Exhibit 10.23

ADDENDUM DATED AS OF AUGUST 31, 2000
TO THE MASTER LEASE AGREEMENT
DATED AS OF AUGUST 2,2000 (THE "AGREEMENT")
BETWEEN EXELIXIS, INC. ("LESSEE")
ACTING ON BEHALF OF ITSELF AND ITS AFFILIATES,
AND COMDISCO LABORATORY AND SCIENTIFIC GROUP,
A DIVISION OF COMDISCO, INC. ("LESSOR")

The terms and conditions of this Addendum shall be incorporated into the
Agreement and supersedes the Agreement to the extent expressly provided herein.
Each capitalized terms used herein and not otherwise defined shall have the same
meaning attributed to it in the Agreement.

The terms and conditions of the following sections of the Agreement are hereby
modified:

Add a new SECTION 1A, AFFILIATES

"Exelixis, Inc. shall, without notice, be jointly and severally liable for the
due performance of the obligations of its Affiliates under all Equipment
Schedules executed hereunder, including, without limitation, all terms and
conditions negotiated by its Affiliate."

SECTION 3, RENT AND PAYMENT

Delete the last sentence and replace with the following: "If any payment is not
made within ten (10) days of the due date, Lessee will pay interest from the due
date at the Overdue Rate."

SECTION 7.1, CARE, USE AND MAINTENANCE

Delete the second, third and fourth sentences and replace with the following:
"Lessee shall be responsible for maintenance of the Equipment and, if Lessee
does not purchase the Equipment pursuant to the terms of a Schedule, Lessee
shall bring the Equipment to original manufacturer specifications applicable at
the Commencement Date of the Schedule, normal wear and tear excepted, and
re-certify the Equipment as eligible for manufacturer's maintenance at the
expiration of the lease term."

SECTION 7.2, ATTACHMENTS AND RECONFIGURATIONS

At the end of line 1, insert the words "which consent will not be unreasonably
withheld,".

SECTION 8, REPRESENTATIONS AND WARRANTIES OF LESSEE

In paragraph (e), line 2, before the word "clinical" insert the word "human".

SECTION 9, DELIVERY AND RETURN OF EQUIPMENT

In line 9, after the word "depreciation)", delete the remainder of the sentence
and replace with the following: "and in accordance with Section 7.1, and
accompanied by all spare parts and accessories and maintenance records for the
duration of the Schedule."

SECTION 13.3, MITIGATION

In line 2, delete the words "its best" and insert the words "commercially
reasonable".

In paragraph (b), delete the parenthetical and replace with the following:
"(discounted at the implicit interest rate of the re- lease as determined by
Lessor based upon the new lessee's credit rating)".

SECTION 14.3, BINDING NATURE

Line 3, after the word "OBLIGATIONS" insert the words "WITHOUT THE PRIOR WRITTEN
CONSENT OF LESSOR, WHICH SHALL NOT BE UNREASONABLE WITHHELD".

SECTION 14.10, ADDITIONAL DOCUMENTS

In line 5, before the word "counsel" insert the words "in-house". Add the
following at the end of this section: "Lessor will accept Lessee's certified
board resolutions in lieu of an opinion from Lessee's in-house counsel with
respect to the representations and warranties set forth in Section 8."

SECTION 14.12, DEFINITIONS

Add the following definition: "Affiliates of Exelixis, Inc," shall mean those
enterprises in which Exelixis, Inc., or its parent company owns and/or shall own
at anytime after the date hereof, directly or indirectly, the majority of the
voting stock, or a controlling interest, including without limitation all
present Affiliates of Exelixis, Inc.

Add the following definition: "Lessee" shall mean, with respect to any Equipment
Schedule, the Affiliate of Exelixis, Inc. entering into such Equipment Schedule,
or Exelixis, Inc., if Exelixis, Inc. enters into such Equipment Schedule.

IN WITNESS WHEREOF, the parties have caused this Addendum to be executed by
their authorized representatives as of the date and year set forth below.

ACCEPTED AND AGREED TO:

Exelixis, Inc.

Comdisco Laboratory and Scientific Group, a
division of Comdisco, Inc.

By:

By:

Printed Name:

Printed Name:

Title:

Title:

Date:

Date: