EXHIBIT 10.47

                                  ATTACHMENT A

        As a supplement to the letter agreement dated September 18, 2002 between
La Jolla Pharmaceutical Company ("LJP") and David Duncan, Jr. ("DUNCAN") related
to Duncan's employment by LJP, Duncan and LJP hereby agree as follows:

        In connection with Duncan's employment with LJP, LJP's management will
recommend to LJP's Board of Directors that LJP grant to Duncan an option to
purchase up to 60,000 shares of common stock of LJP. Such option, if granted,
shall be the "OPTION" for purposes hereof.

        If Duncan's employment is terminated by LJP without cause (as defined
below), or if a Change in Control of LJP (as defined below) occurs and Duncan's
employment with LJP or its successor "terminates in connection with" (as defined
below) that Change in Control and in the absence of any event or circumstance
constituting Cause, then:

        (i)     Duncan will be entitled to receive from LJP a severance payment
                equal to his then-current base salary for a period of six full
                calendar months from the date of termination and an additional
                three full calendar months if and when after the first six
                months he has not found suitable employment, payable consistent
                with LJP's normal payroll practices, provided that such payment
                will be contingent upon execution and delivery by Duncan and LJP
                of a mutual release, in form satisfactory to LJP, of all claims
                arising in connection with Duncan's employment with LJP and
                termination thereof, and

        (ii)    Duncan will be entitled to receive for a period of six full
                calendar months from the date of termination and an additional
                three full calendar months if and when after the first six
                months he has not found suitable employment, medical and dental
                benefits coverage for Duncan and/or his dependents through the
                Company's available plans at the time and LJP will be
                responsible to continue payment of all applicable deductions for
                premium costs. After LJP's obligation to pay the premiums for
                health and dental coverage Duncan and/or his dependents will be
                eligible to continue plan participation under COBRA.

        (iii)   Notwithstanding anything to the contrary in the option plan (the
                "PLAN") pursuant to which all of Duncan's existing options were
                granted, the Options shall automatically vest and become fully
                exercisable as of the date of termination of Executive's
                employment (the "TERMINATION DATE"), notwithstanding any vesting
                or performance conditions applicable thereto, and shall remain
                exercisable for a period of one year following the Termination
                Date or such longer period as is provided by the Plan or grant
                pursuant to which the Options were granted. However,
                notwithstanding the foregoing, in no case will the Options be
                exercisable beyond the duration of the original term thereof,
                and if the Options qualify as an incentive stock option under
                the Internal Revenue Code and applicable regulations thereunder,
                the exercise period thereof shall not be extended in such a
                manner as to cause the Options to cease to qualify as an
                incentive stock option unless Executive elects to forego
                incentive stock option treatment and extend the exercise period
                thereof as provided herein.

        For purposes hereof, "CHANGE IN CONTROL" of LJP has the meaning set
        forth in the Plan in its form as the date of grant of the Options.

        For purposes hereof, "CAUSE" means Duncan has (i) engaged in serious
        criminal activity or other wrongful conduct that has an adverse impact
        on LJP, (ii) disregarded instructions given to him under the authority
        of LJP's Board of Directors, (iii) performed services for any person or
        entity other than LJP and appropriate civic organizations, or (iv)
        otherwise materially breached his employment or fiduciary
        responsibilities to LJP.



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        For purposes hereof, Duncan's employment with LJP or its successor will
        be deemed to "TERMINATE IN CONNECTION WITH" a Change in Control if,
        within 180 days after the consummation of the Change of Control, (i)
        Duncan is removed from Duncan's employment by, or resigns his employment
        upon the request of, a person exercising practical voting control over
        LJP or its successor following the Change in Control or a person acting
        upon authority or at the instruction of such person; or (ii) Duncan's
        position is eliminated as a result of a reduction in force made to
        reduce over-capacity or unnecessary duplication of personnel and Duncan
        is not offered a replacement position with LJP or its successor as a
        Vice President with compensation and functional duties substantially
        similar to the compensation and duties in effect immediately before the
        Change in Control; or (iii) Duncan resigns his employment with the
        Company or its successor rather than comply with a relocation of his
        primary work site more than 50 miles from LJP's headquarters.

                In Witness Whereof, LJP and Duncan have entered into this
        agreement as of September 23, 2002.



        La Jolla Pharmaceutical Company

        By: /s/ Steven B. Engle                    /s/ David Duncan, Jr.
            ---------------------------            -----------------------------
            Steven B. Engle                        David Duncan, Jr.
            Chairman & CEO                         Chief Financial Officer


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