<PAGE>

                                                                    EXHIBIT 10.7

                            THIRD AMENDMENT TO LEASE

         This Third Amendment to Lease ("THIRD AMENDMENT") is made as of
September 15, 2001, by and between ARE-100 PHILIPS PARKWAY, LLC, a Delaware
limited liability company ("LANDLORD"), and MEMORY PHARMACEUTICALS CORP., a
Delaware corporation ("TENANT")

                                    RECITALS

         A. Landlord is the landlord and Tenant is the tenant under a Lease
dated as of June 4, 1999, as amended by letter agreement dated June 16, 1999,
between Landlord and Tenant, by that certain First Amendment to Lease dated as
of February 4, 2000, between Landlord and Tenant and by that certain Second
Amendment to Lease dated as of November 15, 2000, between Landlord and Tenant
(collectively the "LEASE"), under which Tenant leases approximately 52,000
rentable square feet of space in the building commonly known as 100 Philips
Parkway, Montvale, New Jersey. Capitalized terms used herein without definition
shall have the meanings defined for such terms in the Lease.

         B. Landlord and Tenant desire to amend the Lease to expand the Premises
demised under the Lease by adding approximately 11,472 rentable square feet, as
defined below (the 'SECOND EXPANSION SPACE") generally located at the northeast
end of the first floor of the building.

         C. Landlord and Tenant desire to amend the Lease to, among other
things, add the Second Expansion Space to the Premises demised under the Lease
and to provide for the improvement of such space.

                                    AGREEMENT

         Now, therefore, the parties hereto agree that the Lease is hereby
amended as follows:

         1.       PREMISES. Landlord shall lease to Tenant, and Tenant shall
lease from Landlord, the Second Expansion Space, consisting of 11,472 rentable
square feet in the Building and depicted on EXHIBIT A attached hereto and
incorporated herein by this reference. Following such Amendment, Tenant will
lease approximately 63,472 rentable square feet in the Building and Tenants
Share shall be 85.77%. The actual size of the Second Expansion Space, Tenant's
Premises (including the Second Expansion Space) and the Building shall be
measured 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). The Rent payable hereunder, Tenants Share and the
aggregate Tenant Improvement Allowance hereunder shall all be adjusted, if
required, on the basis of such measurement. Tenant shall have the right to use
190 parking spaces at the Project based upon Tenants total Premises of
approximately 63,472 rentable square feet, subject to adjustment following any
measurement as provided above.

         2.       COMMENCEMENT AND TERM. The Lease of the Second Expansion Space
shall commence on January 1, 2002 (the "SECOND EXPANSION SPACE COMMENCEMENT
DATE"), and shall expire May 31, 2010, unless sooner terminated pursuant to the
Lease; provided, however, that if more than an average of $20 per rentable
square foot of the Tenant Improvement Allowance for the Second Expansion
Premises is used by Tenant, the Term of the Lease shall be extended as provided
in Section 5 hereof.

         3.       RENT. Tenant shall pay Base Rent at the rate of $13.00 per
rentable square foot of the Second Expansion Space, which rent shall be subject
to periodic adjustment when and as provided in the Lease and the First Amendment
and shall be further subject to adjustment as provided in Section 5 hereof.

(C) ALL RIGHTS RESERVED 2001 ALEXANDRIA REAL          CONFIDENTIAL - DO NOT COPY
ESTATE EQUITIES, INC.

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         4.       SECURITY DEPOSIT. Tenant shall within 3 business days of the
date hereof deliver to Landlord an additional deposit in the amount of $74,568
as security for Tenant's performance under the Lease and this Third Amendment,
for a total Security Deposit of $504,568.00. Such Security Deposit may be in the
form of a Letter of Credit as provided in the Lease and shall be held and
applied as provided in the Lease.

