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                                                                   EXHIBIT 10.76



                                                                   March 5, 1999

                                    SUBLEASE

                                    ARTICLE I

                                 REFERENCE DATA


       1.1      SUBJECTS REFERRED TO.

       Each reference in this Sublease to any of the following subjects shall be
construed to incorporate the data stated for that subject in this Section 1.1:

Date of Sublease:                   March 5, 1999.

Sublandlord:                        The Pioneer Group, Inc.

Sublandlord's Address:              60 State Street
                                    Boston, Massachusetts 02109

Sublandlord Representative: Ms. Diane Benson

Subtenant:                          Leerink Swann & Company

Subtenant's Address:                60 State Street
                                    Boston, Massachusetts 02109

Subtenant Representative:           Mr. Jeffrey A. Leerink

Overlandlord:                       Trustees of 60 State Street Trust under 
                                    Declaration of Trust dated September 10, 
                                    1970 and recorded with Suffolk Deeds in 
                                    Book 8389, Page 286, as amended by First 
                                    Amendment dated as of December 23, 1988, 
                                    recorded with said Deeds in Book 15258, 
                                    Page 66.

Overlandlord's Address:             c/o CC&F Asset Management Company, Inc.
                                    60 State Street
                                    Boston, Massachusetts 02109

Overlease:                          Lease dated July 3, 1991 between 
                                    Overlandlord as Landlord and Sublandlord as
                                    Tenant, a (redacted) copy of which is
                                    attached hereto as Exhibit A, consisting of
                                    the 





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                                    original lease between Overlandlord and
                                    Sublandlord dated July 3, 1991, as
                                    heretofore amended (as redacted) and (ii)
                                    the Sixth Amendment to Lease dated October
                                    5, 1998. Sublandlord represents that (a) the
                                    redacted portions of Exhibit A and (b) the
                                    First, Second, Third, Fourth and Fifth
                                    Amendments to the Overlease do not affect
                                    the terms of the Overlease applicable to
                                    Subtenant.

Subleased Premises:                 That entirety of Sublandlord's Floor 15 
                                    Premises under the Overlease as described in
                                    the Sixth Amendment to the Overlease and 
                                    shown on Exhibit B attached hereto, 
                                    containing approximately 22,407 rentable 
                                    square feet of space and up to fifteen (15) 
                                    non-reserved parking spaces in the Building 
                                    garage, according to the current market 
                                    rates and terms provided for parking, as 
                                    referenced in the Sixth Amendment to the 
                                    Overlease.

Commencement Date:                  April 1, 1999.

Term Expiration Date:               March 31, 2002, or as specified in 
                                    accordance with Section 2.3 hereinbelow.

Annual Fixed Rent:                  The Annual Fixed Rent shall be $27.00 per 
                                    rentable square foot. Subtenant shall pay 
                                    additional rent for the Subleased Premises 
                                    on the same terms and conditions as provided
                                    in the Overlease for the initial Premises, 
                                    which additional rent is currently estimated
                                    at $13.47 per rentable square foot.

Permitted Uses:                     All uses permitted in the Overlease.


         1.2      EXHIBITS.

         The exhibits listed below in this section are incorporated in this
Sublease by reference and are to be construed as part of this Sublease:

                  EXHIBIT A         Overlease

                  EXHIBIT B         Floor Plan of Subleased Premises




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                                   ARTICLE II

                           SUBLEASED PREMISES AND TERM

         2.1 SUBLEASED PREMISES. Subject to and with the benefit of the
provisions of this Sublease, Sublandlord hereby subleases the Subleased Premises
to Subtenant, and Subtenant subleases the Subleased Premises from Sublandlord.

         The Subleased Premises are subleased in their condition "as is" on the
Commencement Date. Subtenant accepts the Subleased Premises in such condition.

