Ibrutinib-associated bleeding: pathogenesis, management and risk reduction strategies

Management of ibrutinib treatment in patients with B-cell malignancies: clinical practice in Portugal and multidisciplinary recommendations

OBJECTIVES

Ibrutinib, a potent inhibitor of the Bruton tyrosine kinase, has revolutionized the treatment of many B-cell malignancies. Ibrutinib has an established favorable toxicity profile with up to 8 years of experience in clinical trials; however, despite ibrutinib's favorable toxicity profile, dose reductions and treatment discontinuations are becoming more evident in clinical practice, particularly in the setting of specific clinical contexts and patient characteristics. This manuscript is set to provide practical recommendations on the management of patients treated with this agent in daily practice.

METHODS

A group of multidisciplinary experts from Portugal met to discuss and highlight practical recommendations, supported on both literature and clinical insights, for the management of the treatment with ibrutinib.

RESULTS/DISCUSSION

Handling of both toxicities and drug-drug interactions during ibrutinib treatment poses several challenges to healthcare providers and can benefit from a multidisciplinary approach. The involvement of specialties, such as cardiology, infectiology and pharmacology, can bring an added value to patient care, not only in anticipating/managing safety issues and dose adjustments but also in enhancing adherence to treatment, ultimately improving the risk/benefit balance.

CONCLUSION

By involving a multidisciplinary group of experts, this work provides a set of key recommendations to optimize care and outcomes for ibrutinib-treated patients. Despite not being a fully comprehensive review on the topic, it is intended as a framework to hematologists and other healthcare professionals who manage these patients in their daily clinical practice.

The Toll-Like Receptor 2 Ligand Pam2CSK4 Activates Platelet Nuclear Factor-κB and Bruton's Tyrosine Kinase Signaling to Promote Platelet-Endothelial Cell Interactions

Circulating platelets establish a variety of immunological programs and orchestrate inflammatory responses at the endothelium. Platelets express the innate immunity family of Toll-like receptors (TLRs). While TLR2/TLR1 ligands are known to activate platelets, the effects of TLR2/TLR6 ligands on platelet function remain unclear. Here, we aim to determine whether the TLR2/TLR6 agonists Pam2CSK4 and FSL-1 activate human platelets. In addition, human umbilical vein endothelial cells (HUVECs) and platelets were co-cultured to analyze the role of platelet TLR2/TLR6 on inflammation and adhesion to endothelial cells. Pam2CSK4, but not FSL-1, induced platelet granule secretion and integrin α_IIbβ₃ activation in a concentration-dependent manner. Moreover, Pam2CSK4 promoted platelet aggregation and increased platelet adhesion to collagen-coated surfaces. Mechanistic studies with blocking antibodies and pharmacologic inhibitors demonstrated that the TLR2/Nuclear factor-κB axis, Bruton’s-tyrosine kinase, and a secondary ADP feedback loop are involved in Pam2CSK4-induced platelet functional responses. Interestingly, Pam2CSK4 showed cooperation with immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling to enhance platelet activation. Finally, the presence of platelets increased inflammatory responses in HUVECs treated with Pam2CSK4, and platelets challenged with Pam2CSK4 showed increased adhesion to HUVECs under static and physiologically relevant flow conditions. Herein, we define a functional role for platelet TLR2-mediated signaling, which may represent a druggable target to dampen excessive platelet activation in thrombo-inflammatory diseases.

Clinical pharmacology and PK/PD translation of the second-generation Bruton's tyrosine kinase inhibitor, zanubrutinib

Introduction: Bruton's tyrosine kinase (BTK) inhibitors have revolutionized the treatment of B-cell lymphomas. Zanubrutinib was designed to achieve improved therapeutic concentrations and minimize off-target activities putatively accounting, in part, for the adverse effects seen with other BTK inhibitors.Areas covered: This drug profile covers zanubrutinib clinical pharmacology and the translation of pharmacokinetics (PK) and pharmacodynamics (PD) to clinical efficacy and safety profiles, by highlighting key differences between zanubrutinib and other BTK inhibitors. We discuss PK, sustained BTK occupancy, and potential factors affecting PK of zanubrutinib, including food effects, hepatic impairment, and drug-drug interactions. These data, along with exposure-response analyses, were used to support the recommended dose of 320 mg, either once daily or as 160 mg twice daily. Translation of PK/PD attributes into clinical effects was demonstrated in a randomized, phase 3 head-to-head study comparing it with ibrutinib in patients with Waldenström macroglobulinemia.Expert opinion: Among the approved BTK inhibitors, zanubrutinib is less prone to PK modulation by intrinsic and extrinsic factors, leading to more consistent, sustained therapeutic exposures and improved dosing convenience. Zanubrutinib PK/PD has translated into durable responses and improved safety, representing an important new treatment option for patients who benefit from BTK therapy.

Ibrutinib effect in acquired von Willebrand syndrome secondary to Waldenström macroglobulinemia

The pathological increase of clonal IgM in Waldenström macroglobulinemia can be associated with acquired von Willebrand syndrome and can be a major risk of bleeding symptoms in this subgroup of patients with Waldenström macroglobulinemia. The Bruton tyrosine kinase inhibitor ibrutinib is one of the approved treatments for symptomatic Waldenström macroglobulinemia. However, some controversy exists regarding the use of ibrutinib in these patients with high risk of bleeding because of its antiaggregant effect that could increase the risk of bleeding. Here, we present the case of a patient with Waldenström macroglobulinemia with associated acquired von Willebrand syndrome and progressively significant bleeding symptoms, who experienced a rapid increase in von Willebrand factor with ibrutinib treatment, despite only reaching a partial response in IgM levels similar to those reached with other previous treatments. We suggest that the control over the monoclonal protein is not the only mechanism that explains the good response, improvement in the bleeding symptoms and von Willebrand factor levels. This fact could be explained by the reduced glycoprotein Ib receptor expression induced by ibrutinib and the consequent von Willebrand factor increase in peripheral blood.

Neurologic complications in patients with lymphoid cancer

Neurologic complications of lymphoid cancer can be challenging to recognize and treat. The nervous system can be affected directly by hematogenous or local spread of lymphoma. Indirect neurologic effects of lymphoma include paraneoplastic syndromes and vascular complications. Lymphoma treatments can also cause neurologic complications. Early identification and treatment are crucial to stabilize or reverse neurologic deficits, prevent further nervous system injury, and to optimize overall oncologic therapy. This article provides an overview of different neurologic complications of lymphoma and its treatments, in addition to presentation of case studies that emphasize commonly encountered clinical scenarios.

