Document:

<PAGE>

                                  EXHIBIT 10.16

The Company has omitted from this Exhibit portions of the Lease for which the
Company has requested confidential treatment from the Securities and Exchange
Commission. The portions of the Lease for which confidential treatment has been
requested have been deleted and marked with asterisks surrounded by brackets
([****]) and have been filed separately with the Securities and Exchange
Commission.

                                      LEASE

                                 by and between

                               KENDALL SQUARE, LLC

                                    LANDLORD,

                                       and

                       VERTEX PHARMACEUTICALS INCORPORATED

                                     TENANT
<PAGE>

                                    ARTICLE I

                                 REFERENCE DATA

1.1   SUBJECTS REFERRED TO

ANNUAL FIXED RENT RATE:             Subject to Sections 2.3 and 4.1(b) hereof,
                                    (i) [*****Confidential*****]/rentable square
                                    foot ("r.s.f.") for the Premises or (ii) if
                                    Landlord advances the Tenant Allowance, the
                                    Annual Fixed Rent Rate set forth above shall
                                    be [*****Confidential*****]/r.s.f. for the
                                    Premises.

APPROXIMATE TERM:                   Approximately 15 years and 4 months, subject
                                    to the Options to Extend.

BUILDING:                           The Building known as Building A, Cambridge
                                    Research Park, Cambridge, Massachusetts, to
                                    be constructed by Landlord and containing
                                    six levels and an enclosed rooftop
                                    mechanical penthouse and approximately
                                    275,000 r.s.f., of which approximately
                                    15,000 r.s.f. shall be ground floor retail
                                    space (the "Retail Space").

COMPLEX:                            An approximately ten acre parcel of land,
                                    including the Lot and all buildings thereon
                                    and improvements thereto hereafter
                                    constructed by Landlord or by an Affiliate
                                    of Landlord (as such term is defined below
                                    in this Section 1.1), in Cambridge,
                                    Massachusetts, currently owned by Landlord
                                    and shown on a plan entitled "Master Plan"
                                    dated June 1, 1999, Scale 1"=50', a reduced
                                    copy of which is attached as Exhibit A
                                    hereto, but excluding any portion of the
                                    Complex which is not hereafter owned by
                                    Landlord or an Affiliate of Landlord.

INITIAL ESTIMATED ANNUAL
ADDITIONAL RENT FOR PREMISES:       [*****Confidential*****] based upon
                                    [*****Confidential*****]/r.s.f.

INITIAL ESTIMATED ANNUAL
ADDITIONAL RENT FOR COMPLEX:        [*****Confidential*****] based upon
                                    [*****Confidential*****]/r.s.f.

                                       -2-
<PAGE>

LANDLORD:                           Kendall Square, LLC, formerly known as
                                    Cambridge Research Park, LLC, a Delaware
                                    limited liability company.

LANDLORD'S ARCHITECT:               Steven Ehrlich Architects

LANDLORD'S ADDRESS:                 c/o Lyme Properties, LLC
                                    101 Main Street
                                    Cambridge, Massachusetts 02142

LANDLORD'S CONTRACTOR:              To be determined by Landlord pursuant to
                                    Section 3.1.1 hereof.

LANDLORD'S REPRESENTATIVE:          Each of David E. Clem and Robert L. Green

LEASE YEAR:                         Each consecutive period of twelve (12)
                                    calendar months commencing on the
                                    Commencement Date if it occurs on the first
                                    day of a calendar month and otherwise
                                    commencing on the first day of the month
                                    immediately following the month in which the
                                    Commencement Date occurs, and each
                                    anniversary of such date, except that the
                                    first Lease Year shall be approximately one
                                    year and four months beginning with the
                                    Commencement Date so as to include the
                                    four-month period from the Commencement Date
                                    through the Rent Commencement Date or until
                                    the first day of the following month in the
                                    event that the Rent Commencement Date does
                                    not occur on the first day of a calendar
                                    month.

LOT:                                The land on which the Building is to be
                                    constructed and shown on Exhibit A as being
                                    generally bounded by Athenaeum Street,
                                    Kendall Street, Linskey Way and Third
                                    Street, the legal description of which (and
                                    a plan for which) shall be prepared by
                                    Landlord prior to September 1, 2001 and
                                    attached hereto as Exhibit A-1 and which
                                    plan shall be attached hereto as Exhibit
                                    A-2.

MANAGING AGENT:                     To be determined by Landlord, provided
                                    however, that Tenant may submit to Landlord
                                    the names of managing agents

                                       -3-
<PAGE>

                                    proposed by Tenant but Landlord shall retain
                                    the right to select the Managing Agent.

OPTIONS TO EXTEND:                  Two (2) Options to Extend the Term of this
                                    Lease for successive periods of ten (10)
                                    years each, in accordance with Section 10.12
                                    hereof.

PERMITTED USES:                     Technical office for research and
                                    development, laboratory and research
                                    facility, and, subject to applicable
                                    requirements of the Cambridge Zoning
                                    Ordinance, limited manufacturing as an
                                    accessory use.

PREMISES:                           Approximately 260,000 r.s.f. of space in the
                                    Building to be constructed by Landlord on
                                    the Lot as shown on Exhibit A.

PUBLIC LIABILITY
INSURANCE LIMITS:                   Bodily injury:    $10,000,000
                                    Property Damage:  $10,000,000

RENTABLE SQUARE                     As determined pursuant to Section 2.3
FOOTAGE OF BUILDING:                hereof, but the Building is currently
                                    estimated to consist of 275,000 r.s.f. of
                                    space.

RENTABLE SQUARE                     As determined pursuant to Section 2.3
FOOTAGE OF PREMISES:                hereof, but the Premises is currently
                                    estimated to consist of approximately
                                    260,000 r.s.f. of space in the Building to
                                    be constructed by Landlord on the Lot.

SCHEDULED SUBSTANTIAL
COMPLETION DATE:                    May 1, 2002

SCHEDULED RENT
COMMENCEMENT DATE:                  September 1, 2002

SCHEDULED TERM
COMMENCEMENT DATE:                  May 1, 2002

SECURITY DEPOSIT:                   As further described in Section 10.11
                                    hereof, a letter of credit or cash in the
                                    initial amount of [*****Confidential*****]
                                    plus an amount equal to

                                       -4-
<PAGE>

                                    the Initial Estimated Annual Additional Rent
                                    for Premises [*****Confidential*****] and an
                                    amount equal to the Initial Estimated Annual
                                    Additional Rent for Complex
                                    [*****Confidential*****], subject to
                                    adjustment in accordance with Sections 2.3
                                    and 10.11 hereof.

TENANT:                             Vertex Pharmaceuticals Incorporated

TENANT'S ADDRESS                    130 Waverly Street
(For Notice and Billing):           Cambridge, Massachusetts 02139-4242

TENANT ALLOWANCE:                   Subject to Section 2.3 hereof,
                                    [*** Confidential***]

TENANT'S ARCHITECT:                 Tsoi/Kobus & Associates, Inc.

TENANT'S PROPORTIONATE
FRACTION FOR BUILDING:              Subject to Section 2.3 hereof, 94.55%

TENANT'S PROPORTIONATE
FRACTION FOR COMPLEX:               As determined pursuant to Section 2.3
                                    hereof.

TENANT'S REPRESENTATIVE:            Alfred Vaz, Jr.

TERM COMMENCEMENT DATE:             The earlier of (a) the date that is four (4)
                                    months after the Substantial Completion Date
                                    or (b) the date on which Tenant's personnel
                                    occupy all or any portion of the Premises
                                    for the conduct of any aspect of Tenant's
                                    business (as opposed to the conduct by
                                    Tenant of any of Tenant's Work or the
                                    installation in the Premises of fixtures,
                                    furnishings, equipment or personal
                                    property).

TERM EXPIRATION DATE:               The last day of the fifteenth Lease Year,
                                    subject to two (2) Options to Extend for
                                    successive periods of ten (10) years each,
                                    in accordance with Section 10.12.

The foregoing and following capitalized terms shall have the respective meanings
set forth above, below or as referenced in this Lease, as applicable:

ADA Requirements: The Americans with Disabilities Act (42 U.S.C.ss. 12101 et
seq.) and the regulations and Accessibility Guidelines for Buildings and
Facilities issued pursuant thereto.

                                       -5-
<PAGE>

Additional Rent Adjustment Date: As defined in Section 4.2.4

Additional Rent: All rent, charges and other sums, other than Fixed Rent, due
Landlord pursuant to this Lease.

Affiliate of Landlord: A person or entity controlled by, controlling or under
common control with Landlord.

Affiliate of Tenant: Any entity controlled by, controlling or under common
control with Tenant.

Annual Building Maintenance and Operation Charge: As defined in Section 4.2.4

Annual Complex Maintenance and Operation Charge: As defined in Section 4.2.4.

Annual Maintenance Charge: The sum of the Annual Building Maintenance and
Operation Charge, the Annual Complex Maintenance and Operation Charge and the
Nonstandard Charge.

Annual Tax, Insurance and Utility Charge: The sum of the Initial Tax Charge, the
Initial Insurance Charge and the Initial Utility Charge.

Base Building Improvements: As defined in Section 3.1.1.

Broker: Insignia/ESG, Inc.

Building Common Areas: Interior and exterior common areas and facilities of the
Building and the Lot, including walkways and sidewalks necessary for access to
the Building, entrances, lobbies, stairs, elevators and corridors, if any,
designated by Landlord for access to the Premises, loading docks in the
Building, and heating, ventilating, air conditioning, plumbing, electrical and
other mechanical systems and equipment serving the Premises in common with other
portions of the Building, all of which shall be shown on a plan prepared by
Landlord and delivered to Tenant on or before the date upon which the building
permit for the Base Building Improvements is issued.

Casualty Restoration Completion Date: As defined in Section 6.1.

CDD: Community Development Department of the City of Cambridge, Massachusetts.

Change Order: As defined in Section 3.1.2.

Chapter 91 Determination: As defined in Section 3.1.4.

Commencement Date: As defined and determined pursuant to Section 2.2.

Complex Common Areas: Interior and exterior common areas and facilities of the
Complex to which Tenant has access in common with other tenants of buildings in
the Complex, including streets, parks, open space, walkways and sidewalks
necessary for access to the Lot and heating, ventilating, air conditioning,
plumbing, electrical and other mechanical systems and equipment serving common
areas of the Complex. The exterior Complex Common Areas shall be in the
approximate locations of Open Space 1, Open Space 2, Open Space 3, Kendall
Street, Kendall

                                       -6-
<PAGE>

Street West, Kendall Street East and Athenaeum Street Extension, all as shown on
a plan entitled Kendall Square, Parcel Worksheet 7 in Cambridge, Massachusetts,
dated 15 November 2000 prepared by Gunther Engineering, Inc., a copy of which
has been delivered to Tenant.

Confidential Information: Any and all knowledge, information, data, materials,
trade secrets, and other work product of a confidential nature gained, obtained,
derived, produced, generated or otherwise acquired by Landlord with respect to
Tenant's business.

Construction Documents: As defined in Section 3.2.1.

Design Development Documents: As defined in Section 3.1.1.

Development Approvals: As defined in Section 3.1.4.

Environmental Agreement: The Environmental Agreement between Landlord and Tenant
in the form of Exhibit F hereto.

Environmental Remediation: As defined in Section 3.1.3.

Estimated Annual Additional Rent: Landlord's estimate of the total amount of
Additional Rent which may be due from Tenant for any particular Lease Year with
respect to the Building, Lot and Complex.

Estimated Annual Maintenance Charge: Landlord's reasonable estimate of the
Annual Maintenance Charge.

Estimated Annual Tax, Insurance and Utility Charge: Landlord's reasonable
estimate of the Annual Tax, Insurance and Utility Charge.

Event of Default: As defined in Section 7.1.

Excluded Taxes: Any income taxes, excess profits taxes, excise taxes, franchise
taxes, or any taxes or assessments with respect to the Garage and other
buildings leased or available for lease (and the parcels of land upon which such
buildings are situated), other than the Building, the Lot and any building or
portion of a building in the Complex which is not available for lease (and the
parcel(s) of land on which the same may be located), in the Complex.

Exercise Notice: As defined in Section 10.12.

Extension Periods: As defined in Section 10.12.

Extension Rent: As defined in Section 10.12.

Fair Market Rent: As defined in Section 10.12.

Final Design Documents: As defined in Section 3.1.1.

Fixed Rent: As defined in Section 4.1.

                                       -7-
<PAGE>

Force Majeure Events: As defined in Section 3.2.

Garage Owner: The owner of the Garage.

Garage Parking Spaces: Tenant's Parking Spaces.

Garage Security Services: As defined in Section 10.14.

Garage: As defined in Section 10.14.

Holder: As defined in Section 8.1.

Impositions: As defined in Section 4.2.4(1)(a).

Indemnified Parties: As defined in Section 5.1.6.

Initial Estimated Annual Additional Rent for Building: As defined in Section
4.2.

Inquiry Notice: As defined in Section 10.12.

Landlord's Statement: As defined in Section 4.2.4.

Landlord's Work: The construction of the Base Building Improvements in
accordance with the Final Design Documents as affected by Change Orders.

MCP: Massachusetts Contingency Plan, 310 CMR 40.0000 et seq., as amended.

MEPA Certificate: Certificate of the Secretary of Environmental Affairs on the
Final Environmental Impact Report dated April 15, 1999.

Minor Alteration: As defined in Section 3.2.1.

Mortgage: Mortgages, deeds of trust or other similar instruments evidencing
other voluntary liens or encumbrances, and modifications, consolidations,
extensions, renewals, replacements and substitutes thereof.

Nonstandard Charge: As defined in Section 4.2.4.

Nonstandard Costs: As defined in Section 4.2.4.

Options to Extend: As defined in Section 10.12.

Order of Conditions: Order of Conditions issued July 12, 1999 by the City of
Cambridge Conservation Commission.

Outside Completion Date: As defined in Section 3.2.

Parking Fee: As defined in Section 10.14.

                                       -8-
<PAGE>

Preliminary Design Concept: As defined in Section 3.1.1.

Progress Schedule: As set forth in Exhibit B-1 hereto.

PTDM Approval: The PTDM Decision, the PTDM Letter and PTDM Plan.

PTDM Decision: PTDM Ordinance Final Decision issued April 20, 1999 by the CDD.

PTDM Letter: The Letter dated April 20, 1999 to Robert L. Green of Lyme
Properties from Susanne Rasmussen of the CDD attached to the PTDM Decision.

PTDM Plan: Landlord's Parking Transportation Demand Management Plan dated April
9, 1999.

PUD Approval: The PUD Permit and the Settlement Agreement.

PUD Permit: A Special Permit issued by the City of Cambridge Planning Board,
Case No. PB #141 filed April 7, 1999 (the "PUD Permit"), recorded with the
Middlesex South District Registry of Deeds (the "Registry") in Book 31137, Page
89.

Punch List Items: Minor items which can be fully completed by Landlord within
thirty (30) days without material interference with Tenant and other items which
because of the season or weather or the nature of the item are not practicable
to do at the time, provided that none of said items is necessary to perform
Tenant's Work.

Remediation Documents: The documents set forth on Exhibit F-1 hereto.

Rentable Square Feet, Rentable Square Footage or r.s.f.: The rentable square
footage of the space in question as measured in accordance with the standard set
forth in Section 2.3.

Response Action Outcome: As such term is defined in the MCP.

Schematic Design Documents: As defined in Section 3.1.1.

Settlement Agreement: A Settlement Agreement dated May 24, 1999 among Barbara
Broussard, Mary DeFreitas, the East Cambridge Planning Team and Landlord.

SNDA: Subordination, Non-disturbance and Attornment Agreement.

Subdivision: As defined in Section 9.1.6.

Sublease Costs: As defined in Section 5.2.1.

Sublease Profits: As defined in Section 5.2.1.

Subsequent Approvals: As defined in Section 3.1.4.

Substantial Completion Date: As defined in Section 3.2.

Substitute Taxes: As defined in Section  4.2.1.

                                       -9-
<PAGE>

Tenant Allowance Notice: As defined in Section 2.3.

Tenant Delay: As defined in Section 3.2.

Tenant's Property: All of the furnishings, fixtures, equipment, effects and
property of every kind, nature and description owned or leased by Tenant or by
any person claiming by, through or under Tenant which, during the continuance of
this Lease or any occupancy of the Premises by Tenant or anyone claiming under
Tenant, may be on the Premises.

Tenant's Proportionate Fraction for Building: As defined in Section 2.3

Tenant's Proportionate Fraction for Complex: As defined in Section 2.3.

Tenant's Work: As defined in Section 3.2.1.

Title Exceptions: Item Nos. 2 through 12, inclusive set forth in Schedule B,
Part 1 of the Title Policy.

Title Policy: Owner's Policy No. 136-00-336684 dated August 19, 1998, issued by
Lawyer's Title Insurance Corporation.

TMA: The Charles River Transportation Management Association or any other
transportation management association of which Landlord is a member.

Transfer: As defined in Section 9.1.6.

Utilities: As defined in Section 4.2.3.

Utility Service Provider or Utility Service Providers: As defined in Section
4.2.3.

Utility Services: As defined in Section 4.2.3.

                                      -10-
<PAGE>

1.2   EXHIBITS.

      The Exhibits listed below in this section are incorporated in this Lease
by reference and are to be construed as a part of this Lease:

EXHIBIT A                               Plan showing Complex
EXHIBIT A-1                             Legal Description
EXHIBIT A-2                             Plan showing Lot
EXHIBIT A-3                             Confirmation of Commencement Date and
                                         Rentable Square Footage
EXHIBIT B                               Base Building Description
EXHIBIT B-1                             Progress Schedule
EXHIBIT C                               Rules and Regulations
EXHIBIT D                               SNDA Form
EXHIBIT E                               Schedule of Equipment to be Removed
                                         by Tenant
EXHIBIT F                               Environmental Agreement
EXHIBIT F-1                             Remediation Documents

1.3   TABLE OF CONTENTS

ARTICLE I......................................................................2
 1.1  SUBJECTS REFERRED TO.....................................................2
 1.2  EXHIBITS................................................................11
 1.3  TABLE OF CONTENTS.......................................................11
ARTICLE II....................................................................14
 2.1  PREMISES................................................................14
 2.2  TERM....................................................................15
 2.3  MODIFICATION OF CERTAIN DEFINITIONS; CERTIFICATE
      REGARDING COMMENCEMENT DATE.............................................15
ARTICLE III...................................................................16
 3.1  INITIAL CONSTRUCTION....................................................16
   3.1.1  Development of Plans................................................16
   3.1.2  Change Orders.......................................................19
   3.1.3  Environmental Remediation...........................................19
   3.1.4  Development Approvals and Title Exceptions..........................19
 3.2  PREPARATION OF PREMISES FOR PERFORMANCE OF TENANT'S
      WORK....................................................................21
   3.2.1. Performance of Tenant's Work........................................22
 3.3  GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION...........................25
 3.4  REPRESENTATIVES.........................................................27
 3.5  CORRECTION OF LANDLORD'S WORK...........................................27
ARTICLE IV....................................................................27
 4.1  FIXED RENT..............................................................27
 4.2  ADDITIONAL RENT.........................................................28

                                      -11-
<PAGE>

   4.2.1  Real Estate Taxes...................................................29
   4.2.2  Insurance...........................................................30
     4.2.2.1  Insurance Taken Out by Tenant...................................30
     4.2.2.2  Insurance Taken Out by Landlord.................................31
     4.2.2.3  Tenant Reimbursement of Insurance Taken Out by Landlord.........31
     4.2.2.4  Certain Requirements Applicable to Insurance Policies...........32
     4.2.2.5  Waiver of Subrogation...........................................32
   4.2.3  Utilities...........................................................33
   4.2.4  Common Area Maintenance and Expenses................................34
   4.2.5  Payments on Account of Taxes, Insurance and Utilities...............38
 4.3  LATE PAYMENT OF RENT....................................................39
ARTICLE V.....................................................................40
 5.1  AFFIRMATIVE COVENANTS...................................................40
   5.1.1  Perform Obligations.................................................40
   5.1.2  Occupancy and Use...................................................40
   5.1.3  Repair and Maintenance..............................................41
   5.1.4  Compliance with Law.................................................42
   5.1.5  Tenant's Work.......................................................44
   5.1.6  Indemnity...........................................................44
   5.1.7  Landlord's Right to Enter...........................................45
   5.1.8  Personal Property at Tenant's Risk..................................45
   5.1.9  Payment of Landlord's Cost of Enforcement...........................45
   5.1.10 Yield Up............................................................45
   5.1.11 Estoppel Certificate................................................46
   5.1.12 Landlord's Expenses Re Consents.....................................46
   5.1.13 Rules and Regulations...............................................47
   5.1.14 Loading.............................................................47
   5.1.15 Holdover............................................................47
 5.2  NEGATIVE COVENANTS......................................................47
   5.2.1  Assignment and Subletting...........................................47
   5.2.2  Nuisance............................................................49
   5.2.3  Installation, Alterations or Additions..............................49
ARTICLE VI....................................................................49
 6.1  DAMAGE BY FIRE..........................................................49
 6.2  CONDEMNATION............................................................52
 6.3  AWARD...................................................................52
ARTICLE VII...................................................................53
 7.1  EVENTS OF DEFAULT.......................................................53
 7.2  REMEDIES................................................................54
 7.3  REMEDIES CUMULATIVE.....................................................55
 7.4  LANDLORD'S RIGHT TO CURE DEFAULTS.......................................55
 7.5  EFFECT OF WAIVERS OF DEFAULT............................................55
 7.6  NO ACCORD AND SATISFACTION..............................................56
ARTICLE VIII..................................................................56
 8.1  RIGHTS OF MORTGAGE HOLDERS..............................................56
 8.2  SUPERIORITY OF LEASE; OPTION TO SUBORDINATE.............................57

                                      -12-
<PAGE>

 8.3  LEASE AMENDMENTS........................................................57
ARTICLE IX....................................................................58
 9.1  AFFIRMATIVE COVENANTS...................................................58
   9.1.1  Perform Obligations.................................................58
   9.1.2  Repairs.............................................................58
   9.1.3  Compliance with Law.................................................58
   9.1.4  Indemnity...........................................................59
   9.1.5  Estoppel Certificate................................................59
   9.1.6  Subdivision.........................................................59
   9.1.7  Utilities...........................................................59
ARTICLE X.....................................................................60
 10.1   NOTICES FROM ONE PARTY TO THE OTHER...................................60
 10.2   QUIET ENJOYMENT.......................................................60
 10.3   EASEMENTS; CHANGES TO LOT LINES.......................................60
 10.4   LEASE NOT TO BE RECORDED..............................................60
 10.5   BIND AND INURE; LIMITATION OF LANDLORD'S LIABILITY....................61
 10.6   FORCE MAJEURE.........................................................61
 10.7   LANDLORD'S DEFAULT....................................................61
 10.8   BROKERAGE.............................................................62
 10.9   APPLICABLE LAW AND CONSTRUCTION.......................................62
 10.10  SUBMISSION NOT AN OFFER...............................................63
 10.11  SECURITY DEPOSIT......................................................63
 10.12  OPTIONS TO EXTEND.....................................................64
 10.13  INTENTIONALLY OMITTED.................................................66
 10.14  PARKING...............................................................66
 10.15  CONFIDENTIAL INFORMATION..............................................67
 10.16  SIGNAGE...............................................................67
 10.17  TELECOMMUNICATIONS EQUIPMENT..........................................68

                                      -13-
<PAGE>

                                   ARTICLE II

                                PREMISES AND TERM

2.1   PREMISES.

      Landlord hereby leases and demises to Tenant and Tenant hereby leases from
Landlord, subject to and with the benefit of the terms, covenants, conditions
and provisions of this Lease, the Premises. Tenant shall have, as appurtenant to
the Premises, the right to use in common with others, if any, entitled thereto
(i) Building Common Areas and Complex Common Areas, (ii) the building service
fixtures and equipment serving the Premises, and (iii) subject to Section 10.14
hereof, the right to use that number of nonreserved parking spaces determined by
multiplying the Rentable Square Footage of Premises by .0015 ("Tenant's Parking
Spaces") in the Garage. If the loading dock serving the Building is located in
the Premises, the tenants of the Retail Space shall have the right to use such
loading dock in accordance with reasonable rules and regulations to be mutually
agreed upon by Landlord and Tenant. Tenant shall have no right to approve
tenants for the Retail Space but Landlord represents that the retail uses of the
Retail Space shall be consistent with first-class mixed use projects in the
Boston/Cambridge, Massachusetts market.

      Landlord reserves the right from time to time, without unreasonable
interference with Tenant's use, (a) to install, repair, replace, use, maintain
and relocate for service to the Premises and to other parts of the Building, or
either, building service fixtures and equipment wherever located in the
Building, including the perimeter walls of the Premises, on the roof of the
Building, in mechanical penthouses and in any space in or adjacent to the
Premises used for shafts, stacks, pipes, conduits, wires and appurtenant
fixtures, ducts, electric or other utilities, telecommunications equipment or
other Building facilities, as well as the right of access (which right of access
shall be at reasonable times and upon reasonable notice, except in the case of
emergency) through the Premises for the purpose of operation, maintenance and
repair, provided, however, that the Annual Fixed Rent, Additional Rent (as
defined in Section 4.2 hereof) and other charges payable hereunder by Tenant
shall be proportionately reduced in the event that any such installation or
relocation of service materially reduces the usable floor area of the Premises
(other than a temporary reduction to accommodate installation, repair,
replacement, maintenance and relocation of such service); notwithstanding the
foregoing provisions of this clause (a), to the extent that the Premises include
all of the rentable square footage on a particular floor of the Building,
Landlord's right to install, repair, replace, use, maintain and relocate such
building service fixtures and equipment on such floor of the Building shall be
limited to placing or installing such building service fixtures and equipment in
shafts, pipes, stacks, conduits, chases and risers located within the central
core common area of such floor or in such other locations on such floor as may
be set forth in the Final Design Documents; or (b) to construct, alter or
relocate any Building Common Areas and/or Complex Common Areas, provided
however, that any such construction, alteration or relocation (1) shall be in
compliance with applicable zoning laws, the Development Approvals or Subsequent
Approvals, (2) shall be substantially equivalent or substantially similar to
common areas of first-class, mixed use projects in Boston or Cambridge,
Massachusetts and (3) shall not reduce the number of Tenant's Parking Spaces.

                                      -14-
<PAGE>

2.2   TERM.

      To have and to hold for a period (the "Term") commencing on the date which
is the later of the Scheduled Term Commencement Date or the Substantial
Completion Date (whichever of said dates is appropriate being referred to herein
as the "Commencement Date" or the "Term Commencement Date"), and continuing
until the Term Expiration Date, unless sooner terminated as provided in Section
3.2 or in Article VII, and subject to extension in accordance with the terms of
Section 10.12 hereof. As used herein the term "Rent Commencement Date" shall
mean that date which is four (4) calendar months after the Commencement Date.
Tenant shall have the right to access the Premises prior to the Commencement
Date for purposes of installing equipment and furnishings and performing
Tenant's Work (as hereinafter defined) in accordance with and subject to the
provisions of Section 3.2.

2.3   MODIFICATION OF CERTAIN DEFINITIONS; CERTIFICATE REGARDING COMMENCEMENT
      DATE.

      Landlord and Tenant acknowledge that the actual rentable square footage of
the Premises and the Building may, upon completion of construction of the Base
Building Improvements (as hereinafter defined), be different than the estimates
set forth in Article I hereof. Accordingly, after completion of construction of
the Base Building Improvements, Landlord will notify Tenant of the actual
Rentable Square Footage of Premises and the Rentable Square Footage of Building,
which shall be measured in accordance with the ANSI/BOMA 265.1-1996 Standard
Method for Measuring Building Rentable Area, approved June 7, 1996, for a single
tenant building. Landlord's Architect's measurements shall be subject to
verification by Tenant's Architect for conformity to the foregoing standard. If
necessary, Landlord and Tenant will execute an amendment to this Lease modifying
the definitions of Rentable Square Footage of Premises, Rentable Square Footage
of Building, Tenant's Proportionate Fraction for Building, Tenant's
Proportionate Fraction for Complex, Initial Estimated Annual Additional Rent for
Premises, Initial Estimated Annual Additional Rent for Complex, the amount of
the Security Deposit (as specified in Section 10.11) and the Tenant Allowance if
Tenant has elected to have Landlord advance the Tenant Allowance as hereinafter
set forth, and such other terms and provisions, if any, of this Lease as may be
necessary to reflect such actual measurements. Tenant shall have a period of
forty-five (45) days after the date hereof within which to notify Landlord in
writing whether Tenant intends to have Landlord advance the Tenant Allowance
(the "Tenant Allowance Notice"). In the absence of a Tenant Allowance Notice by
such date, Tenant shall be deemed to have elected not to have Landlord advance
the Tenant Allowance, in which event the last paragraph of Section 3.2.1 hereof
shall be of no force or effect. If Tenant elects to have Landlord advance the
Tenant Allowance, Landlord and Tenant shall execute an amendment to this Lease
evidencing such election, acknowledging an increase in the amount of the
Security Deposit (as specified in Section 10.11), and amending such other terms
and provisions, if any, of this Lease as may be necessary to reflect such
election. Landlord and Tenant will also execute, upon request of either, a
certificate, substantially in the form of Exhibit A-3 hereto, acknowledging the
Commencement Date of this Lease as provided for in Section 2.2 hereof, after
such Commencement Date has occurred (as described in Section 3.2 hereof).
Anything in this Lease to the contrary notwithstanding, the Premises shall
include all of the Rentable Square Footage in the Building other than the Retail
Space. "Tenant's Proportionate Fraction for

                                      -15-
<PAGE>

Building" shall be the ratio, expressed as a percentage, of the Rentable Square
Footage of Premises to the Rentable Square Footage of Building. "Tenant's
Proportionate Fraction for Complex" shall be the ratio, expressed as a
percentage, of the Rentable Square Footage of Premises to the Rentable Square
Footage of all buildings (other than any garages in the Complex and any building
or portion thereof which is not available for lease such as an information
kiosk), including the Building, which Landlord is permitted to develop in the
Complex pursuant to the PUD Approval. Landlord shall have the right to estimate
on a good faith basis, from time to time, the Rentable Square Footage of all
such buildings prior to the construction thereof. From time to time after
construction of each building in the Complex, Landlord shall notify Tenant of
the Rentable Square Footage of such buildings and shall provide to Tenant, upon
Tenant's request, such information as Tenant may reasonably request with respect
to the calculation thereof. Within thirty (30) days after notice of such
Rentable Square Footage, Tenant shall pay to Landlord or Landlord shall credit
to Additional Rent next due from Tenant, as applicable, any underpayment owed or
overpayment made, as applicable, by Tenant based upon the estimated Rentable
Square Footage of such buildings, on account of Tenant's Proportionate Fraction
for Complex of taxes and assessments and Tenant's Proportionate Fraction for
Complex of the Annual Complex Maintenance and Operation Charge and the actual
Rentable Square Footage of such buildings.

                                   ARTICLE III

                                  IMPROVEMENTS

3.1   INITIAL CONSTRUCTION.

      3.1.1 Development of Plans. Landlord has developed and Tenant hereby
approves the detailed base building description (the "Preliminary Design
Concept") set forth or referenced in Exhibit B hereto for the Building and
Premises describing in general terms the principal items of work and materials
to be performed and supplied by Landlord. Attached hereto as Exhibit B-1 is a
schedule (the "Progress Schedule") setting forth items and completion dates for
various aspects of the development and construction of the Building. Landlord
and Tenant agree to cooperate and use reasonable efforts to complete the items
in the Progress Schedule by the respective completion dates so that the
Substantial Completion Date occurs on or before the Scheduled Substantial
Completion Date. In connection therewith, Landlord shall cause Landlord's
Architect to prepare schematic architectural plans, structural and engineering
plans, elevations and building sections, and site plans for the Building based
upon the Preliminary Design Concept ("Schematic Design Documents"), which shall
mean a conceptual design of the Base Building Improvements illustrating the
scale and relationship of the components of the Base Building Improvements. The
Schematic Design Documents shall show walkways and plazas for the Building and
Lot, major landscape features, hardscaping, scale and relationship of other
major components of the Building and Lot, pedestrian and vehicular (including
service) access and flow through the Lot, lighting, survey information such as
existing elevations, benchmarks and utilities, and any known construction
limits. The Schematic Design Documents shall also include models, color
renderings and outline specifications indicating all basic materials and systems
of the proposed Base Building Improvements. The Schematic Design Documents and

                                      -16-
<PAGE>

all subsequent Design Documents shall be prepared and distributed by Landlord's
Architect in both hard copy and electronic format.

      During the development of the Schematic Design Documents, Landlord and
Tenant shall meet with representatives of the CDD (as defined in Section 3.1.4
hereof) and their respective consultants to review and refine the design of the
Building and the Lot. Thereafter, Landlord shall seek approval of the Schematic
Design Documents by the Planning Board (as defined in Section 3.1.4 hereof), and
Tenant shall cooperate with Landlord in connection therewith. If despite the
good faith efforts of Landlord and Tenant the Planning Board rejects the design
reflected in the Schematic Design Documents or insists upon major changes to the
Schematic Design Documents which are unacceptable to Landlord due to anticipated
material increases in the cost of Landlord's Work or a material delay in the
commencement or completion of Landlord's Work and if as a result thereof
Landlord is unable to obtain approval of the Schematic Design Documents by the
Planning Board by the date set forth in the Progress Schedule, as the same may
be changed by any Tenant Delay, Landlord may terminate this Lease upon thirty
(30) days prior written notice unless within such thirty-day period Tenant
agrees to pay to Landlord the increases in the cost of Landlord's Work resulting
from such changes and delays. If Tenant does not agree within such thirty-day
period to pay to Landlord the increases in the cost of Landlord's Work resulting
from such changes and delays and Planning Board approval of the Schematic Design
Documents is not obtained by the end of such thirty-day period, this Lease shall
thereupon terminate. Planning Board approval of the Schematic Design Documents
shall be a Subsequent Approval (as defined in Section 3.1.4 hereof). Landlord
and Tenant agree to cooperate in connection with any conditions imposed by the
Planning Board in connection with the Planning Board's approval of the Schematic
Design Documents, such as further review of the Design Documents by the CDD.

      At such time as the Schematic Design Documents have been approved by
Landlord and by the Planning Board, Landlord shall cause Landlord's Architect to
prepare further details and development of the Schematic Design Documents (the
"Design Development Documents") for the Building and the Base Building
Improvements, which shall mean plans, sections and elevations, typical
construction details, and equipment layouts showing the scope, relationships,
forms, size and appearance of the Base Building Improvements. Design Development
Documents shall include architectural, mechanical and electrical drawings and
details of the Building, exterior materials to be incorporated in the Building,
walkways and other plaza areas on the Lot, a site and landscape plan for the Lot
showing all site development and landscape detail for lighting, paving,
landscaping, utilities, grading, drainage, access and service areas. The Design
Development Documents shall also include outline specifications indicating all
basic materials and mechanical and electrical systems of the proposed Base
Building Improvements. As with the Schematic Development Documents, the Design
Development Documents shall be prepared and distributed in both hard copy and
electronic format.

      At such time as the Design Development Documents have been approved by
Landlord, Landlord shall cause Landlord's Architect to prepare detailed
construction drawings and specifications ("Final Design Documents") which shall
set forth in detail the requirements for construction of Landlord's Work
(including all architectural, mechanical, electrical and structural drawings and
detailed specifications), shall be fully coordinated with one another and with
field conditions as they exist on the Lot, and shall show all work necessary to
complete Landlord's

                                      -17-
<PAGE>

Work, including all cutting, fitting, and patching and all connections to the
mechanical and electrical systems and components of the Base Building
Improvements. The Final Design Documents shall be used for the construction of
the Base Building Improvements and shall be based upon the Design Development
Documents and other information which is relevant to the design and construction
of the Base Building Improvements. The Final Design Documents shall be prepared
and stamped by Landlord's Architect. The Preliminary Design Concept, the
Schematic Design Documents and the Final Design Documents (collectively, the
"Design Documents") shall not include any of Tenant's Work (as hereinafter
defined). As used herein, the term "Base Building Improvements" shall mean the
items of work and materials to be performed and supplied by Landlord in
accordance with the Final Design Documents as affected by Change Orders (as such
term is hereafter defined) and the term "Landlord's Work" shall mean the
construction of the Base Building Improvements in accordance with the Final
Design Documents as affected by Change Orders. Prior to the solicitation of bids
by Landlord from general contractors for the performance of Landlord's Work,
Tenant may submit the names of general contractors to be included on the list of
such bidders, but Landlord shall retain the right to select Landlord's
Contractor.

      The preliminary and final Schematic Design Documents, the preliminary and
final Design Development Documents, and the Final Design Documents shall be
submitted to both Landlord and Tenant for review and comment. In each instance
Tenant shall have five business days to review each submission and to notify
Landlord of any objections. Tenant may object to any new items shown on a
submission which are not in compliance with (i) the Preliminary Design Concept
with regard to the Schematic Design Documents, (ii) the Schematic Design
Documents with regard to the Design Development Documents, or (iii) the Design
Development Documents with regard to the Final Design Documents, specifying and
detailing in each case such objections. To the extent that any such submission
is consistent with prior submissions approved by Tenant, Tenant shall have no
right to object thereto, but Tenant may nonetheless offer comments thereon,
which comments Landlord agrees to consider if the implementation thereof will
not increase the cost of Landlord's Work or delay the commencement or completion
thereof, provided that if Tenant agrees to pay Landlord for increases in such
cost of Landlord's Work and the cost of any such delays, Landlord agrees that
Landlord will not unreasonably refuse to implement such comments. If Tenant
objects to any such submission because such submission is inconsistent with the
prior submission approved by Tenant, Landlord shall cause Landlord's Architect
to modify such submission to respond to Tenant's objection and submit such
modified submission to Tenant within five (5) business days after receipt of
Tenant's objections for review by Tenant in the same manner as with regard to
the prior submission. Landlord and Tenant agree to cooperate with one another
diligently and in good faith to complete the review of all Design Document
submissions and to resolve any objections of Tenant with respect to such
submissions. Tenant's Architect, on behalf of Tenant, may participate in the
review of all Design Document submissions and in the resolution of any
objections of Tenant with respect to such submissions. Tenant acknowledges that
a number of additional licenses, permits and approvals may be required in order
for Landlord to commence and complete construction of the Base Building
Improvements and Tenant agrees to cooperate with Landlord in obtaining the same.

      3.1.2 Change Orders. As used herein, the term "Change Order" shall mean
(A) a written order from Landlord which Landlord determines is necessary to
carry out the approved

                                      -18-
<PAGE>

design and construction of the Base Building Improvements, whether due to any
mistake or omission in, or clarification of, the Design Documents, or (B) a
written order to Landlord from Tenant requesting or authorizing a Change in
Landlord's Work or an adjustment of the Progress Schedule. If Tenant requests
any change order for the Base Building Improvements, Landlord shall submit all
such Change Orders with plans, specifications, pricing and a schedule of values
if appropriate to Tenant for its review and approval. No Change Order for a
change in the Base Building Improvements requested by Tenant shall be effective
unless approved by Landlord's Representative and Tenant's Representative in
writing, such approval not to be unreasonably withheld or delayed. Tenant shall
pay an amount equal to all costs directly incurred by Landlord as a result of
any Change Orders signed by Tenant and Landlord affecting Landlord's Work or the
Base Building Improvements, including the cost to Landlord of Landlord's
Contractor's overhead and profit equal to 10% of those costs exclusive of
overhead and profit. Amounts due and payable on account of such Change Orders
shall be paid within fifteen (15) days of billing therefor, and in all events by
the Substantial Completion Date. If, however, Tenant has elected to have
Landlord advance the Tenant Allowance, amounts due and payable by Tenant on
account of such Change Orders may be applied to the extent of the unadvanced
balance, if any, of the Tenant Allowance. After completion of the Base Building
Improvements, Landlord shall deliver a set of as built plans for the Base
Building Improvements to Tenant upon Landlord's receipt thereof. Landlord agrees
to provide Tenant with copies of all Change Orders for the Base Building
Improvements from Landlord. Tenant shall have five (5) business days after the
receipt thereof to review and approve or disapprove of any such Change Orders.
Tenant may disapprove a Change Order from Landlord only if such Change Order
would materially and adversely affect Base Building Improvements. If Tenant does
not notify Landlord of Tenant's disapproval within such five-business day
period, Tenant shall be deemed to have approved such Change Order.

      3.1.3 Environmental Remediation.

      Landlord shall be responsible for undertaking and completing environmental
remediation of the Lot ("Environmental Remediation") pursuant to an
Environmental Agreement (the "Environmental Agreement") between Landlord and
Tenant in the form of Exhibit F hereto. Landlord has delivered to Tenant the
documents set forth on Exhibit F-1 hereto (the "Remediation Documents") and
Landlord will provide Tenant with such additional information pertaining to
Environmental Remediation and hazardous substances present on other portions of
the Lot as Tenant reasonably may request, including correspondence with
regulatory authorities and other governmental bodies with respect to the
Environmental Remediation.

      3.1.4 Development Approvals and Title Exceptions.

      Reference is hereby made to (i) a Special Permit issued by the City of
Cambridge Planning Board (the "Planning Board"), Case No. PB #141 filed April 7,
1999 (the "PUD Permit"), recorded with the Middlesex South District Registry of
Deeds (the "Registry") in Book 31137, Page 89 as affected by a Settlement
Agreement dated May 24, 1999 among Barbara Broussard, Mary DeFreitas, the East
Cambridge Planning Team and Landlord (the "Settlement Agreement") (the PUD
Permit and the Settlement Agreement are herein collectively referred to herein
as the "PUD Approval"), (ii) PTDM Ordinance Final Decision issued April 20, 1999
by the Community Development Department ("CDD") of the City of Cambridge (the
"PTDM Decision"), the Letter dated April 20, 1999 to Robert L. Green of Lyme
Properties from Susanne

                                      -19-
<PAGE>

Rasmussen of the CDD (the "PTDM Letter") attached to the PTDM Decision, and
Landlord's Parking Transportation Demand Management Plan dated April 9, 1999
(the "PTDM Plan") (the PTDM Decision, the PTDM Letter and PTDM Plan are
collectively referred to herein as the "PTDM Approval"), (iii) a Certificate of
the Secretary of Environmental Affairs on the Final Environmental Impact Report
dated April 15, 1999 (the "MEPA Certificate"), (iv) an Order of Conditions
issued July 12, 1999 by the City of Cambridge Conservation Commission (the
"Order of Conditions") and (v) a Determination for Issuance of a Waterways
License Amendment dated December 8, 1999, issued by the Executive Office of
Environmental Affairs of the Commonwealth of Massachusetts (the "Chapter 91
Determination"), (collectively, the "Development Approvals"). Reference is also
hereby made to Item Nos. 2 through 12, inclusive (the "Title Exceptions") set
forth in Schedule B, Part 1 of Owner's Policy No. 136-00-336684 dated August 19,
1998, issued by Lawyer's Title Insurance Corporation (the "Title Policy").
Tenant acknowledges that Landlord has delivered to Tenant copies of the
Development Approvals, the Title Exceptions and the Title Policy. This Lease,
and the development, construction and operation of the Building, the Lot and the
Complex, shall be subject to the Development Approvals, the license to be issued
pursuant to the Chapter 91 Determination, the Title Exceptions and all other
determinations, approvals, decisions and actions of governmental authorities
having jurisdiction of the Complex hereafter issued pursuant to or contemplated
by the Development Approvals and delivered to Tenant ("Subsequent Approvals").
Each of Landlord and Tenant, in the exercise of their respective rights and the
performance of their respective obligations pursuant to this Lease, shall
observe and comply with all requirements of the Development Approvals and
Subsequent Approvals.

      Without limiting the generality of the foregoing, to the extent required
for compliance with the PUD Permit and the PTDM Approval, as the same may be
affected by Subsequent Approvals (but only for so long as the same remain in
force and effect from time to time), Tenant shall comply with the following: (a)
Tenant shall comply with the obligations of the PTDM Approval applicable to
tenants, employers and/or employees in the Complex, (b) Tenant shall cooperate
with Landlord in the implementation of the Additional Recommendations set forth
in the PTDM Letter if the mode split goal of the PTDM Approval is not achieved,
(c) Tenant shall cooperate with Landlord and/or the Charles River Transportation
Management Association or any other transportation management association of
which Landlord is a member (a "TMA") in implementing the PTDM Approval and TMA
programs (and Tenant is hereby encouraged to participate in all TMA programs),
(d) Tenant shall establish a guaranteed ride home program for Tenant's employees
as provided in the PUD Approval and the PTDM Approval, as the same may be
affected by Subsequent Approvals, (e) Tenant shall, either directly or through a
program established by Landlord or a TMA for tenants of the Complex, complete
surveys pursuant to Section III D of the PTDM Plan, (f) as required by the PUD
Approval and PTDM Approval, as the same may be affected by Subsequent Approvals,
Tenant shall contract with the MBTA and subsidize transit passes and commuter
rail passes in an amount not less than 60% of the cost thereof or such higher
percentage as Landlord may require if mode split commitments are not achieved,
(g) as provided in the PTDM Approval, as the same may be affected by Subsequent
Approvals, Tenant shall cooperate with Landlord in connection with surveys
concerning attitudes of employees and customers of Tenant in order to refine and
develop transportation demand management programs, (h) Tenant shall provide
Tenant's employees with information provided to Tenant by or on behalf of
Landlord pursuant to the PTDM Plan, including information on the advantages and
benefits of telecommuting, flexible time, compressed work week programs, the

                                      -20-
<PAGE>

materials to be provided pursuant to Section VII A of the PTDM Plan and other
programs recommended by the City of Cambridge, (i) as provided in the PTDM
Approval, as the same may be affected by Subsequent Approvals, Tenant is hereby
encouraged to use a commuter choice program which allows qualifying employees
the option of receiving the cash value of a Tenant's Parking Space, (j) Tenant
shall participate in and pay a reasonable share (which shall not be less than
Tenant's Proportionate Fraction for Complex) of the cost of any TMA shuttle bus
service serving the Complex, as contemplated by the PTDM Approvals, and (k)
Tenant shall cooperate with Landlord with respect to all other aspects of the
PTDM Approval.

3.2   PREPARATION OF PREMISES FOR PERFORMANCE OF TENANT'S WORK.

Landlord agrees to use reasonable efforts to have the Premises ready for the
performance of Tenant's Work on or before the Scheduled Substantial Completion
Date which shall, however, be extended for a period equal to that of (a) any
delays due to Acts of God, or by labor disputes, fire, unusual delays in
deliveries, unavoidable casualties or other causes beyond Landlord's reasonable
control (collectively, "Force Majeure Events") and (b) any delays due to (i) any
changes in any of the Design Documents (other than the Preliminary Design
Concept or any objections of Tenant to a submission of Design Documents because
of inconsistencies with the prior submission of Design Documents) requested by
Tenant and approved by Landlord or any changes in the Base Building Improvements
requested by Tenant and approved by Landlord, (ii) any act or neglect of Tenant,
or of any employee, agent, or separate contractor of Tenant, (iii) the
concurrent performance of the Base Building Improvements and Tenant's Work, (iv)
Tenant's failure to respond to any request by Landlord for information or
approval within five (5) business days of Landlord's request, or (v) any breach
or default by Tenant in the performance of Tenant's obligations pursuant to this
Lease, even if such breach or default is cured (collectively, "Tenant Delay").
The Premises shall be deemed ready for the performance of Tenant's Work on the
Substantial Completion Date (as hereinafter defined). As used herein, the term
"Substantial Completion Date" shall mean and refer to the date on which: (i) the
Base Building Improvements are substantially complete as certified by Landlord's
Architect and verified by Tenant's Architect, with the exception of minor items
which can be fully completed by Landlord within thirty (30) days without
material interference with Tenant and other items which because of the season or
weather or the nature of the item are not practicable to do at the time,
provided that none of said items is necessary to perform Tenant's Work
(collectively "Punch List Items"), (ii) if Tenant's Work has not then commenced,
a Certificate of Occupancy from the City of Cambridge (or a Temporary
Certificate of Occupancy with conditions which can be satisfied without material
interference with the performance of Tenant's Work ) shall have been obtained,
(iii) the Premises is broom clean and free of debris except to the extent, if
any, resulting from Tenant's Work, and (iv) all utilities required for the use
of the Premises have been brought by Landlord to the Utility Switching Points
(as defined in Section 4.2.3 hereof); provided, however, that if the Substantial
Completion Date does not occur on or before the Scheduled Substantial Completion
Date due to any Tenant Delay then the Base Building Improvements shall be deemed
to be substantially completed, and the Substantial Completion Date shall be
deemed to have occurred, on the date on which the Substantial Completion Date
would have occurred taking into account any Force Majeure Events but without
taking into account any Tenant Delay. If Landlord's Architect has certified that
the Base Building Improvements are substantially complete but Tenant's Architect
does not verify the same within five (5) business days thereafter, Landlord's
Architect and Tenant's Architect shall immediately select a third

                                      -21-
<PAGE>

independent architect who shall conclusively determine whether the Base Building
Improvements are substantially complete. Landlord and Tenant shall share equally
the costs of such third architect. Landlord's obligations under Sections 3.1 and
3.2 shall be deemed to have been performed on the Substantial Completion Date
except for Punch List Items and items which do not conform with the requirements
of Sections 3.1 and 3.2 and as to which Tenant or Tenant's Architect shall have
given written notice to Landlord prior to such date. If Tenant or Tenant's
Architect does not provide such written notice prior to the Substantial
Completion Date, a certificate of substantial completion by a licensed architect
or registered engineer shall be conclusive evidence that Landlord has performed
all such obligations except for Punch List Items and items stated in such
certificate to be incomplete or not in conformity with such requirements.

      Notwithstanding the foregoing, Tenant shall have the right to terminate
this Lease upon notice given to Landlord on or before the date which is 180 days
after the Scheduled Substantial Completion Date in the event that the
Substantial Completion Date, as extended due to the occurrence of any Tenant
Delay, has not occurred on or before the date which is 180 days after the
Scheduled Substantial Completion Date, as so extended for Tenant Delay (as so
determined, the "Outside Completion Date").

      3.2.1. Performance of Tenant's Work.

      Except for the Base Building Improvements to be performed by Landlord in
accordance with the Final Design Documents as affected by Change Orders, all of
Tenant's initial interior improvements, fixtures, finishes, furnishings,
furniture, telephones, movable equipment and signs visible from the exterior of
the Building (collectively, "Tenant's Work"), shall be performed at the sole
cost and expense of Tenant, provided however, that subject to this Section 3.2.1
Landlord shall advance up to the amount of the Tenant Allowance if Tenant elects
to have Landlord advance the Tenant Allowance. Tenant's Representative shall
serve as construction manager for Tenant's Work. Tenant's performance of
Tenant's Work shall be coordinated with any work being performed by Landlord in
such manner as to maintain harmonious labor relations during the performance of
the Base Building Improvements and not to damage the Building or Lot or
interfere with Building or Lot operations. All work described in Tenant's Work
shall be performed by Landlord's Contractor (if Tenant enters into a contract
with Landlord's Contractor for the initial Tenant's Work) or by a contractor
selected by Tenant and approved by Landlord, which approval shall not be
unreasonably withheld ("Tenant's Contractor"). The performance of Tenant's Work
in accordance with this Lease shall not be deemed to be a violation of the
Permitted Uses of the Premises. Except as set forth in Sections 3.3 and 5.1.10
hereof and Exhibit E hereto, all Tenant's Work shall become a part of the
Premises and upon termination of this Lease shall be considered to be the
property of the Landlord.

      Tenant shall not effect any Tenant's Work (or any alterations or additions
to the Premises after performance of Tenant's Work) that might (i) diminish the
value of the Premises for laboratory/office use, or (ii) require any unusual
expense to re-adapt the Premises for any laboratory/office use.

