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                                                                   EXHIBIT 10.53

                     FIRST AMENDMENT TO EMPLOYMENT AGREEMENT

     THIS FIRST AMENDMENT TO EMPLOYMENT AGREEMENT (the "Amendment"), dated as of
September 1, 2002, is by and between GENAISSANCE PHARMACEUTICALS, INC., a
Delaware corporation (the "Corporation") and KEVIN RAKIN ("Executive").

     WHEREAS, the Corporation and Executive have entered into that certain
Employment Agreement, dated as of August 24, 1998 (the "Employment Agreement");
and

     WHEREAS, the Corporation and Executive wish to amend the Employment
Agreement in the manner set forth in this Amendment.

     NOW THEREFORE, in consideration of the mutual covenants and agreements
hereinafter set forth, and other good and valuable consideration, the receipt
and sufficiency of which is hereby acknowledged, the parties hereto, intending
to be legally bound, agree as follows:

     1. DEFINED TERMS. Capitalized terms used herein but not defined in this
Amendment shall have the meaning given to such terms in the Employment
Agreement.

     2. Paragraph 1 of the Employment Agreement is hereby amended to read as
follows:

          "1. EMPLOYMENT. The Corporation hereby continues the employment of
     Executive in the capacity of President and Chief Executive Officer
     (collectively, the "CEO") of the Corporation during the term of this
     Agreement, and Executive hereby accepts such continued employment, on the
     terms and conditions hereinafter set forth. Executive represents that his
     employment by the Corporation pursuant to this Agreement does not violate
     any agreement, covenant or obligation to which he is a party or by which he
     is bound."

     3. Paragraph 2 of the Employment Agreement is hereby amended to read as
follows:

          "2. DUTIES. During the term of this Agreement, Executive shall perform
     all duties, consistent with his position as CEO, assigned or delegated to
     him by the Board of Directors of the Corporation (the "Board"), and
     normally associated with the position of CEO, and he shall devote
     substantially all of his full business time and best efforts to the
     advancement of the interests and business of the Corporation; provided that
     Executive may pursue passive investments and interests which in the
     aggregate do not result in the diversion of a material amount of
     Executive's business time. The Corporation will use its best efforts to
     cause Executive to continue to be elected a member of the Board throughout
     the Employment Term. Executive will have complete operating and
     administrative responsibility and authority over the Corporation subject to
     reasonable policies established by the Board. The Corporation shall provide
     and maintain an office located in New Haven, Connecticut, from where
     Executive may perform his duties."

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     4. Paragraph 4.a. of the Employment Agreement is hereby amended to read as
follows:

          "a. BASE SALARY. The Corporation shall pay Executive a Base Salary,
     payable in equal installments at such payment intervals as are the usual
     custom of the Corporation, but not less often than monthly, at an annual
     rate of $329,600, less such deductions or amounts to be withheld as shall
     be required by applicable law (the "Base Salary"). The Base Salary shall be
     reviewed annually by the Board in the third quarter of each fiscal year of
     the Corporation (commencing with the fiscal year ending December 31, 1999)
     and shall be increased (effective as of September 1 in such fiscal year) by
     such amount, if any, as the Board, in its sole discretion, shall determine.
     Neither the Corporation nor the Board may reduce the Base Salary as so
     increased."

     5. Paragraph 4.c.(v) of the Employment Agreement is hereby amended to read
as follows:

          "(iv) Throughout the Employment Term, the Corporation, at its expense,
     shall furnish an automobile to Executive (owned or leased by the
     Corporation) commensurate with his position as CEO and shall reimburse
     Executive for reasonable maintenance, operating and insurance expenses
     incurred in the use of such automobile in connection with business
     activities conducted on behalf of the Corporation."

     6. ENTIRE AGREEMENT. The Employment Agreement, as amended by this
Amendment, contains the entire understanding between the parties hereto with
respect to the subject matter hereof and supersedes any prior or contemporaneous
contracts, agreements, understandings and/or negotiations, whether oral or
written.

                      [THE NEXT PAGE IS THE SIGNATURE PAGE]

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     IN WITNESS WHEREOF, the parties hereto have made this First Amendment
effective as of the day and year first above written.

                                  CORPORATION:

                                  GENAISSANCE PHARMACEUTICALS, INC.

