The genomic landscape of Waldenström macroglobulinemia is characterized by highly recurring MYD88 and WHIM-like CXCR4 mutations, and small somatic deletions associated with B-cell lymphomagenesis

Single-cell RNA sequencing defines distinct disease subtypes and reveals hypo-responsiveness to interferon in asymptomatic Waldenstrom's Macroglobulinemia

Waldenstrom's Macroglobulinemia (WM) is an IgM-secreting bone marrow (BM) lymphoma that is preceded by an asymptomatic state (AWM). To dissect tumor-intrinsic and immune mechanisms of progression, we perform single-cell RNA-sequencing on 294,206 BM tumor and immune cells from 30 patients with AWM/WM, 26 patients with Smoldering Myeloma, and 23 healthy donors. Despite their early stage, patients with AWM present extensive immune dysregulation, including in normal B cells, with disease-specific immune hallmarks. Patient T and NK cells show systemic hypo-responsiveness to interferon, which improves with interferon administration and may represent a therapeutic vulnerability. MYD88-mutant tumors show transcriptional heterogeneity, which can be distilled in a molecular classification, including a DUSP22/CD9-positive subtype, and progression signatures which differentiate IgM MGUS from overt WM and can help advance WM research and clinical practice.

Inflammatory Waldenström macroglobulinemia is associated with clonal hematopoiesis: a multicentric cohort

ABSTRACT

Inflammatory form of Waldenström macroglobulinemia (iWM) predicts outcomes after immuno-chemotherapy and Bruton tyrosine kinase inhibitors, but its origin is unknown. Here, we unravel increased clonal hematopoiesis in patients with iWM (61% vs 23% in noninflammatory WM), suggesting a contribution of environmental cells to iWM.

Lymphoplasmacytic lymphoma and Waldenström macroglobulinemia, a decade after the discovery of MYD88L265P

There has been remarkable progress over the past 80 years since Jan Waldenstrom first described patients with a hyperviscosity syndrome related to IgM paraprotein in 1944. The definition of Waldenstrom macroglobulinemia (WM) has evolved from a clinical syndrome to a distinct clinicopathologic entity with characteristic morphology, immunophenotype and molecular features. The landmark discovery of MYD88 mutation among most WM cases in 2012 marked the dawning of an era of molecular genomic exploration that led to a paradigm shift in clinical practice. In the current World Health Organization (WHO) classification of hematologic neoplasms, WM is included in the category of lymphoplasmacytic lymphoma (LPL) of which WM represents over 90% of cases. LPL/WM is also better defined, resolving ambiguity in many cases that would have been classified as "low-grade B-cell lymphoma with plasmacytic differentiation" a decade before. Nevertheless, challenges still face pathologists because criteria for distinguishing LPL/WM from other types of low-grade B-cell lymphoma, particularly marginal zone lymphoma (MZL), remain imperfect. In this review, we highlight the current understanding of LPL and WM brought to light by new discoveries, which in turn are increasingly translated to improved diagnosis and personalized therapy. Key concepts in the diagnosis and their clinical implications are emphasized. Controversies and challenges are also discussed.

Mutational Landscape of Bone Marrow CD19 and CD138 Cells in Waldenström Macroglobulinemia (WM) and IgM Monoclonal Gammopathy of Undetermined Significance (IgM MGUS)

BACKGROUND

Despite recurrent and activating mutations, including MYD88, CXCR4, ARID1A, KMT2D, and CD79B were identified, the genetic basis for Waldenström's Macroglobulinemia (WM) and the risk of progression of IgM MGUS to WM remain to be fully elucidated.

METHODS

We investigated the mutation status of WM (n = 8), sWM (n = 7), and IgM MGUS (n = 5) patients, by performing high-throughput targeted AmpliSeq NGS on 117 target genes. Specifically, we analyzed the CD19+ cells from 15 WM/sWM patients and five IgM MGUS patients. We also analyzed the CD138+ cells from four WM/sWM patients and two IgM MGUS patients.

RESULTS

We detected the classic mutation MYD88L265P in 93% of WM/sWM and in 60% of IgM MGUS patients. The CXCR4S338Ter mutation was identified in 26% of WM/sWM patients, whereas it was undetectable in IgM MGUS subjects. Interestingly, we identified new mutated genes, including WNK2 somatic mutations affecting 46% of WM/sWM patients, for which a recurrent allelic variant (V1635Ter) was observed in this cohort. Moreover, sequencing evaluation revealed recurrently frameshift or missense mutations involving NFKB2 (L473Afs) in 60% of IgM MGUS and 20% of WM/sWM, PTPN13 (P1546Tfs) in 20% of IgM MGUS and 7% of WM/sWM, CARD11 (S622del) in 20% of IgM MGUS and 20% of WM/sWM, KMT2C (I823T) in all IgM MGUS and 93% of WM/sWM, and ATM in 20% of IgM MGUS and 47% of WM/sWM patients.

CONCLUSION

In conclusion, we uncovered new insights into the mutational landscape of WM, depicting a more complex involvement of the NF-kB pathway, and providing evidence of the recurrence of some variants (MYD88, IL17RB, NFKB2, ATM, CARD11, PTPN13, and WNK2) also in IgM MGUS.

A Rare Case of Chronic Lymphocytic Leukemia Transforming Into Waldenström Macroglobulinemia During Ibrutinib Therapy

Chronic lymphocytic leukemia (CLL) can rarely transform into Waldenström macroglobulinemia (WM), posing diagnostic and therapeutic challenges. The diagnosis of WM requires bone marrow infiltration by lymphoplasmacytic cells and the presence of IgM gammopathy. Immunophenotypic markers include FMC7+, CD19+, CD20+, and CD138+. The MYD88 mutation is characteristic. Symptoms arise from tumor infiltration and monoclonal protein production. Here, we present a case of CLL transforming into WM during treatment with ibrutinib. Given the rarity of such a transformation, this case may serve as a valuable reference, and further investigation is needed to understand the pathology underlying this transformation.

