Ibrutinib in Waldenström macroglobulinemia: latest evidence and clinical experience

Simplified Risk Stratification Model for Patients With Waldenström Macroglobulinemia

PURPOSE

Patients with Waldenström macroglobulinemia (WM) have disparate outcomes. Newer therapies have emerged since the development of International Prognostic Scoring System, and MYD88L265P mutation is now frequently assessed at diagnosis, warranting reexamination of the prognostic parameters.

PATIENTS AND METHODS

We reviewed records of 889 treatment-naïve patients with active WM, consecutively seen between January 01, 1996, and December 31, 2017, to identify clinical predictors of overall survival (OS) in univariate analyses. Patients with complete data for the parameters significant on the univariate analyses (n = 341) were included in a multivariable analysis to derive a prognostic model, subsequently validated in a multi-institutional cohort.

RESULTS

In the derivation cohort (n = 341), age (hazard ratio [HR], 1.9 [95% CI, 1.2 to 2.1]; P = .0009), serum lactate dehydrogenase (LDH) above upper limit of normal (HR, 2.3 [95% CI, 1.3 to 4.5]; P = .007), and serum albumin <3.5 g/dL (HR, 1.5 [95% CI, 0.99 to 2.3]; P = .056) were independently prognostic. By assigning a score of 1 point each to albumin <3.5 g/dL (HR, 1.5) and age 66-75 years (HR 1.4) and 2 points for age >75 years (HR, 2.6) or elevated LDH (HR, 2.3), four groups with distinct outcomes were observed on the basis of the composite scores. Five-year OS was 93% for the low-risk (score 0), 82% for low-intermediate risk (score 1), 69% for intermediate-risk (score 2), and 55% for the high-risk (score ≥3; P < .0001) groups. In the validation cohort (N = 335), the model maintained its prognostic value, with a 5-year OS of 93%, 90%, 75%, and 57% for the four groups, respectively (P < .0001).

CONCLUSION

Modified Staging System for WM (MSS-WM), utilizing age, albumin, and LDH is a simple, clinically useful, and externally validated prognostic model that reliably risk-stratifies patients with symptomatic WM into four groups with distinct prognosis.

How to manage waldenström's macroglobulinemia in 2024

Clinical management of Waldenström's Macroglobulinemia has seen major progress in the recent years, triggered by our improved understanding of the biology of the disease and the development of new therapies. Based on this there are multiple treatment options available for patients with WM ranging from classical immunochemotherapy to targeted approaches blocking key enzymes involved in lymphoma growth. This review summarizes our current knowledge about diagnostics and treatment of this rare but recurrent lymphoma subtype, which often presents a major clinical challenge in daily clinical life.

Clinical, biological, electrophysiological and therapeutic profile of patients with anti-MAG neuropathy according to MYD88L265P and CXCR4 mutations and underlying haemopathy

INTRODUCTION

Anti-MAG neuropathies are associated with an IgM monoclonal gammopathy of undetermined significance (MGUS) or with a malignant haemopathy. Our objective was to determine whether the presence of a haemopathy or somatic mutations of MYD88 and CXCR4 genes influences disease presentation and response to rituximab (RTX).

METHODS

We included 79 patients (mean age 74 years, disease duration 9.68 years) who had a bone marrow aspiration with morphologic and immunophenotypic analysis. MYD88L265P and CXCR4 mutations were analysed in peripheral B cells. Information collected included: inflammatory neuropathy cause and treatment sensory sum score (ISS), MRC testing, overall neuropathy limitation scale (ONLS), Rash-built Overall Disability Score (RODS), ataxia score, anti-MAG titres, peak IgM dosage, neurofilament light chain levels, motor and sensory amplitudes, motor unit index (MUNIX) and motor unit size index (MUSIX) sum scores. Efficacy of RTX was evaluated at 12 months in 26 patients.

RESULTS

Malignant haematological disorders were discovered in 17 patients (22%): 13 Waldenstrom macroglobulinemia, 3 marginal zone lymphoma and one mantle cell lymphoma. MYD88L265P mutation was detected in 29/60 (48%) patients and CXCR4 in 1 single patient. Disease severity, biological and electrophysiological data and response to RTX were comparable in patients with MGUS/lymphoma and patients with/without MYD88L265P mutation. ISS was lower and MUSIX higher in patients improved by RTX.

