Ibrutinib in Chronic Lymphocytic Leukemia: Clinical Applications, Drug Resistance, and Prospects

Targeted small molecule therapy and inhibitors for lymphoma

Lymphoma, a blood tumor, has become the ninth most common cancer in the world in 2020. Targeted inhibition is one of the important treatments for lymphoma. At present, there are many kinds of targeted drugs for the treatment of lymphoma. Studies have shown that Histone deacetylase, Bruton's tyrosine kinase and phosphoinositide 3-kinase all play an important role in the occurrence and development of tumors and become important and promising inhibitory targets. This article mainly expounds the important role of these target protein in tumors, and introduces the mechanism of action, structure-activity relationship and clinical research of listed small molecule inhibitors of these targets, hoping to provide new ideas for the treatment of lymphoma.

The complexities of T-cell dysfunction in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is a B-cell malignancy characterized by profound alterations and defects in the T-cell compartment. This observation has gained renewed interest as T-cell treatment strategies, which are successfully applied in more aggressive B-cell malignancies, have yielded disappointing results in CLL. Despite ongoing efforts to understand and address the observed T-cell defects, the exact mechanisms and nature underlying this dysfunction remain largely unknown. In this review, we examine the supporting signals from T cells to CLL cells in the lymph node niche, summarize key findings on T-cell functional defects, delve into potential underlying causes, and explore novel strategies for reversing these deficiencies. Our goal is to identify strategies aimed at resolving CLL-induced T-cell dysfunction which, in the future, will enhance the efficacy of autologous T-cell-based therapies for CLL patients.

Fyn, Blk, and Lyn kinase inhibitors: A mini-review on medicinal attributes, research progress, and future insights

Fyn, Blk, and Lyn are part of a group of proteins called Src family kinases. They are crucial in controlling cell communication and their response to the growth, changes, and immune system. Blocking these proteins with inhibitors can be a way to treat diseases where these proteins are too active. The primary mode of action of these inhibitors is to inhibit the phosphorylation of Fyn, Blk, and Lyn receptors, which in turn affects how signals pass within the cells. This review shows the structural and functional aspects of Fyn, Blk, and Lyn kinases, highlighting the significance of their dysregulation in diseases such as cancer and autoimmune disorders. The discussion encompasses the design strategies, SAR analysis, and chemical characteristics of effective inhibitors, shedding light on their specificity and potency. Furthermore, it explores the progress of clinical trials of these inhibitors, emphasizing their potential therapeutic applications.

Quality by design endorsed fabrication of Ibrutinib-loaded human serum albumin nanoparticles for the management of leukemia

Ibrutinib (IB), a BCS class II drug suffers from limited aqueous solubility, short half-life and extensive first-pass metabolism. In this project, we aim to recruit the desirable properties of human serum albumin (HSA) as a biocompatible drug carrier to circumvent nanoparticle-associated drawbacks. Quality by design and multivariate analysis was used for the optimization of IB-NPs. Cell culture studies performed on the K562 cell line revealed that the Ibrutinib-loaded HSA NPs demonstrated improved cytotoxicity, drug uptake, and reactive oxygen species generation in the leukemic K562 cells. Cell cycle analysis revealed G2/M phase retention of the leukemia cells. In vitro protein corona and hemolysis studies revealed superior hematological stability compared to the free drug which showed greater than 40 % hemolysis. In vitro drug release studies showed prolonged release profile till 48 h. Pharmacokinetic studies demonstrated a 2.31-fold increase in AUC and an increase in half-life from 0.43 h to 2.887 h with a tremendous reduction in clearance and elimination rate indicating prolonged systemic circulation which is desirable in leukemia. Hence, we conclude that IB-loaded albumin nanoparticles could be a promising approach for the management of leukemia.

