January 12, 2026
1 min read
The FDA has issued a second complete response letter to Atara Biotherapeutics for its biologics license application of tabelecleucel for adults and children with Epstein-Barr virus-positive post-transplant lymphoproliferative disease.
The company had submitted the application for Ebvallo (tabelecleucel) — an off-the-shelf allogeneic Epstein-Barr virus-specific cytotoxic T-cell therapy — as monotherapy for affected adult and pediatric patients aged 2 years and older who had received at least one prior therapy, including an anti-CD20 containing regimen.
The FDA wrote that it is unable to approve the biologics license application in its present form. The application had been resubmitted in 2025 after Atara and the FDA reached agreement on certain criteria and fulfillment of conditions identified in the first complete response letter, namely a deficiency in Good Manufacturing Practice compliance. No safety, efficacy or trial designs concerns had been raised, according to Atara.
However, despite confirming the compliance issue had been resolved and no new safety signals identified, the FDA stated in its second letter that the single-arm ALLELE trial can no longer adequately provide evidence of efficacy and that its design, conduct and analysis could confound data interpretability.
Atara called the agency’s new stance “contrary to the FDA’s prior guidance to Atara, the FDA’s alignment with Atara on the clinical trial dataset, and the acceptance of the trial design as a single-arm study as relevant for this patient population at [biologics license application] submission.”
“We are surprised and disappointed by this FDA decision for EBV+ PTLD patients who have a significant unmet need, highlighted by tabelecleucel’s orphan drug designation and by the granting of breakthrough status at the time we submitted the ALLELE primary data,” Cokey Nguyen, PhD, Atara’s president and CEO, said in the release. “The issues highlighted in the [complete response letter] were issues Atara and the FDA aligned on in previous reviews or communications.”
“We strongly believe that tabelecleucel can bring substantial benefit to post-transplant lymphoproliferative disease patients and look forward to addressing the concerns of the FDA clinical review team newly in place alongside our partners,” he added.
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