Extramedullary disease in Waldenström macroglobulinemia: A population-based observational study

INTRODUCTION

Extramedullary disease (EMD) is a rare manifestation of Waldenström macroglobulinemia (WM), and its clinical and prognostic implications are poorly understood.

METHODS

In this single-center study, we investigated the clinical significance of EMD in a cohort of 469 WM patients.

RESULTS

EMD was identified in 30 (6.4%) patients, with the central nervous system, kidneys, and lungs being the most frequently affected sites. The cumulative incidence of EMD was 12.6% at 15 years. Median overall survival rates at 5 and 10 years for patients with EMD were 63% and 37%, respectively.

CONCLUSION

Our findings indicate a persistent risk of EMD throughout the disease course, with no significant impact on long-term survival.

Review of BCL2 inhibitors for the treatment of Waldenström's macroglobulinaemia and non-IgM lymphoplasmacytic lymphoma

Lymphoplasmacytic lymphoma (LPL) is a relatively rare form of indolent B-cell non-Hodgkin's lymphoma, termed Waldenström's macroglobulinaemia (WM) in the presence of an IgM paraprotein. Although traditionally treated with combination chemoimmunotherapy, the management is evolving in the era of targeted molecular therapies including Bruton's tyrosine kinase inhibitors (BTKi). However, intolerance and refractoriness to BTKi mean newer agents are required, and the prognosis of so-called quadruple-refractory patients is poor. BCL2 is an anti-apoptotic, pro-survival protein that promotes lymphoma cell survival. Inhibition of BCL2 using first-in-class agent venetoclax has already altered the treatment paradigm in other conditions, including chronic lymphocytic leukaemia (CLL). In-vivo inhibition of BCL2 has been shown to lead to apoptosis of LPL/WM cells. Five studies have published results on the use of BCL2 inhibitors in WM to date, including oblimersen sodium, venetoclax, and sonrotoclax. Fixed-duration venetoclax resulted in high response rates, but many patients relapsed following the completion of therapy. The combination of venetoclax with ibrutinib resulted in higher and relatively deep response rates, but unexpected deaths due to ventricular events mean this combination cannot be explored. Two pivotal trials are currently evaluating the use of fixed-duration venetoclax, either in combination with rituximab or pirtobrutinib, whereas another multi-arm study is studying the use of continuous sonrotoclax monotherapy for R/R WM or in fixed-duration combination with Zanubrutinib for treatment-naïve patients. The potential role of BCL2 inhibitors in WM/LPL remains under study, with many hopeful that they may provide an additional chemotherapy-free oral alternative for patients requiring treatment. In an indolent condition with existing effective treatment regimens, including CIT and cBTKi, cost-effectiveness and toxicity profile will be key, although an additional treatment modality for quadruple-refractory patients with limited treatment options is urgently required.

Unexpected diagnosis of WHIM syndrome in refractory autoimmune cytopenia

ABSTRACT

WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome is a rare primary immunodeficiency predominantly caused by heterozygous gain-of-function mutations in the C-terminus of the gene CXCR4. These CXCR4 variants display impaired receptor trafficking with persistence of the CXCR4 receptor on the surface, resulting in hyperactive downstream signaling after CXCL12 stimulation. In turn, this results in defective lymphoid differentiation, and reduced blood neutrophil and lymphocyte numbers. Here, we report a CXCR4 mutation that in 2 members of a kindred, led to life-long autoimmunity and lymphoid hypertrophy as the primary clinical manifestations of WHIM syndrome. We examine the functional effects of this mutation, and how these have affected phosphorylation, activation, and receptor internalization.

Pathophysiology and Treatments of Complications of Waldenström's Macroglobulinemia

Waldenstrom's macroglobulinemia (WM) or lymphoplasmacytic lymphoma is a B-cell malignancy characterized by lymphoplasmacytic cells in the bone marrow that secrete high amounts of immunoglobulin (Ig) M. The large pentameric structure of IgM leads to a variety of unique complications in WM, such as hyperviscosity syndrome, cryoglobulinemia and sensory neuropathy. Furthermore, malignant cells can infiltrate the central nervous system and lead to a variety of neurological complications, also known as Bing Neel Syndrome. Because of the unique pathophysiology of WM and these complications, their diagnostic work up and treatment regimens vary greatly. Given the rarity of the disease and their complications, there are little to no randomized controlled trials regarding treatments of these complications and, therefore, suggested treatment regimens are usually based on observational studies. In this case series, we will present three cases of WM, each with their own unique complication, and discuss the pathophysiology along with current and future treatment options for each of the complications presented.

A Rare Case of Combined Direct Retinal Involvement and Suspected Bing-Neel Syndrome in a Patient With Waldenstrom's Macroglobulinemia

A 75-year-old male with a history of Waldenström macroglobulinemia (WM), diagnosed in 2022, presented with several months of progressive blurred vision and floaters in his right eye, impairing his ability to drive, particularly at night. The ophthalmologic evaluation revealed vitreous haemorrhage and sub-retinal pigment epithelial lesions in the superonasal and inferonasal quadrants of the right eye. A pars plana vitrectomy with vitreous biopsy was performed, which was consistent with ocular involvement by WM. The patient underwent orbital radiotherapy. Shortly after completing radiotherapy, he developed acute neurological symptoms, including involuntary movements and erratic behaviour. Based on imaging and clinical presentation, the lesion was highly suspected to represent central nervous system (CNS) involvement by WM (Bing-Neel syndrome), though a tissue diagnosis could not be obtained due to the fitness of the patient. The patient was treated with rituximab and high-dose methotrexate, but after three cycles, follow-up imaging showed progressive CNS disease. Due to his declining condition, any further could not be pursued. At the time of this report, his visual acuity in the right eye was reduced to 6/60 due to silicone oil used during the vitreoretinal surgery, and further review is awaiting. This case illustrates a very rare occurrence of combined direct ocular involvement and suspected CNS infiltration in WM, highlighting the challenges of diagnosing and treating these uncommon but serious manifestations.

