Practical issues surrounding the explosion of tyrosine kinase inhibitors for the management of chronic myeloid leukemia

Turkey real-life data: demographic features, treatment results and effects of comorbidities in chronic myeloid leukemia

Aim:

This study aimed to identify patient characteristics, treatment patterns and outcomes and to evaluate the effects of presence of comorbidities at diagnosis in chronic phase (CP)-chronic myeloid leukemia (CML) patients in Turkey.

Materials & methods:

Hospital records between 2005 and 2018 were retrospectively reviewed.

Results:

Of 861 CP-CML patients included, 31% had at least one comorbidity at diagnosis. Sex, cardiovascular disease status at diagnosis and molecular (at least major) and cytogenetic (partial and complete) responses were the independent predictors of survival.

Conclusion:

The response rates of CP-CML patients to the tyrosine kinase inhibitors were satisfactory. In addition to tolerability and side effect profiles of drugs, comorbidity status of patients should also be considered in treatment choice in CML patients.

This study aimed to identify patient characteristics, treatment patterns and outcomes and to evaluate the effects of presence of comorbidities at diagnosis in chronic phase (CP)-chronic myeloid leukemia (CML) patients in Turkey. Hospital records of patients between 2005 and 2018 were retrospectively reviewed. Of the included 861 CP-CML patients, 31% had at least one comorbidity at diagnosis. The survival of the patients was affected by sex, cardiovascular disease status at diagnosis, and molecular (at least major) and cytogenetic (partial and complete) responses. The response rates of CP-CML patients to the tyrosine kinase inhibitors were satisfactory. In addition to tolerability and side effect profiles of drugs, comorbidity status of patients should also be considered in treatment choice in CML patients.

Higher red blood cell distribution width at diagnose is a simple negative prognostic factor in chronic phase-chronic myeloid leukemia patients treated with tyrosine kinase inhibitors: A retrospective study

The aim of this study was to evaluate the ability of the red blood cell distribution width (RDW) to predict prognosis and treatment response in chronic myeloid leukemia (CML)-chronic phase (CP) patients treated with tyrosine kinase inhibitor (TKIs).We retrospectively enrolled 93 newly diagnosed CML-CP patients treated with TKIs from 2009 to 2018 at the First Hospital of Lanzhou University. Patients were divided into 2 groups using an RDW of 18.65% determined by receiver operating characteristic curve analysis. We analyzed the correlation of treatment responses and the RDW compared to common scoring systems, as well as the correlation of the RDW with disease outcome, including overall survival (OS) and progression-free survival (PFS), and demographic and laboratory factors affecting outcome. Univariate analysis and Cox regression analysis were used.The median age of patients was 40 years, and 51 patients (54.8%) were men. A high RDW could predict treatment response at 3 months (P = .03) and 6 months (P = .02). The RDW was significantly lower in patients who achieved molecular response by 3 months (P < .001) and complete cytogenetic response by 6 months (P = .001) than in those who did not respond. Patients with a high RDW (>18.65%, n = 35) had significantly worse 5-year OS (77.1% vs 96.6%; P = .008) and PFS (80.0% vs 98.3%; P = .002) than those with a low RDW (≤18.65%, n = 58). Multivariate analysis demonstrated that a high RDW was an adverse predictor of OS (P = .005, HR (hazard ratio) = 9.741) and PFS (P = .009, HR = 16.735).The RDW is a readily available prognostic marker of outcome in patients with CML-CP and can predict treatment response to TKIs. Further larger and prospective studies are required.

Tyrosine Kinase Inhibitors and the Relationship With Adherence, Costs, and Health Care Utilization in Commercially Insured Patients With Newly Diagnosed Chronic Myeloid Leukemia: A Retrospective Claims-Based Study

OBJECTIVE

To examine the association among tyrosine kinase inhibitor (TKI) out-of-pocket costs, adherence, and health care costs and utilization in a large group of commercially insured patients with chronic myeloid leukemia (CML).

