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                                                                   EXHIBIT 10.24


                             MASTER EQUIPMENT LEASE

Under this Master Equipment Lease (the "Lease"), dated as of September 1, 1993,
Phoenix Leasing Incorporated ("Lessor") hereby leases to Signal Pharmaceuticals,
Inc. ("Lessee"), and Lessee hereby leases from Lessor, the equipment (herein
called "Equipment") which is described on the schedule attached hereto or any
subsequently-executed schedule entered into by Lessor and Lessee and which
incorporates this Lease by reference. Any such schedules shall hereinafter
individually be referred to as a "Schedule" and collectively be referred to as
the "Schedules." Lessor hereby leases the Equipment to Lessee upon the following
terms and conditions:

      1.    TERM OF AGREEMENT. The term of this Lease begins on the date set
forth above and shall continue thereafter and be in effect so long as and at any
time any Schedule entered into pursuant to this Lease is in effect. The Initial
Term and rent payable with respect to each leased item of Equipment shall be as
set forth in and as stated in the respective Schedule(s). The terms of each
Schedule hereto are subject to all conditions and provisions of this Lease as
may at any time be amended.

      2.    NON-CANCELLABLE LEASE. This Lease and any Schedule cannot be
cancelled or terminated except as expressly provided herein. This Lease
(including all Schedules to this Lease) constitutes a net lease and Lessee
agrees that its obligations to pay all rent and other sums payable hereunder
(and under any Schedule) and the rights of Lessor and assignee in and to such
rent and other sums, are absolute and unconditional and are not subject to any
abatement, reduction, setoff, defense, counterclaim or recoupment due or alleged
to be due to, or by reason of, any past, present or future claims which Lessee
may have against Lessor, any assignee, the manufacturer or seller of the
Equipment, or against any person for any reason whatsoever.

      3.    LESSOR COMMITMENT. So long as no Event of Default or event which
with the giving of notice or passage of time, or both, could become an Event of
Default has occurred or is continuing, Lessor agrees to lease to Lessee the
groups of Equipment described on each Schedule, subject to the following
conditions: (i) that in no event shall Lessor be obligated to lease Equipment to
Lessee hereunder where the aggregate purchase price of all Equipment leased to
Lessee hereunder would exceed $1,000,000 no more than $100,000 of which may be
non-standard equipment and soft costs (such non-standard equipment and soft
costs may not, at any time, constitute greater than 10% of the then aggregate
funding amounts); (ii) the amount of Equipment purchased by Lessor at any one
time shall be at least equal to $50,000 except for a final advance which may be
less than $50,000; (iii) Lessor shall not be obligated to purchase Equipment
hereunder after May 1, 1994; (iv) all Lease documentation required by Lessor has
been executed by Lessee or provided by Lessee no later than October 1, 1993; (v)
the equipment described on the Schedule is acceptable to Lessor; (vi) with
respect to each funding Lessee has provided to Lessor each of the closing
documents described in Exhibit A hereto (which documents shall be in form and
substance acceptable to Lessor) and which list may be modified for each
subsequent funding; (vii) there is no material adverse change in Lessee's
condition, financial or otherwise and Lessee so certifies, from (yy) the date of
the most recent financial statements delivered by Lessee to Lessor prior to
execution of this Lease, to (zz) the date of the proposed lease of the
Equipment; (viii) Lessee is performing according to its business plan dated July
20, 1993 ("Business Plan"), as may be amended from time to time in form and
substance acceptable to Lessor; (ix) Lessor or its agent has inspected and
placed identification labels on the Equipment; (x) Lessee shall offer to Lessor
all lease transactions for Equipment contemplated by Lessee during the
commitment period of this Lease; however if Lessor declines to finance any such
transaction or Lessee and Lessor cannot agree upon terms, then Lessee shall be
free to seek such financing from


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any other third party; and (xi) Lessor has received in form and substance
acceptable to Lessor: (a) Lessee's interim financial statements signed by a
financial officer of Lessee; (b) evidence of Lessee's receipt of $2,100,000
equity; and (c) evidence of Lessee's $699,500 cash position as of July 31, 1993.