Immunoglobulin class-switch recombination: Mechanism, regulation, and related diseases

Maturation of the secondary antibody repertoire requires class-switch recombination (CSR), which switches IgM to other immunoglobulins (Igs), and somatic hypermutation, which promotes the production of high-affinity antibodies. Following immune response or infection within the body, activation of T cell-dependent and T cell-independent antigens triggers the activation of activation-induced cytidine deaminase, initiating the CSR process. CSR has the capacity to modify the functional properties of antibodies, thereby contributing to the adaptive immune response in the organism. Ig CSR defects, characterized by an abnormal relative frequency of Ig isotypes, represent a rare form of primary immunodeficiency. Elucidating the molecular basis of Ig diversification is essential for a better understanding of diseases related to Ig CSR defects and could provide clues for clinical diagnosis and therapeutic approaches. Here, we review the most recent insights on the diversification of five Ig isotypes and choose several classic diseases, including hyper-IgM syndrome, Waldenström macroglobulinemia, hyper-IgD syndrome, selective IgA deficiency, hyper-IgE syndrome, multiple myeloma, and Burkitt lymphoma, to illustrate the mechanism of Ig CSR deficiency. The investigation into the underlying mechanism of Ig CSR holds significant potential for the advancement of increasingly precise diagnostic and therapeutic approaches.

Waldenström Macroglobulinemia - A State-of-the-Art Review: Part 1: Epidemiology, Pathogenesis, Clinicopathologic Characteristics, Differential Diagnosis, Risk Stratification, and Clinical Problems

Waldenström macroglobulinemia (WM) is an infrequent variant of lymphoma, classified as a B-cell malignancy identified by the presence of IgM paraprotein, infiltration of clonal, small lymphoplasmacytic B cells in the bone marrow, and the MYD88 L265P mutation, which is observed in over 90% of cases. The direct invasion of the malignant cells into tissues like lymph nodes and spleen, along with the immune response related to IgM, can also lead to various health complications, such as cytopenias, hyperviscosity, peripheral neuropathy, amyloidosis, and Bing-Neel syndrome. Chemoimmunotherapy has historically been considered the preferred treatment for WM, wherein the combination of rituximab and nucleoside analogs, alkylating drugs, or proteasome inhibitors has exhibited notable efficacy in inhibiting tumor growth. Recent studies have provided evidence that Bruton Tyrosine Kinase inhibitors (BTKI), either used independently or in conjunction with other drugs, have been shown to be effective and safe in the treatment of WM. The disease is considered to be non-curable, with a median life expectancy of 10 to 12 years.

Bing-Neel syndrome, a rare manifestation of WM; a case report and review of literature

Bing-Neel syndrome (BNS) is a rare manifestation in individuals suffering from Waldenström macroglobulinemia (WM). Neurological signs and symptoms in this syndrome are almost difficult to be differentiated from other common neurological manifestations of hyper-viscosity or Waldenström-associated polyneuropathy. In this paper, we report a new case of WM with concurrent BNS, then review the clinical picture and treatment of this syndrome.

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.

Mutational landscape in Waldenström macroglobulinemia evaluated using a next-generation sequencing lymphoma panel in routine clinical practice

Next-generation sequencing (NGS) affords comprehensive insights into the genomic landscape of lymphomas. We examined the mutational pattern in patients with Waldenström macroglobulinemia (WM) or lymphoplasmacytic lymphoma (LPL) as well as the diagnostic and clinical utility of a tailored NGS lymphoma panel. A consecutive series of 45 patients was reviewed and NGS analysis was performed as part of a routine diagnostic setup. The custom designed NGS panel assayed all coding sequences of 59 genes of known clinical significance in lymphoid neoplasms. The most frequently mutated genes were MYD88, CXCR4, BIRC3, CD79B, and ARID1A. Additional somatic mutations were detected in 17 genes with four mutations categorized as pathogenic or likely pathogenic. BIRC3 and TP53 mutations were associated with adverse clinical phenotypes. NGS performance for the MYD88L265P variant was 96% when compared to qPCR. In conclusion, targeted NGS provided important diagnostic and prognostic information in a routine clinical setting.

The landscape of rare genetic variants in familial Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare hematological malignancy. Risk for WM is elevated 20-fold among first-degree relatives of patients with WM. However, the list of variants and genes that cause WM remains incomplete. In this study we analyzed exomes from 64 WM pedigrees for evidence of genetic susceptibility for this malignancy. We determined the frequency of pathogenic (P) or likely pathogenic (LP) variants among patients with WM; performed variant- and gene-level association analyses with the set of 166 WM cases and 681 unaffected controls; and examined the segregation pattern of deleterious variants among affected members in each pedigree. We identified P/LP variants in TREX1 and SAMHD1 (genes that function at the interface between innate immune response, genotoxic surveillance, and DNA repair) segregating in patients with WM from 2 pedigrees. There were additional P/LP variants in cancer-predisposing genes (eg, POT1, RECQL4, PTPN11, PMS2). In variant- and gene-level analyses, no associations were statistically significant after multiple testing correction. On a pathway level, we observed involvement of genes that play a role in telomere maintenance (q-value = 0.02), regulation of innate immune response (q-value = 0.05), and DNA repair (q-value = 0.08). Affected members of each pedigree shared multiple deleterious variants (median, n = 18), but the overlap between the families was modest. In summary, P/LP variants in highly penetrant genes constitute a modest proportion of the deleterious variants; each pedigree is largely unique in its genetic architecture, and multiple genes are likely involved in the etiology of WM.

