Bosutinib for the treatment of chronic myeloid leukemia in chronic phase

The clinical outcome for patients with chronic myeloid leukemia in chronic phase (CML-CP) is currently very favorable due to the availability of tyrosine kinase inhibitors (TKIs) that are well tolerated and effectively suppress the constitutively activated BCR-ABL1 kinase that underlies the pathogenesis of this malignancy. Three TKIs -imatinib, nilotinib and dasatinib- have been approved as frontline therapy in CML-CP. Another TKI, bosutinib, inhibits with high potency numerous tyrosine kinases, including BCR-ABL1, Src family of kinases and MAPK, among others. Like nilotinib and dasatinib, bosutinib is a second-generation TKI that inhibits the majority of mutations associated with imatinib resistance, with the exception of T315I. In patients with CML-CP with prior intolerance or resistance to imatinib therapy, bosutinib rendered response rates similar to those observed in the same patient population treated with nilotinib or dasatinib. Preliminary results from the ongoing phase III BELA study in which bosutinib is compared in a randomized fashion to imatinib for patients with newly diagnosed CML-CP have been recently reported. We herein summarize the preclinical and clinical experience of bosutinib in CML.     

Mechanisms of resistance to FLT3 inhibitors

The success of the small molecule tyrosine kinase receptor inhibitor (TKI) imatinib mesylate (Gleevec) in the treatment of chronic myeloid leukemia (CML) constitutes an eminent paradigm shift advocating the rational design of cancer therapeutics specifically targeting the transformation events that drive tumorigenicity. In acute myeloid leukemias (AMLs), the most frequent identified transforming events are activating mutations in the FLT3 receptor tyrosine kinase that constitutively activate survival and proliferation pathways. FLT3 TKIs that are in various phases of clinical trials are showing some initial promise. However, primary and secondary acquired resistance stands to severely compromise long-term and durable efficacy of these inhibitors as a therapeutic strategy. Here, we discuss the mechanisms of resistance to FLT3 inhibitors and possible strategies to overcome resistance through closer examination of the events of leukemogenesis and design of combination therapy.     

A safety evaluation of omacetaxine mepesuccinate for the treatment of chronic myeloid leukemia

ABSTRACT

Introduction: Therapy of chronic myeloid leukemia (CML) has been completely transformed by the development of tyrosine kinase inhibitors (TKIs). However, a subset of patients will fail TKI therapy due to resistance or intolerance. Omacetaxine mepesuccinate (OM), a protein translation inhibitor, is currently the only approved therapy that does not directly target the kinase domain. It has activity for CML patients irrespective of the phase or underlying kinase domain mutation status.

Areas covered: We searched the MEDLINE database for articles published in English on homoharringtonine or omacetaxine from 1970 to present. This article reviews the pharmacokinetics of OM and its clinical evolution for the treatment of CML pre- and post TKI development. Toxicity profile, drug administration and future directions are also discussed.

Expert opinion: OM represents a unique addition to the CML therapeutic armamentarium with its distinct mechanism of action and activity. The adverse event profile is manageable and with subcutaneous administration at the approved dose, cardiac toxicity is no longer a concern. The recent approval of home administration will facilitate access to this therapy and increase patient compliance. We conclude with specific scenarios where OM use should be considered in CP and AP-CML patients in the era of TKI therapy.     

慢性髓系白血病无治疗缓解的研究进展

随着酪氨酸激酶抑制剂（TKI）的引入,慢性髓系白血病（CML）的治疗取得了前所未有的突破性进展,大大提高了患者的生存及预后。国内外临床试验表明,部分获得深度分子学反应的慢性髓系白血病在数年后可以成功停药,并维持无治疗缓解。本文主要通过总结酪氨酸激酶抑制剂治疗慢性髓系白血病患者获得深度分子学缓解后停药的临床试验,对如何把握安全停药,达到无治疗缓解（TFR）作一综述。     