      4.    NO WARRANTIES BY LESSOR. (a) Lessee has selected both (i) the
Equipment and (ii) the suppliers (herein called "Vendor") from whom Lessor is to
purchase the Equipment. LESSOR MAKES NO WARRANTY EXPRESS OR IMPLIED AS TO ANY
MATTER WHATSOEVER, INCLUDING THE CONDITION OF THE EQUIPMENT, ITS MERCHANTABILITY
OR ITS FITNESS FOR ANY PARTICULAR PURPOSE, AND AS TO LESSOR, LESSEE LEASES THE
EQUIPMENT "AS IS" AND WITH ALL FAULTS. (b) If the Equipment is not properly
installed, does not operate as represented or warranted by Vendor or is
unsatisfactory for any reason, Lessee shall make any claim on account thereof
solely against Vendor and shall, nevertheless, pay Lessor all rent payable under
this Lease, Lessee hereby waiving any such claims as against Lessor. Lessor
hereby agrees to assign to Lessee solely for the purpose of making and
prosecuting any said claim, to the extent assignable, all of the rights which
Lessor has against Vendor for breach of warranty or other representation
respecting the Equipment. Lessor shall have no responsibility for delay or
failure to fill the order. (c) Lessee understands and agrees that neither the
Vendor nor any salesman or other agent of the Vendor is an agent of Lessor. No
salesman or agent of Vendor is authorized to waive or alter any term or
condition of this Lease, and no representations as to the Equipment or any other
matter by the Vendor shall in any way affect Lessee's duty to pay the rent and
perform its other obligations as set forth in this Lease. (d) Lessee hereby
requests Lessor to purchase Equipment from Vendor and to lease Equipment to
Lessee on the terms and conditions of the Lease set forth herein. (e) Lessee
hereby authorizes Lessor to insert in this Lease and each Schedule hereto the
serial numbers and other identification data of the Equipment when determined by
Lessor.

      5.    LESSEE'S REPRESENTATIONS AND WARRANTIES. Lessee represents and
warrants that (a) it is a corporation in good standing under the laws of the
state of its incorporation, and duly qualified to do business in each state
where the Equipment will be located; (b) it has full authority to execute and
deliver this Lease and perform the terms hereof, and this Lease has been duly
authorized and constitutes valid and binding obligations of Lessee enforceable
in accordance with its terms; (c) this Lease will not contravene any law,
regulation or judgment affecting Lessee or result in any breach of any agreement
or other instrument binding on Lessee; (d) no consent of Lessee's shareholders
or holder of any indebtedness, or filing with, or approval of, any governmental
agency or commission, is a condition to the performance of the terms hereof; (e)
there is no action or proceeding pending or threatened against Lessee before any
court or administrative agency which might have a materially adverse effect on
the business, financial condition or operations of Lessee; (f) no deed of trust,
mortgage or third party interest arising through Lessee will attach to the
Equipment or the Lease; (g) the Equipment will remain at all times under
applicable law, removable personal property, free and clear of any lien or
encumbrance in favor of Lessee or any other person, notwithstanding the manner
in which the Equipment may be attached to any real property; and (h) all credit,
financial and any other information submitted to Lessor herewith or any other
time is true and correct.

      6.    EQUIPMENT ORDERING. Lessee shall be responsible for all packing,
rigging, transportation and installation charges for the Equipment and Lessor
may separately invoice Lessee for such charges. Lessee has selected the
Equipment itself and shall arrange for delivery of Equipment so that it can be
accepted in accordance with Section 7 hereof. Lessee hereby agrees to indemnify
and hold Lessor harmless from any claims,


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liabilities, costs and expenses, including reasonable attorneys' fees, incurred
by Lessor arising out of any purchase orders or assignments executed by Lessor
with respect to any Equipment or services relating thereto.

      7.    LESSEE ACCEPTANCE. Lessee shall return to Lessor the signed and
dated Acceptance Notice attached to each Schedule hereto (a) acknowledging the
Equipment has been received, installed and is ready for use and (b) accepting it
as satisfactory in all respects for the purposes of this Lease. Lessor is
authorized to fill in the Rent Start Date on each Schedule in accordance with
the foregoing.

