Final 5-year findings from the phase 3 HELIOS study of ibrutinib plus bendamustine and rituximab in patients with relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma

Metabolic and toxicological considerations of Bruton's tyrosine kinase inhibitors for the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma

INTRODUCTION

Bruton tyrosine kinase inhibitors (BTKi) have been used for the management of human diseases since the approval of the first-in class agent, ibrutinib, by the Food and Drug Administration in 2013 for the treatment of patients with mantle cell lymphoma (MCL). Ibrutinib is a covalent inhibitor along with second-class BTKis: acalabrutinib and zanubrutinib. These well-tolerated agents have transformed the treatment landscape of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). A new class of these inhibitors, non-covalent, might become an answer to the emerging resistance by avoiding the sustained contact with the kinase binding domain.

AREAS COVERED

This article examines the chemical composition, mechanism of action, metabolic characteristics, and potential toxicity of inhibitors targeting Bruton tyrosine kinase. A comprehensive search was conducted across English-language articles in PubMed, Web of Science, and Google Scholar.

EXPERT OPINION

Bruton tyrosine kinase inhibitors have greatly enhanced the armamentarium against lymphoid malignancies including CLL/SLL. Their future lies in the choice of appropriate patients who will benefit from the treatment without significant adverse reaction. Combination chemotherapy-free fixed-duration regimens with targeted molecules will allow for MRD-driven approach in patients with CLL/SLL in the near future.

Time to next treatment in patients with chronic lymphocytic leukemia initiating first-line ibrutinib or acalabrutinib

Aim: To investigate real-world time to next treatment in patients with chronic lymphocytic leukemia initiating first-line (1L) ibrutinib or acalabrutinib. Materials & methods: US specialty pharmacy electronic medical records (21/11/2018-30/4/2022) were used; patients initiated 1L on/after 21/11/2019 (acalabrutinib approval). Results: Among 710 patients receiving ibrutinib, 5.9% initiated next treatment (mean time to initiation = 9.2 months); among 373 patients receiving acalabrutinib, 7.5% initiated next treatment (mean time to initiation = 5.9 months). Adjusting for baseline characteristics, acalabrutinib-treated patients were 89% more likely to initiate next treatment (hazard ratio = 1.89; p = 0.016). Conclusion: This study addresses a need for real-world comparative effectiveness between 1L ibrutinib and acalabrutinib and shows that next treatment (a clinically meaningful measure for real-world progression) occurred less frequently with 1L ibrutinib.

Diagnosis and Management of Cardiovascular Effects of Bruton's Tyrosine Kinase Inhibitors

PURPOSE OF REVIEW

Bruton's tyrosine kinase inhibitors (BTKis) have changed the treatment and prognosis of several B-cell malignancies. However, since the approval of the first BTKi, ibrutinib, reports of cardiovascular adverse events especially atrial fibrillation have arisen. In this review, we discuss the cardiovascular side effects of BTKis and the management of these toxicities in clinical practice.

RECENT FINDINGS

BTKIs increase the risks of atrial fibrillation, bleeding, hypertension, heart failure, and potentially ventricular arrhythmia. Newer second and third-generation BTKis appear to have a lower risk of cardiovascular adverse events; however, long-term follow-up data are not available for these new BTKis. BTKis are an effective treatment for some B-cell malignancies; however, they can cause cardiovascular side effects. The best preventive strategies to minimize cardiovascular complications remain undefined. Currently, a practical approach for managing patients receiving BTKis includes the management of cardiovascular risk factors and side effects of BTKis to prevent interruption of cancer treatment.

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

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

B-cell Receptor Pathway Mutations Are Infrequent in Patients with Chronic Lymphocytic Leukemia on Continuous Ibrutinib Therapy

PURPOSE

Acquired mutations in Bruton's tyrosine kinase (BTK) or phospholipase C-γ2 (PLCG2) genes are associated with clinical progressive disease (PD) in patients with chronic lymphocytic leukemia (CLL) treated with BTK inhibitors. Data on mutation rates in patients without PD on ibrutinib treatment are limited.

