INVESTOR ALERT: Securities Class Action Filed Against Atara Biotherapeutics, Inc. – Investors Encouraged to Contact Kirby McInerney LLP

NEW YORK--(BUSINESS WIRE)--The law firm of Kirby McInerney LLP announces that a class action lawsuit has been filed on behalf of investors who acquired Atara Biotherapeutics, Inc. (“Atara” or the “Company”) (NASDAQ:ATRA) securities during the period of May 20, 2024 through January 9, 2026, inclusive (“the Class Period”).

If you suffered a loss on your Atara investments, you have until May 22, 2026 to request lead plaintiff appointment. Courts do not consider lead plaintiff applications submitted after this deadline. If you choose to take no action, you may remain an absent class member. For more information about the lawsuit:

[CONTACT THE FIRM IF YOU SUFFERED A LOSS]

What Is This Lawsuit About? The lawsuit alleges that (i) certain manufacturing issues, as well as deficiencies inherent in the ALLELE study, made it unlikely that the FDA would approve the tabelecleucel BLA; (ii) accordingly, tabelecleucel's regulatory prospects were overstated; (iii) the aforementioned manufacturing issues also subjected Atara to a heightened risk of regulatory scrutiny, as well as jeopardized its ongoing clinical trials; and (iv) all the foregoing was likely to have a significant negative impact on Atara's business and financial condition.

On January 16, 2025, Atara issued a press release announcing its receipt of a Complete Response Letter (“CRL”) regarding the tabelecleucel BLA, stating that “[t]he CRL was solely related to observations as part of a standard pre-license inspection of a third-party manufacturing facility for EBVALLO.” On this news, the price of Atara shares declined by $5.33 per share, or approximately 40.5%, from $13.16 per share on January 15, 2025 to close at $7.83 on January 16, 2025.

On January 21, 2025, Atara issued a press release announcing “that the [FDA] has placed a clinical hold on Atara’s active Investigational New Drug (IND) applications” due to “inadequately addressed GMP [good manufacturing practice] compliance issues identified during the pre-license inspection of the third-party manufacturing facility referenced in the [CRL]” issued in connection with the tabelecleucel BLA. On this news, the price of Atara shares declined by $0.52 per share, or approximately 8%, from $6.57 per share on January 17, 2025 to close at $6.05 on January 21, 2025.

On January 12, 2026, Atara issued a press release announcing that the FDA had issued another CRL regarding the tabelecleucel BLA-which the Company had resubmitted to the FDA in July 2025-stating that “[t]he CRL indicates that the FDA is unable to approve the EBVALLO BLA in its present form” because “the single arm ALLELE trial . . . is no longer considered to be adequate to provide evidence of effectiveness for accelerated approval” and “the trial’s interpretability is confounded due to trial study design, conduct, and analysis.” On this news, the price of Atara shares declined by $7.79 per share, or approximately 57%, from $13.67 per share on January 9, 2026 to close at $5.88 on January 12, 2026.

[LEARN MORE ABOUT THE LAWSUIT]

The Lead Plaintiff Appointment Process. The federal securities laws permit any investor who acquired eligible securities during the class period to seek appointment as lead plaintiff in a class action lawsuit. Courts typically appoint the investor(s) with the largest financial loss in the case and the ability to represent the class rather than investors with simply the largest investment portfolio. Courts regularly appoint individual investors, whether acting alone or as a group, as lead plaintiffs. The rights of any investor who bought shares during the class period are generally already protected. However, lead plaintiffs have the power to influence case strategy and have a say in settlement decisions, as well as decisions concerning allocation of settlement funds among class members.

[LEARN MORE ABOUT THE LEAD PLAINTIFF PROCESS]

What Should I Do? If you purchased or otherwise acquired Atara securities, have information, or would like to learn more about this investigation, please contact Lauren Molinaro of Kirby McInerney LLP by email at [e-mail], or fill out the contact form below, to discuss your rights or interests with respect to these matters at no cost.

Kirby McInerney LLP is a New York-based plaintiffs’ law firm concentrating in securities, antitrust, whistleblower, and consumer litigation. The firm’s efforts on behalf of shareholders in securities litigation have resulted in recoveries totaling billions of dollars. Additional information about the firm can be found at Kirby McInerney LLP’s website.

This press release may be considered Attorney Advertising in some jurisdictions under the applicable law and ethical rules.