Ibrutinib in patients with atrial fibrillation - the challenge of thromboembolic prophylaxis

Ibrutinib is a novel drug used in haematological malignancies. Its use is associated with an increased risk of atrial fibrillation (AF), which, in turn, exposes patients to embolic risk, including stroke. Reducing this risk requires anticoagulant therapy which is a matter of concern in the context of the increased bleeding risk of patients with haematological malignancies. In this context the presence of thrombocytopenia related to haematological disorder, ibrutinib-anticoagulants and ibrutinib-platelets interactions contribute to the amplification of the problem. The correct assessment of the thrombosis vs. haemorrhage balance represents a significant challenge for the clinician. In this paper we discuss practical issues related to anticoagulation in patients treated with ibrutinib and incident AF.

Bruton's tyrosine kinase Inhibitors and Cardiotoxicity: More Than Just Atrial Fibrillation

Purpose of Review

The purpose of this review is to summarize the epidemiology, mechanisms, and management of cardiovascular complications of Bruton’s Tyrosine Kinase inhibitors (BTKIs).

Recent Findings

Ibrutinib increases the risk of atrial fibrillation, bleeding, and hypertension compared with non-BTKI therapies. The evidence to support an association between ibrutinib and other cardiovascular complications including ventricular tachyarrhythmias or cardiomyopathy is limited. Ibrutinib metabolism can be inhibited by some medications used to treat cardiovascular complications. The cardiovascular effects of more selective BTKIs, such as acalabrutinib, remain to be determined.

Summary

Future research should address the mechanisms underlying the cardiovascular complications of BTKIs and how best to manage them. The risks and benefits of more selective BTKIs as compared with ibrutinib require further evaluation.

Characteristics and outcomes of patients on concurrent direct oral anticoagulants and targeted anticancer therapies-TacDOAC registry: Communication from the ISTH SSC Subcommittee on Hemostasis and Malignancy

BACKGROUND

Cancer patients are increasingly prescribed direct oral anticoagulants (DOACs) and targeted anticancer therapies, but limited data are available on the outcomes during concurrent use.

OBJECTIVES

We conducted an international registry through the Scientific and Standardization Committee of the ISTH to evaluate the characteristics, bleeding, and thrombotic outcomes in patients receiving concurrent DOACs and targeted anticancer therapies.

PATIENTS/METHODS

Patients receiving concurrent DOACs for venous thromboembolism (VTE) or atrial fibrillation and selected targeted anticancer therapies were followed for 6 months after the start of concurrent use. Data including patient and cancer characteristics, major bleeding, non-major bleeding events, and venous or arterial thromboses were collected.

RESULTS

Two hundred and two patients were included from six institutions in the United States and Israel. The most common malignancies were hematologic (N = 57, 28.2%), followed by breast (N = 50, 24.8%) and lung (N = 44, 21.8%). The most common anticancer therapies were epidermal growth factor receptor (EGFR) and anaplastic lymphoma kinase (ALK) inhibitors (N = 43, 21.3%), followed by Bruton's tyrosine kinase (BTK) inhibitors (N = 42, 20.8%) and palbociclib (N = 42, 20.8%). During follow-up, there were 9 major bleeding and 12 non-major bleeding events, corresponding to cumulative incidences of 4% (95% confidence interval [CI]: 2-8%) and 6% (95% CI: 3-10%), respectively. The cumulative incidence of major bleeding events was highest in BTK inhibitor users (10%). There were 3 VTE and 2 arterial thromboses, corresponding to cumulative incidences of 1.5% (95% CI: 0.4-4.0%) and 1.0% (95% CI: 0.2-3.3%), respectively.

CONCLUSIONS

In this cohort receiving concurrent DOACs and targeted anticancer therapies, the incidence of bleeding is higher compared to thrombosis, particularly with BTK inhibitors. Future larger prospective studies are needed.

Single, Dual, and Triple Antithrombotic Therapy in Cancer Patients with Coronary Artery Disease: Searching for Evidence and Personalized Approaches

Improvement in life expectancy of patients suffering from oncohematologic disorders has turned cancer from an acute into a chronic condition, making the management of comorbidities problematic, especially when it comes to both acute and chronic cardiovascular diseases. Treatment-related adverse events and drug-drug interactions often influence the therapeutic approach of patients with active malignancies and cardiovascular disease. Furthermore, tumor cells and platelets maintain a complex crosstalk that on one hand enhances tumor dissemination and on the other hand induces hemostasis abnormalities. Hence, clinicians should move carefully in the intricate land mines established by patients with active cancer under antithrombotic therapy. To date, there is no consensus on the antithrombotic treatment of patients with cardiovascular diseases and concomitant malignancies. The aim of this review is to collect the available scientific evidence, including the latest clinical trials and guidelines, in order to provide guidance on the management of antithrombotic treatment (both antiplatelet and anticoagulant therapy) in cancer patients with either pre-existent or new-onset coronary artery disease. Randomized-controlled trials on antithrombotic treatment in oncologic populations, which by far have thus far been excluded, have to be promoted to supply recommendations in the oncohematologic setting.

Palliative Chemotherapy and the Surgical Oncologist

Outcomes are improving for patients with advanced cancer, in part because of increasing diversity and efficacy of systemic therapy, often described as "palliative chemotherapy." Patients with advanced cancer receiving systemic treatment sometimes require surgical interventions, and their cancer care teams must collaborate to optimally manage medical and surgical challenges while also considering patients' goals and values. Structured communication can overcome the inherent ambiguity of the term "palliative chemotherapy" and facilitate optimal quality of care and quality of life for patients with advanced cancer who require surgical interventions.

Reining in BTK: Interdomain Interactions and Their Importance in the Regulatory Control of BTK

Since Dr. Ogden Bruton's 1952 paper describing the first human primary immunodeficiency disease, the peripheral membrane binding signaling protein, aptly named Bruton's tyrosine kinase (BTK), has been the target of intense study. Dr. Bruton's description of agammaglobulinemia set the stage for ultimately understanding key signaling steps emanating from the B cell receptor. BTK is a multidomain tyrosine kinase and in the decades since Dr. Bruton's discovery it has become clear that genetic defects in the regulatory domains or the catalytic domain can lead to immunodeficiency. This finding underscores the intricate regulatory mechanisms within the BTK protein that maintain appropriate levels of signaling both in the resting B cell and during an immune challenge. In recent decades, BTK has become a target for clinical intervention in treating B cell malignancies. The survival reliance of B cell malignancies on B cell receptor signaling has allowed small molecules that target BTK to become essential tools in treating patients with hematological malignancies. The first-in-class Ibrutinib and more selective second-generation inhibitors all target the active site of the multidomain BTK protein. Therapeutic interventions targeting BTK have been successful but are plagued by resistance mutations that render drug treatment ineffective for some patients. This review will examine the molecular mechanisms that drive drug resistance, the long-range conformational effects of active site inhibitors on the BTK regulatory apparatus, and emerging opportunities to allosterically target the BTK kinase to improve therapeutic interventions using combination therapies.

