<SUBMISSION>
<ACCESSION-NUMBER>0000950134-03-010011
<TYPE>8-K
<PUBLIC-DOCUMENT-COUNT>2
<PERIOD>20030710
<ITEMS>5
<ITEMS>7
<FILING-DATE>20030711
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>LEXICON GENETICS INC/TX
<CIK>0001062822
<ASSIGNED-SIC>2835
<IRS-NUMBER>760474169
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>8-K
<ACT>34
<FILE-NUMBER>000-30111
<FILM-NUMBER>03782823
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>8800 TECHNOLOGY FOREST PLACE
<CITY>THE WOODLANDS
<STATE>TX
<ZIP>77381
<PHONE>2818633000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>8800 TECHNOLOGY FOREST PLACE
<CITY>THE WOODLANDS
<STATE>TX
<ZIP>77381
</MAIL-ADDRESS>
</FILER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>h07360e8vk.txt
<DESCRIPTION>LEXICON GENETICS INCORPORATED - JULY 10, 2003
<TEXT>
<PAGE>
================================================================================


                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549



                                    FORM 8-K


                                 CURRENT REPORT
     PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934



         DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): JULY 10, 2003


                          LEXICON GENETICS INCORPORATED
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)


<TABLE>
<S>                                 <C>                          <C>
           DELAWARE                        000-30111                   76-0474169
(STATE OR OTHER JURISDICTION OF     (COMMISSION FILE NUMBER)        (I.R.S. EMPLOYER
 INCORPORATION OR ORGANIZATION)                                  IDENTIFICATION NUMBER)
</TABLE>


                          8800 TECHNOLOGY FOREST PLACE
                           THE WOODLANDS, TEXAS 77381
                         (ADDRESS OF PRINCIPAL EXECUTIVE
                              OFFICES AND ZIP CODE)


                                 (281) 863-3000
                         (REGISTRANT'S TELEPHONE NUMBER,
                              INCLUDING AREA CODE)


================================================================================

<PAGE>
ITEM 5. OTHER EVENTS AND REGULATION FD DISCLOSURE

         On July 10, 2003, RCM Financial Services, L.P. and Cogene Biotech
Ventures, L.P. purchased an aggregate of 5,000,000 shares of our common stock
from the Estate of Gordon A. Cain and The Gordon and Mary Cain Foundation in a
private transaction not registered under the Securities Act of 1933. The
aggregate purchase price for the shares, which was negotiated by the parties in
June 2003 based upon prices prevailing at such time, was $23,750,000. The
purchased shares remain "restricted securities" under the Securities Act and may
not be sold absent an effective registration statement or an exemption from the
registration requirements of the Securities Act.

         RCM Financial Services, L.P. and Cogene Biotech Ventures, L.P. are
limited partnerships in which Robert C. McNair is the principal investor. The
Chairman of our Board of Directors, C. Thomas Caskey, M.D., is President and
Chief Executive Officer of Cogene Biotech Ventures, L.P. Dr. Caskey holds
investment and voting power over the 1,000,000 shares purchased by Cogene
Biotech Ventures, L.P. and, as a result, is deemed to have beneficial ownership
of these shares. Dr. Caskey disclaims beneficial ownership of such shares.

         In connection with the transaction, we entered into a letter agreement
with RCM Financial Services, L.P. and Cogene Biotech Ventures, L.P. that (1)
confirms that the purchasers are entitled to the benefits provided under our
registration rights agreement and (2) modifies our existing obligations under
the registration rights agreement by committing to maintain the effectiveness of
any resale registration statement requested by the purchasers for a minimum of
two years or until the distribution contemplated by such registration statement
is complete. Both the letter agreement and the registration rights agreement are
included in this filing as exhibits.

ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS

         (c)      Exhibits

  EXHIBIT NO.                         DESCRIPTION
  -----------                         -----------
     99.1      --   Amended and Restated Registration Rights Agreement dated as
                    of May 7, 1998 by and among Lexicon Genetics Incorporated
                    and the stockholders named therein (filed as Exhibit 4.1 to
                    the Company's Registration Statement on Form S-3
                    (Registration No. 333-67294) and incorporated by reference
                    herein).

     99.2      --   Letter Agreement relating to Registration Rights dated as of
                    July 10, 2003 by and among Lexicon Genetics Incorporated,
                    RCM Financial Services, L.P. and Cogene Biotech Ventures,
                    L.P.


                                       2
<PAGE>
                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.