                                      -22-
<PAGE>

      Tenant's Work shall be performed in accordance with complete, consistent,
final construction drawings and specifications ("Construction Documents")
approved in advance by Landlord in writing, which approval shall not be
unreasonably withheld. The Construction Documents shall be prepared and stamped
by Tenant's Architect and approved by Landlord in writing. Landlord reserves the
right to reject, in whole or in part, the Construction Documents which in its
reasonable opinion fail to comply with the provisions of this Lease within
fifteen (15) business days of its receipt thereof (the "Review Period"). The
Review Period shall not commence unless and until Tenant delivers a complete set
of Construction Documents. If Landlord shall disapprove the Construction
Documents, it shall state specifically the reasons therefor, and Tenant shall
promptly revise and resubmit the Construction Documents. If Landlord fails to
respond to Tenant's request for approval of the Construction Documents within
the Review Period then the Construction Documents shall be deemed approved.

      Tenant shall be solely responsible for the liabilities of and expenses of
all architectural and engineering services relating to Tenant's Work and for the
adequacy, accuracy, and completeness of the Construction Documents approved by
Landlord unless Tenant elects that Landlord advance the Tenant Allowance (and if
so elected, then only to the extent of the Tenant Allowance). The Construction
Documents (i) shall set forth in detail the requirements for construction of the
Tenant's Work (including all architectural, mechanical, electrical and
structural drawings and detailed specifications), (ii) shall be fully
coordinated with one another, with field conditions as they exist in the
Premises and elsewhere in the Building and the Final Design Documents, and (iii)
shall show all work necessary to complete the Tenant's Work including all
cutting, fitting, and patching and all connections to the mechanical and
electrical systems and components of the Building. Tenant agrees to hold
Landlord harmless if any Tenant's Work described in the Construction Documents
(a) fails to comply with all applicable laws, regulations, building codes, and
building design standards, (b) in any manner affects any structural component of
the Building (including, without limitation, exterior walls, exterior windows,
core walls, roofs or floor slabs), (c) in any respect is incompatible with the
electrical and mechanical components and systems of the Building, (d) affects
the exterior of the Building, (e) fails to conform to floor loading limits, and
(f) with respect to all materials, equipment and special designs, processes, or
products, infringes on any patent or other proprietary rights of others.
Landlord's approval or deemed approval of the Construction Documents and the
performance of Tenant's Work pursuant to the Construction Documents shall not
result in any liability of Landlord, except to the extent that Tenant elects to
have Landlord advance the Tenant Allowance, and Landlord's approval of
Construction Documents shall signify only Landlord's consent to Tenant's Work
shown thereon and shall not result in any responsibility of Landlord concerning
compliance of Tenant's Work with laws, regulations, or codes, coordination of
any aspect of Tenant's Work with any other aspect of Tenant's Work, or the
feasibility of constructing Tenant's Work without material damage or harm to the
Building, all of which shall be the sole responsibility of Tenant.

      After Tenant's Contractor has been approved, then the same may thereafter
be used by Tenant until Landlord notifies Tenant that Tenant's Contractor is no
longer approved due to Tenant's Contractor's failure to comply in any material
respect with the requirements of the Construction Documents and/or this Lease.
Tenant shall procure all necessary governmental permits, licenses and approvals
before undertaking any Tenant's Work. Tenant shall perform all

                                      -23-
<PAGE>

Tenant's Work at Tenant's risk in compliance with all applicable laws, codes and
regulations and in a good and workmanlike manner employing new materials of good
quality. When any Tenant's Work is in progress, Tenant shall cause to be
maintained (i) insurance as may be required by Landlord covering any additional
hazards due to such Tenant Work, and (ii) a statutory lien bond pursuant to
M.G.L. c.254, ss.12 or any successor statute (or such other protection of
Landlord's interest in the Building and Lot against liens as Landlord may
reasonably require), in each case for the benefit of Landlord. It shall be a
condition of Landlord's approval of any Tenant's Work that certificates of such
insurance and a lien bond in recordable form, both issued by responsible
insurance companies qualified to do business in Massachusetts and reasonably
approved by Landlord, shall have been deposited with Landlord, that Tenant has
provided Tenant's certification of the insurable value of the work in question
for casualty insurance purposes, and that all of the other conditions of the
Lease have been satisfied. Tenant shall reimburse up to [*****Confidential*****]
for Landlord's reasonable costs of reviewing proposed Tenant's Work and
inspecting installation of the same, provided however, that if Tenant elects to
have Landlord advance the Tenant Allowance, such costs may be paid from the
Tenant Allowance. At all times while performing Tenant's Work, Tenant shall
require any Tenant's Contractor to comply with all applicable laws, regulations,
permits and policies relating to such work. In performing Tenant's Work, each
Tenant's Contractor shall comply with the Development Approvals, the Subsequent
Approvals (in each case to the extent applicable), Landlord's requirements set
forth in Section 3.2.1, the first paragraph of Section 3.3, Section 5.1.5 and
Section 5.2.3 hereof relating to the time and methods for such work, use of
delivery elevators and other Building facilities and each Tenant's Contractor
shall not interfere or disrupt Landlord's Contractor. Each Tenant's Contractor
shall in all events work on the Premises without causing labor disharmony,
coordination difficulties, or delay, and without impairing any guaranties,
warranties or obligations of any contractors of Landlord. If any Tenant's
Contractor uses any Building services or facilities, such Contractor, jointly
and severally with Tenant, shall agree to reimburse Landlord for the cost
thereof based on Landlord's schedule of charges established from time to time
(and if no such charges have been established, then based on Landlord's
reasonable charge established at the time). Each Tenant's Contractor shall, by
entry into the Building, be deemed to have agreed to indemnify and hold Landlord
harmless from any claim, loss or expense arising in whole or in part out of any
act or neglect committed by such person while in the Building, to the same
extent as Tenant has so agreed in this Lease, the indemnities of Tenant and
Tenant's Contractor to be joint and several.

      Tenant shall pay on or prior to date when any such payment is due, either
from its own funds or from the Tenant Allowance if Tenant elects to have
Landlord advance the Tenant Allowance, the entire cost of all Tenant's Work so
that the Premises shall always be free of liens for labor or materials. If any
mechanic's lien (which term shall include all similar liens relating to the
furnishing of labor and materials) is filed against the Premises or the Building
or any part thereof which is claimed to be attributable to Tenant, its agents,
employees or contractors, Tenant shall promptly discharge the same by payment or
filing any necessary bond within thirty (30) days after Tenant has notice (from
any source) of such mechanic's lien. Landlord may, as a condition of its
approval of any Tenant's Work, require Tenant to deposit with Landlord a bond,
letter of credit or other similar security in the amount of Landlord's
reasonable estimate of the value of such Work securing Tenant's obligations to
make payments for such Work.

                                      -24-
<PAGE>

      Landlord shall permit Tenant and Tenant's Contractor access to the
Premises prior to the Commencement Date for the performance of Tenant's Work if
Tenant employs Landlord's Contractor or another contractor approved by Landlord
for the performance of Tenant's Work and if the concurrent performance of the
Base Building Improvements and Tenant's Work will not delay the Substantial
Completion Date. Subject to the foregoing, Landlord shall cooperate with
Tenant's Contractor in connection with Tenant's Work. Subject to Sections 7.1(h)
and 10.6 hereof, Tenant shall, in any event, substantially complete all Tenant's
Work required for the initial occupancy of (a) fifty percent (50%) of the
Premises by Tenant within six (6) months after the Commencement Date, (b)
seventy-five percent (75%) of the Premises within twenty-four (24) months after
the Commencement Date, and (c) one hundred percent (100%) of the Premises within
thirty-six (36) months after the Commencement Date.

      If Tenant elects to have Landlord advance the Tenant Allowance, Tenant
shall provide Landlord with a budget and copies of all contracts entered into
with respect to Tenant's Work and such other information as Landlord reasonably
may request. The Tenant Allowance shall be advanced to Tenant by Landlord no
more frequently than monthly against costs then incurred but unpaid by Tenant
with respect to Tenant's Work. The Tenant Allowance shall be advanced to Tenant
in the proportion which the Tenant Allowance bears to Tenant's budget, as the
same may be updated, for Tenant's Work. Tenant shall make application to
Landlord for an advance of the Tenant Allowance at least ten (10) business days
prior to the date upon which an advance is to be made. Such application shall be
on such form or forms as Landlord reasonably may require, and shall be
accompanied by invoices, receipts, lien waivers and such other documents as
Landlord reasonably may require.

3.3   GENERAL PROVISIONS APPLICABLE TO CONSTRUCTION.

      All construction work required or permitted by this Lease, whether by
Landlord or by Tenant, shall be done in a good and workmanlike manner and in
compliance with all Development Approvals, Subsequent Approvals, applicable laws
and all lawful ordinances, regulations and orders of any governmental authority
or insurer of the Building. Either party may inspect the work of the other at
reasonable times and shall give notice of observed defects. Landlord shall not
be responsible for any loss, damage, or injury resulting from the installation
of any components, fixtures, or equipment provided they were appropriately
specified and installed in accordance with the manufacturer's or supplier's
instructions; provided, however, that Landlord shall assign any and all
contractor's, manufacturer's and supplier's warranties with respect to all
components, fixtures, or equipment, including, without limitation, Landlord's
Contractor's warranty, to Tenant for the Term of this Lease, upon the expiration
or sooner termination of which such warranties shall automatically revert to
Landlord.

      After the performance of Tenant's Work, Tenant will not make any
alterations or additions to the Premises without Landlord's approval, which
approval shall not be unreasonably withheld or delayed provided that Landlord
and Tenant shall agree in writing whether Tenant will be required to, permitted
to or forbidden to, at Tenant's sole cost and expense, remove any such
alteration or addition upon the expiration or termination of this Lease.
Landlord's approval of any alteration or addition which is not a Minor
Alteration (as defined below in this Section 3.3) shall be deemed to have been
given if Landlord fails to notify Tenant of its objection thereto

                                      -25-
<PAGE>

within fifteen (15) business days after Tenant's request for such approval. In
circumstances in which Tenant desires the right to remove additions or
alterations at the expiration or termination of this Lease, Landlord shall
reasonably agree, and such agreement shall not be unreasonably withheld or
delayed (and shall be deemed to have been given if Landlord fails to notify
Tenant of its objection thereto within fifteen (15) business days after Tenant's
request for such agreement), to permit such removal (i) where items installed by
Tenant are in the nature of equipment, but are so affixed to Building that such
items may be construed as fixtures or (ii) where additions or alterations of
Tenant include specific items that after removal from the Building will have in
the aggregate for each such alteration or addition a fair market value of
$25,000.00 or greater. Tenant's rights to remove additions or alterations
hereunder shall not apply to replacement of items included in Tenant's Work that
are replaced due to the fact that such items have worn out or become
substantially obsolete. In the event the Tenant is required to or permitted to
remove any such alteration or addition, as a condition to Landlord's approval of
such alteration or addition, Tenant shall agree in writing to readapt, repair
and restore the Premises to the condition the same were in prior to such
alteration or addition. After the performance of Tenant's Work, all changes and
additions shall be part of the Building except such items as by writing at the
time of approval the parties agree either shall be removed by Tenant on
termination of this Lease, or shall be removed or left at Tenant's election.

      Notwithstanding the foregoing, the parties hereby agree that for any
non-structural alterations or additions to the Premises which do not involve
modifications to the Building operating systems and for which the cost may be
reasonably estimated to be less than $100,000 (each a "Minor Alteration"): (i)
Landlord's prior written consent shall not be required unless such Minor
Alteration requires a building permit from the City of Cambridge, in which case
Landlord's reasonable consent shall be required, provided that such consent
shall be deemed to have been given if Landlord fails to notify Tenant of its
objection to such Minor Alteration within 2 days after Tenant's request for
Landlord's consent with respect thereto, and (ii) upon the expiration or
termination of this Lease, Tenant shall readapt, repair and restore the Premises
to the condition the same were in prior to such Minor Alteration, regardless of
whether Landlord's consent was required or obtained with respect thereto.
Additionally, Tenant shall give prior written notice to Landlord of any Minor
Alteration for which the cost may be reasonably estimated to be less than
$100,000 but greater than $25,000 and regardless of whether Landlord's consent
is required.

      The parties further agree that after the performance of Tenant's Work (a)
any request for consent to any alteration or addition (including, without
limitation, any Minor Alteration) shall be accompanied by drawings and
specifications in reasonable detail given the size and scope of the proposed
alteration or addition, and (b) Tenant shall furnish Landlord as-built drawings
showing any and all alterations or additions (including, without limitation, any
and all Minor Alterations) made by Tenant or any assignee, sublessee or licensee
of Tenant within 30 days after completion of the same.

3.4   REPRESENTATIVES.

      Each party authorizes the other to rely in connection with their
respective rights and obligations under this Article III upon approval and other
actions on the party's behalf by Land-

                                      -26-
<PAGE>

lord's Representative in the case of Landlord and Tenant's Representative in the
case of Tenant or by any person hereafter designated in substitution or addition
by notice to the party relying.

3.5   CORRECTION OF LANDLORD'S WORK.

      If within one year after the Substantial Completion Date (i) any item of
Base Building Improvements does not conform with the Final Design Documents, as
affected by Change Orders, or (ii) there is any defect in the Base Building
Improvements caused by faulty workmanship performed on behalf of Landlord or
materials installed on behalf of Landlord, Landlord, upon written notice thereof
from Tenant prior to the expiration of such one-year period, shall forthwith
cause the contractor(s) who or which performed such work to correct such
nonconformity or defect without cost or expense to Tenant. Nothing set forth in
this Section shall affect or impair any warranties specified in Section 3.3
hereof or any right of Tenant to pursue any action, right or remedy otherwise
available to Tenant due to a breach by Landlord of its obligations pursuant to
this Lease.

                                   ARTICLE IV

                                      RENT

4.1   FIXED RENT.

      (a) Monthly Installments; Definitions. Commencing on the Rent Commencement
Date, Tenant covenants and agrees to pay Fixed Rent (as hereinafter defined) for
the Premises to Landlord by wire transfer as Landlord may from time to time
direct in writing, without any offset or reduction whatsoever (except as may be
made in accordance with the express provisions of this Lease), or in the absence
of wire transfer instructions from Landlord, at the Original Address of Landlord
or at such other place or to such other person or entity as Landlord may by
notice to Tenant from time to time direct, in the amount of (x) the Annual Fixed
Rent Rate set forth in Article I multiplied by (y) the Rentable Square Footage
of Premises, and subject to adjustment as set forth in Sections 4.1(b) 10.11 and
10.12 hereof (collectively "Fixed Rent" or "Annual Fixed Rent"), in equal
installments equal to 1/12th of the Annual Fixed Rent Rate in advance on the
first day of each calendar month included in the Term; and for any portion of a
calendar month at the beginning or end of the Term, at that rate payable in
advance for such portion.

      (b) Adjustment for CPI. On the fifth anniversary of the Rent Commencement
Date , on the tenth anniversary of the Rent Commencement Date, and on the fifth
anniversary of the commencement of each Extension Period (as such term is
defined in Section 10.12 hereof) (each an "Adjustment Date") the Annual Fixed
Rent Rate shall be increased by multiplying said rate by the lesser of (i) a
fraction, the numerator of which shall be the Price Index (as hereinafter
defined) most recently published prior to the Adjustment Date, and the
denominator of which shall be the Base Price Index (as hereinafter defined), or
(ii) one hundred four percent (104%) per year, compounded annually over the then
prior five (5) years of the Term of this Lease. As used herein, the term "Price
Index" shall mean and refer to the "Consumer Price Index for Urban Wage Earners
and Clerical Workers, for the Boston, Massachusetts area, All Items
(1982-84=100)" published by the Bureau of Labor Statistics of the United States
Department of

                                      -27-
<PAGE>

Labor or successor or substitute index appropriately adjusted, and the term
"Base Price Index" shall mean and refer to the Price Index most recently
established prior to (a) the Commencement Date or (b) with respect to any
Extension Period, the commencement date of such Extension Period, as applicable.
In the event the Price Index (or a successor or substitute index) shall not be
published for the City of Boston, or for the months indicated above, the
corresponding index for the United States City Average (and if this is not
available, a reliable governmental or other nonpartisan publication evaluating
similar or equivalent information as used in the Price Index) shall be used. In
the event the Price Index ceases to use the 1982-84 average of 100 as the basis
of calculation, or if a substantial change is made in the terms or numbers of
items contained in the Price Index, then the Price Index shall be adjusted to
the figure that would have been arrived at had the manner of computing the Price
Index in effect at the date of this Lease not been changed.

4.2   ADDITIONAL RENT.

      As used herein, the term "Additional Rent" shall mean all rent, charges
and other sums, other than Fixed Rent, due Landlord pursuant to this Lease. All
regularly recurring items of Additional Rent, such as the Annual Maintenance
Charge, shall be paid by Tenant to Landlord by wire transfer as Landlord may
from time to time direct in writing, or in the absence of wire transfer
instructions from Landlord, at the Original Address of Landlord. Nonrecurring
items of Additional Rent shall be paid by Tenant to Landlord by check or wire
transfer as Tenant may from time to time elect. In order that the Fixed Rent
shall be absolutely net to Landlord, commencing on the Commencement Date, Tenant
covenants and agrees to pay, as Additional Rent, without any offset or reduction
whatsoever except as expressly set forth in this Lease, taxes, municipal or
state betterment assessments, insurance costs, utility charges and the Annual
Maintenance Charge with respect to the Premises as provided in this Section 4.2
as follows:

      As used herein, the term "Estimated Annual Additional Rent" shall mean and
refer to Landlord's estimate of the total amount of Additional Rent which may be
due from Tenant for any particular Lease Year with respect to the Building, Lot
and Complex. Landlord shall furnish Tenant with a statement within sixty (60)
days after the commencement of each Lease Year setting forth the amount of
Landlord's Estimated Annual Additional Rent for such Lease Year. Landlord's good
faith estimate of the Estimated Annual Additional Rent for the first "fiscal
year" (as such term is defined in Section 4.2.4 hereof) of the Term is set forth
in Section 1.1 as the "Initial Estimated Annual Additional Rent for Premises"
and "Initial Estimated Annual Additional Rent for Complex".

      4.2.1 Real Estate Taxes. Tenant shall pay directly to the Landlord: (i)
Tenant's Proportionate Fraction for Building and Tenant's Proportionate Fraction
for Complex, respectively, of all taxes, assessments (special or otherwise),
levies, fees, water and sewer rents and charges, and all other government levies
and charges, general and special, ordinary and extraordinary, foreseen and
unforeseen, which are, at any time during the Term hereof, imposed or levied
upon or assessed against the Premises, the Building, the Lot or the Complex, and
(ii) the full amount of any tax or assessment imposed or levied upon or against
(A) any Fixed Rent, Additional Rent or other sum payable hereunder, (B) this
Lease, or the leasehold estate hereby created, or which arise in respect of the
operation, possession or use of the Premises; (C) all gross receipts or similar
taxes imposed or levied upon, assessed against or measured by any

                                      -28-
<PAGE>

Fixed Rent, Additional Rent or other sum payable hereunder; and (D) all sales,
value added, use and similar taxes at any time levied, assessed or payable on
account of the acquisition, leasing or use of the Premises (and Tenant's
Proportionate Fraction for Building and Tenant's Proportionate Fraction for
Complex, respectively, of any such taxes if they are levied, assessed or payable
on account of the acquisition, leasing or use of the entire Building, Lot or the
Complex) which may become a lien on the Building, the Lot, the Premises or the
Complex (collectively "taxes and assessments" or if singular "tax or
assessment"). For each tax or assessment period, or installment period thereof,
wholly included in the Term, all such payments shall be made by Tenant not more
than twenty (20) days after receipt of an invoice therefor. For any fraction of
a tax or assessment period, or installment period thereof, included in the Term
at the beginning or end thereof, Tenant shall pay to Landlord, within twenty 20
days after receipt of an invoice therefor, Tenant's Proportionate Fraction for
Building and Tenant's Proportionate Fraction for Complex, as applicable, of
taxes and assessments so levied or assessed or becoming payable which is
allocable to such included period. At Landlord's option, Tenant shall pay taxes
and assessments in accordance with Section 4.2.5 hereof. Subject to Tenant's
payment to Landlord of taxes and assessments as and when required by this
Section 4.2.1, Landlord agrees to pay such tax and assessments to the proper
authorities prior to delinquency and to provide Tenant with evidence of such
payment upon request therefor. Anything herein to the contrary notwithstanding,
(i) until the Lot is a separately assessed parcel, Landlord shall make a
reasonable allocation of any taxes and assessments between the Lot and the
Building and the Complex of which the Lot is a part, (ii) taxes and assessments
for the Building and Lot shall not include any taxes and assessments for other
portions of the Complex and (iii) taxes and assessments for the Complex shall
not include taxes and assessments for the Building or Lot.

      Nothing contained in this Lease shall, however, require Tenant to pay any
income taxes, excess profits taxes, excise taxes, franchise taxes, or any taxes
or assessments with respect to the Garage and other buildings leased or
available for lease (and the parcels of land upon which such buildings are
situated), other than the Building, the Lot and any building or portion of a
building in the Complex which is not designed and available for lease to third
parties (and the parcel(s) of land on which the same may be located) in the
Complex ("Excluded Taxes"), estate, succession, inheritance or transfer taxes,
provided, however, that if at any time during the Term the present system of ad
valorem taxation of real property shall be changed so that in lieu of the whole
or any part of the ad valorem tax on real property, there shall be assessed on
Landlord a capital levy or other tax on the gross rents received with respect to
the Building, the Lot, or the Complex or all of them, or a federal, state,
county, municipal, or other local income, franchise, excise or similar tax,
assessment, levy or charge (distinct from any now in effect) measured by or
based, in whole or in part, upon gross rents, then any and all of such taxes,
assessments, levies or charges, to the extent so measured or based ("Substitute
Taxes"), Tenant's Proportionate Fraction for Building and Tenant's Proportionate
Fraction for Complex, respectively, of Substitute Taxes shall be payable by
Tenant; provided, however, that (i) Tenant's obligation with respect to the
aforesaid Substitute Taxes shall be limited to the amount thereof as computed at
the rates that would be payable if the Building and Lot and buildings not
available for lease (and the parcel(s) of land on which the same may be located)
were the only property of Landlord, and (ii) only that portion of the Substitute
Taxes in excess of the Excluded Taxes shall be payable by Tenant. Landlord shall
furnish to Tenant a copy of any notice of any public, special or betterment
assessment received by Landlord concerning the Building and Lot.

                                      -29-
<PAGE>

      In the event that Tenant requests that Landlord apply for any abatement
of, or otherwise contest, any tax or assessment, Landlord shall file such
abatement or otherwise contest such tax or assessment and shall diligently
pursue the same to completion, provided that (i) Landlord receives notice of
such request from Tenant be made under applicable law, and (ii) the expenses of
such proceedings, including, without limitation, any penalties, interest, late
fees or charges, and attorneys' fees incurred as a result thereof, shall be
included in the Annual Maintenance Charge of the then current fiscal year.

      4.2.2 Insurance.

            4.2.2.1 Insurance Taken Out by Tenant.

                  Tenant shall take out and maintain throughout the Term the
following insurance:

                  (a) Comprehensive liability insurance indemnifying Landlord
and Tenant against all claims and demands for (i) injury to or death of any
person or damage to or loss of property, on the Premises or adjoining walks,
streets or ways, or connected with the use, condition or occupancy of any
thereof unless caused by the negligence of Landlord or its servants or agents,
(ii) violation of this Lease, or (iii) any act, fault or omission, or other
misconduct of Tenant or its agents, contractors, licensees, sublessees or
invitees, in amounts which shall, at the beginning of the Term, be at least
equal to the limits set forth in Section 1.1, and, from time to time during the
Term, shall be for such higher limits, if any, as are customarily carried in the
area in which the Premises are located on property similar to the Premises and
used for similar purposes; and shall be written on the "Occurrence Basis" and
include Host Liquor liability insurance;

                  (b) Worker's compensation insurance with statutory limits
covering all of the Tenant's employees working on the Premises; and

                  (c) All risk, fire and casualty insurance on a 100%
replacement cost basis covering all Tenant's Work.

            4.2.2.2 Insurance Taken Out by Landlord.

                  Landlord shall take out and maintain throughout the Term the
following insurance:

                  (a) Comprehensive liability insurance for the Building, the
Lot and the Complex of the same nature and type as described in Section
4.2.2.1(a) of this Lease, and with the same policy limits or such higher policy
limits as Landlord may reasonably determine; and

                  (b) All risk, fire and casualty insurance on a 100%
replacement cost basis, together with rental loss coverage and, if the Building
is located in a flood zone, flood

                                      -30-
<PAGE>

coverage to the extent the same is available, insuring the Building and its
rental value and Complex Common Areas; and

                  (c) Insurance against loss or damage from sprinklers and from
leakage or explosions or cracking of boilers, pipes carrying steam or water, or
both, pressure vessels or similar apparatus, in the so-called "broad form", in
such amounts as are customary and commercially reasonable for buildings in the
Cambridge, Massachusetts area which are of like kind and quality to the Building
and have laboratory uses, and insurance against such other hazards and in such
amounts as may from time to time be required by any bank, insurance company or
other lending institution holding a first mortgage on the Building, the Lot or
the Complex.

                  Landlord shall have no obligation to insure Tenant's personal
property or chattels, including without limitation, Tenant's trade fixtures.

            4.2.2.3 Tenant Reimbursement of Insurance Taken Out by Landlord.

                  Tenant shall from time to time reimburse Landlord within
thirty days of Landlord's invoice for Tenant's Proportionate Fraction for
Building and Tenant's Proportionate Fraction for Complex of Landlord's costs
incurred in providing the insurance provided pursuant to Section 4.2.2.2 of this
Lease for the Building, Lot and Complex Common Areas, which will be equitably
allocated by Landlord in the case of blanket policies to reflect the insurance
coverage reasonably attributable to the Premises, the Building, the Lot, other
buildings in the Complex, and Complex Common Areas and provided further that
Tenant shall reimburse Landlord for all of Landlord's costs incurred in
providing such insurance which is attributable to any special endorsement or
increase in premium resulting from the business or operations of Tenant, and any
special or extraordinary risks or hazards resulting therefrom, including without
limitation, any risks or hazards associated with the generation, storage and
disposal of medical waste. At Landlord's option, Tenant shall reimburse Landlord
for insurance costs in accordance with Section 4.2.5 hereof.

            4.2.2.4 Certain Requirements Applicable to Insurance Policies.

                  Policies for insurance provided for under the provisions of
Sections 4.2.2.2(b) and 4.2.2.2(c) shall, in case of loss, be first payable to
the holders of any mortgages on the Building, the Lot or the Complex under a
standard mortgagee's clause, and shall be deposited with the holder of any
mortgage or with Landlord, as Landlord may elect. All policies for insurance
required to be obtained by either party under the provisions of Section 4.2.2
shall be obtained from responsible companies qualified to do business in the
state in which the Premises are located and in good standing therein, which
companies and the amount of insurance allocated thereto shall be subject to
Landlord's approval. Each party agrees to furnish the other with certificates of
all such insurance which such party is obligated to obtain pursuant to Section
4.2.2 prior to the beginning of the Term hereof and with renewal certificates at
least 30 days prior to the expiration of the policy they renew. In addition,
Tenant agrees to furnish Landlord with any policies of insurance which Tenant is
obligated to obtain hereunder, including any renewal policies, upon request of
any of Landlord's mortgagees (provided that Tenant may redact from

                                      -31-
<PAGE>

such policies any Confidential Information, as defined in Section 10.15 hereof).
Each such policy required to be maintained by Tenant shall name Landlord and
Landlord's Managing Agent as additional insureds and shall be noncancellable
with respect to the interest of Landlord, Landlord's Managing Agent and such
mortgagees without at least 30 days' prior written notice thereto.

            4.2.2.5. Waiver of Subrogation.

                  All insurance which is carried by either party with respect to
the Premises or to furniture, furnishings, fixtures or equipment therein or
alterations or improvements thereto, whether or not required, shall include
provisions which either designate the other party as one of the insured or deny
to the insurer acquisition by subrogation of rights of recovery against the
other party to the extent such rights have been waived by the insured party
prior to occurrence of loss or injury, insofar as, and to the extent that such
provisions may be effective without making it impossible to obtain insurance
coverage from responsible companies qualified to do business in the state in
which the Premises are located (even though extra premium may result therefrom)
and without voiding the insurance coverage in force between the insurer and the
insured party. In the event that extra premium is payable by either party as a
result of this provision, the other party shall reimburse the party paying such
premium the amount of such extra premium. If at the request of one party, this
non-subrogation provision is waived, then the obligation of reimbursement shall
cease for such period of time as such waiver shall be effective, but nothing
contained in this Section 4.2.2.5 shall derogate from or otherwise affect
releases elsewhere herein contained of either party for claims. Each party
hereby waives all rights of recovery against the other for loss or injury
against which the waiving party is protected by insurance containing said
provisions, reserving, however, any rights with respect to any excess of loss or
injury over the amount recovered by such insurance. Tenant shall not acquire as
insured under any insurance carried on the Premises under the provisions of this
Section 4.2.2 any right to participate in the adjustment of loss or to receive
insurance proceeds and agrees upon request promptly to endorse and deliver to
Landlord any checks or other instruments in payment of loss in which Tenant is
named as payee.

      4.2.3 Utilities.

            Landlord and Tenant agree that the Design Documents shall include
separate metering or submetering of all Utility Services (as hereinafter
defined) for the Premises and the Retail Space. Accordingly, to the extent such
Utility Services are separately metered or submetered, Tenant shall pay directly
to the proper authorities charged with the collection thereof all charges for
water, sewer, gas, electricity, steam, telephone and other utilities or services
(singularly "Utility Service" and collectively, "Utility Services") used or
consumed on the Premises, whether called charge, tax, assessment, fee or
otherwise, including, without limitation, water and sewer use charges and taxes,
if any, all such charges to be paid as the same from time to time become due. If
Tenant is not charged directly by the respective utility for any of such Utility
Services, Tenant shall from time to time, within 20 days of receipt of
Landlord's invoice therefor, pay to Landlord Tenant's Proportionate Fraction of
the total of such charges for the Building, Lot or Complex provided that, at
Landlord's option, all such charges shall be payable by Tenant in accordance
with Section 4.2.5. It is understood and agreed that (i)

                                      -32-
<PAGE>

Landlord shall be responsible for bringing Utility Services to a common
switching point(s) at the Building, which, in the case of electricity shall mean
the switch gear and not the transformer (collectively, the "Utility Switching
Points") as shown on the Final Design Documents at Landlord's cost and expense;
(ii) Tenant shall pay for any and all costs to connect such Utility Services
from such Utility Switching Points to the Premises; (iii) Landlord shall be
under no obligation to furnish any Utility Services to the Premises (beyond the
foregoing responsibility to bring such Utility Services to the Utility Switching
Points and as may be shown on the Final Design Documents; and (iv) subject to
Section 3.2 hereof, Landlord shall not be liable for any interruption or failure
in the supply of any such utilities to the Premises; provided, however, that in
the event such loss or failure is due to Landlord's negligence or willful
misconduct, Landlord shall be responsible for restoring the supply of such
Utility Services to the Premises but otherwise shall have no liability to
Tenant. Subject to the foregoing, Landlord agrees that heating, ventilating and
air conditioning service and all other Utility Services serving the Premises
shall be available to Tenant twenty-four (24) hours per day, seven (7) days per
week.

            To the extent permitted by law, Landlord shall have the right at any
time and from time to time during the Term to contract for or purchase one or
more Utility Services from any company or third party, including without
limitation, electricity, steam, chilled water and natural gas (collectively
"Utilities") providing Utilities (the "Utility Service Provider" or "Utility
Service Providers"), which contracts or purchases, in Landlord's reasonable
opinion, are likely to result in a reduction in costs for Utility Services to
the occupants of the Building or of the Complex taken as a whole. Tenant, at no
cost to Tenant, agrees to reasonably cooperate with Landlord and the Utility
Service Providers and at all times and, as reasonably necessary, and on
reasonable advance notice, shall allow Landlord and the Utility Service
Providers reasonable access to any utility lines, equipment, feeders, risers,
fixtures, wiring and any other such machinery or personal property within the
Premises and associated with the delivery of Utility Services. Tenant may, but
shall not be required to, purchase Utilities from respective Utility Service
Providers.

      4.2.4  Common Area Maintenance and Expenses.

            Landlord shall maintain the Building Common Areas and Complex Common
Areas in the same quality and condition as other comparable buildings in
Cambridge, including without limitation, keeping the Building Common Areas and
the Complex Common Areas clean and free of debris, keeping the sidewalks,
driveways and parking areas reasonably clear of snow and ice, maintaining the
exterior landscaping, lighting, parking areas and sidewalks of the Lot and
Complex, maintaining passenger and freight elevator service, providing Utility
Services to the Premises (if any of such Utility Services are not separately
metered or submetered), Building Common Areas and Complex Common Areas,
including hot water for lavatory purposes and cold water (at temperatures
supplied by the provider thereof) for drinking, lavatory and toilet purposes,
and providing security services for the Building, Lot and Complex to a standard
comparable to security services provided at other comparable buildings in
Cambridge. Tenant shall provide cleaning and janitorial services for the
Premises, shall maintain the interior of the Premises, including the mechanical,
electrical and plumbing systems of the Premises in good order, repair and
condition (provided that if Tenant shall fail to effect such repairs or
maintenance or Tenant shall elect to have Landlord perform such repairs or
maintenance,

                                      -33-
<PAGE>

Landlord may or shall, as applicable, effect such repairs or maintenance and
charge the entire cost thereof to Tenant as Additional Rent) and may maintain
security services for the Premises. Notwithstanding the foregoing, it is
expressly understood and agreed that Landlord shall have no liability or
responsibility for the storage, containment or disposal of any hazardous or
medical waste generated, stored or contained by Tenant, Tenant hereby agreeing
to store, contain and dispose of any and all such hazardous or medical waste at
Tenant's sole cost and expense in accordance with the provisions of Article V
hereof.

            Tenant shall pay to Landlord as Additional Rent the Annual
Maintenance Charge computed and payable as follows:

            (1)   The Annual Maintenance Charge shall be equal to the sum of the
                  "Annual Building Maintenance and Operation Charge", the
                  "Annual Complex Maintenance and Operation Charge" and the
                  "Nonstandard Charge" as hereinafter defined.

                        (a) The "Annual Building Maintenance and Operation
                  Charge" shall be equal to Tenant's Proportionate Fraction for
                  Building on account of all costs incurred by Landlord during
                  the then current fiscal year in operating the Building and Lot
                  and providing maintenance, including without limitation
                  maintenance, operation and repair of the Lot and the Building
                  and all heating, plumbing, electrical, air conditioning and
                  mechanical fixtures and equipment serving Building Common
                  Areas, Utility Services for Building Common Areas, maintenance
                  of Lot and Building signage, elevators, landscaping, snow
                  removal, trash dumpster rental, trash removal, management fees
                  (which management fees shall not exceed those commercially
                  reasonable for buildings in first-class, mixed use projects in
                  Cambridge and which are used for purposes similar to the use
                  of the Building and which management fees may be based upon a
                  percentage of rent payable by tenants of the Building),
                  amortization of equipment to the extent used for Building or
                  Lot operation and maintenance, and all costs incurred by
                  Landlord in order for Landlord to comply with the Development
                  Approvals and Subsequent Approvals and which are recurring or
                  properly categorized as operating or maintenance costs
                  ("Impositions") and equitably attributable or allocated to the
                  Building or Lot.

                        (b) The "Annual Complex Maintenance and Operation
                  Charge" shall be equal to Tenant's Proportionate Fraction for
                  Complex on account of all costs incurred by Landlord during
                  the then current fiscal year in operating the Complex Common
                  Areas and providing Complex Common Areas maintenance,
                  including without limitation, maintenance, operation and
                  repair of all heating, plumbing, electrical, air conditioning
                  and mechanical fixtures and equipment serving Complex Common
                  Areas, Utility Services for Complex Common Areas, maintenance
                  of Complex Common Area signage, elevators, landscaping, snow
                  removal, trash dumpster rental, trash removal, management fees
                  (which management fees

                                      -34-
<PAGE>

                  shall not exceed those commercially reasonable for buildings
                  in Cambridge and which are used for purposes similar to the
                  use of the Building and which management fees may be based
                  upon a percentage of rent payable by tenants of the Complex),
                  amortization of equipment to the extent used for Complex
                  Common Areas operation and maintenance and all Impositions
                  equitably attributable to or allocated to the Complex.

                        (c) Anything herein to the contrary notwithstanding, (i)
                  the Annual Maintenance Charge shall not include (1) leasing
                  and sales commissions for the Building or any portion thereof
                  or any other building in the Complex, (2) fees paid in
                  connection with any tenant improvement costs for the Building
                  or any other building in the Complex, (3) such other fees and
                  commissions paid in connection with the leasing, re-leasing,
                  extension or renewal of leases for the Building or any other
                  building in the Complex, (4) costs incurred with respect to
                  the operation and maintenance of any other building in the
                  Complex which is leased or available for lease, any rentable
                  space therein or any common areas or facilities in such
                  buildings (except to the extent that Landlord maintains a
                  management office therein or in the Building, in which event
                  Tenant shall pay Tenant's Proportionate Fraction for Complex
                  of the fair market rental value thereof as equitably
                  determined by Landlord), (5) any cost or expense attributable
                  to the underground garage(s) within the Complex, including but
                  not limited to the Garage, (6) costs and expenses which are
                  properly attributable to a particular building (other than the
                  Building) or a particular tenant thereof, (7) third party
                  management fees for the Building and Complex included in the
                  Annual Maintenance Charge to the extent such fees exceed
                  market rate fees, (8) any management or supervisory fee of
                  Landlord if a third party is managing the Building or Complex
                  (but if Landlord is self-managing the Building or Complex,
                  Landlord shall be entitled to reimbursement of its reasonable
                  costs for managing the Building and Complex provided that in
                  no event may Landlord's costs and fees for self-managing the
                  Building or Complex exceed the costs and fees that a
                  market-rate third party management company would charge for
                  providing comparable services), (9) in the event that any
                  capital repair, improvement or replacement to the Building
                  Common Areas or the Complex Common Areas made by Landlord has
                  a useful life of over one year (as determined in accordance
                  with generally accepted accounting practices consistently
                  applied), then only the amortized cost of such repair,
                  improvement or replacement over said useful life shall be
                  included in the Annual Building Maintenance and Operation
                  Charge or Annual Complex Maintenance and Operation Charge, as
                  applicable, provided that replacement of a capital item shall
                  be of substantially the same quality and/or usefulness as the
                  capital item being replaced or shall be expected to reduce the
                  Annual Maintenance Charge or otherwise provide some other
                  economic benefit to the operation of the Premises, Building,
                  Lot or Complex, as applicable, such as conserving energy or
                  environmental resources, or if such capital item is required
                  by any law enacted after the

                                      -35-
<PAGE>

                  date hereof, (10) wages, salaries, or other compensation or
                  benefits paid to any persons above the grade of Building
                  manager and Complex manager (or equivalent position), (11)
                  debt service, (12) capital expenditures (except to the extent
                  expressly permitted under this Section), (13) depreciation and
                  amortization (except to the extent expressly permitted under
                  this Section), (14) legal and accounting fees relating to (A)
                  disputes with occupants of the Building or Complex, or (B)
                  disputes with purchasers, prospective purchasers, mortgagees
                  or prospective mortgagees, (15) any rent under any ground or
                  underlying lease, (16) any fines or penalties incurred due to
                  violations of law by Landlord or any tenant or other occupant
                  of the Building or Complex, (17) any amount incurred to any
                  entity affiliated with Landlord to the extent the same exceeds
                  the amount which would have been incurred on an arm's length
                  basis in the absence of such affiliation, (18) any interest,
                  fines or penalties incurred or resulting from late payment by
                  Landlord of any operating expense, (19) costs incurred in
                  connection with the Environmental Remediation, (20) any
                  amounts incurred for repairs or other work occasioned by fire,
                  windstorm or other casualty to the extent Landlord is
                  reimbursed by insurance or would have been reimbursed by
                  insurance had Landlord maintained the insurance it is required
                  to maintain under this Lease, (21) costs incurred in
                  connection with the permitting, financing, refinancing,
                  purchase or sale, or construction of the Building and Complex,
                  and (22) any so-called asset management fees, (ii) the Annual
                  Building Maintenance and Operation Charge shall not include
                  any cost properly included in the Annual Complex Maintenance
                  and Operation Charge or properly included in the Nonstandard
                  Charge, (iii) the Annual Complex Maintenance and Operation
                  Charge shall not include any cost properly included in the
                  Annual Building Maintenance and Operation Charge or properly
                  included in the Nonstandard Charge, and (iv) the Nonstandard
                  Charge shall not include any cost properly included in the
                  Annual Building Maintenance and Operation Charge or the Annual
                  Complex Maintenance and Operation Charge.

                        (d) Notwithstanding anything herein to the contrary, if
                  Landlord furnishes or makes available any service, utility or
                  facility to less than all of the tenants of the Building or
                  Complex, as applicable, Landlord shall allocate all costs
                  incurred by Landlord on account of such services, utilities or
                  facilities to the tenants of the Building or Complex, as
                  applicable, to whom or to which such services, utilities or
                  facilities are furnished or made available (all such costs
                  being herein referred to as the "Nonstandard Costs"). The
                  "Nonstandard Charge" shall be equal to Tenant's share of
                  Nonstandard Costs equitably allocated to Tenant by Landlord.
                  By way of example, if Landlord furnishes Garage Security
                  Services, trash services and/or cleaning services to
                  laboratory tenants of the Building, but not to other tenants,
                  Landlord shall allocate the cost thereof to laboratory tenants
                  and Tenant shall pay Tenant's share thereof as equitably
                  allocated by Landlord. In no event shall any cost incurred by

                                      -36-
<PAGE>

                  Landlord and payable by Tenant for insurance, Utility Services
                  for the Premises which are separately metered or submetered,
                  and taxes and assessments be included in the Annual
                  Maintenance Charge payable by Tenant.

            Attached hereto as Exhibit B-2 is a list (without estimated or
actual amounts) of the Annual Maintenance Charge categories for Building Common
Areas and Complex Common Areas, insurance, Mitigation Expenses and taxes and
assessments. Landlord shall have the right to reasonably modify such list from
time to time. Tenant shall make payments on account of the Annual Maintenance
Charge monthly in advance on the first day of each calendar month during the
Term. At the beginning of every fiscal year, Landlord shall deliver to Tenant
its reasonable estimate of the Annual Maintenance Charge (the "Estimated Annual
Maintenance Charge") for the said fiscal year which estimate may include a
reasonable contingency of up to 5%, and Tenant shall make payments on account of
the Annual Maintenance Charge monthly in advance on the first day of each
calendar month during the Term in the amount of one-twelfth of the Estimated
Annual Maintenance Charge. Landlord reserves the right to reasonably re-estimate
and modify the Estimated Annual Maintenance Charge by notice to Tenant once
annually on or about July 1 of each Lease Year (the "Additional Rent Adjustment
Date"), and Tenant's payments shall thereupon be adjusted accordingly. Not later
than sixty (60) days after the end of each fiscal year during the Term and after
Lease termination, Landlord shall render a statement ("Landlord's Statement") in
reasonable detail and according to usual accounting practices certified by
Landlord and showing for the preceding fiscal year or fraction thereof, as the
case may be, the actual Annual Maintenance Charges for the said fiscal year or
fraction thereof, and thereupon any balance owed by Tenant or excess paid by
Tenant under this Section shall be paid to Landlord, or credited to Tenant, as
the case may be, on the next rent payment date. Tenant shall have the right for
a period of one (1) year following its receipt of Landlord's Statement to
examine Landlord's books and records concerning the Annual Maintenance Charge.
Such examination may be made only by an independent certified public accounting
firm or a full service real estate firm approved by Landlord, which approval
shall not be unreasonably withheld, conditioned or delayed. Landlord may
withhold its approval of any examiner of Tenant who or which is being paid by
Tenant, in whole or in part, on a contingent fee basis. As a condition to
performing any such examination, Tenant and its examiner shall be required to
execute and deliver to Landlord an agreement, in form acceptable to Landlord,
agreeing to keep confidential any information which it discovers about Landlord,
the Building or the Complex in connection with such examination. If the Annual
Maintenance Charge due was less than the Annual Maintenance Charge paid by
Tenant, Landlord shall either promptly refund to Tenant the difference or credit
same against rent next due from Tenant. If the Annual Maintenance Charge due was
less than ninety-five percent (95%) of the Annual Maintenance Charge paid by
Tenant, Landlord shall reimburse Tenant for the reasonable third-party costs of
reviewing Landlord's books and records.

            For purposes of this Lease, the first "fiscal year" shall be the
annual period commencing on the Commencement Date and ending on December 31 of
the year in which the Commencement Date occurs; subsequently, the term "fiscal
year,, shall mean each consecutive annual period thereafter, commencing on the
day following the end of the preceding fiscal year. Landlord shall have the
right from time to time to change the periods of accounting under this Section
4.2.4 to any annual period other than a fiscal year, and upon any such change
all items

                                      -37-
<PAGE>

referred to in this Section shall be appropriately apportioned. In all
Landlord's Statements rendered under this Section, amounts for periods partially
within and partially without the accounting periods shall be appropriately
apportioned, and any items which are not determinable at the time of a
Landlord's Statement shall be included therein on the basis of Landlord's
estimate, and with respect thereto Landlord shall render promptly after
determination a supplemental Landlord's Statement, and appropriate adjustment
shall be made according thereto. All of Landlord's Statements shall be prepared
on an accrual basis of accounting.

            Notwithstanding any other provision of this Section 4.2.4, if the
Term expires or is terminated as of a date other than the last day of a fiscal
year, then for such fraction of a fiscal year at the end of the Term, Tenant's
last payment to Landlord under this Section 4.2.4 shall be made on the basis of
Landlord's best estimate of the items otherwise includable in Landlord's
Statement and shall be made on or before the later of (a) 10 days after Landlord
delivers such estimate to Tenant or (b) the last day of the Term. Landlord shall
thereafter prepare a Landlord's Statement showing the actual Annual Maintenance
Charge for such fiscal year, as hereinabove provided, and an appropriate payment
or refund shall thereafter promptly be made upon submission of such Landlord's
Statement to Tenant.

      4.2.5 Payments on Account of Taxes, Insurance and Utilities.

      Tenant shall make payments on account of the Annual Tax, Insurance and
Utility Charge (as hereinafter defined) monthly in advance on the first day of
each calendar month during the Term, which payments shall initially be in the
amount of the sum of the Initial Tax Charge, the Initial Insurance Charge and
the Initial Utility Charge (the "Estimated Initial Tax, Insurance and Utility
Charges"). At the beginning of every fiscal year, Landlord shall deliver to
Tenant its reasonable estimate of the Annual Tax, Insurance and Utility Charge
("the Estimated Annual Tax, Insurance and Utility Charge") for said fiscal year,
and, in lieu of payments of one twelfth of the Estimated Initial Tax, Insurance
and Utility Charge, Tenant shall make payments on account of the Annual Tax,
Insurance and Utility Charge monthly in advance on the first day of each
calendar month during the Term in the amount of one-twelfth of the Estimated
Annual Tax, Insurance and Utility Charge. Landlord reserves the right to
reasonably re-estimate and modify the Estimated Annual Tax, Insurance and
Utility Charge by notice to Tenant once annually on the Additional Rent
Adjustment Date (as defined in Section 4.2.4 hereof), and Tenant's payments
shall thereupon be adjusted accordingly.

      Not later than ninety (90) days after the end of each fiscal year during
the Term and after Lease termination, Landlord shall render a statement in
reasonable detail and according to usual accounting practices certified by
Landlord and showing for the preceding fiscal year or fraction thereof, as the
case may be, the actual Annual Tax, Insurance and Utility Charge for the said
fiscal year or fraction thereof, and thereupon any balance owed by Tenant or
excess paid by Tenant under this Section shall be paid to Landlord, or credited
to Tenant, as the case may be, on the next rent payment date. As used herein,
the term "Annual Tax, Insurance and Utility Charge" shall mean and refer to the
amount of funds paid by Tenant pursuant to Section 4.2.1, 4.2.2 and 4.2.3 for
the fiscal year in question for costs actually incurred by Landlord (without any
mark-up for Landlord's overhead or profit). All payments under this Section
shall to the extent thereof relieve Tenant of its obligations under said
Sections 4.2.1, 4.2.2 and 4.2.3 hereof.

                                      -38-
<PAGE>

      Landlord shall have the right from time to time to change the periods of
accounting under this Section 4.2.5 to any annual period other than a fiscal
year, and upon any such change all items referred to in this Section shall be
appropriately apportioned. In all Landlord's annual statements rendered under
this Section, amounts for periods partially within and partially without the
accounting periods shall be appropriately apportioned, and any items which are
not determinable at the time of such a statement shall be included therein on
the basis of Landlord's estimate, and with respect thereto Landlord shall render
promptly after determination a supplemental statement, and an appropriate
adjustment shall be made according thereto. All of landlord's statements under
this Section shall be prepared on an accrual basis of accounting.

      Notwithstanding any other provision of this Section 4.2.5, if the Term
expires or is terminated as of a date other than the last day of a fiscal year,
then for such fraction of a fiscal year at the end of the Term, Tenant's last
payment to Landlord under this Section 4.2.5 shall be made on the basis of
Landlord's best estimate of the items otherwise includable in the annual
statement rendered by Landlord under this Section and shall be made on or before
the later of (a) 10 days after Landlord delivers such estimate to Tenant or (b)
the last day of the Term, with an appropriate payment or refund to be made upon
submission of Landlord's statement.

4.3   LATE PAYMENT OF RENT.

      If any installment of rent is paid after the date the same was due, it
shall bear interest from the due date at the higher of (i) the annual rate of
interest payable by Landlord to its mortgagee(s) or (ii) the prime commercial
rate of Fleet National Bank or its successor(s), as it may be adjusted from time
to time, plus, in either case, 4% per annum, but in no event more than the
highest rate of interest allowed by applicable law. Any amounts due under this
Section 4.3 shall be Additional Rent. The foregoing provisions of this Section
4.3 shall not apply to the first two installments of rent paid after the date
the same were due during each twelve consecutive month period during the Term.

                                    ARTICLE V

                          TENANT'S ADDITIONAL COVENANTS

5.1   AFFIRMATIVE COVENANTS.

      Tenant covenants at its expense at all times during the Term and for such
further time as Tenant occupies the Premises or any part thereof:

      5.1.1 Perform Obligations.

            To perform promptly all of the obligations of Tenant set forth in
this Lease; and to pay when due the Fixed Rent and Additional Rent and all
charges, rates and other sums which by the terms of this Lease are to be paid by
Tenant.

                                      -39-
<PAGE>

      5.1.2 Occupancy and Use.

            Continuously from the Commencement Date, to use and occupy the
Premises only for the Permitted Uses, and from time to time to procure all
licenses and permits necessary therefor at Tenant's sole expense.

