Long-Term Follow-Up of Ibrutinib Monotherapy in Symptomatic, Previously Treated Patients With Waldenström Macroglobulinemia

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

Waldenström macroglobulinemia: a review of pathogenesis, current treatment, and future prospects

Waldenström macroglobulinemia (WM) is a chronic B-cell lymphoproliferative disorder characterized by lymphoplasmacytic cell overgrowth in the bone marrow and increased secretion of IgM immunoglobulins into the serum. Patients with WM have a variety of clinical outcomes, including long-term survival but inevitable recurrence. Recent advances in disease knowledge, including molecular and genetic principles with the discovery of MYD88 and CXCR4 mutations, have rapidly increased patient-tolerable treatment options. WM patients may benefit from chemotherapy regimens that include rituximab-based regimens, alkylating drugs, proteasome inhibitors, monoclonal antibodies, and drugs targeting Bruton tyrosine kinase inhibitors. In light of these advancements, patients can now receive treatment customized to their specific clinical characteristics, focusing on enhancing the depth and durability of their response while limiting the adverse effects. Despite the rapidly developing therapeutic armament against WM, a lack of high-quality evidence from extensive phase 3 trials remains a significant challenge in the research. We believe clinical outcomes will keep improving when new medicines are introduced while preserving efficacy and minimizing toxicity.

B-cell non-Hodgkin lymphomas

B-cell lymphomas occur with an incidence of 20 new cases per 100 000 people per year in high-income countries. They can affect any organ and are characterised by heterogeneous clinical presentations and courses, varying from asymptomatic, to indolent, to very aggressive cases. Since the topic of B-cell non-Hodgkin lymphomas was last reviewed in The Lancet in 2017, a deeper understanding of the biological background of this heterogeneous group of malignancies, the availability of new diagnostic methods, and the development and implementation of new targeted and immunotherapeutic approaches have improved our ability to treat patients. This Seminar provides an overview of the pathobiology, classification, and prognostication of B-cell non-Hodgkin lymphomas and summarises the current knowledge and standard of care regarding biology and clinical management of the most common subtypes of mature B-cell non-Hodgkin lymphomas. It also highlights new findings in deciphering the molecular background of disease development and the implementation of new therapeutic approaches, particularly those targeting the immune system.

A phase II study of ibrutinib in combination with ixazomib in patients with Waldenström macroglobulinaemia

This phase II study evaluated time-limited (24 cycles) treatment with ibrutinib and ixazomib in newly diagnosed (NDWM; n = 9) and relapsed/refractory (RRWM; n = 12) Waldenström macroglobulinaemia (WM). The overall response rate (ORR) was 76.2% (n = 16) in 21 evaluable patients with no patient achieving a complete response (CR). The median duration of treatment was 15.6 months, and after a median follow-up time of 25.7 months, the median progression-free survival (PFS) was 22.9 months. While the primary end-point was not met (CR rate at any time) and 28.5% discontinued treatment due to toxicity, ibrutinib plus ixazomib led to a clinically meaningful ORR and PFS. Combined Bruton's tyrosine kinase (BTK) and proteasome inhibition merits further evaluation in WM.

How I use genomics and BTK inhibitors in the treatment of Waldenström macroglobulinemia

ABSTRACT

Mutations in MYD88 (95%-97%) and CXCR4 (30%-40%) are common in Waldenström macroglobulinemia (WM). TP53 is altered in 20% to 30% of patients with WM, particularly those previously treated. Mutated MYD88 activates hematopoietic cell kinase that drives Bruton tyrosine kinase (BTK) prosurvival signaling. Both nonsense and frameshift CXCR4 mutations occur in WM. Nonsense variants show greater resistance to BTK inhibitors. Covalent BTK inhibitors (cBTKi) produce major responses in 70% to 80% of patients with WM. MYD88 and CXCR4 mutation status can affect time to major response, depth of response, and/or progression-free survival (PFS) in patients with WM treated with cBTKi. The cBTKi zanubrutinib shows greater response activity and/or improved PFS in patients with WM with wild-type MYD88, mutated CXCR4, or altered TP53. Risks for adverse events, including atrial fibrillation, bleeding diathesis, and neutropenia can differ based on which BTKi is used in WM. Intolerance is also common with cBTKi, and dose reduction or switchover to another cBTKi can be considered. For patients with acquired resistance to cBTKis, newer options include pirtobrutinib or venetoclax. Combinations of BTKis with chemoimmunotherapy, CXCR4, and BCL2 antagonists are discussed. Algorithms for positioning BTKis in treatment naïve or previously treated patients with WM, based on genomics, disease characteristics, and comorbidities, are presented.

A phase 2, open-label study of ibrutinib plus rituximab in Japanese patients with Waldenstrom's macroglobulinemia

Ibrutinib is a first-in-class Bruton kinase inhibitor against B-cell neoplasms including Waldenström macroglobulinemia (WM). This study evaluated the efficacy and safety of ibrutinib-rituximab in Japanese patients with WM. Patients received ibrutinib 420 mg orally once daily plus weekly rituximab 375 mg/m2 IV (8 infusions total). The primary end point was major response rate (MRR; PR or better) by Independent Review Committee assessment. Secondary endpoints were progression-free survival (PFS), safety, pharmacokinetics, and biomarkers. Primary analysis was conducted in 16 patients [baseline, treatment naïve: 8 (50.0%); relapsed/refractory WM: 8 (50.0%)] who received ibrutinib-rituximab, after all patients completed Week 57 or end of treatment. At primary analysis, MRR was 87.5% [14/16 patients; 95% CI: 61.7, 98.4%; p < 0.0001 (null hypothesis: 32% response rate)]. At final analysis (median study intervention duration: 34.4 months, median follow-up: 35.0 months), MRR was unchanged at 87.5%, but VGPR [6/16 (37.5%)] and PR [8/16 (50.0%)] improved. Prior treatment status did not affect response. At final analysis, median PFS was not reached [36-month PFS rate: 86% (95% CI: 55, 96%)]. No critical safety signals were reported. This study demonstrated a positive benefit/risk profile of ibrutinib-rituximab in Japanese patients with WM, consistent with the iNNOVATE study.

