Multicenter Clinical Trial of Bortezomib in Relapsed/Refractory Waldenstrom's Macroglobulinemia: Results of WMCTG Trial 03-248

Sequential treatment escalation improves survival in patients with Waldenstrom macroglobulinemia

Waldenstrom macroglobulinemia (WM) is a type of incurable, indolent B-cell lymphoma that is prone to relapse. Over time, treatment strategies have progressed from cytotoxic drugs to rituximab (R)- or bortezomib (V)-based regimens, and have now entered into an era of Bruton tyrosine kinase inhibitor (BTKi)-based regimens. However, the optimal treatment for the relapsed patients is still unclear. Herein, we analyzed the outcomes of the first- and second-line therapies in 377 patients with WM to illustrate the optimal choices for second-line therapy. After a median follow-up of 45.4 months, 89 patients received second-line therapy, and 53 patients were evaluated for response. The major response rates (MRR) of first- and second-line treatment were 65.1% and 67.9% (P = 0.678). The median progression-free survival (PFS) for the second-line therapy (PFS2) was shorter than that for the first-line therapy (PFS1) (56.3 vs 40.7 months, P = 0.03). However, PFS2 in targeted drugs group (R-/V-/BTKi-based regimens) was comparable to PFS1 (60.7 months vs 44.7 months, respectively, P = 0.21). Regarding second-line therapy, patients who underwent sequential treatment escalation-such as transitioning from cytotoxic drugs to R-/V-/BTKi-based regimens or from R-/V-based to BTKi-based regimens (escalation group) -had higher MRR (80.6% vs 47.1%, respectively, P = 0.023) and longer PFS2 (50.4 vs 23.5 months, respectively, P < 0.001) compared to the non-escalation group. Patients in the escalation group also had longer post-relapse overall survival compared with the non-escalation group (median, 50.4 vs 23.5 months, respectively, P = 0.039). Our findings indicate that sequential treatment escalation may improve the survival of patients with WM.

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.

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.

Proteasome Inhibitor-Based Regimens in the Frontline Management of Waldenström Macroglobulinemia

Proteasome inhibitors (PIs) have long been used in myeloma therapy but also for Waldenström macroglobulinemia. Their use has been successful and has also been investigated for the frontline management of the disease. Bortezomib was effective either as a single agent or in combination with other regimens with high response rates observed in most studies, despite its adverse effects, especially neurotoxicity, which remains a major concern. Clinical trials with second-generation PIs such as carfilzomib and ixazomib have also been conducted, always in combination with immunotherapy in previously untreated patients. They have been shown to be active and neuropathy-sparing treatment options.

Minimal residual disease status improved the response evaluation in patients with Waldenström's macroglobulinemia

Introduction

Minimal residual disease (MRD) has been recognized as an important prognostic factor of survival in patients with hematological malignancies. However, the prognostic value of MRD in Waldenström macroglobulinemia (WM) remains unexplored.

Methods

We analyzed 108 newly diagnosed WM patients receiving systematic therapy and assessed for MRD by multiparameter flow cytometry (MFC) using bone marrow samples.

Results

Of the total patients, 34 (31.5%) achieved undetectable MRD (uMRD). A hemoglobin level of >115 g/L (P=0.03), a serum albumin level of >35 g/L (P=0.01), a β2-MG level of ≤3 mg/L (P=0.03), and a low-risk International Prognostic Scoring System for WM (IPSSWM) stage (P<0.01) were associated with a higher rate of uMRD. Improvements in monoclonal immunoglobulin (P<0.01) and hemoglobin (P=0.03) levels were more evident in uMRD patients compared with that in MRD-positive patients. The 3-year progression-free survival (PFS) was better in uMRD patients compared with that in MRD-positive patients (96.2% vs. 52.8%; P=0.0012). Landmark analysis also showed that uMRD patients had better PFS compared with MRD-positive patients after 6 and 12 months. Patients who achieved partial response (PR) and uMRD had a 3-year PFS of 100%, which was significantly higher than that of patients with MRD-positive PR (62.6%, P=0.029). Multivariate analysis showed that MRD positivity was an independent factor of PFS (HR: 2.55, P=0.03). Moreover, the combination of the 6th International Workshop on WM assessment (IWWM-6 Criteria) and MRD assessment had a higher 3-year AUC compared with the IWWM-6 criteria alone (0.71 vs. 0.67).

Discussion

MRD status assessed by MFC is an independent prognostic factor for PFS in patients with WM, and its determination could improve the precision of response evaluation, especially in patients who achieved PR.

Report of consensus panel 2 from the 11th international workshop on Waldenström's macroglobulinemia on the management of relapsed or refractory WM patients

The consensus panel 2 (CP2) of the 11th International Workshop on Waldenström's macroglobulinemia (IWWM-11) has reviewed and incorporated current data to update the recommendations for treatment approaches in patients with relapsed or refractory WM (RRWM). The key recommendations from IWWM-11 CP2 include: (1) Chemoimmunotherapy (CIT) and/or a covalent Bruton tyrosine kinase (cBTKi) strategies are important options; their use should reflect the prior upfront strategy and are subject to their availability. (2) In selecting treatment, biological age, co-morbidities and fitness are important; nature of relapse, disease phenotype and WM-related complications, patient preferences and hematopoietic reserve are also critical factors while the composition of the BM disease and mutational status (MYD88, CXCR4, TP53) should also be noted. (3) The trigger for initiating treatment in RRWM should utilize knowledge of patients' prior disease characteristics to avoid unnecessary delays. (4) Risk factors for cBTKi related toxicities (cardiovascular dysfunction, bleeding risk and concurrent medication) should be addressed when choosing cBTKi. Mutational status (MYD88, CXCR4) may influence the cBTKi efficacy, and the role of TP53 disruptions requires further study) in the event of cBTKi failure dose intensity could be up titrated subject to toxicities. Options after BTKi failure include CIT with a non-cross-reactive regimen to one previously used CIT, addition of anti-CD20 antibody to BTKi, switching to a newer cBTKi or non-covalent BTKi, proteasome inhibitors, BCL-2 inhibitors, and new anti-CD20 combinations are additional options. Clinical trial participation should be encouraged for all patients with RRWM.