            Without limitation, Tenant shall strictly comply with all federal,
state, and municipal laws, ordinances, and regulations governing, and all
Development Approvals, Subsequent Approvals and Title Exceptions applicable to,
Tenant's particular use or manner of use of the Premises, and the generation,
storage, containment and disposal of medical or hazardous waste. Tenant shall be
solely responsible for procuring and complying at all times with any and all
necessary permits directly relating or incident to: the conduct of its
activities on the Premises; its scientific experimentation, transportation,
storage, handling, use and disposal of any chemical or radioactive or
bacteriological or pathological substances or organisms or other hazardous
wastes or environmentally dangerous substances or materials or medical waste.
Within ten (10) days of a request by Landlord, which request shall be made not
more than once during each period of twelve (12) consecutive months during the
Term hereof, unless otherwise requested by any mortgagee of Landlord, Tenant
shall furnish Landlord with copies of all such permits which Tenant possesses or
has obtained together with a certificate certifying that such permits are all of
the permits which Tenant possesses or has obtained with respect to the Premises.
Tenant shall be entitled to redact any Confidential Information from the copies
of such permits and accompanying certificates of Tenant. Tenant shall promptly
give notice to Landlord of any warnings or violations relative to the above
received from any federal, state, or municipal agency or by any court of law and
shall promptly cure the conditions causing any such violations. Tenant shall not
be deemed to be in default of its obligations under the preceding sentence to
promptly cure any condition causing any such violation in the event that, in
lieu of such cure, Tenant shall contest the validity of such violation by
appellate or other proceedings permitted under applicable law, provided that:
(i) any such contest is made reasonably and in good faith, (ii) Tenant makes
provisions, including, without limitation, posting bond(s) or giving other
security, acceptable to Landlord to protect Landlord, the Building and the Lot
from any liability, costs, damages or expenses arising in connection with such
violation and failure to cure, (iii) Tenant shall agree to indemnify, defend
(with counsel reasonably acceptable to Landlord) and hold Landlord harmless from
and against any and all liability, costs, damages, or expenses arising in
connection with such condition and/or violation, (iv) Tenant shall promptly cure
any violation in the event that its appeal of such violation is overruled or
rejected, and (v) Tenant shall certify to Landlord's satisfaction that Tenant's
decision to delay such cure shall not result in any actual or threatened bodily
injury or property damage to Landlord, any tenant or occupant of the Building or
the Lot, or any other person or entity. Landlord agrees that any Confidential
Information gained or obtained by Landlord pursuant to this Section 5.1.2 shall
be kept confidential in accordance with Section 10.15 hereof.

      5.1.3 Repair and Maintenance.

            Except as otherwise provided in Article VI, to keep the Premises
including, without limitation, all fixtures and equipment now or hereafter on
the Premises, or exclusively serving the Premises, but excluding the exterior
(exclusive of glass and doors) and structural

                                      -40-
<PAGE>

elements of the Building and the Building Common Areas and Complex Common Areas,
which Landlord shall maintain and repair unless such repairs are required
because of Tenant's willful misconduct or negligence, in good order, condition
and repair and at least as good order, condition and repair as they are in on
the Commencement Date or may be put in during the Term, reasonable use and wear
only excepted; to keep in a safe, secure and sanitary condition all trash and
rubbish temporarily stored at the Premises; and to make all repairs and
replacements and to do all other work necessary for the foregoing purposes
whether the same may be ordinary or extraordinary, foreseen or unforeseen.
Tenant shall be responsible for heating and air-conditioning systems serving the
Premises to the extent that such systems are not a part of Base Building
Improvements, and Tenant shall secure, pay for and keep in force contracts with
appropriate and reputable service companies providing for the regular
maintenance of the heating and air-conditioning systems serving the Premises to
the extent that such systems are not a part of Base Building Improvements, and
copies of such contracts shall be furnished to Landlord. It is further agreed
that the exception of reasonable use and wear shall not apply so as to permit
Tenant to keep the Premises in anything less than suitable, tenantlike, and
efficient and usable condition considering the nature of the Premises and the
use reasonably made thereof, or in less than good and tenantlike repair.

      5.1.4 Compliance with Law.

            To make all repairs, alterations, additions or replacements to the
Premises required by any law or ordinance or any order or regulation of any
public authority other than major capital repairs, alterations, additions or
replacements to the foundations and structural elements of the Building which
are not required because of Tenant's failure to comply with the provisions of
Section 5.1.3 hereof; to keep the Premises equipped with all safety appliances
so required; to pay all municipal, county, or state taxes assessed against the
leasehold interest hereunder, or against personal property of any kind on or
about the Premises; and to comply with the orders and regulations of all
governmental authorities with respect to zoning, building, fire, health and
other codes, regulations, ordinances or laws applicable to the Premises.

            Tenant shall not use, generate, manufacture, produce, handle, store,
release, discharge or dispose of in, on, under or about the Premises or
transport to or from the Premises, or allow its employees, agents, contractors,
invitees or any other person or entity to do so, any oil, hazardous or toxic
materials or hazardous or toxic wastes or medical waste (collectively,
"hazardous materials") except to the extent that the following conditions
regarding the use, generation, manufacture, production, handling, storing,
releasing, discharging, disposal or transport (individually or collectively, the
"Use") of hazardous materials shall be satisfied: (i) the Use shall be directly
related to the operation of Tenant's business as permitted herein, (ii) Tenant
shall first provide Landlord with the list of the types and quantities of such
proposed hazardous materials which Tenant is required to furnish to the
applicable governmental authorities for purposes of compliance with the Resource
Conservation and Recovery Act, as amended (42 U.S.C. ss. 9601, et seq.) (the
"RCRA List") (or, in the event that the RCRA List ceases to be required to be
filed under such law, a list containing the same information required to be
listed on the RCRA List as of the date hereof), and shall update such list as
necessary for continuing accuracy, and such other information reasonably
satisfactory to Landlord as Landlord may reasonably require concerning such Use,
and (iii) such Use shall be in strict compliance (at

                                      -41-
<PAGE>

Tenant's expense) with all applicable laws, regulations, licenses and permits.
Landlord hereby covenants and agrees that the information contained in any list,
or update thereof, referred to in the foregoing clause (ii) shall be kept
confidential in accordance with Section 10.15 hereof. Notwithstanding the
foregoing, Tenant hereby agrees to consult and coordinate with Landlord prior to
transporting any hazardous materials to or from the Premises whenever (i) such
transportation is not of the kind regularly made during the ordinary course of
business by a person or entity operating a laboratory facility for the Permitted
Uses or (ii) Tenant has reason to believe that such transportation may result in
a public demonstration, protest or other similar disturbance at the Building,
the Lot or the Complex. If the transportation, generation, manufacture,
production, handling, release, storage, use or disposal of any hazardous
materials anywhere on the Premises or in the Complex in connection with the
Tenant's use of the Premises results in (1) contamination of the soil, surface
or ground water or (2) loss or damage to person(s) or property, then Tenant
agrees to respond in accordance with the following paragraph:

            Tenant agrees (i) to notify Landlord immediately of any
            contamination, claim of contamination, loss or damage, (ii) after
            consultation and approval by Landlord, to clean up the contamination
            in full compliance with all applicable statutes, regulations and
            standards, and (iii) to indemnify, defend (with counsel acceptable
            to Landlord) and hold Landlord harmless from and against any claims,
            suits, causes of action, costs and fees, including attorneys' fees,
            arising from or connected with any such contamination, claim of
            contamination, loss or damage. No consent or approval of Landlord
            shall in any way be construed as imposing upon Landlord any
            liability for the means, methods, or manner of removal, containment
            or other compliance with applicable law for and with respect to the
            foregoing.

            Tenant shall promptly notify Landlord upon Tenant's receipt of any
inquiry, notice, or threat to give notice by any government authority or any
other third party with respect to any hazardous materials. Notwithstanding the
foregoing, Tenant shall not be liable to Landlord hereunder for any
contamination, claim of contamination, loss or damage arising in connection with
hazardous materials to the extent the same is the result of (A) hazardous
materials existing in the Building and the Lot prior to Tenant's use or
occupancy of the Premises, (B) migration of hazardous materials from any site
onto the Lot not caused by Tenant, (C) the generation, manufacture, production,
handling, release, storage, use or disposal of any hazardous materials at the
Building or the Lot by Landlord, any other tenant or occupant, or any so-called
"mid-night dumpers" or (D) the Use (as defined above in this Section) by any
party other than Tenant of hazardous materials at the Building or the Lot after
the date upon which Tenant has completely vacated the same, including removal of
all of its property (to the extent permitted herein) and hazardous materials.
Tenant's indemnification obligations under this Section shall survive the
expiration or earlier termination of this Lease.

            Prior to vacating the Premises at the expiration of the Term hereof,
Tenant at its sole cost and expense shall provide Landlord with an environmental
audit by a qualified environmental engineering firm satisfactory to Landlord,
which audit shall include reasonable subsurface testing if requested by
Landlord. The aforesaid environmental audit shall

                                      -42-
<PAGE>

affirmatively certify that the Premises are free from any and all contaminants,
pollutants, radioactive materials, hazardous wastes or materials, medical waste,
bacteriological agents or organisms which would render the Premises in violation
of M.G.L. c. 21E, the Comprehensive Environmental Response, Compensation, and
Liability Act of 1980, as amended, 42 U.S.C. Section 9602 et seq., or any other
applicable laws, rules, regulations or orders, as they may be amended or
supplemented by administrative regulations, from time to time. Nothing herein
contained shall be construed to limit or impair Tenant's obligation to comply
with any law, code, rule or regulation which requires Tenant to notify any
governmental authority or any other person concerning the Use (as defined above
in this Section) of hazardous materials by Tenant at the Premises.

            Tenant agrees that, with respect to the Premises, it shall be
responsible for compliance with the Americans with Disabilities Act (42 U.S.C.
ss. 12101 et seq.) and the regulations and Accessibility Guidelines for
Buildings and Facilities issued pursuant thereto (collectively, the "ADA
Requirements"), except to the extent that the Base Building Improvements are
subject to ADA Requirements, in which event Landlord shall be responsible for
compliance of the Base Building Improvements therewith. Tenant covenants and
agrees that its use of the Premises shall not cause a discharge of more than its
pro rata share on a square foot basis of the design flow gallonage per day of
sanitary (non-industrial) sewage allowed under the sewage discharge permit(s)
for the Building. Discharges in excess of that amount, and any discharge of
industrial sewage, shall only be permitted if Tenant, at its sole expense, shall
have obtained all necessary permits and licenses therefor, including without
limitation permits from state and local authorities having jurisdiction thereof.

      5.1.5 Tenant's Work.

            To procure at Tenant's sole expense all necessary permits and
licenses before Tenant undertakes any work on the Premises; to do all such work
in compliance with the applicable provisions of Sections 3.2.1, 3.3 and 5.2.3
hereof; to do all such work in a good and workmanlike manner employing materials
of good quality and so as to conform with all applicable zoning, environmental,
building, fire, health and other codes, regulations, ordinances and laws and the
ADA Requirements; to furnish to Landlord prior to the commencement of any such
work, or any other such work for which the cost may reasonably be estimated to
exceed $100,000, a bond or other security acceptable to Landlord assuring that
any work commenced or continued by Tenant will be completed in accordance with
specifications approved in advance in writing by Landlord; to keep the Premises
at all times free of liens for labor and materials; to employ for such work one
or more responsible contractors whose labor will work without interference with
other labor working on the Premises; to require such contractors employed by
Tenant to carry worker's compensation insurance in accordance with statutory
requirements and comprehensive public liability insurance covering any general
contractors on or about the Premises in amounts that at least equal the limits
set forth in Section 1.1 and to submit certificates evidencing such coverage to
Landlord prior to the commencement of such work; and to save Landlord harmless
and indemnified from all injury, loss, claims or damage to any person or
property occasioned by or growing out of such work. Notwithstanding any other
provision of this Section 5.1.5 or any other provision of this Lease to the
contrary, Landlord shall not, subject to applicable law, prohibit Tenant from
using non-union labor to perform any work at the

                                      -43-
<PAGE>

Premises, including Tenant's Work. Without limitation of the foregoing, Landlord
shall not require Tenant's employees to unionize.

      5.1.6 Indemnity.

            To defend, with counsel approved by Landlord, all actions against
Landlord, any partner, trustee, stockholder, officer, director, employee or
beneficiary of Landlord, holders of mortgages secured by the Premises or the
Building and Lot and any other party having an interest in the Premises
("Indemnified Parties") with respect to, and to pay, protect, indemnify and save
harmless, to the extent permitted by law, all Indemnified Parties from and
against, any and all liabilities, losses, damages, costs, (including reasonable
attorneys' fees and expenses), causes of action, suits, claims, demands or
judgments of any nature arising from (i) injury to or death of any person, or
damage to or loss of property, on the Premises or on adjoining streets or ways
connected with the use or occupancy thereof by Tenant or its agents,
contractors, licensees, employees, sublessees or invitees, unless and to the
extent caused by the negligence of Landlord or its servants or agents, (ii)
violation of this Lease by Tenant or its agents, contractors, licensees,
employees, sublessees or invitees, or (iii) any act, fault, omission, or other
misconduct of Tenant or its agents, contractors, licensees, employees,
sublessees or invitees.

      5.1.7 Landlord's Right to Enter.

            To permit Landlord and its agents to enter into the Premises at
reasonable times and upon at least 24 hours advance notice (except in case of
emergency in which event no prior notice shall be required) to examine the
Premises, make such repairs and replacements as Landlord may elect, without
however, any obligation to do so except as may be otherwise expressly set forth
in this Lease, and show the Premises to prospective purchasers and lenders, and,
during the last twelve months of the Term, to show the Premises to prospective
tenants and to keep affixed in suitable places notices of availability of the
Premises. Landlord's right to enter the Premises in accordance with the
foregoing shall be subject to Landlord's obligations pursuant to Section 10.15
hereof. Notwithstanding the foregoing, Landlord agrees that in the event that
Landlord shows the Premises to any prospective purchaser or tenant, Landlord
shall: (i) provide at least three (3) days' notice to Tenant identifying the
prospective purchaser or tenant, (ii) only show the Premises to such purchaser
or tenant if Landlord believes in good faith that such person or entity is a
bona fide prospective purchaser or tenant, (iii) conduct such showing in
compliance with such reasonable requests and instructions as Tenant may make for
purposes of protecting Tenant's Confidential Information.

      5.1.8 Personal Property at Tenant's Risk.

            All of the furnishings, fixtures, equipment, effects and property of
every kind, nature and description owned or leased by Tenant or by any person
claiming by, through or under Tenant which, during the continuance of this Lease
or any occupancy of the Premises by Tenant or anyone claiming under Tenant, may
be on the Premises (collectively, "Tenant's Property"), shall, as between the
parties, be at the sole risk and hazard of Tenant and if the whole or any part
thereof shall be destroyed or damaged by fire, water or otherwise, or by the
leakage or bursting of water pipes, steam pipes, or other pipes, by theft or
from any other cause, no part

                                      -44-
<PAGE>

of said loss or damage is to be charged to or to be borne by Landlord, except
that Landlord shall in no event be indemnified or held harmless or exonerated
from any liability to Tenant or to any other person, for any injury, loss,
damage or liability to the extent (i) such injury, loss, damage or liability is
the result of the negligence or willful misconduct of Landlord, its contractors,
agents or employees, or (ii) such indemnification, agreement to hold harmless or
exoneration is prohibited by law.

      5.1.9 Payment of Landlord's Cost of Enforcement.

            To pay on demand Landlord's expenses, including reasonable
attorney's fees, incurred in enforcing any obligation of Tenant under this Lease
or in curing any default by Tenant under this Lease as provided in Section 7.4.

      5.1.10 Yield Up.

            Subject to Section 3.2.1 hereof, at the expiration of the Term or
earlier termination of this Lease: to surrender all keys to the Premises; to
remove all of its trade fixtures and personal property in the Premises; to
remove such installations and improvements made by Tenant as Landlord may
request and all Tenant's signs and Tenant's telecommunications equipment
wherever located, except that Tenant shall leave all cabling and wiring for its
telecommunications equipment, but such cabling and wiring shall be appropriately
and safely capped by Tenant; to repair all damage caused by such removal; and to
yield up the Premises (including all installations and improvements made by
Tenant except for trade fixtures and such of said installations or improvements
as Landlord shall request Tenant to remove), broom-clean and in the same good
order and repair in which Tenant is obliged to keep and maintain the Premises by
the provisions of this Lease. Subject to Section 3.2.1 hereof, any property not
so removed shall be deemed abandoned and may be removed and disposed of by
Landlord in such manner as Landlord shall determine and Tenant shall pay
Landlord the entire cost and expense incurred by Landlord in effecting such
removal and disposition and in making any incidental repairs and replacements to
the Premises and for use and occupancy during the period after the expiration of
the Term and prior to Tenant's performance of its obligations under this Section
5.1.10. Tenant shall further indemnify Landlord against all loss, cost and
damage resulting from Tenant's failure and delay in surrendering the Premises as
above provided.

      5.1.11 Estoppel Certificate.

            Upon not less than 10 days' prior notice by Landlord, to execute,
acknowledge and deliver to Landlord a statement in writing certifying that this
Lease is unmodified and in full force and effect and that except as stated
therein Tenant has no knowledge of any defenses, offsets or counterclaims
against its obligations to pay the Fixed Rent and Additional Rent and any other
charges and to perform its other covenants under this Lease (or, if there have
been any modifications that the Lease is in full force and effect as modified
and stating the modifications and, if there are any defenses, offsets or
counterclaims, setting them forth in reasonable detail), the dates to which the
Fixed Rent and Additional Rent and other charges have been paid and a statement
that, to the best of Tenant's knowledge, Landlord is not in default hereunder
(or if in default, the nature of such default, in reasonable detail) and such
other matters reasonably

                                      -45-
<PAGE>

required by Landlord or any prospective purchaser or mortgagee of the Premises.
Any such statement delivered pursuant to this Section 5.1.11 may be relied upon
by any prospective purchaser or mortgagee of the Premises, or any prospective
assignee of any such mortgage.

      5.1.12 Landlord's Expenses Re: Consents.

            To reimburse Landlord promptly on demand for all reasonable legal
expenses incurred by Landlord in connection with all requests by Tenant for
consent or approval under this Lease. Notwithstanding the foregoing, Tenant
shall not be liable for any reasonable legal expenses incurred by Landlord for
the first two (2) such requests made by Tenant during each period of twelve (12)
consecutive calendar months during the Term.

      5.1.13 Rules and Regulations.

            To comply with the Rules and Regulations set forth in Exhibit C, as
the same may be amended from time to time by Landlord to provide for the
beneficial operation of the Building, the Lot and/or the Complex, provided that
such amendments do not materially interfere with Tenant's right of use and
enjoyment of the Premises pursuant to this Lease.

      5.1.14 Loading.

            Not to place Tenant's Property, as defined in Section 5.1.8, upon
the Premises so as to exceed the floor load limits set forth in the Design
Documents and not to move any safe, vault or other heavy equipment in, about or
out of the Premises except in such manner and at such times as Landlord shall in
each instance approve; Tenant's business machines and mechanical equipment which
cause vibration or noise that may be detectable outside of the Building shall be
placed or maintained by Tenant in settings of cork, rubber, spring, or other
types of vibration eliminators sufficient to reduce such vibration or noise to a
level reasonably acceptable to Landlord.

      5.1.15 Holdover.

            To pay to Landlord (i) the greater of twice (a) the then fair market
rent as reasonably determined by Landlord or (b) the total of the Fixed Rent,
Additional Rent, and all other payments then payable hereunder, for each month
or portion thereof Tenant shall retain possession of the Premises or any part
thereof after the termination of this Lease, whether by lapse of time or
otherwise, and (ii) all damages sustained by Landlord on account thereof;
provided, however, that any payments made by Tenant under the foregoing clause
(i) in excess of the then fair market rent for the Premises as so reasonably
determined by Landlord shall be applied against any damages under the foregoing
clause (ii). The provisions of this subsection shall not operate as a waiver by
Landlord of the right of re-entry provided in this Lease.

5.2   NEGATIVE COVENANTS.

      Tenant covenants at all times during the Term and for such further time as
Tenant occupies the Premises or any part thereof:

                                      -46-
<PAGE>

      5.2.1 Assignment and Subletting.

            Not without the prior written consent of Landlord to assign this
Lease, to make any sublease, or to permit occupancy of the Premises or any part
thereof by anyone other than Tenant, voluntarily or by operation of law, except
as hereinafter provided; as Additional Rent, to reimburse Landlord promptly for
reasonable legal and other expenses incurred by Landlord in connection with any
request by Tenant for consent to assignment or subletting (subject to the
provisions of Section 5.1.12 hereof); no assignment or subletting shall affect
the continuing primary liability of Tenant (which, following assignment, shall
be joint and several with the assignee); no consent to any of the foregoing in a
specific instance shall operate as a waiver in any subsequent instance.
Landlord's consent to any proposed assignment or subletting is required both as
to the terms and conditions thereof and as to the consistency of the proposed
assignee's or subtenant's business with other uses and tenants in the Building.
In addition, as to any assignee (but not as to any sublessee) Landlord's consent
shall be required as to the reasonable creditworthiness of the proposed assignee
in view of market conditions then prevailing for leases having terms and
conditions comparable to this Lease. Landlord's consent to any assignment or
subletting by Tenant shall not be unreasonably withheld, provided that Tenant is
not then in default under this Lease and that such assignee or subtenant pays
therefor the greater of the Fixed Rent, Additional Rent, and all other payments
then payable hereunder, or the then fair market rent for the Premises. If Tenant
requests Landlord's consent to assign this Lease or to sublet any portion of the
Premises such that Tenant shall not occupy at least 50,000 r.s.f. of the
Premises after the date of commencement of such sublease, Landlord shall have
the option, exercisable by written notice to Tenant given within 10 days after
receipt of such request, to terminate this Lease as of the date of commencement
the proposed sublease or assignment; provided, however, that Tenant shall have
the right to rescind any such request in the event Landlord elects to so
terminate this Lease by notice given to Landlord within five (5) days after the
date of such termination notice from Landlord, in which event such termination
notice shall be of no further force or effect;

            If, at any time during the Term of this Lease, Tenant is:

                  (i) a corporation or a trust (whether or not having shares of
beneficial interest) and there shall occur any change in the identity of any of
the persons then having power to participate in the election or appointment of
the directors, trustees or other persons exercising like functions and managing
the affairs of Tenant; or

                  (ii) a partnership or association or otherwise riot a natural
person (and is not a corporation or a trust) and there shall occur any change in
the identity of any of the persons who then are members of such partnership or
association or who comprise Tenant;

Tenant shall so notify Landlord and Landlord may terminate this Lease by notice
to Tenant given within 90 days thereafter if, in Landlord's reasonable judgment,
the credit of Tenant is thereby impaired. This paragraph shall not apply if the
initial Tenant named herein is a corporation and the outstanding voting stock
thereof is listed on a recognized securities exchange.

                                      -47-
<PAGE>

      Notwithstanding the foregoing provisions of this Section 5.2.1, Tenant may
assign this Lease or sublet any portion of the Premises without Landlord's
consent to (i) any successor of Tenant resulting from an acquisition of all or
substantially all of Tenant's assets or a merger or consolidation of Tenant and
(ii) any Affiliate of Tenant (as hereinafter defined) whose net worth is equal
to or greater than the net worth of Tenant as of the date hereof, provided that
Tenant provides Landlord at least thirty (30) days prior notice of such
assignment or subletting pursuant to either of the foregoing clauses (i) or
(ii). As used herein, the term "Affiliate of Tenant" shall mean and refer to any
entity controlled by, controlling or under common control with Tenant.

      In the event that any assignee or subtenant pays to Tenant any amounts in
excess of the Fixed Rent, Additional Rent, and all other payments then payable
hereunder, or pro rata portion thereof on a square footage basis for any portion
of the Premises (such excess being hereinafter referred to as "Sublease
Profits"), Tenant shall promptly pay fifty percent (50%) of said Sublease
Profits to Landlord as and when received by Tenant after deduction of Tenant's
Sublease Costs (as hereinafter defined). The term "Sublease Costs" shall mean
and refer to Tenant's reasonable legal, brokerage and construction costs and
expenses incurred in good faith in view of the size and expected term of any
applicable sublease or assignment. Sublease Costs shall be amortized over the
term of the applicable sublease or assignment.

      5.2.2 Nuisance.

            Not to injure, deface or otherwise harm the Premises; nor commit any
nuisance; nor permit the emission of any noise, vibration or odor which is
contrary to any law or ordinance; nor make, allow or suffer any waste; nor make
any use of the Premises which is improper, offensive or contrary to any law or
ordinance or which will invalidate any of Landlord's insurance.

      5.2.3 Installation, Alterations or Additions.

            Subject to the provisions of Section 3.2.1, 3.3 and Section 5.1.5
hereof, not to make any installations, alterations, or additions in, to or on
the Premises (including, without limitation, buildings, lawns, planted areas,
walks, roadways, parking and loading areas, but expressly excluding the initial
Tenant's Work, provided the same is approved by Landlord, such approval not to
be unreasonably withheld or delayed), nor, except for Tenant's Work approved by
Landlord, to permit the making of any apertures in the walls, partitions,
ceilings or floors without on each occasion obtaining the prior written consent
of Landlord and then only pursuant to plans and specifications approved by
Landlord in advance in each instance.

                                   ARTICLE VI

                               CASUALTY OR TAKING

6.1   DAMAGE BY FIRE.

      In the event of loss of, or damage to, the Premises or the Building or the
Garage by fire or other casualty, the rights and obligations of the parties
hereto shall be as follows:

                                      -48-
<PAGE>

            (a) (i) If the Premises, or any part thereof, shall be damaged by
fire or other casualty, Tenant shall give prompt notice thereof to Landlord, and
Landlord, upon receiving such notice, shall proceed promptly and with due
diligence, subject to Force Majeure Events, to repair, or cause to be repaired,
such damage except as otherwise provided herein. With respect to portions of the
Building or Lot outside of the Premises that shall be damaged by fire or other
casualty, Landlord shall proceed promptly and with due diligence, subject to
Force Majeure Events, to repair, or to cause to be repaired, such damage after
such damage occurs except as otherwise provided herein; and (ii) if the Garage,
or any part thereof, shall be damaged by fire or other casualty and if the
Garage is then owned by Landlord or an Affiliate of Landlord, Landlord shall
cause the Garage Owner to proceed promptly and with due diligence, subject to
Force Majeure Events, to repair or cause to be repaired, such damage except as
otherwise provided herein. If Landlord or an Affiliate of Landlord is not the
Garage Owner at the time of such damage by fire or other casualty, Landlord
shall use all reasonable efforts to cause the Garage Owner to proceed promptly
to repair such damage.

            (b)(i) If the Premises, or any part thereof, shall be rendered
untenantable by reason of such damage, whether to the Premises or to the
Building or if such damage materially interferes with Tenant's access to the
Premises, Annual Fixed Rent and Additional Rent shall proportionately (i.e.,
based on rentable square footage) abate for that portion of the Premises which
is untenantable for the period from the date of such damage or from the date
when material interference with Tenant's access due to such damage commences to
the date when such damage shall have been repaired or such access shall have
been restored, as applicable; and (ii) if the Garage or any part thereof shall
be rendered untenantable by reason of such damage or if such damage prevents
Tenant's access to the Garage then to the extent that Landlord does not provide
Tenant with substitute parking spaces in the Complex or within 1,000 feet of the
Premises ("Substitute Parking Spaces"), the Parking Fee (as defined in Section
10.14) shall proportionately abate (based upon the number of Tenant's Parking
Spaces for each of the Garage Parking Spaces (as defined in Section 10.14) in
excess of the Substitute Parking Spaces which are unavailable to Tenant for the
period from the date of such damage or from the date when access to the Garage
ceases due to such damage to the date when such damage shall have been repaired
or such access shall have been restored, as applicable.

            (c)(i) If, as a result of fire or other casualty, the whole or a
substantial part of the Building is rendered untenantable, Landlord, within
ninety (90) days from the date of such fire or casualty, may terminate this
Lease by notice to Tenant, specifying a date not less than twenty (20) nor more
than forty (40) days after the giving of such notice on which the Term of this
Lease shall terminate. If Landlord does not so elect to terminate this Lease,
then Landlord shall proceed with diligence to repair the damage to the Building
and Premises and all facilities serving the same, and the Annual Fixed Rent and
Additional Rent shall meanwhile proportionately abate, all as provided in
Paragraph (b)(i) of this Section 6.1. Landlord within one hundred twenty (120)
days after the fire or other casualty shall notify Tenant in writing whether or
not, in its reasonable judgment, the Building and the Premises can be restored
to substantially their condition prior to such damage and Utility Services
restored to the Utility Switching Points within twelve (12) months of the date
of the casualty. If such notification shall state that such restoration cannot
be so accomplished, then Tenant may terminate this Lease within thirty (30) days
from Tenant's receipt of such notification. Furthermore, if Tenant does not so
terminate this Lease and if such damage is not repaired, Utility Services are
not restored

                                      -49-
<PAGE>

and the Premises and the remainder of the Building are not restored to
substantially the same condition as they were prior to such damage within twelve
(12) months from the date of such damage, Tenant within thirty (30) days from
the expiration of such twelve (12) month period or from the expiration of any
extension thereof by reason of Force Majeure Events (the "Casualty Restoration
Completion Date"), may terminate this Lease by notice to Landlord, specifying a
date not more than forty-five (45) days after the giving of such notice on which
the term of this Lease shall terminate. The period within which the required
repairs may be accomplished shall be extended by the number of days lost as a
result of Force Majeure Events, provided however that such period shall in no
event be extended beyond six (6) months from the Casualty Restoration Completion
Date. Substantial part for purposes of this Section 6.1(c)(i) and Section 6.1(d)
shall mean fifty percent (50%) or more of the Building; and (ii) if as a result
of fire or other casualty, the whole or a substantial part of the Garage is
rendered untenantable, Landlord, within ninety (90) days from the date of such
fire or casualty, shall notify Tenant whether the Garage Owner will repair the
damage to the Garage. If the Garage Owner is unwilling to repair such damage and
Landlord does not provide substitute parking in the Complex or within 1,000 feet
of the Premises, then Tenant may terminate this Lease by notice to Landlord,
specifying a date not less than twenty (20) nor more than forty (40) days after
the giving of such notice on which the Term of this Lease shall terminate.
"Substantial part" for this Section 6.1(c)(ii) shall mean fifty percent (50%) or
more of Tenant's Parking Spaces.

            If Tenant fails to terminate in accordance within the foregoing time
periods set forth in this Section 6.1, Tenant shall have waived its right to
terminate.

            (d) If a substantial part of the Premises shall be rendered
untenantable by fire or other casualty during the last eighteen (18) months of
the then current Term of this Lease and Tenant has not exercised an Option to
Extend (as set forth in Section 10.12 hereof), Landlord may terminate this Lease
effective as of the date of such fire or other casualty upon notice to Tenant
given within sixty (60) days after such fire or other casualty.

            (e) With respect to Sections 6.1 and 6.2 hereof, Landlord shall not
be required to repair or replace any of Tenant's trade fixtures, business
machinery, equipment, cabinet work, furniture, personal property or other
installations or improvements not originally installed by Landlord or otherwise
required to be insured by Tenant under the terms of this Lease, or any damage to
the Premises or Building caused by Tenant, or any damage to the Premises or
Building not covered by insurance proceeds or condemnation proceeds, or any
damage or destruction which Landlord is unable to restore due to Landlord's
inability, after exercising reasonable and diligent efforts, to obtain final
approval therefor from applicable governmental authorities, and no damages,
compensation or claim shall be payable by Landlord for inconvenience, loss of
business or annoyance arising from any repair or restoration of any portion of
the Premises or of the Building.

            (f) The provisions of this Section 6.1 shall be considered an
express agreement governing any instance of damage or destruction of the
Building, the Premises or the Garage by fire or other casualty, and any law now
or hereafter in force providing for such contingency in the absence of express
agreement shall have no application.

                                      -50-
<PAGE>

            (g) In the event of any termination of this Lease pursuant to this
Section 6.1, the Term of this Lease shall expire as of the effective termination
date as fully and completely as if such date were the date herein originally
scheduled as the Term Expiration Date; provided that Landlord shall within
thirty (30) days thereafter refund any prepaid Rent.

            (h) Landlord's architect's certificate, given in good faith, shall
be deemed conclusive of the statements therein contained and binding upon Tenant
with respect to the extent of the damage to the Building and the performance and
completion of any repair or restoration work undertaken by Landlord pursuant to
Sections 6.1 or 6.2 hereof. Tenant may have Tenant's architect verify the
statements included within such certificate within five (5) days after Tenant's
receipt thereof.

6.2   CONDEMNATION.

      In the event that the whole or any substantial part of the Building shall
be taken or appropriated by eminent domain or shall be condemned for any public
or quasi-public use, or (by virtue of any such taking, appropriation or
condemnation) shall suffer any damage (direct, indirect or consequential) for
which Landlord or Tenant shall be entitled to compensation, then (and in any
such event) this Lease and the Term hereof may be terminated at the election of
Landlord by a notice in writing of its election so to terminate which shall be
given by Landlord to Tenant within ninety (90) days following the date on which
Landlord shall have received notice of such taking, appropriation or
condemnation. In the event that a substantial part of the Premises or of the
means of access thereto or of the Garage Parking Spaces (as such term is defined
in Section 10.14 hereof) (unless replaced without undue delay by substitute
facilities within 1,000 feet of the Building) shall be so taken, appropriated or
condemned so as to substantially interfere with the Permitted Uses of the
Premises, then this Lease and the Term hereof may be terminated at the election
of Tenant by a notice in writing of its election so to terminate which shall be
given by Tenant to Landlord within sixty (60) days following the date on which
Tenant shall have received notice of such taking, appropriation or condemnation.
Substantial part for purposes of this Section 6.2 shall mean fifty percent (50%)
or more of the Premises or fifty percent (50%) or more of the Garage Parking
Spaces, as applicable.

      Upon giving of any such notice of termination (either by Landlord or
Tenant), this Lease and the Term hereof shall terminate as of the date on which
Tenant shall be required to vacate any part of the Premises or shall be deprived
of a substantial part of the means of access thereto. In the event of any such
termination, this Lease and the Term hereof shall expire as of the effective
termination date as fully and completely as if such date were the date herein
originally scheduled as the Term Expiration Date. If neither party elects to
terminate, Landlord will with reasonable diligence and at Landlord's expense,
restore the remainder of the Premises and Building, or the remainder of the
means of access and Garage Parking Spaces, to substantially the same condition
as practicable as existed prior to such taking, appropriation or condemnation in
which event a just proportion of the Annual Fixed Rent and Additional Rent,
according to the nature and extent of the taking, appropriation or condemnation
and the resultant injury sustained by the Premises and the means of access
thereto, shall be abated until what remains of the Premises and the means of
access thereto shall have been restored as fully as may be for permanent use and
occupancy by Tenant hereunder. In the event of any taking of the Premises or any
part thereof for temporary use, (i) this Lease shall be and remain unaffected
thereby, and

                                      -51-
<PAGE>

(ii) Tenant shall be entitled to receive for itself any award made for such use,
provided, that if any taking is for a period extending beyond the Term of this
Lease, such award shall be apportioned between Landlord and Tenant as of the
Term Expiration Date.

6.3   AWARD.

      Irrespective of the form in which recovery may be had by law, all rights
to damages or compensation payable pursuant to Section 6.2 shall belong to
Landlord in all cases except as set forth in Section 6.2 hereof or below in this
Section 6.3. Tenant hereby grants to Landlord all of Tenant's rights to such
damages and compensation and covenants to deliver such further assignments
thereof as Landlord may from time to time request. It is agreed and understood,
however, that Landlord does not reserve to itself, and Tenant does not assign to
Landlord, any damages payable for (i) movable trade fixtures or any items listed
on Exhibit E hereto installed by Tenant or anyone claiming under Tenant, at its
own cost and expense or (ii) relocation expenses or damages for loss of business
(in excess of any such damages attributable to the value of this lease)
recoverable by Tenant from such authority in a separate action.

                                   ARTICLE VII

                                    DEFAULTS

7.1   EVENTS OF DEFAULT.

      (a) If Tenant shall default in the performance of any of its obligations
to pay the Fixed Rent or Additional Rent hereunder and if such default shall
continue for 10 days after notice from Landlord to Tenant (provided, however,
that Landlord shall not be required to provide such notice more than two (2)
times in any period of twelve (12) consecutive calendar months) or if within
thirty (30) days after notice from Landlord to Tenant specifying any other
default or defaults Tenant has not commenced diligently to correct the default
or defaults so specified or has not thereafter diligently pursued such
correction to completion, or (b) if any assignment for the benefit of creditors
shall be made by Tenant, or by any guarantor of Tenant, or (c) if Tenant's
leasehold interest shall be taken on execution or other process of law in any
action against Tenant, or (d) if a lien or other involuntary encumbrance is
filed against Tenant's leasehold interest, and is not discharged within thirty
(30) days thereafter, or (e) if a petition is filed by Tenant or any guarantor
of Tenant for liquidation, or for reorganization or an arrangement or any other
relief under any provision of the Bankruptcy Code as then in force and effect,
or (f) if an involuntary petition under any of the provisions of said Bankruptcy
Code is filed against Tenant or any guarantor of Tenant and such involuntary
petition is not dismissed within ninety (90) days thereafter, or (g) if Tenant
fails to maintain the insurance required under Section 4.2.2.1 hereof, or (h) if
Tenant fails to substantially complete Tenant's Work required for the initial
occupancy of the percentages of the Premises by Tenant specified in Section
3.2.1 hereof by the respective dates determined pursuant to Section 3.2.1
hereof, Tenant shall have a six-month cure period after notice from Landlord to
Tenant within which to substantially complete such percentages of the Premises
(the foregoing events described in clauses (a) through (h) being individually
referred to as an "Event of Default" and collectively as "Events of Default"),
then, and upon any Event of Default, Landlord and the agents and servants of
Landlord lawfully may, in addition to and not in derogation of any remedies for
any preceding breach of covenant, immediately or at

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any time thereafter and without demand or notice, at Landlord's election, do any
one or more of the following: (1) give Tenant written notice stating that the
Lease is terminated, effective upon the giving of such notice or upon a date
stated in such notice, as Landlord may elect, in which event the Lease shall be
irrevocably extinguished and terminated as stated in such notice without any
further action, or (2) with or without process of law, in a lawful manner and
without illegal force, enter and repossess the Premises as of Landlord's former
estate, and expel Tenant and those claiming through or under Tenant, and remove
its and their effects, without being guilty of trespass, in which event the
Lease shall be irrevocably extinguished and terminated at the time of such
entry, or (3) pursue any other rights or remedies permitted by law. Any such
termination of the Lease shall be without prejudice to any remedies which might
otherwise be used for arrears of rent or prior breach of covenant, and in the
event of such termination Tenant shall remain liable under this Lease as
hereinafter provided. Tenant hereby waives all statutory rights of redemption
and Landlord, without notice to Tenant, may store Tenant's effects, and those of
any person claiming through or under Tenant, at the expense and risk of Tenant,
and, if Landlord so elects, may sell such effects at public auction or private
sale and apply the net proceeds to the payment of all sums due to Landlord from
Tenant, if any, and pay over the balance, if any, to Tenant.

7.2   REMEDIES.

      In the event that this Lease is terminated under any of the provisions
contained in Section 7.1 or shall be otherwise terminated for breach of any
obligation of Tenant, Tenant covenants to pay forthwith to Landlord, as
compensation, the excess of the total rent reserved for the residue of the Term
over the fair market rental value of the Premises for said residue of the Term.
In calculating the rent reserved there shall be included, in addition to the
Fixed Rent and Additional Rent, the value of all other considerations agreed to
be paid or performed by Tenant during said residue. Tenant further covenants (as
additional and cumulative obligations) after any such termination to pay
punctually to Landlord all the sums and to perform all the obligations which
Tenant covenants in this Lease to pay and to perform in the same manner and to
the same extent and at the same time as if this Lease had not been terminated.
In calculating the amounts to be paid by Tenant pursuant to the next preceding
sentence Tenant shall be credited with any amount paid to Landlord as
compensation as in this Section 7.2 provided and also with the net proceeds of
any rent obtained by Landlord by reletting the Premises, after deducting all of
the Landlord's reasonable expenses in connection with such reletting, including,
without limitation, all repossession costs, brokerage commissions, fees for
legal services and expenses of preparing the Premises for such reletting, it
being agreed by Tenant that Landlord may (i) relet the Premises or any part or
parts thereof, for a term or terms which may at Landlord's option be equal to or
less than or exceed the period which would otherwise have constituted the
balance of the Term and may grant such concessions and free rent as Landlord in
its reasonable judgment considers advisable or necessary to relet the same and
(ii) make such alterations, repairs and decorations in the Premises as Landlord
in its reasonable judgment considers advisable or necessary to relet the same,
and no action of Landlord in accordance with the foregoing or failure to relet
or to collect rent under reletting shall operate or be construed to release or
reduce Tenant's liability as aforesaid.

                                      -53-
<PAGE>

      In lieu of any other damages or indemnity and in lieu of full recovery by
Landlord of all sums payable under all the foregoing provisions of this Section
7.2, Landlord may by notice to Tenant, at any time after this Lease is
terminated under any of the provisions contained in Section 7.1 or is otherwise
terminated for breach of any obligation of Tenant and before such full recovery,
elect to recover, and Tenant shall thereupon pay, as liquidated damages, an
amount equal to the aggregate of the Fixed Rent and Additional Rent accrued in
the 12 months ended next prior to such termination, plus the amount of rent of
any kind accrued and unpaid at the time of termination and less the amount of
any recovery by Landlord under the foregoing provisions of this Section 7.2 up
to the time of payment of such liquidated damages.

      Nothing contained in this Lease shall, however, limit or prejudice the
right of Landlord to prove for and obtain in proceedings for bankruptcy or
insolvency by reason of the termination of this Lease, an amount equal to the
maximum allowed by any statute or rule of law in effect at the time when, and
governing the proceedings in which, the damages are to be proved, whether or not
the amount be greater than, equal to, or less than the amount of the loss or
damages referred to above.

7.3   REMEDIES CUMULATIVE.

      Any and all rights and remedies which either Landlord or Tenant may have
under this Lease, and at law and equity, shall be cumulative and shall not be
deemed inconsistent with each other, and any two or more of all such rights and
remedies may be exercised at the same time insofar as permitted by law.

7.4   LANDLORD'S RIGHT TO CURE DEFAULTS.

      Landlord may, but shall not be obligated to, cure, at any time, following
10 days' prior notice to Tenant, except in cases of emergency when no notice
shall be required, any default by Tenant under this Lease; and whenever Landlord
so elects, all costs and expenses incurred by Landlord, including reasonable
attorneys' fees, in curing a default shall be paid by Tenant to Landlord as
Additional Rent on demand, together with interest thereon at the rate provided
in Section 4.3 from the date of payment by Landlord to the date of payment by
Tenant.

7.5   EFFECT OF WAIVERS OF DEFAULT.

      Any consent or permission by Landlord or Tenant to any act omission by the
other party which otherwise would be a breach of any covenant or condition
herein, or any waiver by Landlord or Tenant of the breach of any covenant or
condition herein by the other party, shall not in any way be held or construed
(unless expressly so declared) to operate so as to impair the continuing
obligation of any covenant or condition herein, or otherwise, except as to the
specific instance, operate to permit similar acts or omissions.

      The failure of Landlord or Tenant to seek redress for violation of, or to
insist upon the strict performance of, any covenant or condition of this Lease
by the other party shall not be deemed a waiver of such violation nor prevent a
subsequent act, which would have originally constituted a violation, from having
all the force and effect of an original violation. The receipt

                                      -54-
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by Landlord, or the payment by Tenant, as the case may be, of rent with
knowledge of the breach of any covenant of this Lease shall not be deemed to
have been a waiver of such breach by Landlord or Tenant, as the case may be. No
consent or waiver, express or implied, by Landlord or Tenant, as the case may
be, to or of any breach of any agreement or duty shall be construed as a waiver
or consent to or of any other breach of the same or any other agreement or duty.

7.6   NO ACCORD AND SATISFACTION.

      No acceptance by Landlord of a lesser sum than the Fixed Rent, Additional
Rent or any other charge then due shall be deemed to be other than on account of
the earliest installment of such rent or charge due, unless Landlord elects by
notice to Tenant to credit such sum against the most recent installment due, nor
shall any endorsement or statement on any check or any letter accompanying any
check or payment as rent or other charge be deemed an accord and satisfaction,
and Landlord may accept such check or payment without prejudice to Landlord's
right to recover the balance of such installment or pursue any other remedy in
this Lease provided.

                                  ARTICLE VIII

                                    MORTGAGES

8.1   RIGHTS OF MORTGAGE HOLDERS.

      The word "mortgage" as used herein includes mortgages, deeds of trust or
other similar instruments evidencing other voluntary liens or encumbrances, and
modifications, consolidations, extensions, renewals, replacements and
substitutes thereof. The word "holder" shall mean a mortgagee, and any
subsequent holder or holders of a mortgage. Until the holder of a mortgage shall
enter and take possession of the Premises for the purpose of foreclosure, such
holder shall have only such rights of Landlord as are necessary to preserve the
integrity of this Lease as security. Upon entry and taking possession of the
Premises for the purpose of foreclosure, such holder shall have all the rights
of Landlord. Notwithstanding any other provision of this Lease to the contrary,
including without limitation Section 10.5, no such holder of a mortgage shall be
liable either as mortgagee or as assignee to perform, or be liable in damages
for failure to perform, any of the obligations of Landlord unless and until such
holder shall enter and take possession of the Premises for the purpose of
foreclosure, and such holder shall not in any event be liable to perform or for
failure to perform the obligations of Landlord under Section 3.1. Upon entry for
the purpose of foreclosure, such holder shall be liable to perform all of the
obligations of Landlord (except for the obligations under Article III), subject
to and with the benefit of the provisions of Section 10.5, provided that a
discontinuance of any foreclosure proceeding shall be deemed a conveyance under
said provisions to the owner of the equity of the Premises. No Fixed Rent,
Additional Rent or any other charge shall be paid more than 10 days prior to the
due dates thereof and payments made in violation of this provision shall (except
to the extent that such payments are actually received by a mortgagee in
possession or in the process of foreclosing its mortgage) be a nullity as
against such mortgagee and Tenant shall be liable for the amount of such
payments to such mortgagee.

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<PAGE>

      The covenants and agreements contained in this Lease with respect to the
rights, powers and benefits of a holder of a mortgage (including, without
limitation, the covenants and agreements contained in this Section 8.1)
constitute a continuing offer to any person, corporation or other entity, which
by accepting a mortgage subject to this Lease, assumes the obligations herein
set forth with respect to such holder; such holder is hereby constituted a party
of this Lease as an obligee hereunder to the same extent as though its name were
written hereon as such; and such holder shall be entitled to enforce such
provisions in its own name. Tenant agrees on request of Landlord to execute and
deliver from time to time a Subordination, Non-disturbance and Attornment
Agreement ("SNDA"), substantially in the form of Exhibit D hereto or any other
agreement which may be necessary to implement the provisions of this Section 8.1
and Section 8.2 hereof.

8.2   SUPERIORITY OF LEASE; OPTION TO SUBORDINATE.

      This Lease shall be superior to and shall not be subordinate to any future
mortgage or other voluntary lien or other encumbrance of the Lot, the Building
or the Complex; provided, however, that Landlord shall have the option to
subordinate this Lease to any such mortgage of the Lot, Building or Complex
provided that Landlord obtains from the holder of record of any existing or
future mortgage an SNDA in the form of Exhibit D hereto or another form of
agreement with Tenant by the terms of which such holder will agree (a) to
recognize the rights of Tenant under this Lease, (b) to perform Landlord's
obligations hereunder arising after the date of such holder's acquisition of
title as hereinafter described, expressly excluding, however, Landlord's
obligations under Article III of this Lease, and (c) to accept Tenant as tenant
of the Premises under the terms and conditions of this Lease in the event of
acquisition of title by such holder through foreclosure proceedings or
otherwise, provided that Tenant will agree to recognize the holder of such
mortgage as Landlord in such event, which agreement shall be made expressly to
bind and inure to the benefit of the successors and assigns of Tenant and of the
holder and upon anyone purchasing said Premises at any foreclosure sale. Tenant
and Landlord agree to execute and deliver any appropriate instruments necessary
to carry out the agreements contained in this Section 8.2. Any such mortgage to
which this Lease shall subordinate may contain such terms, provisions and
conditions as the holder deems usual or customary.

8.3   LEASE AMENDMENTS.

Tenant agrees to make such changes in this Lease as may be reasonably required
by the holder of any mortgage of which the Premises are a part, or any
institution which may purchase all or a substantial part of Landlord's interest
in the Premises, provided that such changes may not increase the Fixed Rent or
other payments due hereunder or otherwise materially affect the obligations of
Tenant hereunder, and provided further that such changes do not (i) materially
interfere with Tenant's right of use and enjoyment of the Premises pursuant to
this Lease, (ii) limit, impair or delay Tenant's rights to sublease or assign
all or portion of this Lease pursuant to Section 5.2.1 hereof, (iii) limit,
impair or delay Tenant's right to obtain a reduction or abatement of rent
pursuant to Section 6.2, (iv) limit, impair or delay Tenant's right to terminate
this Lease pursuant to Section 3.2 or Section 6.2 or (v) otherwise unreasonably
limit, impair or delay Tenant's rights hereunder.

                                      -56-
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                                   ARTICLE IX

                         LANDLORD'S ADDITIONAL COVENANTS

9.1   AFFIRMATIVE COVENANTS.
      Landlord covenants at all times during the Term:

      9.1.1 Perform Obligations.

            To perform promptly all of the obligations of Landlord set forth in
this Lease, including, without limitation, furnishing, through Landlord's
employees or independent contractors, the services (the cost of which is to be
included in the Annual Maintenance Charge).

      9.1.2 Repairs.

            Except as otherwise provided in Article VI, to make such repairs
(the cost of which is to be included in the Annual Maintenance Charge) to the
roof, exterior walls, exterior windows and waterproofing, floor slabs, other
structural components, parking areas, walks, landscaping, courtyard and any
other common areas and facilities of the Building as may be necessary to keep
them in good, serviceable and neat condition. Landlord shall be responsible for
the maintenance and repair of the heating and air-conditioning systems and the
components thereof serving the Building to the extent that such systems and
components are included in Base Building Improvements.

      9.1.3 Compliance with Law.

            To make all repairs, alterations, additions or replacements to the
Building or the Lot (the costs of which are to be included in the Annual
Maintenance Charge) required by any law, ordinance or order or regulation of any
public authority including repairs, alterations, additions or replacements to
the foundations and structural elements of the Building, except as required
because of Tenant's failure to comply with the provisions of Section 5.1.3
hereof; to keep the Building equipped with all safety appliances so required
(the costs of which are to be included in the Annual Maintenance Charge);
subject to Section 4.2.1, to pay all municipal, county, or state taxes assessed
against the Building or the Lot, or against Landlord's personal property of any
kind on or about the Building or the Lot; and to comply with the orders and
regulations of all governmental authorities with respect to zoning, building,
fire, health and other codes, regulations, ordinances or laws applicable to the
Building or the Lot, including the ADA Requirements (as defined in Section 5.1.4
hereof) and any codes, regulations, ordinances or laws relating to hazardous
materials (as defined in Section 5.1.4), subject to, and without limitation of,
Tenant's obligations with respect to such codes, regulations, ordinances or
laws. The costs incurred by Landlord in connection with the foregoing compliance
obligations shall be included in the Annual Maintenance Charge. All of the
foregoing covenants and obligations are subject to, and without limitation of,
all of Tenant's obligations under this Lease, including, without limitation,
those set forth in Sections 4.2 and 5.1.4.

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<PAGE>

      9.1.4 Indemnity.

            To defend, with counsel reasonably approved by Tenant, all actions
against Tenant, any partner, trustee, stockholder, officer, director, employee
or beneficiary of Tenant ("Tenant's Indemnified Parties") with respect to, and
to pay, protect, indemnify and save harmless, to the extent permitted by law,
all Tenant's Indemnified Parties from and against any and all liabilities,
losses, damages, costs, expenses (including reasonable attorneys' fees and
expenses), causes of action, suits, claims, demands or judgments of any nature
to which any of Tenant's Indemnified Parties is subject arising from and to the
extent of any negligent or willful act, fault, omission, or other misconduct of
Landlord or its agents, contractors or employees.

      9.1.5 Estoppel Certificate.

            Upon not less than 10 days' prior notice by Tenant, to execute,
acknowledge and deliver to Tenant a statement in writing certifying that this
Lease is unmodified and in full force and effect and that except as stated
therein Landlord has no knowledge of any defenses, offsets or counterclaims
against its obligations under this Lease (or, if there have been any
modifications that the Lease is in full force and effect as modified and stating
the modifications and, if there are any defenses, offsets or counterclaims,
setting them forth in reasonable detail), the dates to which the Fixed Rent and
Additional Rent and other charges have been paid and a statement that, to the
best of Landlord's knowledge, Tenant is not in default hereunder (or if in
default, the nature of such default, in reasonable detail) and such other
matters reasonably required by Tenant or any prospective assignee of Tenant. Any
such statement delivered pursuant to this Section 9.1.5 may be relied upon by
any prospective assignee.

