BCR-ABL Tyrosine Kinase Inhibitors: Which Mechanism(s) May Explain the Risk of Thrombosis?

Endothelium as a Source of Cardiovascular Toxicity From Antitumor Kinase Inhibitors

Kinase inhibitors (KIs) targeting oncogenic molecular pathways have revolutionized cancer therapy. By directly targeting specific tumor-driving kinases, targeted therapies have fewer side effects compared with chemotherapy. Despite the enhanced specificity, cardiovascular side effects have emerged with many targeted cancer therapies that limit long-term outcomes in patients with cancer. Endothelial cells lining all blood vessels are critical to cardiovascular health and are also exposed to circulating levels of systemic anticancer therapies. Both on- and off-target perturbation of signaling pathways from KIs can cause endothelial dysfunction, resulting in cardiovascular toxicity. As such, the endothelium is a potential source, and also a therapeutic target for prevention, of cardiovascular toxicity. In this review, we examine the evidence for KI-induced endothelial cell dysfunction as a mechanism for the cardiovascular toxicities of vascular endothelial growth factor inhibitors, BCR-Abl (breakpoint cluster region-Abelson proto-oncogene) KIs, Bruton tyrosine inhibitors, and emerging information regarding endothelial toxicity of newer classes of KIs.

Ponatinib Induces a Procoagulant Phenotype in Human Coronary Endothelial Cells via Inducing Apoptosis

BCR-ABL tyrosine kinase inhibitors (TKIs) are effective drugs in the treatment of patients with chronic myeloid leukemia. However, based on clinical studies, ponatinib was associated with the development of thrombotic complications. Since endothelial cells (ECs) regulate blood coagulation, their abnormal phenotype may play a role in the development of thrombotic events. We here aimed to investigate the effect of ponatinib on the procoagulant activity of cultured endothelial cells in vitro. Human coronary artery endothelial cells (HCAECs) were incubated with 50, 150, and 1000 nM of ponatinib. Subsequently, phosphatidylserine (PS) exposure and endothelial microvesicles (EMVs) were measured by flow cytometry. In addition, EC- and EMV-dependent thrombin generation was analyzed. To investigate pro-apoptotic effects of ponatinib, the level of Bax and Bcl-xL proteins were studied using Western blot and F3, THBD, and VCAM1 mRNAs were quantified by qPCR. Therapeutic concentrations of ponatinib significantly increased PS expression on ECs and the amount of EMVs which significantly shortened the time parameters of thrombin generation. In addition, these changes were associated with an increased ratio of Bax and Bcl-xL proteins in the presence of the decreased THBD mRNA level. Overall, ponatinib enhances the procoagulant activity of ECs via inducing apoptosis, which may contribute to thrombotic events.

Differential vascular endothelial cell toxicity of established and novel BCR-ABL tyrosine kinase inhibitors

BCR-ABL tyrosine kinase inhibitors (TKIs) have dramatically improved survival in Philadelphia chromosome-positive leukemias. Newer BCR-ABL TKIs provide superior cancer outcomes but with increased risk of acute arterial thrombosis, which further increases in patients with cardiovascular comorbidities and mitigates survival benefits compared to imatinib. Recent studies implicate endothelial cell (EC) damage in this toxicity by unknown mechanisms with few side-by-side comparisons of multiple TKIs and with no available data on endothelial impact of recently approved TKIs or novels TKIs being tested in clinical trials. To characterize BCR-ABL TKI induced EC dysfunction we exposed primary human umbilical vein ECs in 2D and 3D culture to clinically relevant concentrations of seven BCR-ABL TKIs and quantified their impact on EC scratch-wound healing, viability, inflammation, and permeability mechanisms. Dasatinib, ponatinib, and nilotinib, the TKIs associated with thrombosis in patients, all significantly impaired EC wound healing, survival, and proliferation compared to imatinib, but only dasatinib and ponatinib impaired cell migration and only nilotinib enhanced EC necrosis. Dasatinib and ponatinib increased leukocyte adhesion to ECs with upregulation of adhesion molecule expression in ECs (ICAM1, VCAM1, and P-selectin) and leukocytes (PSGL1). Dasatinib increased permeability and impaired cell junctional integrity in human engineered microvessels, consistent with its unique association with pleural effusions. Of the new agents, bafetinib decreased EC viability and increased microvessel permeability while asciminib and radotinib did not impact any EC function tested. In summary, the vasculotoxic TKIs (dasatinib, ponatinib, nilotinib) cause EC toxicity but with mechanistic differences, supporting the potential need for drug-specific vasculoprotective strategies. Asciminib and radotinib do not induce EC toxicity at clinically relevant concentrations suggesting a better safety profile.

