Atara details FDA path to resubmit tab-cel BLA

Rhea-AI Filing Summary

Atara Biotherapeutics reported a regulatory update on tabelecleucel (tab-cel) after a recent Type A meeting with the FDA following the Complete Response Letter issued on January 9, 2026 for its Biologics License Application held by partner Pierre Fabre Pharmaceuticals.

The FDA agreed that a single-arm study using an appropriate pre-specified historical control could be considered an adequate and well-controlled study to provide safety and efficacy data for a future marketing application in relapsed or refractory EBV+ PTLD after transplant in patients two years of age and older.

Pierre Fabre plans to submit an updated dataset with additional patients and longer follow-up from the pivotal Phase 3 ALLELE study, along with supportive data, as part of a resubmission plan being defined with the FDA. Atara expects to provide a further regulatory update in the third quarter.

Insights

Biotech regulatory analyst

FDA outlines a viable resubmission path for tab-cel, but approval timing and outcome remain uncertain.

The update centers on tabelecleucel (tab-cel) for relapsed or refractory EBV+ PTLD after transplant. Following the FDA’s Complete Response Letter dated January 9, 2026, Atara and partner Pierre Fabre held a Type A meeting to clarify requirements for a potential resubmission.

The FDA agreed that a single-arm study with a prespecified historical control could be treated as an adequate and well-controlled study to support a future marketing application. Pierre Fabre intends to submit an updated dataset with more patients and longer follow-up from the pivotal Phase 3 ALLELE trial, plus supportive data.

Regulatory risk remains, as the agency must still review any resubmission and determine whether remaining deficiencies are resolved. Atara also notes that Pierre Fabre controls the tab-cel BLA strategy and timing, while Atara plans another regulatory update in the third quarter.

8-K Event Classification

2 items: 8.01, 9.01

2 items

Item 8.01 Other Events Other

Voluntary disclosure of events the company deems important to shareholders but not covered by other items.

Item 9.01 Financial Statements and Exhibits Exhibits

Financial statements, pro forma financial information, or exhibit attachments filed with this report.

Key Figures

CRL date: January 9, 2026 Press release date: May 7, 2026 Minimum patient age: two years of age and older +2 more

5 metrics

CRL date January 9, 2026 Complete Response Letter for tab-cel BLA

Press release date May 7, 2026 Regulatory update on tab-cel and FDA meeting

Minimum patient age two years of age and older Phase 3 ALLELE study population for EBV+ PTLD

Next update timing third quarter Planned further regulatory update on tab-cel

Trial phase Phase 3 ALLELE single-arm study of tabelecleucel

Key Terms

Complete Response Letter, Type A meeting, Biologics License Application (BLA), EBV+ PTLD, +1 more

5 terms

Complete Response Letter regulatory

"to discuss the Complete Response Letter (CRL) to the Biologics License Application"

A complete response letter is an official communication from a drug or medical-device regulator, such as the U.S. Food and Drug Administration (FDA), telling a company that a marketing application cannot be approved in its current form and listing the specific deficiencies to be fixed. For investors it matters because it pauses or delays a product’s path to market—like a building inspector issuing a list of repairs before a certificate of occupancy—affecting revenue timing, costs and stock value.

Type A meeting regulatory

"update following the recent Type A meeting with the U.S. Food and Drug Administration"

A Type A meeting is an urgent, short-notice session requested between a company and a regulatory agency (for example, the FDA in the U.S.) to resolve critical issues that block a development program, such as a clinical hold or safety concern. Investors care because the outcome can immediately affect whether a clinical trial or approval process resumes, changing timelines, costs and the company’s near-term value — like calling an emergency mechanic when a car won’t start so a trip can continue.

Biologics License Application (BLA) regulatory

"Complete Response Letter (CRL) to the Biologics License Application (BLA) for tabelecleucel"

A biologics license application (BLA) is a formal request to a government agency seeking approval to sell a biological medicine, such as vaccines or gene therapies, in the market. It is similar to a detailed report that proves the product is safe, effective, and manufactured properly. For investors, a BLA signifies a critical step toward commercial availability, often impacting a company's valuation and market prospects.