         Sublandlord further grants Subtenant the right to use, as appurtenant
to the Subleased Premises and in accord with the provisions of Article II,
Section 2.2 of the Overlease, attached hereto as Exhibit A, the Common
Facilities described therein. Sublandlord also grants Subtenant the right to
occupy up to fifteen (15) parking spaces at the current market rates charged
from time to time by Overlandlord for market rate parking in the Building
garage.

         2.2 TERM. To have and to hold beginning on the Commencement Date and
continuing until the Term Expiration Date (the "Term").

         2.3 EARLY ACCESS. Sublandlord shall use commercially reasonable efforts
to assist Subtenant to gain access to the Subleased Premises prior to the
Commencement Date in order to enable Subtenant to install its wiring and cabling
to the mechanical closet in the Premises; notwithstanding the foregoing, the
inability of Subtenant to gain early access shall not modify the terms and
provisions of this Sublease.


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                                   ARTICLE III

                                      RENT

         3.1      ANNUAL FIXED RENT. Commencing on the Commencement Date,
Subtenant shall pay the Annual Fixed Rent on a monthly basis at the times
specified in the Overlease, except that Subtenant shall pay the Annual Fixed
Rent to Sublandlord. Notwithstanding the foregoing provisions of this Section
3.1, Sublandlord and Subtenant agree that Subtenant shall be entitled to an
abatement of the monthly installment for Annual Fixed Rent for the following
monthly periods: (a) April 1999, (b) December 2001 and (c) January, February and
March 2002 (each individually an "Abatement Period" and collectively the
"Abatement Periods"), subject to the following provisos:

         (1)      Subtenant shall continue to be liable during all time periods
                  during the Term (including all Abatement Periods) for
                  Operating Expenses and Real Estate Taxes as set forth in
                  Sections 3.2 and 3.3 hereof, and

         (2)      In the event that Subtenant shall, at any time during the Term
                  hereof, default after the expiration of applicable notice and
                  grace periods (as set forth in the Overlease) on any terms and
                  conditions of this Sublease, the abatement of Annual Fixed
                  Rent set forth in this sentence shall become null and void and
                  Subtenant shall thereupon owe to Sublandlord the full amount
                  of all installments of Annual Fixed Rent for all Abatement
                  Periods.

         3.2      ADJUSTMENTS FOR OPERATING EXPENSES. Under Article II, Section
2.6 of the Overlease, Sublandlord is required to pay "Operating Expenses
Allocable to the Premises," as defined therein. Subtenant shall pay Sublandlord
as Additional Rent that portion of the Operating Expenses Allocable to the
Premises that is attributable to the Subleased Premises (the "Operating Expenses
Allocable to the Subleased Premises") during periods of time included in the
Term. Commencing on the Commencement Date, Subtenant shall pay such amount in
advance on the first calendar day of each month included in the Term. Any
surplus shall be promptly refunded to Subtenant and any deficit in such payment
shall be promptly paid by Subtenant after the Overlandlord finally determines
the amounts payable by the Sublandlord under the Overlease.

         3.3      ADJUSTMENTS FOR REAL ESTATE TAXES. Under Article II, Section
2.7 of the Overlease, Sublandlord is required to pay "Landlord's Tax Expenses
Allocable to the Premises," as defined therein. Subtenant shall pay Sublandlord
as Additional Rent the Subtenant's Percentage Share of Landlord's Tax Expenses
Allocable to the Premises (the "Landlord's Tax Expenses Allocable to the
Subleased Premises") during periods of time included in the Term. Commencing on
the Commencement Date, Subtenant shall pay such amount in advance on the first
calendar day of each month included in the Term. Any surplus shall be promptly
refunded to Subtenant and any deficit in such payment shall be promptly paid 


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by Subtenant after the Overlandlord finally determines the amounts payable by
the Sublandlord under the Overlease.

         3.4 PAYMENT. All payments of Annual Fixed Rent, Operating Expenses
Allocable to the Subleased Premises and Landlord's Tax Expenses Allocable to the
Subleased Premises shall be made to Sublandlord by wire transfer or to such
other address as Sublandlord may designate by notice to Subtenant from time to
time.


