Document:

<PAGE>

                                                                        EX-10.40

                                 Lease Amendment

         This Agreement is entered into as of December 30, 1994, by and between
TORREY SORRENTO, INC., a California corporation (hereinafter called "Landlord"),
and IDEC PHARMACEUTICALS, CORPORATION, a California corporation (hereinafter
called "Tenant"), with reference to the following facts:

         A.       Prior hereto the Landlord and Tenant entered into that certain
Lease dated July 9, 1992, for the premises located at 11011 Torreyana Road, San
Diego, California (the "Lease"), as amended by that certain First Amendment to
Lease dated November 9, 1992.

         B.       Landlord and Tenant now desire to amend the Lease on the terms
set forth herein.

         C.       All capitalized terms not defined herein shall have the same
meaning as set forth in the Lease.

         NOW, THEREFORE, the parties hereto agree as follows:

         1.       Exhibit D to the Lease, the Early Termination Agreement, shall
be deleted in its entirety and all rights of the Tenant and/or any successors
and assigns, for early termination under the Lease pursuant to Section 3.2 of
the Lease, Exhibit D (Early Termination Agreement) to the Lease, and/or any and
all other references thereto, shall be waived.

         2.       The third sentence of Section 6.2.1.(vi) is hereby amended by
adding the words "for the eleventh year of the term of the Lease" after the
words "herein, the Fair Rental Value".

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
if the date first set forth above.

                                        TORREY SORRENTO, INC.,
                                        a California Corporation

                                        By: /s/ [ILLEGIBLE]
                                            -----------------------------

                                        IDEC PHARMACEUTICALS  CORPORATION,
                                        a California corporation

                                        By: /s/ Phillip Schneider
                                            -----------------------------<PAGE>

                                                                        EX-10.41

                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 1

                                 LEASE AGREEMENT

         THIS LEASE AGREEMENT is made as of this 24th day of June, 1999, between
ARE-10933 NORTH TORREY PINES, LLC, a Delaware limited liability company
("LANDLORD"), and IDEC PHARMACEUTICALS CORPORATION, a Delaware corporation
("TENANT").

ADDRESS:      3000 Science Park Road, San Diego, California

PROJECT:      The real property legally described on EXHIBIT B, together with
              all improvements thereon and appurtenances thereto; as depicted on
              the site plan in EXHIBIT B

BUILDING:     The specific building in the Project in which the Premises are
              located, as shown on Exhibit B

PREMISES:     That portion of the Building, containing approximately 41,328
              rentable square feet, as shown on EXHIBITS A-1 AND A-2, together
              with an exclusive use hazardous materials storage pad outside the
              Building, as shown on EXHIBIT B-1.

BASE RENT:    $2.37 per rentable square foot, per month for the portion of the
              Premises shown on Exhibit A-1

<TABLE>
<S>                                         <C>
RENT ADJUSTMENT PERCENTAGE: 2.5%            TENANT'S SHARE: 55.85%

RENTABLE AREA OF PREMISES: 41,328 sq.ft.    RENTABLE AREA OF BUILDING: 74,000 sq. ft.

RENTABLE AREA OF PROJECT: 182,133 sq. ft.   BUILDING'S SHARE OF PROJECT: 40.63%

TARGET COMMENCEMENT DATE: July 1, 2000      SECURITY DEPOSIT: $87,690
</TABLE>

TERM:             120 months from the first day of the month following the month
                  in which the Commencement Date occurs

PERMITTED USE:    Scientific laboratory, research and related office and
                  warehouse uses

ADDRESS FOR RENT PAYMENT:                    LANDLORD'S NOTICE ADDRESS:
135 N. Los Robles Avenue, Suite 250          135 N. Los Robles Avenue, Suite 250
Pasadena, CA 91101                           Pasadena, CA 91101
Attention: Accounts Receivable               Attention: General Counsel

TENANT'S NOTICE ADDRESS:
IDEC Pharmaceuticals Corporation
11011 Torreyana Road
San Diego, California 92121
Attention: Corporate Secretary

The following Exhibits and Addenda are attached hereto and incorporated herein
by this reference:
[X] EXHIBIT A - PREMISES DESCRIPTION  [X] EXHIBIT B - DESCRIPTION OF PROJECT
[X] EXHIBIT C - WORK LETTER           [X] EXHIBIT D - COMMENCEMENT DATE
[X] EXHIBIT E - RULES AND REGULATIONS [X] EXHIBIT F - TENANT'S PERSONAL PROPERTY
[X] EXHIBIT G - ESTOPPEL CERTIFICATE  [X] EXHIBIT H - NONDISTURBANCE AGREEMENT

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 2

         1.       LEASE OF PREMISES. Upon and subject to all of the terms and
conditions hereof, Landlord hereby leases the Premises to Tenant and Tenant
hereby leases the Premises from Landlord, effective as of the date hereof. The
portions of the Project which are for the non-exclusive use of tenants of the
Project are collectively referred to herein at the "COMMON AREAS." Landlord
reserves the right to modify Common Areas, provided that such modifications do
not materially adversely affect Tenant's use of the Premises. At any time Tenant
may elect to lease the exclusive use storage area on the surface parking level
of the Building as shown on Exhibit A-3 (the "STORAGE AREA") for the then
remaining term of the Lease, including any extensions thereof. If at any time
any other tenant of the Building wishes to lease such Storage Area, Landlord
shall give Tenant notice of such request and Tenant shall have 15 business days
in which to elect to Lease such Storage Area for the then remaining term of the
Lease, including any extensions thereof, or to waive its right to lease such
space. Rent in the amount of $350 per month for such Storage Area shall commence
upon delivery of the Storage Area for Tenant's use.

         2.       DELIVERY; ACCEPTANCE OF PREMISES; COMMENCEMENT DATE. Landlord
shall use reasonable efforts to deliver the Premises to Tenant on or before the
Target Commencement Date, subject to extension for Force Majeure Delays and
Tenant Delay, with Landlord's Work, if any, Substantially Completed and the
Baseline Assessment (as defined in the Work Letter done ("DELIVERY" or
"DELIVER"). If Landlord fails to timely Deliver the Premises, Base Rent payable
hereunder shall be abated after the first 30 days of any such delay not arising
by reason of Force Majeure Delay or Tenant Delay as follows: (i) one day for
each of the next 30 days of any such delay, (ii) one and one-half days for each
of the next 30 days of any such delay, and (iii) two days for each day of any
such delay thereafter until December 31, 2000. Except for such abatement of Base
Rent, Landlord shall not be liable to Tenant for any loss or damage resulting
from any such delay, and this Lease shall not be void or voidable except as
provided herein. If Landlord does not Deliver the Premises on or before December
31, 2000, as such date shall be extended one day for each day of Tenant Delay
under the Work Letter (as extended, the "OUTSIDE DATE"), Tenant shall have the
right to terminate this Lease by delivery of written notice to Landlord no later
than three business days after the Outside Date. If Tenant fails to deliver such
notice within three business day of the Outside Date, this Lease shall continue
if full force and effect. If Tenant timely delivers notice terminating this
Lease: (a) Landlord shall (i) reimburse Tenant for any costs or expenses paid or
incurred by Tenant under the Budget (as defined in the Work Letter), (ii) return
the Security Deposit, and (b) neither Landlord nor Tenant shall have any further
rights, duties or obligations under this Lease, except with respect to
provisions which expressly survive termination of this Lease. As used herein,
the terms "LANDLORD'S WORK," "TENANT DELAYS," "EXCESS TENANT DELAYS" and
"SUBSTANTIALLY COMPLETED" shall have the meanings set forth for such terms in
the Work Letter.

         The "COMMENCEMENT DATE" shall be earliest of: (i) the date Landlord
Delivers the Premises to Tenant; (ii) the date Landlord could have Delivered the
Premises but for Excess Tenant Delays; and (iii) the date Tenant conducts any
business in the Premises or any part thereof; provided, however, that the
installation and testing of Tenant's fixtures and equipment shall not constitute
the conduct of business in the Premises. Upon request of Landlord, Tenant shall
execute and deliver a written acknowledgment of the Term Commencement Date and
the expiration date of the Term when such are established and shall attach the
acknowledgment to this Lease as part of EXHIBIT D; provided, however. Tenant's
failure to execute and deliver such acknowledgment shall not affect Landlord's
rights hereunder.

         Except as set forth in the Work Letter, Tenant shall accept the
Premises in their condition as of the Commencement Date, subject to all
applicable laws, ordinances, regulations, covenants and restrictions of record.
Neither Landlord nor any agent of Landlord has made any representation or
warranty with respect to the condition of any or all of the Premises (other than
Landlord's Work, if any) or the Project, and/or the suitability of the Premises
for the conduct of Tenant's business, and Tenant waives any implied warranty
that the Premises are suitable for Tenant's intended purposes. Except as set
forth in the Work Letter, if applicable: (i) Landlord has no obligation for any
defects

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 3

in the Premises; and (ii) Tenant's taking possession of the Premises shall be
conclusive evidence that Tenant accepts the Premises and that the Premises were
in good condition at the time possession was taken. Any occupancy of the
Premises by Tenant before the Commencement date shall be subject to all of the
terms and conditions of this Lease, including the obligation to pay Rent.

         3.       RENT.

         (a)      BASE RENT. The Security Deposit shall be due and payable on
delivery of an executed copy of this Lease to Landlord. The first month's Base
Rent shall be due and payable on the Commencement Date. Tenant shall pay to
Landlord in advance, without demand, abatement, deduction or set-off, monthly
installments of Base Rent on or before the first day of each calendar month
during the Term hereof, in lawful money of the United States of America, at the
office of Landlord for payment of Rent set forth above, or to such other person
or at such other place as Landlord may from time designate in writing. Payments
of Base Rent for any fractional calendar month shall be prorated and paid on the
basis of a thirty (30) day month. The obligation of Tenant to pay Base Rent and
other sums to Landlord and the obligations of Landlord under this Lease are
independent obligations. Tenant shall have no right at any time to abate,
reduce, or set-off any Rent due hereunder except for any abatement as may be
expressly provided in this Lease.

         (b)      ADDITIONAL RENT. In addition to Base Rent, Tenant agrees to
pay to Landlord as additional rent ("Additional Rent"): (i) Tenant's Share of
"Operating Expenses," and (ii) any and all other amounts Tenant assumes or
agrees to pay under the provisions of this Lease, including, without limitation,
any and all other sums that may become due by reason of any default of Tenant or
failure to comply with the agreements, terms, covenants and conditions of this
Lease to be performed by Tenant, after any applicable notice and cure period.

         4.       BASE RENT ADJUSTMENTS. Base Rent shall be increased on each
annual anniversary of the first day of the first full month during the Term of
this Lease by multiplying the Base Rent payable immediately before such
adjustment by the Rent Adjustment Percentage and adding the resulting amount to
the Base Rent payable immediately before such adjustment. Base Rent, as so
adjusted, shall thereafter be due as provided herein. Base Rent adjustments for
any fractional calendar month shall be prorated.

         5.       OPERATING EXPENSE PAYMENTS. Landlord shall use reasonable
efforts to deliver to Tenant a written estimate of Operating Expenses for each
calendar year (the "ANNUAL ESTIMATE") at least 30 days before the Commencement
Date and at least 30 days before the commencement of each such calendar year
during the Term hereof, which Annual Estimate may be revised by Landlord from
time to time during such calendar year, but not more than twice unless any
material expense reflected in such Annual Estimate changes by 10% or more.
During each month of the Term, on the same date that Base Rent is due, Tenant
shall pay Landlord an amount equal to 1/12 of the annual cost, as reasonably
estimated by Landlord from time to time, of Tenant's Share of Operating
Expenses. Payments for any fractional calendar month shall be prorated. The term
"OPERATING EXPENSES" means all costs and expenses of any kind or description
whatsoever incurred or accrued by Landlord with respect to the Building
(including the Building's Share of all costs and expenses of any kind or
description incurred or accrued by Landlord with respect to the Project which
are not specific to the Building or to any other building located in the
Project, administration rent in the amount of 2.0% of Base Rent and capital
improvements and repairs (to the extent not excluded below) amortized over the
lesser of the useful life of any such capital item or 7 years), excluding only:

         (a)      the original construction costs of the Project and renovation
                  prior to the Commencement Date of the Lease, costs of
                  correcting defects in such original construction or renovation
                  (other than the Tenant Improvements and the machinery and
                  equipment making up the Central Plant (as such terms are
                  defined in the Work Letter)), initial replacement or material
                  repair of the parking area shown on Exhibit

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 4

                  B as "existing parking" and initial construction of any
                  material landscape and/or hardscape for the Project;

         (b)      completing, fixturing, improving, renovating, painting,
                  redecorating or other work, which Landlord pays for or
                  performs for specific tenants within their premises, any ADA
                  compliance in Common Areas required as a result of any such
                  work by Landlord or any tenant and costs of correcting defects
                  in such work;

         (c)      capital expenditures for expansion of the Project or for the
                  remodeling or refurbishment of the Project to a materially
                  higher standard than existed on the date of this Lease;

         (e)      interest, financing costs and amortization of funds borrowed
                  by Landlord, whether secured or unsecured;

         (f)      depreciation of the Project (except for capital improvements
                  the cost of which are specifically includable in Operating
                  Expenses);

         (g)      advertising, legal and space planning expenses, leasing
                  commissions and other costs and expenses incurred in procuring
                  tenants for the Project, including any leasing office
                  maintained in the Project;

         (h)      salaries, wages, benefits and other compensation paid to
                  officers and employees of Landlord who (i) are not assigned in
                  whole or in part to the operation, management, maintenance or
                  repair of the Project; (ii) are assigned to the Project, in
                  whole or in part, but serve as property managers, asset
                  managers or otherwise perform services intended to be
                  compensated by Landlord's administration rent set forth above,
                  or (iii) are assigned to the Project, in whole or in part, and
                  are not included in clause (h)(ii) above, to the extent such
                  employees also perform services for other properties owned by
                  Landlord;

         (i)      costs of utilities outside normal business hours sold to
                  tenants of the Project;

         (j)      any expenses otherwise includable within Operating Expenses to
                  the extent actually reimbursed by persons other than tenants
                  of the Project under leases for space in the Project;

         (k)      legal and other expenses incurred in the negotiation or
                  enforcement of leases;

         (l)      costs relating to maintaining Landlord's existence, either as
                  a corporation, partnership, or other entity;

         (m)      costs (including attorneys' fees and costs of settlement,
                  judgments and payments in lieu thereof) arising from claims,
                  disputes or potential disputes pertaining to Landlord and/or
                  the Project or from Landlord's failure to make any payment
                  required to be made by Landlord hereunder before delinquency;

         (n)      costs incurred by Landlord due to the violation by Landlord,
                  its employees, agent or contractors or any tenant of the terms
                  and conditions of any lease of space in the Project;

         (o)      tax penalties incurred as a result of Landlord's negligence,
                  inability or unwillingness to make payment and/or to file any
                  tax or informational returns when due;

<PAGE>

                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 5

         (p)      overhead and profit increment paid to the Landlord or to
                  subsidiaries or affiliates of Landlord for goods and/or
                  services in or to the Project to the extent the same exceeds
                  the costs of such goods and/or services rendered by
                  unaffiliated third parties on a competitive basis;

         (q)      costs arising from Landlord's charitable or political
                  contributions or fine art maintained at the Project;

         (r)      costs to be reimbursed by other tenants of the Project,
                  whether or not actually paid;

         (s)      Costs in connection with services (including electricity),
                  items or other benefits of a type which are not standard for
                  the Project and which are not available to Tenant without
                  specific charges therefor, but which are provided to another
                  tenant or occupant of the Project, whether or not such other
                  tenant or occupant is specifically charged therefore by
                  Landlord;

         (t)      costs of Landlord's general overhead and general
                  administrative expenses (individual, partnership or corporate,
                  as the case may be), as determined in accordance with general
                  accepted accounting principals, consistently applied;

         (u)      operating reserves for capital items to the extent the capital
                  cost of replacement of such items are, or are planned to be,
                  amortized as an Operating Expense;

         (v)      costs of earthquake premiums in excess of those charged for
                  similar buildings in similar risk zones as determined by the
                  California Earthquake Authority;

         (w)      costs incurred in the sale or refinancing of the Project; and

         (x)      net income, franchise, capital stock, estate or inheritance
                  taxes.

         If Landlord estimates that the actual expenses for any calendar year
during the term hereof will exceed the then current estimate of such expenses
for such year, not later than 30 days before the end of any such calendar year,
Landlord shall provide to Tenant a non-binding reconciliation of the anticipated
actual expenses for the year then ending against the then current estimate of
expenses for such year. Within 90 days after the end of each calendar year (or
such longer period as may be reasonably required), Landlord shall furnish to
Tenant a statement (an "ANNUAL STATEMENT") showing in reasonable detail: (a) the
total and Tenant's Share of actual Operating Expenses for the previous calendar
year, and (b) the total of Tenant's payments in respect of Operating Expenses
for such year. If Tenant's Share of actual Operating Expenses for such year
exceeds Tenant's payments of Operating Expenses for such year, the excess shall
be immediately due and payable by Tenant as Rent. If Tenant's payments of
Operating Expenses for such year exceed Tenant's Share of actual Operating
Expenses for such year Landlord shall pay the excess to Tenant within 30 days
after delivery of such Annual Statement.

         The Annual Statement shall be final and binding upon Landlord and
Tenant unless Tenant, within 30 days after Tenant's receipt thereof, shall
contest any item therein by giving written notice to Landlord, specifying each
item contested and the reason therefor. If, during such 30 day period, Tenant
reasonably and in good faith questions or contests the correctness of Landlord's
statement of Tenant's Share of Operating Expenses, Landlord will provide Tenant
with access to Landlord's books and records and such information as Landlord
reasonably determines to be responsive to Tenant's questions. If after Tenant's
review of such information, Landlord and Tenant cannot agree upon the amount of
Tenant's Share of Operating Expenses, then Tenant shall have the right to have
an independent public accounting firm selected from among the 6 largest in the
United States, hired by Tenant (at Tenant's sole cost and expense) and approved
by Landlord (which approval shall not be unreasonably withheld or delayed),
audit and/or review such Landlord's books and

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 6

records for the year in question (the "Independent Review"). The results of any
such Independent Review shall be binding on Landlord and Tenant. If the
Independent Review shows that Tenant's pro rata share of the Operating Expenses
actually paid by Tenant for the calendar year in question exceeded Tenant's
obligations for such calendar year, Landlord shall at Landlord's option either
(i) credit the excess amount to the next succeeding installments of estimated
Operating Expenses or (ii) pay the excess to Tenant within 30 days after
delivery of such statement, except that after expiration of, or termination of
the Term, Landlord shall pay the excess to Tenant after deducting all other
amounts due Landlord. If the Independent Review shows that Tenant's payments of
Tenant's Share of Operating Expenses for such calendar year were less than
Tenant's obligation for the calendar year, Tenant shall pay the deficiency to
the Landlord within 30 days after delivery of such statement. If the Independent
Review shows that Tenant has overpaid Tenant's pro rata share of Operating
Expenses by more than 5% then Landlord shall reimburse Tenant for all costs
incurred by Tenant for the Independent Review. Operating Expenses for the
calendar years in which Tenant's obligation to share therein begins and ends
shall be prorated. Notwithstanding anything set forth herein to the contrary, if
the Building is not fully occupied during any year of the Term, Tenant's Share
of Operating Expenses for such year shall be computed as though the Building had
been fully occupied during such year.

         "TENANT'S SHARE" and the "BUILDING'S SHARE OF PROJECT" shall be,
respectively, the percentages set forth on the first page of this Lease as
Tenant's Share and the Building's Share of Project as either or both may be
reasonably adjusted by Landlord following a measurement of the rentable square
footage of the Building and the Premises (not including the storage area, if
any, and the hazardous materials storage pad) to be done by Landlord within 90
days of the Commencement Date, or as soon as reasonably possible thereafter, and
shall be subject to further adjustment for changes in the physical size of the
Premises, the Building or the Project occurring thereafter within 90 days of the
substantial completion of any such change in the Premises, the Building or the
Project. Any such measurement shall be performed in accordance with the 1996
Standard Method of Measuring Floor Area in Office Buildings as adopted by the
Building Owners and Managers Association (ANSI/BOMA Z65.1-1996). Landlord may
equitably increase Tenant's Share for any item of expense or cost reimbursable
by Tenant that relates to a repair, replacement, or service that benefits only
the Premises or only a portion of the Building or the Project that includes the
Premises or that varies with occupancy or use. Base Rent, Tenant's Share of
Operating Expenses and all other amounts payable by Tenant to Landlord hereunder
are collectively referred to herein as "RENT."

         6.       SECURITY DEPOSIT. The Security Deposit shall be held by
Landlord as security for the performance of Tenant's obligations under this
Lease. The Security Deposit is not an advance rental deposit or a measure of
Landlord's damages in case of Tenant's default. Upon each occurrence of a
Default, Landlord may use all or part of the Security Deposit to pay delinquent
payments due under this Lease, and the cost of any damage, injury, expense or
liability caused by such Default, without prejudice to any other remedy provided
herein or provided by law. Upon any such use of all or any portion of the
Security Deposit, Tenant shall pay Landlord on demand the amount that will
restore the Security Deposit to its original amount. Upon bankruptcy or other
debtor-creditor proceedings against Tenant, the Security Deposit shall be deemed
to be applied first to the payment of Rent and other charges due Landlord for
periods prior to the filing of such proceedings. Landlord's obligation
respecting the Security Deposit is that of a debtor, not a trustee; no interest
shall accrue thereon. The Security Deposit shall be the property of Landlord,
but shall be paid to Tenant when Tenant's obligations under this Lease have been
completely fulfilled. Landlord shall be released from any obligation with
respect to the Security Deposit upon transfer of this Lease and the Premises to
a person or entity assuming Landlord's obligations under this Section 6. Tenant
hereby waives the provisions of any law, now or hereafter in force, which
provide that Landlord may claim from a security deposit only those sums
reasonably necessary to remedy defaults in the payment of Rent, to repair damage
caused by Tenant or to clean the Premises, it being agreed that Landlord may, in
addition, claim those sums reasonably necessary to compensate Landlord for any
other loss or damage, foreseeable or unforeseeable, caused by the

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 7

act or omission of Tenant or any officer, employee, agent or invitee of Tenant,
as provided herein. If Tenant shall fully perform every provision of this Lease
to be performed by Tenant, the Security Deposit, or any balance thereof, shall
be returned to Tenant (or, at Landlord's option, to the last assignee of
Tenant's interest hereunder) within 90 days after the expiration or earlier
termination of this Lease.

         7.       USE. The Premises shall be used solely for the Permitted Use
set forth in the Basic Lease Provisions and for lawful purposes incidental
thereto, all in compliance with all laws, orders, judgments, ordinances,
regulations, codes, directives, permits, licenses, covenants and restrictions of
record now or hereafter applicable to the Premises, and the use and occupancy
thereof (collectively, "LEGAL REQUIREMENTS"). Tenant shall, upon 5 days' written
notice from Landlord, discontinue any use of the Premises which is declared by
any governmental authority having jurisdiction to be a violation of any Legal
Requirement. Tenant will not use or permit the Premises to be used for any
purpose (other than the Permitted Uses) or in any manner that would void
Tenant's or Landlords insurance, increase the insurance risk, or cause the
disallowance of any sprinkler or other credits. Tenant shall reimburse Landlord
promptly upon demand for any additional premium charged for any such policy by
reason of Tenant's failure to comply with the provisions of this Section. Tenant
will use the Premises in a careful, safe and proper manner and will not commit
waste, overload the floor or structure of the Premises, subject the Premises to
use that would damage the Premises or obstruct or interfere with the rights of
Landlord or other tenants or occupants of the Project, including conducting or
giving notice of any auction, liquidation, or going out of business sale on the
Premises, or using or allowing the Premises to be used for any unlawful purpose.
Tenant shall cause any office equipment or machinery to be installed in the
Premises so as to reasonably prevent sounds (assuming building standard demising
walls) or vibrations therefrom from extending into Common Areas, or other space
in the Building or the Project. Tenant shall not place any equipment weighing
500 pounds or more in or upon the Premises or transport or move such items
through the Common Areas or in the Building elevators without the prior written
consent of Landlord, which shall not be unreasonably withheld or delayed. Except
as may be provided under the Work Letter, Tenant shall not, without the prior
written consent of Landlord, use the Premises in any manner which will require
ventilation, air exchange, heating, gas, steam, electricity or water beyond the
existing capacity of the Building as proportionately allocated to the Premises
based upon Tenant's Share as usually furnished for the Permitted Use; provided,
however, that to the extent Tenant at its sole cost and expense expands the
capacity of the ventilation, air exchange, heating, gas, steam, electricity or
water systems serving the Building, Tenant shall be entitled to use 100% of such
added capacity.