EXPERIMENTAL DESIGN

We evaluated frequency and time to detection of BTK and PLCG2 mutations in peripheral blood samples from 388 patients with previously untreated (n = 238) or relapsed/refractory (n = 150) CLL across five clinical trials.

RESULTS

With median follow-up of 35 months (range, 0-72) without PD at last sampling, mutations in BTK (3%), PLCG2 (2%), or both genes (1%) were rare in previously untreated patients. With median follow-up of 35 months (range, 1-70) without PD at last sample, mutations in BTK (30%), PLCG2 (7%), or both genes (5%) were more common in patients with relapsed/refractory CLL. Median time to first detection of BTK C481S mutation was not reached in previously untreated patients and was >5 years in patients with relapsed/refractory CLL. Among patients evaluable at PD, previously untreated patients (n = 12) had lower rates than those with relapsed/refractory disease (n = 45) of BTK (25% vs. 49%) and PLCG2 mutations (8% vs. 13%). Time from first detection of BTK C481S mutation to PD was 11.3 months in 1 previously untreated patient and median 8.5 months (range, 0-35.7) among 23 patients with relapsed/refractory CLL.

CONCLUSIONS

This systematic investigation describes development of mutations over time in patients without PD and informs the potential clinical opportunity to optimize ongoing benefits for such patients.

Measurable Residual Disease in Chronic Lymphocytic Leukemia: Current Understanding and Evolving Role in Clinical Practice

OPINION STATEMENT

Treatment of chronic lymphocytic leukemia (CLL) has evolved dramatically during the last decade, from chemoimmunotherapy (CIT)-based therapies to newer B-cell receptor (BCR) signaling targeting agents, which are sometimes given as continuous schemes. Response to treatment was traditionally defined according to clinical variables designed to assign a response category. Interest in assessing for deeper responses in CLL by the means of measurable residual disease (MRD) testing has been the subject of research during the last several years. Analyses and sub-analyses of clinical trials have shown that achieving undetectable MRD (uMRD) in CLL is an important prognostic factor. In this review, we summarize the available evidence about MRD in CLL, from the various assays available for measurement, the compartment to test, the impact of reaching uMRD according to the treatment regimen, and the results of fixed duration treatment guided by MRD trials. Finally, we summarize how MRD can be incorporated in clinical practice and how it may guide fixed duration treatment in the future should evidence continue to accumulate in that direction.

Oral formulation of bendamustine hydrochloride for patients with advanced solid tumors; a phase 1 study

To determine the maximum tolerated dose (MTD) and recommended dose (RD) of orally-administered bendamustine in Japanese patients with advanced solid tumors. The optimal dosing schedule, safety, pharmacokinetics, and preliminary antitumor effects were also evaluated. A multicenter, open-label trial with a standard 3 + 3 design and dose escalation by dose-limiting toxicity (DLT) was conducted. The treatment schedules were once daily for 7, 14, and 21 days every 3 weeks as one cycle. The total dose per cycle was increased from 175 to 840 mg/m². Eighteen patients were enrolled in this study. DLT occurred in one of six patients at 75 mg/m²/day × 7 days, and one of three patients at 37.5 mg/m²/day × 14 days and 25 mg/m²/day × 21 days. However, the delayed recovery from a decrease in neutrophil or platelet count hampered the start of subsequent treatment cycles, and the trend was more prominent at 37.5 mg/m²/day × 14 days and 25 mg/m²/day × 21 days than in 75 mg/m²/day × 7 days. MTD was determined as 75 mg/m²/day × 7 days to allow acceptable hematologic recovery. The pharmacokinetics of orally-administered bendamustine were generally dose-dependent; however, the inter-individual variability is relatively large. The major adverse events were hematologic toxicities; gastrointestinal disorders were generally mild. Adverse drug reactions did not lead to the discontinuation of the drug. A partial response was observed in two of six patients (prostatic small cell carcinoma and thymic carcinoma) at 75 mg/m²/day × 7 days. The RD and optimal dosing schedule of orally-administered bendamustine was 75 mg/m² once daily for 7 days every 3 weeks for the treatment of advanced solid tumors. (Trial registration number ClinicalTrials.gov NCT03604679. Registration date July 27, 2018).