                                  By: /s/ Gualberto Ruano
                                     -------------------------------
                                     Name: Gualberto Ruano
                                     Its Vice Chairman and
                                     Chief Scientific Officer

                                  EXECUTIVE:

                                  /s/ Kevin Rakin
                                  -----------------------------------
                                  Kevin Rakin<Page>

                                                             EXHIBIT NO. 10.54

          CONFIDENTIAL MATERIALS OMITTED AND FILED SEPARATELY WITH THE
         SECURITIES AND EXCHANGE COMMISSION. ASTERISKS DENOTE OMISSIONS.

                     AMENDMENT TO THE HAP2000(TM) AGREEMENT

     This Amendment to the HAP2000(TM) Agreement (the "Amendment") dated
November 22, 2002 (the "Effective Date"), is made by and between Genaissance
Pharmaceuticals, Inc., a Delaware corporation having its principal place of
business at Five Science Park, New Haven, Connecticut 06511 ("Genaissance"), and
Johnson & Johnson Pharmaceutical Research & Development, L.L.C., having its
principal place of business at 920 U.S. Route 202, Raritan, NJ 08869 ("JJPRD").
JJPRD and Genaissance are sometimes referred to herein individually as a party
and collectively as the parties. Reference to a party herein includes a
reference to its Affiliates (as hereinafter defined) unless otherwise indicated.

WITNESSETH:

     WHEREAS, Genaissance and Janssen Research Foundation, a division of Janssen
Pharmaceutical, N.V., have previously entered into the HAP2000(TM) Agreement
dated November 22, 2000 (the "Agreement");

     WHEREAS, Janssen Pharmaceutica, N.V. has assigned all of the rights and
obligations of its Janssen Research Foundation division to its Johnson & Johnson
Pharmaceutical Research & Development division ("Janssen") as of January 1,
2002;

     WHEREAS, JJPRD is an Affiliate of Janssen Pharmaceutica, N.V. hereunder,
Genaissance and Janssen Pharmaceutica, N.V. wish to make JJPRD a party to this
Amendment, JJPRD wishes to be a party to this Amendment, and any reference to
Janssen hereunder shall be a reference to Janssen Pharmaceutica, N.V. and JJPRD;
and

     WHEREAS, the parties desire to amend certain terms of the Agreement and
incorporate this Amendment therein.

     NOW THEREFORE, in consideration of the premises and of the mutual covenants
and agreements contained herein and for other good and valuable consideration,
the receipt and sufficiency of which are hereby acknowledged, the parties
intending to be legally bound agree as follows:

1.   DEFINITIONS. All capitalized terms used herein and not otherwise defined
zherein shall have the respective meanings given to them in the Agreement.

2.   AMENDMENTS TO AGREEMENT.  The Agreement is, effective as of the Effective
Date hereof, hereby amended as follows:

     A.   Throughout the Agreement, "DECOGEN(TM)" is replaced with "DECOGEN(R)".

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     B.   Section 1.22 is hereby amended to read as follows:

                 1.22   "HAP(TM) MARKER ASSOCIATION" shall mean all associations
          between HAP(TM) Markers or HAP(TM) Marker Combinations and (a) the
          response to a Drug within a Drug Class or (b) the presence of, or a
          susceptibility for, any disease or condition in humans, where such
          association is discovered [**].

     C.   A new section 1.55 is hereby added, which reads as follows:

                 1.55   "[**] RESEARCH PROJECT" shall mean the Research Project
          performed jointly by Janssen and Genaissance to look for HAP Marker
          Associations relating to response to [**] to be more fully described
          in EXHIBIT H3 to be appended hereto within [**] days of the Effective
          Date of this Amendment and any updates thereto which are added prior
          to the end of the Access Period.

     D.   A new section 1.56 is hereby added, which reads as follows:

                 1.56   "[**] RESEARCH PROJECT" shall mean the Research Project
          performed jointly by Janssen and Genaissance to look for HAP Marker
          Associations relating to response to [**], to be more fully described
          in an EXHIBIT H4 to be appended hereto prior to [**].

     E.   A new section 1.57 is hereby added, which reads as follows:

                 1.57   "[**] RESEARCH PROJECT" shall mean the Research Project
          performed jointly by Janssen and Genaissance to look for HAP Marker
          Associations relating to [**] genes, to be more fully described in an
          EXHIBIT H2 appended hereto, and any updates thereto which are added
          within [**] days of the Effective Date of this Amendment.

