Atara Bio Announces Positive Results From Phase 1 Clinical Trial of Wilms’ Tumor 1 Targeted Cytotoxic T Lymphocytes (WT1-CTL) Product Candidate in Hematologic Malignancies

Response Duration >2 Years Observed in a Patient with Plasma Cell Leukemia

Findings Reported at American Society of Hematology (ASH) Annual Meeting 2015

SOUTH SAN FRANCISCO, Calif., Dec. 05, 2015 (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 positive Phase 1 clinical data for Atara’s WT1-CTL product candidate during the 2015 ASH Annual Meeting. The findings describe the safety and activity of primary donor-derived WT1-CTLs following allogeneic hematopoietic cell transplantation (alloHCT) for the treatment of patients with relapsed-refractory multiple myeloma (MM), including plasma cell leukemia (PCL).

Dr. Guenther Koehne, M.D. and colleagues are reporting positive clinical data from the ongoing Phase 1 trial:

• 7 patients with relapsed-refractory MM, including PCL were treated with alloHCT followed by WT1-CTLs.
• By one year, 3 achieved a complete remission (CR), 1 achieved a partial response (PR), 2 had stable disease (SD), and 1 had progressive disease.
• 2 patients who developed a CR remain in remission for more than 1 year.
• There were no serious adverse events reported related to treatment with WT1-CTLs.

“These data broaden the potential utility of Atara’s innovative T-cell immunotherapy platform to an important cancer antigen target,” said Chris Haqq M.D., Ph.D., Chief Medical Officer of Atara Bio. “Patients with a response duration greater than 1 to 2 years is encouraging in light of historical median survival rates for patients with PCL. We believe this approach may offer a potential therapeutic alterative for patients with these difficult-to-treat, refractory cancers.”

The ASH 2015 oral presentation, titled “Wilms' Tumor 1 Protein Is Highly Expressed on Malignant Plasma Cells and Provides a Novel Target for Immunotherapeutic Approaches,” will take place this afternoon in room W314 of the Orange County Convention Center, Saturday, December 5, at 12:15 p.m. ET.

About WT1-CTL

Atara Bio’s WT1-CTL product candidate targets cancers expressing the antigen Wilms’ Tumor 1, or WT1. WT1 is an intracellular protein that is overexpressed in a number of cancers, including acute myeloid leukemia (AML), multiple myeloma (MM), and non-small cell lung, breast, pancreatic, ovarian, and colorectal cancers. WT1-CTL is currently being studied in two ongoing Phase 1 clinical trials to assess safety and initial anti-tumor efficacy of transplant donor derived WT1-CTL in patients with AML and MM.

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 muscle wasting conditions, oncology and viral-associated diseases. Atara Bio’s programs include molecularly targeted product candidates and T-cell product candidates. Molecularly targeted product candidates include PINTA 745, STM 434 and ATA 842. These product candidates target myostatin and activin, members of the TGF-beta family of proteins, and have demonstrated the potential to have therapeutic benefit in a number of clinical indications. The 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. For example, forward-looking statements include statements regarding the fact that we believe this therapeutic approach may offer a potential therapeutic alterative for patients with these difficult-to-treat, refractory cancers”. 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.

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