<PAGE>

May 31, 2000



Mr. Kevin Rakin
Senior Vice President and
Executive Financial Officer
Genaissance Pharmaceuticals, Inc.
Five Science Park
New Haven, CT  06511                                 REVISED JUNE 7, 2000
                                                     --------------------

Dear Mr. Rakin:

FINOVA Capital Corporation ("we" or "Lessor") is pleased to enter into the
following leasing arrangement with Genaissance Pharmaceuticals, Inc. ("you" or
"Lessee") on the terms and conditions hereinafter set forth.

The outline of this Commitment is as follows:

LESSEE:                             Genaissance Pharmaceuticals, Inc.

LESSOR:                             FINOVA Capital Corporation.

EQUIPMENT:                          Perkin Elmer ABI Prism 3700 DNA Analyzers

CREDIT LINE:                        $10,000,000 line of credit for Equipment.
                                    All Equipment is subject to review and
                                    acceptance by Lessor.

EQUIPMENT LOCATION:                 Five Science Park, New Haven, CT  06511

ANTICIPATED DELIVERY:               May 2000 through December 2000

CLOSING DATE:                       The date that the Lessor makes payment
                                    for the Equipment covered under each
                                    schedule to the Master Lease (each a
                                    "Schedule" and collectively the "Schedules")
                                    with an aggregate cost of not less than
                                    $250,000, but no later than December 20,
                                    2000.

TERM - A:                           For take downs funded (1.) prior to Lessee's
                                    Initial Public Offering OR (2.) after
                                    Lessee's Initial Public Offering for less
                                    than $65,000,000, from each Closing Date
                                    until 38 months from the first day of the
                                    month next following or coincident with that
                                    Lease Term Commencement.

TERM - B:                           For take downs funded after Lessee's Initial
                                    Public Offering for equal to or greater than
                                    $65,000,000, from each Closing Date until 48
                                    months from the first day of the month next
                                    following or coincident with that Lease Term
                                    Commencement.

                                       1
<PAGE>

MONTHLY RENT - A:                   Monthly Rent equal to 2.925% of Equipment
                                    Cost would be payable monthly in advance.
                                    First and last months rent due in advance.

MONTHLY RENT - B:                   Monthly Rent equal to 2.448% of Equipment
                                    Cost would be payable monthly in advance.
                                    First and last months rent due in advance.

ADJUSTMENT TO MONTHLY
RENT PAYMENTS - A:                  If on the second business day preceding the
                                    Closing Date for each Schedule, the highest
                                    yield for three-year U.S. Treasury Notes as
                                    published in THE WALL STREET JOURNAL is
                                    greater or less than the yield on April 14,
                                    2000, the Monthly Rent Payments shall be
                                    increased or decreased to reflect such
                                    change in the yield. The yield as of April
                                    14, 2000 was 6.30%. As of the Closing Date,
                                    the Monthly Rent Payments shall be fixed for
                                    the entire term.

ADJUSTMENT TO
RENTAL PAYMENTS - B:                If on the second business day preceding the
                                    Closing Date for each Schedule, the highest
                                    yield for four-year U.S. Treasury Notes as
                                    published in THE WALL STREET JOURNAL is
                                    greater or less than the yield on April 14,
                                    2000, the Monthly Rent Payments shall be
                                    increased or decreased to reflect such
                                    change in the yield. The yield as of April
                                    14, 2000 was 6.36%. As of the Closing Date,
                                    the Monthly Rent Payments shall be fixed for
                                    the entire term

INTERIM RENT:                       Interim Rent shall accrue from each Closing
                                    Date until the 29th day of the month (27th
                                    day of the month in the case of February)
                                    unless the Closing Date is on the 30th or
                                    31st day of a month. If the Closing Date is
                                    the 31st day of a month, Interim Rent shall
                                    accrue until the 29th day of the next
                                    following month. If the Closing Date is the
                                    30th day of a month, there shall be no
                                    Interim Rent. Interim Rent shall be at the
                                    daily equivalent of the currently adjusted
                                    Monthly Rent Payment.

PURCHASE AGREEMENT - A:             The Lessee shall purchase all (but not less
                                    than all) the Equipment at the expiration of
                                    the term of each Schedule for twelve and
                                    one-half percent (12.5%), plus applicable
                                    sales and other taxes.

PURCHASE AGREEMENT - B:             The Lessee shall purchase all (but not less
                                    than all) the Equipment at the expiration of
                                    the term of each Schedule for ten percent
                                    (10%), plus applicable sales and other
                                    taxes.

NET LEASE:                          The Lease shall be a net-net-net lease
                                    containing the usual provisions in the
                                    Lessor's lease agreements and such other or
                                    different provisions that are agreed to by
                                    the parties. The


                                       2
<PAGE>

                                    Lessee shall be responsible for maintenance,
                                    insurance, taxes, and all other costs and
                                    expenses.

TAXES:                              Sales or use taxes shall be added to the
                                    Equipment Cost or collected on the gross
                                    rentals, as appropriate. In the event that
                                    Lessee claims a tax exempt status, the
                                    Lessee shall provide to Lessor a tax
                                    exemption certificate acceptable to Lessor.

