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                                                           EXHIBIT NO. 10.49


                        GENAISSANCE PHARMACEUTICALS, INC.
                                Five Science Park
                               New Haven, CT 06511
                                 (203) 773-1450



                                                              February 18, 2002



VIA FACSIMILE AND FEDERAL EXPRESS

[Name Registration Rights Holder]
[Address of Registration Rights Holder]

         Re: Genaissance Pharmaceuticals, Inc. - Registration Rights Waiver
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Dear Investor:

         On October 18, 2001, Genaissance Pharmaceuticals, Inc. ("Genaissance")
filed a registration statement ("Registration Statement") with the United States
Securities and Exchange Commission ("SEC") on Form S-3. The Registration
Statement has been declared effective by the SEC. The Registration Statement is
a "universal shelf registration statement." It relates to the possible offering
of Genaissance common stock, preferred stock, debt and/or warrants to purchase
such securities in the future. To proceed with an offering, Genaissance would
need to, among other things, file a prospectus supplement with the SEC
specifying the type of securities to be offered (e.g., common stock) and the
terms and conditions of the offering (e.g., the number of shares to be offered,
the price per share, and whether the offering would be underwritten). You may
view the Registration Statement by accessing our EDGAR filings on the SEC's
website (//www.sec.gov). Genaissance filed the Registration Statement in order
to complete in advance some of the regulatory requirements which must be met
before Genaissance can access the capital markets.

         You are a party to the [Amended and Restated Registration Rights
Agreement] (the "Agreement"), dated as of [March 10, 2000], by and among
Genaissance and certain investors that purchased shares of Genaissance Series
[B/KBH Preferred Stock] in [February and/or March 2000]. The Series [B/KBH
Preferred Stock] was converted into Genaissance common stock in August 2000 in
connection with Genaissance's initial public offering. Shares of common stock
received upon the conversion are considered Restricted Securities under the
Agreement so long as they are held by the original purchasers or by certain
transferees who acquired the shares in private transactions. Our records
indicate that your shares of common stock are considered Restricted Securities
and continue to be covered by the Agreement.

         Section 6 of the Agreement provides holders of Restricted Securities
with certain incidental or "piggy-back" registration rights, which generally
afford holders of Restricted

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[Investor name]
February 18, 2002
Page 2


Securities with the right to include, under certain circumstances, their
Restricted Securities or a portion thereof in certain securities offerings of
Genaissance. Section 12 of the Agreement provides that Genaissance will give you
prior written notice of the filing of certain registration statements by
Genaissance. Section 17 of the Agreement provides, in relevant part, that the
observance of any term of the Agreement may be waived with the written consent
of Genaissance and the holders of a majority of the Restricted Securities.

         Although your Restricted Securities are covered by the Agreement, you
may sell these securities under SEC Rule 144. Rule 144 exempts certain resales
of restricted securities (as defined in the rule) from the registration
requirements of the Securities Act, provided that certain volume, manner of
sale, public information and notice conditions are satisfied, and provided that
at least one year has elapsed from the later of the date of the acquisition of
the securities from the issuer or from an affiliate (as defined in the rule) of
the issuer. Rule 144(k) exempts the resale of restricted securities by persons
who are not (and for the previous three months have not been) affiliates of the
issuer, provided that at least two years have elapsed from the later of the date
of the acquisition of the securities from the issuer or from an affiliate of the
issuer. Affiliate is defined in Rule 144 as any person that, directly or
indirectly, controls, is controlled by, or is under common control with the
issuer of the securities in question.

         Our records indicate that you acquired your Restricted Securities from
Genaissance on [February 17, 2000]. Accordingly, [so long as you are not (and
for the preceding three months have not been) an affiliate of Genaissance, you
may freely resell your Restricted Securities under Rule 144(k). We do not
believe you are (or during the past three months have been) an affiliate of
Genaissance for purposes of Rule 144(k).]

         By this letter, Genaissance is requesting that you waive, and by
signing below you agree to waive:

         o  your right under Section 6 of the Agreement to include, for a period
            of 180 days from the effective date of this waiver, any Restricted
            Securities (that is, any shares of common stock that continue to be
            covered by the Agreement) in any securities offering conducted by
            Genaissance pursuant to the Registration Statement; and

         o  your right to receive prior notice of the filing with the SEC of the
            Registration Statement and any prospectus supplement to the
            Registration Statement.

This waiver of your right to receive prior notice of the filing with the SEC of
any prospectus supplement to the Registration Statement will be effective for a
period of 180 days from the effective date of this waiver.

         We believe the waiver will benefit Genaissance (and you as a
stockholder of Genaissance) by allowing Genaissance to more easily access the
capital markets. We also believe the waiver is appropriate because the
Registration Statement is a universal shelf registration statement and, as such,
is not an appropriate form of registration statement to include

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[Investor name]
February 18, 2002
Page 3

shares held by stockholders. We also believe the waiver will not diminish your
ability to resell your Genaissance stock in the future should you decide to do
so because, as noted above, [we believe you are already free to resell your
Genaissance common stock under Rule 144(k)]. Accordingly, it is our desire that
you consent to this waiver.

         Please confirm your waiver by signing the counterpart original of this
letter in the space provided below, and return it to my attention by facsimile
(203-786-3656) by Friday, February 22, 2002. Please note that Genaissance has
requested, and expects to receive, waivers from the holders of a majority of the
Restricted Securities. This waiver will be effective at the time that
Genaissance receives waivers from the holders of a majority of the Restricted
Securities. If you have any questions, please call Mr. Joseph Keyes at
203-786-3674.

                   [BALANCE OF PAGE LEFT INTENTIONALLY BLANK]


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[Investor name]
February 18, 2002
Page 4


         We thank you in advance for your cooperation and your waiver.

                                         Very truly yours,

                                         GENAISSANCE PHARMACEUTICALS, INC.



                                         By:
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                                            Gualberto Ruano, M.D., Ph.D.
                                            Chief Executive Officer

The undersigned hereby agrees to the above-described waiver:



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Name of Investor



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