Delaware		46-0920988
( State or other jurisdiction of incorporation or organization)		(I.R.S. Employer Identification No.)
701 Gateway Blvd., Suite 200 South San Francisco, CA		94080
(Address of principal executive offices)		(Zip Code)

Securities registered pursuant to Section 12(b) of the Act: Common Stock, Par Value $0.001 Per Share; Common stock traded on the NASDAQ stock market

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. YES ¨ NO x

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. YES ¨ NO x

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. YES x NO ¨

Indicate by check mark whether the Registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit and post such files). YES x NO ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405) is not contained herein, and will not be contained, to the best of Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. x

Indicate by check mark whether the Registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definition of “large accelerated filer”, “accelerated filer”, and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

Large accelerated filer	¨	Accelerated filer	¨

Non-accelerated filer	x (Do not check if a small reporting company)	Small reporting company	¨

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). YES ¨ NO x

The Registrant did not have a public float on the last business day of its most recently completed second fiscal quarter because there was no public market for the registrant’s common equity as of such date.

The number of shares of Registrant’s Common Stock outstanding as of February 18, 2015 was 24,360,247.

Portions of the Registrant’s definitive proxy statement relating to its 2015 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report where indicated. Such proxy statement will be filed with the US Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.

Atara Biotherapeutics, Inc. (the “Company”) is filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to its Annual Report on Form 10-K (“Form 10-K”) for the fiscal year ended December 31, 2014, filed with the Securities and Exchange Commission on February 26, 2015, solely to file Exhibit 21.1, List of Subsidiaries of the Company, to this Amendment. Exhibit 21.1 was inadvertently omitted from the original filing of the Form 10-K.

As required by the applicable rules, currently-dated Section 302 certifications from the Company’s Chief Executive Officer and Chief Financial Officer are included as exhibits to this Amendment. Because no financial statements have been included in this Amendment and this Amendment does not contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K, paragraphs 3, 4 and 5 of the certifications have been omitted.

Except as described above, no other revisions or amendments have been made to any other portion of the Form 10-K. This Amendment does not reflect events that may have occurred after February 26, 2015, the date of the original filing of the Form 10-K, or modify or update any disclosures that may have been affected by subsequent events.



Exhibit Number	Exhibit Description

21.1	List of subsidiaries
31.1	Certification by Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.
31.2	Certification by Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of South San Francisco, State of California, on the 6th day of March, 2015.


Atara Biotherapeutics, Inc.

By:	/s/ John F. McGrath, Jr.
	John F. McGrath, Jr.
	Chief Financial Officer


		Incorporated by Reference				Filed Herewith
Exhibit Number	Exhibit Description	Form	File No.	Exhibit	Filing Date
21.1	List of subsidiaries					X
31.1	Certification by Chief Executive Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.					X
31.2	Certification by Chief Financial Officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.					X