Incidence of and risk factors for major haemorrhage in patients treated with ibrutinib: An integrated analysis

Realizing precision medicine in chronic lymphocytic leukemia: Remaining challenges and potential opportunities

Patients with chronic lymphocytic leukemia (CLL) exhibit diverse clinical outcomes. An expanding array of genetic tests is now employed to facilitate the identification of patients with high-risk disease and inform treatment decisions. These tests encompass molecular cytogenetic analysis, focusing on recurrent chromosomal alterations, particularly del(17p). Additionally, sequencing is utilized to identify TP53 mutations and to determine the somatic hypermutation status of the immunoglobulin heavy variable gene. Concurrently, a swift advancement of targeted treatment has led to the implementation of novel strategies for patients with CLL, including kinase and BCL2 inhibitors. This review explores both current and emerging diagnostic tests aimed at identifying high-risk patients who should benefit from targeted therapies. We outline existing treatment paradigms, emphasizing the importance of matching the right treatment to the right patient beyond genetic stratification, considering the crucial balance between safety and efficacy. We also take into consideration the practical and logistical issues when choosing a management strategy for each individual patient. Furthermore, we delve into the mechanisms underlying therapy resistance and stress the relevance of monitoring measurable residual disease to guide treatment decisions. Finally, we underscore the necessity of aggregating real-world data, adopting a global perspective, and ensuring patient engagement. Taken together, we argue that precision medicine is not the mere application of precision diagnostics and accessibility of precision therapies in CLL but encompasses various aspects of the patient journey (e.g., lifestyle exposures and comorbidities) and their preferences toward achieving true personalized medicine for patients with CLL.

Evidence-based expert consensus on clinical management of safety of Bruton's tyrosine kinase inhibitors (2024)

Bruton's tyrosine kinase inhibitors (BTKis) have revolutionized the treatment of B-cell lymphomas. However, safety issues related to the use of BTKis may hinder treatment continuity and further affect clinical efficacy. A comprehensive and systematic expert consensus from a pharmacological perspective is lacking for safety issues associated with BTKi treatment. A multidisciplinary consensus working group was established, comprising 35 members from the fields of hematology, cardiovascular disease, cardio-oncology, clinical pharmacy, and evidence-based medicine. This evidence-based expert consensus was formulated using an evidence-based approach and the Delphi method. The Joanna Briggs Institute Critical Appraisal (JBI) tool and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach were used to rate the quality of evidence and grade the strength of recommendations, respectively. This consensus provides practical recommendations for BTKis medication based on nine aspects within three domains, including the management of common adverse drug events such as bleeding, cardiovascular events, and hematological toxicity, as well as the management of drug-drug interactions and guidance for special populations. This multidisciplinary expert consensus could contribute to promoting a multi-dimensional, comprehensive and standardized management of BTKis.

Bruton Tyrosine Kinase Inhibition: an Effective Strategy to Manage Waldenström Macroglobulinemia

PURPOSE OF REVIEW

The treatment of Waldenström macroglobulinemia (WM) has evolved over the past decade. With the seminal discoveries of MYD88 and CXCR warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) mutations in WM cells, our understanding of the disease biology and treatment has improved. The development of a new class of agents, Bruton tyrosine kinase inhibitors (BTKi), has substantially impacted the treatment paradigm of WM. Herein, we review the current and emerging BTKi and the evidence for their use in WM.

RECENT FINDINGS

Clinical trials have established the role of covalent BTKi in the treatment of WM. Their efficacy is compromised among patients who harbor CXCR4WHIM mutation or MYD88WT genotype. The development of BTKC481 mutation-mediated resistance to covalent BTKi may lead to disease refractoriness. Novel, non-covalent, next-generation BTKi are emerging, and preliminary results of the early phase clinical trials show promising activity in WM, even among patients refractory to a covalent BTKi. Covalent BTK inhibitors have demonstrated meaningful outcomes in treatment-naïve (TN) and relapsed refractory (R/R) WM, particularly among those harboring the MYD88L265P mutation. The next-generation BTKi demonstrate improved selectivity, resulting in a more favorable toxicity profile. In WM, BTKi are administered until progression or the development of intolerable toxicity. Consequently, the potential for acquired resistance, the emergence of cumulative toxicities, and treatment-related financial burden are critical challenges associated with the continuous therapy approach. By circumventing BTK C481 mutations that alter the binding site to covalent BTKi, the non-covalent BTKi serve as alternative agents in the event of acquired resistance. Head-to-head comparative trials with the conventional chemoimmunotherapies are lacking. The findings of the RAINBOW trial (NCT046152), comparing the dexamethasone, rituximab, and cyclophosphamide (DRC) regimen to the first-generation, ibrutinib are awaited, but more studies are needed to draw definitive conclusions on the comparative efficacy of chemoimmunotherapy and BTKi. Complete response is elusive with BTKi, and combination regimens to improve upon the efficacy and limit the treatment duration are also under evaluation in WM.

Evaluating zanubrutinib for the treatment of adults with chronic lymphocytic leukemia or small lymphocytic lymphoma

INTRODUCTION

This review evaluates zanubrutinib as a treatment option for adults with chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL). Zanubrutinib, a covalent BTK (Bruton's tyrosine kinase) inhibitor, was recently approved by the US FDA based in part on head-to-head data demonstrating improved efficacy and safety compared to ibrutinib.

AREAS COVERED

The review discusses the efficacy, safety, and comparative advantages of zanubrutinib, highlighting its safety profile compared to other BTK inhibitors. It also addresses the unmet needs of current therapies in CLL/SLL and provides an overview of competitor compounds and ongoing research in BTK inhibition.

EXPERT OPINION

Zanubrutinib, the first BTK inhibitor to demonstrate superior efficacy and safety compared to another BTK inhibitor in CLL, is likely to be widely adopted due to its high-quality data and ease of use. Looking ahead, pirtobrutinib, a novel non-covalent BTK inhibitor, has shown promise in heavily pretreated CLL patients, including those unresponsive to covalent inhibitors, with ongoing phase 3 trials comparing it against ibrutinib. The field is also exploring time-limited therapies like the combination of ibrutinib and venetoclax, with ongoing trials evaluating different combinations to optimize efficacy and minimize toxicity, indicating a promising future for combination therapies in CLL treatment.

Chronic Lymphocytic Leukemia: Management of Adverse Events in the Era of Targeted Agents

The treatment landscape for CLL has undergone a profound transformation with the advent of targeted agents (TAs) like Bruton's Tyrosine Kinase inhibitors (BTKis) and BCL-2 inhibitors (BCL-2is). These agents target crucial cellular pathways in CLL, offering superior efficacy over traditional chemo-immunotherapy, which has led to improved progression-free and overall survival rates. This advancement promises enhanced disease control and potentially normal life expectancy for many patients. However, the journey is not without challenges, as these TAs are associated with a range of adverse events (AEs) that can impact treatment efficacy and patient quality of life. This review focuses on detailing the various AEs related to TA management in CLL, evaluating their frequency and clinical impact. The aim is to present a comprehensive guide to the effective management of these AEs, ensuring optimal tolerability and efficacy of TAs. By reviewing the existing literature and consolidating findings, we provide insights into AE management, which is crucial for maximizing patient outcomes in CLL therapy.