EBV+ PTLD medical

"with R/R EBV+ PTLD following solid organ transplant or hematopoietic cell transplant"

A condition in which the Epstein‑Barr virus (EBV) triggers uncontrolled growth of a transplant patient’s immune cells, called post‑transplant lymphoproliferative disorder (PTLD). It behaves like invasive weeds taking over a garden when the body’s immune “fence” is weakened by anti‑rejection drugs, and can be life‑threatening without rapid diagnosis and treatment. Investors watch EBV+ PTLD because it creates a focused, urgent market for diagnostics, therapies and hospital care, so clinical trial results, approvals or new treatments can materially affect companies working in transplant, oncology and infectious disease.

allogeneic T-cell immunotherapy medical

"regulatory approval of an allogeneic T-cell immunotherapy"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What regulatory update did Atara Biotherapeutics (ATRA) provide on tabelecleucel?

Atara reported that, after a Type A FDA meeting, regulators agreed a single-arm study with an appropriate historical control could support a future marketing application for tabelecleucel in EBV+ PTLD. This gives Atara and partner Pierre Fabre a clearer framework for resubmitting the BLA.

What was the FDA’s feedback on the tab-cel Biologics License Application for Atara (ATRA)?

The FDA issued a Complete Response Letter on January 9, 2026 for the tab-cel BLA, then discussed next steps in a Type A meeting. The agency agreed that a single-arm trial using a prespecified historical control could potentially serve as an adequate and well-controlled study.

How does Pierre Fabre’s role affect Atara Biotherapeutics’ (ATRA) tab-cel program?

Pierre Fabre Pharmaceuticals holds the tab-cel BLA and leads the timing, content, and strategy for any resubmission to the FDA, with Atara providing support. This structure means Atara’s direct control over regulatory interactions and resubmission details is limited, despite its scientific involvement.

What clinical data will support Atara Biotherapeutics’ (ATRA) planned tab-cel resubmission?

Pierre Fabre plans to submit an updated dataset from the pivotal Phase 3 ALLELE study of tabelecleucel in relapsed or refractory EBV+ PTLD, adding more patients and longer follow-up. Additional supportive data will also be included as part of the resubmission plan with the FDA.

When does Atara Biotherapeutics (ATRA) expect further regulatory news on tabelecleucel?

Atara stated it anticipates providing a further regulatory update on tabelecleucel in the third quarter. The timing of the actual BLA resubmission and subsequent FDA decisions depends on Pierre Fabre’s preparations and the agency’s review process once materials are filed.

What is the target patient population for Atara’s tabelecleucel (tab-cel)?

Tabelecleucel is being developed for adults and children two years of age and older with relapsed or refractory EBV+ post-transplant lymphoproliferative disease after solid organ or hematopoietic cell transplant. This population faces limited treatment options, making new therapies particularly important.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 05/07/2026 - 08:10 AM Learn about SEC filing dates

0001604464false00016044642026-05-072026-05-07

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 07, 2026

Atara Biotherapeutics, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware			001-36548	46-0920988
(State or Other Jurisdiction of Incorporation)			(Commission File Number)	(IRS Employer Identification No.)
1280 Rancho Conejo Blvd
Thousand Oaks, California				91320
(Address of Principal Executive Offices)				(Zip Code)

Registrant’s Telephone Number, Including Area Code: (805) 623-4211

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, par value $0.0001 per share		ATRA		The Nasdaq Stock Market LLC

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

On May 7, 2026, Atara Biotherapeutics, Inc. (the “Company”) issued a press release titled “Atara Biotherapeutics Provides Regulatory Update on Tabelecleucel” providing an update following the Type A meeting with the U.S. Food and Drug Administration (the “FDA”) to discuss the Complete Response Letter for the EBVALLO™ Biologics License Application issued on January 9, 2026.