A diagnostic dilemma-to operate or not to operate-a rare case report

A 41-year-old male presented with a swelling in the right flank present since 2 years. Initially, it was small in size but increased in size for the past 6 months. Examination revealed a large swelling in the right flank that was soft in consistency and attached to the deeper muscle. CT scan revealed a heterogenous complex swelling with attachment to the underlying muscle. Core biopsy of the lesion was reported as undifferentiated sarcoma. After immunohistochemistry markers, the diagnosis was revised to a malignancy of a lymphomatous origin. Gene sequencing studies and extensive higher marker studies were done and a final diagnosis of plasmacytic infiltrate of uncertain clinical significance was reported. With no further diagnostic options available, the case still remains to be a diagnostic challenge as the choice of treatment between surgical resection and nonsurgical treatment with chemotherapy and/or radiation cannot be decided upon.

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.

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.

Genetic alterations in mature B- and T-cell lymphomas - a practical guide to WHO-HAEM5

The identification of recurrent genomic alterations in tumour cells has a significant role in the classification of mature B- and T-cell lymphomas. Following the development of new technologies, such as next generation sequencing and the improvement of classical technologies such as conventional and molecular cytogenetics, a huge catalogue of genomic alterations in lymphoid neoplasms has been established. These alterations are relevant to refine the taxonomy of the classification of lymphomas, to scrutinize the differential diagnosis within different lymphoma entities and to help assessing the prognosis and clinical management of the patients. Consequently, here we describe the key genetic alterations relevant in mature B- and T-cell lymphomas.

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.

A tower of babel of acronyms? The shadowlands of MGUS/MBL/CHIP/TCUS

With the advent of outperforming and massive laboratory tools, such as multiparameter flow cytometry and next-generation sequencing, hematopoietic cell clones with putative abnormalities for a variety of blood malignancies have been appreciated in otherwise healthy individuals. These conditions do not fulfill the criteria of their presumed cancer counterparts, and thus have been recognized as their precursor states. This is the case of monoclonal gammopathy of unknown significance (MGUS), the first blood premalignancy state described, preceding multiple myeloma (MM) or Waldenström macroglobulinemia (WM). However, in the last 2 decades, an increasing list of clonopathies has been recognized, including monoclonal B cell lymphocytosis (MBL), which antecedes chronic lymphocytic leukemia (CLL), clonal hematopoiesis of indeterminate potential (CHIP) for myeloid neoplasms (MN), and T-cell clones of uncertain significance (TCUS) for T-cell large chronic lymphocytic leukemia (LGLL). While for some of these entities diagnostic boundaries are precisely set, for others these are yet to be fully defined. Moreover, despite mostly considered of "uncertain significance," they have not only appeared to predispose to malignancy, but also to be capable of provoking set of immunological and cardiovascular complications that may require specialized management. The clinical implications of the aberrant clones, together with the extensive knowledge generated on the pathogenetic events driving their evolution, raises the question whether earlier interventions may alter the natural history of the disease. Herein, we review this Tower of Babel of acronyms pinpointing diagnostic definitions, differential diagnosis, and the role of genomic profiling of these precursor states, as well as potential interventional strategies.

Single-cell analysis of MYD88L265P and MYD88WT Waldenström macroglobulinemia patients

Waldenström macroglobulinemia (WM) is characterized by the expansion of clonal lymphoplasmacytic cells; the MYD88L265P somatic mutation is found in >90% of patients, but malignant B cells may still display intra-clonal heterogeneity. To assess clonal heterogeneity in WM, we generated and performed single-cell RNA sequencing of CD19+ sorted cells from five patients with MYD88 L265P and two patients with MYD88 WT genotype as well as two healthy donors. We identified distinct transcriptional patterns in the clonal subpopulations not only between the two genetically distinct WM subgroups but also among MYD88 L265P patients, which affected the B cell composition in the different subgroups. Comparison of clonal and normal/polyclonal B cells within each patient sample enabled the identification of patient-specific transcriptional changes. We identified gene signatures active in a subset of MYD88L265P patients, while other signatures were active in MYD88 WT patients. Finally, gene expression analysis showed common transcriptional features between patients compared to the healthy control but also differentially expressed genes between MYD88 L265P and MYD88 WT patients involved in distinct pathways, including NFκΒ, BCL2, and BTK. Overall, our data highlight the intra-tumor clonal heterogeneity in WM with potential prognostic and therapeutic implications.

Bing-Neel syndrome: a rare neurological complication of Waldenström macroglobulinaemia

Bing-Neel syndrome (BNS) is a very rare manifestation of Waldenström macroglobulinaemia (WM), in which lymphoplasmacytic cells invade the central nervous system. The clinical presentation includes symptoms of headaches, visual floaters, neuropathy, seizures and gait abnormalities. Here, we describe an elderly woman, who presented with complaints of visual floaters, progressive neuropathy and cognitive changes. Workup including a bone marrow biopsy confirmed the diagnosis of WM. Shortly afterwards, the patient experienced a seizure leading to hospitalisation, which revealed a right frontal lobe lesion on brain MRI. A biopsy of the lesion showed a small B cell lymphoma positive for an MYD88 mutation, confirming BNS. The patient was initially treated with ibrutinib, before transitioning to zanubrutinib. However, she developed disease progression necessitating radiotherapy with lenalidomide and rituximab maintenance therapy, which achieved remission. This case sheds light on the diagnosis and management of a very rare complication of a rare disease.