         5.       TENANT IMPROVEMENTS. Landlord shall make available to Tenant
an allowance for the Second Expansion Space (the "TENANT IMPROVEMENT ALLOWANCE")
in the amount of $150 per rentable square foot of the Second Expansion Space,
not to exceed an aggregate Tenant Improvement Allowance of $1,720,800; provided
that the Base Rent shall be adjusted as provided in Section 4(a) of the Lease to
the extent that Tenant uses more than $20 per rentable square foot of the Second
Expansion Space of the Tenant Improvement Allowance. Such Tenant Improvements
shall be designed and constructed pursuant to the Work Letter attached hereto as
EXHIBIT B. The Tenant Improvement Allowance may be used by Tenant only in
connection with the design and construction of improvements to the Second
Expansion Space (the "TENANT IMPROVEMENTS"); provided, however, that no
disbursement of the Tenant Improvement Allowance shall be made after December
31, 2003. Base Rent for the Second Expansion Space shall be adjusted as provided
in the Lease when and as the Tenant Improvement Allowance is disbursed. If more
than an average of $20 per rentable square foot of the Expansion Premises is
used by Tenant, the Term of the Lease is hereby automatically extended to
expire 10 years after the first day of the first full month during which Tenant
pays Base Rent based upon the full amount of the Tenant Improvement Allowance so
used by Tenant.

         6.       MISCELLANEOUS.

                  (a)      This Third Amendment is the entire agreement between
         the parties with respect to the subject matter hereof and supersedes
         all prior and contemporaneous oral and written agreements and
         discussions with respect to the matters addressed herein. This Third
         Amendment may be amended only by an agreement in writing, signed by the
         parties hereto.

                  (b)      This Third Amendment is binding upon and shall inure
         to the benefit of the parties hereto, their respective agents,
         employees, representatives, officers, directors, divisions,
         subsidiaries, affiliates, assigns, heirs, successors in interest and
         shareholders.

                  (c)      This Third Amendment may be executed in any number of
         counterparts, each of which shall be deemed an original; but all of
         which when taken together shall constitute one and the same instrument.
         The signature page of any counterpart may be detached therefrom without
         impairing the legal effect of the signature(s) thereon provided such
         signature page is attached to any other counterpart identical thereto
         except having additional signature pages executed by other parties to
         this Third Amendment attached thereto.

                  (d)      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 except Cushman &
         Wakefield of New Jersey, Inc., who shall be compensated by Landlord
         pursuant to a separate agreement, and that no other Broker brought
         about this transaction. Landlord and Tenant each hereby agree to
         indemnify and hold the other harmless from and against any claims by
         any 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.

(C) ALL RIGHTS RESERVED 2001 ALEXANDRIA REAL          CONFIDENTIAL - DO NOT COPY
ESTATE EQUITIES, INC.

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                  (e)      Except as amended and/or modified by this Third
         Amendment, the Lease is hereby ratified and confirmed and all other
         terms of the Lease shall remain in full force and effect, unaltered and
         unchanged by this Third Amendment. In the event of any conflict between
         the provisions of this Third Amendment and the provisions of the Lease,
         the provisions of this Third Amendment shall prevail. Whether or not
         specifically amended by this Third Amendment, all of the terms and
         provisions of the Lease are hereby amended to the extent necessary to
         give effect to the purpose and intent of this Third Amendment.

                            [SIGNATURES ON NEXT PAGE]

(C) ALL RIGHTS RESERVED 2001 ALEXANDRIA REAL          CONFIDENTIAL - DO NOT COPY
ESTATE EQUITIES, INC.

                                       3

<PAGE>

         IN WITNESS WHEREOF, this Third Amendment to Lease has been duly
executed and delivered by Landlord and Tenant as of the date first above
written.