                                   ARTICLE IV

                     SUBLANDLORD'S COVENANTS AND WARRANTIES

         4.1 SUBLANDLORD'S OBLIGATIONS. Sublandlord shall make reasonable
efforts to cause Overlandlord to fulfill its obligations set forth in the
Overlease with respect to the Subleased Premises.

         4.2. OVERLEASE. The copy of the Overlease attached hereto as Exhibit A
is complete, true and accurate. Except as shown on Exhibit A, the Overlease has
not been modified, amended or terminated and is in full force and effect.
Sublandlord is not in default under the Overlease, nor has Sublandlord done or
failed to do anything which with notice, the passage of time or both could ripen
into a default. To Sublandlord's knowledge, Overlandlord is not in default under
any of its obligations under the Overlease.

         4.3 QUIET ENJOYMENT. Upon payment of the rent and performance of and
compliance with the covenants, terms and conditions upon Subtenant's part to be
performed and complied with hereunder, Subtenant shall lawfully, peacefully and
quietly have, hold, occupy and enjoy the Subleased Premises during the Term
without hindrance or molestation by Sublandlord or any persons lawfully claiming
by, through or under Sublandlord, subject to the terms and conditions of this
Sublease and the Overlease.


                                    ARTICLE V

                              SUBTENANT'S COVENANTS

         Subtenant covenants during the Term and such further time as Subtenant
occupies any part of the Subleased Premises:

         5.1 SUBTENANT'S PAYMENTS. Subtenant shall pay all Annual Fixed Rent,
Operating Expenses Allocable to the Subleased Premises and Landlord's Tax
Expenses Allocable to the Subleased Premises when due. Subtenant shall also pay
all costs of utilities furnished to the Subleased Premises.



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         5.2      MAINTENANCE AND REPAIR. Subtenant shall maintain the Subleased
Premises in the condition required by the Overlease.

         5.3      OCCUPANCY AND USE.

                  (a) Subtenant shall not use the Subleased Premises for any
         uses other than the Permitted Uses, and shall not make any use of the
         Subleased Premises which is prohibited by any applicable law,
         ordinance, code, regulation, license, permit, variances or governmental
         order.

                  (b) It is acknowledged and agreed that Overlandlord is
         responsible for causing the Building Common Areas (i.e. not including
         Premises) to comply with Boston Fire and Building Codes and ADA
         Guidelines. Subtenant shall not make alterations, additions or
         renovations to the Subleased Premises ("Subtenant Work") except in
         accordance with plans and specifications therefor ("Subtenant's Plans")
         first approved by Sublandlord and Overlandlord with respect to any of
         the work on such plans which (i) might adversely affect any structural
         or exterior element of the Building, any area outside of the Subleased
         Premises or any Building systems, or (ii) will require unusual expense
         to readapt the Subleased Premises to normal office use on Sublease
         expiration or termination or increase the cost of insurance or taxes on
         the Building or of any services provided to the Building. Within twenty
         (20) business days after delivery to Sublandlord and Overlandlord of
         Subtenant's Plans, or within ten (10) business days after delivery to
         Sublandlord and Overlandlord of any revisions to Subtenant's Plans,
         Sublandlord and Overlandlord shall provide Subtenant with notice of
         their approval or disapproval of Subtenant's Plans or such revisions,
         as appropriate. If Sublandlord and Overlandlord fail to so notify
         Subtenant within said twenty (20) business day period or ten (10)
         business day period, as appropriate, and if such failure shall continue
         for seven (7) additional business days after notice from Subtenant,
         Sublandlord and Overlandlord shall be deemed to have approved
         Subtenant's Plans. In the case of disapproval, Sublandlord or
         Overlandlord's notice shall specify in detail the part of Subtenant's
         Plans which are being disapproved and the reasons therefor. No review
         or approval by Sublandlord or Overlandlord of Subtenant's Plans shall
         be deemed an acknowledgment, representation or warranty by Sublandlord
         or Overlandlord that Subtenant's Plans comply with the requirements of
         applicable law or sound design, architectural and engineering
         standards, nor shall such review or approval relieve Subtenant of any
         obligation or liability with respect to Subtenant's Plans or the
         Subtenant Work.