CONCLUSIONS

MYD88L265P mutation and underlying haemopathies are not predictive of a more severe disease. However, in cases of resistant and progressive neuropathy, they provide an opportunity to prescribe newly available drugs such as Bruton tyrosine kinase inhibitors.

Ibrutinib impairs IGF-1-dependent activation of intracellular Ca handling in isolated mouse ventricular myocytes

Background

The Bruton tyrosine kinase (BTK) inhibitor Ibrutinib is associated with a higher incidence of cardiotoxic side effects including heart failure (HF).

Objectives

Ibrutinib is capable of inhibiting PI3K/Akt signaling in neonatal rat ventricular cardiomyocytes when stimulated with insulin-like growth factor 1 (IGF-1). We therefore hypothesized that Ibrutinib might disrupt IGF-1-mediated activation of intracellular Ca handling in adult mouse cardiomyocytes by inhibiting PI3K/Akt signaling.

Methods

Isolated ventricular myocytes (C57BL6/J) were exposed to IGF-1 at 10 nmol/L in the presence or absence of Ibrutinib (1 µmol/L) or Acalabrutinib (10 µmol/L; cell culture for 24 ± 2 h). Intracellular Ca handling was measured by epifluorescence (Fura-2 AM) and confocal microscopy (Fluo-4 AM). Ruptured-patch whole-cell voltage-clamp was used to measure ICa. Levels of key cardiac Ca handling proteins were investigated by immunoblots.

Results

IGF-1 significantly increased Ca transient amplitudes by ∼83% as compared to vehicle treated control cells. This was associated with unaffected diastolic Ca, enhanced SR Ca loading and increased ICa. Co-treatment with Ibrutinib attenuated both the IGF-1-mediated increase in SR Ca content and in ICa. IGF-1 treated cardiomyocytes had significantly increased levels of pS473Akt/Akt and SERCA2a expression as compared to cells concomitantly treated with IGF-1 and Ibrutinib. SR Ca release (as assessed by Ca spark frequency) was unaffected by either treatment. In order to test for potential off-target effects, second generation BTK inhibitor Acalabrutinib with greater BTK selectivity and lower cardiovascular toxicity was tested for IGF1-mediated activation of intracellular Ca handling. Acalabrutinib induced similar effects on Ca handling in IGF-1 treated cultured myocytes as Ibrutinib in regard to decreased Ca transient amplitude and slowed Ca transient decay, hence implying a functional class effect of BTK inhibitors in cardiac myocytes.

Conclusions

Inhibition of BTK by Ibrutinib impairs IGF-1-dependent activation of intracellular Ca handling in adult ventricular mouse myocytes in the face of disrupted Akt signaling and absent SERCA2a upregulation.

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 (MYD88L265P) 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.

Ibrutinib, Lenalidomide and Dexamethasone in Patients with Relapsed and/or Refractory Multiple Myeloma: Phase I Trial Results

Therapeutic strategies that target novel pathways are urgently needed for patients with relapsed/refractory multiple myeloma (RRMM). Ibrutinib is an oral covalent inhibitor of Bruton tyrosine kinase, which is overexpressed in MM cells. This phase 1 dose-escalation study examined various doses of ibrutinib in combination with standard doses of lenalidomide (25mg) and dexamethasone (40mg) using a standard 3+3 design in RRMM patients. The primary objective was to determine the maximum tolerated dose (MTD) of ibrutinib in combination with lenalidomide and dexamethasone. Patients (n=15) had received a median of 4 prior regimens, 53% were triple-class exposed, 33% were penta-exposed, and 54% were lenalidomide-refractory. The MTD of ibrutinib was 840mg (n=6) and only 1 dose-limiting toxicity (DLT); a grade 3 rash possibly related to ibrutinib was noted. The most common ≥grade 3 adverse events (AEs) were rash in 2 (13%), lymphopenia in 2(13%), leukopenia, neutropenia, thrombocytopenia, and anemia all occurring in 3 (20%) patients each. One patient achieved a partial response for an overall response rate of 7%. The clinical benefit rate was 80%. The median time to progression was 3.8 months. Ibrutinib, lenalidomide and dexamethasone appears to be a safe and well-tolerated regimen with reasonable efficacy in heavily pretreated RRMM patients. This article is protected by copyright. All rights reserved.