      8.    LOCATION; INSPECTION; LABELS. Equipment shall be delivered to and
shall not be removed from the Equipment "Location" shown on each Schedule
without Lessor's prior written consent. Lessor shall have the right to inspect
Equipment at any reasonable time. Lessee shall be responsible for all labor,
material and freight charges incurred in connection with any removal or
relocation of such Equipment which is requested by the Lessee and consented to
by Lessor, as well as for any charges due to the installation or moving of the
Equipment. The rental payments shall continue during any period in which the
Equipment is in transit during a relocation. Lessor or its agent shall mark and
label Equipment, which labels shall state Equipment is owned by Lessor, and
Lessee shall keep such labels on the Equipment as labeled by Lessor or its
agent.

      9.    EQUIPMENT MAINTENANCE. (a) General. Lessee will locate or base each
item of Equipment where designated in an Acceptance Notice and will reasonably
permit Lessor to inspect such item of Equipment and its maintenance records.
Lessee will at its sole expense comply with all applicable laws, rules,
regulations, requirements and orders with respect to the use, maintenance,
repair, condition, storage and operation of each item of Equipment. Except as
required herein, Lessee will not make any addition or improvement to any item of
Equipment that is not readily removable without causing material damage to any
item or impairing its original value or utility. Any addition or improvement
that is so required or cannot be so removed will immediately become the property
of Lessor. (b) Service and Repair. With respect to computer equipment, Lessee
has entered into, and will maintain in effect, Vendor's standard maintenance
contract or another contract satisfactory to Lessor for a period equal to the
term of each Schedule and extensions thereto which provides for the maintenance
of the Equipment and repairs and replacement parts thereof in good condition and
working order, all in accordance with the terms of such maintenance contract.
Lessee shall have the Equipment certified for the Vendor's standard maintenance
agreement prior to delivery to Lessor upon expiration of this Lease. With
respect to any other Equipment, Lessee will, at its sole expense, maintain and
service, and repair any damage to, each item of Equipment in a manner consistent
with prudent industry practice and Lessee's own practice so that such item of
Equipment is at all times (i) in the same condition as when delivered to Lessee,
except for ordinary wear and tear, (ii) in good operating order for the function
intended by its manufacturer's warranties and recommendations.

      10.   LOSS OR DAMAGE. Lessee assumes the entire risk of loss to the
Equipment through use, operation or otherwise. Lessee hereby indemnifies and
holds harmless Lessor from and against all claims, loss of rental payments,
costs, damages, and expenses relating to or resulting from any loss, damage or
destruction of the Equipment, any such occurrence being hereinafter called a
"Casualty Occurrence." On the first rental payment date following such Casualty
Occurrence, or, if there is no such rental payment date, thirty (30) days after
such Casualty Occurrence, Lessee shall (i) repair the Equipment, returning it to
good operating condition or (ii) replace the Equipment with identical equipment
in good condition and repair, the title to which shall vest in Lessor and which
thereafter shall be subject to the terms of this Lease; or (iii) pay to Lessor
(a) any


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unpaid amounts relating to such Equipment due Lessor under this Lease up to the
date of the Casualty Occurrence, and (b) a sum equal to the Casualty Value as
set forth in the Casualty Value table attached to each Schedule hereto for such
Equipment. Upon the making of such payment, the term of this Lease as to each
unit of Equipment with respect to which the Casualty Value was paid shall
terminate.

      11.   GENERAL INDEMNITY. Lessee will protect, indemnify and save harmless
Lessor from and against all liabilities, obligations, claims, damages,
penalties, causes of action, costs and expenses, imposed upon or incurred by or
asserted against Lessor or any assignee of Lessor by Lessee or any third party
by reason of the occurrence or existence (or alleged occurrence or existence) of
any act or event relating to or caused by the Equipment, including but not
limited to, consequential or special damages of any kind, or any failure on the
part of Lessee to perform or comply with any of the terms of this Lease. In the
event that any action, suit or proceeding is brought against Lessor by reason of
any such occurrence, Lessee, upon request of Lessor, will at Lessee's expense
resist and defend such action, suit or proceeding or cause the same to be
resisted and defended by counsel designated and approved by Lessor. Lessee's
obligations under this Section 11 shall survive the expiration of this Lease
with respect to acts or events occurring or alleged to have occurred prior to
the return of the Equipment to Lessor at the end of the Lease term.