A copy of the press release is filed herewith as Exhibit 99.1 and is incorporated by reference into this Item 8.01.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit No.		Description
99.1		Press Release, dated May 7, 2026
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

			ATARA BIOTHERAPEUTICS, INC.
Date:	May 7, 2026	By:	/s/ AnhCo Thieu Nguyen
			AnhCo Thieu Nguyen, Ph.D. President and Chief Executive Officer (Duly Authorized Officer and Principal Executive Officer)

Exhibit 99.1

Atara Biotherapeutics Provides Regulatory Update on Tabelecleucel

THOUSAND OAKS, Calif.--(BUSINESS WIRE)-- Atara Biotherapeutics, Inc. (Nasdaq: ATRA), a leader in T-cell immunotherapy, leveraging its novel allogeneic Epstein-Barr virus (EBV) T-cell platform to develop transformative therapies for patients with cancer and autoimmune diseases, today provided an update following the recent Type A meeting with the U.S. Food and Drug Administration (FDA) to discuss the Complete Response Letter (CRL) to the Biologics License Application (BLA) for tabelecleucel (tab-cel) held by our partner Pierre Fabre Pharmaceuticals, Inc. (PFP).

PFP, with Atara’s support, had a productive meeting with the FDA and discussed a potential path forward to resubmitting the tab-cel BLA. The FDA agreed that a single arm study using an appropriate historical control applicable to the trial population, conducted in a pre-specified manner, could serve as an adequate and well controlled study and provide safety and efficacy data in support of a future marketing application of tab-cel for the proposed indication. PFP has indicated they intend to submit an updated dataset with additional patients and longer follow up from the pivotal Phase 3 single arm ALLELE study of tabelecleucel in adults and children two years of age and older with R/R EBV+ PTLD following solid organ transplant or hematopoietic cell transplant as well as supportive data, as a part of the resubmission plan being defined with the FDA.

“We are grateful to the agency for engaging in a collaborative conversation with our partners, Pierre Fabre, and us. We appreciate the FDA’s continued engagement with PFP and Atara, and we believe the Type A Meeting provided helpful alignment on the regulatory framework to resubmit,” said Cokey Nguyen, President and Chief Executive Officer of Atara. “We will continue to support Pierre Fabre as it prepares the resubmission and anticipate providing a further regulatory update in the third quarter.”

About Atara Biotherapeutics, Inc.

Atara is harnessing the natural power of the immune system to develop off-the-shelf cell therapies for difficult-to-treat cancers and autoimmune conditions that can be rapidly delivered to patients from inventory. With cutting-edge science and differentiated approach, Atara is the first company in the world to receive regulatory approval of an allogeneic T-cell immunotherapy. Our advanced and versatile T-cell platform does not require T-cell receptor or HLA gene editing and forms the basis of a diverse portfolio of investigational therapies that target EBV, the root cause of certain diseases. Atara is headquartered in Southern California. For more information, visit atarabio.com and follow @Atarabio on X and LinkedIn.

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 and Section 21E of the Securities Exchange Act of 1934. For example, forward-looking statements include statements regarding: (1) the development, timing and progress of tab-cel, including the timing of PFP’s resubmission of the tab-cel BLA, the potential characteristics and benefits of tab-cel; and (2) the prospect of bringing tab-cel to U.S. patients with EBV+ PTLD. Because such statements deal with future events and are based on Atara’s current expectations, they are subject to various risks and uncertainties and actual results, performance or achievements of Atara 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, risks and uncertainties associated with the costly and time-consuming pharmaceutical product development process and the uncertainty of clinical success; risks related to FDA’s review of tab-cel, including the risk that a resubmission of the tab-cel BLA may not address the deficiencies identified in the CRL or other issues that may be raised by the FDA on review; the fact that PFP, and not Atara, holds the tab-cel BLA and controls the timing, content and strategy of any resubmission and related FDA interactions, and Atara's ability to influence the resubmission process is limited; our ability to access capital, and the sufficiency of Atara’s cash resources and access to additional capital on favorable terms or at all; and other risks and uncertainties affecting Atara, including those discussed in Atara’s filings with the

Securities and Exchange Commission, including in the “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of Atara’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 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.

Investor and Media Relations
Amber Daugherty
Sr. Director, Strategy and Operations
adaugherty@atarabio.com

Filing Exhibits & Attachments

2 documents

Press Releases

• EX-99.1 EX-99.1 13.4 KB

Other Documents

• EX-101 XBRL TAXONOMY EXTENSION SCHEMA WITH EMBEDDED LINKBASES DOCUMENT 23.3 KB