Tyrosine kinase inhibitors in acute and chronic leukemias

INTRODUCTION: Since the initial approval of imatinib much has been learned about its resistance mechanisms, and efforts have continued to improve upon BCR-ABL tyrosine kinase inhibitor therapy. Targeted therapy with TKIs has continued to be an area of active research and development in the care of acute and chronic leukemia patients. AREAS COVERED: This article reviews current approved and investigational TKI treatments for chronic myelogenous leukemia (CML), Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph + ALL) and acute myelogenous leukemia (AML). EXPERT OPINION: There are now more potent BCR-ABL TKIs approved, which allow for additional options when determining front-line and second-line CML and Ph + ALL treatments. The T315I mutation is an ever-present challenge. Ponatinib, a pan BCR-ABL TKI, while still under investigation, is very hopeful with its ability to overcome T315I mutations in resistant CML and Ph + ALL patients. Because nilotinib and dasatinib have not been directly compared, at present we recommend selecting one or the other based on the side-effect profile, drug interactions, patient comorbidities, and mutational status. FLT-3 inhibition is of particular interest in AML patients with FLT-3 internal tandem duplication mutations; this type of targeted therapy continues to be studied.     

Current concerns of undertreatment and overtreatment in chronic myeloid leukemia based on European LeukemiaNet 2013 recommendations

Introduction: The aim of this paper is to indicate optimal tyrosine kinase inhibitor (TKI) administration practices based on European LeukemiaNet (ELN) 2013 recommendations for chronic myeloid leukemia (CML). Likewise, current concerns of undertreatment and overtreatment with TKIs during the long-term clinical course of CML will be outlined.

Areas covered: Currently available TKIs for the management of CML are reviewed. The survival benefit of TKIs (imatinib, dasatinib, nilotinib, bosutinib, ponatinib) for the CML is excellent. The CML and TKI literature search was made in PubMed with particular focus on the clinical trials, recommendations, guidelines and expert opinions, as well as the ELN CML 2013 recommendations.

Expert opinion: Initial TKI treatment for low-risk chronic phase CML is imatinib 400 mg; high-Sokal risk and/or CML patients with complex karyotypic abnormalities would require more powerful second-generation TKIs (dasatinib 100 mg or nilotinib 600 mg). Absence of early molecular response after 6 months, complete cytogenetic response after 12 months and major molecular response after 18 months may require a more powerful TKI switch. If one of the two second-generation TKIs (nilotinib or dasatinib) was used as first-line therapy and failed, the other (dasatinib or nilotinib) could be administered.     

Bcr-Abl酪氨酸激酶抑制剂联合用药治疗慢性粒细胞白血病研究进展

以伊马替尼为代表的酪氨酸激酶抑制剂对慢性粒细胞白血病(CML)的治疗产生了重要影响,但其耐药性已成为CML治疗领域的关键问题。伊马替尼、尼洛替尼、达沙替尼以及普纳替尼等Bcr-Abl酪氨酸激酶抑制剂与其他药物联合使用,可以协同抑制Bcr-Abl及其磷酸化蛋白的表达,显著降低STAT5、CRKL、ERK5等信号通路的磷酸化水平,改善肿瘤微环境,降低肿瘤细胞多药耐药性,已在基础研究和临床Ⅰ期研究中取得阶段性成果,为治疗CML提供新策略。     

Roots of imatinib resistance: A question of self-renewal?

The BCR-ABL-fusion gene is critical for the development of chronic myeloid leukemia (CML) and BCR-ABL positive acute lymphatic leukemia (Ph+ ALL). Blocking BCR-ABL by the ABL tyrosine kinase inhibitor imatinib mesylate (IM, Gleevec) is clinically highly efficient. Treatment response is unfortunately compromised by the emergence of IM resistance, which is regularly seen in accelerated and blastic phase of CML (CML-AP/BP) and in Ph+ ALL. BCR-ABL kinase domain mutations are then considered the causative mechanism of IM resistance, because 50-60% of the IM resistant patients harbour such mutations. In contrast, IM resistance arises very rarely in patients that are treated with IM in early chronic phase of CML. This implies that BCR-ABL independent factors such as the cellular context of BCR-ABL expression and stage of disease decisively control the evolution of IM resistance. In line with this, novel Abl-kinase inhibitors such as dasatinib (DA) or nilotinib (NI) - although capable of inhibiting most of the BCR/-BL kinase mutants - still often fail to overcome resistance and do mostly not induce durable cytogenetic responses in IM resistant CML-AP/BC and Ph+ ALL patients. On the basis of available evidence it is proposed here that alternative genetic aberrations, which synergize with BCR-ABL to enable leukemic self-renewal are of causal importance for the evolution of clinical kinase inhibitor resistance. Kinase mutations may in turn reflect clonal variants of cells that emerge on the basis of an already existing IM resistant and self-renewing leukemic cell population. This model has clinical implications as it implies that even highly potent Abl-kinase inhibition can not target the genetic basis of IM resistance and will also not resolve the problem of Abl-kinase inhibitor resistance.     

