Filed Pursuant to Rule 424(b)(3)
                                                          File Number 333-96335
           Prospectus Supplement to Prospectus dated April 10, 2000

                              [LOGO OF EXELIXIS]

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    The purpose of this prospectus supplement is to reflect a change in the
mathematical calculation of the weighted average number of shares outstanding
of Exelixis' stock used to calculate the net loss per share and pro forma net
loss per share, basic and diluted, for the years ended December 31, 1997, 1998
and 1999.

    The revised net loss per share, basic and diluted, for the years ended
December 31, 1997, 1998 and 1999 were $9.97, $7.88 and $4.60, respectively,
compared to amounts of $8.76, $3.83 and $3.47, respectively, previously
reported on page 5, "Summary Financial Data," and page 19, "Selected Financial
Data." Further, revised pro forma net loss per share, basic and diluted, for
the year ended December 31, 1999 was $0.70 per share, compared to $0.67 per
share as previously reported on page 5, "Summary Financial Data," and page 19,
"Selected Financial Data." In addition, the change to the calculation of the
weighted average number of shares outstanding affected the share and per share
amounts on pages F-4, F-9, F-10, F-18, F-19, F-22 and F-37 of the financial
statements.

    All of the information in the prospectus regarding the number of shares
outstanding at the time of the initial public offering is correct. The revised
net loss per share amounts also had no impact on Exelixis' previously reported
revenues, net loss, cash flows or balance sheets for any period.

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                  Prospectus Supplement dated April 25, 2000.