Systematic Literature Review of Real-World Effectiveness Results Data for First-Line Ibrutinib in Chronic Lymphocytic Leukemia and Small Lymphocytic Lymphoma

BACKGROUND AND OBJECTIVE

Ibrutinib, an oral Bruton's tyrosine kinase inhibitor, has demonstrated efficacy as a first-line treatment for chronic lymphocytic leukemia in multiple, phase III, randomized clinical trials. This systematic literature review assessed the clinical effectiveness of ibrutinib in the first-line treatment of chronic lymphocytic leukemia in real-world clinical settings.

METHODS

MEDLINE, EMBASE, and relevant conference websites were searched for articles published in the USA from 1 January, 2014 to 30 June, 2020. Overall survival, progression-free survival, overall response rate, and time to next treatment were summarized.

RESULTS

This analysis included a total of 12 publications representing data from 112 to 2033 patients from community and academic centers, and the multicenter informCLL registry. Patients were predominantly male (60-99%) with a median age range from 62 to 77 years, and included those with high-risk genomic features (del[17p]: 21-33%; del[11q]: 33%; and unmutated immunoglobulin heavy chain variable gene: 59%). Real-world effectiveness with ibrutinib complemented the efficacy demonstrated in randomized clinical trials. Across various studies, the 12-month overall survival rates ranged from 95% to 96%; 18-month overall survival rates were similarly high (91%). Twelve-month progression-free survival rates ranged from 89% to 93%, and the overall response rate ranged from 71% to 90% across four studies. In the studies that reported time to next treatment, 91% and 87% of patients treated with first-line ibrutinib did not initiate new treatment at 12 months and 24 months, respectively.

CONCLUSIONS

This systematic literature review confirms the benefit of ibrutinib as a first-line treatment in patients with chronic lymphocytic leukemia in real-world clinical settings and is consistent with results from randomized clinical trials, including in patients with high-risk genomic features.

BTK inhibitors in the treatment of hematological malignancies and inflammatory diseases: mechanisms and clinical studies

Bruton's tyrosine kinase (BTK) is an essential component of multiple signaling pathways that regulate B cell and myeloid cell proliferation, survival, and functions, making it a promising therapeutic target for various B cell malignancies and inflammatory diseases. Five small molecule inhibitors have shown remarkable efficacy and have been approved to treat different types of hematological cancers, including ibrutinib, acalabrutinib, zanubrutinib, tirabrutinib, and orelabrutinib. The first-in-class agent, ibrutinib, has created a new era of chemotherapy-free treatment of B cell malignancies. Ibrutinib is so popular and became the fourth top-selling cancer drug worldwide in 2021. To reduce the off-target effects and overcome the acquired resistance of ibrutinib, significant efforts have been made in developing highly selective second- and third-generation BTK inhibitors and various combination approaches. Over the past few years, BTK inhibitors have also been repurposed for the treatment of inflammatory diseases. Promising data have been obtained from preclinical and early-phase clinical studies. In this review, we summarized current progress in applying BTK inhibitors in the treatment of hematological malignancies and inflammatory disorders, highlighting available results from clinical studies.

Selecting the optimal BTK inhibitor therapy in CLL: rationale and practical considerations

Bruton’s tyrosine kinase (BTK) inhibitors have dramatically changed the treatment of newly diagnosed and relapsed/refractory chronic lymphocytic leukemia (CLL). Ibrutinib, acalabrutinib, and zanubrutinib are Food and Drug Administration (FDA)-approved BTK inhibitors that have all demonstrated progression-free survival (PFS) benefit compared with chemoimmunotherapy. The efficacy of these agents compared to one another is under study; however, current data suggest they provide similar efficacy. Selectivity for BTK confers different adverse effect profiles, and longer follow-up and real-world use have characterized side effects over time. The choice of BTK inhibitor is largely patient-specific, and this review aims to highlight the differences among the agents and guide the choice of BTK inhibitor in clinical practice.