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.

Aspirin and antiplatelet treatments in cancer

Platelets have been hypothesized to promote certain neoplastic malignancies; however, antiplatelet drugs are still not part of routine pharmacological cancer prevention and treatment protocols. Paracrine interactions between platelets and cancer cells have been implicated in potentiating the dissemination, survival within the circulation, and extravasation of cancer cells at distant sites of metastasis. Signals from platelets have also been suggested to confer epigenetic alterations, including upregulating oncoproteins in circulating tumor cells, and secretion of potent growth factors may play roles in promoting mitogenesis, angiogenesis, and metastatic outgrowth. Thrombocytosis remains a marker of poor prognosis in patients with solid tumors. Experimental data suggest that lowering of platelet count may reduce tumor growth and metastasis. On the basis of the mechanisms by which platelets could contribute to cancer growth and metastasis, it is conceivable that drugs reducing platelet count or platelet activation might attenuate cancer progression and improve outcomes. We will review select pharmacological approaches that inhibit platelets and may affect cancer development and propagation. We begin by presenting an overview of clinical cancer prevention and outcome studies with low-dose aspirin. We then review current nonclinical development of drugs targeted to platelet binding, activation, and count as potential mitigating agents in cancer.

Janus kinase inhibitors ruxolitinib and baricitinib impair glycoprotein-VI mediated platelet function

Several Janus kinase (JAK) inhibitors (jakinibs) have recently been approved to treat inflammatory, autoimmune and hematological conditions. Despite emerging roles for JAKs and downstream signal transducer and activator of transcription (STAT) proteins in platelets, it remains unknown whether jakinibs affect platelet function. Here, we profile platelet biochemical and physiological responses in vitro in the presence of five different clinically relevant jakinibs, including ruxolitinib, upadacitinib, oclacitinib, baricitinib and tofacitinib. Flow cytometry, microscopy and other assays found that potent JAK1/2 inhibitors baricitinib and ruxolitinib reduced platelet adhesion to collagen, as well as platelet aggregation, secretion and integrin α_IIbβ₃ activation in response to the glycoprotein VI (GPVI) agonist collagen-related peptide (CRP-XL). Western blot analysis demonstrated that jakinibs reduced Akt phosphorylation and activation following GPVI activation, where ruxolitinib and baricitinib prevented DAPP1 phosphorylation. In contrast, jakinibs had no effects on platelet responses to thrombin. Inhibitors of GPVI and JAK signaling also abrogated platelet STAT5 phosphorylation following CRP-XL stimulation. Additional pharmacologic experiments supported roles for STAT5 in platelet secretion, integrin activation and cytoskeletal responses. Together, our results demonstrate that ruxolitinib and baricitinib have inhibitory effects on platelet function in vitro and support roles for JAK/STAT5 pathways in GPVI/ITAM mediated platelet function.

Acalabrutinib: A Selective Bruton Tyrosine Kinase Inhibitor for the Treatment of B-Cell Malignancies

Bruton tyrosine kinase (BTK) is a validated target for treatment of B-cell malignancies, and oral inhibitors of BTK have emerged as a standard of care for these diseases. Acalabrutinib is a second generation, highly selective, potent, covalent BTK inhibitor that exhibits minimal off-target activity in in vitro assays, providing the potential to improve tolerability over the first-in-class BTK inhibitor, ibrutinib. Acalabrutinib was approved for the treatment of relapsed/refractory mantle cell lymphoma (MCL) and chronic lymphocytic leukemia (CLL) in the US in 2017 and 2019, respectively. Acalabrutinib is also undergoing trials for other B-cell malignancies, both as monotherapy and in combinations. In this review, we discuss results from clinical trials evaluating the efficacy and safety of acalabrutinib in patients with CLL, MCL, and Waldenstrom's macroglobulinemia. Recent phase 3 data showed that acalabrutinib improved progression-free survival (PFS) compared with rituximab plus idelalisib or rituximab plus bendamustine in patients with relapsed/refractory CLL, and acalabrutinib with or without obinutuzumab improved PFS compared with chlorambucil plus obinutuzumab in patients with treatment-naïve CLL. Overall, acalabrutinib had a tolerable safety profile, with most adverse events being grade 1/2 severity (most commonly headache and diarrhea) and a low rate of discontinuation due to adverse events.

Chronic lymphocytic leukemia and the skin: implications for the dermatologist

B-cell chronic lymphocytic leukemia (CLL) is the most prevalent leukemia in the United States, and its diagnosis can have many dermatologic implications. For one, the cutaneous manifestations of CLL include several entities, most notably leukemia cutis, eosinophilic dermatosis of hematologic malignancy, and a heightened risk of skin infections. Additionally, CLL patients are at an increased risk of secondary malignancies, most commonly of the skin. Furthermore, a number of commonly utilized treatments for CLL have cutaneous implications which should be considered in the interdisciplinary management of CLL patients. In this review, we will provide an update on the diverse cutaneous manifestations of CLL and CLL-directed therapies in order to help guide dermatologic management of this increasingly prevalent patient population.