BTK inhibitors in CLL: second-generation drugs and beyond

ABSTRACT

BTK inhibitors (BTKis) are established standards of care in multiple B-cell malignancies including chronic lymphocytic leukemia, mantle cell lymphoma, and Waldenstrom macroglobulinemia. The first-generation BTKi ibrutinib demonstrated superiority over standard chemoimmunotherapy regimens in multiple randomized trials but is limited by cardiovascular side effects such as atrial fibrillation and hypertension. Second-generation BTKis have improved selectivity and demonstrate reduced rates of cardiovascular complications in 3 head-to-head ibrutinib studies. The emergence of BTK C481S mutation has led to the development of noncovalent, "reversible" BTKis, such as pirtobrutinib, which are agnostic to the C481S mutation. However, these inhibitors are associated with resistant mutations outside the C481 hot spot. These variant non-C481 mutations are of great clinical interest because some are shared among pirtobrutinib, zanubrutinib, and acalabrutinib, with potential implications for cross resistance and treatment sequencing. Finally, BTK protein degraders with in vitro activity against C481 and non-C481 mutations are currently in clinical development. Here, we review the evolution of therapeutic BTK-targeting and discuss future directions for clinical research.

Ibrutinib-induced pulmonary angiotensin-converting enzyme activation promotes atrial fibrillation in rats

The molecular mechanism of ibrutinib-induced atrial fibrillation (AF) remains unclear. We here demonstrate that treating rats with ibrutinib for 4 weeks resulted in the development of inducible AF, left atrial enlargement, atrial fibrosis, and downregulation of connexin expression, which were associated with C-terminal Src kinase (CSK) inhibition and Src activation. Ibrutinib upregulated angiotensin-converting enzyme (ACE) protein expression in human pulmonary microvascular endothelial cells (HPMECs) by inhibiting the PI3K-AKT pathway, subsequently increasing circulating angiotensin II (Ang II) levels. However, the expression of ACE and Ang II in the left atria was not affected. Importantly, we observed that perindopril significantly mitigated ibrutinib-induced left atrial remodeling and AF promotion by inhibiting the activation of the ACE and its downstream CSK-Src signaling pathway. These findings indicate that the Ibrutinib-induced activation of the ACE contributes to AF development and could serve as a novel target for potential prevention strategies.

Bleeding risk with concurrent use of anticoagulants and ibrutinib: A population-based nested case-control study

Data regarding the safety of co-administration of ibrutinib with anticoagulants in real-life settings are scarce. Using a nationwide database, we conducted a nested case-control study in a cohort of new users of ibrutinib to assess the risk of clinically relevant bleeding (CRB) associated with anticoagulation. Cases were patients with a diagnosis of CRB, defined as hospitalization with a diagnosis of bleeding. The date of CRB constituted the index date. Up to four controls were matched on sex, age at index date and duration of follow-up. The risk of CRB associated with anticoagulation in patients receiving ibrutinib was estimated using conditional logistic regression models, providing odds ratios (OR) adjusted for risk factors of bleeding. Among 614 cases and 2407 matched controls, the risk of CRB was significantly higher in patients receiving both ibrutinib and anticoagulants (adjusted OR [aOR] 2.54, confidence interval [CI] 95% [1.94; 3.32]). When considering anticoagulant class, aOR was 1.99 (CI 95% [1.19; 3.33]) for VKA, 2.48 (CI 95% [1.76; 3.47]) for direct oral anticoagulants and 3.40 (CI 95% [2.01; 5.75]) for parenteral anticoagulants. In conclusion, this study found a 2.5-fold increased risk of CRB in patients receiving both ibrutinib and anticoagulants in real-life settings, and similar aOR among oral anticoagulants.

Current concepts and novel targets for antiplatelet therapy

Platelets have a crucial role in haemostasis and atherothrombosis. Pharmacological control of platelet hyper-reactivity has become a cornerstone in the prevention of thrombo-ischaemic complications in atherosclerotic diseases. Current antiplatelet therapies substantially improve clinical outcomes in patients with coronary artery disease, but at the cost of increased risk of bleeding. Beyond their role in thrombosis, platelets are known to regulate inflammatory (thrombo-inflammatory) and microcirculatory pathways. Therefore, controlling platelet hyper-reactivity might have implications for both tissue inflammation (myocardial ischaemia) and vascular inflammation (vulnerable plaque formation) to prevent atherosclerosis. In this Review, we summarize the pathophysiological role of platelets in acute myocardial ischaemia, vascular inflammation and atherosclerotic progression. Furthermore, we highlight current clinical concepts of antiplatelet therapy that have contributed to improving patient care and have facilitated more individualized therapy. Finally, we discuss novel therapeutic targets and compounds for antiplatelet therapy that are currently in preclinical development, some of which have a more favourable safety profile than currently approved drugs with regard to bleeding risk. These novel antiplatelet targets might offer new strategies to treat cardiovascular disease.

Incidence of major bleeding in patients with chronic lymphocytic leukemia receiving ibrutinib and therapeutic anticoagulation

Increased rates of clinically significant bleeding have been reported with ibrutinib, however, limited data is available on the risk when given with concomitant therapeutic anticoagulation. We analyzed the incidence of major bleeding in 64 patient exposures that received ibrutinib with concomitant therapeutic anticoagulation. Major bleeding was observed in 5/64 (8%) patient exposures. The highest incidence was observed with rivaroxaban (3/17, 18%), followed by apixaban (2/35, 6%). No major bleeding events were seen with enoxaparin (n = 10). A total of 38% of patient exposures received a concomitant antiplatelet agent along with therapeutic anticoagulation. Among these patients, one (4%) experienced a fatal hemorrhage while taking ibrutinib, apixaban, and clopidogrel concomitantly. Our retrospective study observed a higher rate of major hemorrhage with combined DOAC with ibrutinib than historically reported with ibrutinib alone. This combination may be associated with increased risk of major bleeding and further prospective studies evaluating this risk are necessary.

Adverse effects of tyrosine kinase inhibitors in cancer therapy: pathophysiology, mechanisms and clinical management

Since their invention in the early 2000s, tyrosine kinase inhibitors (TKIs) have gained prominence as the most effective pathway-directed anti-cancer agents. TKIs have shown significant utility in the treatment of multiple hematological malignancies and solid tumors, including chronic myelogenous leukemia, non-small cell lung cancers, gastrointestinal stromal tumors, and HER2-positive breast cancers. Given their widespread applications, an increasing frequency of TKI-induced adverse effects has been reported. Although TKIs are known to affect multiple organs in the body including the lungs, liver, gastrointestinal tract, kidneys, thyroid, blood, and skin, cardiac involvement accounts for some of the most serious complications. The most frequently reported cardiovascular side effects range from hypertension, atrial fibrillation, reduced cardiac function, and heart failure to sudden death. The potential mechanisms of these side effects are unclear, leading to critical knowledge gaps in the development of effective therapy and treatment guidelines. There are limited data to infer the best clinical approaches for the early detection and therapeutic modulation of TKI-induced side effects, and universal consensus regarding various management guidelines is yet to be reached. In this state-of-the-art review, we examine multiple pre-clinical and clinical studies and curate evidence on the pathophysiology, mechanisms, and clinical management of these adverse reactions. We expect that this review will provide researchers and allied healthcare providers with the most up-to-date information on the pathophysiology, natural history, risk stratification, and management of emerging TKI-induced side effects in cancer patients.

