Pretransplantation use of the second-generation tyrosine kinase inhibitors has no negative impact on the HCT outcome

Therapeutic options for chronic myeloid leukemia following the failure of second-generation tyrosine kinase inhibitor therapy

The management of chronic myeloid leukemia in the chronic phase (CML-CP) has witnessed significant advancements since the identification of a common chromosomal translocation anomaly involving chromosomes 9 and 22, which results in the formation of the Philadelphia chromosome driven by the BCR-ABL1 fusion protein. This discovery paved the way for the development of tyrosine kinase inhibitors (TKIs) that target the adenosine triphosphate (ATP) binding site of ABL1 through the BCR-ABL-1 fusion protein. Following the approval of Imatinib by the Food and Drug Administration (FDA) as the first TKI for CML treatment in 2001, the median overall survival (OS) for chronic phase CML (CML-CP) has significantly improved, approaching that of the general population. However, achieving this milestone crucially depends on reaching certain treatment response milestones. Since the introduction of imatinib, five additional TKIs have been approved for CML-CP treatment. Despite the availability of these treatments, many patients may experience treatment failure and require multiple lines of therapy due to factors such as the emergence of resistance, such as mutations in the ATP binding site of ABL, or intolerance to therapy. This review will primarily focus on exploring treatment options for patients who fail second-generation TKI therapy due to true resistance.

The Impact of Pretransplant Use of Tyrosine Kinase Inhibitors on Allogeneic Stem Cell Transplantation in Patients with Chronic Myeloid Leukemia - A Single-institution Retrospective Study

Objective Chronic myeloid leukemia (CML) is a malignant hematological disorder, and allogeneic stem cell transplantation (allo-SCT) was its only curative treatment until the introduction of tyrosine kinase inhibitors (TKIs). Allo-SCT is still considered for CML patients who are resistant to TKIs and in an advanced phase. Currently, second- and third-generation (2/3G TKIs are typically incorporated into the first-line treatment of CML. However, the impact of 2/3G TKIs on subsequent allo-SCT remains unclear. We therefore evaluated the effect of 2/3G TKIs on allo-SCT. Methods We retrospectively evaluated the effect of pretransplant therapy with TKIs on the outcome of allo-SCT for CML using clinical data at our institution. Patients Thirty-two CML patients who received their first allo-SCT procedure at our institute from 2001 to 2020 were included. We divided the patients into three subgroups based on TKI treatment before allo-SCT. Patients receiving no TKIs, only imatinib (IM), and 2/3G TKIs were classified into the Non-TKI, IM, and 2/3G TKI groups, respectively. Results In a univariate analysis, the pretransplant use of 2/3G TKIs was significantly associated with a higher 5-year overall survival (91.7%) and relapse-free survival (75.0%) than the use of IM (37.5% and 12.5%) in patients presenting with or progressing to the advanced phase. In addition, pretransplant use of 2/3G TKIs did not increase the incidence of graft-versus-host disease (GVHD). Conclusion We demonstrated that the pretransplant use of 2/3G TKIs was safe and improved the outcome of CML patients who presented with or progressed to the advanced phase without increasing the frequency of GVHD.

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.

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

Molecular therapy with tyrosine kinase inhibitors (TKIs) has significantly reduced the indication for allogeneic hematopoietic stem cell transplantation (allo-HSCT) in chronic myeloid leukemia (CML). Treatment-free remission can be obtained in about 50% of patients with an optimal response. However, cure rates up to 90% are restricted to patients receiving HSCT. Timing is essential since HSCT in the early stages of the disease has the best outcome. Patients in a more advanced phase (AdP) than chronic-phase (chP) CML undergo HSCT with suboptimal outcomes, and the gap between chP and AdP disease is widening. First-line therapy should start with first- or second-generation (G) TKIs. Patients failing treatment (BCR-ABL1 transcripts of greater than 10% at 3 and 6 months and greater than 1% at 12 months) should be switched to second-line TKIs, and HSCT should be considered. Patients not responding to 2G-TKI therapy as well as patients in an accelerated phase (AP) or blast crisis (BC) are candidates for HSCT. Therapy resistant BCR-ABL1 mutations, high-risk additional cytogenetic abnormalities, and molecular signs of leukemia progression should trigger the indication for HSCT. Patients who, despite dose adjustments, do not tolerate or develop severe adverse events, including vascular events, to multiple TKIs are also candidates for HSCT. In AdP CML, TKIs do not show long-lasting results, and the outcome of HSCT is less optimal without pretransplant therapy. In these patients the induction of chP2 with TKIs, either alone (AP) or in combination with intensive chemotherapy (BC), followed by HSCT should be pursued.