                                     TENANT:

                                     MEMORY PHARMACEUTICALS CORP.,
                                     a Delaware corporation

                                     By: /s/ Joanne Leonard
                                         --------------------------------------
                                      Its: SR VP, CFO

                                     LANDLORD:

                                     ARE - 100 PHILLIPS PARKWAY, LLC,
                                     a Delaware limited liability company

                                     By:  ALEXANDRIA REAL ESTATE EQUITIES, L.P.,
                                          a Delaware limited partnership,
                                          managing member

                                          By: ARE-QRS CORP.,
                                              a Maryland corporation,
                                              general partner

                                              By: /s/ Laurie A. Allen
                                                  -------------------
                                              Its:       LAURIE A. ALLEN
                                                      SENIOR VICE PRESIDENT
                                                      BUSINESS DEVELOPMENT
                                                         & LEGAL AFFAIRS

(C) ALL RIGHTS RESERVED 2001 ALEXANDRIA REAL          CONFIDENTIAL - DO NOT COPY
ESTATE EQUITIES, INC.

                                       4

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                                    EXHIBIT A

                                  [FLOOR PLAN]

<PAGE>

                                    EXHIBIT B

                                  WORK LETTER

         THIS WORK LETTER dated as of September 15, 2001 (this "WORK LETTER") is
made and entered into by and between ARE - 100 PHILIPS PARKWAY, LLC, a Delaware
limited liability company ("LANDLORD"), and MEMORY PHARMACEUTICALS CORP., a
Delaware corporation ("TENANT"), and is attached to and made a part of the
Third Amendment to Lease dated September 15, 2001 (the "THIRD AMENDMENT"), by
and between Landlord and Tenant. Any initially capitalized terms used but not
defined herein shall have the meanings given them in the Third Amendment.

         1. General Requirements

                  (a) Tenant's Authorized Representative. Tenant designates
         Joanne Leonard and Dan Brandeth (either acting alone, "TENANT'S
         REPRESENTATIVE") as the only persons authorized to act for Tenant
         pursuant to this Work Letter. Landlord shall not be obligated to
         respond to or act upon any request, approval, inquiry or other
         communication ("COMMUNICATION") from or on behalf of Tenant in
         connection with this Work Letter unless such Communication is in
         writing from a Tenant's Representative. Tenant may change Tenant's
         Representatives 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.

                  (b) Landlord's Authorized Representative. Landlord designates
         Vincent Ciruzzi and Oliver Sherrill ("LANDLORD'S REPRESENTATIVE") as
         the only persons 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 may change
         Landlord's Representatives 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.

                  (c) Architects, Consultants and Contractors. The architect
         ("ARCHITECT"), engineering consultants, design team, general contractor
         ("CONTRACTOR") and all subcontractors' responsible for construction of
         Tenant's Work, as defined below, shall be selected by Tenant, and
         approved by Landlord in Landlord's reasonable discretion.

         2. Tenant Improvements

                  (a) Tenant Improvements Defined. As used herein, "TENANT
         IMPROVEMENTS" shall mean all improvements to the Second Expansion Space
         desired by Tenant of a fixed and permanent nature. Other than providing
         the TI Allowance hereunder, Landlord shall not have any obligation
         whatsoever with respect to finishing the Premises for Tenant's use and
         occupancy. The construction of the Tenant Improvements is herein
         referred to as "TENANT'S WORK."

                  (b) Tenant's Space Plans. Tenant may, until June 30, 2003,
         prepare and submit for Landlord's review and approval schematic
         drawings and outline specifications (the "DESIGN DRAWINGS") detailing
         Tenant's requirements for the Tenant Improvements, which Tenant
         Improvements shall be consistent with the Permitted Use. Not more than
         10 Business Days after each such submission, Landlord shall deliver to
         Tenant Landlord's reasonable written objections, questions or comments
         with regard to the Design Drawings so submitted. Tenant shall cause the
         Design Drawings to be revised to address such written comments and
         shall

                                       6

<PAGE>

         resubmit said drawings to Landlord for approval. Such process shall
         continue until Landlord has approved the Design Drawings. If any
         proposed work of improvement set forth on the Design Drawings or any
         logical development of the Design Drawings has an adverse impact on the
         structure or operational efficiency of the Building or portions of the
         Building lying outside the Premises, all costs of mitigating such
         adverse impacts shall be paid from the TI Fund.