Assessment of the effects of Syk and BTK inhibitors on GPVI-mediated platelet signaling and function

Spleen tyrosine kinase (Syk) and Bruton's tyrosine kinase (BTK) play critical roles in platelet physiology, facilitating intracellular immunoreceptor tyrosine-based activation motif (ITAM)-mediated signaling downstream of platelet glycoprotein VI (GPVI) and GPIIb/IIIa receptors. Small molecule tyrosine kinase inhibitors (TKIs) targeting Syk and BTK have been developed as antineoplastic and anti-inflammatory therapeutics and have also gained interest as antiplatelet agents. Here, we investigate the effects of 12 different Syk and BTK inhibitors on GPVI-mediated platelet signaling and function. These inhibitors include four Syk inhibitors, Bay 61-3606, R406 (fostamatinib), entospletinib, TAK-659; four irreversible BTK inhibitors, ibrutinib, acalabrutinib, ONO-4059 (tirabrutinib), AVL-292 (spebrutinib); and four reversible BTK inhibitors, CG-806, BMS-935177, BMS-986195, and fenebrutinib. In vitro, TKIs targeting Syk or BTK reduced platelet adhesion to collagen, dense granule secretion, and alpha granule secretion in response to the GPVI agonist cross-linked collagen-related peptide (CRP-XL). Similarly, these TKIs reduced the percentage of activated integrin αIIbβ3 on the platelet surface in response to CRP-XL, as determined by PAC-1 binding. Although all TKIs tested inhibited phospholipase C γ2 (PLCγ2) phosphorylation following GPVI-mediated activation, other downstream signaling events proximal to phosphoinositide 3-kinase (PI3K) and PKC were differentially affected. In addition, reversible BTK inhibitors had less pronounced effects on GPIIb/IIIa-mediated platelet spreading on fibrinogen and differentially altered the organization of PI3K around microtubules during platelets spreading on fibrinogen. Select TKIs also inhibited platelet aggregate formation on collagen under physiological flow conditions. Together, our results suggest that TKIs targeting Syk or BTK inhibit central platelet functional responses but may differentially affect protein activities and organization in critical systems downstream of Syk and BTK in platelets.

The Molecular Mechanisms of Cardiotoxicity Induced by HER2, VEGF, and Tyrosine Kinase Inhibitors: an Updated Review

AIM

In recent decades, there has been a revolutionary decrease in cancer-related mortality and an increase in survival due to the introduction of novel targeted drugs. Nevertheless, drugs targeting human epidermal growth factor receptor 2 (HER-2), angiogenesis, and other tyrosine kinases also come with unexpected cardiac side effects, including heart failure, hypertension, arterial thrombosis, and arrhythmias, and have mechanisms that are unlike those of classic chemotherapeutic agents. In addition, it is challenging to address some problems, as the existing guidelines need to be more specific, and further large-scale clinical trials and experimental studies are required to confirm the benefit of administering cardioprotective agents to patients treated with targeted therapies. Therefore, an improved understanding of cardiotoxicity becomes increasingly important to minimize the pernicious effects and maximize the beneficial effects of targeted agents.

METHODS

"Cardiotoxicity", "targeted drugs", "HER2", "trastuzumab", "angiogenesis inhibitor", "VEGF inhibitor" and "tyrosine kinase inhibitors" are used as keywords for article searches.

RESULTS

In this article, we report several targeted therapies that induce cardiotoxicity and update knowledge of the clinical evidence, molecular mechanisms, and management measures.

Novel synthetic drugs for the treatment of non-Hodgkin lymphoma

Introduction: Over the past two decades, deeper understanding of B-cell signaling pathways and other mechanisms of lymphomagenesis have yielded promising targets for novel drugs in the treatment of non-Hodgkin lymphoma.Areas covered: This article provides a comprehensive review of approved synthetic drugs targeting the BTK, PI3K, immunomodulation, proteasome, HDAC, EZH2, and nuclear export pathways in non-Hodgkin lymphoma. The review includes coverage of the pharmacology, efficacy, toxicity, and active areas of research for each drug. The authors also provide their expert perspectives on the field and their opinions for the future.Expert opinion: Although novel synthetic drugs have generally not impacted clinical practice to the same extent as immune and cellular therapies, there remains an important role for targeted drugs in the treatment of non-Hodgkin lymphoma, particularly in the relapsed setting and for patients ineligible for more intensive therapies. Clinical outcomes and tolerability may improve further with the development of newer generations of synthetic drugs and emerging combination regimens with other targeted and immune therapies.

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.

Preclinical Efficacy and Anti-Inflammatory Mechanisms of Action of the Bruton Tyrosine Kinase Inhibitor Rilzabrutinib for Immune-Mediated Disease

Bruton tyrosine kinase (BTK) is expressed in B cells and innate immune cells, acting as an essential signaling element in multiple immune cell pathways. Selective BTK inhibition has the potential to target multiple immune-mediated disease pathways. Rilzabrutinib is an oral, reversible, covalent BTK inhibitor designed for immune-mediated diseases. We examined the pharmacodynamic profile of rilzabrutinib and its preclinical mechanisms of action. In addition to potent and selective BTK enzyme and cellular activity, rilzabrutinib inhibited activation and inflammatory activities of B cells and innate cells such as macrophages, basophils, mast cells, and neutrophils, without cell death (in human and rodent assay systems). Rilzabrutinib demonstrated dose-dependent improvement of clinical scores and joint pathology in a rat model of collagen-induced arthritis and demonstrated reductions in autoantibody-mediated FcγR signaling in vitro and in vivo, with blockade of rat Arthus reaction, kidney protection in mouse Ab-induced nephritis, and reduction in platelet loss in mouse immune thrombocytopenia. Additionally, rilzabrutinib inhibited IgE-mediated, FcεR-dependent immune mechanisms in human basophils and mast cell-dependent mouse models. In canines with naturally occurring pemphigus, rilzabrutinib treatment resulted in rapid clinical improvement demonstrated by anti-inflammatory effects visible within 2 wk and all animals proceeding to complete or substantial disease control. Rilzabrutinib is characterized by reversible covalent BTK binding, long BTK residence time with low systemic exposure, and multiple mechanistic and biological effects on immune cells. Rilzabrutinib's unique characteristics and promising efficacy and safety profile support clinical development of rilzabrutinib for a broad array of immune-mediated diseases.

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.

Dabigatran in ibrutinib-treated patients with atrial fibrillation and chronic lymphocytic leukemia: experience of three cases

Ibrutinib is the first clinically approved inhibitor of Bruton's tyrosine kinase, an essential enzyme for survival and proliferation of B cells by activating the B-cell receptor-signalling pathway. Ibrutinib has been shown to be highly effective in B-cell malignancies and is recommended in current international guidelines as a first-line and/or second-line treatment of chronic lymphocytic leukemia. The drug has a favorable tolerability and safety profile but the occurrence of specific side effects (e.g. atrial fibrillation, bleeding and hypertension). If atrial fibrillation is diagnosed, anticoagulant therapy may be required. Such patients receiving concomitant anticoagulation should be followed closely. DOAC is preferred over a VKA because of the lower risk of major bleeding events and because of the favorable stroke risk--benefit profile. Of all, Dabigatran offers the availability of an antidote and shows reduced potential for CYP3A4 interactions. We report the cases relating to three patients in concomitant therapy with Ibrutinib and Dabigatran.

