Atara Bio Announces Proposed Offering of Common Stock

SOUTH SAN FRANCISCO, Calif., July 7, 2015 (GLOBE NEWSWIRE) -- Atara Biotherapeutics, Inc. (Nasdaq:ATRA), a biopharmaceutical company with a focus on developing innovative therapies for patients with debilitating diseases, today announced that it has commenced an underwritten public offering of shares of its common stock and expects to raise gross proceeds of approximately $125.0 million. In addition, Atara Bio expects to grant the underwriters a 30-day option to purchase up to an additional 15 percent of the number of shares of common stock sold in connection with the offering. All of the shares in the offering will be sold by Atara Bio.

Goldman, Sachs & Co. and Citigroup Global Markets Inc. are acting as joint book-running managers for the proposed offering. William Blair & Company, LLC, Canaccord Genuity Group, Inc. and JMP Securities LLC are acting as co-managers.

A registration statement related to the offering has been filed with the Securities and Exchange Commission but has not yet become effective.

The offering is being made only by means of a written prospectus forming part of the effective registration statement. Copies of the preliminary prospectus relating to the offering may be obtained, when available, from Goldman, Sachs & Co., Attention: Prospectus Department, 200 West Street, New York, New York 10282, by telephone at (866) 471-2526, by facsimile at (212) 902-9316, or by email at prospectus-ny@ny.email.gs.com, or from Citigroup Global Markets Inc., c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY, 11717, by email at prospectus@citi.com or by phone at (800) 831-9146.

This press release shall not constitute an offer to sell or a solicitation of an offer to buy these securities, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

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. Molecularly targeted product candidates include PINTA 745, STM 434 and ATA 842, members of the TGF-beta family of proteins that target myostatin and activin, and 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 Atara Bio's proposed public offering. These forward-looking statements are subject to other risks and uncertainties, including those discussed under the heading "Risk Factors" in Atara Bio's registration statement on Form S-1 originally filed with the Securities and Exchange Commission (SEC) on June 29, 2015, as amended, 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.

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

         MEDIA CONTACT:
         Susan Heins, Pure Communications, Inc.
         864-286-9597
         susan@purecommunicationsinc.com

Released July 7, 2015