Spleen tyrosine kinase (SYK) signals are implicated in cardio-cerebrovascular diseases

Post-translational modifications regulate numerous biochemical reactions and functions through covalent attachment to proteins. Phosphorylation, acetylation and ubiquitination account for over 90% of all reported post-translational modifications. As one of the tyrosine protein kinases, spleen tyrosine kinase (SYK) plays crucial roles in many pathophysiological processes and affects the pathogenesis and progression of various diseases. SYK is expressed in tissues outside the hematopoietic system, especially the heart, and is involved in the progression of various cardio-cerebrovascular diseases, such as atherosclerosis, heart failure, diabetic cardiomyopathy, stroke and others. Knowledge on the role of SYK in the progress of cardio-cerebrovascular diseases is accumulating, and many related mechanisms have been discovered and validated. This review summarizes the role of SYK in the progression of various cardio-cerebrovascular diseases, and aims to provide a theoretical basis for future experimental and clinical research targeting SYK as a therapeutic option for these diseases.

Ibrutinib Is Associated With Increased Cardiovascular Events and Major Bleeding in Older CLL Patients

Background

Early ibrutinib trials showed an association between ibrutinib use and risk of bleeding and atrial fibrillation (AF) in younger chronic lymphocytic leukemia (CLL) patients. Little is known about these adverse events in older CLL patients and whether increased AF rates are associated with increased stroke risk.

Objectives

To compare the incidence of stroke, AF, myocardial infarction, and bleeding in CLL patients treated with ibrutinib with those who were treated without ibrutinib in a linked SEER-Medicare database.

Methods

The incidence rate of each adverse event for treated and untreated patients was calculated. Among those treated, inverse probability weighted Cox proportional hazards regression models were used to calculate HRs and 95% CIs for the association between ibrutinib treatment and each adverse event.

Results

Among 4,958 CLL patients, 50% were treated without ibrutinib and 6% received ibrutinib. The median age at first treatment was 77 (IQR: 73-83) years. Compared with those treated without ibrutinib, those treated with ibrutinib had a 1.91-fold increased risk of stroke (95% CI: 1.06-3.45), 3.65-fold increased risk of AF (95% CI: 2.42-5.49), a 4.92-fold increased risk of bleeding (95% CI: 3.46-7.01) and a 7.49-fold increased risk of major bleeding (95% CI: 4.32-12.99).

Conclusions

In patients a decade older than those in the initial clinical trials, treatment with ibrutinib was associated with an increased risk of stroke, AF, and bleeding. The risk of major bleeding is higher than previously reported and underscores the importance of surveillance registries to identify new safety signals.

The Btk inhibitor AB-95-LH34 potently inhibits atherosclerotic plaque-induced thrombus formation and platelet procoagulant activity

BACKGROUND

New antithrombotic therapies with less effect on bleeding are needed for coronary artery disease. The Btk inhibitor ibrutinib blocks atherosclerotic plaque-mediated thrombus formation. However, it is associated with increased bleeding, possibly due to non-Btk-mediated effects. Btk-deficient patients do not have bleeding issues, suggesting selective Btk inhibition as a promising antithrombotic strategy.

OBJECTIVES

To compare the antithrombotic effects of the highly selective Btk inhibitor AB-95-LH34 (LH34) with ibrutinib.

METHODS

Glycoprotein VI and G-protein coupled receptor-mediated platelet function and signaling were analyzed in healthy human donor platelets by lumi-aggregometry, flow adhesion, and western blot following 1 h treatment with inhibitors in vitro.

RESULTS

LH34 showed similar inhibition of Btk-Y223 phosphorylation as ibrutinib, but had no off-target inhibition of Src-Y418 phosphorylation. Similar dose-dependent inhibition of aggregation to atherosclerotic plaque material was observed for both. However, in response to Horm collagen, which also binds integrin α2β1, LH34 exhibited less marked inhibition than ibrutinib. Both LH34 and ibrutinib inhibited platelet adhesion and aggregation to plaque material at arterial shear. Ibrutinib demonstrated the most potent effect, with complete blockade at high concentrations. Platelet activation (P-selectin) and procoagulant activity (phosphatidylserine exposure) in thrombi were inhibited by LH34 and completely blocked by ibrutinib at high concentrations. Furthermore, plaque-induced thrombin generation was reduced by higher concentrations of LH34 and ibrutinib.

CONCLUSIONS

LH34 potently inhibits atherosclerotic plaque-induced thrombus formation and procoagulant platelet activity in vitro, with less off-target inhibition of Src than ibrutinib, suggesting it is a promising antiplatelet therapy with the potential for reduced bleeding side effects.

Adenosine 2A Receptor Activation Amplifies Ibrutinib Antiplatelet Effect; Implications in Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia patients have an increased bleeding risk with the introduction of Bruton tyrosine kinase (BTK) inhibitors. BTK is a signaling effector downstream of the platelet GPVI receptor. Innate platelet dysfunction in CLL patients and the contribution of the leukemia microenvironment to the anti-platelet effect of BTK inhibitors are still not well defined. Herein, we investigated platelet function in stable, untreated CLL patients in comparison to age-matched healthy subjects as control. Secondly, we proposed a novel mechanism of platelet dysfunction via the adenosinergic pathway during BTK inhibitor therapy. Our data indicate that the nucleotidase that produces adenosine, CD73, was expressed on one-third of B-cells in CLL patients. Inhibition of CD73 improved platelet response to ADP in the blood of CLL patients ex vivo. Using healthy platelets, we show that adenosine 2A (A2A) receptor activation amplifies the anti-platelet effect of ibrutinib (10 nM). Ibrutinib plus an A2A agonist-but not ibrutinib as a single agent-significantly inhibited collagen (10 µg/mL)-induced platelet aggregation. Mechanistically, A2A activation attenuated collagen-mediated inhibition of p-VASP and synergized with ibrutinib to inhibit the phosphorylation of AKT, ERK and SYK kinases. This manuscript highlights the potential role of adenosine generated by the microenvironment in ibrutinib-associated bleeding in CLL patients.

Risk of bleeding associated with BTK inhibitor monotherapy: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The risk of bleeding associated with Bruton's tyrosine kinase inhibitor (BTKi) monotherapy remains to be understood. This systematic review aims to evaluate BTKi monotherapy related bleeding risk.

RESEARCH DESIGN AND METHODS

PubMed, Embase, and CENTRAL were searched up to December 5, 2021. We included randomized controlled trials (RCTs) comparing BTKi monotherapy with control drugs or placebo, or comparing different BTKi monotherapies. The risk ratios (RR) with 95% confidence intervals (95% CI) were calculated.