Biomarker analysis of the ASPEN study comparing zanubrutinib with ibrutinib for patients with Waldenström macroglobulinemia

ABSTRACT

The phase 3 ASPEN trial (NCT03053440) compared Bruton tyrosine kinase inhibitors (BTKis), zanubrutinib and ibrutinib, in patients with Waldenström macroglobulinemia (WM). Post-hoc biomarker analysis was performed using next-generation sequencing on pretreatment bone marrow samples from 98 patients treated with zanubrutinib and 92 patients treated with ibrutinib with mutated (MUT) MYD88 and 20 patients with wild-type (WT) MYD88 treated with zanubrutinib. Of 329 mutations in 52 genes, mutations in CXCR4 (25.7%), TP53 (24.8%), ARID1A (15.7%), and TERT (9.0%) were most common. TP53MUT, ARID1AMUT, and TERTMUT were associated with higher rates of CXCR4MUT (P < .05). Patients with CXCR4MUT (frameshift or nonsense [NS] mutations) had lower very good partial response (VGPR) and complete response rates (CR; 17.0% vs 37.2%, P = .020) and longer time to response (11.1 vs 8.4 months) than patients with CXCR4WT treated with BTKis. CXCR4NS was associated with inferior progression-free survival (PFS; hazard ratio [HR], 3.39; P = .017) in patients treated with ibrutinib but not in those treated with zanubrutinib (HR, 0.67; P = .598), but VGPR + CR rates were similar between treatment groups (14.3% vs 15.4%). Compared with ibrutinib, patients with CXCR4NS treated with zanubrutinib had a favorable major response rate (MRR; 85.7% vs 53.8%; P = .09) and PFS (HR, 0.30; P = .093). In patients with TP53MUT, significantly lower MRRs were observed for patients treated with ibrutinib (63.6% vs 85.7%; P = .04) but not for those treated with zanubrutinib (80.8% vs 81.9%; P = .978). In TP53MUT, compared with ibrutinib, patients treated with zanubrutinib had higher VGPR and CR (34.6% vs 13.6%; P < .05), numerically improved MRR (80.8% vs 63.6%; P = .11), and longer PFS (not reached vs 44.2 months; HR, 0.66; P = .37). Collectively, patients with WM with CXCR4MUT or TP53MUT had worse prognosis compared with patients with WT alleles, and zanubrutinib led to better clinical outcomes.

Ibrutinib and venetoclax as primary therapy in symptomatic, treatment-naïve Waldenström macroglobulinemia

ABSTRACT

Concurrent Bruton tyrosine kinase and BCL2 inhibition has not yet been investigated in Waldenström macroglobulinemia (WM). We performed an investigator-initiated trial of ibrutinib and venetoclax in symptomatic treatment-naïve patients with MYD88-mutated WM. Patients received ibrutinib 420 mg once daily (cycle 1), followed by a ramp-up of venetoclax to 400 mg daily (cycle 2). The combination was then administered for 22 additional 4-week cycles. The attainment of very good partial response (VGPR) was the primary end point. Forty-five patients were enrolled in this study. The median baseline characteristics were as follows: age 67 years, serum IgM 43 g/L, and hemoglobin 102 g/L. Seventeen patients (38%) carried CXCR4 mutations. Nineteen patients (42%) achieved VGPR. Grade 3 or higher adverse events included neutropenia (38%), mucositis (9%), and tumor lysis syndrome (7%). Atrial fibrillation occurred in 3 (9%), and ventricular arrhythmia in 4 (9%) patients that included 2 grade 5 events. With a median follow-up of 24.4 months, the 24-month progression-free survival (PFS) and overall survival (OS) rates were 76% and 96%, respectively, and were not impacted by CXCR4 mutations. The median time on therapy was 10.2 months, and the median time after the end of therapy (EOT) was 13.3 months. Eleven of the 12 progression events occurred after EOT, and the 12-month PFS rates after EOT were 79%; 93% if VGPR was attained, and 69% for other patients (P = .12). Ibrutinib and venetoclax induced high VGPR rates and durable responses after EOT, although they were associated with a higher-than-expected rate of ventricular arrhythmia in patients with WM, leading to early study treatment termination. This trial was registered at www.clinicaltrials.gov as #NCT04273139.

Ibrutinib Efficacy, Safety, and Pharmacokinetics in Chinese Patients with Relapsed or Refractory Waldenström's Macroglobulinemia: A Multicenter, Single-Arm, Phase 4 Study

INTRODUCTION

Waldenström's macroglobulinemia (WM) is a rare malignant B cell lymphoma which occurs in around 1-2% of all hematologic tumors. Ibrutinib was approved in China for WM on the basis of two global pivotal studies which enrolled no Chinese patients. The aim of this study was to determine the efficacy, safety, and pharmacokinetics of ibrutinib in Chinese patients with relapsed or refractory (r/r) WM.

METHODS

This was an open-label, single-arm, multicenter phase 4 study conducted across five sites in China. Enrolled patients with clinicopathological confirmed WM received ibrutinib 420 mg once daily orally until disease progression or unacceptable toxicity. The primary endpoint was major response rate (MRR, partial response [PR], or better) according to the modified consensus criteria from the Sixth International Workshop on WM.

RESULTS

Seventeen patients were enrolled; at data cutoff (March 19, 2022), MRR was 64.7% (90% confidence interval [CI] 42.0-83.4) and overall response rate was 100% (90% CI 83.8-100.0). One (5.9%) patient achieved very good PR, 10 (58.8%) achieved PR, and six (35.3%) achieved minor response. The median duration of response (PR or better) was 14.8 months (95% CI 10.8-not estimable [NE]). Median progression-free survival was 18.4 months (95% CI 12.9-NE). All patients experienced at least one treatment-emergent adverse event (TEAE) related to the study drug, and grade ≥ 3 TEAEs were reported in 13 (76.5%) patients. There were no TEAEs leading to dose reduction or death. The median model estimated maximum plasma concentration and area under the plasma concentration-time curve during 24 h after dosing at steady state were 40.5 ng/mL and 204 ng·h/mL, respectively.

CONCLUSIONS

Ibrutinib demonstrated durable responses in Chinese patients with r/r WM. Treatment was well tolerated with no new safety signals compared with the pivotal global studies. Ibrutinib exposure was also comparable between Chinese and non-Chinese patients.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT04042376.

Unmet clinical needs in the use of zanubrutinib in malignant lymphomas (Waldenström macroglobulinemia, marginal zone lymphoma and mantle cell lymphoma): A consensus-based position paper from an ad hoc expert panel

Zanubrutinib has been approved for the treatment of patients with different lymphoproliferative disorders, and now represents a major breakthrough in the treatment of patients resistant or relapsing after the recommended therapies. Because few systematic studies or comparative randomized clinical trials have been conducted, optimal use of the drug in approved indications is challenging, and questions are emerging on its use in earlier stages of the disorders. This article presents the results of group discussion among an ad hoc constituted panel of experts aimed at identifying and addressing unmet clinical needs (UCNs) in the use of zanubrutinib in the lymphomas which have received the approval of use, specifically Waldenström macroglubulinemia, marginal zone lymphoma and mantle cell lymphoma. Key UCNs were selected according to the criterion of clinical relevance using the Delphi process. The panel produced recommendations and proposals for new studies for the management of the identified UCNs. These recommendations are intended for use not only by expert centers but above all by not experienced hematologists as well as general practitioners.

