Atara Biotherapeutics has announced that the US Food and Drug Administration (FDA) has issued a complete response letter (CRL) for the biologics licence application (BLA) of Ebvallo (tabelecleucel).
The application sought approval for Ebvallo as monotherapy in adult and paediatric patients aged two years and above with Epstein-Barr virus-positive post-transplant lymphoproliferative disease (EBV+ PTLD), who have previously received at least one treatment, including anti-CD20 therapy.
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The FDA’s CRL means the application cannot be approved in its current form.
The BLA was resubmitted last year, after Atara and the FDA aligned on resubmission criteria and addressed conditions from the initial CRL dated 15 January 2025.
The first CRL identified a single good manufacturing practice (GMP) compliance deficiency, without concerns over trial design, efficacy, or safety.
In the latest CRL received after market close on 9 January 2026, the FDA stated that concerns regarding GMP compliance had been addressed and reported no additional safety issues.
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By GlobalDataHowever, the FDA reversed its prior position and stated that the single-arm ALLELE trial, earlier accepted as adequate for supporting BLA filing, was now not considered sufficient to demonstrate effectiveness for accelerated approval. The agency cited confounding factors in the study’s analysis, design and conduct.
This position differs from previous guidance provided to Atara and contradicts prior documented alignment between the company and the FDA over more than five years, regarding the suitability of the clinical trial data set and acceptance of a single-arm study design for this population at BLA submission.
In November 2025, Atara transferred the BLA to a US subsidiary of Pierre Fabre Laboratories, Pierre Fabre Pharmaceuticals (PFP).
PFP plans to request a Type A meeting, expecting it within 45 days.
Both PFP and Atara intend to urgently engage with the FDA to discuss potential accelerated approval paths for Ebvallo, given limited treatment options and low life expectancy for patients with EBV+ PTLD.
Atara president and CEO Cokey Nguyen said: “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.
“The issues highlighted in the CRL were issues Atara and the FDA aligned on in previous reviews or communications. We had aligned with the agency to accept an accelerated approval and to perform a post-marketing confirmatory study to support full approval.”
In January 2025, Atara Therapeutics’ pipeline faced another obstacle after the US FDA halted clinical trials evaluating two of the company’s T-cell immunotherapies, following the receipt of a CRL.
