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                                                                   EXHIBIT 10.57

                            FIRST AMENDMENT TO LEASE

      THIS FIRST AMENDMENT TO LEASE is made this 4th day of May 2001, by and
between Spieker Properties, L.P., a California Limited Partnership,
successor-in-interest to WCB II-S BRD Limited Partnership (the "Landlord") and
La Jolla Pharmaceuticals Company, a Delaware corporation (the "Tenant").

      WHEREAS, Landlord and Tenant entered into a Lease Agreement executed on
September 6, 1996 (the "Lease"), for certain premises located at Westridge I,
6465 Nancy Ridge Drive, San Diego, CA (the "Premises"), as more fully described
in the Lease; and

      WHEREAS, Landlord and Tenant desire to modify the Lease accordingly;

      NOW, THEREFORE, in consideration of the covenants and agreements contained
herein, the parties hereby mutually agree as follows:

1.    The term of this Lease shall renew for an additional thirty-three (33)
      months commencing November 1, 2001 and expiring July 31, 2004.

2.    The monthly Base Rent, net of all operating expenses, shall be as follows:

 November 1, 2001 - October 31, 2002      $21,840.00
 November 1, 2002 - October 31, 2003      $22,714.00
 November 1, 2003 - July 31, 2004         $23,622.00

3.    Tenant shall deposit with Landlord an additional Security Deposit in the
      amount of $5,600.00. The total Security Deposit for the Premises shall be
      $23,600.00.

4.    Tenant shall occupy the Premises on an "As-Is" basis. Landlord shall not
      provide any tenant improvements for the Premises.

5.    Tenant warrants that all necessary corporate actions have been duly taken
      to permit Tenant to enter into this First amendment To Lease and that each
      undersigned officer has been duly authorized and instructed to execute
      this First Amendment to Lease.

6.    Except as expressly modified above, all terms and conditions of the Lease
      remain in full force and effect and are hereby ratified and confirmed.

LANDLORD:                                       TENANT:

Spieker Properties, L.P.,                      La Jolla Pharmaceuticals Company,
a California limited partnership               a Delaware corporation

By: Spieker Properties, Inc.,
    a Maryland corporation,
    its General Partner

By: /s/ Richard L. Romney                      By:   /s/ Gail A. Sloan
    ----------------------------                     --------------------------
    Richard L. Romney                          Title Controller and Secretary
    Senior Vice President

Date: 5/8/01                                   Date: 5/4/01<PAGE>

                                                                   EXHIBIT 10.58

                                SECOND AMENDMENT

THIS SECOND AMENDMENT (the "AMENDMENT") is made and entered into as of July 8,
2004, by and between EOP-INDUSTRIAL PORTFOLIO, L.L.C., A DELAWARE LIMITED
LIABILITY COMPANY ("LESSOR") and LA JOLLA PHARMACEUTICAL COMPANY, A DELAWARE
CORPORATION ("LESSEE").

                                    RECITALS

A.    Lessor (as successor in interest pursuant to merger with Spieker
      Properties, L.P., a California limited partnership, as successor in
      interest to WCB II-S BRD Limited Partnership, a Delaware limited
      partnership) and Lessee are parties to that certain standard
      industrial/commercial lease dated September 6, 1996, which lease has been
      previously amended by Acceptance of Space letter dated November 12, 1996
      and First Amendment to Lease dated May 4, 2001 (collectively, the
      "LEASE"). Pursuant to the Lease, Lessor has leased to Lessee space
      currently containing approximately 16,800 square feet (the "PREMISES") in
      the building commonly known as Westridge I located at 6465 Nancy Ridge
      Drive, San Diego, California (the "BUILDING").

B.    The Lease by its terms shall expire on JULY 31, 2004 ("PRIOR EXTENDED
      EXPIRATION DATE"), and the parties desire to extend the Lease for the
      Option Period (as defined in Section 39 of the Addendum attached to and
      made a part of the Lease), all on the following terms and conditions.

      NOW, THEREFORE, in consideration of the above recitals which by this
reference are incorporated herein, the mutual covenants and conditions contained
herein and other valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, Lessor and Lessee agree as follows:

1.    EXTENSION. The Lease is hereby extended for a period of sixty (60) months
      and shall expire on JULY 31, 2009 ("SECOND EXTENDED EXPIRATION DATE"),
      unless sooner terminated in accordance with the terms of the Lease. The
      period commencing the day immediately following the Prior Extended
      Expiration Date ("SECOND EXTENSION DATE") and ending on the Second
      Extended Expiration Date shall be referred to herein as the "SECOND OPTION
      PERIOD".

2.    BASE RENT. As of the Second Extension Date, the schedule of Base Rent
      payable with respect to the Premises during the Second Option Period is
      the following:

<PAGE>

<TABLE>
<CAPTION>
               PERIOD                  ANNUAL RATE PER SQUARE FOOT   MONTHLY BASE RENT
<S>                                    <C>                           <C>
August 1, 2004 through July 31, 2005             $13.20                 $18,480.00
August 1, 2005 through July 31, 2006             $13.73                 $19,222.00
August 1, 2006 through July 31, 2007             $14.28                 $19,992.00
August 1, 2007 through July 31, 2008             $14.85                 $20,790.00
August 1, 2008 through July 31, 2009             $15.44                 $21,616.00
</TABLE>

      All such Base Rent shall be payable by Lessee in accordance with the terms
of the Lease.

3.    ADDITIONAL SECURITY DEPOSIT. No additional security deposit shall be
      required in connection with this Amendment.