Monogenic Immune Diseases Provide Insights Into the Mechanisms and Treatment of Chronic Graft-Versus-Host Disease

Chronic graft-versus-host disease (GvHD) has become a leading cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT) and can burden patients with devastating and lifelong health effects. Our understanding of the pathogenic mechanisms underlying chronic GvHD remains incomplete and this lack of understanding is reflected by lack of clear therapeutic approaches to steroid refractory disease. Observations predominantly from mouse models and human correlative studies currently support a three phase model for the initiation and development of chronic GvHD: 1) early inflammation and tissue damage triggers the innate immune system. This leads to inflammatory cytokine/chemokine patterns that recruit effector immune cell populations; 2) chronic inflammation causes the loss of central and peripheral tolerance mechanisms leading to emergence of pathogenic B and T cell populations that promote autoimmune and alloimmune reactions; 3) the dysregulated immunity causes altered macrophage polarization, aberrant tissue repair leading to scarring and end organ fibrosis. This model has led to the evaluation of many new therapies aimed at limiting inflammation, targeting dysregulated signaling pathways and restoring tolerance mechanisms. However, chronic GvHD is a multisystem disease with complex clinical phenotypes and it remains unclear as to which cluster of patients will respond best to specific therapeutic strategies. However, it is possible to gain novel insights from immune-related monogenic diseases. These diseases either share common clinical manifestations, replicate steps from the three phase chronic GvHD model or serve as surrogates for perfectly targeted drugs being investigated in chronic GvHD therapy. In this review, we will summarize the evidence from these monogenic immune related diseases that provide insight into pathogenic pathways in chronic GvHD, rationales for current therapies and novel directions for future drug discovery.

High-Risk Mantle Cell Lymphoma in the Era of Novel Agents

PURPOSE OF REVIEW

Mantle cell lymphoma (MCL) is a heterogenous disease with a variety of morphologic and genetic features, some of which are associated with high risk disease. Here we critically analyze the current state of the understanding of MCL's biology and its implications in therapy, with a focus on chemotherapy-free and targeted therapy regimens.

RECENT FINDINGS

Mantle cell lymphoma (MCL) is a rare subtype of non-Hodgkin's lymphoma, defined by a hallmark chromosomal translocation t(11;14) which leads to constitutive expression of cyclin D1. Recent discoveries in the biology of MCL have identified a number of factors, including TP53 mutations and complex karyotype, that lead to unresponsiveness to traditional chemoimmunotherapy and poor outcomes. Bruton tyrosine kinase inhibitors, BH3-mimetics and other novel agents thwart survival of the neoplastic B-cells in a manner independent of high-risk mutations and have shown promising activity in relapsed/refractory MCL. These therapies are being investigated in the frontline setting, while optimal responses to chemotherapy-free regimens, particularly in high-risk disease, might require combination approaches. High-risk MCL does not respond well to chemoimmunotherapy. Targeted agents are highly active in the relapsed refractory setting and show promise in high-risk disease. Novel approaches may soon replace the current standard of care in both relapsed and frontline settings.

Multifactorial Background for a Low Biological Response to Antiplatelet Agents Used in Stroke Prevention

Effective platelet inhibition is the main goal of the antiplatelet therapy recommended as a standard treatment in the secondary prevention of non-embolic ischemic stroke. Acetylsalicylic acid (aspirin) and clopidogrel are commonly used for this purpose worldwide. A low biological response to antiplatelet agents is a phenomenon that significantly reduces the therapeutic and protective properties of the therapy. The mechanisms leading to high on-treatment platelet reactivity are still unclear and remain multifactorial. The aim of the current review is to establish the background of resistance to antiplatelet agents commonly used in the secondary prevention of ischemic stroke and to explain the possible mechanisms. The most important factors influencing the incidence of a low biological response were demonstrated. The similarities and the differences in resistance to both drugs are emphasized, which may facilitate the selection of the appropriate antiplatelet agent in relation to specific clinical conditions and comorbidities. Despite the lack of indications for the routine assessment of platelet reactivity in stroke subjects, this should be performed in selected patients from the high-risk group. Increasing the detectability of low antiaggregant responders, in light of its negative impact on the prognosis and clinical outcomes, can contribute to a more individualized approach and modification of the antiplatelet therapy to maximize the therapeutic effect in the secondary prevention of stroke.

Steroid-refractory chronic graft-versus-host disease: treatment options and patient management

Chronic graft-versus-host disease (cGVHD) is one of the major causes of late mortality after allogenic hematopoietic stem cell transplantation. Moderate-to-severe cGVHD is associated with poor health-related quality of life and substantial disease burden. While corticosteroids with or without calcineurin inhibitors comprise the first-line treatment option, the prognosis for patients with steroid-refractory cGVHD (SR-cGVHD) remains poor. The mechanisms underlying steroid resistance are unclear, and there are no standard second-line treatment guidelines for patients with SR-cGVHD. In this review, we provide an overview on current treatment options of cGVHD and use a series of theoretical case studies to elucidate the rationale of choices of second- and third-line treatment options for patients with SR-cGVHD based on individual patient profiles.

Revving the CAR - Combination strategies to enhance CAR T cell effectiveness

Chimeric antigen receptor (CAR) T cell therapy is currently approved for treatment of refractory B-cell malignancies. Response rates in these diseases are impressive by historical standards, but most patients do not have a durable response and there remains room for improvement. To date, CAR T cell activity has been even more limited in solid malignancies. These limitations are thought to be due to several pathways of resistance to CAR T cells, including cell-intrinsic mechanisms and the immunosuppressive tumor microenvironment. In this review, we discuss current experimental strategies that combine small molecules and monoclonal antibodies with CAR T cells to overcome these resistance mechanisms. We describe the biological rationale, pre-clinical data and clinical trials in progress that test the efficacy and safety of these combinations.

Effects of Ibrutinib on biophysical parameters of platelet in patients with chronic lymphocytic leukaemia

Patients with chronic lymphocytic leukemia (CLL) treated with Ibrutinib often present hemorrhagic complications. Platelets dysfunction is well documented by aggregometry and flow cytometry, but the mechanisms by which Ibrutinib treatment influences the platelets status is yet to be evaluated. The aim of this study is to identify platelet membrane parameters in chronic lymphocytic leukemia (CLL) that could be altered by Ibrutinib administration. In this paper we propose a set of fluorescence measurements of the following parameters: membrane fluidity, resting membrane potential, and reactive oxygen species production of platelets suspensions obtained from CLL patients treated or not with Ibrutinib as markers for platelets status in this pathological situation. Platelets from CLL patients treated with Ibrutinib have higher membrane fluidity, lower resting membrane potential and higher level of reactive oxygen species production compared to the untreated CLL patients. These patients are also presenting higher membrane fluidity and lower resting membrane potential compared to healthy volunteers.

