Transplantation in CML in the TKI era: who, when, and how?

Management of chronic-phase CML in later lines: a Hong Kong consensus recommendation

Chronic myeloid leukemia (CML) usually requires long-term therapy with tyrosine kinase inhibitors (TKIs). While these agents have markedly advanced the clinical management and prognosis of CML, a subset of patients experience treatment resistance or suboptimal response, necessitating multiple lines of TKI therapy. Few treatment options exist for patients who are resistant or intolerant to first- and second-line therapies. To provide guidance for the management of patients in chronic-phase failing at least two lines of treatment, a literature review followed by consensus generation from an expert panel with a modified Delphi process was conducted. This was followed by a meeting in person and subsequent online iterations for the establishment of a list of consensus guidelines. Consensus was defined as ≥ 75% of respondents selecting either 'accept completely' or 'accept with some reservation'. Overall, 17 statements were formulated covering five topics - defining treatment failure and acceptable treatment response, in terms of efficacy and intolerance; sequencing therapy to prevent disease progression and improve quality of life; managing patients with broad resistance, specific mutations, and risk of cardiovascular events; considering timing of cytogenetic or molecular response; and mitigating risk when using novel therapies and allogeneic hematopoietic stem cell transplantation. These comprehensive, evidence-based recommendations will assist clinicians in managing their patients with CML in third and later lines of treatment.

Advanced-Stage Chronic Myeloid Leukemia: Options for Difficult Treatment Situations

A small number of patients with chronic myeloid leukemia (CML) either present with or progress to the accelerated phase (AP) or blast phase (BP). This occurs in approximately 4-7% of patients with CML. Most patients who progress to BP-CML are of myeloid lineage, while approximately 30% are of lymphoid lineage. Due to the rarity of this condition, there are no large or randomized trials that can inform clinical decisions. Most data are from retrospective chart reviews or data from old studies when tyrosine kinase inhibitors (TKIs) were initially approved. In addition, the definition of these categories has been in continuous flux over the last 20 years, making applicability of data even more confusing. In some classifications, the cutoff is 30% blasts for the definition of BP-CML, while in others a cutoff of 20% is used. In addition, more recently the World Health Organization (WHO) classification omitted the accelerated phase and recognized only a two-phase disease, while the International Consensus Classification retained a three-phase definition and retained the accelerated phase. Therapy for patients with AP/BP-CML depends on several factors, including prior therapy, BCR::ABL1 mutation, co-morbidities, cell lineage, and eligibility for allogeneic stem cell transplantation (alloHCT). Patients with AP-CML at presentation have a relatively favorable prognosis and may not need alloHCT if they respond appropriately to therapy. For patients with AP-CML who progressed while on TKI therapy or those with BP-CML, alloHCT is considered the only curative therapy. Our goal is to review the available data on the therapy of patients with AP-CML and BP-CML.

Understanding and overcoming resistance to tyrosine kinase inhibitors (TKIs) in Chronic myeloid leukemia (CML)

INTRODUCTION

Chronic myeloid leukemia (CML) represents one of the first neoplasms whose molecular pathogenesis was successfully unraveled, with tyrosine kinase inhibitors (TKIs) representing one of the first-targeted therapies. TKIs have revolutionized long-term outcomes of CML patients and their life expectancy. Nonetheless, a minority of patients will develop TKI resistance due to a complex and multifactorial process that ultimately leads to the emergence of an unresponsive cancer clone. Overcoming TKI resistance is considered one of the major challenges in CML management.

AREAS COVERED

In this review, the main findings extrapolated from published research, guidelines, and clinical trials regarding TKI resistance (published before October 2024) are discussed. Data have been obtained through broad research on Medline, Embase, Pubmed, and archives from EHA and ASH congresses.

EXPERT OPINION

Nowadays, asciminib and ponatinib have expanded the therapeutic arsenal for resistant-CML management and allogenic transplant still represents an important alternative in the context of multiple TKI failures. Off-label use of TKIs combination therapies, although theoretically appealing, lacks robust clinical evidence and regulatory approval. Looking ahead, the introduction of novel technologies such as digital PCR (dPCR) and next generation sequencing (NGS) holds great potential to revolutionize the management of TKI-resistant CML cases.