      12.   INSURANCE. Lessee at its expense shall keep the Equipment insured
for the entire term and any extensions of this Lease against all risks for the
value of the Equipment and in no event for less than the Casualty Value of such
Equipment as specified on Exhibit C. Such insurance shall contain insurer's
agreement to give thirty (30) days written notice to Lessor before cancellation
or material change of any policy of insurance, and shall provide for (a) loss
payable endorsement to Lessor or any assignee of Lessor, and (b) public
liability and property damage insurance in an amount not less than $1,000,000,
naming Lessor as additional insured. Lessee will provide Lessor and any assignee
of Lessor with a certificate of insurance from the insurer evidencing Lessor's
or such assignee's interest in the policy of insurance. Such insurance shall
cover any Casualty Occurrence to any unit of Equipment. Notwithstanding anything
in Section 10 or this Section 12 to the contrary, this Lease and Lessee's
obligations hereunder and under each Schedule shall remain in full force and
effect with respect to any unit of Equipment which is not subject to a Casualty
Occurrence. If Lessee fails to provide or maintain insurance as required herein,
Lessor shall have the right, but shall not be obligated to obtain such
insurance. In that event, Lessee shall pay to Lessor the cost thereof.

      13.   TAXES. Lessee agrees to reimburse Lessor for, (or pay directly if
instructed by Lessor), and agrees to indemnify and hold Lessor harmless from,
all fees (including, but not limited to, license, documentation, recording and
registration fees), and all sales, use, gross receipts, personal property,
occupational, value added or other taxes, levies, imposts, duties, assessments,
charges, or withholdings of any nature whatsoever, together with any penalties,
fines, additions, to tax, or interest thereon (all of the foregoing being
hereafter referred to as "Impositions") except same as may be attributable to
Lessor's income, arising at any time prior to or during the term of this Lease,
or upon termination or early termination of this Lease and levied or imposed
upon Lessor directly or otherwise by any Federal, state or local government in
the United States or by any foreign country or foreign or international taxing
authority upon or with respect to (i) the Equipment, (ii) the exportation,
importation, registration, purchase, ownership, delivery, leasing, possession,
use, operation, storage, maintenance, repair, return, sale, transfer of title,
or other disposition thereof, (iii) the rentals, receipts, or earnings arising
from the Equipment, or any disposition of the rights to such rentals, receipts,
or earnings, (iv) any payment pursuant to this Lease, and (v) this Lease or the
transaction


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or any part thereof. Lessee's obligations under this Section 13 shall survive
the expiration of this Lease with respect to acts or events occurring or alleged
to have occurred prior to the return of the Equipment to Lessor at the end of
the Lease term.

      14.   PAYMENT BY LESSOR. If Lessee shall fail to make any payment or
perform any act required hereunder, then Lessor may, but shall not be required
to, after such notice to Lessee as is reasonable under the circumstances, make
such payment or perform such act with the same effect as if made or performed by
Lessee. Lessee will upon demand reimburse Lessor for all sums paid and all costs
and expenses incurred in connection with the performance of any such act.

      15.   SURRENDER OF EQUIPMENT. Upon termination or expiration of this
Lease, with respect to each group of Equipment, Lessee will forthwith surrender
the Equipment to Lessor delivered in as good order and condition as originally
delivered, reasonable wear and tear excepted. Lessor may, at its sole option,
arrange for removal and transportation of the Equipment provided that Lessee's
obligations under Sections 10, 11 and 12 shall not be released. Lessee shall
bear all expenses of returning (which include, but are not limited to, the
de-installation, insurance, packaging and transportation of) the Equipment to
Lessor's location or other location within the continental United States as
Lessor may request. In the event Lessee fails to return the Equipment as
directed above, all obligations of Lessee under this Lease, including rental
payments, shall remain in full force and effect until Lessee returns the
Equipment to Lessor.