Zanubrutinib Versus Ibrutinib in Symptomatic Waldenström Macroglobulinemia: Final Analysis From the Randomized Phase III ASPEN Study

The phase III ASPEN study demonstrated the comparable efficacy and improved safety of zanubrutinib versus ibrutinib in patients with Waldenström macroglobulinemia (WM). Here, we report long-term follow-up outcomes from ASPEN. The primary end point was the sum of very good partial response (VGPR) + complete response (CR) rates; secondary and exploratory end points were also reported. Cohort 1 comprised 201 patients (myeloid differentiation primary response 88-mutant WM: 102 receiving zanubrutinib; 99 receiving ibrutinib); cohort 2 comprised 28 patients (myeloid differentiation primary response 88 wild-type WM: 28 zanubrutinib; 26 efficacy evaluable). At 44.4-month median follow-up, VGPR + CR rates were 36.3% with zanubrutinib versus 25.3% with ibrutinib in cohort 1 and 30.8% with one CR in cohort 2. In patients with CXC motif chemokine receptor 4 mutation, VGPR + CR rates were 21.2% with zanubrutinib versus 10.0% with ibrutinib (cohort 1). Median progression-free survival and overall survival were not reached. Any-grade adverse events (AEs) of diarrhea (34.7% v 22.8%), muscle spasms (28.6% v 11.9%), hypertension (25.5% v 14.9%), atrial fibrillation/flutter (23.5% v 7.9%), and pneumonia (18.4% v 5.0%) were more common with ibrutinib versus zanubrutinib; neutropenia (20.4% v 34.7%) was less common with ibrutinib versus zanubrutinib (cohort 1). Zanubrutinib was associated with lower risk of AE-related treatment discontinuation. Overall, these findings confirm the long-term response quality and tolerability associated with zanubrutinib.

Advances in Treatment of Waldenström Macroglobulinemia

PURPOSE OF REVIEW

The discovery of recurring somatic mutations, in particular MYD88 and CXCR4 mutations, in Waldenström macroglobulinemia (WM), a rare B-cell lymphoproliferative disorder, led in the last decade to the development of several therapeutic agents with high efficacy. This review aims to provide an overview of available treatments in WM and novel agents, focusing on studies published over recent years.

RECENT FINDINGS

There is no international consensus on the best first-line option in treatment-naïve patients. Randomized clinical trials are rare in WM and there has been no prospective comparison of chemoimmunotherapy and BTK inhibitors in the frontline setting. Chemoimmunotherapy and BTK inhibitors, the two feasible and most widely used treatments in first-line treatment, represent very different options in terms of duration of therapy, route of administration, cost, and adverse effect. In addition to tumor genotype and patient comorbidities, choice of therapy in WM should take into account these parameters. Results of ongoing and future clinical trials evaluating fixed-duration combinations with BTK inhibitors and novel agents are awaited.

Current approach to Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a unique CD20+, B-cell non-Hodgkin lymphoma, characterized by lymphoplasmacytic infiltration of the bone marrow and circulating monoclonal immunoglobulin M. The clinical manifestations and outcomes of patients are highly variable. High-level evidence supports integration of monoclonal anti-CD20 antibody, rituximab, to the chemotherapy backbone to treat WM. However, its contemporary management has become more nuanced, with deeper understanding of the pathophysiology and incorporation of Bruton's tyrosine kinase (BTK) inhibitors to the treatment paradigm. Prior knowledge of the patients' MYD88L265P and CXCR4 mutation status may aid in the treatment decision-making. Currently, the two frequently utilized approaches include fixed-duration chemoimmunotherapy and BTK inhibitor-based continuous treatment until progression. Randomized trials comparing these two vastly divergent approaches are lacking. Recent studies demonstrating efficacy of B cell lymphoma-2 (BCL2) inhibitors and non-covalent BTK inhibitors in patients, previously exposed to a covalent BTK inhibitor, are a testament to the rapidly expanding options against WM.

Chinese expert consensus on Bruton tyrosine kinase inhibitors in the treatment of B-cell malignancies

Targeted therapy with Bruton tyrosine kinase (BTK) inhibitors have revolutionized the treatment of patients with various B-cell malignancies. BTK inhibitors such as ibrutinib, zanubrutinib, orelabrutinib, and acalabrutinib have shown good clinical efficacy and better safety profiles than those of traditional chemotherapy and chemoimmunotherapy regimens. Multiple studies on new BTK inhibitors are ongoing, which may provide more therapeutic options for the treatment of B-cell malignancies. Considering the unmet need of evidence on BTK inhibitors in all clinical settings and to standardize the use of BTK inhibitors available in mainland China, Taiwan, Hong Kong, and Macau regions, this consensus has been formulated for the treatment of various B-cell malignancies based on the clinical practice and available evidences on the use of BTK inhibitors. The recommendations of this consensus will provide guidance to physicians and clinical researchers on the effective treatment of B-cell malignancies with BTK inhibitors.

Next generation sequencing in routine diagnostics of mature non-Hodgkin's B-cell lymphomas

INTRODUCTION

Integration of molecular characterization of lymphomas in clinical diagnostics may improve subclassification and risk-stratification, and we implemented a next generation sequencing (NGS) analysis as part of routine diagnostic work-up of all mature B-cell non-Hodgkin's lymphoma (B-NHL). Here, we present data of mutational profiles with potential complementary diagnostic, prognostic, and predictive value detected in our consecutive non-selected cohort of B-NHL patients.

METHODS

NGS results from 298 patients with both newly diagnosed and relapsed/refractory disease were included as a single center study. NGS was performed as routine analysis together with standard diagnostic work-up using a custom-made amplicon PCR-based multiplex NGS panel covering all coding exons and consensus splice sites in 59 genes.

RESULTS

Mutations were detected in 94% of the 298 samples. Most lymphomas could be classified definitively, but 24 cases were classified as small B-cell lymphomas without defining characteristics. Of these, 50% (12/24 cases) could retrospectively be assigned a likely diagnostic subtype according to mutational findings.

CONCLUSION

Implementation of a 59 gene exome sequencing panel added diagnostic value to 50% of unclassified cases and provided in 94% of the cases possible biomarkers for disease monitoring as well as potential diagnostic, prognostic, and predictive markers for future studies.