MATERIALS AND METHODS

Patients with CML aged 18 to 64 years were identified using IBM MarketScan Commercial Database between April 1, 2011 and December 31, 2014. Patients were required to be continuously enrolled 3 months before and 12 months after TKI (imatinib, dasatinib, or nilotinib) initiation. TKI adherence is estimated using the proportion of days covered (PDC), defined as the percentage of the PDC by the prescription fill during the 12-month study period (adherent patients have PDC ≥80%). Health care cost differences between adherent and nonadherent patients were estimated using generalized linear models. Health care utilization was compared using negative binomial regression models. All models were controlled for potential confounding factors.

RESULTS

The study sample consisted of 863 patients, where 355 (41.1%) patients were classified as adherent. Over the study period, nonadherent patients incurred US$10,974 more in medical costs (P<0.001), and US$1663 more in non-TKI pharmacy costs (P<0.01). Adherent patients incurred US$28,184 more in TKI pharmacy costs (P<0.001) that resulted in US$18,305 more in overall total health care costs (P<0.001). Adherent patients, however, were estimated to be less likely to have all-cause hospitalizations (incidence rate ratio, 0.32; P<0.001), or CML-specific hospitalizations (incidence rate ratio, 0.31; P<0.01).

CONCLUSIONS

Patients with CML with better adherence experienced fewer hospitalizations, resulting in medical service cost savings. These lower medical costs, however, were more than offset by higher TKI medication costs observed during the first year of TKI therapy.

Involvement of MCL1, c-myc, and cyclin D2 protein degradation in ponatinib-induced cytotoxicity against T315I(+) Ph+leukemia cells

T315I mutation found in chronic myelogenous leukemia (CML) and Ph + ALL patients is the most serious one among resistance against BCR/ABL kinase inhibitors including imatinib and is only responsive to ponatinib (PNT). However, the novel strategy is required to reduce life-threatening adverse effects of PNT including ischemic cardiovascular disease. We examined the mechanism of PNT-induced cytotoxicity against a T315I(+) Ph + ALL cell line, TccY/Sr. PNT induced apoptosis (increased sub G1 cells, and cleaved caspase3 and PARP), and suppressed protein expression of MCL1, cyclin D2 and c-myc, which were reversed by a proteasome inhibitor, MG132, suggesting enhanced proteasomal degradation by PNT. Among BCL2 family inhibitors, MCL1 inhibitors (maritoclax and AZD5991) robustly induced cell death, showing the MCL1-dependent survival of TccY/Sr cells. Decreased MCL1 and c-myc expression by PNT was also observed in T315I(+) MEGA2/STIR cells. PNT suppressed PI3K activation followed by AKT inhibition and GSK3 dephosphorylation. PI3K/AKT inhibitors mimicked PNT, suggesting that PI3K/AKT signaling is important for survival of TccY/Sr cells. Moreover, GSK3 inhibitor (SB216763) reduced PNT-induced cytotoxicity and degradation of c-myc and MCL1. AZD5991 exhibited the synergistic action with PNT, anti-cancer drugs and venetoclax (BCL2 inhibitor), suggesting the utility of MCL1 inhibitor alone or in combination as a future clinical option for Ph + leukemia patients.

AMPK activation induced by promethazine increases NOXA expression and Beclin-1 phosphorylation and drives autophagy-associated apoptosis in chronic myeloid leukemia

Relapse and drug resistance is still major challenges in the treatment of leukemia. Promethazine, an antihistaminic phenothiazine derivative, has been used to prevent chemotherapy-induced emesis, although there is no report about its antitumor potential. Thus, we evaluated the promethazine cytotoxicity against several leukemia cells and the underlying mechanisms were investigated. Promethazine exhibited potent and selective cytotoxicity against all leukemia cell types in vitro at clinically relevant concentrations. Philadelphia positive chronic myeloid leukemia (CML) K562 cells were the most sensitive cell line. The cytotoxicity of promethazine in these cells was triggered by the activation of AMPK and inhibition of PI3K/AKT/mTOR pathway. The subsequent downstream effects were NOXA increase, MCL-1 decrease, and Beclin-1 activation, resulting in autophagy-associated apoptosis. These data highlight targeting autophagy may represent an interesting strategy in CML therapy, and also the antitumor potential of promethazine by acting in AMPK and PI3K/AKT/mTOR signaling pathways. Since this drug is currently used with relative low side effects, its repurposing may represent a new therapeutic opportunity for leukemia treatment.