Bendamustine: A review of pharmacology, clinical use and immunological effects (Review)

Bendamustine is an alkylating agent classified into the group of nitrogen mustard analogues, synthesized almost sixty years ago. It was registered in former East Germany in 1971 and approved by the US Food and Drug Administration in 2008 for treatment of chronic lymphocytic leukemia and indolent B-cell non-Hodgkin lymphoma. Considering its beneficial properties in the therapy of relapsed or refractory hematological malignancies, synergistic effects with other antineoplastic agents and increasing recent reports on its immunomodulatory effects, bendamustine has once again gained its justified attention. The uniqueness of bendamustine-mediated effects should be observed keeping in mind its distinctive structure with structural similarities to both alkylating agents and purine analogs. In the present review, the current knowledge on the use of bendamustine in oncology, its pharmacokinetics, mechanism of action and toxicity was summarized. In addition, its immune-modulating effects that have not been fully elucidated so far are emphasized, hoping to encourage further investigations of this unique drug.

Managing the Risk of Infection in Chronic Lymphocytic Leukemia in the Era of New Therapies

Purpose of Review

Patients diagnosed with CLL have an increased susceptibility to infections. Over the years, there has been a shift of the treatment arsenal to an increasing use of chemotherapy-free regimens, particularly small molecule inhibitors. These therapies have proven to be effective and have a favorable toxicity profile. Infections continue to represent a significant complication in the era of novel therapies.

Recent Findings

Recent studies continue to bring new insights into the effects of modern therapies on the immune system. Evidence supporting infection prevention strategies is scarce. We will review the available recommendations to prevent infections in patients with CLL treated with novel therapies.

Summary

New CLL therapies are broadly adopted in routine practice, requiring optimization of their side effects. Timely prevention, recognition, and treatment of infections should remain an important aspect of the standard management of a patient with CLL.

Recognizing Unmet Need in the Era of Targeted Therapy for CLL/SLL: "What's Past Is Prologue" (Shakespeare)

The management of chronic lymphocytic leukemia (CLL) has undergone unprecedented changes over the last decade. Modern targeted therapies are incorporated into clinical practice. Unfortunately, patients have begun to develop resistance or intolerance to multiple classes. Symptomatic patients previously treated with a BTK inhibitor (BTKi) and venetoclax represent a new and rapidly growing unmet need in CLL. Here, we define unmet needs in a modern treatment context. We also critically review the literature for PI3K inhibitors and chemoimmunotherapy and lack of data to support their utility following BTKis and venetoclax. Finally, we suggest opportunities to ensure the continued innovation for patients with CLL.

Long-term efficacy of first-line ibrutinib treatment for chronic lymphocytic leukaemia in patients with TP53 aberrations: a pooled analysis from four clinical trials

TP53 aberrations [del(17p) or TP53 mutation] predict poor survival with chemoimmunotherapy in patients with chronic lymphocytic leukaemia (CLL). We evaluated long-term efficacy and safety of first-line ibrutinib-based therapy in patients with CLL bearing TP53 aberrations in a pooled analysis across four studies: PCYC-1122e, RESONATE-2 (PCYC-1115/16), iLLUMINATE (PCYC-1130) and ECOG-ACRIN E1912. The pooled analysis included 89 patients with TP53 aberrations receiving first-line treatment with single-agent ibrutinib (n = 45) or ibrutinib in combination with an anti-CD20 antibody (n = 44). All 89 patients had del(17p) (53% of 89 patients) and/or TP53 mutation (91% of 58 patients with TP53 sequencing results available). With a median follow-up of 49·8 months (range, 0·1-95·9), median progression-free survival was not reached. Progression-free survival rate and overall survival rate estimates at four years were 79% and 88%, respectively. Overall response rate was 93%, including complete response in 39% of patients. No new safety signals were identified in this analysis. Forty-six percent of patients remained on ibrutinib treatment at last follow-up. With median follow-up of four years (up to eight years), results from this large, pooled, multi-study data set suggest promising long-term outcomes of first-line ibrutinib-based therapy in patients with TP53 aberrations. Registered at ClinicalTrials.gov (NCT01500733, NCT01722487, NCT02264574 and NCT02048813).