Recent research of BTK inhibitors: Methods of structural design, pharmacological activities, manmade derivatives and structure-activity relationship

Protein kinases constitute the largest group within the kinase family, and mutations and translocations of protein kinases due to genetic alterations are intimately linked to the pathogenesis of numerous diseases. Bruton's tyrosine kinase (BTK) is a member of the protein kinases and plays a pivotal role in the development and function of B cells. BTK belongs to the tyrosine TEC family. The aberrant activation of BTK is closely associated with the pathogenesis of B-cell lymphoma. Consequently, BTK has always been a critical target for treating hematological malignancies. To date, two generations of small-molecule covalent irreversible BTK inhibitors have been employed to treat malignant B-cell tumors, and have exhibited clinical efficacy in hitherto refractory diseases. However, these drugs are covalent BTK inhibitors, which inevitably lead to drug resistance after prolonged use, resulting in poor tolerance in patients. The third-generation non-covalent BTK inhibitor Pirtobrutinib has obtained approval for marketing in the United States, thereby circumventing drug resistance caused by C481 mutation. Currently, enhancing safety and tolerance constitutes the primary issue in developing novel BTK inhibitors. This article systematically summarizes recently discovered covalent and non-covalent BTK inhibitors and classifies them according to their structures. This article also provides a detailed discussion of binding modes, structural features, pharmacological activities, advantages and limitations of typical compounds within each structure type, providing valuable references and insights for developing safer, more effective and more targeted BTK inhibitors in future studies.

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.

Exploring the significance of PAK1 through chromosome conformation signatures in ibrutinib-resistant chronic lymphocytic leukaemia

Ibrutinib exerts promising anticancer effects in chronic lymphocytic leukaemia (CLL). However, acquired resistance occurs during treatment, necessitating the exploration of underlying mechanisms. Although three‐dimensional genome organization has been identified as a major player in the development and progression of cancer, including drug resistance, little is known regarding its role in CLL. Therefore, we investigated the molecular mechanisms underlying ibrutinib resistance through multi‐omics analysis, including high‐throughput chromosome conformation capture (Hi‐C) technology. We demonstrated that the therapeutic response to ibrutinib is associated with the expression of p21‐activated kinase 1 (PAK1). PAK1, which was up‐regulated in CLL and associated with patients' survival, was involved in cell proliferation, glycolysis and oxidative phosphorylation. Furthermore, the PAK1 inhibitor IPA‐3 exerted an anti‐tumour effect and its combination with ibrutinib exhibited a synergistic effect in ibrutinib‐sensitive and ‐resistant cells. These findings suggest the oncogenic role of PAK1 in CLL progression and drug resistance, highlighting PAK1 as a potential diagnostic marker and therapeutic target in CLL including ibrutinib‐resistant CLL.

Differential Response to Cytotoxic Drugs Explains the Dynamics of Leukemic Cell Death: Insights from Experiments and Mathematical Modeling

This study presents a framework whereby cancer chemotherapy could be improved through collaboration between mathematicians and experimentalists. Following on from our recently published model, we use A20 murine leukemic cells transfected with monomeric red fluorescent proteins cells (mCherry) to compare the simulated and experimental cytotoxicity of two Federal Drug Administration (FDA)-approved anticancer drugs, Cytarabine (Cyt) and Ibrutinib (Ibr) in an in vitro model system of Chronic Lymphocytic Leukemia (CLL). Maximum growth inhibition with Cyt (95%) was reached at an 8-fold lower drug concentration (6.25 μM) than for Ibr (97%, 50 μM). For the proposed ordinary differential equations (ODE) model, a multistep strategy was used to estimate the parameters relevant to the analysis of in vitro experiments testing the effects of different drug concentrations. The simulation results demonstrate that our model correctly predicts the effects of drugs on leukemic cells. To assess the closeness of the fit between the simulations and experimental data, RMSEs for both drugs were calculated (both RMSEs < 0.1). The numerical solutions of the model show a symmetrical dynamical evolution for two drugs with different modes of action. Simulations of the combinatorial effect of Cyt and Ibr showed that their synergism enhanced the cytotoxic effect by 40%. We suggest that this model could predict a more personalized drug dose based on the growth rate of an individual’s cancer cells.