Tyrosine Kinase Inhibitors Initiation, Cost Sharing, and Health Care Utilization in Patients with Newly Diagnosed Chronic Myeloid Leukemia: A Retrospective Claims-Based Study

BACKGROUND

For newly diagnosed chronic myeloid leukemia (CML) patients, early access to tyrosine kinase inhibitors (TKIs) is a consistent predictor of adherence and optimal response. The expense of targeted therapies, however, may result in high out-of-pocket costs for initiating therapy that could be a barrier to starting treatment.

OBJECTIVE

To examine the association between TKI out-of-pocket costs, initiation, and health care utilization and costs among patients who initiated TKI within 12 months after initial CML diagnosis.

METHODS

Individuals aged 18-64 years with an initial diagnosis of CML were identified in the IBM MarketScan Commercial Database between April 11, 2011, and December 31, 2014. The association between cost sharing and TKI initiation was evaluated using a multivariable logistic regression model applied to patients receiving therapy within a month of diagnosis and within 1-12 months after diagnosis. Health care utilization was compared using negative binomial regression models. Health care cost differences between the 2 patient groups were estimated using generalized linear models. All models were controlled for potential confounding factors.

RESULTS

The study sample consisted of 477 patients, with 397 (83.2%) patients initiating TKI within the first month of CML diagnosis and 80 (16.8%) after the first month. Out-of-pocket costs for the initial 30-day supply of TKI medications were not found to be a significant predictor of TKI initiation time. Patients initiating therapy within a month were less likely to have all-cause hospitalizations (IRR = 0.35; P = 0.02) or CML-specific hospitalizations (IRR = 0.27; P < 0.01). Over the 12-month follow-up period, they incurred $9,923 more in TKI pharmacy costs (P < 0.05), but patients initiating therapy after the first month of diagnosis incurred $7,582 more in medical costs, $218 more in non-TKI pharmacy costs, and $2,680 more in total health care costs (P > 0.05).

CONCLUSIONS

Patients with TKI initiation within the first month of diagnosis had higher TKI pharmacy costs that were partially offset by lower medical and non-TKI pharmacy costs, resulting in lower overall total health care costs. Findings suggest that earlier TKI initiation may reduce the risks of hospitalizations, which could result in potential medical cost savings in the first 12 months of treatment.

DISCLOSURES

No outside funding supported this study. The authors have no relationships or financial interests to report with any entity that would pose a conflict of interest with the subject matter of this article. A poster presentation of the study was made at the 11th American Association for Cancer Research (AACR) Conference on The Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved, on November 2-5, 2018, in New Orleans, LA.

Gold nanoparticles for sustained antileukemia drug release: development, optimization and evaluation by quality-by-design approach

AIM

To design, develop, optimize and evaluate sustained-release dasatinib-loaded gold nanoparticles (DSB-GNPs) to treat chronic myeloid leukemia (CML) by using quality by design.

MATERIALS & METHODS

In this study, we performed risk assessment, optimization, in vitro characterizations, stability study, drug release studies, cytotoxicity study and in vivo pharmacokinetic evaluation.

RESULTS

DSB-GNPs of desired size, entrapment, smooth, spherical, stable and sustained drug release for 48 h were achieved. DSB-GNPs exhibited significantly more percentage growth inhibition and enhanced systemic bioavailability compared with pure DSB.

CONCLUSION

The in vitro and in vivo evaluation exhibited that the DSB-GNPs have a potential cytotoxic effect, systemic bioavailability and sustained release making them a promising system of DSB delivery in the treatment of chronic myeloid leukemia.

Risk factors and mechanisms contributing to TKI-induced vascular events in patients with CML