                  Before starting the Subtenant Work, Subtenant shall: secure
         all licenses and permits necessary therefor; cause each contractor to
         carry worker's compensation insurance in statutory amounts covering all
         of the contractor's and subcontractor's employees; cause its general
         contractor to carry commercial general liability insurance and property
         damage insurance with a combined single limit of not less than


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         $3,000,000.00 and cause each subcontractor to carry commercial general
         liability insurance and property damage insurance with a combined
         single limit of not less than $2,000,000.00 (all such insurance to be
         subject to the additional requirements as described in Article III,
         Section 3.5 of the Overlease, and to include as additional insureds the
         Sublandlord and Subtenant), and to deliver to Sublandlord and
         Overlandlord certificates of all such insurance and renewals thereof.

                  Subtenant agrees to pay promptly when due the entire cost of
         any Subtenant Work and not to cause or permit any liens for labor or
         materials performed or furnished in connection therewith to attached to
         the Subleased Premises or the Property and immediately to discharge or
         cause to be bonded off any such liens which may so attach and, at the
         request of Sublandlord or Overlandlord, to deliver to Sublandlord or
         Overlandlord security satisfactory to Sublandlord or Overlandlord
         protecting Sublandlord or Overlandlord against liens arising out of the
         furnishing of such labor and material. In the event Subtenant fails to
         discharge or cause to be bonded off any such liens, the Sublandlord or
         Overlandlord shall have the right, but not the obligation, to pay and
         discharge any such lien after ten (10) days prior notice to Subtenant
         of its intent to pay and discharge any such lien, and Subtenant shall
         promptly reimburse Sublandlord or Overlandlord for all reasonable costs
         incurred by Sublandlord or Overlandlord in connection therewith.

                  (c) Subject to Sublandlord's approval (not to be unreasonably
         withheld or delayed) and to Overlandlord's approval, Subtenant shall
         have the right to place its corporate sign or logo in the lobby of the
         Premises and Subtenant's name on the Building directory in the main
         Building lobby, all such signage and installations to be at Subtenant's
         sole cost and expense.

         Sublandlord agrees to exercise Sublandlord's rights under Section 2.2.2
of the Overlease to the extent that such exercise may facilitate Subtenant's
carrying out of the matters covered by this Section 5.3(c).

         5.4      ASSIGNMENT AND SUBLETTING. Subject to the provisions of this
Section 5.4, Subtenant shall have the right to sub-sublease all or part of the
Subleased Premises to a third party subject to the prior reasonable consent of
Sublandlord and subject to the prior consent of Overlandlord:

         With respect to any sub-sublease agreement entered into by and between
Subtenant and a third party:

         (a)      If the aggregate rent received by Subtenant from such third
         party exceeds the aggregate rent paid by Subtenant hereunder respecting
         the same premises, Subtenant shall (a) first deduct its reasonable
         costs and expenses, including, without limitation, marketing expenses
         (including brokerage commissions and advertising expenses), legal 


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         fees, expenses of preparing such space for sub-subletting and costs for
         tenant improvements as reasonably amortized by Subtenant over a period
         no less than the initial term of the applicable sub-sublease and (b)
         pay to Sublandlord, as additional rent, 100% of the remaining excess
         rent received, if any; and

         (b)      Notwithstanding any sub-sublease agreement, Subtenant shall
         continue to remain liable as a primary obligor under this Sublease.