Anti-MAG neuropathy: From biology to clinical management

The acquired chronic demyelinating neuropathies include a growing number of disease entities that have characteristic, often overlapping, clinical presentations, mediated by distinct immune mechanisms, and responding to different therapies. After the discovery in the early 1980s, that the myelin associated glycoprotein (MAG) is a target antigen in an autoimmune demyelinating neuropathy, assays to measure the presence of anti-MAG antibodies were used as the basis to diagnose the anti-MAG neuropathy. The route was open for describing the clinical characteristics of this new entity as a chronic distal large fiber sensorimotor neuropathy, for studying its pathogenesis and devising specific treatment strategies. The initial use of chemotherapeutic agents was replaced by the introduction in the late 1990s of rituximab, a monoclonal antibody against CD20⁺ B-cells. Since then, other anti-B cells agents have been introduced. Recently a novel antigen-specific immunotherapy neutralizing the anti-MAG antibodies with a carbohydrate-based ligand mimicking the natural HNK-1 glycoepitope has been described.

Systemic Amyloidosis due to Low-Grade Lymphoma

Lymphoma-related amyloidosis is a rare entity. Systemic AL amyloidosis is generally caused by an underlying plasma cell clone in the bone marrow with an intact monoclonal immunoglobulin G (IgG) or IgA protein. The rarity of the lymphoma-related amyloidosis makes the generation of data in randomized trials and the determination of the optimal treatment almost impossible. Therefore, treatment recommendations discussed here are based on either retrospective or small prospective trials of single centers.

TLR-mediated activation of Waldenström macroglobulinemia B cells reveals an uncoupling from plasma cell differentiation

Waldenström macroglobulinemia (WM) is a rare malignancy in which clonal B cells infiltrate the bone marrow and give rise to a smaller compartment of neoplastic plasma cells that secrete monoclonal immunoglobulin M paraprotein. Recent studies into underlying mutations in WM have enabled a much greater insight into the pathogenesis of this lymphoma. However, there is considerably less characterization of the way in which WM B cells differentiate and how they respond to immune stimuli. In this study, we assess WM B-cell differentiation using an established in vitro model system. Using T-cell-dependent conditions, we obtained CD138+ plasma cells from WM samples with a frequency similar to experiments performed with B cells from normal donors. Unexpectedly, a proportion of the WM B cells failed to upregulate CD38, a surface marker that is normally associated with plasmablast transition and maintained as the cells proceed with differentiation. In normal B cells, concomitant Toll-like receptor 7 (TLR7) activation and B-cell receptor cross-linking drives proliferation, followed by differentiation at similar efficiency to CD40-mediated stimulation. In contrast, we found that, upon stimulation with TLR7 agonist R848, WM B cells failed to execute the appropriate changes in transcriptional regulators, identifying an uncoupling of TLR signaling from the plasma cell differentiation program. Provision of CD40L was sufficient to overcome this defect. Thus, the limited clonotypic WM plasma cell differentiation observed in vivo may result from a strict requirement for integrated activation.

Response to Ibrutinib of a Refractory IgA Lymphoplasmacytic Lymphoma Carrying the MYD88 L265P Gene Mutation

In 2014 a 66-year-old woman presented with anemia and an IgAk monoclonal spike. Bone marrow (BM) biopsy showed 80% lymphocytes and lymphoplasmacytoid cells. Computed Tomography (CT) scan documented neither adenopathy nor splenomegaly. Diagnosis of IgA lymphoplasmacytic lymphoma was made. After three lines of treatment, progressive disease with adenopathies, splenomegaly, and ascites were documented on a CT scan. Our patient developed thrombocytopenia, transfusion-dependent anemia, and clinical deterioration. We performed genetic studies of peripheral blood lymphocytes with the NGS approach. Given the identification of MYD88 L265P mutation, in February 2018 our patient started ibrutinib off-label. Hb and PLT improved from day +35. In July 2018 no ascites and 50% reduction of adenopathies and spleen were shown on a CT scan. In April 2019 the patient was still on ibrutinib with transfusion independence and good performance status.

