Ownership Submission

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:

3235-0104

Estimated average burden hours per response...

0.5

(Print or Type Responses)

1. Name and Address of Reporting Person ^*

Domain Partners VIII, L.P.

2. Date of Event Requiring Statement (Month/Day/Year)
10/15/2014

3. Issuer Name and Ticker or Trading Symbol
Atara Biotherapeutics, Inc. [ATRA]

(Last)

(First)

(Middle)

C/O DOMAIN ASSOCIATES, LLC, ONE PALMER SQUARE

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

_____ Director	__X__ 10% Owner
_____ Officer (give title below)	_____ Other (specify below)

5. If Amendment, Date Original Filed(Month/Day/Year)

(Street)

PRINCETON, NJ 08542

6. Individual or Joint/Group Filing(Check Applicable Line)
___ Form filed by One Reporting Person
_X_ Form filed by More than One Reporting Person

(City)

(State)

(Zip)

Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security
(Instr. 4)

2. Amount of Securities Beneficially Owned
(Instr. 4)

3. Ownership Form: Direct (D) or Indirect (I)
(Instr. 5)

4. Nature of Indirect Beneficial Ownership
(Instr. 5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)
Series A Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	1,272,607	$ ⁽¹⁾	D ⁽²⁾ ⁽³⁾
Series B Preferred Stock	⁽¹⁾	⁽¹⁾	Common Stock	620,776	$ ⁽¹⁾	D ⁽²⁾ ⁽³⁾

Reporting Owners

Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
Domain Partners VIII, L.P. C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
BLAIR JAMES C C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
DOVEY BRIAN H C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
TREU JESSE I C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
SCHOEMAKER KATHLEEN K C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
VITULLO NICOLE C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X
Halak Brian K C/O DOMAIN ASSOCIATES, LLC ONE PALMER SQUARE PRINCETON, NJ 08542		X

Signatures

/s/ Kathleen K. Schoemaker, as Managing Member of One Palmer Square Associates VIII, LLC, General Partner of Domain Partners VIII, L.P., individually, and as Attorney-in-Fact for J. Blair, B. Dovey, J. Treu, N. Vitullo and B. Halak		10/15/2014
^**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	All outstanding Preferred Stock will automatically convert into Common Stock upon the closing of the Issuer's initial public offering for no additional consideration. The Preferred Stock has no expiration date.
(2)	The securities reported as directly beneficially owned by the designated Reporting Person may be deemed to be indirectly beneficially owned by each of the Reporting Owners listed below, each of whom is a managing member of One Palmer Square Associates VIII, LLC, the sole general partner of the designated Reporting Person. Pursuant to Instruction 5(b)(iv) of Form 3, each such individual has elected to report as indirectly beneficially owned the entire number of securities owned by the designated Reporting Person, however each of them disclaims beneficial ownership of any securities, and any proceeds thereof, that exceed his or her pecuniary interest therein and/or that are not actually distributed to him or her.
(3)	As managing members of the sole general partner of DP VIII Associates, L.P., each Reporting Owner listed below may also be deemed to indirectly beneficially own the securities of the Issuer held by DP VIII Associates, L.P., as reported on a Form 3 for DP VIII Associates, L.P. filed on the same date as this Form 3.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure.

Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.