Bruton Tyrosine Kinase Inhibitors in B-Cell Malignancies: Their Use and Differential Features

Starting with the first-in-class agent ibrutinib, the development of Bruton tyrosine kinase (BTK) inhibitors has led to dramatic improvements in the management of B-cell malignancies. Subsequently, more-highly selective second-generation BTK inhibitors (including acalabrutinib, zanubrutinib, tirabrutinib and orelabrutinib) have been developed, primarily with an aim to reduce off-target toxicities. More recently, third-generation agents including the non-covalent BTK inhibitors pirtobrutinib and nemtabrutinib have entered later-stage clinical development. BTK inhibitors have shown strong activity in a range of B-cell malignancies, including chronic lymphocytic leukaemia/small lymphocytic lymphoma, mantle cell lymphoma, Waldenström's macroglobulinaemia and marginal zone lymphoma. The agents have acceptable tolerability, with adverse events generally being manageable with dosage modification. This review article summarises the evidence supporting the role of BTK inhibitors in the management of B-cell malignancies, including highlighting some differential features between agents.

The road to chemotherapy-free treatment in chronic lymphocytic leukaemia

PURPOSE OF REVIEW

The treatment landscape of chronic lymphocytic leukaemia (CLL) has tremendously evolved in the last decades, from chemo to chemoimmunotherapy (CIT) and, eventually, to pathway inhibitors that target critical pathways for leukaemic cells survival. Also, treatment goals are moving towards achieving undetectable minimal residual disease with little toxicity.

RECENT FINDINGS

We performed a thorough review of the history of treatment approvals by both the Food and Drug Administration (FDA) and the European Medicines Agency (EMA). This review especially focuses on therapies that are currently approved by both agencies. The indications and particular characteristics of each drug are examined.

SUMMARY

Currently available treatment approaches for CLL offer the opportunity to individualize therapy for every single patient with CLL. Inhibitors of B-cell receptor (BCR) signalling pathways and antiapoptotic proteins are nowadays the treatment of choice for most CLL patients, but CIT can be an option for younger and fit patients with low-risk disease [mutated IGHV, no del(11q) or del(17p)/TP53 mutations].

Treatment strategies for a rapidly evolving landscape in chronic lymphocytic leukemia management

With the advent of targeted therapies for chronic lymphocytic leukemia (CLL), treatment choice has expanded and patients are living longer. Careful consideration is needed regarding treatment duration and sequence, how best to meet patients' needs, balancing toxicities while improving long-term survival and maximizing depth of response. This review addresses these considerations and discusses current targeted treatment dilemmas. Targeted therapies have dramatically transformed the CLL treatment landscape. Two treatment paradigms have emerged using B-cell lymphoma 2 inhibitors (BCL2i) and Bruton's tyrosine kinase (BTK): (i) fixed duration and (ii) continuous treatment. The BCL2i venetoclax can attain deep remissions with a fixed-duration approach, resulting in high rates of undetectable minimal residual disease (uMRD) in treatment-naïve and relapsed/refractory (R/R) patients with CLL. BTKis such as ibrutinib and acalabrutinib achieve high objective response rates and long-term disease control, although they rarely attain complete response or uMRD status as monotherapy. Numerous studies are evaluating the clinical utility of BTKi and BCL2i as combination therapies, where deep remissions have been found to occur. MRD status may also be a useful marker for deciding when to stop continuous therapy, and randomized trials on MRD-guided treatment strategies are currently ongoing. The current treatment choice between continuous or fixed-duration therapy should be based on comorbidities, risks, preferences, and treatment goals, whilst areas of emerging clinical interest include the potential utility of BTKi-BCL2i combination therapies, as well as an MRD-guided treatment strategies in the future.