Critical review of clinical data and expert-based recommendations for the use of bosutinib in the treatment of chronic myeloid leukemia

Chronic myeloid leukemia (CML), characterized by the presence of the BCR::ABL1 fusion gene, has undergone a transformative shift with the introduction of tyrosine kinase inhibitors (TKIs). The current availability of six different TKIs (imatinib, dasatinib, nilotinib, bosutinib, ponatinib, and asciminib) in clinical practice makes it important to know their efficacy and toxicity profile for treatment optimization. This review examines the latest insights regarding the use of bosutinib in CML treatment. Clinical trials have demonstrated the effectiveness of bosutinib, positioning it as a first-line treatment that can induce sustained molecular responses. Importantly, it can also be effective in patients who have experienced treatment failure or intolerance with prior TKIs, revealing the potential of bosutinib also in second- and later-line settings. Even in the advanced phase of CML, bosutinib has demonstrated its capacity to achieve molecular responses, expanding its usefulness. Real-world evidence studies echo these findings, emphasizing bosutinib's effectiveness in achieving deep molecular responses, maintaining remissions, and serving as an alternative for patients intolerant or resistant to other TKIs as a second-line therapy. Notably, one of the greatest strengths of bosutinib is its favorable safety profile, in particular the low incidence of vascular complications with its use, which is undoubtedly a comparative advantage over other TKIs. In summary, the latest research highlights the versatility of bosutinib in CML treatment and underscores its pivotal role in optimizing patient management in challenging cases. Continuing research and investigation will further establish bosutinib's place in the evolving landscape of CML therapy, offering an alternative for CML patients across different treatment stages.

The Role of Molecular or Cytogenetic Response as a Favorable Prognostic Factor Before Hematopoietic Stem Cell Transplantation for Chronic Myeloid Leukemia

Tyrosine kinase inhibitors (TKIs) have revolutionized therapy for patients with chronic myeloid leukemia (CML) over the last two decades. However, some patients still do not achieve an adequate response to these drugs, and hematopoietic stem cell transplantation (HSCT) is indicated in this scenario. We present the results of a 20-year follow-up study of 70 patients who underwent transplantation after TKI failure. The primary objective of this study was to evaluate overall survival (OS) and the secondary objective was to evaluate the outcomes of relapse-free survival (RFS), GVHD-free, relapse-free survival (GFRS) and the incidences of relapse (RI), non-relapse mortality (NRM), acute and chronic GVHD. Median survival was 11 years, with a 1-year OS of 70% (57.8 to 79.3) and a 5-year OS of 57.7% (45.1 to 68.5). The estimated 5-year OS was not different for CP1 (60%) versus advanced stages (45%); P = .60. The degree of response immediately before transplantation was directly associated with worse outcomes [HR 5.89 (1.19-29.16); P = .03] for patients with only a hematological response compared with patients with a cytogenetic or molecular response. This study corroborates the potential of HSCT in the scenario of therapeutic failure and highlights the role of molecular or cytogenetic response as a potential target to be achieved before transplantation.

The Contemporary Role of Hematopoietic Stem Cell Transplantation in the Management of Chronic Myeloid Leukemia: Is It the Same in All Settings?

Hematopoietic stem cell transplantation (HSCT) for chronic myeloid leukemia (CML) patients has transitioned from the standard of care to a treatment option limited to those with unsatisfactory tyrosine kinase inhibitor (TKI) responses and advanced disease stages. In recent years, the threshold for undergoing HSCT has increased. Most CML patients now have life expectancies comparable to the general population, and therefore, the goal of therapy is shifting toward achieving treatment-free remission (TFR). While TKI discontinuation trials in CML show potential for achieving TFR, relapse risk is high, affirming allogeneic HSCT as the sole curative treatment. HSCT should be incorporated into treatment algorithms from the time of diagnosis and, in some patients, evaluated as soon as possible. In this review, we will look at some of the recent advances in HSCT, as well as its indication in the era of aiming for TFR in the presence of TKIs in CML.

Erythroid variant evolving from chronic myeloid leukemia resistant to multiple tyrosine kinase inhibitors: a rare case report

BACKGROUND

Chronic myeloid leukemia (CML) is characterized by the presence of BCR::ABL1 fusion gene resulting from a reciprocal translocation, t(9;22)(q34;q11.2), leading to prominent granulocytic proliferation. The majority of patients initially present in chronic phase (CP), which may progress to advanced CML with predominantly granulocytic phenotypes in the absence of proper treatment or response to tyrosine kinase inhibitors (TKIs). We present an exceptionally rare case in which an erythroid variant emerged from a CML patient resistant to multiple TKIs. This variant is characterized by the detection of t(9;22) BCR::ABL1 fusion in erythroid precursors at various maturation stages and the absence of granulocytic progenitor hyperplasia typically seen in classical CML.