Endothelial function measured by peripheral arterial tonometry in patients with chronic myeloid leukemia on tyrosine kinase inhibitor therapy: a pilot study

BACKGROUND

Arterial occlusive events are an emerging problem in patients with chronic myeloid leukemia (CML) receiving tyrosine kinase inhibitor (TKI) therapy. Endothelial cell damage is thought to play an important role in the development of vascular events. Measurement of the peripheral vasodilator response by peripheral arterial tonometry (PAT) has reportedly been useful in the non-invasive assessment of endothelial dysfunction. To date, no studies have assessed endothelial function using PAT in patients with CML receiving TKIs.

METHOD

We measured the reactive hyperemia index (RHI) using PAT in young patients with CML (men aged ≤ 55 years and women aged ≤ 65 years) receiving TKIs.

RESULTS

Thirty patients with CML were examined (mean age, 43.5 ± 9.8 years; men, 57%). The median RHI was 1.81. Among these patients, 16.7% and 83.3% were taking imatinib and second- or third-generation TKIs, respectively. There were no differences in the baseline characteristics between the low RHI (< 1.67, n = 10), borderline RHI (≥ 1.67 and < 2.10, n = 14), and normal RHI (≥ 2.10, n = 6) groups. Serum uric acid (UA) levels and the RHI were significantly negatively correlated (r = -0.40, p = 0.029).

CONCLUSION

One-third of young patients with CML receiving TKI therapy were classified as having a low RHI. The RHI was negatively correlated with serum UA level. Larger prospective studies are necessary to examine whether the RHI predicts cardiovascular events in such patients.

Impact of Tyrosine Kinase Inhibitors Applied for First-Line Chronic Myeloid Leukemia Treatment on Platelet Function in Whole Blood of Healthy Volunteers In Vitro

The tyrosine kinase inhibitors (TKIs) imatinib, dasatinib, bosutinib, and nilotinib are established for first-line treatment of chronic myeloid leukemia (CML) but may cause side effects such as bleeding and thrombotic complications. We investigated the impact of TKIs on platelet function ex vivo in anticoagulated whole blood (WB) samples from healthy adults by lumiaggregometry and PFA-100 test. Samples (n = 15 per TKI) were incubated for 30 minutes with TKI at therapeutically relevant final concentrations. Aggregation and ATP release were induced by collagen (1 µg/mL), arachidonic acid (0.5 mmol/L), and thrombin (0.5 U/mL). Imatinib, bosutinib, and nilotinib significantly increased collagen-induced aggregation compared with controls. In addition, for bosutinib and nilotinib, a significant increase in aggregation after induction with arachidonic acid was detected. ATP-release and PFA-100 closure times were not influenced significantly by these three TKI. In contrast, dasatinib demonstrated a concentration-dependent inhibition of collagen-induced aggregation and ATP release and a significant prolongation of the PFA-100 closure time with the collagen/epinephrine cartridge. Aggregation and ATP release by other agonists as well as closure time with the collagen/ADP cartridge were not influenced significantly. In conclusion, we clearly show a concentration-dependent inhibition of collagen-induced platelet function in WB by dasatinib confirming prior results obtained in platelet-rich plasma. Bosutinib and nilotinib exerted no impairment of platelet activation. On the contrary, both TKI showed signs of platelet activation. When comparing our results with existing data, imatinib in therapeutic relevant concentrations does not impair platelet function.