Real-world treatment patterns, discontinuation and clinical outcomes in patients with B-cell lymphoproliferative diseases treated with BTK inhibitors in China

Introduction

Bruton tyrosine kinase inhibitor (BTKi) has demonstrated substantial efficacy in treating B-cell lymphoproliferative diseases (BLPD). Nonetheless, the significant discontinuation rates due to toxicity or financial reasons cannot be overlooked. In China, empirical evidence on the usage of BTKi remains scarce.

Methods

To address this, a retrospective cohort study was conducted focused on 673 Chinese patients with BLPD who underwent at least one month of BTKi therapy.

Results

Median age at BTKi initiation was 60 years. The median duration on BTKi treatment of the whole cohort was 36.4 months. The median post-BTK survival was not reach. BTKi-based treatment was permanently discontinued in 288 (43.8%) patients during follow-up, mostly attributed to progressive disease. Within the first 6 months of BTKi treatment, 76 patients (26.3%) had early treatment discontinuation. Patients with early discontinuation had extreme worse outcome with a median post-discontinuation survival of only 6.9 months. On multivariate analysis, withdrawal BTKi by toxicity and withdrawal BTKi within 6 months retained to be independent predictors of post-BTK survival, after taking account of the response depth, lines of therapy and baseline cytogenetics including 17p deletion. The decision between BTKi monotherapy and combination therapy, along with the preference for first or second-generation BTKi, exerted no significant impact on survival.

Discussions

These observations contribute valuable real-world insights into the utilization of BTKi in China. We concluded that BTKi is an effective and well-tolerated treatment for long-term use in Chinese patient population. However, it is imperative to stress that a proportion of patients discontinue BTKi early, leading to suboptimal outcomes. This study underscores the importance of adherence to BTKi therapy for improved clinical outcomes in real-world patients.

New developments in the diagnosis and characterization of Waldenström's macroglobulinemia

INTRODUCTION

Waldenström's macroglobulinemia (WM) is defined as a lymphoplasmacytic lymphoma (LPL) with immunoglobulin M (IgM) monoclonal gammopathy and morphologic evidence of bone marrow infiltration by LPL. Immunophenotyping and genotyping provide a firm pathological basis for diagnosis and are particularly valuable in differential diagnosis between WM and related diseases. Emerging technologies in mutational analysis present new opportunities, but challenges remain around standardization of methodologies and reporting of mutational data across centers.

AREAS COVERED

The review provides an overview of the diagnosis of WM, with a particular focus on the role of immunophenotyping and genotyping.

EXPERT OPINION

Demonstration of LPL with a bone marrow biopsy is essential to reach a definitive diagnosis of WM. However, MYD88L265P and a typical WM immunophenotypic profile are valuable for the differential diagnosis of WM and related diseases, such as marginal zone lymphoma, multiple myeloma, and chronic lymphocytic leukemia. These methodologies must be utilized across centers and with appropriate standards followed in the evaluation and reporting of sensitivities and specificities. The diagnostic and/or prognostic value of mutations in genes such as CXCR4 and TP53 that are currently not routinely evaluated in the diagnosis of WM should be explored.

Bruton tyrosine kinase inhibitors: can they be optimized for the treatment of neuroinflammatory disorders?

INTRODUCTION

Bruton's tyrosine kinase (BTK) is a multifaceted player of the immune system which has been involved in the survival of hematological malignancies but also in the pathogenesis of immune-mediated diseases. Oral BTK inhibitors (BTKi) have become a cornerstone for the treatment of patients with B-cell malignancies, and are under investigation for several immune-mediated diseases.

AREAS COVERED

We reviewed the biology of BTK and emerging data on BTKi in patients with neuroinflammatory disorders of both the peripheral and central nervous system.

EXPERT OPINION

We support the use of BTKi in relapsed/refractory patients with multiple sclerosis and anti-MAG antibody neuropathies. However, other immune-mediated neuroinflammatory disorders are likely to benefit from BTKi. Whether BTKi will improve the response rates than conventional therapies in previously untreated patients is unknown and will be assessed within future clinical trials. Furthermore, the availability of more selective BTKi, with less adverse events, will improve patients' tolerability and expand our treatment landscape.

[The efficacy and safety of Bruton tyrosine kinase inhibitors as monotherapy in the treatment of newly diagnosed patients with Waldenström macroglobulinemia]

Objective: To investigate the efficacy and safety of Bruton tyrosine kinase inhibitors (BTKi) ibrutinib or zanubrutinib monotherapy in newly diagnosed patients with Waldenström macroglobulinemia (WM) . Methods: The efficacy and adverse effects of 58 patients with newly diagnosed WM receiving BTKi monotherapy in Ruijin Hospital Affiliated to Shanghai Jiao Tong University School of Medicine were analyzed retrospectively from January 2018 to August 2022. Results: The response of 55 patients may be examined. Forty patients received ibrutinib monotherapy for a median of 15 months, with an overall response rate (ORR) of 85%, a main remission rate (MRR) of 70%, and a very good partial remission (VGPR) rate of 10%. Fifteen patients received zanubrutinib monotherapy for a median of 13 months, with an ORR of 93%, an MRR of 73%, and a VGPR rate of 0%. For various reasons, 10 patients were converted from ibrutinib to zanubrutinib. Ibrutinib treatment lasted an average of 7.5 months before conversion. The median duration of zanubrutinib therapy after conversion was 3.5 months. The ORRs before and after conversion were 90% and 100%, MRRs were 80% and 80%, and VGPR rates were 10% and 50%, respectively. After a median of 16 months, the 24-month progression-free survival (PFS) rate of patients who received both BTKi was 86%. PFS did not differ statistically across individuals with low, medium, and high-risk ISS scores (P=0.998). All of the patients survived. The most common side effects of BTKi were neutropenia and thrombocytopenia, which occurred in 12% and 10% of all patients, respectively. Ibrutinib accounts for 5% of atrial fibrillation, and zanubrutinib has a 7% risk of bleeding. Conclusions: In treating WM, ibrutinib or zanubrutinib provides good efficacy and tolerable adverse effects.

Dose of ibrutinib in Waldenström macroglobulinaemia: Less can be more

Ibrutinib changed the landscape of treatment in Waldenström macroglobulinaemia (WM) with excellent responses; however, there are high rates of dose reduction due to adverse events. The impact of this reduced dosing is unclear with regards to outcomes. Sarosiek and colleagues provide valuable data in a very large retrospective study demonstrating that dose reduction is effective in managing adverse events in the majority, with equivalent, if not better, outcomes than those without dose reductions.

