Atara Biotherapeutics Presents Updated Tab-cel Clinical Effectiveness Data at ASCO 2023

Atara Biotherapeutics, Inc. (Nasdaq: ATRA), a leader in T-cell immunotherapy, leveraging its novel allogeneic Epstein-Barr virus (EBV) T-cell platform to develop transformative therapies for patients with cancer and autoimmune diseases, today announced updated effectiveness and safety data for tabelecleucel (tab-cel or EBVALLO) from the multicenter Expanded Access Program (EAP) study in Europe. The results will be featured in a poster presentation at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting taking place June 2-6 in Chicago.

Atara supported 27 EAP requests in Europe for patients with relapsed or refractory (r/r) Epstein-Barr virus-positive post-transplant lymphoproliferative disease (EBV+ PTLD) following solid organ transplant (SOT) or hematopoietic cell transplant (HCT). 24 EBV+ PTLD patients, 16 SOT recipients and eight HCT recipients, consented to use of data and received at least one dose of tab-cel, including four patients with EBV+ primary central nervous system (PCNS) PTLD.

An objective response rate (ORR) of 66.7% (16/24) was observed for both SOT and HCT groups (95% CI: 44.7, 84.4), 56.3% (9/16) for patients following SOT (95% CI: 29.9, 80.2) and 87.5% (7/8) for HCT patients (95% CI: 47.3, 99.7) with a best overall response of Complete Response (CR; 33.3%; n=4, SOT, n=4, HCT) or Partial Response (PR; 33.3%; n=5, SOT, n=3, HCT).

"These real-world results affirm the favorable risk-benefit profile seen in the pivotal Phase 3 ALLELE study which supported tab-cel as the first-ever allogeneic T-cell immunotherapy approved," said AJ Joshi, MD, Chief Medical Officer at Atara. "Tab-cel was well tolerated and delivered a one-year survival rate of nearly 91% in responders, reinforcing its potential to address an urgent unmet medical need for EBV+ PTLD patients.”

The median time to response (TTR) in all patients was 1.0 month (range: 0.8–2.2). Of the subgroup of patients with EBV+ PCNS PTLD, three out of four (75%; 95% CI: 19.4, 99.4) treated patients achieved a response with one CR and two PRs.

One-year survival rates were 73.7% (95% CI: 47.3, 88.3) across both groups, 66.5% for SOT patients (95% CI: 32.7, 86.2) and 87.5% for HCT patients (95% CI: 38.7, 98.1). EBV+ PTLD patients responding to tab-cel had longer one-year survival compared to the non-responders, with a one-year survival rate of 90.9% (95% CI: 50.8, 98.7) versus 34.3% (95% CI: 4.8, 68.5) for non-responders.