Cancer Therapies and Vascular Toxicities

OPINION STATEMENT

Vascular events have become an important issue in the overall management of cancer patients. They usually result from a combination of (i) direct or indirect toxicity of anticancer treatments, (ii) a higher prevalence of cardiovascular risk factors in cancer patients, and (iii) prolonged exposure to treatments due to an increasing patient survival rate. In addition to conventional chemotherapies and radiotherapy, targeted therapies and immunotherapies have been developed which improve the prognosis of cancer patients but sometimes at the cost of vascular toxicity, which can lead to systemic or pulmonary hypertension and arterial/venous thromboembolic events. Endothelial dysfunction, a procoagulant state and metabolic disorders are the three main pathophysiological patterns leading to cancer treatment-related vascular toxicity. This issue is challenging because serious vascular adverse events can necessitate cancer treatment being put on hold or stopped, which could compromise patient survival. In addition to increasing the risk of thrombotic adverse events, cancer therapies may lead to an increased risk of bleeding, especially in treatments with vascular endothelial growth factor inhibitors. Therefore, we can define vasculo-oncology as a part of the cardio-oncology specialty; its aims are to predict, prevent, screen, and treat vascular toxicity related to cancer treatments. While the level of evidence is low regarding the management of vascular toxicity during cancer therapy, cardiologists and specialists in vascular diseases should closely collaborate with oncologists and hematologists to determine the optimal strategy for each patient.

Exploiting polypharmacology to dissect host kinases and kinase inhibitors that modulate endothelial barrier integrity

Kinase inhibitors are promising drugs to stabilize the endothelial barrier following inflammatory damage. However, our limited knowledge of how kinase signaling activates barrier-restorative pathways and the complexity of multi-target drugs have hindered drug discovery and repurposing efforts. Here, we apply a kinase regression approach that exploits drug polypharmacology to investigate endothelial barrier regulation. A screen of 28 kinase inhibitors identified multiple inhibitors that promote endothelial barrier integrity and revealed divergent barrier phenotypes for BCR-ABL drugs. Target deconvolution predicted 50 barrier-regulating kinases from diverse kinase families. Using gene knockdowns, we identified kinases with a role in endothelial barrier regulation and dissected different mechanisms of action of barrier-protective kinase inhibitors. These results demonstrate the importance of polypharmacology in the endothelial barrier phenotype of kinase inhibitors and provide promising new leads for barrier-strengthening therapies.

Prevention of venous thromboembolism in hematologic neoplasms: an expert consensus from SEHH-SETH

Venous thromboembolism (VTE) is a serious complication in hematologic neoplasms, so finding adequate prevention strategies is an urgent requirement. However, prospective studies with large enough cohorts are scarce, limiting the development of evidence-based thromboprophylaxis guidelines. The present position paper is addressed to all hematologists treating patients affected by hematologic neoplasms with the aim to provide clinicians with a useful tool for the prevention of VTE.

Predictive value of clinical examination parameters for cardiovascular adverse events during treatment of chronic myeloid leukemia with tyrosine kinase inhibitors

Treatment of chronic myelogenous leukemia (CML) requires management of long-term use of tyrosine kinase inhibitors (TKIs). Although cardiovascular adverse events (CAEs) caused by off-target effects of TKIs can be life-threatening, the optimal method of monitoring for CAEs has not been established. Here, we comprehensively evaluated the clinical utility of various cardiovascular parameters, including ankle-brachial blood pressure index (ABI), cardiac ankle vascular index (CAVI), and carotid ultrasonography and electrocardiogram measurements, for monitoring and predicting CAEs in 74 patients with CML receiving TKIs. Based on concordance statistics, the predictive value of established risk factor models was significantly improved by addition of both ABI and CAVI, as follows: model 1 (hypertension, smoking history, and dyslipidemia), 0.680 versus 0.817 (p = 0.041); model 2 (hypertension, dyslipidemia, and diabetes mellitus), 0.685 vs. 0.830 (p = 0.047); and model 3 (age, hypertension, dyslipidemia and diabetes mellitus) 0.737 versus 0.818 (p = 0.044). However, no single cardiovascular parameter independently improved the predictive value of established risk factor models. In conclusion, addition of combined assessment of ABI and CAVI to established risk factors can improve prediction of future CAEs and may enable better clinical management of patients with CML receiving TKIs.

Tyrosine Kinase Inhibitors and Vascular Adverse Events in Patients with Chronic Myeloid Leukemia: A Population-Based, Propensity Score-Matched Cohort Study

BACKGROUND

Tyrosine kinase inhibitors (TKIs) have shown long-term survival benefits in patients with chronic myeloid leukemia (CML). Nevertheless, significant concern has been raised regarding long-term TKI-associated vascular adverse events (VAEs). The objective of this retrospective cohort study was to investigate the incidence of VAEs in Taiwanese patients with CML treated with different TKIs (imatinib, nilotinib, and dasatinib) as well as potential risk factors.