Inpatient Management of Mucocutaneous GVHD

Purpose of Review

Graft-versus-host disease (GVHD) is an immune mediated disorder affecting 30 - 70% of patients after allogeneic hematopoietic stem cell transplantation (alloHSCT), and is a major cause of morbidity and non-relapse mortality (NRM) [1]. Dermatologists play a critical role in acute and chronic GVHD, as skin involvement is common and often the earliest involved site of disease [2].

Recent Findings

GVHD shares clinical and histopathological features with a variety of other skin diseases, requiring thorough consideration of differential diagnoses in hematopoietic stem cell transplantation (HSCT) recipients with lesions suggestive of cutaneous GVHD. Treatment considerations for GVHD are influenced by factors such as disease classification, overall grading, organ involvement, associated symptoms, and immunological anti-tumor effect. Several treatments are available and may be indicated as monotherapy or adjuvant therapy to allow faster withdrawal or tapering of immunosuppression. While corticosteroids are often first line therapy, oral ruxolitinib has been recently approved for treatment of steroid-refractory aGHVD, and oral ibrutinib has been approved for steroid-refractory cGHVD.

Summary

This article provides current clinical, diagnostic, and therapeutic considerations relevant to the hospitalist for both acute and chronic mucocutaneous GVHD. Optimal inpatient management of these diseases requires an interdisciplinary team.

Novel antiplatelet strategies targeting GPVI, CLEC-2 and tyrosine kinases

Antiplatelet medications comprise the cornerstone of treatment for diseases that involve arterial thrombosis, including acute coronary syndromes (ACS), stroke and peripheral arterial disease. However, antiplatelet medications may cause bleeding and, furthermore, thrombotic events may still recur despite treatment. The interaction of collagen with GPVI receptors on the surface of platelets has been identified as one of the major players in the pathophysiology of arterial thrombosis that occurs following atherosclerotic plaque rupture. Promisingly, GPVI deficiency in humans appears to have a minimal impact on bleeding. These findings together suggest that targeting platelet GPVI may provide a novel treatment strategy that provides additional antithrombotic efficacy with minimal disruption of normal hemostasis compared to conventional antiplatelet medications. CLEC-2 is gaining interest as a therapeutic target for a variety of thrombo-inflammatory disorders including deep vein thrombosis (DVT) with treatment also predicted to cause minimal disruption to hemostasis. GPVI and CLEC-2 signal through Src, Syk and Tec family tyrosine kinases, providing additional strategies for inhibiting both receptors. In this review, we summarize the evidence regarding GPVI and CLEC-2 and strategies for inhibiting these receptors to inhibit platelet recruitment and activation in thrombotic diseases.

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.

Dermatological Toxicities of Bruton's Tyrosine Kinase Inhibitors

The development of Bruton's tyrosine kinase (BTK) inhibitors represents a major breakthrough in the treatment of chronic lymphocytic leukemia and other B cell malignancies. The first-generation inhibitor ibrutinib works by covalent irreversible binding to BTK, a non-receptor tyrosine kinase of the TEC (transient erythroblastopenia of childhood) family that plays a critical role in the B-cell receptor signaling pathway. It also induces an 'off-target' inhibition of a range of other kinases including (but not limited to) epidermal growth factor receptor (EGFR), SRC, and other kinases of the TEC family (interleukin-2-inducible T-cell kinase [ITK], Tec, BMX). Dermatological toxicities are among the most common toxicities of ibrutinib, but remain of mild to moderate intensity in most cases and are readily manageable. Their incidence is highest during the first year of treatment and declines over time. In addition, it has been postulated that ibrutinib-related dermatologic adverse events are mediated by the direct binding to both BTK and other 'off-target' kinases. Bruising, ecchymoses, and petechiae represent the most characteristic dermatologic adverse events. Nail and hair changes are also common, as skin infections (opportunistic infections including herpes simplex and herpes zoster virus reactivations, and Staphylococcus aureus superinfection), folliculitis, and other types of rashes. Panniculitis, aphthous-like ulcerations with stomatitis, neutrophilic dermatosis, peripheral edema, and skin cracking can also occur. Next-generation BTK inhibitors, acalabrutinib and zanubrutinib, have been designed to optimize BTK inhibition and minimize off-target inhibition of alternative kinases (Tec, ITK, EGFR, SRC-family kinases). These drugs have been recently FDA-approved for relapsed or refractory mantle cell lymphoma. Although the overall incidence of their toxicities is expected to be more limited, acalubrutinib and zanubrutinib are associated with a range of dermatologic toxic effects that appear to be similar to those previously described with ibrutinib, including bruising and ecchymoses, panniculitis, human herpesvirus infections, cellulitis, and skin rash. In particular, both drugs induce skin bleeding events in more than 30% of patients treated. However, the available dermatological data are still rather limited and will have to be consolidated prospectively. This review article analyses the wide spectrum of dermatological toxicities that can be encountered with first- and second-generation BTK inhibitors. Finally, recommendations for appropriate treatment as well as a synthesis algorithm for management are also proposed.

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.

A randomized phase 3 trial of zanubrutinib vs ibrutinib in symptomatic Waldenström macroglobulinemia: the ASPEN study

Bruton tyrosine kinase (BTK) inhibition is an effective treatment approach for patients with Waldenström macroglobulinemia (WM). The phase 3 ASPEN study compared the efficacy and safety of ibrutinib, a first-generation BTK inhibitor, with zanubrutinib, a novel highly selective BTK inhibitor, in patients with WM. Patients with MYD88L265P disease were randomly assigned 1:1 to treatment with ibrutinib or zanubrutinib. The primary end point was the proportion of patients achieving a complete response (CR) or a very good partial response (VGPR) by independent review. Key secondary end points included major response rate (MRR), progression-free survival (PFS), duration of response (DOR), disease burden, and safety. A total of 201 patients were randomized, and 199 received ≥1 dose of study treatment. No patient achieved a CR. Twenty-nine (28%) zanubrutinib patients and 19 (19%) ibrutinib patients achieved a VGPR, a nonstatistically significant difference (P = .09). MRRs were 77% and 78%, respectively. Median DOR and PFS were not reached; 84% and 85% of ibrutinib and zanubrutinib patients were progression free at 18 months. Atrial fibrillation, contusion, diarrhea, peripheral edema, hemorrhage, muscle spasms, and pneumonia, as well as adverse events leading to treatment discontinuation, were less common among zanubrutinib recipients. Incidence of neutropenia was higher with zanubrutinib, although grade ≥3 infection rates were similar in both arms (1.2 and 1.1 events per 100 person-months). These results demonstrate that zanubrutinib and ibrutinib are highly effective in the treatment of WM, but zanubrutinib treatment was associated with a trend toward better response quality and less toxicity, particularly cardiovascular toxicity.