      9.1.6 Subdivision.

            The Lot is currently a portion of the Complex and on or before
September 1, 2001 Landlord shall subdivide the Complex so as to, inter alia,
establish the Lot as a separate taxable parcel and establish easements which
benefit and/or burden the Lot and remaining portions of the Complex
(collectively, the "Subdivision"). Upon or after the Subdivision, Landlord may
convey the Lot and assign this Lease to an Affiliate of Landlord (the
"Transfer"). Tenant agrees to cooperate with Landlord in connection with such
Subdivision and Transfer, including without limitation, the execution,
acknowledgment and delivery of an instrument pursuant to which this Lease shall
be subordinated to easements reasonably established in connection with the
Subdivision and Transfer and such other documents as Landlord reasonably may
request so long as such Subdivision and Transfer do not materially interfere
with Tenant's use of the Premises or any of Tenant's rights under this Lease to
other portions of the Complex. Landlord represents and warrants that currently
there is no mortgage on the Premises.

      9.1.7 Utilities.

            Subject to Section 4.2.3 hereof, to bring (or cause to brought)
Utility Services for the Premises to the Utility Switching Points at Landlord's
sole cost and expense.

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                                    ARTICLE X

                            MISCELLANEOUS PROVISIONS

10.1  NOTICES FROM ONE PARTY TO THE OTHER.

      All notices required or permitted hereunder shall be in writing and
addressed, if to the Tenant, at the Original Address of Tenant or such other
address as Tenant shall have last designated by notice in writing to Landlord
and, if to Landlord, at Landlord's Address or such other address as Landlord
shall have last designated by notice in writing to Tenant. Any notice shall be
deemed duly given if mailed to such address postage prepaid, registered or
certified mail, return receipt requested, when deposited with the U.S. Postal
Service, or if delivered by a recognized courier service (e.g. Federal Express)
when deposited with such courier service, or if delivered to such address by
hand, when so delivered.

10.2  QUIET ENJOYMENT.

      Landlord agrees that upon Tenant's paying the rent and performing and
observing the terms, covenants, conditions and provisions on its part to be
performed and observed, Tenant shall and may peaceably and quietly have, hold
and enjoy the Premises during the Term without any manner of hindrance or
molestation from Landlord or anyone claiming under Landlord, subject, however,
to the terms of this Lease.

10.3  EASEMENTS; CHANGES TO LOT LINES.

      Landlord reserves the right, from time to time, to grant easements
affecting the Premises or the Building, the Lot or the Complex and to change or
alter existing boundaries of the Lot for purpose of developing and using the Lot
so long as such easements or such changes or alterations to existing boundaries
of the Lot do not materially interfere with Tenant's use of the Premises, and to
enter upon the Premises for purposes of constructing and maintaining any pipes,
wires and other facilities serving any portion of the Lot, the Building or the
Complex, subject to the terms of Section 5.1.7 hereof.

10.4  LEASE NOT TO BE RECORDED.

      Neither party shall record this Lease. Both parties shall execute and
deliver a notice of this Lease in such form, if any, as may be permitted by
applicable statute, which notice shall include provisions with respect to
Tenant's Parking Spaces in the Garage and Tenant's right to use the Complex
Common Areas. If this Lease is terminated before the Term Expiration Date the
parties shall execute, deliver and record an instrument acknowledging such fact
and the actual date of termination of this Lease, and Tenant hereby appoints
Landlord its attorney-in-fact, coupled with an interest, with full power of
substitution to execute such instrument.

                                      -59-
<PAGE>

10.5  BIND AND INURE; LIMITATION OF LANDLORD'S LIABILITY.

      The obligations of this Lease shall run with the land, and this Lease
shall be binding upon and inure to the benefit of the parties hereto and their
respective successors and assigns. No owner of the Premises shall be liable
under this Lease except for breaches of Landlord's obligations occurring while
owner of the Premises. The obligations of Landlord shall be binding upon the
assets of Landlord which comprise the Premises, the Building and the Lot but not
upon other assets of Landlord. Without limiting the generality of the foregoing,
upon any assignment of this Lease and the Security Deposit by Kendall Square,
LLC to an Affiliate of Landlord or a third party, Kendall Square, LLC shall have
no further liability or obligation arising pursuant to this Lease after the date
of such assignment. No member, partner, trustee, stockholder, officer, director,
employee or beneficiary (or the members, partners, trustees, stockholders,
officers, directors or employees of any such member) of Landlord shall be
personally liable under this Lease and Tenant shall look solely to Landlord's
interest in the Premises, the Building and the Lot in pursuit of its remedies
upon an event of default hereunder, and the general assets of the members,
partners, trustees, stockholders, officers, directors, employees or
beneficiaries (and the members, partners, trustees, stockholders, officers,
directors or employees of any such member) of Landlord shall not be subject to
levy, execution or other enforcement procedure for the satisfaction of the
remedies of Tenant; provided that the foregoing provisions of this sentence
shall not constitute a waiver of any obligation evidenced by this Lease and
provided further that the foregoing provisions of this sentence shall not limit
the right of Tenant to name Landlord or any member thereof as party defendant in
any action or suit in connection with this Lease so long as no personal money
judgment shall be asked for or taken against any such member or any individual
partner, trustee, stockholder, officer, employee or beneficiary of Landlord or
any such member.

10.6  FORCE MAJEURE.

      In any case where either party hereto is required to do any act, delays
caused by or resulting from the occurrence of one or more Force Majeure Events
shall not be counted in determining the time during which work shall be
completed, whether such time be designated by a fixed date, a fixed time or a
"reasonable time", and such time shall be deemed to be extended by the period of
such delay.

10.7  LANDLORD'S DEFAULT.

      Landlord shall not be deemed to be in default in the performance of any of
its obligations hereunder unless it shall fail to perform such obligations and
such failure shall continue for a period of 30 days following receipt of notice
from Tenant or such additional time as is reasonably required to correct any
such default after notice has been given by Tenant to Landlord specifying the
nature of Landlord's alleged default. Landlord shall not be liable in any event
for incidental or consequential damages to Tenant by reason of any default by
Landlord hereunder, whether or not Landlord is notified that such damages may
occur. Except as expressly set forth in Section 3.2 and Section 6.2 hereof,
Tenant shall have no right to terminate this Lease for any default by Landlord
hereunder and no right, for any such default, to offset or counterclaim against
any rent due hereunder.

                                      -60-
<PAGE>

      Notwithstanding the foregoing, if any repairs to the Premises required by
this Lease or any maintenance, cleaning, or lighting of Building Common Areas
are not performed by Landlord within thirty (30) days after notice from Tenant
(or such longer period as may be reasonably required in the event that any such
repair, maintenance, cleaning or lighting cannot be completed within said thirty
(30) day period), Tenant shall have the right to perform such obligation of
Landlord. If Tenant performs any such obligation of Landlord, Landlord shall pay
to Tenant the reasonable cost thereof within thirty (30) days after notice from
Tenant, provided, however, that in no event shall Tenant have the right to
offset or deduct the amount thereof against any payment of rent due hereunder.

      If an emergency occurs where a repair is required to be done immediately
in order to avoid imminent danger to persons or material damage to the Premises,
Tenant shall have the right to self-help consistent with the immediately
preceding grammatical paragraph of this Section 10.7 after giving Landlord only
such notice as is reasonable under the circumstances, provided, however, that
formal notice shall be promptly given thereafter. However, the right of
self-help afforded to Tenant in this Section 10.7 shall be carefully and
judiciously exercised by Tenant, it being understood and agreed that except in
the case of an emergency, Landlord shall be given sufficient opportunity to take
the action required of Landlord to avoid such default, in order to avoid any
conflict with respect to whether or not self-help should have been availed of by
Tenant, or with respect to the reasonableness of the expenses incurred by
Tenant.

10.8  BROKERAGE.

      Each party warrants and represents to the other party that it has had no
dealings with any broker or agent in connection with this Lease other than
Insignia/ESG, Inc. ("Broker") and covenants to defend with counsel reasonably
approved by such other party, hold harmless and indemnify such other party from
and against any and all cost, expense or liability arising from any breach of
the foregoing warranty and representation.

10.9  APPLICABLE LAW AND CONSTRUCTION.

      This Lease shall be governed by and construed in accordance with the laws
of the state in which the Premises are located. If any term, covenant, condition
or provision of this Lease or the application thereof to any person or
circumstances shall be declared invalid, or unenforceable by the final ruling of
a court of competent jurisdiction having final review, the remaining terms,
covenants, conditions and provisions of this Lease and their application to
persons or circumstances shall not be affected thereby and shall continue to be
enforced and recognized as valid agreements of the parties, and in the place of
such invalid or unenforceable provision, there shall be substituted a like, but
valid and enforceable provision which comports to the findings of the aforesaid
court and most nearly accomplishes the original intention of the parties.

      There are no prior oral or written agreements between Landlord and Tenant
affecting this Lease. The Letter of Intent dated September 13, 2000 from Broker
to Tenant shall be of no further force or effect. This Lease may be amended, and
the provisions hereof may be waived or modified, only by instruments in writing
executed by Landlord and Tenant. The titles of the

                                      -61-
<PAGE>

several Articles and Sections contained herein are for convenience only and
shall not be considered in construing this Lease. Unless repugnant to the
context, the words "Landlord" and "Tenant" appearing in this Lease shall be
construed to mean those named above and their respective heirs, executors,
administrators, successors and assigns, and those claiming through or under them
respectively. If there be more than one tenant the obligations imposed by this
Lease upon Tenant shall be joint and several.

10.10 SUBMISSION NOT AN OFFER.

      The submission of a draft of this Lease or a summary of some or all of its
provisions does not constitute an offer to lease or demise the Premises, it
being understood and agreed that neither Landlord nor Tenant shall be legally
bound with respect to the leasing of the Premises unless and until this Lease
has been executed by both Landlord and Tenant and a fully executed copy
delivered to each of them.

10.11 SECURITY DEPOSIT.

      Tenant will provide within five (5) business days of the date of full
execution hereof by Landlord and Tenant and as a condition of this Lease shall
keep in effect throughout the Term, a standby letter of credit in the Security
Deposit Amount (as hereinafter defined) as security for the performance of the
obligations of Tenant hereunder in accordance with the following requirements.
As used herein, the term "Security Deposit Amount" shall mean and refer to the
sum of the Initial Estimated Annual Additional Rent for Premises, the Initial
Estimated Annual Rent for Complex plus the Annual Fixed Rent, as the same may be
adjusted in accordance with Section 2.3, Section 4.1(b) and Section 10.12
hereof. If Tenant elects to have Landlord advance the Tenant Allowance, the
Security Deposit Amount shall thereupon be increased by
[*****Confidential*****]. On the effective date of any such adjustment of the
Annual Fixed Rent Rate, Tenant shall provide a replacement letter of credit for
the amount of the adjusted Security Deposit Amount. Any letter of credit
provided by Tenant shall be in form and substance acceptable to Landlord and
shall be drawn on Fleet National Bank (or another Boston clearinghouse bank
reasonably satisfactory to Landlord) for the Security Deposit Amount in
Landlord's favor. Tenant shall provide for replacements thereto to be issued and
delivered to Landlord at least 30 days prior to the expiration of the then
effective letter of credit, time being of the essence. The letter of credit
shall be payable to Landlord upon presentation at the issuing bank's offices in
Boston of a sight draft signed by Landlord stating that Landlord is entitled
thereto, and a certification of Landlord that the person signing the
certification is duly authorized to do so, that an uncured default exists under
the Lease, that the default has continued after the expiration of any applicable
cure period, and that the amount of the draft does not exceed the amount
reasonably required to cure such default (the "Default Certification"). Landlord
agrees that it shall present such sight draft and Default Certification only if
Tenant defaults in performance of its obligations hereunder and such default
shall have continued past any applicable notice and grace period. Any letter of
credit in effect during the last year of the Term shall expire no earlier than
30 days after the expiration of the Term of the Lease. The letter of credit
shall provide for partial draws and shall be assignable by Landlord. If Tenant
shall fail to perform any of its obligations under this Lease including a
failure timely to provide a replacement letter of credit, Landlord may, but
shall not be obligated to, apply the letter of credit

                                      -62-
<PAGE>

to the extent necessary to cure the default, and Tenant shall be obligated to
reinstate the letter of credit to the Security Deposit Amount then in effect.
Tenant shall not have the right to call upon Landlord to draw upon all or any
part of the letter of credit to cure any default or fulfill any obligation of
Tenant, but such use shall be solely in the discretion of Landlord. Provided
that Landlord gives Tenant notice of the name of such grantee or transferee,
upon any conveyance by Landlord of its interest under this Lease, the letter of
credit may be delivered by Landlord to Landlord's grantee or transferee. Upon
any such delivery, Tenant hereby releases Landlord herein named of any and all
liability with respect to the letter of credit, its application and return, and
Tenant agrees to look solely to such grantee or transferee. It is further
understood that this provision shall also apply to subsequent grantees and
transferees. Notwithstanding the foregoing, in lieu of a letter of credit,
Tenant may deliver cash in the Security Deposit Amount to Landlord, in which
event applicable provisions of this Section 10.11 shall apply to Landlord's use
and delivery thereof. If Tenant elects to deliver cash to Landlord in the
Security Deposit Amount, Tenant, subject to Landlord's prior written approval,
may designate the investment thereof, and interest earned thereon shall be
disbursed to Tenant on a yearly basis so long as no default has occurred and is
then continuing.

10.12 OPTIONS TO EXTEND.

      (a) Tenant shall have two (2) options to extend the Term of this Lease
(the "Options to Extend") for successive periods of ten (10) years each (the
"Extension Periods"), subject to and on the terms set forth herein. Tenant may
only exercise the Options to Extend with respect to the entire Premises. If
Tenant shall desire to exercise any Option to Extend, it shall give Landlord a
notice (the "Inquiry Notice") of such desire not later than eighteen (18) months
prior to the expiration of the Initial Term of this Lease or the preceding
Extension Period, as the case may be. Thereafter, the Fair Market Rent (as
defined in Subsection (c) below) for the applicable Extension Period shall be
determined in accordance with Subsection (d) below. After the applicable Fair
Market Rent has been so determined, Tenant shall exercise each Option to Extend
by giving Landlord notice (the "Exercise Notice") of its election to do so not
later than fifteen (15) months prior to the expiration of the Initial Term of
this Lease, or the preceding Extension Period, as the case may be. If Tenant
fails to timely give either the Inquiry Notice or the Exercise Notice to
Landlord with respect to any Option to Extend, Tenant shall be conclusively
deemed to have waived such Option to Extend hereunder.

      (b) Notwithstanding any contrary provision of this Lease, each Option to
Extend and any exercise by Tenant thereof shall be void and of no force or
effect unless on the dates Tenant gives Landlord its Inquiry Notice and Exercise
Notice for each Option to Extend and on the date of commencement of the each
Extension Period (i) this Lease is in full force and effect, (ii) there is no
Event of Default of Tenant under this Lease, and (iii) Tenant has not assigned
or subleased (or agreed to assign or sublease) more than fifty percent (50%) of
the rentable floor area of the Premises.

      (c) All of the terms, provisions, covenants, and conditions of this Lease
shall continue to apply during each Extension Period, except that the Annual
Fixed Rent Rate during each Extension Period (the "Extension Rent") shall be
equal to the 100% of the fair market rent for the Premises determined as of the
date twelve (12) months prior to expiration of the Initial

                                      -63-
<PAGE>

Term or the preceding Extension Period, as the case may be, in accordance with
the procedure set forth in Subsection (d) below (the "Fair Market Rent"), but in
no event shall the Fair Market Rent for the first Extension Period be less than
the Annual Fixed Rent for the fifteenth Lease Year and in no event shall the
Fair Market Rent for the second Extension Period be less than the Annual Fixed
Rent for the twenty-fifth Lease Year.

      (d) The Fair Market Rent for each Extension Period shall be determined as
follows: Within five (5) days after Tenant gives Landlord its Inquiry Notice
with respect to any Option to Extend, Landlord shall give Tenant notice of
Landlord's determination of the Fair Market Rent for the applicable Extension
Period. Within ten (10) days after Tenant receives such notice, Tenant shall
notify Landlord of its agreement with or objection to Landlord's determination
of the Fair Market Rent, whereupon the Fair Market Rent shall be determined by
arbitration conducted in the manner set forth below. If Tenant does not notify
Landlord within such ten (10) day period of Tenant's agreement with or objection
to Landlord's determination of the Fair Market Rent, then the Fair Market Rent
for the applicable Extension Period shall be deemed to be Landlord's
determination of the Fair Market Rent as set forth in the notice from Landlord
described in this subsection.

      (e) If Tenant notifies Landlord of Tenant's objection to Landlord's
determination of Fair Market Rent under the preceding subsection, such notice
shall also set forth a request for arbitration and Tenant's appointment of a
commercial real estate broker having at least ten (10) years experience in the
commercial leasing market in the City of Cambridge, Massachusetts (an
"Arbitrator"). Within five (5) days thereafter, Landlord shall by notice to
Tenant appoint a second Arbitrator. Each Arbitrator shall be advised to
determine the Fair Market Rent for the applicable Extension Period within thirty
(30) days after Landlord's appointment of the second Arbitrator. On or before
the expiration of such thirty-(30) day period, the two Arbitrators shall confer
to compare their respective determinations of the Fair Market Rent. If the
difference between the amounts so determined by the two Arbitrators is less than
or equal to ten percent (10%) of the lower of said amounts then the final
determination of the Fair Market Rent shall be equal to the average of said
amounts. If such difference between said amounts is greater than ten percent
(10%), then the two arbitrators shall have ten (10) days thereafter to appoint a
third Arbitrator (the "Third Arbitrator"), who shall be instructed to determine
the Fair Market Rent for the applicable Extension Period within ten (10) days
after its appointment by selecting one of the amounts determined by the other
two Arbitrators. Each party shall bear the cost of the Arbitrator selected by
such party. The cost for the Third Arbitrator, if any, shall be shared equally
by Landlord and Tenant.

      (f) Regardless of the manner in which the Extension Rent is determined,
the Annual Fixed Rent for each Extension Period shall be subject to adjustment
as set forth in Section 4.1(b) hereof.

10.13 INTENTIONALLY OMITTED.

                                      -64-
<PAGE>

10.14 PARKING.

      Commencing as of the Commencement Date, Tenant shall pay monthly, in
advance, as Additional Rent the then fair market value (the "Parking Fee") as
determined by Landlord (adjusted no more frequently than annually) for each of
Tenant's Parking Spaces to be leased to Tenant. All of Tenant's Parking Spaces
leased hereby may only be utilized by Tenant's employees, visitors, sublessees
of the Premises or assignees of the Lease, visiting or working at the Premises.
All of Tenant's Parking Spaces shall be located in the underground parking
structure to be constructed and/or owned by Landlord or an Affiliate of Landlord
(as hereinafter defined) south of Kendall Street, as shown on Exhibit A hereto
(the "Garage"). The owner of the Garage from time to time is herein referred to
as the "Garage Owner", and the Tenant's Parking Spaces are sometimes herein
referred to as the "Garage Parking Spaces." Landlord covenants and agrees that
if the Garage is conveyed by Landlord to any other person or entity, including
an Affiliate of Landlord, such conveyance shall be subject to a lease, permanent
easement or similar instrument by and between Landlord and the Garage Owner so
that the Tenant shall have, throughout the Term, the right to use the Garage
Parking Spaces, subject to the terms of this Lease.

      The Garage Owner shall have the right, from time to time but not more
often than every six (6) months, to relocate, on a temporary basis as may be
necessary to effect repairs and improvements to the Garage or for other business
reasons, parking spaces located in the Garage to another location within 1,000
feet of the Lot, provided that in each instance such other location may be
lawfully used for accessory parking, and provided further that the monthly rent
to be paid by Tenant for each temporarily relocated parking space shall be an
amount equal to the fair market value thereof but in no event more than the rent
then being paid by Tenant for a parking space in the Garage. Anything herein to
the contrary notwithstanding, Landlord shall have the right to relocate all or
any number of the Garage Parking Spaces to a garage which may be constructed by
Landlord or an Affiliate of Landlord in the northerly portion of the Complex
provided that access from the Building to such other garage is substantially as
convenient as access between the Building and the Garage, whereupon provisions
of this Lease applicable to the Garage, the Garage Owner and the Garage Parking
Spaces shall apply, mutatis mutandis, to such garage, garage owner and the
Garage Parking Spaces located therein. Upon request of either Landlord or
Tenant, the parties hereto shall execute and deliver an amendment of this Lease
to reflect the relocation of Tenant's Parking Spaces.

      Neither Landlord nor the Garage Owner shall be responsible for money,
jewelry, automobiles or other personal property lost in or stolen from the
Garage, regardless of whether such loss or theft occurs when the Garage or other
areas therein are locked or otherwise secured against entry, or liable for any
loss, injury or damage to persons using the Garage or automobiles or other
property therein, it being agreed that the use of the Garage and the Garage
Parking Spaces shall be at the sole risk of Tenant and its employees, visitors
and guests. Landlord and the Garage Owner shall have the right from time to time
to promulgate reasonable rules and regulations regarding the Garage, the Garage
Parking Spaces and the use thereof, including, but not limited to, rules and
regulations controlling the flow of traffic to and from various parking areas,
the angle and direction of parking and the like, which rules and regulations and
any additions and amendments thereto Garage Owner shall use reasonable efforts
to consistently apply to all users of the Garage. Tenant shall comply with and
cause its employees, visitors and

                                      -65-
<PAGE>

guests to comply with all such rules and regulations as well as all reasonable
additions and amendments thereto.

      Except for emergency repairs using authorized repair services, no person
using the Garage Parking Spaces shall perform any work on any automobiles while
located in the Garage. An approved assignment of this Lease by Tenant or an
assignment of this Lease by Tenant not requiring Landlord's consent shall
include an assignment of Tenant's right to use all of Tenant's Parking Spaces in
accordance with this Lease. An approved sublease by Tenant or a sublease by
Tenant not requiring Landlord's consent shall include the right to use a
substantially proportionate number of Tenant's Parking Spaces in light of the
r.s.f. subleased by Tenant. Except in connection with an approved assignment of
the Lease or an approved subletting of all or a portion of the Premises in
accordance with the terms hereof, Tenant shall not assign or sublease any of the
Garage Parking Spaces. Landlord shall have the right to terminate this Lease
with respect to any Garage Parking Spaces that Tenant sublets or assigns in
violation of the foregoing sentence. Landlord or the Garage Owner may elect to
provide parking cards or keys to control access to the Garage. In such event,
Landlord or the Garage Owner shall provide Tenant with one card or key for each
Garage Parking Space that Tenant is leasing hereunder, provided that Landlord or
the Garage Owner shall have the right to require Tenant or its employees to
place a reasonable deposit on such access cards or keys and to pay a reasonable
fee for any lost or damaged cards or keys. If the Garage Owner does not provide
24-hour per day, seven day per week manned security and/or controlled access for
the Garage (collectively, "Garage Security Services"), Landlord shall arrange
for such Garage Security Services and the costs of such Garage Security Services
(prorated, if appropriate, among all users of the Garage requesting Garage
Security Services) shall be included in the Nonstandard Charge payable by Tenant
pursuant to Section 4.2.4 hereof. Tenant, at its sole cost and expense, may
obtain extra cards and keys from Landlord or the Garage Owner if any cards are
lost, stolen or destroyed.

10.15 CONFIDENTIAL INFORMATION.

      Landlord hereby agrees that any and all knowledge, information, data,
materials, trade secrets, and other work product of a confidential nature
gained, obtained, derived, produced, generated or otherwise acquired by Landlord
with respect to Tenant's business (collectively "Confidential Information")
shall be kept confidential. Landlord shall use diligent efforts to ensure that
no Confidential Information is revealed, divulged, communicated, related, or
described to any person or entity without the written consent of Landlord,
except as may be required by applicable law.

10.16 SIGNAGE.

      Tenant shall be permitted, at its sole cost and expense, to install and
maintain signs on the exterior of the Building bearing Tenant's name (or
something similar reasonably approved by Landlord), provided that: (i) the size,
location, quality, color and style of such signs shall be subject to Landlord's
approval, such approval not to be unreasonably withheld or delayed, and (ii)
such signs shall be subject to the Development Approvals, the Subsequent
Approvals and limitations of applicable law, including, without limitation, the
Cambridge Zoning Ordinance, as amended from time to time. Tenant shall secure
all permits and approvals necessary for the

                                      -66-
<PAGE>

installation of such signs at its sole cost and expense. Upon the expiration or
sooner termination of the Term of this Lease, Tenant shall remove such signs and
repair any damage resulting therefrom at Tenant's sole cost and expense.

10.17 TELECOMMUNICATIONS EQUIPMENT.

      Landlord shall provide Tenant with reasonable and adequate space on the
roof of the Building for Tenant's telecommunications equipment, which Tenant may
install at Tenant's sole cost and expense, provided however, that (i) the size,
location and plans and equipment shall be subject to Landlord's approval, such
approval not to be unreasonably withheld or delayed, (ii) the installation and
maintenance thereof shall be subject to the Development Approvals, the
Subsequent Approvals and limitations of applicable law, including without
limitation, the Cambridge Zoning Ordinance, as amended from time to time and
(iii) the use of such telecommunications equipment shall be limited to Tenant in
the conduct of the Permitted Uses and not as a principal or accessory use of the
Premises. Tenant shall secure all permits and approvals necessary for the
installation of such equipment at its sole cost and expense. Upon the expiration
or sooner termination of the Term of this Lease, Tenant shall remove such
equipment and repair any damage resulting from such removal at Tenant's sole
cost and expense, provided however, that Tenant shall leave all cabling and
wiring for its telecommunications equipment, but such cabling and wiring shall
be appropriately and safely capped by Tenant. The installation of such equipment
shall be deemed to be part of Tenant's Work and all provisions of this Lease,
including insurance provisions, shall be applicable thereto.

      WITNESS the execution hereof under seal as of the 18th day of January,
2001.

                  LANDLORD:        KENDALL SQUARE, LLC

                                   By:  Lyme Properties LLC, a New Hampshire
                                        limited liability company, its Manager

                                   /s/ David E. Clem
                                   -----------------
                                   David E. Clem, Member

                  TENANT:          VERTEX PHARMACEUTICALS
                                   INCORPORATED

                                   By: /s/ Joshua S. Boger
                                       -------------------
                                       Its: Chief Executive Officer
                                       hereunto duly authorized

                                      -67-
<PAGE>

                                    EXHIBIT A

                              Plan Showing Complex
<PAGE>

                                     [Plan]
<PAGE>

                                   EXHIBIT A-1

                                Legal Description
                          (to be provided by Landlord)
<PAGE>

                                   EXHIBIT A-2

                                Plan Showing Lot
                          (to be provided by Landlord)
<PAGE>

                                   EXHIBIT A-3

                        Confirmation of Commencement Date
                           And Rentable Square Footage

      Reference is made to that certain Lease dated December ____, 2000 (the
"Lease") by and between KENDALL SQUARE, LLC ("Landlord"), a Delaware limited
liability company, and VERTEX PHARMACEUTICALS INCORPORATED ("Tenant"), a
Massachusetts corporation, for certain space in Building A located at Cambridge
Research Park, Cambridge, Massachusetts (the "Premises").

      In accordance with the terms and provisions of the above-referenced Lease,
Landlord and Tenant hereby confirm the following as of the date hereof:

      The Commencement Date of the Lease is ___________ ____, 2002.

      A.    The rentable square footage of the Premises is _______ square feet.

      B.    The rentable square footage of the Building is _______ square feet.

      C.    Tenant's Proportionate Fraction for Building is ___%.

      D.    Tenant's Proportionate Fraction for Complex is ___%.

      Agreed and Accepted as of the Commencement Date:

VERTEX PHARMACEUTICALS INCORPORATED

By:__________________________________________________

Title:_______________________________________________

Date of Execution:__________________________, 2002

KENDALL SQUARE, LLC

By:__________________________________________________

Title:_______________________________________________

Date of Execution __________________________, 2002
<PAGE>

                                    EXHIBIT B

                            Base Building Description

      Part I hereof sets forth the elements of the fire protection, plumbing,
HVAC, electrical and subslab venting systems for the Building.

      Part II hereof sets forth guidelines which are to serve as a source of
information for the Landlord's design team as more fully set forth in Part II
hereof. Anything in Part II to the contrary notwithstanding, Landlord and Tenant
acknowledge and agree that, as currently contemplated, the Building will not
include a basement, but that a basement may be included in the Building if
Landlord and Tenant hereafter agree to include a basement in the Building, which
agreement with respect thereto shall require an amendment to this Lease.

PART I

FIRE PROTECTION

      o     New water service with double check valve assembly and alarms.

      o     Distribution risers and mains.

      o     Common areas shall be finished with recessed heads.

      o     Tenant area shall have upright heads.

PLUMBING

      o     New water service with meter.

      o     Cold water distribution to toilet cores.

      o     Local electric domestic hot water heaters for toilet cores.

      o     Common area toilet cores.

      o     Roof drainage and storm system.

      o     New waste system.

      o     Ph adjustment and acid waste system to be provided by Tenant.

HVAC

      o     2 CFM per square foot, 100% outside air delivered from custom air
            handling units.
<PAGE>

      o     Water cooled chillers with 15% additional capacity for supplemental
            cooling.

      o     Hot water boilers for ventilation and heating.

      o     Chilled water risers with valve and capped stub outs per floor for
            supplemental cooling.

      o     Hot water risers with valve and cap stubs outs per floor for reheats
            and heating.

      o     Cooling towers.

      o     Chilled water pumps and distribution piping to equipment and risers.

      o     Condenser water pump and distribution piping to equipment and
            risers.

      o     Hot water pump and distribution piping to equipment and risers.

      o     Automatic Temperature Control utilizing direct digital control for
            Base Building Equipment.

      o     Common area distribution ductwork with fan powered terminal unit
            (hot water).

      o     Heat at entrance ways.

      o     Toilet exhausts systems.

      o     Mechanical Room and Electrical Room heat and ventilation systems.

      o     Medium pressure distribution ductwork risers with stub outs on each
            floor.

      o     Allocation for exhaust air shafts.

      o     Allocation for return air shafts.

ELECTRICAL

      o     Building primary service shall be sized for a capacity of 20 VA/SF
            from the Utility Company.

      o     Exterior pad-mounted transformer or interior vault transformer will
            be 13.8 kV-480/277 V, 3-phase, 60 Hertz. Location of transformer to
            be determined by utility company.

      o     Interior switchgear will be 480/277V, 3-phase, 60 Hertz for
            secondary service.

      o     Feeders to water cooled chillers.

      o     Feeders to passenger elevators and service elevator.

                                       -2-
<PAGE>

      o     Feeders to busduct risers.

      o     Busduct risers for 'future' tenant use.

      o     House distribution equipment to serve 'Common' Areas.

      o     House motor control center to serve air handling units, hot water
            boilers, cooling towers, chilled water / condenser water / hot water
            pumps and exhaust fans.

      o     Expandable addressable fire alarm system including devices in
            'Common' Areas, and future tenant areas.

      o     Exterior site lighting.

      o     Exterior ductbank and interior conduit provisions for telephone and
            cable TV service.

      o     Lighting Protection system.

      o     Lighting in 'Common Areas', exit lighting and emergency lighting
            (battery packs).

      o     Lighting in Mechanical Areas.

SUBSLAB VENTING

      o     Plastic geomembrane vapor barrier installed directly beneath the
            floor slab, which is to be sealed to foundation elements such as
            grade beams, pile caps, elevator sumps and utility penetrations so
            that vapors cannot enter the Building.

      o     Perforated piping to be installed directly beneath the vapor barrier
            throughout the Building footprint within a one-foot layer of gravel
            placed after piles, pile caps, grade beams and other foundation
            elements are constructed.

      o     One or more riser pipes will be installed from the venting piping
            through the floor slabs of the Building to the Building roof by way
            of the utility cores of the Building.

      o     A wind driven turbine may be installed on riser pipe(s) at the
            terminus thereof on the roof of the Building to provide negative
            pressure for the system.

      o     Blowers are to be installed on the riser pipe(s) and a vapor
            treatment system is to be installed.

PART II

1.    GOAL OF DESIGN GUIDELINES

      The purpose behind these Guidelines is to identify the typical Tenant
fit-up requirements in order to ensure that these standards are acknowledged in
the Base Building

                                      -3-
<PAGE>

Improvements. They are to serve as a source of information to the Landlord's
architectural team regarding Tenant's current approach toward the fit-up of
Tenant's facilities. These Guidelines are intended to be specific enough that
they satisfy the needs of the Tenant, and yet generic to the point that they do
not limit or inhibit the design intent for the shell & core of the Building.
Most of the issues identified in these Guidelines will require review and
coordination between the Landlord's and Tenant's architecture teams in order
that exterior architecture and interior architecture and engineering support one
another, and maintain the aesthetic expression established in conceptual design.

2.    BUILDING SHELL & CORE

      Exterior Entrance

      The exterior entry of the typical facility of Tenant is generally a
prominent gesture on the exterior of the building, one that clearly defines the
"front door" of the facility to the incoming public and staff. The significance
of this public threshold should be expressed on the Building's exterior.

      With security being a major issue, a single public entry is preferred over
multiple entrances. Although multiple entries can be accommodated successfully
if a defined Tenant control point is established within the lobby, a clear
zoning of the circulation is established, and unobstructed sightlines are
maintained. This entry point will provide for public pedestrian access from the
street, as well as the foot traffic approaching the Building from the adjacent,
exterior courtyard, and the vehicular drop-off and parking areas. The provision
for short-term parking spaces that have proximity to the main entrance is
desirable. The main entry door will also most likely be the access point for
certain incoming packages and deliveries (i.e. Fed-Ex, couriers, taxis,
limousines, etc.), making short term parking for these types of vehicles
desirable as well.

      Lobby/Reception/Atrium

      Tenant has consistently dedicated the most architecturally significant or
prominent areas in its buildings as public or common spaces for its staff, as
opposed to dedicating these areas to individual users. This includes multi-story
spaces, those areas within the highest floor level of the building that offer
significant views of the surrounding city, or those zones within the floor plate
that occur along or at the intersections of highly public circulation paths. The
programs that generally occupy these significant areas are typically common
staff or building areas, such as the main building lobby/atrium, reception, food
service/cafeteria, fitness center, library space, and conference/assembly areas
(see description of tenant fit-up/common areas below).

      The main lobby and/or atrium will house the public reception area for the
complex. It is generally the single, controlled access point to the facility for
incoming public traffic, including that associated with staff, general visitors,
and vendors. This main lobby creates one's first impression of Tenant, and
therefore it should characterize the culture and vitality of the company. It is
anticipated that this atrium space will be a fairly grand, multi-story volume,
with an abundance of natural light; this central space should also serve to
enhance the level of interaction among the staff of Tenant.

                                      -4-
<PAGE>

      The acoustic and environmental issues related to the lobby, atrium and
reception areas have been a concern on past projects. The owner has generally
been in support of materials that have acoustically absorptive properties in
order to maintain comfortable sound levels within these spaces. In addition,
appropriate architectural and mechanical zoning that serves to reduce the
potential for drafts or thermal gains in these highly active areas is also
desirable. Materials considered should be in keeping with the overall aesthetic
of the Building, and yet are durable, easily maintained, and slip resistant.

      The reception station/area will need to accommodate two individuals, each
having a concealed computer monitor, file space, and security / tele-data
connections. The reception area should have direct access to restrooms for
visitors, display space for Tenant's products, coat closet / storage, and the
potential of a concealed mail and operator rooms. The desk design and materials
should be in keeping with the aesthetic expression of the Building, while also
incorporating durable materials in order to withstand the high volume of traffic
it will experience. Even though it is not necessary that the security office be
located adjacent to the reception/lobby areas, it will need a reasonable
proximity to this area.

      Retail Space

      The Retail Space outside of Tenant's Premises will need to have direct
public access from the exterior of the Building. Tenant may permit limited
secondary access from the interior atrium space, though this access will need to
be coordinated with Tenant's security program. All loading and service
facilities related to the Retail Space will need to be coordinated with Tenant's
loading and service facilities and subject to Building Rules and Regulations.

      Restrooms

      The restrooms are generally positioned in a conspicuous and consistent
location on the floor plate, having proximity to the highly public areas of the
Building. Having multiple restroom cores on each floor is desirable, and will
need to be verified with the occupant loads anticipated on each level. The
materials and detailing of these areas should be in keeping with the aesthetic
expression of the Building, and should incorporate durable materials, details,
and fixtures that are easily maintained, such as ceiling hung, brushed stainless
steel toilet partitions, and wall hung toilets. All toilet accessories are
typically brushed stainless steel, recessed elements.

      Elevators

      The elevator core of the Building needs to be centrally located, adjacent
to the main Building lobby, and within proximity of the atrium space. The
elevator works are generally an electric, traction type assembly, with an
average speed of 150 fpm - 175 fpm, although hydraulic elevators are often
preferred by the Tenant in some circumstances; the elevator type, size and speed
will need to be reviewed and coordinated with Tenant's intended programs. The
hoistway doors and frames are typically constructed of a brushed stainless
steel; all elevator accessories are also brushed stainless steel. The cab
finishes should include a brushed stainless steel control panel on each side of
the elevator door, with durable wall and ceiling panels that are consistent

                                       -5-
<PAGE>

with the aesthetic expression of the Building. Like the wall surfaces, the
flooring should be highly durable and easily maintained. The lighting levels
within the cabs should approximate those design levels within the adjacent
elevator lobbies.

      Service/Freight Elevators

      Typically, a minimum of one service elevator is provided to each level of
the proposed building, and extends to the mechanical penthouse level. The speed
of the service elevator will need to be comparable to that of the public
elevators. The service elevator cab is typically oversized in terms of its
width, length and height, being large enough to accommodate a standard fumehood
(approximately 8' x 10.5'). The hoistway doors are typically oversized as well,
with a preferred opening of approximately 9'-0" clear. The cab finishes are
generally brushed stainless steel panels, with brushed stainless steel hoistway
doors, frames, and control panels. The flooring within this cab is generally
sheet vinyl or vct.

      Loading Docks/Service Entrance

      The typical program related to the loading and service dock area includes
two active loading berths for full size trucks, and one additional berth for a
trash compactor. If the dock itself is ramped to allow the trailer floor surface
to be co-planar with the dock elevation within the Building, a hydraulic lift
will need to be provided adjacent to the sloped dock; this device will allow
smaller trucks and vans that unload on grade to lift their palettes and
materials to the dock level. Provisions for coiling overhead doors and
industrial grade, moveable lighting is also recommended. A main door that
provides access to the service area will also be necessary for short term
deliveries, with a security control point to prevent unauthorized access into
the Building. The loading dock is generally located out of the public view, with
convenient service access to the adjacent streets.

      Mechanical Penthouse

      The typical penthouse standards are as defined by the MEP/FP engineers'
criteria (see below). The penthouse floor area generally occupies up to 70% of
the typical building footprint, and requires an average, vertical clearance of
approximately 20'-0" for MEP/FP equipment and its distribution. Service aisles
will need to be provided for the maintenance and/or replacement of penthouse
equipment. Access from the penthouse level to the roof level will be necessary
in order to allow for the routine service and maintenance of all roof-mounted
equipment and of the Base Building Improvements at this level. All rooftop
mechanical equipment included in the Base Building Improvements will need to be
located on steel donnage with grating platforms for ease of servicing. The
structural and acoustical issues related to the proposed penthouse equipment
will need to be analyzed and coordinated with the base building scope. As
previously mentioned, service elevator access to the penthouse level is also
necessary.

      Basement Level (Optional)

      Basement levels are generally preferred within the scope of a project in
order to provide housing for various support areas, such as waste treatment pH
neutralization, pump rooms, electric rooms, dedicated phone and tele-data rooms,
the potential of tank storage for the emergency generator fuel source, and other
Tenant and shell & core elements of the program.

                                      -6-
<PAGE>

The basement floor area that is typically required for these program elements is
approximately 15,000 sf, and requires stair and freight elevator access. If a
basement is not provided, space will need to be dedicated to these functions on
the first level of the building, adjacent to the loading /service dock area.

      Exterior Envelope

      The exterior envelope for the Building will need to be coordinated with
the Tenant's interior fit-up in order to assure the appropriate accommodation of
the current program, and also to allow for future flexibility related to
unforeseen demands. The average floor to floor height is recommended to be
approximately 14'-6" -15'-0" between each floor level, which will allow adequate
space for MEP/FP distribution while maintaining a minimum 9"-0" ceiling height
above the finished floor within the tenant spaces. As a result, the frame of
exterior window heads are typically set at 9'-0" above the finished floor, with
the windowsill at 3'-8" minimum above the finished floors of the lab and office
areas. The MEP/FP distribution of services at the perimeter wall of the Lab
Zones will need to be coordinated in order to maintain the original design
intent.

      Floor to ceiling glass within the working areas of a building has
generally proven to be problematic, resulting in unanticipated spandrel
conditions at the exterior wall. Sills below this datum within the office zones
can also limit the future flexibility of converting office areas into lab or
support zones. All exterior glass is to be insulating, and fixed in its frame.
The exterior curtainwall systems will also need to accommodate the thermal
criteria of the mechanical specifications, providing for an average of 30% RH
throughout the Building, with an occasional support area requiring higher
humidity levels. The interior and exterior finish selections for the base
building scope will also need to be coordinated with the Tenant design during
the early phases of the Building's development.

      Structural System

      The Building's structural system will most likely be a braced steel frame
with composite floor slabs. This approach offers the most flexibility in future
alterations to the Building, and is also an economical approach to a building
structure in the New England construction market. The typical floor loading
criteria that should be expected is the following:

      Uniformly Distributed Design Loads

      - Offices                    80 lbs. psf + 20 lbs. psf partition allowance
      - Corridors                  80 lbs. psf (above Level One)
      - Stairs                    100 lbs. psf
      - Mechanical Areas          150 lbs. psf
                                  (or actual equip. weights if greater)
      - Elevator Machine Room     150 lbs. psf

      All anticipated floor loading for the Building, including the uniformly
      distributed loads, roof live loads, concentrated live loads, live load
      reductions, wind and seismic loads, etc., should be reviewed with the
      structural engineer of record.

                                      -7-
<PAGE>

      The structural system and its grid spacing should conform to the standard
lab module identified below, with a 22'-0" wide column spacing along the length
of the building, as shown on Drawings A1.01 - A1.08 dated December 20, 2000. As
previously mentioned, the optimum, average floor to floor height for the
Building is approximately 14'-6" to 15'-0" from finished floor to the adjacent
finished floors. The average penthouse volume requires approximately 20'-0"
clear for MEP distribution, with an additional 2'-6" of structure at the
penthouse roof.

      Electrical Rooms/Plumbing Closets/Shaft Areas

      The typical shell & core areas required for the mechanical, normal
electrical, emergency electrical, plumbing, and fire protection equipment will
need to be sized and located in accordance with the MEP/FP Guidelines, and
coordinated with the schematic layout of the Tenant areas of the Building. All
additional shaft areas that are necessary as a result of the development of the
interior fit-up will be coordinated with the Shell & Core scope during the
subsequent phases.

                                      -8-
<PAGE>

                                   EXHIBIT B-1

                                Progress Schedule

<TABLE>
<CAPTION>
     ITEM                                                          COMPLETION DATE
     ----                                                          ---------------
<S>  <C>                                                             <C>
1.   Selection of Landlord's Architect and agreement upon            Completed prior to
     Preliminary Design Concept                                      Lease execution

2.   Plans

     Preliminary Schematic Design Documents
            delivered to Tenant and Landlord                         February 1, 2001

     Tenant's Response to Preliminary Schematic
            Design Documents                                         February 8, 2001

     Final Schematic Design Documents
            delivered to Tenant and Landlord                         February 15, 2001

     Tenant's Response to Final Schematic
            Design Documents                                         February 22, 2001

     Planning Board Design Review Hearing                            February 6, 2001

     Planning Board Design Review Approval                           March 6, 2001

     Preliminary Design Development Documents
            delivered to Tenant and Landlord                         April 16, 2001

     Tenant's Response to Preliminary Design
            Development Documents                                    April 23, 2001

     Final Design Development Documents including partial
            building permit set delivered to Tenant and Landlord     April 30, 2001

     Tenant's Response to Final Design Development
            Documents                                                May 7, 2001

     Final Design Documents delivered to
            Tenant and Landlord                                      September 12, 2001

     Tenant's Response to Final Design Documents                     September 19, 2001

     Partial Building Permit Issued                                  June 6, 2001

     Full Building Permit Issued                                     October 3, 2001
</TABLE>

<PAGE>

<TABLE>
<S>  <C>                                                             <C>
     Tenant's Construction Drawings Complete                         January 15, 2002

     Commencement of Construction of Tenant's Work                   April 16, 2002

     Substantial Completion of Base Building
            Improvements                                             September 15, 2002
</TABLE>

                                       -2-
<PAGE>

                                   EXHIBIT B-2

  Items/Categories of Annual Maintenance Charge, Insurance, Mitigation Expenses
                            and Taxes and Assessments

Cleaning:
   Daily Cleaning Service
   Window Cleaning
   Trash Removal - Routine
   Trash Removal - Other
   Exterminating
   Other Cleaning
                                     Total Cleaning

Repairs & Maintenance:
   Maintenance Salaries
   Elevator Service Contracts
   Elevator Repairs
   HVAC - System Contracts
   HVAC - Extra Repairs
   Electrical Repairs
   Plumbing Repairs
   Roofing Repairs
   Alarm Systems Maintenance
   Alarm Systems Inspections
   Other Maintenance &
   Supplies (including architectural
   repairs, finishes, hardware, etc.)
                           Total Mechanical Systems

Utilities:
   Electricity
   Gas
   Water & Sewer
   Steam
   Telephone
   Data
   Other
          Total Utilities net of Tenant Electricity

Roads/Grounds/Security
   Landscaping Contracts
   Snowplowing Contracts
   Other Roads/Grounds Expenses
   Skating Rink Expenses
   Small Boat Ramp Expenses
   Security Payroll
   Security Contracts
                       Total Roads/Grounds/Security
<PAGE>

Administrative:
   Admin Salaries
   Management Fee
   Monitoring Fee
   Legal Expense
   Office Supplies
   Postage & Delivery
   Telephone Expense
   Office Rent
   Other Admin Expenses
                               Total Admin Expenses

Mitigation Expenses:
   PTDM Fees
   Other Mitigation Expenses
                          Total Mitigation Expenses

Insurance:
   General Liability
   Property Insurance
   Rental Interruption
   Other Insurance
                                    Total Insurance

                        Total Expenses Before Taxes

Taxes and Assessments:
   Real Estate Taxes
   Other Taxes
                                     TOTAL EXPENSES

                                       -2-
<PAGE>

                                    EXHIBIT C

                              Rules and Regulations
                              ---------------------

1.    The common entrances, lobbies, elevators, sidewalks, and stairways of the
      Building, the Lot and the Complex shall not be encumbered or obstructed by
      Tenant, Tenant's agents, servants, employees, licensees or visitors or
      used by them for any purposes other than ingress or egress to and from the
      Building.

2.    Landlord reserves the right to have Landlord's structural engineer review
      Tenant's floor loads on the Building at Tenant's expense.

3.    Tenant, or the employees, agents, servants, visitors or licensees of
      Tenant shall not at any time place, leave or discard any rubbish, paper,
      articles, or objects of any kind whatsoever outside of the Building.
      Bicycles shall not be permitted in the Building unless Landlord provides
      for the parking thereof in the Building.

4.    Tenant shall not place objects against glass partitions or doors or
      windows or adjacent to any common space which would be unsightly from the
      exterior of the Building and will promptly remove the same upon notice
      from Landlord.

5.    Tenant shall not make noises, cause disturbances, create vibrations, odors
      or noxious fumes or use or operate any electric or electrical devices or
      other devices that emit sound waves or that would interfere with the
      operation of any device or equipment or radio or television broadcasting
      or reception from or within the Building or elsewhere, or with the
      operation of roads or highways in the vicinity of the Building and shall
      not place or install any projections, antennae, aerials, or similar
      devices inside or outside of the Building, without the prior written
      approval of Landlord.

6.    Tenant shall not: (a) use the Building for lodging, or for any immoral or
      illegal purposes; (b) use the Building to engage in the manufacture or
      sale of spirituous, fermented, intoxicating or alcoholic beverages in the
      Building; (c) use the Building to engage in the manufacture or sale of, or
      permit the use of, any illegal drugs on the Building.

7.    No awning or other projections shall be attached to the outside walls or
      windows. No curtains, blinds, shades, screens or signs, other than those,
      if any, furnished by Landlord, shall be attached to, hung in, or used in
      connection with any exterior window or door of the Building without the
      prior written consent of Landlord. No sign, advertisement, object, notice
      or other lettering shall be exhibited, inscribed, painted or affixed on
      any part of the outside or inside of the Building if visible from outside
      of the Building without the prior written consent of Landlord.

8.    Door keys, pass cards or similar devices for doors in the Building will be
      furnished on the Commencement Date by Landlord. If Tenant shall affix
      additional locks on doors then Tenant shall furnish Landlord with copies
      of keys or pass cards or similar devices for said locks.
<PAGE>

10.   Tenant shall cooperate and participate in all reasonable security programs
      affecting the Building and Complex.

11.   Tenant assumes full responsibility for protecting its space from theft,
      robbery and pilferage, which includes keeping doors locked and other means
      of entry to its space in the Building closed and secured.

12.   The water and wash closets and other plumbing fixtures shall not be used
      for any purposes other than those for which they were constructed, and no
      sweepings, rubbish, rags, or other substances shall be thrown therein.

13.   Discharge of industrial sewage shall only be permitted if Tenant, at its
      sole expense, shall have obtained all necessary permits and licenses
      therefor, including without limitation permits from state and local
      authorities having jurisdiction thereof.

14.   Tenant shall not mark, paint, drill into, or in any way deface any part of
      the Building or Premises. No boring, driving of nails or screws, cutting
      or stringing of wires shall be permitted except with the prior written
      consent of Landlord not to be unreasonably withheld, and as Landlord may
      direct. Tenant shall not install any resilient tile or similar floor
      covering in the Premises except with the prior written approval of
      Landlord not to be unreasonably withheld. The use of asbestos containing
      cement or other similar asbestos containing adhesive material is expressly
      prohibited.

15.   In the event of any conflict between the provisions of this Exhibit C and
      the provisions of the Lease, the provisions of the Lease shall govern.

                                       -2-
<PAGE>

                                    EXHIBIT D

                                  Form of SNDA
                                  ------------
                                   (attached)
<PAGE>

                       SUBORDINATION, NON-DISTURBANCE AND
                              ATTORNMENT AGREEMENT

      THIS SUBORDINATION, NON-DISTURBANCE AND ATTORNMENT AGREEMENT ("Agreement")
is entered into this ____ day of ___________, 200__, between
_____________________ ("Lender"), and Vertex Pharmaceuticals Incorporated, a
Massachusetts corporation ("Tenant").

                                R E C I T A L S:
                                ----------------

      A. Lender is the owner and the holder of a Promissory Note (the "Note")
dated ______________, 200__, in the face amount of $____________ payable to the
order of Lender. The Note is secured by a Mortgage, Security Agreement and
Fixture Filing with Assignment of Leases and Rents (hereinafter called the
"Mortgage") dated of even date with said Note, secured by the real property
described in Exhibit "A" attached hereto and by reference made part hereof (the
"Property").

      B. Tenant is the tenant under that certain Lease dated ____________, 2000
(the "Lease"), between Tenant, as tenant, and Kendall Square, LLC, a Delaware
limited liability company, as landlord (said landlord and its successors and
assigns under the Lease hereinafter called "Landlord"), covering all or part of
the Property as set forth in the Lease (the "Demised Premises").