Dual-target Janus kinase (JAK) inhibitors: Comprehensive review on the JAK-based strategies for treating solid or hematological malignancies and immune-related diseases

Janus kinases (JAKs) are the non-receptor tyrosine kinases covering JAK1, JAK2, JAK3, and TYK2 which regulate signal transductions of hematopoietic cytokines and growth factors to play essential roles in cell growth, survival, and development. Dysregulated JAK activity leading to a constitutively activated signal transducers and activators of transcription (STAT) is strongly associated with immune-related diseases and cancers. Targeting JAK to interfere the signaling of JAK/STAT pathway has achieved quite success in the treatment of these diseases. However, inadequate clinical response and serious adverse events come along by the treatment of monotherapy of JAK inhibitors. With better and deeper understanding of JAK/STAT pathway in the pathogenesis of diseases, researchers start to show huge interest in combining inhibition of JAK and other oncogenic targets to realize a broader regulation on pathological processes to block disease development and progression, which has hastened extensive research of dual JAK inhibitors over the past decades. Until now, studies of dual JAK inhibitors have added BTK, SYK, FLT3, HDAC, Src, and Aurora kinases to the overall inhibitory profile and demonstrated significant advantage and superiority over single-target inhibitors. In this review, we elucidated the possible mechanism of synergic effects caused by dual JAK inhibitors and briefly describe the development of these agents.

A Prospective Cross-Sectional Study on the Comparison of Ultrasound Assessment vs. Palpation in Chronic Lymphocytic Leukemia Patients in the Era of Targeted Therapy

Background. In IWCLL guidelines, progressive splenomegaly and lymphadenopathy are signs of active disease. In this study, we have tested the hypotheses if US could be a reliable tool for both superficial lymphnodes (SupLNs) and splenic assessment in chronic lymphocytic leukemia (CLL) patients. Methods. We enrolled N = 75 patients. SupLN and the spleen were assessed by two independent physicians (M1 and M2) by palpation and by a third physician (M3) with ultrasound sonography (US) using two different sonographers (US1 and US2). The results of M1 vs. M2 assessment, US1 vs. US2, palpation vs. US were compared. The echostructure of N = 1037 SupLN and of the spleen was also investigated. Results. The dimensions of SupLNs assessed by MD1 vs. MD2 were statistically discordant. Splenic size was concordant. There was concordance between US1 and US2 SupLN and splenic assessment. US found a higher number of pathological SupLN (Cohen’s Kappa < 0.1) than palpation, which misses remarkable-sized SupLNs. LN echostructure and splenic involvement patterns were described. Conclusions. US is a reliable, radiation-free tool useful in clinical practice to assess SupLN and splenic involvement in CLL.

Medicinal Chemistry Strategies for the Development of Bruton's Tyrosine Kinase Inhibitors against Resistance

Despite significant efficacy, one of the major limitations of small-molecule Bruton's tyrosine kinase (BTK) agents is the presence of clinically acquired resistance, which remains a major clinical challenge. This Perspective focuses on medicinal chemistry strategies for the development of BTK small-molecule inhibitors against resistance, including the structure-based design of BTK inhibitors targeting point mutations, e.g., (i) developing noncovalent inhibitors from covalent inhibitors, (ii) avoiding steric hindrance from mutated residues, (iii) making interactions with the mutated residue, (iv) modifying the solvent-accessible region, and (v) developing new scaffolds. Additionally, a comparative analysis of multi-inhibitions of BTK is presented based on cross-comparisons between 2916 unique BTK ligands and 283 other kinases that cover 7108 dual/multiple inhibitions. Finally, targeting the BTK allosteric site and uding proteolysis-targeting chimera (PROTAC) as two potential strategies are addressed briefly, while also illustrating the possibilities and challenges to find novel ligands of BTK.

The resistance mechanisms and treatment strategies of BTK inhibitors in B-cell lymphoma

Bruton's tyrosine kinase inhibitors (BTKi) have revolutionized the treatment of B‐cell lymphoma (BCL). These drugs interfere with the mechanisms underlying malignant B‐cell pathophysiology, allowing better drug response as well as low toxicity. However, these multiple mechanisms also lead to drug resistance, which compromised the treatment outcome and needs to be solved urgently. This review focuses on genomic variations (such as BTK and its downstream PCLG2 mutations as well as Del 8p, 2p+, Del 6q/8p, BIRC3, TRAF2, TRAF3, CARD11, MYD88, and CCND1 mutations) and related pathways (such as PI3K/Akt/mTOR, NF‐κB, MAPK signaling pathways, overexpression of B‐cell lymphoma 6, platelet‐derived growth factor, toll‐like receptors, and microenvironment, cancer stem cells, and exosomes) involved in cancer pathophysiology to discuss the mechanisms underlying resistance to BTKi. We have also reviewed the newly reported drug resistance mechanisms and the proposed potential treatment strategies (the next‐generation BTKi, proteolysis‐targeting chimera‐BTK, XMU‐MP‐3, PI3K‐Akt‐mTOR pathway, MYC or LYN kinase inhibitor, and other small‐molecule targeted drugs) to overcome drug resistance. The findings presented in this review lay a strong foundation for further research in this field.