         Tenant, at its sole expense, shall make any alterations or
modifications, to the interior of the Premises that are required by Legal
Requirements (including, without limitation, compliance of the Premises with the
Americans With Disabilities Act, 42 U.S.C. Section 12101, et seq. (together with
regulations promulgated pursuant thereto, "ADA")) related to Tenant's use or
occupancy of the Premises for the Permitted Uses. Landlord shall, as an
Operating Expense (to the extent such Legal Requirement is generally applicable
to similar buildings in the San Diego area) or at Tenant's expenses (to the
extent such Legal Requirement is applicable solely by reason of Tenant's, as
compared to other tenants of the Building, particular use of the Premises) make
any alterations or modifications to the Common Areas or the exterior or the
Building that are required by Legal Requirements, including the ADA.
Notwithstanding any other provision herein to the contrary, but subject to the
limitations of this Section 7, Tenant shall be responsible for any and all
demands, claims, liabilities, losses, costs, expenses, actions, causes of
action, damages or judgments, and all reasonable expenses incurred in
investigating or resisting the same (including, without limitation, reasonable
attorneys' fees, charges and disbursements and costs of suit) (collectively,
"CLAIMS") arising out of or in connection with Legal Requirements and Tenant
shall indemnify, defend, hold and save Landlord harmless from and against any
and all Claims arising out of or in connection with any failure of the Premises
to comply with any Legal Requirement.

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 8

         8.       HOLDING OVER. If, with Landlord's express written consent,
Tenant retains possession of the Premises after the termination of the Term,
unless otherwise agreed in writing, such possession shall be subject to
immediate termination by Landlord at any time, and all of the other terms and
provisions of this Lease (including, without limitation, the adjustment of Base
Rent pursuant to Section 4 hereof) shall remain in full force and effect
(excluding any expansion or renewal option or other similar right or option)
during such holdover period, and in such case Tenant shall continue to pay Base
Rent in the amount payable upon the date of the expiration or earlier
termination of this Lease or such other amount as Landlord may indicate, in
Landlord's sole and absolute discretion, in such written consent. All other
payments shall continue under the terms of this Lease. If Tenant remains in
possession of the Premises after the expiration or earlier termination of the
Term without the express written consent of Landlord, Tenant shall become a
tenant at sufferance upon the terms of this Lease except that the rental shall
be equal to 150% of the Rent in effect during the last 30 days of the Term. Such
Rent shall accrue and be due and payable in advance on a per diem basis during
the first month of any such holdover and thereafter such Rent shall accrue and
be due and payable monthly in advance on the first day of each month.
Notwithstanding the payment by Tenant or the acceptance by Landlord of any such
holdover Rent, Tenant shall be responsible for all damages suffered by Landlord
resulting from or occasioned by Tenant's holding over. No holding over by
Tenant, whether with or without consent of Landlord, shall operate to extend
this Lease except as otherwise expressly provided, and this Section 8 shall not
be construed as consent for Tenant to retain possession of the Premises.
Acceptance by Landlord of Rent after the Term Expiration Date or earlier
termination of this Lease shall not result in a renewal or reinstatement of this
Lease.

         9.       TAXES. Landlord shall pay, as part of Operating Expenses, all
taxes, levies, assessments and governmental charges of any kind (collectively
referred to as "TAXES") imposed by any federal, state, regional, municipal,
local or other governmental authority or agency, including, without limitation,
quasi-public agencies (collectively, "GOVERNMENTAL AUTHORITY") during the Term,
including, without limitation all Taxes: (i) imposed on or measured by or based,
in whole or in part, on rent payable to Landlord under this Lease and/or from
the rental by Landlord of the Project or any portion thereof, or (ii) based on
the square footage, assessed value or other measure or evaluation of any kind of
the Premises, the Building or the Project, or (iii) assessed or imposed by or
on the operation or maintenance of any portion of the Premises or the Project,
including parking, or (iv) assessed or imposed by, or at the direction of, or
resulting from statutes or regulations, or interpretations thereof, promulgated
by, any Governmental Authority, or (v) imposed as a license or other fee on
Landlord's business of leasing space in the Project; but excluding during the
initial Term hereof any increase in Taxes resulting solely from a sale or other
transfer of the Project or any portion thereof. Landlord may contest by
appropriate legal proceedings the amount, validity, or application of any Taxes
or liens securing Taxes. Taxes shall not include any net income taxes imposed on
Landlord unless such net income taxes are in substitution for any Taxes payable
hereunder. If any such Tax is levied or assessed directly against Tenant, then
Tenant shall be responsible for and shall pay the same at such times and in such
manner as the taxing authority shall require. Tenant shall pay, prior to
delinquency, any and all Taxes levied or assessed against any personal property
or trade fixtures placed by Tenant in the Premises, whether levied or assessed
against Landlord or Tenant. If any Taxes on Tenant's personal property or trade
fixtures are levied against Landlord or Landlord's property, or if the assessed
valuation of the Project or any portion thereof is increased by a value
attributable to improvements in or alterations to the Premises, whether owned by
Landlord or Tenant and whether or not affixed to the real property so as to
become a part thereof, higher than the base valuation on which Landlord from
time-to-time allocates Taxes to all tenants in the Building, Landlord shall have
the right, but not the obligation, to pay such Taxes. Landlord's determination
of any excess assessed valuation shall be binding and conclusive, absent
manifest error. The amount of any such payment by Landlord shall constitute
Additional Rent due from Tenant to Landlord immediately upon demand.

         10.      PARKING. Subject to any applicable local governmental
restrictions or requirements, Tenant shall have the right to park 2.5 cars per
thousand rentable square feet from time-to-time in

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                    ARC Science Center/IDEC Pharmaceuticals Corporation - Page 9

the Premises in common with other tenants of the Project in those areas
designated for non-reserved parking subject in each case to Landlord's rules and
regulations. Tenant shall, within such 2.5 cars per thousand rentable square
feet allotment, be entitled to Tenant's Share of the parking available in the
basement level of the Building. Landlord shall allocate the right to use parking
in the Building among Tenant and other tenants in the Building in a
non-discriminatory manner. If Landlord determines that the parking facilities
are becoming crowded, Landlord may reserve spaces or otherwise act to resolve
such parking issues. Landlord shall reserve 20 designated visitor spaces for the
nonexclusive use of Tenant's guests and invitees as shown on Exhibit B. Landlord
shall not be responsible for enforcing Tenant's parking rights against any third
parties, including other tenants of the Project.

         11.      UTILITIES, SERVICES. Landlord shall provide, subject to the
terms of this Section 11, water, electricity, HVAC, light, power, telephone,
sewer, and other utilities (including gas and fire sprinklers to the extent the
Building is plumbed for such services), refuse and trash collection
(collectively, "Utilities"). Although Tenant shall have access to the Premises
24 hours per day, 365/366 days per year, the normal hours of operation of the
Building are 8:00 a.m. to 6:00 p.m., Monday through Friday and 8:00 a.m. to 1:00
p.m. on Saturday, legal holidays excepted. Landlord's actual cost of any use by
Tenant of Utilities outside of such normal hours of operation, including
Landlord's actual overhead and administrative costs in connection therewith (not
to exceed 10% of the cost of such utilities), shall be allocated to and paid by
Tenant on such basis as Landlord shall reasonably determine for the Building.
Landlord shall pay, as Operating Expenses or subject to Tenant's reimbursement
obligation, for all Utilities used on the Premises, all maintenance charges for
Utilities, and any storm sewer charges or other similar charges for Utilities
imposed by any governmental entity or Utility provider, and any taxes,
penalties, surcharges or similar charges thereon. Landlord or Tenant may elect,
in either case at Tenant's expense, to cause any Utilities to be separately
metered or charged directly to Tenant by the provider. Tenant shall pay directly
to the Utility provider, prior to delinquency, any separately metered Utilities
and services which may be furnished to Tenant or the Premises during the Term.
Tenant shall pay, as part of Operating Expenses, its share of all charges for
jointly metered Utilities based upon consumption, as reasonably determined by
Landlord and shall pay the cost of any after hours Utilities allocated to it by
Landlord. No interruption or failure of Utilities, from any cause whatsoever
other than Landlord's willful misconduct, shall result in eviction or
constructive eviction of Tenant, termination of this Lease or the abatement of
Rent. Tenant agrees to limit use of water and sewer with respect to Common Areas
to normal restroom use. Tenant shall, at all times during the Term, be entitled
to use up to Tenant's Share of the Utilities provided by the Central Plant.

         12.      ALTERATIONS AND TENANT'S PROPERTY. Any alterations, additions,
or improvements made to the Premises by or on behalf of Tenant, including
additional locks or bolts of any kind or nature upon any doors or windows in the
Premises, but excluding (i) installation, removal or realignment of furniture
systems (other than removal of furniture systems owned or paid for by Landlord)
not involving any modifications to the structure or connections (other then by
ordinary plugs or jacks) to building systems (as hereinafter defined) and (ii)
alterations, additions and improvements that (A) do not affect the Building
structure or exterior or the building systems and (B) do not exceed a total cost
in any 12 month period in the aggregate of $50,000.00, ("ALTERATIONS") shall be
subject to Landlord's prior written consent, which shall not be unreasonably
withheld or delayed. If Landlord's approval for any Alterations is required,
Landlord may impose such conditions on Tenant in connection with the
commencement, performance and completion of such Alterations as Landlord may
deem appropriate in Landlord's reasonable discretion. Any request for approval
shall be in writing, delivered not less than 15 business days in advance of any
proposed construction, and accompanied by plans, specifications, bid proposals,
work contracts and such other information concerning the nature and cost of the
alterations as may be reasonably requested by Landlord, including the identities
and mailing addresses of all persons performing work or supplying materials.
Landlord's right to review plans and specifications and to monitor construction
shall be solely for its own benefit, and Landlord shall have no duty to see that
such plans and specifications or construction comply with applicable Legal
Requirements. Tenant shall

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 10

cause, at its expense, all Alterations to comply with insurance requirements and
with Legal Requirements and shall implement at its sole cost and expense any
alteration or modification required by Legal Requirements as a result of any
Alterations. Tenant shall pay to Landlord, as Additional Rent, on demand an
amount equal to Landlord's actual costs and expenses, including the time of
Landlord's employees spent on such matters at their actual wage and benefit
rates, not to exceed 10% of the aggregate cost of such Alteration, for plan
review, coordination, scheduling and supervision. Before beginning any
Alteration, Landlord may post on and about the Premises notices of
non-responsibility pursuant to applicable law. Tenant shall reimburse Landlord
for, and indemnify and hold Landlord harmless from, any extra expense incurred
by Landlord by reason of faulty work done by Tenant or its contractors, delays
caused by such work, or inadequate cleanup.

         Tenant shall furnish security or make other arrangements satisfactory
to Landlord to assure payment for the completion of all work free and clear of
liens, and shall provide certificates of insurance for worker's compensation and
other coverage in amounts and from an insurance company satisfactory to Landlord
protecting Landlord against liability for personal injury or property damage
during construction. Upon completion of any Alterations, Tenant shall deliver to
Landlord: (i) sworn statements setting forth the names of all contractors and
subcontractors who did the work and final lien waivers from all such contractors
and subcontractors; and (ii) as built plans for any such Alteration.

         The items, if any, listed on EXHIBIT F attached hereto, any items
agreed by Landlord in writing to be included on EXHIBIT F in the future, and any
trade fixtures, machinery, equipment and other personal property not paid for
out of the TI Allowance, as defined in the Work Letter, which may be removed
without material damage to the Premises, which damage shall be repaired
(including capping or terminating utility hookups behind walls) by Tenant during
the Term (collectively, "TENANT'S PROPERTY"). Tenant's Property may be removed
by Tenant at any time during the Term. All other property of any kind paid for
with the TI Fund other than Tenant's Property, all Alterations, real property
fixtures, built-in machinery and equipment, built-in laboratory casework and
cabinets and other similar additions and improvements built into the Premises so
as to become an integral part of the Premises, such as fume hoods which
penetrate the roof or plenum area, built-in cold rooms, built-in warm rooms,
walk-in cold rooms, walk-in warm rooms, deionized water system, chillers,
built-in plumbing, electrical and mechanical equipment and systems, and any
power generator and transfer switch (collectively, "INSTALLATIONS") shall be
and shall remain the property of Landlord during the Term and following the
expiration or earlier termination of the Term. The Installations shall not be
removed by Tenant at any time during the Term and shall remain upon and be
surrendered with the Premises as a part thereof following the expiration or
earlier termination of this Lease; provided, however, that Landlord shall, at
the time its approval of such Installation is requested notify Tenant if it has
elected to cause Tenant to remove such Installation upon the expiration or
earlier termination of this Lease. If Landlord so elects, Tenant shall remove
such Installation upon the expiration or earlier termination of this Lease and
restore any damage caused by or occasioned as a result of such removal. Tenant
shall also repair any damage caused or occasioned by the removal of any of
Tenant's Property. In the case of removal of either an Installation or Tenant's
Property, all hookups and connections to Utilities or other Building systems
shall be capped off in compliance with all Legal Requirements behind the walls
of the Premises and all holes in the walls shall be repaired. During any such
restoration period, Tenant shall pay Rent to Landlord as provided herein as if
said space were otherwise occupied by Tenant.

         13.      LANDLORD'S REPAIRS. Landlord, as an Operating Expense, shall
maintain all of the structural, exterior, parking and other Common Areas of the
Building and the Project, including HVAC, plumbing, fire sprinklers, elevators
and all other building systems serving the Premises and other portions of the
Building ("BUILDING SYSTEMS"), in good repair, reasonable wear and tear and
uninsured losses and damages caused by Tenant, its agents, servants, employees
invitees and contractors excluded. Landlord shall maintain the Central Plant in
good condition and repair and at least in accordance with the manufacturer's
recommended maintenance schedule. Losses and damages caused by Tenant, its
agents, servants, employees, invitees and contractors shall be

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 11

repaired by Landlord, to the extent not covered by insurance actually maintained
by Landlord, at Tenant's sole cost and expense. Landlord reserves the right to
stop Building System services when necessary: (i) by reason of accident or
emergency, or (ii) for planned repairs, alterations or improvements, which are,
in the judgment of Landlord, desirable or necessary to be made, until said
repairs, alterations or improvements shall have been completed. Landlord shall
have no responsibility or liability for failure to supply Building System
services during any such period of interruption; provided, however, that
Landlord shall give Tenant not less than 24 hours advance notice of any planned
stoppage of Building System services for routine maintenance, repairs,
alterations or improvements. Tenant shall promptly give Landlord written notice
of any repair required by Landlord pursuant to this Section, after which
Landlord shall have a reasonable opportunity to effect such repair. Landlord
shall not be liable for any failure to make any repairs or to perform any
maintenance unless such failure shall persist for an unreasonable time after
Tenant's written notice of the need for such repairs or maintenance. Tenant
waives it rights under any state or local law to terminate this Lease or to make
such repairs at Landlord's expense and agrees that the parties' respective
rights with respect to such matters shall be solely as set in the Lease,
including Section 31 hereof. Repairs required as the result of fire, earthquake,
flood, vandalism, war, or similar cause of damage or destruction shall be
controlled by Section 18. Landlord shall use reasonable efforts, given the
nature of the repairs to be made, to minimize any disruption of Tenant's
business in the Premises by reason of any repairs by Landlord under this Section
13.

         14.      TENANT'S REPAIRS. Subject to Section 13 hereof, Tenant, at its
expense, shall repair, replace and maintain in good condition all portions of
the Premises, including, without limitation, entries, doors, ceilings, interior
windows, interior walls, and the interior side of demising walls, reasonable
wear and tear excepted. Such repair and replacements may include capital
expenditures and repairs whose benefit may extend beyond the Term. Should Tenant
fail to make any such repair or replacement or fail to maintain the Premises
Landlord shall give Tenant notice of such failure. If Tenant fails to commence
cure of such default within 10 days of Landlord's notice, and thereafter
diligently prosecute such cure to completion, Landlord may perform such work and
shall be reimbursed by Tenant within 10 days after demand therefor; provided,
however, that if such default by Tenant creates or could create an emergency,
Landlord may immediately commence cure of such default and shall thereafter be
entitled to recover the costs of such cure from Tenant. Subject to Sections 17
and 18, Tenant shall bear the full cost of any repair or replacement to any part
of the Building that results from damage caused by Tenant, its agents,
contractors, or invitees and any repair that benefits only the Premises.

         15.      MECHANIC'S LIENS. Tenant shall discharge, by bond or
otherwise, any mechanic's lien filed against the Premises or against the Project
or any portion thereof for work claimed to have been done for, or materials
claimed to have been furnished to, Tenant within 30 days after the filing
thereof, at Tenant's sole cost and shall otherwise keep the Premises and the
Project free from any liens arising out of work performed, materials furnished
or obligations incurred by Tenant. Should Tenant fail to discharge any lien
described herein, Landlord shall have the right, but not the obligation, to pay
such claim or post a bond or otherwise provide security to eliminate the lien as
a claim against title to the Project and the cost thereof shall be immediately
due from Tenant as Additional Rent. If Tenant shall lease or finance the
acquisition of office equipment, furnishings, or other personal property of a
removable nature utilized by Tenant in the operation of Tenant's business,
Tenant warrants that any Uniform Commercial Code Financing Statement executed by
Tenant will upon its face or by exhibit thereto indicate that such Financing
Statement is applicable only to removable personal property of Tenant located
within the Premises. In no event shall the address of the Building be furnished
on the statement without qualifying language as to applicability of the lien
only to removable personal property, located in an identified suite held by
Tenant.

         16.      INDEMNIFICATION. Tenant hereby indemnifies and agrees to
defend, save and hold Landlord harmless from and against any and all Claims for
injury or death to persons or damage to property occurring within or about the
Premises, arising directly or indirectly out of use or

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 12

occupancy of the Premises or a breach or default by Tenant in the performance of
any of its obligations hereunder, except to the extent caused by the willful
misconduct or gross negligence of Landlord. Landlord shall not be liable to
Tenant for, and Tenant assumes all risk of damage to, personal property
(including, without limitation, loss of records kept within the Premises).
Tenant further waives any and all Claims for injury to Tenant's business or loss
of income relating to any such damage or destruction of personal property
(including, without limitation, any loss of records). Landlord shall not be
liable for any damages arising from any act, omission or neglect of any tenant
in the Project or of any other third party. Landlord hereby indemnifies and
agrees to defend, save and hold Tenant harmless from and against any and all
Claims for injury or death to persons occurring within or about the Project
(other than the Premises), arising directly out of a default by Landlord in the
performance of any of its obligations hereunder, except to the extent caused by
the willful misconduct or gross negligence of Tenant.

         17.      INSURANCE. Landlord shall maintain all insurance against any
peril generally included within the classification "Fire and Extended Coverage,"
sprinkler damage (if applicable), vandalism and malicious mischief covering the
full replacement cost of the Building including the Tenant Improvements (as
defined in the Work Letter) or such lesser coverage amount as Landlord may elect
provided such coverage amount is not less than 90% of such full replacement
cost. If the cost of including the Tenant Improvements in Landlord's property
insurance results in other tenants in the Building bearing a disproportionate
share of the overall costs of such insurance, Landlord may allocate the costs of
insurance on the basis of the value of the tenant improvements in each tenant's
premises, rather than on the basis of the square footage occupied. Landlord
shall further carry commercial general liability insurance with a combined
single loss limit of not less than $2,000,000 for death or bodily injury, or
property damage with respect to the Project. Landlord may, but is not obligated
to, maintain such other insurance and additional coverages as it may deem
necessary and which it generally maintains for its or its affiliates' holdings
in southern California, including, but not limited to, flood, environmental
hazard and earthquake, loss or failure of building equipment, rental loss during
the period of repair or rebuilding, workmen's compensation insurance and
fidelity bonds for employees employed to perform services and insurance for any
improvements installed by Tenant or which are in addition to the standard
improvements customarily furnished by Landlord without regard to whether or not
such are made a part of the Building. All such insurance shall be included as
part of the Operating Expenses. The Building and Project may be included in a
blanket policy (in which case the cost of such insurance allocable to the
Building will be determined by Landlord based upon the insurer's cost
calculations). Tenant shall also reimburse Landlord for any increased premiums
or additional insurance which Landlord reasonably deems necessary as a result of
Tenant's particular use of the Premises.

         Tenant, at its expense, shall maintain during the Term: all risk
property insurance covering the full replacement cost of all property and
improvements installed or placed in the Premises by Tenant at Tenant's (expense
other than the Tenant Improvements, as defined in the Work Letter); worker's
compensation insurance with no less than the minimum limits required by law;
employer's liability insurance with such limits as required by law; and
commercial general liability insurance, with a combined single loss limit of not
less than $2,000,000 per occurrence for death or bodily injury and not less than
$1,000,000 for property damage with respect to the Premises. Landlord may from
time to time require reasonable increases in any such limits. The commercial
general liability insurance policies shall name Landlord, its officers,
directors, employees, managers, agents, invitees and contractors (collectively,
"RELATED PARTIES"), as additional insureds; insure on an occurrence and not a
claims-made basis; be issued by insurance companies which have a rating of not
less than policyholder rating of A and financial category rating of at least
Class XII in "Best's Insurance Guide"; shall not be cancelable unless 30 days
prior written notice shall have been given to Landlord from the insuror; contain
a hostile fire endorsement and a contractual liability endorsement; and provide
primary coverage to Landlord (any policy issued to Landlord providing duplicate
or similar coverage shall be deemed excess over Tenant's policies). Such
policies or certificates thereof shall be delivered to Landlord by Tenant upon
commencement of the Term and upon each renewal of said insurance. Tenant's
policy may be a "blanket policy" which specifically

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 13

provides that the amount of insurance shall not be prejudiced by other losses
covered by the policy. Tenant shall, at least 30 days prior to the expiration of
such policies, furnish Landlord with a notice from the insurer stating its
intent to renew such insurance and shall provide renewals or binders for such
insurance not less than 5 days before the expiration of any such policy. Tenant
agrees that if Tenant does not take out and maintain such insurance, Landlord
may (but shall not be required to) procure said insurance on Tenant's behalf and
at its cost to be paid as Additional Rent.

         In each instance where insurance is to name Landlord as additional
insured, Tenant shall upon written request of Landlord also designate and
furnish certificates so evidencing Landlord as additional insured to: (i) any
lender of Landlord holding a security interest in the Project or any portion
thereof, (ii) the landlord under any lease wherein Landlord is tenant of the
real property whereupon the building in which the Premises are located if the
interest of Landlord is or shall become that of a tenant under a ground lease
rather than that of a fee owner, and/or (iii) any management company retained by
Landlord to manage the Project.

         The insurance obtained by Landlord and Tenant shall include a waiver of
subrogation by the insurers and all rights based upon an assignment from its
insured, against Landlord or Tenant, and their respective Related Parties, in
connection with any loss or damage thereby insured against. Neither party nor
its respective Related Parties shall be liable to the other for loss or damage
caused by any risk insured against under insurance required to be maintained
hereunder, and each party waives any claims against the other party, and its
respective Related Parties for such loss or damage. The failure of a party to
obtain the insurance required hereunder shall not void this waiver. Landlord and
its respective Related Parties shall not be liable for, and Tenant hereby waives
all claims against such parties for, business interruption and losses occasioned
thereby sustained by Tenant or any person claiming through Tenant resulting from
any accident or occurrence in or upon the Premises or the Project from any cause
whatsoever, including without limitation, damage caused in whole or in part,
directly or indirectly, by the negligence of Landlord or its respective Related
Parties. If the foregoing waivers shall contravene any law with respect to
exculpatory agreements, the liability of Landlord or Tenant shall be deemed not
released but shall be secondary to the other's insurer.

