8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of

the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 14, 2015

Atara Biotherapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware	001-36548	46-0920988
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

701 Gateway Boulevard, Suite 200 South San Francisco, CA	94080
(Address of Principal Executive Offices)	(Zip Code)

Registrant’s Telephone Number, Including Area Code: (650) 278-8930

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instructions A.2. below):

¨ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 7.01.Regulation FD Disclosure. 

On December 14, 2015, Atara Biotherapeutics, Inc. (the “Company”) issued a press release announcing the results of its Phase 2 clinical trial of PINTA 745 for protein energy wasting in patients with end stage renal disease. A copy of the press release issued concerning the foregoing is furnished as Exhibit 99.1 hereto.

On December 14, 2015, the Company also announced that it received feedback from the U.S. Food and Drug Administration (the “FDA”) regarding a special protocol assessment (“SPA”) for the Company’s proposed single arm pivotal trial of Epstein-Barr Virus targeted cytotoxic T-lymphocyte in patients with rituximab-refractory post-transplant lymhoproliferative disorders (“PTLD”) after hematopoietic cell transplant.  The FDA indicated that a single arm study with response rate as the primary endpoint may provide an adequate basis for approval but it would be unlikely to grant an SPA for the Company’s proposed trial. The Company intends to continue the dialogue with the FDA regarding this trial design under breakthrough designation and expects to initiate this pivotal trial in the second half of 2016.  Additionally, the Company intends to initiate a randomized pivotal trial in patients with PTLD after solid organ transplant in the second half of 2016.

Item 9.01.Financial Statements and Exhibits.

Exhibit No.	Description
99.1	Press Release, dated December 14, 2015, titled “Atara Bio Announces Results from the Phase 2 Proof-of-Concept PINTA 745 Clinical Trial for Protein Energy Wasting in Patients with End Stage Renal Disease.”

The information in this report, including the exhibit hereto, is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Securities Exchange Act”), or otherwise subject to the liabilities of Section 11 and 12(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”). The information in this report and the attached Exhibit 99.1 shall not be incorporated by reference into any filing with the U.S. Securities and Exchange Commission (the “SEC”), whether made before or after the date hereof, except as shall be expressly set forth by specific reference in such filing.

Forward-Looking Statements

This report contains or may imply “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act. For example, forward-looking statements include statements regarding the Company’s regulatory strategy. Because such statements deal with future events and are based on the Company’s current expectations, they are subject to various risks and uncertainties and actual results, performance or achievements of the Company could differ materially from those described in or implied by the statements in this report. These forward-looking statements are subject to risks and uncertainties, including those discussed under the heading “Risk Factors” in the Company’s quarterly report on Form 10-Q filed with the SEC on November 6, 2015, including the documents incorporated by reference therein, and subsequent filings with the SEC. Except as otherwise required by law, the Company disclaims any intention or obligation to update or revise any forward-looking statements, which speak only as of the date hereof, whether as a result of new information, future events or circumstances or otherwise.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized.

Atara Biotherapeutics, Inc.
By:	/s/ John McGrath
	John McGrath
	Chief Financial Officer

Date:   December 14, 2015

EX-99.1

Exhibit 99.1

Atara Bio Announces Results from the Phase 2 Proof-of-Concept PINTA 745 Clinical Trial for Protein Energy Wasting in Patients with End Stage Renal Disease

Atara Bio to Host Conference Call and Webcast Today at 8:00 a.m. Eastern Time

South San Francisco, CA– December 14, 2015 – Atara Biotherapeutics, Inc. (Nasdaq: ATRA) today announced results from its Phase 2 proof-of-concept clinical trial for PINTA 745 for the treatment of protein energy wasting (PEW) in patients with end stage renal disease (ESRD).  The trial did not meet its primary endpoint, defined as the percent change from baseline in Lean Body Mass (LBM) as measured by Dual Energy X-Ray Absorptiometry (DXA) at week 12 following weekly treatment with PINTA 745.

PINTA 745 also did not improve physical function, measures of glycemic control and markers of inflammation.  There were no treatment related serious adverse events observed in the trial.

“We are very disappointed that PINTA 745 did not meet the primary endpoint of this Phase 2 clinical trial. These data are unambiguous and contrast with prior clinical and preclinical results,” said Isaac Ciechanover, M.D. President and Chief Executive Officer of Atara Bio.  “We want to sincerely thank the patients and investigators for their participation in this trial.”