     F.   A new section 1.58 is hereby added, which reads as follows:

                 1.58   "[**] RESEARCH PROJECT" shall mean the Research Project
          performed jointly by Janssen and Genaissance to look for HAP Marker
          Associations relating to [**], to be more fully described in an
          EXHIBIT H5 to be appended hereto within [**] days of the Effective
          Date of this Amendment and any updates thereto which are added prior
          to [**].

     G.   A new section 1.59 is hereby added, which reads as follows:

                 1.59   "GENOTYPING PROJECT" shall have the meaning set forth in
          Section 3.1(c).

     H.   A new section 1.60 is hereby added, which reads as follows:

                 1.60   "[**] GENOTYPING PROJECT" shall mean the Genotyping
          Project in which Genaissance will genotype Janssen Patient Samples on
          [**] genes as more fully described in EXHIBIT J1 to be appended hereto
          within [**] days of the

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          Effective Date of this Amendment and any updates thereto which are
          added prior to the end of the Access Period.

     I.   A new section 1.61 is hereby added, which reads as follows:

                 1.61   "GENOTYPING SERVICES" shall have the meaning set forth
                 in Section 3.1(c).

     J.   A new section 1.62 is hereby added, which reads as follows:

                 1.62   "JANSSEN PATIENT SAMPLE" shall mean any blood or DNA
          sample that is (a) utilized by Janssen in a Research Project or (b)
          supplied by Janssen to Genaissance for performing a Research Project
          or a Genotyping Project.

     K.   Section 2.1.2 is hereby amended to read as follows:

                 2.1.2  RESEARCH LICENSES.  Subject to the terms of this
          Agreement, Genaissance hereby grants to Janssen the following
          worldwide licenses under the Genaissance Know-How and Genaissance
          Patent Rights:

                        (a)    upon payment of the Product License Fee A set
          forth in Section 4.5, an [**] license, with the right to grant
          sublicenses in accordance with Section 2.1.8, to use (i) all genotype
          and HAP Marker data generated by Janssen or Genaissance on Janssen
          Patient Samples in the [**] Research Project and (ii) all HAP Marker
          Associations and all HAP Marker Combinations discovered in the [**]
          Research[**]Project solely for internal research to discover and
          develop Drugs within a Drug Class; and

                        (b)    upon payment of the Product License Fee B set
          forth in Section 4.5, an [**] license, with the right to grant
          sublicenses in accordance with Section 2.1.8, to use (i) all genotype
          and HAP Marker data generated by Janssen or Genaissance on Janssen
          Patient Samples in the [**] Research Project and (ii) all HAP Marker
          Associations and all HAP Marker Combinations discovered in the [**]
          Research Project solely for internal research to discover and develop
          Drugs within a Drug Class; and

                        (c)    an [**] license, with the right to grant
          sublicenses in accordance with Section 2.1.8, to use (i) all genotype
          and HAP Marker data generated by Janssen or Genaissance on Janssen
          Patient Samples in any Research Project other than the [**] Research
          Project or the [**] Research Project and (ii) all HAP Marker
          Associations and all HAP Marker Combinations discovered in a Research
          Project , other than the [**] Research Project or the [**] Research
          Project, solely for internal research to discover and develop Drugs
          within a Drug Class; and

                        (d)    a [**] license, with the right to grant
          sublicenses in accordance with Section 2.1.8, to use all HAP Marker
          Associations and HAP

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          Marker Combinations not included in subsection (a), (b) or (c) of this
          Section 2.1.2 solely for internal research and development purposes;
          and

                        (e)    a [**] license, without the right to grant
          sublicenses, to use the HAP(TM) Markers from the ISOGENOMICS(TM)
          Database (and any corresponding Isogene Clones ordered by Janssen
          pursuant to Section 3.7 hereof) solely for internal research and
          development purposes during the Access Period and the Additional Use
          Period, if applicable.

                 The [**] research and development licenses granted pursuant to
          this section 2.1.2 will be subject to: (i) Genaissance's retention of
          a [**] license [**] to use such HAP Marker Associations and HAP Marker
          Combinations to develop and commercialize Diagnostic Products,
          PROVIDED THAT Genaissance's [**] license under this Section 2.1.2
          shall not include the right to make, have made, use, have used,
          market, have marketed, sell and have sold any [**]; and (ii) any
          rights granted by Genaissance to Third Parties before the discovery of
          the licensed HAP Marker Associations and HAP Marker Combinations
          referenced in subsection (a), (b) or (c) of this section 2.1.2,
          pursuant to Section 5.1.3.