         Landlord may require insurance policy limits to be raised to conform
with requirements of Landlord's lender and/or to bring coverage limits to levels
then being reasonably required of new tenants within the Project.

         18.      RESTORATION. If at any time during the Term (i) the Premises
or (ii) the Building or any other portion of the Project, are damaged by a fire
or other insured casualty and, in the case of damage described in clause (ii),
such damage has a material adverse effect on Tenant's use or occupancy of the
Premises, Landlord shall notify Tenant within 60 days after discovery of such
damage as to the amount of time Landlord reasonably estimates it will take to
restore the Premises, the Building or the Project, as applicable. If the
restoration time is estimated to exceed 6 months, Landlord may, in such notice,
elect to terminate this Lease as of the date that is 75 days after the date of
discovery of such damage or destruction; provided, however, that notwithstanding
Landlord's election to restore the Premises, Tenant may elect to terminate this
Lease by written notice to Landlord delivered within ten (10) business days of
receipt of Landlord's notice electing to restore the Premises. Unless either
Landlord or Tenant elects to terminate this Lease, Landlord shall, subject to
receipt of sufficient insurance proceeds, promptly restore the Premises
(excluding any improvements installed after the Commencement Date by Tenant or
by Landlord and paid for by Tenant unless covered by the insurance Landlord
maintains as an Operating Expense hereunder, in which case such improvements
shall be included, to the extent of such insurance proceeds, in Landlord's
restoration), subject to delays arising from the collection of insurance
proceeds, from Force Majeure events or as needed to obtain any license,
clearance or other authorization of any kind required to enter into and restore
the Premises issued by any governmental or quasi-governmental agency having
jurisdiction over the use, storage, release or removal of Hazardous Materials
in, on or about the Premises (collectively referred to herein as

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 14

"HAZARDOUS MATERIALS CLEARANCES"); provided, however, that if repair or
restoration of the Premises is not Substantially Complete as of the end of 8
months from the date of damage or destruction, Landlord may, in its sole and
absolute discretion, elect not to proceed with such repair and restoration, in
which event Landlord shall be relieved of its obligations to make such repairs
or restoration and this Lease shall terminate as of the later of (i) the date of
Landlord's election, or (ii) the date all required Hazardous Materials
Clearances are obtained. If such repair or restoration of the Premises is not
Substantially Complete within 90 days of the time originally estimated by
Landlord for such restoration (as such 90 day period may be extended for Force
majeure Delay and any delays caused by Tenant), Tenant may elect to terminate
this Lease by written notice to Landlord, and this Lease shall terminate as of
the later of (i) the date of Tenant's election, or (ii) the date all required
Hazardous Materials Clearances are obtained.

         Tenant, at its expense, shall promptly perform, subject to delays
arising from the collection of insurance proceeds, from Force Majeure events or
to obtain Hazardous Material Clearances, all repairs or restoration for Tenant's
use of the Premises not required to be done by Landlord and shall promptly
re-enter the Premises and commence doing business in accordance with this Lease.
Notwithstanding the foregoing, Landlord may terminate this Lease if the Premises
are damaged during the last eighteen months of the Term and Landlord reasonably
estimates that it will take more than sixty days to repair such damage, or if
insurance proceeds are not available for such restoration. Rent shall be abated
from the date all required Hazardous Material Clearances are obtained until the
Premises are repaired and restored, in the proportion which the area of the
Premises, if any, which is not usable by Tenant bears to the total area of the
Premises, unless Landlord provides Tenant with other space during the period of
repair that is suitable for the temporary conduct of Tenant's business. Such
abatement shall be the sole remedy of Tenant, and except as provided herein,
Tenant waives any right to terminate the Lease by reason of damage or casualty
loss.

         The provisions of this Lease, including this Section 18, constitute an
express agreement between Landlord and Tenant with respect to any and all damage
to, or destruction of, all or any part of the Premises, or any other portion of
the Project, and any statute or regulation which is now or may hereafter be in
effect, shall have no application to this Lease or any damage or destruction to
all or any part of the Premises or any other portion of the Project, the parties
hereto expressly agreeing this Section 18 sets forth their entire understanding
and agreement with respect to such matters.

         19.      CONDEMNATION. If any part of the (i) the Premises or (ii) the
Building or any other portion of the Project are taken for any public or
quasi-public use under governmental law, ordinance, or regulation, or by right
of eminent domain, or by private purchase in lieu thereof (a "TAKING" or
"TAKEN"), and the Taking would in Landlord's reasonable judgment either prevent
or materially interfere with Tenant's use of the Premises or materially
interfere with or impair Landlord's ownership or operation of the Building or
the Project, then upon written notice by Landlord this Lease shall terminate and
Rent shall be apportioned as of said date. If part of the Premises shall be
Taken, and this Lease is not terminated as provided above, Landlord shall
promptly restore the Premises and the Building as nearly as is commercially
reasonable under the circumstances to their condition prior to such partial
taking and the Rent payable hereunder during the unexpired Term shall be reduced
to such extent as may be fair and reasonable under the circumstances. Upon any
such Taking, Landlord shall be entitled to receive the entire price or award
from any such Taking without any payment to Tenant, and Tenant hereby assigns to
Landlord Tenant's interest, if any, in such award. Tenant shall have the right,
to the extent that same shall not diminish Landlord's award, to make a separate
claim against the condemning authority (but not Landlord) for such compensation
as may be separately awarded or recoverable by Tenant for business interruption,
moving expenses and damage to Tenant's Property, if a separate award for such
items is made to Tenant. Tenant hereby waives any and all rights it might
otherwise have pursuant to any provision of state law to terminate this Lease
upon a partial Taking of the Premises or the Building.

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 15

         20.      EVENTS OF DEFAULT. Each of the following events shall be a
default ("DEFAULT") by Tenant under this Lease:

         (a)      PAYMENT DEFAULTS. Tenant shall fail to pay any installment of
Rent or any other payment hereunder when due; provided, however, that Landlord,
not more than twice in any 12 month period, will give Tenant notice of such
default in the payment of Rent and Tenant shall have 5 days in which to make
such payment after which period Tenant shall be in Default hereunder. Tenant
agrees that such notice shall be in lieu of and not in addition to any notice
required by law;

         (b)      INSURANCE. Any insurance required to be maintained by Tenant
pursuant to this Lease shall be canceled or terminated or shall expire or shall
be reduced or materially changed, or Landlord shall receive a notice of
nonrenewal of any such insurance and Tenant shall fail to obtain replacement
insurance at least 5 days before the expiration of the current coverage.

         (c)      IMPROPER TRANSFER. Tenant shall assign, sublease or otherwise
transfer or attempt to transfer all or any portion of Tenant's interest in this
Lease or the Premises except as expressly permitted herein, or Tenant's interest
in this Lease shall be attached, executed upon, or otherwise judicially seized
and such action is not released within 90 days of the action.

         (d)      LIENS. Tenant shall fail to discharge or otherwise obtain the
release of any lien placed upon the Premises in violation of this Lease within
30 days after any such lien is filed against the Premises.

         (e)      INSOLVENCY EVENTS. Tenant or any guarantor or surety of
Tenant's obligations hereunder shall: (A) make a general assignment for the
benefit of creditors; (B) commence any case, proceeding or other action seeking
to have an order for relief entered on its behalf as a debtor or to adjudicate
it a bankrupt or insolvent, or seeking reorganization, arrangement, adjustment,
liquidation, dissolution or composition of it or its debts or seeking
appointment of a receiver, trustee, custodian or other similar official for it
or for all or of any substantial part of its property (collectively a
"PROCEEDING FOR RELIEF"); (C) become the subject of any Proceeding for Relief
which is not dismissed within 90 days of its filing or entry; or (D) die or
suffer a legal disability (if Tenant, guarantor, or surety is an individual) or
be dissolved or otherwise fail to maintain its legal existence (if Tenant,
guarantor or surety is a corporation, partnership or other entity) except as a
result of any merger, consolidation or corporate reorganization, or the purchase
of all or substantially all of the assets or the ownership interests of the
Tenant in connection with a permitted Affiliate Transfer, as hereinafter
defined.

         (f)      ESTOPPEL CERTIFICATE OR SUBORDINATION AGREEMENT. Tenant fails
to execute any document required from Tenant under Sections 24 or 27 within 5
business days after a second notice requesting such document.

         (g)      OTHER DEFAULTS. Tenant shall fail to comply with any provision
of this Lease other than those specifically referred to in this Section 20, and
except as otherwise expressly provided herein, such failure shall continue for a
period of 10 days after written notice thereof from Landlord to Tenant.

Any notice given under Section 20(e), (g) or (h) hereof, shall: (i) specify the
alleged default, (ii) demand that Tenant cure such default,(iii) be in lieu of,
and not in addition to, or shall be deemed to be any notice required under any
provision of applicable law, and (iv) not be deemed a forfeiture or a
termination of this Lease unless Landlord elects otherwise in such notice;
provided that if the nature of Tenant's default under Section 20(g) is such that
it cannot be cured by the payment of money and reasonably requires more than 10
days to cure, then Tenant shall not be deemed to be in default if Tenant
commences such cure within said 10 day period and thereafter diligently

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 16

prosecutes the same to completion; provided, however, that such cure shall be
completed no later than 90 days from the date of Landlord's notice.

         21.      LANDLORD'S REMEDIES.

         (a)      PAYMENT BY LANDLORD; INTEREST. Upon a Default by Tenant
hereunder, Landlord may, without waiving or releasing any obligation of Tenant
hereunder, make such payment or perform such act. All sums so paid or incurred
by Landlord, together with interest thereon, from the date such sums were paid
or incurred, at the annual rate equal to 12% per annum or the highest rate
permitted by law (the "DEFAULT RATE"), whichever is less, shall be payable to
Landlord on demand as Additional Rent. Nothing herein shall be construed to
create or impose a duty on Landlord to mitigate any damages resulting from
Tenant's Default hereunder.

         (b)      LATE PAYMENT RENT. Late payment by Tenant to Landlord of Rent
and other sums due will cause Landlord to incur costs not contemplated by this
Lease, the exact amount of which will be extremely difficult and impracticable
to ascertain. Such costs include, but are not limited to, processing and
accounting charges and late charges which may be imposed on Landlord under any
Mortgage covering the Premises. Therefore, if any installment of Rent due from
Tenant is not received by Landlord within 5 days after the date such payment is
due, Tenant shall pay to Landlord an additional sum of 6% of the overdue Rent as
a late charge. The parties agree that this late charge represents a fair and
reasonable estimate of the costs Landlord will incur by reason of late payment
by Tenant. In addition to the late charge, Rent not paid when due shall bear
interest at the lesser of (i) 12% per annum or (ii) the maximum rate permitted
by law from the 5th day after the date due until paid. Notwithstanding the
foregoing, no late charge nor interest shall be due on the first two such
failures to pay Rent in any 12 month period until 5 days after Landlord has
given Tenant notice and an opportunity to cure any such failure to pay Rent and
Tenant has failed so to pay Rent. Any such notice shall be in lieu of and not in
addition to any notice required by law;

         (c)      REMEDIES. Upon the occurrence of a Default, Landlord, at its
option, without further notice or demand to Tenant, shall have in addition to
all other rights and remedies provided in this Lease, at law or in equity, the
option to pursue any one or more of the following remedies, each and all of
which shall be cumulative and nonexclusive, without any notice or demand
whatsoever.

                  (i)      Terminate this Lease, or at Landlord's option,
         Tenant's right to possession only, in which event Tenant shall
         immediately surrender the Premises to Landlord, and if Tenant fails to
         do so, Landlord may, without prejudice to any other remedy which it may
         have for possession or arrearages in rent, enter upon and take
         possession of the Premises and expel or remove Tenant and any other
         person who may be occupying the Premises or any part thereof, without
         being liable for prosecution or any claim or damages therefor;

                  (ii)     Upon any termination of this Lease, whether pursuant
         to the foregoing Section 21(c)(i) or otherwise, Landlord may recover
         from Tenant the following:

                           (A)      The worth at the time of award of any unpaid
                  rent which has been earned at the time of such termination;
                  plus

                           (B)      The worth at the time of award of the amount
                  by which the unpaid rent which would have been earned after
                  termination until the time of award exceeds the amount of such
                  rental loss that Tenant proves could have been reasonably
                  avoided; plus

                           (C)      The worth at the time of award of the amount
                  by which the unpaid rent for the balance of the Term after the
                  time of award exceeds the amount of such rental loss that
                  Tenant proves could have been reasonably avoided; plus

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 17

                           (D)      Any other amount necessary to compensate
                  Landlord for all the detriment proximately caused by Tenant's
                  failure to perform its obligations under this Lease or which
                  in the ordinary course of things would be likely to result
                  therefrom, specifically including but not limited to,
                  brokerage commissions and advertising expenses incurred,
                  reasonable expenses of remodeling the Premises or any portion
                  thereof for a new tenant, whether for the same or a different
                  use, and any reasonable special concessions made to obtain a
                  new tenant; and

                           (E)      At Landlord's election, such other amounts
                  in addition to or in lieu of the foregoing as may be permitted
                  from time to time by applicable law.

         The term "RENT" as used in this Section 21 shall be deemed to be and to
         mean all sums of every nature required to be paid by Tenant pursuant to
         the terms of this Lease, whether to Landlord or to others. As used in
         Sections 21(c)(i) (A) and (B), above, the "WORTH AT THE TIME OF AWARD"
         shall be computed by allowing interest at the Default Rate. As used in
         Section 21(c)(i)(C) above, the "WORTH AT THE TIME OF AWARD" shall be
         computed by discounting such amount at the discount rate of the Federal
         Reserve Bank of San Francisco at the time of award plus 1%.

                  (iii)    Landlord may continue this Lease in effect after
         Tenant's Default and recover rent as it becomes due. Accordingly, if
         Landlord does not elect to terminate this Lease following a Default by
         Tenant, Landlord may, from time to time, without terminating this
         Lease, enforce all of its rights and remedies hereunder, including the
         right to recover all Rent as it becomes due.

                  (iv)     Whether or not Landlord elects to terminate this
         Lease following a Default by Tenant, Landlord shall have the right to
         terminate any and all subleases, licenses, concessions or other
         consensual arrangements for possession entered into by Tenant and
         affecting the Premises or may, in Landlord's sole discretion, succeed
         to Tenant's interest in such subleases, licenses, concessions or
         arrangements. Upon Landlord's election to succeed to Tenant's interest
         in any such subleases, licenses, concessions or arrangements, Tenant
         shall, as of the date of notice by Landlord of such election, have no
         further right to or interest in the rent or other consideration
         receivable thereunder.

         (d)      EFFECT OF EXERCISE. Exercise by Landlord of any remedies
hereunder or otherwise available shall not be deemed to be an acceptance of
surrender of the Premises and/or a termination of this Lease by Landlord, it
being understood that such surrender and/or termination can be effected only by
the express written agreement of Landlord and Tenant. Any law, usage, or custom
to the contrary notwithstanding, Landlord shall have the right at all times to
enforce the provisions of this Lease in strict accordance with the terms hereof;
and the failure of Landlord at any time to enforce its rights under this Lease
strictly in accordance with same shall not be construed as having created a
custom in any way or manner contrary to the specific terms, provisions, and
covenants of this Lease or as having modified the same and shall not be deemed a
waiver of Landlord's right to enforce one or more of its rights in connection
with any subsequent default. A receipt by Landlord of Rent or other payment with
knowledge of the breach of any covenant hereof shall not be deemed a waiver of
such breach, and no waiver by Landlord of any provision of this Lease shall be
deemed to have been made unless expressed in writing and signed by Landlord. To
the greatest extent permitted by law, Tenant waives the service of notice of
Landlord's intention to re-enter, re-take or otherwise obtain possession of the
premises as provided in any statute, or to institute legal proceedings to that
end, and also waives all right of redemption in case Tenant shall be
dispossessed by a judgment or by warrant of any court or judge. Any reletting of
the Premises or any portion thereof shall be on such terms and conditions as
Landlord in its sole discretion may determine. Landlord shall not be liable, nor
shall Tenant's obligations hereunder be diminished because of, Landlord's
failure to relet the Premises or collect rent due in respect of such reletting
or otherwise to mitigate any damages arising by reason of Tenant' Default.

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 18

         22.      ASSIGNMENT AND SUBLETTING.

         (a)      GENERAL PROHIBITION. Without Landlord's prior written consent,
Tenant shall not, directly or indirectly, voluntarily or by operation of law,
assign this Lease or sublease the Premises or any part thereof or mortgage,
pledge, or hypothecate its leasehold interest or grant any concession or license
within the Premises and any attempt to do any of the foregoing shall be void and
of no effect. For purposes of this Section, a transfer of ownership interests
controlling Tenant shall be deemed an assignment of this Lease unless such
ownership interests are publicly traded. Notwithstanding the foregoing, so long
as Tenant is not in Default hereunder and provided that Tenant gives Landlord
prior written notice of such transaction and such proposed transaction otherwise
complies with or satisfies the requirements and conditions of Section 22(c)
hereof, Landlord's consent shall not be required, in connection with: (i) an
assignment of this Lease to a corporation or other entity which is a
successor-in-interest to Tenant, by way of merger, consolidation or corporate
reorganization, or by the purchase of all or substantially all of the assets or
the ownership interests of the Tenant provided that (A) such merger or
consolidation, or such acquisition or assumption, as the case may be, is for a
good business purpose and not principally for the purpose of transferring the
Lease, (B) the net worth (as determined in accordance with GAAP) of the assignee
is not less than the net worth (as determined in accordance with GAAP) of Tenant
as of the Effective Date, and (C) such assignee shall agree in writing to assume
all of the terms, covenants and conditions of this Lease arising after the
effective date of the assignment, or (ii) an assignment of this Lease or
subletting of the Premises to any entity controlled by, under common control
with or controlling Tenant (either, an "AFFILIATE TRANSFER").

         (b)      PERMITTED TRANSFERS. Except for Affiliate Transfers, if Tenant
desires to assign, sublease, hypothecate or otherwise transfer this Lease or
sublet the Premises, then at least 15 business days, but not more than 60
business days, before the date Tenant desires the assignment or sublease to be
effective (the "ASSIGNMENT DATE"), Tenant shall give Landlord a notice (the
"ASSIGNMENT NOTICE") containing such information about the proposed assignee or
sublessee, including the proposed use of the Premises and any Hazardous
Materials proposed to be used or stored in the Premises, the Assignment Date,
any relationship between Tenant and the proposed assignee or sublessee, and all
material terms and conditions of the proposed assignment or sublease, and such
other information as Landlord may deem reasonably necessary or appropriate to
its consideration whether to grant its consent. Landlord may, by giving written
notice to Tenant within 10 business days after receipt of the Assignment Notice,
grant or refuse such consent, in its sole discretion with respect to a proposed
assignment, or grant or refuse such consent, in its reasonable discretion with
respect to a proposed subletting. Tenant shall reimburse Landlord for all of
Landlord's reasonable out-of-pocket expenses in connection with its
consideration of any Assignment Notice.

         (c)      ADDITIONAL CONDITIONS. As a condition to any such assignment
or subletting, including an Affiliate Transfer, Landlord may require:

                  (i)      That any agreement pertaining to Tenant's transfer of
         this Lease or subletting of any portion of the Premises and Landlord's
         approval thereof be in a form acceptable to Landlord in Landlord's
         reasonable discretion, and no such agreement shall be modified or
         amended without Landlord's prior written consent, which consent shall
         not be unreasonably withheld, conditioned or delayed;

                  (ii)     That Tenant deliver to Landlord one original executed
         copy of any and all written instruments evidencing or relating to
         Tenant's transfer of rights or subletting of the Premises;

                  (iii)    That any assignee or subtenant agree, in writing at
         the time of such assignment or subletting, that if Landlord gives such
         third party notice Tenant is in default under this

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 19

         Lease, such third party shall thereafter make all payments otherwise
         due Tenant directly to Landlord, which payments will be received by
         Landlord without any liability except to credit such payment against
         those due under the Lease, and any such third party shall agree to
         attorn to Landlord or its successors and assigns should this Lease be
         terminated for any reason; provided, however, in no event shall
         Landlord or its successors or assigns be obligated to accept such
         attornment; and

                  (iv)     A list of Hazardous Materials, certified by the
         proposed assignee or sublessee to be true and correct, which the
         proposed assignee or sublessee intends to use or store in the Premises
         together with the Documents referred to in Section 38.2 with respect to
         such proposed assignee or sublessee and a statement either (A) that
         such proposed assignee or sublessee has never been required by any
         prior landlord, lender or governmental authority to take any remedial
         action in connection with Hazardous Materials contaminating a property
         and has never been subject to an enforcement order issued by any
         governmental authority in connection with the use, disposal or storage
         of a Hazardous Materials, or (B) disclosing the details of any such
         required prior remedial action or enforcement order. Tenant
         acknowledges and agrees that it shall not be unreasonable for Landlord
         to withhold its consent to any proposed assignment or subletting to an
         assignee or subtenant who must disclose any required prior remedial
         action or enforcement order pursuant to clause (B) above.

         (d)      NO RELEASE OF TENANT. Notwithstanding any assignment or
subletting, Tenant and any guarantor or surety of Tenant's obligations under
this Lease shall at all times remain fully and primarily responsible and liable
for the payment of Rent and for compliance with all of Tenant's other
obligations under this Lease.

         (e)      EXCESS PROCEEDS. If the sum of all amounts due and payable by
a sublessee or assignee with respect to its occupancy of all or a portion of the
Premises (or a combination of the amounts payable under such sublease or
assignment plus any bonus or other consideration therefor or incident thereto)
exceeds (i) the Rent payable under this Lease, (ii) the reasonable costs of such
assignment or subletting, (iii) any operating expenses paid directly by Tenant
to a third party provider included in such subtenant's rent, and (iv) the
unamortized cost of any Excess Tl Costs expended in such sublet space, then
Tenant shall be bound and obligated to pay Landlord as Additional Rent hereunder
one half of such excess rental and other excess consideration within 10 days
following receipt thereof by Tenant. If Tenant shall sublet the Premises or any
part thereof, Tenant hereby immediately and irrevocably assigns to Landlord, as
security for Tenant's obligations under this Lease, all rent from any such
subletting and Landlord as assignee and as attorney-in-fact for Tenant, or a
receiver for Tenant appointed on Landlord's application, may collect such rent
and apply it toward Tenant's obligations under this Lease; except that, until
the occurrence of a Default, Tenant shall have the right to collect such rent.

         (f)      NO WAIVER. The consent by Landlord to an assignment or
subletting shall not relieve Tenant or any assignees of this Lease or any
sublessees of the Premises from obtaining the consent of Landlord to any further
assignment or subletting nor shall it release Tenant or any assignee or
sublessee of Tenant from full and primary liability under the Lease. The
acceptance of Rent hereunder, or the acceptance of performance of any other
term, covenant, or condition thereof, from any other person or entity shall not
be deemed to be a waiver of any of the provisions of this Lease or a consent to
any subletting, assignment or other transfer of the Premises.

         23.      ESTOPPEL CERTIFICATE. Tenant shall within 10 business days of
written notice from Landlord, execute, acknowledge and deliver a statement in
writing substantially in the form attached to this Lease as EXHIBIT G with the
blanks filled in, and on any other form reasonably requested by a proposed
lender or purchaser, (i) certifying that this Lease is unmodified and in full
force and effect (or, if modified, stating the nature of such modification and
certifying that this Lease as so modified is in full force and effect) and the
dates to which the rental and other charges are paid in

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 20

advance, if any, (ii) acknowledging that there are not, to Tenant's knowledge,
any uncured defaults on the part of Landlord hereunder, or specifying such
defaults if any are claimed, and (iii) setting forth such further information
with respect to the status of this Lease or the Premises as may be requested
thereon. Any such statement may be relied upon by any prospective purchaser or
encumbrancer of all or any portion of the real property of which the Premises
are a part. Tenant's failure to deliver such statement within such time shall,
at the option of Landlord, constitute a Default under this Lease, and, in any
event, shall be conclusive upon Tenant that the Lease is in full force and
effect and without modification except as may be represented by Landlord in any
certificate prepared by Landlord and delivered to Tenant for execution.