Negligible role of TRAIL death receptors in cell death upon endoplasmic reticulum stress in B-cell malignancies

Impairments in protein folding in the endoplasmic reticulum (ER) lead to a condition called ER stress, which can trigger apoptosis via the mitochondrial or the death receptor (extrinsic) pathway. There is controversy concerning involvement of the death receptor (DR)4 and DR5-Caspase-8 -Bid pathway in ER stress-mediated cell death, and this axis has not been fully studied in B-cell malignancies. Using three B-cell lines from Mantle Cell Lymphoma, Waldenström's macroglobulinemia and Multiple Myeloma origins, we engineered a set of CRISPR KOs of key components of these cell death pathways to address this controversy. We demonstrate that DR4 and/or DR5 are essential for killing via TRAIL, however, they were dispensable for ER-stress induced-cell death, by Thapsigargin, Brefeldin A or Bortezomib, as were Caspase-8 and Bid. In contrast, the deficiency of Bax and Bak fully protected from ER stressors. Caspase-8 and Bid were cleaved upon ER-stress stimulation, but this was DR4/5 independent and rather a result of mitochondrial-induced feedback loop subsequent to Bax/Bak activation. Finally, combined activation of the ER-stress and TRAIL cell-death pathways was synergistic with putative clinical relevance for B-cell malignancies.

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.

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.

Bortezomib-based chemotherapy for patients with Waldenström macroglobulinemia: a single-center experience

Waldenström Macroglobulinemia (WM) is a rare type of non-Hodgkin lymphoma with no standard first-line treatment, and the disease is still incurable. This study evaluated the clinical efficacy, safety, and prognostic factors of bortezomib-based chemotherapy as initial treatment in WM patients. We retrospectively analyzed the clinical data collected from 44 newly diagnosed WM patients treated with bortezomib-based regimens at the Affiliated Hospital of Nantong University from December 2011 to June 2021. Univariate and multivariate analyses were used to assess prognostic factors for overall survival (OS) and progression-free survival (PFS). The median age was 67 years old, with an overall response rate (ORR) of 93.2%, complete response (CR) rate of 6.8%, and very good partial response (VGPR) rate of 29.5%. With a median follow-up of 39 months, the 2-year overall survival (OS) and 2-year PFS rates were 88.0% and 59.0%, respectively. By the last follow-up, eight patients (18.2%) had died. Univariate analysis showed patients with B symptoms, elevated LDH, international prognostic stage system of WM (IPSSWM) stage III, high Revised IPSSWM (R-IPSSWM) score, and those who did not achieve VGPR were associated with shorter PFS. And patients with B symptoms, with high R-IPSSWM score, and who do not achieve VGPR also had shorter OS than their counterparts. Multivariate analysis confirmed that failure to achieve VGPR was an independent adverse prognostic factor for OS and PFS. In conclusion, we showed that bortezomib-based chemotherapy effectively treated newly diagnosed patients with WM. However, combinations of drugs with different mechanisms are recommended for patients with a high tumor burden. In addition, deep remission can improve patients' survival.

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.

IgM-Related Immunoglobulin Light Chain (AL) Amyloidosis

Waldenström macroglobulinemia (WM) is a rare lymphoplasmacytic disorder characterized by an IgM paraprotein. The clinical presentation of WM varies and can include common manifestations such as anemia and hyperviscosity, in addition to less common features such as cryoglobulinemia, IgM-related neuropathy, and immunoglobulin light chain (AL) amyloidosis. Amyloidosis is a protein-folding disorder in which vital organ damage occurs due to the accumulation of misfolded protein aggregates. The most common type of amyloidosis in patients with an IgM paraprotein is AL amyloidosis, although other types of amyloidosis may occur. IgM-related amyloidosis has distinct clinical features when compared with other subtypes of AL amyloidosis. This review highlights the diagnostic criteria of IgM-related AL amyloidosis, as well as the clinical characteristics and treatment options for this disorder.

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.

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.

Treatment paradigm in Waldenström macroglobulinemia: frontline therapy and beyond

Waldenström macroglobulinemia (WM) is an indolent lymphoplasmacytic lymphoma. Recent strides made in the genomic profiling of patients with WM have led to the identification of many novel therapeutic targets. Patients with WM can present with asymptomatic disease and not all patients require treatment. When criteria for initiating systemic therapy are met, the choice of therapy depends on the tumor genotype (MYD88 and CXCR4 mutation status), patient preference (fixed versus continuous duration therapy, oral versus intravenous route, cost), associated medical comorbidities, and adverse effect profile of the treatment. In the absence of head-to-head comparison between chemoimmunotherapy and Bruton’s tyrosine kinase inhibitors in otherwise fit patients with a MYD88^L265P mutation, our preference is fixed duration therapy with four to six cycles of chemoimmunotherapy with bendamustine–rituximab. In this review, we discuss the role of MYD88 and CXCR4 mutation in treatment selection, and current data for frontline and salvage treatment options in patients with WM.