         5.5      INDEMNIFICATION. Subtenant shall indemnify Sublandlord and
hold Sublandlord harmless from and against any and all claims, demands, suits,
judgments, liabilities, costs and expenses, including reasonable attorneys fees,
arising out of or in connection with Subtenant's use and possession of the
Subleased Premises (including, without limitation, any damages to or around the
Subleased Premises or the Building caused by Subtenant's Work), or arising out
of the failure of Subtenant, its agents, contractors or employees to perform any
covenant, term or condition of this Sublease or of the Overlease to be performed
by Subtenant hereunder.


                                   ARTICLE VI

                               CASUALTY AND TAKING

         6.1      TERMINATION OF OVERLEASE. In the event that during the Term,
all or any part of the Subleased Premises are destroyed or damaged by fire or
other casualty or taken by eminent domain, and either Sublandlord or
Overlandlord terminates the Overlease pursuant to its terms because of such
damage, destruction or taking, then this Sublease shall likewise terminate on
the same date that the Overlease terminates. Sublandlord shall give Subtenant
prompt notice of such termination and the date on which it shall occur. In the
event that during the Term, all or any part of the Subleased Premises are
destroyed or damaged by fire or other casualty to such an extent that such
damage or destruction could not be restored (in a manner which would not have
any material adverse effect on Subtenant's business operations) within ninety
(90) days of the date of such casualty, then Subtenant shall have the right,
exercisable by notice given within fifteen (15) days of the date of such
casualty, to terminate this Sublease.

         6.2      REPAIR AND RESTORATION. In the event any such damage,
destruction or taking of the Subleased Premises occurs and this Sublease is not
terminated pursuant to Section 6.1 above, then Sublandlord shall cause
Overlandlord to repair and restore the Subleased Premises as required by the
terms of the Overlease. A just proportion of the Annual Fixed Rent, Operating
Expenses Allocable to the Subleased Premises, Landlord's Tax Expenses Allocable
to the Subleased Premises and any other additional rent hereunder shall be
abated until Overlandlord shall have put the Subleased Premises or what may
remain thereof into proper condition for use and occupancy, and in the case of a
taking which permanently reduces the area of the Subleased Premises, a just
proportion of such rent shall be abated for the remainder of the Term.


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<PAGE>   9

         6.3      RESERVATION OF AWARD. Any and all rights to receive awards
made for damages to the Subleased Premises and the leasehold hereby created
accruing by reason of exercise of eminent domain or by reason of anything
lawfully done in pursuance of public or other authority, are reserved to
Sublandlord and Overlandlord. Subtenant hereby releases and assigns to
Sublandlord and Overlandlord all Subtenant's rights to such award and covenants
to deliver such further assignments and assurances thereof as Sublandlord or
Overlandlord may from time to time request.


                                   ARTICLE VII

                                    OVERLEASE


         7.1      SUBLEASE SUBJECT TO OVERLEASE. This Sublease is subject to the
Overlease. Subject to this Section 7.1, all terms and conditions of the
Overlease, attached as Exhibit A, are incorporated into and made a part of this
Sublease as if Sublandlord were the landlord thereunder and Subtenant were the
tenant. Sublandlord represents that (a) the redacted portions of Exhibit A and
(b) the First, Second, Third, Fourth and Fifth Amendments to the Overlease do
not affect the terms of the Overlease applicable to Subtenant. In case of
conflict between the incorporated provisions of the Overlease and the remaining
provisions of this Sublease, the latter shall control. Subtenant assumes and
agrees to perform the tenant's obligations under the Overlease during the Term,
except that the obligation to pay rent or other amounts to Overlandlord under
the Overlease shall not be an obligation of Subtenant, and Subtenant shall
instead pay the rent under this Sublease. Subtenant shall not commit or suffer
any act or omission that will violate any of the provisions of the Overlease.
Overlandlord has covenanted under the Overlease to perform repairs and
maintenance and provide services pursuant to the Overlease. Sublandlord shall
exercise due diligence in attempting to cause Overlandlord to perform its
obligations under the Overlease for the benefit of Subtenant. In addition, if
Overlandlord defaults in its obligations under the Overlease to maintain the
Subleased Premises or to furnish services to the Subleased Premises and such
default materially interferes with Subtenant's use and enjoyment of the
Subleased Premises, Sublandlord authorizes Subtenant to deal directly with
Overlandlord regarding such default. Sublandlord agrees to perform all of the
obligations of Sublandlord (as Tenant) under the Overlease, except those agreed
to be performed by Subtenant hereunder; Subtenant shall have the right but not
the obligation to cure any Sublandlord default (as Tenant) under the Overlease.
During the Term of the Sublease, Sublandlord will, upon Subtenant's request,
exercise due diligence in attempting to obtain rent abatement from Overlandlord
when such abatement is available under the terms of the Overlease. Subtenant
shall be entitled to rent abatement under this Sublease to the extent the amount
of any rent abatement received by Sublandlord under the Overlease relates to the
Subleased Premises.