         24.      QUIET ENJOYMENT. If Tenant shall perform all of the covenants
and agreements herein required to be performed by Tenant, Tenant shall, subject
to the terms of this Lease, at all times during the Term, have peaceful and
quiet enjoyment of the Premises against any person claiming by, through or under
Landlord.

         25.      PRORATIONS. All prorations required or permitted to be made
hereunder shall be made on the basis of a 360 day year and 30 day months.

         26.      RULES AND REGULATIONS. Tenant shall, at all times during the
Term and any extension thereof, comply with all reasonable rules and regulations
at any time or from time to time established by Landlord covering use of the
Premises and the Project. The current rules and regulations are attached hereto.
If there is any conflict between said rules and regulations and other provisions
of this Lease, the terms and provisions of this Lease shall control. Landlord
shall not have any liability or obligation for the breach of any rules or
regulations by other tenants in the Project.

         27.      SUBORDINATION. This Lease and Tenant's interest and rights
hereunder are and shall be subject and subordinate at all times to the lien of
any first mortgage, now existing or hereafter created on or against the Project
or any portion thereof or the Premises, and all amendments, restatements,
renewals, modifications, consolidations, refinancing, assignments and extensions
thereof, without the necessity of any further instrument or act on the part of
Tenant; provided, however that so long as there is no Default hereunder,
Tenant's right to possession of the Premises shall not be disturbed by the
holder of any such first mortgage. Tenant agrees, at the election of the holder
of any such mortgage, to attorn to any such holder. Tenant agrees upon demand to
execute, acknowledge and deliver a Subordination, Non-disturbance and Attornment
Agreement in the form attached hereto as EXHIBIT H, or such other instruments,
confirming such subordination and such instruments of attornment as shall be
requested by any such holder, provided any such instruments contain appropriate
non-disturbance provisions assuring Tenant's quiet enjoyment of the Premises as
set forth in Section 24 hereof. Tenant hereby appoints Landlord attorney-in-fact
for Tenant irrevocably (such power of attorney being coupled with an interest)
to execute, acknowledge and deliver any such instrument and instruments for and
in the name of Tenant and to cause any such instrument to be recorded following
Tenant's failure timely to do so as herein required. Notwithstanding the
foregoing, any such holder may at any time subordinate its mortgage to this
Lease, without Tenant's consent, by notice in writing to Tenant, and thereupon
this Lease shall be deemed prior to such mortgage without regard to their
respective dates of execution, delivery or recording and in that event such
holder shall have the same rights with respect to this Lease as though this
Lease had been executed prior to the execution, delivery and recording of such
mortgage and had been assigned to such holder. The term "MORTGAGE" whenever used
in this Lease shall be deemed to include deeds of trust, security assignments
and any other encumbrances, and any reference to the "HOLDER" of a mortgage
shall be deemed to include the beneficiary under a deed of trust.

         28.      SURRENDER. Upon expiration of the Term or earlier termination
of Tenant's right of possession, Tenant may, subject to the exercise of any
remedies by Landlord, remove Tenant's Property and shall surrender the Premises
to Landlord in the same condition as received, broom

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 21

clean, ordinary wear and tear and casualty loss and condemnation covered by
Sections 17 and 18 excepted and shall return to Landlord all keys to offices and
restrooms furnished to, or otherwise procured by, Tenant. If any such key is
lost, Tenant shall pay to Landlord, at Landlord's election, either the cost of
replacing such lost key or the cost of changing the lock or locks opened by such
lost key. Any Trade Fixtures, Alterations and property not so removed by Tenant
as permitted or required herein shall be deemed abandoned and may be stored,
removed, and disposed of by Landlord at Tenant's expense, and Tenant waives all
claims against Landlord for any damages resulting from Landlord's retention
and/or disposition of such property. All obligations of Tenant hereunder not
fully performed as of the termination of the Term shall survive the termination
of the Term, including without limitation, indemnity obligations, payment
obligations with respect to Rent and obligations concerning the condition and
repair of the Premises, including the obligation to obtain all required
Hazardous Materials Clearances.

         29.      WAIVER OF JURY TRIAL. TENANT AND LANDLORD WAIVE ANY RIGHT TO
TRIAL BY JURY OR TO HAVE A JURY PARTICIPATE IN RESOLVING ANY DISPUTE, WHETHER
SOUNDING IN CONTRACT, TORT, OR OTHERWISE, BETWEEN LANDLORD AND TENANT ARISING
OUT OF THIS LEASE OR ANY OTHER INSTRUMENT, DOCUMENT, OR AGREEMENT EXECUTED OR
DELIVERED IN CONNECTION HEREWITH OR THE TRANSACTIONS RELATED HERETO.

         30.      ENVIRONMENTAL REQUIREMENTS.

         (a)      PROHIBITION/COMPLIANCE. Tenant shall not cause or permit any
Hazardous Materials (as hereinafter defined) to be brought upon, kept or used in
or about the Premises or the Project in violation of applicable law by Tenant,
its agents, employees, contractors or invitees. If Tenant breaches the
obligation stated in the preceding sentence, or if the presence of Hazardous
Materials brought upon, kept or used in or about the Premises or the Project by
any person other than Landlord, its agents, employees, contractors or invitees
results in contamination of the Premises, the Project or any adjacent property
during the term of this Lease or any extension or renewal hereof or holding over
hereunder, Tenant hereby indemnifies and shall defend and hold Landlord, its
officers, directors, employees, agents and contractors harmless from any and all
claims, judgments, damages, penalties, fines, costs, liabilities, or losses
(including, without limitation, diminution in value of the Premises or any
portion of the Project, damages for the loss or restriction on use of rentable
or usable space or of any amenity of the Premises or the Project, damages
arising from any adverse impact on marketing of space in the Premises or the
Project, and sums paid in settlement of claims, attorneys' fees, consultant fees
and expert fees) which arise during or after the Lease term as a result of such
contamination. This indemnification of Landlord by Tenant includes, without
limitation, costs incurred in connection with any investigation of site
conditions or any cleanup, remedial, removal, or restoration work required by
any federal, state or local governmental agency or political subdivision because
of Hazardous Materials present in the air, soil or ground water above, on, or
under the Premises. Without limiting the foregoing, if the presence of any
Hazardous Materials on the Premises, the Project or any adjacent property,
caused or permitted by Tenant results in any contamination of the Premises, the
Project or any adjacent property, Tenant shall promptly and diligently take all
actions at its sole expense as are necessary to return the Premises, the Project
or any adjacent property, as nearly as reasonably practical to the condition
existing prior to the time of such contamination, provided that Landlord's
approval of such action shall first be obtained, which approval shall not
unreasonably be withheld so long as such actions would not potentially have any
material adverse long-term or short-term effect on the Premises or the Project.

         (b)      BUSINESS. Landlord acknowledges that it is not the intent of
this Article 30 to prohibit Tenant from operating its business as described in
Section 2.1.9 above. Tenant may operate its business according to the custom of
the industry so long as the use or presence of Hazardous Materials is strictly
and properly monitored according to all applicable governmental requirements. As
a material inducement to Landlord to allow Tenant to use Hazardous Materials

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 22

in connection with its business, Tenant agrees to deliver to Landlord prior to
the Term Commencement Date a list identifying each type of Hazardous Materials
to be present on the Premises and setting forth any and all governmental
approvals or permits required in connection with the presence of such Hazardous
Materials on the Premises ("Hazardous Materials List"). Tenant shall deliver to
Landlord an updated Hazardous Materials List at least once a year and shall also
deliver an updated list upon request from time-to-time of Landlord. Tenant shall
deliver to Landlord true and correct copies of the following documents (the
"Documents") relating to the handling, storage, disposal and emission of
Hazardous Materials prior to the Term Commencement Date, or if unavailable at
that time, concurrent with the receipt from or submission to a governmental
agency: permits; approvals; reports and correspondence; storage and management
plans, notice of violations of any laws; plans relating to the installation of
any storage tanks to be installed in or under the Project (provided, said
installation of tanks shall only be permitted after Landlord has given Tenant
its written consent to do so, which consent may be withheld in Landlord's sole
and absolute discretion); and all closure plans or any other documents required
by any and all federal, state and local governmental agencies and authorities
for any storage tanks installed in, on or under the Project for the closure of
any such tanks. Tenant is not required, however, to provide Landlord with any
portion(s) of the Documents containing information of a proprietary nature
which, in and of themselves, do not contain a reference to any Hazardous
Materials or hazardous activities. It is not the intent of this Section to
provide Landlord with information which could be detrimental to Tenant's
business should such information become possessed by Tenant's competitors. At
the written request of Landlord, Tenant agrees that it shall enter into a
written agreement with other tenants at the Building concerning the equitable
allocation of fire control areas (as defined in the Uniform Building Code, and
adopted by the City of San Diego ("UBC")) within the Building for the storage of
Hazardous Materials. If Tenant's use of Hazardous Materials is such that it
utilizes fire control areas in the Building in excess of Tenant's Share, Tenant
agrees that it shall, at its own expense, and upon the written request of
Landlord, establish and maintain a separate area of the Premises classified by
the UBC as an"H" occupancy area, for the use and storage of Hazardous Materials,
or take such other action so that its share of the fire control areas of the
Building is not greater than Tenant's Share of the Building.

         (c)      TERMINATION OF LEASE. Except as disclosed by Tenant to
Landlord in a Disclosure Schedule attached hereto as Schedule 30(c),
notwithstanding the provisions of Section 30(a) above, if (i) Tenant, as of the
date hereof, has been required by any prior landlord, lender or governmental
authority to take remedial action in connection with Hazardous Materials
contaminating a property if the contamination resulted from Tenant's action or
use of the property in question, or (ii) Tenant is subject to an enforcement
order issued by any governmental authority in connection with the use, disposal
or storage of a Hazardous Materials, Landlord shall have the right to terminate
this Lease in Landlord's sole and absolute discretion. If any statement made to
Landlord by any prospective subtenant pursuant to Section 22(c)(iv) hereof shall
prove to be untrue in any material respect, Landlord may direct Tenant to
terminate any such subtenant's sublease. If Tenant shall fail to terminate such
subtenant's sublease within 30 days of Landlord's notice, Landlord may terminate
this Lease. In addition, if any statement made to Landlord by any prospective
assignee pursuant to Section 22(c)(iv) hereof shall prove to be untrue in any
material respect, Landlord may terminate this Lease.

         (d)      TESTING. Landlord shall have the right, on not less than 30
days prior notice, to conduct annual inspections and tests of the Premises to
determine whether any contamination in breach of Tenant's obligations under this
Section 30 has occurred as a result of Tenant's use thereof. Such inspections
and tests shall be conducted at Landlord's expense, unless such inspections and
tests reveal that such contamination has occurred as a result of Tenant's use of
the Premises, in which case Tenant shall reimburse Landlord for the reasonable
cost of such inspections and tests, not to exceed $1,000 annually. In addition,
at any time, and from time to time, prior to the expiration or earlier
termination of the Term, Landlord shall have the right to conduct appropriate
tests of the Premises and the Project or any portion thereof to demonstrate that
contamination has occurred as a result of Tenant's use of the Premises. If
contamination has

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 23

occurred for which Tenant is liable under this Section 30, Tenant shall pay all
costs to conduct such tests. If no such contamination is found, Landlord shall
pay the costs of such tests (which shall not constitute an Operating Expense).
Landlord shall provide Tenant with a copy of all reports and tests of the
Premises made by or on behalf of Landlord. Tenant shall be solely responsible
for and shall defend, indemnify and hold the Landlord, its agents and
contractors harmless from and against any and all claims, costs and liabilities
including actual attorneys' fees, charges and disbursements, arising out of or
in connection with any removal, clean up, restoration and materials required
hereunder to return the Premises, the Project or any adjacent property, as
nearly as reasonably practical, to the their condition existing prior to the
time of any such contamination. Landlord's receipt of or satisfaction with any
environmental assessment in no way waives any rights that Landlord holds against
Tenant.

         (e)      UNDERGROUND TANKS. If underground or other storage tanks
storing Hazardous Materials are located on the Premises or are hereafter placed
on the Premises by any party, Tenant shall monitor the storage tanks, maintain
appropriate records, implement reporting procedures, properly close any
underground storage tanks, and take or cause to be taken all other steps
necessary or required under applicable state and federal law, as such now exists
or may hereafter be adopted or amended.

         (f)      TENANT'S OBLIGATIONS. Tenant's obligations under this Article
30 shall survive the expiration or earlier termination of the Lease. During any
period of time after the expiration or earlier termination of this Lease
required by Tenant or Landlord to complete the removal from the Premises of any
Hazardous Materials and the release and termination of any licenses or permits
restricting the use of the Premises, Tenant shall continue to pay the full Rent
in accordance with this Lease, which Rent shall be prorated daily.

         (g)      DEFINITION OF "HAZARDOUS MATERIALS." As used herein, the term
"Hazardous Materials" means any hazardous or toxic substance, material or waste
which is or becomes regulated by any local governmental authority, the State of
California or the United States government and includes, without limitation, any
material or substance which is (i) defined as a "hazardous waste," "extremely
hazardous waste" or "restricted hazardous waste" under Section 25515 or 25117,
or listed pursuant to Section 25140, of the California Health and Safety Code,
Division 20, Chapter 6.5 (Hazardous Waste Control Law), (ii) defined as a
"hazardous substance" under Section 25316 of the California Health and Safety
Code, Division 2, Chapter 6.8 (Carpenter-Presly-Tanner Hazardous Substance
Account Act), (iii) defined as a "hazardous material," "hazardous substance" or
"hazardous waste" under Section 25501 of the California Health and Safety Code,
Division 20, Chapter 6.95 (Hazardous Substances), (v) petroleum, (vi) asbestos,
(vii) listed under Article 9 and defined as hazardous or extremely hazardous
pursuant to Article 11 of Title 22 of the California Administrative Code,
Division 4, Chapter 20, (viii) designated as a "hazardous substance" pursuant to
Section 311 of the Federal Water Pollution Control Act (33 U.S.C. Section 1317),
(ix) defined as a "hazardous waste" pursuant to Section 1004 of the Federal
Resource Conversation and Recovery Act, 42 U.S.C. Section 6901, et. seq. (42
U.S.C. Section 6903), or (x) defined as a "hazardous substance" pursuant to
Section 101 of the Comprehensive Environmental Response Compensation and
Liability Act, 42 U.S.C. Section 9601 et. seq. (42 U.S.C. Section 9601).

         31.      TENANT'S REMEDIES/LIMITATION OF LIABILITY. Landlord shall not
be in default hereunder unless Landlord fails to perform any of its obligations
hereunder within 30 days after written notice from Tenant specifying such
failure (unless such performance will, due to the nature of the obligation,
require a period of time in excess of 30 days, then after such period of time as
is reasonably necessary). Upon any default by Landlord, Tenant shall give notice
by registered or certified mail to any beneficiary of a deed of trust or
Mortgagee of a Mortgage covering the Premises and to any landlord of any lease
of property in or on which the Premises are located and Tenant shall offer such
beneficiary, Mortgagee and/or landlord a reasonable opportunity to cure the
default, including time to obtain possession of the Project by power of sale or
a judicial action if

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 24

such should prove necessary to effect a cure; provided Landlord shall have
furnished to Tenant in writing the names and addresses of all such persons who
are to receive such notices.

         Notwithstanding the foregoing, if any claimed Landlord default
hereunder will immediately, materially and adversely affect Tenant's ability to
conduct its business in the Premises (a "MATERIAL LANDLORD DEFAULT"), Tenant
shall, as soon as reasonably possible but in any event within 2 business days of
obtaining knowledge of such claimed Material Landlord Default, give Landlord
written notice of such claim and shall at the same time call Landlord's local
administrative office and give telephonic notice of such claimed Material
Landlord Default. Landlord shall then have 2 business days to commence cure of
such claimed Material Landlord Default and shall diligently prosecute such cure
to completion. If such claimed Material Landlord Default is not a default by
Landlord hereunder, or if Tenant failed to give Landlord the notice required
hereunder within 48 hours of learning of the conditions giving rise the claimed
Material Landlord Default, Landlord shall be entitled to recover from Tenant, as
Additional Rent, any costs incurred by Landlord in connection with such cure in
excess of the costs, if any, that Landlord would otherwise have been liable to
pay hereunder. If Landlord fails to commence cure of any claimed Material
Landlord Default, Tenant may commence and prosecute such cure to completion, and
shall be entitled to recover the costs of such cure from Landlord, subject to
the limitations set forth in the immediately preceding sentence of this
paragraph.

         All obligations of Landlord hereunder shall be construed as covenants,
not conditions; and, except as may be otherwise expressly provided in this
Lease, Tenant may not terminate this Lease for breach of Landlord's obligations
hereunder. All obligations of Landlord under this Lease will be binding upon
Landlord only during the period of its ownership of the Premises and not
thereafter; provided, however, Landlord shall be liable for the proper use, or
delivery to any successor Landlord hereunder, of any Excess TI Deposit made by
Tenant under the Work Letter. The term "LANDLORD" in this Lease shall mean only
the owner, for the time being of the Premises, and upon the transfer by such
owner of its interest in the Premises, such owner shall thereupon be released
and discharged from all obligations of Landlord thereafter accruing, but such
obligations shall be binding during the Term upon each new owner for the
duration of such owner's ownership. Any liability of Landlord under this Lease
shall be limited solely to its interest in the Project (including Landlord's
interest in any condemnation or casualty proceeds), and in no event shall any
personal liability be asserted against Landlord in connection with this Lease
nor shall any recourse be had to any other property or assets of Landlord or any
of Landlord's officers, employees, agents or contractors. Under no circumstances
shall Landlord or any of Landlord's officers, employees, agents or contractors
be liable for injury to Tenant's business or for any loss of income or profit
therefrom.

         32.      INSPECTION AND ACCESS. Landlord and its agents,
representatives, and contractors may enter the Premises at any reasonable time
to inspect the Premises and to make such repairs as may be required or permitted
pursuant to this Lease and for any other business purpose. Landlord and
Landlord's representatives may enter the Premises during business hours on not
less than 48 hours advance written notice (except in the case of emergencies in
which case no such notice shall be required and such entry may be at any time)
for the purpose of effecting any such repairs, inspecting the Premises, showing
the Premises to prospective purchasers and, during the last year of the Term, to
prospective tenants or for any other business purpose. Tenant shall have the
right to provide escorts for any such entry into all or any portion of the
Premises provided such escorts don't materially interfere with Landlord's rights
hereunder. During the last 12 months of the Term, Landlord may erect a suitable
sign on the Premises stating the Premises are available to let or that the
Project is available for sale. Landlord may grant easements, make public
dedications, designate common areas and create restrictions on or about the
Premises, provided that no such easement, dedication, designation or restriction
materially interferes with Tenant's use or occupancy of the Premises for the
Permitted Use. At Landlord's request, Tenant shall execute such instruments as
may be necessary for such easements, dedications or restrictions.

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 25

         33.      SECURITY. Tenant acknowledges and agrees that security devices
and services, if any, while intended to deter crime may not in given instances
prevent theft or other criminal acts and that Landlord is not providing any
security services with respect to the Premises. Tenant agrees that Landlord
shall not be liable to Tenant for, and Tenant waives any claim against Landlord
with respect to, any loss by theft or any other damage suffered or incurred by
Tenant in connection with any unauthorized entry into the Premises or any other
breach of security with respect to the Premises. Tenant shall be solely
responsible for the personal safety of Tenant's officers, employees, agents,
contractors, guests and invitees while any such person is in, on or about the
Premises and/or the Project. Tenant shall at Tenant's cost obtain insurance
coverage to the extent Tenant desires protection against such criminal acts.

         34.      FORCE MAJEURE. With exception of obligations to pay money,
neither party shall be held responsible for delays in the performance of its
obligations hereunder when caused by strikes, lockouts, labor disputes, weather,
natural disasters, inability to obtain labor or materials or reasonable
substitutes therefor (other than by reason of an inability to pay therefor),
governmental restrictions, governmental regulations, governmental controls,
delay in issuance of permits, enemy or hostile governmental action, civil
commotion, fire or other casualty, and other causes beyond the reasonable
control of such party ("FORCE MAJEURE").

         35.      BROKERS, ENTIRE AGREEMENT, AMENDMENT. Landlord and Tenant each
represent and warrant that it has not dealt with any broker, agent or other
person (collectively, "BROKER) in connection with this transaction and that no
Broker brought about this transaction, other than John Burnham & Company, who
shall be paid a commission by Landlord pursuant to a separate agreement.
Landlord and Tenant each hereby agree to indemnify and hold the other harmless
from and against any claims by any other Broker claiming a commission or other
form of compensation by virtue of having dealt with Tenant or Landlord, as
applicable, with regard to this leasing transaction. This Lease constitutes the
complete agreement of Landlord and Tenant with respect to the subject matter
hereof. No representations, inducements, promises or agreements, oral or
written, have been made by Landlord or Tenant, or anyone acting on behalf of
Landlord or Tenant, including any Brokers representing either Landlord or
Tenant, which are not contained herein, and any prior agreements, promises,
negotiations, or representations are superseded by this Lease. Tenant represents
and warrants that no broker or agent has made any representation or warranty
relied upon by Tenant in Tenant's decision to enter into this Lease. Landlord in
executing this Lease does so in reliance upon Tenant's representations and
warranties contained herein. This Lease may not be amended except by an
instrument in writing signed by both parties hereto.

         36.      LIMITATION ON LANDLORD'S LIABILITY. NOTWITHSTANDING ANYTHING
SET FORTH HEREIN OR IN ANY OTHER AGREEMENT BETWEEN LANDLORD AND TENANT TO THE
CONTRARY: (A) LANDLORD SHALL NOT BE LIABLE TO TENANT OR ANY OTHER PERSON FOR
(AND TENANT AND EACH SUCH OTHER PERSON ASSUME ALL RISK OF) LOSS, DAMAGE OR
INJURY, WHETHER ACTUAL OR CONSEQUENTIAL TO: TENANT'S PERSONAL PROPERTY OF EVERY
KIND AND DESCRIPTION, INCLUDING, WITHOUT LIMITATION TRADE FIXTURES, EQUIPMENT,
INVENTORY, SCIENTIFIC RESEARCH, SCIENTIFIC EXPERIMENTS, LABORATORY ANIMALS,
PRODUCT, SPECIMENS, SAMPLES, AND/OR SCIENTIFIC, BUSINESS, ACCOUNTING AND OTHER
RECORDS OF EVERY KIND AND DESCRIPTION KEPT AT THE PREMISES AND ANY AND ALL
INCOME DERIVED OR DERIVABLE THEREFROM; (B) THERE SHALL BE NO PERSONAL RECOURSE
TO LANDLORD FOR ANY ACT OR OCCURRENCE IN, ON OR ABOUT THE PREMISES OR ARISING IN
ANY WAY UNDER THIS LEASE OR ANY OTHER AGREEMENT BETWEEN LANDLORD AND TENANT WITH
RESPECT TO THE SUBJECT MATTER HEREOF AND ANY LIABILITY OF LANDLORD HEREUNDER
SHALL BE STRICTLY LIMITED TO LANDLORD'S INTEREST IN THE PROPERTY OF WHICH THE
PREMISES ARE A PART.

         37.      SEVERABILITY. If any clause or provision of this Lease is
illegal, invalid or unenforceable under present or future laws, then and in that
event, it is the intention of the parties

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 26

hereto that the remainder of this Lease shall not be affected thereby. It is
also the intention of the parties to this Lease that in lieu of each clause or
provision of this Lease that is illegal, invalid or unenforceable, there be
added, as a part of this Lease, a clause or provision as similar in terms to
such illegal, invalid or unenforceable clause or provision as may be possible
and be legal, valid and enforceable.