Zanubrutinib for the treatment of adults with Waldenstrom macroglobulinemia

INTRODUCTION

The development of Bruton tyrosine kinase (BTK) inhibitors has significantly changed the treatment landscape for patients with Waldenström macroglobulinemia (WM). Ibrutinib was the first BTK inhibitor to receive FDA approval for this disease, but in recent years additional more selective BTK inhibitors have become available. Zanubrutinib, the most recently FDA-approved therapy for WM, has demonstrated comparable efficacy regarding hematologic response, but with an improved side effect profile compared to other BTK inhibitors.

AREAS COVERED

In this review, we highlight the pivotal studies that have formed the foundation for the use of zanubrutinib in WM, including safety and efficacy data from prospective clinical trials of the currently available BTK inhibitors.

EXPERT OPINION

BTK inhibitors are very effective in WM and have an overall response rate higher than 90%. The side effect profile of these medications is manageable, but does include a risk of atrial fibrillation, infection, and bleeding. The newer BTK inhibitors, such as acalabrutinib and zanubrutinib, are known to have less off-target effects and are potential treatment options. BTK inhibitors should be considered as a treatment option in treatment-naïve and previously treated disease depending on the individual patient preferences, comorbidities, and molecular profile.

Current approach to Waldenström Macroglobulinemia

Waldenström Macroglobulinemia (WM) is a unique, low grade, IgM lymphoplasmacytic lymphoma with a heterogeneous clinical course. A paucity of high-grade evidence from large phase 3 trials remains a major issue in the field despite a rapidly expanding therapeutic armamentarium against WM. Prior knowledge of the patients' MYD88^L265P and CXCR4 mutation status aids in treatment decision making if Bruton's tyrosine kinase (BTK) inhibitor therapy is being considered. Head-to head comparative data to inform optimal approach are lacking, and a particularly vexing issue for the clinicians is choosing between fixed-duration bendamustine-rituximab (BR) therapy and an indefinite BTK inhibitor-based regimen, given that both approaches are well tolerated and effective, particularly for the patient population harboring MYD88^L265P mutation. For the patients with MYD88^WT genotype, chemo-immunotherapy such as BR is preferred, although zanubrutinib, a potent second generation BTK inhibitor, with its reduced off target effects and greater BTK occupancy compared to its predecessor, ibrutinib, has also recently shown activity in MYD88^WT WM. This review summarizes the current literature pertaining to the diagnosis, prognosis, and the treatment of WM.

Protein clearance strategies for disease intervention

Protein homeostasis, or proteostasis, is essential for cell function and viability. Unwanted, damaged, misfolded and aggregated proteins are degraded by the ubiquitin–proteasome system (UPS) and the autophagy-lysosome pathway. Growing evidence indicates that alterations in these major proteolytic mechanisms lead to a demise in proteostasis, contributing to the onset and development of distinct diseases. Indeed, dysregulation of the UPS or autophagy is linked to several neurodegenerative, infectious and inflammatory disorders as well as cancer. Thus, modulation of protein clearance pathways is a promising approach for therapeutics. In this review, we discuss recent findings and open questions on how targeting proteolytic mechanisms could be applied for disease intervention.

Managing complications secondary to Waldenström's macroglobulinemia

Introduction: Waldenström's macroglobulinemia (WM) is a rare lymphoma characterized by the accumulation of IgM-secreting lymphoplasmacytic cells in the bone marrow and other organs. Clinical sequelae relate to direct tissue infiltration by malignant cells but also to the physicochemical and immunological properties of the monoclonal IgM, resulting in a variety of disease-related complications.Areas covered: This narrative review, following a thorough Pubmed search of pertinent published literature, discusses complications secondary to WM, related to direct tumor infiltration, monoclonal IgM circulation, and deposition, as well as other less common ones. The description and pathophysiology of these complications were described together with their specific management strategies and in the context of available treatment options for WM (anti-CD20 monoclonal antibody-based combinations, proteasome inhibitors, BTK inhibitors, and other emerging ones).Expert opinion: The availability of many novel, active and less toxic regimens for the treatment of WM allows the management of the disease with strategies that depend on clinical presentation and disease-related complications, age, toxicity considerations, and presence of comorbidities.

Reducing treatment toxicity in Waldenström macroglobulinemia

Introduction: Waldenström macroglobulinemia (WM) is a rare subtype of non-Hodgkin lymphoma characterized by the presence of IgM-secreting clonal lymphocytes, plasma cells, and lymphoplasmacytic cells. Many well-established treatment options are available for patients with WM. However, a unique array of side effects may occur in patients during therapy related to the underlying disease, as well as the chosen treatment regimen.Areas covered: This review summarizes the most common adverse effects that occur during treatment of WM, as well as potential strategies to decrease the risk of toxicity.Expert opinion: There are multiple highly effective treatment options for patients with WM. All these treatment options, however, can be associated with a variety of adverse events. For example, chemotherapy has been associated with the development of myeloid neoplasms, anti-CD20 monoclonal antibodies with paradoxical IgM flares and infusion reactions, proteasome inhibitors with neuropathy, and BTK inhibitors with bleeding and cardiac arrhythmias. Dose reductions, lower number of cycles and changes in route of administration are some of the tools a clinician has available for managing and minimizing toxicity. Future research will focus on improving patient safety without sacrificing the efficacy of treatment.

