A multicenter phase II study of single-agent enzastaurin in previously treated Waldenstrom macroglobulinemia

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.

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.

Waldenstrom's Macroglobulinemia: An Update

Waldenstrom Macroglobulinemia is a rare lymphoproliferative disorder with distinctive clinical features. Diagnostic and prognostic characterisation in WM significantly changed with the discovery of two molecular markers: MYD88 and CXCR4. Mutational status of these latter influences both clinical presentation and prognosis and demonstrated therapeutic implications. Treatment choice in Waldenstrom disease is strictly guided by patients age and characteristics, specific goals of therapy, the necessity for rapid disease control, the risk of treatment-related neuropathy, disease features, the risk of immunosuppression or secondary malignancies and potential for future autologous stem cell transplantation. The therapeutic landscape has expanded during the last years and the approval of ibrutinib, the first drug approved for Waldenstrom Macroglobulinemia, represents a significant step forward for a better management of the disease.

Waldenstrom's Macroglobulinemia: An Update

Waldenstrom Macroglobulinemia is a rare lymphoproliferative disorder with distinctive clinical features. Diagnostic and prognostic characterisation in WM significantly changed with the discovery of two molecular markers: MYD88 and CXCR4. Mutational status of these latter influences both clinical presentation and prognosis and demonstrated therapeutic implications. Treatment choice in Waldenstrom disease is strictly guided by patients age and characteristics, specific goals of therapy, the necessity for rapid disease control, the risk of treatment-related neuropathy, disease features, the risk of immunosuppression or secondary malignancies and potential for future autologous stem cell transplantation. The therapeutic landscape has expanded during the last years and the approval of ibrutinib, the first drug approved for Waldenstrom Macroglobulinemia, represents a significant step forward for a better management of the disease.

Inhibition of Akt and other AGC kinases: A target for clinical cancer therapy?

AGC kinases have been identified to contribute to cancer development and progression. Currently, most AGC inhibitors in clinical development are Akt inhibitors such as MK-2206 or GDC-0068, which are known to promote cell growth arrest and to sensitize cancer cells to radiotherapy. Response rates in clinical trials with single agent Akt inhibitors are typically low. The observed adverse events are within the expected limits for compounds inhibiting the PI3K-mTOR axis. Preclinical and early clinical data for combination therapies are accumulating. Based on these data, several Akt inhibitors are about to enter phase 3 trials. Besides drugs that target Akt, p70S6K inhibitors have entered clinical development. Again, the response rates were rather low. In addition, relevant toxicities were identified, including a risk for coagulopathies with these compounds. Multi-AGC kinase inhibitors are also in early clinical development but the data is not sufficient yet to draw conclusions regarding their efficacy and side-effect profile. PKC inhibitors have been tested in the phase 3 setting but were found to lack efficacy. More trials with isoform-specific PKC inhibitors are expected. Taken together, therapies with AGC kinase inhibitors as single agents are unlikely to meet success. However, combination therapies and a precise stratification of patients according to the activation of signaling axes may increase the probability to see relevant efficacy with these compounds. The emergence of onco-immunotherapies holds some new challenges for these agents.

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.

Enzastaurin inhibits ABCB1-mediated drug efflux independently of effects on protein kinase C signalling and the cellular p53 status

The PKCβ inhibitor enzastaurin was tested in parental neuroblastoma and rhabdomyosarcoma cell lines, their vincristine-resistant sub-lines, primary neuroblastoma cells, ABCB1-transduced, ABCG2-transduced, and p53-depleted cells. Enzastaurin IC₅₀s ranged from 3.3 to 9.5 μM in cell lines and primary cells independently of the ABCB1, ABCG2, or p53 status. Enzastaurin 0.3125 μM interfered with ABCB1-mediated drug transport. PKCα and PKCβ may phosphorylate and activate ABCB1 under the control of p53. However, enzastaurin exerted similar effects on ABCB1 in the presence or absence of functional p53. Also, enzastaurin inhibited PKC signalling only in concentrations ≥ 1.25 μM. The investigated cell lines did not express PKCβ. PKCα depletion reduced PKC signalling but did not affect ABCB1 activity. Intracellular levels of the fluorescent ABCB1 substrate rhodamine 123 rapidly decreased after wash-out of extracellular enzastaurin, and enzastaurin induced ABCB1 ATPase activity resembling the ABCB1 substrate verapamil. Computational docking experiments detected a direct interaction of enzastaurin and ABCB1. These data suggest that enzastaurin directly interferes with ABCB1 function. Enzastaurin further inhibited ABCG2-mediated drug transport but by a different mechanism since it reduced ABCG2 ATPase activity. These findings are important for the further development of therapies combining enzastaurin with ABC transporter substrates.