Severe Hepatotoxicity due to Ibrutinib with a Review of Published Cases

Ibrutinib, an irreversible Bruton's tyrosine kinase inhibitor, is an effective treatment for Waldenström's macroglobulinemia, chronic lymphocytic leukemia, and several other types of lymphoma. Studies prior to FDA approval in 2015 failed to demonstrate any hepatotoxicity. However, since then, there have been 2 reports in the literature of severe hepatic injury. We present a third case of a 77-year-old woman presenting with nausea and jaundice after recent discontinuation of ibrutinib and compare the presentation as well as course of all 3 known cases. The sudden onset of acute hepatotoxicity is idiosyncratic, occurring weeks after starting ibrutinib treatment. Liver biopsies in all cases revealed mixed hepatocellular and cholestatic features. Improvement progressed slowly upon discontinuation of ibrutinib. Awareness of ibrutinib hepatotoxicity, periodic surveillance of liver function tests, early recognition of any abnormalities, and prompt discontinuation of the medication are recommended.

Novel Therapeutic Approaches to Allosensitization and Antibody-mediated Rejection

Modification of pathogenic antibodies for autoimmune diseases illuminated the biologic relevance of B cells, plasma cells, and pathogenic antibodies in autoimmunity. They have also rejuvenated interest in how B cells mediate multiple effector functions that include antibody production, antigen presentation to T cells, costimulation, and the production of immune stimulating and immune modulatory cytokines. Repurposing these drugs from autoimmunity and cancer immunotherapy has yielded important advancements in the care of antibody-mediated rejection patients and novel drug development aimed at HLA desensitization have recently emerged. We now stand on an important threshold that promises many advances in the care of our allosensitized patients. We hope that these initial advances will encourage basic scientist, clinical investigators, industry, National Institutes of Health, our academic societies, and the Food and Drug Administration to continue support of these important objectives. These advances clearly have implications for sensitized patients receiving solid organ transplants and antibody-mediated rejection treatment. Modification of alloimmunity and alloantibodies will also have relevance to xenotransplantation where the xenoantibodies present a formidable obstacle to advancement of this important therapy. Working together, we can advance transplant therapeutics where biologic agents are likely to play novel and important roles. Here, we discuss novel drugs emerging in this area.

Targeting Bruton's Tyrosine Kinase Across B-Cell Malignancies

Bruton's tyrosine kinase (BTK) is crucial in B-cell development and survival. The role of BTK as a downstream kinase in the B-cell receptor (BCR) signaling pathway is well described. As a key player in the pathogenesis of B-cell malignancies, targeting of dysregulated BCR signaling has been explored by development of inhibitors of downstream mediators. Discovery of the biological function of BTK and the development of covalent inhibitors for clinical use, ibrutinib as the lead agent and acalabrutinib as the second clinically approved BTK inhibitor, have revolutionized the treatment options for B-cell malignancies. Currently, ibrutinib is approved for mantle cell lymphoma, chronic lymphocytic leukemia, lymphoplasmacytic lymphoma/Waldenström macroglobulinemia, small lymphocytic lymphoma, marginal zone lymphoma and chronic graft versus host disease, while acalabrutinib is approved for mantle cell lymphoma. Potential expansion of indications in other diseases is under investigation in several clinical trials, while combination of BTK inhibitors with either chemoimmunotherapy or other targeted agents is being systematically explored in B-cell malignancies.

Kidney diseases associated with Waldenström macroglobulinemia

Waldenström macroglobulinemia (WM) is a rare B-cell lymphoma characterized by lymphoplasmacytic cell infiltration in the bone marrow and other organs and the presence of a monoclonal immunoglobulin M protein in the serum. Although uncommon, several kidney diseases have been associated with WM. In addition to kidney diseases related to lymphoplasmacytic lymphoma infiltration, a variety of glomerular and tubular lesions have been described in patients with WM. Immunoglobulin light chain (AL) amyloidosis and cryoglobulinemic glomerulonephritis are the two predominant glomerular pathologies seen in WM. In this article we review the kidney diseases associated with WM. We also briefly review some nephrotoxicities of novel chemotherapeutic and targeted therapies used for the treatment of WM.