INSURANCE:                          Prior to any delivery of Equipment, the
                                    Lessee shall furnish confirmation of
                                    insurance acceptable to the Lessor covering
                                    the Equipment including primary, all risk,
                                    physical damage, property damage and bodily
                                    injury with appropriate loss payee
                                    endorsement in favor of the Lessor.



WARRANT COVERAGE:                   In consideration for this Commitment by the
                                    Lessor, Lessee shall grant to the Lessor
                                    upon Lessee's acceptance of this Commitment
                                    Letter, warrants to purchase 41,666 shares
                                    of the common stock of the Lessee at an
                                    exercise price of $12.00 per share (the
                                    "Pre-IPO Warrants"). These warrants shall be
                                    exercisable from their date of grant until
                                    the close of business five years from the
                                    date of grant. These warrants shall contain
                                    (a) piggyback registration rights, including
                                    underwriter cutbacks or eliminations
                                    substantially similar to these contained in
                                    the warrant from Lessee to Lessor issued as
                                    of March 31, 2000, (b) antidilution
                                    protection and nondiscriminatory liquidation
                                    rights, substantially similar to these
                                    contained in the warrant from Lessee to
                                    Lessor issued as of March 31, 2000, and (c)
                                    cashless exercise (conversion) provisions.
                                    The Pre-IPO Warrants however will be subject
                                    to conversion at a later date (at Lessee's
                                    option) into warrants for common shares in
                                    whole or in part if Lessee consummates an
                                    initial public offering of equity securities
                                    of Lessee with proceeds of a least
                                    $65,000,000, a "Qualified IPO", on or before
                                    December 20, 2000 (expiration of line
                                    commitment). For each Closing following a
                                    Qualified IPO and for only that portion of
                                    the line still available, a calculated
                                    number of Pre-IPO Warrants shall be
                                    convertible to common stock warrants having
                                    an exercise price equal to 125% of the IPO
                                    price (herein referred to as the
                                    "Post-Qualified IPO


                                       3
<PAGE>

                                    Warrants"). The calculation, where "AF" is
                                    the amount funded at all post-Qualifed IPO
                                    closings is:

                                    ($10,000,000 - AF)/ ($10,000,000) x 41,666 =
                                    Pre-IPO Warrants

                                    (AF x .03)/(1.25 x IPO Price) =
                                    Post-Qualified IPO Warrants

ADDITIONAL COVENANTS:               There shall be no actual or threatened
                                    material conflict with, or material
                                    violation of, any regulatory statute,
                                    standard or rule relating to the Lessee, its
                                    present or future operations, or the
                                    Equipment.

                                    All statements made by the Lessee shall be
                                    correct and shall not omit any statement
                                    necessary to make the information supplied
                                    not be misleading. There shall be no breach
                                    of the representations and warranties of the
                                    Lessee in the Lease. The representations
                                    shall include that the Equipment Cost of
                                    each item of the Equipment does not exceed
                                    the fair and usual price for like quantity
                                    purchases of such item and reflects all
                                    discounts, rebates and allowances for the
                                    Equipment given to Lessee or any affiliate
                                    of Lessee by the manufacturer, supplier or
                                    anyone else including, without limitation,
                                    discounts for advertising, prompt payment,
                                    testing or other services.

                                    The Lessor shall not be responsible for any
                                    failure of suppliers or manufacturers of the
                                    Equipment or their distributors to perform
                                    their obligations to the Lessor or the
                                    Lessee.



                                    FINANCIAL REPORTING. During the period of
                                    the Commitment and the Term of the Lease,
                                    Lessee shall deliver to Lessor or cause to
                                    be delivered to Lessor the Lessee's
                                    quarterly financial statements within 45
                                    days following the end of each respective
                                    fiscal quarter and annual financial
                                    statements within 90 days following the end
                                    of each respective fiscal year. All annual
                                    financial statements shall be prepared in
                                    accordance with generally accepted
                                    accounting principles ("GAAP") and be
                                    audited by a reputable firm of certified
                                    public accountants acceptable to Lessor, and
                                    shall be accompanied by a certificate
                                    executed by such certified public
                                    accountants to the effect that the Lessee
                                    has complied with all covenants contained in
                                    the Lease Documents and there are no events
                                    of default thereunder ("Compliance
                                    Certificate"). All quarterly


                                       4
<PAGE>

                                    financial statements may be internally
                                    prepared in accordance with GAAP, and
                                    accompanied by a Compliance Certificate
                                    executed by the Lessee's Chief Financial
                                    Officer.

FEES AND EXPENSES:                  The Lessee shall be responsible for the
                                    Lessor's fees and expenses in connection
                                    with the transaction, including the expenses
                                    of counsel to prepare and review the
                                    documentation.