     L.   Section 2.1.3 is hereby amended to read as follows:

                 2.1.3  COMMERCIAL LICENSE(S) TO HAP(TM) MARKER COMBINATIONS AND
          HAP(TM) MARKER ASSOCIATIONS. Subject to the terms of this Agreement,
          Genaissance hereby grants to Janssen the following licenses:

                        (a)    an exclusive, perpetual worldwide commercial
          license (even as to Genaissance), with the right to grant sublicenses
          in accordance with Section 2.1.8, under the Genaissance Patent Rights
          and Genaissance Know-How to use all HAP(TM) Marker Associations
          discovered in the [**]Research Project and all HAP(TM) Marker
          Combinations relating to such Associations, to perform prospective
          clinical trials, to make, have made, use, have used, market, have
          marketed, sell and have sold (i) any Drug within a Drug Class for [**]
          and (ii) any Diagnostic Product for [**];

                        (b)    notwithstanding the exclusive license granted to
          Janssen in Section 2.1.3(a), Genaissance shall have a co-exclusive,
          perpetual worldwide commercial license (with only Genaissance and
          Janssen retaining rights), with the right to grant sublicenses in
          accordance with Section 2.1.8, under the Genaissance Patent Rights and
          Genaissance Know-How to use all of the HAP(TM) Marker Associations and
          HAP(TM) Marker Combinations referred to in the foregoing subsection
          (a) to make, have made, use, have used, market, have marketed, sell
          and have sold any Diagnostic Product PROVIDED THAT Genaissance's
          co-exclusive license under this Section 2.1.3(b) shall not include the
          right to make, have made, use, have used, market, have marketed, sell
          and have sold any [**];

                        (c)    an exclusive, perpetual worldwide commercial
          license (even as to Genaissance), with the right to grant sublicenses
          in accordance with

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          Section 2.1.8, under the Genaissance Patent Rights and Genaissance
          Know-How to use all HAP(TM) Marker Associations discovered in the
          [**]Research Project or any other specific Research Project other than
          the [**]Research Project and all HAP(TM) Marker Combinations relating
          to such Associations, to perform prospective clinical trials, to make,
          have made, use, have used, market, have marketed, sell and have sold
          (i) any Drug within the Drug Class for [**] and (ii) any Diagnostic
          Product for [**];

                        (d)    notwithstanding the exclusive license granted to
          Janssen in Section 2.1.3(c), Genaissance shall have a co-exclusive,
          perpetual, worldwide commercial license (with only Genaissance and
          Janssen retaining rights), with the right to grant sublicenses in
          accordance with Section 2.1.8, under the Genaissance Patent Rights and
          Genaissance Know-How to use all of the HAP(TM) Marker Associations and
          HAP(TM) Marker Combinations referred to in the foregoing subsection
          (c) to make, have made, use, have used, market, have marketed, sell
          and have sold any Diagnostic Product, PROVIDED THAT Genaissance's
          co-exclusive license under this Section 2.1.3(d) shall not include the
          right to make, have made, use, have used, market, have marketed, sell
          and have sold any [**];

                 PROVIDED THAT:

                        (i)    the licenses in the foregoing subsections (a),
                 (b), (c) and (d) with respect to the [**] Research Project and
                 the [**]Research Project will be subject to any rights reserved
                 by Genaissance before the discovery of the HAP Marker
                 Associations and HAP Marker Combinations, where such
                 reservation by Genaissance of pre-existing rights is evidenced
                 by contemporary written documentation, and

                        (ii)   the licenses in the foregoing subsections (a),
                 (b), (c) and (d) will be subject to any rights granted by
                 Genaissance to Third Parties before the discovery of the HAP
                 Marker Associations and HAP Marker Combinations, where such
                 grant of pre-existing rights by Genaissance is evidenced by
                 contemporary written documentation.

                 Genaissance shall [**] grant to Janssen a [**]commercial
          license, with the right to grant sublicenses in accordance with
          Section 2.1.8, under any other Patent Rights of Genaissance necessary
          for Janssen to exercise its rights under the commercial licenses
          obtained to HAP(TM) Marker Combinations and HAP(TM) Marker
          Associations, except that such license shall not include any HAP(TM)
          Marker Association Patent Rights not otherwise licensed to Janssen.

