Benzinga | Jun 7, 2021 10:31AM EDT

Atara Biotherapeutics Highlights Presentation Of Tab-cel Long-Term Overall Survival Data For Epstein-Barr Virus-Driven Post-Transplant Lymphoproliferative Disease After Solid Organ Transplant: All Patients Showed Complete Or Partial Response At 1 Year

All patients with a complete response (CR) or a partial response (PR) to tab-cel(r) alive at one year

Overall tab-cel(r) survival benefit demonstrated across previous treatment subgroups

Phase 2 results validate potential life-saving benefit of treatment with tab-cel(r) in seriously ill patient population with no approved therapeutic options

SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)-- Atara Biotherapeutics, Inc. (NASDAQ:ATRA), a pioneer in T-cell immunotherapy, leveraging its novel allogeneic EBV T-cell platform to develop transformative therapies for patients with cancer and autoimmune diseases, today announced a combined long-term overall survival (OS) analysis from three clinical studies of tabelecleucel (tab-cel(r)) in patients with Epstein-Barr virus-driven post-transplant lymphoproliferative disease (EBV+ PTLD) after solid organ transplantation (SOT). The results are featured in an oral plenary presentation at the American Transplant Congress (ATC 2021 Virtual Connect), taking place June 4-9, 2021.

Combined objective response rate (ORR) and OS data across two SOT subgroups -- patients relapsed or refractory (R/R) to rituximab monotherapy and patients R/R to rituximab + chemotherapy (CT) -- showed one- and two-year OS for patients achieving either complete response (CR) or those achieving partial response (PR). Data presented at ATC 2021 confirm benefit of tab-cel in SOT PTLD and show similar one- and two-year probability of OS irrespective of patients achieving CR or PR (according to Lugano criteria). Treatment response and OS data were assessed from two completed single-arm, Phase 2 studies (95-024, NCT00002663 and 11-130, NCT01498484) and the multi-center expanded access (EAP-201) study (NCT02822495).

"Patients who have received a solid organ transplant such as a new kidney, lung, heart or liver and go on to develop EBV+ PTLD that is relapsed or refractory to rituximab monotherapy or R-chemotherapy face a poor prognosis, with median survival of only about three months," said Jakob Dupont, M.D., Head of Global Research & Development at Atara. "There is a significant unmet need in these patients for whom there are no approved therapies, let alone therapies specifically designed to treat EBV+ PTLD. Combined data from across three clinical studies in SOT recipients with relapsed or refractory disease demonstrated similar long-term survival benefit in those who had either partial or complete response to treatment. These data indicate that tab-cel may help address an urgent unmet need in these patients with high rates of mortality."

Overall Survival (OS) by Best Overall Response (BOR)

SOT Subgroup 1 (n= SOT Subgroup 2 (n= 7) 19) All SOT Recipients with SOT recipients SOT recipients

EBV+ PTLD (n=26) with EBV+ PTLD R/R with EBV+ PTLD R/R

to rituximab to rituximab + CT

BOR CR (n=8) PR (n=9) CR (n=4) PR (n=2) CR (n=4) PR (n=7)

1-year OS rate 100% 100% 100% 100% 100% 100%

2-year OS rate 87.5% 83.3% (95% CI) 100% (38.7, 100% 100% 100% (27.3, 98.1) 97.5)

Median follow-up 24.5 26.2 (5.4, 22.8 38.4 25.1 24.6 (5.4,(min, max) months (6.0, 115.0) (12.9, (26.2, (6.0, 115.0) 45.4) 25.7) 50.7) 45.4)

All SOT recipients with EBV+ PTLD R/R to rituximab as monotherapy or combined with chemotherapy were treated with tabelecleucel, receiving a median (range) of 2.0 (1-9) cycles

Atara has previously shown benefit in patients with EBV+ PTLD after SOT who responded to tab-cel, including up to 100 percent two-year survival rates1,2. Data presented at EBMT 2021 demonstrated similar results in terms of overall survival in EBV+ PTLD patients who received tab-cel following hematopoietic cell transplantation (HCT).

Safety

Tab-cel was well-tolerated in this immunocompromised population with high disease burden and multiple comorbidities. Notably, there was no emerging safety concern and no instances of tumor flare reaction, infusion-related reactions, graft versus host disease (GvHD), cytokine release syndrome (CRS), neurotoxicity or organ rejection reported in these patients.

"We are excited to see the data presented at ATC 2021 reinforce the clinical benefit in patients who responded to tab-cel, including up to 100 percent two-year survival rates," said Pascal Touchon, President and Chief Executive Officer at Atara. "Atara understands the imperative to provide treatment options for these very sick, treatment-refractory and immunocompromised patients."

Atara Presentation at ATC 2021:

Title: Overall Survival by Best Overall Response with Tabelecleucel in Patients with Epstein-Barr Virus-Driven Post-Transplant Lymphoproliferative Disease after Solid Organ Transplant

Date & Time: Monday, June 7, 2021 at 10:30 a.m. ET

Oral Session & Number: Plenary Oral Abstract Session 3