Vascular adverse events (VAE) are an emerging problem in patients with chronic myeloid leukemia (CML) receiving second-generation BCR-ABL1 tyrosine kinase inhibitors (TKI). Relevant VAE comprise peripheral, cerebral, and coronary artery changes in patients receiving nilotinib, venous and arterial occlusive events during ponatinib therapy, and pulmonary hypertension in patients receiving dasatinib. Although each TKI binds to a unique profile of molecular targets in leukemic cells and vascular cells, the exact etiology of drug-induced vasculopathies remains uncertain. Recent data suggest that predisposing molecular factors, pre-existing cardiovascular risk factors as well as certain comorbidities contribute to the etiology of VAE in these patients. In addition, direct effects of these TKI on vascular endothelial cells have been demonstrated and are considered to contribute essentially to VAE evolution. In the current article, we discuss mechanisms underlying the occurrence of VAE in TKI-treated patients with CML, with special emphasis on vascular and perivascular target cells and involved molecular (vascular) targets of VAE-triggering TKI. In addition, we discuss optimal patient selection and drug selection through which the risk of occurrence of cardiovascular events can hopefully be minimized while maintaining optimal anti-leukemic effects in CML, thereby following the principles of personalized medicine.

Pseudozyma and other non-Candida opportunistic yeast bloodstream infections in a large stem cell transplant center

Non-Candida opportunistic yeasts are emerging causes of bloodstream infection (BSI) in immunocompromised hosts. However, their clinical presentation, management, and outcomes in stem cell transplant (SCT) recipients are not well described. We report the first case to our knowledge of Pseudozyma BSI in a SCT recipient. He had evidence of cutaneous involvement, which has not been previously described in the literature. He became infected while neutropenic and receiving empiric micafungin, which is notable because Pseudozyma is reported to be resistant to echinocandins. He was successfully treated with the sequential use of liposomal amphotericin B and voriconazole. A review of the literature revealed nine reported instances of Pseudozyma fungemia. We performed a retrospective review of 3557 SCT recipients at our institution from January 2000 to June 2015 and identified four additional cases of non-Candida yeast BSIs. These include two with Cryptococcus, one with Trichosporon, and one with Saccharomyces. Pseudozyma and other non-Candida yeasts are emerging pathogens that can cause severe and disseminated infections in SCT recipients and other immunocompromised hosts. Clinicians should have a high degree of suspicion for echinocandin-resistant yeasts, if patients develop breakthrough yeast BSIs while receiving echinocandin therapy.

Response to Tyrosine Kinase Inhibitors in Myeloproliferative Neoplasia with 8p11 Translocation and CEP110-FGFR1 Rearrangement

This brief communication reports on a patient with an exceedingly rare "8p11 (eight-p-eleven) myeloproliferative syndrome" (EMS) with CEP110-FGFR1 rearrangement who responded to treatment with the multi-tyrosine kinase inhibitor (TKI) dasatinib. Dasatinib improved quality of life substantially by increasing blood counts and reducing the need for transfusions. This report demonstrates that the second-generation TKI may provide a therapeutic option for elderly and frail EMS patients who cannot be offered aggressive therapy, including allogeneic hematopoietic cell transplantation. The Oncologist 2017;22:480-483.

Current trends in molecular diagnostics of chronic myeloid leukemia

Nearly 1.5 million people worldwide suffer from chronic myeloid leukemia (CML), characterized by the genetic translocation t(9;22)(q34;q11.2), involving the fusion of the Abelson oncogene (ABL1) with the breakpoint cluster region (BCR) gene. Early onset diagnosis coupled to current therapeutics allow for a treatment success rate of 90, which has focused research on the development of novel diagnostics approaches. In this review, we present a critical perspective on current strategies for CML diagnostics, comparing to gold standard methodologies and with an eye on the future trends on nanotheranostics.

Recognizing Endocrinopathies Associated With Tyrosine Kinase Inhibitor Therapy in Children With Chronic Myelogenous Leukemia

Side effects of tyrosine kinase inhibitor (TKI) treatment vary in children and adults with chronic myelogenous leukemia (CML). As children have a much longer life expectancy than adults, TKI therapy may continue for decades and with long-term consequences that differ from adults. Children may develop endocrinopathies related to "off-target" effects of TKIs, such as delayed growth, changes in bone metabolism, thyroid abnormalities, and effects on puberty and fertility. These endocrinopathies present additional challenges for pediatric patients with CML. This review critically evaluates the literature on long-term endocrine side effects of TKIs in the pediatric CML population and provides suggested recommendations.