The Real-World Experience With Single Agent Ibrutinib in Relapsed/Refractory CLL

INTRODUCTION/BACKGROUND

The emergence of novel agents targeting the B-cell receptor pathway and BCL-2 has significantly changed the therapeutic landscape of CLL. We evaluated the safety and efficacy of single-agent ibrutinib in relapsed/refractory CLL in real-world settings.

PATIENTS/METHODS

A total of 200 relapsed/refractory CLL patients with a median age of 68 were included in this retrospective, multicenter, non-interventional study. Data of the study were captured from the patient charts of the participating centers.

RESULTS

The median for lines of previous chemotherapy was 2 (1-6); 62 (31.8%) patients had del17p and/or p53 mutations (del17p⁺/p53mut). Of the study group, 146 (75%) patients achieved at least PR, while 16 (8.7%) patients discontinued ibrutinib due to TEA. The most common drug-related adverse events were neutropenia (n: 31; 17.4%) and thrombocytopenia (n: 40; 22.3%), which were ≥ grade 3 in 9 (5%) and 5 (3.9%) patients, respectively. Pneumonia (n: 42; 23.7%) was the most common nonhematologic TEA. Atrial fibrillation (n: 5; 2.8%) and bleeding (n: 11; 6.3%) were relatively rare during the study period. Within a median follow-up period of 17 (1-74) months, 42 (21%) patients died. The estimated median OS of the study cohort was 52 months. Only the response to ibrutinib (CR/PR vs. SD/PD) was significantly associated with OS.

CONCLUSION

Our results indicate good safety and efficacy for single-agent ibrutinib in R/R CLL in daily practice.

Autoimmune Cytopenia in CLL: Prognosis and Management in the Era of Targeted Therapies

ABSTRACT

Chronic lymphocytic leukemia (CLL) is frequently associated with autoimmune hemolytic anemia and immune thrombocytopenia and, less frequently, with pure red cell aplasia and immune neutropenia. The emergence of these complications is related to an intertwined and complex relationship between patient, disease, and treatment characteristics. The prognostic repercussion of autoimmune cytopenia (AIC) in patients with CLL mainly depends on its response to therapy. For patients with AIC and nonactive CLL, treatment is as in primary, uncomplicated AIC, keeping in mind that no response is an indication for CLL therapy. The success of treating active CLL-related AIC widely relies on a flexible strategy that should include initial therapy with corticosteroids and a rapid shift to effective CLL therapy in nonresponding patients. Targeted therapies (e.g., ibrutinib) that have already demonstrated to be effective in CLL-related AIC will likely offer a unique possibility of treating both AIC and CLL as a single target.

Targeting Bruton's Tyrosine Kinase in CLL

Targeting the B-cell receptor signaling pathway through BTK inhibition proved to be effective for the treatment of chronic lymphocytic leukemia (CLL) and other B-cell lymphomas. Covalent BTK inhibitors (BTKis) led to an unprecedented improvement in outcome in CLL, in particular for high-risk subgroups with TP53 aberration and unmutated immunoglobulin heavy-chain variable-region gene (IGHV). Ibrutinib and acalabrutinib are approved by the US Food and Drug Administration for the treatment of CLL and other B-cell lymphomas, and zanubrutinib, for patients with mantle cell lymphoma. Distinct target selectivity of individual BTKis confer differences in target-mediated as well as off-target adverse effects. Disease progression on covalent BTKis, driven by histologic transformation or selective expansion of BTK and PLCG2 mutated CLL clones, remains a major challenge in the field. Fixed duration combination regimens and reversible BTKis with non-covalent binding chemistry hold promise for the prevention and treatment of BTKi-resistant disease.