Nilotinib for the treatment of Philadelphia-chromosome-positive chronic myeloid leukemia

Importance of the field: Although the introduction of imatinib revolutionized the management of chronic myeloid leukemia (CML), some patients exhibit resistance or intolerance to the drug. Nilotinib induces high and rapid rates of cytogenetic and molecular responses. With recent approval for newly diagnosed patients with chronic phase CML, the current algorithm for treatment will probably be transformed.

Areas covered in this review: This review will describe evaluations of nilotinib in all phases of CML from 1995 to the present. Early preclinical data and Phase I, Phase II and Phase III evaluations will demonstrate the role of nilotinib in newly diagnosed CML, as well as in imatinib-resistant or imatinib-intolerant disease.

What the reader will gain: Mutations in the BCR-ABL kinase domain are responsible for the majority of resistance to imatinib. In comparison with imatinib, nilotinib displays increased selectivity and potency at inhibiting proliferation of BCR-ABL expressing cells. Although several mutations, including T315I, remain resistant to nilotinib, activity in all phases of CML has been reported.

Take home message: Nilotinib induces high and rapid rates of cytogenetic and molecular response, with less progression to advanced forms of disease compared with imatinib. Considering that the rapid achievement of these clinical milestones has been associated with positive long-term outcomes, nilotinib as initial therapy in patients with CML in chronic phase represents the future in CML treatment. Longer follow-up is necessary to recognize survival advantages.     

Telomere loss is accompanied by decreased pool of shelterin proteins TRF2 and RAP1, elevated levels of TERRA and enhanced glycolysis in imatinib-resistant CML cells

Telomere length may be maintained by telomerase nucleoprotein complex and shelterin complex, namely TRF1, TRF2, TIN2, TPP1, POT1 and RAP1 proteins and modulated by TERRA expression. Telomere loss is observed during progression of chronic myeloid leukemia (CML) from the chronic phase (CML-CP) to the blastic phase (CML-BP). The introduction of tyrosine kinase inhibitors (TKIs), such as imatinib (IM), has changed outcome for majority of patients, however, a number of patients treated with TKIs may develop drug resistance. The molecular mechanisms underlying this phenomenon are not fully understood and require further investigation. In the present study, we demonstrate that IM-resistant BCR::ABL1 gene-positive CML K-562 and MEG-A2 cells are characterized by decreased telomere length, lowered protein levels of TRF2 and RAP1 and increased expression of TERRA in comparison to corresponding IM-sensitive CML cells and BCR::ABL1 gene-negative HL-60 cells. Furthermore, enhanced activity of glycolytic pathway was observed in IM-resistant CML cells. A negative correlation between a telomere length and advanced glycation end products (AGE) was also revealed in CD34⁺ cells isolated from CML patients. In conclusion, we suggest that affected expression of shelterin complex proteins, namely TRF2 and RAP1, TERRA levels, and glucose consumption rate may promote telomere dysfunction in IM-resistant CML cells.     

Medication adherence,molecular monitoring,and clinical outcomes in patients with chronic myelogenous leukemia in a large HMO

Objective

Our objective was to examine the association between adherence to tyrosine kinase inhibitors (TKIs) and molecular monitoring and the risk of disease progression or mortality among patients with chronic phase chronic myeloid leukemia (CML).

酪氨酸激酶抑制剂治疗慢性粒细胞白血病的不良反应及处理的研究进展

酪氨酸激酶抑制剂(TKI)抑制BCR-ABL基因,改善慢性粒细胞白血病(CML)患者长期生存,与正常人寿命无差异.CML患者使用TKI早期出现不良反应较轻,可对症处理或自行恢复,较严重时可考虑更换TKI.国内报道TKI长期使用的安全性问题多表现在血液学不良反应,其他不良反应文献报道少见,本文通过查询国内外文献,对TKI...     