                 Notwithstanding the rights granted to Janssen in subsections
          (a), (b), (c) and (d) above, Genaissance reserves the right to grant
          to other HAP2000(TM) Members research and development licenses under
          similar terms and conditions as those granted to Janssen under Section
          2.1.1 and subsections (d) and (e) of section 2.1.2.

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                 For purposes of this Agreement, "HAP(TM) Marker Combination"
          shall mean the specific HAP(TM) Marker or the specific group or
          combination of HAP(TM) Markers [**] HAP(TM) Marker[**] HAP(TM) Markers
          [**] HAP(TM) Marker [**] HAP(TM) Markers [**] HAP(TM) Marker
          [**]HAP(TM) Marker [**] HAP(TM) Marker(s) [**] HAP(TM) Marker[**]
          HAP(TM) Marker [**] HAP(TM) Markers [**] HAP(TM) Marker [**].

                 For purposes of this Agreement, "Disease Fields" shall mean (i)
          with respect to a Drug for which a license is granted to Janssen under
          Section 2.1.3(a) or 2.1.3(c) and which is covered by a Valid Claim of
          Janssen Patent Rights owned by Janssen, any and all disease
          indications (unless such Janssen Patent Rights are limited to the use
          of the Drug for specific disease indications, in which case the
          Disease Fields shall be limited to the disease indications included
          within the scope of such Janssen Patent Rights) or (ii) with respect
          to a Drug for which a license is granted to Janssen under Section
          2.1.3(a) and which is covered by a Valid Claim of Janssen Patent
          Rights licensed to Janssen, any and all disease indications included
          in the field of the license to Janssen.

                 The existence of the license granted to Janssen under this
          Section 2.1.3 will be noted in the ISOGENOMICS(TM) Database without
          revealing the identity of Janssen, unless authorized by Janssen. In
          the event similar license(s) are granted by Genaissance to another
          HAP2000(TM) Member, the existence of such licenses will be noted in
          the Isogenomics(TM) Database without revealing the identity of such
          other HAP2000(TM) Member, unless authorized by such HAP2000(TM)
          Member.

     M.   Section 2.1.4 is hereby amended to read as follows:

                 2.1.4  R&D LICENSE TO HAP MARKERS FOR JANSSEN PROPRIETARY
          DATABASE. Subject to the terms of this Agreement, Genaissance hereby
          grants to Janssen a worldwide [**] license, [**], under the
          Genaissance Patent Rights and Genaissance Know-How to use one or more
          HAP Markers derived from the Janssen Proprietary Database (and any
          corresponding Isogene Clones ordered by Janssen pursuant to section
          3.7 hereof) solely for internal research and development purposes.

     N.   Section 2.1.8 is hereby amended to read as follows:

                 2.1.8  SUBLICENSING BY JANSSEN. Janssen shall have the right to
          grant sublicenses of the rights granted to Janssen pursuant to
          Sections 2.1.2, 2.1.3, 2.1.4, and 2.1.5 to Third Parties for the
          development and marketing of Products; PROVIDED that each Third Party
          sublicensee shall execute a written agreement pursuant to which it
          assumes the applicable obligations of Janssen hereunder.

     O.   A new sentence is added to the end of Section 2.4, NO GRANT OF OTHER
          TECHNOLOGY OR PATENT RIGHTS, which reads as follows:

          For purposes of clarity, Genaissance shall not obtain any ownership of
          or license rights to discoveries, other than HAP Markers, HAP Marker
          Associations and

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          HAP Marker Combinations, that are made solely by Janssen using the
          ISOGENOMICS Database, the DECOGEN(R) Informatics Platform or other
          Genaissance Know-How and Genaissance Patent Rights licensed hereunder.

     P.   A new Section 2.5 is hereby added, which reads as follows:

                 2.5    LIMITATION ON GENAISSANCE'S [**] LICENSES.  During the
          Access Period, Genaissance will not use the ISOGENOMICS Database or
          the HAP Markers in the ISOGENOMICS Database to research, develop or
          commercialize Diagnostic Products for use in connection with any Drug
          that (a) is within Janssen Patent Rights or (b) [**].

