(ATRA) Exercises Exclusive License to T-Cell Technology

Activated T-Cell Technology Designed to Harness Immune System to Fight Cancer and Infectious Disease

SOUTH SAN FRANCISCO, Calif., June 15, 2015  — Atara Biotherapeutics, Inc. (Nasdaq:ATRA) today announced that it has exercised its exclusive option with Memorial Sloan Kettering Cancer Center (MSK) to license certain clinical stage, allogeneic T-cell therapies for the treatment of cancers and persistent viral infections. In connection with the exercise of the option, the Atara Bio license agreement with MSK grants Atara Bio exclusive worldwide rights to the following three allogeneic T-cell therapies:

• T-cells activated against Epstein Barr Virus, or EBV (Phase 2);
• T-cells activated against Cytomegalovirus, or CMV (Phase 2); and
• T-cells activated against Wilms Tumor 1, or WT1 (Phase 1)

These three programs share a common technology, under which third-party donor-derived whole blood is collected and enriched for T lymphocytes, or T-cells. The T-cells are then exposed to certain antigens, and the resulting activated T-cells are characterized and stored for future therapeutic use. Using a proprietary algorithm, patients are treated with a partially human leukocyte antigen, or HLA, matched cell line, providing an “off-the-shelf,” allogeneic, cellular therapeutic option for patients. These T-cell products are intended to work by targeting the abnormal cells expressing the applicable target antigen and killing them.

Atara Bio announced earlier this year that its collaborating investigator at MSK received breakthrough therapy designation from the U.S. Food and Drug Administration for its cytotoxic T lymphocytes (CTL) activated against Epstein-Barr Virus (EBV-CTL) in the treatment of patients with rituximab-refractory, EBV-associated lymphoproliferative disease (EBV-LPD).

Clinical data have been presented as follows:

• EBV-CTL in the treatment of patients with EBV-LPD after solid organ transplantation at the 2015 American Society of Clinical Oncology Annual Meeting.
• EBV-CTL in the treatment of  patients with EBV-LPD after allogeneic hematopoietic cell transplantation (HCT) at a Clinical Trial Plenary Session at American Association for Cancer Research Annual Meeting 2015
• CMV-CTL in the treatment of patients with anti-viral resistant CMV after HCT including viremia only and CMV disease at the American Society of Hematology Annual Meeting 2014.

“Licensing these programs more than doubles the clinical stage programs active at Atara Bio and provides a potential platform technology that can be directed at other targets,” said Isaac Ciechanover, MD, Chief Executive Officer and President of Atara Bio. “Our T-cell programs use third party donor cells, and, if approved by regulatory authorities, will be available as “off-the-shelf” therapies for patients in need.”

Richard O’Reilly, MD, Chair of the Department of Pediatrics and Chief of the Pediatric Bone Marrow Transplant Service at MSK, notes that “We are delighted that Atara will continue to develop our existing T-cell technologies that have shown promising clinical benefit in patients. We also look forward to expanding the platform to treat patients with other types of cancer through our sponsored research efforts with Atara.” Dr. O’Reilly will join Atara Bio’s Scientific Advisory Board.

In connection with the exercise of the option and entry into the exclusive license agreement, MSK received an upfront license fee and will be eligible to receive additional payments based on the achievement of certain development, regulatory and sales-related milestones, as well as royalty payments. Atara Bio and MSK have agreed to collaborate on further research to develop additional cellular therapies, which may include T-cell therapies targeted against other antigens and/or chimeric antigen receptor-modified T-cells, known as CAR-T.

About Atara Biotherapeutics, Inc.

Atara Biotherapeutics, Inc. is a biopharmaceutical company focused on developing innovative therapies for patients with debilitating diseases. Atara Bio’s programs include molecularly-targeted product candidates and T-cell product candidates. The molecularly-targeted product candidates include PINTA 745, STM 434 and ATA 842, targeting myostatin and activin, members of the TGF-beta family of proteins that have demonstrated the potential to have therapeutic benefit in a number of clinical indications.  T-cell product candidates include EBV-CTL, CMV-CTL and WT1-CTL.

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. 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. For example, forward-looking statements include statements regarding the clinical development of product candidates and Atara Bio’s collaboration with MSK. These forward-looking statements are subject to other risks and uncertainties, including those discussed under the heading “Risk Factors” in Atara Bio’s quarterly report on Form 10-Q for the quarter ended March 31, 2015 and subsequent filings with the Securities and Exchange Commission. 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.

CONTACT: INVESTOR & MEDIA CONTACT:
         Tina Gullotta, Atara Biotherapeutics, Inc.
         650-741-1613
         tgullotta@atarabio.com