Atara Biotherapeutics To Present Positive New Tab-cel Clinical Data During Oral Session at ESMO Immuno-Oncology Annual Congress 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 positive new data for tabelecleucel (tab-cel or EBVALLO) in patients with relapsed or refractory (r/r) or treatment-naïve Epstein-Barr virus-positive post-transplant lymphoproliferative disease involving the central nervous system (CNS) (EBV+ CNS PTLD) following solid organ transplant (SOT) or hematopoietic cell transplant (HCT). These results will be presented as an oral session at the European Society for Medical Oncology Immuno-Oncology (ESMO I‑O) Annual Congress taking place December 6-8, 2023, in Geneva, Switzerland.

The clinical experience from this combined analysis of four single-arm, open-label studies, including the multicohort Phase 2 EBVision trial (NCT04554914, n=4) expands on previous data from two single-center, Phase 2 studies (NCT00002663, n=10; NCT01498484, n=2), and multicenter, expanded-access protocol (NCT02822495, n=2).

“EBV+ CNS PTLD is a rare but extremely serious disease, and patients often face a poor prognosis that underscores the urgent medical need,” said AJ Joshi, M.D., Executive Vice President, Chief Medical Officer at Atara. “We’re pleased to share new multicenter data, including the first results from our ongoing multicohort EBVision trial and first clinical trial report of treatment with tab-cel in the first line setting. Tab-cel shows a strong objective response rate in these high-risk patients with a favorable safety profile for patients with EBV-driven diseases.”

In this pooled analysis, a total of 18 patients, including one previously untreated patient, with EBV+ CNS PTLD received cycles of three weekly infusions of tab-cel at ~2x10⁶ cells/kg. Key endpoints were objective response rate (ORR), overall survival (OS), and safety parameters. Patients received a median (range) of 1 (0 to 5) lines of prior therapy.

An ORR of 77.8% (14/18) was observed in all patients (95% CI: 52.4, 93.6), with a best overall response of Complete Response (CR; 38.9%; n=7) or Partial Response (PR; 38.9%; n=7). The median time to response (TTR) in all patients was 1.8 months (range: 0.7–6.4).

The estimated one-year overall survival (OS) rate was 70.6% (95% CI: 43.0, 86.6) for all patients. The one-year OS rate for responders was 85.7% versus 0% for non-responders.

Tab-cel was well-tolerated. No reports of serious treatment-emergent adverse events, including neurotoxicity, organ rejection, graft versus host disease, or tumor flare reaction of any grade, were identified related to tab-cel.