Waldenström's macroglobulinemia: a clinical perspective in the era of novel therapeutics

Waldenström's macroglobulinemia (WM) is a rare, low-grade malignancy with no established standard of care. Rituximab regimens are most commonly used, supported by their efficacy in hematologic malignancies, including WM. A growing number of investigational regimens for WM have been evaluated in phase II clinical trials, including single-agent and combination strategies that include newer-generation monoclonal antibodies (ofatumumab and alemtuzumab), proteasome inhibitors (bortezomib and carfilzomib), immunomodulatory agents (thalidomide and lenalidomide), phosphoinositide 3-kinase/protein kinase B (Akt)/mammalian target of rapamycin pathway inhibitors (everolimus and perifosene), a Bruton's tyrosine kinase inhibitor (ibrutinib), and a histone deacetylase inhibitor (panobinostat). Other novel agents are in early-stage development for WM. International treatment guidelines for WM suggest suitable regimens in the newly diagnosed and relapsed/refractory settings, in accordance with patient age, disease presentation, and efficacy and safety profiles of particular drugs. These factors must be considered when choosing appropriate therapy for individual patients with WM, to maximize response and prolong survival, while minimizing the risk of adverse events. This review article provides a clinical perspective of the modern management of patients with WM, in the context of available trial data for novel regimens and recently updated treatment guidelines.

Disruption of pre-B-cell receptor signaling jams the WNT/β-catenin pathway and induces cell death in B-cell acute lymphoblastic leukemia cell lines

Targeting components of the B-cell receptor (BCR) pathway have dramatically improved clinical outcomes in a variety of B-cell malignancies. Despite the well-documented pathogenic role of BCR precursor (pre-BCR) pathway in B-cell acute lymphoblastic leukemia (B-ALL), there is limited available data of therapies that aim to disrupt this pathway. To investigate the role of protein kinase Cβ (PKCβ), a crucial mediator of BCR and pre-BCR signaling, in B-ALL survival, we studied the activity of the PKCβ selective inhibitor enzastaurin (ENZ) in seven B-ALL cell lines. Treatment with ENZ resulted in a dose- and time-dependent growth inhibition in all cell lines with a relatively higher efficacy in pro-B ALL with translocation t(4;11)(q21;q23). The mechanism of growth inhibition was by apoptotic induction and cell cycle arrest. A rapid reduction in phosphorylation of AKT and its downstream target glycogen synthase kinase 3β (GSK3β) were observed at 30min after treatment and remaining for 48h. The reduction in GSK3β phosphorylation was associated with a paradoxical accumulation of β-catenin, which was due to a transient loss of β-catenin phosphorylation at ser33-37. In addition, accumulation of β-catenin was associated with downregulation of c-Myc, upregulatiuon of c-Jun, and a subsequent protective effect on the tumor suppressor p73. Data in this paper were presented in part at 2012 American Society of Hematology Annual Meeting, abstract 1350.

Emerging therapeutic options for Waldenström macroglobulinemia/lymphoplasmacytic lymphoma

Lymphoplasmacytic lymphoma is an indolent B-cell, non-Hodgkin lymphoma (NHL), the majority of which are characterized by production of a monoclonal immunoglobulin M (IgM) protein and are known as Waldenström macroglobulinemia. Identification of highly recurrent activating somatic mutation in MYD88 has improved our understanding of the pathogenesis of Waldenström macroglobulinemia and has therapeutic implications. Here, we review novel therapeutic agents in Waldenström macroglobulinemia/lymphoplasmacytic lymphoma, which have emerged in the past decade and discuss their comparative efficacy and safety, with emphasis on a Bruton's tyrosine kinase (BTK) inhibitor, which has been recently approved by the US FDA, specifically for Waldenström macroglobulinemia/lymphoplasmacytic lymphoma. Future research should focus on identifying targeted agents against activating mutations and long-term data for currently available novel agents should be critically evaluated, both in treatment-naïve and in relapsed/refractory settings.

