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Background Ibrutinib is an oral inhibitor of Bruton’s tyrosine kinase (BTK) that is FDA-approved for several lymphoproliferative disorders and chronic GVHD. Objective To characterize cutaneous eruptions arising from ibrutinib and highlight overlap with epidermal growth factor receptor inhibitor (EGFRi)-induced dermatologic adverse events (dAEs). Methods Single-center retrospective cohort of patients referred to the Skin Toxicities Program for management of cutaneous eruptions while taking ibrutinib. Results Among 19 patients, cutaneous eruptions manifested as facial-predominant papulopustular eruptions, petechiae or ecchymoses, photosensitivity, panniculitis, xerosis, and clinical staphylococcal overgrowth. The majority of patients were able to continue ibrutinib therapy with focused management of their cutaneous toxicities. Limitations This study represents cases at a single tertiary care center and is limited to patients referred for toxicity. Conclusions With the exception of petechiae, the cutaneous toxicities of ibrutinib overlap with those associated with selective EGFR inhibitors. We observed that these reactions can be successfully managed using approaches for EGFR inhibitor-induced cutaneous adverse events.

Primary central nervous system lymphoma (PCNSL) is a rare extranodal lymphomatous malignancy that affects the brain, spinal cord, leptomeninges, or vitreoretinal space, without evidence of systemic involvement. The diagnosis of PCNSL requires a high level of suspicion because clinical presentation varies depending upon involved structures. Initiation of treatment is time sensitive for optimal neurologic recovery and disease control. In general, the prognosis of PCNSL has improved significantly over the past few decades, largely as a result of the introduction and widespread use of high-dose methotrexate (MTX) chemotherapy, which is considered the backbone of first-line polychemotherapy treatment. Upon completion of MTX-based treatment, a consolidation strategy is often required to prolong duration of response. Consolidation can consist of radiation, maintenance therapy, nonmyeloablative chemotherapy, or myeloablative treatment followed by autologous stem cell transplant. Unfortunately, even with consolidation, relapse is common, and 5-year survival rates stand at only 30% to 40%. Novel insights into the pathophysiology of PCNSL have identified key mechanisms in tumor pathogenesis, including activation of the B-cell receptor pathway, immune evasion, and a suppressed tumor immune microenvironment. These insights have led to the identification of novel small molecules targeting these aberrant pathways. The Bruton tyrosine kinase inhibitor ibrutinib and immunomodulatory drugs (lenalidomide or pomalidomide) have shown promising clinical response rates for relapsed/refractory PCNSL and are increasingly used for the treatment of recurrent disease. This review provides a discussion of the clinical presentation of PCNSL, the approach to work-up and staging, and an overview of recent advancements in the understanding of the pathophysiology and current treatment strategies for immunocompetent patients.

Bruton’s tyrosine kinase (Btk) and spleen tyrosine kinase (Syk) are major signaling proteins in human platelets that are implicated in atherothrombosis and thrombo-inflammation, but the mechanisms controlling their activities are not well understood. Previously, we showed that Syk becomes phosphorylated at S297 in glycoprotein VI (GPVI)-stimulated human platelets, which limits Syk activation. Here, we tested the hypothesis that protein kinases C (PKC) and A (PKA) and protein phosphatase 2A (PP2A) jointly regulate GPVI-induced Btk activation in platelets. The GPVI agonist convulxin caused rapid, transient Btk phosphorylation at S180 (pS180↑), Y223 and Y551, while direct PKC activation strongly increased Btk pS180 and pY551. This increase in Btk pY551 was also Src family kinase (SFK)-dependent, but surprisingly Syk-independent, pointing to an alternative mechanism of Btk phosphorylation and activation. PKC inhibition abolished convulxin-stimulated Btk pS180 and Syk pS297, but markedly increased the tyrosine phosphorylation of Syk, Btk and effector phospholipase Cγ2 (PLCγ2). PKA activation increased convulxin-induced Btk activation at Y551 but strongly suppressed Btk pS180 and Syk pS297. PP2A inhibition by okadaic acid only increased Syk pS297. Both platelet aggregation and PLCγ2 phosphorylation with convulxin stimulation were Btk-dependent, as shown by the selective Btk inhibitor acalabrutinib. Together, these results revealed in GPVI-stimulated platelets a transient Syk, Btk and PLCγ2 phosphorylation at multiple sites, which are differentially regulated by PKC, PKA or PP2A. Our work thereby demonstrated the GPVI–Syk–Btk signalosome as a tightly controlled protein kinase network, in agreement with its role in atherothrombosis.

Bing-Neel syndrome (BNS) is a rare syndrome that occurs in patients with Waldenstrom macroglobulinemia and is characterized by lymphoplasmacytic infiltration into the leptomeningeal tissue and/or the central nervous system. It represents an extramedullary manifestation which may translate into various neurological symptoms. Accurate diagnosis of BNS can be established via histologic sampling and cerebrospinal fluid examination with molecular analysis of some genetic markers including immunoglobulin heavy locus rearrangements and MYD88 L265P mutation. The use of Bruton tyrosine kinase inhibitors such as ibrutinib resulted in promising outcomes. In this review, we discuss the pathophysiology, clinical manifestations, diagnostic characteristics, and an overview of the current treatment modalities of BNS.