     Q.   A new section 3.1(c) is hereby added, which reads as follows:

          3.1(c)  GENOTYPING SERVICES.  During the Access Period and the
          Additional Use Period, if applicable, Janssen may request that
          Genaissance determine for Janssen the genotypes for a set of one or
          more Polymorphisms in a set of Janssen Patient Samples. Such
          Genotyping Services shall not include Genaissance deriving HAP Markers
          from such genotypes or performing any statistical analyses to
          correlate genotypes with a phenotype. Furthermore, such Genotyping
          Services shall not be considered to be part of any Research Project
          hereunder except at the sole discretion of Janssen. Prior to
          commencing Genotyping Services for a particular project, the parties
          shall agree in writing on the scope of the services to be provided,
          including, without limitation, whether the project will be considered
          to be a Research Project hereunder, the Polymorphisms and the time
          frame for completing the services, and the written description of this
          project ("Genotyping Project") shall be appended to EXHIBIT J of this
          Agreement. Janssen, at its option, may pay Genaissance for such
          Genotyping Services from the minimum HAP Typing Services
          payment owed by Janssen pursuant to Section 4.4 at the same rate of
          $[**]. Upon full utilization by Janssen of such minimum HAP Typing
          Services payment for HAP Typing Services or Genotyping Services,
          Janssen shall pay Genaissance a fee of $[**].[**]

     R.   Section 4.1 is hereby amended to read as follows:

                 4.1    SUBSCRIPTION FEES.  In consideration of the rights
          granted to Janssen under Section 2.1, Janssen agrees to pay
          Genaissance a subscription fee ("Subscription Fee") as follows:

                 For the first Agreement Year, [**] Dollars ($[**]);

                 For the second Agreement Year, [**] Dollars ($[**]); and

                 For the third Agreement Year, [**] Dollars ($[**])

          which payments for each year shall be made either: (i) in equal
          calendar quarterly payments in advance beginning within [**] days
          after the Effective Date, except that the amounts of the first and
          last payments for each Agreement year shall be prorated based on the
          number of days in the applicable partial calendar quarter or

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          (ii) with respect to the third Agreement Year, in full within [**]
          after the second anniversary of the Effective Date. [**] Janssen [**]
          Genaissance [**] Genaissance [**] Janssen [**] Genaissance [**]
          Genaissance [**].

                 The Subscription Fee covers: (i) access to the ISOGENOMICS
          Database in accordance with this Agreement; (ii) the installation,
          technology transfer, training and support as provided in EXHIBIT C and
          EXHIBIT D; (iii) the site license for the DECOGEN(R) Informatics
          Platform; (iv) reserved capacity for HAP Typing Services; (v)
          performance by Genaissance of Research Projects pursuant to Section
          3.1(a), subject to payment of any applicable Set-up Fee set forth in
          Section 4.2; and (vi) the Janssen Gene Allocation.

     S.   Section 4.2 is hereby amended to read as follows:

                 4.2.   SET-UP FEE. For each Research Project mutually agreed to
          be performed by Genaissance pursuant to Section 3.1(a) involving a
          Drug or Diagnostic Product for which more than [**] of Genaissance's
          services, excluding the time of the Genaissance project manager
          described in EXHIBIT F, will be required to assist in preparation of
          the plan for the Research Project, Janssen shall pay to Genaissance a
          nonrefundable set-up fee (the "Set-Up Fee") in an amount to be
          determined by the Steering Committee, based on payment to Genaissance
          at the rate of $[**]. No set-up fee shall be due for the first [**]
          such Research Projects initiated during the Access Period. For
          purposes of clarity, the first [**] such Research Projects for which
          no set-up [**] is due are the [**] Research Project described in
          EXHIBIT H2, the [**] Research Project described in EXHIBIT H3, and the
          [**] Research Project described in EXHIBIT H4. The Set-Up Fee shall be
          provided to Genaissance within [**] days after the date the written
          description for the Research Project is appended to this Agreement.