RESULTS

10 studies with 3139 patients were included. Ibrutinib (vs. control drugs or placebo) significantly increased the risk of overall bleeding and major bleeding (RR=2.22, 95% CI 1.80-2.75, P<0.00001; RR=1.80, 95% CI 1.02-3.18, P=0.04, respectively). Acalabrutinib (vs. control drugs) had a significantly increased overall bleeding risk (RR=3.45, 95% CI 2.39-4.99, p<0.00001). A significant difference was found in overall bleeding between ibrutinib and acalabrutinib (RR=1.35, 95% CI 1.11-1.64, P=0.002). Compared to zanubrutinib, ibrutinib tended to increase the risk of major bleeding (RR=1.55, 95% CI 0.57-4.18, P=0.39).

CONCLUSIONS

Ibrutinib and acalabrutinib (vs. control drugs or placebo) have a higher risk of bleeding and overall bleeding, respectively. Limited evidence suggests that ibrutinib (vs. acalabrutinib) significantly increases overall bleeding risk, but the differences are not observed in other comparisons.

The Use of Bruton Tyrosine Kinase Inhibitors in Waldenström’s Macroglobulinemia

The use of Bruton Tyrosine Kinase (BTK) inhibitors in Waldenström’s Macroglobulinemia (WM) is evolving. Ibrutinib, a first-generation BTK inhibitor, is currently approved for use in frontline and relapsed/refractory disease. Second-generation BTK inhibitors are being used and studied to improve clinical outcomes and/or safety profile. Zanubrutinib, one such second-generation inhibitor, was recently approved in treatment-naive and refractory/relapsed patients. Here, we review the use of BTK inhibitors in WM in front-line and refractory or relapsed settings. We also highlight common adverse events, the emergence of BTK inhibitors resistance, and future directions of their use.

Cardiotoxicity of BTK inhibitors: ibrutinib and beyond

INTRODUCTION

The development of Bruton<apos;>s Tyrosine Kinase (BTK) inhibitors has transformed the treatment of B-cell malignancies and other non-malignant conditions. Management of the unique cardiotoxic profile of these agents requires prompt recognition and a multi-disciplinary approach.

AREAS COVERED

The increasing indications and addition of newer agents to clinical practice and emergence of BTK inhibitor-related cardiac adverse events have complicated the management decisions for utilization of this class of therapy. We review the incidence, mechanisms, and management approaches for BTK inhibitor-related atrial fibrillation, hypertension, and ventricular arrhythmias.

EXPERT OPINION

The newer BTK inhibitor acalabrutinib represents a new standard of care in front-line chronic lymphocytic leukemia (CLL) given the results of the ELEVATE-RR trial demonstrating comparable efficacy and a more favorable toxicity profile especially with regard to cardiac adverse events as compared to ibrutinib. Often not recognized by clinicians, BTK inhibitor-induced hypertension is common and can be severe, requiring prompt recognition and initiation or adjustment of anti-hypertensive medications to prevent major adverse cardiac outcomes. Novel BTK inhibitors in development are being designed to overcome the patterns of resistance from first-generation agents and to minimize off-target kinase activity, with promising toxicity profiles in early trials.

The Ascension of Targeted Covalent Inhibitors

Covalent drugs have made a major impact on human health but until recently were shunned by the pharmaceutical industry over concerns about the potential for toxicity. A resurgence has occurred driven by the clinical success of targeted covalent inhibitors (TCIs), with eight drugs approved over the past decade. The opportunity to create unique drugs by exploiting the covalent mechanism of action has enabled clinically decisive target product profiles to be achieved. TCIs have revolutionized the treatment paradigm for non-small-cell lung cancer and chronic lymphocytic leukemia. This Perspective will highlight the clinical and financial success of this class of drugs and provide early insight into toxicity, a key factor that had hindered progress in the field. Further innovation in the TCI approach, including expanding beyond cysteine-directed electrophiles, kinases, and cancer, highlights the broad opportunity to deliver a new generation of breakthrough therapies.

Case Report: Intraocular Hemorrhage in a Primary Vitreoretinal Lymphoma Patient Treated With Zanubrutinib

Purpose

To report a case of primary vitreoretinal lymphoma (PVRL) treated with oral zanubrutinib, who had bilateral intraocular hemorrhage after intravitreal injection of methotrexate (MTX).

Case report

A 69-year-old Chinese female presented with vision decrease in both eyes. After diagnostic vitrectomy, the patient was diagnosed as PVRL in both eyes, and was treated with intravenous rituximab, oral zanubrutinib and bilateral intravitreal MTX. There were bilateral anterior chamber and vitreous hemorrhage after the fourth intravitreal MTX combined with paracentesis. After discontinuation of zanubrutinib, vitrectomy and silicon oil tamponade were performed on the left eye, and the blood in the right eye was absorbed.

Conclusion

Bleeding is a major concern in the use of zanubrutinib. It is suggested that drugs be held for a few days prior to procedures and surgeries.

Current and Novel Antiplatelet Therapies for the Treatment of Cardiovascular Diseases

Over the last decades, antiplatelet agents, mainly aspirin and P2Y₁₂ receptor antagonists, have significantly reduced morbidity and mortality associated with arterial thrombosis. Their pharmacological characteristics, including pharmacokinetic/pharmacodynamics profiles, have been extensively studied, and a significant number of clinical trials assessing their efficacy and safety in various clinical settings have established antithrombotic efficacy. Notwithstanding, antiplatelet agents carry an inherent risk of bleeding. Given that bleeding is associated with adverse cardiovascular outcomes and mortality, there is an unmet clinical need to develop novel antiplatelet therapies that inhibit thrombosis while maintaining hemostasis. In this review, we present the currently available antiplatelet agents, with a particular focus on their targets, pharmacological characteristics, and patterns of use. We will further discuss the novel antiplatelet therapies in the pipeline, with the goal of improved clinical outcomes among patients with atherothrombotic diseases.

The CLL12 trial: Ibrutinib versus placebo in treatment-naïve, early stage chronic lymphocytic leukemia

Observation is the current standard of care for patients with early stage asymptomatic chronic lymphocytic leukemia (CLL), as chemotherapy-based interventions have failed to prolong survival. We hypothesized that early intervention with ibrutinib would be well tolerated and lead to superior disease control in a subgroup of early stage patients with CLL. The phase 3, double-blind, placebo-controlled CLL12 trial randomly assigned asymptomatic, treatment-naïve Binet stage A CLL patients at increased risk of progression in a 1:1 ratio to receive ibrutinib (N=182) or placebo (N=181) at a dose of 420 mg daily. At a median follow up of 31 months the study met its primary endpoint by significantly improving event-free survival in the ibrutinib group (median, not reached vs. 47.8 months; hazard ratio=0.25; 95% confidence interval=0.14-0.43, P<0.0001). Compared to placebo, ibrutinib did not increase overall toxicity, yielding similar incidence and severity of adverse events. The most common serious adverse events were atrial fibrillation, pneumonia and rash in the ibrutinib group, and basal cell carcinoma, pneumonia and myocardial infarction in the placebo group. Ibrutinib-associated risk for bleeding (33.5%) was decreased by prohibiting use of oral anticoagulants through an amendment of the study protocol and by avoiding CYP3A4 drug-drug interactions. Taken together, ibrutinib confirms efficacy in CLL patients at early stage with increased risk of progression. However, the results do not justify to change the current standard of 'watch and wait'. The trial is registered at clinicaltrials.gov as NCT02863718.

