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2019 ASCO Annual Meeting!

Session: Developmental Immunotherapy and Tumor Immunobiology

Type: Poster Session

Time: Saturday June 1, 8:00 AM to 11:00 AM

Location: Hall A

Correlation of circulating EBV-targeted cytotoxic T lymphocyte precursors (EBV-CTLp) and clinical response following tabelecleucel (tab-cel) infusion in patients with EBV-driven disease.

Cellular Immmunotherapy

Developmental Immunotherapy and Tumor Immunobiology

2019 ASCO Annual Meeting

Abstract No:

Poster Board Number:
Poster Session (Board #176)

J Clin Oncol 37, 2019 (suppl; abstr 2532)

Author(s): Blake T. Aftab, Daniel Munson, Kevin Rasor, Philippe Foubert, Donald Edward Tsai, Wen-Kai Weng, Armin Ghobadi, Koen Van Besien, Yan Sun, Minoti Hiremath, Willis H. Navarro, Susan Prockop; Atara Biotherapeutics, Thousand Oaks, CA; Abramson Cancer Center, Philadelphia, PA; Stanford University Medical Center, Stanford, CA; Washington University in St. Louis, St. Louis, MO; Weill Cornell Medcl Coll, New York, NY; Atara Biotherapeutics, Inc., Thousand Oaks, CA; Atara Biotherapeutics, South San Francisco, CA; Memorial Sloan Kettering Cancer Center, New York, NY

Abstract Disclosures


Background: EBV is implicated in a variety of diseases. Tab-cel is an investigational off-the-shelf, allogeneic T-cell immunotherapy utilizing endogenous T cell receptors targeting EBV antigens. We hypothesized the clinical activity of tab-cel is mediated by expansion and persistence of EBV-specific T cells. Therefore, we quantified circulating EBV- CTLp after tab-cel administration and examined the correlation between expansion and clinical response. Methods: Samples from 10 patients with EBV+ post-transplant lymphoproliferative disease (PTLD) and other EBV-associated diseases enrolled in an multicenter expanded access protocol (EAP) study (NCT02822495) were analyzed. To evaluate CTLp frequencies, limited dilution analysis was performed on samples taken at baseline and day 34 post first tab-cel dose (end cycle 1). The day 34 persistence of circulating EBV-CTLp from best overall response to initial tab-cel product was tested using the two-tailed Mann-Whitney test. Changes in inflammatory cytokines were also measured. Results: Responders represented in this sampling (n=6; 2 PR and 4 CR) showed a median 5.8-fold increase in circulating CTLp between baseline and day 34 (range: 0.8 to 133-fold). Five of 6 responders showed an increase in EBV-CTLp at day 34 of ≥ 3.8-fold while 1 pt showed no change in CTLp (0.8-fold change). In contrast, the 4 non-responders (3 SD; 1 PD) showed a median 0.3-fold decrease in EBV-CTLp from baseline (range: 1.2 to 0.02-fold; ns). Cumulative analyses revealed a statistically significant correlation between the fold-change of circulating CTLp at day 34 and clinical response (p=0.038) which did not appear to correlate with the type of the EBV-associated disease. Inflammatory cytokines showed no meaningful change from baseline. The safety profile remains consistent with previously reported data. Conclusions: These data support the correlation of clinical activity of tab-cel with the expansion and persistence of EBV-specific T-cells at day 34 post-treatment, as well as the use of circulating CTLp as a biomarker for response in clinical studies. Clinical trial information: NCT02822495

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