Atara Bio Announces Results from Ongoing Phase 2 Trial of Allogeneic Cytomegalovirus (CMV)-specific Cytotoxic T Lymphocytes (CTL) at the American Society of Hematology (ASH) Annual Meeting 2016

Response Rate (RR) and 6-month Overall Survival (OS) > 70% and Safety Findings in Hematopoietic Stem Cell Transplant (HCT) Patients with Genetically Resistant CMV Infection

SOUTH SAN FRANCISCO, Calif., Dec. 03, 2016 (GLOBE NEWSWIRE) -- Atara Biotherapeutics, Inc. (Nasdaq:ATRA), a biopharmaceutical company focused on developing meaningful therapies for patients with unmet medical needs in diseases that have seen limited therapeutic innovation, today announced that its collaborating investigators at Memorial Sloan Kettering Cancer Center (MSK) are reporting Phase 2 results for Atara’s allogeneic T-cell product candidate, CMV-CTL, during the 58^th ASH Annual Meeting being held in San Diego, California. Data from the Phase 2 trial describe the efficacy and safety of CMV-CTL in the treatment of 15 patients with documented CMV mutations conferring resistance to anti-viral therapies. Patients had received a median of 3 prior therapies before receiving allogeneic CMV-CTL. CMV-CTL is an investigational therapy in which a healthy donor’s T-cells are stimulated to recognize CMV antigens, or viral proteins, expressed in the cells of patients infected with CMV.

Dr. Susan Prockop, M.D. and colleagues are reporting the following clinical results from the trial:

• Response Rate: 73.3% with 6 complete responses (CR) and 5 partial responses (PR).
   
• 6-month Overall Survival: 72.7% in responders (CR+PR) versus 25% in non-responders.
   
• Safety: 16 grade ≥ 3 serious adverse events (SAE) deemed possibly related to CMV-CTL among 66 patients.

"We are encouraged by the efficacy and safety results reported at ASH on the use of CMV-CTL in patients with genetically resistant CMV infection," said Chris Haqq M.D., Ph.D., Executive Vice President of Research and Development and Chief Scientific Officer of Atara Bio. "These results support late stage development of CMV-CTL for patients with few therapeutic options."

The ASH 2016 oral presentation, titled "Third Party CMV-Specific Cytotoxic T Cells for Treatment of Antiviral Resistant CMV Infection after Hematopoietic Stem Cell Transplant," will take place this morning, Saturday, December 3, at 7:30 a.m. PT in Grand Hall B of the Manchester Grand Hyatt in San Diego, CA.

About CMV-CTL

In patients with weakened immune systems, CMV infection can result in a range of symptoms including blindness, brain damage, difficulty breathing, or even death, depending on which organ is affected. T-cells are a critical component of the body's immune system and can be harnessed to counteract viral infections and some cancers. By focusing the T-cells on specific proteins involved in cancers and infections, the power of the immune system can be employed to combat these diseases. Atara's CMV-CTL utilizes a technology in which T-cells are collected from the blood of third-party donors and then exposed to CMV antigens. The resulting activated T-cells are then expanded, characterized, and stored for future therapeutic use in an appropriate partially human leukocyte antigen, or HLA, matched patient, providing an allogeneic, cellular therapeutic option for patients.  In the context of CMV infection, Atara's CMV-CTL finds the cells expressing CMV and kills them. CMV-CTL is currently being studied in an ongoing Phase 2 clinical trial.

About Atara Biotherapeutics’ Allogeneic Cellular Therapy Platform

Atara Bio’s cellular therapy platform provides healthy immune capability to a patient and arms the immune system to precisely target and combat disease. Cells derived from healthy donors are manufactured in advance and stored as inventory so that a customized unit of cells can be chosen for each patient. The cells are ready to infuse in approximately 3 to 5 days. Once administered, the cells home to their target, expand in-vivo to eliminate diseased cells, and eventually recede. This versatile platform can be directed towards a broad array of disease causing targets and has demonstrated clinical proof of concept across both viral and non-viral targets in conditions ranging from liquid and solid tumors to infectious and autoimmune diseases. The company’s lead product candidate derived from this platform, Epstein Barr virus targeted Cytotoxic T-cells (EBV-CTL), is expected to enter pivotal trials in 2016. The company has pursued prospective feedback from health authorities on both manufacturing and clinical trial design. Its lead product candidate has the potential to be the first commercial allogeneic T-cell therapy for a viral target implicated in cancer.

About Atara Biotherapeutics, Inc.

Atara Biotherapeutics, Inc. is a biopharmaceutical company developing meaningful therapies for patients with severe and life-threatening diseases that have been underserved by scientific 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 Wilms Tumor 1 targeted Cytotoxic T-cells (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. 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 late stage development of CMV-CTL for patients with few therapeutic options. 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 annual report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on November 4, 2016, 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:
Steve Klass
212-213-0006 x331
sklass@burnsmc.com

Media:
Justin Jackson
212-213-0006 x327
jjackson@burnsmc.com

Released December 3, 2016