It was recently recognized that some chronic myeloid leukemia patients with a complete molecular response could sustain that response after discontinuation of imatinib. To characterize the clinical outcomes and profiles of chronic phase chronic myeloid leukemia patients who could discontinue imatinib, we conducted a nationwide survey in Japan. Among 3,242 imatinib-treated chronic myeloid leukemia patients, we identified 50 who had discontinued imatinib for at least six months; of these we analyzed 43. Molecular recurrence was detected in 19 patients, and a complete molecular response rate was estimated to be 47% following imatinib discontinuation. Based on multivariate regression analysis, imatinib dose intensity and prior interferon-α administration were independently predictive of molecular recurrence within 12 months. The depth of the molecular response should be a factor influencing long-term sustained complete molecular response after discontinuation of imatinib. Additionally, an immunological mechanism modified by interferon-α might control chronic myeloid leukemia stem cells.

Blast crisis (BC) predicts dismal outcomes in patients with chronic myeloid leukaemia (CML). Although additional genetic alterations play a central role in BC, the landscape and prognostic impact of these alterations remain elusive. Here, we comprehensively investigate genetic abnormalities in 136 BC and 148 chronic phase (CP) samples obtained from 216 CML patients using exome and targeted sequencing. One or more genetic abnormalities are found in 126 (92.6%) out of the 136 BC patients, including the RUNX1-ETS2 fusion and NBEAL2 mutations. The number of genetic alterations increase during the transition from CP to BC, which is markedly suppressed by tyrosine kinase inhibitors (TKIs). The lineage of the BC and prior use of TKIs correlate with distinct molecular profiles. Notably, genetic alterations, rather than clinical variables, contribute to a better prediction of BC prognosis. In conclusion, genetic abnormalities can help predict clinical outcomes and can guide clinical decisions in CML.

This report addresses whether small molecules can deplete FoxP3-expressing regulatory T (T reg) cells, thereby augmenting antitumor immunity. Imatinib, a tyrosine kinase inhibitor of oncogenic BCR-ABL protein expressed by chronic myelogenous leukemia (CML) cells, possesses off-targets including LCK expressed in T cells. We showed that imatinib-treated CML patients in complete molecular remission (CMR) exhibited selective depletion of effector T reg (eT reg) cells and significant increase in effector/memory CD8⁺ T cells while non-CMR patients did not. Imatinib at CML-therapeutic concentrations indeed induced apoptosis specifically in eT reg cells and expanded tumor antigen–specific CD8⁺ T cells in vitro in healthy individuals and melanoma patients, and suppressed colon tumor growth in vivo in mice. Mechanistically, because of FoxP3-dependent much lower expression of LCK and ZAP-70 in T reg cells compared with other T cells, imatinib inhibition of LCK further reduced their TCR signal intensity, rendering them selectively susceptible to signal-deprived apoptotis. Taken together, eT reg cell depletion by imatinib is instrumental in evoking effective immune responses to various cancers.

The purpose of this trial was to evaluate the efficacy of two-year consolidation therapy with nilotinib, at a dose of 300 mg twice daily, for achieving treatment-free remission in chronic myeloid leukemia patients with a deep molecular response (BCR-ABL1IS ≤ 0.0032%). Successful treatment-free remission was defined as no confirmed loss of deep molecular response. We recruited 96 Japanese patients, of whom 78 sustained a deep molecular response during the consolidation phase and were therefore eligible to discontinue nilotinib in the treatment-free remission phase; of these, 53 patients (67.9%; 95% confidence interval, 56.4-78.1%) remained free from molecular recurrence in the first 12 months. The estimated 3-year treatment-free survival was 62.8%. Nilotinib was readministered in all patients (n=29) who experienced a molecular recurrence during the treatment-free remission phase. After restarting treatment, rapid deep molecular response returned in 25 patients (86.2%), with 50% of patients achieving a deep molecular response within 3.5 months. Tyrosine kinase inhibitor withdrawal syndrome was reported in 11/78 patients during the early treatment-free remission phase. The treatment-free survival curve was significantly better in patients with undetectable molecular residual disease than in patients without (3-year treatment-free survival, 75.6 vs. 48.6%, respectively; P=0.0126 by log-rank test). There were no significant differences in treatment-free survival between subgroups based on tyrosine kinase inhibitor treatment before the nilotinib consolidation phase, tyrosine kinase inhibitor-withdrawal syndrome, or absolute number of natural killer cells. The results of this study indicate that stopping tyrosine kinase inhibitor therapy after two-year consolidation with sustained deep molecular response by nilotinib is safe and feasible. This study was registered with UMIN-CTR (UMIN000005904).