Tyrosine kinase inhibitors in acute and chronic leukemias

Introduction: Since the initial approval of imatinib much has been learned about its resistance mechanisms, and efforts have continued to improve upon BCR-ABL tyrosine kinase inhibitor therapy. Targeted therapy with TKIs has continued to be an area of active research and development in the care of acute and chronic leukemia patients.

Areas covered: This article reviews current approved and investigational TKI treatments for chronic myelogenous leukemia (CML), Philadelphia-chromosome positive acute lymphoblastic leukemia (Ph + ALL) and acute myelogenous leukemia (AML).

Expert opinion: There are now more potent BCR-ABL TKIs approved, which allow for additional options when determining front-line and second-line CML and Ph + ALL treatments. The T315I mutation is an ever-present challenge. Ponatinib, a pan BCR-ABL TKI, while still under investigation, is very hopeful with its ability to overcome T315I mutations in resistant CML and Ph + ALL patients. Because nilotinib and dasatinib have not been directly compared, at present we recommend selecting one or the other based on the side-effect profile, drug interactions, patient comorbidities, and mutational status. FLT-3 inhibition is of particular interest in AML patients with FLT-3 internal tandem duplication mutations; this type of targeted therapy continues to be studied.     

慢性粒细胞白血病骨髓磁共振成像表现及临床应用分析

目的探讨慢性粒细胞白血病(chronicmyeloid leukemia,CML)骨髓磁共振成像(MRI)表现及临床价值。方法收集成人CML50例,其中初诊慢性期患者16例,治疗后病情稳定于慢性期者18例,病情发展到加速期者7例,发生急性变者9例。所有患者均行骨盆及股骨中上段MRI检查。结果初诊慢性期及进展到加速和急变期的患者SE序列T1WI表现为髂骨及股骨骨髓弥漫性低信号或仅有在股骨头、大转子处残留斑片状高信号。治疗后维持在慢性期的患者SE序列T1WI表现为髂骨弥漫性低信号为主,夹杂点片状高信号,股骨主要表现为高低混杂信号。初诊慢性期组与治疗后组、治疗后组与加速急变组MRI表现差异有统计学意义(P<0.01);初诊慢性期组与加速急变期组差异无统计学意义(P>0.05)。结论CML患者骨髓MRI能反映其病程演变,与临床特点结合,有助于CML的诊断分期,对监测病情发展、提示加速和急变有重要价值。     

Mechanisms of resistance imatinib (STI571) in preclinical models and in leukemia patients.

The tyrosine kinase inhibitor imatinib (STI571, Glivec) blocks the activity of the BCR/ABL oncogene and induces hematologic remissions in the majority of patients with chronic myeloid leukemia (CML). Glivec is an aminopyrimidine derivative that interacts with the ATP-binding site within the kinase domain of ABL and several other tyrosine kinases, including c-KIT, PDGF beta receptor, and ARG. The compound is currently in phase III clinical trials. Although patients with chronic phase CML have been found to develop drug resistance only rarely so far, patients in more advanced phases of the leukemia develop resistance frequently. The available information on Glivec resistance will be reviewed.     

BCR-ABL inhibitors in chronic myeloid leukemia: process chemistry and biochemical profile

Chronic myeloid leukemia (CML) is a myeloproliferative disease originating from a constitutively active tyrosine kinase, called BCR-ABL, expressed by an oncogene resulting from a reciprocal translocation between chromosome 9 and chromosome 22, coded as (t[9,22][q34;q11]). Inhibition of BCR-ABL with tyrosine kinase inhibitors (TKI) proved to be an efficient targeted therapy of Philadelphia-positive (Ph+) CML in the chronic phase. This review mainly addresses the synthetic pathways and process chemistry leading to the large scale preparation for pre-clinical demands and clinical supply of the three TKIs approved for Ph+ CML, i.e., imatinib, dasatinib and nilotinib and three more investigational drugs, i.e., bosutinib, ponatinib and bafetinib. Recent progress on the biochemical profiling of the six examined TKIs has been also reported.     