      16.   ASSIGNMENT. WITHOUT LESSOR'S PRIOR WRITTEN CONSENT, LESSEE SHALL NOT
(a) ASSIGN, TRANSFER, PLEDGE, HYPOTHECATE OR OTHERWISE DISPOSE OF THIS LEASE,
EQUIPMENT, OR ANY INTEREST THEREIN, OR (b) SUBLET OR LEND EQUIPMENT OR PERMIT IT
TO BE USED BY ANYONE OTHER THAN LESSEE OR LESSEE'S EMPLOYEES. LESSOR MAY ASSIGN
THIS LEASE OR GRANT A SECURITY INTEREST IN ANY OR ALL EQUIPMENT, OR BOTH, IN
WHOLE OR IN PART TO ONE OR MORE ASSIGNEES OR SECURED PARTIES WITHOUT NOTICE TO
LESSEE. If Lessee is given notice of such assignment it agrees to acknowledge
receipt thereof in writing and Lessee shall execute such additional
documentation as Lessor's assignee shall require. Each such assignee and/or
secured party shall have all of the rights, but none of the obligations, of
Lessor under this Lease, unless such assignee or secured party expressly agrees
to assume such obligations in writing. Lessee shall not assert against any
assignee and/or secured party any defense, counterclaim or offset that Lessee
may have against Lessor. Notwithstanding any such assignment, and providing no
Event of Default has occurred and is continuing, Lessor, or its assignees,
secured parties, or their agents or assigns, shall not interfere with Lessee's
right to quietly enjoy use of Equipment subject to the terms and conditions of
this Lease. Subject to the foregoing, this Lease inures to the benefit of and is
binding upon the successors and assignees of the parties hereto.

      17.   DEFAULT. (a) Event of Default. Any of the following events or
conditions shall constitute an "Event of Default" hereunder: (i) Lessee's
failure to pay any monies due to Lessor hereunder or under any Schedule beyond
the tenth (10th) business day after the same is due; (ii) Lessee's failure to
materially comply with its obligations under Section 12 or Section 16; (iii)
Lessee's failure to comply with or perform any term, covenant, condition,
warranty or representation of this Lease or any Schedule hereto or under any
other agreement between Lessee and Lessor if such failure to comply or perform
is not cured by Lessee within ten (10) days of receipt of notice thereof; (iv)
seizure of the Equipment under legal process; (v) the filing by or against
Lessee of a petition for reorganization or liquidation under the Bankruptcy Code
or any amendment thereto or under any other insolvency law providing for the
relief of debtors; (vi) the voluntary or involuntary making of an assignment of
a substantial portion of its assets by Lessee, or any guarantor under any
guaranty executed in connection with this Lease ("Guaranty"), for


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the benefit of its creditors, the appointment of a receiver or trustee for
Lessee or any Guarantor for any of Lessee's or Guarantor's assets, the
institution by or against Lessee or any Guarantor of any formal or informal
proceeding for dissolution, liquidation, settlement of claims against or winding
up of the affairs of Lessee or any Guarantor; or (vii) the making by Lessee or
any Guarantor of a transfer of all or a material portion of Lessee's or
Guarantor's assets or inventory not in the ordinary course of business. (b)
Remedies. If any Event of Default shall have occurred:

      (i)   Lessor may proceed by appropriate court action or actions either at
law or in equity to enforce performance by Lessee, of the applicable covenants
of this Lease, or to recover damages therefor; or

      (ii)  Lessee will on the next rent payment date following the Event of
Default, pay to Lessor as liquidated damages which the parties agree are fair
and reasonable under the circumstances existing at the time this Lease is
entered into, and not as a penalty, an amount equal to the Casualty Value of
the Equipment set forth in Exhibit C together with any rent or other amounts
past due and owing by Lessee hereunder; or

      (iii) Lessor may, without notice to or demand upon Lessee;

            (a)   Take possession of the Equipment and lease the same or any
portion thereof, for such period, amount, and to such entity as Lessor shall
elect. The proceeds of such lease will be applied by Lessor (A) first, to pay
all costs and expenses, including reasonable legal fees and disbursements,
incurred by Lessor as a result of the default and the exercise of its remedies
with respect thereto, (B) second, to pay Lessor an amount equal to any unpaid
rent or other amounts past due and payable plus the Casualty Value, to the
extent not previously paid by Lessee, and (C) third, to reimburse Lessee for the
Casualty Value to the extent previously paid. Any surplus remaining thereafter
will be retained by Lessor.

