SecProbe.io

July 2, 2015

Via E -mail
Isaac E. Ciechanover, M.D.
Chief Executive Officer
Atara Biotherapeutics, Inc.
701 Gateway Blvd., Suite 200
South San Francisco, California 94080

Re: Atara  Biotherapeutics, Inc.
  Registration Statement on Form S-1
Filed  June 29, 2015
  File No.  333-205347

Dear Dr. Ciechanover :

We have limited our review of your registration statement to the issue addressed in our
comment.  If you do not believe our comment appl ies to your facts and circumstances or do not
believe an amendment is appropriate, please tell us why in a response.

Exhibit Index

1. We note that you are submitting an application for confidential treatment for several of
the exhibits include d with this registration statement. We will not be in a position to grant
effectiveness to your filing until such time as comments to the confidential treatment
application, if any, have been cleared.

We urge all persons who are responsible for the accur acy and adequacy of the disclosure
in the filing to be certain that the filing includes the information the Securities Act of 193 3 and
all applicable Securities  Act rules require.   Since the company and its management are in
possession of all facts relatin g to a company’s disclosure, they are responsible for the accuracy
and adequacy of the disclosures they have made.

Notwithstanding our comment, in the event you request acceleration of the effective date
of the pending registration statement , please pro vide a written statement from the company
acknowledging that:

 should the Commission or the staff, acting pursuant to delegated authority, declare the
filing effective, it does not foreclose the Commission from taking any action with respect
to the filing;

Isaac C. Ciechanover, M.D.
Atara Biotherapeutics, Inc.
July 2, 2015
Page 2

  the action of the Commission or the staff, acting pursuant to delegated authority, in
declaring the filing effective, does not relieve the company from its full responsibility for
the adequacy and accuracy of the disclosure in the filing; and

 the company may not assert staff comments and the declaration of effectiveness as a
defense in any proceeding initiated by the Commission or any person under the federal
securities laws of the United States.

Please refer to Rules 460 and 461 regarding requests for  acceleration .  We will consider a
written request for acceleration of the effective date of the registration statement as confirmation
of the fact that those requesting acceleration are aware of their respective responsibilities under
the Secu rities Act of 1933 and the Securities Exchange Act of 1934 as they relate to the proposed
public offering of the securities specified in the above registration statement.  Please allow
adequate time  for us to review any amendment prior to the requested eff ective date of the
registration statement.

Please contact S cot Foley at (202) 551 -3383, Daniel Greenspan at (202) 551 -3623  or me
at (202) 551 -3715 with any other questions.

Sincerely,

 /s/ Daniel  Greenspan for

Jeffrey P. Riedler
Assistant Director

cc: Kenneth L. Gue rnsey
 Jodie M. Bourdet
 Carlton Fleming
Cooley  LLP
101 California Street, 5th Floor
San Francisco, California  94111