Exhibit 5.1
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 | | SIDLEY AUSTIN LLP ONE SOUTH DEARBORN STREET CHICAGO, IL 60603 +1 312 853 7000 +1 312 853 7036 FAX AMERICA • ASIA PACIFIC • EUROPE |
February 8, 2023
Atara Biotherapeutics, Inc.
2380 Conejo Spectrum Street, Suite 200
Thousand Oaks, California 91320
| Re: | 5,027,104 Shares of Common Stock, $0.0001 par value per share (“Common Stock”) |
Ladies and Gentlemen:
We refer to the Registration Statement on Form S-8 (the “Registration Statement”) being filed by Atara Biotherapeutics, Inc., a Delaware corporation (the “Company”), with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration of (i) 4,796,335 shares of Common Stock which may be issued under the Atara Biotherapeutics, Inc. Amended and Restated 2014 Equity Incentive Plan (the “2014 Plan”) and (ii) 230,769 shares of Common Stock which may be issued under the Atara Biotherapeutics, Inc. 2014 Employee Stock Purchase Plan (collectively with the 2014 Plan, the “Plans” and the aggregate shares of Common Stock to be registered under the Registration Statement, the “Registered Shares”).
This opinion letter is being delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act.
We have examined the Registration Statement, the Company’s Amended and Restated Certificate of Incorporation, the Company’s Second Amended and Restated Bylaws, the Plans, and the resolutions adopted by the board of directors and stockholders of the Company relating to the Registration Statement and the Plans. We have also examined originals, or copies of originals certified to our satisfaction, of such agreements, documents, certificates and statements of the Company and other corporate documents and instruments, and have examined such questions of law, as we have considered relevant and necessary as a basis for this opinion letter. We have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures, the legal capacity of all persons and the conformity with the original documents of any copies thereof submitted to us for examination. As to facts relevant to the opinions expressed herein, we have relied without independent investigation or verification upon, and assumed the accuracy and completeness of, certificates, letters and oral and written statements and representations of public officials and officers and other representatives of the Company.
Sidley Austin LLP is a limited liability partnership practicing in affiliation with other Sidley Austin partnerships.
