FDA To Reconsider Rare Cancer Drug Ebvallo After Surprise Rejection

The U.S. Food and Drug Administration announced Tuesday it will reconsider the rare cancer drug Ebvallo, developed by Atara Biotherapeutics, after previously rejecting its approval in January. The initial rejection came as a surprise despite positive internal reviews, with sources attributing the decision to concerns over manufacturing processes rather than clinical efficacy or safety.

The FDA’s decision to reconsider Ebvallo follows a complete response letter issued on Jan. 16, 2026, which rejected the drug’s Biologics License Application despite positive internal reviews supporting approval, according to sources familiar with the matter. The rejection was described as a “complete reversal” and a surprise given that no deficiencies were identified in the drug’s clinical efficacy, safety, or production processes. A former FDA employee cited by STAT News attributed the initial rejection partly to changes in the agency’s leadership.

Ebvallo, also known by its generic name tabelecleucel, is an allogeneic Epstein-Barr virus (EBV)-specific T-cell immunotherapy developed by Atara Biotherapeutics in partnership with Pierre Fabre Pharmaceuticals.

The primary reason for the FDA’s initial rejection was concerns related to the manufacturing site of Ebvallo, a third-party facility used in the drug’s production. Atara Biotherapeutics, the developer of Ebvallo, confirmed in a Jan. 16 news release that the manufacturing site was the “main issue” raised by the FDA. The agency did not request additional clinical trials or raise questions about the drug’s safety or effectiveness, officials said.

It is intended to treat relapsed or refractory EBV-positive post-transplant lymphoproliferative disease (PTLD), a rare blood cancer affecting roughly 500 patients annually in the United States, including children older than two years and adults. PTLD occurs after stem cell or organ transplants and is linked to EBV infection, with patients often facing only weeks or months to live without effective treatment.

The drug received approval in the European Union in 2022 under the brand name Ebvallo, marking a significant advance for patients with limited therapeutic options. Atara President and CEO Cokey Nguyen, PhD, said the company is actively working with Pierre Fabre and the manufacturing partner to address the FDA’s concerns. Nguyen told reporters the company plans to resolve the manufacturing issues and resubmit the BLA promptly and expects FDA approval within six months of resubmission.

The FDA’s announcement of its intent to reconsider Ebvallo came after constructive discussions between the agency and Atara, which clarified misunderstandings and provided additional data and analysis addressing the chief regulatory concerns. This agreement allows the FDA to re-evaluate the benefits and risks of Ebvallo under its established framework for drug approvals, officials said.

Atara’s partnership with Pierre Fabre Laboratories has been integral to remediation efforts, focusing on ensuring compliance with manufacturing standards required for cell therapies. The challenges reflect broader regulatory oversight issues in the production of complex biologic drugs, particularly those targeting rare diseases.

PTLD is a rare cancer that arises after transplants and is associated with EBV infection, which causes abnormal lymphocyte proliferation. The condition has a poor prognosis, especially in relapsed or refractory cases, underscoring the unmet medical need that Ebvallo seeks to address. Current treatment options for EBV-positive PTLD are limited, making the drug’s potential approval significant for patients and clinicians.

The FDA’s initial rejection and subsequent reconsideration illustrate evolving regulatory scrutiny for rare disease therapies, particularly those involving advanced cell-based products. Sources familiar with the FDA’s internal deliberations noted that while clinical reviewers supported Ebvallo’s approval, the agency’s leadership at the time raised concerns about manufacturing compliance, leading to the January 2026 rejection.

Atara’s efforts to resolve the manufacturing issues and resubmit the BLA are ongoing, with the company and its partners committed to meeting FDA standards. The agency’s forthcoming decision will be closely watched as a measure of regulatory approaches toward innovative rare cancer treatments.