         38.      SIGNS; EXTERIOR APPEARANCE. Tenant shall not, without the
prior written consent of Landlord, which may be granted or withheld in
Landlord's sole discretion, except with respect to (v) below as to which
Landlord's consent shall not be unreasonably withheld: (i) attach any awnings,
exterior lights, decorations, balloons, flags, pennants, banners, painting or
other projection to any outside wall of the Building, (ii) use any curtains,
blinds, shades or screens other than Landlord's standard window coverings, (iii)
coat or otherwise sunscreen the interior or exterior of any windows, (iv) place
any bottles, parcels, or other articles on the window sills, (v) place any
equipment, furniture or other items of personal property on any exterior
balcony, (vi) paint, affix or exhibit on any part of the Premises, the Building
or the Project any signs, notices, window or door lettering, placards,
decorations, or advertising media of any type which can be viewed from the
exterior of the Premises, except for (i) signage on the exterior of the Building
and on any signage monument that may be located in the Project, which shall be
subject to any applicable local governmental restrictions or requirements, and
(ii) local (interbuilding) communications antennas on the roof of the Building,
in each case in such location, size and deign as shall be reasonably approved by
Landlord, and, with respect to the antennas, provided that such equipment does
not interfere with any other tenant in the project and is located, maintained
and operated in compliance with all applicable laws and regulations. Interior
signs on doors and the directory tablet shall be inscribed, painted or affixed
for Tenant by Landlord at the sole cost and expense of Tenant, and shall be of a
size, color and type acceptable to Landlord. Nothing may be placed on the
exterior of corridor walls or corridor doors other than Landlord's standard
lettering. The directory tablet shall be provided exclusively for the display of
the name and location of tenants.

         39.      RIGHT TO EXPAND

         (a)      EXPANSION IN THE BUILDING. Tenant shall have the right, but
not the obligation, to expand the Premises (the "EXPANSION RIGHT") to include
any space available in the Building which has never been leased to any other
tenant (the "EXPANSION SPACE") upon the terms and conditions set forth in this
Section 39. Tenant's Expansion Right shall not apply to any space in the
Building once it has been let to any third party tenant. If at any time Landlord
reasonably believes that a prospective tenant (a "NEW TENANT") for any of the
Expansion Space is about to sign a letter of intent to lease all or any portion
of the Expansion Space, Landlord shall deliver to Tenant: (i) written notice of
such fact (the "EXPANSION NOTICE") describing the portion of the Expansion Space
(the "NOTICE SPACE") to be subject to such letter of intent, and (ii) a draft
amendment to this Lease (the "EXPANSION AMENDMENT") adding the Notice Space to
the Premises demised hereunder to be leased for the then remaining Term hereof
(and any Extension Terms duly elected by Tenant), for the Base Rent then payable
hereunder, to be improved subject to, and with the same Tenant Improvement
Allowance as is set forth in, the Work Letter hereto, and otherwise on the same
terms and conditions as are set forth in this Lease and with (i) the schedule
for build-out of such Expansion Space to start as of the date of execution of
the Lease amendment under which such Expansion Space is to be let as the
beginning of such schedule and (ii) appropriate adjustments to Tenant's Share.
Tenant shall have 10 business days following delivery of the Expansion Notice in
which to exercise the Expansion Right by delivering to Landlord 4 fully executed
copies of the Expansion Amendment. Upon receipt, Landlord shall promptly execute
two copies of such Expansion Amendment and return them to Tenant. In addition,
Tenant may, at any time it has an Expansion Right with respect to any Expansion
Space deliver a notice to Landlord electing to Lease all or a portion of such
Expansion Space (unless the remaining Expansion Space on either floor on the
Building would be 10,000 square feet or less, In which case Tenant must elect to
lease all of such Expansion Space) on the terms described above.

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 27

         (b)      AMENDED LEASE. If Tenant fails to exercise its Expansion Right
by delivering four fully executed copies of such Expansion Amendment to Landlord
within 10 business days following delivery of the Expansion Notice, Tenant shall
be deemed to have waived its right to lease the Notice Space; provided, however,
that if Landlord has not executed a lease for the Notice Space with the New
tenant or any other person within 180 days of delivery of the Expansion Notice
to Tenant, Tenant's Expansion Rights with respect to the Notice Space shall be
reinstated; provided, further, that if Landlord and such New Tenant are in
active negotiations for a lease of the Notice Space 150 days after delivery of
the Expansion Notice to Tenant, Landlord may at any time thereafter give Tenant
a second Expansion Notice with respect to such Expansion Space, which shall be
accepted or rejected by Tenant as described in Section 39(a) hereof.

         (c)      EXCEPTIONS. Notwithstanding the above, the Expansion Right
shall not be in effect and may not be exercised by Tenant:

                  (i)      during any period of time that Tenant is in Default
         under any provision of the Lease; or

                  (ii)     if Tenant has been in Default under any provision of
         the Lease 3 or more times, whether or not the Defaults are cured,
         during the 12 month period prior to the date on which Tenant seeks to
         exercise the Expansion Right.

         (d)      TERMINATION. The Expansion Right shall terminate and be of no
further force or effect even after Tenant's due and timely exercise of the
Expansion Right, if, after such exercise, but prior to the commencement date of
the Expansion Space, (i) Tenant fails to timely cure any Default by Tenant under
the Lease; or (ii) Tenant has Defaulted 3 or more times during the period from
the date of the exercise of the Expansion Right to the date of the commencement
of the Expansion Space, whether or not such Defaults are cured.

         40.      RIGHT TO NEGOTIATE. If Landlord, in its sole discretion,
elects to develop one or more additional buildings on the real property on which
the Project is located ("NEW CONSTRUCTION SPACE"), Landlord shall give Tenant
notice of such potential development. If Tenant elects to do so, Landlord and
Tenant shall negotiate in good faith for Tenant's prospective occupancy of all
or a portion of such New Construction Space, provided, however, that Landlord
shall have the right to terminate such negotiations if no lease has been signed
within thirty days of the commencement of such negotiations.

         41.      RIGHT TO EXTEND TERM. Tenant shall have the right to extend
the Term of the Lease upon the following terms and conditions:

         (a)      EXTENSION RIGHTS. Tenant shall have two consecutive rights
(each, an "Extension Right") to extend the term of this Lease for 5 years each
(each, an "Extension Term") on the same terms and conditions as this Lease by
giving Landlord written notice of its election to exercise each Extension Right
at least 180 days prior to the expiration of the initial term of the Lease or
the expiration of any prior Extension Term. During any Extension Term, Base Rent
shall be payable at the rate of 95% of the Market Rate (as defined below), but
in no event less than the Base Rent payable as of the date immediately preceding
the commencement such Extension Term. Base Rent shall be adjusted on the
commencement of each Extension Term and on each annual anniversary of the
commencement of such Extension Term shall be increased by a percentage as
determined by Landlord and agreed to by Tenant at the time Market Rent is
determined, but in no event less than the Rent Adjustment Percentage hereunder.
As used herein, "Market Rate" shall mean the then market rental rate as
determined by Landlord and agreed to by Tenant.

         If, on or before the date which is 120 days prior to the expiration of
the initial Term of this Lease, or the expiration of any Extension Term, Tenant
has not agreed with Landlord's determination of the Market Rate and the rent
escalations during such subsequent Extension Term

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 28

after negotiating in good faith, Tenant may by written notice to Landlord elect
arbitration as described in Section 41 (b) below. If Tenant does not elect such
arbitration, Tenant shall be deemed to have waived any right to extend, or
further extend, the Term of the Lease and all of the remaining Extension Rights
shall terminate.

         (b)      ARBITRATION.

                  (i)      Within 10 days of Tenant's notice to Landlord of its
         election to arbitrate Market Rate and escalations, each party shall
         deliver to the other a proposal containing the Market Rate and
         escalations that the submitting party believes to be correct
         ("EXTENSION PROPOSAL") subject to the minimum Base Rent and escalation
         rate set forth in Section 41 (a) hereof. If either party fails to
         timely submit an Extension Proposal, the other party's submitted
         proposal shall determine the Base Rent for the Extension Term. If both
         parties submit Extension Proposals, then Landlord and Tenant shall meet
         within 7 days after delivery of the last Extension Proposal and make a
         good faith attempt to mutually appoint a single Arbitrator (as defined
         below) to determine the Market Rate and escalations. If Landlord and
         Tenant are unable to agree upon a single Arbitrator, then each shall,
         by written notice delivered to the other within 10 days after the
         meeting, select an Arbitrator. If either party fails to timely giver
         notice of its selection for an Arbitrator, the other party's submitted
         proposal shall determine the Base Rent for the Extension Term. The 2
         Arbitrators so appointed shall, within 5 business days after their
         appointment, appoint a third Arbitrator. If the 2 Arbitrators so
         selected cannot agree on the selection of the third Arbitrator within
         the time above specified, then either party, on behalf of both parties
         may request such appointment of such third Arbitrator by application to
         any state court of general jurisdiction in the jurisdiction in which
         the Premises are located, upon 10 days prior written notice to the
         other party of such intent.

                  (ii)     The authority of the Arbitrator(s) shall be limited
         strictly to a selection of either Landlord's Extension Proposal in its
         entirety or Tenant's Extension Proposal in its entirety as the
         Extension Proposal which most closely approximates the Market Rate and
         escalations. The Arbitrator(s) shall have no authority to create an
         independent structure of Market Rate and escalations, combine elements
         of both Extension Proposals to create a third, or compromise or alter
         in any way any of the components of the Extension Proposals submitted
         by the parties. The sole decision to be made shall be which of the
         parties' Extension Proposals in its entirety shall determine the Market
         Rate and escalations for the Renewal Term. Notwithstanding the
         foregoing, if the Arbitrator(s) select an Extension Proposal which
         results in a Base Rent less than the Base Rent payable as of the date
         immediately preceding the commencement such Extension Term or
         escalations less than the Rent Adjustment Percentage hereunder, the
         Base Rent and/or Rent Adjustment Percentage hereunder for the Extension
         Term shall be increased to the Base Rent payable as of the date
         immediately preceding the commencement such Extension Term or the Rent
         Adjustment Percentage hereunder, as applicable.

                  (iii)    The decision of the Arbitrator(s) shall be made
         within 30 days after the appointment of a single Arbitrator or the
         third Arbitrator, as applicable. The decision of the single Arbitrator
         or majority of the 3 Arbitrators shall be final and binding upon the
         parties. Each party shall pay the fees and expenses of the Arbitrator
         appointed by or on behalf of such party and the fees and expenses of
         the third Arbitrator shall be borne equally by both parties. If the
         Market Rate and escalations are not determined by the first day of the
         Renewal Term, then Tenant shall pay Landlord Base Rent in an amount
         equal to the Base Rent in effect immediately prior to the Renewal Term
         until such determination is made. After the determination of the Market
         Rate and escalations, the parties shall make any necessary adjustments
         to such payments made by Tenant. Landlord and Tenant shall then execute
         an amendment recognizing the Market Rate and escalations for the
         Renewal Term.

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 29

                  (iv)     An "ARBITRATOR" shall be any person appointed by or
         on behalf of either party or appointed pursuant to the provisions
         hereof and: (i) shall be (A) a member of the American Institute of Real
         Estate Appraisers with not less than 10 years of experience in the
         appraisal of improved office and high tech industrial real estate in
         the greater San Diego metropolitan area, or (B) a licensed commercial
         real estate broker with not less than 15 years experience representing
         landlords and/or tenants in the leasing of high tech or life sciences
         space in the greater San Diego metropolitan area, (ii) devoting
         substantially all of their time to professional appraisal or brokerage
         work, as applicable, at the time of appointment and (iii) be in all
         respects impartial and disinterested.

         (c)      RIGHTS PERSONAL. Extension Rights are personal to IDEC
Pharmaceuticals Corporation and are not assignable except in connection with an
Affiliate Transfer or other assignment of this Lease approved by Landlord.

         (d)      EXCEPTIONS. Notwithstanding anything set forth above to the
contrary, Extension Rights shall not be in effect and Tenant may not exercise
any of the Extension Rights:

                  (i)      during any period of time that Tenant is in Default
         under any provision of this Lease; or

                  (ii)     if Tenant has been in Default under any provision of
         this Lease 3 or more times, whether or not the Defaults are cured,
         during the 12 month period immediately prior to the date that Tenant
         intends to exercise an Extension Right, whether or not the Defaults are
         cured.

         (e)      NO EXTENSIONS. The period of time within which any Extension
Rights may be exercised shall not be extended or enlarged by reason of the
Tenant's inability to exercise the Extension Rights.

         (f)      TERMINATION. The Extension Rights shall terminate and be of no
further force or effect even after Tenant's due and timely exercise of an
Extension Right, if, after such exercise, but prior to the commencement date of
an Extension Term, (i) Tenant fails to timely cure any Default by Tenant under
this Lease; or (ii) Tenant has Defaulted 3 or more times during the period from
the date of the exercise of an Extension Right to the date of the commencement
of the Extension Term, whether or not such Defaults are cured.

         42.      MISCELLANEOUS.

         (a)      NOTICES. All notices or other communications between the
parties shall be in writing and shall be deemed duly given, if delivered in
person or by reputable overnight guaranty courier, addressed and sent to the
parties at their addresses set forth above. Landlord and Tenant may from time to
time by written notice to the other designate another address for receipt of
future notices.

         (b)      JOINT AND SEVERAL LIABILITY. If and when included within the
term "TENANT," as used in this instrument, there is more than one person, firm
or corporation, each shall be jointly and severally liable for the obligations
of Tenant.

         (c)      LANDLORD CONSENTS. Except as otherwise expressly provided in
this Lease or as otherwise required by law, Landlord retains the absolute right
to withhold any consent or approval.

         (d)      FINANCIAL INFORMATION. At Landlord's request from time to time
Tenant shall furnish Landlord with true and complete copies of its most recent
annual and quarterly financial statements

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                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 30

prepared by Tenant or Tenant's accountants and any other financial information
or summaries that Tenant typically provides to its lenders or shareholders.

         (e)      RECORDATION. Neither this Lease nor a memorandum of lease
shall be filed by or on behalf of Tenant in any public record. Landlord may
prepare and file, and upon request by Landlord Tenant will execute, a memorandum
of lease.

         (f)      INTERPRETATION. The normal rule of construction to the effect
that any ambiguities are to be resolved against the drafting party shall not be
employed in the interpretation of this Lease or any exhibits or amendments
hereto. Words of any gender used in this Lease shall be held and construed to
include any other gender, and words in the singular number shall be held to
include the plural, unless the context otherwise requires. The captions inserted
in this Lease are for convenience only and in no way define, limit or otherwise
describe the scope or intent of this Lease, or any provision hereof, or in any
way affect the interpretation of this Lease.

         (g)      NOT BINDING UNTIL EXECUTED. The submission by Landlord to
Tenant of this Lease shall have no binding force or effect, shall not constitute
an option for the leasing of the Premises, nor confer any right or impose any
obligations upon either party until execution of this Lease by both parties.

         (h)      LIMITATIONS ON INTEREST. It is expressly the intent of
Landlord and Tenant at all times to comply with applicable law governing the
maximum rate or amount of any interest payable on or in connection with this
Lease. If applicable law is ever judicially interpreted so as to render usurious
any interest called for under this Lease, or contracted for, charged, taken,
reserved, or received with respect to this Lease, then it is Landlord's and
Tenant's express intent that all excess amounts theretofore collected by
Landlord be credited on the applicable obligation (or, if the obligation has
been or would thereby be paid in full, refunded to Tenant), and the provisions
of this Lease immediately shall be deemed reformed and the amounts thereafter
collectible hereunder reduced, without the necessity of the execution of any new
document, so as to comply with the applicable law, but so as to permit the
recovery of the fullest amount otherwise called for hereunder.

         (i)      CHOICE OF LAW. Construction and interpretation of this Lease
shall be governed by the internal laws of the state in which the Premises are
located, excluding any principles of conflicts of laws.

         (j)      TIME. Time is of the essence as to the performance of Tenant's
obligations under this Lease. All references to "days" herein shall mean
calendar days unless business days are indicated.

         (k)      INCORPORATION BY REFERENCE. All exhibits and addenda attached
hereto are hereby incorporated into this Lease and made a part hereof. If there
is any conflict between such exhibits or addenda and the terms of this Lease,
such exhibits or addenda shall control.

<PAGE>

                   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 31

         IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease as of
the day and year first above written.

                                     TENANT:

                                     IDEC PHARMACEUTICALS CORPORATION,
                                     a Delaware corporation

                                     By:/s/ Phillip Schneider
                                        ---------------------------------------
                                     Its: VP & CFO

                                     LANDLORD:

                                     ARE -10933 NORTH TORREY PINES, LLC,
                                     a Delaware limited liability company

                                     By: ALEXANDRIA REAL ESTATE EQUITIES, INC.,
                                         a Maryland corporation, Managing Member

                                         By: /s/ Lynn Anne Shapiro
                                             -----------------------------------
                                         Its: GENERAL COUNSEL

[NOTARY SEAL]

<PAGE>

                                   EXHIBIT A-1

                                  THE PREMISES

                                  [FLOOR PLAN]

<PAGE>

                                   EXHIBIT A-2

                                  THE PREMISES

                                  [FLOOR PLAN]

<PAGE>

                                   EXHIBIT A-3

                                  THE PREMISES

                                  [FLOOR PLAN]

<PAGE>

                             ARC Science Center/IDEC Pharmaceuticals Corporation

                                    EXHIBIT B

                          LEGAL DESCRIPTION OF PROJECT

Lot 1 of Torrey Pines Science Park Unit No. 1 in the City of San Diego, County
of San Diego, State of California, according to Map thereof No. 6229, filed in
the Office of the County Recorder of San Diego County on November 21, 1968.

<PAGE>

                                  EXHIBIT B-1

                                  THE PROJECT

                                  [SITE PLAN]

<PAGE>

IDEC - Landlord Build                                ARC-Science Center - Page 1

                                   EXHIBIT C

                                  WORK LETTER

         THIS WORK LETTER dated as of June 24, 1999 (this "Work Letter") is made
and entered into by and between ARE-10933 NORTH TORREY PINES, LLC, a Delaware
limited liability company ("Landlord"), and IDEC PHARMACEUTICALS CORPORATION, a
Delaware corporation ("Tenant"), and is attached to and made a part of the Lease
dated as of June 24, 1999 (the "Lease"), by and between Landlord and Tenant. Any
initially capitalized terms used but not defined herein shall have the meanings
given them in the Lease.

1.       General Requirements

         1.1      Tenant's Authorized Representative. Tenant designates Robert
F. Dilworth and Bert Van Loon collectively, "Tenant's Representative") as the
only persons authorized to act for Tenant pursuant to this Work Letter. Landlord
may rely and act on, without further inquiry of any kind, any written request,
approval, inquiry or other communication ("Communication") from or on behalf of
Tenant in connection with this Work Letter given by either Tenant's
Representative. Tenant's Representative may be contacted at the voice, facsimile
and pager telephone numbers and e-mail addresses set forth on Schedule C-1,
attached hereto and incorporated herein by this reference. When Landlord has
attempted to contact Tenant's Representative by each of such means, Landlord
shall have no further obligation of any kind to attempt to locate either
Tenant's Representative or Tenant with respect to any Communication under this
Work Letter. Tenant may change Tenant's Representatives or any telephone number
or e-mail address set forth on Schedule C-1 at any time upon not less than 5
Business Days advance written notice to Landlord. No period set forth herein for
any approval of any matter by Tenant's Representative shall be extended by
reason of any change in Tenant's Representative. Neither Tenant nor Tenant's
Representative shall be authorized to direct Landlord's contractors in the
performance of Landlord's Work (as hereinafter defined).

         1.2      Landlord's Authorized Representative. Landlord designates
Vincent Ciruzzi ("LANDLORD'S REPRESENTATIVE") as the only person authorized to
act for Landlord pursuant to this Work Letter. Tenant shall not be obligated to
respond to or act upon any request, approval, inquiry or other Communication
from or on behalf of Landlord in connection with this Work Letter unless such
Communication is in writing from Landlord's Representative. Landlord's
Representative may be contacted at the voice, facsimile and pager telephone
numbers and e-mail addresses set forth on Schedule C-2, attached hereto and
incorporated herein by this reference. When Tenant has attempted to contact
Landlord's Representative by each of such means, Tenant shall have no further
obligation of any kind to attempt to locate Landlord's Representative or
Landlord with respect to any Communication under this Work Letter. Landlord may
change Landlord's Representatives or any telephone number or e-mail address set
forth on Schedule C-2 at any time upon not less than 5 Business Days advance
written notice to Tenant. No period set forth herein for any approval of any
matter by Landlord's Representative shall be extended by reason of any change in
Landlord's Representative.

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IDEC - Landlord Build                                ARC-Science Center - Page 2

         1.3      Development Schedule. The schedule for design and development
of Landlord's Improvements (as defined below), the Tenant Improvements (as
defined below) and the Central Plant (as defined below), including without
limitation the time periods for delivery of construction documents and
performance of construction, shall be in accordance with the Development
Schedule attached hereto as Schedule A, subject to adjustment as mutually agreed
by the parties in writing or as provided in this Work Letter (the "Development
Schedule").

         1.4      Architects, Consultants and Contractors. Landlord and Tenant
hereby acknowledge and agree that the architect for the Tenant Improvements (the
"Tl Architect") shall be McGraw Baldwin Architects, and (ii) the general
contractor for the Tenant Improvements shall be DPR Construction, Inc.

2.       Tenant Improvements.

         2.1      Tenant Improvements Defined. As used herein, "Tenant
Improvements" shall mean all improvements to the Building desired by Tenant of a
fixed and permanent nature, but excluding the Central Plant and the improvements
described on Schedule B attached hereto ("Landlord's Improvements"). Landlord
shall provide HVAC and electrical service to the Premises by means of a central
HVAC and electrical distribution plant ("Central Plant"), the design of which
shall be reasonably approved by Landlord and Tenant at or prior to the approval
of the Preliminary Construction Drawings pursuant to Section 2.3 below;
provided, however, that Tenant may disapprove any design of the Central Plant to
the extent that Tenant's pro rata share of the capacity of such Central Plant
and the temperature, humidity and air flow are not sufficient for Tenant's
requirements as detailed on the TI Design/Engineering Drawings. The costs of any
such Central Plant shall be allocated to Tenant in accordance with Tenant's
Share of the Building and shall be charged to the TI Allowance. Other than the
Tenant Improvements, Landlord's Improvements and the Central Plant, Landlord
shall not have any obligation whatsoever with respect to the finishing of the
Premises for Tenant's use and occupancy. The term "Tenant Improvements" shall
mean the Tenant Improvements to be constructed prior to Tenant's initial
occupancy of the Building.

         2.2      Tenant's Space Plans. Tenant shall deliver to Landlord
schematic drawings and outline specifications (the "TI Design/Engineering
Drawings") detailing Tenant's requirements for the Tenant Improvements
(including Tenant's required capacity from the Central Plant) within five
business days of the execution of this Work Letter. Not more than 10 Business
Days thereafter, Landlord shall deliver to Tenant Landlord's reasonable written
objections, questions or comments with regard to the TI Design/Engineering
Drawings. Tenant shall act reasonably to cause the TI Design/Engineering
Drawings to be revised to address such written comments in a mutually
satisfactory manner and shall resubmit said drawings to Landlord for approval
within 10 Business Days thereafter. Such process shall continue until Landlord
has approved the TI Design/Engineering Drawings. In no event shall Landlord have
the right to direct upgrades in the quality (above the generic Laboratory
standard of Tenant's improvements in its facility at 11011 Torreyana Road, San
Diego, California) or quantity (other than to comply with any Legal Requirement)
of any of the materials or equipment to be installed in connection with the
Tenant Improvements, nor shall any such changes adversely affect the safety or
quality of the Tenant Improvements.

<PAGE>

IDEC - Landlord Build                                ARC-Science Center - Page 3

         2.3      Landlord's Approval. Promptly after receiving Landlord's
approval of the TI Design/Engineering Drawings, Tenant shall cause the Tl
Architect to complete working drawings and specifications ("Preliminary
Construction Drawings") based upon the approved TI Design/Engineering Drawings.
Within 10 Business Days after receipt by Landlord of said Preliminary
Construction Drawings, Landlord shall notify Tenant of the manner, if any, in
which said Preliminary Construction Drawings as submitted by Tenant are
unacceptable in Landlord's reasonable judgment, and Tenant shall re-submit such
Preliminary Construction Drawings to Landlord for approval. In no event shall
Landlord have the right to direct upgrades in the quality (above the generic
Laboratory standard of Tenant's improvements in its facility at 11011 Torreyana
Road, San Diego, California) or quantity (other than to comply with any Legal
Requirement) of any of the materials or equipment to be installed in connection
with the Tenant Improvements, nor shall any such changes adversely affect the
safety or quality of the Tenant Improvements. Landlord shall notify Tenant of
any objections to a resubmission within 10 Business Days after receipt. Upon
Landlord's final approval, the Preliminary Construction Drawings shall become
the "TI Construction Drawings". It is hereby acknowledged by Landlord and Tenant
that the TI Construction Drawings must be completed and approved not later than
November 30, 1999, in order for the Tenant Improvements to be Substantially
Complete by the Target Term Commencement Date. Any subsequent changes,
modifications or alterations to the TI Construction Drawings following
Landlord's and Tenant's approval of same shall be processed in the manner
provided in Section 4 of this Work Letter.