            (b)   Take possession of the Equipment and sell the same or any
portion thereof at public or private sale and without demand or notice of
intention to sell. The proceeds of such sale will be applied by Lessor (A)
first, to pay all costs and expenses, including reasonable legal fees and
disbursements, incurred by Lessor as a result of the default and the exercise of
its remedies with respect thereto, (B) second, to pay Lessor an amount equal to
any unpaid rent or other amounts past due and payable plus the Casualty Value,
to the extent not previously paid by Lessee, and (C) third, to reimburse Lessee
for the Casualty Value to the extent previously paid by Lessee. Any surplus
remaining thereafter will be retained by Lessor.

            (c)   Take possession of the Equipment and hold and keep idle the
same or any portion thereof.

            Lessee agrees to pay reasonable internal and out-of-pocket costs of
Lessor related to the exercise of its remedies, including direct costs of its
in-house counsel and out-of-pocket legal fees and expenses. At Lessor's request,
Lessee shall assemble the Equipment and make it available to Lessor at such
location in the continental United States as Lessor may designate. Lessee waives
any right it may have to redeem the Equipment.

                  Repossession of any or all Equipment shall not terminate this
Lease or any Schedule unless Lessor notifies Lessee in writing. Any amount
required to be paid but not paid under this Section shall be increased by a
service charge of 1.5% per month, or


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the highest rate of interest permitted by applicable law, whichever is less,
accruing from the date the Casualty Value or other amounts are payable hereunder
until such amounts are paid.

                  Except as otherwise set forth in this Agreement, none of the
above remedies is intended to be exclusive, but each is cumulative and in
addition to any other remedy available to Lessor, and all may be enforced
separately or concurrently.

                  In addition to the foregoing remedies, if an Event of Default
hereunder shall have occurred and be continuing for a period of 10 business days
without cure, Lessee shall promptly provide Lessor with copies of the minutes of
each meeting of Lessee's board of directors or any committee thereof and copies
of each written consent taken by the board or such committees.

      18.   LATE PAYMENTS. A service charge of 1.5% per month, or the highest
service charge permitted by applicable law, whichever is less, shall be paid by
Lessee to Lessor on all funds owed Lessor by Lessee. If such funds have not been
received by Lessor at Lessor's place of business or by Lessor's designated agent
by the date such funds are due under this Lease, Lessor shall bill Lessee for
such charges. Lessee acknowledges that invoices for rentals due hereunder are
sent by Lessor for Lessee's convenience only. Lessee's non-receipt of an invoice
will not relieve Lessee of its obligation to make rent payments hereunder.

      19.   LESSOR'S EXPENSE. Lessee shall pay Lessor all costs and expenses
including reasonable attorney's fees and the fees of the collection agencies,
incurred by Lessor in enforcing any of the terms, conditions or provisions
hereof.

      20.   OWNERSHIP; PERSONAL PROPERTY. The Equipment shall be and remain
personal property of Lessor, and Lessee shall have no right, title or interest
therein or thereto except as expressly set forth in this Lease, notwithstanding
the manner in which it may be attached or affixed to real property, and upon
termination or expiration of the Lease term, Lessee shall have the duty and
Lessor shall have the right to remove the Equipment from the premises where the
same be located whether or not affixed or attached to the real property or any
building, at the cost and expense of Lessee.

      21.   ALTERATIONS; ATTACHMENTS. No alterations or attachments shall be
made to the Equipment without Lessor's prior written consent, which shall not be
given for changes that will affect the reliability and utility of the Equipment
or which cannot be removed without damage to the Equipment, or which in any way
affect the value of the Equipment for purposes of resale or re-lease.

