Know
all by these presents, that the undersigned hereby constitutes and appoints
George A. Scangos, Frank Karbe, Pamela A. Simonton and James B. Bucher of
Exelixis, Inc., a Delaware corporation (the “Company”), or any one of them
acting singly, and with full power of substitution, the undersigned’s true and
lawful attorney-in-fact to: (i) complete and execute for and on behalf of the
undersigned, in the undersigned’s capacity as an officer or director of the
Company, Forms 3, 4 and 5 in accordance with Section 16(a) of the Securities Act
of 1934 (the “Exchange Act”) and the rules and regulations of the Securities and
Exchange Commission (the “SEC”) thereunder; (ii) execute for and on behalf of
the undersigned, in the undersigned’s capacity as an officer or director of the
Company, any Schedule 13D or 13G in accordance with Section 13(c) of the
Exchange Act and the rules and regulations of the SEC thereunder; (iii) do and
perform any and all acts for and on behalf of the undersigned which may be
necessary or desirable to complete and execute any such Form 3, 4 or 5 or
Schedule 13D or 13G, complete and execute any amendment or amendments thereto,
and timely file or cause to be filed with the SEC and any securities exchange or
similar authority such form, schedule, amendment or amendments thereto; and (iv)
take any other action in connection with the foregoing which, in the opinion of
such attorney-in-fact, may be of benefit to, in the best interest of, or legally
required by, the undersigned, it being understood that the documents executed by
such attorney-in-fact on behalf of the undersigned pursuant to this Power of
Attorney shall be in such form and shall contain such terms and conditions as
such attorney-in-fact may approve in such attorney-in-fact’s
discretion.
The
undersigned hereby grants to each such attorney-in-fact full power and authority
to do and perform any and every act and thing whatsoever requisite, necessary,
or proper to be done in the exercise of any of the rights and powers herein
granted, as fully to all intents and purposes as the undersigned might or could
do if personally present, with full power of substitution or revocation, hereby
ratifying and confirming all that such attorney-in-fact, or such
attorney-in-fact’s substitute or substitutes, shall lawfully do or cause to be
done by virtue of this Power of Attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned’s responsibilities to comply
with Section 13 or Section 16 of the Exchange Act.
This
Power of Attorney shall remain in full force and effect until the undersigned is
no longer required to file Forms 3, 4 and 5 and Schedules 13D and 13G with
respect to the undersigned’s holdings of, and transactions in, securities issued
by the Company, unless otherwise earlier revoked by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact. By signing this Power of
Attorney the undersigned revokes as of the date hereof all powers of attorney
previously executed by the undersigned for the same purposes as this Power of
Attorney.
In Witness Whereof, the
undersigned has caused this Power of Attorney to be executed as of this 31st
day of July, 2008.
/s/ Frances
K. Heller