Evaluation and Management of Disease Transformation in Waldenström Macroglobulinemia

Histologic transformation (HT) to diffuse large B-cell lymphoma occurs rarely in Waldenström macroglobulinemia, with higher incidence in MYD88 wild-type patients. HT is suspected clinically when rapidly enlarging lymph nodes, elevated lactate dehydrogenase levels, or extranodal disease occur. Histologic assessment is required for diagnosis. HT carries a worse prognosis compared with nontransformed Waldenström macroglobulinemia. A validated prognostic score based on three adverse risk factors stratifies three risk groups. The most common frontline treatment is chemoimmunotherapy, such as R-CHOP. Central nervous system prophylaxis should be considered if feasible and consolidation with autologous transplant should be discussed in fit patients responding to chemoimmunotherapy.

The Management of Relapsed or Refractory Waldenström's Macroglobulinemia

Waldenström's macroglobulinemia (WM) is an immunoglobulin M monoclonal gammopathy produced by a bone marrow lymphoplasmacytic lymphoma, an indolent non-Hodgkin lymphoma in which the cure is still an unmet challenge. Combinations with alkylating agents, purine analogs, and monoclonal antibodies, Bruton tyrosine kinase, and proteasome inhibitors are used for the treatment of relapsed and refractory patients. Moreover, new additional agents can be seen on the horizon as potential effective therapies. No consensus on a preferred treatment in the relapsed setting is available yet.

BTK Inhibitors in the Frontline Management of Waldenström Macroglobulinemia

The discovery of MYD88 (L265P) mutation led to investigating BTK inhibitors in Waldenström macroglobulinemia (WM). Ibrutinib, the first-in-class agent, was approved based on a phase II trial in relapsed/refractory patients. In the phase III iNNOVATE study, the combination of rituximab and ibrutinib was compared with rituximab and placebo in treatment-naïve and relapsed/refractory patients. Second-generation BTK inhibitor, zanubrutinib, was compared with Ibrutinib in MYD88-mutated WM patients in the phase III ASPEN trial, whereas acalabrutinib was investigated in a phase II trial. Here, we discuss the role of BTK inhibitors in treatment-naïve patients with WM based on currently available evidence.

Novel Agents in Waldenström Macroglobulinemia

Owing to the indolent nature of Waldenström macroglobulinemia, most patients experience a prolonged life expectancy, although many lines of therapy will likely be required to maintain disease control. Despite the currently available therapies, most patients will develop intolerance or resistance to multiple treatments. Therefore, new therapeutic options are being developed with a focus on targeted agents, such as novel Bruton tyrosine kinase (BTK) inhibitors and BTK degraders, as well as C-X-C chemokine receptor type 4, mucosa-associated lymphoid tissue translocation protein 1, and interleukin-1 receptor-associated kinase 4.

Bortezomib-Dexamethasone, Rituximab, and Cyclophosphamide as First-Line Treatment for Waldenström's Macroglobulinemia: A Prospectively Randomized Trial of the European Consortium for Waldenström's Macroglobulinemia

PURPOSE

Rituximab/chemotherapy is a cornerstone of treatment for Waldenström's macroglobulinemia (WM). In addition, bortezomib has shown significant activity in WM. This study evaluated the efficacy and safety of dexamethasone, rituximab, and cyclophosphamide (DRC) as first-line treatment in WM.

METHODS

In this European study, treatment-naïve patients were randomly assigned to DRC or bortezomib-DRC B-DRC for six cycles. The primary end point was progression-free survival. Secondary end points included response rates, overall survival, and safety.

RESULTS

Two hundred four patients were registered. After a median follow-up of 27.5 months, the estimated 24-month progression-free survival was 80.6% (95% CI, 69.5 to 88.0) for B-DRC and 72.8% (95% CI, 61.3 to 81.3) for DRC (P = .32). At the end of treatment, B-DRC and DRC induced major responses in 80.6% versus 69.9% and a complete response/very good partial response in 17.2% versus 9.6% of patients, respectively. The median time to first response was shorter for B-DRC with 3.0 (95% CI, 2.8 to 3.2) versus 5.5 (95% CI, 2.9 to 5.8) months for DRC. This resulted in higher major response rates (57.0% v 32.5%; P < .01) after three cycles of B-DRC compared with DRC. At best response, the complete response/very good partial response increased to 32.6% for B-DRC. Both treatments were well tolerated: grade ≥ 3 adverse events occurred in 49.2% of all patients (B-DRC, 49.5%; DRC, 49.0%). Peripheral sensory neuropathy grade 3 occurred in two patients treated with B-DRC and in none with DRC.

CONCLUSION

This large randomized study illustrates that B-DRC is highly effective and well tolerated in WM. The data demonstrate that fixed duration immunochemotherapy remains an important pillar in the clinical management of WM.

Ibrutinib in relapsed/refractory patients with Waldenström macroglobulinemia: a real-life, retrospective study on behalf of the "RTL" (regional Tuscan lymphoma network)

Ibrutinib represents the first approved treatment for patients with Waldenström macroglobulinemia (WM). There are very few published experiences outside of a clinical trial. In this study, we investigated treatment response, survival, and safety in a real life setting. We retrospectively analyzed 49 consecutive R/R WM patients, managed in 8 Tuscan onco-hematological centers, that received ibrutinib after its approval, at a maximum dose of 420 mg once per day, until disease progression or unacceptable toxicity. Median age was 65 years (range 32-86), and the median number of previous regimens was 2 (range 1-5). Overall and major response rate were 91.8% and 87.7%, respectively. At best response, median IgM level declined from 3,094 to 831 mg/dl, and Hb level increased from 10.4 to 12.7 g/dl. In an intention-to-treat analysis, 36/49 patients (73.5%) were still receiving treatment, while 13/49 (26.5%) had discontinued therapy. Six out of 49 cases (12.2%) relapsed after an initial response, and 13/49 (26.5%) had a dose reduction. Estimated 2-year PFS, DOR, and OS were 76.7%, 88.7%, and 84.1%, respectively. After a median follow-up of 18.3 months, 43/49 patients (87.8%) were alive. The most frequent AE included atrial fibrillation or flutter (6/49 cases, 12.2%), bleeding (6/49 cases, 12.2%), arthralgia/myalgia (5/49 cases, 10.2%). Ibrutinib is a suitable treatment option for R/R WM patients and also suggested by ESMO, NCCN, and other societies. PFS and OS were durable, and DOR was sustained for responsive patients. Treatment toxicity is not negligible, but manageable in most cases without treatment discontinuation.

