Persistence of pre-leukemic clones during first remission and risk of relapse in acute myeloid leukemia

Some patients with acute myeloid leukemia (AML) who are in complete remission after induction chemotherapy harbor persisting pre-leukemic clones, carrying a subset of leukemia-associated somatic mutations. There is conflicting evidence on the prognostic relevance of these clones for AML relapse. Here, we characterized paired pre-treatment and remission samples from 126 AML patients for mutations in 68 leukemia-associated genes. Fifty patients (40%) retained ⩾1 mutation during remission at a variant allele frequency of ⩾2%. Mutation persistence was most frequent in DNMT3A (65% of patients with mutations at diagnosis), SRSF2 (64%), TET2 (55%), and ASXL1 (46%), and significantly associated with older age (P<0.0001) and, in multivariate analyses adjusting for age, genetic risk, and allogeneic transplantation, with inferior relapse-free survival (hazard ratio, 2.34; P=0039) and overall survival (hazard ratio, 2.14; P=036). Patients with persisting mutations had a higher cumulative incidence of relapse before, but not after allogeneic stem cell transplantation. Our work underlines the relevance of mutation persistence during first remission as a novel risk factor in AML. Persistence of pre-leukemic clones may contribute to the inferior outcome of elderly AML patients. Allogeneic transplantation abrogated the increased relapse risk associated with persisting pre-leukemic clones, suggesting that mutation persistence may guide postremission treatment.Leukemia accepted article preview online, 18 December 2017. doi:10.1038/leu.2017.350.

Blockade of the PD-1/PD-L1 axis augments lysis of AML cells by the CD33/CD3 BiTE antibody construct AMG 330: reversing a T-cell-induced immune escape mechanism

Bispecific T-cell engagers (BiTEs) are very effective in recruiting and activating T cells. We tested the cytotoxicity of the CD33/CD3 BiTE antibody construct AMG 330 on primary acute myeloid leukemia (AML) cells ex vivo and characterized parameters contributing to antileukemic cytolytic activity. The E:T ratio and the CD33 expression level significantly influenced lysis kinetics in long-term cultures of primary AML cells (n=38). AMG 330 induced T-cell-mediated proinflammatory conditions, favoring the upregulation of immune checkpoints on target and effector cells. Although not constitutively expressed at the time of primary diagnosis (n=123), PD-L1 was strongly upregulated on primary AML cells upon AMG 330 addition to ex vivo cultures (n=27, P<0.0001). This phenomenon was cytokine-driven as the sole addition of interferon (IFN)-γ and tumor necrosis factor-α also induced expression. Through blockade of the PD-1/PD-L1 interaction, AMG 330-mediated lysis (n=9, P=0.03), T-cell proliferation (n=9, P=0.01) and IFN-γ secretion (n=8, P=0.008) were significantly enhanced. The combinatorial approach was most beneficial in settings of protracted AML cell lysis. Taken together, we have characterized a critical resistance mechanism employed by primary AML cells under AMG 330-mediated proinflammatory conditions. Our results support the evaluation of checkpoint molecules in upcoming clinical trials with AMG 330 to enhance BiTE antibody construct-mediated cytotoxicity.