyer"), and Investors Trust & Custodial Services (Ireland) Ltd., solely in
its capacity as Trustee of Royalty Pharma, a unit trust organized under the laws
of the Republic of Ireland ("Parent").  Capitalized terms used herein but not
defined herein shall have the meanings ascribed to them in the Option Agreement,
as defined below.

        WHEREAS, Seller, Buyer and Parent are parties to that certain Option
Agreement dated as of October 1, 2003 (the "Option Agreement"), pursuant to
which Parent received the option to acquire the October 2003 Option, and Parent
exercised such option;

        WHEREAS, pursuant to Section 6 of the Option Agreement, Parent assigned
the right to purchase the October 2003 Option to Buyer, and Buyer so purchased
such option directly from Seller; and

     WHEREAS, Seller, Buyer and Parent desire to amend the Option Agreement as
set forth herein.

        NOW, THEREFORE, in consideration of the mutual promises and covenants
contained in this Amendment and the Option Agreement, the parties hereto hereby
amend the Option Agreement as follows:

     1. Section 4 is hereby amended by deleting it in its entirety and replacing
it with "Reserved."

     2. Governing Law.  This Amendment shall be construed in accordance with and
governed by the law of the State of New York.

     3. Entire Agreement.  The Option Agreement, as amended hereby, constitutes
the full and entire understanding between the parties regarding the subject
matter herein.  Except as otherwise expressly provided herein, the provisions
hereof shall be binding upon and inure to the benefit of the parties hereto and
their respective successors and assigns.

     4. Full Force and Effect.  Except as amended hereby, the Option Agreement
shall remain in full force and effect.

     5. Counterparts.  This Amendment may be signed in any number of
counterparts, each of which shall be an original, with the same effect as if the
signatures thereto and hereto were upon the same instrument.  This Amendment
shall become effective when each party hereto shall have received a counterpart
hereof signed by the other party hereto.

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     6. Captions.  The titles and captions herein are included for convenience
of reference only and shall be ignored in the construction or interpretation
hereof.

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     IN WITNESS WHEREOF, the parties hereof have caused this Amendment Number 1
to the Option Agreement to be duly executed and delivered as a deed by their
respective authorized officers of the day and year first written above.

SELLER
LIGAND PHARMACEUTICALS INCORPORATED

By:     /s/ Warner R. Broaddus
    --------------------------------------
Name:   Warner R. Broaddus
    --------------------------------------

Title:  VP, GC, Sect'y
    --------------------------------------


PARENT
INVESTORS TRUST & CUSTODIAL SERVICES (IRELAND) LTD.,
SOLELY IN ITS CAPACITY AS TRUSTEE FOR ROYALTY PHARMA

By:     /s/ Michael F. Rogers
   --------------------------------------

Name:   Michael F. Rogers
   --------------------------------------

Title:  Director
   --------------------------------------



BUYER
ROYALTY PHARMA FINANCE TRUST

By:     RP Management LLC, as Administrator

/s/ Pablo Legorreta
   --------------------------------------
Pablo Legorreta, Member