FDA Issues Complete Response Letter for Atara’s EBVALLO Therapy

Atara Biotherapeutics has received a setback in its efforts to bring EBVALLO™ (tabelecleucel) to patients with Epstein-Barr virus–positive post-transplant lymphoproliferative disease (EBV+ PTLD), after the U.S. Food and Drug Administration issued a Complete Response Letter (CRL) for the therapy’s Biologics License Application. EBVALLO is being developed as a monotherapy for adult and pediatric patients aged two years and older who have received at least one prior treatment, including an anti-CD20–containing regimen.

The CRL, received after market close on January 9, 2026, states that the FDA is unable to approve the application in its current form. The decision follows a resubmission of the BLA in 2025, which Atara said was made after aligning with the FDA on resubmission criteria and addressing issues identified in an earlier CRL issued in January 2025. That initial response letter cited a single deficiency related to Good Manufacturing Practice compliance and did not raise concerns about safety, efficacy, or clinical trial design.

In the latest CRL, the FDA confirmed that the previously identified GMP issues have been satisfactorily resolved and emphasized that no safety concerns were identified. However, the agency reversed its earlier position on the clinical data package, stating that the single-arm ALLELE trial is no longer considered adequate to support accelerated approval. The FDA also noted that the trial’s interpretability was confounded by aspects of its design, conduct, and analysis.

Atara said the FDA’s current stance contradicts years of prior guidance and alignment between the company and the agency, including documented meetings over more than five years in which the ALLELE trial design was accepted as appropriate for this rare and life-threatening patient population. The company had planned to conduct a post-marketing confirmatory study following accelerated approval.

In November 2025, Atara transferred the BLA to Pierre Fabre Pharmaceuticals, which now plans to request a Type A meeting with the FDA within the next 45 days to seek a path forward. Both companies emphasized the urgent unmet need for EBV+ PTLD patients, whose life expectancy is often measured in weeks to months.

Atara leadership expressed surprise and disappointment at the decision, reaffirming its belief that tabelecleucel could provide meaningful benefit to patients with limited treatment options.