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

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                                    FORM 8-K

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


       DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): NOVEMBER 30, 2005


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



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



                          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)


     Check the  appropriate  box below if the Form 8-K  filing  is  intended  to
simultaneously satisfy the filing obligations of the registrant under any of the
following provisions:


        
     [ ]   Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

     [ ]   Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

     [ ]   Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

     [ ]    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))








ITEM 1.01 ENTRY INTO A MATERIAL DEFINITIVE AGREEMENT

     On  November  30,  2005,  we entered  into a Second  Amended  and  Restated
Collaboration  and  License  Agreement  (the  "Collaboration   Agreement")  with
Genentech, Inc. for the advanced research,  development and commercialization of
new biologic drugs. In the expanded alliance,  we will conduct advanced research
on a broad subset of targets included in Genentech's  Secreted Protein Discovery
Initiative  (SPDI)  program and validated  using our  proprietary  gene knockout
technology. We may develop and commercialize drugs modulating up to six of these
targets.   Genentech  retains  an  option  on  the  potential   development  and
commercialization  of these drugs under a cost and profit  sharing  arrangement,
while we have  certain  conditional  rights to  co-promote  drugs on a worldwide
basis. We retain non-exclusive rights for the development and  commercialization
of small molecule drugs addressing the targets included in the alliance.

     We will receive $25 million in upfront and milestone  payments and research
funding from Genentech  during the three-year  advanced  research portion of the
expanded  alliance and will receive  additional  payments  upon  achievement  of
milestones  related to the development and regulatory  approval of certain drugs
resulting from the alliance that are developed and  commercialized by Genentech.
We are entitled to receive  royalties on net sales of these  products,  provided
they are not included in a cost and profit  sharing  relationship.  Genentech is
entitled to receive milestone  payments in the event of regulatory  approval and
royalties  on net sales of products  commercialized  by us outside of a cost and
profit sharing arrangement

     In  connection  with the  execution  of the  Collaboration  Agreement,  the
maturity  date of the Note  Agreement  dated  December  17,  2002,  under  which
Genentech  loaned to us a principal amount of $4 million as part of the original
alliance, was extended to December 31, 2006.

     The Collaboration  Agreement amends the Amended and Restated  Collaboration
and License  Agreement  with  Genentech  dated  November 19, 2003,  which itself
amended the  Collaboration  and License  Agreement with Genentech dated December
17, 2002.





                                   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:   December 2, 2005                        By: /s/ JEFFREY L. WADE
                                                    ----------------------------
                                                    Jeffrey L. Wade
                                                    Executive Vice President and
                                                    General Counsel