      C. Tenant and Lender desire to confirm their understanding with respect to
the Lease and the Mortgage.

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
herein contained and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged by all parties, Lender and Tenant
hereby agree and covenant as follows:

            1. Subordination. The Lease now is, and shall at all times and for
all purposes continue to be, subject and subordinate, in each and every respect,
to the Mortgage, with the provisions of the Mortgage (including but not limited
to the provisions of the Mortgage pertaining to the application of insurance
proceeds and condemnation awards) controlling in all respects over the
provisions of the Lease; moreover the Lease is subordinate and subject, in each
and every respect, to any and all increases, renewals, modifications,
extensions, and/or consolidations of the Mortgage, and all other loan documents
securing the Note, provided that any and all such increases, renewals,
modifications, extensions and/or consolidations shall nevertheless be subject to
the terms of this Agreement.

            2. Non-Disturbance. So long as Tenant is not in any then current,
uncured default as of the time of Lender's exercise of its rights under the
Mortgage (beyond any period given Tenant to cure such default in the Lease) in
the payment of rent or additional rent or in the performance of any of the
terms, covenants or conditions of the Lease on Tenant' s part to be performed,
(i) Tenant' s possession, occupancy, use and quiet enjoyment of the Demised
<PAGE>

Premises and Tenant's other rights under the Lease, or any extensions or
renewals thereof, which may be effected in accordance with any option therefor
in the Lease, shall not be terminated or interfered with by Lender in the
exercise of any of its rights under the Mortgage, or as may otherwise be
provided for at law or in equity and (ii) Lender 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.

            3. Attornment. If any proceedings are brought for the foreclosure of
the Mortgage or if the Property is sold pursuant to a power of sale under the
Mortgage, or Lender shall succeed to the interest of Landlord under the Lease in
any manner, Tenant shall attorn and be bound to such party (whether Lender or
another party) upon any such succession in interest or foreclosure sale and
shall recognize such party as the Landlord under the Lease. Such attornment
shall be effective and self-operative without the execution of any further
instrument on the part of any of the parties hereto. Tenant agrees, however, to
execute and deliver at any time and from time to time, upon the request of
Lender or of any holder(s) of any of the indebtedness or other obligations
secured by the Mortgage or any purchaser of the Property at a foreclosure sale,
any instrument or certificate which may be necessary or appropriate (in any such
foreclosure proceeding or otherwise) to evidence such attornment. In the event
of any such attornment, Tenant further waives the provisions of any statute or
rule of law, now or hereafter in effect, which may give or purport to give
Tenant any right or election to terminate or otherwise adversely affect the
Lease and the obligations of Tenant thereunder as a result of any such
foreclosure proceeding.

            4. Obligations of Lender. If Lender shall succeed to the interest of
the Landlord under the Lease, or if any purchaser acquires the Property, upon
any foreclosure of the Mortgage, Lender or such purchaser, as the case may be,
shall have the same remedies by entry, action or otherwise in the event of any
default by Tenant (beyond any period given Tenant to cure such default) in the
payment of rent or additional rent by Tenant or in the performance of any of the
terms, covenants and conditions of the Lease on Tenant's part to be performed
that the Landlord under the Lease had or would have had if Lender or such
purchaser had not succeeded to the interest of Landlord. From and after any such
attornment, Lender or such purchaser shall be bound to Tenant under all of the
terms, covenants, and conditions of the Lease, and Tenant shall, from and after
the succession to the interest of Landlord under the Lease by Lender or such
purchaser, have the same remedies against Lender or such purchaser for the
breach of any agreement contained in the Lease that Tenant might have had under
the Lease against the Landlord if Lender or such purchaser had not succeeded to
the interest of Landlord; provided further, however, that Lender or such
purchaser shall not be liable or bound to Tenant as follows:

            (a) for any act or omission of any prior landlord (including
Landlord) provided, however, that nothing in this clause (a) shall release
Lender or any such purchaser, after such attornment, from any obligation of a
prior landlord to: (i) reconstruct or repair the Property following any fire,
casualty or condemnation which may have occurred prior to such attornment, to
the extent that insurance proceeds or condemnation awards are available and
otherwise as required under Article VI of the Lease; or (ii) perform any
on-going maintenance, repair and/or Building operation obligations of the prior
landlord under the Lease even if the need for such item of repair, maintenance
or Building operation arose prior to such attornment;

                                       -2-
<PAGE>

and provided further, nothing in this clause (a) shall affect or limit Tenant's
express rights to terminate the Lease under Sections 3.2 and 6.1 of the Lease
under the applicable circumstances set forth in each such section; or

            (b) for any offsets or defenses which Tenant might have against any
landlord prior to Lender (including Landlord); or

            (c) for or by any rent or additional rent which Tenant has paid for
more than the current month or the next succeeding month to any prior landlord
(including Landlord) unless such rent payment is actually paid or credited to
Lender or such purchaser by the prior landlord; or

            (d) by any amendment or modification of the Lease made without
Lender's written consent, which consent shall not be unreasonably withheld,
conditioned or delayed if Lender determines that such amendment or modification
will not materially and adversely affect the value of the Lease as collateral
security for the Note; or

            (e) for any security deposit, rental deposit or other deposit paid
by Tenant to a prior landlord (including Landlord) unless such deposit is
actually paid over or credited to Lender or such purchaser by the prior
landlord;

            (f) by any notice of a landlord default given by Tenant to a prior
landlord (including Landlord) unless a copy thereof was also then given to
Lender in accordance with this Agreement; or

            (g) under any indemnification provisions set forth in the lease or
for any damages Tenant may suffer as a result of any false representation set
forth in the Lease, the breach of any warranty set forth in the Lease, or any
act of, or failure to act by any party other than Lender or such purchaser, as
applicable.

            The person or entity to whom Tenant attorns shall be liable to
Tenant under the Lease only to the extent of the interest of such person or
entity in the Premises, the Building and the Lot (as such terms are defined in
the Lease) and only for matters arising during such person's or entity's period
of ownership, and, except for any liability arising during the period of
ownership of such person or entity, such liability shall terminate upon the
transfer by such person or entity of its interest in the Lease and the Property
and the assumption of the Lease by the transferee.

            Lender hereby agrees that if at the time of such attornment (x)
Landlord has commenced but not substantially completed Landlord's Work and (y)
Tenant has commenced Tenant's Work, then in order to complete Landlord's Work,
(i) Lender may elect to complete Landlord's Work, or (ii) if Lender does not
elect to complete Landlord's Work, Tenant may advance funds to complete
Landlord's Work, in which event Tenant shall receive an abatement of Annual
Fixed Rent, commencing on the Rent Commencement Date, in an amount equal to the
funds so advanced from time to time by Tenant with interest thereon at the
non-default rate of interest set forth in the Note on the outstanding amount of
such advances and continuing until

                                       -3-
<PAGE>

such abatement is exhausted. If Lender does not elect to complete Landlord's
Work or if Lender elects to complete Landlord's Work but fails to substantially
complete Landlord's Work by the Outside Completion Date, Tenant, shall have the
right to terminate the Lease in accordance with the last paragraph of Section
3.2 of the Lease. If, however, Tenant advances funds to complete Landlord's Work
in accordance with clause (iii) hereof, Tenant shall have no right to terminate
this Lease pursuant to the last paragraph of Section 3.2 of the Lease if
Landlord's Work is not substantially complete by the Outside Completion Date.

            5. Rent Payment. Tenant agrees to pay all rents directly to Lender
in accordance with the Lease immediately upon receipt of written notice from
Lender or Landlord of Lender's succeeding to the Landlord's interest under the
Lease or upon receipt of written notice that Lender is exercising its rights
under the Mortgage or any other loan documents which secure the Note following a
default by Landlord or other applicable party. Tenant shall be entitled to full
credit under the Lease to the extent of all rents paid to Lender pursuant to
this paragraph of this Agreement. By its signature to and consent to this
Agreement, Landlord agrees to this paragraph and releases Tenant from any
liability to Landlord to the extent of the payment of all rents delivered to
Lender under this provision.

            6. Notice of Mortgage. To the extent that the Lease shall entitle
the Tenant to notice of any mortgage or security agreement, this Agreement shall
constitute such notice to the Tenant with respect to the Mortgage.

            7. Successor of Lender . The term "Lender" as used throughout this
Agreement includes any successor, assigns or holder(s) in interest of the
indebtedness secured by the Mortgage.

            8. Landlord Defaults. Tenant agrees with Lender that effective as of
the date of this Agreement: (i) that Tenant shall not take any steps to
terminate the Lease for any default by Landlord or any succeeding owner of the
Property until after giving Lender written notice of such default, stating the
nature of the default and giving Lender thirty (30) days from receipt of such
notice to effect a cure of the same, or if a cure cannot be effected within said
thirty (30) days due to the nature of the default, Lender shall have a
reasonable time to cure provided that it commences to cure within said thirty
(30) day period of time and diligently pursues such cure to completion; and (ii)
that notice to the Landlord under the Lease (oral or written) shall not
constitute notice to Lender.

            9. No Abridgment. Nothing herein contained is intended, nor shall it
be, construed to abridge or adversely affect any right or remedy of the Landlord
under the Lease in the event of any default by Tenant (beyond any period given
Tenant to cure such default) in the payment of rent or additional rent or in the
performance of any of the terms, covenants or conditions of the Lease on
Tenant's part to be performed.

            10. No Amendment or Termination of Lease. Lender and Tenant agree
that Tenant's interest in and obligations under the Lease shall not be (i)
altered or modified without the prior written consent of Lender, which consent
shall not be unreasonably withheld, delayed or conditioned if Lender determines
that such amendment or modification will not materially and

                                       -4-
<PAGE>

adversely affect the value of the Lease as collateral security for the Note or
(ii) terminated (other than in accordance with the express terms of the Lease
and this Agreement) without the prior written consent of Lender. Lender and
Tenant also agree that Tenant shall neither assign the Lease or allow it to be
assigned in any manner nor sublet the Demised Premises or any part thereof
without the prior written consent of Lender in any situation where Landlord' s
consent to any such action is required under the Lease. Lender agrees that its
consent to any such assignment or subletting shall be subject to the same terms,
standards and conditions as may be considered by Landlord pursuant to Section
5.2.1 of the Lease.

            11. Interpretation. This Agreement may not be modified orally or in
any manner other than by an agreement in writing signed by the parties hereto or
their respective successors in interest. This Agreement shall inure to the
benefit of and be binding upon the parties hereto, their successors and assigns,
and any purchaser or purchasers at foreclosure of the Property, and their
respective heirs, personal representatives, successors and assigns. This
Agreement is subject to the laws of the Commonwealth of Massachusetts.

                                       -5-
<PAGE>

            IN WITNESS WHEREOF, the parties hereto have hereunto caused this
Agreement to be duly executed as of the day and year first above written.

                                        LENDER:

                                        By______________________________________
                                        Name:___________________________________
                                        Title:__________________________________

                                        TENANT:

                                        VERTEX PHARMACEUTICALS INCORPORATED

                                        By______________________________________
                                        Name:___________________________________
                                        Title:__________________________________

LANDLORD:

Landlord consents to this Agreement and Landlord's
obligations under Paragraph 5 hereof,
as of ________________________, 200__.

KENDALL SQUARE, LLC

By:  Lyme Properties LLC, a New Hampshire
     limited liability company, its Manager

By:_____________________________________
   David E. Clem, Member

                                       -6-
<PAGE>

                                    EXHIBIT A

                             DESCRIPTION OF PROPERTY
                             -----------------------
                                (to be provided)
<PAGE>

                                    EXHIBIT E

                  Schedule of Equipment to be Removed by Tenant
                  ---------------------------------------------
        (Tenant to Provide for Landlord's Approval After Lease Execution)
<PAGE>

                                    EXHIBIT F

                             Environmental Agreement
                                   (attached)
<PAGE>

                             ENVIRONMENTAL AGREEMENT
                             -----------------------

      THIS ENVIRONMENTAL AGREEMENT, ("Agreement"), is entered into as of the
____ day of January, 2001 by and between KENDALL SQUARE, LLC a Delaware limited
liability company, having an address at 101 Main Street, 18th Floor, Cambridge,
Massachusetts 02142 ("Landlord"), and VERTEX PHARMACEUTICALS INCORPORATED, a
Massachusetts corporation, having an address of 130 Waverly Street, Cambridge,
Massachusetts 02139 ("Tenant"), and is made in conjunction with a Lease dated
the date hereof (the "Lease") by and between Landlord and Tenant, regarding the
Lot, as described and defined in the Lease, located in Cambridge, Middlesex
County, Massachusetts (the Lot is hereinafter referred to as the "Property").

      RECITALS

            A. Landlord is the current owner of the Property, having acquired
the right, title and interest of Com/Energy Research Park Realty ("Com/Energy")
in the Property, together with certain other real property (approximately ten
acres of land, including the Property, hereinafter the "Cambridge Research Park
Site"). In connection with the acquisition of the Cambridge Research Park Site
by Landlord, Landlord entered into a Release and Indemnity Agreement and a
Remediation Agreement, both of which are by and between Com/Energy and Landlord
and dated August 18, 1998 (hereinafter the "Release and Indemnity Agreement" and
the "Remediation Agreement"), which govern certain rights, responsibilities,
releases, indemnities and remediation obligations with respect to the Cambridge
Research Park Site, including the Property.

            B. Landlord and Com/Energy have made commitments to each other
pursuant to the Release and Indemnity Agreement and the Remediation Agreement,
including commitments with respect to the Property. These commitments include,
among others, (1) the commitment by Landlord to release and indemnify Com/Energy
for certain matters relating to the environmental condition of the Cambridge
Research Park Site, including the Property, and the remediation thereof, and (2)
the commitment by Landlord to require its lessees to agree to be bound by
certain terms of the Release and Indemnity Agreement and the Remediation
Agreement.

      In consideration of the Recitals stated above and for other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, and solely with respect to the Property (and no other properties),
the parties agree as follows:

1. Definitions. All terms not otherwise defined herein shall have the
definitions set forth in the Release and Indemnity Agreement and the Remediation
Agreement, as indicated herein.

2. Release and Indemnity Agreement. A copy of the Release and Indemnity
Agreement is attached hereto as Exhibit A.

      (a) Release. Tenant acknowledges that it is a Releasing Party as that term
is defined in the Release and Indemnity Agreement and expressly understands and
agrees that the Release
<PAGE>

and Indemnity Agreement runs with the land, which includes the Property, and is
binding upon Tenant, except as otherwise provided herein.

      (b) Indemnity. The parties acknowledge that Paragraph 5 of the Release and
Indemnity Agreement provides in part that Landlord may perform remediation and
subsequent development at the Cambridge Research Park Site, including the
Property, on a phased-basis and that for each such phase, the Indemnity
Expiration Date (as that term is defined in the Release and Indemnity Agreement)
with respect to Releasing Parties (as that term is defined in the Release and
Indemnity Agreement) which are owners, successors or assigns to such remediated
phases of the Cambridge Research Park Site shall occur on the later to occur of
the RAO Date or the Foundation Date (as those terms are defined in the Release
and Indemnity Agreement), for claims made thereafter.

      Prior to the Substantial Completion Date (as such term is defined in the
Lease) Landlord will deliver to Tenant (i) the certification of Landlord's
Licensed Site Professional certifying that the RAO has been completed in
accordance with the MCP (as hereinafter defined) with respect to the Property
and (ii) an estoppel certificate of COM/Energy pursuant to Paragraph 15 of the
Release and Indemnity Agreement certifying, to the best of COM/Energy's
knowledge, there is no default on the part of Landlord under the Release and
Indemnity Agreement and further stating that the Indemnity Expiration Date has
occurred with respect to the Property.

3. Remediation Agreement. A copy of the Remediation Agreement is attached hereto
as Exhibit B.

      The parties acknowledge that the Remediation Agreement provides in part
that: The Remediation Agreement shall be binding upon Landlord, its successors,
heirs, administrators and assigns and with respect to the remediation
obligations set forth therein, the Remediation Agreement shall run with the
land, consisting of all or any portion of the Cambridge Research Park Site,
including the Property, be binding upon any and all subsequent owners, ground
tenants, and mortgagees of the Cambridge Research Park Site, including the
Property, or any portion thereof or interest therein. The Remediation Agreement
further provides that notwithstanding the preceding sentence, that (a) Landlord
may, at its election, perform its remediation and development obligations under
the Remediation Agreement in phases and (b) with respect to any subsequent
owner, ground tenant or mortgagee of any such phase or any portion thereof, the
remediation obligation set forth in the Remediation Agreement shall not be
binding upon any such subsequent owner, ground tenant or mortgagee, provided the
obligations under the Remediation Agreement have been satisfied with respect to
such phase. Prior to the Substantial Completion Date Landlord shall deliver to
Tenant (i) the certification of Landlord's Licensed Site Professional certifying
that the RAO (as such term is defined in the MCP) has been completed in
accordance with the MCP with respect to the Property and (ii) an estoppel
certificate of COM/Energy pursuant to Paragraph 14 of the Remediation Agreement
certifying, to the best of COM/Energy's knowledge, there is no default on the
part of Landlord under the Remediation Agreement and further stating that
COM/Energy has approved the RAO and that Landlord has satisfied Landlord's
obligations under the Remediation Agreement with respect to the Property.

                                       -2-
<PAGE>

4. Landlord Indemnity of Tenant. Effective as of the date hereof, Landlord
agrees to defend, hold harmless and indemnify Tenant from and against any and
all claims, fees, costs, disbursements and expenses that may be imposed upon,
incurred by or asserted or awarded against Tenant that relate to or arise from
the presence, release or threatened release of, or the mitigation or remediation
of, any Hazardous Materials (as defined herein) on, at or below the Property,
including migration onto the Property from the Cambridge Research Park Site, for
which Landlord is responsible or liable pursuant to the terms and provisions of
the Remediation Agreement or the Release and Indemnity Agreement or for which
Landlord is responsible or liable pursuant to the operation of the Massachusetts
Oil and Hazardous Materials Release Prevention and Response Act, Massachusetts
General Laws Chapter 21E, as amended ("Chapter 21E"). Hazardous Materials as
used herein shall mean "hazardous materials" and "oils" as defined in Chapter
21E and regulations adopted pursuant to said act, including, but not limited to,
the Massachusetts Contingency Plan, 310 CMR 40.0000 et seq. as amended (the
"MCP") and "hazardous substances" shall mean "hazardous substances" as defined
in the Comprehensive Environmental Response Compensation and Liability Act of
1980, as amended, and regulations adopted pursuant to said act; and "hazardous
wastes" as defined in the Resource Conservation and Recovery Act, as amended,
the Massachusetts Hazardous Waste Management Act, Massachusetts General Laws
Chapter 21C, as amended, and regulations adopted pursuant to said acts.

Landlord's obligation to indemnify Tenant as set forth in this Section 4 shall
not include indemnification for any claims, fees, costs, disbursements or
expenses that relate to the release or threatened release of Hazardous Materials
on, at or from the Property which release or threatened release first occurs on
or after the date hereof.

5. Tenant Indemnity of Landlord. Tenant, for itself and for each of the other
Transferring Parties (as hereinafter defined), jointly and severally, agrees to
indemnify, defend (with counsel acceptable to Landlord) and hold Landlord
harmless from and against any claims, suits, causes of action, costs and fees,
including attorneys' fees that may be imposed upon, incurred by or asserted or
awarded against Tenant that relate to or arise from the presence, release or
threatened release of any Hazardous Materials on, at or from the Property which
release or threatened release is due to the act, omission or neglect of Tenant.

6. Site Access Upon MADEP Audit of RAO. The parties acknowledge that pursuant to
Chapter 21E and the MCP, the Massachusetts Department of Environmental
Protection ("MADEP") may perform an audit of the RAO documentation submitted to
MADEP for the Property. It is the intention of the parties that in the event
that such audit occurs, Landlord shall be solely responsible for providing
response to such audit and shall be solely responsible for providing response to
any inquiries raised by MADEP in such audit and curing any deficiencies or
defects which may be revealed during such audit. Tenant hereby agrees to
cooperate, at no expense to Tenant, with Landlord to the extent reasonably
necessary to respond to any audit by MADEP.

7. Exhibits. The Exhibits to this Agreement are incorporated by reference as if
fully set forth in this Agreement.

                                       -3-
<PAGE>

8. Notices. All notices and other communications given or made pursuant hereto
shall be in writing and shall be deemed to have been duly given or made as of
the date delivered or mailed if delivered personally or mailed by registered or
certified mail (postage prepaid, return receipt requested), or sent by facsimile
transmission, (confirmation received) to the parties at the following addresses
and facsimile transmission numbers (or at such other number for a party as shall
be specified by like notice), except that notices after the giving of which
there is a designated period within which to perform an act and notices of
changes of address or number shall be effective only upon receipt:

     i.  if to Landlord:

         Kendall Square, LLC
         101 Main Street, 18th Floor
         Cambridge, MA 02142
         Attention: Robert L. Green
         Fax No. (617) 225-2133

         with copies to:

         Lyme Properties LLC
         16 On The Common
         Post Office Box 266
         Lyme, NH 03678
         Attention: David E. Clem
         Fax No. (603) 795-4789

         Gadsby Hannah LLP
         225 Franklin Street
         Boston, MA 02110
         Attention: Leigh A. Gilligan, Esq.
                    Patrick C. Toomey, Esq.
         Fax No. (617) 345-7050

ii.      if to Tenant:

         Vertex Pharmaceuticals Incorporated
         130 Waverly Street
         Cambridge, MA 02139
         Attention: Alfred Vaz, Jr.
         Fax No. (617) ___________

         with a copy to:

         Kirkpatrick & Lockhart LLP
         75 State Street
         Boston, MA  02108
         Attention: Paul C. Bauer, Esquire
         Fax No. (617) 261-3175

                                       -4-
<PAGE>

9. Successors and Permitted Assigns. This Agreement shall be binding upon and
shall inure to the benefit of the parties to this Agreement and their successors
and permitted assigns; provided, however, that this Agreement may not be
assigned by Tenant without Landlord's express written consent, which shall not
be unreasonably withheld if this Agreement is to be assigned in connection with
an assignment of the Lease. Tenant shall further require that any party to whom
Tenant assigns this Agreement acknowledge its acceptance of this Agreement (as
well as said Assignee's agreement to enter into and be bound by this Agreement)
in writing to Landlord. Tenant shall further require any party to whom Tenant
subleases all or any portion of the Premises (as such term is defined in the
Lease) to enter into and be bound by this Agreement or a similar agreement
acceptable to Landlord. Tenant, its successors and assigns, and all other
parties referred to in this Paragraph 9 (specifically excluding Landlord and its
successors and assigns) shall be referred to herein as the "Transferring
Parties".

10. No Third Party Beneficiaries. This Agreement is for the sole benefit of the
parties hereto, and their permitted assigns and nothing herein expressed or
implied shall give or be construed to give any person or entity, other than the
parties hereto, and their permitted assigns, any legal or equitable rights
hereunder.

11. Amendment or Modification. This Agreement may not be amended or modified
except by an instrument in writing signed by Landlord and Tenant.

12. Drafting of Agreement. This Agreement is the joint product of the parties
and each provision hereof has been subject to the mutual consultation,
negotiation and agreement of those parties and shall not be construed for or
against any party hereto.

13. Governing Law. This Agreement shall be governed by, and construed in
accordance with, the laws of the Commonwealth of Massachusetts (without giving
effect to its choice of law principles).

14. Dispute Resolution. Any dispute, controversy or claim between the parties
relating to, arising out of or in connection with this Agreement (or any
subsequent agreements or amendments thereto), including as to its existence,
enforceability, validity, interpretation, performance, breach or damages,
including claims in tort, whether arising before or after the termination of
this Agreement, shall be settled only by binding arbitration pursuant to the
Commercial Arbitration Rules, as then amended and in effect, of the American
Arbitration Association (the "Rules"), subject to the following:

      i. The arbitration shall take place in Boston, Massachusetts.

      ii. There shall be three arbitrators, who shall be selected under the
      normal procedures prescribed in the Rules, except that one such arbitrator
      shall be a certified public accountant and one arbitrator (who shall chair
      the arbitration panel) shall be a member of the American Board of Trial
      Advocates or the American College of Trial Lawyers. The arbitrator so
      designated shall not be an employee, consultant, officer, director or
      stockholder of any party hereto or any affiliate of any party to this
      Agreement.

      iii. Subject to legal privileges, each party shall be entitled to
      discovery in accordance with the Federal Rules of Civil Procedure.

                                      -5-
<PAGE>

      iv. At the arbitration hearing, each party may make written and oral
      presentations to the arbitrator, present testimony and written evidence
      and examine witnesses.

      v. The arbitrators' decision shall be in writing, shall be binding and
      final and may be entered and enforced in any court of competent
      jurisdiction.

      vi. The arbitrators shall have the authority to grant injunctive relief
      and order specific performance.

      vii. No party shall be eligible to receive, and the arbitrators shall not
      have the authority to award, exemplary or punitive damages. viii. The
      arbitrators shall have the authority to allocate the fees and expenses of
      the arbitrators and the American Arbitration Association as well as the
      fees and expenses of the parties based upon the arbitrators' determination
      as to the merits of the parties' respective position in the arbitration.
      If the arbitrators fail to make a specific determination as to fees and
      expenses, then such fees and expenses of the arbitrators and the American
      Arbitration Association shall be paid by the parties in equal amounts and
      the parties shall each bear their own fees and expenses.

      ix. The arbitrators shall adhere to paragraph 13. Within 15 days after the
      designation of the arbitrators, the arbitrators (or chair of the
      arbitration panel), Tenant and Landlord shall meet, at which time Landlord
      and Tenant shall be required to set forth in writing all disputes,
      controversies or claims under and a proposed ruling on each such dispute,
      controversy or claim. The arbitrators (or chair of the arbitration panel)
      shall set a date for the arbitration hearing to discuss each dispute,
      controversy or claim identified by the Tenant and Landlord, which hearing
      shall commence no later than 30 days after the submittal of written
      proposals pursuant to the immediately preceding sentence. The arbitrators
      shall use best efforts to rule on each dispute, controversy or claim
      within 30 days after the completion of the arbitration hearing described
      in the immediately preceding sentence.

15. Counterparts. This Agreement may be executed in one or more counterparts,
and by the different parties hereto in separate counterparts, each of which when
executed shall be deemed to be an original but all of which taken together shall
constitute one and the same agreement.

16. Integration. This Agreement, together with Exhibits hereto, and the
documents and instruments and other agreements among the parties delivered
pursuant hereto, constitute the entire agreement and supersede all prior
agreements and undertakings, both written and oral, among Landlord and Tenant
with respect to the subject matter hereof and are not intended to confer upon
any other Person any rights or remedies hereunder, except as otherwise expressly
provided herein. Without limiting the foregoing, the parties acknowledge that
this Agreement shall survive the termination or expiration of the Lease. The
terms of this Agreement may not be terminated, modified or waived except by a
written agreement signed by Landlord and Tenant.

                                       -6-
<PAGE>

      IN WITNESS WHEREOF, the Parties have caused this Agreement to be executed
under seal.

KENDALL SQUARE, LLC

By: Lyme Properties LLC, a New Hampshire
    limited liability company, its Manager

    By:___________________________________________
       David E. Clem, Member

VERTEX PHARMACEUTICALS INCORPORATED

By:_______________________________________________
   Name:
   Title:

                                       -7-
<PAGE>

                                   EXHIBIT F-1

                          List of Remediation Documents
                          -----------------------------

o Release Abatement Measure Plan, NAPL Stabilization, Cambridge Research Park,
                  364 Third Street, Cambridge, prepared by ThermoRetec
                  Consulting Corporation ("ThermoRetec") and dated March, 2000;

o Phase II - Comprehensive Site Assessment, Buildings C and D Area, Cambridge
                  Research Park, 364 Third Street, Cambridge, prepared by
                  ThermoRetec and dated March, 2000;

o Phase III - Remedial Action Plan, Buildings C and D Area, Cambridge Research
                  Park, 364 Third Street, Cambridge, prepared by ThermoRetec and
                  dated March, 2000; and

o Environmental Response, Compensation and Liability Insurance Policy issued by
                  Kemper Environmental, Ltd. to Cambridge Research Park, LLC and
                  The Lyme Timber Company (Policy No. 4LY000169).<PAGE>

                                  Exhibit 10.26

The Company has omitted from this Exhibit portions of the Agreement for which
the Company has requested confidential treatment from the Securities and
Exchange Commission. The portions of the Agreement for which confidential
treatment has been requested have been deleted and marked with asterisks
surrounded by brackets ([****]) and have been filed separately with the
Securities and Exchange Commission.

                               RESEARCH AGREEMENT

                                     between

                       Vertex Pharmaceuticals Incorporated

                                       and

                            Laboratoires Serono S.A.
<PAGE>

                               Research Agreement

                                Table of Contents

                                                                     Page Number

INTRODUCTION...............................................................1

ARTICLE I -- DEFINITIONS...................................................1

ARTICLE II -- RESEARCH PROGRAM.............................................6

   2.1.  Conduct of the Research Program...................................6
   2.2.  Term..............................................................6
   2.3.  Payment With Respect to Past Research.............................6
   2.4.  Research Support Payments.........................................7
   2.5.  Joint Research Committee..........................................8
   2.6.  Research Plan.....................................................9
   2.7.  Exchange and Use of Information..................................10
   2.8.  Ownership of Program Technology..................................10
   2.9.  Redirection or Termination of Research Program...................11
   2.10. Research Exclusivity.............................................11

ARTICLE III -- LICENSE, DEVELOPMENT AND COMMERCIALIZATION RIGHTS..........14

   3.1.  License and Development Election.................................14
   3.2.  Exercise of Development Election.................................15
   3.3.  Refused Candidate................................................15
   3.4   Final Report Election............................................17
   3.5.  SERONO Licenses..................................................19

ARTICLE IV -- CONFIDENTIALITY.............................................20

   4.1.  Undertaking......................................................20
   4.2.  Exceptions.......................................................21
   4.3.  Publicity........................................................21
   4.4.  Survival.........................................................22

ARTICLE V -- PUBLICATION..................................................22

ARTICLE VI -- INDEMNIFICATION.............................................23

   6.1.  Indemnification by VERTEX........................................23
   6.2.  Indemnification by SERONO........................................24
   6.3.  Claims Procedures................................................25

ARTICLE VII -- PROGRAM TECHNOLOGY.........................................26

   7.1.  Ownership........................................................26
   7.2.  Patent Procurement, Maintenance and Defense......................26
   7.3.  Costs............................................................27
   7.4.  No Implied Rights................................................28

ARTICLE VIII -- TERM AND TERMINATION......................................28

   8.1.  Term.............................................................28
   8.2.  Termination of the Research Program by SERONO for Cause..........28
   8.3.  Termination of the Research Program by VERTEX for Cause..........29

                  Research Agreement -- Confidential -- Page i
<PAGE>

                               Research Agreement

                          Table of Contents (continued)

                                                                     Page Number

   8.4.   Early Termination of Research Program by SERONO.................29
   8.5.   No Termination upon Bankruptcy:.................................29
   8.6.   Effect of Termination...........................................30

ARTICLE IX -- REPRESENTATIONS AND WARRANTIES..............................30

   9.1.   Representations and Warranties of VERTEX........................30
   9.2.   Representations and Warranties of SERONO........................31

ARTICLE X -- DISPUTE RESOLUTION...........................................32

   10.1.  Governing Law...................................................32
   10.2.  Dispute Resolution Process......................................32

ARTICLE XI -- MISCELLANEOUS PROVISIONS....................................32

   11.1.  Official Language...............................................32
   11.2.  Waiver..........................................................32
   11.3.  Force Majeure...................................................32
   11.4.  Severability....................................................33
   11.5.  Government Acts.................................................33
   11.6.  Government Approvals............................................34
   11.7.  Export Controls.................................................34
   11.8.  Assignment; Successors and Assigns..............................34
   11.9.  Affiliates......................................................35
   11.10. Counterparts....................................................35
   11.11. No Agency.......................................................35
   11.12. Notice..........................................................35
   11.13. Headings........................................................36
   11.14. Entire Agreement................................................36

Exhibit A     License, Development and Commercialization Agreement
Schedule 1.4  [*******************************]
Schedule 1.10 Countries of the Far East
Schedule 2.4  [*******************************************]
Schedule 3.2  Minimum Development Criteria

                  Research Agreement -- Confidential -- Page ii
<PAGE>

                               RESEARCH AGREEMENT

      THIS RESEARCH AGREEMENT (the "Agreement") is made and entered into as of
this 11th day of December 2000 between VERTEX PHARMACEUTICALS INCORPORATED
("VERTEX"), a Massachusetts corporation with principal offices at 130 Waverly
Street, Cambridge, MA 02139-4242, and LABORATOIRES SERONO S.A. ("SERONO"), a
Swiss corporation with principal offices at Zone Industrielle de l'Ouriettaz,
1170 Aubonne, Switzerland.

                                  Introduction

      WHEREAS, VERTEX has undertaken a broad drug discovery program with the
objective of designing novel, small-molecule Caspase (as defined below)
inhibitors as human therapeutics for a variety of clinical indications;

      WHEREAS, SERONO is also interested in developing and commercializing drugs
targeting Caspases and has particular expertise in developing, marketing and
selling pharmaceuticals worldwide;

      WHEREAS, both parties desire to enter into a collaboration the objective
of which will be to design novel, small-molecule compounds which act through
inhibition of one or more Caspases, for the treatment or prevention of human
disease, and to develop, market and sell those compounds as pharmaceuticals upon
the terms and conditions set forth herein and in a License, Development and
Commercialization Agreement identical in substance to Exhibit A hereto;

      NOW THEREFORE, in consideration of the foregoing premises, the mutual
covenants set forth in this Agreement, and other good and valuable
consideration, the parties agree as follows:

                            ARTICLE I -- DEFINITIONS

      1.1. "Affiliate" shall mean, with respect to any Person, any other Person
which directly or indirectly controls, is controlled by, or is under common
control with such Person. The term "control" means the possession, direct or
indirect, of the power to direct or cause the direction of the management and
policies of a Person, whether through the ownership of voting securities, by
contract or otherwise. Control will be presumed if one Person owns, either of
record or beneficially, more than forty percent (40%) of the voting stock of any
other Person.

                  Research Agreement -- Confidential -- Page 1
<PAGE>

      1.2. "Bulk Drug Substance" shall mean a Drug Product Candidate in bulk
crystal, powder, solution or other form suitable for incorporation in a Drug
Product, which if required in order to stabilize the Drug Product Candidate
shall be formulated with stabilizing excipients.

      1.3. "Caspases" shall mean cysteine-proteases that cleave target proteins
preferentially after an aspartic-acid residue.

      1.4. "Compound" shall mean [**********************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
*******************************************].

      1.5. "Controlled" shall mean the legal authority or right of a party
hereto to grant a license or sublicense of intellectual property rights to
another party hereto, or to otherwise disclose proprietary or trade secret
information to such other party, without breaching the terms of any agreement
with a Third Party or misappropriating the proprietary or trade secret
information of a Third Party.

      1.6. "Development Election" shall have the meaning set forth in Section
3.1 hereof.

      1.7. "Drug Product" shall mean a finished dosage form which is prepared
from Bulk Drug Substance and is ready for administration to the ultimate
consumer as a pharmaceutical.

      1.8. "Drug Product Candidate" shall mean a Compound as to which SERONO has
exercised its Development Election under Article III hereof and which is
therefore the subject of a License Agreement in accordance with the provisions
of Sections 3.2, 3.3 or 3.4 hereof.

      1.9. "Effective Date" shall mean the effective date of this Agreement as
set forth on the first page hereof.

      1.10. "Far East" shall mean all countries set forth on Schedule 1.10
hereof.

                  Research Agreement -- Confidential -- Page 2
<PAGE>

      1.11. "FDA" shall mean the United States Food and Drug Administration.

      1.12. "Field" shall mean the treatment or prevention of conditions or
diseases in humans using pharmaceutical products the principal mode of action of
which is [******************* **********************************************].

      1.13. "ICE" shall mean [***********************************]

      1.14. "IND" shall mean the investigational new drug application relating
to a drug product filed with the FDA pursuant to 21 C.F.R. Part 312, including
any amendments thereto. References herein to IND shall include, to the extent
applicable, any comparable filing(s) made with a Regulatory Authority in other
countries in the Territory (such as a clinical trial exemption (CTX) in the
European Union).

      1.15. "Indication" shall mean a generally acknowledged disease or
condition, a significant manifestation of a disease or condition, or symptoms
associated with a disease or syndrome for which use of a pharmaceutical product
is indicated, as customarily identified in the pharmaceutical product's label
under applicable FDA regulations or the foreign equivalent thereof.

      1.16. "Joint Know-How" shall have the meaning set forth in Section 7.1 of
this Agreement.

      1.17. "Joint Patents" shall have the meaning set forth in Section 7.1 of
this Agreement.

      1.18. "JRC" shall have the meaning set forth in Section 2.5 of this
Agreement.

      1.19. "Know-How" shall mean all Program Technology other than inventions
which are the subject of Patents.

      1.20. "License Agreement" shall mean a License, Development and
Commercialization Agreement, identical in substance to Exhibit A hereto, to be
executed by VERTEX and SERONO in conjunction with the exercise by SERONO of its
Development Election with respect to a Drug Product Candidate.

      1.21. "Patents" shall mean all existing patents and patent applications
and all patent applications hereafter filed, including any continuation,
continuation-in-part, division, provisional or any substitute applications, any
patent issued with respect to any such patent applications, any reissue,
reexamination, renewal or extension (including any supplementary protection

                  Research Agreement -- Confidential -- Page 3
<PAGE>

certificate) of any such patent, and any confirmation patent or registration
patent or patent of addition based on any such patent, and all foreign
counterparts of any of the foregoing.

      1.22. "Person" shall mean any individual, corporation, partnership,
association, joint-stock company, trust, unincorporated organization or
government or political subdivision thereof.

      1.23. "Phase II Clinical Trial" shall mean shall mean a human clinical
trial conducted for inclusion in (i) that portion of the FDA submission and
approval process which provides for trials of a pharmaceutical product on a
limited number of patients for the purposes of collecting data on dosages,
evaluating safety and collecting preliminary information regarding efficacy in
the proposed therapeutic Indication, as more fully defined in 21 C.F.R.
ss.312.21(b), and (ii) equivalent submissions with similar requirements in other
countries in the Territory.

      1.24. "Phase III Clinical Trial" shall mean a human clinical trial
conducted for inclusion in (i) that portion of the FDA submission and approval
process which provides for the continued trials of a pharmaceutical product on
sufficient numbers of patients to generate safety and efficacy data to support
Regulatory Approval in the proposed therapeutic Indication, as more fully
defined in 21 C.F.R. ss. 312.21(c), and (ii) equivalent submissions with similar
requirements in other countries in the Territory.

      1.25. "Program Technology" shall mean all data, technical information,
know-how, discoveries, inventions (whether or not patented or patentable), trade
secrets, processes, techniques, materials, compositions, methods, formulas or
improvements (i) invented, discovered or developed by either party hereto or its
Affiliates under the Research Program, (ii) invented, discovered or developed by
VERTEX prior to the Effective Date in the course of a research program directed
toward the discovery of Caspase inhibitors other than inhibitors of ICE or (iii)
to which VERTEX has been granted a license or otherwise received some form of
right, title or interest from its Far East collaborator; that, in each case,
relate to the Compounds or their manufacture or use. Notwithstanding the
foregoing, the term Program Technology shall not apply to VERTEX's general drug
design technology whether in software or hardware, tangible or intangible, form.

      1.26. "Refused Candidate" shall have the meaning set forth in Section 3.3
hereof.

      1.27. "Regulatory Approval" shall mean, with respect to any country, all
authorizations by the appropriate governmental entity or entities necessary for
commercial sale of a pharmaceutical product in that country including, without
limitation and where applicable, approval of labeling, price, reimbursement and
manufacturing. "Regulatory Approval" in the

                  Research Agreement -- Confidential -- Page 4
<PAGE>

United States shall mean final approval of a new drug application pursuant to 21
C.F.R. ss. 314 (or any successor regulation having the same purpose or effect),
permitting marketing of the applicable pharmaceutical product in interstate
commerce in the United States. "Regulatory Approval" in the European Union shall
mean final approval of a Marketing Authorization Application pursuant to Council
Directive 75/319/EEC, as amended, or Council Regulation 2309/93/EEC, as amended,
or pursuant to any successor regulation having the same purpose or effect.

      1.28. "Research Plan" shall have the meaning set forth in Section 2.6
hereto.

      1.29. "Research Program" shall mean all research activities undertaken
under this Agreement with the objective of creating, identifying, designing or
evaluating Compounds as provided herein, including but not limited to activities
described in the Research Plan.

      1.30. "Research Year" shall mean a twelve-month period during the term of
the Research Program commencing on October 1, and ending on September 30, of
each year.

      1.31. "SERONO Know-How" shall mean all Know-How Controlled by SERONO or
its Affiliates.

      1.32. "SERONO Patents" shall mean all Patents Controlled by SERONO or its
Affiliates claiming Program Technology.

      1.33. "SERONO Program Technology" shall mean all SERONO Patents and SERONO
Know-How, including SERONO's and its Affiliates' right, title and interest in
any Joint Patents and Joint Know-How.

      1.34. "Territory" shall mean all countries of the world, except for the
countries of the Far East identified as such on Schedule 1.10 hereto.

      1.35. "Third Party" shall mean any Person that is not a party or an
Affiliate of any party to this Agreement.

      1.36. "VERTEX Know-How" shall mean all Know-How Controlled by VERTEX or
its Affiliates.

      1.37. "VERTEX Patents" shall mean all Patents Controlled by VERTEX or its
Affiliates claiming Program Technology.

                  Research Agreement -- Confidential -- Page 5
<PAGE>

      1.38. "VERTEX Program Technology" shall mean all VERTEX Patents and VERTEX
Know-How, including VERTEX's and its Affiliates' right, title and interest in
any Joint Patents and Joint Know-How.

                         ARTICLE II -- RESEARCH PROGRAM

      2.1. Conduct of the Research Program.

            2.1.1. Responsibility. VERTEX shall have principal responsibility
for the conduct of the Research Program, and SERONO shall provide consultation,
advice and such research effort as may be deemed appropriate by the JRC and
accepted by SERONO. The JRC shall review and coordinate each party's efforts
with respect to the Research Program.

            2.1.2. Efforts. VERTEX will use its commercially reasonable and
diligent efforts, consistent with prevailing practices within the pharmaceutical
and biotechnology industries, to conduct, and as necessary to cause its agents
to conduct, the Research Program, with the objective of identifying Compounds as
soon as practicable which might be suitable for designation as Drug Product
Candidates. VERTEX will conduct the Research Program in accordance with the
terms and conditions of this Agreement, and in accordance with prevailing
laboratory standards and practices where its laboratories are located,
including, where applicable, the standards set forth in the current Good
Laboratory Practices regulations promulgated by the FDA, published at C.F.R.
Part 58, as such regulations may be amended from time to time, and equivalent
foreign regulations or standards as applicable.

            2.1.3. Records. VERTEX shall prepare and maintain complete and
accurate written records, accounts, notes, reports and data with respect to all
laboratory work conducted in the performance of the Research Program in
conformity with standard pharmaceutical and biotechnology industry practices.

      2.2. Term.

            The Research Program shall commence as soon as practicable after the
Effective Date and will conclude at the end of the fifth (5th) Research Year,
unless earlier terminated in accordance with the provisions hereof. The Research
Program may be extended from year to year thereafter with the written consent of
both parties.

      2.3. Payment With Respect to Past Research.

            SERONO will make the following payments to VERTEX, on the dates
referenced below, in consideration of certain of VERTEX's past research costs,
and in recognition of

                  Research Agreement -- Confidential -- Page 6
<PAGE>

VERTEX's research program relative to Caspases having achieved certain research
milestones prior to the Effective Date:

            1.    Within thirty (30) days of the Effective Date:    $3,000,000

            2.    On or before the first anniversary of the
                  Effective Date:                                   $2,000,000

      2.4. Research Support Payments.

            2.4.1 Payments. SERONO will make research support payments to VERTEX
in the amount of [*****************] for each Research Year. The first Research
Year will be deemed to have commenced on October 1, 2000. Payments due for each
Research Year shall be made quarterly in advance on or before October 1, January
1, April 1 and July 1, of each Research Year, except that the first quarterly
payment due on or before October 1, 2000 shall be made within thirty (30) days
of the Effective Date. All payments shall be made in United States dollars to
the credit of such bank account as may be designated by VERTEX in writing to
SERONO. Any payments which fall due on a Saturday, Sunday or date which is a
legal holiday in the Commonwealth of Massachusetts may be made on the next
following day which is not a Saturday, Sunday or legal holiday in the
Commonwealth of Massachusetts.

            2.4.2. Report. [****************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************]

            2.4.3. Withholding. SERONO has advised that the payments referenced
in Section 2.3 and Section 2.4.1 above, if made to VERTEX, are currently not
subject to withholding tax in Switzerland. If during the term of this Agreement,
withholding tax should be required by law to be deducted from such payments, the
parties will agree on an equitable division of liability for any sum which is
withheld and for which VERTEX is not compensated or reimbursed by way of usable
tax credits or otherwise.

                  Research Agreement -- Confidential -- Page 7
<PAGE>

      2.5. Joint Research Committee.

            2.5.1. Composition and Purposes. VERTEX and SERONO will establish
within thirty (30) days of the Effective Date a Joint Research Committee ("JRC")
which shall consist of at least six (6) representatives (as may be increased or
decreased by the JRC), half of whom shall be designated from time to time by
each party. Meetings of the JRC other than regularly scheduled quarterly
meetings may be held only if a quorum of at least two (2) representatives of
each party participates; except that lack of a quorum shall not prevent the
scheduling and conduct of a meeting by either party after that party has made
good faith but unsuccessful attempts for more than ninety (90) days to schedule
and convene the meeting. The JRC shall meet formally at least quarterly, or with
such other frequency, and at such time and location, as may be established by
the JRC, for the following purposes:

                  (i) To receive and review reports by VERTEX and its project
teams, and by SERONO if it is conducting research under the Research Plan, which
shall be prepared and submitted to the other party and to the JRC on a quarterly
basis within fifteen (15) days after the end of each calendar quarter
(commencing with the calendar quarter ending December 31, 2000), summarizing
data and information generated under the Research Plan and other progress with
respect thereto. The first such report provided by VERTEX will provide
information regarding all Compounds invented, discovered or developed by VERTEX
prior to the Effective Date in the course of a research program directed toward
the discovery of Compounds, and that data will be updated in subsequent reports
to reflect new Compounds invented, discovered or developed by VERTEX since the
date of the last report;

                  (ii) To coordinate and review research activity and
interactions between VERTEX and SERONO;

                  (iii) To review any Compounds proposed by either party for
development;

                  (iv) To review, consider and approve revisions to the Research
Plan;

                  (v) To periodically review the overall goals and strategy of
the Research Program and to consider whether redirection or termination of the
Research Program should be recommended under Section 2.9 hereof; and

                  (vi) To discuss matters relating to Patents claiming Program
Technology.

            VERTEX will prepare the initial draft of an agenda for each JRC
meeting and will submit the draft to SERONO for comments a reasonable period
before the scheduled meeting

                  Research Agreement -- Confidential -- Page 8
<PAGE>

date. The party hosting a particular JRC meeting shall prepare and deliver to
the members of the JRC, within thirty (30) days after the date of each meeting,
minutes of such meeting setting forth, among other things, all decisions of the
JRC, and including a summary of the status of research work as reported to the
JRC. The party not preparing the minutes may suggest changes or amendments to
the minutes, and may provide a supplement addressing activities at the meeting
which are not reported in the minutes, which shall be distributed to the parties
and filed with the meeting minutes. In case the JRC meets by means of telephone
or video conferences, the responsibility for preparing minutes shall lie with
VERTEX.

            2.5.2. Decision Making.

                  (i) Each of VERTEX and SERONO shall have one vote on the JRC.
The objective of the JRC shall be to reach agreement by consensus on all matters
within the scope of the Research Plan. However, in the event of a deadlock with
respect to any action (which shall be deemed to have occurred if either party
shall request a vote of the JRC on a matter and that vote shall either not be
taken within thirty (30) days of the request or if taken shall result in a tie
vote), [************************************************************************
********************************************************************************
*********************].

                  (ii) Each party shall retain the rights, powers, and
discretion granted to it under this Agreement, and the JRC shall not be
delegated or vested with any such rights, powers or discretion except as
expressly provided in this Agreement. The JRC shall not have the power to amend
or modify this Agreement, which may only be amended or modified as provided in
Section 11.14 hereof.

      2.6. Research Plan.

            2.6.1. General. By the end of the first meeting of the JRC, VERTEX
and SERONO shall agree upon (i) an outline research plan (the "Research Plan")
for identifying, conceiving, synthesizing, structurally characterizing, testing,
evaluating and otherwise discovering one or more Compounds that the parties
believe to be commercially viable candidates for development; and (ii) as a
component of the Research Plan, a detailed research plan for the first Research
Year, including an appropriate schedule therefor.

            2.6.2. Plan Review and Approval. The Research Plan will be revised
and updated by VERTEX at least annually and submitted to the JRC for its review
and approval.

                  Research Agreement -- Confidential -- Page 9
<PAGE>

VERTEX, in revising and updating the Research Plan, will take into account
material scientific and commercial developments relevant to the objectives of
the Research Program.

      2.7. Exchange and Use of Information.

            2.7.1. Review of Research. Each party will enable any
representatives of the other party on the JRC, or other authorized
representatives of such party, to review the ongoing research being conducted by
the first party under the Research Program and to discuss that research with its
officers, all at such reasonable times and as often as may be reasonably
requested. The parties also shall institute periodic working meetings between
scientists from VERTEX and SERONO, to enhance the coordination and application
of each party's resources and to provide an effective vehicle for sharing and
exchanging Research Program results. Representatives of VERTEX or SERONO
(including for this purpose agents) receiving Confidential Information (as
defined in Section 4.1) from representatives of the other party, and any
representatives of one party who may by agreement participate in an exchange of
scientists with the other party, or who may otherwise spend a significant period
of time at the laboratories of the other party, shall sign appropriate
agreements ensuring that information disclosed to them is held in confidence in
accordance with the provisions of Article IV of this Agreement.

            2.7.2. Far East Collaborator. VERTEX's agreement with its Far East
collaborator for development and sale of Compounds in the Far East obligates
each party to share with the other party information which is relevant to the
research and development of Compounds. VERTEX will share with SERONO information
received by it from its Far East collaborator pursuant to the foregoing, in
consideration of the reciprocal right hereby granted to VERTEX by SERONO to
share information received by it from SERONO with VERTEX's Far East
collaborator, relative to the research and development of Compounds in the
Territory.

      2.8. Ownership of Program Technology.

            2.8.1. No Ownership by Employees. All employees of VERTEX and SERONO
who are expected to participate in the Research Program have signed, or before
any such participation will sign, agreements with VERTEX or SERONO,
respectively, regarding proprietary information and inventions, in a form
reasonably considered by the employer and its counsel to assure the employer's
Control of Program Technology invented, discovered or developed by such
employees.

            2.8.2. No Ownership by Agents. VERTEX and SERONO shall each enter
into customary agreements with its agents that provide that all of such agents'
right, title and interest

                  Research Agreement -- Confidential -- Page 10
<PAGE>

in, to and under any Program Technology invented, discovered or developed by
such agents shall be assigned or licensed to VERTEX or SERONO as the case may
be.

      2.9. Redirection or Termination of Research Program.

            If at any time during the term of this Agreement, the JRC shall
determine in good faith (i) that the Research Program or any portion thereof is
not likely to be successfully completed or if so completed is not likely to
produce Compounds that are commercially viable, or (ii) that in other material
respects the Research Program will not conform to the parties' reasonable
expectations when entering into this Agreement, then the JRC may suggest
revision, reorientation or termination of the Research Program to each party's
top management, and upon mutual consent VERTEX and SERONO shall thereafter
promptly modify their respective activities in connection with the Research
Program, or terminate the Research Program, accordingly.

