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                                                                 EXHIBIT 10.18

                                           *** TEXT OMITTED AND FILED SEPARATELY
                                    PURSUANT TO A CONFIDENTIAL TREATMENT REQUEST
                                            UNDER 17 C.F.R. SECTION 200.80(b)(4)
                                               AND RULE 406 UNDER THE SECURITIES
                                                         ACT OF 1933, AS AMENDED

                             AMENDMENT TO AGREEMENT

         THIS AMENDMENT TO AGREEMENT (the "Amendment") is made and entered into
effective as of July 1, 2003 (the "Amendment Effective Date"), by and between
STRUCTURAL GENOMIX, INC., a corporation organized and existing under the laws of
the State of Delaware and having its principal place of business located at
10505 Roselle Street, San Diego, CA 92121 ("SGX") and ELI LILLY AND COMPANY., a
corporation organized and existing under the laws of the state of Indiana and
having its principal place of business at Lilly Corporate Center, Indianapolis,
Indiana 46285, ("Lilly"). Lilly and SGX may be referred to herein as a "Party"
or, collectively, as "Parties".

                                    RECITALS

         A. Lilly and SGX have entered into a Collaboration and License
Agreement (the "Agreement") effective April 14, 2003, under which the Parties
have agreed to conduct a collaborative research program.

         B. The Parties desire to amend the terms of the Agreement to provide,
among other things, for the transfer between the parties of additional
biological materials in furtherance of the research program, as provided in this
Amendment.

         NOW, THEREFORE, the Parties agree as follows:

1.       AMENDMENT OF THE AGREEMENT

         The Parties hereby agree to amend the terms of the Agreement as
provided below, effective as of the Amendment Effective Date. To the extent that
the Agreement is explicitly amended by this Amendment, the terms of the
Amendment will control where the terms of the Agreement are contrary to or
conflict with the following provisions. Where the Agreement is not explicitly
amended, the terms of the Agreement will remain in force. Capitalized terms used
in this Amendment that are not otherwise defined herein shall have the same
meanings as such terms are defined in the Agreement.

         1.1 AMEND SECTION 2.1. Section 2.1 of the Agreement is hereby amended
to delete the third sentence in its entirety and replace it with the following:
"SGX will commit a total of at least [...***...] ([...***...]) [...***...] to
the Research Collaboration during the period between March 26, 2003 and the
[...***...] of the Effective Date, with a minimum of [...***...] ([...***...])
[...***...] being used between March 26, 2003 and December 31, 2003."

         1.2 INSERT NEW SECTION 2.4A. The following Section 2.4A is inserted:
"2.4A Additional Materials. In addition to any SGX Materials and Lilly Materials
which may be provided by the parties under Sections 2.3 and 2.4, from time to
time during the Term of the Research Collaboration, SGX and Lilly (each a
"Disclosing Party") may, at the Disclosing Party's discretion, provide the other
Party (the "Receiving Party") with other biological and/or chemical materials,
which materials may be used by the Receiving Party solely for the purposes of
the Research Collaboration. For the purposes of Articles 8 and 9, materials
provided by SGX

                                       1.    ***CONFIDENTIAL TREATMENT REQUESTED
<PAGE>

under this Section will be deemed SGX Materials, and materials provided by Lilly
under this Section will be deemed Lilly Materials.

         1.3 AMEND SECTION 4.1. Section 4.1 of the Agreement is hereby amended
to delete subsection (b) in its entirety and replace it with the following: "(b)
Within forty-five (45) days after December 31, 2003, Lilly will pay SGX a
non-refundable research fee of $[...***...], provided that SGX has met the FTE
commitment set forth in Section 2.1 for the period from March 26, 2003 to
December 31, 2003."

         1.4 AMEND SECTION 5.2. Section 5.2 of the Agreement is hereby amended
to add the following sentence: "Notwithstanding the rights granted in Section
5.1(a), Lilly may only use SGX Materials which include or are generated by SGX
using, reagents obtained by SGX from [...***...] Corporation and which are
identified by SGX in writing as "[...***...] Materials", for Lilly's internal
research purposes (on its own behalf or on behalf of its collaborators).

