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                        LA JOLLA PHARMACEUTICAL COMPANY
                                 EXHIBIT 10.41

                                  ATTACHMENT A

        As a supplement to the letter agreement dated April 10, 2001 between La
Jolla Pharmaceutical Company ("LJP") and William J. Welch ("WELCH") related to
Welch's employment by LJP, Welch and LJP hereby agree as follows:

        In connection with Welch's employment with LJP, LJP's management will
recommend to LJP's Board of Directors that LJP grant to Welch an option to
purchase up to 80,000 shares of common stock of LJP. Such option, if granted,
shall be the "OPTION" for purposes hereof.

        If Welch's employment is terminated by LJP without Cause (as defined
below), or if a Change in Control of LJP (as defined below) occurs and Welch'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)       Welch will be entitled to receive from LJP a severance
                    payment equal to his then-current base salary for a period
                    of nine (9) full calendar months from the date of
                    termination, payable consistent with LJP's normal payroll
                    practices, provided that such payment will be contingent
                    upon execution and delivery by Welch and LJP of a mutual
                    release, in form satisfactory to LJP, of all claims arising
                    in connection with Welch's employment with LJP and
                    termination thereof, and

          (ii)      Notwithstanding anything to the contrary in the option plan
                    pursuant to which the Option is granted (the "PLAN"), the
                    Option (or any successor option received by Welch in
                    connection with the Change in Control) 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 Option was granted. However,
                    notwithstanding the foregoing, in no case will the Option be
                    exercisable beyond the duration of the original term
                    thereof, and if the Option qualifies 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 Option 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 Option.

       For purposes hereof, "CAUSE" means Welch 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

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Welch-Attachment A
April 10, 2001
Page 2


        any person or entity other than LJP and appropriate civic organizations,
        or (iv) otherwise materially breached his employment or fiduciary
        responsibilities to LJP.

        For purposes hereof, Welch'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)
        Welch is removed from Welch'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) Welch's
        position is eliminated as a result of a reduction in force made to
        reduce over-capacity or unnecessary duplication of personnel and Welch
        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) Welch 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 Welch have entered into this
        agreement as of April 16, 2001.


        LA JOLLA PHARMACEUTICAL COMPANY


        By: /s/ STEVEN B. ENGLE                   /s/ WILLIAM J. WELCH
           -----------------------------         -----------------------------
                Steven B. Engle                       William J. Welch
                Chairman & CEO