Ibrutinib for the treatment of Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a B-cell non-Hodgkin lymphoma (NHL) characterized by IgM monoclonal gammopathy and bone marrow infiltration by lymphoplasmacytic cells. Until recently, there was no drug specifically approved for WM by the US FDA, leading to wide variations in therapeutic strategies across the globe. Ibrutinib, an oral Bruton tyrosine kinase (BTK) inhibitor, is the first drug approved specifically for WM by the FDA after a clinical trial showed impressive response in previously treated WM. Ibrutinib is a non-stem cell toxic and non-neurotoxic option and suitable for long-term oral maintenance therapy, with the potential of improving survival in WM. With identification of novel genetic mutations impacting response to ibrutinib, it would be possible to individualize therapy based on MYD88 and CXCR4 genotypes. However, long-term safety and efficacy data are required, and cost-effectiveness needs to be addressed before ibrutinib can gain widespread acceptance for front-line therapy of WM.

Waldenström macroglobulinemia: What a hematologist needs to know

Waldenström macroglobulinemia (WM) is a distinct hematologic malignancy characterized by a lymphoplasmacytic bone marrow infiltration and the presence of immunoglobulin (Ig)M monoclonal protein. Patients typically present at an advanced age, and a substantial proportion are asymptomatic at diagnosis. A unifying diagnosis of WM may be missed by an unsuspecting hematologist, as symptomatic patients present with a multitude of non-specific manifestations. Although constitutional and neuropathy-related symptoms predominate, concomitant IgM-induced hyperviscosity-associated features can provide useful diagnostic clues. There are specific indications for initiation of therapy. This review focuses on the most up-to-date management strategies of WM, in addition to highlighting the recent discoveries of MYD88 and CXCR4 mutations that have shed unprecedented light on the complex signaling pathways, and opened avenues for novel therapeutic targeting. Although WM remains incurable, with the rapid emergence and integration of effective novel therapies, its clinical course appears poised to improve in the foreseeable future.

B-cell receptor pathway modulators in NHL

With the recent success of the Bruton's tyrosine kinase (BTK) inhibitor, ibrutinib, and the phosphoinositide-3-kinase (PI3K) inhibitor, idelalisib, in the treatment of patients with relapsed or refractory non-Hodgkin's lymphoma (NHL), a number of new agents targeting the B-cell receptor (BCR) pathway are in clinical development. In addition, multiple trials combining these agents with conventional cytotoxic chemotherapy, immunomodulatory agents, monoclonal antibodies, or other kinase inhibitors are underway. This review will summarize the current data with the use of single agent and combination therapy with BCR inhibitors in NHL. In addition, commonly encountered as well as serious toxicities and hypothesized resistance mechanisms will be discussed. Lastly, this review will examine the future of these agents and opportunities to maneuver them into the front-line setting in selected NHL subtypes.

Novel treatment options for Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM), first described by Jan Waldenström in 1944, is a lymphoplasmacytic lymphoma characterized by the presence of an immunoglobulin M monoclonal gammopathy in the blood and monoclonal small lymphocytes and lymphoplasmacytoid cells in the bone marrow. WM is a rare and indolent disease but remains incurable. In this review we discuss the pathogenesis of WM and focus on novel treatment options that target pathways deregulated in this disease. Recent studies have helped us identify specific genetic mutations that are commonly seen in WM and might prove to be important therapeutic targets in the future. We discuss the role of epigenetics and the changes in the bone marrow microenvironment that are important in the pathogenesis of WM. The commonly used drugs are discussed with a focus on novel agents that are currently being used as single agents or in combination to treat WM. We finally focus on some agents that have shown preclinical efficacy and might be available in the near future.