4.    COMMON AREA OPERATING EXPENSES AND REAL PROPERTY TAXES. For the period
      commencing on the Second Extension Date and ending on the Second Extended
      Expiration Date, Lessee shall pay for Lessee's Share of Common Area
      Operating Expenses and Real Property Taxes in accordance with the terms of
      the Lease.

5.    IMPROVEMENTS TO PREMISES.

      5.01. CONDITION OF PREMISES. Lessee is in possession of the Premises and
            accepts the same "as is" without any agreements, representations,
            understandings or obligations on the part of Lessor to perform any
            alterations, repairs or improvements, except as may be expressly
            provided otherwise in the Lease or this Amendment.

      5.02. RESPONSIBILITY FOR IMPROVEMENTS TO PREMISES. Any construction,
            alterations or improvements to the Premises shall be performed by
            Lessee at its sole cost and expense using contractors selected by
            Lessee and reasonably approved by Lessor and shall be governed in
            all respects by the provisions of the Lease.

6.    MISCELLANEOUS.

      6.01. This Amendment and the attached exhibits, which are hereby
            incorporated into and made a part of this Amendment, set forth the
            entire agreement between the parties with respect to the matters set
            forth herein. There have been no additional oral or written
            representations or agreements. Under no circumstances shall Lessee
            be entitled to any Rent abatement, improvement allowance, leasehold
            improvements, or other work to the Premises, or any similar economic
            incentives

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            that may have been provided Lessee in connection with entering into
            the Lease, unless specifically set forth in this Amendment.

      6.02. Except as herein modified or amended, the provisions, conditions and
            terms of the Lease shall remain unchanged and in full force and
            effect.

      6.03. In the case of any inconsistency between the provisions of the Lease
            and this Amendment, the provisions of this Amendment shall govern
            and control.

      6.04. Submission of this Amendment by Lessor is not an offer to enter into
            this Amendment. Lessor shall not be bound by this Amendment until
            Lessor has executed and delivered the same to Lessee.

      6.05. The capitalized terms used in this Amendment shall have the same
            definitions as set forth in the Lease to the extent that such
            capitalized terms are defined therein and not redefined in this
            Amendment.

      6.06. Lessee hereby represents to Lessor that Lessee has dealt with no
            broker other than The Irving Hughes Group in connection with this
            Amendment. Lessee agrees to indemnify and hold Lessor, its members,
            principals, beneficiaries, partners, officers, directors, employees,
            mortgagee(s) and agents, and the respective principals and members
            of any such agents (collectively, the "LESSOR RELATED PARTIES")
            harmless from all claims of any brokers other than The Irving Hughes
            Group claiming to have represented Lessee in connection with this
            Amendment. Lessor hereby represents to Lessee that Lessor has dealt
            with no broker in connection with this Amendment. Lessor agrees to
            indemnify and hold Lessee, its members, principals, beneficiaries,
            partners, officers, directors, employees, and agents, and the
            respective principals and members of any such agents (collectively,
            the "LESSEE RELATED PARTIES") harmless from all claims of any
            brokers claiming to have represented Lessor in connection with this
            Amendment.

      6.07. Lessor and Lessee each represents that each signatory of this
            Amendment has the authority to execute and deliver the same on
            behalf of the party hereto for which such signatory is acting.

      6.08. CALIFORNIA WAIVERS. Notwithstanding anything to the contrary
            contained in the Lease, Lessee hereby waives any and all rights
            under and benefits of subsection 1 of Section 1932, Sections 1941
            and 1942 (Tenant's Repairs and Alterations), 1932(2) (Casualty
            Damage), and Section 1265.130 (Condemnation) of the California Code
            of Civil Procedure, or any similar or successor laws now or
            hereinafter in effect.

      6.09. Equity Office Properties Management Corp. ("EOPMC") is an affiliate
            of Lessor and represents only the Lessor in this transaction. Any
            assistance rendered by any agent or employee of EOPMC in connection
            with the Lease or any subsequent amendment or modification hereto
            has been or will be made as an accommodation to Lessee solely in
            furtherance of consummating the transaction on behalf of Lessor, and
            not as agent for Lessee.

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      6.10. NO EXTENSION OR EXPANSION OPTIONS DURING THE SECOND OPTION PERIOD.
            The parties hereto acknowledge and agree that during the Second
            Option Period Lessee shall have no rights to extend the term of the
            Lease, or expand or contract the Premises. The parties agree that
            any rights existing in the Lease to extend the term of the Lease, or
            expand or contract the Premises shall be deleted in their entirety
            and are of no further force and effect.

      IN WITNESS WHEREOF, Lessor and Lessee have duly executed this Amendment as
of the day and year first above written.

                          LESSOR:

                          EOP-INDUSTRIAL PORTFOLIO, L.L.C.,
                          A DELAWARE LIMITED LIABILITY COMPANY

                          By: EOP Operating Limited Partnership, a
                              Delaware limited partnership, its sole member

                                 By: Equity Office Properties Trust, a
                                     Maryland real estate investment trust, its
                                     general partner

                                     By: /s/ Robert E. Dezzutti
                                         -------------------------------
                                     Name:  Robert E. Dezzutti
                                     Title: Senior Vice President

                          LESSEE:

                          LA JOLLA PHARMACEUTICAL COMPANY,
                          A DELAWARE CORPORATION

                          By: /s/ Steven B. Engle
                              ------------------------------------------
                          Name: Steven B. Engle
                          Title: Chairman and CEO
                          Tenant's FEIN: 33-0361285

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