Deactylase inhibition in myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal haemopoietic progenitor cell disorders characterized by the proliferation of one or more of the haemopoietic lineages (myeloid, erythroid and/or megakaryocytic). The MPNs include eight haematological disorders: chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), systemic mastocytosis (SM), chronic eosinophilic leukemia, not otherwise specified (CEL, NOS), chronic neutrophilic leukemia (CNL), and unclassifiable MPN (MPN, U). Therapeutic interventions for MPNs include the use of tyrosine kinase inhibitors (TKIs) for BCR-ABL1(+) CML and JAK2 inhibitors for PV, ET and PMF. Histone deacetylase inhibitors (HDACi) are a novel class of drugs capable of altering the acetylation status of both histone and non-histone proteins, thereby affecting a repertoire of cellular functions in neoplastic cells including proliferation, differentiation, immune responses, angiogenesis and survival. Preliminary studies indicate that HDACi when used in combination with tyrosine kinase or JAK2 inhibitors may overcome resistance to the latter agents and enhance the pro-apoptotic effects on MPN cells. This review provides a review of pre-clinical and clinical studies that have explored the use of HDACi as potential therapeutics for MPNs.     

How has treatment changed for blast phase chronic myeloid leukemia patients in the tyrosine kinase inhibitor era? A review of efficacy and safety

Introduction: Management of chronic myeloid leukemia (CML) patients in advanced phases of disease has drastically changed since the introduction of tyrosine kinase inhibitors (TKIs) which provide tailored treatment strategies.

Areas covered: In this review, efficacy data of different TKIs are reported and reviewed when used as single agent or in combination for the management of blast phase (BP) CML.

Expert opinion: Although brilliant results were achieved, the outcome of BP patients did not change when TKIs were used as single agents. Newer strategies of association of TKI with intensified chemotherapy or new agents for different pathways are strongly needed as a bridge to possible allogeneic transplant.     

Some 2-[4-(1H-benzimidazol-1-yl) phenyl]-1H-benzimidazole derivatives overcome imatinib resistance by induction of apoptosis and reduction of P-glycoprotein activity

Imatinib (IMA) is a tyrosine kinase inhibitor (TKI) introduced for the chronic myeloid leukemia (CML) therapy. Emergence of IMA resistance leads to the relapse and failure in CML therapy. Benzimidazole is a heterocyclic organic compound which is widely investigated for the development of anticancer drugs. In this study, we aimed to explore the anticancer effects of some 2-[4-(1H-benzimidazol-1-yl) phenyl]-1H-benzimidazole derivatives on K562S (IMA-sensitive) and K562R (IMA-resistant) cells. To analyze the cytotoxic and apoptotic effects of the compounds, K562S, K562R, and L929 cells were exposed to increasing concentrations of the derivatives. Cytotoxic effects of compounds on cell viability were analyzed with MTT assay. Apoptosis induction, caspase3/7 activity were investigated with flow cytometry and BAX, BIM, and BAD genes expression levels were analyzed with qRT-PCR. Rhodamine123 (Rho-123) staining assays were carried out to evaluate the effect of compounds on P-glycoprotein (P-gp) activity. The hit compounds were screened using molecular docking, and the binding preference of each compounds to BCR-ABL protein was evaluated. Our results indicated that compounds triggered cytotoxicity, caspase3/7 activation in K562S and K562R cells. Rho-123 staining showed that compounds inhibited P-gp activity in K562R cells. Overall, our results reveal some benzimidazole derivatives as potential anticancer agents to overcome IMA resistance in CML.     

BMS-354825: a novel drug with potential for the treatment of imatinib-resistant chronic myeloid leukaemia

The BCR-ABL tyrosine kinase inhibitor imatinib has greatly improved the outcome for patients with chronic myeloid leukaemia (CML). Unfortunately, mutations causing resistance to imatinib are leading to relapses in some patients. In addition to inhibiting the wild-type BCR-ABL, BMS-354825 inhibited 14 of 15 BCR-ABL mutants. BMS-354825 treatment of immunodeficient mice prevented the progression of the disease in mice treated with the most clinical common imatinib-resistant mutant Met351Thr. The safety and efficacy of BMS-354825 is presently being evaluated in a phase I/II clinical trial in CML patients with imatinib resistance. The frequency of clinical use of BMS-3548125 in CML patients will depend on its efficacy/safety profile in clinical trial.