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                            March 19, 2024

       Christopher Senner
       Executive Vice President and Chief Financial Officer
       EXELIXIS, INC.
       1851 Harbor Bay Parkway
       Alameda, CA 94502

                                                        Re: EXELIXIS, INC.
                                                            Form 10-K for the 
Year Ended December 29, 2023
                                                            Filed February 6, 
2024
                                                            File No. 000-30235

       Dear Christopher Senner:

              We have limited our review of your filing to the financial 
statements and related
       disclosures and have the following comment.

              Please respond to this letter within ten business days by 
providing the requested
       information or advise us as soon as possible when you will respond. If 
you do not believe
       the comment applies to your facts and circumstances, please tell us why 
in your response.

                                                        After reviewing your 
response to this letter, we may have additional comments.

       Form 10-K for the Year Ended December 29, 2023 filed February 6, 2024

       Management's Discussion and Analysis of Financial Condition and Results 
of Operations
       Results of Operations, page 73

   1.                                                   Please address the 
following regarding your disclosure on page 76 that you "do not track
                                                        fully burdened research 
and development expenses on a project-by-project basis."
                                                            Revise your 
disclosure in future filings to clarify whether you do or do not track your
                                                             research and 
development expenses by project on something less than a fully
                                                             burdened basis.
                                                            To the extent you 
do track any research and development expenses on a project-by-
                                                             project basis, 
revise to provide a breakdown of the expenses tracked by project.
                                                            Please provide us 
with your proposed disclosure.

              In closing, we remind you that the company and its management are 
responsible for the
       accuracy and adequacy of their disclosures, notwithstanding any review, 
comments, action or
       absence of action by the staff.
 Christopher Senner
EXELIXIS, INC.
March 19, 2024
Page 2

       Please contact Vanessa Robertson at 202-551-3649 or Kevin Vaughn at 
202-551-3494
with any questions.



FirstName LastNameChristopher Senner                   Sincerely,
Comapany NameEXELIXIS, INC.
                                                       Division of Corporation 
Finance
March 19, 2024 Page 2                                  Office of Life Sciences
FirstName LastName