Zanubrutinib for the treatment of Waldenström Macroglobulinemia

Introduction: Waldenström Macroglobulinaemia (WM) is a heterogeneous, incurable condition which often relapses after chemoimmunotherapy. Novel therapies such as Bruton tyrosine-kinase (BTK) inhibitors have shown to be efficacious in treating WM but with an established, significant toxicity profile seen in the first-generation inhibitor Ibrutinib. Zanubrutinib is a selective, potent BTK inhibitor with the potential to reduce toxicity and improve efficacy. Areas covered: This review examines the activity of Zanubrutinib in treating treatment-naïve and relapsed refractory WM and it's toxicity profile when compared to Ibrutinib. Outcomes from the AU003 and ASPEN studies will be examined in detail including a particular focus on MYD88^WT and CXCR4^WHIM disease. Strengths and weaknesses of this treatment approach will be highlighted and future directions for research will be identified. Expert opinion: Zanubrutinib induces deeper responses and have greater activity in MYD88^WT and CXCR4^WHIM WM. Zanubrutinib also has a favorable toxicity profile when compared to Ibrutinib. This may potentially translate to lower discontinuation rates, improved quality of life and ultimately longer progression-free survival in patients with WM.

A multicenter, open-label, phase II study of tirabrutinib (ONO/GS-4059) in patients with Waldenström's macroglobulinemia

Tirabrutinib is a second-generation Bruton's tyrosine kinase inhibitor with greater selectivity than ibrutinib. Here, we conducted a multicenter, phase II study of tirabrutinib in patients with treatment-naïve (Cohort A) or with relapsed/refractory (Cohort B) Waldenström's macroglobulinemia (WM). Patients were treated with tirabrutinib 480 mg once daily. The primary endpoint was major response rate (MRR; ≥ partial response). Secondary endpoints included overall response rate (ORR; ≥ minor response), time to major response (TTMR), progression-free survival (PFS), overall survival (OS), and safety. In total, 27 patients (18 in Cohort A; 9 in Cohort B) were enrolled. The median age was 71 y, and the median serum immunoglobulin M level was 3600 mg/dL. Among the patients, 96.2% had the MYD88^L265P mutation. MRR and ORR were 88.9% and 96.3%, respectively (Cohort A: MRR, 88.9%; ORR, 94.4%; Cohort B: MRR, 88.9%; ORR, 100%). Median TTMR was 1.87 mo. PFS and OS were not reached with a median follow-up of 6.5 and 8.3 mo for Cohorts A and B, respectively. The most common adverse events (AEs) were rash (44.4%), neutropenia (25.9%), and leukopenia (22.2%), with most AEs classified as grade 1 or 2. Grade ≥ 3 AEs included neutropenia (11.1%), lymphopenia (11.1%), and leukopenia (7.4%). No grade 5 AEs were noted. All bleeding events were grade 1; none were associated with drug-related atrial fibrillation or hypertension. Although the follow-up duration was relatively short, the study met the primary endpoint. Therefore, tirabrutinib monotherapy is considered to be highly effective for both untreated and relapsed/refractory WM with a manageable safety profile. (JapicCTI-173646).

Current and Emerging Treatments for Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare lymphoplasmacytic lymphoma. The primary goal of therapy is to reduce symptoms related to direct infiltration of the bone marrow and decrease monoclonal IgM-associated complications. Active agents in the management of WM can be broadly classified as rituximab-alkylator combination therapy, proteasome inhibitor-based therapy, and Bruton's tyrosine kinase inhibitor-based therapy. MYD88L265P and CXCR4 genetic status are pivotal for tailoring treatment options. Ibrutinib is a suitable treatment option for both treatment-naïve and relapsing WM patients. Recent advances in the intracellular B cell and cytokine signaling pathways have contributed to the development of novel therapeutic strategies. Current clinical trials are promising and may further advance WM-directed therapy.

Novel tumor-targeted liposomes comprised of an MDM2 antagonist plus proteasome inhibitor display anti-tumor activity in a xenograft model of bortezomib-resistant Waldenstrom macroglobulinemia

Targeted drug delivery remains an active area of investigation in hematologic cancers. We have previously reported on a novel nanoparticle formulation (D1X) that can encapsulate drugs within a liposome whose lipid bilayer contains dexamethasone, which serves as a targeting ligand for drug delivery to tumor cells that express glucocorticoid receptors. We tested the activity of D1X-encapsulated bortezomib (D1XB) in combination with D1X-encapsulated nutlin (D1XN) in B-lymphoma/Waldenstrom macroglobulinemia (WM) cells. WM cells treated with D1XB + D1XN experienced cell cycle arrest, ER stress and apoptosis. In mice xenografted with bortezomib-resistant WM cells, D1XB + D1XN treatment resulted in significantly lower tumor burden compared to vehicle or nonliposomal parent drugs. In vivo biodistribution studies showed minimal uptake of D1X-based drugs in normal mice tissues. Our studies demonstrate that highly targeted delivery of both bortezomib and nutlin encapsulated in D1X nanoparticles are cytotoxic to and delay in vivo growth of bortezomib-resistant WM cells.

How I treat Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is an uncommon lymphoma characterized by the infiltration of the bone marrow by clonal lymphoplasmacytic cells that produce monoclonal immunoglobulin M (IgM). The disease may have an asymptomatic phase, or patients may present with symptoms and complications resulting from marrow or other tissue infiltration, or from physicochemical or immunological properties of the monoclonal IgM. Diagnosis of WM has been clearly defined, and genetic testing for somatic mutation of MYD88L265P is a useful tool for differential diagnosis from other conditions. Specific criteria that define symptomatic disease that needs treatment offer clinical guidance. The treatment of WM has evolved rapidly, with treatment options that include anti-CD20 monoclonal antibody-based combinations and BTK inhibitors. The choice of therapy is based on the need for rapid disease control, presence of specific disease complications, and patient's age. With the use of BTK inhibitors, the use of continuous therapy has been introduced as another option over fixed-duration chemoimmunotherapy. In this review, we focus on different clinical scenarios and discuss treatment options, based on the available data.