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         If the Overlease terminates as a result of a default or breach of
Sublandlord or Subtenant under this Sublease and/or the Overlease, then the
defaulting party shall be liable to the non-defaulting party for the direct
damage suffered as a result of such termination. Sublandlord covenants not to
commit or suffer any act or omission that will violate the Overlease. Neither
Sublandlord nor Subtenant shall be liable to the other under this Section 7.1 of
any indirect, special or consequential damages, including business interruption
or lost profits.

         7.2      EXCLUDED OBLIGATIONS. Notwithstanding anything to the contrary
herein, the incorporated provisions of the Overlease are amended or qualified as
follows:

                  (a) Sublandlord shall not be liable under any circumstances
         for a loss of or injury to property, or interference with Subtenant's
         business, however occurring, incidental to any failure to furnish any
         utilities or services.

                  (b) Sublandlord shall have no responsibility to perform or
         construct (or to pay the cost of performing or constructing) any
         repair, maintenance or improvement in or to the Subleased Premises.

                  (c) Except as expressly set forth in Section 3.1 hereof, Rent
         shall be abated under this Sublease only to the extent that Sublandlord
         receives a corresponding rent abatement under the Overlease.

                  (d) Wherever the Overlease grants to Sublandlord a grace or
         cure period, the corresponding grace or cure period under this Sublease
         shall be two (2) business days shorter in duration.

         The parties acknowledge that Sublandlord's ability to satisfy certain
of its obligations to Subtenant under this Sublease is contingent upon the full
and timely performance of Overlandlord's obligations under the Overlease. The
parties further acknowledge that, while Sublandlord will use reasonable efforts
to cause Overlandlord to perform its obligations under the Overlease,
Sublandlord will not be liable to Subtenant for any breach of Sublandlord's
obligations under this Sublease, nor shall such breach diminish Sublandlord's
rights hereunder, where the same is caused by or attributable to the failure of
Overlandlord to perform its obligations under the Overlease.

         7.3      OVERLANDLORD'S RIGHTS. Overlandlord shall have all rights with
respect to the Subleased Premises which it has reserved to itself as landlord
under the Overlease.

         7.4      TERMINATION OF OVERLEASE. In the event that Overlandlord
terminates the Overlease pursuant to its terms or the Overlease otherwise
terminates or expires, this Sublease shall likewise and simultaneously
terminate.



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                                  ARTICLE VIII

                                  MISCELLANEOUS

         8.1      NOTICES FROM ONE PARTY TO THE OTHER. All notices required or
permitted hereunder shall be in writing and addressed, if to the Subtenant, at
Subtenant's Address or such other address as Subtenant shall have last
designated by notice in writing to Sublandlord and, if to Sublandlord, at
Sublandlord's Address or such other address as Sublandlord shall have last
designated by notice in writing to Subtenant. Any notice shall be deemed duly
given when mailed to such address postage prepaid, registered or certified mail,
return receipt requested, or when delivered to such address by hand.