Invasive Cutaneous Candidiasis, Autoimmune Hemolytic Anemia and Pancytopenia: A Challenging Scenario for Waldenström Macroglobulinemia in an Elderly Patient

Waldenström macroglobulinemia (WM) is a slowly progressive hematologic malignancy that usually responds rapidly to treatment. Being a lymphoplasmacytoid neoplasm, it is associated with a monoclonal IgM component, which may be associated with multiple manifestations and symptoms. We report the case of a 77-year-old woman diagnosed with WM following the development of severe and sudden pancytopenia associated with a cold agglutinin syndrome. In order to treat the WM and the underlying hemolysis, treatment with rituximab, corticosteroids and cyclophosphamide was started. Despite the improvement in hemolysis parameters, pancytopenia persisted, and we started a second line with ibrutinib. During treatment the patient developed an uncommon invasive fungal infection (IFI) with bone marrow granulomatosis and myelofibrosis. This case shows an unusual clinical course with a poor hematopoietic response to treatment and a large number of intercurrent complications.

Bruton tyrosine kinase inhibitors in the management of Waldenström macroglobulinemia

Bruton tyrosine kinase (BTK) inhibitors have taken a central role in the management of patients with Waldenström macroglobulinemia and are the only agents approved by the Food and Drug Administration (FDA) to treat these patients. Although associated with high rates of durable responses, unmet needs with BTK inhibitor therapy include indefinite duration therapy, high cost, scarcity of complete responses, and lower rates and shorter duration of response in patients with CXCR4 mutations. Herein, we review the data supporting the use of covalent BTK inhibitors, selected management issues, clinical trials with covalent BTK inhibitor combination regimens, and up-and-coming non-covalent BTK inhibitors.

Management of indolent B-cell Lymphomas: A review of approved and emerging targeted therapies

The indolent B-cell non-Hodgkin lymphomas (B-NHL) comprise a heterogenous group of lymphoproliferative disorders characterized by slow growth kinetics and a relapsing/remitting course. Management has, until recently, been uniform across all indolent B-NHL subtypes. Improving insight into pathophysiological and molecular features of each disease has led to development of several targeted therapies. Consequently, each subtype must now be considered an individual entity. In this review, we consider the three commonest indolent B-NHLs: follicular lymphoma, marginal zone lymphoma and Waldenstrom's macroglobulinemia and review in detail the data on approved and emerging targeted therapeutic agents for each B-NHL subtype.

A rare case report of waldenström macroglobulinemia converted to serum low IgM

Waldenström Macroglobulinemia (WM) is a rare chronic lymphoproliferative disease, accounting for less than 2% of hematological malignancies. It is characterized by plasma cytoid lymphocyte infiltration in bone marrow and abnormal increase of monoclonal IgM in peripheral blood. Only 5%-10% of cases of WM secrete monoclonal IgG and IgA components or do not secrete monoclonal long immunoglobulin. This case is the first to report of serum protein recombination from lgM and Igkappa band mutation to abnormal lgG and Igkappa band after 6 years of treatment in a male patient with WM.

Dose reductions in patients with Waldenström macroglobulinaemia treated with ibrutinib

Waldenström macroglobulinaemia (WM) is characterized by the presence of a MYD88^L265P mutation. This mutation promotes growth and survival of malignant cells through Bruton tyrosine kinase (BTK) activation. Ibrutinib was the first BTK inhibitor approved for WM. Intolerance to ibrutinib frequently leads to dose reductions, though the impact of reducing ibrutinib dosing has not been systematically studied. We performed a retrospective study to determine the frequency and impact of reducing ibrutinib dosing in WM patients. With a median treatment time of 64 months, 96 (27%) of 353 WM patients required a dose reduction due to adverse events such as musculoskeletal symptoms, cardiac events, dermatologic symptoms, cytopenias, and gastrointestinal symptoms. The median time to initial dose reduction was 9.3 months (range, 0.5-74). Dose reductions were more common in those 65 years of age or older versus under 65 [hazard ratio (HR) 2.46, 95% confidence interval (CI) 1.55-3.90; p < 0.001], and in females versus males (HR 2.20, 95% CI 1.41-3.28, p < 0.001). Most patients (65%) had improvement or resolution of adverse effects after initial dose reduction. With a median follow-up of three years from dose reduction, hematologic response sustained or deepened in 79% of patients. These data suggest that dose reduction of ibrutinib is a reasonable treatment approach for patients with intolerable side effects.

Treatment of relapsed and refractory Waldenstrom Macroglobulinemia

Waldenström's Macroglobulinemia (WM) is a rare type of indolent non-Hodgkin lymphoma (NHL) that remains incurable. Several effective agents such as monoclonal antibodies (in combination with chemotherapy), Bruton's tyrosine kinase inhibitors, proteasome inhibitors, and BCL2 inhibitors are (becoming) available for the treatment of relapsed and refractory WM. There is however no consensus on a preferred treatment in the relapsed setting. Choice of therapy in relapsed WM should be individualized by taking several treatment and patients characteristics into account, such as treatment duration, toxicity, age, comorbidities and MYD88^L265P and CXCR4 mutational status. Due to better understanding of WM biology and the arrival of novel anti-lymphoma agents, the therapeutic options are increasing. Non-cytotoxic and fixed duration regimens, such as those explored in other indolent NHLs should be the focus of future clinical trials in WM.

[Waldenström disease: News and perspectives in 2022]

Waldenström's disease is a B-cell neoplasm characterized by the accumulation of lymphoplasmacytic cells (LPCs) in the bone marrow, and more rarely in the lymph nodes and the spleen, which produce a monoclonal immunoglobulin M (IgM) protein. The diagnosis requires the identification of LPCs in the bone marrow, using specific markers in flow cytometry. The MYD88L265P mutation is found in 95% of cases and the CXCR4 mutation in 30-40% of cases. These markers must be sought because they have a diagnostic and prognostic role, and they might become predictive in the future. The clinical presentation is very variable, and includes anomalies related to the bone marrow infiltration of the LPCs (such as anemia), but also anomalies of the physico-chemical and/or immunological activity of the overproduced IgM (hyperviscosity, AL amyloidosis, cryoglobulinemia, anti-MAG neuropathies, etc.). Prognostic scores (IPSSWM) now make it possible to understand the prognosis of symptomatic WM requiring appropriate treatment. The therapeutic management depends on many parameters, such as the specific clinical presentation, the speed of evolution and of course the age and comorbidities. Immuno-chemotherapy is often the 1st line treatment (rituximab-cyclophosphamide-dexamethasone (RCD) or bendamustine-rituximab (BR)) but the role of targeted therapies is becoming preponderant. Bruton tyrosine kinase inhibitors (BTKi) are used today in first relapse. Other therapeutic perspectives will certainly allow us tomorrow to better understand this incurable chronic disease, such as new generations of BTKi, BCL2 inhibitors, anti-CXCR4, bi-specific antibodies, and CAR-T cells.