The safety of available chemo-free treatments for mantle cell lymphoma

INTRODUCTION

Conventional treatment for mantle cell lymphoma (MCL) patients includes regimens combining rituximab with other cytotoxic drugs, followed or not by consolidation with autologous stem cell transplantation and rituximab maintenance. However, older, unfit, and relapsed/refractory patients are often ineligible for intense treatment. Currently, available new targeted treatment options seem to offer hope in this group of patients.

AREAS COVERED

This article reviews the safety profiles of new therapeutic chemotherapy-free options for MCL patients. Publications in English from 2010 through June 2020 were surveyed on the MEDLINE database for articles. Proceedings of the American Society of Hematology during the last 5 years were also included.

EXPERT OPINION

MCL is a clinically heterogenous disease predominantly affecting elderly patients. Its variable clinical course requires personalization and individualization of treatment to achieve optimal survival and acceptable safety profiles, especially in poor prognosis patients. Results of clinical trials performed in the past decade indicated that novel drugs used as a single agent or as part of a conventional chemotherapeutic treatment offer promise in minimalizing the relapse rate for MCL and may allow more effective and safer treatment options by reducing the risk of adverse events, especially cytopenias and infections.

Oral Bruton tyrosine kinase inhibitors block activation of the platelet Fc receptor CD32a (FcγRIIA): a new option in HIT?

Activation of the platelet Fc-receptor CD32a (FcγRIIA) is an early and crucial step in the pathogenesis of heparin-induced thrombocytopenia type II (HIT) that has not been therapeutically targeted. Downstream FcγRIIA Bruton tyrosine kinase (BTK) is activated; however, its role in Fc receptor-induced platelet activation is unknown. We explored the potential to prevent FcγRIIA-induced platelet activation by BTK inhibitors (BTKi's) approved (ibrutinib, acalabrutinib) or in clinical trials (zanubrutinib [BGB-3111] and tirabrutinib [ONO/GS-4059]) for B-cell malignancies, or in trials for autoimmune diseases (evobrutinib, fenebrutinib [GDC-0853]). We found that all BTKi's blocked platelet activation in blood after FcγRIIA stimulation by antibody-mediated cross-linking (inducing platelet aggregation and secretion) or anti-CD9 antibody (inducing platelet aggregation only). The concentrations that inhibit 50% (IC50) of FcγRIIA cross-linking-induced platelet aggregation were for the irreversible BTKi's ibrutinib 0.08 µM, zanubrutinib 0.11 µM, acalabrutinib 0.38 µM, tirabrutinib 0.42 µM, evobrutinib 1.13 µM, and for the reversible BTKi fenebrutinib 0.011 µM. IC50 values for ibrutinib and acalabrutinib were four- to fivefold lower than the drug plasma concentrations in patients treated for B-cell malignancies. The BTKi's also suppressed adenosine triphosphate secretion, P-selectin expression, and platelet-neutrophil complex formation after FcγRIIA cross-linking. Moreover, platelet aggregation in donor blood stimulated by sera from HIT patients was blocked by BTKi's. A single oral intake of ibrutinib (280 mg) was sufficient for a rapid and sustained suppression of platelet FcγRIIA activation. Platelet aggregation by adenosine 5'-diphosphate, arachidonic acid, or thrombin receptor-activating peptide was not inhibited. Thus, irreversible and reversible BTKi's potently inhibit platelet activation by FcγRIIA in blood. This new rationale deserves testing in patients with HIT.

Managing Patients at Risk of Medication Related Complications Requiring Dental Extractions in Primary Care

When undertaking dental extractions in modern dental practice, two of the complications that have the potential to cause most apprehension for clinicians are the risks of osteonecrosis of the jaws and uncontrollable haemorrhage. This is especially the case when treating older patients because of the increased likelihood of co-morbidities and accompanying polypharmacy which can predispose patients to these problems. Specific medications of concern to practitioners in relation to osteonecrosis risk are antiangiogenic and antiresorptive drugs. Patients taking dual antiplatelet therapy and direct oral anticoagulants require consideration in relation to bleeding risk. With these medications coming increasingly to the forefront over recent years, guidance has been developed by organisations such as the Scottish Dental Clinical Effectiveness Programme (SDCEP). Appropriate use of these guideline should ensure that patients felt to be at particular risk of these complications can frequently be safely managed in primary care. This article aims to provide advice on recognising patients at risk, and to discuss how to utilise key messages within published guidelines when making treatment decisions. The overall intent is to help primary care clinicians who are likely to encounter these patients more and more.

Drug interactions with Bruton's tyrosine kinase inhibitors: clinical implications and management

Bruton's tyrosine kinase (BTK) plays an essential role in B-cell development, differentiation and B-cell receptor (BCR) signaling. The use of Bruton's tyrosine kinase inhibitors (BTKi) in the treatment of lymphoid malignancies has dramatically increased, owing to both impressive efficacy and ease of administration. However, BTKi have a range of drug-drug and drug-food interactions, which may alter drug efficacy and/or increase toxicity. Healthcare professionals should be aware of the probability of drug interactions with BTKi and make recommendations accordingly. In this article, we discuss the relevant drug-drug and drug-food interactions associated with ibrutinib, acalabrutinib, and zanubrutinib, and provide clinical practice recommendations for managing these interactions based on the available literature.

