Illuminating novel biological aspects and potential new therapeutic approaches for chronic myeloproliferative malignancies.

This review reflects the presentations and discussion at the 14th post-American Society of Hematology (ASH) International Workshop on Chronic Myeloproliferative Malignancies, which took place on the December 10 and 11, 2019, immediately after the 61st ASH Annual Meeting in Orlando, Florida. Rather than present a resume of the proceedings, we address some of the topical translational science research and clinically relevant topics in detail. We consider how recent studies using single-cell genomics and other molecular methods reveal novel aspects of hematopoiesis which in turn raise the possibility of new therapeutic approaches for patients with myeloproliferative neoplasms (MPNs). We discuss how alternative therapies could benefit patients with chronic myeloid leukemia who develop BCR-ABL1 mutant subclones following ABL1-tyrosine kinase inhibitor therapy. In MPNs, we focus on efforts beyond JAK-STAT and the merits of integrating activin receptor ligand traps, interferon-α, and allografting in the current treatment algorithm for patients with myelofibrosis.

Tyrosine Kinase Inhibitor Treatment for Newly Diagnosed Chronic Myeloid Leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder that accounts for approximately 10% of new cases of leukemia. The introduction of tyrosine kinase inhibitors has led to a reduction in mortalities. Thus, the estimated prevalence of CML is increasing. The National Comprehensive Cancer Network and the European Leukemia Net guidelines incorporate frequent molecular monitoring of the fusion BCR-ABL transcript to ensure that patients reach and keep treatment milestones. Most patients with CML are diagnosed in the chronic phase, and approximately 10% to 30% of these patients will at some time in their course meet definition criteria of resistance to imatinib.

Molecular monitoring of chronic myeloid leukemia: present and future.

INTRODUCTION: Fusion of BCR-ABL1 genes causes chronic myeloid leukemia (CML). As a reliable marker of disease burden, it also serves as the target of tyrosine kinase inhibitors (TKIs). New more sensitive molecular diagnostic tools for BCR-ABL1 can contribute to therapeutic decision-making, especially in considering drug discontinuation for patients enjoying prolonged deep molecular response. Areas covered: Several novel platforms are transforming CML molecular diagnostics to enable faster point-of-care devices, better understanding of clonal diversity and resistance mutations. Here, we review these molecular platforms, knowing implementation in other hematological malignancies will ensue. Expert commentary: Treatment with TKI in CML is the first example of a highly effective targeted therapy. Monitoring of BCR-ABL1 mRNA is standard in assessing disease burden being highly predictive of outcomes recommended by both European LeukemiaNet (ELN) and National Comprehensive Cancer Network (NCCN); however, studies has demonstrated poor adherence to these recommendations. In both clinical practice and assay performance, further optimizing of BCR-ABL1 monitoring can be envisioned including point-of-care methods for increased availability of rapid, standardized testing and increasingly sensitive molecular assays that allow for quantification of MRD and detecting resistance mutations.

Long-term response to imatinib is not affected by the initial dose in patients with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase: final update from the Tyrosine Kinase Inhibitor Optimization and Selectivity (TOPS) study.

The TOPS trial evaluated high- (800 mg/day; n = 319) versus standard-dose (400 mg/day; n = 157) imatinib in patients newly diagnosed with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase. Patients had a minimum follow-up of 42 months or discontinued early. Major molecular response (MMR) rates were similar between arms at (51.6 vs 50.2 % for 400 and 800 mg/day, respectively; P = 0.77) and by (75.8 vs 79.0 %; P = 0.4807) 42 months. There were no differences in event-free survival (EFS), progression-free survival(PFS), or overall survival (OS) between arms. The estimated rates of PFS on treatment and OS at 42 months were significantly higher in patients with MMR at 6, 12, and 18 months compared with those without MMR.Adverse events were more frequent with high-dose imatinib. Patients with B1 treatment interruption (vs [1) and those able to maintain imatinib C600 mg/day (vs\600 mg/day) in the first year of treatment had faster and higher response rates, but no improvement in EFS or PFS. Adherence to prescribed dose without interruption may be more important than initiation of therapy with higher doses of imatinib. Achievement of MMR correlated with longterm clinical outcomes.

Integrating current treatment options for TKI-resistant chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder that accounts for approximately 10% of new cases of leukemia. The introduction of tyrosine kinase inhibitors (TKIs) has led to a reduction in mortality rates, and the estimated prevalence of CML is increasing accordingly. Most patients with CML are diagnosed in the chronic phase, and approximately 15% to 30% of these patients will meet some definition of resistance to imatinib. In the more advanced phases of disease, the rates of imatinib resistance are much higher. Both the National Comprehensive Cancer Network (NCCN) and the European LeukemiaNet (ELN) guidelines emphasize adequate monitoring of patients to ensure that they are meeting treatment milestones. Loss of response is most commonly associated with the acquisition of resistance-conferring kinase domain point mutations within BCR-ABL1. The multiple treatment options available for patients with imatinib-resistant CML include dasatinib, nilotinib, bosutinib, and ponatinib, as well as the non-TKI salvage agent omacetaxine mepesuccinate. Treatment selection is based on factors such as the patient's disease state, prior therapies, comorbidities, treatment toxicity, and goals of therapy. This clinical roundtable monograph provides expert discussion on the monitoring of TKI-resistant CML, when to change therapy, and how to select the best treatment option.