3.       Performance of Landlord's Work.

         3.1      Definition of Landlord's Work. As used herein, "Landlord's
Work" shall mean the work of constructing Landlord's Improvements, the Central
Plant and the Tenant Improvements. The contract for construction of the Tenant
Improvements shall be a guaranteed maximum price contract, in a form mutually
approved by Landlord and Tenant. Tenant shall be expressly made a third party
beneficiary of all warranties set forth in such contract. Any subcontracts for
work or materials in an aggregate amount of $100,000 or more, and any work
(other than general conditions) to be done directly by the general contractor
for the Tenant Improvements shall be subject to the mutual approval of Landlord
and Tenant. No approval required under this Section 3.1 shall be unreasonably
withheld or delayed.

         3.2      Commencement and Permitting of Landlord's Work. Landlord shall
commence construction of Landlord's Improvements upon obtaining a building
permit authorizing the construction of Landlord's Improvements (the "Building
Permit"), which Building Permit shall be obtained at Landlord's expense.
Landlord shall commence construction of the Tenant Improvements upon the later
of (i) obtaining a building permit authorizing the construction of the Tenant
Improvements consistent with the TI Construction Drawings (the "TI Permit"), or
(ii) having sufficiently completed Landlord's Improvements such that the work of
constructing the Tenant Improvements can be efficiently prosecuted. The cost of
obtaining the TI Permit shall be payable from the TI Fund. Tenant shall assist
Landlord in obtaining the Building Permit and the TI Permit. If any Governmental
Authority having jurisdiction over the construction of Landlord's Work or any
portion thereof shall impose terms or conditions upon the construction thereof
which: (i) are inconsistent with Landlord's obligations hereunder, (ii) increase
the cost of constructing Landlord's Work, or (iii) will materially

<PAGE>

IDEC - Landlord Build                                ARC-Science Center - Page 4

delay the construction of Landlord's Work, Landlord and Tenant shall reasonably
and in good faith seek means by which to mitigate or eliminate any such adverse
terms and conditions.

         3.3      Completion of Landlord's Work. On or before the Term
Commencement Date (subject to Tenant Delay and Force-Majeure Delays), Landlord
shall substantially complete or cause to be substantially completed Landlord's
Work in a good and workmanlike manner, in accordance with the Building Permit
and the TI Permit, shall obtain a temporary certificate of occupancy for the
Premises subject, in each case, to Minor Variations and normal "punch list"
items of a non-material nature which do not interfere with the use of the
Premises for the Permitted Uses and shall have conducted, at Landlord's cost and
not to be paid from the TI Fund, an environmental assessment (the "Baseline
Assessment") of the Premises ("Substantial Completion"). Upon the Substantial
Completion of Landlord's Work, the TI Architect and the general contractor shall
execute and deliver, for the benefit of Tenant and Landlord, a Certificate of
Substantial Completion in the form of the American Institute of Architects
document G704. For purposes of this Work Letter, "Minor Variations" shall mean
any modifications reasonably required: (i) to comply with all applicable Legal
Requirements and/or to obtain or to comply with any required permit (including
the Building Permit and the TI Permit) which are not material; (ii) to comply
with any request by the Tenant for modifications to Landlord's Work; (iii) to
comport with good design, engineering, and construction practices which are not
material; or (iv) to make reasonable adjustments for field deviations or
conditions encountered during the construction of Landlord's Work which are not
material.

         3.4      Selection of Materials, Etc. As to all building materials and
equipment which Land-lord is obligated to supply for Landlord's Improvements
under this Work Letter, Landlord shall select the manufacturer thereof in its
sole discretion. Tenant and Landlord shall mutually select the manufacturer of
all building materials and equipment which Landlord is obligated to supply for
the Tenant Improvements under this Work Letter, including the major mechanical
components of the Central Plant.

         3.5      Delivery of the Premises. When Landlord's Work is
Substantially Complete, subject to the remaining terms and provisions of this
Section 3.5, Tenant shall accept the Premises. Tenant's taking possession and
acceptance of the Premises shall not constitute a waiver of: (i) any warranty
with respect to workmanship (including installation of equipment) or material
(exclusive of equipment provided directly by manufacturers), (ii) any
non-compliance of Landlord's Work with Code, (iii) Landlord's obligation to
cause any "punch list" items to be corrected, or (iv) any claim that the Tenant
Improvements were not completed substantially in accordance with the TI
Construction Drawings (subject to Minor Variations and such other changes as are
permitted hereunder) (collectively, a "Construction Defect"). Tenant shall have
one year after Substantial Completion within which to notify Landlord of any
such Construction Defect discovered by Tenant during such one-year period, and
Landlord shall use reasonable efforts to remedy or cause the responsible
contractor to remedy any such Construction Defect within 30 days thereafter.
Notwithstanding the foregoing, Landlord shall not be in default under the Lease
if:

                  (a) with respect to the Tenant Improvements, the applicable
         contractor, despite Landlord's reasonable efforts, fails to remedy such
         Construction Defect within such 30 day period, in which case Landlord
         shall have no further obligation with respect to such

<PAGE>

IDEC - Landlord Build                                ARC-Science Center - Page 5

         Construction Defect other than to cooperate, at no cost to Landlord,
         with Tenant should Tenant elect to pursue a claim against such
         contractor, provided that Tenant indemnifies and holds Landlord
         harmless from and against any liability, loss, cost damage or expense
         in connection with any such claim, or

                  (b) with respect to Landlord's Improvements and the Central
         Plant, the applicable contractor, despite Landlord's reasonable
         efforts, fails to remedy such Construction Defect within such 30 day
         period, but Landlord, within 30 days thereafter commences and
         diligently and continuously prosecutes such remedial action to
         completion.

Tenant shall be entitled to receive the benefit of all construction warranties
and manufacturer's equipment warranties relating to equipment installed in the
Premises. If requested by Tenant, Landlord shall attempt to obtain extended
warranties from manufacturers and suppliers of such equipment, but the cost of
any such extended warranties shall be borne solely out of the TI Fund. Landlord
shall diligently pursue any claims arising out of latent defects in the Landlord
Improvements and the Central Plant. Landlord shall promptly undertake and
complete, or cause to be completed, all punch list items.

         3.6      Commencement Date Delay. The Commencement Date shall occur
when Landlord's Work has been Substantially Completed (the "Completion Date"),
except to the extent that completion of Landlord's Work shall have been actually
delayed by any one or more of the following causes (a "Tenant Delay"):

                  3.6.1    No Tenant's Representative was available to give or
         receive any Communication or to take any other action required to be
         taken by Tenant hereunder;

                  3.6.2    Tenant's Change Requests whether or not any such
         Change Request is actually implemented;

                  3.6.3    Construction of any Changes;

                  3.6.4    Tenant's request for materials, finishes or
         installations requiring unusually long lead times;

                  3.6.5    Tenant's delay in reviewing, revising or approving
         plans and specifications or the Budget beyond the periods set forth
         herein or any period of redesign requested by Tenant to reduce the
         total costs of the Tenant Improvements following the receipt of the
         Budget pursuant to Section 5.1;

                  3.6.6    Tenant's delay in providing information critical to
         the normal progression of construction of Landlord's Work. Tenant shall
         provide such information as soon as reasonably possible, but in no
         event longer than 5 Business Days after receipt of any request for such
         information from Landlord;

                  3.6.7    Tenant's delay in making payments to Landlord for
         Excess TI Costs;

<PAGE>

IDEC - Landlord Build                                ARC-Science Center - Page 6

                  3.6.8    Any other act or omission by Tenant, its agents,
         contractors or persons employed by any of such persons which impedes
         the construction of Landlord's Work following notice of such delay from
         Landlord to Tenant's Representative.

Tenant Delay shall further include, at Landlord's option, any period that
Landlord was excused from proceeding with Landlord's Work hereunder as a result
of an Event of Default under the Lease pursuant to Section 8 hereof. If the
Commencement Date is delayed for any of the foregoing reasons, the TI Architect
shall on a monthly basis certify the number of days of Tenant Delay hereunder.
If there are more than 30 days of Tenant Delay ("Excess Tenant Delay"), the
Commencement Date under the Lease shall for all purposes be the number of days
of Excess Tenant Delay before the date of Substantial Completion.

4.       Changes. Any changes requested by Tenant to Landlord's Improvements at
any time, or to the Tenant Improvements or the capacities required from the
Central Plant after the delivery and approval by Landlord of the TI
Design/Engineering Drawings, shall be requested and instituted in accordance
with the provisions of this Section 4 and shall be subject to the written
approval of Landlord and the Tl Architect, such approval not to be unreasonably
withheld, conditioned or delayed.

         4.1      Tenant's Right to Request Changes. If Tenant shall request
changes to Landlord's Work ("Changes"), Tenant shall request such Changes by
notifying Landlord in writing in substantially the same form as the AIA standard
change order form (a "Change Request"), which Change Request shall detail the
nature and extent of any such Change. Such Change Request must be signed by
Tenant's Representative.

                  4.1.1    If such Change Request relates to Landlord's
         Improvements or the Central Plant, Landlord shall, before proceeding
         with any Change, use its best efforts to respond to Tenant as soon as
         reasonably possible with an estimate of: (i) the time it will take, and
         (ii) the architectural and engineering fees and costs which will be
         incurred, to analyze such Change Request. Landlord shall thereafter
         submit to Tenant in writing, within 5 Business Days of receipt of the
         Change Request (or such longer period of time as is reasonably required
         depending on the extent of the Change Request), an analysis of the
         additional cost or savings involved, including, without limitation
         architectural and engineering costs and the period of time, if any,
         that the Change will extend the date on which Landlord's Work will be
         Substantially Complete.

                  4.1.2    If such Change Request relates to the Tenant
         Improvements, Tenant shall cause the TI Architect to estimate: (i) the
         time it will take, and (ii) the architectural and engineering fees and
         costs which will be incurred, to analyze such Change Request.
         Thereafter Landlord, the TI Architect and Landlord's general contractor
         for the Tenant Improvements shall analyze the Change Request and submit
         to Tenant in writing, within 5 Business Days of receipt of the Change
         Request (or such longer period of time as is reasonably required
         depending on the extent of the Change Request), an analysis of the
         additional cost or savings involved, including, without limitation,
         architectural and engineering costs and the period of time, if any,
         that the Change will extend the date on which Landlord's Work will be
         Substantially Complete.

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IDEC - Landlord Build                                ARC-Science Center - Page 7

Any delay in the completion of Landlord's Work caused by a Change, including any
suspension of Landlord's Work to the extent affected or potentially affect by
the proposed Change while any such Change is being evaluated and/or designed,
shall be a Tenant Delay; provided, however, that Tenant shall have the right to
approve or disapprove any suspension of Landlord's Work of building the Tenant
Improvements and/or the Central Plant while any such Change is being evaluated,
provided, further that if Tenant disapproves any suspension of such work, Tenant
shall be solely responsible for all costs of removing and/or rebuilding any such
Work to the extent affected by any approved Change.

         4.2      Implementation of Changes. If Tenant: (i) approves in writing
the cost or savings and the estimated extension in the time for completion of
Landlord's Work, if any, and (ii) deposits with Landlord any Excess TI Costs (as
defined below) required in connection with such Change (including any costs
arising pursuant to Section 4.1), Landlord shall cause the approved Change to be
instituted. Notwithstanding any approval or disapproval by Tenant of any
estimate of the delay caused by such proposed Change, the TI Architect's
determination of the amount of Tenant Delay in connection with such Change shall
be final and binding on Landlord and Tenant.

5.       Costs.

         5.1      Budget For Tenant Improvements. Before the commencement of
construction of the Tenant Improvements, Landlord shall obtain a detailed
breakdown, by trade, of the costs incurred or which will be incurred, in
connection with the design and construction of the Tenant Improvements,
including Tenant's Share of the costs of the Central Plant (the "Budget"). The
Budget shall be based upon the TI Construction Drawings approved by Tenant and
shall include a payment to Landlord, of administrative rent ("Administrative
Rent") equal to 3% of the cost of designing and constructing the Tenant
Improvements (including an allocation of the costs of the Central Plant) for
monitoring and inspecting the construction of the Tenant Improvements, which sum
shall be payable from the TI Fund. Such Administrative Rent shall include,
without limitation, all out-of-pocket costs, expenses and fees incurred by or on
behalf of Landlord, including the cost of any overhead, arising from, out of or
in connection with such monitoring of the construction of the Tenant
Improvements, incurred by or on behalf of Landlord regardless whether Landlord's
actual costs and expenses exceed the Administrative Rent. Tenant shall approve
or disapprove the Budget within 10 business days after receipt thereof from
Landlord. Tenant's failure to deliver notice of disapproval shall constitute
Tenant's approval thereof. If Tenant disapproves the Budget, Tenant shall notify
Landlord of such disapproval within such 10 Business Day period and the parties
shall as soon as reasonably possible meet in order to revise the TI Construction
Drawings to reduce the Budget to a level that is acceptable to Tenant, provided
that any delay in approving the Budget beyond the 10 Business Days provided
above shall constitute Tenant Delay. Notwithstanding anything set forth in this
Work Letter of the Lease, Tenant shall not be required to pay for the cost of
any completion or performance bond in connection with any of the work performed
by any contractor pursuant to this Work Letter, unless Tenant shall request any
such bond.

         5.2      TI Allowance. Landlord shall provide to Tenant a tenant
improvement allowance ("TI Allowance") of $100 per rentable square foot of the
Premises. The TI Allowance shall be disbursed in accordance with this Work
Letter. If upon the Substantial Completion of the Tenant Improvements any
portion of the TI Allowance remains, Tenant shall thereafter, at any time and

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IDEC - Landlord Build                                ARC-Science Center - Page 8

from time-to-time during the initial 12 months of the Term, have the right to
submit for Landlord's approval, as described in Section 2.2 hereof, TI
Design/Engineering Drawings with respect to any additional Tenant Improvements
Tenant wishes to have constructed in the Premises. Thereafter the design of such
additional Tenant Improvements shall proceed on the schedule, and shall be
subject to the approval process, set forth in Section 2 hereof, and such
additional Tenant Improvements shall be constructed by Landlord as described
herein, provided that Landlord shall be obligated to pursue the construction of
such additional Tenant Improvements with reasonable diligence, but shall not be
obligated to Substantially Complete such additional Tenant Improvements by any
fixed date; and provided further, that Landlord shall not have any obligation to
disburse any portion of the TI Allowance more than 12 months after the Lease
Commencement Date. No failure by Tenant to use all of the TI Allowance shall
result in any adjustment of Rent under the Lease.

         5.3      Costs Includable in TI Allowance. The TI Allowance shall be
used solely for the payment of design and construction costs in connection with
the construction of the Tenant Improvements, including, without limitation, the
cost of preparing the TI Design/Engineering Drawings, the Preliminary TI Plans,
and the TI Construction Drawings, all costs set forth in the Budget (including
Landlord's Administrative Rent, extended warranties, if any, Landlord's
out-of-pocket expenses and an allocation of the costs of the Central Plant),
costs resulting from Tenant Delay and the cost of Changes. The TI Allowance
shall not be used to purchase any furniture, personal property or other
non-building system materials or equipment not incorporated into the
Improvements, including, without limitation, biological safety cabinets and
other scientific equipment.

         5.4      Excess TI Costs. It is understood and agreed that Landlord is
under no obligation to bear any portion of the cost of any of the Tenant
Improvements, or Tenant's Share of the costs of the Central Plant, except to the
extent of the TI Allowance. If at any time and from time-to-time, the aggregate
TI Costs under the Budget exceed the aggregate TI Allowance ("Excess TI Costs"),
Tenant shall deposit with Landlord, as a condition precedent to Landlord's
obligation to complete the Tenant Improvements, one-quarter of the difference,
in cash (the "Excess TI Deposit"), prior to the commencement of construction of
the Tenant Improvements, to be held by Landlord until Tenant has funded the
balance of any such Excess TI Costs as provided herein. Each month, in
connection with the monthly draws to pay for the Tenant Improvements, Tenant
shall pay a pro rata portion of such monthly draw equal to the amount of such
monthly draw, multiplied by a fraction, the numerator of which is the Excess TI
Costs and the denominator of which is the TI Fund. When all of the Excess Costs
other than the Excess TI Deposit have been directly funded by Tenant, Landlord
shall disburse the Excess TI Deposit in payment for Tenant Improvements. If
Tenant fails to deposit, or is late in depositing, the Excess TI Deposit with
Landlord or if Tenant fails to pay each monthly draw within 10 business days of
receipt of the contractor's monthly draw as approved for payment by Landlord,
Landlord shall have all of the rights and remedies set forth in the Lease for
nonpayment of Rent (including, but not limited to, the right to interest at the
Default Rate and the right to assess a late charge), and for purposes of any
litigation instituted with regard to such amounts the same will be considered
Rent. Such Excess TI Costs, together with the TI Allowance, is herein referred
to as the "TI Fund". Funds so deposited by Tenant shall be, at Landlord's
option, the last thereafter disbursed to pay TI Costs. Notwithstanding anything
to the contrary set forth in this Section 5.4, Tenant shall be fully and solely
liable for TI Costs and the cost of Minor Variations

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IDEC - Landlord Build                                ARC-Science Center - Page 9

in excess of the TI Allowance. If upon Substantial Completion of the Tenant
Improvements and the payment of all sums due in connection therewith there
remains any undisbursed TI Allowance, Tenant shall be entitled to such
undisbursed TI Allowance solely to the extent of any Excess TI Deposit Tenant
has actually made with Landlord.

         5.5      Payment for Landlord's Improvements. The Landlord shall bear
all costs, expenses and fees incurred by or on behalf of Landlord in connection
with the construction of Landlord's Improvements, other than as a result of
Tenant requested Changes, subject to the terms hereof and the terms of the
Lease. Such payment shall be made by Landlord, to the extent of Landlord's
approval thereof, no later than 30 days following receipt of a full draw package
in a format to be mutually approved by Landlord and Tenant.

6.       Tenant Access.

         6.1      Tenant's Access Rights. Landlord hereby agrees to permit
Tenant access, at Tenant's sole risk and expense, to the Building (i) 60 days
prior to the Term Commencement Date to perform any work ("Tenant's Work")
required by Tenant other than Landlord's Work and provided that such Tenant's
Work is coordinated with the TI Architect and the general contractor, and
complies with the Lease and all other reasonable restrictions and conditions
Landlord may impose, and (ii) prior to the completion of Landlord's Work, to
inspect and observe work in process; all such access shall be during normal
business hours or at such other times as are reasonably designated by Landlord.
Notwithstanding the foregoing, Tenant shall have no right to enter onto the
Premises or the Building unless and until Tenant shall deliver to Landlord
evidence reasonably satisfactory to Landlord demonstrating that any insurance
reasonably required by Landlord in connection with such pre-commencement access
(including, but not limited to, any insurance which Landlord may require
pursuant to the Lease) is in full force and effect.

         6.2      No Interference. Neither Tenant nor its employees,
consultants, agents, contractors, and suppliers shall interfere with the
performance of Landlord's Work, nor with any inspections or issuance of final
approvals by San Diego County or the City of San Diego, and upon any such
interference, Landlord shall have the right to exclude Tenant and Tenant's
employees, consultants, contractors and agents from the Premises and the
Building until Substantial Completion of Landlord's Work.

         6.3      No Acceptance of Premises. The fact that Tenant may, with
Landlord's consent, enter into the Building prior to the date Landlord's Work is
Substantially Complete for the purpose of performing any Tenant's Work shall not
be deemed an acceptance by Tenant of possession of the Premises, but in such
event Tenant shall indemnify and hold Landlord harmless from any loss of or
damage to Tenant property, completed work, fixtures, equipment, materials or
merchandise, and from liability for death of, or injury to, any person to the
extent such loss of damage is caused by the willful misconduct or negligence of
Tenant or its agents.

7.       Notification of Delays. Not less than once each calendar month from the
date of this Work Letter through the Term Commencement Date, Landlord shall
deliver to Tenant written notification of the number of days during the
immediately preceding calendar month Landlord's performance under this Work
Letter or the Lease was delayed as a result of Tenant Delay or Force Majeure

<PAGE>

IDEC - Landlord Build                               ARC-Science Center - Page 10

Delays, which written notification shall also include a description of the
nature of such Tenant Delay or Force Majeure Delay.

8.       Lease Defaults. Notwithstanding anything set forth herein or in the
Lease to the contrary, Landlord shall have no obligation to perform any
Landlord's Work hereunder or to advance all or any portion of the TI Fund during
any period an Event of Default under the Lease exists.

9.       Dispute Resolution.

         9.1      Upon any dispute regarding the design or construction
(including substitutions of materials) of the Tenant Improvements or the
required capacity of Tenant's share of, or the specifications for the services
provided through, the Central Plant, which is not settled within 5 Business Days
after notice of such dispute is delivered by one party to the other, Tenant
shall make the final decision regarding the design and/or construction of the
Tenant Improvements or the required capacity of Tenant's share of, or the
specifications for the services provided through, the Central Plant, provided
Tenant acts reasonably and such final decision is consistent with the intent of
the TI Design/Engineering Drawings, the Preliminary Construction Drawings and
the Construction Drawings, as applicable, provided further that all costs and
expenses resulting from any such decision by Tenant (including, without
limitation, any costs imposed on Landlord, as reasonably estimated by Landlord
to modify Landlord's Improvements to accommodate the Tenant Improvements, but
excluding Landlord's "carry" costs and overhead) shall be payable out of the TI
Fund, as defined in Section 5.4 above, and provided that such resolution does
not, in Landlord's reasonable judgement, adversely affect or any portion of the
Building outside the Premises or any Building system.

         9.2      Upon any dispute regarding the design or construction
(including substitutions of materials) of the Landlord Improvements which is not
settled within 5 Business Days after notice of such dispute is delivered by one
party to the other, Landlord shall make the final decision regarding the design
and/or construction of the Landlord Improvements and the Central Plant (other
than as described in Section 9.1 hereof), provided Landlord acts reasonably and
such final decision is consistent with the intent of the drawings for Landlord's
Improvements delivered and developed in connection with the TI
Design/Engineering Drawings, the Preliminary Construction Drawings and the
Construction Drawings, as applicable, provided further that all costs and
expenses resulting from any such decision by Landlord shall be payable by
Landlord and not charged to the Tl Fund and provided that such resolution does
not, in Landlord's reasonable judgement, adversely affect the Premises.

10.      Miscellaneous

         10.1     Consents. Whenever consent or approval of either party is
required under this Work Letter, that party shall not unreasonably withhold,
condition or delay such consent or approval, except as may be expressly set
forth herein to the contrary.

         10.2     Modification. No modification, waiver or amendment of this
Work Agreement or of any of its conditions or provisions shall be binding upon
Landlord or Tenant unless in writing signed by Landlord and Tenant.

<PAGE>

IDEC - Landlord Build                               ARC-Science Center - Page 11

         10.3     Counterparts. This Work Letter may be executed in any number
of counterparts but all counterparts taken together shall constitute a single
document.

         10.4     Governing Law. This Work Letter shall be governed by,
construed and enforced in accordance with the internal laws of the state in
which the Premises are located, without regard to choice of law principles of
such State.

         10.5     Time of the Essence. Time is of the essence of this Work
Agreement and of each and all provisions thereof.

         10.6     Severability. If any term or provision of this Work Letter is
declared invalid or unenforceable, the remainder of this Work Letter shall not
be affected by such determination and shall continue to be valid and
enforceable.

         10.7     Merger. All understandings and agreements, oral or written,
heretofore made between the parties hereto and relating to Landlord's Work are
merged in this Work Letter, which alone (but inclusive of provisions of the
Lease incorporated herein and the final approved constructions drawings and
specifications prepared pursuant hereto) fully and completely expresses the
agreement between Landlord and Tenant with regard to the matters set forth in
this Work Letter.