      2.10. Research Exclusivity.

            2.10.1. Conduct of Research and Development. Neither VERTEX nor
SERONO nor any of their respective Affiliates will conduct research or
development activities in the Field during the term of the Research Program
(except, as to VERTEX, activities conducted with its collaborator in the Far
East) other than pursuant to the provisions of this Agreement. Neither VERTEX
nor SERONO will enter into any agreement with a Third Party which would prevent
it from performing its obligations under this Agreement.

            2.10.2. In-Licensing Opportunity. Notwithstanding the foregoing, if
a Third Party offers SERONO the opportunity to license and develop a chemical
compound for which an IND has been accepted by the relevant Regulatory Authority
(an "In-Licensed Compound") in the Field in any country in the Territory (an
"In-Licensing Opportunity"), then prior to accepting any such In-Licensing
Opportunity SERONO will provide VERTEX with all material information in its
possession concerning the In-Licensing Opportunity and will offer VERTEX the
opportunity to share the In-Licensing Opportunity with SERONO on the following
basis:

                  (i) [*********************************************************
********************************************************************************
********************************************************************************
********************************************************************************

                  Research Agreement -- Confidential -- Page 11
<PAGE>

********************************************************************************
********************************************************************************
********************************************************************************
*******************************************************************************]

                  (ii) [********************************************************
********************************************************************************
********************************************************************************
********************************************************************************
*******************************************************************************]

                  (iii) [*******************************************************
********************************************************************************
*******************************************************************************]

                  (iv) VERTEX shall not be required to accept the In-Licensing
Opportunity offered by SERONO, and shall be deemed to have declined the
In-Licensing Opportunity if it shall not have accepted the In-Licensing
Opportunity by notice in writing to SERONO within sixty (60) days after VERTEX's
receipt of the information relative to the In-Licensing Opportunity referenced
in the first sentence of this Section 2.10.2. If VERTEX does not accept the
In-Licensing Opportunity, it shall have no responsibility to, and will be
entitled to

                  Research Agreement -- Confidential -- Page 12
<PAGE>

no payment or other benefits from, SERONO or the Third Party in connection with
the In-Licensing Opportunity. If VERTEX does accept the In-Licensing
Opportunity, VERTEX and SERONO will negotiate an agreement with respect to such
In-Licensing Opportunity incorporating applicable provisions of the License
Agreement as well as such other customary representations, warranties, covenants
and conditions as are necessary or appropriate for transactions of this type,
not inconsistent with the terms and conditions hereof and satisfactory in form
and substance to the parties and their legal advisors.

[*******************************************************************************
********************************************************************************
****************]

                  Research Agreement -- Confidential -- Page 13
<PAGE>

[*******************************************************************************
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********************]

        ARTICLE III -- LICENSE, DEVELOPMENT AND COMMERCIALIZATION RIGHTS

      3.1. License and Development Election.

            VERTEX hereby grants to SERONO (i) a nonexclusive license and/or
sublicense in the Territory under VERTEX Program Technology to exercise its
rights and fulfill its obligations under this Agreement, and (ii) an exclusive
right, exercisable as set forth in Sections 3.2, 3.3 and 3.4 and otherwise
subject to the provisions of this Agreement (the "Development Election"), to
license one or more Compounds and to develop, manufacture and have manufactured,
use, sell, offer to sell, and import Bulk Drug Substance, Drug Product
Candidates and Drug Products incorporating those Compounds in the Territory,
upon the terms and conditions set forth in a License Agreement. VERTEX will not
grant to any Third Party rights to VERTEX Program Technology which are
inconsistent with the grant of the Development Election to SERONO under this
Article III.

      The Development Election, and the included right to license Compounds,
shall expire and SERONO shall no longer have the right to license any Compounds
not theretofore the subject of a Development Election and License Agreement,
upon the first to occur of:

            (i)   Termination of the Research Program by VERTEX for cause under
                  Section 8.3 hereof;

            (ii)  [********************] following termination of the Research
                  Program by SERONO for cause under Section 8.2 hereof; and

            (iii) [*********************] following the Final Report Date under
                  Section 3.4, following expiration of the five-year term of the
                  Research Program or its early termination under Section 8.4
                  hereof.

Notwithstanding the foregoing, (a) if a Selection Notice or Second Opportunity
Notice with respect to a Proposed Candidate is provided by VERTEX to SERONO
under Sections 3.2.1 or 3.3.1 below prior to expiration of the Development
Election as provided above, then the Development Election with respect to that
Proposed Candidate shall not expire until the end of the Notice Period or Second
Opportunity relative to that Proposed Candidate as specified in Sections 3.2.1
or 3.3.1, as applicable; and (b) the Development Election with respect to
certain

                  Research Agreement -- Confidential -- Page 14
<PAGE>

Refused Candidates shall survive termination or expiration of the Research
Program as provided in Section 3.3.2 below.

      3.2. Exercise of Development Election.

            3.2.1. Exercise. VERTEX will notify SERONO as soon as VERTEX has
selected a Compound for formal pre-clinical development hereunder (each, a
"Proposed Candidate"). Along with that notice (the "Selection Notice"), VERTEX
will also provide SERONO and the JRC with all material information known to
VERTEX at the time of the Selection Notice (the "Selection Information"),
including analysis results and raw data, which could be material to SERONO's
decision whether to exercise its Development Election with respect to the
Proposed Candidate. Any Compound proposed by VERTEX for development will meet
the minimum development criteria set forth on Schedule 3.2 to this Agreement. As
to any Proposed Candidate SERONO may exercise its Development Election and
select that Proposed Candidate for development (a "Drug Product Candidate") by
delivery to VERTEX, within [*********************************] after receipt of
the Selection Information with respect to the Proposed Candidate (the "Notice
Period"), of written notice of exercise of its Development Election with respect
to that Proposed Candidate. The parties shall then promptly execute a License
Agreement with respect to that Drug Product Candidate. SERONO shall not be
obligated but shall have complete discretion to determine whether to exercise
its Development Election with respect to any Proposed Candidate.

            3.2.2. Failure to Exercise. Subject to the provisions of Section 3.3
below, the Development Election with respect to any Proposed Candidate will
expire at 5:00 P.M. Boston time on the last day of the Notice Period with
respect to that Proposed Candidate, unless SERONO prior to that time has
exercised its Development Election in accordance with this Agreement.

      3.3. Refused Candidate.

            3.3.1. Second Opportunity. If SERONO does not exercise the
Development Election with respect to a Proposed Candidate during the Notice
Period referenced in Section 3.2 above, then the Development Election shall
expire as provided in Section 3.2.2 with respect to that Proposed Candidate
(which shall then become a "Refused Candidate" hereunder) subject to the proviso
set forth below, and VERTEX will thereafter be free to develop and commercialize
the Refused Candidate at its expense free of any further obligation to SERONO
hereunder except as set forth below, including the obligation to submit
information concerning

                  Research Agreement -- Confidential -- Page 15
<PAGE>

that Refused Candidate for review by the JRC; provided that VERTEX will not
enter into any agreement with a Third Party to develop or commercialize the
Refused Candidate prior to [***************************************************]
If VERTEX continues development of the Refused Candidate it will notify SERONO
[**************************] of its decision to do so. VERTEX will thereafter
notify SERONO in writing after VERTEX has received all material data from its
Phase II Clinical Trials of that Refused Candidate for the initial Indication
tested (the "Second Opportunity Notice"). [*************************************
******************************************]. SERONO may request and VERTEX will
promptly provide to SERONO all analysis results and raw data available at the
time of the request which are material to, and will form the basis for, VERTEX's
decision to commence its first Phase III Clinical Trial or other pivotal
registration study (or to file for Regulatory Approval, if an application for
Regulatory Approval is planned based on data from the Phase II Clinical Trial
alone) with respect to the Refused Candidate (the "Development Information").
VERTEX will also provide to SERONO as part of the Development Information with
respect to the Refused Candidate, a detailed schedule of the development costs
incurred by VERTEX with respect to the development of that Refused Candidate to
date, including all direct and indirect costs associated with preclinical
studies, clinical trials, manufacturing of drug substance and drug product,
scale-up and formulation research, and regulatory activities, but excluding any
allocation of corporate overheads, determined in a manner not at variance with
Generally Accepted Accounting Principles (GAAP), International Accounting
Standards (IAS) and the party's usual practices. During [***********************
********************************************************************************
************************************************], SERONO shall have the right
to exercise the Development Election with respect to that Refused Candidate;
except that the provisions of Article VII of the License Agreement shall be
applicable to any Drug Product Candidate which is licensed at the Second
Opportunity. SERONO's right to exercise the Development Election with respect to
any Refused Candidate at the Second Opportunity [*******************************
************************************************] with respect to that Refused
Candidate. If SERONO exercises the Development Election, the parties shall then
promptly execute a License Agreement. SERONO shall not be obligated but shall
have complete discretion to determine whether to exercise its Development
Election with respect to any Refused Candidate.

            3.3.2. Rights Upon Expiration or Termination of the Research
Program. (a) If the Research Program expires in the ordinary course at the end
of the term provided in Section

                  Research Agreement -- Confidential -- Page 16
<PAGE>

2.2 hereof or SERONO terminates this Agreement [***************************],
prior to the completion of Phase II Clinical Trials with respect to a Refused
Candidate, VERTEX will include with the Final Report provided under Section 3.4
hereof all material information known to VERTEX as of the end of the Final
Report Period relative to the Refused Candidate and its suitability as a Drug
Product Candidate. SERONO may thereafter exercise the Development Election with
respect to that Refused Candidate on or before [********************************
*********************], and in such event the Development Election will be
deemed to have been exercised by SERONO with respect to that Refused Candidate
at the Second Opportunity, with the consequences provided in Section 3.3.1 and
under the License Agreement with respect to that Candidate.

            (b) If the Research Program expires in the ordinary course at the
end of the five-year term provided in Section 2.2 hereof, or is terminated by
SERONO [************************************************************************
************************], then SERONO will nevertheless retain the right after
termination of this Agreement: to receive a Second Opportunity Notice from
VERTEX, as provided in Section 3.3.1, with respect to any Refused Candidates as
to which the Development Election was not exercised by SERONO under Subsection
3.3.2(a) above; to receive the Development Information with respect to that
Refused Candidate as provided in Section 3.3.1; and to exercise the Development
Election with respect to that Refused Candidate notwithstanding termination or
expiration of this Agreement generally, all as if this Agreement were still in
full force and effect with respect to that Refused Candidate.

            3.3.3. [[*****************] VERTEX's right to develop and
commercialize a Refused Candidate pursuant to Section 3.3.1 shall not apply to
[*******************************************************************************
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********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************

                  Research Agreement -- Confidential -- Page 17
<PAGE>

[*******************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
*********************]

      3.4. Final Report Election.

            3.4.1. Final Report Period. Upon expiration of the Research Program
in the ordinary course at the end of the five-year term provided in Section 2.2
hereof ("Normal Expiration"), or upon early termination of the Research Program
by SERONO under Section 8.4 hereof at the end of the second Research Year or at
the end of the fourth Research Year ("Early Termination"), VERTEX will submit a
final report (the "Final Report") to the JRC and SERONO which will cover the
period beginning on the Effective Date and ending in the case of Normal
Expiration on the [*************************************] following expiration
of the Research Program and in the case of Early Termination, on the
[******************] following the effective date of termination of the Research
Program (in each case, the "Final Report Period"), and which will contain all
material information known to VERTEX, and not previously reported to the JRC and
SERONO, relative to Compounds invented, discovered or developed during the Final
Report Period. To the extent that it is conducting research relative to
Compounds, SERONO will provide a similar report to VERTEX and the JRC. The Final
Report will be delivered within [****************] after the end of the Final
Report Period and the date upon which it is delivered will be called the "Final
Report Date."

            3.4.2. Election. Under the Development Election, SERONO shall also
have the right (the "Final Report Election"), exercisable by delivery of written
notice (a "Final Report Election Notice") to VERTEX at any time during the
[***********] period following the Final Report Date, to select any Compound or
Compounds (each, a "Final Report Compound") not previously

                  Research Agreement -- Confidential -- Page 18
<PAGE>

designated for development by VERTEX for immediate development under the terms
of a License Agreement; provided, that [****************************************
********************************************************************************
********************************************************************************
******************************************************************************].
SERONO will provide with the Final Report Election Notice a proposed development
plan and estimated budget for each Final Report Compound. Within
[*****************] after receipt of the Final Report Election Notice, VERTEX
shall notify SERONO in writing whether (a) it accepts the Final Report Compound
for development, in which case development of that Compound shall proceed as if
it were originally proposed by VERTEX and accepted for development by SERONO
under Section 3.2.1 hereof; or (b) it chooses not to join SERONO in development
and commercialization of that Final Report Compound, in which case the parties
shall execute and deliver a License Agreement and SERONO shall proceed with
development of that Compound (a "Final SERONO Candidate") under Article VII of
the License Agreement.

      3.5. SERONO Licenses.

            3.5.1. Grant. Subject to SERONO's rights under this Agreement and
any License Agreement, SERONO hereby grants to VERTEX (a) a royalty-free,
exclusive, worldwide license and/or sublicense, with the right to further
sublicense, to SERONO's interest (and the interest of SERONO's Affiliates) in
any Joint Patent claiming a Compound or the uses or methods of manufacture
thereof; and (b) a royalty-free, non-exclusive, worldwide license and/or
sublicense, with the right to further sublicense, under all other SERONO Program
Technology claiming a Compound or the uses or methods of manufacture thereof.
The foregoing licenses and rights to further sublicense shall extend only to
making, having made, using, selling, offering to sell and importing Compounds
and pharmaceutical products incorporating Compounds. SERONO retains all rights
to SERONO Program Technology except to the extent explicitly granted to VERTEX
hereunder.

            3.5.2. Sublicensees. VERTEX shall guarantee and be responsible to
SERONO for the performance of any of its sublicensees under any sublicense with
respect to the rights granted to VERTEX by SERONO and the obligations assumed by
VERTEX hereunder. VERTEX shall not permit any sublicensees to use SERONO Program
Technology without provisions safeguarding confidentiality equivalent to those
provided in this Agreement. Any

                  Research Agreement -- Confidential -- Page 19
<PAGE>

such provisions will allow SERONO the right to directly enforce the obligations
of confidentiality with respect to SERONO Program Technology in the possession
of the sublicensee.

                         ARTICLE IV -- CONFIDENTIALITY

      4.1. Undertaking.

            Each party shall keep confidential and, other than as provided
herein, shall not disclose, directly or indirectly, any trade secrets, other
knowledge, information, documents or materials owned or Controlled by the other
party which have been disclosed (in tangible or electronic form or as evidenced
by meeting minutes or similar materials) to such party after the Effective Date
and designated confidential by the disclosing party (any such information,
"Confidential Information"). All Program Technology shall be deemed Confidential
Information. Neither VERTEX nor SERONO shall use such Confidential Information
of the other party for any purpose, including the filing of patent applications
containing such information, without the other party's consent (which shall not
be unreasonably withheld), other than for conducting the Research Program or as
otherwise permitted under this Agreement.

            4.1.1. Nondisclosure and Nonuse. Each party shall take any and all
lawful measures to prevent the unauthorized use and disclosure of such
Confidential Information, and to prevent unauthorized persons or entities from
obtaining or using such Confidential Information.

            4.1.2. Disclosure to Affiliates and Agents. Each party will refrain
from directly or indirectly taking any action which would constitute or
facilitate the unauthorized use or disclosure of such Confidential Information.
Each party may disclose such Confidential Information to its Affiliates, their
officers, employees and agents, to authorized licensees and sublicensees
(including VERTEX's Far East collaborator as provided in Section 2.7 hereof),
and to subcontractors in connection with the development of a Drug Product
Candidate or the manufacture of Bulk Drug Substance, or Drug Products, but only
to the extent necessary to enable such parties to perform their obligations
hereunder or under the applicable license, sublicense or subcontract, as the
case may be; provided, that such officers, employees, agents, licensees,
sublicensees and subcontractors have entered into appropriate confidentiality
agreements for secrecy and non-use of such Confidential Information.

            4.1.3. Liability. Each party shall be liable for any unauthorized
use and disclosure of such Confidential Information by its Affiliates, officers,
employees and agents and any such licensees, sublicensees and subcontractors.

                  Research Agreement -- Confidential -- Page 20
<PAGE>

      4.2. Exceptions.

            Notwithstanding the foregoing, the provisions of Section 4.1 hereof
shall not apply to Confidential Information which the receiving party can
conclusively establish:

            (i) has entered the public domain without such party's or its
Affiliates' breach of any obligation owed to the disclosing party;

            (ii) is permitted to be disclosed by the prior written consent of
the disclosing party;

            (iii) has become known to the receiving party or any of its
Affiliates from a source other than the disclosing party, other than by breach
of an obligation of confidentiality owed to the disclosing party;

            (iv) is disclosed by the disclosing party to a Third Party without
restrictions on its disclosure;

            (v) is independently developed by the receiving party or its
Affiliates without use of or reference to the Confidential Information; or

            (vi) is required to be disclosed by the receiving party to comply
with applicable laws or regulations or to defend or prosecute litigation,
provided that the receiving party takes reasonable and lawful actions to avoid
or minimize the degree of such disclosure and to have confidential treatment
accorded to any Confidential Information disclosed, and provides prior written
notice to the disclosing party within a time period sufficiently prior to such
disclosure to permit the disclosing party to apply for a protective order or
take other appropriate action to restrict disclosure. The receiving party shall
fully cooperate with the disclosing party in connection with the disclosing
party's efforts to obtain any such remedy.

      4.3. Publicity.

            The parties will agree upon the timing and content of any initial
press release or other public communications relating to this Agreement and the
transactions contemplated herein.

            Except to the extent already disclosed in that initial press release
or other public communication, no public announcement concerning the existence
or the terms of this Agreement or concerning the transactions described herein
shall be made, either directly or indirectly, by VERTEX or SERONO, except as may
be legally required by applicable laws, regulations, or judicial order, without
first obtaining the approval of the other party and agreement upon the nature,
text, and timing of such announcement, which approval and agreement shall not be
unreasonably withheld. If in the reasonable opinion of a party's legal

                  Research Agreement -- Confidential -- Page 21
<PAGE>

counsel, such a public announcement is legally required by applicable laws,
regulations or judicial order, then the disclosing party will provide the other
party notice reasonable under the circumstances of such intended announcement,
and to the extent feasible under the circumstances will consult with the other
party relative to the nature and scope of such intended announcement.

            In addition to the foregoing restrictions on public disclosure, if
VERTEX concludes that a copy of this Agreement must be filed with the U.S.
Securities and Exchange Commission, it will provide SERONO with a copy of the
Agreement showing any sections as to which VERTEX proposes to request
confidential treatment, will provide SERONO with an opportunity to comment on
any such proposal and to suggest additional portions of the Agreement for
confidential treatment, and will take SERONO's reasonable comments into
consideration, before filing the same.

      4.4. Survival.

            The provisions of this Article IV shall survive the termination of
this Agreement and shall extend for a period of [**************] thereafter.

                            ARTICLE V -- PUBLICATION

      Each of SERONO and VERTEX reserves the right to publish or publicly
present the results (the "Results") of the Research Program, subject to the
following terms and conditions. The party proposing to publish or publicly
present the Results (the "Publishing Party") will submit a draft of any proposed
manuscript, abstract or speech to the other party (the "Non-publishing Party")
for comments at least [***************] prior to submission for publication or
oral presentation. The Non-publishing Party shall notify the Publishing Party in
writing within [****** ***********] of receipt of such draft whether such draft
contains (i) information of the Non-publishing Party which it considers to be
confidential under the provisions of Article IV hereof, (ii) information that if
published would have an adverse effect on a patent application covering the
subject matter of this Agreement, or (iii) information which the Non-publishing
Party reasonably believes would be likely to have a material adverse impact on
the development or commercialization of a Compound, a Drug Product Candidate or
a Drug Product. In any such notification, the Non-publishing Party shall
indicate with specificity its suggestions regarding the manner and degree to
which the Publishing Party may disclose such information. In the case of item
(i) above, no party may publish Confidential Information of the other party
without its consent in violation of Article IV of this Agreement. In the case of
item (ii) above, the Non-

                  Research Agreement -- Confidential -- Page 22
<PAGE>

publishing Party may request a delay and the Publishing Party shall delay such
publication or presentation, for a period not exceeding [****************], to
permit the timely preparation and filing of a patent application or an
application for a certificate of invention on the information at issue. In the
case of item (iii) above, if the Publishing Party shall disagree with the
Non-publishing Party's assessment of the impact of the publication or
presentation, then the issue shall be referred by the Publishing Party to the
JRC for resolution. If the JRC is unable to reach agreement on the matter within
[****************] after such referral, then the matter, if it involves the
disclosure of confidential structural information with respect to a Compound,
shall be referred to the Chief Executive Officers of SERONO and VERTEX, or to
other members of senior management of such parties who report directly to their
respective Chief Executive Officers, who shall attempt in good faith to reach a
fair and equitable resolution of this disagreement. If the disagreement is not
resolved in this manner within [*************] after referral to the JRC or (as
to publications or presentations involving structural information) referral to
the Chief Executive Officer of each party or his designee, as aforesaid, then
the Chief Executive Officer of the Publishing Party shall notify the Chief
Executive Officer of the Non-publishing Party of the decision of the Publishing
Party as to publication or presentation of any information generated by it,
subject always to the confidentiality provisions of Article IV hereof. This
decision shall be final, provided that such decision shall be made with
reasonable regard for the interests of the Non-publishing Party and provided
further that no decision shall be made to publish or present information the
publication or presentation of which would have a material adverse effect on the
commercial prospects of any Drug Candidate or Drug Product. The parties agree
that authorship of any publication or presentation will be determined based on
the customary standards then being applied in the relevant scientific journal or
conference. The parties will require any agents conducting the Research Program
on their behalf to comply with publication and presentation restrictions
comparable to those set forth herein.

      This Article V shall terminate with the termination of this Agreement, but
the provisions of Article IV hereof shall continue to govern the disclosure by
one party, whether by publication or otherwise, of Confidential Information of
the other, during the period set forth in Section 4.4.

                         ARTICLE VI -- INDEMNIFICATION

      6.1. Indemnification by VERTEX.

            VERTEX will indemnify and hold SERONO and its Affiliates, and their
employees, officers and directors harmless from and against any loss, damage,
action, suit,

                  Research Agreement -- Confidential -- Page 23
<PAGE>

claim, demand, liability, judgment, cost or expense (a "Loss") that may be
brought, instituted or arise against or be incurred by such Persons to the
extent such Loss is based on or arises out of:

            (i) [***************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
*******************************************************************************]

            (ii) the breach by VERTEX of any of its covenants, representations
or warranties set forth in this Agreement; and

            (iii) provided however, that the foregoing indemnification and hold
harmless obligation shall not apply to any Loss to the extent such Loss is
caused by the negligent or willful misconduct of SERONO or its Affiliates.

      6.2. Indemnification by SERONO.

            SERONO will indemnify and hold VERTEX, and its Affiliates, and their
employees, officers and directors harmless from and against any Loss that may be
brought, instituted or arise against or be incurred by such Persons to the
extent such Loss is based on or arises out of:

            (i) [***************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
*******************************************************************************]

            (ii) the breach by SERONO of any of its covenants, representations
or warranties set forth in this Agreement; and

            (iii) provided that the foregoing indemnification and hold harmless
obligation shall not apply to any Loss to the extent such Loss is caused by the
negligent or willful misconduct of VERTEX or its Affiliates.

                  Research Agreement -- Confidential -- Page 24
<PAGE>

      6.3. Claims Procedures.

            Each Party entitled to be indemnified by the other Party (an
"Indemnified Party") pursuant to Section 6.1 or 6.2 hereof shall give notice to
the other Party (an "Indemnifying Party") promptly after such Indemnified Party
has actual knowledge of any threatened or asserted claim as to which indemnity
may be sought, and shall permit the Indemnifying Party to assume the defense of
any such claim or any litigation resulting therefrom; provided:

            (i) That counsel for the Indemnifying Party, who shall conduct the
defense of such claim or any litigation resulting therefrom, shall be approved
by the Indemnified Party (whose approval shall not unreasonably be withheld) and
the Indemnified Party may participate in such defense at such party's expense
(unless (i) the employment of counsel by such Indemnified Party has been
authorized by the Indemnifying Party; or (ii) the Indemnified Party shall have
reasonably concluded that there may be a conflict of interest between the
Indemnifying Party and the Indemnified Party in the defense of such action, in
each of which cases the Indemnifying Party shall pay the reasonable fees and
expenses of one law firm serving as counsel for the Indemnified Party, which law
firm shall be subject to approval, not to be unreasonably withheld, by the
Indemnifying Party);

            (ii) The failure of any Indemnified Party to give notice as provided
herein shall not relieve the Indemnifying Party of its obligations under this
Agreement to the extent that the failure to give notice did not result in harm
to the Indemnifying Party;

            (iii) No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the approval of each Indemnified Party which
approval shall not be unreasonably withheld, consent to entry of any judgment or
enter into any settlement which (i) would result in injunctive or other relief
being imposed against the Indemnified Party; or (ii) does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation. The Indemnified Party shall have no right to settle or compromise
any such claim or litigation without the Indemnifying Party's prior written
consent; and

            (iv) Each Indemnified Party shall furnish such information regarding
itself or the claim in question as an Indemnifying Party may reasonably request
in writing and shall be reasonably required in connection with the defense of
such claim and litigation resulting therefrom.

                  Research Agreement -- Confidential -- Page 25
<PAGE>

                       ARTICLE VII -- PROGRAM TECHNOLOGY

      7.1. Ownership.

            All Program Technology invented exclusively by either party or its
Affiliates (directly or through others acting on its behalf) shall be owned and
Controlled by such party or its Affiliates, subject to the provisions of this
Agreement. Program Technology invented jointly shall be owned and Controlled
jointly by the parties or their Affiliates, subject to the provisions of this
Agreement. Inventorship shall be determined in accordance with United States
patent and other applicable laws. All Know-How otherwise developed or discovered
exclusively by either party or its Affiliates (directly or through others acting
on its behalf) shall be owned and Controlled by such party or its Affiliates,
subject to the provisions of this Agreement. Know-How otherwise developed or
discovered jointly shall by owned and Controlled jointly by the parties or their
Affiliates, subject to the provisions of this Agreement. Know-How that is owned
and Controlled jointly by the parties or their Affiliates shall be "Joint
Know-How" and Program Technology invented jointly and therefore owned and
Controlled jointly by the parties or their Affiliates, and which is the subject
of a Patent, shall be "Joint Patents."

      7.2. Patent Procurement, Maintenance and Defense.

            7.2.1. Procurement and Maintenance. VERTEX shall take responsibility
for the preparation, filing, prosecution and maintenance of all VERTEX Patents,
and any Joint Patents, and SERONO shall be responsible for the preparation,
filing, prosecution and maintenance of all SERONO Patents, in each case after
consulting from time to time with the other party and the JRC with respect
thereto and providing an opportunity for such other party and the JRC to
comment. The filing party, with the advice of the other party, shall determine
the countries in which applications will be filed. VERTEX shall furnish SERONO
with copies of all substantive communications between VERTEX and applicable
patent offices regarding the Joint Patents. VERTEX and SERONO shall each provide
the JRC with periodic reports listing, by name, any such Patents filed by it in
the United States or the European Union, along with a general summary of the
claims made and the jurisdictions of filing in the Territory. Each party will
provide such assistance as the other party may reasonably request in order to
protect the other party's rights to Patents for which it is responsible under
this Section 7.2.

            7.2.2 Defense. If either party learns of (i) any infringement or
potential infringement of a Joint Patent by a third party in the Territory
and/or (ii) any claim by a third party that a Joint Patent is invalid in the
Territory, it shall promptly notify the other party and the

                  Research Agreement -- Confidential -- Page 26
<PAGE>

parties shall then agree upon a course of action with respect to such
infringement or claim. VERTEX agrees to take reasonable actions to protect
VERTEX Patents from infringement and from unauthorized possession or use. If
VERTEX chooses not to prosecute an infringement action in connection with any
alleged infringement or potential infringement of a VERTEX Patent or defend a
claim that a VERTEX Patent is invalid in the Territory, and its decision in that
regard is reasonably likely to have a material adverse impact on the value of
SERONO's rights under this Agreement, then SERONO may prosecute such action or
defend such claim at its own expense. VERTEX shall in such event give SERONO
reasonable assistance and authority to prosecute such action or defend such
claim and shall if necessary consent to be joined as a party plaintiff. In the
event SERONO undertakes any such prosecution or defense, then SERONO shall be
entitled to withhold up to [*******************] of the payments otherwise
thereafter due VERTEX pursuant this Agreement and/or any License Agreement then
in effect and apply the same toward reimbursement of SERONO's litigation-related
cost and expenses, including without limitation reasonable attorney's fees in
connection with such prosecution or defense.

      7.3. Costs.

            [*******************************************************************
********************************************************************************
********************************************************************************
******************************************************************************];
except that the provisions of a License Agreement governing responsibility and
sharing of costs for VERTEX Patents and SERONO Patents covering Program
Technology licensed thereunder will supercede any contrary provisions of this
Article VII with respect to those Patents as and from the time that such License
Agreement becomes effective. [**************************************************
************************************************], subject to the provisions set
forth below. Either party may at any time elect, by written notice to the other
party, to discontinue support for one or more such Joint Patents (a
"Discontinued Patent") and shall not be responsible for any costs relating to a
Discontinued Patent which are incurred more than [***************] after receipt
of that notice by the other party. In such case, the other party may elect at
its sole discretion to continue preparation, filing, prosecution or maintenance
of the Discontinued Patent at its sole expense. The party so continuing shall
own any such Discontinued Patent, and the party electing to discontinue support
shall execute such documents of transfer or assignment and perform such acts as
may be reasonably necessary to transfer sole ownership of the

                  Research Agreement -- Confidential -- Page 27
<PAGE>

Discontinued Patent to the other party and enable that party to file or to
continue prosecution or maintenance of such Discontinued Patent, if the other
party elects to do so. In the event VERTEX elects to discontinue support for a
Discontinued Patent, the license granted to VERTEX by SERONO pursuant to Section
3.5 hereof shall terminate with respect to that Discontinued Patent.
Discontinuance may be on a country-by-country basis or for a Patent series in
total.

      7.4. No Implied Rights.

            Except as expressly provided in this Agreement, no right or license
to use any intellectual property of either party is granted hereunder by
implication or otherwise.

                      ARTICLE VIII -- TERM AND TERMINATION

      8.1. Term.

            This Agreement will extend until the occurrence of the earliest
event giving rise to expiration of the Development Election under Section 3.1
hereof, unless the Agreement is extended by mutual agreement of the parties.

      8.2. Termination of the Research Program by SERONO for Cause.

            Upon written notice to VERTEX, SERONO may at its sole discretion
terminate the Research Program and this Agreement upon the occurrence of any of
the following events:

            (i) VERTEX shall breach any of its material obligations under this
Agreement, and such breach shall not have been remedied or steps initiated to
remedy the same to SERONO's reasonable satisfaction, within sixty (60) days
after SERONO sends notice of breach to VERTEX; or

            (ii) VERTEX shall cease to function as a going concern by suspending
or discontinuing its business for any reason except for interruptions caused by
Force Majeure.

            In the event of any termination under this Section 8.2, SERONO shall
not be required to make any payments under Sections 2.3 or 2.4 hereof which are
not due and payable prior to receipt by VERTEX of the notice of breach
referenced under Section 8.2(i) or receipt by VERTEX of the notice of
termination pursuant to Section 8.2(ii), as the case may be. Within fifteen (15)
days of the effective date of such termination, VERTEX will provide to SERONO
and the JRC a description of any Compounds not previously disclosed to SERONO
and the JRC as well as all material information known to VERTEX, including
analysis results and raw data, which could be material to SERONO's decision
pursuant to Section 3.1 whether to exercise its Development Election with
respect to such a Compound.

                  Research Agreement -- Confidential -- Page 28
<PAGE>

      8.3. Termination of the Research Program by VERTEX for Cause.

            Upon written notice to SERONO, VERTEX may at its sole discretion
terminate the Research Program and this Agreement upon the occurrence of any of
the following events:

            (i) SERONO shall breach any of its material obligations under this
Agreement, and such breach shall not have been remedied or steps initiated to
remedy the same to VERTEX's reasonable satisfaction, within sixty (60) days
after VERTEX sends notice of breach to SERONO; or

            (ii) SERONO shall cease to function as a going concern by suspending
or discontinuing its business for any reason except for interruptions caused by
Force Majeure.

      8.4. Early Termination of Research Program by SERONO.

            SERONO may in its absolute discretion terminate the Research Program
and this Agreement prior to the end of the Program's full term, effective either
(i) at the end of the second Research Year, or (ii) at the end of the fourth
Research Year, in either case upon not less than ninety (90) days prior written
notice to VERTEX (the "Early Termination Notice Period"). SERONO will make all
of the payments required to be made hereunder which accrue or fall due during
the Early Termination Notice Period and prior to the effective date of any such
early termination.

      8.5. No Termination upon Bankruptcy.

            8.5.1. VERTEX Bankruptcy. All rights and licenses granted under or
pursuant to this Agreement by VERTEX to SERONO are, and shall otherwise be
deemed to be, for purposes of Section 365(n) of the United States Bankruptcy
Code, as amended from time to time (the "Bankruptcy Code"), licenses or rights
to "intellectual property" as defined under Section 101(35A) of the Bankruptcy
Code. The parties agree that SERONO, as a recipient of such rights and licenses
under this Agreement, shall retain and may fully exercise those rights and
licenses notwithstanding a filing by or against VERTEX under the Bankruptcy
Code, to the full extent provided under the Bankruptcy Code.

            8.5.2. SERONO Bankruptcy. All rights and licenses granted under or
pursuant to this Agreement by SERONO to VERTEX are, and shall otherwise be
deemed to be, under any statutes or regulations that may govern SERONO's
bankruptcy under Swiss law, licenses or rights to "intellectual property." The
parties agree that VERTEX, as recipient of such rights and licenses under this
Agreement, shall retain and may fully exercise those rights and licenses

                  Research Agreement -- Confidential -- Page 29
<PAGE>

notwithstanding a filing by or against SERONO under such bankruptcy statutes or
regulations, to the full extent provided under such statutes or regulations.

      8.6. Effect of Termination.

            Except where explicitly provided elsewhere herein, termination of
this Agreement for any reason, or expiration of this Agreement, will not affect:
(i) obligations which have accrued as of the date of termination or expiration,
and (ii) obligations and rights which are expressly intended to survive
termination or expiration of this Agreement, including rights and obligations
under the licenses granted by SERONO under Section 3.5 hereof, rights and
obligations pursuant to Sections 7.2 and 7.3 and Articles IV, VI, X and XI
hereof, to the extent applicable, and the rights and obligations of both parties
under any License Agreement in effect on the effective date of termination of
this Agreement. Any right to terminate this Agreement shall be in addition to
and not in lieu of all other rights or remedies that the party giving notice of
termination may have at law or in equity or otherwise, including without
limitation rights under the United States Bankruptcy Code.

                  ARTICLE IX -- REPRESENTATIONS AND WARRANTIES

      9.1. Representations and Warranties of VERTEX.

            VERTEX represents and warrants to SERONO as follows:

            (i) Authorization. This Agreement has been duly executed and
delivered by VERTEX and constitutes the valid and binding obligation of VERTEX,
enforceable against VERTEX in accordance with its terms except as enforceability
may be limited by bankruptcy, fraudulent conveyance, insolvency, reorganization,
moratorium and other laws relating to or affecting creditors' rights generally
and by general equitable principles. The execution, delivery and performance of
this Agreement have been duly authorized by all necessary action on the part of
VERTEX, its officers and directors. The execution, delivery and performance of
this Agreement does not breach, violate, contravene or constitute a default
under any contracts, arrangements or commitments to which VERTEX is a party or
by which it is bound nor does the execution, delivery and performance of this
Agreement by VERTEX violate any order, law or regulation of any court,
governmental body or administrative or other agency having authority over it.

            (ii) No Third Party Rights. VERTEX owns or possesses adequate
licenses or other rights to use all VERTEX Program Technology and to grant the
licenses and rights herein.

                  Research Agreement -- Confidential -- Page 30
<PAGE>

The granting of the Development Election to SERONO hereunder does not violate
any right known to VERTEX of any Third Party.

            (iii) Third Party Patents. Except as disclosed in writing between
the parties to this Agreement or their respective agents, VERTEX is not aware of
any issued patents or pending patent applications that, if issued, would be
infringed by the development, manufacture, use, import, offer to sell or sale of
any Compound, Drug Product Candidate, Bulk Drug Substance or Drug Product
pursuant to this Agreement or a License Agreement.

            (vi) Disclosure. To the best of VERTEX's knowledge, all material
information regarding the VERTEX Program Technology disclosed by VERTEX to
SERONO in writing prior to the Effective Date was accurate and complete in all
material respects when disclosed.

      9.2. Representations and Warranties of SERONO.

            SERONO represents and warrants to VERTEX as follows:

            (i) Authorization. This Agreement has been duly executed and
delivered by SERONO and constitutes the valid and binding obligation of SERONO,
enforceable against SERONO in accordance with its terms except as enforceability
may be limited by bankruptcy, fraudulent conveyance, insolvency, reorganization,
moratorium and other laws relating to or affecting creditors' rights generally
and by general equitable principles. The execution, delivery and performance of
this Agreement have been duly authorized by all necessary action on the part of
SERONO, its officers and directors. The execution, delivery and performance of
this Agreement does not breach, violate, contravene or constitute a default
under any contracts, arrangements or commitments to which SERONO is a party or
by which it is bound nor does the execution, delivery and performance of this
Agreement by SERONO violate any order, law or regulation of any court,
governmental body or administrative or other agency having authority over it.

            (ii) Third Party Rights. SERONO owns or possesses adequate licenses
or other rights to use all SERONO Program Technology in accordance with the
provisions of this Agreement.

            (iii) Third Party Patents. Except as disclosed in writing between
the parties to this Agreement or their respective agents, SERONO is not aware of
any issued patents or pending patent applications that, if issued, would be
infringed by the development, manufacture, use, import, offer to sell or sale of
any Compound, Drug Product Candidate, Bulk Drug Substance or Drug Product
pursuant to this Agreement or a License Agreement.

                  Research Agreement -- Confidential -- Page 31
<PAGE>

                        ARTICLE X -- DISPUTE RESOLUTION

      10.1. Governing Law.

            This Agreement shall be governed by and construed in accordance with
the internal laws of the Commonwealth of Massachusetts and of the United States
of America, without giving effect to the doctrine of conflict of laws.

      10.2. Dispute Resolution Process.

            Except as otherwise explicitly provided herein, in the event of any
controversy or claim arising out of or relating to any provision of this
Agreement, or the collaborative effort contemplated hereby, the parties shall,
and either party may, initially refer such dispute to the JRC, and failing
resolution of the controversy or claim within thirty (30) days after such
referral, the matter shall be referred to the Chief Executive Officer of VERTEX
and the Chief Executive Officer of SERONO, or other members of senior management
of such parties who report directly to their respective Chief Executive Officers
and who are not otherwise directly involved in the controversy or claim at
issue, each with full authority from the Chief Executive Officer to settle the
dispute, who shall, as soon as practicable, attempt in good faith to resolve the
controversy or claim. If such controversy or claim is not resolved within sixty
(60) days of the date of initial referral of the dispute to the JRC, either
party shall be free to initiate proceedings based on such controversy or claim
in any court having requisite jurisdiction.

                     ARTICLE XI -- MISCELLANEOUS PROVISIONS

      11.1. Official Language.

            English shall be the official language of this Agreement, and all
communications between the parties hereto shall be conducted in that language.

      11.2. Waiver.

            No provision of this Agreement may be waived except in writing by
both parties hereto. No failure or delay by either party hereto in exercising
any right or remedy hereunder or under applicable law will operate as a waiver
thereof, or a waiver of that or any other right or remedy on any subsequent
occasion.

      11.3. Force Majeure.

            Neither party will be in breach hereof by reason of its delay in the
performance of or failure to perform any of its obligations hereunder, if that
delay or failure is caused by strikes, acts of God or the public enemy, riots,
incendiaries, interference by civil or military authorities, or

                  Research Agreement -- Confidential -- Page 32
<PAGE>

any similar cause beyond its control and without its fault or negligence;
provided, however, the party claiming force majeure shall promptly notify the
other party of the existence of such force majeure, shall use its best efforts
to avoid or remedy such force majeure and shall continue performance hereunder
with the utmost dispatch whenever such force majeure is avoided or remedied.
Notwithstanding the foregoing, in the event that VERTEX provides notice of force
majeure to SERONO, SERONO shall have the right not to make any future payments
otherwise payable hereunder until such time as VERTEX resumes performance
hereunder, and the schedule for payments hereunder shall be revised to apply any
payments already made in advance by SERONO for the performance so delayed or
suspended by VERTEX hereunder to such performance once it is resumed or to
refund any such payments to SERONO in the event that such performance is not for
any reason resumed.

      11.4. Severability.

            Should one or more provisions of this Agreement be or become
invalid, then the parties hereto shall attempt to agree upon valid provisions in
substitution for the invalid provisions, which in their economic effect come so
close to the invalid provisions that it can be reasonably assumed that the
parties would have accepted this Agreement with those new provisions. If the
parties are unable to agree on such valid provisions, the invalidity of such one
or more provisions of this Agreement shall nevertheless not affect the validity
of the Agreement as a whole, unless the invalid provisions are of such essential
importance to this Agreement that it may be reasonably presumed that the parties
would not have entered into this Agreement without the invalid provisions.

      11.5. Government Acts.

            In the event that any act, regulation, directive, or law of a
country or its government, including its departments, agencies or courts, should
make impossible or prohibit, restrain, modify or limit any material act or
obligation of SERONO or VERTEX under this Agreement, the party, if any, not so
affected, shall have the right, at its option, to suspend or terminate this
Agreement as to such country, if good faith negotiations between the parties to
make such modifications therein as may be necessary to fairly address the impact
thereof are not successful after a reasonable period of time in producing
mutually acceptable modifications to this Agreement.

                  Research Agreement -- Confidential -- Page 33
<PAGE>

      11.6. Government Approvals.

            Each party will obtain any government approval required in its
country of domicile, or under any treaties or international agreements to which
its country of domicile is a signatory, to enable this Agreement to become
effective, or to enable any payment hereunder to be made, or any other
obligation hereunder to be observed or performed. Each party will keep the other
informed of progress in obtaining any such government approval, and will
cooperate with the other party in any such efforts.

      11.7. Export Controls.

            This Agreement is made subject to any restrictions concerning the
export of materials and technology from the United States which may be imposed
upon either party to this Agreement from time to time by the United States
Government. In the event any such restrictions are imposed after the Effective
Date and thereby render any provisions of this Agreement invalid or
unenforceable, the provisions of Section 11.4 of this Agreement shall be
applicable to those provisions. SERONO will not export, directly or indirectly,
any VERTEX Program Technology to any countries for which the United States
Government or any agency thereof at the time of such export requires an export
license or other governmental approval without first obtaining the written
consent to do so from the Department of Commerce or other applicable agency of
the United States Government in accordance with the applicable statute or
regulation.

      11.8. Assignment; Successors and Assigns.

            This Agreement may not be assigned or otherwise transferred by
either party without the prior written consent of the other party; provided,
however, that either party may assign this Agreement, without the consent of the
other party, (i) to any of its Affiliates, if the assigning party guarantees the
full performance of its Affiliates' obligations hereunder, or (ii) in connection
with the transfer or sale of all or substantially all of its assets or business
or in the event of its merger or consolidation with another company. Any
purported assignment in contravention of this Section 11.8 shall, at the option
of the nonassigning party, be null and void and of no effect. No assignment
shall release either party from responsibility for the performance of any of its
accrued obligations hereunder. This Agreement shall be binding upon and
enforceable against the successor to or any permitted assignees of either of the
parties hereto.

                  Research Agreement -- Confidential -- Page 34
<PAGE>

      11.9. Affiliates.

            Each party may perform its obligations hereunder personally or
through one or more Affiliates, although each party shall nonetheless be solely
responsible for the performance of its Affiliates. Neither party shall permit
any of its Affiliates to commit any act (including any omission) which such
party is prohibited hereunder from committing directly.

      11.10. Counterparts.

            This Agreement may be signed in any number of counterparts with the
same effect as if the signatures to each counterpart were upon a single
instrument, and all such counterparts together shall constitute the same
agreement.

      11.11. No Agency.

            Nothing herein contained shall be deemed to create an agency, joint
venture, amalgamation, partnership or similar relationship between SERONO and
VERTEX. Notwithstanding any of the provisions of this Agreement, neither party
to this Agreement shall at any time enter into, incur, or hold itself out to
third parties as having authority to enter into or incur, on behalf of the other
party, any commitment, expense, or liability whatsoever, and all contracts,
expenses and liabilities in connection with or relating to the obligations of
each party under this Agreement shall be made, paid, incurred and undertaken
exclusively by such party on its own behalf and not as an agent or
representative of the other.

      11.12. Notice.

            All communications between the parties with respect to any of the
provisions of this Agreement will be sent to the addresses set out below, or to
such other addresses as may be designated by one party to the other by notice
pursuant hereto, by air courier (which shall be deemed received by the other
party on the third (3rd) business day following deposit with the air courier),
or by facsimile transmission, or other electronic means of communication (which
shall be deemed received when transmitted), with confirmation by air courier,
sent by the close of business on or before the next following business day:

                  Research Agreement -- Confidential -- Page 35
<PAGE>

            if to SERONO, at:

               Laboratoires Serono S.A.
               Zone Industrielle de l'Ouriettaz
               1170 Aubonne
               Switzerland
               Fax: 41-22-354-5020
               Attention: General Manager

            with a copy to:

               Serono International S.A.
               15 bis Chemin des Mines
               1202 Geneva
               Switzerland
               Fax: 41-22-739-3070
               Attention: General Counsel

            if to VERTEX, at:

               Vertex Pharmaceuticals Incorporated
               130 Waverly Street
               Cambridge, MA U.S.A. 02139-4211
               Fax: (617) 577-6680
               Attention: Joshua S. Boger, Chief Executive Officer

            with a copy to:

               Kirkpatrick & Lockhart LLP
               75 State Street
               Boston, MA U.S.A. 02109
               Fax: (617) 951-9151
               Attention: Kenneth S. Boger, Esq.

      11.13. Headings.

            The section and paragraph headings are for convenience of reference
only and will not be deemed to affect in any way the language of the provisions
to which they refer.

      11.14. Entire Agreement.

            This Agreement, including the schedules appended hereto, contains
the entire understanding of the parties relating to the matters referred to
herein, and may only be amended by a written document referencing this
Agreement, duly executed on behalf of the respective parties.

                            [Signature Page Follows]

                  Research Agreement -- Confidential -- Page 36
<PAGE>

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

                          VERTEX PHARMACEUTICALS INCORPORATED

                          By: /s/ Joshua S. Boger
                              ------------------------------------------
                                 Joshua S. Boger
                          Title: Chief Executive Officer

                          LABORATOIRES SERONO S.A.

                          By: /s/ Ernesto Bertarelli
                              ------------------------------------------

                          Title: Ernesto Bertarelli
                                 ---------------------------------------

                                 Authorized Representative

                  Research Agreement -- Confidential -- Page 37
<PAGE>

                                  SCHEDULE 1.4

                            [***********************]
--------------------------------------------------------------------------------

[*******************************************************************************
*********************************************].

                       Research Agreement -- Confidential
<PAGE>

                                  SCHEDULE 2.4

                          [**************************]
--------------------------------------------------------------------------------

[***********************]

[******************]

[**********]                             [*************************************]

[********************]                   [*************************************]

[***********************]                [*************************************]

[****************]                       [*************************************]

[*******************]                    [*************************************]

[*********************]                  [*************************************]

[*****************]
                                            [***********************]
[*****************]                         [*****************]
[*****************]                             [*********]
[*****************]                         [************]
[*****************]                             [**********]
[*****************]                             [**********]
[**************]                                [************]
[************************]

                       Research Agreement -- Confidential
<PAGE>

                                            [*************]:
[********************************]          [*******]
[********************************]          [********]
[********************************]          [*********]
[********************************]          [*********]
[********************************]          [**********]
[**************************************]

                       Research Agreement -- Confidential
<PAGE>

                                  SCHEDULE 1.10

                            Countries of the Far East
--------------------------------------------------------------------------------

            Brunei

            Burma (Myanmar)

            Cambodia (Kampuchea)

            Indonesia

            Japan

            Laos

            Malaysia

            Mongolia

            Philippines

            Singapore

            Thailand

            Vietnam

            Korea (South and North)

            Taiwan

            People's Republic of China

                       Research Agreement -- Confidential
<PAGE>

                                  SCHEDULE 3.2

                          Minimum Development Criteria
--------------------------------------------------------------------------------

With respect to each Proposed Candidate, at least the following information and
materials shall be available, and processes established, at the time of the
Selection Notice:

[*********************]

[*********************]
[***********************]
[************************]
[**************************]
[**************************]
[**************************]
[*************************]

                       Research Agreement -- Confidential
<PAGE>

                                    EXHIBIT A

              License, Development and Commercialization Agreement
--------------------------------------------------------------------------------

                       Research Agreement -- Confidential
<PAGE>

                                    EXHIBIT A

              License, Development and Commercialization Agreement

                                     between

                       Vertex Pharmaceuticals Incorporated

                                       and

                            Laboratoires Serono S.A.
<PAGE>

              License, Development and Commercialization Agreement

                                Table of Contents

                                                                   Page Number

ARTICLE I-- DEFINITIONS......................................................1

ARTICLE II-- LICENSE.........................................................8

  2.1   Grant to SERONO......................................................8
  2.2   Grant to VERTEX......................................................8
  2.3   Information Sharing..................................................9

ARTICLE III-- DEVELOPMENT...................................................10

  3.1   Commencement of Development Program.................................10
  3.2   Joint Development Committee.........................................10
  3.3   Development Plan....................................................12
  3.4   Development Costs...................................................12
  3.5   Regulatory Matters..................................................13
  3.6   Assistance Rights...................................................13
  3.7   Conduct of the Development Program..................................14
  3.8   Coordination of Far East Development Activities.....................15

ARTICLE IV-- MANUFACTURE AND SUPPLY.........................................15

  4.1   Supply of Bulk Drug Substance and Drug Product for Development......15
  4.2   Supply of Bulk Drug Substance and Drug Product for Commercial
        Purposes............................................................16
  4.3   Manufacturing Technology............................................16
  4.4   Packaging...........................................................16
  4.5   Subcontracting......................................................19

ARTICLE V-- COMMERCIALIZATION...............................................17

  5.1   Global Marketing and Sales..........................................17
  5.2   Marketing in North America..........................................17
  5.3   Co-labeling.........................................................19
  5.4   Due Diligence.......................................................20

ARTICLE VI-- PAYMENTS.......................................................21

  6.1   Development Payments by SERONO......................................21
  6.2   Commercial Supply Price.............................................22
  6.3   Sales Reports.......................................................24
  6.4   Withholding Tax.....................................................25
  6.5   Adjustment in Connection with Development of a Follow-On Compound...30

ARTICLE VII-- REFUSED CANDIDATES AND FINAL SERONO CANDIDATES................27

  7.1   General.............................................................27
  7.2   Refused Candidates..................................................27
  7.3   Final SERONO Candidate..............................................28

ARTICLE VIII-- TECHNOLOGY...................................................29

  8.1   Ownership...........................................................29
  8.2   Patent Procurement and Maintenance..................................29
  8.3   Costs...............................................................30

     License, Development and Commercialization Agreement -- Confidential --
                           Table of Contents -- Page i
<PAGE>

              License, Development and Commercialization Agreement

                          Table of Contents (continued)

                                                                   Page Number

  8.4   Infringement Claims by Third Parties................................30
  8.5   Infringement Claims Against Third Parties...........................31
  8.6   Notice of Certification.............................................32
  8.7   Patent Term Extensions..............................................32
  8.8   No Implied Rights...................................................32

ARTICLE IX-- Representations and Warranties.................................32

  9.1   Representations and Warranties of VERTEX............................32
  9.2   Representations and Warranties of SERONO............................33

ARTICLE X-- Confidentiality.................................................34

  10.1  Undertaking.........................................................34
  10.2  Exceptions..........................................................35
  10.3  Publicity...........................................................35
  10.4  Survival............................................................36

ARTICLE XI-- Publication....................................................36

ARTICLE XII-- Dispute Resolution............................................37

  12.1  Governing Law, and Jurisdiction.....................................37
  12.2  Dispute Resolution Process..........................................37

ARTICLE XIII-- Term and Termination.........................................38

  13.1  Term................................................................38
  13.2  Termination For Cause...............................................38
  13.3  Termination for Bankruptcy..........................................38
  13.4  Termination by SERONO...............................................39
  13.5  Effect of Termination...............................................39

ARTICLE XIV-- Indemnification...............................................40

  14.1  Indemnification by VERTEX...........................................40
  14.2  Indemnification by SERONO...........................................41
  14.3  Claims Procedures...................................................41
  14.4  Insurance...........................................................42

ARTICLE XV-- MISCELLANEOUS PROVISIONS.......................................42

  15.1  Waiver..............................................................42
  15.2  Force Majeure.......................................................42
  15.3  Registration of License.............................................43
  15.4  Severability........................................................43
  15.5  Government Acts.....................................................43
  15.6  Government Approvals................................................44
  15.7  Assignment; Successors and Assigns..................................44
  15.8  Export Controls.....................................................44
  15.9  Affiliates..........................................................45
  15.10 Counterparts........................................................45

     License, Development and Commercialization Agreement -- Confidential --
                          Table of Contents -- Page ii
<PAGE>

              License, Development and Commercialization Agreement

                          Table of Contents (continued)

                                                                   Page Number

  15.11 No Agency...........................................................45
  15.12 Notice..............................................................45
  15.13 Headings............................................................46
  15.14 Entire Agreement....................................................46

SCHEDULES

Schedule 1.4 --  [*****************]
Schedule 1.11 -- Drug Product Candidate
Schedule 1.16 -- Countries of the Far East
Schedule 1.40 -- SERONO Patents
Schedule 1.47 -- VERTEX Patents

     License, Development and Commercialization Agreement -- Confidential --
                          Table of Contents -- Page iii
<PAGE>

              LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

      THIS LICENSE, DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (the
"Agreement") is made and entered into as of ________, _____ between VERTEX
PHARMACEUTICALS INCORPORATED (hereinafter "VERTEX"), a Massachusetts corporation
with principal offices at 130 Waverly Street, Cambridge, MA 02139-4242, and
LABORATOIRES SERONO S.A. (hereinafter "SERONO"), a Swiss corporation with
principal offices at Zone Industrielle de l'Ouriettaz, 1170 Aubonne,
Switzerland.