Ibrutinib discontinuation in Waldenström macroglobulinemia: Etiologies, outcomes, and IgM rebound

Ibrutinib is the first approved therapy for symptomatic patients with Waldenström macroglobulinemia (WM). The reasons for discontinuing ibrutinib and subsequent outcomes have not been previously evaluated in WM patients. We therefore conducted a retrospective review of 189 WM patients seen at our institution who received treatment with ibrutinib, of whom 51 (27%) have discontinued therapy. Reasons for discontinuation include: disease progression (n = 27; 14%), toxicity (n = 15; 8%), nonresponse (n = 5; 3%), and other unrelated reasons (n = 4; 2%). The cumulative incidence of ibrutinib discontinuation at 12, 24, 36, and 48 months from treatment initiation was 22%, 26%, 35%, and 43%, respectively. A baseline platelet count ≤100 K/µL and presence of tumor CXCR4 mutations were independently associated with 4-fold increased odds of ibrutinib discontinuation. An IgM rebound (≥25% increase in serum IgM) was observed in 37 patients (73%) following ibrutinib discontinuation and occurred within 4 weeks for nearly half of patients. The response rate to salvage therapy was 71%; responses were higher in patients without an IgM rebound and when salvage therapy was initiated within 2 weeks of stopping ibrutinib. Patients who discontinued ibrutinib due to disease progression versus nonprogression events had significantly shorter overall survival (21 versus 32 months; P = .046). Response to salvage therapy was associated with an 82% reduction in the risk of death following ibrutinib discontinuation. WM patients who discontinue ibrutinib require close monitoring, and continuation of ibrutinib until the next therapy should be considered to maintain disease control.

Ibrutinib alone or with dexamethasone for relapsed or relapsed and refractory multiple myeloma: phase 2 trial results

Novel therapies with unique new targets are needed for patients who are relapsed/refractory to current treatments for multiple myeloma. Ibrutinib is a first‐in‐class, once‐daily, oral covalent inhibitor of Bruton tyrosine kinase, which is overexpressed in the myeloma stem cell population. This study examined various doses of ibrutinib ± low‐dose dexamethasone in patients who received ≥2 prior lines of therapy, including an immunomodulatory agent. Daily ibrutinib ± weekly dexamethasone 40 mg was assessed in 4 cohorts using a Simon 2‐stage design. The primary objective was clinical benefit rate (CBR; ≥minimal response); secondary objectives included safety. Patients (n = 92) received a median of 4 prior regimens. Ibrutinib + dexamethasone produced the highest CBR (28%) in Cohort 4 (840 mg + dexamethasone; n = 43), with median duration of 9·2 months (range, 3·0–14·7). Progression‐free survival was 4·6 months (range, 0·4–17·3). Grade 3–4 haematological adverse events included anaemia (16%), thrombocytopenia (11%), and neutropenia (2%); grade 3–4 non‐haematological adverse events included pneumonia (7%), syncope (3%) and urinary tract infection (3%). Ibrutinib + dexamethasone produced notable responses in this heavily pre‐treated population. The encouraging efficacy, coupled with the favourable safety and tolerability profile of ibrutinib, supports its further evaluation as part of combination treatment.

Cost-effectiveness analysis of ibrutinib in patients with Waldenström macroglobulinemia in Italy

Background and Objective: Ibrutinib has recently been approved in Europe for Waldenström Macroglobulinemia (WM) in symptomatic patients who have received at least one prior therapy, or in first-line treatment for patients unsuitable for chemo-immunotherapy. The aim of the study is to estimate the incremental cost-effectiveness ratio (ICER) of ibrutinib in relapse/refractory WM, compared with the Italian current therapeutic pathways (CTP). Methods: A Markov model was adapted for Italy considering the National Health System perspective. Input data from literature as well as global trials were used. The percentage use of therapies, and healthcare resources consumption were estimated according to expert panel advice. Drugs ex-factory prices and national tariffs were used for estimating costs. The model had a 15-year time horizon, with a 3.0% discount rate for both clinical and economic data. Deterministic and probabilistic sensitivity analyses were performed to test the results strength. Results: Ibrutinib resulted in increased Life Years Gained (LYGs) and increased costs compared to CTP, with an ICER of €52,698/LYG. Sensitivity analyses confirmed the results of the BaseCase. Specifically, in the probabilistic analysis, at a willingness to pay threshold of €60,000/LYG ibrutinib was cost-effective in 84% of simulations. Conclusions: Ibrutinib has demonstrated a positive cost-effectiveness profile in Italy.