Cardiovascular Risk Associated With Ibrutinib Use in Chronic Lymphocytic Leukemia: A Population-Based Cohort Study

PURPOSE

Ibrutinib reduces mortality in chronic lymphocytic leukemia (CLL). It increases the risk of atrial fibrillation (AF) and bleeding and there are concerns about heart failure (HF) and central nervous system ischemic events. The magnitude of these risks remains poorly quantified.

METHODS

Using linked administrative databases, we conducted a population-based cohort study of Ontario patients who were treated for CLL diagnosed between 2007 and 2019. We matched ibrutinib-treated patients with controls treated with chemotherapy but unexposed to ibrutinib on prior AF, age ≥ 66 years, anticoagulant exposure, and propensity for receiving ibrutinib. Study outcomes were AF-related health care contact, hospital-diagnosed bleeding, new diagnoses of HF, and hospitalizations for stroke and acute myocardial infarction (AMI). The cumulative incidence function was used to estimate absolute risks. We used cause-specific regression to study the association of ibrutinib with bleeding rates, while adjusting for anticoagulation as a time-varying covariate.

RESULTS

We matched 778 pairs of ibrutinib-treated and unexposed patients with CLL (N = 1,556). The 3-year incidence of AF-related health care contact was 22.7% (95% CI, 19.0 to 26.6) in ibrutinib-treated patients and 11.7% (95% CI, 9.0 to 14.8) in controls. The 3-year risk of hospital-diagnosed bleeding was 8.8% (95% CI, 6.5 to 11.7) in ibrutinib-treated patients and 3.1% (95% CI, 1.9 to 4.6) in controls. Ibrutinib-treated patients were more likely to start anticoagulation after the index date. After adjusting for anticoagulation as a time-varying covariate, ibrutinib remained positively associated with bleeding (HR, 2.58; 95% CI, 1.76 to 3.78). The 3-year risk of HF was 7.7% (95% CI, 5.4 to 10.6%) in ibrutinib-treated patients and 3.6% (95% CI, 2.2 to 5.4) in controls. There was no significant difference in the risk of ischemic stroke or AMI.

CONCLUSION

Ibrutinib is associated with higher risk of AF, bleeding, and HF, but not AMI or stroke.

Comparison of inhibitory effects of irreversible and reversible Btk inhibitors on platelet function

All irreversible Bruton tyrosine kinase (Btk) inhibitors including ibrutinib and acalabrutinib induce platelet dysfunction and increased bleeding risk. New reversible Btk inhibitors were developed, like MK-1026. The mechanism underlying increased bleeding tendency with Btk inhibitors remains unclear. We investigated the effects of ibrutinib, acalabrutinib and MK-1026 on platelet function in healthy volunteers, patients and Btk-deficient mice, together with off-target effects on tyrosine kinase phosphorylation. All inhibitors suppressed GPVI- and CLEC-2-mediated platelet aggregation, activation and secretion in a dose-dependent manner. Only ibrutinib inhibited thrombus formation on vWF-co-coated surfaces, while on collagen this was not affected. In blood from Btk-deficient mice, collagen-induced thrombus formation under flow was reduced, but preincubation with either inhibitor was without additional effects. MK-1026 showed less off-target effects upon GPVI-induced TK phosphorylation as compared to ibrutinib and acalabrutinib. In ibrutinib-treated patients, GPVI-stimulated platelet activation, and adhesion on vWF-co-coated surfaces were inhibited, while CLEC-2 stimulation induced variable responses. The dual inhibition of GPVI and CLEC-2 signalling by Btk inhibitors might account for the increased bleeding tendency, with ibrutinib causing more high-grade bleedings due to additional inhibition of platelet-vWF interaction. As MK-1026 showed less off-target effects and only affected activation of isolated platelets, it might be promising for future treatment.

Ibrutinib plus rituximab for the treatment of adult patients with Waldenström's macroglobulinemia: a safety evaluation

Introduction: Waldenström's macroglobulinemia (WM), an orphan disease, is a rare low-grade B-cell lymphoplasmacytic lymphoma with unique clinical features and monoclonal IgM production. Rituximab remains to this date the backbone of most commonly used treatment combinations. The FDA/EMA approval of Ibrutinib, the first-in-class BTK inhibitor, either as monotherapy or in combination with rituximab, changed the treatment landscape of the disease.Areas covered: Clinical trial data that demonstrate mode of action, efficacy, and the safety profile of each agent will be covered. A safety analysis of the combination treatment will also be performed to point out its high efficacy and overall favorable toxicity profile. The disadvantages and treatment gaps that still exist in the treatment of WM which relate to the need for long-term ibrutinib administration and the lack of deep remissions and subsequent disease relapse, will also be reviewed.Expert opinion: The ibrutinib-rituximab combination is both effective and safe, in the newly-diagnosed and relapsed-refractory disease setting. The optimal therapeutic approach for WM patients remains however to be established. The question of which combinatory (or synergistic) regimen can allow for a fixed-treatment duration, deep and durable responses with a safe toxicity profile is being addressed in ongoing clinical trials.

First-Line Therapy for Chronic Lymphocytic Leukemia: Bruton Tyrosine Kinase or BCL2 or Both?

Novel therapies largely have replaced chemoimmunotherapy as optimal first-line treatment of chronic lymphocytic leukemia (CLL). Approved novel therapies for CLL in the first-line setting include Bruton tyrosine kinase inhibitors, ibrutinib and acalabrutinib, and the BCL2 inhibitor venetoclax. Each of these novel agents has its own unique attributes and they have not been compared head to head in randomized trials. This review summarizes the pivotal trials that led to the approval of novel agents and compares the features of each agent to guide treatment decisions in treatment-naïve CLL. Ongoing studies investigating combinations of novel agents in the first-line setting also are discussed.

Integrating New Therapies for Chronic Lymphocytic Leukemia

ABSTRACT

Over the last 2 decades, treatment of chronic lymphocytic leukemia (CLL) therapy has drastically changed, resulting in greatly improved survival and treatment tolerance with current targeted therapies. First, the transition from chemotherapy (alkylating agents, nucleoside analogs) to chemoimmunotherapy with the addition of anti-CD20 antibodies resulted in deeper and more complete remissions, with an improvement in progression-free and overall survival. Over the last few years, chemoimmunotherapy has gradually been replaced by new targeted agents, based on further improvement in survival, especially in patients with high-risk CLL, and fewer adverse effects, that is, a lack of myelosuppression and lack of DNA damage and associated risk of secondary acute myeloid leukemia/myelodysplastic syndrome. The most active targeted treatments for CLL patients are the kinase inhibitors, which inhibit signaling of surface receptors, especially the B-cell antigen receptor, and the BCL-2 antagonist venetoclax. Among the kinase inhibitors, Bruton tyrosine kinase inhibitors are highly effective and generally well-tolerated and induce durable responses in the vast majority of patients. PI3 kinase inhibitors are alternatives for patients with intolerance to Bruton tyrosine kinase inhibitors. This review discusses the rationale for the transition from chemotherapy-based treatment to the novel agents, the activity, adverse effects, sequencing, and combinations of the novel agents and provides an outlook into future CLL therapy for the next decade.

