Document:

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                                                                   EXHIBIT 10.31

                                  ATTACHMENT B

      As a supplement to the letter agreement dated October 7, 2004 between La
Jolla Pharmaceutical Company ("LJP") and Josefina Elchico. ("ELCHICO") related
to Elchico's employment by LJP, Elchico and LJP hereby agree as follows:

      In connection with Elchico's employment with LJP, LJP's management will
recommend to LJP's Board of Directors that LJP grant to Elchico an option to
purchase up to 50,000 shares of common stock of LJP. Such option, if granted,
shall be the "OPTION" for purposes hereof.

      If Elchico's employment is terminated by LJP without cause (as defined
below), or if a Change in Control of LJP (as defined below) occurs and Elchico'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)   Elchico will be entitled to receive from LJP a severance payment
            equal to her 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 Elchico and LJP of a mutual release,
            in form satisfactory to LJP, of all claims arising in connection
            with Elchico's employment with LJP and termination thereof, and

      (ii)  Elchico 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 she has
            not found suitable employment, medical and dental benefits coverage
            for Elchico and/or her 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 Company's
            obligation to pay the premiums for health and dental coverage
            Elchico and/or her 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 Elchico'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 Elchico 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 her
employment or fiduciary responsibilities to LJP.

                                       1
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For purposes hereof, Elchico'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) Elchico is removed from
Elchico's employment by, or resigns her 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) Elchico's position is eliminated as a result of a reduction
in force made to reduce over-capacity or unnecessary duplication of personnel
and Elchico 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) Elchico resigns her employment with the Company or its successor rather
than comply with a relocation of her primary work site more than 50 miles from
LJP's headquarters.

      In Witness Whereof, LJP and Elchico have entered into this agreement as of
October 12, 2004.

La Jolla Pharmaceutical Company

By: /s/ Steven B. Engle                        /s/ Josefina Elchico
    -------------------                        --------------------
    Steven B. Engle                            Josefina Elchico
    Chairman & CEO                             Vice President, Quality Systems

                                       2<PAGE>

                                                                   EXHIBIT 10.60

                                 PROMISSORY NOTE

                                     9/28/04
                                     (DATE)

FOR VALUE RECEIVED, LA JOLLA PHARMACEUTICAL COMPANY a corporation located at the
address stated below ("MAKER") promises, jointly and severally if more than one,
to pay to the order of GENERAL ELECTRIC CAPITAL CORPORATION or any subsequent
holder hereof (each, a "PAYEE") at its office located at 83 WOOSTER HEIGHTS
ROAD, DANBURY, CT or at such other place as Payee or the holder hereof may
designate, the principal sum of ONE HUNDRED FIFTY SEVEN THOUSAND FOUR HUNDRED
TWENTY FOUR AND 14/00 ($157,424.14), with interest on the unpaid principal
balance, from the date hereof through and including the dates of payment, at a
fixed interest rate of Eight and Forty-Four Hundredths percent (8.44%) per
annum, to be paid in lawful money of the United States, in Forty-Two (42)
consecutive monthly installments of principal and interest as follows:

<TABLE>
<CAPTION>
   Periodic
  Installment                  Amount
  -----------                  ------
<S>                            <C>
Thirty-Six (36)                $4,810.82
Five (5)                       $834.61
</TABLE>

each ("Periodic Installment") and a final installment which shall be in the
amount of the total outstanding principal and interest. The first Periodic
Installment shall be due and payable on ______10/1/04______________ and the
following Periodic Installments and the final installment shall be due and
payable on the same day of each succeeding month (each, a "Payment Date"). Such
installments have been calculated on the basis of a 360 day year of twelve
30-day months. Each payment may, at the option of the Payee, be calculated and
applied on an assumption that such payment would be made on its due date.

The acceptance by Payee of any payment which is less than payment in full of all
amounts due and owing at such time shall not constitute a waiver of Payee's
right to receive payment in full at such time or at any prior or subsequent
time.

The Maker hereby expressly authorizes the Payee to insert the date value is
actually given in the blank space on the face hereof and on all related
documents pertaining hereto.

This Note may be secured by a security agreement, chattel mortgage, pledge
agreement or like instrument (each of which is hereinafter called a "SECURITY
AGREEMENT").

Time is of the essence hereof. If any installment or any other sum due under
this Note or any Security Agreement is not received within ten (10) days after
its due date, the Maker agrees to pay, in addition to the amount of each such
installment or other sum, a late payment charge of five percent (5%) of the
amount of said installment or other sum, but not exceeding any lawful maximum.
If (i) Maker fails to make payment of any amount due hereunder within ten (10)
days after the same becomes due and payable; or (ii) Maker is in default under,
or fails to perform under any term or condition contained in any Security
Agreement, then the entire principal sum remaining unpaid, together with all
accrued interest thereon and any other sum payable under this Note or any
Security Agreement, at the election of Payee, shall immediately become due and
payable, with interest thereon at the lesser of eighteen percent (18%) per annum
or the highest rate not prohibited by applicable law from the date of such
accelerated maturity until paid (both before and after any judgment).

Notwithstanding anything to the contrary contained herein or in the Security
Agreement, Maker may not prepay in full or in part any indebtedness hereunder
without the express written consent of Payee in its sole discretion.