         10.8     Entire Agreement. This Work Letter is made as a part of and
pursuant to the Lease and, together with the Lease, constitutes the entire
agreement of the parties with respect to the subject matter hereof. This Work
Letter is subject to all of the terms and limitation set forth in the Lease, and
neither party shall have any rights or remedies under this Work Letter separate
and apart from their respective remedies pursuant to the Lease.

                         [SIGNATURES BEGIN ON NEXT PAGE]

<PAGE>

IDEC - Landlord Build                               ARC-Science Center - Page 12

         IN WITNESS WHEREOF, Landlord and Tenant have executed this Work Letter
to be effective on the date first above written.

                                     TENANT:

                                     IDEC PHARMACEUTICALS CORPORATION,
                                     a Delaware corporation

                                     By: Phillip Schneider
                                         ---------------------------------------
                                     Its: VP & CFO

                                     LANDLORD

                                     ARE -10933 NORTH TORREY PINES, LLC,
                                     a Delaware limited liability company

                                     By: ALEXANDRIA REAL ESTATE EQUITIES, INC.,
                                         a Maryland corporation, Managing Member

                                         By: /s/ Lynn Anne Shapiro
                                             -----------------------------------
                                         Its: General Counsel

<PAGE>

IDEC - Landlord Build                               ARC-Science Center - Page 13

                            SCHEDULE A to Work Letter

                              Development Schedule

<TABLE>
<CAPTION>
                        Event                                               Date
                        -----                                               ----
<S>                                                                     <C>
Execution of lease                                                          As of

Delivery of space plans for Tl Design/Engineering Drawings              5 Business Days
pursuant to Section 2.2 of the Work Letter                              after execution

Commencement of construction of Landlord's Improvements                     8/1/99

Delivery of Preliminary Tl Plans pursuant to                                9/1/99
Section 2.3 of the Work Letter

Delivery of Tl Construction Drawings                                      11/15/99
pursuant to Section 2.3 of the Work Letter

Tenant's approval of Budget for Tenant Improvements                       12/10/99
pursuant to Section 5.1 of the Work Letter

Commence construction of Tenant Improvements                                1/1/00

Substantial Completion of Tenant Improvements                               7/1/00

Issuance of Temporary Certificate of Occupancy                              7/1/00
</TABLE>

<PAGE>

                            SCHEDULE B TO WORK LETTER

                                 LANDLORD'S WORK

                             OUTLINE SPECIFICATIONS
                  ALEXANDRIA TECHNOLOGY CENTER AT SCIENCE PARK

                      SHELL BUILDING, CORE & SITEWORK SCOPE

                                  JUNE 17,1999

                           MCGRAW/BALDWIN ARCHITECTS
                             701 B STREET, SUITE 200
                               SAN DIEGO, CA 92101

<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 2

                                  PROJECT DATA

PROJECT:                 ALEXANDRIA TECHNOLOGY CENTER AT SCIENCE PARK

LOCATION:                LOT 1
                         TORREY PINES SCIENCE PARK

DATE:                    JUNE 17, 1999

1.   Construction Type              Type II-NR, Sprinklered

2.   Number of Buildings            One(1)

3.   Number of Stories              Two (2) over Basement

4.   Use                            Laboratory and Offices

5.   Gross Square Footage (approx.)

<TABLE>
<S>            <C>                <C>                 <C>
Basement       41,860 SF          Core Areas          4,786 SF

1st Floor      38,350 SF          1st Floor            2,502SF
2nd Floor      38.048 SF          2nd Floor            2,284SF
------------------------          ----------------------------
Total Bldg.    76,398 SF          Total Core           4,786SF
</TABLE>

6.   Estimated Site Area            16.08 acres (700,450 sq. ft.)

7.   Estimated Site Coverage        22.2%

8.   Parking provided               Approximately 3/1000 parking spaces

9.   Trash Dumpsters                One (1) trash enclosure for five (5)
                                    standard (4'x7') trash bins.

10.  Floor-to-Floor Height          Garage Floor to First Floor:         10"-10"
                                    First Floor to Second Floor:         14"-3"
                                    Second Floor to Parapet:             15"-3"

11.  Ceilings                       2x2 tegular lay-in at lobby.
                                    Continuous gypsum board ceiling at
                                    restrooms.
                                    Other ceilings by Tenant Improvement.

12.  Drive Aisle Widths             As required by Code

13.  Fire Sprinkling                Fully Fire Sprinklered - Fire riser to shell
                                    building and core distribution only.

14.  Electrical                     480Y/277 Volt, 4000 AMP, 3 phase, 4 wire
                                    service to building.

                                        2
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 3

DESCRIPTION:                 The project consists of (1) Two-story office
                             building approximately 80 car basement parking
                             garage totaling 118,258 gross square feet. All site
                             improvements, shell building and core improvements
                             (lobby, restrooms, and elevators) are part of this
                             project.

SCOPE:                       All building and site improvements shall be
                             complete in every respect as defined by, but not
                             limited to, the content of the schematic drawings
                             and outline specifications. Exceptions to this
                             scope will be tenant driven improvements such as
                             interior tenant spaces, central mechanical plant
                             enclosure and hazardous materials enclosure
                             requirements, that are all part of the Tenant
                             Improvements. Site/Shell/Core project will provide
                             location only for plumbing rooms, and location,
                             foundation and concrete pads only for central plant
                             and emergency generators. Design fees, permit fees,
                             inspection fees and Builder's Risk Insurance to be
                             provided as required for Site/Shell/Core
                             improvements.

CODES:                       The building shall be Type II, non-rated, B
                             occupancy. All construction shall conform to local,
                             state and federal codes and regulations in effect
                             at the time of building department plan check
                             submittal. All placement of concrete, reinforcing
                             steel in masonry units and/or concrete and all
                             field weld plates and field welding shall be
                             inspected by an independent testing laboratory,
                             where required.

DIVISION 1 GENERAL REQUIREMENTS

                             All work shall be in conformance with all
                             applicable building codes and regulations.
                             Contractor shall be responsible for coordination of
                             all work to be performed and for conformance to the
                             contract documents. Special considerations shall be
                             made to accommodate and minimize disruptions to
                             existing tenants on site.

DIVISION 2 SITEWORK

Earthwork                    Provide all grading and reshaping of existing site
                             as required to achieve conformance with new finish
                             grade elevations for building, parking, and central
                             plant.

Site Utilities               Provide all sewer, gas, water, storm drain,
                             electrical, telephone, cable television and data /
                             fiber-optic services as required stubbed inside
                             building or as necessary to serve core
                             improvements. Distribution of utility of services
                             other than core provided by Tenant Improvement.

Irrigation                   All landscaped areas to be fully irrigated and
                             operated by a central automatic controller. Provide
                             planter drainage to comply per minimum City of San
                             Diego standards.

                                        3
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 4

Landscaping                  Provide plant material and soil amendments per City
                             of San Diego landscape guideline standards.

Enhanced Concrete Paving     Provide approximately 2,100 sf integral color, 7"
                             nominal thickness, reinforced 3,500 psi concrete
                             slab over Class II base, per soils report.

Enhanced Architectural       Provide approximately 8,000 sf integral color, 4"
Paving                       nominal thickness enhanced over natural grade with
                             combination of broom finish main building entrance.
                             All other walkways to be natural color concrete
                             broom finish. All enhanced paving to be sealed.

Asphalt Concrete             Asphalt concrete paving over Class II crushed
                             aggregate base minimum thickness to be 3" A.C. over
                             4" base at parking; A.C. over 4" base at drives or
                             as specified per soils report. Provide sand seal
                             finish and striping.

Curb & Mow Strips            All curb and gutters shall be constructed of
                             concrete in accordance to City of San Diego
                             standards.

DIVISION 3 CONCRETE

Foundations                  Continuous grade beam and spread footings of
                             reinforced concrete below grade for lateral frames,
                             columns and retaining walls in accordance with the
                             soils report.

Basement Floor Slab          Slab-on-grade minimum 5" thick 3000 p.s.i. concrete
                             slab on grade, reinforced with #3 bars at 18" o.c.,
                             over 2" sand. Include 6 mil visqueen under slab
                             areas underlain by an additional 2 inches of sand.

First/Second Floor           2 1/2" thick lightweight structural concrete over
                             metal decking with 6x6 by 1.4 x 1.4 welded wire
                             mesh reinforcing.

Walls                        Precast or GFRC panels with selected exposed
                             aggregate architecture finish. Thickness as
                             determined by the structural engineer.

Trash Enclosures             6'-0" high cast in-place, precast concrete or
                             masonry with finish to match building. Enclosure
                             will provide for a total of 5 trash bins located
                             per plan.

Concrete Pads                Concrete pad only provided for mechanical central
                             plant, hazardous materials enclosure area and
                             emergency generator.

DIVISION 4 MASONRY

Basement/Garage              Basement wall to be solid grouted CMU. High-
                             strength CMU reinforced to resist lateral soil
                             pressure.

                                        4
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 5

Retaining Walls              Construct retaining walls as required by site plan.
                             Waterproof all basement and site retaining walls.

Mechanical Screening         Allocated portion of screening and gates provided
                             by Tenant Improvement in accordance with Tenant's
                             respective rentable square footage.

DIVISION 5 METALS

Columns                      Steel columns, (approximate 30'x30' bay spacing)
                             base plates and connections as determined by the
                             structural engineer. Steel columns located in
                             parking areas will require concrete protection from
                             vehicles up to a height of 42".

Roof Framing                 All major roof framing to consist of wide flange
                             steel girders (approximate 30'x30' bay spacing)
                             over 20 gauge metal decking. Roof loading will be
                             20 psf live load.

First and Second Floor       First and second floor framing to consist of
design Framing               composite steel beam over 3" 20-gauge vented metal
                             decking. Floor loading provided as follows:

                             Exit corridors          100 psf live load
                             Floor loads             125 psf live load

                             Floor assembly (2 1/2" L.W. concrete over metal
                             deck) is a one-hour rated assembly. Fire proofing
                             is proposed at beams and columns at basement/ first
                             floor occupancy separation. Special vibration
                             protection/assembly or added thickness concrete by
                             Tenant Improvement.

Exit Stairs                  Provide seven (7) flights of steel stairs with
                             concrete poured pan treads. Architectural shaped
                             stainless steel handrails with guardrails on both
                             sides of stairs.

Miscellaneous                Concrete panels embeds, mechanical screen posts,
                             steel roof access ladder and trash enclosures
                             hardware will be provided under this section of
                             work.

Mechanical Louver Shafts     Aluminum louver system with high performance
                             "metallic xl" (kynar) finish, including all
                             necessary structural support.

DIVISION 6 WOOD AND PLASTIC

Rough Carpentry              All wood-framing and bracing shall conform to
                             applicable requirements for lumber grading as
                             specified in West Coast Lumber Inspection Bureau
                             Grading and Dressing Rule No. 16 the Western Wood
                             Products Association, and the American Plywood. In
                             addition to complying with applicable codes and
                             regulations, comply with

                                        5
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 6

                             pertinent recommendations contained in 1994 edition
                             UBC chapter 25.

Finished Carpentry           All finished carpentry shall conform to the
                             applicable requirements for "Custom Grade" of the
                             Manual of Millwork of the Woodwork Institute of
                             California, the West Cost Lumberman's Association
                             Grading and Dressing Rules No. 16 the Western Wood
                             Products Association, The National Hardwood Lumber
                             Association and The American Plywood Association.

DIVISION 7 MOISTURE AND THERMAL PROTECTION

Membrane Roofing             Roof shall have a 10-year bondable, four-ply
                             fiberglass built-up roofing system with capsheet
                             (i.e., Manville specification 4 GIC with R-19
                             polyisocyanurate rigid insulation board, or
                             approved equal).

Building/Sound & Thermal     Batt acoustical insulation at core restroom and
Insulation                   elevator room walls. All other acoustical
                             insulation to be provided by Tenant Improvement.

Basement and Site Retaining  Paraseal waterproofing membrane system with
Walls                        prefabricated site retaining walls. Drainage
                             composite board and perforated subdrains.

Roof Drainage                Provide internal PVC roof and overflow drains. Roof
                             drains to connect to below grade storm drain where
                             accessible or daylight at face of curb or building
                             wall in loading areas. Minimum roof slope to be
                             1/4" per foot.

Sealants                     Utilize silicone base sealant at all glazing
                             conditions. Concrete panel joints are to receive
                             polyurethane sealant with 1" polyurethane backer
                             rod. Sealant used in walking surfaces shall be
                             polyurethane type. Colors to be selected by
                             Architect.

Sheet Metal                  Provide all sheet metal work for the building,
                             complete; including reglets, and counter flashing
                             for roofing. Materials to be galvanized sheet
                             metal, 24 gauge minimum thickness.

DIVISION 8 DOOR AND WINDOWS

Main Entrance                Provide "Herculite" all glass system including two
                             pair of 3'-0" x 8'-0" doors at main entrance.
                             (First and Second Floor)

Secondary Entrance Doors     Provide a total of (4) double and (6) single narrow
                             stile aluminum glass doors or as required by code.
                             Frame finish to be as specified in "Aluminum
                             Framing" below.

Garage Doors                 High cycle motorized overhead coiling door at
                             garage entry and at loading dock.

                                        6
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 7

Hollow Metal Doors           3'-0 x 7'-0 painted hollow metal at building core
                             restrooms and garage elevator vestibules.

Hardware                     Hardware for exterior doors and building core
                             included in shell building

Aluminum                     Extruded aluminum sections with off-set flush
                             glazed; both captured and silicone butt joints at
                             horizontal and vertical mullions framing system.
                             Interior and exterior color finish to be factory
                             applied, high performance "metallic XL" (kynar)
                             finish.

Glass & Glazing              Glass to be provided as follows:
                             Curtain Wall Glass: 1/4" High performance: Greylite
                             14/Solar grey/Solar grey eclipse and clear, or
                             comparable color 1/4" Spandrel glass

DIVISION 9 FINISHES - (PROVIDED AT CORE/LOBBY/PUBLIC RESTROOM AREAS ONLY)

Carpeting                    Carpet in Tenant Areas to be provided by Tenant
                             Improvement. Carpeting in common areas to be
                             provided by Landlord where applicable.

Vinyl Flooring               Vinyl flooring in Tenant Areas to be provided by
                             Tenant Improvement. Vinyl flooring in common areas
                             to be provided by Landlord where applicable.

Ceramic Tile                 Ceramic tile flooring with 48" high, ceramic tile
                             wainscot at all wet walls and returns from wet
                             walls. Full height ceramic tile at showers.

Painting                     Enamel paint on exterior steel surfaces, metal
                             doors and frames to receive paint: Primer + 2 coats
                             at exterior.

Metal Framing & Furring      Steel studs shall be 16, 20 and 25 gauge as
                             indicated on drawings or as required. Drywall
                             furring channels shall be 26 gauge "hat" sections.
                             Backing plates shall be 18 Ga. steel of proper size
                             to accommodate fastenings and fastened to 20 gauge
                             steel studs. See drawings for specific size and
                             location.

Gypsum & Drywall             Provide gypsum wallboard at designated locations
                             shown. Board thickness to be 5/8" at vertical and
                             5/8" at horizontal surface applications. In areas
                             requiring fire ratings, wallboard shall be 5/8"
                             "Type X". In areas subject to moisture, use
                             water-resistant (WR) gypsum board.

                             Elevator shaft, electrical/tel rooms, and stairs
                             shafts included in shell building. Mechanical
                             shafts/enclosures provided by tenant.

Acoustical Ceilings          2x4 suspended tegular acoustical ceiling in T-bar
                             ceiling grid.

                                        7
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 8

DIVISION 10 SPECIALITIES- (PROVIDED BY LANDLORD AT CORE AREAS ONLY)

Toilet Accessories           Automatic Sensor type plumbing features

Toilet Partitions            Ceiling and/or floor supported solid laminate
                             toilet partitions & doors

Interior Signage             Accessibility signage at restrooms, building
                             directory, and life safety signage as required by
                             code to be provided by Landlord. All other interior
                             signage by Tenant Improvement.

Exterior Signage             One new monument sign outside this building.
                             Lettering and graphics by Tenant.

Fire Extinguishers           Provide as required by code for shell building. All
                             others provided by Tenant Improvement.

Roof Hatch                   Roof access hatch and ladder provided above one
                             stairwell.

DIVISION 11 EQUIPMENT

                             Dock bumpers provided. Dock leveler by Tenant
                             Improvement, if needed.

DIVISION 12 FURNISHINGS

                             Not Applicable

DIVISION 13 SPECIAL CONSTRUCTION

                             Not Applicable

DIVISION 14 CONVEYING SYSTEMS

Elevators                    Provide one 2500 Ib. capacity, 150 feet per minute,
                             3-stop hydraulic passenger elevator located in main
                             lobby, complete with standard cab finishes. Provide
                             one 4500 Ib. capacity, 3-stop service elevator.

DIVISION 15 PLUMBING & HVAC SYSTEMS

Plumbing                     Sanitary waste, domestic cold and hot water,
                             industrial cold and hot waste and natural gas
                             stubbed to building shell and central plant yard.
                             Main service backflow preventer is provided.
                             Complete plumbing systems provided to core
                             improvements (restrooms, janitor's closet at

                                        8
<PAGE>

Alexandria Technology Center - Science Park
OUTLINE SPECIFICATIONS
June 17, 1999 Page 9

                             each of two floors; showers at 1st Floor).
                             Roof/overflow drains and hose bibs are provided for
                             shell. All other plumbing distribution and systems
                             provided by Tenant Improvement.

HVAC                         Garage exhaust system and core restroom exhaust
                             provided by Landlord. All other HVAC systems
                             including central mechanical plant and central
                             mechanical plant control systems to be allocated by
                             respective Tenant Improvement.

DIVISION 16 ELECTRICAL SYSTEMS

                             Main service switchgear and main feeder conduits to
                             garage level provided. Distribution provided only
                             to shell and core improvements. Site lighting
                             provided at drives and parking areas. All other
                             distribution provided by Tenant Improvements.
                             Electrical distribution to central plant, hazardous
                             materials enclosure, and tenant areas in garage to
                             be allocated by respective Tenant Improvement.

                             Telephone, data and cable TV service provided to
                             garage.

                             Electrical related to controls within tenant space,
                             plumbing equipment and HVAC systems (except
                             restrooms and garage exhaust) to be provided by
                             Tenant Improvement.

                        ***END OUTLINE SPECIFICATIONS***

                                        9
<PAGE>

Commencement Date   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 1

                                    EXHIBIT D

                                COMMENCEMENT DATE

                       ACKNOWLEDGMENT OF COMMENCEMENT DATE

         This ACKNOWLEDGMENT OF COMMENCEMENT DATE dated as of ___________,1999
is made by ARE -10933 NORTH TORREY PINES, LLC, a Delaware limited liability
company ("LANDLORD"), and IDEC PHARMACEUTICALS CORPORATION, a Delaware
corporation ("TENANT") and is attached to and made a part of the Lease dated
June 24, 1999 (the "Lease"), by and between Landlord and Tenant. Any initially
capitalized terms used but not defined herein shall have the meanings given them
in the Lease.

         Landlord and Tenant hereby acknowledge and agree, for all purposes of
the Lease, that the Commencement Date of the Term of the Lease is_____________,
1999.

         IN WITNESS WHEREOF, Landlord and Tenant have executed this
ACKNOWLEDGMENT OF COMMENCEMENT DATE to be effective on the date first above
written.

                                  TENANT:

                                  IDEC PHARMACEUTICALS CORPORATION,
                                  a Delaware corporation

                                  By:___________________________________________
                                  Its:__________________________________________

                                  LANDLORD:

                                  ARE-10933 NORTH TORREY PINES, LLC,
                                  a Delaware limited liability company

                                  By:    ALEXANDRIA REAL ESTATE EQUITIES, INC.,
                                         a Maryland corporation, Managing Member

                                         By:____________________________________
                                         Its:___________________________________

<PAGE>

Rules and Regulations                    ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 1

                                    EXHIBIT E

                              RULES AND REGULATIONS

         1.       The sidewalk, entries, and driveways of the Project shall not
be obstructed by Tenant, or its agents, or used by them for any purpose other
than ingress and egress to and from the Premises.

         2.       Tenant shall not place any objects, including antennas,
outdoor furniture, etc., in the parking areas, landscaped areas or other areas
outside of its Premises, or on the roof of the Project.

         3.       Except for seeing-eye dogs and animals directly used in the
conduct of Tenant's business in the Premises which are kept in controlled
environments ("LABORATORY ANIMALS"), no animals shall be allowed in the offices,
halls, or corridors in the Project.

         4.       Tenant shall not disturb the occupants of the Building or
adjoining buildings by the use of any radio or musical instrument or by the
making of loud or improper noises.

         5.       Tenant shall not install or operate any steam or gas engine or
boiler, or other mechanical apparatus in the Premises, except as specifically
provided in the Lease. The use of oil, gas or inflammable liquids for heating,
lighting or any other purpose is expressly prohibited. Explosives or other
articles deemed extra hazardous shall not be brought into the Project.

         6.       Parking any type of recreational vehicles is specifically
prohibited on or about the Project. Except for the overnight parking of
operative vehicles, no vehicle of any type shall be stored in the parking areas
at any time. In the event that a vehicle is disabled, it shall be removed within
48 hours. There shall be no "For Sale" or other advertising signs on or about
any parked vehicle. All vehicles shall be parked in the designated parking areas
in conformity with all signs and other markings. All parking will be open
parking, and no reserved parking, numbering or lettering of individual spaces
will be permitted except as specified in the Lease.

         7.       Tenant shall maintain the Premises free from rodents, insects
and other pests, except for Laboratory Animals.

         8.       Landlord reserves the right to exclude or expel from the
Project any person who, in the judgment of Landlord, is intoxicated or under the
influence of liquor or drugs or who shall in any manner do any act in violation
of the Rules and Regulations of the Project.

         9.       Tenant shall not cause any unnecessary labor by reason of
Tenant's carelessness or indifference in the preservation of good order and
cleanliness. Landlord shall not be responsible to Tenant for any loss of
property on the Premises, however occurring, or for any damage done to the
effects of Tenant by the janitors or any other employee or person.

         10.      Tenant shall give Landlord prompt notice of any defects in the
water, lawn sprinkler, sewage, gas pipes, electrical lights and fixtures,
heating apparatus, or any other service equipment affecting the Premises.

         11.      Except as provided or permitted in the Lease, Tenant shall not
permit storage outside the Premises, including without limitation, outside
storage of trucks and other vehicles, or dumping of waste or refuse or permit
any harmful materials to be placed in any drainage system or sanitary system in
or about the Premises.

<PAGE>

Rules and Regulations                    ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 2

         12.      All moveable trash receptacles provided by the trash disposal
firm for the Premises must be kept in the trash enclosure areas, if any,
provided for that purpose.

         13.      No auction, public or private, will be permitted on the
Premises or the Project.

         14.      No awnings shall be placed over the windows in the Premises
except with the prior written consent of Landlord.

         15.      The Premises shall not be used for lodging, sleeping or
cooking (other than using convenience microwaves, drink and food vending
machines and similar items for Tenant's employees) or for any immoral or illegal
purposes or for any purpose other than that specified in the Lease. No gaming
devices shall be operated in the Premises.

         16.      Tenant shall ascertain from Landlord the maximum amount of
electrical current which can safely be used in the Premises, taking into account
the capacity of the electrical wiring in the Building and the Premises and the
needs of other tenants, and shall not use more than such safe capacity.
Landlord's consent to the installation of electric equipment shall not relieve
Tenant from the obligation not to use more electricity than such safe capacity.

         17.      Tenant assumes full responsibility for protecting the Premises
from theft, robbery and pilferage.

         18.      Tenant shall not install or operate on the Premises any
machinery or mechanical devices of a nature not directly related to Tenant's
ordinary use of the Premises (other than using convenience microwaves, drink and
food vending machines and similar items for Tenant's employees) and shall keep
all such machinery free of vibration, noise and air waves which may be
transmitted beyond the Premises.