As a consequence of these results, Atara Bio will suspend further development of PINTA 745.  To date, third-party direct costs for the development of PINTA 745 from our inception through the third quarter of 2015 were approximately $10 million.

The Company will focus its resources on its portfolio of clinical stage oncology and immunotherapy product candidates, including:

· Epstein-Barr Virus (EBV) Targeted Cytotoxic T-Lymphocyte (EBV-CTL), which received breakthrough designation in rituximab refractory EBV associated post-transplant lymphoproliferative disorders after allogeneic hematopoietic cell transplant (alloHCT) and is in two ongoing Phase 2 trials for EBV malignancies;

· Cytomegalovirus (CMV) Targeted Cytotoxic T-Lymphocytes (CMV-CTL), which is in two Phase 2 clinical trials for refractory CMV infections that occur in patients who have received an alloHCT;

· Wilms' Tumor 1 Targeted Cytotoxic T-Lymphocytes (WT1-CTL), which is in two ongoing Phase 1 clinical trials assessing safety and initial anti-tumor efficacy in patients with hematologic malignancies; and

· STM 434, an activin inhibitor, which is in an ongoing Phase 1 clinical trial assessing safety and initial anti-tumor efficacy in patients with ovarian cancer and other advanced solid tumors.

Atara ended the third quarter of 2015 with approximately $334.3 million in cash and cash equivalents and short-term available-for-sale investments, providing sufficient resources to further advance the Company’s oncology and immunotherapy portfolio, including completion of the ongoing clinical studies and the planned initiation of two pivotal trials for EBV-CTL.

Conference Call Information

Members of the Atara Bio management team will host a live conference call and webcast today, December 14, 2015 at 8:00 a.m. Eastern Time.  The live webcast can be accessed by visiting the investor relations section of the Atara Bio’s website at www.atarabio.com.  Please connect 15 minutes prior to the live webcast to ensure adequate time for any software download that may be needed to access the webcast.  Alternatively, please call 866-416-1813 (U.S.) or 704-

908-0390 (International) to listen to the conference call.  The conference ID number for the live call will be 5510030.  An archive of the webcast will be available on the investor relations section of the Atara Bio’s website for 14 days.

About Atara Biotherapeutics, Inc.

Atara Biotherapeutics, Inc. is a biopharmaceutical company developing meaningful therapies for patients with unmet medical needs in diseases that have seen limited therapeutic innovation, with an initial focus on immunotherapy and oncology. Atara Bio’s programs include T-cell product candidates and molecularly targeted product candidates. The T-cell product candidates include EBV-CTL, CMV-CTL and WT1-CTL and harness the power of the immune system to recognize and attack cancer cells and cells infected with certain viruses. The molecularly targeted product candidates include STM 434 and ATA 842. These product candidates target activin and myostatin, members of the TGF-beta family of proteins, and have demonstrated the potential to have therapeutic benefit in a number of clinical indications.

Forward-Looking Statements

This press release contains or may imply “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. For example, forward-looking statements include statements regarding plans to suspend the further development of PINTA 745, Atara Bio’s intent to focus its resources on its portfolio of clinical stage oncology and immunotherapy product candidates, and the sufficiency of Atara Bio’s capital resources. Because such statements deal with future events and are based on Atara Bio’s current expectations, they are subject to various risks and uncertainties and actual results, performance or achievements of Atara Bio could differ materially from those described in or implied by the statements in this press release. These forward-looking statements are subject to risks and uncertainties, including those discussed under the heading “Risk Factors” in Atara Bio’s quarterly report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on November 6, 2015, including the documents incorporated by reference therein, and subsequent filings with the SEC. Except as otherwise required by law, Atara Bio disclaims any intention or obligation to update or revise any forward-looking statements, which speak only as of the date hereof, whether as a result of new information, future events or circumstances or otherwise.

INVESTOR & MEDIA CONTACT:

Investors:	Media:
Lisa Burns	Justin Jackson
lburns@burnsmc.com	212-213-0006 x327
Or	jjackson@burnsmc.com
Steve Klass
sklass@burnsmc.com
212-213-0006