Evolution of T-Cell Fitness through AML Progression: Enhanced Bispecific T-Cell Engager-mediated Function of Bone Marrow T Cells at Remission Compared to Initial Diagnosis and Relapse [transcriptome analysis]

To date, bispecific antibodies designed to engage T cells have failed to show sustained responses in relapsed/refractory acute myeloid leukemia (R/R AML). Bispecific antibodies, including bispecific T-cell-engager (BiTE) molecules, predominantly recruit T cells from the local immune microenvironment. Because they are mainly applied in the R/R setting, understanding the fitness of T cells from bone marrow in AML progression, is fundamental for advancing this platform. Here, by flow cytometry analysis of bone marrow-derived T cells, we identified distinct differentiation stages and expression of inhibitory receptors at initial diagnosis (ID) and relapse (RL). Longitudinal transcriptional analyses of paired ID and RL T cells showed a senescent phenotype at ID, whereas an exhausted and memory phenotype was dominant at RL. In line with these observations, T cells at RL exhibited higher BiTE-mediated cytotoxicity than ID T cells. Finally, we provide evidence that T cells, both from ID and RL, exhibit limited functional capacity following continuous BiTE exposure compared to T cells from complete remission. Our study provides insights into the different stages of T-cell phenotype and function during AML evolution. Correlative biomarker studies in patients treated with T-cell-based immunotherapies are needed, to better understand resistance mechanisms and to advance the platform. BMMCs from AML patients at time of initial diagnosis (ID) and relapse (RL) were retrospectively collected. Bone marrow CD3+ T cells from matched ID and RL samples as well as healthy donors (HD) were sorted and subjected to transcriptome analysis.