<PAGE>

Tenant's Personal Property               ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 1

                                    EXHIBIT F

                           TENANT'S PERSONAL PROPERTY

1.       Autoclave(s)

2.       Glass Washer(s)

3.       Glass Dryer(s)

4.       Phone Systems (excluding cabling)

5.       Computer Network Hardware (excluding cabling)

6.       Security System(s) (excluding cabling)

<PAGE>

Estoppel Certificate                     ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 1

                                    EXHIBIT G

                              ESTOPPEL CERTIFICATE

         THIS TENANT ESTOPPEL CERTIFICATE ("CERTIFICATE"), dated as of________,
19___, is executed by___________________("TENANT") in favor of [BUYER],
a_________________ , together with its nominees, designees and assigns
(collectively, "BUYER"), and in favor of _________________, together with its
nominees, designees and assigns (collectively, "LENDER").

                                    RECITALS

         A. Buyer and ___________("LANDLORD"), have entered into that certain
Purchase and Sale Agreement and Joint Escrow Instructions, dated as
of___________________, 19___(the "PURCHASE AGREEMENT"), whereby Buyer has agreed
to purchase, among other things, the improved real property located in the City
of______________, County of______________, State of_____________, more
particularly described on Exhibit A attached to the Purchase Agreement (the
"PROPERTY").

         B. Tenant and Landlord have entered into that certain Lease Agreement,
dated as of _______________ (together with all amendments, modifications,
supplements, guarantees and restatements thereof, the "LEASE"), for a portion of
the Property.

         C. Pursuant to the Lease, Tenant has agreed that upon the request of
Landlord, Tenant would execute and deliver an estoppel certificate certifying
the status of the Lease.

         D. In connection with the Purchase Agreement, Landlord has requested
that Tenant execute this Certificate with an understanding that Lender will rely
on the representations and agreements below in granting to Buyer a loan.

         NOW, THEREFORE, Tenant certifies, warrants, and represents to Buyer and
Lender as follows:

         SECTION 1. LEASE.

         Attached hereto as Exhibit B is a true, correct and complete copy of
the Lease, including the following amendments, modifications, supplements,
guarantees and restatements thereof, which together represent all of the
amendments, modifications, supplements, guarantees and restatements thereof:

_______________________________________________________________________
_______________________________________________________________________.
(If none, please state "None.")

         SECTION 2. LEASED PREMISES.

         Pursuant to the Lease, Tenant leases those certain premises (the
"LEASED PREMISES") consisting of approximately______________________rentable
square feet within the Property, as more particularly described in the Lease. In
addition, pursuant to the terms of the Lease, Tenant has the [non-exclusive]
right to use [_____parking spaces/the parking area] located on the Property
during the term of the Lease. [Cross-out the preceding sentence or portions
thereof if inapplicable.]

         SECTION 3. FULL FORCE OF LEASE.

         The Lease has been duly authorized, executed and delivered by Tenant,
is in full force and effect, has not been terminated, and constitutes a legally
valid instrument, binding and enforceable

<PAGE>

Estoppel Certificate                     ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 2

against Tenant in accordance with its terms, subject only to applicable
limitations imposed by laws relating to bankruptcy and creditor's rights.

         SECTION 4. COMPLETE AGREEMENT.

         The Lease constitutes the complete agreement between Landlord and
Tenant for the Leased Premises and the Property, and except as modified by the
Lease amendments noted above (if any), has not been modified, altered or
amended.

         SECTION 5. ACCEPTANCE OF LEASED PREMISES.

         Tenant has accepted possession and is currently occupying the Leased
Premises.

         SECTION 6. LEASE TERM.

         The term of the Lease commenced on_____________________ and ends on
______________________, subject to the following options to extend:____________

______________________________.
(If none, please state "None.")

         SECTION 7. PURCHASE RIGHTS.

         Tenant has no option, right of first refusal, right of first offer, or
other right to acquire or purchase all or any portion of the Leased Premises or
all or any portion of, or interest in, the Property, except as follows:_________
____________________________________________________________________.
(If none, please state "None.")

         SECTION 8. RIGHTS OF TENANT.

         Except as expressly stated in this Certificate, Tenant:

         (a) has no right to renew or extend the term of the Lease;

         (b) has no option or other right to purchase all or any part of the
Leased Premises or all or any part of the Property;

         (c) has no right, title, or interest in the Leased Premises, other than
as Tenant under the LEASE.

         SECTION 9. RENT.

         (a) The obligation to pay rent under the Lease commenced on__________.
The rent under the Lease is current, and Tenant is not in default in the
performance of any of its obligations under the Lease.

         (b) Tenant is currently paying base rent under the Lease in the amount
of $___________________ per month. Tenant has not received and is not presently
entitled to any abatement, refunds, rebates, concessions or forgiveness of rent
or other charges, free rent, partial rent, or credits, offsets or reductions in
rent, except as follows:________________________________________________________
_______________________________________________________________________.
(If none, please state "None.")

<PAGE>

Estoppel Certificate                     ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 3

         (c) Tenant's estimated share of operating expenses, common area
charges, insurance, real estate taxes and administrative and overhead expenses
is________% and is currently being paid at the rate of $_____________per month,
payable to:_________________________________________________________

         (d) There are no existing defenses or offsets against rent due or to
become due under the terms of the Lease, and there presently is no default or
other wrongful act or omission by Landlord under the Lease or otherwise in
connection with Tenant's occupancy of the Leased Premises, nor is there a state
of facts which with the passage of time or the giving of notice or both could
ripen into a default on the part of Tenant, or to the best knowledge of Tenant,
could ripen into a default on the part of Landlord under the Lease, except as
follows:________________________________________________________________________
____________________________________________________.
(If none, please state "None.")

         SECTION 10. SECURITY DEPOSIT.

         The amount of Tenant's security deposit held by Landlord under the
Lease is $________________.

         SECTION 11. PREPAID RENT.

         The amount of prepaid rent, separate from the security deposit, is
$________________, covering the period from_________to________.

         SECTION 12. INSURANCE.

         All insurance, if any, required to be maintained by Tenant under the
Lease is presently in effect.

         SECTION 13. PENDING ACTIONS.

         There is not pending or, to the knowledge of Tenant, threatened against
or contemplated by the Tenant, any petition in bankruptcy, whether voluntary or
otherwise, any assignment for the benefit of creditors, or any petition seeking
reorganization or arrangement under the federal bankruptcy laws or those of any
state.

         SECTION 14. TENANT IMPROVEMENTS.

         As of the date of this Certificate, to the best of Tenant's knowledge,
Landlord has performed all obligations required of Landlord pursuant to the
Lease; no offsets, counterclaims, or defenses of Tenant under the Lease exist
against Landlord; and no events have occurred that, with the passage of time or
the giving of notice, would constitute a basis for offsets, counterclaims, or
defenses against Landlord, except as follows:__________________________________
_______________________________________________________________________________.
(If none, please state "None.")

         SECTION 15. ASSIGNMENTS BY LANDLORD.

         Tenant has received no notice of any assignment, hypothecation or
pledge of the Lease or rentals under the Lease by Landlord. Tenant hereby
consents to an assignment of the Lease and rents to be executed by Landlord to
Lender in connection with the Loan and acknowledges that said assignment does
not violate the provisions of the Lease. Tenant acknowledges that the interest
of the Landlord under the Lease is to be assigned to Lender solely as security
for the purposes specified in said assignment and Lender shall have no duty,
liability or obligation whatsoever under

<PAGE>

Estoppel Certificate                     ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 4

the Lease or any extension or renewal thereof, either by virtue of said
assignment or by any subsequent receipt or collection of rents thereunder,
unless Lender shall specifically undertake such liability in writing or, subject
to Section 18(a) hereof, Lender forecloses and takes title to the Properly.
Tenant agrees that upon receipt of a written notice from Lender of a default by
Landlord under the Loan, Tenant will thereafter pay rent to Lender in accordance
with the terms of the Lease.

         SECTION 16. ASSIGNMENTS BY TENANT.

         Tenant has not sublet or assigned the Leased Premises or the Lease or
any portion thereof to any sublessee or assignee. No one except Tenant and its
employees will occupy the Leased Premises. The address for notices to be sent to
Tenant is as set forth in the Lease.

         SECTION 17. ENVIRONMENTAL MATTERS.

         The operation and use of the Leased Premises does not involve the
generation, treatment, storage, disposal or release into the environment of any
hazardous materials, regulated materials and/or solid waste, except those used
in the ordinary course for the Permitted Use, as defined in the Lease, or
otherwise used in accordance with all applicable laws.

         SECTION 18. SUCCESSION OF INTEREST.

         Tenant agrees that, in the event Buyer or Lender succeeds to the
interest of Landlord under the Lease:

         (a) Buyer or Lender shall not be liable for any act or omission of any
prior landlord (including Landlord);

         (b) Lender shall not be liable for the return of any security deposit;

         (c) Buyer or Lender shall not be bound by any rent or additional rent
which Tenant might have prepaid under the Lease for more than the current month;

         (d) Buyer or Lender shall not be bound by any amendments or
modifications of the Lease made without prior consent of Buyer or Lender;

         (e) Buyer or Lender shall not be subject to any offsets or defenses
which Tenant might have against any prior landlord (including Landlord); or

         (f) Buyer or Lender shall not be liable under the Lease to Tenant for
the performance of Landlord's obligations under the Lease beyond Buyer or
Lender's interest in the Property except to the extent of any Excess Tl Costs
held by any such Buyer or Lender and not delivered to any successor Buyer or
Lender.

         SECTION 20. NOTIFICATION BY TENANT.

         From the date of this Certificate and continuing until ______________,
Tenant agrees to immediately notify Buyer and Lender, in writing by registered
or certified mail, return receipt requested, at the following addresses, on the
occurrence of any event or the discovery of any fact that would make any
representation contained in this Certificate inaccurate:

         If To Buyer:      __________________________________
                           __________________________________
                           __________________________________
                           __________________________________
                           __________________________________

<PAGE>

Estoppel Certificate                     ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 5

         With A Copy To:   __________________________________
                           __________________________________
                           __________________________________
                           __________________________________
                           __________________________________

         If To Lender:     __________________________________
                           __________________________________
                           __________________________________
                           __________________________________
                           __________________________________

         Tenant makes this Certificate with the knowledge that it will be relied
upon by Buyer and Lender in agreeing to purchase the Property.

         Tenant has executed this Certificate as of the date first written above
by the person named below, who is duly authorized to do so.

TENANT:                    ________________________________________________,
                           a_____________________________________________

                           By:
                                __________________________________
                                Name: ____________________________
                                Its:  ____________________________

<PAGE>

Legal Description   ARC Science Center/IDEC Pharmaceuticals Corporation - Page 1

                                    EXHIBIT A

                                LEGAL DESCRIPTION

<PAGE>

Copy of Lease       ARC Science Center/IDEC Pharmaceuticals Corporation - Page 1

                                    EXHIBIT B

                                  COPY OF LEASE

<PAGE>

Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 1

                                    EXHIBIT H

                       SUBORDINATION, NON-DISTURBANCE AND
                              ATTORNMENT AGREEMENT

         THIS SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT is made
and entered into as of_____________________, 19___("AGREEMENT"), by and between
ARE-10933 NORTH TORREY PINES, LLC, a Delaware limited liability company together
with its nominees, designees and assigns (collectively, "LANDLORD"), __________,
a____________________ ("TENANT"), and____________________________,
a___________________("MORTGAGEE").

         WHEREAS, Mortgagee is making a loan to Landlord and others evidenced by
a certain promissory note ("NOTE"), and secured by, among other things, a deed
of trust/mortgage to be recorded prior hereto in the public records of the City
of___________, County of____________, State of _____________________("MORTGAGE")
constituting a lien upon the real property described in Exhibit A hereto (the
"REAL PROPERTY"): and

         WHEREAS,_____________________and Tenant have entered into a Lease
Agreement dated as of______________ ___, 19__ ("LEASE"), for certain leased
premises encompassing_____________________ located in _________________,
containing approximately________________________________ net square feet
(hereinafter collectively referred to as "PREMISES"); and

         WHEREAS, the Lease is subordinate to the Mortgage and to the right,
title, and interests of Mortgagee thereto and thereunder; and

         WHEREAS, Mortgagee wishes to obtain from Tenant certain assurances that
Tenant will attom to Mortgagee in the event of a foreclosure by Mortgagee or the
exercise of other rights under the Mortgage; and

         WHEREAS, Tenant wishes to obtain from Mortgagee certain assurances that
Tenant's possession of the Premises will not, subject to the terms and
conditions of this Agreement, be disturbed by reason of a foreclosure of the
lien of the Mortgage on the Real Property; and

         WHEREAS, Tenant and Mortgagee are both willing to provide such
assurances to each other upon and subject to the terms and conditions of this
Agreement.

         NOW, THEREFORE, in consideration of the above, the mutual promises
hereinafter set forth, and other good and valuable consideration, the receipt
and sufficiency of which are hereby acknowledged, the parties hereto mutually
agree as follows:

         1.       AFFIRMATION. Tenant hereby agrees that the Lease now is and
shall be subject and subordinate in all respects to the Mortgage and to all
renewals, modifications and extensions thereof until such time that the Mortgage
is released, satisfied or otherwise discharged, subject to the terms and
conditions of this Agreement. Landlord and Tenant hereby affirm that the Lease
is in full force and effect and that the Lease has not been modified or amended.
Mortgagee hereby confirms that it is the holder of the Note and the beneficiary
of the Mortgage and has full power and authority to enter into this Agreement.

         2.       ATTORNMENT AND NON-DISTURBANCE.

         (a)      So long as Tenant is not in default under the Lease (beyond
Tenant's receipt of notice from Landlord and any grace period granted tenant
under the Lease to cure such default)

<PAGE>

Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 2

as would entitle the Landlord to terminate the Lease or would cause without any
further action of the Landlord, the termination of the Lease or would entitle
the Landlord to dispossess Tenant thereunder then Mortgagee agrees with Tenant
that in the event the interest of Landlord shall be acquired by Mortgagee or in
the event Mortgagee comes into possession of or acquires title to the Real
Property by reason of foreclosure or foreclosure sale or the enforcement of the
Mortgage or the Note or other obligation secured thereby or by a conveyance in
lieu thereof, or as a result of any other means then:

                  (i)      Subject to the provisions of this Agreement, Tenant's
         occupancy and possession of the Premises and Tenant's rights and
         privileges under the Lease or any extensions, modifications or renewals
         thereof or substitutions therefor (in accordance with the Lease and the
         Mortgage) shall not be disturbed, diminished or interfered with by
         Mortgagee during the term of the Lease (or any extensions or renewals
         thereof provided for in the Lease);

                  (ii)     Mortgagee will not join Tenant as a party defendant
         in any action or proceeding for the purpose of terminating Tenant's
         interest and estate under the Lease because of any default under the
         Mortgage; and

                  (iii)    The Lease shall continue in full force and effect and
         shall not be terminated except in accordance with the terms of the
         Lease.

         (b)      Tenant shall be bound to Mortgagee under all of the terms,
covenants and conditions of the Lease for the balance of the term thereof
remaining (and any extensions or renewals thereof which may be effected in
accordance with any option contained in the Lease) with the same force and
effect as if Mortgagee were the landlord under the Lease, and Tenant does hereby
agree to attorn to Mortgagee as its landlord, said attornment to be effective
and self-operative without the execution of any other instruments on the part of
either party hereto immediately upon Mortgagee's succeeding to the interest of
Landlord under the Lease. Upon request of Lender or such Purchaser, Tenant shall
execute and deliver to Lender or such Purchaser an agreement reaffirming such
attornment. Tenant hereby agrees that any right of first refusal or right of
first offer to purchase the Property which Tenant may have pursuant to the terms
of the Lease shall not be applicable to Mortgagee's or any Purchaser's
acquisition of the Property by foreclosure, deed in lieu of foreclosure, other
transaction related thereto or in substitution thereof, trustee sale or other
similar statutory conveyance. The foregoing shall not be construed as
diminishing or eliminating any of Tenant's Right of First Refusal or First Offer
to purchase the property that remain valid in the Lease after such Mortgagee's
or Purchaser's acquisition.

         (c)      In the event that the Mortgage is foreclosed and any party
("PURCHASER") other than Mortgagee purchases the Premises and succeeds to the
interest of Landlord under the Lease, Tenant shall likewise be bound to
Purchaser and Tenant hereby covenants and agrees to attom to Purchaser in
accordance with all of the provisions of this Agreement; provided, however, that
Purchaser shall have transmitted to Tenant a written document in recordable
form, whereby Purchaser agrees to recognize Tenant as its lessee under the Lease
and agrees to be directly bound to Tenant for the performance and observance of
all the terms and conditions of the Lease required to be performed or observed
by Landlord thereunder, subject to and in accordance with the terms of this
Agreement.

         (d)      Mortgagee agrees that if Mortgagee shall succeed to the
interest of Landlord under the Lease as above provided, Mortgagee shall be bound
to Tenant under all of the terms, covenants, and conditions of this Lease, and
Tenant shall, from and after Mortgagee's succession to the interest of Landlord
under the Lease, have the same remedies against Mortgagee that Tenant might have
had under the Lease against Landlord if Mortgagee had not succeeded to the
interest of Landlord; provided, however, that Mortgagee (and Purchaser, as the
case may be) shall not be:

<PAGE>

Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 3

                  (i)      liable for any act or omission of any prior lessor
         (including Landlord) occurring prior to the date that Mortgagee or
         purchaser acquired title to the Premises; or

                  (ii)     subject to any offsets, counterclaims or defenses
         which Tenant might have against any prior lessor (including Landlord);
         or

                  (iii)    bound by any previous payment of rent or additional
         rent for a period greater than 1 month unless such prepayment shall
         have been consented to in writing by Mortgagee; or

                  (iv)     bound by any amendment or modification of the Lease
         made prior to the date Mortgagee or Purchaser succeeds to the interest
         of Landlord without Mortgagee's written consent; or

                  (v)      liable to Tenant for any loss of business or any
         other indirect or consequential damages from whatever cause; provided,
         however, no inference shall be drawn from this clause (v) that Tenant
         would otherwise be entitled (or not entitled) to recover for loss of
         business or any other indirect or consequential damages; or

                  (vi)     liable for the return of any security deposit unless
         such deposit has been paid over to the Mortgagee.

         The foregoing shall not be construed to modify or limit any right
         Tenant may have at law or in equity against Landlord or any other prior
         owner of the Real Property.

         3.       NOTICES. All notices required or permitted to be given
pursuant to this Agreement shall be in writing and shall be sent postage
prepaid, by certified mail, return receipt requested or other nationally
utilized overnight delivery service. All notices shall be deemed delivered when
received or refused. Rejection or other refusal to accept or inability to
deliver because of changed address of which no notice has been given shall
constitute receipt of the notice, demand or request sent. Any such notice if
given to Tenant shall be addressed as follows:

                         _______________________________________
                         _______________________________________
                         _______________________________________
                         _______________________________________
                         _______________________________________

         if given to Landlord shall be addressed as follows:

                         ARE-10933 North Torrey Pines, LLC
                         135 N. Los Robles Avenue
                         Suite 250
                         Pasadena, California 91101
                         Attention: General Counsel

         if given to Mortgagee shall be addressed as follows:

                         _______________________________________
                         _______________________________________
                         _______________________________________
                         _______________________________________

<PAGE>

Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 4

         4.       SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon
and inure to the benefit of the parties hereto and their respective successors
and assigns. The words "foreclosure" and "foreclosure sale" as used herein shall
be deemed to also include the acquisition of Landlord's estate in the Real
Property by voluntary deed, assignment or other conveyance or transfer in lieu
of foreclosure.

         5.       MODIFICATIONS TO LEASE. Tenant shall not modify or amend the
Lease or terminate the same without Mortgagee's prior written consent. If
Mortgagee fails to provide Tenant with a written approval of the proposed
modification, amendment or termination within 10 Business Days after notice to
Mortgagee of such proposal, then Mortgagee shall be deemed to have rejected such
proposal.

         6.       ADDITIONAL AGREEMENTS. Tenant agrees that:

         (a)      it shall give Mortgagee copies of all notices of default and
requests for approval or consent by Landlord that Tenant gives to Landlord
pursuant to the Lease in the same manner as they are given to Landlord and no
such notice or other communication shall be deemed to be effective until a copy
is given to Mortgagee;

         (b)      whenever any consent or approval by Landlord is required to be
obtained by Tenant or is requested by Tenant such consent or approval shall not
be effective until it is also confirmed by or obtained from Mortgagee, provided
that Mortgagee shall respond within 30 days after Mortgagee's receipt of
Tenant's request and failure of Mortgagee to respond in such time period shall
be deemed to be a denial of such consent or approval;

         (c)      in all provisions of the Lease where Landlord is indemnified,
the reference to Landlord as an indemnitee shall be deemed to include Mortgagee
and any Purchaser and such agreement of indemnification shall survive the
repayment of the loan secured by the Mortgage and, to the extent provided in the
Lease, the expiration or termination of the Lease;

         (d)      Tenant shall name Mortgagee and any Purchaser as additional
insureds and loss payees, as applicable and appropriate, on all insurance
policies required by the Lease; and

         (e)      this Agreement satisfies any condition or requirement in the
Lease relating to the granting of a non-disturbance agreement by Mortgagee, and
in the event that there are inconsistencies between the terms and provisions of
this Agreement and the terms and provisions of the Lease dealing with
non-disturbance by Mortgagee, the terms and provisions hereof shall be
controlling; and

         (f)      Mortgagee shall have no liability under the Lease until
Mortgagee succeeds to the rights of the Landlord under the Lease, and then only
during such period as Mortgagee is the Landlord. At all times during which
Mortgagee is liable under the Lease, Mortgagee's liability shall be limited to
Mortgagee's interest in the Real Property.

         7.       MORTGAGEE CURE RIGHTS. If Landlord shall have failed to cure
any default within the time period provided for in the Lease (including any
applicable notice and grace periods), but not prior thereto Tenant exercises any
right to terminate the Lease, Mortgagee, shall have an additional 30 days within
which to cure such default, or if such default cannot by the exercise of
reasonable efforts by Mortgagee be cured within such period, then such
additional time as may be reasonable necessary to effect such a cure (including,
if necessary, sufficient time to complete foreclosure proceedings) provided that
within such 30-day period Mortgagee shall commence and thereafter diligently
pursue remedies to cure such default. The Lease shall not be terminated (i)
while such remedies are being diligently pursued or (ii) based upon a default
which is personal to Landlord and therefore not susceptible to cure by Mortgagee
or which requires possession of the Premises to cure. Mortgagee shall in no
event be obligated to cure any such default by Landlord unless it

<PAGE>

Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 5

forecloses. Nothing in this Section 7 shall affect any of Tenant's termination
rights under the Lease due to casualty or condemnation or Tenant's "self-help"
rights under Section 31 of the Lease.

         8.       DIRECTION TO PAY. Landlord hereby directs Tenant and Tenant
agrees to make all payments of amounts owed by Tenant under the Lease directly
to Mortgagee from and after receipt by Tenant of notice from Mortgagee directing
Tenant to make such payments to Mortgagee. (As between Landlord and Mortgagee,
the foregoing provision shall not be construed to modify any rights of Landlord
under or any provisions of the Mortgage or any other instrument securing the
Note).

         9.       CONDITIONAL ASSIGNMENT. With reference to any assignment by
Landlord of Landlord's interest in the Lease, or the rents payable thereunder,
conditional in nature or otherwise, which assignment is made to Mortgagee,
Tenant agrees that the execution thereof by Landlord, and the acceptance thereof
by Mortgagee shall never be treated as an assumption by Mortgagee of any of the
obligations of Landlord under the Lease unless and until Mortgagee shall have
succeeded to the interest of Landlord. The foregoing sentence shall not affect
any of Tenant's rights against Landlord under the Lease.

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Subordination Agreement                  ARC Science Center/IDEC Pharmaceuticals
                                                            Corporation - Page 6

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
properly executed by their duly authorized representatives as of the date first
above written.

LANDLORD:                ________________________________________________,
                         a_____________________________________________

                         By:
                              __________________________________
                              Name: ____________________________
                              Its:  ____________________________

TENANT:                  ________________________________________________,
                         a_____________________________________________

                         By:
                              __________________________________
                              Name: ____________________________
                              Its:  ____________________________

MORTGAGEE:               ________________________________________________,
                         a_____________________________________________

                         By:
                              __________________________________
                              Name: ____________________________
                              Its:  ____________________________

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