Waldenström Macroglobulinemia: Targeted Agents Taking Center Stage

With the worldwide approval of the oral covalent Bruton tyrosine kinase (BTK) inhibitors ibrutinib and zanubrutinib for treating patients with Waldenström macroglobulinemia (WM), targeted agents have certainly taken center stage in the therapeutic landscape of WM. This review discusses the biological and clinical data supporting current and up-and-coming targeted agents in WM. Bruton tyrosine kinase inhibitors induce fast, deep, and durable responses in patients with WM, comparable to chemoimmunotherapy; however, there is a glaring absence of comparative studies between these regimens. The high response and progression-free survival rate and the ease of administration of BTK inhibitors must be balanced against their specific adverse-event profile with unique toxicity (e.g., bleeding and cardiac arrhythmia) and the indefinite duration of the therapy. Novel targeted agents of interest include BCL2 antagonists (e.g., venetoclax and sonrotoclax) and non-covalent BTK inhibitors (e.g., pirtobrutinib and nemtabrutinib), among others. The therapeutic landscape of patients with WM will benefit from the robust participation of patients in clinical trials.

B-Cell Receptor Signaling and Beyond: The Role of Igα (CD79a)/Igβ (CD79b) in Normal and Malignant B Cells

B-cell receptor (BCR) is a B cell hallmark surface complex regulating multiple cellular processes in normal as well as malignant B cells. Igα (CD79a)/Igβ (CD79b) are essential components of BCR that are indispensable for its functionality, signal initiation, and signal transduction. CD79a/CD79b-mediated BCR signaling is required for the survival of normal as well as malignant B cells via a wide signaling network. Recent studies identified the great complexity of this signaling network and revealed the emerging role of CD79a/CD79b in signal integration. In this review, we have focused on functional features of CD79a/CD79b, summarized signaling consequences of CD79a/CD79b post-translational modifications, and highlighted specifics of CD79a/CD79b interactions within BCR and related signaling cascades. We have reviewed the complex role of CD79a/CD79b in multiple aspects of normal B cell biology and how is the normal BCR signaling affected by lymphoid neoplasms associated CD79A/CD79B mutations. We have also summarized important unresolved questions and highlighted issues that remain to be explored for better understanding of CD79a/CD79b-mediated signal transduction and the eventual identification of additional therapeutically targetable BCR signaling vulnerabilities.

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.

Clonal Relationship and Mutation Analysis in Lymphoplasmacytic Lymphoma/Waldenström Macroglobulinemia Associated With Diffuse Large B-cell Lymphoma

Patients with lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL/WM) occasionally develop diffuse large B-cell lymphoma (DLBCL). This mostly results from LPL/WM transformation, although clonally unrelated DLBCL can also arise. LPL/WM is characterized by activating MYD88L265P (>95%) and CXCR4 mutations (~30%), but the genetic drivers of transformation remain to be identified. Here, in thirteen LPL/WM patients who developed DLBCL, the clonal relationship of LPL and DLBCL together with mutations contributing to transformation were investigated. In 2 LPL/WM patients (15%), high-throughput sequencing of immunoglobulin gene rearrangements showed evidence of >1 clonal B-cell population in LPL tissue biopsies. In the majority of LPL/WM patients, DLBCL presentations were clonally related to the dominant clone in LPL, providing evidence of transformation. However, in 3 patients (23%), DLBCL was clonally unrelated to the major malignant B-cell clone in LPL, of which 2 patients developed de novo DLBCL. In this study cohort, LPL displayed MYD88L265P mutation in 8 out of eleven patients analyzed (73%), while CXCR4 mutations were observed in 6 cases (55%). MYD88WT LPL biopsies present in 3 patients (27%) were characterized by CD79B and TNFAIP3 mutations. Upon transformation, DLBCL acquired novel mutations targeting BTG1, BTG2, CD79B, CARD11, TP53, and PIM1. Together, we demonstrate variable clonal B-cell dynamics in LPL/WM patients developing DLBCL, and the occurrence of clonally unrelated DLBCL in about one-quarter of LPL/WM patients. Moreover, we identified commonly mutated genes upon DLBCL transformation, which together with preserved mutations already present in LPL characterize the mutational landscape of DLBCL occurrences in LPL/WM patients.

IRAK-4 inhibition: emavusertib for the treatment of lymphoid and myeloid malignancies

Several studies have identified mutations in the MYD88L265P gene as a key driver mutation in several B-cell lymphomas. B-cell lymphomas that harbor the MYD88L265P mutation form a complex with phosphorylated Bruton's tyrosine kinase (BTK) and are responsive to BTK inhibition. However, BTK inhibition in B-cell lymphomas rarely results in a complete response and most patients experience eventual disease relapse. Persistent survival signaling though downstream molecules such as interleukin 1 receptor-associated kinase 4 (IRAK-4), an integral part of the "myddosome" complex, has been shown to be constitutively active in B-cell lymphoma patients treated with BTK inhibitors. Emerging evidence is demonstrating the therapeutic benefit of IRAK-4 inhibition in B-cell lymphomas, along with possibly reversing BTK inhibitor resistance. While MYD88 gene mutations are not present in myeloid malignancies, downstream overexpression of the oncogenic long form of IRAK-4 has been found in acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), particularly in AML and MDS that harbor mutations in splicing factors U2AF1 and SF3B1. These data suggest that the anti-leukemic activity of IRAK-4 inhibition can be exploited in relapsed/refractory (R/R) AML/MDS. In this review article, we discuss the currently available pre-clinical and clinical data of emavusertib, a selective, orally bioavailable IRAK-4 inhibitor in the treatment of R/R B-cell lymphomas and myeloid malignancies.