Waldenstrom's macroglobulinemia in the era of immunotherapy

Waldenstrom macroglobulinemia (WM) is a lymphoplasmacytic lymphoma that presents with symptomatic anemia, thrombocytopenia, constitutional symptoms, extramedullary disease and rarely hyperviscosity syndrome. The presence of both IgM monoclonal protein and ≥10% monoclonal lymphoplasmacytic cells is required for the diagnosis. MyD88 is present in 67-90% of patients but is not pathognomonic for WM. Many patients who fulfill the criteria of WM are asymptomatic and do not require treatment. Recent advances in the understanding of the biology of WM have paved the way for new treatment options. The use of novel agents with or without rituximab enables the use of effective chemotherapy-free regiments upfront and in the relapsed setting. New targeted treatments such as venetoclax and CXCR4 antagonists are being investigated.

Bortezomib for the Treatment of Hematologic Malignancies: 15 Years Later

Bortezomib is a dipeptidyl boronic acid that selectively inhibits the ubiquitin proteasome pathway, which plays a role in the degradation of many intracellular proteins. It is the first-in-class selective and reversible inhibitor of the 26S proteasome, with antiproliferative and antitumor activity. It exerts its anti-neoplastic action mainly via the inhibition of the nuclear factor-κB pathway components associated with cell proliferation, apoptosis, and angiogenesis. The drug has revolutionized the treatment of multiple myeloma and, more recently, mantle cell lymphoma. In 2003, bortezomib received accelerated approval from the US Food and Drug Administration for the treatment of relapsed/refractory multiple myeloma and in 2008 for patients with previously untreated multiple myeloma. In 2006, bortezomib was approved for the treatment of refractory/relapsed mantle cell lymphoma and, in 2014, for previously untreated mantle cell lymphoma. Bortezomib has also demonstrated clinical efficacy both as a single drug and in combination with other agents in light chain amyloidosis, lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia, and peripheral T-cell lymphomas. Furthermore, continued clinical studies are required to confirm its value for patients with indolent and aggressive B-cell non-Hodgkin lymphomas and acute leukemias.

Proteasome Inhibitors in Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) remains an incurable B-cell lymphoproliferative disorder, yet therapy is only considered for patients with symptomatic disease. Primary therapy options for WM include combinations based on anti-CD20 monoclonal antibodies, mainly rituximab. However, proteasome inhibitors have become an important part of WM therapy both as primary therapy and as salvage option. Bortezomib is the proteasome inhibitor most studied and with extensive clinical experience, but new proteasome inhibitors (carfilzomib, ixazomib, oprozomib), with different toxicity profiles, routes of administration, and probably with preserved or improved activity, have become available and may also find their way into WM therapy.

First-Generation and Second-Generation Bruton Tyrosine Kinase Inhibitors in Waldenström Macroglobulinemia

Waldenström macroglobulinemia (WM) is an indolent B-cell lymphoma that is heavily dependent on Bruton tyrosine kinase (BTK) hyperactivation. Ibrutinib is a first-generation BTK inhibitor that has shown high activity and durable responses in patients with relapsed/refractory WM. Newer and more selective BTK inhibitors are currently being tested in several clinical trials and are expected to address the toxicity and the acquired resistance observed in patients receiving ibrutinib. Updates on ibrutinib and second-generation BTK inhibitors are summarized in this review.

A safety profile of medications used to treat Waldenström's macroglobulinemia

INTRODUCTION

Waldenström's macroglobulinemia (WM) is a B-cell lymphoproliferative disease with serum IgM monoclonal component and bone marrow infiltration by lymphoplasmacytic lymphoma. Traditional therapy was based on that regimens used for closely related entities, such as chronic lymphocytic leukemia or multiple myeloma. This resulted in a lack of drugs specifically approved for WM, until the discovery of the Bruton Tyrosine Kinase (BTK) inhibitors.

AREAS COVERED

Two main therapeutic attitudes are possible: (1) conventional therapies based on combinations with alkylating agents or proteasome inhibitors with steroids and anti-CD20 monoclonal antibodies or (2) new approaches with BTK inhibitors, usually alone. Other possibilities such as BCL2 inhibitors, PI3K/AKT inhibitors, and others are currently under evaluation, but we will focus the review on the most consolidated approaches that are available for patients with WM at different stages of the disease. PubMed, Web of Science, and clinicaltrials.gov were queried for the keywords 'Waldenstrom macroglobulinemia' and the different drugs here evaluated through 1 February 2018.

EXPERT OPINION

Although WM has no many specific drugs, there are many possible therapies, including Ibrutinib, the first formally approved drug for this disorder.

The importance of the genomic landscape in Waldenström's Macroglobulinemia for targeted therapeutical interventions

The Literature has recently reported on the importance of genomics in the field of hematologic malignancies, including B-cell lymphoproliferative disorders such as Waldenström's Macrolgobulinemia (WM). Particularly, whole exome sequencing has led to the identification of the MYD88L265P and CXCR4C1013G somatic variants in WM, occurring in about 90% and 30% of the patients, respectively. Subsequently, functional studies have demonstrated their functional role in supporting WM pathogenesis and disease progression, both in vitro and in vivo, thus providing the pre-clinical evidences for extremely attractive targets for novel therapeutic interventions in WM. Of note, recent evidences have also approached and defined the transcriptome profiling of WM cells, revealing a signature that mirrors the somatic aberrations demonstrated within the tumor clone. A parallel research field has also reported on microRNAs (miRNAs), highlighting the oncogenic role of miRNA-155 in WM. In the present review, we focus on the latest reports on genomics and miRNAs in WM, providing an overview of the clinical relevance of the latest acquired knowledge about genomics and miRNA aberrations in WM.