      22.   FINANCING STATEMENT. Lessee will execute financing statements
pursuant to the Uniform Commercial Code.

      23.   MISCELLANEOUS. (a) Lessee shall provide Lessor with such corporate
resolutions, financial statements, opinions of counsel and other documents as
Lessor shall request from time to time. (b) Lessee represents that the Equipment
is being leased hereunder for business purposes. (c) Time is of the essence with
respect to this Lease. (d) Lessee shall keep its books and records in accordance
with generally accepted accounting principles and practices consistently applied
and shall deliver to Lessor its annual audited financial statements, unaudited
monthly financial statements to include any financial information given to
Lessee's Board of Directors, and signed by an officer of Lessee and such other
unaudited financial statements as may be reasonably requested by


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Lessor. (e) Any action by Lessee against Lessor for any default by Lessor under
this Lease, including breach of warranty or indemnity, shall be commenced within
one (1) year after any such cause of action accrues.

      24.   NOTICES. All notices hereunder shall be in writing, by registered
mail, and shall be directed, as the case may be, to Lessor at 2401 Kerner
Boulevard, San Rafael, California 94901, Attention: Lease Administration and to
Lessee at 11545 Sorrento Valley Road, Suite 315, San Diego, California 92121,
Attention: President.

      25.   ENTIRE AGREEMENT. Lessee acknowledges that Lessee has read this
Lease, understands it and agrees to be bound by its terms, and further agrees
that it and each Schedule constitute the entire agreement between Lessor and
Lessee with respect to the subject matter hereof and supersedes all previous
agreements, promises, or representations. The terms and conditions hereof shall
prevail notwithstanding any variance with the terms of any purchase order
submitted by the Lessee with respect to any Equipment covered hereby.

      26.   AMENDMENT. This Lease may not be changed, altered or modified except
by an instrument in writing signed by an officer of the Lessor and the Lessee.

      27.   WAIVER. Any failure of Lessor to require strict performance by
Lessee or any waiver by Lessor of any provision herein shall not be construed as
a consent or waiver of any other breach of the same or any other provision.

      28.   SEVERABILITY. If any provision of this Lease is held invalid, such
invalidity shall not affect any other provisions hereof.

      29.   JURISDICTION AND WAIVER OF JURY TRIAL. This Lease shall be governed
by and construed under the laws of the State of California. It is agreed that
exclusive jurisdiction and venue for any legal action between the parties
arising out of this Lease shall be in the Superior Court for Marin County,
California, or, in cases where Federal diversity jurisdiction is available, in
the United States District Court for the Northern District of California.
LESSEE, TO THE EXTENT IT MAY LAWFULLY DO SO, HEREBY WAIVES ITS RIGHT TO TRIAL BY
JURY IN ANY ACTION BROUGHT ON OR WITH RESPECT TO THIS LEASE, ANY SCHEDULE, OR
ANY AGREEMENT EXECUTED IN CONNECTION HEREWITH.

      30.   NATURE OF TRANSACTION. Lessor makes no representation whatsoever,
express or implied, concerning the legal character of the transaction evidenced
hereby, for tax or any other purpose.

      31.   SECURITY INTEREST. (a) One executed copy of the Lease will be marked
"Original" and all other counterparts will be duplicates. To the extent, if any,
that this Lease constitutes chattel paper (as such term is defined in the
Uniform Commercial Code as in effect in any applicable jurisdiction) no security
interest in the lease may be created in any documents other than the "Original."
(b) There shall be only one original of each Schedule and it shall be marked
"Original," and all other counterparts will be duplicates. To the extent, if
any, that any Schedule(s) to this Lease constitutes chattel paper (or as such
term is defined in the Uniform Commercial Code as in effect in any applicable
jurisdiction) no security interest in any Schedule(s) may be created in any
documents other than the "Original."

      32.   SUSPENSION OF OBLIGATIONS. The obligations of Lessor hereunder will
be suspended to the extent that it is hindered or prevented from complying
therewith because of labor disturbances, including but not limited to strikes
and lockouts, acts of God,


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fires, storms, accidents, failure of the manufacturer to deliver any item of
Equipment, governmental regulations or interference, or any cause whatsoever not
within the sole and exclusive control of Lessor.