2. MISCELLANEOUS

         2.1 FULL FORCE AND EFFECT. This Amendment amends the terms of the
Agreement and is deemed incorporated into, and governed by all other terms of,
the Agreement. The provisions of the Agreement, as amended by this Amendment,
remain in full force and effect.

         2.2 COUNTERPARTS. This Amendment may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

         IN WITNESS WHEREOF, the Parties have executed this Amendment in
duplicate originals by their authorized officers as of the date and year first
above written.

                                    ELI LILLY AND COMPANY

                                    By: /s/ [Illegible]
                                        ----------------------------------

                                    Title: Vice President DCRT
                                           -------------------------------

                                    STRUCTURAL GENOMIX, INC.

                                    By: /s/ [Illegible]
                                        ----------------------------------

                                    Title: President
                                           -------------------------------

                                       2.    ***CONFIDENTIAL TREATMENT REQUESTED<PAGE>
                                                                 EXHIBIT 10.19

                                           *** TEXT OMITTED AND FILED SEPARATELY
                                    PURSUANT TO A CONFIDENTIAL TREATMENT REQUEST
                                            UNDER 17 C.F.R. SECTION 200.80(b)(4)
                                               AND RULE 406 UNDER THE SECURITIES
                                                         ACT OF 1933, AS AMENDED

                             AMENDMENT TO AGREEMENT

         THIS AMENDMENT TO AGREEMENT (the "Amendment") is made and entered into
effective as of January 30, 2004 (the "Amendment Effective Date"), by and
between STRUCTURAL GENOMIX, INC., a corporation organized and existing under the
laws of the State of Delaware and having its principal place of business located
at 10505 Roselle Street, San Diego, CA 92121 ("SGX") and ELI LILLY AND COMPANY.,
a corporation organized and existing under the laws of the state of Indiana and
having its principal place of business at Lilly Corporate Center, Indianapolis,
Indiana 46285, ("Lilly"). Lilly and SGX may be referred to herein as a "Party"
or, collectively, as "Parties".

         RECITALS

         A. Lilly and SGX have entered into a Collaboration and License
Agreement effective April 14, 2003 as amended July 1, 2003, (the "Agreement")
under which the Parties have agreed to conduct a collaborative research program.

         B. The Parties desire to amend the terms of the Agreement as provided
in this Amendment.

         NOW, THEREFORE, the Parties agree as follows:

1. AMEND SECTION 5.5(a). Section 5.5(a) of the Agreement is hereby amended to
delete the final sentence in its entirety and replace it with the following::
"Notwithstanding anything to the contrary in this Agreement: (i) this Section
5.5(a) shall not apply to the Collaboration Targets: [...***...], [...***...],
[...***...], [...***...], [...***...] and such other Collaboration Targets as
Lilly or any Lilly representative on the JSC may from time to time add to this
list on written notice to SGX; and (ii) SGX shall have the right at all times to
use and practice Collaboration Technology relating to any Collaboration Target
which Lilly or any Lilly representative on the JSC confirms in writing to SGX is
not a drug target, for drug discovery purposes on its own behalf or under
collaborations with third parties who are [...***...] for such activities."
Lilly hereby confirms to SGX that members of the [...***...] family and
[...***...] are not drug targets.

2. FULL FORCE AND EFFECT. This Amendment, effective as of the Amendment
Effective Date, amends the terms of the Agreement and is deemed incorporated
into, and governed by all other terms of, the Agreement. The provisions of the
Agreement, as amended by this Amendment, remain in full force and effect. To the
extent that the Agreement is explicitly amended by this Amendment, the terms of
the Amendment will control where the terms of the Agreement are contrary to or
conflict with the following provisions. Where the Agreement is not explicitly
amended, the terms of the Agreement will remain in force.

         IN WITNESS WHEREOF, the Parties have executed this Amendment in
duplicate originals by their authorized officers as of the date and year first
above written.

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<S>                                                           <C>
ELI LILLY AND COMPANY                                         STRUCTURAL GENOMIX, INC.

By:  /s/ Steven M. Paul                                       By:  /s/ Herbert G. Mutter
     ---------------------------------------------------           --------------------------------------------------------

Title:  Executive Vice President, Science and Technology      Title: Vice President, Finance
     ---------------------------------------------------             ------------------------------------------------------
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                                             ***CONFIDENTIAL TREATMENT REQUESTED

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