Low-dose bortezomib and dexamethasone as primary therapy in elderly patients with Waldenstrӧm macroglobulinemia

OBJECTIVE

This retrospective study was designed to determine the efficacy and safety of low-dose bortezomib and dexamethasone (lBD) in elderly Chinese patients with Waldenstrӧm macroglobulinemia (WM).

METHODS

Ten patients with WM aged over 60 years received first-line treatment with lBD.

RESULTS

The median age was 70 years (range, 61-77 years). The overall response rate was 80%, including 1 patient who achieved a complete response, 1 patient with very good partial response, and 6 patients with a partial response. Median time to response was 1.8 months after treatment with lBD. Six (60%) patients achieved a partial response, including 2 (20%) patients who had a more than 75% reduction in serum immunoglobulin M levels. A rapid reduction in paraprotein was observed in three patients who received plasmapheresis. After a median follow-up period of 36 months, all patients were still alive and six had no disease progression. The estimated median time to progression was 39 months (range, 15-60 months). The most common adverse events were anemia, thrombocytopenia, neuropathy, and neutropenia. Peripheral neuropathy was the most common non-hematological toxicity in six (60%) patients, but did not result in the discontinuation of bortezomib.

CONCLUSIONS

Our findings show that lBD is an effective and tolerable treatment regimen for elderly patients with WM.

The p97 Inhibitor CB-5083 Is a Unique Disrupter of Protein Homeostasis in Models of Multiple Myeloma

Inhibition of the AAA ATPase, p97, was recently shown to be a novel method for targeting the ubiquitin proteasome system, and CB-5083, a first-in-class inhibitor of p97, has demonstrated broad antitumor activity in a range of both hematologic and solid tumor models. Here, we show that CB-5083 has robust activity against multiple myeloma cell lines and a number of in vivo multiple myeloma models. Treatment with CB-5083 is associated with accumulation of ubiquitinated proteins, induction of the unfolded protein response, and apoptosis. CB-5083 decreases viability in multiple myeloma cell lines and patient-derived multiple myeloma cells, including those with background proteasome inhibitor (PI) resistance. CB-5083 has a unique mechanism of action that combines well with PIs, which is likely owing to the p97-dependent retro-translocation of the transcription factor, Nrf1, which transcribes proteasome subunit genes following exposure to a PI. In vivo studies using clinically relevant multiple myeloma models demonstrate that single-agent CB-5083 inhibits tumor growth and combines well with multiple myeloma standard-of-care agents. Our preclinical data demonstrate the efficacy of CB-5083 in several multiple myeloma disease models and provide the rationale for clinical evaluation as monotherapy and in combination in multiple myeloma. Mol Cancer Ther; 16(11); 2375-86. ©2017 AACR.

A phase II Bayesian sequential clinical trial in advanced Waldenström macroglobulinemia patients treated with bortezomib: interest of addition of dexamethasone

In patients with advanced Waldenström macroglobulinemia (WM), overall response rate (ORR) and median progression-free survival (PFS) achieved with bortezomib alone and bortezomib rituximab combination were 27-85% and 7.9 months, and 81% and 16.4 months, respectively. We checked the role of dexamethasone in combination with bortezomib by enrolling in a phase II trial 34 patients with relapsed/refractory WM. Bortezomib (1.3 mg/m² IV D1, 4, 8, and 11 every 21 days) was used for six cycles. In non-responding patients, dexamethasone (20 mg daily for two days) was added to each infusion after the second cycle. After two cycles, the Bayes estimated ORR was 43.2 (95% Credible Interval: 28.0-59.1%) using the informative prior. Two-year survival rate was 84.0% and the median PFS 15.3 months without difference between patients treated with or without dexamethasone. We conclude that dexamethasone must be associated to bortezomib-based regimen.

Waldenström Macroglobulinemia: Review of Pathogenesis and Management

Waldenström macroglobulinemia (WM) is a low-grade B-cell clonal disorder characterized by lymphoplasmacytic bone marrow involvement associated with monoclonal immunoglobulin M. Although WM remains to be an incurable disease with a heterogeneous clinical course, the recent discovery of mutations in the MYD88 and CXCR4 genes further enhanced our understanding of its pathogenesis. Development of new therapies including monoclonal antibodies, proteasome inhibitors, and Bruton tyrosine kinase inhibitors have made the management of WM increasingly complex. Treatment should be tailored to the individual patient while considering many clinical factors. The clinical outcomes are expected to continue to improve, given the emergence of novel therapeutics and better understanding of the underlying pathogenesis.

BDR in newly diagnosed patients with WM: final analysis of a phase 2 study after a minimum follow-up of 6 years

BDR is a chemotherapy-free, non-stem-cell–toxic regimen associated with high response rates and long-term remissions. The long-term safety profile of BDR is favorable, with high probability of response to reintroduction of rituximab-based regimens at relapse.