                                  INTRODUCTION

      WHEREAS, VERTEX and SERONO are parties to a certain Research Agreement
dated December 11, 2000 (the "Research Agreement") under which VERTEX and SERONO
are attempting to design novel, small-molecule compounds targeting certain
Caspases (as defined below); and

      WHEREAS, SERONO may elect under the terms set forth in the Research
Agreement to develop and commercialize one or more Compounds (as defined below)
identified during the Research Program thereunder, in accordance with the terms
and conditions set forth in this Agreement; and

      WHEREAS, in accordance with the Research Agreement SERONO has elected to
develop and commercialize the Drug Product Candidate (as defined below), and the
parties therefore wish to execute this Agreement, which is identical in
substance to the agreement attached as Exhibit A to the Research Agreement, to
memorialize the provisions specific to development and commercialization of such
Drug Product Candidate and Drug Product (as defined below); and

      NOW THEREFORE, in consideration of the foregoing premises, the mutual
covenants set forth herein, and other good and valuable consideration, the
parties agree as follows:

                            ARTICLE I -- DEFINITIONS

      1.1 "Affiliate" shall mean, with respect to any Person, any other Person
which directly or indirectly controls, is controlled by, or is under direct or
indirect common control with, such Person. The term "control" means the
possession, direct or indirect, of the power to direct or cause the direction of
the management and policies of a Person, whether through the ownership of voting
securities, by contract or otherwise. Control will be presumed if one Person
owns, either of record or beneficially, more than forty percent (40%) of the
voting stock of any other Person.

 License, Development and Commercialization Agreement -- Confidential -- Page 1
<PAGE>

      1.2 "Bulk Drug Substance" shall mean the Drug Product Candidate in bulk
crystal, powder, solution or other form suitable for incorporation in the Drug
Product, which if required in order to stabilize the Drug Product Candidate
shall be formulated with stabilizing excipients.

      1.3 "Caspases" shall mean cysteine-proteases that cleave target proteins
preferentially after an aspartic-acid residue.

      1.4 "Compound" shall mean [***********************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
***********************************.

      1.5 "Controlled" shall mean the legal authority or right of a party hereto
to grant a license or sublicense of intellectual property rights to another
party hereto, or to otherwise disclose proprietary or trade secret information
to such other party, without breaching the terms of any agreement with a Third
Party, misappropriating the proprietary or trade secret information of a Third
Party or incurring any financial obligation or potential financial obligation to
a Third Party.

      1.6 "Core Development Activities" shall mean all activities regardless of
where they are performed which are part of a Development Program for the Drug
Product Candidate and which the JDC believes are reasonably necessary in order
to obtain Regulatory Approval from the FDA and the EMEA or its comparable
successor for marketing the corresponding Drug Product in the United States and
the European Union for the Indications selected.

      1.7 "Core Development Costs" shall mean the total of all costs incurred by
a party hereto in the conduct of Core Development Activities under the Core
Development Plan for the Drug Product Candidate, including but not limited to
all direct and indirect costs associated with preclinical studies, clinical
trials, manufacturing of drug substance and drug product, scale-up and
formulation research and regulatory activities, but excluding any allocation of
corporate overheads, determined in a manner not at variance with applicable
Generally Accepted

 License, Development and Commercialization Agreement -- Confidential -- Page 2
<PAGE>

Accounting Principles (GAAP), International Accounting Standards (IAS) and the
party's usual practices.

      1.8 "Development Plan" and "Core Development Plan" shall have the meanings
set forth in Section 3.3.1 hereof.

      1.9 "Development Program" shall mean activities associated with
development of the Drug Product Candidate for sale as a Drug Product, including
but not limited to (a) preparation for preclinical assessment of the Drug
Product Candidate; (b) formulation and manufacture of the Drug Product Candidate
for use in preclinical studies; (c) preclinical animal studies performed in
preparation for the filing of an IND; (d) manufacture and formulation of the
Drug Product Candidate for clinical trials; (e) planning, implementation,
evaluation, monitoring and management of human clinical trials; (f)
manufacturing process development and scale-up for the commercial manufacture of
Bulk Drug Substance and Drug Product; (g) preparation and submission of
applications for Regulatory Approval; and (h) post-market surveillance of
Indications, as required or agreed as part of Regulatory Approval by any
governmental regulatory authority.

      1.10 "Drug Product" shall mean a finished dosage form which is prepared
from Bulk Drug Substance and is ready for administration to the ultimate
consumer as a pharmaceutical.

      1.11 "Drug Product Candidate" shall mean a Compound identified on Schedule
1.11 hereof as to which SERONO has exercised the Development Election under the
Research Agreement and which has become a subject of this Agreement in
accordance with the provisions thereof.

      1.12 "Effective Date" shall mean the effective date of this Agreement as
set forth on the first page hereof.

      1.13 "EMEA" shall mean the European Agency for the Evaluation of Medicinal
Products.

      1.14 "European Union" shall mean those countries which are now or later
become members of the European Union.

      1.15 "Exclusive Territory" shall mean all countries of the Territory other
than the countries of North America.

      1.16 "Far East" shall mean all countries set forth on Schedule 1.16
hereof.

      1.17 "First Commercial Sale" shall mean the first sale of the Drug Product
by SERONO or an Affiliate or sublicensee of SERONO in a country in the Territory
following Regulatory Approval of the Drug Product in that country, or if no such
Regulatory Approval or similar marketing approval is required, the date upon
which the Drug Product is first sold in such

 License, Development and Commercialization Agreement -- Confidential -- Page 3
<PAGE>

country by SERONO or an Affiliate or sublicensee of SERONO pursuant to a plan of
commercial launch.

      1.18 "FDA" shall mean the United States Food and Drug Administration.

      1.19 "ICE" shall mean [****************]

      1.20 "Indication" shall mean a generally acknowledged disease or
condition, a significant manifestation of a disease or condition, or symptom
associated with a disease or syndrome for which use of the Drug Product is
indicated, as would be identified in the Drug Product's label under applicable
FDA regulations or the foreign equivalent thereof.

      1.21 "IND" shall mean the investigational new drug application relating to
the Drug Product Candidate filed with the FDA pursuant to 21 C.F.R. Part 312,
including any amendments thereto. References herein to IND shall include, to the
extent applicable, any comparable filing(s) made with a Regulatory Authority in
other countries in the Territory (such as a clinical trial exemption (CTX) in
the European Union).

      1.22 "JDC" shall have the meaning set forth in Section 3.2 hereof.

      1.23 "JMC" shall have the meaning set forth in Section 5.2 hereof.

      1.24 "Joint Know-How" shall have the meaning set forth in Section 8.1
hereof.

      1.25 "Joint Patents" shall have the meaning set forth in Section 8.1
hereof.

      1.26 "Know-How" shall mean all data, technical information, know-how,
inventions, discoveries, trade secrets, processes, techniques, materials,
compositions, methods, formulas or improvements, whether (i) invented,
discovered or developed by either party hereto or its Affiliates under a
Development Program hereunder, (ii) invented, discovered or developed by VERTEX
or its Affiliates under the Research Program under the Research Agreement, (iii)
invented, discovered or developed by VERTEX prior to the Effective Date of the
Research Agreement in the course of a research program directed toward the
discovery of Caspase inhibitors, (iv) otherwise invented, discovered or
developed, and Controlled, by VERTEX or its Affiliates; or (v) Controlled by
VERTEX or its Affiliates pursuant to a license or other grant of right, title or
interest from its Far East collaborator, SERONO or a Third Party, and whether or
not patentable or confidential, that relate to the development, manufacture,
use, sale, offer for sale or import of any Bulk Drug Substance, Drug Product
Candidate or Drug Product, or a formulation or prodrug thereof; provided
however, that the term "Know-How" shall not apply to VERTEX's general drug
design technology, whether in software or hardware, tangible or intangible,
form.

      1.27 "Manufacturing Cost" shall mean [**********************************].

 License, Development and Commercialization Agreement -- Confidential -- Page 4
<PAGE>

      1.28 "Net Sales" with respect to the Drug Product shall mean [************
********************************************************************************
********************************************************************************
***********************]

            (a) [***************************************************************
***********************************************************************]

            (b) [***************************************************************
***********************************************************************];

            (c) [***************************************************************
**********************************************************************]

[*******************************************************************************
********************************************************************************
**********************************]

      1.29 "North America" shall mean the United States and Canada.

      1.30 "North American Joint Venture" shall have the meaning set forth in
Section 5.2.

      1.31 "Patents" shall mean all existing patents and patent applications and
all patent applications hereafter filed, including any continuation,
continuation-in-part, division, provisional or any substitute applications, any
patent issued with respect to any such patent applications, any reissue,
reexamination, renewal or extension (including any supplementary protection
certificate) of any such patent, and any confirmation patent or registration
patent or patent of addition based on any such patent, and all foreign
counterparts of any of the foregoing.

      1.32 "Person" shall mean any individual, corporation, partnership,
association. joint-stock company, trust, unincorporated organization or
government or political subdivision thereof.

      1.33 "Phase I Clinical Trial" shall mean an initial human clinical trial
conducted for inclusion in (i) that portion of the FDA submission and approval
process which provides for the initial trial of the Drug Product Candidate in a
small number of subjects, to establish the safety profile of the Drug Product
Candidate and to collect initial data on its pharmacokinetics and
pharmacological effects, as more fully defined in 21 C.F.R. ss. 312.21(a), and
(ii) equivalent submissions with similar requirements in other countries in the
Territory.

      1.34 "Phase II Clinical Trial" shall mean shall mean a human clinical
trial conducted for inclusion in (i) that portion of the FDA submission and
approval process which provides for trials of the Drug Product Candidate on a
limited number of patients for the purposes of collecting data on dosages,
evaluating safety and collecting preliminary information regarding efficacy in

 License, Development and Commercialization Agreement -- Confidential -- Page 5
<PAGE>

the proposed therapeutic Indication, as more fully defined in 21 C.F.R.
ss.312.21(b), and (ii) equivalent submissions with similar requirements in other
countries in the Territory.

      1.35 "Phase III Clinical Trial" shall mean a human clinical trial
conducted for inclusion in (i) that portion of the FDA submission and approval
process which provides for the continued trials of the Drug Product Candidate on
sufficient numbers of patients to generate safety and efficacy data to support
Regulatory Approval in the proposed therapeutic Indication, as more fully
defined in 21 C.F.R. ss. 312.21(c), and (ii) equivalent submissions with similar
requirements in other countries in the Territory

      1.36 "Regulatory Approval" shall mean, with respect to any country, all
authorizations by the appropriate governmental entity or entities necessary for
commercial sale of the Drug Product in that country including, without
limitation and where applicable, approval of labeling, price, reimbursement and
manufacturing. "Regulatory Approval" in the United States shall mean final
approval of a new drug application pursuant to 21 C.F.R. ss. 314 (or any
successor regulation having the same purpose or effect), permitting marketing of
the Drug Product in interstate commerce in the United States. "Regulatory
Approval" in the European Union shall mean final approval of a Marketing
Authorization Application pursuant to Council Directive 75/319/EEC, as amended,
or Council Regulation 2309/93/EEC, as amended, or pursuant to any successor
regulation having the same purpose or effect.

      1.37 "Research Agreement" shall mean that certain Research Agreement
between VERTEX and SERONO dated December 11, 2000.

      1.38 "Second Opportunity" shall mean the second opportunity for SERONO to
exercise its Development Election with respect to a Refused Candidate as set
forth in Section 3.3 of the Research Agreement.

      1.39 "SERONO Know-How" shall mean all Know-How Controlled by SERONO or any
of its Affiliate.

      1.40 "SERONO Patents" shall mean all Patents Controlled by SERONO or any
of its Affiliates claiming Bulk Drug Substance, the Drug Product Candidate or
the Drug Product, or a formulation or prodrug thereof, or a method of making or
using Bulk Drug Substance, the Drug Product Candidate or the Drug Product, or a
formulation or prodrug thereof, or an improvement to the subject matter of a
Patent covering any of the foregoing, that is invented under the Development
Program hereunder. A list of SERONO Patents is appended hereto as Schedule 1.40
and will be updated periodically to reflect additions thereto during the term of
this Agreement.

 License, Development and Commercialization Agreement -- Confidential -- Page 6
<PAGE>

      1.41 "SERONO Technology" shall mean all SERONO Patents, all SERONO
Know-How and SERONO's and its Affiliates' right, title and interest in Joint
Patents and Joint Know-How which is applied by SERONO to the development,
manufacture or use of Bulk Drug Substance, the Drug Product Candidate or the
Drug Product.

      1.42 "Technology" shall mean VERTEX Technology and SERONO Technology.

      1.43 "Territory" shall mean all countries of the world except for the
countries of the Far East identified as such on Schedule 1.16 hereto.

      1.44 "Third Party" shall mean any person or entity which is not a party or
an Affiliate of any party to this Agreement.

      1.45 "Valid Patent Claim" shall mean either a claim of an issued and
unexpired Patent which has not lapsed, been revoked or abandoned or held
permanently unenforceable or invalid by a decision of a court or other
governmental agency of competent jurisdiction, unappealable or unappealed within
the time allowed for appeal, and which has not been disclaimed, denied or
admitted to be invalid or unenforceable through reissue, reexamination,
disclaimer or otherwise.

      1.46 "VERTEX Know-How" shall mean all Know-How Controlled by VERTEX or any
of its Affiliates.

      1.47 "VERTEX Patents" shall mean all Patents Controlled by VERTEX or any
of its Affiliates claiming Bulk Drug Substance, the Drug Product Candidate or
the Drug Product, or a formulation or prodrug thereof, or a method of making or
using Bulk Drug Substance, the Drug Product Candidate or the Drug Product, or a
formulation or prodrug thereof, or an improvement to the subject matter of a
Patent covering any of the foregoing, that is (i) invented by VERTEX or its
Affiliates prior to the Effective Date of the Research Agreement, (ii) invented
under the Research Program under the Research Agreement or under a Development
Program hereunder, (iii) otherwise invented and Controlled by VERTEX or its
Affiliates, or (iv) Controlled by VERTEX or its Affiliates pursuant to a license
or other grant of right, title or interest from its Far East collaborator,
SERONO or a Third Party. A list of VERTEX Patents is appended hereto as Schedule
1.47 and will be updated periodically to reflect additions thereto during the
term of this Agreement.

      1.48 "VERTEX Technology" shall mean all VERTEX Patents, all VERTEX
Know-How and VERTEX's and its Affiliates' right, title and interest in Joint
Patents and Joint Know-How.

 License, Development and Commercialization Agreement -- Confidential -- Page 7
<PAGE>

                             ARTICLE II -- LICENSE

      2.1 Grant to SERONO.

            2.1.1 License. Subject to the other provisions of this Agreement,
VERTEX hereby grants to SERONO a license (or sublicense, as appropriate) in the
Territory under the VERTEX Technology, exclusive in the Exclusive Territory, and
co-exclusive in North America with VERTEX and/or the North American Joint
Venture, with the right to sublicense (after prior consultation with VERTEX), to
exercise its rights and fulfill its obligations under this Agreement and to
research, develop, manufacture, have manufactured, use, sell, offer to sell and
import Bulk Drug Substance (subject to VERTEX's exclusive manufacturing rights
under Article IV and Section 6.2 hereof), Drug Product Candidates and Drug
Products. Subject to the provisions of this Agreement, VERTEX shall have the
right to use VERTEX Technology to fulfill its obligations and exercise its
rights under this Agreement, including but not limited to its exclusive rights
to manufacture and supply Bulk Drug Substance under Article IV and Section 6.2
hereof, its rights under Section 3.6 hereof, and any rights and obligations with
respect to the North American Joint Venture. VERTEX retains all rights to VERTEX
Technology except to the extent explicitly granted to SERONO hereunder.

            2.1.2 Sublicensees and Subcontractors. SERONO shall guarantee and be
responsible to VERTEX for the performance of any of its sublicensees or
subcontractors under any sublicense or other agreement with respect to the
rights granted to SERONO by VERTEX and the obligations assumed by SERONO
hereunder. SERONO shall not permit any subcontractors or sublicensees to use
VERTEX Technology without provisions safeguarding confidentiality equivalent to
those provided in this Agreement. Any such provisions will allow VERTEX the
right to directly enforce the obligations of confidentiality with respect to
VERTEX Technology in the possession of the subcontractor or sublicensee.

      2.2 Grant to VERTEX.

            2.2.1 License. Subject to the other provisions of this Agreement,
SERONO hereby grants to VERTEX (i) a royalty-free non-exclusive, worldwide
license (or sublicense, as appropriate) under the SERONO Technology, with the
right to sublicense, to exercise its rights and fulfill its obligations under
this Agreement and to meet its obligations to its collaborator in the Far East
with respect to the manufacture, development and sale of Bulk Drug Substance,
Drug Product Candidates and Drug Product in the Far East, and (ii) to the extent
not inconsistent with SERONO's exclusive rights in the Exclusive Territory and
co-exclusive rights in North America, to research, develop, manufacture, have
manufactured, use, sell, offer to sell and import Bulk Drug Substance, Drug
Product Candidates and Drug Products, a royalty-free non-exclusive, worldwide
license (or sublicense, as appropriate), with the right to sublicense, to
practice and

 License, Development and Commercialization Agreement -- Confidential -- Page 8
<PAGE>

use the SERONO Technology. SERONO retains all rights to SERONO Technology except
to the extent explicitly granted to VERTEX hereunder.

            2.2.2 Sublicensees and Subcontractors. VERTEX shall guarantee and be
responsible to SERONO for the performance of any of its sublicensees or
subcontractors under any sublicense or other agreement with respect to the
rights granted to VERTEX by SERONO and the obligations assumed by VERTEX
hereunder. VERTEX shall not permit any subcontractors or sublicensees to use
SERONO Technology without provisions safeguarding confidentiality equivalent to
those provided in this Agreement. Any such provisions will allow SERONO the
right to directly enforce the obligations of confidentiality with respect to
SERONO Technology in the possession of the subcontractor or sublicensee.

      2.3 Information Sharing.

            2.3.1 Between Parties. Each party shall deliver to the other all
Know-How Controlled by it or its Affiliates and requested by the other party
from time to time, pursuant to the exercise by such other party of the licenses
granted hereunder. The Know-How shall be delivered in a form as shall reasonably
facilitate the use of such Know-How and shall include copies of all Patents and
all other manifestations of the intellectual property embodied in the Bulk Drug
Substance, Drug Product Candidate or Drug Product, or formulation or prodrug
thereof, whether in human or machine readable form.

            2.3.2 With VERTEX's Far East Collaborator. VERTEX's agreement with
its Far East collaborator for development and sale of drug product candidates
and drug products in the Far East obligates each party to share with the other
party information which is relevant to the development of such drug product
candidates and drug products. That information includes raw data from
development and clinical trials of Compounds in the Far East and in the rest of
the world, information relating to manufacture of drug product candidates and
drug products and copies of material written communications between VERTEX and
its licensees (including its Far East collaborator), on the one hand, and
regulatory authorities, on the other, in the Far East and in the rest of the
world relating to such drug product candidates and drug products. The agreement
also provides that VERTEX and its licensees outside the Far East will have the
right to cross reference, in their regulatory filings made outside the Far East
covering Drug Product Candidates or Drug Products, all regulatory filings, and
information contained therein, made in the Far East relative to such Drug
Product Candidates or Drug Products developed there by VERTEX's Far East
collaborator; provided that a reciprocal right is made available to VERTEX's Far
East collaborator, in connection with comparable regulatory filings in the Far
East, by VERTEX and its licensees outside the Far East. VERTEX will share with
SERONO information received by it from its Far East collaborator pursuant to the
foregoing, and will provide SERONO

 License, Development and Commercialization Agreement -- Confidential -- Page 9
<PAGE>

with a right to cross-reference in its regulatory filings made in the Territory
regulatory filings made by VERTEX's Far East collaborator in the Far East
relative to the Drug Product Candidate or Drug Product, as provided above, in
consideration of the reciprocal right hereby granted to VERTEX by SERONO
pursuant to the foregoing to share information received by it from SERONO with
VERTEX's Far East collaborator and to permit VERTEX and its Far East
collaborator to cross-reference regulatory filings made by SERONO in the
Territory relative to the Drug Product Candidate or Drug Product in regulatory
filings made by VERTEX or its collaborator in the Far East relative to the Drug
Product Candidate or Drug Product.

                           ARTICLE III -- DEVELOPMENT

      3.1 Commencement of Development Program.

            SERONO and VERTEX shall promptly and diligently commence and pursue
a Development Program with respect to the Drug Product Candidate as soon as
practicable after exercise by SERONO of its Development Election, as set forth
in the Research Agreement, with respect to that Drug Product Candidate.

      3.2 Joint Development Committee.

            3.2.1 Formation and Responsibilities. Within thirty (30) days of the
Effective Date, VERTEX and SERONO will establish a Joint Development Committee
(the "JDC") made up of equal numbers of VERTEX and SERONO personnel to be
designated from time to time by each party. Each of VERTEX and SERONO shall have
one vote on the JDC. The JDC will be responsible for the preparation and overall
implementation of the Development Program with respect to the Drug Product
Candidate, and may act directly or through such sub-committees as it may deem
appropriate to establish. Meetings of the JDC other than regularly scheduled
quarterly meetings may be held only if a quorum of at least two (2)
representatives of each party participates; except that lack of a quorum shall
not prevent the scheduling and conduct of a meeting by either party after that
party has made good faith but unsuccessful attempts for more than ninety (90)
days to schedule and convene the meeting. The JDC shall meet formally at least
quarterly, or with such other frequency, and at such time and location, as may
be established by the JDC, for the following purposes, among others:

                  (i) To review and, if necessary, revise the Development Plan
as set forth in Section 3.3 below, and to oversee and coordinate the parties'
development activities and the associated development budget;

                  (ii) To assign operational responsibility to VERTEX or SERONO
for the conduct of particular activities specified in the Development Plan;

License, Development and Commercialization Agreement -- Confidential -- Page 10
<PAGE>

                  (iii) To receive and review reports by VERTEX and SERONO,
which shall be prepared by each party and submitted to the other party and to
the JDC on a quarterly basis within thirty (30) days after the end of the
quarter, setting forth in reasonable detail, with supporting data, the results
of work performed during the preceding quarter under the Development Plan by the
party submitting the report;

                  (iv) To assist in coordinating scientific interactions and
resolving disagreements between VERTEX and SERONO during the course of the
Development Program; and

                  (v) To discuss matters relating to Patents claiming Bulk Drug
Substance, the Drug Product Candidate or Drug Product, or methods of using or
making the same, including but not limited to issues of inventorship and
decisions relating to the filing, prosecution and maintenance of those Patents.

            SERONO will prepare the initial draft of an agenda for each JDC
meeting and will submit the draft to VERTEX for comments a reasonable period
before the scheduled meeting date. The party hosting a particular JDC meeting
shall prepare and deliver to the members of the JDC, within thirty (30) days
after the date of each meeting, minutes of such meeting setting forth, among
other things, all decisions of the JDC, and including a summary of the status of
development activities as reported to the JDC. The party not preparing the
minutes may suggest changes or amendments to the minutes, and may provide a
supplement addressing activities at the meeting which are not reported in the
minutes, which shall be distributed to the parties and filed with the meeting
minutes. In case the JDC meets by means of telephone or video conferences, the
responsibility for preparing minutes shall lie with VERTEX.

            3.2.2 Retention of Rights. Notwithstanding the foregoing, each party
shall retain the rights, powers, and discretion expressly granted to it under
this Agreement, and the JDC shall not be delegated or vested with any such
rights, powers or discretion except as expressly provided in this Agreement. The
JDC shall not have the power to amend or modify this Agreement, which may only
be amended or modified as provided in Section 15.14 hereof.

            3.2.3 Decision Making. The objective of the JDC shall be to reach
agreement by consensus on all matters falling within its authority hereunder
within the scope of the Development Plan. However, if the JDC cannot reach
consensus on a particular matter, [*********************************************
********************************************************************************
********************************************************************************
********************************************************************************

License, Development and Commercialization Agreement -- Confidential -- Page 11
<PAGE>

********************************************************************************
***********************************].

      3.3 Development Plan.

            3.3.1 General. The JDC shall oversee the implementation of the
development plan (the "Development Plan") for the Drug Product Candidate which
shall be completed by the JDC within ninety (90) days after the exercise by
SERONO of its Development Election, as set forth in the Research Agreement, with
respect to the Drug Product Candidate, and which shall describe fully the
proposed preclinical studies, toxicology, clinical trials, regulatory plans,
clinical trial and commercial material requirements and any other key elements
of obtaining Regulatory Approval in each country where the Drug Product is to be
marketed. The Development Plan will include, among other things, a plan (the
"Core Development Plan") for the conduct of Core Development Activities, and
will provide for the allocation of development tasks between VERTEX and SERONO.
Each party assigned a development task will, in a timely fashion, prepare a
detailed plan for the accomplishment of that task, including a schedule
therefor, and will submit that plan to the JDC for its review. Development tasks
shall be advanced in parallel rather than serially where practicable and
appropriate, if doing so would be likely to advance the ultimate date of product
approval and launch and is otherwise commercially reasonable.

            3.3.2 Process Development. VERTEX will be responsible for the
development of processes for manufacture of Bulk Drug Substance, and for the
preparation and implementation of a plan to accomplish that task. SERONO will be
responsible for the development of processes for formulation and manufacture of
the Drug Product from Bulk Drug Substance, and for the preparation and
implementation of a plan to accomplish that task. Each party will work with the
JDC to coordinate its plans with those of the other party, with the objective of
ensuring operationally effective and timely integration of the two plans, as
necessary to meet the overall schedule for process development and the supply of
Bulk Drug Substance and Drug Product as set forth in the Development Plan.

      3.4 Development Costs.

            3.4.1 Apportionment. [**********************************************
********************************************************************************
********************************************************************************
********************************************************************************
********************************************************************************
****************************].

License, Development and Commercialization Agreement -- Confidential -- Page 12
<PAGE>

            3.4.2 Audit. Each party shall keep or cause to be kept accurate
records in sufficient detail to enable Core Development Costs to be determined.
Each party, upon the written request and at the expense of the other party, and
in any event not more frequently than once in any calendar year, shall permit an
independent public accountant of national prominence selected by the other
party, and approved by the first party (with approval not to be unreasonably
withheld), to have access during normal business hours to those records of such
party as may be reasonably necessary to verify the accuracy of the cost reports
submitted by such party pursuant to this Section 3.4 in respect of any calendar
year ending not more than three (3) years prior to the date of the
aforementioned written request. The parties shall mutually determine a general
strategy for such review in advance of its conduct. Such accountant shall not
disclose any information except that which should properly be contained in a
cost report required under this Agreement The parties agree that all information
subject to review under this Section 3.4 is confidential and that any reviewing
party shall retain and cause its accountant to retain all such information in
confidence. A party shall not be entitled under this Section 3.4.2 to audit more
than once the records of the other party with respect to any calendar year.

      3.5 Regulatory Matters.

            3.5.1 Regulatory Approvals. Unless otherwise required by law in the
relevant jurisdiction, [********************************************************
**********************************] Each party shall use commercially reasonable
efforts to file for and obtain all necessary Regulatory Approvals for which it
is responsible hereunder within a reasonable period.

            3.5.2 Interaction with Regulatory Agencies. [***********************
********************************************************************************
********************************************************************************
***************]

            3.5.3 Regulatory Reporting. During the term of this Agreement, in
order to comply with applicable regulations of the FDA and other applicable
regulatory agencies, the parties agree that they shall establish procedures for
reporting to the appropriate regulatory agencies any adverse events, technical
complaints or other reportable events that may occur with respect to the
manufacture, supply, use and clinical testing of Bulk Drug Substance, the Drug
Product Candidate or Drug Product hereunder.

      3.6 Assistance Rights.

            If either party (the "First Party") fails unreasonably, other than
as a result of Force Majeure or a failure of the other party to discharge its
obligations hereunder, to carry out the

License, Development and Commercialization Agreement -- Confidential -- Page 13
<PAGE>

Core Development Activities allocated to it under the Core Development Plan in
accordance with the schedule therefor, then the other party may, after ninety
(90) days prior written notice to the First Party, undertake that particular
activity and complete it at its own expense if the First Party has not at such
time begun to carry out such activity in a manner reasonably likely to cure its
default. Such party shall be entitled to reasonable cooperation and assistance
from the First Party to accommodate its efforts, including assignment to such
party of sponsorship of regulatory filings if necessary to permit the exercise
by such party of its rights under this Section 3.6. If any such activity is
properly conducted, conforms to the requirements of the Core Development Plan,
and is used in any part by the First Party to advance development of the Drug
Product Candidate or the Drug Product hereunder, the out-of-pocket cost of
performing that activity will be reimbursed to the party incurring the cost as
promptly as practicable.

      3.7 Conduct of the Development Program.

            3.7.1 Efforts. Both VERTEX and SERONO will use diligent and
commercially reasonable efforts, consistent with the provisions of this
Agreement, the requirements of the Development Plan and sound and reasonable
business practices and judgment, to develop the Drug Product Candidate and
obtain Regulatory Approval, as soon as reasonably practicable, for commercial
sale of the Drug Product in North America and the European Union, devoting the
same degree of attention and diligence that each such party devotes to the
development of its other compounds of comparable commercial potential. VERTEX
and SERONO will each promptly notify the other in writing if it should determine
that development of the Drug Product Candidate or Drug Product is not
technically feasible or commercially justifiable, specifying in reasonable
detail the reasons for that determination.

            3.7.2 Standards. Both parties agree to conduct the Development
Program in accordance with the terms and conditions of this Agreement and in
conformity with generally accepted standards of good laboratory practices and
good clinical practices and with all applicable national, state and local laws,
guidelines, rules and regulations including without limitation the United States
Food, Drug and Cosmetic Act and guidelines, rules and regulations promulgated by
the FDA.

            3.7.3 Records. In conformity with standard pharmaceutical and
biotechnology industry practices and the terms and conditions of this Agreement,
each party shall prepare and maintain complete and accurate written records,
accounts, notes, reports and data with respect to all laboratory work conducted
in the performance of the Development Program. Each party shall prepare and
maintain, or have prepared and maintained, complete and accurate written
records, data and information with respect to all clinical trials performed in
the conduct of the

License, Development and Commercialization Agreement -- Confidential -- Page 14
<PAGE>

Development Plan as required by applicable national, state and local laws,
guidelines, rules and regulations, including without limitation the United
States Food, Drug and Cosmetic Act and guidelines, rules and regulations
promulgated by the FDA.

            3.7.4 Ownership of Technology.

                  (a) No Ownership by Employees. All employees of VERTEX and
SERONO who are expected to participate in the Development Program have signed,
or before any such participation will sign, agreements with VERTEX or SERONO,
respectively, regarding proprietary information and inventions in a form
reasonably considered by the employer and its counsel to assure the employer's
Control of any Technology invented, discovered or developed by such employees.

                  (b) No Ownership by Agents. VERTEX and SERONO shall each enter
into customary agreements with its agents that provide that all of such agents'
right, title and interest in, to and under any Technology invented, discovered
or developed by such agents shall be assigned or licensed to VERTEX or SERONO as
the case may be.

      3.8 Coordination of Far East Development Activities.

            VERTEX will be responsible for coordinating those development
activities being conducted by its collaborator in the Far East with Core
Development Activities being conducted hereunder.

                      ARTICLE IV -- MANUFACTURE AND SUPPLY

      4.1 Supply of Bulk Drug Substance and Drug Product for Development.

            VERTEX will be responsible for manufacturing and supply of all Bulk
Drug Substance, and SERONO will be responsible for preparing the Drug Product
from Bulk Drug Substance, in each case as necessary for the conduct of the
Development Plan in the Territory. [********************************************
********************************************************************************
*******************************************************************************]
Supply of Bulk Drug Substance and Drug Product for development purposes shall be
undertaken pursuant to the provisions of a supply agreement to be negotiated by
the parties, including such customary representations, warranties, covenants and
conditions as are necessary or appropriate for transactions of this type, not
inconsistent with the terms and conditions hereof and satisfactory in form and
substance to the parties and their legal advisors.

License, Development and Commercialization Agreement -- Confidential -- Page 15
<PAGE>

      4.2 Supply of Bulk Drug Substance and Drug Product for Commercial
Purposes.

            VERTEX will supply and SERONO shall purchase from VERTEX all of
SERONO's requirements for Bulk Drug Substance for manufacture of Drug Product
sold in the Exclusive Territory, pursuant to terms and conditions set forth in
Section 6.2 hereof. In North America, pursuant to the North American Joint
Venture as described in Section 5.2, VERTEX will supply all requirements for
Bulk Drug Substance, and SERONO will supply all requirements for Drug Product
formulated from Bulk Drug Substance provided by VERTEX,
[************************ ***************************] and otherwise pursuant to
the provisions of a supply agreement to be negotiated by the parties, including
such customary representations, warranties, covenants and conditions as are
necessary or appropriate for transactions of this type, not inconsistent with
the terms and conditions hereof and satisfactory in form and substance to the
parties and their legal advisors.

      4.3 Manufacturing Technology.

            Manufacturing technology not developed under the Research Program or
a Development Program, which belongs to one party and which would be useful to
the other party in discharging its manufacturing obligations hereunder, shall be
made available to the manufacturing party for that purpose, subject to
negotiation of a reasonable royalty or other compensation arrangement. If either
party (a "Contracting Party") engages an Affiliate or a Third Party in the
course of the Development Program to provide assistance to the Contracting Party
in the development of processes useful for the manufacture of Bulk Drug
Substance or Drug Product, the Contracting Party will ensure that any processes
belonging to that Affiliate or Third Party and made available to the Contracting
Party will also be made available to the other party on the same terms offered
to the Contracting Party.

      4.4 Packaging.

            SERONO will be responsible for packaging the Drug Product Candidate
and Drug Product for development purposes and for commercial sale.

      4.5 Subcontracting.

            VERTEX shall not contract with any Third Party to manufacture Bulk
Drug Substance without prior consultation and review with SERONO and will not
contract with any such Third Party which does not have a demonstrated ability to
deliver high quality pharmaceutical products on a timely basis at volumes likely
to be required by VERTEX and SERONO. VERTEX will notify SERONO of its intention
to subcontract manufacture of Bulk Drug Substance not less than
[***********************************] prior to concluding a manufacturing

License, Development and Commercialization Agreement -- Confidential -- Page 16
<PAGE>

arrangement with any Third Party. [*********************************************
*****************************************************]

                         ARTICLE V -- COMMERCIALIZATION

      5.1 Global Marketing and Sales.

            As set forth in Section 2.1 above, SERONO has exclusive rights to
the Drug Product in the Exclusive Territory, and the parties have co-exclusive
rights to the Drug Product in North America pursuant to the North American Joint
Venture to be established under Section 5.2 below. SERONO will prepare a
detailed marketing plan for the launch of the Drug Product in the Exclusive
Territory, and will provide the plan to VERTEX not later than [***************]
after submission of the initial application for Regulatory Approval of the Drug
Product anywhere in the Exclusive Territory. The parties will attempt to
coordinate their marketing activities relative to the Drug Product in North
America and the Exclusive Territory.

      5.2 Marketing in North America

            VERTEX and SERONO will market and sell the Drug Product in North
America under the terms of a joint venture or other mutually agreeable structure
(the "North American Joint Venture") which shall be negotiated between the
parties in good faith and established within [**********************************
************************************] The documentation for the North American
Joint Venture will incorporate such customary representations, warranties,
covenants and conditions as are necessary or appropriate for transactions of
this type, will be satisfactory in form and substance to the parties and their
legal advisors, and will also incorporate all of the principles set forth below.

            (a) Joint Marketing Committee. VERTEX and SERONO will form a Joint
Marketing Committee ("JMC") which will include an equal number of
representatives designated by each party. At least one of SERONO's
representatives shall also be a member of the group within SERONO responsible
for development and implementation of SERONO's marketing plan for the Drug
Product in the Exclusive Territory, and therefore capable of assisting in the
coordination of the parties' marketing efforts throughout the Territory. The JMC
will be the principal organization through which the marketing of the Drug
Product in North America is planned, administered, evaluated and effected. The
JMC may choose to designate a Committee Chair. In such event, if one party is
making a contribution to Direct Marketing Costs (as defined in Section 5.2(c)
below) for any year which is disproportionately greater than the contribution of
the other party, the former party shall be entitled to designate the Chair for
that year. Otherwise, the right

License, Development and Commercialization Agreement -- Confidential -- Page 17
<PAGE>

to designate the Chair shall rotate from party to party on an annual basis. The
JMC will periodically meet as necessary, depending on the level of marketing
activity at the time; provided that either party may request at any time that a
meeting of the JMC be scheduled and in such event the parties shall cooperate in
good faith to hold the meeting at a mutually convenient place and time (but in
any event within [*******************] after the original request). The JMC will
prepare and oversee the implementation of a detailed marketing plan (the "North
American Marketing Plan") for the launch of the Drug Product in North America.
The North American Marketing Plan will contain among other things budgets,
schedules, product positioning, pricing, market research plans and results,
sales force deployment, information concerning competition and competitors, and
other customary planning and marketing material with respect to marketing and
launch of the Drug Product. The North American Marketing Plan will be
periodically updated to reflect changes in market information, sales performance
and forecasts, sales force deployment, and information concerning competition
and competitors.

            (b) Profit-sharing. VERTEX and SERONO will share equally in
Operating Profits and Operating Losses from sales of the Drug Product in North
America. [**********************************************************************
********************************************************************************
*****************************] The JMC will direct payment by one party to the
other of any amount necessary to equalize each party's share of Operating
Profits or Operating Losses for the reporting period; provided that neither
party will be reimbursed for any portion of its actual Allowable Expenses
incurred in any year which exceeds [*******************************] of its
budgeted share of Allowable Expenses for that year under the North American
Marketing Plan, unless such excess amount has been approved in advance by the
JMC. The parties respective shares of Operating Profits may be subject to
adjustment pursuant to Section 5.2(f) below.

            (c) Roles and Responsibilities of the Parties. The North American
Joint Venture will provide each party the opportunity
[*******************************************************************************
********************************************************************************
**************************************] In allocating tasks between VERTEX and
SERONO, the JMC will attempt to assign roles to each party which are reasonable
in relation to that party's capabilities and consistent with relevant marketing
requirements. As used in this Agreement, [**************************************
********************************************************************************
*********************] As part of the North American Joint Venture to be
negotiated between the Parties pursuant to this Section 5.2, the Parties will
negotiate in good faith how Direct Marketing

License, Development and Commercialization Agreement -- Confidential -- Page 18
<PAGE>

Costs will be allocated where the Drug Product is Detailed together with another
product or products.

            (d) Operational Issues. Except for those matters which are the
responsibility of the JMC or as otherwise provided in this Agreement, each party
will be free to make its own decisions concerning the Detailing of the Drug
Product by its sales force in North America. The role of the JMC in this respect
shall be one of coordination, such that the individual efforts of each party may
be maximized and that duplication of effort may be kept to a minimum.

            (e) Booking of Sales. Customer orders for the Drug Product in North
America will be credited by the North American Joint Venture or as the parties
may hereafter agree.

            (f) Revision of Profit-sharing Formula. The parties acknowledge that
in the future one party may wish to commit substantially greater financial or
other resources than the other party to the sales and marketing of the Drug
Product in North America. In such event, if VERTEX and SERONO shall disagree on
the total amount of the annual proposed budget for years subsequent to the first
full calendar year following the First Commercial Sale of the Drug Product, and
[*******************************************************************************
********************************************************************************
******************]

            (g) Training. The parties will consult on training programs to
ensure a consistent, focused promotional strategy for the Drug Product.

            (h) Advertising. Neither party shall engage in any advertising or
use any label, package, literature or other written material in connection with
the promotion of the Drug Product in North America unless the specific form and
content is approved by the JMC.

            (i) Supply of Bulk Drug Substance and Drug Product. VERTEX shall
supply Bulk Drug Substance to SERONO for manufacture into Drug Product for sale
in North America, and SERONO shall manufacture Drug Product from Bulk Drug
Substance supplied by VERTEX, in each case for compensation
[*********************************].

      5.3 Co-labeling.

            5.3.1 North America. To the extent not prohibited by law or
regulation and subject to Regulatory Approval, the Drug Product (including
labels, packaging and inserts) and all promotional materials for the same sold
in North America will bear the company names and logos of both SERONO and VERTEX
(and/or, the name and logo of the North American Joint Venture or as the parties
may otherwise agree) with equal prominence (including equal sized type face), or
if equal prominence is prohibited by law, with such relative prominence as may
otherwise be

License, Development and Commercialization Agreement -- Confidential -- Page 19
<PAGE>

permitted by law. Trademarks used in North America will be jointly owned by
VERTEX and SERONO, or by the North American Joint Venture, or as the parties may
otherwise agree.

            5.3.2 European Union. If not prohibited under regulations of the
European Union or any of its agencies responsible for Regulatory Approval of
pharmaceuticals, the labels, packaging and inserts for the Drug Product packaged
for sale in the European Union will bear the company names and logos of both
SERONO and VERTEX with equal prominence (including equal sized type face) or if
equal prominence is not permitted under applicable regulations with such
relative prominence as may in fact be permitted. If the foregoing is prohibited
under applicable regulations of the European Union, then to the extent not
prohibited under applicable regulations, the labels, packaging and inserts for
the Drug Product will bear VERTEX's company name and logo with the term "under
license from." SERONO will also determine the right of VERTEX under relevant
regulations of the European Union to be referenced, and its name and logo
featured, in any promotional material relative to the Drug Product used in the
European Union. VERTEX's name and logo will be included, in the manner provided
above relative to packaging and labeling, if the relevant regulations do not
prohibit it. SERONO will permit VERTEX to review all material regulatory filings
in the Exclusive Territory which relate to product labeling, and all proposed
labels, packaging, package inserts and promotional materials required under the
foregoing provisions to bear VERTEX's name, prior to the filing of any such
material with any regulatory authority.

            5.3.3 Communications. SERONO will immediately inform VERTEX of any
material regulatory communications received by SERONO or its agents which might
operate to restrict VERTEX's labeling rights under this section, and of any
advice which it receives from its advisors with respect to any such
restrictions.

      5.4 Due Diligence.

            Following the First Commercial Sale of the Drug Product and until
the expiration of this Agreement, SERONO shall use diligent and commercially
reasonable efforts to keep the Drug Product reasonably available to the public
in the Major Market countries, devoting the same degree of attention and
diligence to such efforts that it devotes to such activities for other of its
products of comparable market potential. For purposes of this Section 5.4,
"Major Markets" shall mean the countries of the European Union, Brazil and
Argentina. SERONO shall promptly notify VERTEX if it shall determine that the
marketing and sale of the Drug Product in any Major Market country is not
commercially reasonable or economically profitable or if for other unforeseen
reasons further commercial support of the Drug Product in any country is no
longer prudent or practical.

License, Development and Commercialization Agreement -- Confidential -- Page 20
<PAGE>

                             ARTICLE VI -- PAYMENTS

      6.1 Development Payments by SERONO.

            6.1.1 Payments. In consideration of the grant of the license set
forth in Section 2.1 hereof, SERONO will make the following payments to VERTEX
upon the achievement of any of the following milestones with respect to the Drug
Product Candidate or Drug Product in the Territory, upon the further terms and
conditions set forth below.

                      Milestone                            Payment
                      ---------                            -------
        1.   [*******************]                  [*******************]
        2.   [************************].            [*******************]
        3.   [************************].            [*******************]
        4.   [************************].            [*******************]
        5.   [*******************]
             [***************************]          [*******************]
             [***************************]          [*******************]
        6.   [*******************************].
                                                    [*****************]
             [**********************]
                                                    [****************]
             [**********************]               ___________
                                                    [*************]

            6.1.2 Payments to be Made Only Once. Milestone payments are payable
only once with respect to the Drug Product Candidate and Drug Product. In
addition, if the Drug Product Candidate has the same active metabolite as a drug
product candidate being developed under a separate License Agreement (as defined
in the Research Agreement) between the parties (the "Alternative Candidate"),
then the Drug Product Candidate shall be deemed a "Prodrug" of the Alternative
Candidate. If the Prodrug is being developed hereunder for one or more
Indications for which it is not commercially or scientifically feasible to
develop the Alternative Candidate, then the Prodrug shall be considered a
separate drug product candidate from the Alternative Candidate, and therefore
milestones may be collected in connection with its development hereunder.
Milestones shall not otherwise be payable with respect to the Prodrug if
comparable milestones have previously been paid in connection with the
development of the Alternative Candidate pursuant to the separate License
Agreement between the parties. If any milestone is achieved with respect to the
development of the Drug Product Candidate or Drug Product, any previously
unpaid, lower numbered milestone for the Drug Product Candidate or Drug Product
will become immediately due and payable; provided that milestone 5.a. with
respect

License, Development and Commercialization Agreement -- Confidential -- Page 21
<PAGE>

to the Drug Product will not be payable solely by reason of attainment of
milestone 6.b. with respect to the Drug Product, and similarly, milestone 5.b.
will not be payable solely by reason of the attainment of milestone 6.a.

            6.1.3 Timing and Method of Payments. Milestone payments shall be
made on or before the [******************] following the occurrence of the event
giving rise to the milestone payment obligation hereunder; provided that the
first milestone payment referenced above with respect to the Drug Product
Candidate shall be due and payable within [**************] of SERONO's receipt
from VERTEX of an executed original of this Agreement. All payments shall be
made by wire transfer in United States dollars to the credit of such bank
account as may be designated by VERTEX in writing to SERONO from time to time.
Any payment which falls due on a date which is a Saturday, Sunday or a legal
holiday in the Commonwealth of Massachusetts may be made on the next succeeding
day which is not a Saturday, Sunday or a legal holiday in the Commonwealth of
Massachusetts.

            6.1.4 Substitute Drug Product Candidate or Drug Product. If the Drug
Product Candidate or Drug Product is developed to replace a drug product
candidate or drug product being developed for the same Indication or Indications
under a separate License Agreement (as defined in the Research Agreement)
between the parties and such other drug product candidate or drug product has
been abandoned during the term of this Agreement for any scientific or medical
reasons after any one or more comparable milestone payments under such License
Agreement have been made, then no milestone payment shall be required hereunder
with respect to the Drug Product Candidate or Drug Product if such comparable
milestone payment has already been made with respect to the abandoned drug
product candidate or drug product.

      6.2 Commercial Supply Price.

            6.2.1 Purchase of Bulk Drug Substance. Except as otherwise provided
herein, SERONO, its Affiliates and sublicensees shall purchase from VERTEX all
of their respective requirements of Bulk Drug Substance for manufacture of Drug
Product for sale in the Exclusive Territory.

            6.2.2 Supply Price. [***********************************************
**********************************]

      [*************************************************************************
**********************************]

      [****************]

                  [****************************************************
                  **************************]

License, Development and Commercialization Agreement -- Confidential -- Page 22
<PAGE>

                  [****************************************************
                  ************************]

                  [***************************************************
                  **************************]

      [***************************************************]

[*******************************************************************]

            6.2.3 Payment. The supply price for each unit of Bulk Drug Substance
purchased by SERONO from VERTEX under this Section 6.2 shall initially be
calculated during any year based on [*******************************************
*********************************], which shall be provided by SERONO to VERTEX
within [********** ***************] prior to commencement of that year.
Forecasts shall be updated quarterly to reflect actual experience and
[********************************************************************
********************************************************************************
*****************************] Payments due to VERTEX based upon
[**********************] shall be made within
[*********************************] of receipt from VERTEX of an invoice for
Bulk Drug Substance purchased by SERONO under the terms of the Supply Agreement
described in Section 6.2.6 hereof,
and[****************************************************************************
********************************************************************************
*******************]

            6.2.4 Adjustment to Supply Price. If in any country no Valid Patent
Claims of a VERTEX Patent or a Joint Patent claiming the Drug Product exist,
then [**************************************************************************
********************************************************************************
***********************]

            6.2.5 Third Party Manufacture. Subject to the terms of Section 4.5
hereof, VERTEX may contract with any Third Party as a manufacturing
subcontractor.

            6.2.6 Bulk Drug Substance Supply Terms. All Bulk Drug Substance
manufactured by VERTEX for SERONO hereunder shall be supplied to SERONO (for
formulation and packaging) pursuant to the terms of a supply agreement to be
negotiated by the parties and containing such customary representations,
warranties, covenants and conditions as are necessary or appropriate for
transactions of this type, not inconsistent with the terms and conditions hereof
and satisfactory in form and substance to the parties and their legal advisors.