MATERIALS AND METHODS

We conducted a retrospective cohort study using the Taiwan Cancer Registry Database and National Health Insurance Research Database. Adult patients diagnosed with CML from 2008 to 2016 were identified and categorized into three groups according to their first-line TKI treatment (imatinib, nilotinib, and dasatinib). Propensity score matching was performed to control for potential confounders. Cox regressions were used to estimate the hazard ratio (HR) of VAEs in different TKI groups.

RESULTS

In total, 1,111 patients with CML were included in our study. We found that the risk of VAEs in nilotinib users was significantly higher than that in imatinib users, with an HR of 3.13 (95% confidence interval (CI), 1.30-7.51), whereas dasatinib users also showed a nonsignificant trend for developing VAEs, with an HR of 1.71 (95% CI, 0.71-4.26). In multivariable logistic regression analysis, only nilotinib usage, older age, and history of cerebrovascular diseases were identified as significant risk factors. The annual incidence rate of VAEs was highest within the first year after the initiation of TKIs.

CONCLUSION

These findings can support clinicians in making treatment decisions and monitoring VAEs in patients with CML in Taiwan.

IMPLICATIONS FOR PRACTICE

This study found that patients with chronic myeloid leukemia (CML) treated with nilotinib and dasatinib may be exposed to a higher risk of developing vascular adverse events (VAEs) compared with those treated with imatinib. Thus, this study suggests that patients with CML who are older or have a history of cerebrovascular diseases should be under close monitoring of VAEs, particularly within the first year after the initiation of tyrosine kinase inhibitors.

High-grade B-cell lymphoma developed during the treatment of chronic myeloid leukemia with bosutinib

Tyrosine kinase inhibitor (TKI) can help to increase the survival time in chronic myeloid leukemia (CML) patients; however, the risk of secondary malignancies due to TKIs is a growing concern. Only few reports showed clinical course of patients who developed lymphoma during TKI therapies. Herein, we report a case of high-grade B-cell lymphoma diagnosed in the course of CML treatment with bosutinib. The 75-year-old male patient had been diagnosed with CML 25 years ago. After receiving TKIs (imatinib, nilotinib, and bosutinib), he achieved a major molecular response. Over 3 years after starting bosutinib, he was diagnosed with a high-grade B-cell lymphoma. A total of six courses of DA-EPOCH-R therapy brought complete remission of the lymphoma. Moreover, BCR-ABL1 transcript copies remained undetectable by RT-PCR, 8 months after stopping bosutinib. The risk of secondary malignancy due to TKI has been controversial. It is reported that TKI induces irreversible chromosomal abnormalities or chromosome aberrations and inhibits the proliferation or function of T cells, B cells, and NK cells. These mechanisms of TKI may contribute to the development of secondary malignancy. There remains no consensus on the management of secondary lymphoma during TKI therapies. At present, the only alternative is to observe patients receiving TKI treatment cautiously and to treat secondary lymphoma in the same manner as de novo lymphoma.

Cardiovascular Events throughout the Disease Course in Chronic Myeloid Leukaemia Patients Treated with Tyrosine Kinase Inhibitors-A Single-Centre Retrospective Study

INTRODUCTION

Cardiovascular risk factors, pre-existing comorbidities, molecular factors, and the direct effects of second- and third-generation BCR-ABL1 tyrosine kinase inhibitors on the vascular endothelium contribute to the progression of cardiovascular (CV) events, especially atherothrombotic conditions. The study objective was to evaluate comorbidities, the cardiovascular risk profile, and events throughout the chronic myeloid leukaemia disease course.

METHODS

Retrospective data from adults who experienced haematology treatment at a single centre were continuously updated and followed throughout the disease course. A total of 43 subjects conforming with the inclusion and exclusion criteria of the study protocol were finally recruited. The median disease course was 77.0 ± 17.5 months. Statistical analyses were performed.

RESULTS

More than three CV risk factors were identified in 41.9% of cases. Almost half of the cases had relevant comorbidities (Charlson Comorbidity Index (CCI) ≥ 4), and no statistically significant comorbidities were found when comparing the tyrosine kinase inhibitor (TKI) treatment subgroups (p = 0.53). The patients at high and very high CV risk, according to Systematic Coronary Risk Evaluation (SCORE) risk classification, had 75.0% CV events (12/22 patients), p = 0.45. Throughout the disease course, 19 cardiovascular events were reported in 37.2% patients (13 males/3 females, p < 0.03).