Prospective, Multicenter Clinical Trial of Everolimus as Primary Therapy in Waldenstrom Macroglobulinemia (WMCTG 09-214)

Purpose: Everolimus inhibits mTOR, a component of PI3K/AKT prosurvival signaling triggered by MYD88 and CXCR4-activating mutations in Waldenstrom macroglobulinemia.Experimental design: We evaluated everolimus in a prospective, multicenter study of 33 symptomatic, previously untreated Waldenstrom macroglobulinemia patients. Intended therapy consisted of everolimus (10 mg/day) until progression or unacceptable toxicity. Dose deescalation was permitted. The study was registered at www.clinicaltrials.gov (NCT00976248).Results: At best response, median serum IgM levels declined from 4,440 to 1,360 mg/dL (P < 0.0001), median hemoglobin rose from 10.8 to 12 g/dL (P = 0.001), and median bone marrow disease burden declined from 75% to 52.5% in serially biopsied patients. The ORR and major response rates were 72.7% and 60.6%, respectively. Among genotyped patients, nonresponders associated with wild-type MYD88 and mutated CXCR4 status. Median time to response was 4 weeks. Discordance between serum IgM levels and bone marrow disease burden was remarkable. With a median follow-up of 13.1 (range, 1.6-64.6 months), the median time to progression was 21 months for all patients and 33 months for major responders. Discontinuation of everolimus led to rapid serum IgM rebound in 7 patients and symptomatic hyperviscosity in 2 patients. Toxicity led to treatment discontinuation in 27% of patients, including 18% for pneumonitis.Conclusions: Everolimus is active in previously untreated Waldenstrom macroglobulinemia. IgM discordance is common, and treatment cessation can often lead to rapid serum IgM rebound. Pneumonitis also appears more pronounced in untreated versus previously treated Waldenstrom macroglobulinemia patients. The risks and benefits of everolimus should be carefully weighed against other primary Waldenstrom macroglobulinemia therapy options. Clin Cancer Res; 23(10); 2400-4. ©2016 AACR.

Current therapy guidelines for Waldenstrom's macroglobulinaemia

Waldenstrom's macroglobulinaemia (WM) is a B-cell neoplasm in which bone marrow is infiltrated by lymphoplasmacytic cells that secrete monoclonal immunoglobulin M (IgM). More than a decade ago, specific criteria were agreed to define diagnosis and symptomatic disease requiring therapy; however, treatment recommendations change as new options emerge. Treatment decisions consider specific disease characteristics (burden of disease, IgM levels, presence of cytopenias) and patient characteristics (age, comorbidities, toxicity). Recently, the impact of specific mutations (in MYD88 and CXCR4) in response to specific therapies has been reported, and this may affect treatment decisions in the future. Chemo-immunotherapy combinations based on rituximab with cyclophosphamide/dexamethasone, bendamustine or bortezomib/dexamethasone are indicated for most patients. The BTK inhibitor ibrutinib was recently approved for patients with WM, and is a new option for selected newly diagnosed or relapsing patients. New B-cell receptor inhibitors, second-generation proteasome inhibitors and mammalian target of rapamycin inhibitors are promising; however, more data are needed from high-quality clinical trials.

Coinhibition of the deubiquitinating enzymes, USP14 and UCHL5, with VLX1570 is lethal to ibrutinib- or bortezomib-resistant Waldenstrom macroglobulinemia tumor cells

The survival of Waldenstrom macroglobulinemia (WM) tumor cells hinges on aberrant B-cell receptor (BCR) and MYD88 signaling. WM cells upregulate the proteasome function to sustain the BCR-driven growth while maintaining homeostasis. Clinically, two treatment strategies are used to disrupt these complementary yet mutually exclusive WM survival pathways via ibrutinib (targets BTK/MYD88 node) and bortezomib (targets 20 S proteasome). Despite the success of both agents, WM patients eventually become refractory to treatment, highlighting the adaptive plasticity of WM cells and underscoring the need for development of new therapeutics. Here we provide a comprehensive preclinical report on the anti-WM activity of VLX1570, a novel small-molecule inhibitor of the deubiquitinating enzymes (DUBs), ubiquitin-specific protease 14 (USP14) and ubiquitin carboxyl-terminal hydrolase isozyme L5 (UCHL5). Both DUBs reside in the 19 S proteasome cap and their inhibition by VLX1570 results in rapid and tumor-specific apoptosis in bortezomib- or ibrutinib-resistant WM cells. Notably, treatment of WM cells with VLX1570 downregulated BCR-associated elements BTK, MYD88, NFATC, NF-κB and CXCR4, the latter whose dysregulated function is linked to ibrutinib resistance. VLX1570 administered to WM-xenografted mice resulted in decreased tumor burden and prolonged survival (P=0.0008) compared with vehicle-treated mice. Overall, our report demonstrates significant value in targeting USP14/UCHL5 with VLX1570 in drug-resistant WM and carries a high potential for clinical translation.

Future therapeutic options for patients with Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare lymphoma characterized by the accumulation of IgM-producing lymphoplasmacytic cells. Although WM patients can experience prolonged remissions, the disease invariably recurs. Therefore, novel treatments associated with higher success rates and lower toxicity profiles are needed. The discovery of recurrent mutations in the MYD88 and CXCR4 genes has unraveled potential therapeutic targets in WM patients. As a result of these findings and based on the design and execution of a prospective clinical trial, the FDA granted approval to ibrutinib, an oral Bruton tyrosine kinase (BTK) inhibitor, to treat patients with symptomatic WM. The present review focuses on potential therapies that could change the landscape of treatment of patients with WM, specifically focusing on inhibitors or antagonists or the proteasome, BTK, CD38, BCL2 and the CXCR4 and MYD88 genes themselves. Novel agents with novel mechanisms of action should be evaluated in the context of carefully designed clinical trials.