License, Development and Commercialization Agreement -- Confidential -- Page 23
<PAGE>

      6.3 Sales Reports.

            6.3.1 Reports. During the term of this Agreement and after the First
Commercial Sale of the Drug Product in the Exclusive Territory, SERONO shall
furnish or cause to be furnished to VERTEX on a quarterly basis a written report
covering such calendar quarter showing (i) the Net Sales of the Drug Product in
each country in the Exclusive Territory during such calendar quarter by SERONO
and each Affiliate and sublicensee; (ii) amounts due VERTEX or SERONO under
Section 6.2 hereof with respect to the purchase of Bulk Drug Substance, and the
basis for calculating those amounts due (including unit sales data); (iii)
withholding taxes, if any required by law to be deducted in respect of any such
sales, and evidence of payment thereof; and (iv) dispositions of the Drug
Product other than pursuant to sale for cash. With respect to Net Sales of the
Drug Product received in a currency other than U.S. Dollars, the Net Sales shall
be expressed in the domestic currency of the party making the sale, together
with the U.S. Dollar equivalent of the amount, calculated using SERONO's
then-current standard exchange rate methodology (which shall be specified, along
with the rates actually used) for the translation of foreign currency sales into
U.S. Dollars. In each report the methodology will be disclosed, will be
identical to that employed by SERONO, generally, in its external financial
reporting, as reviewed and approved by its independent auditors and will be in
conformity with SERONO's usual and customary general accounting principles
consistently applied. The foregoing quarterly reports shall be due on or before
the thirtieth (30th) day following the close of each calendar quarter. SERONO
will also provide VERTEX, within ten (10) business days after the end of each
calendar quarter, with a report showing SERONO's best estimate of Net Sales for
that calendar quarter based on information available to SERONO at the time of
the report.

            6.3.2 Currency. All payments hereunder shall be made in U.S.
Dollars. If at any time legal restrictions prevent the prompt remittance of any
payments with respect to any country of the Exclusive Territory where the Drug
Product is sold, SERONO or its Affiliates or sublicensees shall have the right
and option to make such payments by depositing the amount thereof in local
currency to VERTEX's account in a bank or depository in such country.

            6.3.3 Audit. SERONO shall keep and shall cause to be kept accurate
records in sufficient detail to enable the amounts due hereunder to be
determined and to be verified by VERTEX. Upon the written request of VERTEX, at
VERTEX's expense and not more than once in any calendar year, SERONO shall
permit an independent accountant of national prominence selected by VERTEX, and
approved by SERONO, to have access during normal business hours to those records
of SERONO as may be reasonably necessary to verify the accuracy of the sales
reports furnished by SERONO pursuant to this Section 6.3, in respect of any
calendar year ending not more than two (2) years prior to the date of such
notice. The parties shall mutually

License, Development and Commercialization Agreement -- Confidential -- Page 24
<PAGE>

determine a general strategy for such audit in advance of its conduct. Such
accountant shall not disclose any information except that which should properly
be contained in a sales report required under this Agreement. SERONO shall
include in each sublicense entered into by it pursuant to this Agreement a
provision requiring the sublicensee to keep and maintain adequate records of
sales made pursuant to such sublicense and to grant access to such records by
the aforementioned independent accountant for the reasons specified in this
Section 6.3. Upon the expiration of two (2) years following the end of any
calendar year, the calculation of amounts payable with respect to such calendar
year shall be binding and conclusive upon VERTEX, and SERONO and its Affiliates
and sublicensees shall be released from any liability or accountability with
respect to payments for such year. The report prepared by such independent
accountant, a copy of which shall be sent or otherwise provided to SERONO by
such independent accountant at the same time it is sent or otherwise provided to
VERTEX, shall contain the conclusions of such independent accountant regarding
the audit and will specify that the amounts paid to VERTEX pursuant thereto were
correct or, if incorrect, the amount of any underpayment or overpayment. If such
independent accountant's report shows any underpayment, SERONO shall remit or
shall cause its Affiliates or sublicensees to remit to VERTEX within thirty (30)
days after SERONO' receipt of such report, (i) the amount of such underpayment
and (ii) if such underpayment exceeds ten percent (10%) of the total amount owed
for the calendar year then being audited, the reasonable and necessary fees and
expenses of such independent accountant performing the audit, subject to
reasonable substantiation thereof. Any overpayments shall be fully creditable
against amounts payable in subsequent payment periods or remitted to SERONO, at
SERONO's request. VERTEX agrees that all information subject to review under
this Section 6.3 or under any sublicense agreement is confidential and that
VERTEX shall retain and cause its accountant to retain all such information in
confidence.

            6.3.4 Interest. In case of any delay in payment by one party to the
other hereunder not occasioned by Force Majeure, interest at the rate of
[**************] per month, assessed from the thirty-first (31st) day after the
due date of the payment until the date paid, shall accrue on such payment and
shall be due from such party upon prior written notice.

      6.4 Withholding Tax.

            If during the term of this Agreement, withholding tax should be
required by law to be deducted from any payments required to be made by SERONO
to VERTEX hereunder, SERONO, its Affiliates or sublicensees shall deduct such
withholding tax from such payment and pay it to the proper taxing authority and
evidence of such payment shall be secured and sent to VERTEX within one (1)
month of such payment. The parties shall do all such lawful acts and

License, Development and Commercialization Agreement -- Confidential -- Page 25
<PAGE>

things and sign all such lawful deeds and documents as either party may
reasonably request from the other party to enable SERONO, its Affiliates and/or
sublicensees to take advantage of any applicable legal provision or any double
taxation treaties with the object of paying the sums due to VERTEX hereunder
without withholding any tax.

      6.5 Adjustment in Connection with Development of a [********************].

            6.5.1 VERTEX Sole Development. If VERTEX notifies SERONO pursuant to
the last sentence of Section 3.3.3 of the Research Agreement that it has chosen
to continue development and commercialization of a Refused Candidate which is a
[*******************************************************************************
***********************], then the provisions set forth below shall be
applicable thereafter to the further development and commercialization under
this Agreement of the Drug Product Candidate and Drug Product.

            (a) The Drug Product Candidate and Drug Product shall be developed
and marketed thereafter [*******************************************************
****************************************************************************];

            (b) VERTEX will transition the manufacture of Bulk Drug Substance
incorporated into the Drug Product to SERONO, at VERTEX's cost, by delivering to
SERONO the VERTEX Technology and providing to SERONO the technical support in
connection therewith reasonably necessary to enable SERONO to manufacture the
Bulk Drug Substance in compliance with any and all current Regulatory Approvals.
Such VERTEX Technology shall be delivered to SERONO in such a way as to
communicate it to SERONO promptly, effectively and economically. Until such
transition is completed, VERTEX shall continue to supply Bulk Drug Substance to
SERONO hereunder [**************************];

            (c) The provisions of Article V of this Agreement relating to the
creation and operation of the North American Joint Venture will be inapplicable
to the Drug Product, and any North American Joint Venture already in existence
with respect to the Drug Product shall be dissolved in a reasonable and orderly
manner by agreement of the parties;

            (d) SERONO shall pay to VERTEX an annual royalty hereunder equal to
[***** *********************************************************];

            (e) [***************************************************************
*****************************************************************************];
and

            (f) The parties will act reasonably and in good faith to accomplish
the foregoing as expeditiously as practicable under the circumstances, including
without limitation by executing and delivering any necessary or appropriate
amendments to this Agreement.

License, Development and Commercialization Agreement -- Confidential -- Page 26
<PAGE>

            6.5.2 Joint Development. If SERONO elects to exercise its
Development Election [********************************************************],
then the following provisions shall apply to the development of any
[*************************************************] as to which an application
for Regulatory Approval was not filed in either the United States or the
European Union on the date of exercise of the Development Election. If SERONO
chooses not to continue development of the Reference Compound it will so notify
VERTEX in writing at any time prior to the submission of the first application
for Regulatory Approval with respect to the Reference Compound in either the
United States or the European Union. The notice shall contain a schedule of
[*******************************************************************************
*************************************]. By notice delivered to SERONO within
[*************] after receipt of SERONO's notice, VERTEX may in the alternative
either: (a) elect to concur with SERONO and suspend development of the Reference
Compound, which shall thereafter remain subject to the provisions of this
Agreement except for those provisions which would require continuing development
of the Reference Compound, or (b) terminate this Agreement with respect to the
Reference Compound and acquire all rights to the Reference Compound held by
SERONO under this Agreement. In the event VERTEX chooses alternative (b) above,
it shall pay to SERONO within [*************************************************
**********************************], and SERONO shall use reasonable efforts to
transfer to VERTEX any existing regulatory filings and clinical trials
agreements, and otherwise assist in a smooth transition to VERTEX of the
Development Program relative to the Reference Compound.

                       ARTICLE VII -- REFUSED CANDIDATES
                           AND FINAL SERONO CANDIDATES

      7.1 General.

            If the Drug Product Candidate is a "Refused Candidate" as provided
in Section 3.3 of the Research Agreement, the specific provisions of Section 7.2
shall apply, and if the Drug Product Candidate is a Final SERONO Candidate under
Section 3.4 of the Research Agreement, the specific provisions of Section 7.3
shall apply.

      7.2 Refused Candidate.

            7.2.1 Additional Payment. VERTEX will provide to SERONO as part of
the Development Information (as defined in the Research Agreement) with respect
to the Drug Product Candidate a detailed estimate of the Core Development Costs
incurred by VERTEX with respect to the development of the Drug Product Candidate
as of the date VERTEX provides such Development Information to SERONO (the
"Second Opportunity Costs"). If SERONO has exercised its Development Election
(as defined in the Research Agreement) with respect to the Drug Product
Candidate, it shall pay to VERTEX [*********************************************

License, Development and Commercialization Agreement -- Confidential -- Page 27
<PAGE>

********************************************************************************
********************************************************************************
*************************************].

            7.2.2 Other Payments. Any milestone payments under Section 6.1
hereof which would have become due under this Agreement had the Drug Product
Candidate been selected by SERONO when initially proposed by VERTEX pursuant to
the Research Agreement will be made by SERONO within [***************] of
SERONO's receipt from VERTEX of an executed original of this Agreement.

            7.2.3 [*************************************************************
*********************************]

      7.3 Final SERONO Candidate.

            7.3.1 Development. SERONO shall have the sole right and
responsibility, at its expense, for the development of the Drug Product
Candidate, and the provisions of Article III hereof other than Sections 3.1, 3.7
and 3.8 (which to the extent inconsistent with such rights and responsibilities
of SERONO shall be amended) shall be inapplicable to the Drug Product.

            7.3.2 Supply. SERONO shall have the sole right and responsibility,
at its expense, for the manufacture of all Bulk Drug Substance to meet its needs
in connection with the development and commercial sale of the Drug Product
Candidate; provided, however, that at SERONO's expense, VERTEX will deliver to
SERONO the VERTEX Technology and provide to SERONO the technical support in
connection therewith reasonably necessary to enable SERONO to manufacture Bulk
Drug Substance in compliance with any and all current Regulatory Approvals. Such
VERTEX Technology shall be delivered to SERONO in such a way as to communicate
it to SERONO promptly, effectively and economically. Notwithstanding the
foregoing, at the written request of SERONO, VERTEX will supply SERONO with Bulk
Drug Substance [****************************************************************
*************************************]. Such supply shall be made pursuant to
the provisions of a supply agreement to be negotiated by the parties, including
such customary representations, warranties, covenants and conditions as are
necessary or appropriate for transactions of this type, not inconsistent with
the terms and conditions hereof and satisfactory in form and substance to the
parties and their legal advisors. The provisions of Article IV and Section 6.2
of this Agreement shall be inapplicable to the Drug Product.

            7.3.3 Marketing. SERONO shall have the sole right and
responsibility, at its expense, for selling and marketing the Drug Product
worldwide and the provisions of Section 5.2

License, Development and Commercialization Agreement -- Confidential -- Page 28
<PAGE>

shall be inapplicable to the Drug Product. The provisions of Sections 5.1 and
5.3 hereof to the extent inconsistent with such rights and responsibilities of
SERONO shall be amended.

            7.3.4 Milestones. Each of the milestone payments referenced in
Section 6.1 above and payable in connection with the development of the Drug
Product Candidate or Drug Product [**************************].

            7.3.5 Royalty. SERONO shall pay to VERTEX, pursuant to Section 6.3
hereof (which shall be amended to the extent inconsistent with the provisions of
this Section 7.3), a royalty on Net Sales of the Drug Product equal to:

            (a) [*********************************];

            (b) [****************************************]

            (c) [****************************].

                           ARTICLE VIII -- TECHNOLOGY

      8.1 Ownership.

            All Know-How discovered or developed under a Development Program
hereunder exclusively by either party or its Affiliates (directly or through
others acting on its behalf) shall be owned and Controlled by such party,
subject to the provisions of this Agreement. All Patents claiming Bulk Drug
Substance, the Drug Product Candidate or the Drug Product, or a formulation or
prodrug thereof, invented under a Development Program hereunder by either party
or its Affiliates (directly or through others acting on its behalf) shall be
owned and Controlled by such party, subject to the provisions of this Agreement.
All such Patents and Know-How invented, discovered, or developed, as applicable,
jointly by the parties or their Affiliates (directly or through others acting on
their behalf) shall be owned and Controlled jointly, subject to the provisions
of this Agreement. Inventorship shall be determined in accordance with United
States patent and other applicable laws. Know-How that is owned and Controlled
jointly by the parties or their Affiliates shall be "Joint Know-How" and Patents
that are owned and Controlled jointly by the parties or their Affiliates shall
be "Joint Patents."

      8.2 Patent Procurement and Maintenance.

            VERTEX shall be responsible for the preparation, filing, prosecution
and maintenance of all VERTEX Patents, and any Joint Patents, and SERONO shall
be responsible for the preparation, filing, prosecution and maintenance of all
SERONO Patents. The filing party, with the advice of the other party, shall
determine the countries in which applications will be filed. VERTEX shall
provide draft applications for Joint Patents to SERONO sufficiently in advance
of filing for SERONO to have the opportunity to comment thereon. VERTEX shall
furnish SERONO

License, Development and Commercialization Agreement -- Confidential -- Page 29
<PAGE>

with copies of all substantive communications between VERTEX and applicable
patent offices regarding the Joint Patents. VERTEX and SERONO shall each provide
the JDC with periodic reports listing, by name, any such Patents filed by it in
the United States or the European Union, along with a general summary of the
claims made and the jurisdictions of filing in the Territory. Each party will
provide such assistance as the other party may reasonably request in order to
protect the other party's rights to Patents for which it is responsible under
this Section 8.2.

      8.3 Costs.

            [*******************************************************************
********************************************************************************
*************************]. Either party may at any time elect, by written
notice to the other party, to discontinue support for one or more such Patents
(a "Discontinued Patent") and shall not be responsible for any costs relating to
a Discontinued Patent which are incurred more than sixty (60) days after receipt
of that notice by the other party. In such case, the other party may elect at
its sole discretion to continue preparation, filing, prosecution or maintenance
of the Discontinued Patent at its sole expense. The party so continuing shall
own any such Discontinued Patent, and the party electing to discontinue support
shall execute such documents of transfer or assignment and perform such acts as
may be reasonably necessary to transfer sole ownership of the Discontinued
Patent to the other party and enable that party to file or to continue
prosecution or maintenance of the Discontinued Patent, if the other party elects
to do so. In the event VERTEX elects to discontinue support for a Discontinued
Patent, the license granted to VERTEX by SERONO pursuant to Section 2.2 of this
Agreement shall terminate with respect to that Discontinued Patent.
Discontinuance may be on a country-by-country basis or for a Patent series in
total.

      8.4 Infringement Claims by Third Parties.

            8.4.1 Notice. If the manufacture, import, use, offer to sell or sale
of Bulk Drug Substance, the Drug Product Candidate and/or the Drug Product
results in a claim or reasonable apprehension of a claim against a party hereto
for patent infringement or for inducing or contributing to patent infringement
("Infringement Claim"), the party first having notice of an Infringement Claim
shall promptly notify the other in writing. The notice shall set forth the facts
of the Infringement Claim in reasonable detail.

            8.4.2 Third-Party Licenses. In the event that practicing the
Technology in connection with the manufacture, import, use, offer to sell or
sale of the Drug Product Candidate and/or the Drug Product in any country would
require a license under a Third Party's patent, then SERONO will attempt to
obtain a license under the Third Party's patent, will consult VERTEX

License, Development and Commercialization Agreement -- Confidential -- Page 30
<PAGE>

regarding the terms of such license, and [**************************************
********************************************************************************
*********************************]

            8.4.3 Discontinued Sales, License or Defense of Suit. If the
required license is either unavailable or its terms are unacceptable to SERONO,
then SERONO may elect in its sole discretion to discontinue sales of the Drug
Product in such country or to undertake the defense of a patent infringement
action or the prosecution of a declaratory judgment action with respect to the
Third Party patents. [**********************************************************
********************************************************************************
***********************] No settlement or consent judgment or other voluntary
final disposition of a suit under this Section 8.4 may be entered into without
the joint consent of VERTEX and SERONO (which consent shall not be unreasonably
withheld).

      8.5 Infringement Claims Against Third Parties.

            8.5.1 Protection of Technology. VERTEX and SERONO each agree to take
reasonable actions to protect their respective Technology from infringement and
from unauthorized possession or use.

            8.5.2 Infringement of Technology. If any VERTEX Patents, SERONO
Patents or Joint Patents are infringed or claimed to be invalid or VERTEX
Know-How, SERONO Know-How or Joint Know-How is misappropriated, as the case may
be, by a Third Party, the party to this Agreement first having knowledge of such
infringement, claim or misappropriation, or knowledge of a reasonable
probability of such infringement, claim or misappropriation, shall promptly
notify the other in writing. The notice shall set forth the facts of such
infringement. claim or misappropriation in reasonable detail. The owner of the
Technology, or VERTEX, in the case of joint ownership between the parties
hereto, shall have the primary right, but not the obligation, to institute,
prosecute, and control with its own counsel any action or proceeding with
respect to infringement, claimed invalidity or misappropriation of such
Technology and the other party shall have the right, at its own expense, to be
represented in such action by its own counsel. If the party having the primary
right or responsibility to institute, prosecute, and control such action or
proceeding fails to do so within a period of ninety (90) days after receiving
notice of the infringement, claim or misappropriation, the other party shall
have the right to bring and control any such action or proceeding by counsel of
its own choice, and the party which had the primary responsibility shall have
the right, at its own expense, to be represented in any such action or
proceeding by counsel of its own choice. If one party brings any such action or
proceeding, the second party may be joined as a party plaintiff, and, in case of
joining, the second party agrees to give the first party reasonable assistance
and authority to file and to

License, Development and Commercialization Agreement -- Confidential -- Page 31
<PAGE>

prosecute such suit. In any case the second party shall provide all reasonable
cooperation to the first party in connection with such action or proceeding.
[*******************************************************************************
*******************************************************************************]
No settlement or consent judgment or other voluntary final disposition of a suit
under this Section 8.5 may be entered into without the joint consent of VERTEX
and SERONO (which consent shall not be unreasonably withheld).

      8.6 Notice of Certification.

            VERTEX and SERONO each shall immediately give notice to the other of
any certification filed under the U.S. Drug Price Competition and Patent Term
Restoration Act of 1984 claiming that a VERTEX Patent or a SERONO Patent is
invalid or that any infringement will not arise from the manufacture, use or
sale of any product by a Third Party. If VERTEX decides not to bring
infringement proceedings against the party making such a certification, VERTEX
shall give notice to SERONO of its decision not to bring suit within twenty-one
(21) days after receipt of notice of such certification. SERONO may then, but is
not required to, bring suit against the party that filed the certification. Any
suit by SERONO or VERTEX shall either be in the name of SERONO or in the name of
VERTEX, or jointly by SERONO and VERTEX, as may be required by law. For this
purpose, the party not bringing suit shall execute such legal papers necessary
for the prosecution of such suit as may be reasonably requested by the party
bringing suit.

      8.7 Patent Term Extensions.

            The parties shall cooperate in good faith with each other in gaining
patent term extension wherever applicable to VERTEX Patents and SERONO Patents
covering the Drug Product Candidate or Drug Product. SERONO and VERTEX shall
mutually determine which patents shall be extended. All filings for such
extension shall be made by the party who owns the patent, provided, however,
that in the event that the party who owns the patent elects not to file for an
extension, such party shall (i) inform the other party of its intention not to
file and (ii) grant the other party the right to file for such extension.

      8.8 No Implied Rights.

            Except as expressly provided in this Agreement, no right or license
to use any intellectual property of either party is granted hereunder by
implication or otherwise.

                  ARTICLE IX -- REPRESENTATIONS AND WARRANTIES

      9.1 Representations and Warranties of VERTEX.

            VERTEX represents and warrants to SERONO as follows:

            (a) Authorization. This Agreement has been duly executed and
delivered by VERTEX and constitutes the valid and binding obligation of VERTEX,
enforceable against

License, Development and Commercialization Agreement -- Confidential -- Page 32
<PAGE>

VERTEX in accordance with its terms except as enforceability may be limited by
bankruptcy, fraudulent conveyance, insolvency, reorganization, moratorium and
other laws relating to or affecting creditors' rights generally and by general
equitable principles. The execution, delivery and performance of this Agreement
have been duly authorized by all necessary action on the part of VERTEX, its
officers and directors. The execution, delivery and performance of this
Agreement does not breach, violate, contravene or constitute a default under any
contracts, arrangements or commitments to which VERTEX is a party or by which it
is bound nor does the execution, delivery and performance of this Agreement by
VERTEX violate any order, law or regulation of any court, governmental body or
administrative or other agency having authority over it.

            (b) No Third Party Rights. VERTEX owns or possesses adequate
licenses or other rights to use all VERTEX Technology and to grant the licenses
and rights herein.

            (c) Third Party Patents. Except as disclosed in writing between the
parties to this Agreement or their respective agents, VERTEX is not aware of any
issued patents or pending patent applications that, if issued, would be
infringed by the development, manufacture, use, import, offer to sell or sale of
the Drug Product Candidate, Bulk Drug Substance or Drug Product pursuant to this
Agreement.

      9.2 Representations and Warranties of SERONO.

            SERONO represents and warrants to VERTEX as follows:

            (a) Authorization. This Agreement has been duly executed and
delivered by SERONO and constitutes the valid and binding obligation of SERONO,
enforceable against SERONO in accordance with its terms except as enforceability
may be limited by bankruptcy, fraudulent conveyance, insolvency, reorganization,
moratorium and other laws relating to or affecting creditors' rights generally
and by general equitable principles. The execution, delivery and performance of
this Agreement have been duly authorized by all necessary action on the part of
SERONO, its officers and directors. The execution, delivery and performance of
this Agreement does not breach, violate, contravene or constitute a default
under any contracts, arrangements or commitments to which SERONO is a party or
by which it is bound nor does the execution, delivery and performance of this
Agreement by SERONO violate any order, law or regulation of any court,
governmental body or administrative or other agency having authority over it.

            (b) Third Party Rights. SERONO owns or possesses adequate licenses
or other rights to use all SERONO Technology in accordance with the provisions
of this Agreement and to grant the licenses herein.

License, Development and Commercialization Agreement -- Confidential -- Page 33
<PAGE>

            (c) Third Party Patents. Except as disclosed in writing between the
parties to this Agreement or their respective agents, SERONO is not aware of any
issued patent or pending patent applications that, if issued, would be infringed
by the development, manufacture, use, import, offer to sell or sale of the Drug
Product Candidate, Bulk Drug Substance or Drug Product pursuant to this
Agreement.

                          ARTICLE X -- CONFIDENTIALITY

      10.1 Undertaking.

            Each party shall keep confidential, and other than as provided
herein, shall not use or disclose, directly or indirectly, any trade secrets,
other knowledge, information, documents or materials, owned or Controlled by the
other party, which have been disclosed (in tangible or electronic form or as
evidenced by meeting minutes or similar materials) to such party after the
Effective Date and designated confidential by the disclosing party (any such
information, "Confidential Information"). All Technology and all Confidential
Information under the Research Agreement shall be deemed Confidential
Information. Neither VERTEX nor SERONO shall use such Confidential Information
of the other party for any purpose, including the filing of patent applications
containing such information, without the other party's consent (which shall not
be unreasonably withheld), other than for conducting the Development Program or
as otherwise permitted under this Agreement.

            10.1.1 Nondisclosure and Nonuse. Each party shall take any and all
lawful measures to prevent the unauthorized use and disclosure of such
Confidential Information, and to prevent unauthorized persons or entities from
obtaining or using such Confidential Information.

            10.1.2 Disclosure to Affiliates and Agents. Each party will refrain
from directly or indirectly taking any action which would constitute or
facilitate the unauthorized use or disclosure of such Confidential Information.
Each party may disclose such Confidential Information to its Affiliates, their
officers, employees and agents, to authorized licensees and sublicensees
(including VERTEX's Far East collaborator as provided in Section 2.3.2 hereof),
and to subcontractors in connection with the development of the Drug Product
Candidate or the manufacture of Bulk Drug Substance, or Drug Product, but only
to the extent necessary to enable such parties to perform their obligations
hereunder or under the applicable license, sublicense or subcontract, as the
case may be; provided, that such officers, employees, agents, licensees,
sublicensees and subcontractors have entered into appropriate confidentiality
agreements for secrecy and non-use of such Confidential Information.

            10.1.3 Liability. Each party shall be liable for any unauthorized
use and disclosure of such Confidential Information by its Affiliates, officers,
employees and agents and any such licensees, sublicensees and subcontractors.

License, Development and Commercialization Agreement -- Confidential -- Page 34
<PAGE>

      10.2 Exceptions.

            Notwithstanding the foregoing, the provisions of Section 10.1 hereof
shall not apply to Confidential Information which the receiving party can
conclusively establish:

            (a) has entered the public domain without such party's or its
Affiliates' breach of any obligation owed to the disclosing party;

            (b) is permitted to be disclosed by the prior written consent of the
disclosing party;

            (c) has become known to the receiving party or any of its Affiliates
from a source other than the disclosing party, other than by breach of an
obligation of confidentiality owed to the disclosing party;

            (d) is disclosed by the disclosing party to a Third Party without
restrictions on its disclosure;

            (e) is independently developed by the receiving party or its
Affiliates without use of or reference to the Confidential Information; or

            (f) is required to be disclosed by the receiving party to comply
with applicable laws or regulations or to defend or prosecute litigation, or to
seek Regulatory Approval pursuant to this Agreement, provided that the receiving
party takes reasonable and lawful actions to avoid or minimize the degree of
such disclosure, and to have confidential treatment accorded to any Confidential
Information disclosed, and provides prior written notice to the disclosing party
within a time period sufficiently prior to such disclosure to permit the
disclosing party to apply for a protective order or take other appropriate
action to restrict disclosure. The receiving party shall fully cooperate with
the disclosing party in connection with the disclosing party's efforts to obtain
any such remedy.

      10.3 Publicity.

            The parties will agree upon the timing and content of any initial
press release or other public communications relating to this Agreement and the
transactions contemplated herein.

            (a) Except to the extent already disclosed in that initial press
release or other public communication, no public announcement concerning the
existence or the terms of this Agreement or concerning the transactions
described herein shall be made, either directly or indirectly, by VERTEX or
SERONO, except as may be legally required by applicable laws, regulations, or
judicial order, without first obtaining the approval of the other party and
agreement upon the nature, text, and timing of such announcement, which approval
and agreement shall not be unreasonably withheld. If in the reasonable opinion
of a party's legal counsel, such a public announcement is legally required by
applicable laws, regulations or judicial order, then the disclosing party will
provide the other party notice reasonable under the

License, Development and Commercialization Agreement -- Confidential -- Page 35
<PAGE>

circumstances of such intended announcement, and to the extent feasible under
the circumstances will consult with the other party relative to the nature and
scope of such intended announcement.

            (b) In addition to the foregoing restrictions on public disclosure,
if VERTEX concludes that a copy of this Agreement must be filed with the U.S.
Securities and Exchange Commission, it will provide SERONO with a copy of the
Agreement showing any sections as to which VERTEX proposes to request
confidential treatment, will provide SERONO with an opportunity to comment on
any such proposal and to suggest additional portions of the Agreement for
confidential treatment, and will take SERONO's reasonable comments into
consideration, before filing the same.

      10.4 Survival.

            The provisions of this Article X shall survive the termination of
this Agreement and shall extend for a period of five (5) years thereafter.

                           ARTICLE XI -- PUBLICATION

            Each of SERONO and VERTEX reserves the right to publish or publicly
present the results (the "Results") of the Development Program, subject to the
following terms and conditions. The party proposing to publish or publicly
present the Results (the "Publishing Party") will submit a draft of any proposed
manuscript, abstract or speech to the other party (the "Non-publishing Party")
for comments at least [*************] prior to submission for publication or
oral presentation. The Non-publishing Party shall notify the Publishing Party in
writing within [********* *************] of receipt of such draft whether such
draft contains (i) information of the Non-publishing Party which it considers to
be confidential under the provisions of Article X hereof, (ii) information that
if published would have an adverse effect on a patent application covering the
subject matter of this Agreement, or (iii) information which the Non-publishing
Party reasonably believes would be likely to have a material adverse impact on
the development or commercialization of the Drug Product Candidate or Drug
Product. In any such notification, the Non-publishing Party shall indicate with
specificity its suggestions regarding the manner and degree to which the
Publishing Party may disclose such information. In the case of item (i) above,
no party may publish Confidential Information of the other party without its
consent in violation of Article X of this Agreement. In the case of item (ii)
above, the Non-publishing Party may request a delay and the Publishing Party
shall delay such publication or presentation, for a period not exceeding
[*****************], to permit the timely preparation and filing of a patent
application or an application for a certificate of invention on the information
at issue. In the case of item (iii) above, if the Publishing Party shall
disagree with the Non-publishing Party's assessment of the impact of the
publication or presentation, then the issue shall be referred by

License, Development and Commercialization Agreement -- Confidential -- Page 36
<PAGE>

the Publishing Party to the JDC for resolution. If the JDC is unable to reach
agreement on the matter within [****************] after such referral, then the
matter, if it involves the disclosure of confidential structural information
with respect to a Compound, shall be referred to the Chief Executive Officers of
SERONO and VERTEX, or to other members of senior management of such parties who
report directly to their respective Chief Executive Officer, who shall attempt
in good faith to reach a fair and equitable resolution of this disagreement. If
the disagreement is not resolved in this manner within [****************] after
referral to the JDC or (as to publications or presentations involving structural
information) referral to the Chief Executive Officer of each party or his
designee, as aforesaid, then the Chief Executive Officer of the Publishing Party
shall notify the Chief Executive Officer of the Non-publishing Party of the
decision of the Publishing Party as to publication or presentation of any
information generated by it, subject always to the confidentiality provisions of
Article X hereof. This decision shall be final, provided that such decision
shall be made with reasonable regard for the interests of the Non-publishing
Party and provided further that no decision shall be made to publish or present
information the publication or presentation of which would have a material
adverse effect on the commercial prospects of any Drug Candidate or Drug
Product. The parties agree that authorship of any publication or presentation
will be determined based on the customary standards then being applied in the
relevant scientific journal or conference. The parties will require any agents
conducting the Development Program on their behalf to comply with publication
and presentation restrictions comparable to those set forth herein.

      This Article XI shall terminate with the termination of this Agreement,
but the provisions of Article X hereof shall continue to govern the disclosure
by one party, whether by publication or otherwise, of Confidential Information
of the other, during the period set forth in Section 10.4.

                       ARTICLE XII -- DISPUTE RESOLUTION

      12.1 Governing Law, and Jurisdiction.

            This Agreement shall be governed by and construed in accordance with
the internal laws of the Commonwealth of Massachusetts and of the United States
of America, without giving effect to the doctrine of conflict of laws.

      12.2 Dispute Resolution Process.

            Except as otherwise explicitly provided herein, in the event of any
controversy or claim arising out of or relating to any provision of this
Agreement, or the collaborative effort contemplated hereby, the parties shall,
and either party may, refer such dispute to the JDC, and failing resolution of
the controversy or claim within thirty (30) days after such referral, the matter
shall be referred to the Chief Executive Officer of VERTEX and the Chief
Executive Officer of SERONO, or other members of senior management of such
parties who report directly to their

License, Development and Commercialization Agreement -- Confidential -- Page 37
<PAGE>

respective Chief Executive Officers and who are not otherwise directly involved
in the controversy or claim at issue, each with full authority from the Chief
Executive Officer to settle the dispute, who shall, as soon as practicable,
attempt in good faith to resolve the controversy or claim. If such controversy
or claim is not resolved within sixty (60) days of the date of initial referral
of the dispute to the JDC, either party shall be free to initiate proceedings
based on such controversy or claim in any court having requisite jurisdiction.

                      ARTICLE XIII -- TERM AND TERMINATION

      13.1 Term.

            The term of this Agreement shall extend with respect to the Drug
Product in a particular country from the Effective Date until the later of: (a)
the last to expire or be invalidated of any VERTEX Patents or Joint Patents
containing a Valid Patent Claim claiming the Drug Product or a method of making
or using the same in that country; or (b) if there is no such Valid Patent Claim
under a VERTEX Patent or Joint Patent in a particular country,
[********************* ********************************] This Agreement shall
expire in any event upon the later of the expiration or invalidation of the last
of such Valid Patent Claims or [**************************
**************************], unless the Agreement is terminated at an earlier
date pursuant to Sections 13.2, 13.3 or 13.4 hereof.

      13.2 Termination For Cause.

            In addition to rights of termination which may be granted to either
party under other provisions of this Agreement, either party may terminate this
Agreement upon sixty (60) days prior written notice to the other party upon the
breach by such other party of any of its material obligations under this
Agreement, provided that such termination shall become effective only if the
breaching party shall fail to remedy or cure the breach, or to initiate steps to
remedy the same to the other party's reasonable satisfaction, within such sixty
(60) day period.

      13.3 Termination for Bankruptcy.

            If at any time during the term of this Agreement, an Event of
Bankruptcy (as defined below) relating to either party (the "Bankrupt Party")
occurs, the other party (the "Other Party") shall have, in addition to all other
legal and equitable rights and remedies available hereunder, the option to
terminate this Agreement upon thirty (30) days' written notice to the Bankrupt
Party. It is agreed and understood that if the Other Party does not elect to
terminate this Agreement upon the occurrence of an Event of Bankruptcy, except
as may otherwise be agreed with the trustee or receiver appointed to manage the
affairs of the Bankrupt Party, the Other Party shall continue to make all
payments required of it under this Agreement as if the Event of Bankruptcy had
not occurred, and the Bankrupt Party shall not have the right to terminate any

License, Development and Commercialization Agreement -- Confidential -- Page 38
<PAGE>

license granted herein. It is agreed and understood that all rights and licenses
granted under or pursuant to this Agreement by VERTEX to SERONO are, and shall
otherwise be deemed to be, for purposes of Section 365(n) of the United States
Bankruptcy Code, as amended from time to time (the "Bankruptcy Code"), licenses
or rights to "intellectual property" as defined under Section 101(35A) of the
Bankruptcy Code. The parties agree that SERONO, as a recipient of such rights
under this Agreement, shall retain and may fully exercise all of its rights and
elections under the Bankruptcy Code. Following the occurrence of an Event of
Bankruptcy with respect to VERTEX and so long as that Event of Bankruptcy
continues, VERTEX will not without SERONO's prior written consent sell,
transfer, assign, or otherwise dispose of, or purport to sell, transfer, assign
or otherwise dispose of, any right, title or interest in, to and under VERTEX
Technology that is necessary or useful for SERONO to exercise its rights under
this Agreement, if those rights would be impaired in any material respect by
such sale, transfer, assignment or other disposition. As used above, the term
"Event of Bankruptcy" shall mean (a) dissolution, termination of existence,
liquidation or business failure of either party; (b) the appointment of a
custodian or receiver for either party who has not been terminated or dismissed
within ninety (90) days of such appointment; (c) the institution by either party
of any proceeding under national, federal or state bankruptcy, reorganization,
receivership or other similar laws affecting the rights of creditors generally
or the making by either party of a composition or any assignment or trust
mortgage for the benefit of creditors or under any national, federal or state
bankruptcy, reorganization, receivership or other similar law affecting the
rights of creditors generally, which proceeding is not dismissed within ninety
(90) days of filing.

      13.4 Termination by SERONO.

            SERONO may terminate this Agreement [*******************************
*********************************]. In such event SERONO, at the request of
VERTEX, shall assign or otherwise transfer to VERTEX all of its Regulatory
Approvals with respect to the Drug Product.

      13.5 Effect of Termination.

            If this Agreement is not terminated at an earlier date, then upon
its expiration in accordance with the last sentence of Section 13.1 hereof in a
given country SERONO shall have an irrevocable, fully paid-up exclusive license,
with the right to sublicense, in such country under the VERTEX Technology to
develop, manufacture, have manufactured, use, sell, offer to sell and import the
Bulk Drug Substance, Drug Product Candidate and Drug Product. If this Agreement
is not terminated at an earlier date, then upon its expiration in accordance
with Section 13.1 hereof in all countries in the Territory, SERONO shall have an
irrevocable, fully paid-up exclusive license, with the right to sublicense, in
the Territory under the VERTEX Technology to develop, manufacture, have
manufactured, use, sell, offer to sell and import the Bulk Drug Substance,

License, Development and Commercialization Agreement -- Confidential -- Page 39
<PAGE>

Drug Product Candidate and Drug Product. Upon any such termination of this
Agreement in any country, VERTEX will deliver to SERONO the VERTEX Technology
and provide to SERONO the technical support in connection therewith reasonably
necessary to enable SERONO to manufacture Bulk Drug Substance in compliance with
any and all current Regulatory Approvals. Such VERTEX Technology shall be
delivered to SERONO in such a way as to communicate it to SERONO promptly,
effectively and economically. At the written request of SERONO, VERTEX will
continue to supply SERONO with Bulk Drug Substance under the terms of this
Agreement for such period, not to exceed eighteen (18) months, as may be
reasonably necessary for SERONO to procure its own supply of Bulk Drug
Substance. Upon any termination of this Agreement pursuant to Sections 13.2
through 13.4 hereof, SERONO shall have the right to sell its inventory of the
Drug Product for a period of six (6) months from the date of termination
provided SERONO complies with the provisions of Sections 6.2 through 6.4 hereof.
In the event the license granted to SERONO under Section 2.1 hereof terminates
for any reason, each of SERONO's sublicensees at such time shall continue to
have the rights and license set forth in their sublicense agreements; provided,
however, that such sublicensee agrees in writing that VERTEX is entitled to
enforce all relevant terms and conditions of such sublicense agreement directly
against such sublicensee. Termination of this Agreement for any reason, or
expiration of this Agreement, will not affect: (i) obligations, including the
obligation for payment of any supply payments, which have accrued as of the date
of termination or expiration, and (ii) rights and obligations which, from the
context thereof, are intended to survive termination or expiration of this
Agreement including obligations pursuant to Articles VI, VIII, X, XII, XIII, XIV
and XV, to the extent applicable. Any right to terminate this Agreement shall be
in addition to and not in lieu of all other rights or remedies that the party
giving notice of termination may have at law or in equity or otherwise,
including without limitation rights under the United States Bankruptcy Code.

                         ARTICLE XIV -- INDEMNIFICATION

      14.1 Indemnification by VERTEX.

            VERTEX will indemnify and hold SERONO and its Affiliates, and their
employees, officers and directors harmless from and against any loss, damage,
action, suit, claim, demand, liability, judgment, cost or expense (a "Loss"),
that may be brought, instituted or arise against or be incurred by such Persons
to the extent such Loss is based on or arises out of:

            (a) [***************************************************************
**************************************]

            (b) the breach by VERTEX of any of its covenants, representations or
warranties set forth in this Agreement; and

License, Development and Commercialization Agreement -- Confidential -- Page 40
<PAGE>

            (c) provided however, that the foregoing indemnification and hold
harmless obligation shall not apply to any Loss to the extent such Loss is
caused by the negligent or willful misconduct of SERONO or its Affiliates.

      14.2 Indemnification by SERONO.

            SERONO will indemnify and hold VERTEX, and its Affiliates, and their
employees, officers and directors harmless from and against any Loss that may be
brought, instituted or arise against or be incurred by such Persons to the
extent such Loss is based on or arises out of:

            (a) [***************************************************************
*********************************************]

            (b) the breach by SERONO of any of its covenants, representations or
warranties set forth in this Agreement; and

            (c) provided that the foregoing indemnification and hold harmless
obligation shall not apply to any Loss to the extent such Loss is caused by the
negligent or willful misconduct of VERTEX or its Affiliates.

      14.3 Claims Procedures.

            Each Party entitled to be indemnified by the other Party (an
"Indemnified Party") pursuant to Section 14.1 or 14.2 hereof shall give notice
to the other Party (an "Indemnifying Party") promptly after such Indemnified
Party has actual knowledge of any threatened or asserted claim as to which
indemnity may be sought, and shall permit the Indemnifying Party to assume the
defense of any such claim or any litigation resulting therefrom; provided:

            (a) That counsel for the Indemnifying Party, who shall conduct the
defense of such claim or any litigation resulting therefrom, shall be approved
by the Indemnified Party (whose approval shall not unreasonably be withheld) and
the Indemnified Party may participate in such defense at such party's expense
(unless (i) the employment of counsel by such Indemnified Party has been
authorized by the Indemnifying Party; or (ii) the Indemnified Party shall have
reasonably concluded that there may be a conflict of interest between the
Indemnifying Party and the Indemnified Party in the defense of such action, in
each of which cases the Indemnifying Party shall pay the reasonable fees and
expenses of one law firm serving as counsel for the Indemnified Party, which law
firm shall be subject to approval, not to be unreasonably withheld, by the
Indemnifying Party);

            (b) The failure of any Indemnified Party to give notice as provided
herein shall not relieve the Indemnifying Party of its obligations under this
Agreement to the extent that the failure to give notice did not result in harm
to the Indemnifying Party;

License, Development and Commercialization Agreement -- Confidential -- Page 41
<PAGE>

            (c) No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the approval of each Indemnified Party which
approval shall not be unreasonably withheld, consent to entry of any judgment or
enter into any settlement which (i) would result in injunctive or other relief
being imposed against the Indemnified Party; or (ii) does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation. The Indemnified Party shall have no right to settle or compromise
any such claim or litigation without the Indemnifying Party's prior written
consent; and

            (d) Each Indemnified Party shall furnish such information regarding
itself or the claim in question as an Indemnifying Party may reasonably request
in writing and shall be reasonably required in connection with the defense of
such claim and litigation resulting therefrom.

      14.4 Insurance.

            Each party shall maintain and keep in force for the term of this
Agreement comprehensive general liability insurance including Products/Completed
Operations, Contractual and Broad Form Property Damage covering its
indemnification obligations hereunder with a minimum limit of
[*******************************************************************************
*********************************]. It is understood that such insurance shall
not be construed to limit a party's liability with respect to such
indemnification obligations. Such insurance shall be placed with a first class
insurance carrier with at least a BBB rating by Standard & Poor. Promptly after
execution and delivery of this Agreement, each party shall furnish a certificate
of insurance to the other party evidencing the foregoing endorsements, coverage
and limits, and providing that such insurance shall not expire or be canceled or
modified without at least thirty (30) days prior notice to the other party.

                     ARTICLE XV -- MISCELLANEOUS PROVISIONS

      15.1 Waiver.

            No provision of the Agreement may be waived except in writing by
both parties hereto. No failure or delay by either party hereto in exercising
any right or remedy hereunder or under applicable law will operate as a waiver
thereof, or a waiver of that or any other right or remedy on any subsequent
occasion.

      15.2 Force Majeure.

            Neither party will be in breach hereof by reason of its delay in the
performance of or failure to perform any of its obligations hereunder, if that
delay or failure is caused by strikes, acts of God or the public enemy, riots,
incendiaries, interference by civil or military authorities, or

License, Development and Commercialization Agreement -- Confidential -- Page 42
<PAGE>

any similar cause beyond its control and without its fault or negligence;
provided, however, the party claiming force majeure shall promptly notify the
other party of the existence of such force majeure, shall use its best efforts
to avoid or remedy such force majeure and shall continue performance hereunder
with the utmost dispatch whenever such force majeure is avoided or remedied.
Notwithstanding the foregoing, in the event that VERTEX provides notice of force
majeure to SERONO, SERONO shall have the right not to make any future payments
otherwise payable hereunder until such time as VERTEX resumes performance
hereunder, and the schedule for payments hereunder shall be revised to apply any
payments already made in advance by SERONO for the performance so delayed or
suspended by VERTEX hereunder to such performance once it is resumed or to
refund any such payments to SERONO in the event that such performance is not for
any reason resumed.

      15.3 Registration of License.

            SERONO may, at its expense, register the license granted under this
Agreement in any country where the use, sale, importation, offer to sell or
manufacture of a Drug Product in such country would be covered by a Valid Patent
Claim. Upon request by SERONO, VERTEX agrees promptly to execute any "short
form" licenses submitted to it by SERONO in order to effect the foregoing
registration in such country, but such licenses shall in no way alter or affect
the obligations of the parties hereunder.

      15.4 Severability.

            Should one or more provisions of this Agreement be or become
invalid, then the parties hereto shall attempt to agree upon valid provisions in
substitution for the invalid provisions, which in their economic effect come so
close to the invalid provisions that it can be reasonably assumed that the
parties would have accepted this Agreement with those new provisions. If the
parties are unable to agree on such valid provisions, the invalidity of such one
or more provisions of this Agreement shall nevertheless not affect the validity
of the Agreement as a whole, unless the invalid provisions are of such essential
importance to this Agreement that it may be reasonably presumed that the parties
would not have entered into this Agreement without the invalid provisions

      15.5 Government Acts.

            In the event that any act, regulation, directive, or law of a
country or its government, including its departments, agencies or courts, should
make impossible or prohibit, restrain, modify or limit any material act or
obligation of SERONO or VERTEX under this Agreement, the party, if any, not so
affected, shall have the right, at its option, to suspend or terminate this
Agreement as to such country, if good faith negotiations between the parties to

License, Development and Commercialization Agreement -- Confidential -- Page 43
<PAGE>

make such modifications therein as may be necessary to fairly address the impact
thereof are not successful after a reasonable period of time in producing
mutually acceptable modifications to this Agreement.

      15.6 Government Approvals.

            Each party will obtain any government approval required in its
country of domicile, or under any treaties or international agreements to which
its country of domicile is a signatory, to enable this Agreement to become
effective, or to enable any payment hereunder to be made, or any other
obligation hereunder to be observed or performed. Each party will keep the other
informed of progress in obtaining any such government approval, and will
cooperate with the other party in any such efforts.

      15.7 Assignment; Successors and Assigns.

            This Agreement may not be assigned or otherwise transferred by
either party without the prior written consent of the other party; provided,
however, that either party may assign this Agreement, without the consent of the
other party, (i) to any of its Affiliates, if the assigning party guarantees the
full performance of its Affiliates' obligations hereunder, or (ii) in connection
with the transfer or sale of all or substantially all of its assets or business
or in the event of its merger or consolidation with another company. Any
purported assignment in contravention of this Section 15.7 shall, at the option
of the nonassigning party, be null and void and of no effect. No assignment
shall release either party from responsibility for the performance of any of its
accrued obligations hereunder. This Agreement shall be binding upon and
enforceable against the successor to or any permitted assignee of either of the
parties hereto.

      15.8 Export Controls.

            This Agreement is made subject to any restrictions concerning the
export of materials and Technology from the United States which may be imposed
upon either party to this Agreement from time to time by the United States
Government. In the event any such restrictions are imposed after the Effective
Date and thereby render any provisions of this Agreement invalid or
unenforceable, the provisions of Section 15.4 of this Agreement shall be
applicable to those provisions. SERONO will not export, directly or indirectly,
any VERTEX Technology or any Bulk Drug Substance, Drug Product Candidates or
Drug Products utilizing such Technology to any countries for which the United
States Government or any agency thereof at the time of such export requires an
export license or other governmental approval, without first obtaining the
written consent to do so from the Department of Commerce or other applicable
agency of the United States Government in accordance with the applicable statute
or regulation.

License, Development and Commercialization Agreement -- Confidential -- Page 44
<PAGE>

      15.9 Affiliates.

            Each party may perform its obligations hereunder personally or
through one or more Affiliates, although each party shall nonetheless be solely
responsible for the performance of its Affiliates. Neither party shall permit
any of its Affiliates to commit any act (including any act of omission) which
such party is prohibited hereunder from committing directly.

      15.10 Counterparts.

             This Agreement may be signed in any number of counterparts with the
same effect as if the signatures to each counterpart were upon a single
instrument, and all such counterparts together shall constitute the same
agreement.

      15.11 No Agency.

            Nothing herein contained shall be deemed to create an agency, joint
venture, amalgamation, partnership or similar relationship between SERONO and
VERTEX. Notwithstanding any of the provisions of this Agreement, neither party
shall at any time enter into, incur, or hold itself out to third parties as
having authority to enter into or incur, on behalf of the other party, any
commitment, expense, or liability whatsoever, and all contracts, expenses and
liabilities in connection with or relating to the obligations of each party
under this Agreement shall be made, undertaken, incurred or paid exclusively by
that party on its own behalf, and not as an agent or representative of the other
party.

      15.12 Notice.

            All communications between the parties with respect to any of the
provisions of this Agreement will be sent to the addresses set out below, or to
other addresses as designated by one party to the other by notice pursuant
hereto, by air courier (which shall be deemed received by the other party on the
third (3rd) business day following deposit with the air courier company), or by
facsimile transmission, or other electronic means of communication (which shall
be deemed received when transmitted), with confirmation by air courier, sent by
the close of business on or before the next following business day:

License, Development and Commercialization Agreement -- Confidential -- Page 45
<PAGE>

             If to SERONO, at:

               Laboratoires Serono S.A.
               Zone Industrielle de l'Ouriettaz
               1170 Aubonne
               Switzerland
               Fax: 41-22-354-5020
               Attention: General Manager

            with a copy to:

               Serono International S.A.
               15 bis Chemin des Mines
               1202 Geneva
               Switzerland
               Fax: 41-22-739-3070
               Attention: General Counsel

            and

            if to VERTEX, at:

                 Vertex Pharmaceutical Incorporated
                 130 Waverly Street
                 Cambridge, MA U.S.A. 02139-4211
                 Fax: (617) 577-6680
                 Attention: Chief Executive Officer

            with a copy to:

                 Kirkpatrick & Lockhart LLP
                 75 State Street
                 Boston, MA U.S.A. 02109
                 Fax: (617) 951-9151
                 Attention: Kenneth S. Boger, Esq.

      15.13 Headings.

            The section and paragraph headings are for convenience of reference
only and will not be deemed to affect in any way the language of the provisions
to which they refer.

      15.14 Entire Agreement.

            This Agreement, including the Schedules appended hereto, contains
the entire understanding of the parties relating to the matters referred to
herein, except as matters referenced herein are also addressed in the Research
Agreement, and may only be amended by a written document referencing this
Agreement, duly executed on behalf of the respective parties.

                            [Signature Page Follows]

License, Development and Commercialization Agreement -- Confidential -- Page 46
<PAGE>

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

                               VERTEX PHARMACEUTICALS INCORPORATED

                               By:
                                  --------------------------------------------

                               Title:

                               LABORATOIRES SERONO S.A.

                               By:
                                  --------------------------------------------

                               Title:
                                     -----------------------------------------

                               By:
                                  --------------------------------------------

                               Title:
                                     -----------------------------------------

License, Development and Commercialization Agreement -- Confidential -- Page 47
<PAGE>

                                  Schedule 1.4

                      [***********************************]

--------------------------------------------------------------------------------

[*******************************************************************************
********************************************************************************
*****************].

      License, Development and Commercialization Agreement -- Confidential
<PAGE>

                                  Schedule 1.11

                             Drug Product Candidate

--------------------------------------------------------------------------------

                                 To be supplied

      License, Development and Commercialization Agreement -- Confidential
<PAGE>

                                  Schedule 1.40

                                 SERONO Patents

--------------------------------------------------------------------------------

      License, Development and Commercialization Agreement -- Confidential
<PAGE>

                                  Schedule 1.16

                            Countries of the Far East

--------------------------------------------------------------------------------

            Brunei

            Burma (Myanmar)

            Cambodia (Kampuchea)

            Indonesia

            Japan

            Laos

            Malaysia

            Mongolia

            Philippines

            Singapore

            Thailand

            Vietnam

            Korea (South and North)

            Taiwan

            People's Republic of China

      License, Development and Commercialization Agreement -- Confidential
<PAGE>

                                  Schedule 1.47

                                 VERTEX Patents

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      License, Development and Commercialization Agreement -- Confidential

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