                  (c) Preliminary Plans. Following Landlord's approval of the
         Design Drawings, Tenant shall prepare and submit for Landlord's review
         and approval preliminary plans and specifications for Tenant's Work
         (the "PRELIMINARY PLANS"). Landlord shall have the right to approve or
         disapprove the Preliminary Plans, which approval shall not be
         unreasonably withheld or delayed, provided, however, that except for
         matters affecting the Structure, as defined below, and matters that do
         not comply with all applicable building and land use laws, rules and
         regulations, Landlord may not disapprove any matter that is consistent
         with the Design Drawings. "STRUCTURE" shall mean: (i) structural
         portions of the Building including exterior walls, roof, foundation or
         the core of the Building, (ii) the exterior of the Building, or (iii)
         any of the Building systems, including, without limitation, elevator,
         plumbing, air conditioning, heating electrical, security, life safety
         or power. Tenant shall cause the Preliminary Plans to be revised to
         address such written comments and shall resubmit said drawings to
         Landlord for approval. Such process shall continue until Landlord has
         approved the Preliminary Plans. If Landlord fails to give written
         notice of its approval or disapproval within 5 business days following
         its receipt of the Preliminary Plans or any required modification or
         amendment thereof, the same shall be deemed to have been approved by
         Landlord. Tenant shall be solely responsible for ensuring that the
         Preliminary Plans reflect Tenant's requirements for Tenant's Work.

                  (d) Final Plans and Specifications.

                           (i)      Following Landlord's approval of the
                  Preliminary Plans, Tenant shall cause the Architect to prepare
                  and deliver to Landlord for review: (i) construction plans,
                  specifications and drawings for Tenant's Work ("CONSTRUCTION
                  DRAWINGS"), and (ii) a detailed cost estimate for Tenant's
                  Work broken down by trade (i.e., mechanical, electrical,
                  plumbing, etc.), unit prices for the items specified in the
                  Construction Drawings and a project construction schedule in a
                  format reasonably acceptable to both parties (collectively
                  such items listed in clauses (i) and (ii) are referred to
                  herein as the "CONSTRUCTION DATA"). Landlord shall have the
                  right to approve or disapprove the Construction Drawings,
                  which approval shall not be unreasonably withheld or delayed.
                  Landlord may participate in all design meetings with Tenant,
                  the Architect, Contractor and other design professional as
                  appropriate in the course of the development of the
                  Construction Data. Landlord shall deliver its approval or
                  disapproval of the Construction Drawings to Tenant not later
                  than 5 business days after Landlord's receipt of same. If
                  Landlord disapproves the Construction Drawings such
                  disapproval shall be accompanied by detailed written comments
                  setting forth the basis for such disapproval. Tenant and the
                  Architect shall, within 5 business days after receipt of
                  Landlord's disapproval of the Construction Drawings cause the
                  Construction Drawings to be redrafted to address such issues,
                  and shall resubmit them for Landlord's approval as described
                  herein until Landlord approves the Construction Drawings.
                  Tenant shall be solely responsible for ensuring that the
                  Construction Drawings reflect Tenant's requirements for the
                  Tenant Improvements.

                           (ii)     Landlord shall have the right to disapprove
                  the Construction Drawings which: (i) do not comply with all
                  applicable building and land use laws, rules and regulations,
                  (ii) in Landlord's reasonable opinion, adversely impact the
                  Structure, or (iii) are not consistent with the Preliminary
                  Plans.

                                       7

<PAGE>

                           (iii)    No Tenant's Work may begin until final cost
                  estimates for such Tenant's Work have been received and
                  reasonably approved by Landlord.

         3. Performance of Tenant's Work.

                  (a) Commencement and Permitting of Tenant's Work. Tenant shall
         commence construction of Tenant's Work upon obtaining all applicable
         governmental approvals and a building permit authorizing the
         construction of Tenant's Work (collectively, the "BUILDING PERMITS"),
         which Building Permits shall be paid for out of the TI Fund (as defined
         in Section 5.4 below), and shall diligently prosecute such construction
         to Substantial Completion. Landlord shall assist Tenant in obtaining
         the Building Permits.