Novel therapeutic targets in Waldenstrom macroglobulinemia

Understanding of molecular mechanisms that drive Waldenstrom macroglobulinemia (WM) cell survival are rapidly evolving. This review briefly highlights emerging "WM-relevant" targets; for which therapeutic strategies are currently being investigated in preclinical and clinical studies. With the discovery of MYD88_L265P signaling and remarkable activity of ibrutinib in WM, other targets within the B-cell receptor pathway are now being focused on for therapeutic intervention. Additional targets which play a role in WM cell survival include TLR7, 8 and 9, proteasome-associated deubiquitinating enzymes (USP14 and UCHL5), XPO1/CRM1 and AURKA. New drugs for established targets are also discussed. Lastly, we spotlight 3 highly innovative WM-specific therapies: MYD88 peptide inhibitors, MYD88_L265P-directed immune activation and CD19-directed chimeric antigen receptor T-cell therapy, which are in various stages of development. Indeed, treatment of WM is poised to undergo a paradigm shift in the coming years towards highly disease-driven and more personalized therapeutic modalities with curative intent.

The role of stem cell transplantation in Waldenstrom's macroglobulinemia

Waldenstrom's macroglobulinemia (WM) is an indolent B-cell lymphoma, which is highly chemosensitive, with an overall response rate over 90% to novel agents. However, most patients eventually relapse after response to first-line chemotherapy, necessitating further treatment. The possibility of long-lasting remission after high-dose cytotoxic chemotherapy followed by stem cell rescue is high in WM due to the chemosensitive nature of the disease and lower proliferative activity compared to multiple myeloma. In this paper, we have reviewed current evidence on autologous (auto-) and allogeneic (allo-) stem cell transplantation (SCT) in WM. Auto-SCT can be safely performed in WM and is recommended as second-line treatment or beyond in eligible patients. It is associated with extremely low transplant-related mortality. Allo-SCT is effective in WM with incremental benefit due to graft-versus-WM effect, but is associated with high non-relapse mortality of 30%, hence should be preferably considered investigational as part of clinical trials in selected patients who have exhausted other treatment options.

Evolution of Management and Outcomes in Waldenström Macroglobulinemia: A Population-Based Analysis

INTRODUCTION

Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM) is a rare lymphoma affecting older patients. Its management largely relies on small phase II trials and it is unclear how their results translate into clinical practice in the community.

METHOD

We evaluated changes in the presentation, management, and survival among 2,666 Medicare beneficiaries diagnosed with WM between 1994 and 2011, using Medicare claims linked to Surveillance, Epidemiology and End Results data.

RESULTS

Prevalence of transfusions, anemia, thrombocytopenia, and neuropathy at diagnosis significantly increased over time, whereas the use of plasmapheresis was low (2.5%) and stable. The proportion of patients starting chemotherapy within 1 year of WM diagnosis increased from 39% in 1994 to 62% in 2011 (p < .0001). Treatments based on classic alkylators and purine analogs predominated in the 1990s, but were quickly replaced by rituximab-containing regimens after 2000. Rituximab monotherapy has been prescribed for >50% of patients since 2004, and combination chemoimmunotherapy for a further 30%. Most patients initiating multiagent regimens in 2012-2013 received rituximab with bortezomib or bendamustine. These changes were accompanied by significant improvements in overall and WM-related survival, but also by a significant increase in cost of chemotherapy. Mean Medicare payments for chemotherapy drugs accrued in the first year of treatment rose from $9,464 in 1994-2000 to $29,490 after 2008.

CONCLUSION

Hematologists have rapidly adopted innovative, expensive therapies for WM before completion of randomized trials. This underscores the need to assess the comparative value of such therapies in rare malignancies through a combination of clinical and observational data.

IMPLICATIONS FOR PRACTICE

Most older patients with Waldenström macroglobulinemia currently treated in the U.S. receive rituximab as monotherapy or in combination with bortezomib or bendamustine. Newly designed trials should consider control arms aligned with this prevalent real-life standard. Compared with the 1990s, patients diagnosed according to current criteria are more likely to have anemia or neuropathy, or to receive early chemotherapy, but only 2.5% require plasmapheresis at diagnosis. The incremental clinical value of newly introduced agents needs to be assessed through a combination of clinical and health services research, taking into consideration their associated survival benefits, toxicities, and associated costs of care.

Waldenström macroglobulinemia: biology, genetics, and therapy

Waldenström macroglobulinemia (WM) is a distinct clinicopathologic entity characterized by the presence of a lymphoplasmacytic lymphoma, a non-Hodgkin lymphoma, and IgM monoclonal gammopathy. WM is an indolent, uncommon malignancy mostly affecting the elderly. Patient outcomes have modestly improved since the introduction of rituximab to conventional cytotoxic chemotherapy more than 20 years ago. However, the pivotal discovery of the somatic MYD88 L265P mutation, harbored by most patients with WM, and the somatic CXCR4 WHIM mutations, similar to germline CXCR4 mutations seen in the warts, hypogammaglobulinemia, immunodeficiency, and myelokathexis (WHIM) syndrome, present in approximately one-third of patients with WM, has fundamentally changed our understanding of this disease and expanded the potential therapeutic targets. Within this new paradigm, ibrutinib emerged as a promising new drug. Ibrutinib targets Bruton’s tyrosine kinase, a downstream protein in the B-cell receptor pathway that is overactivated by the MYD88 L265P mutation. A seminal Phase II trial of ibrutinib in previously treated WM patients showed impressive response rates and confirmed the effects of MYD88 L265P and CXCR4 WHIM mutations in response to therapy. Ibrutinib is the first and only US Food and Drug Administration–approved drug specifically for the treatment of WM. However, before ibrutinib can be established as the standard of care for WM, long-term data regarding efficacy and safety are required. Further research to address ibrutinib resistance and cost-effectiveness is also imperative before ibrutinib can gain widespread acceptance. This review will cover the present pathophysiologic understanding of WM in light of the recent MYD88 and CXCR4 discovery, as well as current and emergent treatment regimens with focus on ibrutinib.