MYD88 L265P Mutation Detection by ddPCR: Recommendations for Screening and Minimal Residual Disease Monitoring : ddPCR for Highly Sensitive Detection of MYD88 L265P Mutation

MYD88^L265P is a gain-of-function mutation, arising from the missense alteration c.794T>C, that frequently occurs in B-cell malignancies such as Waldenstrom macroglobulinemia and less frequently in IgM monoclonal gammopathy of undetermined significance (IgM-MGUS) or other lymphomas. MYD88^L265P has been recognized as a relevant diagnostic flag, but also as a valid prognostic and predictive biomarker, as well as an investigated therapeutic target. Up until now, allele-specific quantitative PCR (ASqPCR) has been widely used for MYD88^L265P detection providing a higher level of sensitivity than Sanger sequencing. However, the recently developed droplet digital PCR (ddPCR) shows a deeper sensitivity, compared to ASqPCR, that is necessary for screening low infiltrated samples. Actually, ddPCR could represent an improvement in daily laboratory practice since it allows mutation detection in unselected tumor cells, allowing to bypass the time-consuming and costly B-cell selection procedure. ddPCR accuracy has been recently proved to be suitable also for mutation detection in "liquid biopsy" samples that might be used as a noninvasive and patient-friendly alternative to bone marrow aspiration especially during the disease monitoring. The relevance of MYD88^L265P, both in daily management of patients and in prospective clinical trials investigating the efficacy of novel agents, makes crucial to find a sensitive, accurate, and reliable molecular technique for mutation detection. Here, we propose a protocol for MYD88^L265P detection by ddPCR.

Managing Waldenström's macroglobulinemia with BTK inhibitors

Bruton's tyrosine kinase (BTK) inhibition is one of the treatment standards for patients with relapsed/refractory Waldenström's macroglobulinemia (WM) and for patients with WM who are unsuitable for immunochemotherapy (ICT). It offers deep and durable responses with a manageable safety profile that is generally favorable compared with ICT regimens. However, the limitations of the first approved BTK inhibitor (BTKi), ibrutinib, include reduced efficacy in patients lacking the characteristic WM mutation (MYD88^L265P) and toxicities related to off-target activity. The risk of atrial fibrillation (AF) and other cardiovascular side effects are a notable feature of ibrutinib therapy. Several next-generation covalent BTKis with greater selectivity for BTK are at various stages of development. In November 2021, zanubrutinib became the first of these agents to be approved by the European Medicines Agency for the treatment of WM. Head-to-head trial data indicate that it has comparable efficacy to ibrutinib for patients with WM overall, although it may be more effective in patients with CXCR4 mutations or wild-type MYD88. In the clinical trial setting, its greater selectivity translates into a reduced risk of cardiovascular side effects, including AF. Acalabrutinib, which is pre-approval in WM, appears to offer similar advantages over ibrutinib in terms of its safety profile. Beyond the next-generation covalent BTKis, non-covalent BTKis are an emerging class with the potential to provide a therapeutic option for patients who relapse on covalent BTKis. In the future, BTKis may be increasingly utilized within combination regimens. Several ongoing trials in WM are investigating the potential for BTKi use in combination with established and novel targeted agents.

Neurological Complications of Conventional and Novel Anticancer Treatments

Various neurological complications, affecting both the central and peripheral nervous system, can frequently be experienced by cancer survivors after exposure to conventional chemotherapy, but also to modern immunotherapy. In this review, we provide an overview of the most well-known adverse events related to chemotherapy, with a focus on chemotherapy induced peripheral neurotoxicity, but we also address some emerging novel clinical entities related to cancer treatment, including chemotherapy-related cognitive impairment and immune-mediated adverse events. Unfortunately, efficacious curative or preventive treatment for all these neurological complications is still lacking. We provide a description of the possible mechanisms involved to drive future drug discovery in this field, both for symptomatic treatment and neuroprotection.

Genomic profiling for clinical decision making in lymphoid neoplasms

With the introduction of large-scale molecular profiling methods and high-throughput sequencing technologies, the genomic features of most lymphoid neoplasms have been characterized at an unprecedented scale. Although the principles for the classification and diagnosis of these disorders, founded on a multidimensional definition of disease entities, have been consolidated over the past 25 years, novel genomic data have markedly enhanced our understanding of lymphomagenesis and enriched the description of disease entities at the molecular level. Yet, the current diagnosis of lymphoid tumors is largely based on morphological assessment and immunophenotyping, with only few entities being defined by genomic criteria. This paper, which accompanies the International Consensus Classification of mature lymphoid neoplasms, will address how established assays and newly developed technologies for molecular testing already complement clinical diagnoses and provide a novel lens on disease classification. More specifically, their contributions to diagnosis refinement, risk stratification, and therapy prediction will be considered for the main categories of lymphoid neoplasms. The potential of whole-genome sequencing, circulating tumor DNA analyses, single-cell analyses, and epigenetic profiling will be discussed because these will likely become important future tools for implementing precision medicine approaches in clinical decision making for patients with lymphoid malignancies.

Transformed Waldenström Macroglobulinemia: Update on Diagnosis, Prognosis and Treatment

Histological transformation (HT) to an aggressive lymphoma results from a rare evolution of Waldenström macroglobulinemia (WM). A higher incidence of transformation events has been reported in MYD88 wild-type WM patients. HT in WM can be histologically heterogeneous, although the diffuse large B-cell lymphoma of activated B-cell subtype is the predominant pathologic entity. The pathophysiology of HT is largely unknown. The clinical suspicion of HT is based on physical deterioration and the rapid enlargement of the lymph nodes in WM patients. Most transformed WM patients present with elevated serum lactate dehydrogenase (LDH) and extranodal disease. A histologic confirmation regarding the transformation to a higher-grade lymphoma is mandatory for the diagnosis of HT, and the choice of the biopsy site may be dictated by the findings of the 18fluorodeoxyglucose-positron emission tomography/computed tomography. The prognosis of HT in WM is unfavorable, with a significantly inferior outcome compared to WM patients without HT. A validated prognostic score based on 3 adverse risk factors (elevated LDH, platelet count < 100 × 109/L and any previous treatment for WM) stratifies patients into 3 risk groups. The most common initial treatment used is a chemo-immunotherapy (CIT), such as R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone). The response duration is short and central nervous system relapses are frequent. Whether autologous stem cell transplantation could benefit fit patients responding to CIT remains to be studied.

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.

Evaluation of orelabrutinib monotherapy in patients with relapsed or refractory Waldenström's macroglobulinemia in a single-arm, multicenter, open-label, phase 2 study

BACKGROUND

Orelabrutinib is a novel, small molecule, selective irreversible Bruton tyrosine kinase inhibitor. The purpose of this study was to evaluate the efficacy and safety of orelabrutinib in patients with relapsed or refractory Waldenström's macroglobulinemia (R/R WM).