Ibrutinib, but not zanubrutinib, induces platelet receptor shedding of GPIb-IX-V complex and integrin αIIbβ3 in mice and humans

The Bruton's tyrosine kinase (Btk) inhibitor ibrutinib has proven to be efficacious in the treatment of B-cell chronic lymphocytic leukemia (B-CLL) and related diseases. However, a major adverse side effect of ibrutinib is bleeding, including major hemorrhages. The bleeding associated with ibrutinib use is thought to be due to a combination of on-target irreversible Btk inhibition, as well as off-target inhibition of other kinases, including EGFR, ITK, JAK3, and Tec kinase. In this study, we investigated the effects of ibrutinib vs zanubrutinib (a more selective Btk inhibitor) on platelet activation, glycoprotein expression, and thrombus formation. Ibrutinib, but not zanubrutinib, induced a time- and dose-dependent shedding of GPIb-IX complex and integrin αIIbβ3, but not of GPVI and GPV, from the platelet surface. The shedding of GPIbα and GPIX was blocked by GM6001 and TAPI-2, an ADAM17 inhibitor but not ADAM10 inhibitor. Ibrutinib but not zanubrutinib treatment of human platelets increased ADAM17 activation. Pretreatment of C57BL/6 mice with ibrutinib (10 mg/kg), but not zanubrutinib (10 mg/kg), inhibited ex vivo and in vivo thrombus growth over time. Platelets from ibrutinib-treated patients with CLL showed reduced GPIb-IX complex and integrin αIIbβ3 surface expression and reduced ex vivo thrombus formation under arterial flow, which was not observed in zanubrutinib-treated patients. In mice, ibrutinib, but not zanubrutinib, led to increased soluble GPIbα and soluble αIIb levels in plasma. These data demonstrate that ibrutinib induces shedding of GPIbα and GPIX by an ADAM17-dependent mechanism and integrin αIIbβ3 by an unknown sheddase, and this process occurs in vivo to regulate thrombus formation.

[Haemorrhagic complications following ibrutinib intake after dermatological surgery]

INTRODUCTION

Ibrutinib is a selective oral inhibitor of Bruton's tyrosine kinase. It is used in haematology to treat lymphoid B disorders. Haemorrhagic complications in dermatological surgery are occasionally associated with the use of anti-platelet and/or anticoagulant medication. Herein, we report a case of haemorrhage under ibrutinib following skin surgery.

PATIENTS AND METHODS

A 70-year-old male patient began treatment with ibrutinib for chronic lymphocytic leukaemia had 2 basal cell carcinomas of the face. The next day he had a persistent haemorrhage lasting more than 48h, with no effects on the final scarring result.

DISCUSSION

Ibrutinib is a tyrosine kinase inhibitor whose mechanism of action plays a role in platelet adhesion. It is known to cause haemorrhaging, either spontaneously or following invasive procedures, especially at the beginning of treatment. In the case of low-risk haemorrhagic procedures in which bleeding may be controlled by mechanical haemostasis, ibrutinib should be discontinued 3 days before and after surgery. In the event of recent initiation of ibrutinib and in the absence of urgent dermatological management, it is preferable to schedule any surgical procedures 3 months after the start of ibrutinib.

Adverse cardiac effects of cancer therapies: cardiotoxicity and arrhythmia

Remarkable progress has been made in the development of new therapies for cancer, dramatically changing the landscape of treatment approaches for several malignancies and continuing to increase patient survival. Accordingly, adverse effects of cancer therapies that interfere with the continuation of best-possible care, induce life-threatening risks or lead to long-term morbidity are gaining increasing importance. Cardiovascular toxic effects of cancer therapeutics and radiation therapy are the epitome of such concerns, and proper knowledge, interpretation and management are needed and have to be placed within the context of the overall care of individual patients with cancer. Furthermore, the cardiotoxicity spectrum has broadened to include myocarditis with immune checkpoint inhibitors and cardiac dysfunction in the setting of cytokine release syndrome with chimeric antigen receptor T cell therapy. An increase in the incidence of arrhythmias related to inflammation such as atrial fibrillation can also be expected, in addition to the broadening set of cancer therapeutics that can induce prolongation of the corrected QT interval. Therefore, cardiologists of today have to be familiar not only with the cardiotoxicity associated with traditional cancer therapies, such as anthracycline, trastuzumab or radiation therapy, but even more so with an ever-increasing repertoire of therapeutics. This Review provides this information, summarizing the latest developments at the juncture of cardiology, oncology and haematology.

Patterns of use and safety of ibrutinib in real-life practice

AIMS

To provide real-life data on patterns of use and safety of ibrutinib.

METHODS

A cohort study including all patients initiating ibrutinib between 21 November 2014 and 21 November 2018, and followed for 1 year was conducted. Patient characteristics, ibrutinib use and adverse drug reactions (ADRs) were collected from medical records. Kaplan-Meier analysis estimated the probability of developing ibrutinib-associated serious ADRs (SADRs) with a 95% confidence interval (CI). A Cox proportional hazards model was used to investigate factors associated with SADR occurrence.

RESULTS

In total, 102 patients were included in the study. The median age was 70.3 years (interquartile range 64.7-75.6), the male/female gender ratio was 2.9. Almost half the patients (47.1%) were prescribed ibrutinib for chronic lymphocytic leukaemia (CLL). Forty-three patients (42.1%) permanently discontinued ibrutinib in the first year, mostly for progression (51.2%) or ADRs (32.6%). Forty-eight patients (47.1%) experienced at least one ibrutinib-associated SADR. Haematological, infectious and vascular disorders were the most frequent SADRs. The probability of developing ibrutinib-associated SADR was 35.1% (95% CI 26.3-45.7%) at 3 months, 44.8% (35.2%; 55.8%) at 6 months and 54.3% (44.0%; 65.2%) at 12 months. Age ≥80 years (hazard ratio [HR] 2.03; 95% CI 1.02-4.05) and CLL (HR 1.81; 95% CI 1.01-3.25) were significantly associated with a higher risk of SADR occurrence.

CONCLUSION

This study found a high cumulative incidence of ibrutinib-associated SADRs within the first year of treatment. In view of the risk of SADR, patients aged ≥80 years or treated for CLL deserve special attention.

Progress toward a Glycoprotein VI Modulator for the Treatment of Thrombosis

Pathogenic thrombus formation accounts for the etiology of many serious conditions including myocardial infarction, stroke, deep vein thrombosis, and pulmonary embolism. Despite the development of numerous anticoagulants and antiplatelet agents, the mortality rate associated with these diseases remains high. In recent years, however, significant epidemiological evidence and clinical models have emerged to suggest that modulation of the glycoprotein VI (GPVI) platelet receptor could be harnessed as a novel antiplatelet strategy. As such, many peptidic agents have been described in the past decade, while more recent efforts have focused on the development of small molecule modulators. Herein the rationale for targeting GPVI is summarized and the published GPVI modulators are reviewed, with particular focus on small molecules. A qualitative pharmacophore hypothesis for small molecule ligands at GPVI is also presented.