CONCLUSION

To the best of our knowledge, this is the first study exploring cardiovascular risk factors in Romanian chronic myeloid leukaemia patients. This study reinforces the need for close long-term follow-up that should be performed by a multidisciplinary team. The target should be not only the disease and specific drug-related toxicities but, also, the identification of cardiovascular and metabolic risk factors before the commencement of and throughout TKI therapy.

An ultra-long circulating nanoparticle for reviving a highly selective BCR-ABL inhibitor in long-term effective and safe treatment of chronic myeloid leukemia

Nanotechnology has demonstrated great promise for the development of more effective and safer cancer therapies. We recently developed a highly selective inhibitor of BCR-ABL fusion tyrosine kinase for chronic myeloid leukemia (CML). However, the poor drug-like properties were hurdles to its further clinical development. Herein, we re-investigate it by conjugating an amphiphilic polymer and self-assembling into a nanoparticle (NP) with a high loading (~10.3%). The formulation greatly improved its solubility and drastically extended its circulation half-life from ~5.3 to ~117 h (>20-fold). In the 150 days long-term engraftment model experiment, long intravenous dosing intervals of the NPs (every 4 or 8 days) exhibited much better survival and negligible toxicities as compared to daily oral administration of the inhibitor. Moreover, the NPs showed excellent inhibition of tumor growth in the subcutaneous xenograft model. All results suggest that the ultra-long circulating pro-drug NP may provide an effective and safe therapeutic strategy for BCR-ABL-positive CML.

The Risk of Arterial Thrombosis in Patients With Chronic Myeloid Leukemia Treated With Second and Third Generation BCR-ABL Tyrosine Kinase Inhibitors May Be Explained by Their Impact on Endothelial Cells: An In-Vitro Study

BCR-ABL tyrosine kinase inhibitors (TKIs) revolutionized the treatment of chronic myeloid leukemia, inducing deep molecular responses, largely improving patient survival and rendering treatment-free remission possible. However, three of the five BCR-ABL TKIs, dasatinib, nilotinib, and ponatinib, increase the risk of developing arterial thrombosis. Prior investigations reported that nilotinib and ponatinib affect the endothelium, but the mechanisms by which they exert their toxic effects are still unclear. The impact of dasatinib and bosutinib on endothelial cells has been poorly investigated. Here, we aimed to provide an in vitro homogenous evaluation of the effects of BCR-ABL TKIs on the endothelium, with a special focus on the type of cell death to elucidate the mechanisms responsible for the potential cytotoxic effects of BCR-ABL TKIs nilotinib and ponatinib on endothelial cells. We tested the five BCR-ABL TKIs at three concentrations on human umbilical venous endothelial cells (HUVECs). This study highlights the endothelial toxicity of ponatinib and provides insights about the mechanisms by which it affects endothelial cell viability. Ponatinib induced apoptosis and necrosis of HUVECs after 72 h. Dasatinib affected endothelial cells in vitro by inhibiting their proliferation and decreased wound closure as soon as 24 h of treatment and even at infra-therapeutic dose (0.005 µM). Comparatively, imatinib, nilotinib, and bosutinib had little impact on endothelial cells at therapeutic concentrations. They did not induce apoptosis nor necrosis, even after 72 h of treatment but they inhibited HUVEC proliferation. Overall, this study reports various effects of BCR-ABL TKIs on endothelial cells and suggests that ponatinib and dasatinib induce arterial thrombosis through endothelial dysfunction.

Acute coronary syndromes in cancer patients

: Cardiovascular disease and cancer are responsible for the majority of deaths in the Western world. These two entities share common risk factors and their intersection will be more and more frequent in future due to general population aging and long-term cancer control. Clinical presentation, management and outcome of acute coronary syndromes (ACS) in cancer patients could differ from noncancer ones. Cancer patients were frequently excluded from clinical trials and so the paucity of data further complicates the scenario. The management of ACS in cancer patients represents a unique setting in which the risk/benefit ratio of invasive treatment should be carefully evaluated. This review focused on the available evidence of all aspects of ACS in cancer patients providing a guide to a multidisciplinary approach.