Exhibit 10.24

August 11, 2000

Peter Lamb, Ph.D.
11032 Paseo Castanada
La Mesa, California 91941

Dear Peter:

We are proud to invite you to join our team.

Our revised offer of employment is to join Exelixis, Inc. as a Senior Director,
Structural Biology and Molecular Pharmacology reporting to Michael Morrissey,
Vice President, New Lead Discovery. Other terms of employment include:

Compensation: You will receive seven thousand two hundred ninety one dollars and
sixty-seven cents ($7,291.67) per pay period. There two pay periods per month.
Additionally, you will receive a sign-on bonus of ten thousand dollars ($10,000)
payable the first pay date after hire. Should you elect to voluntarily terminate
employment with the Company within twelve (12) months of your hire date, the
sign-on bonus will be entirely re-paid by you to the Company. This re-payment of
the sign-on bonus shall occur within thirty (30) days of termination.

Options for Equity: Subject to approval by the Board of Directors, you will
receive a stock option for forty seven thousand two hundred fifty (47,250)
shares of Exelixis stock pursuant to our standard Stock Plan. Options vest over
4 years, and are 25% vested on the first anniversary of employment and then
continue to vest 1/48th of the total grant on the monthly anniversary date each
month thereafter over the next 3 years. The Company issues new hire stock
options twice a month on the 14th and last business day of the month with the
grant price being determined by the closing Fair Market Value of Exelixis stock
on either of these applicable dates.

Loan: We will make available a loan to assist you in relocation in the amount of
one hundred thousand ($100,000) dollars. Subject to the paragraph below, the
loan will have a term of four (4) years and is subject to one hundred percent
(100%) forgiveness of principal upon your fourth employment anniversary date if
you have been a full-time employee during the preceding forty eight (48) months.
The loan will be evidenced by a promissory note and made available within five
(5) business days of a contract or other evidence of an accepted offer for a
home in the Bay Area. Forgiven principal amounts will be subject to annual
withholding and reported on your Form W-2 upon completion of your fourth year of
service with Exelixis, Inc.

The interest will accrue annually and is not considered forgivable with the rate
being the lowest available for a loan of this term in effect as of the date of
the loan under the rules and regulations of the U.S. Treasury. The accrued
simple interest may be payable within thirty (30) days of each December 31st
during the term of the loan. Alternatively, upon issuance of the loan you have
the discretion to decide if you would instead prefer to defer payment of
compounded accrued interest at the end of the four year term of the loan.

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August 11, 2000
Peter Lamb, Ph.D.
Page Two

The loan will be made available to you within five (5) business days of your
presentation of a signed contract for the purchase of a home in the Bay Area.
Additionally, we will agree upon your written request to prepare the paperwork
to have this loan secured by the new home you purchase in the Bay Area.

Outstanding principal and interest on the loan will be subject to full repayment
prior to maturity on the earlier of: (a) your resignation of employment with
Exelixis or (b) the first business day that the value of your vested stock
options exceeds five hundred thousand ($500,000) dollars if you are eligible to
exercise and sell your vested Exelixis options on that date.

Additionally, Exelixis, Inc. will provide you with a loan in the amount of
twenty thousand dollars ($20,000) to cover the outstanding loan amount provided
to you by your current employer Ligand Pharmaceuticals. The loan will be
evidenced by a promissory note to be issued to you upon acceptance of this offer
of employment and submission of a copy of the executed loan contract between you
and Ligand. Except for applicable interest rate (which shall be the minimum
permitted by law for a loan of the term in question), the loan will have the
same repayment and due date terms as the remainder of the loan with Ligand.

Relocation: In order to accommodate a new hire's personal situation and
individual preference as to how they would like to coordinate the activities
associated with their move to the Bay Area, Exelixis provides employees the
opportunity to elect at his/her discretion one of two relocation benefit
packages available under the Company's Relocation Plan. Employees are eligible
to receive the specific benefits offered under either Relocation Assistance
Option A or B as outlined in the attached policy. Please contact Human Resources
regarding any specific questions you may have pertaining to this program.

We will also reimburse you the cost of closing costs you may incur that are
associated with the sale of your current home in San Diego including real estate
commissions and brokerage fees. Payment will be issued upon submission of an
itemized closing statement upon the disposition of your residence.

Benefits: All full-time employees of Exelixis, Inc. enjoy a generous benefits
package, which is outlined on the attached Summary of Benefits.

Performance Review: Your performance will be formally reviewed no less than
annually. Additionally, if at some point in time in the future, the Company
implements a company-wide performance management bonus system, you would be
eligible to participate in this program.

Confidentiality: As you are aware, it is very important for us to protect our
confidential information and proprietary material. Therefore, as a condition of
employment, you will need to sign the attached Confidentiality Agreement.

Start Date: To be determined.

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August 11, 2000
Peter Lamb, Ph.D.
Page Three

Other: This offer expires on August 16, 2000, unless accepted by you prior to
this date. In addition to performing the duties and responsibilities of your
position, you will be expected to perform other duties and responsibilities that
may be assigned to you from time to time. No provision of this letter shall be
construed to create an express or implied employment contract for a specific
period of time. Either you or the Company may terminate this employment
relationship at any time. This letter shall be governed by the laws of the State
of California. Also, by signing this letter, you are indicating that you are
legally authorized to work in the U.S.

You may accept this offer of employment by signing both copies of this letter
and returning to my attention at Exelixis, Inc one copy along with the completed
employment documents that have been included in this offer packet.

Peter, we look forward to your coming on board!

Sincerely,

/s/ Lisa Benthein
Lisa Benthein
Director, Human Resources

ACCEPTED BY:

/s/ Peter Lamb                                    8/15/00    
Peter Lamb                                Date

Enclosures:    
Benefit Summary
Confidentiality Agreement
DE-4 (optional)
Direct Deposit Form (optional)
Employee Information Form
I-9 document verification list
Insider Trading Policy
W-4
Relocation Policy
Ex