      33.   COMMITMENT FEE. Lessee has paid to Lessor a commitment fee ("Fee")
of $10,000. The Fee shall be applied by Lessor first to reimburse Lessor for all
out-of-pocket UCC search costs incurred by Lessor, and then proportionally to
the first and second months' rent for each Schedule hereunder in the proportion
that the purchase price of the Equipment leased pursuant to the Schedule bears
to Lessor's entire commitment. However, the portion of the Fee which is not
applied to rental shall be non-refundable except if Lessor defaults in its
obligations pursuant to Section 3.

      37.   FINANCE LEASE. The parties agree that this lease is a "Finance
Lease" as defined by section 10-103(a)(7) of the California Commercial Code
(Cal.Com.C.). Lessee acknowledges either (a) that Lessee has reviewed and
approved any written Supply Contract (as defined by Cal.Com.C. Section
10-103(a)(25)) covering Equipment purchased from the "Supplier" (as defined by
Cal.Com.C. Section 10-103(a)(24)) thereof for lease to Lessee or (b) that Lessor
has informed or advised Lessee, in writing, either previously or by this Lease
of the following: (i) the identity of the Supplier; (ii) that the Lessee may
have rights under the Supply Contract; and (iii) that the Lessee may contact the
Supplier for a description of any such rights Lessee may have under the Supply
Contract. Lessee hereby waives any rights and remedies Lessee may have under
Cal.Com.C. Sections 10-508 through 522.

      IN WITNESS WHEREOF, the parties hereto have executed this Lease.


PHOENIX LEASING INCORPORATED           SIGNAL PHARMACEUTICAL, INC.


By: [SIG]                              By: /s/ MARK D. CARMAN
    -----------------------------          -------------------------------------

Title: V.P.                            Title: V.P. Operations & Corp. Develop.
       --------------------------             ----------------------------------

Exhibit A - Closing Memorandum


                                      -9-
<PAGE>   10
                                                 Exhibit A
                                                 to MASTER EQUIPMENT LEASE
                                                 Dated September 1, 1993

                               CLOSING MEMORANDUM


1.    Duly Executed Equipment Lease marked "Original."

2.    Duly Executed Schedule marked "Original."

3.    Duly Executed Certificate of Acceptance.

5.    Insurance Certificates.

6.    Resolutions of Lessee's Board of Directors/Incumbency Certificate.

7.    Consent to Removal of Personal Property.

8.    Purchase Agreement Assignment (if applicable).

9.    UCC Financing Statements.

10.   Bill of Sale (for Sale-Leaseback Equipment) (if applicable).

11.   UCC search.

12.   Equipment List, in form and substance satisfactory to Lessor.

13.   Certificate of Chief Financial Officer as to the existence of no defaults
      and as to there being no material adverse change in the condition,
      financial or otherwise, of the Lessee.


                                      -10-
<PAGE>   11
                               ACCEPTANCE NOTICE
                                   SCHEDULE 1


Reference is made to the Master Equipment Lease dated as of September 1, 1993
between Phoenix Leasing Incorporated as Lessor and Signal Pharmaceuticals, Inc.
as Lessee (the "Lease").

Lessee confirms that the following Equipment has been received, installed and
is ready for use by Lessee. The Equipment is satisfactory in all respects for
the purposes of this Lease as of the date Lessee executes this Notice below.


<TABLE>
<CAPTION>
Description of
Equipment
(quantity, model           Purchase                           Mfr./
and serial number)         Price             Rent             Vendor         Location
------------------         --------          ----             ------         --------
<S>                        <C>               <C>              <C>            <C>




Total:                     $                 $
</TABLE>

THE LEASE MAY NOT BE CHANGED, ALTERED OR MODIFIED EXCEPT BY AN INSTRUMENT IN
WRITING SIGNED BY AN OFFICER OF LESSOR AND A DULY AUTHORIZED REPRESENTATIVE OF
LESSEE.

IN WITNESS WHEREOF, Lessee has executed this Acceptance Notice as of
November 1, 1993.


                                        SIGNAL PHARMACEUTICALS, INC.


                                        By:     /s/ Mark D. Carman
                                           ------------------------------------

                                        Name:   MARK D. CARMAN
                                             ----------------------------------

                                        Title:  V.P. OPERATIONS
                                              ---------------------------------