Dexamethasone, rituximab and cyclophosphamide for relapsed and/or refractory and treatment-naïve patients with Waldenstrom macroglobulinemia

The management of Waldenström macroglobulinaemia (WM) relies predominantly on small trials, one of which has demonstrated activity of dexamethasone, rituximab and cyclophosphamide (DRC) in the frontline setting. We report on the efficacy of DRC, focusing on relapsed/refractory (R/R) patients. Ibrutinib, a recently approved agent in WM demonstrated limited activity in patients with MYD88^WT genotype. Herein, we additionally report on the activity of DRC based on the MYD88^L265P mutation status. Of 100 WM patients evaluated between January 2007 and December 2014 who received DRC, 50 had R/R WM. The overall response rate (ORR) was 87%. The median progression-free survival (PFS) and time-to-next-therapy (TTNT) were 32 (95% confidence interval [CI]: 15-51) and 50 (95% CI: 35-60) months, respectively. In the previously untreated cohort (n = 50), the ORR was 96%, and the median PFS and TTNT were 34 months (95% CI: 23-not reached [NR]) and NR (95% CI: 37-NR), respectively. Twenty-five (86%) of 29 genotyped patients harbored MYD88^L265P . The response rates and outcomes were independent of MYD88 mutation status. Grade ≥3 adverse effects included neutropenia (20%), thrombocytopenia (7%) and infections (3%). Similar to the frontline setting, DRC is an effective and well-tolerated salvage regimen for WM. In contrast to ibrutinib, DRC offers a less expensive, fixed-duration option, with preliminary data suggesting efficacy independent of the patients' MYD88 status.

Hepatitis C Virus-Associated Non-Hodgkin Lymphomas: Biology, Epidemiology, and Treatment

Eradication of hepatitis C virus (HCV) in indolent non-Hodgkin lymphomas (NHLs), especially in marginal zone lymphomas, determines the regression of the hematologic disorder in a significant fraction of cases. Because direct antiviral agents show an excellent profile in terms of efficacy, safety, and rapid onset of action, these drugs can be used in any clinical situation and in the presence of any comorbidities. To avoid the progression of the NHL, despite HCV eradication, antiviral therapy should be provided as soon as the viral infection is discovered; before that, the chronic antigenic stimulation determines the irreversible proliferation of neoplastic B cells.

A Specific and Covalent JNK-1 Ligand Selected from an Encoded Self-Assembling Chemical Library

We describe the construction of a DNA-encoded chemical library comprising 148 135 members, generated through the self-assembly of two sub-libraries, containing 265 and 559 members, respectively. The library was designed to contain building blocks potentially capable of forming covalent interactions with target proteins. Selections performed with JNK1, a kinase containing a conserved cysteine residue close to the ATP binding site, revealed the preferential enrichment of a 2-phenoxynicotinic acid moiety (building block A82) and a 4-(3,4-difluorophenyl)-4-oxobut-2-enoic acid moiety (building block B272). When the two compounds were joined by a short PEG linker, the resulting bidentate binder (A82-L-B272) was able to covalently modify JNK1 in the presence of a large molar excess of glutathione (0.5 mm), used to simulate intracellular reducing conditions. By contrast, derivatives of the individual building blocks were not able to covalently modify JNK1 in the same experimental conditions. The A82-L-B272 ligand was selective over related kinases (BTK and GAK), which also contain targetable cysteine residues in the vicinity of the active site.

Ibrutinib-Associated Skin Toxicity: A Case of Maculopapular Rash in a 79-Year Old Caucasian Male Patient with Relapsed Waldenstrom's Macroglobulinemia and Review of the Literature

Waldenstrom's macroglobulinamia (WM) is a rare malignant lymphoproliferative disorder, characterized by monoclonal IgM paraproteinemia and neoplastic proliferation of malignant lymphoplasmacytoid cells in the bone marrow. Traditionally, WM has been treated with modalities similar to those used in the management of other indolent lymphomas. Just recently, based on impressive clinical trial results in heavily pretreated WM patients, a new Bruton Tyrosine Kinase-inhibitor, Ibrutinib, has been approved for the treatment of this disorder. As the use of Ibrutinib in WM outside clinical trials is still limited, only few clinical reports illustrating treatment side effects are currently available. Here we review the current literature specific on Ibrutinib-associated rash in hematologic patients, and report on an elderly patient with WM, who developed a red maculopapular non-pruritic rash 12 weeks after starting Ibrutinib therapy. Without modifications of the ongoing Ibrutinib schedule, the rash regressed within two weeks of treatment with topical steroid-containing dermatological compounds.