         Copies of any notices (default or otherwise) received from, or given
to, the Overlandlord and pertaining to the Subleased Premises will be provided
to the Subtenant by Sublandlord.

         8.2      ESTOPPEL CERTIFICATE. Upon not less than 15 days prior notice
by the requesting party, either party shall execute, acknowledge and deliver to
the other a statement in writing, addressed to such person as the requesting
party shall designate, certifying (a) that this Sublease is unmodified and in
full force and effect, (b) the dates to which Annual Fixed Rent, Operating
Expenses Allocable to the Subleased Premises, Landlord's Tax Expenses Allocable
to the Subleased Premises and additional rent have been paid, and (c) that the
requesting party is not in default hereunder (or, if in default, specifying the
nature of such default in reasonable detail). Any such certificate may be relied
upon by the person to which it is addressed as to the facts stated therein.

         8.3      BROKERAGE. Subtenant and Sublandlord mutually represent and
warrant that they have dealt with no broker in connection with this transaction,
other than Fallon Hines & O'Connor (the "Broker"); Sublandlord shall be
responsible for paying the fee to Broker pursuant to a separate agreement.
Subtenant and Sublandlord each agrees to defend, indemnify and save the other
harmless from and against any and all cost, expense or liability for any
compensation, commissions or charges claimed by any broker or agent other than
Broker with respect to the indemnifying party's dealings in connection with this
Sublease.

         8.4.     APPLICABLE LAW AND CONSTRUCTION. This Sublease shall be
governed by and construed in accordance with the laws of the Commonwealth of
Massachusetts. If any term, covenant, condition or provision of this Sublease 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
Sublease 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.


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<PAGE>   12

         There are no oral or written agreements between Sublandlord and
Subtenant affecting this Sublease. This Sublease may be amended, and the
provisions hereof may be waived or modified, only by instruments in writing
executed by Sublandlord and Subtenant.

         The titles of the several Articles and Sections contained herein are
for convenience only and shall not be considered in construing this Sublease.

         Unless repugnant to the context, the words "Sublandlord" and
"Subtenant" appearing in this Sublease 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 Sublease upon Subtenant shall
be joint and several.

         Any capitalized terms used herein and not otherwise defined have the
meaning ascribed to them in the Overlease.

         8.5      CONSENT BY OVERLANDLORD. This Sublease is conditioned upon
procuring the consent of Overlandlord to this Sublease in accordance with the
Overlease (the "Consent"), and the Sublandlord and Subtenant shall cooperate
with each other in seeking Overlandlord's Consent. If Consent is withheld, this
Sublease shall terminate upon the delivery of written notice to Sublandlord and
Subtenant that Overlandlord's Consent will not be given. If this Sublease is so
terminated: (i) all consideration previously paid by Subtenant to Sublandlord on
account of this Sublease shall be returned to Subtenant; and (ii) the parties
thereupon shall be relieved of any further liability or obligation under this
Sublease, except for those liabilities or obligations which have accrued and
remain unperformed as of the date this Sublease is so terminated.

         Sublandlord agrees that the request for Overlandlord's consent shall
include the following matters (provided Sublandlord does not guarantee that
Overlandlord's consent shall cover all such matters):

         a.       Sublandlord is in possession of the Subleased Premises.
         b.       The Overlease is in full force and effect and has not been
                  modified, except for the six specified amendments.
         c.       Neither Overlandlord nor Sublandlord is in default under the
                  Overlease.
         d.       There are no offsets or defenses existing which Overlandlord
                  has against the enforcement of the Overlease by Sublandlord.
         e.       Overlandlord's interest in the Overlease and in any trade
                  fixtures, inventory, furniture, machinery, equipment or other
                  personal property located on the Subleased Premises has not
                  been assigned, pledged or transferred. Overlandlord has not
                  received any notice that Sublandlord's interest in the
                  Subleased Premises has been assigned, pledged or transferred.