     T.   Section 4.4 is hereby amended to read as follows:

                 4.4    HAP TYPING SERVICE FEE. In the event Janssen requests
          HAP Typing Services pursuant to Section 3.1(b), Janssen shall pay to
          Genaissance a nonrefundable fee (the "HAP Typing Service Fee") of
          $[**] delivered. The HAP Typing Service Fee includes (i) Genaissance
          determining the genotypes for Polymorphisms and (ii) Genaissance
          building the HAP Markers from such genotypes using its proprietary HAP
          Builder program. The HAP Typing Service Fee shall be provided to
          Genaissance quarterly for only those Polymorphisms genotyped during
          the past quarter, upon receipt of an invoice from Genaissance. Janssen
          agrees to pay Genaissance a minimum of $[**] for HAP Typing Services
          during the first two (2) years of the Access Period. If, by the end of
          the second year of the Access Period, Janssen has not paid Genaissance
          at least $[**] for HAP Typing Services (including any additional
          amounts paid at the end of the first year under the previous
          sentence), Janssen agrees to pay Genaissance the difference between
          $[**] and the sum actually paid, which amount may be applied by
          Janssen as a credit towards any fees for HAP Typing Services or

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          Genotyping Services performed by Genaissance during the balance of the
          Access Period or Additional Use Period, if applicable.

     U.   Section 4.5 is hereby amended to read as follows:

                 4.5    PRODUCT LICENSE FEES. Janssen shall pay to Genaissance
          within [**] days after the Effective Date of this Amendment (a) a
          nonrefundable license fee of [**] Dollars ($[**]) in recognition of
          all the licenses conferred to Janssen in Section 2.1.2(a), 2.1.3(a)
          and 2.1.3(b) ("Product License Fee A") and (b) a nonrefundable license
          fee of [**] Dollars ($[**]) in recognition of all other licenses
          conferred to Janssen in Section 2.1.2(b), 2.1.2(c), 2.1.2(d),
          2.1.3(c), 2.1.3(d) and 2.1.4 ("Product License Fee B").

     V.   Section 4.6 is hereby amended to read as follows:

                 4.6    MILESTONE PAYMENTS FOR INITIAL DRUG PRODUCTS AND INITIAL
          DIAGNOSTIC PRODUCTS. Janssen shall pay to Genaissance a [**] payment
          as set forth below upon the achievement of each of the applicable
          milestones for the [**] for an Initial Drug Product and for Initial
          Diagnostic Products. For the avoidance of doubt, it is understood and
          agreed that [**] payment(s) under Sections 4.6.2(a) and 4.6.2(b) shall
          be due and payable to Genaissance by Janssen [**] for all HAP(TM)
          Marker Combinations and HAP(TM) Marker Associations licensed under
          Section 2.1.3 or 2.1.5 hereof for any Initial Drug Product or Initial
          Diagnostic Product. Fees for other Products are set forth in Section
          4.8.

                        4.6.1  INITIAL DRUG PRODUCTS. Janssen shall pay to
          Genaissance a [**] payment in the amount of [**] Dollars ($[**]) upon
          [**]for an Initial Drug Product for which a license is granted to
          Janssen pursuant to Section 2.1.3 or 2.1.5 hereof in any of the United
          States, any Major European Country or Japan (e.g., when a milestone is
          reached first, for example, in the United States, no payment is due
          upon reaching the same milestone in another country for [**] for such
          Initial Drug Product). It is agreed that Initial Drug Products that
          arise from or relate to HAP Marker Combinations or HAP Marker
          Associations discovered in the [**] Research Project or the [**]
          Research Project will be excluded from payment of the lump sum royalty
          for Initial Drug Products.

                        4.6.2  INITIAL DIAGNOSTIC PRODUCTS. Janssen shall pay to
          Genaissance a [**] payment in the amount of [**] Dollars ($[**]) for
          (a) the first Initial Diagnostic Product for which a license is
          granted to Janssen pursuant to Section 2.1.3 or 2.1.5 hereof and which
          is used in the prognosis of the response to an Initial Drug Product
          and (b) each Initial Diagnostic Produc[**] for which a license is
          granted to Janssen pursuant to Section 2.1.3 or 2.1.5 hereof and which
          is not used in the prognosis of the response to an Initial Drug
          Product, upon the receipt of the first regulatory approval in any of
          the United States, any Major European Country or Japan (e.g., when a
          milestone is reached first, for example, in the United States, no
          payment is due upon reaching the same milestone in another country for
          the same Initial Diagnostic Product).

                                        9
<Page>

                 Janssen will immediately notify Genaissance upon the
          accomplishment of the commercial use milestone for each Research
          Project and the accomplishment of the milestone for each Product and,
          within [**] days thereof, Janssen shall make the corresponding
          milestone payment to Genaissance in United States dollars by bank
          check or wire transfer.