Therapeutic drug monitoring and tyrosine kinase inhibitors

The therapeutic activity of drugs can be optimized by establishing an individualized dosage, based on the measurement of the drug concentration in the serum, particularly if the drugs are characterized by an inter-individual variation in pharmacokinetics that results in an under- or overexposure to treatment. In recent years, several tyrosine kinase inhibitors (TKIs) have been developed to block intracellular signaling pathways in tumor cells. These oral drugs are candidates for therapeutic drug monitoring (TDM) due to their high inter-individual variability for therapeutic and toxic effects. Following a literature search on PubMed, studies on TKIs and their pharmacokinetic characteristics, plasma quantification and inter-individual variability was studied. TDM is commonly used in various medical fields, including cardiology and psychiatry, but is not often applied in oncology. Plasma concentration monitoring has been thoroughly studied for imatinib, in order to evaluate the usefulness of TDM. The measurement of plasma concentration can be performed by various analytical techniques, with liquid chromatography-mass spectrometry being the reference method. This method is currently used to monitor the efficacy and tolerability of imatinib treatments. Although TDM is already being used for imatinib, additional studies are required in order to improve this practice with the inclusion of other TKIs.

Chronic myeloid leukemia: reminiscences and dreams

With the deaths of Janet Rowley and John Goldman in December 2013, the world lost two pioneers in the field of chronic myeloid leukemia. In 1973, Janet Rowley, unraveled the cytogenetic anatomy of the Philadelphia chromosome, which subsequently led to the identification of the BCR-ABL1 fusion gene and its principal pathogenetic role in the development of chronic myeloid leukemia. This work was also of major importance to support the idea that cytogenetic changes were drivers of leukemogenesis. John Goldman originally made seminal contributions to the use of autologous and allogeneic stem cell transplantation from the late 1970s onwards. Then, in collaboration with Brian Druker, he led efforts to develop ABL1 tyrosine kinase inhibitors for the treatment of patients with chronic myeloid leukemia in the late 1990s. He also led the global efforts to develop and harmonize methodology for molecular monitoring, and was an indefatigable organizer of international conferences. These conferences brought together clinicians and scientists, and accelerated the adoption of new therapies. The abundance of praise, tributes and testimonies expressed by many serve to illustrate the indelible impressions these two passionate and affable scholars made on so many people's lives. This tribute provides an outline of the remarkable story of chronic myeloid leukemia, and in writing it, it is clear that the historical triumph of biomedical science over this leukemia cannot be considered without appreciating the work of both Janet Rowley and John Goldman.

In Vitro Antileukemia Activity of ZSTK474 on K562 and Multidrug Resistant K562/A02 Cells

Chronic myelogenous leukemia (CML) is a malignant hematological disorder mainly caused by the Bcr-Abl tyrosine kinase. While Bcr-Abl inhibitors including Imatinib showed antitumor efficacy on many CML patients, resistance was frequently reported in recent years. Therefore, novel drugs for CML are still expected. ZSTK474 is a specific phosphatidylinositol 3-kinase (PI3K) inhibitor that we identified. In the present study, the efficacy of ZSTK474, alone or in combination with Imatinib, on K562 CML cells as well as on its multidrug resistance counterpart K562/A02 cells, was investigated. ZSTK474 inhibited the cell proliferation with an IC₅₀ of 4.69 μM for K562 and 7.57 μM for K562/A02 cells, respectively. Treatment by ZSTK474 resulted in cell cycle arrest in G1 phase, which might be associated with upregulation of p27, and downregulation of cyclin D1. ZSTK474 also inhibited phosphorylation of Akt and GSK-3β, which might be involved in the effect on the above cell cycle-related proteins. Moreover, combination of ZSTK474 and Imatinib indicated synergistic effect on both cell lines. In conclusion, ZSTK474 exhibited antileukemia activity alone, and showed synergistic effect when combined with Imatinib, on CML K562 cells as well as the multidrug resistant ones, providing a potential therapeutic approach for CML patients.

Access to new cancer medicines in Australia: dispelling the myths and informing a public debate

Despite the high level of spending on cancer medicines in Australia, consumer organisations and the pharmaceutical industry often make claims of delayed or lack of access to new cancer medicines-claims that are frequently supported by prominent coverage in the Australian media. These claims, while morally and psychologically compelling, tend to ignore the complexity of medicines funding decisions. In this commentary we summarise the current situation regarding the registration and funding of cancer medicines in Australia, elucidate the main challenges associated with access to cancer medicines in the Australian context, and describe some of the steps that have been taken to address these challenges.

