On November 4, 2021 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, reported the upcoming first release of efficacy and safety results from its Phase 3 ALLELE study (Press release, Atara Biotherapeutics, NOV 4, 2021, View Source [SID1234594511]). The pivotal trial is investigating tabelecleucel (tab-cel) for the treatment of Epstein-Barr virus-positive post-transplant lymphoproliferative disease (EBV+ PTLD) following solid organ transplant (SOT) or hematopoietic cell transplant (HCT). Detailed findings, along with combined data from investigator-sponsored Phase 2 and multicenter Expanded Access Program (EAP) studies, will be featured among eight abstracts, including two oral presentations, at the 63rd American Society of Hematology (ASH) (Free ASH Whitepaper) Annual Meeting taking place December 11-14, 2021, in Atlanta.

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"There is significant unmet need in patients with EBV+ PTLD, with poor overall survival measured in weeks to a few months after first-line treatment failure," said Jakob Dupont, MD, Head of Global Research & Development at Atara. "Tab-cel demonstrated a clinically meaningful objective response rate and striking overall survival in a patient population with no approved treatment options, representing a first-in-kind allogeneic therapy with transformative potential. At ASH (Free ASH Whitepaper), we will share data from our Phase 3 ALLELE study, which further supports tab-cel as a potentially safe and effective treatment option for patients with EBV-driven diseases."

As reported in the full abstract available today on the ASH (Free ASH Whitepaper) website, top-line data with additional patients and extended follow up confirm a strong ORR in line with prior Phase 2 and multicenter EAP results and demonstrate durability of response with no new safety signals.

In this ongoing Phase 3 study, 38 evaluable patients as of May 2021 — 24 EBV+ PTLD following SOT patients after failure of rituximab ± chemotherapy and 14 EBV+ PTLD following HCT patients after failure of rituximab monotherapy — were treated with tab-cel and had the opportunity for a six-month follow-up after response. An ORR, as measured by independent oncologic response adjudication (IORA) assessment, of 50% (19/38, 95% CI: 33.4, 66.6) was observed, with an ORR of 50.0% (12/24, 95% CI: 29.1, 70.9) in PTLD following SOT and 50.0% (7/14, CI: 23.0, 77.0) in PTLD following HCT, with a best overall response of Complete Response (CR; n=5, SOT; n=5, HCT) or Partial Response (PR; n=7, SOT; n=2, HCT).

Overall, the median time to response (TTR) was 1.1 months (0.7-4.7). Of 19 responders, 11 had a duration of response (DOR) lasting more than six months and median DOR has not been reached yet. Those who responded had a longer survival compared to the non-responders, with a median OS not evaluable (NE) (95% CI: 16.4, NE) and a 1-year survival rate of 89.2% (95% CI: 63.1, 97.2).

Safety findings were consistent with previously published data, with no new signals or concerns reported. There were no reports of tumor flare reaction, and no confirmed evidence of graft versus host disease (GvHD), organ rejection, infusion reactions, or cytokine release syndrome related to tab-cel.

Further detail on baseline demographics and disease characteristics, and additional safety data including tab-cel exposure details, will be presented on December 11 in the oral presentation.

Atara will present additional data on tab-cel and PTLD through several abstracts, including a second oral presentation on long term OS from Phase 2 and multicenter EAP studies with tab-cel in relapsed/refractory EBV+ PTLD showing median OS of 54.6 months in all patients and OS at two years reaching over 86% in responders whether patients experienced CR or PR. Treatment was well tolerated with no confirmed evidence for graft versus host disease, cytokine release syndrome, SOT rejection, or neurologic events attributable to tab-cel.

In total, five abstracts will be presented at the 63rd ASH (Free ASH Whitepaper) Annual Meeting. An additional three accepted abstracts will be published online in the November supplemental issue of Blood.