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<PAGE>   13

         f.       Overlandlord has not received any notice from any governmental
                  agency or authority or any violation of applicable law
                  relating to the Subleased Premises.
         g.       There are no legal proceedings pending or threatened relating
                  to the Subleased Premises.

         8.6      STORAGE SPACE. Sublandlord and Subtenant acknowledge that
storage space may be available in the parking garage of the Building provided
however (a) that Sublandlord makes no representations and warranties regarding
the availability of such storage space and is not leasing any such storage space
to Subtenant pursuant to this Sublease and (b) Subtenant shall deal directly
with Overlandlord as to the potential availability (and rental) of such storage
space.

         8.7      ELECTRICITY. Sublandlord and Subtenant acknowledge and agree
that Subtenant shall be solely responsible for the cost of all electricity
utilized in the Premises. If and to the extent the Premises are not currently
separately metered for electrical usage, Subtenant shall cause an electrical
meter to be installed prior to the Commencement Date at Subtenant's sole cost
and expense. All of such installation by Subtenant shall be subject to the terms
and conditions of Section 5.3 hereof and the applicable provisions of the
Overlease.

         8.8      CERTAIN LIMITATIONS. In no event shall Subtenant be liable for
any indirect or consequential damages; provided that this clause is not intended
to deprive Sublandlord of any of the rights and remedies available to it under
Article VII of the Overlease (as incorporated into this Sublease).


         EXECUTED as a sealed instrument in two or more counterparts on the day
and year first above written.

         SUBLANDLORD:

         The Pioneer Group, Inc.



         By: /s/ Stephen G. Kasnet
             Name: Stephen G. Kasnet
             Title: Executive Vice President
                    hereunto duly authorized




                                      -13-



<PAGE>   14

         SUBTENANT:

         Leerink Swann & Company



         By: /s/ Peter Flynn
             Name: Peter Flynn
             Title: Chief Legal Officer
                    hereunto duly authorized



                                      -14-
<PAGE>   15


                                    EXHIBIT A

         The following is the Overlease, as defined in Article I, Section 1.1.

         The following provisions of the Overlease are to be treated as
redacted, and are not incorporated into this Sublease:

         2.1.2  -       [Intentionally omitted]
         2.1.3  -       Options to Expand - Premises
         2.1.4  -       Rights of First Offer
         2.1.5  -       Rights of First Refusal
         2.1.6  -       Landlord's Recapture of Floor 18
         2.2(a) -       Rights to Use Common Facilities
         2.2.1  -       Parking
         2.4    -       Term and Commencement Date
         2.5    -       Monthly Fixed Rent Payments (redacted portions only)
         Article III -  Construction 
         4.1.2  -       Additional Building Operation Services 
         4.1.8  -       The Bay Club 
         4.1.11 -       Restrictions on Landlord 
         4.1.12 -       Building Management 
         4.4    -       Redecoration 
         8.16   -       Brokerage 
         8.17   -       Arbitration
         Article IX -   Priority of Lease; Rights of Institutional Mortgagee
         Exhibit D -    Exceptions to Priority of Tenant's Rights 
         Exhibit E -    Base Building Improvements 
         Exhibit F -    Construction Schedule 
         Exhibit G -    List of Engineers, Consultants, Contractors, and 
                        Subcontractors 
         Exhibit H -    Landlord's Work 
         Exhibit I -    Plans and Schedule for Landlord's Work
         Exhibit K -    Arbitration Methodology 
         Exhibit M -    Existing Leases 
         Exhibit N -    Consultant's Budget 
         First Amendment to the Overlease 
         Second Amendment to the Overlease 
         Third Amendment to the Overlease 
         Fourth Amendment to the Overlease 
         Fifth Amendment to the Overlease



                                      -15-

<PAGE>   16



                                    EXHIBIT B

                        Floor Plan of Subleased Premises



                       [Floor Plan Intentionally Omitted]




                                      -16-