                  (b) Completion of Tenant's Work. Tenant shall substantially
         complete or cause to be substantially completed Tenant's Work in a good
         and workmanlike manner, in accordance with the Building Permits,
         subject to Minor Variations and normal "punch list" items of a
         non-material nature which do not interfere with the use of the Premises
         ("SUBSTANTIAL COMPLETION"). Upon the Substantial Completion of Tenant's
         Work, Tenant shall require the Architect and the general contractor to
         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
         Permits); (ii) to comply with any request by the Tenant for
         modifications to Tenant'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 Tenant's Work.

                  (c) Construction Defects. Landlord shall have no obligation or
         liability of any kind to remedy or cause any responsible contractor to
         remedy: (i) any non-compliance of Tenant's Work with Code, (ii) any
         claim that Tenant's Work was not completed substantially in accordance
         with the Construction Drawings, or (iii) any other defect in Tenant's
         Work (collectively a "CONSTRUCTION DEFECT"), other than to cooperate,
         at no cost to Landlord, with Tenant should Tenant elect to pursue a
         claim against any 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. Tenant shall be
         entitled to receive the benefit of all construction warranties and
         manufacturer's equipment warranties relating to equipment installed in
         the Premises.

         4. Changes. If Tenant shall desire any change or series of related
changes to Tenant's Work the implementation of which is estimated to change the
Budget, as defined below, by $25,000 or more (whether increasing or decreasing
the Budget) ("CHANGES"), Tenant shall notify 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. Landlord
shall approve or disapprove such Change Request within 5 Business Days of
receipt of such Change Request; provided, however that Landlord shall only
disapprove Change Requests which: (i) do not comply with all applicable building
and land use laws, rules and regulations, or (ii) in Landlord's reasonable
opinion, adversely impact the Structure. Before proceeding with any such Change
approved by Landlord, Tenant shall submit to Landlord in writing, within 10
Business Days of receipt of Landlord's approval 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 construction, material, architectural and
engineering costs and shall deposit with landlord, if applicable, any additional
Excess Costs resulting from such Change.

                                       8

<PAGE>

5. Costs.

         (a) Budget For Tenant Improvements. Before the commencement of
construction of Tenant's Work, Landlord shall be provided a detailed breakdown,
by trade, of the costs incurred or which will be incurred, in connection with
the design and construction of the Tenant's Work (the "BUDGET"). The Budget
shall be based upon the Construction Drawings approved by Landlord and shall
include a payment to Landlord, of administrative rent equal ("ADMINISTRATIVE
RENT") to 3% of the Budget (but not to exceed $50,000) for monitoring and
inspecting the construction of Tenant's Work including but not limited to the
review of a drawings, plans specifications, permits, budgets, change requests
and other such Tenant required submittal relating to this Work Letter, 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 arising from, out of, or in connection with, such monitoring
of the construction of the Tenant's Work, and shall be payable out of the TI
Fund. If the Budget is greater than the TI Fund (as defined below), Tenant shall
deposit with Landlord the difference, in cash, prior to the commencement of
construction of the Tenant Improvements, for disbursement by Landlord as
described in Section 5(e).

         (b) TI Allowance. Landlord shall provide to Tenant a tenant improvement
Tl Allowance ("TI ALLOWANCE") in the amount of $150 per rentable square foot of
the Second Expansion Space, not to exceed an aggregate Tenant Improvement
Allowance of $1,720.800. Before commencing any Tenant's Work, Tenant shall
notify Landlord how much TI Allowance Tenant has elected to receive from
Landlord. Such election shall be final and binding on Tenant, and may not
thereafter be modified without Landlord's consent, which may granted or withheld
in Landlord's sole and absolute discretion. The TI Allowance shall be disbursed
by Landlord in accordance with this Work Letter.