Summary Cardio-oncology is an emerging field, that transformed the medical management of patients with cancer. It encompasses the prevention and treatment of cardiovascular toxicities related to cancer treatments, aiming to reduce cardiac adverse events among cancer survivors. Cardiovascular toxicities related to cancer treatments are described through data collected during phase I to phase III therapeutic trials, and post-marketing surveillance (phase IV). Pharmacovigilance analyses, based on datamining from these extensive databases, allowed to understanding and identifying new adverse drug reactions, some recently made available, such as immunotherapy or inhibitor of Bruton tyrosine kinase (IBTK).

TLR4 signaling via endotoxemia in macrophages promotes macrophage transition to the inflammatory phenotype through NLRP3 inflammasome activation. This transition event has the potential to trigger acute lung injury (ALI). However, relatively little is known about the regulation of NLRP3 and its role in the pathogenesis of ALI. Here we interrogated the signaling pathway activated by CD38, an ectoenzyme expressed in macrophages, in preventing ALI through suppressing NLRP3 activation. Wild-type and Cd38-knockout (Cd38(−/−)) mice were used to assess inflammatory lung injury, and isolated macrophages were used to delineate underlying TLR4 signaling pathway. We showed that CD38 suppressed TLR4 signaling in macrophages by inhibiting Bruton’s tyrosine kinase (Btk) through the recruitment of Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) and resulting in the dephosphorylation of activated Btk. Cd38(−/−) mice show enhanced lung polymorphonuclear leukocyte extravasation and severe lung injury. LPS- or polymicrobial sepsis-induced mortality in Cd38(−/−) mice were markedly augmented compared with wild types. CD38 in macrophages functioned by inhibiting Btk activation through activation of SHP2 and resulting dephosphorylation of Btk, and thereby preventing activation of downstream targets NF-κB and NLRP3. Cd38(−/−) macrophages displayed markedly increased activation of Btk, NF-κB, and NLRP3, whereas in vivo administration of the Btk inhibitor ibrutinib (a Food and Drug Administration-approved drug) prevented augmented TLR4-induced inflammatory lung injury seen in Cd38(−/−) mice. Our findings together show upregulation of CD38 activity and inhibition of Btk activation downstream of TLR4 activation as potential strategies to prevent endotoxemic ALI.

Summary: This is the first report of meningoencephalitis in an adult male with X-linked agammaglobulinemia caused by a probable Torque teno virus (TTV) infection. TTV was detected in the cerebrospinal fluid samples of the patient by high-throughput sequencing technology. The patient was treated successfully.AbstractX-linked agammaglobulinemia (XLA) is a rare primary immunodeficiency disease caused by mutations in the Bruton's tyrosine kinase (Btk) gene, characterized by recurrent infections and low or undetectable immunoglobulin levels. The most recommended treatment for XLA is lifelong intravenous immunoglobulin (IVIG) replacement therapy. Without treatment, XLA patients are vulnerable to bacterial and viral infections. Meningoencephalitis is a common complication in patients with XLA. Torque teno viruses (TTVs) are ubiquitous in various tissues of healthy people, while TTV infections have been reported only recently. This case study presents the first reported case on the Chinese mainland of meningoencephalitis in an adult male with XLA, most likely caused by TTV. A 27-year-old male presented with fever and severe disturbance of consciousness. Conventional tests, including blood culture and cerebrospinal fluid (CSF) culture, did not reveal any bacterial infections. The clinical presentation, neuroimaging findings, and results of CSF were suggestive of viral meningoencephalitis. Next, TTV was detected in CSF by high-throughput sequencing (HTS) technology. This case suggests that TTV can have a pathogenic effect on patients with severe immunodeficiency disease, and can produce severe clinical symptoms.

Key Points Therapy resistance to both individual and sequential BTK and BCL2 inhibition is clonally complex and most commonly oligoclonal.Single-agent resistance mutations occur in mutually exclusive clones; resistance mutations to sequential monotherapies variably co-occur., The genomic landscape of resistance to targeted agents (TAs) used as monotherapy in chronic lymphocytic leukemia (CLL) is complex and often heterogeneous at the patient level. To gain insight into the clonal architecture of acquired genomic resistance to Bruton tyrosine kinase (BTK) inhibitors and B-cell lymphoma 2 (BCL2) inhibitors in CLL, particularly in patients carrying multiple resistance mutations, we performed targeted single-cell DNA sequencing of 8 patients who developed progressive disease (PD) on TAs (either class). In all cases, analysis of single-cell architecture revealed mutual exclusivity between multiple resistance mutations to the same TA class, variable clonal co-occurrence of multiple mutations affecting different TAs in patients exposed to both classes, and a phenomenon of multiple independent emergences of identical nucleotide changes leading to canonical resistance mutations. We also report the first observation of established BCL2 resistance mutations in a patient with mantle cell lymphoma (MCL) following PD on sequential monotherapy, implicating BCL2 as a venetoclax resistance mechanism in MCL. Taken together, these data reveal the significant clonal complexity of CLL and MCL progression on TAs at the nucleotide level and confirm the presence of multiple, clonally independent, mechanisms of TA resistance within each individual disease context.