Impact of circulating lymphoma cells at diagnosis on outcomes in patients with Waldenstrom macroglobulinemia

Given the paucity of data surrounding the prognostic relevance of circulating lymphoma (CL) in Waldenström macroglobulinemia (WM), we sought to evaluate the impact of CL at diagnosis on outcomes in patients with WM. Patients were divided into CL+ and CL- based on the results of flow cytometry. The endpoints included assessing progression-free survival (PFS), overall survival (OS), and diagnosis-to-treatment interval (DTI) between the two groups. Among the 308 patients with WM, 69 met the eligibility criteria with 42 and 27 in CL+ and CL- groups, respectively. The two groups were well balanced in regard to all the baseline characteristics. The ORR was numerically higher in the CL+ group compared to the CL-group (81% versus 61%, respectively), however, the CR+VGPR rates were similar between the two groups. The median PFS was not significantly different between the two groups (6.3 years in the CL- group versus not reached [NR] in the CL+ group) regardless of the first-line therapy. There was no significant difference in median OS between the CL- and CL+ groups (13 years versus NR). Although the median DTI was shorter in the CL+ group compared to CL- group, the significance was lost in the multivariable analysis. In this study (largest-to-date) evaluating the impact of CL on outcomes in patients with newly diagnosed WM, we did not find the prognostic utility of CL in WM. Future studies should explore the correlation of CL with other biological factors that impact the outcomes in WM patients.

The Histopathology of Cold Agglutinin Disease-Associated B-Cell Lymphoproliferative Disease

OBJECTIVES

Primary cold agglutinin disease is a type of autoimmune hemolytic anemia caused by circulating antibodies against I antigen, a carbohydrate expressed on most cells, including red blood cells. The underlying disease has been characterized in recent years as a distinct B-cell lymphoproliferative disease of the bone marrow, occurring mostly in the elderly. The disease has been now been included as a separate entity in the most recent classifications of mature B-cell neoplasms.

METHODS

A review of the characteristics of cold agglutinin disease is provided, with an emphasis on the pathology features.

RESULTS

A detailed description of the histopathology, immunophenotype, and genetics of cold agglutinin disease is provided and compared to other B-cell lymphoproliferative diseases in the bone marrow with similar features.

CONCLUSIONS

Recognition of the pathology features of cold agglutinin disease allows to distinguish it from other diseases, especially lymphoplasmacytic lymphoma and marginal zone lymphoma.

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.

Clonal architecture and evolutionary history of Waldenström's macroglobulinemia at the single-cell level

To provide insight into the subclonal architecture and co-dependency patterns of the alterations in Waldenström's macroglobulinemia (WM), we performed single-cell mutational and protein profiling of eight patients. A custom panel was designed to screen for mutations and copy number alterations at the single-cell level in samples taken from patients at diagnosis (n=5) or at disease progression (n=3). Results showed that in asymptomatic WM at diagnosis, MYD88L265P was the predominant clonal alteration; other events, if present, were secondary and subclonal to MYD88L265P. In symptomatic WM, clonal diversity was more evident, uncovering combinations of alterations that synergized to promote clonal expansion and dominance. At disease progression, a dominant clone was observed, sometimes accompanied by other less complex minor clones, which could be consistent with a clonal selection process. Clonal diversity was also reduced, probably due to the effect of treatment. Finally, we combined protein expression with mutational analysis to map somatic genotype with the immunophenotype. Our findings provide a comprehensive view of the clonality of tumor populations in WM and how clonal complexity can evolve and impact disease progression.

Clinical Implications of Genomic Profile in Waldenström Macroglobulinemia

With the increasing availability of sequencing techniques and new polymerase chain reaction-based methods, data regarding the genomic profile of Waldenström macroglobulinemia (WM) are being continuously analyzed and reproduced. MYD88 and CXCR4 mutations are highly prevalent in all the stages of WM, including the early IgM monoclonal gammopathy of undetermined significance or a more advanced stage, such as smoldering WM. Thus, there is a need to define genotypes before starting either standard treatment regimens or clinical trials. Here, we review the genomic profile of WM and its clinical implications while focusing on recent advances.

Future Directions in the Frontline Management of Waldenström Macroglobulinemia

Despite substantial progress in the clinical management of Waldenström's Macroglobulinemia (WM) and the emergence of chemotherapy-free approaches such as BTK inhibitors, WM is still a disease in which current treatments fail to cure and are in part associated with significant toxicities, compromising treatment outcome and quality of life. Thus, the vision for future front-line therapy should be to develop regimens which combine improved efficacy and excellent applicability with a low toxicity profile. Conventional immunochemotherapy such as bendamustine-rituximab is highly active but limited by hematotoxicity and long-lasting immunosuppression. Thus, further intensification of this treatment concept will most likely not be successful. Chemotherapy-free approaches such as BTK inhibitors have already changed the treatment landscape in WM, but still have major limitations such as the need for non-fixed duration treatment. Most probably, the combination of non-chemotherapy based, targeted approaches with different modes of action will ensure that we at least come closer to our vision of achieving functional cure in WM in the near future.

Biomarkers of Progression and Risk Stratification in Asymptomatic Waldenström Macroglobulinemia

Waldenström macroglobulinemia is an indolent IgM-secreting B-cell lymphoplasmacytic lymphoma that is preceded by an asymptomatic stage. Clinical and molecular features have been used in risk models to predict progression rates in different asymptomatic subgroups. Risk models used both disease-specific and nonspecific biomarkers for asymptomatic patients. Recently, models that incorporate continuous variables rather than distinct cutoffs have emerged to more accurately predict the risk of progression. Integrating genetic alterations to the clinical models is a promising approach that could improve risk stratification and management of asymptomatic 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.