Vascular Impact of Cancer Therapies: The Case of BTK (Bruton Tyrosine Kinase) Inhibitors

Novel targeted cancer therapies have revolutionized oncology therapies, but these treatments can have cardiovascular complications, which include heterogeneous cardiac, metabolic, and vascular sequelae. Vascular side effects have emerged as important considerations in both cancer patients undergoing active treatment and cancer survivors. Here, we provide an overview of vascular effects of cancer therapies, focusing on small-molecule kinase inhibitors and specifically inhibitors of BTK (Bruton tyrosine kinase), which have revolutionized treatment and prognosis for B-cell malignancies. Cardiovascular side effects of BTK inhibitors include atrial fibrillation, increased risk of bleeding, and hypertension, with the former 2 especially providing a treatment challenge for the clinician. Cardiovascular complications of small-molecule kinase inhibitors can occur through either on-target (targeting intended target kinase) or off-target kinase inhibition. We will review these concepts and focus on the case of BTK inhibitors, highlight the emerging data suggesting an off-target effect that may provide insights into development of arrhythmias, specifically atrial fibrillation. We believe that cardiac and vascular sequelae of novel targeted cancer therapies can provide insights into human cardiovascular biology.

The Use of Bruton's Tyrosine Kinase Inhibitors to Treat Allergic Disorders

Purpose of review

Studies show that inhibitors of Bruton’s tyrosine kinase (BTKis), currently FDA-approved for the treatment of B cell malignancies, can prevent IgE-mediated reactions through broad inhibition of the FcεRI signaling pathway in human mast cells and basophils. This review will summarize recent data supporting the use of these drugs as novel therapies in various allergic disorders.

Recent findings

Recent studies have shown that BTKis can prevent IgE-mediated degranulation and cytokine production in primary human mast cells and basophils. Two oral doses of the second-generation BTKi acalabrutinib can completely prevent moderate passive systemic anaphylaxis in humanized mice and even protect against death during severe anaphylaxis. Furthermore, two doses of ibrutinib can reduce or eliminate skin prick test responses to foods and aeroallergens in allergic subjects. BTKis in development also show efficacy in clinical trials for chronic urticaria. Unlike other therapies targeting IgE, such as omalizumab, BTKis appear to have rapid onset and transient effects, making them ideal candidates for intermittent use to prevent acute reactions such as IgE-mediated anaphylaxis.

Summary

These studies suggest that BTKis may be capable of preventing IgE-mediated anaphylaxis, paving the way for future trials in food allergy and urticaria.

Comparison Between Venetoclax-based and Bruton Tyrosine Kinase Inhibitor-based Therapy as Upfront Treatment of Chronic Lymphocytic Leukemia (CLL): A Systematic Review and Network Meta-analysis

BACKGROUND

Available targeted agents (TAs) for the upfront therapy of chronic lymphocytic leukemia (ie, ibrutinib, acalabrutinib, venetoclax) have rarely been compared in head-to-head clinical trials. In search of data for evidence-based treatment decisions, a systematic literature review and network meta-analysis was performed.

MATERIALS AND METHODS

The screening process adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA).

RESULTS

Only 3 trials were suitable for the base-case network analysis (ILLUMINATE, ELEVATE-TN, and CLL14). Regarding progression-free survival (PFS), fixed-effect analyses comparing ibrutinib-obinutuzumab (IO) with venetoclax-obinutuzumab (VO) (relative risk [RR], 1.52; 95% confidence interval [CI], 0.82-2.81), acalabrutinib (A) with IO (RR, 0.87; 95% CI, 0.47-1.61), and A with VO (RR, 0.57; 95% CI, 0.32-1.01) revealed that the upper limit of the 95% CI for RR did exceed the 1.0 value. This indicates a lack of significant difference in PFS for IO, VO, and A. In contrast, acalabrutinib plus obinutuzumab (AO) improved PFS in comparison with IO (RR, 0.43; 95% CI, 0.22-0.87) and VO (RR, 0.29; 95% CI, 0.15-0.56). No differences in the frequency of adverse events was observed across different TAs. Also, the analysis of PFS in relationship with high-risk genetic features (ie, TP53 aberrations, IGHV unmutated, 11q deletion) showed similar results for different TAs. However, patients with unmutated IGHV status fared better with AO than with VO in terms of PFS.

CONCLUSIONS

This systematic review and network meta-analysis indicated that upfront AO prolongs PFS in comparison with IO and VO, whereas no differences are observed between IO, VO, and single-agent A. Hopefully, ongoing studies will further delineate the position of different TAs in chronic lymphocytic leukemia therapy based on effectiveness, availability, safety, cost, and treatment objectives.

Comparative Analysis of BTK Inhibitors and Mechanisms Underlying Adverse Effects

The cytoplasmic protein-tyrosine kinase BTK plays an essential role for differentiation and survival of B-lineage cells and, hence, represents a suitable drug target. The number of BTK inhibitors (BTKis) in the clinic has increased considerably and currently amounts to at least 22. First-in-class was ibrutinib, an irreversible binder forming a covalent bond to a cysteine in the catalytic region of the kinase, for which we have identified 228 active trials listed at ClinicalTrials.gov. Next-generation inhibitors, acalabrutinib and zanubrutinib, are approved both in the United States and in Europe, and zanubrutinib also in China, while tirabrutinib is currently only registered in Japan. In most cases, these compounds have been used for the treatment of B-lymphocyte tumors. However, an increasing number of trials instead addresses autoimmunity and inflammation in multiple sclerosis, rheumatoid arthritis, pemphigus and systemic lupus erythematosus with the use of either irreversibly binding inhibitors, e.g., evobrutinib and tolebrutinib, or reversibly binding inhibitors, like fenebrutinib. Adverse effects (AEs) have predominantly implicated inhibition of other kinases with a BTKi-binding cysteine in their catalytic domain. Analysis of the reported AEs suggests that ibrutinib-associated atrial fibrillation is caused by binding to ERBB2/HER2 and ERBB4/HER4. However, the binding pattern of BTKis to various additional kinases does not correlate with the common assumption that skin manifestations and diarrhoeas are off-target effects related to EGF receptor inhibition. Moreover, dermatological toxicities, diarrhoea, bleedings and invasive fungal infections often develop early after BTKi treatment initiation and subsequently subside. Conversely, cardiovascular AEs, like hypertension and various forms of heart disease, often persist.

