Atara Biotherapeutics Announces Pricing of $175.0 Million Public Offering

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 serious diseases including solid tumors, hematologic cancers and autoimmune diseases, today announced the pricing of an underwritten public offering of 5,102,041 shares of its common stock at a price to the public of $24.50 per share and, to certain investors, pre-funded warrants to purchase 2,040,816 shares of its common stock at a purchase price of $24.4999 per pre-funded warrant share, which represents the per share public offering price for the common stock, minus the $0.0001 per share exercise price of each such pre-funded warrant share. The aggregate gross proceeds from the offering are expected to be approximately $175.0 million, before deducting the underwriting discounts and commissions and estimated offering expenses payable by Atara Biotherapeutics. The offering is expected to close on or about December 11, 2020, subject to customary closing conditions. In connection with the offering, Atara Biotherapeutics has granted the underwriters a 30-day option to purchase up to an additional 1,071,428 shares of its common stock at the public offering price, less the underwriting discounts and commissions.

Citigroup, Evercore ISI and Mizuho Securities are acting as joint book-running managers for the offering. Canaccord Genuity is acting as lead manager and Roth Capital Partners is acting as manager for the 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 offering have been filed with the SEC, and a final prospectus supplement and accompanying prospectus relating to the 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 final prospectus supplement and the accompanying prospectus relating to the 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 800-831-9146; Evercore Group L.L.C., Attention: Equity Capital Markets, 55 East 52nd Street, 35th Floor, New York, NY 10055, or by telephone at 888-474-0200, or by email at [email protected]; or Mizuho Securities USA LLC, Attention: Equity Capital Markets, 1271 Avenue of the Americas, 3rd Floor, New York, NY 10020, by telephone 212-205-7600, or by email: [email protected].

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

About Atara Biotherapeutics, Inc.

Atara Biotherapeutics, Inc. is a pioneer in T-cell immunotherapy leveraging its novel allogeneic EBV T-cell platform to develop transformative therapies for patients with serious diseases including solid tumors, hematologic cancers and autoimmune diseases.

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, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. For example, forward-looking statements include statements regarding the completion of the public offering. Because such statements deal with future events and are based on Atara Biotherapeutics' current expectations, they are subject to various risks and uncertainties and actual results, performance or achievements of Atara Biotherapeutics 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, without limitation, uncertainties related to market conditions and satisfaction of customary closing conditions related to the public offering, as well as those discussed in Atara Biotherapeutics filings with the Securities and Exchange Commission (SEC), including in the "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operations" sections of the Company's most recently filed periodic reports on Form 10-K and Form 10-Q and subsequent filings and in the documents incorporated by reference therein. Except as otherwise required by law, Atara Biotherapeutics 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.