POWER OF ATTORNEY
Know all by these presents, that the undersigned
hereby constitutes and appoints each of SUJAL SHAH,
DANIEL MENOLD, PAUL T. QUINLAN, DIANA KWON,
MATTHEW HEMINGTON and BRETT WHITE,
signing individually, the undersigned's true and
lawful attorneys-in-fact and agents to:
(1)	execute for and on behalf of the undersigned,
an officer, director or holder of 10% of more of
a registered class of securities of CymaBay
Therapeutics, Inc. (the Company), Forms 3, 4
and 5 in accordance with Section 16(a) of the
Securities Exchange Act of 1934, as amended (the
Exchange Act) and the rules thereunder;
(2)	do and perform any and all acts for and on
behalf of the undersigned that may be necessary
or desirable to complete and execute such Form 3,
4 or 5, complete and execute any amendment or
amendments thereto, and timely file such forms or
amendments with the United States Securities and
Exchange Commission and any stock exchange or
similar authority; and
(3)	take any other action of any nature
whatsoever in connection with the foregoing which,
in the opinion of such attorney-in-fact, may be of
benefit, 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,
responsibilities to comply with Section 16 of the
Exchange Act.
This Power of Attorney shall remain in full force
and effect until the earliest to occur of (a) the
undersigned is no longer required to file Forms 3,
4 and 5 with respect to the undersigned's holdings
of and transactions in securities issued by the
Company, (b) revocation by the undersigned in a
signed writing delivered to the foregoing
attorneys-in-fact, or (c) as to any attorney-in-fact
individually, until such attorney-in-fact shall no
longer be employed by the Company or Cooley LLP, as
the case may be.

/s/ Charles McWherter
Charles McWherter