Initial molecular response at 3 months may predict both response and event-free survival at 24 months in imatinib-resistant or -intolerant patients with Philadelphia chromosome-positive chronic myeloid leukemia in chronic phase treated with nilotinib.

PURPOSE: The association between initial molecular response and longer-term outcomes with nilotinib was examined. PATIENTS AND METHODS: Patients with imatinib-resistant or -intolerant chronic myeloid leukemia in chronic phase from the phase II nilotinib registration study with available postbaseline BCR-ABL1 transcript assessments were included (N = 237). RESULTS: BCR-ABL1 transcript levels (International Scale [IS]) at 3 months correlated with complete cytogenetic response (CCyR) by 24 months. Patients with BCR-ABL1 (IS) of > 1% to ≤ 10% at 3 months with nilotinib had higher cumulative incidence of CCyR by 24 months than patients with BCR-ABL1 (IS) of > 10% (53% v 16%). BCR-ABL1 (IS) at 3 months predicted major molecular response (MMR) by 24 months. Cumulative incidence of MMR by 24 months for patients with BCR-ABL1 (IS) of > 0.1% to ≤ 1%, > 1% to ≤ 10%, and > 10% was 65%, 27%, and 9%, respectively. These differences were observed for patients with or without baseline BCR-ABL1 mutations and for those with imatinib resistance or intolerance. Estimated event-free survival (EFS) rates at 24 months decreased with higher transcript levels at 3 months; patients with BCR-ABL1 (IS) of ≤ 1% had an estimated 24-month EFS rate of 82%, compared with 70% for patients with BCR-ABL1 (IS) of > 1% to ≤ 10% and 48% for patients with BCR-ABL1 (IS) of > 10%. CONCLUSION: Patients with BCR-ABL1 (IS) of > 10% at 3 months had a lower cumulative incidence of CCyR and MMR and lower rates of EFS versus patients with BCR-ABL1 (IS) of ≤ 10%. Prospective studies may determine whether close monitoring or alternative therapies are warranted for patients with minimal initial molecular response.

Phase III, randomized, open-label study of daily imatinib mesylate 400 mg versus 800 mg in patients with newly diagnosed, previously untreated chronic myeloid leukemia in chronic phase using molecular end points: tyrosine kinase inhibitor optimization and selectivity study.

PURPOSE: To evaluate the safety and efficacy of initial treatment with imatinib mesylate 800 mg/d (400 mg twice daily) versus 400 mg/d in patients with newly diagnosed chronic myeloid leukemia in chronic phase. PATIENTS AND METHODS: A total of 476 patients were randomly assigned 2:1 to imatinib 800 mg (n = 319) or 400 mg (n = 157) daily. The primary end point was the major molecular response (MMR) rate at 12 months. RESULTS: At 12 months, differences in MMR and complete cytogenetic response (CCyR) rates were not statistically significant (MMR, 46% v 40%; P = .2035; CCyR, 70% v 66%; P = .3470). However, MMR occurred faster among patients randomly assigned to imatinib 800 mg/d, who had higher rates of MMR at 3 and 6 months compared with those in the imatinib 400-mg/d arm (P = .0035 by log-rank test). CCyR also occurred faster in the 800-mg/d arm (CCyR at 6 months, 57% v 45%; P = .0146). The most common adverse events were edema, gastrointestinal problems, and rash, and all were more common in patients in the 800-mg/d arm. Grades 3 to 4 hematologic toxicity also occurred more frequently in patients receiving imatinib 800 mg/d. CONCLUSION: MMR rates at 1 year were similar with imatinib 800 mg/d and 400 mg/d, but MMR and CCyR occurred earlier in patients treated with 800 mg/d. Continued follow-up is needed to determine the clinical significance of earlier responses on high-dose imatinib.

NCCN task force report: molecular markers in leukemias and lymphomas.

The introduction of targeted therapies has revolutionized treatment and improved outcomes in patients with leukemias and lymphomas. However, many patients experience relapse caused by the persistence of residual malignant cells. Cytogenetic and molecular techniques are increasingly being used to assess and quantify minimal residual disease (MRD). The emergence of advanced technologies has led to the discovery of multiple novel molecular markers that can be used to detect MRD and predict outcome in patients with leukemias and lymphomas. Gene expression signatures that predict clinical outcomes in patients with non-Hodgkin's lymphoma have been identified. In chronic myelogenous leukemia, molecular monitoring has become more important in assessing response and detecting resistance to therapy. In acute leukemias, several new markers have shown potential in prognostication and monitoring treatment. In leukemias and lymphomas, microRNAs have been identified that may be useful in diagnostics and prognostication. To address these issues, the National Comprehensive Cancer Network (NCCN) organized a task force consisting of a panel of experts in leukemia and lymphoma to discuss recent advances in the field of molecular markers and monitoring MRD.