Atara Biotherapeutics Receives Complete Response Letter from FDA

Atara Biotherapeutics announced that the FDA has issued a complete response letter, or CRL, for the Ebvallo biologics license application as monotherapy treatment for adult and pediatric patients two years of age and older with Epstein-Barr virus positive post-transplant lymphoproliferative disease, who have received at least one prior therapy including an anti-CD20 containing regimen. The CRL indicates that the FDA is unable to approve the Ebvallo BLA in its present form. The BLA was resubmitted in 2025 after reaching alignment with the FDA on the acceptability of the resubmission criteria and fulfilment of the conditions as identified in the first complete response letter dated January 15. In the First CRL, the FDA identified a single deficiency regarding good manufacturing practice compliance and did not raise any concerns with respect to the safety, efficacy or trial design. In the current CRL, received after market close on January 9, the FDA confirmed that the GMP compliance issues had been satisfactorily resolved, and importantly, no safety issues were raised. However, in a complete reversal of position by the FDA, the CRL claims that the single arm ALLELE trial, which was previously confirmed by the FDA as adequate to support the BLA filing, is no longer considered to be adequate to provide evidence of effectiveness for accelerated approval. Furthermore, the FDA stated that the trial's interpretability is confounded due to trial study design, conduct, and analysis. The FDA's new position is contrary to the FDA's prior guidance to Atara, the FDA's alignment with Atara on the clinical trial data set, and the acceptance of the trial design as a single arm study as relevant for this patient population at BLA submission. This prior alignment had been reached by Atara and the FDA through multiple, documented meetings held over the past five plus years. In November 2025, Atara transferred the BLA to Pierre Fabre Pharmaceuticals, the U.S. pharmaceutical subsidiary of Pierre Fabre Laboratories. As a first step towards resolution, PFP intends to request a Type A meeting and expects it to be granted within 45 days. PFP and Atara plan to urgently interact with the FDA to find a path forward for the timely accelerated approval of Ebvallo without which patients with EBV+ PTLD have extremely limited treatment options and a life expectancy often measured in weeks to months.