CASE PRESENTATION

A 33-year-old female with CP-CML had received multiple TKI therapies since her initial diagnosis in 2015. Due to intolerable side effects and inconsistent adherence, she exhibited an inadequate response and developed new-onset pancytopenia. Bone marrow (BM) biopsy specimen revealed a hypercellular marrow with significant erythroid hyperplasia (90% of marrow cellularity) and a reversed myeloid-to-erythroid (M: E) ratio of 1:10. Both erythroid and myeloid cells displayed progressive maturation without dysplasia or excess blasts. Chromosomal analysis identified t(9;22) (q34;q11.2) in 19 out of 20 metaphase cells. BCR::ABL1 fusion transcript (p210 isoform) was confirmed by real-time quantitative polymerase chain reaction (RT-qPCR) and next-generation sequencing (NGS). Notably, no additional pathogenic cytogenetic abnormalities or ABL1 kinase domain mutations were detected. Here, we report the first published case of an erythroid variant emerging in a CML patient resistant to multiple TKIs-a distinct entity from the erythroid blast crisis evolving from CML.

CONCLUSION

The erythroid variant of CML is distinguished by the presence of t(9;22) (q34;q11.2) BCR::ABL1 in predominant erythroid precursors at different stages of maturation. In a myeloid neoplasm showing predominant erythroid hyperplasia without typical CML features, it is vital to correlate morphology and t(9;22) BCR::ABL1 cytogenetic testing for accurate diagnosis, and to prevent confusion with PEL transformation in CML.

A rare BCR-ABL1 transcript in chronic myeloid leukemia: Case report and literature review

BACKGROUND

The purpose of this report is to enhance our scientific understanding of the clinicopathologic features of chronic myeloid leukemia (CML) with the e12a3 transcript and to provide insights into potential treatment options for this rare subtype of CML.

CASE SUMMARY

We present the case of a 21-year-old Chinese male patient who was diagnosed with chronic myeloid leukemia (CML) with the e12a3 transcript. Biopsy of his left iliac soft tissue mass indicated that he was in the blast crisis phase of CML. The patient was treated with tyrosine kinase inhibitor (TKI) drugs and achieved remission, but relapsed soon after. Despite receiving prognostic chemotherapy, the disease progressed and eventually led to the patient's death.

CONCLUSION

To avoid missed diagnosis and misdiagnosis, it is recommended to conduct a thorough clinical evaluation and actively identify the underlying etiology.

Progress of research on PD-1/PD-L1 in leukemia

Leukemia cells prevent immune system from clearing tumor cells by inducing the immunosuppression of the bone marrow (BM) microenvironment. In recent years, further understanding of the BM microenvironment and immune landscape of leukemia has resulted in the introduction of several immunotherapies, including checkpoint inhibitors, T-cell engager, antibody drug conjugates, and cellular therapies in clinical trials. Among them, the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) axis is a significant checkpoint for controlling immune responses, the PD-1 receptor on tumor-infiltrating T cells is bound by PD-L1 on leukemia cells. Consequently, the activation of tumor reactive T cells is inhibited and their apoptosis is promoted, preventing the rejection of the tumor by immune system and thus resulting in the occurrence of immune tolerance. The PD-1/PD-L1 axis serves as a significant mechanism by which tumor cells evade immune surveillance, and PD-1/PD-L1 checkpoint inhibitors have been approved for the treatment of lymphomas and varieties of solid tumors. However, the development of drugs targeting PD-1/PD-L1 in leukemia remains in the clinical-trial stage. In this review, we tally up the basic research and clinical trials on PD-1/PD-L1 inhibitors in leukemia, as well as discuss the relevant toxicity and impacts of PD-1/PD-L1 on other immunotherapies such as hematopoietic stem cell transplantation, bi-specific T-cell engager, chimeric antigen receptor T-cell immunotherapy.

The interplay between telomeric complex members and BCR::ABL1 oncogenic tyrosine kinase in the maintenance of telomere length in chronic myeloid leukemia

PURPOSE

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by recurrent genetic aberration in leukemic stem cells, namely Philadelphia chromosome caused by reciprocal translocation t(9;22)(q34;q11). In our study, we analyzed the telomeric complex expression and function in the molecular pathogenesis of CML.

METHODS

We employed CD34+ primary leukemic cells, comprising both leukemic stem and progenitor cell populations, isolated from peripheral blood or bone marrow of CML patients in chronic and blastic phase to analyze the telomere length and telomeric-associated proteins.

RESULTS

The reduction in telomere length during disease progression was correlated with increased expression of BCR::ABL1 transcript and the dynamic changes were neither associated with the enzymatic activity of telomerase nor with gene copy number and expression of telomerase subunits. Increased expression of BCR::ABL1 was positively correlated with expression of TRF2, RAP1, TPP1, DKC1, TNKS1, and TNKS2 genes.

CONCLUSIONS

The dynamics of telomere length changes in CD34+ CML cells is dependent on the expression level of BCR::ABL, which promotes the expression of certain shelterins including RAP1 and TRF2, as well as TNKS, and TNKS2, and results in telomere shortening regardless of telomerase activity. Our results may allow better understanding of the mechanisms responsible for the genomic instability of leukemic cells and CML progression.