Discovery of AS-1763: A Potent, Selective, Noncovalent, and Orally Available Inhibitor of Bruton's Tyrosine Kinase

Although Bruton's tyrosine kinase (BTK) has been recognized as a validated drug target for the treatment of B-cell malignances, the emergence of clinical resistance to the first-generation covalent BTK inhibitors is becoming a serious concern. As a part of our effort to develop noncovalent BTK inhibitors, a series of novel pyrrolopyrimidines was identified as noncovalent inhibitors of both the wild-type and C481S mutant BTKs. Subsequent lead optimization led to the identification of an orally available, potent, and selective BTK inhibitor 13f (AS-1763) as a next-generation noncovalent BTK inhibitor. With significant efficacies in vivo tumor xenograft models, AS-1763 has advanced to phase 1 clinical trials.

Ibrutinib reduces neutrophil infiltration, preserves neural tissue and enhances locomotor recovery in mouse contusion model of spinal cord injury

Following acute spinal cord injury (SCI), excessive recruitment of neutrophils can result in inflammation, neural tissue loss and exacerbation of neurological outcomes. Ibrutinib is a bruton's tyrosine kinase inhibitor in innate immune cells such as the neutrophils that diminishes their activation and influx to the site of injury. The present study evaluated the efficacy of ibrutinib administration in the acute phase of SCI on neural tissue preservation and locomotor recovery. Ibrutinib was delivered intravenously at 3.125 mg/kg either immediately, 12 hours after, or both immediately and 12 hours after SCI induction in adult male C57BL/6 mice. Neutrophil influx into the lesion area was evaluated 24 hours following SCI using light microscopy and immunohistochemistry methods. Animals' body weight changes were recorded, and their functional motor recovery was assessed based on the Basso mouse scale during 28 days after treatment. Finally, spinal cord lesion volume was estimated by an unbiased stereological method. While animals' weight in the control group started to increase one week after injury, it stayed unchanged in treatment groups. However, the double injection of ibrutinib led to a significantly lower body weight compared to the control group at 4 weeks post-injury. Mean neutrophil counts per visual field and the lesion volume were significantly decreased in all ibrutinib-treated groups. In addition, ibrutinib significantly improved locomotor functional recovery in all treated groups, especially in immediate and double-injection groups. Neural tissue protection and locomotor functional recovery suggest ibrutinib treatment as a potent immunotherapeutic intervention for traumatic SCI that warrants clinical testing.

Real-world Prescription Pattern, Discontinuation and Costs of Ibrutinib-Naïve Patients with Chronic Lymphocytic Leukemia: An Italian Healthcare Administrative Database Analysis

BACKGROUND AND OBJECTIVE

In order to integrate the existing and inconsistent information from clinical trials and real-world practice on chronic lymphocytic leukemia (CLL) treated with ibrutinib, this analysis aimed to describe the prescription pattern of new users of ibrutinib affected by CLL, focusing on discontinuation, severe adverse events (AEs) and change of treatment, and to assess the integrated healthcare expenditure from the Italian National Health System (INHS) perspective.

METHODS

Starting from the ReS database, adults with at least a supply of ibrutinib (ATC code L01XE27) were selected from 01/01/2016 to 12/31/2017. Those without any ibrutinib supply in the year before the index prescription were considered new users. Out of them, only patients with at least a primary or secondary in-hospital diagnosis of CLL (ICD-9-CM code 204.1*) from 01/01/2013 to 12/31/2018 were further broken down according to the ibrutinib's line treatment (first line-FL; second or later line-SLL) and analysed. They were characterized by sex and age in the selection period. Mean annual consumption (defined daily doses [DDD]), treatment discontinuation, changes of therapy, interruptions and healthcare costs in charge of the INHS were assessed during two follow-up years.