It is the intention of the parties hereto to comply with the applicable usury
laws; accordingly, it is agreed that, notwithstanding any provision to the
contrary in this Note or any Security Agreement, in no event shall this Note or
any Security Agreement require the payment or permit the collection of interest
in excess of the maximum amount permitted by applicable law. If any such excess
interest is contracted for, charged or received under this Note or any Security
Agreement, or if all of the principal balance shall be prepaid, so that under
any of such circumstances the amount of interest contracted for, charged or
received under this Note or any Security Agreement on the principal balance
shall exceed the maximum amount of interest permitted by applicable law, then in
such event (a) the provisions of this paragraph shall govern and control, (b)
neither Maker nor any other person or entity now or hereafter liable for the
payment hereof shall be obligated to pay the amount of such interest to the
extent that it is in excess of the maximum amount of interest permitted by
applicable law, (c) any such excess which may have been collected shall be
either applied as a credit against the then unpaid principal balance or refunded
to Maker, at the option of the Payee, and (d) the effective rate of interest
shall be automatically reduced to the maximum lawful contract rate allowed under
applicable law as now or hereafter construed

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by the courts having jurisdiction thereof. It is further agreed that without
limitation of the foregoing, all calculations of the rate of interest contracted
for, charged or received under this Note or any Security Agreement which are
made for the purpose of determining whether such rate exceeds the maximum lawful
contract rate, shall be made, to the extent permitted by applicable law, by
amortizing, prorating, allocating and spreading in equal parts during the period
of the full stated term of the indebtedness evidenced hereby, all interest at
any time contracted for, charged or received from Maker or otherwise by Payee in
connection with such indebtedness; provided, however, that if any applicable
state law is amended or the law of the United States of America preempts any
applicable state law, so that it becomes lawful for the Payee to receive a
greater interest per annum rate than is presently allowed, the Maker agrees
that, on the effective date of such amendment or preemption, as the case may be,
the lawful maximum hereunder shall be increased to the maximum interest per
annum rate allowed by the amended state law or the law of the United States of
America.

The Maker and all sureties, endorsers, guarantors or any others (each such
person, other than the Maker, an "OBLIGOR") who may at any time become liable
for the payment hereof jointly and severally consent hereby to any and all
extensions of time, renewals, waivers or modifications of, and all substitutions
or releases of, security or of any party primarily or secondarily liable on this
Note or any Security Agreement or any term and provision of either, which may be
made, granted or consented to by Payee, and agree that suit may be brought and
maintained against any one or more of them, at the election of Payee without
joinder of any other as a party thereto, and that Payee shall not be required
first to foreclose, proceed against, or exhaust any security hereof in order to
enforce payment of this Note. The Maker and each Obligor hereby waives
presentment, demand for payment, notice of nonpayment, protest, notice of
protest, notice of dishonor, and all other notices in connection herewith, as
well as filing of suit (if permitted by law) and diligence in collecting this
Note or enforcing any of the security hereof, and agrees to pay (if permitted by
law) all expenses incurred in collection, including Payee's actual attorneys'
fees. Maker and each Obligor agrees that fees not in excess of twenty percent
(20%) of the amount then due shall be deemed reasonable.

THE MAKER HEREBY UNCONDITIONALLY WAIVES ITS RIGHTS TO A JURY TRIAL OF ANY CLAIM
OR CAUSE OF ACTION BASED UPON OR ARISING OUT OF, DIRECTLY OR INDIRECTLY, THIS
NOTE, ANY OF THE RELATED DOCUMENTS, ANY DEALINGS BETWEEN MAKER AND PAYEE
RELATING TO THE SUBJECT MATTER OF THIS TRANSACTION OR ANY RELATED TRANSACTIONS,
AND/OR THE RELATIONSHIP THAT IS BEING ESTABLISHED BETWEEN MAKER AND PAYEE. THE
SCOPE OF THIS WAIVER IS INTENDED TO BE ALL ENCOMPASSING OF ANY AND ALL DISPUTES
THAT MAY BE FILED IN ANY COURT (INCLUDING, WITHOUT LIMITATION, CONTRACT CLAIMS,
TORT CLAIMS, BREACH OF DUTY CLAIMS, AND ALL OTHER COMMON LAW AND STATUTORY
CLAIMS.) THIS WAIVER IS IRREVOCABLE MEANING THAT IT MAY NOT BE MODIFIED EITHER
ORALLY OR IN WRITING, AND THE WAIVER SHALL APPLY TO ANY SUBSEQUENT AMENDMENTS,
RENEWALS, SUPPLEMENTS OR MODIFICATIONS TO THIS NOTE, ANY RELATED DOCUMENTS, OR
TO ANY OTHER DOCUMENTS OR AGREEMENTS RELATING TO THIS TRANSACTION OR ANY RELATED
TRANSACTION. IN THE EVENT OF LITIGATION, THIS NOTE MAY BE FILED AS A WRITTEN
CONSENT TO A TRIAL BY THE COURT.

This Note and any Security Agreement constitute the entire agreement of the
Maker and Payee with respect to the subject matter hereof and supercedes all
prior understandings, agreements and representations, express or implied.

No variation or modification of this Note, or any waiver of any of its
provisions or conditions, shall be valid unless in writing and signed by an
authorized representative of Maker and Payee. Any such waiver, consent,
modification or change shall be effective only in the specific instance and for
the specific purpose given.

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Any provision in this Note or any Security Agreement which is in conflict with
any statute, law or applicable rule shall be deemed omitted, modified or altered
to conform thereto.

                                      LA JOLLA PHARMACEUTICAL COMPANY

/s/ Lisa Peraza                       By: /s/ Steven B. Engle
--------------------------------          -------------------------------------
(Witness)

Lisa Peraza                           Name: Steven B. Engle
(Print name)

6455 Nancy  Ridge Drive               Title: Chairman & CEO
San Diego, CA 92121
(Address)

                                      Federal Tax ID #:       330361285

                                      Address:  6455 Nancy Ridge Drive, San
                                      Diego, San Diego County, CA 92121

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