A multicenter phase II study of single-agent enzastaurin in previously treated multiple myeloma

Enzastaurin is an oral serine/threonine kinase inhibitor of the protein kinase C (PKC) and phosphatidylinositol 3 (PI3) kinase/Akt pathways that induces apoptosis in multiple myeloma (MM) cell lines in a caspase-independent manner. A phase II study was conducted to assess response rate, time to progression (TTP), safety and biomarker association with clinical outcomes after monotherapy with the PKC inhibitor enzastaurin in previously treated patients with MM. Eligible patients (n = 14) were treated with enzastaurin 250 mg twice daily after receiving loading doses on day 1. One minimal response was observed. The median TTP was 5.11 months. There were two grade 3 adverse events, anemia and prolonged QTc interval, and no grade 4 adverse events. Single-agent enzastaurin was well tolerated but not effective in this heavily pretreated population with MM.

Current and future therapeutic approach for Waldenström's macroglobulinemia

Waldenström's macroglobulinemia is a rare B-cell malignancy defined by medullar infiltration by clonal lymphoplasmocytic cells and monoclonal IgM secretion. Treatment is reserved for symptomatic patients. The main first-line treatment strategies combine immunotherapy (principally the anti-CD20 monoclonal antibody rituximab) with chemotherapeutic agents, including alkylating agents, purine analogs and/or bortezomib. The overall response rate to these conventional treatments is between 70 and 90%, but a cure cannot be expected. For patients with relapsed or refractory disease, drugs that were not used for first-line treatment and other agents such as immunomodulators can be tried, but the response rate is generally lower and the responses are shorter lived. Recently, advances in our understanding of the biology of Waldenström's macroglobulinemia have led to the development of new drugs targeting hyperactive pathways. This review focuses on current treatment options and on new therapeutic developments.

Primary cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome): part II. Prognosis, management, and future directions

Both mycosis fungoides (MF) and Sézary syndrome (SS) have a chronic, relapsing course, with patients frequently undergoing multiple, consecutive therapies. Treatment is aimed at the clearance of skin disease, the minimization of recurrence, the prevention of disease progression, and the preservation of quality of life. Other important considerations are symptom severity, including pruritus and patient age/comorbidities. In general, for limited patch and plaque disease, patients have excellent prognosis on ≥1 topical formulations, including topical corticosteroids and nitrogen mustard, with widespread patch/plaque disease often requiring phototherapy. In refractory early stage MF, transformed MF, and folliculotropic MF, a combination of skin-directed therapy plus low-dose immunomodulators (eg, interferon or bexarotene) may be effective. Patients with advanced and erythrodermic MF/SS can have profound immunosuppression, with treatments targeting tumor cells aimed for immune reconstitution. Biologic agents or targeted therapies either alone or in combination--including immunomodulators and histone-deacetylase inhibitors--are tried first, with more immunosuppressive therapies, such as alemtuzumab or chemotherapy, being generally reserved for refractory or rapidly progressive disease or extensive lymph node and metastatic involvement. Recently, an increased understanding of the pathogenesis of MF and SS with identification of important molecular markers has led to the development of new targeted therapies that are currently being explored in clinical trials in advanced MF and SS.

Waldenström macroglobulinemia: from biology to treatment

Waldenström macroglobulinemia (WM) is distinct B-cell lymphoproliferative disorder primarily characterized by bone marrow infiltration of lymphoplasmacytic cells along with production of a serum monoclonal (IgM). In this review, we describe the biology of WM, the diagnostic evaluation for WM with a discussion of other conditions that are in the differential diagnosis and clinical manifestations of the disease as well as current treatment options. Within the novel agents discussed are everolimus, perifosine, enzastaurin, panobinostat, bortezomib and carfilzomib, pomalidomide and ibrutinib. Many of the novel agents have shown good responses and have a better toxicity profile compared to traditional chemotherapeutic agents, which makes them good candidates to be used as primary therapies for WM in the future.

How to manage Waldenstrom's macroglobulinemia

Waldenstrom's macroglobulinemia (WM) is very distinct from other indolent lymphoma subtypes: by definition it is accompanied by a monoclonal IgM gammopathy; it presents always with bone marrow infiltration and often with clinical symptoms such as neuropathy or hyperviscosity. These disease characteristics and the frequently advanced age of the WM patient pose a major challenge to the treating clinician even today. Recently, there has been not only substantial progress in our understanding of the biology of WM, but we have also significantly improved our tools to prognostify and to treat patients with this disease. This review summarizes our current knowledge about WM and aims at offering a guideline for the clinical management of patients with this lymphoma subtype, covering questions on how to manage diagnosis, prognostification and treatment based on the most recent data.