RESULTS

Out of more than 5 million inhabitants of the ReS database, 69 new ibrutinib users and diagnosed with CLL in 2016 (incidence: 1.6 × 100,000) and 41 in 2017 (incidence: 0.9 × 100,000) were selected. Of these, 21 (19.1%) were FL ibrutinib users and 89 (80.9%) were SLL ones, mostly males and with mean ages (±SD) of 65 ± 14 and 70 ± 10, respectively. The mean annual consumption among FL users decreased from 222.2 DDD per patient treated to 216.0 DDD, while increased among SLL patients from 238.6 DDD to 260.1 DDD, in the first and second follow-up year, respectively. The discontinuation rate was about 40% in the first year, similarly among FL and SLL users. SLL patients discontinued more frequently (52.8% vs 20.0%) in the second year. Very few AEs were recorded. The 62.5% of FL and 55.6% of SLL users discontinuing ibrutinib in 1-year follow-up, while one SLL patient (5.3%) in the second year changed therapy. The 20.0% and 15.9% of all new users in first and second year interrupted ibrutinib. The total integrated cost of FL patients was €55,732 reducing by about €15,000, while it was €58,716 for SLL ones decreasing by €6,000, respectively, in the first and in the second year. Pharmaceuticals were the key cost driver (ibrutinib accounted for more than 77%).

CONCLUSIONS

This analysis on Italian administrative data provided results about prescription patterns of ibrutinib FL and SLL new users with CLL, focusing on discontinuation, treatment change and healthcare costs over 2-year follow-up, and contributed to improve the knowledge on this hard-to-treat disease.

Emerging small-molecule inhibitors of the Bruton's tyrosine kinase (BTK): Current development

Therapy based on Bruton's tyrosine kinase (BTK) inhibitors one of the major treatment options currently recommended for lymphoma patients. The first generation of BTK inhibitor, Ibrutinib, achieved remarkable progress in the treatment of B-cell malignancies, but still has problems with drug-resistance or off-target induced serious side effects. Therefore, numerous new BTK inhibitors were developed to address this unmet medical need. In parallel, the effect of BTK inhibitors against immune-related diseases has been evaluated in clinical trials. This review summarizes recent progress in the research and development of BTK inhibitors, with a focus on structural characteristics and structure-activity relationships. The structure-refinement process of representative pharmacophores as well as their effects on binding affinity, biological activity and pharmacokinetics profiles were analyzed. The advantages and disadvantages of reversible/irreversible BTK inhibitors and their potential implications were discussed to provide a reference for the rational design and development of novel potent BTK inhibitors.

Targeting Bruton tyrosine kinase using non-covalent inhibitors in B cell malignancies

B cell receptor (BCR) signaling is involved in the pathogenesis of B cell malignancies. Activation of BCR signaling promotes the survival and proliferation of malignant B cells. Bruton tyrosine kinase (BTK) is a key component of BCR signaling, establishing BTK as an important therapeutic target. Several covalent BTK inhibitors have shown remarkable efficacy in the treatment of B cell malignancies, especially chronic lymphocytic leukemia. However, acquired resistance to covalent BTK inhibitors is not rare in B cell malignancies. A major mechanism for the acquired resistance is the emergence of BTK cysteine 481 (C481)  mutations, which disrupt the binding of covalent BTK inhibitors. Additionally, adverse events due to the off-target inhibition of kinases other than BTK by covalent inhibitors are common. Alternative therapeutic options are needed if acquired resistance or intolerable adverse events occur. Non-covalent BTK inhibitors do not bind to C481, therefore providing a potentially effective option to patients with B cell malignancies, including those who have developed resistance to covalent BTK inhibitors. Preliminary clinical studies have suggested that non-covalent BTK inhibitors are effective and well-tolerated. In this review, we discussed the rationale for the use of non-covalent BTK inhibitors and the preclinical and clinical studies of non-covalent BTK inhibitors in B cell malignancies.