Pomerantz Law Firm Launches Class Action Against Atara Biotherapeutics Over Alleged Securities Violations

Legal Action Filed Against Atara Biotherapeutics

On May 14, 2026, Pomerantz LLP announced the initiation of a class action lawsuit against Atara Biotherapeutics, Inc. (NASDAQ: ATRA) and certain company officials. This legal action, now recorded in the United States District Court for the Central District of California under case number 26-cv-03083, is positioned on behalf of all individuals and entities, excluding the defendants, who purchased or otherwise acquired Atara securities during a defined class period from May 20, 2024, to January 9, 2026.

The lawsuit aims to recover damages resulting from what the plaintiffs allege to be violations of federal securities laws, specifically under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 alongside Rule 10b-5.

Background of Atara Biotherapeutics

Atara Biotherapeutics is known for its focus on developing advanced therapies for individuals suffering from solid tumors, hematological cancers, and autoimmune disorders in both the U.S. and the U.K. One of their leading product candidates is tabelecleucel, also known as tab-cel or EBVALLO, which targets Epstein-Barr virus-positive post-transplant lymphoproliferative disease (EBV+ PTLD).

The company has forged a partnership with Pierre Fabre Médicament, a branch of the Pierre Fabre Laboratories group, to commercialize tabelecleucel. This collaboration is crucial as Atara relies on milestone payments from Pierre Fabre to continue its operational funding and ensure the development of tabelecleucel.

The Allegations

The allegations detailed in the lawsuit suggest that throughout the aforementioned class period, Atara's executives issued materially false and misleading statements about the company's business status, operations, and future outlook. Specific claims include:
1. Defendants allegedly downplayed certain manufacturing issues and flaws inherent to the ALLELE study, which could compromise the FDA’s approval of tabelecleucel.
2. There were claims that tabelecleucel's regulatory pathway was portrayed more positively than warranted.
3. Manufacturing problems heightened audit and regulatory scrutiny risks for Atara, thus endangering its clinical trials and financial status.
4. These misrepresentations led to a significant adverse effect on Atara's business and financial wellbeing.

Due to these factors, the lawsuit asserts that the defendants’ public statements were fundamentally deceptive throughout the entire period targeted by the class action.

Emergence of the Truth

The situation began to unravel on January 16, 2025, when Atara announced the receipt of a Complete Response Letter (CRL) from the FDA concerning the tabelecleucel Biologics License Application (BLA). This letter indicated that the FDA wouldn't approve the application in its current state, reacting negatively to observations made during a routine pre-licensing inspection of the third-party manufacturing facility for EBVALLO. This revelation led to a sharp decline in Atara's stock price, which plummeted by 40.5% in a single trading session.

Subsequently, on January 21, 2025, another announcement from Atara revealed that the FDA had placed a clinical hold on its active Investigational New Drug (IND) applications. This was again due to unresolved Good Manufacturing Practice (GMP) compliance issues identified previously during the inspection referred to in the CRL. Following this announcement, Atara’s stock saw another drop of 7.91%.

On January 12, 2026, the company issued further unsettling news, announcing an additional CRL regarding the tabelecleucel BLA, stating that the initial ALLELE trial was now deemed insufficient to substantiate effectiveness for accelerated approval. This caused a drastic fall of 56.99% in stock price, closing at just $5.88 per share.

About Pomerantz LLP

Founded over 85 years ago by Abraham L. Pomerantz, Pomerantz LLP has established itself as a leading law firm specializing in corporate, securities, and antitrust class litigation. The firm champions investor rights and has successfully recovered billions in damages on behalf of affected class members over the years. Pomerantz is committed to continuing its tradition of fighting for justice in securities fraud cases, ensuring that those harmed by corporate misconduct have a voice.

For investors who acquired Atara securities during the designated class period, there remains an opportunity to engage in the legal action. Interested parties have until May 22, 2026, to petition the court for lead plaintiff status. Further details are readily accessible on the Pomerantz Law Firm's website, or individuals may contact Danielle Peyton for more information.