METHODS

This is a prospective, multicenter study of orelabrutinib in patients with WM who had at least one prior line of treatment. Orelabrutinib was administered orally at a daily dose of 150 mg until disease progression or unacceptable toxicity. The primary endpoint was major response rate (MRR) assessed by the Independent Review Committee (IRC) according to IWWM-6. This study is registered with ClinicalTrials.gov, NCT04440059. This trial was also registered on Center for Drug Evaluation (www.chinadrugtrials.org.cn) in March 2019, with a number of CTR2019036.

FINDINGS

Between August 2019 and December 2020, 66 R/R WM patients were assessed for eligibility. Forty-seven eligible patients were evaluated for efficacy at a median follow-up of 16.4 months (interquartile range: 12.5, 19.5). As assessed by IRC, the MRR was 80.9%, and the overall response rate was 89.4%. The median time to at least a minor response was 1.9 months. The PFS rates was 89.4% at 12 months. For patients with MYD88^L265P /CXCR4^NEG, MYD88^L265P /CXCR4 ^S338X, and MYD88^NEG /CXCR4^NEG mutations, the MRRs were 84.6%, 100%, and 25.0%. Most adverse events were Grades 1 or 2 (91.0%). The common grade 3 or higher adverse events occurring were neutropenia (10.6%), thrombocytopenia (6.4%), and pneumonia (4.3%). Serious adverse events (SAE) occurred in 10 patients (21.3%). One treatment-related death was reported (hepatitis B reactivation).

INTERPRETATION

Orelabrutinib has shown good efficacy and manageable safety profiles in patients with R/R WM.

FUNDING

InnoCare Pharma.

A Canadian Perspective on the Treatment of Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) is a slowly progressing B-cell non-Hodgkin lymphoma characterized by monoclonal IgM gammopathy in the blood and infiltration of the bone marrow by clonal lymphoplasmacytic cells. As an incurable disease, the goals for therapy for WM are to relieve symptoms, slow disease progression, prevent organ damage, and maintain quality of life. However, given the rarity of WM, clinical trials comparing treatments for WM are limited and there is no definitive standard of care. The selection of first-line WM therapy is thus based on patient factors, disease characteristics, and drug access, with bendamustine-rituximab and Bruton's tyrosine kinase (BTK) inhibitor therapy considered preferred treatments. Other treatments such as proteasome inhibitor- or purine analogue-based therapy, alternative chemoimmunotherapy, and autologous stem cell transplantation are generally reserved for the relapsed setting but may be used in rare circumstances in earlier lines of therapy. This paper summarizes the efficacy and safety of these WM therapies and discusses considerations for treatment from a Canadian perspective.

Waldenstrom Macroglobulinemia: Tailoring Therapy for the Individual

With the introduction of multiple new effective therapeutic options for the treatment of macroglobulinemia, a structured approach to management of this rare lymphoma is currently needed. A review of phase II and III treatment trials over the past 20 years was performed, and high-quality trials are summarized in this manuscript. Because of the lack of large prospective trials comparing different classes of therapy, a uniform recommendation applicable to all patients cannot be made, and the approach must be individualized incorporating patient preferences, comorbidities, and the range of therapeutic toxicities. Therapeutic options for patients with newly diagnosed and previously treated macroglobulinemia are presented on the basis of the best available evidence in the literature.

SOHO State of the Art Updates and Next Questions: Targeted therapies and emerging novel treatment approaches for Waldenström Macroglobulinemia

Waldenström Macroglobulinemia (WM) is a rare hematologic malignancy characterized by the presence of lymphoplasmacytic lymphoma cells involving the bone marrow and production of a monoclonal IgM paraprotein. Recurrent somatic mutations in MYD88^L265P and CXCR4 have been reported in 90% to 95% and 30% to 40% of patients with WM, respectively. Standard treatment regimens combine the anti-CD20 antibody rituximab with alkylating agents (eg, bendamustine, cyclophosphamide), nucleoside analogs (eg, fludarabine, cladribine), or proteasome inhibitors (eg, bortezomib, carfilzomib, and ixazomib). Covalent BTK inhibitors (eg, ibrutinib, acalabrutinib, zanubrutinib) have shown to be safe and highly effective in patients with WM. Novel and promising agents in this disease include next-generation covalent BTK inhibitors (eg, tirabrutinib, orelabrutinib), non-covalent BTK inhibitors (eg, pirtobrutinib, ARQ531), BCL-2 antagonists (eg, venetoclax), and CXCR4-targeted agents (eg, mavorixafor, ulocuplumab), among others. Future studies will focus on developing fixed-duration combinations regimens with these novel agents aimed at increasing durable responses while minimizing toxicity and cost.

Zanubrutinib in Treating Waldenström Macroglobulinemia, the Last Shall Be the First

In Waldenström macroglobulinemia (WM), a lymphoplasmacytic lymphoma characterized by monoclonal immunoglobulin M (IgM) gammopathy, aberrant Bruton tyrosine kinase (BTK) signaling has been identified as one mechanism of pathogenesis. For this reason, selective BTK inhibiting therapies have emerged as an attractive option for treatment within the therapeutic landscape also comprising chemotherapy, monoclonal antibodies, proteasome inhibitors, and B-cell lymphoma 2 (BCL2) inhibitors. The first BTK inhibiting therapy, ibrutinib, showed great efficacy in treating WM. However, response rates were dependent on whether patients had the CXCR4 mutation, a molecular aberration that may confer resistance to BTK inhibitors. Furthermore, ibrutinib’s toxicities, most notably hypertension and atrial arrhythmia, led to dose reductions or discontinuation. The toxicity profile of ibrutinib can be attributed to the inhibition of additional kinases that are structurally related to BTK. Therefore, the next-generation highly selective zanubrutinib was developed to address the concerns regarding toxicity and tolerance related to ibrutinib therapy. Based on the results of the randomized, open-label Phase 3 ASPEN (NCT03053440) trial, the Food and Drug Administration (FDA) approved zanubrutinib for treating WM. This trial directly compared zanubrutinib to ibrutinib in patients with treatment-naïve or relapsed/refractory WM, and the results showed stronger responses with zanubrutinib. More importantly, patients responded strongly to zanubrutinib therapy regardless of CXCR4 mutation status. Additionally, zanubrutinib was associated with fewer grade 3 or higher toxicities and was generally better tolerated. Another Phase 1/2 study has been conducted with just zanubrutinib in WM showcasing high efficacy with few toxicities as well. Even though zanubrutinib has been the third and last BTK inhibitor to currently penetrate the market for B-cell lymphoproliferative malignancies, we highlight the emergence of zanubrutinib as a key player in the forefront of the therapeutic landscape in WM.