COMMITMENT FEE:                     With the acceptance of this Commitment
                                    by the Lessee, a Commitment Fee of $50,000
                                    shall be then due the Lessor. The
                                    Application Fee of $50,000 previously paid
                                    by the Lessee shall be considered as the
                                    Commitment Fee. The Commitment Fee (at our
                                    discretion shall be first applied to our
                                    Fees and Expenses in connection with this
                                    transaction) and any remainder shall be
                                    applied on a pro rata basis to the second
                                    Monthly Rent Payment of each Schedule.

SURVIVAL:                           This Commitment Letter shall survive
                                    closing. However, if there is any conflict
                                    between the terms and conditions of the
                                    Master Lease Agreement and Schedules and
                                    those of this Commitment Letter, the Master
                                    Lease Agreement and Schedules shall control.

This Commitment and the Closing of each Schedule contemplated herein are
subject, amongst other things, to receipt by us, in form and substance
satisfactory to us and our counsel, at or prior to Closing, of:

         (i)      all documentation and other requirements set forth herein
                  including but not limited to the Lease Documents and other
                  requirements set forth herein and as may be required by our
                  counsel; and

         (ii)     our receipt, in form and substance satisfactory to us, of all
                  financial and credit information requested by us, which
                  reflects no material adverse change in your condition,
                  business, financial or otherwise; and

         (iii)    evidence that the Equipment is free and clear of all liens and
                  encumbrances; and

         (iv)     evidence of such insurance required by us, written by insurers
                  and in amounts satisfactory to us; and

         (v)      such opinions of your outside counsel, certificates, waivers,
                  releases, Uniform Commercial Code Financing Statements, due
                  diligence searches, and further documents as may be required
                  by us or our counsel; and


                                       5
<PAGE>

         (vi)     evidence that no payment is past due to the Lessor from the
                  Lessee, whether as a borrower, a lessee, a guarantor or in
                  some other capacity and that there be no default under any
                  agreement, instrument or document between the Lessor and the
                  Lessee (including, without limitation, the Lease Documents);
                  and

         (vii)    evidence that the Lessee is in compliance with the provisions
                  of this Commitment; and

         (viii)   our receipt of evidence satisfactory to us, in our sole
                  discretion that the subject transaction is environmentally
                  acceptable. We shall have the right to require you to retain
                  the services of a firm acceptable to us and knowledgeable in
                  environmental matters to perform environmental investigations
                  of the Equipment and real property owned, operated or occupied
                  by you (including, without limitation, the Equipment Location)
                  and the surrounding areas.

                  Such investigation may include, but not be limited to, soil
                  and ground water testing to fully identify the scope of any
                  environmental issues impacting the transaction (including
                  Phase I and/or Phase II environmental reports). The scope and
                  results of such investigations must be satisfactory to us, in
                  our sole discretion.

In addition to all other conditions and requirements set forth herein, this
Commitment and the closing of each Schedule contemplated hereunder shall be
subject, in our sole judgment, that there be no material adverse change in your
financial, business or other condition. This Commitment is not assignable
without our prior written consent. We reserve the right to cancel this
Commitment in the event you or any of your officers, employees, agents or
representatives has made any misrepresentation to us or has withheld any
information from us with regard to the transaction contemplated hereby.

As used in this Commitment, the terms "satisfactory to us" or "acceptable to us"
or "satisfactory to our counsel" or "acceptable to our counsel" or terms of
similar import mean satisfactory or acceptable to us or our counsel in our or
its sole judgment and discretion.

This Commitment and the Lease Documents shall be governed by the laws of the
State of Delaware. Any dispute arising under this Commitment shall be litigated
by you only in any federal or state court located in the State of Arizona, or
any state court located in Maricopa County, Arizona; and you hereby irrevocably
submit to the personal jurisdiction of such courts and waive any objection that
may exist as to venue or convenience of such forums. Nothing contained herein
shall preclude us from commencing any action in any court having jurisdiction
thereof.

In the event that the Schedules do not close prior to January 1, 2001 because of
your failure to satisfy the conditions for the closing, or because of a material
adverse change in your financial, business or other condition, this Commitment
shall terminate and we shall have no liability to you and we shall retain, as
earned, the Commitment Fee.


                                       6
<PAGE>

In the event we fail to complete this transaction and such failure is not
because of your inability to satisfy all the conditions for closing or a
material adverse change in your financial, business or other condition, our
liability shall be limited to a return of the Commitment Fee, less Fees and
Expenses due hereunder.

Please execute the copy of this letter acknowledging your acceptance of the
terms hereof and return it to us. If a copy of this Commitment is not executed
and returned by you on or before June 13, 2000, this Commitment shall be deemed
withdrawn.


                                             Sincerely,

                                     FINOVA CAPITAL CORPORATION.

                                             By  /s/ Dannion C. Mcgary
                                               -----------------------------
                                                    Dannion C. McGary
                                                    Vice President - Credit


Accepted this ____ day of June, 2000


GENAISSANCE PHARMACEUTICALS, INC.



By:      /s/ Kevin Rakin
   ----------------------------------------------------------
         Kevin Rakin
         Executive Vice President and Chief Financial Officer







                                       7