Highly Sensitive Detection Method of CXCR4 Tumor Hotspot Mutations by Drop-Off Droplet Digital PCR in Patients with IgM Monoclonal Gammopathies

CXCR4 mutations impact disease presentation and treatment outcomes in Waldenström macroglobulinemia. Current techniques used for CXCR4 mutation detection have a number of limitations. The aim of the present study was to develop and analytically validate a novel droplet digital PCR (ddPCR) assay for the simultaneous detection of five of the most common CXCR4 mutations in bone marrow (BM). In silico novel primers and probes designed for simultaneous detection of five hotspot mutations of CXCR4 were first performed. Experimental conditions were optimized, and the assay was analytically validated. The developed assay was further applied in 95 BM samples from patients with IgM gammopathy, 7 BM samples from patients with non-IgM gammopathy and 12 PBMCs from healthy donors, whereas a direct comparison study of Sanger sequencing and allele-specific PCR was performed by using 95 and 39 identical patient tumor DNA samples, respectively. The drop-off ddPCR assay is a robust, cost-effective, highly sensitive, and highly specific screening tool for CXCR4 mutations. Of 95 patients with IgM gammopathy samples, 27 had at least one CXCR4 mutation in their BM samples. With Sanger sequencing, 12 of the 95 samples tested positive, whereas the direct comparison of the developed assay with allele-specific PCR revealed substantial agreement. The clinical performance of the developed assay will be prospectively evaluated in a large number of patients, and the applicability of this assay will be further evaluated.

The wide spectrum of cryoglobulinemic vasculitis and an overview of therapeutic advancements

Immunoglobulins that reversibly precipitate at temperatures below 37 °C are called cryoglobulins (CGs). Cryoglobulinemia often manifests as cryoglobulinemic vasculitis (CV), whose symptoms range in severity from purpuric eruptions to life-threatening features. The majority of CV patients are infected with hepatitis C virus (HCV), whereas lymphoproliferative disorders or connective tissue diseases (CTD) are commonly diagnosed among patients with CV of non-infectious origin. In the absence of detectable associated disease, cryoglobulinemia is classified as "essential" (EMC). All HCV-positive CV patients should be given direct-acting antiviral agents (DAAs) that are consistently able to induce a sustained virologic response (SVR). Glucocorticoids (GCs) can mitigate CV-associated vasculitis, but they have no role as maintenance therapy. Cyclophosphamide restrains the hyperactive phase(s) of the disease and the post-apheresis rebound of newly synthesized CGs. Its use has been largely replaced by rituximab (RTX) in patients unresponsive to DAAs, patients progressing to B-cell non-Hodgkin lymphoma (B-NHL) and patients in whom CV persists or reappears after clearance of HCV. Therapeutic apheresis is an emergency treatment for CV patients with hyperviscosity syndrome. HCV-positive CV patients are at an increased risk of developing NHL, but the achievement of SVR can effectively prevent HCV-related NHL or induce the remission of an already established lymphoma, even without chemotherapy. The treatment of patients with IgM or IgG monoclonal cryoglobulins and an underlying immunoproliferative disorder is based on the regimens adopted for patients with the same B-cell malignancies but without circulating CGs. For patients with CTD, GCs plus alkylating agents or RTX are similarly effective as first-line therapy and in the relapse/refractory setting. In patients with EMC, treatment should consist of GCs plus RTX, with the dose of GCs tapered as soon as possible to reduce the risk of infectious complications.

Waldenström Macroglobulinemia and Non-IgM-Type Lymphoplasmacytic Lymphoma Are Genetically Similar

INTRODUCTION

Waldenström macroglobulinemia (WM) represents a subset of lymphoplasmacytic lymphoma (LPL) with the immunoglobulin (Ig)M paraprotein. MYD88 L265P and CXCR4 mutations are common mutations in WM patients, and mutations in ARID1A and KMT2D (MLL2) have also been reported. However, little information has been accumulated on genetic changes in LPL with other paraproteins like IgG.

METHODS

We therefore aimed to evaluate genetic differences between WM and LPL with non-IgM paraprotein (non-IgM-type LPL) using targeted next-generation sequencing (NGS) in 20 Japanese patients (10 with WM, 10 with non-IgM-type LPL).

RESULTS

Mutations were detected in ARID1A (10%), CXCR4 (20%), MYD88 (90%), and KMT2D (0%) for WM patients and in ARID1A (10%), CXCR4 (20%), MYD88 (70%), and KMT2D (10%) for non-IgM-type LPL patients. No significant differences were identified. No mutations were detected in NOTCH2, PRDM1, CD274 (PD-L1), PDCD1LG2 (PD-L2), RAG2, MYBBP1A, TP53, or CD79B.

DISCUSSION

Mutant allele frequency in MYD88 L265P did not differ significantly between WM and non-IgM-type LPL. Most mutations detected by NGS were subclonal following MYD88 L265P, although one non-IgM-type LPL patient harbored only CXCR4 S338X mutation. Our NGS analyses reveal genetic characteristics in LPL patients and suggest genetic similarities between these two subsets of LPL, WM and non-IgM-type.

Report of consensus panel 7 from the 11th international workshop on Waldenström macroglobulinemia on priorities for novel clinical trials

Recent advances in the understanding of Waldenström macroglobulinemia (WM) biology have impacted the development of effective novel agents and improved our knowledge of how the genomic background of WM may influence selection of therapy. Consensus Panel 7 (CP7) of the 11th International Workshop on WM was convened to examine the current generation of completed and ongoing clinical trials involving novel agents, consider updated data on WM genomics, and make recommendations on the design and prioritization of future clinical trials. CP7 considers limited duration and novel-novel agent combinations to be the priority for the next generation of clinical trials. Evaluation of MYD88, CXCR4 and TP53 at baseline in the context of clinical trials is crucial. The common chemoimmunotherapy backbones, bendamustine-rituximab (BR) and dexamethasone, rituximab and cyclophosphamide (DRC), may be considered standard-of-care for the frontline comparative studies. Key unanswered questions include the definition of frailty in WM; the importance of attaining a very good partial response or better (≥VGPR), within stipulated time frame, in determining survival outcomes; and the optimal treatment of WM populations with special needs.

