Atara Biotherapeutics Announces Proposed Offering of Common Stock and Pre-Funded Warrants

Atara Biotherapeutics, Inc. (Nasdaq:ATRA), a pioneer in T-cell immunotherapy leveraging its novel allogeneic EBV T-cell platform to develop transformative therapies for patients with severe diseases including solid tumors, hematologic cancers and autoimmune diseases, today announced that it has commenced an underwritten public offering of shares of its common stock and, to certain investors, pre-funded warrants to purchase shares of its common stock. The pre-funded warrants will be offered at the same price per share as the common stock, less the $0.0001 per share exercise price of each pre-funded warrant multiplied by the number of shares subject to the warrant. In connection with the proposed offering, Atara Biotherapeutics expects to grant the underwriters a 30-day option to purchase up to an additional 15% of the total of the number of shares of its common stock plus the number of shares underlying the pre-funded warrants to be sold in the offering at the public offering price, less the underwriting discounts and commissions. All of the shares and pre-funded warrants in the proposed offering will be sold by Atara Biotherapeutics. The proposed offering is subject to market and other conditions, and there can be no assurances as to whether or when the proposed offering may be completed, or as to the actual size or terms of the proposed offering.

Citigroup, Cowen and Evercore ISI are acting as joint book-running managers for the proposed offering. Mizuho Securities is acting as lead manager and Canaccord Genuity is acting as co-manager for the proposed offering.

The securities described above are being offered by Atara Biotherapeutics pursuant to a shelf registration statement on Form S-3, including a base prospectus, that was previously filed by Atara Biotherapeutics with the Securities and Exchange Commission (the “SEC”) and that became automatically effective on February 27, 2018. A preliminary prospectus supplement and accompanying prospectus relating to the proposed offering will be filed with the SEC and will be available on the SEC’s website located at http://www.sec.gov. Copies of the preliminary prospectus supplement and the accompanying prospectus relating to the proposed offering, when available, may be obtained from: Citigroup, by mail at Citigroup Global Markets Inc., c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717, or by telephone at 1-800-831-9146; Cowen and Company, LLC, c/o Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, New York 11717, Attn: Prospectus Department, by telephone at [phone], or by email at [e-mail]; or Evercore Group L.L.C., Attention: Equity Capital Markets, 55 East 52nd Street, 35th Floor, New York, NY 10055, or by telephone at [phone], or by email at [e-mail]. The final terms of the proposed offering will be disclosed in a final prospectus supplement to be filed with the SEC.