                                           LEXICON GENETICS INCORPORATED


Date:   July 10, 2003                      By: /s/ JEFFREY L. WADE
                                              ---------------------------------
                                              Jeffrey L. Wade
                                              Executive Vice President and
                                              General Counsel


                                       3
<PAGE>
                                INDEX TO EXHIBITS

  EXHIBIT NO.                         DESCRIPTION
  -----------                         -----------
     99.1      --   Amended and Restated Registration Rights Agreement dated as
                    of May 7, 1998 by and among Lexicon Genetics Incorporated
                    and the stockholders named therein (filed as Exhibit 4.1 to
                    the Company's Registration Statement on Form S-3
                    (Registration No. 333-67294) and incorporated by reference
                    herein).

     99.2      --   Letter Agreement relating to Registration Rights dated as of
                    July 10, 2003 by and among Lexicon Genetics Incorporated,
                    RCM Financial Services, L.P. and Cogene Biotech Ventures,
                    L.P.


</TEXT>
</DOCUMENT>
<DOCUMENT>
<TYPE>EX-99.2
<SEQUENCE>3
<FILENAME>h07360exv99w2.txt
<DESCRIPTION>LETTER AGREEMENT RE: REGISTRATION RIGHTS
<TEXT>
<PAGE>
                                                                    EXHIBIT 99.2



                                  July 10, 2003


RCM Financial Services, L.P.
Cogene Biotech Ventures, L.P.
4400 Post Oak Parkway, Suite 1400
Houston, Texas 77027
Attention:  M. Robert Dussler

Dear Sirs:

         This letter is intended to provide clarification of certain terms of
the Amended and Restated Registration Rights Agreement, dated as of May 7, 1998
(the "Registration Rights Agreement"), among Lexicon Genetics Incorporated
("Lexicon") and the persons named therein, and to supplement the terms of the
Registration Rights Agreement to the extent necessary to effect the provisions
set forth below, in connection with the purchase in a private placement (the
"Purchase") by RCM Financial Services, L.P. and Cogene Biotech Ventures, L.P.
("Purchasers") of an aggregate of 5,000,000 shares (the "Shares") of Lexicon's
common stock from the Estate of Gordon A. Cain and The Gordon and Mary Cain
Foundation. Capitalized terms used without definition in this letter shall have
the meanings given to such terms in the Registration Rights Agreement.

                  1. Lexicon acknowledges and agrees that the Shares are and,
         upon completion of the Purchase will be, Cain Shares and Registrable
         Securities for purposes of the Registration Rights Agreement, and will
         be deemed for purposes of Section 2.1 thereof to be "shares held by
         Gordon A. Cain."

                  2. Lexicon agrees that, in the case of any registration of the
         Shares under the Registration Rights Agreement, at its expense, Lexicon
         will use Commercially Reasonable Best Efforts to keep a Registration
         Statement on Form S-3 (or a substitute form that may be adopted by the
         Commission) effective for five years or until the Purchasers have
         completed the distribution of all of their Registrable Securities
         thereunder, as provided in Section 5(a) thereof; provided, however,
         that if Lexicon files such Registration Statement on Form S-3 (or such
         substitute form) but such registration ceases to be effective during
         the two-year period after the date of the effectiveness of such Form
         S-3, or if Lexicon is not eligible to file a Registration Statement on
         Form S-3 (or such substitute form) when a request for registration is
         made by a Purchaser, Lexicon will file a Registration Statement on Form
         S-1 (or a substitute form that may be adopted by the Commission) and
         keep such registration effective until the second anniversary of the
         effectiveness of such Form S-3 or Form S-1, as the case may be.

                  3. Lexicon agrees that it will not decline, under the
         provisions of Section 2.1(b)(vi), to effect a registration of
         Registrable Securities requested by a Purchaser without the consent of
         the Purchaser requesting such registration.

<PAGE>
         Please acknowledge your agreement to the terms set forth herein by
signing this letter in the space provided below and returning the signed copy to
the undersigned.


                                          Very truly yours,

                                          LEXICON GENETICS INCORPORATED


                                          By: /s/ Jeffrey L. Wade
                                             -----------------------------------
                                               Jeffrey L. Wade
                                               Executive Vice President and
                                               General Counsel


Acknowledged and agreed
this 10th day of July, 2003:

RCM FINANCIAL SERVICES, L.P.


By:  /s/ M. Robert Dussler
   -----------------------------------
     M. Robert Dussler, Vice President


COGENE BIOTECH VENTURES, L.P.


By:  /s/ M. Robert Dussler
   -----------------------------------
     M. Robert Dussler, Vice President

</TEXT>
</DOCUMENT>
</SUBMISSION>