Tyrosine kinase inhibitor associated vascular toxicity in chronic myeloid leukemia

Tyrosine kinase inhibitors (TKIs) have revolutionized the management and outcomes of chronic myeloid leukemia (CML) patients. Improved disease control and prolonged life expectancy now mandate focus on improving TKIs’ safety profile. Recently, vascular adverse events (VAEs) have emerged as a serious consequence of some of the newer TKIs. In this review, we describe the clinical spectrum of TKI-associated VAE, and examine the unique vascular safety profile of the main TKIs currently used in the treatment of CML: imatinib, nilotinib, dasatinib, bosutinib and ponatinib. The issue of TKI-related platelet dysfunction is discussed as well. We describe the contemporary research findings regarding the possible pathogenesis of the VAE. Finally, the different aspects of TKI-associated VAE management are addressed, including prevention methods, monitoring strategies and treatment options.

Old dog, new tricks: extracellular domain arginine methylation regulates EGFR function

Conventional wisdom holds that methylation of RTKs should be restricted to intracellular sites. Alterations--such as deletion, mutation, and proteolytic cleavage events--to the extracellular ligand binding and dimer interface domains of the EGFR can induce EGFR dimer formation, leading to aberrant receptor activation and oncogenic activity. Recently, the extracellular domain of EGFR was also shown to be methylated, suggesting that posttranslational protein methylation events directed to the extracellular dimer interface provide another mechanism to regulate the EGFR activation state by modulating receptor dimerization. Critically, these methylation events abrogate response to conformation-specific therapeutic antibodies such as cetuximab. In this issue of the JCI, Liao et al. investigate the role of protein arginine methyltransferase I (PRMT1) in regulating EGFR function in colorectal cancer. The authors provide evidence that methylation of R198 and R200 within the dimer interface enhances growth factor ligand binding and cetuximab resistance through induction and stabilization of the active EGFR dimer conformation. Delineation of these and other subtleties involved in oncogenic RTK activation and their response to targeted therapies should facilitate the development of improved antibody-based treatments.

Classification of small molecule protein kinase inhibitors based upon the structures of their drug-enzyme complexes

Because dysregulation and mutations of protein kinases play causal roles in human disease, this family of enzymes has become one of the most important drug targets over the past two decades. The X-ray crystal structures of 21 of the 27 FDA-approved small molecule inhibitors bound to their target protein kinases are depicted in this paper. The structure of the enzyme-bound antagonist complex is used in the classification of these inhibitors. Type I inhibitors bind to the active protein kinase conformation (DFG-Asp in, αC-helix in). Type I½ inhibitors bind to a DFG-Asp in inactive conformation while Type II inhibitors bind to a DFG-Asp out inactive conformation. Type I, I½, and type II inhibitors occupy part of the adenine binding pocket and form hydrogen bonds with the hinge region connecting the small and large lobes of the enzyme. Type III inhibitors bind next to the ATP-binding pocket and type IV inhibitors do not bind to the ATP or peptide substrate binding sites. Type III and IV inhibitors are allosteric in nature. Type V inhibitors bind to two different regions of the protein kinase domain and are therefore bivalent inhibitors. The type I-V inhibitors are reversible. In contrast, type VI inhibitors bind covalently to their target enzyme. Type I, I½, and II inhibitors are divided into A and B subtypes. The type A inhibitors bind in the front cleft, the back cleft, and near the gatekeeper residue, all of which occur within the region separating the small and large lobes of the protein kinase. The type B inhibitors bind in the front cleft and gate area but do not extend into the back cleft. An analysis of the limited available data indicates that type A inhibitors have a long residence time (minutes to hours) while the type B inhibitors have a short residence time (seconds to minutes). The catalytic spine includes residues from the small and large lobes and interacts with the adenine ring of ATP. Nearly all of the approved protein kinase inhibitors occupy the adenine-binding pocket; thus it is not surprising that these inhibitors interact with nearby catalytic spine (CS) residues. Moreover, a significant number of approved drugs also interact with regulatory spine (RS) residues.