Bleeding by Bruton Tyrosine Kinase-Inhibitors: Dependency on Drug Type and Disease

Bruton tyrosine kinase (Btk) is expressed in B-lymphocytes, myeloid cells and platelets, and Btk-inhibitors (BTKi) are used to treat patients with B-cell malignancies, developed against autoimmune diseases, have been proposed as novel antithrombotic drugs, and been tested in patients with severe COVID-19. However, mild bleeding is frequent in patients with B-cell malignancies treated with the irreversible BTKi ibrutinib and the recently approved 2nd generation BTKi acalabrutinib, zanubrutinib and tirabrutinib, and also in volunteers receiving in a phase-1 study the novel irreversible BTKi BI-705564. In contrast, no bleeding has been reported in clinical trials of other BTKi. These include the brain-penetrant irreversible tolebrutinib and evobrutinib (against multiple sclerosis), the irreversible branebrutinib, the reversible BMS-986142 and fenebrutinib (targeting rheumatoid arthritis and lupus erythematodes), and the reversible covalent rilzabrutinib (against pemphigus and immune thrombocytopenia). Remibrutinib, a novel highly selective covalent BTKi, is currently in clinical studies of autoimmune dermatological disorders. This review describes twelve BTKi approved or in clinical trials. By focusing on their pharmacological properties, targeted disease, bleeding side effects and actions on platelets it attempts to clarify the mechanisms underlying bleeding. Specific platelet function tests in blood might help to estimate the probability of bleeding of newly developed BTKi.

Current and novel BTK inhibitors in Waldenström's macroglobulinemia

The current therapeutic approach in Waldenström’s macroglobulinemia (WM) is being driven by insights in disease biology and genomic landscape. Bruton’s tyrosine kinase (BTK) plays a key role in signaling pathways for the survival of WM clone. BTK inhibition has changed the treatment landscape of the disease. Ibrutinib has resulted in deep and durable responses both as an upfront and salvage treatment with a manageable toxicity profile. However, the need for fewer off-target effects and deeper responses has resulted in the clinical development of second-generation BTK inhibitors. Zanubrutinib has resulted in clinically meaningful antitumor activity, including deep and durable responses, with a low discontinuation rate due to treatment-related toxicities. Cardiovascular adverse events seem to be milder compared with ibrutinib. Interestingly, the efficacy of zanubrutinib in WM is significant both for MYD88^L265P and MYD88^WT patients. Although the randomized, phase III ASPEN clinical trial did not meet its primary endpoint in terms of showing a superiority of zanubrutinib in deep responses compared with ibrutinib, secondary efficacy and safety endpoints underscore the potential clinical role of zanubrutinib in the treatment algorithm of WM independent of the MYD88 mutational status. Combination regimens and non-covalent BTK inhibitors are emerging as promising treatment strategies. Long-term data will determine whether next-generation BTK inhibitors are more potent and safer compared with ibrutinib, and whether they are able to overcome resistance to ibrutinib, either alone or in combination with inhibitors of other interrelated molecular pathways.

The evolving role of Bruton's tyrosine kinase inhibitors in chronic lymphocytic leukemia

Ibrutinib, the first in class of the oral covalent Bruton tyrosine kinase (BTK) inhibitors, has profoundly changed the treatment landscape of chronic lymphocytic leukemia (CLL). The phase III RESONATE and RESONATE-2 trials first demonstrated the superiority of ibrutinib over ofatumumab in the relapsed/refractory setting and over chlorambucil in older patients with de novo disease. The phase III ECOG–ACRIN trial extended these results to young, fit patients, demonstrating a significant survival advantage to ibrutinib plus rituximab over fludarabine, cyclophosphamide, and rituximab. Similarly, the Alliance trial demonstrated the superiority of ibrutinib over bendamustine with rituximab as frontline in elderly patients. Challenges with ibrutinib include toxicity, development of resistance, and need for indefinite therapy. The second generation BTK inhibitor acalabrutinib may cause less off-target toxicity. The ELEVATE TN trial demonstrated the superiority of acalabrutinib with or without obinutuzumab over chlorambucil and obinutuzumab as frontline therapy for elderly or comorbid patients. Promising early results from the phase II CAPTIVATE and CLARITY trials, which combined ibrutinib with venetoclax, suggest a future role for minimal residual disease (MRD) testing to determine treatment duration. The ongoing phase III GAIA/CLL13, ECOG EA9161, Alliance A041702, CLL17, and [ClinicalTrials.gov identifier: NCT03836261] trials will assess various combinations of ibrutinib/acalabrutinib, venetoclax, and anti-CD20 antibodies. These trials will answer key questions in the treatment of CLL: should novel agents in CLL be used in combination or sequentially? What is the best frontline agent? Can treatment be safely stopped with BTK inhibitors? Can undetectable MRD be used to determine treatment duration? In this review, we will discuss these and other aspects of the evolving role of BTK inhibition in CLL.

Management of Ibrutinib Toxicities: a Practical Guide

PURPOSE OF REVIEW

Ibrutinib is a first-in-class, highly potent Bruton tyrosine kinase inhibitor which has become standard of care for patients with chronic lymphocytic leukaemia and other lymphoproliferative disorders. It requires indefinite administration which places emphasis on toxicity and long-term tolerance.

RECENT FINDINGS

Extensive use of ibrutinib in studies and clinical practice has better defined its full toxicity profile which has made its use more challenging than initially foreseen. In particular, dysrhythmias, bleeding, infections and constitutional symptoms have been reported and can result in dose reduction or discontinuation of ibrutinib. Herein, we review the common as well as rare but important toxicities and discuss approach and management on a practical level. We also highlight that patients should be regularly monitored for adverse events and proactively treated to minimise side effects and avoid disruption.

No increased bleeding events in patients with relapsed chronic lymphocytic leukemia and indolent non-Hodgkin lymphoma treated with idelalisib

The advent of novel B-cell receptor pathway targeting agents like ibrutinib dramatically changed management of B-cell malignancies. However, with concomitant anticoagulation (AC) and antiplatelet (AP) therapy, ibrutinib is associated with increased bleeding. This post hoc analysis aimed to determine the role of AC/AP therapy in patients with idelalisib-treated B-cell malignancies and to establish if it contributes to increased bleeding events. Data from two idelalisib trials (rituximab ± idelalisib in chronic lymphocytic leukemia [CLL] and idelalisib monotherapy in indolent non-Hodgkin lymphoma [iNHL]) were analyzed. Antithrombotic therapy was common (36%-63%), with comparable bleeding incidence across treatment groups (14%-19%; p = 0.56). Bleeding events of grade ≥3 occurred in 0.9% and 3.2% of the idelalisib-treated CLL and iNHL cohorts, respectively. Our findings demonstrate no increase in bleeding events with simultaneous AC/AP treatment and idelalisib use. Hemorrhagic risk is prevalent in these patients and an important consideration when evaluating available treatment options. ClinicalTrials.gov identifiers: NCT01539512 and NCT01282424.

Effects of novel Btk and Syk inhibitors on platelet functions alone and in combination in vitro and in vivo

BACKGROUND

Inhibitors of tyrosine kinases downstream of the B-cell receptor, such as Bruton's tyrosine kinase (Btk) or Spleen tyrosine kinase (Syk), used alone or in combination are new therapeutic options in the treatment of B-cell malignancies. A challenge in the development of second-generation Btk inhibitors is to limit their side effects such as the increased bleeding risk. Considering the pivotal role of Syk in immunoreceptor tyrosine-based activation motif mediated platelet signaling, the impact of inhibiting this kinase on platelet functions is also worth analyzing.