Oral Presentation Details:
Title: Multicenter, Open-Label, Phase 3 Study of Tabelecleucel for Solid Organ or Allogeneic Hematopoietic Cell Transplant Recipients with Epstein-Barr Virus-Driven Post Transplant Lymphoproliferative Disease after Failure of Rituximab or Rituximab and Chemotherapy (ALLELE)

Presenting Author: Susan Prockop, MD, Boston Children’s Hospital/Dana Farber Cancer Institute, Boston, MA
Date & Time: Saturday, December 11, 2021, at 4:00 p.m. EST/1:00 p.m. PST
Abstract Number: 301
Session: 626. Aggressive Lymphomas Prospective Therapeutic Trials: Challenging Populations
Location: Georgia World Congress Center, B401-B402
Title: Overall Survival by Best Overall Response with Tabelecleucel in Patients with Epstein-Barr Virus-Driven Post-Transplant Lymphoproliferative Disease Following Solid Organ or Allogeneic Hematopoietic Cell Transplant

Presenting Author: Susan Prockop, MD, Boston Children’s Hospital/Dana Farber Cancer Institute, Boston, MA
Date & Time: Monday, December 13, 2021, at 7:15 p.m. EST/4:15 p.m. PST
Abstract Number: 887
Session: 627. Aggressive Lymphomas: Clinical and Epidemiological: Real World Evidence for CAR-T Management II
Location: Georgia World Congress Center, C101 Auditorium
Poster Presentation Details:
Title: Clinical Outcomes of Patients with Epstein-Barr Virus-Driven Post-Transplant Lymphoproliferative Disease Following Hematopoietic Stem Cell Transplantation Who Fail Rituximab: A Multinational, Retrospective Chart Review Study

Presenting Author: Jaime Sanz, MD, University Hospital La Fe in Valencia, Valencia, Spain
Date & Time: Saturday, December 11, 2021, at 5:30-7:30 p.m. EST/2:30-4:30 p.m. PST
Abstract Number: 1454
Session: 627. Aggressive Lymphomas: Clinical and Epidemiological: Poster I
Location: Georgia World Congress Center, Hall B5
Title: Clinical Outcomes of Solid Organ Transplant Patients with Epstein-Barr Virus-Driven (EBV+) Post-Transplant Lymphoproliferative Disorder (PTLD) Who Fail Rituximab Plus Chemotherapy: A Multinational, Retrospective Chart Review Study

Presenting Author: Vikas Dharnidharka, MD, MPH, Washington University School of Medicine & St. Louis Children’s Hospital, St Louis, MO
Date & Time: Sunday, December 12, 2021, at 6:00-8:00 p.m. EST/3:00-5:00 p.m. PST
Abstract Number: 2528
Session: 627. Aggressive Lymphomas: Clinical and Epidemiological: Poster II
Location: Georgia World Congress Center, Hall B5
Title: Comprehensive Activation Profiling of the Tabelecleucel Library, an Off-the-Shelf, Allogeneic EBV-Specific T-Cell Therapy

Presenting Author: Joseph M Benoun, PhD, Atara Biotherapeutics, Thousand Oaks, CA
Date & Time: Sunday, December 12, 2021, at 6:00-8:00 p.m. EST/3:00-5:00 p.m. PST
Abstract Number: 2809
Session: 703. Cellular Immunotherapies: Basic and Translational: Poster II
Location: Georgia World Congress Center, Hall B5
About Tabelecleucel
Tabelecleucel (tab-cel) is an off-the-shelf, allogeneic T-cell immunotherapy in development for the treatment of Epstein-Barr virus-positive post-transplant lymphoproliferative disease (EBV+ PTLD). EBV+ PTLD is a type of lymphoma (cancer) that may occur after a solid organ transplant (SOT) or allogeneic hematopoietic cell transplant (HCT). There are currently no approved treatments indicated to treat PTLD and if left untreated, PTLD can have life-threatening consequences.

Tab-cel is currently being investigated in the Phase 3 ALLELE study to assess efficacy and safety for the treatment of EBV+ PTLD in SOT and HCT after failure of standard of care.

Tab-cel has been granted Breakthrough Therapy Designation for EBV+ PTLD following allogeneic HCT by the U.S. Food and Drug Administration (FDA) and PRIME designation by the European Medicines Agency (EMA) for the same indication. Tab-cel has orphan drug designation in the U.S. and EU.