Pediatric chronic myeloid leukemia is a unique disease that requires a different approach

Chronic myelogenous leukemia (CML) in children is relatively rare. Because of a lack of robust clinical study evidence, management of CML in children is not standardized and often follows guidelines developed for adults. Children and young adults tend to have a more aggressive clinical presentation than older adults, and prognostic scores for adult CML do not apply to children. CML in children has been considered to have the same biology as in adults, but recent data indicate that some genetic differences exist in pediatric and adult CML. Because children with CML may receive tyrosine kinase inhibitor (TKI) therapy for many decades, and are exposed to TKIs during a period of active growth, morbidities in children with CML may be distinct from those in adults and require careful monitoring. Aggressive strategies, such as eradication of CML stem cells with limited duration and intensive regimens of chemotherapy and TKIs, may be more advantageous in children as a way to avoid lifelong exposure to TKIs and their associated adverse effects. Blood and marrow transplantation in pediatric CML is currently indicated only for recurrent progressive disease, and the acute and long-term toxicities of this option should be carefully evaluated against the complications associated with lifelong use of TKIs.

Drug Therapy in the Progressed CML Patient with multi-TKI Failure

The aim of this paper is to outline pharmacotherapy of the 'third-line management of CML' (progressive disease course after sequential TKI drugs). Current management of CML with multi-TKI failure is reviewed. TKI (bosutinib, ponatinib, dasatinib, nilotinib) and non-TKI (omacetaxine mepussecinate, IFN or PEG-IFN) drugs are available. The literature search was made in PubMed with particular focus on the clinical trials, recommendations, guidelines and expert opinions, as well as international recommendations. Progressing CML disease with multi-TKI failure should be treated with alloSCT based on the availability of the donor and EBMT transplant risk scores. The TKI and non-TKI drugs shall be used to get best promising (hematological, cytogenetic, molecular) response. During the CP-CML phase of multi-TKI failure, 2nd generation TKIs (nilotinib or dasatinib) should be tried if not previously utilized. Bosutinib and ponatinib (3rd-generation TKIs) should be administered in double- or triple-TKI (imatinib and nilotinib and dasatinib) resistant patients. The presence of T315I mutation at any phase requires ponatinib or omacetaxine mepussecinate therapy before allografting. During the AP/BC-CML phase of multi-TKI failure, the most powerful TKI available (ponatinib or dasatinib if not previously used) together with chemotherapy should be given before alloSCT. Monitoring of CML disease and drug off-target risks (particularly vascular thrombotic events) are vital.

The BCR-ABL inhibitor ponatinib inhibits platelet immunoreceptor tyrosine-based activation motif (ITAM) signaling, platelet activation and aggregate formation under shear

BACKGROUND

Treatment of chronic myelogenous leukemia (CML) with the BCR-ABL tyrosine kinase inhibitor (TKI) imatinib significantly improves patient outcomes. As some patients are unresponsive to imatinib, next generation BCR-ABL inhibitors such as nilotinib have been developed to treat patients with imatinib-resistant CML. The use of some BCR-ABL inhibitors has been associated with bleeding diathesis, and these inhibitors have been shown to inhibit platelet functions, which may explain the hemostasis impairment. Surprisingly, a new TKI, ponatinib, has been associated with a high incidence of severe acute ischemic cardiovascular events. The mechanism of this unexpected adverse effect remains undefined.

OBJECTIVE AND METHODS

This study used biochemical and functional assays to evaluate whether ponatinib was different from the other BCR-ABL inhibitors with respect to platelet activation, spreading, and aggregation.

RESULTS AND CONCLUSIONS

Our results show that ponatinib, similar to other TKIs, acts as a platelet antagonist. Ponatinib inhibited platelet activation, spreading, granule secretion, and aggregation, likely through broad spectrum inhibition of platelet tyrosine kinase signaling, and also inhibited platelet aggregate formation in whole blood under shear. As our results indicate that pobatinib inhibits platelet function, the adverse cardiovascular events observed in patients taking ponatinib may be the result of the effect of ponatinib on other organs or cell types, or disease-specific processes, such as BCR-ABL+cells undergoing apoptosis in response to chemotherapy, or drug-induced adverse effects on the integrity of the vascular endothelium in ponatinib-treated patients.