OBJECTIVES

We investigated the effect of a novel Btk inhibitor, tirabrutinib, and a Syk inhibitor, entospletinib, alone and in combination on platelet signaling and functions in vitro and ex vivo.

METHODS

Platelet aggregation, secretion, and signaling responses as well as thrombus growth under flow were analyzed in the presence of the inhibitors alone or in combination in vitro, at clinically relevant doses, and ex vivo in patients treated with these inhibitors in the context of a phase I trial.

RESULTS

Although tirabrutinib alone had modest effects on platelet activation in vitro and ex vivo, entospletinib alone efficiently inhibited washed platelet aggregation in response to collagen. However, entospletinib weakly affected platelet activation in platelet-rich plasma, in whole blood and ex vivo. Importantly, the combination of tirabrutinib and entospletinib induced a significant decrease in platelet response to collagen in vitro and ex vivo correlating with mild bleedings reported in some of the treated patients.

CONCLUSION

These new results should contribute to improve the safety of these targeted therapies.

Risk of Bleeding Associated With Ibrutinib in Patients With B-Cell Malignancies: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background: Ibrutinib is an oral covalent Bruton's tyrosine kinase inhibitor that has been approved for chronic lymphocytic leukemia (CLL)/small lymphocytic leukemia and some other B-cell malignancies. Some studies have found an increased risk of bleeding with ibrutinib. Some studies, however, found no significant differences in the risk of major bleeding between patients treated with ibrutinib and those with other regimens. So, a systematic review and meta-analysis of randomized controlled trials (RCTs) were performed to estimate the risk of bleeding associated with ibrutinib in patients with B-cell malignancies. Methods: A systematic search of PUBMED, EMBASE, Central Register of Controlled Trials, and ClinicalTrials.gov was conducted from January 2000 to February 2020 to identify RCTs by comparing ibrutinib with other agents or placebo in B-cell malignancies. The RevMan software (version 5.3) was used to carry out this analysis, and the analyzed data were represented by risk ratios (RR) and 95% confidence intervals (CI). Results: There were 11 eligible RCTs (4,288 patients). All studies reported major bleeding, and seven studies reported overall bleeding (any-grade bleeding). Ibrutinib was associated with a significantly increased risk of bleeding (overall bleeding and major bleeding) in patients with B-cell malignancies [RR = 2.56, 95% CI 1.68-3.90, p < 0.0001 and RR = 2.08, 95% CI 1.36-3.16, p = 0.0006, respectively]. The bleeding (overall bleeding and major bleeding) risk in patients with CLL was more obvious [RR = 3.08, 95% CI 2.07-4.58, p < 0.00001 and RR = 2.46, 95% CI 1.37-4.41, p = 0.003, respectively]. There were no statistically significant differences for risk of bleeding between the subgroups based on dose and treatment setting. Conclusion: Ibrutinib was associated with a significantly higher risk of bleeding (both overall bleeding and major bleeding) in patients with B-cell malignancies, especially in CLL.

Incorporating acalabrutinib, a selective next-generation Bruton tyrosine kinase inhibitor, into clinical practice for the treatment of haematological malignancies

Greater understanding of the mechanisms involved in the disease progression of haematological malignancies has led to the introduction of novel targeted therapies with reduced toxicity compared with chemotherapy-based regimens, which has expanded the treatment options for patients with mantle cell lymphoma (MCL) and chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL). Ibrutinib is a first-in-class Bruton tyrosine kinase (BTK) inhibitor indicated for the treatment of patients with CLL/SLL or relapsed/refractory MCL. However, next-generation BTK inhibitors have been developed with improved specificity and the potential to reduce the off-target toxicity observed with ibrutinib. Acalabrutinib is a highly selective, next-generation BTK inhibitor, which was granted accelerated approval by the US Food and Drug Administration in 2017 for the treatment of adult patients with MCL who have received at least one prior therapy. In November 2019, it was also granted approval for the treatment of adult patients with CLL/SLL on the basis of two phase 3 clinical trials. This review describes the current understanding of acalabrutinib according to clinical study data for the treatment of MCL and CLL/SLL and shares recommendations from our practice on how it should be used when treating patients in the clinic, including dosing, administration and management of adverse events.

Current Perspectives on Therapy for Chronic Lymphocytic Leukemia

Therapy for chronic lymphocytic leukemia has improved dramatically over the past decade with the introduction of new targeted therapies and a paradigm shift toward targeted therapies for the majority of patients. Better understanding of prognostic factors has helped tailor therapy for individual patients, and work continues to identify optimal therapy for each patient. When therapy is required, most patients will be treated with targeted therapies, either the Bruton tyrosine kinase (BTK) inhibitors ibrutinib or acalabrutinib or the BCL-2 inhibitor venetoclax in combination with obinutuzumab. Without head-to-head comparisons showing differential efficacy among these options, considerations regarding safety, patient preference, and ability to sequence therapy currently influence treatment decisions. Also, clinical trials investigating combinations of these therapies have the potential to further change the standard of care. In this review, we cover the currently available options for the frontline treatment of chronic lymphocytic leukemia (CLL) and discuss safety considerations and toxicity management with each agent as well as novel combination strategies currently under investigation.

Ibrutinib-Mediated Atrial Fibrillation Attributable to Inhibition of C-Terminal Src Kinase

BACKGROUND

Ibrutinib is a Bruton tyrosine kinase inhibitor with remarkable efficacy against B-cell cancers. Ibrutinib also increases the risk of atrial fibrillation (AF), which remains poorly understood.

METHODS

We performed electrophysiology studies on mice treated with ibrutinib to assess inducibility of AF. Chemoproteomic analysis of cardiac lysates identified candidate ibrutinib targets, which were further evaluated in genetic mouse models and additional pharmacological experiments. The pharmacovigilance database, VigiBase, was queried to determine whether drug inhibition of an identified candidate kinase was associated with increased reporting of AF.

RESULTS

We demonstrate that treatment of mice with ibrutinib for 4 weeks results in inducible AF, left atrial enlargement, myocardial fibrosis, and inflammation. This effect was reproduced in mice lacking Bruton tyrosine kinase, but not in mice treated with 4 weeks of acalabrutinib, a more specific Bruton tyrosine kinase inhibitor, demonstrating that AF is an off-target side effect. Chemoproteomic profiling identified a short list of candidate kinases that was narrowed by additional experimentation leaving CSK (C-terminal Src kinase) as the strongest candidate for ibrutinib-induced AF. Cardiac-specific Csk knockout in mice led to increased AF, left atrial enlargement, fibrosis, and inflammation, phenocopying ibrutinib treatment. Disproportionality analyses in VigiBase confirmed increased reporting of AF associated with kinase inhibitors blocking Csk versus non-Csk inhibitors, with a reporting odds ratio of 8.0 (95% CI, 7.3-8.7; P<0.0001).

CONCLUSIONS

These data identify Csk inhibition as the mechanism through which ibrutinib leads to AF. Registration: URL: https://ww.clinicaltrials.gov; Unique identifier: NCT03530215.