         (c) Costs Includable in TI Fund. The TI Fund shall be used solely for
the payment of design and construction costs in connection with the construction
of the Tenant Improvements, including, without limitation, Tenant's project
management and regulatory consultants, the cost of preparing the Design
Drawings, the Preliminary Plans and the Construction Drawings, all costs set
forth in the Budget, including Landlord's Administrative Rent and the cost of
Changes (collectively, "COSTS"). Notwithstanding anything to the contrary
contained herein, the TI Fund shall not be used to purchase any furniture,
personal property or other non-building system materials or equipment,
including, but not be limited to, biological safety cabinets and other
scientific equipment not incorporated into the Improvements. Landlord shall use
reasonable efforts to notify Tenant 30 days before commencement of construction
of tenant improvements for any third party in any portion of the remaining
space.

         (d) Excess 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
except to the extent of the TI Allowance. If at any time and from time-to-time,
the remaining Costs under the Budget exceed the remaining unexpended TI Fund
("EXCESS COSTS"), Tenant shall pay 100% of all such Excess Costs until the
remaining Costs under the Budget are equal to or less than the remaining
unexpended TI Allowance, as a condition precedent to Landlord's funding the cost
of any further Tenant's Work. If Tenant fails to make any payment of Costs, or
is late in paying such Costs such that Landlord cures such default, Landlord
shall have all of the rights and remedies set forth in the Lease for a Default
thereunder (including, but not limited to, the right to interest at the Default
Rate on amounts so advanced), and for purposes of any litigation instituted with
regard to such amounts the same will be considered Rent. Such Excess Costs
together with the TI Allowance are herein referred to as the 'TI FUND."
Notwithstanding anything to the contrary set forth in this Section, Tenant shall
be fully and solely liable for any costs of Tenant's Work in excess of the Tl
Allowance.

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<PAGE>

         (e) Payment for Tenant's Work. Not more than once a month during the
performance of any of Tenant's Work, upon submission of a disbursement request
in the form of Landlord's standard draw package, which shall include American
Institute of Architects document G702 and G703, an Architect's certificate as to
the work done, a notarized certification from the Contractor, and such invoices
and lien waivers as Landlord shall require (the "DRAW PACKAGE"), all in form and
substance as Landlord shall reasonably require, Landlord shall make
disbursements to pay the then due costs of Tenant's Work as shown in the
approved Draw Package within 10 business days of receipt of the complete Draw
Package. Landlord shall have no obligation to make any disbursements of the
Tenant Improvement Allowance after December 31, 2003. Upon making any such
disbursement of the Tenant Improvement Allowance, Base Rent for the Second
Expansion Space shall be adjusted as provided in Section 7 of the Third
Amendment.

6. Miscellaneous

         (a) 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.

         (b) 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.

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

         (d) 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.

         (e) Time of the Essence. Time is of the essence of this Work Agreement
and of each and all provisions thereof.

         (f) Default. Notwithstanding anything set forth herein or in the Lease
to the contrary, Landlord shall not have any obligation to perform any work
hereunder or to fund any portion of the Tl Fund during any period Tenant is in
Default under the Lease.

         (g) 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.

         (h) Merger. All understanding 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.

         (i) 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.

                                       10

<PAGE>

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

                                   TENANT:

                                   MEMORY PHARMACEUTICALS CORP.
                                   a Delaware corporation

                                   By: /s/ Joanne Leonard
                                       -------------------
                                   Its: SR VP, CFO

                                   LANDLORD:

                                   ARE - 100 PHILLIPS PARKWAY, LLC,
                                   a Delaware limited liability company

                                   By:  ALEXANDRIA REAL ESTATE EQUITIES, L.P.,
                                        a Delaware limited partnership,
                                        managing member

                                        By: ARE-QRS CORP.,
                                            a Maryland corporation,
                                            general partner

                                            By: /s/ Laurie A. Allen
                                                -------------------
                                            Its:       LAURIE A. ALLEN
                                                    SENIOR VICE PRESIDENT
                                                    BUSINESS DEVELOPMENT
                                                      & LEGAL AFFAIRS

                                       11