Diagnostic, Prognostic, and Predictive Role of Next-Generation Sequencing in Mature Lymphoid Neoplasms

Lymphoma is a clinically and biologically heterogeneous disease. Next-generation sequencing (NGS) has expanded our understanding of this heterogeneity at the genetic level, refining disease classification, defining new entities, and providing additional information that can be used in diagnosis and management. This review highlights some of the NGS findings in lymphoma and how they can be used as genetic biomarkers to aid diagnosis and prognosis and guide therapy.

Report of Consensus Panel 3 from the 11th International workshop on Waldenström's Macroglobulinemia: Recommendations for molecular diagnosis in Waldenström's Macroglobulinemia

Apart from the MYD88L265P mutation, extensive information exists on the molecular mechanisms in Waldenström's Macroglobulinemia and its potential utility in the diagnosis and treatment tailoring. However, no consensus recommendations are yet available. Consensus Panel 3 (CP3) of the 11th International Workshop on Waldenström's Macroglobulinemia (IWWM-11) was tasked with reviewing the current molecular necessities and best way to access the minimum data required for a correct diagnosis and monitoring. Key recommendations from IWWM-11 CP3 included: (1) molecular studies are warranted for patients in whom therapy is going to be started; such studies should also be done in those whose bone marrow (BM) material is sampled based on clinical issues; (2) molecular studies considered essential for these situations are those that clarify the status of 6q and 17p chromosomes, and MYD88, CXCR4, and TP53 genes. These tests in other situations, and/or other tests, are considered optional; (3) independently of the use of more sensitive and/or specific techniques, the minimum requirements are allele specific polymerase chain reaction for MYD88L265P and CXCR4S338X using whole BM, and fluorescence in situ hybridization for 6q and 17p and sequencing for CXCR4 and TP53 using CD19+ enriched BM; (4) these requirements refer to all patients; therefore, sample should be sent to specialized centers.

SWI/SNF complexes in hematological malignancies: biological implications and therapeutic opportunities

Hematological malignancies are a highly heterogeneous group of diseases with varied molecular and phenotypical characteristics. SWI/SNF (SWItch/Sucrose Non-Fermentable) chromatin remodeling complexes play significant roles in the regulation of gene expression, being essential for processes such as cell maintenance and differentiation in hematopoietic stem cells. Furthermore, alterations in SWI/SNF complex subunits, especially in ARID1A/1B/2, SMARCA2/4, and BCL7A, are highly recurrent across a wide variety of lymphoid and myeloid malignancies. Most genetic alterations cause a loss of function of the subunit, suggesting a tumor suppressor role. However, SWI/SNF subunits can also be required for tumor maintenance or even play an oncogenic role in certain disease contexts. The recurrent alterations of SWI/SNF subunits highlight not only the biological relevance of SWI/SNF complexes in hematological malignancies but also their clinical potential. In particular, increasing evidence has shown that mutations in SWI/SNF complex subunits confer resistance to several antineoplastic agents routinely used for the treatment of hematological malignancies. Furthermore, mutations in SWI/SNF subunits often create synthetic lethality relationships with other SWI/SNF or non-SWI/SNF proteins that could be exploited therapeutically. In conclusion, SWI/SNF complexes are recurrently altered in hematological malignancies and some SWI/SNF subunits may be essential for tumor maintenance. These alterations, as well as their synthetic lethal relationships with SWI/SNF and non-SWI/SNF proteins, may be pharmacologically exploited for the treatment of diverse hematological cancers.

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.

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.

Prognostic impact of MYD88 and CXCR4 mutations assessed by droplet digital polymerase chain reaction in IgM monoclonal gammopathy of undetermined significance and smouldering Waldenström macroglobulinaemia

Waldenström macroglobulinaemia (WM) is characterized by recurrent somatic mutations in MYD88 and CXCR4 genes. However, limitations arise when analysing these mutations in IgM monoclonal gammopathy of undetermined significance (MGUS) or smouldering WM (SWM) given the lower tumour load. Here, we used droplet digital polymerase chain reaction (ddPCR) to analyse MYD88 L265P and CXCR4 S338* mutations (C1013G and C1013A) in unsorted bone marrow (BM) or cell-free DNA (cfDNA) samples from 101 IgM MGUS and 69 SWM patients. ddPCR was more sensitive to assess MYD88 L265P compared to allele-specific PCR, especially in IgM MGUS (64% vs 39%). MYD88 mutation burden correlated with other laboratory biomarkers, particularly BM infiltration (r = 0.8; p < 0.001). CXCR4 C1013G was analysed in MYD88-mutated samples with available genomic DNA and was detected in 19/54 (35%) and 18/42 (43%) IgM MGUS and SWM cases respectively, also showing correlation with BM involvement (r = 0.9; p < 0.001). ddPCR also detected 8 (38%) and 10 (63%) MYD88-mutated cfDNA samples in IgM MGUS and SWM respectively. Moreover, high BM mutation burden (≥8% MYD88 and ≥2% CXCR4) was associated with an increased risk of progression to symptomatic WM. We show the clinical applicability of ddPCR to assess MYD88 and CXCR4 in IgM MGUS and SWM and provide a molecular-based risk classification.

[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.