     W.   A new sentence is hereby added to the end of Section 4.8.1 (a) Other
          Drug Products, which reads as follows:

          It is agreed that Drug Products that arise from or relate to HAP
          Marker Combinations or HAP Marker Associations discovered in the
          [**]Research Project or the [**]Research Project will be excluded from
          payment of any [**] for Drug Products.

     X.   A new sentence is hereby added to the end of Section 4.8.2 (a) Other
          Drug Products, which reads as follows:

          It is agreed that Drug Products that arise from or relate to HAP
          Marker Combinations or HAP Marker Associations discovered in the
          [**]Research Project or the [**]Research Project will be excluded from
          payment of any [**] for Drug Products.

     Y.   Section 5.1.3 is hereby amended to read as follows:

                 5.1.3  OWNERSHIP OF HAP(TM) MARKER ASSOCIATIONS AND HAP(TM)
          MARKER COMBINATIONS. Genaissance shall have sole ownership of all
          right, title and interest in all HAP Marker Associations and all HAP
          Marker Association Patent Rights. Janssen shall disclose to
          Genaissance any HAP Marker Associations from a Research Project
          discovered solely by employees of Janssen or others acting on behalf
          of Janssen and such HAP Marker Associations shall be treated as the
          Confidential Information of Genaissance. Janssen shall execute and
          deliver, without charge to Genaissance, assignment of all its right,
          title and interest in and to HAP Marker Associations to Genaissance
          subject to Janssen's right to use the HAP Marker Associations and HAP
          Marker Combinations pursuant to the terms of this Agreement.

3.   REPRESENTATIONS AND WARRANTIES. Each party hereby represents and warrants
to the other that it has full authority and power to enter into this Amendment,
that it has secured any and all necessary approvals, permits or consents deemed
necessary or advisable for the consummation of the transactions contemplated
hereby and that upon execution by such party, this Amendment shall immediately
be a valid and binding obligation of such party, enforceable against it in
accordance with its terms.

4.   EFFECT OF AMENDMENTS. On and after the Effective Date hereof, the Agreement
shall be deemed to be amended and supplemented as hereinabove set forth, as
fully and with the same force and effect as if the amendments set forth herein
had originally been set forth in the Agreement.

                                       10
<Page>

5.   LIMITATIONS. Except as amended and supplemented hereby, all the terms and
provisions of the Agreement shall remain unchanged and in full force and effect.
No alteration or amendment to this Amendment shall be binding on any party
hereto unless reduced to writing signed by both parties.

6.   COUNTERPARTS. This Amendment may be executed in two or more counterparts,
all such counterparts taken together shall constitute the original thereof.

7.   FACSIMILE COPIES. For purposes of this Amendment a signed facsimile copy
shall have the same force and effect as an original signed agreement.

                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK.]

                                       11
<Page>

IN WITNESS WHEREOF, the undersigned have executed this Amendment as of the date
first above written.

GENAISSANCE PHARMACEUTICALS, INC.          JANSSEN PHARMACEUTICA, N.V.

By:    /s/ Gerald F. Vovis              By:      /s/ L.F. Lauwers
       ------------------------------          ---------------------------------

Name:  Gerald F. Vovis                  Name:    L.F. Lauwers, M.D.
                                                 Vice President
Title: Executive Vice President and     Title: Johnson & Johnson Pharmaccutical
       Chief Technology Officer                R & D

Date:  25 November 2002                 Date:    20 Nov 2002

By:
       ------------------------------
Name:
       ------------------------------
Title:
       ------------------------------
Date:
       ------------------------------

                                       12
<Page>

                                   EXHIBIT H3

                              [**] RESEARCH PROJECT

                     To be Agreed by Janssen and Genaissance

                                        1
<Page>

                                   EXHIBIT H4

                              [**] RESEARCH PROJECT

                     To be Agreed by Janssen and Genaissance

                                        2
<Page>

                                   EXHIBIT H5

                              [**] RESEARCH PROJECT

                     To be Agreed by Janssen and Genaissance

                                        3
<Page>

                                    EXHIBIT J

                               GENOTYPING PROJECTS

                     To Be Agreed by Janssen and Genaissance

                                        4
<Page>

                                   EXHIBIT J1

                             [**] GENOTYPING PROJECT

                     To be Agreed by Janssen and Genaissance

                                        5

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