Outcomes and toxicity of allogeneic hematopoietic cell transplantation in chronic myeloid leukemia patients previously treated with second-generation tyrosine kinase inhibitors: a prospective non-interventional study from the Chronic Malignancy Working Party of the EBMT

Allogeneic hematopoietic cell transplantation (allo-HCT) remains a treatment option for patients with chronic myeloid leukemia (CML) who fail to respond to tyrosine kinase inhibitors (TKIs). While imatinib seems to have no adverse impact on outcomes after transplant, little is known on the effects of prior use of second-generation TKI (2GTKI). We present the results of a prospective non-interventional study performed by the EBMT on 383 consecutive CML patients previously treated with dasatinib or nilotinib undergoing allo-HCT from 2009 to 2013. The median age was 45 years (18-68). Disease status at transplant was CP1 in 139 patients (38%), AP or >CP1 in 163 (45%), and BC in 59 (16%). The choice of 2GTKI was: 40% dasatinib, 17% nilotinib, and 43% a sequential treatment of dasatinib and nilotinib with or without bosutinib/ponatinib. With a median follow-up of 37 months (1-77), 8% of patients developed either primary or secondary graft failure, 34% acute and 60% chronic GvHD. There were no differences in post-transplant complications between the three different 2GTKI subgroups. Non-relapse mortality was 18% and 24% at 12 months and at 5 years, respectively. Relapse incidence was 36%, overall survival 56% and relapse-free survival 40% at 5 years. No differences in post-transplant outcomes were found between the three different 2GTKI subgroups. This prospective study demonstrates the feasibility of allo-HCT in patients previously treated with 2GTKI with a post-transplant complications rate comparable to that of TKI-naive or imatinib-treated patients.

Tyrosine Kinase Inhibitors and Beyond for Chronic Myeloid Leukemia in Children

Chronic myeloid leukemia (CML) is rare in children but presents a unique challenge as recent drug innovations have turned CML into a chronic disease with implications for treatment into adulthood. With the approval of newer-generation tyrosine kinase inhibitors (TKIs) in addition to imatinib, providers have more options for the treatment of chronic-phase CML (CML-CP) in children. The second-generation TKIs approved for use in children, nilotinib and dasatinib, have higher response rates than first-generation imatinib; however, overall survival rates appear to be the same. Even more options may soon become available with ongoing investigations into the use of bosutinib and ponatinib and other new agents in children. Possible long-term side effects of TKIs, including growth failure, should be carefully acknowledged by the treating provider. Although these known associations may not preclude treatment, providers should be aware of them to guide their management of pediatric patients with CML being treated long term with TKI therapy. Treatment-free remission is a desired goal for pediatric patients and providers alike, but current recommendations are for attempts at achieving this to be restricted to clinical study settings.

Complexity of chronic-phase CML management after failing a second-generation TKI

The treatment landscape of chronic myeloid leukemia (CML) was radically changed with the introduction of imatinib in 2001. With the emergence of treatment failure with imatinib, more specific and potent second- and third-generation tyrosine kinase inhibitors (TKIs) were developed. Currently, 6 TKIs and one protein synthesis inhibitor are available on the market for CML treatment. Despite the availability of these agents, it is not uncommon for some patients to experience treatment failure across several lines of therapy. Sequencing the available treatment options is a challenging task that becomes more complex after patients fail the more potent second- and third-generation TKIs. The ability to successfully salvage such patients is limited. In this paper, we will briefly review the mechanisms of treatment failure in chronic-phase CML (CP-CML) and focus on the complexity of managing patients who fail a second-generation TKI.

How I treat chronic myeloid leukemia in children and adolescents

Evidence-based recommendations have been established for treatment of chronic myeloid leukemia (CML) in adults treated with tyrosine kinase inhibitors (TKIs), but the rarity of this leukemia in children and adolescents makes it challenging to develop similar recommendations in pediatrics. In addition to imatinib, which was approved for pediatric CML in 2003, the second-generation TKIs dasatinib and nilotinib were recently approved for use in children, expanding the therapeutic options and pushing allogeneic stem cell transplantation to a third-line treatment of most pediatric cases. Yet, without sufficient data on efficacy and safety specific to pediatric patients, the selection of a TKI continues to rely on clinical experience in adults. Here, we present 4 case scenarios highlighting common yet challenging issues encountered in the treatment of pediatric CML (suboptimal response, poor treatment adherence, growth retardation, and presentation in advanced phases). Limited experience with very young children, the transition of teenagers to adult medicine, and the goal of achieving treatment-free remission for this rare leukemia are additional significant obstacles that require further clinical investigation through international collaboration.

Clinical impact of pretransplant use of multiple tyrosine kinase inhibitors on the outcome of allogeneic hematopoietic stem cell transplantation for chronic myelogenous leukemia

Tyrosine kinase inhibitors (TKIs) are widely used to treat patients with chronic myelogenous leukemia in the chronic phase (CML-CP), and outcomes of TKI treatment for patients with CML-CP have been excellent. Since multiple TKIs are currently available, second-line or third-line TKI therapy is considered for patients who are intolerant of or resistant to the previous TKI treatment. Therefore, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered only for patients with disease progression or for patients after treatment failure with multiple TKIs. To reflect the current clinical situation of patients with CML-CP, we tried to clarify whether prior TKI treatment affects the outcome of allo-HSCT. Data from 237 patients for whom the number of pretransplant TKIs varied from one to three were used for analysis. Before allo-HSCT, 153 patients were treated with one TKI, 49 patients were treated with two TKIs and 35 patients were treated with three TKIs. In addition to conventional risk factors, i.e., disease status at transplantation and patient's age, the use of three TKIs before transplantation was identified as a significant adverse factor for prognosis. Nonrelapse mortality rate was higher in patients treated with three TKIs than in patients treated with one or two TKIs. Our results suggest that allo-HSCT could be considered for young patients with CML-CP who manifest resistance to second-line TKI therapy and who have an appropriate donor.