Purpose: Activation of Bruton tyrosine kinase (BTK) and phosphatidylinositol-3-kinase (PI3K) represent parallel, synergistic pathways in lymphoma pathogenesis. As predominant PI3Kδ inhibition is a possible mechanism of tumor escape, we proposed a clinical trial of dual BTK and pan-PI3K inhibition. Patients and Methods: We conducted a single-center phase I/Ib trial combining a BTK inhibitor (ibrutinib) and a pan-PI3K inhibitor (buparlisib) in 37 patients with relapsed/refractory (R/R) B-cell lymphoma. Buparlisib and ibrutinib were administered orally, once daily in 28-day cycles until progression or unacceptable toxicity. The clinical trial is registered with clinicaltrials.gov, NCT02756247. Results: Patients with mantle cell lymphoma (MCL) receiving the combination had a 94% overall response rate (ORR) and 33-month median progression-free survival; ORR of 31% and 20% were observed in patients with diffuse large B-cell lymphoma and follicular lymphoma, respectively. The maximum tolerated dose was ibrutinib 560 mg plus buparlisib 100 mg and the recommended phase II dose was ibrutinib 560 mg plus buparlisib 80 mg. The most common grade 3 adverse events were rash/pruritis/dermatitis (19%), diarrhea (11%), hyperglycemia (11%), and hypertension (11%). All grade mood disturbances ranging from anxiety, depression, to agitation were observed in 22% of patients. Results from serial monitoring of cell-free DNA samples corresponded to radiographic resolution of disease and tracked the emergence of mutations known to promote BTK inhibitor resistance. Conclusions: BTK and pan-PI3K inhibition in mantle cell lymphoma demonstrates a promising efficacy signal. Addition of BCL2 inhibitors to a BTK and pan-PI3K combination remain suitable for further development in mantle cell lymphoma.

Despite advances in the treatment of chronic urticaria, in a significant percentage of the patients symptoms are not fully controlled with conventional approaches. New strategies under development include blocking intracellular mediators of mast cell and basophil activation. We aim to investigate the effects of the Bruton's tyrosine kinase (BTK) inhibitor remibrutinib on human blood basophils and CD34+-derived mast cells activation induced by serum obtained from chronic urticaria patients. Twenty-two patients with chronic spontaneous urticaria (mean age 52 years, 27% women) and 22 patients with chronic inducible urticaria (46 years, 27% women) were included in the study together with a sex-matched control group. Patients were classified as responders or non-responders to anti-IgE therapy on the basis of their clinical data, FcεR1a expression on blood basophils and total IgE levels. Changes on CD63 expression—as an activation marker-, were used to evaluate in vitro the response of basophils and mast cells to serum exposure and the inhibitory effects of remibrutinib. Remibrutinib inhibits degranulation induced by IgE cross-linking in mast cells and basophils and also the activation triggered by factors present in the sera of spontaneous and inducible chronic urticaria patients. Patient's serum induces a greater degranulation of effector cells than controls. Activation of mast cells and basophils by patient sera and remibrutinib effects were not related to omalizumab responsiveness. Remibrutinib inhibits activation of human basophils and mast cells induced in vitro by exposure to the serum of chronic urticaria patients independently of their response to omalizumab.

Kronična limfocitna leukemija (KLL) najčešća je leukemija razvijenog svijeta. Bolest je odrasle dobi, koja se češće javlja kod muškaraca. Otkriće novih lijekova koji ciljano djeluju na tumorske stanice uvelike je promijenilo pristup u liječenju bolesnika oboljelih od tumora, a tako i onih s kroničnom limfocitnom leukemijom. Jedan od tih lijekova je i ibrutinib (Imbruvica), prvi otkriven ireverzibilni blokator Brutonove tirozin kinaze (BTK). BTK je molekula koja ima ključnu ulogu u signalom putu B limfocita, središnje stanice KLL-a. Osim ciljanog djelovanja, koje sa sobom donosi bolje podnošenje terapije s manje nuspojava, ova vrsta liječenja ima i druge prednosti. Lijek se uzima oralno jednom dnevno, što za bolesnika uvelike olakšava liječenje. Sve navedeno dovelo je do velikog napretka u liječenju KLL-a i omogućilo liječenje pacijenata koji nisu kandidati za ili ne podnose kemoterapiju. Ovaj diplomski rad prikazat će iskustvo Zavoda za hematologiju Kliničke bolnice Merkur u liječenju bolesnika s KLL-om ibrutinibom. Retrospektivno su prikupljeni podaci od 58 pacijenata iz BIS-a i dalje obrađeni. Od tih 58 pacijenata njih 41 nastavlja terapiju. Od ostalih 17 šest je pacijenata umrlo, a 11 je prekinulo dobivati terapiju. Od toga devet zbog progresije, a dvoje zbog nuspojava. Naši rezultati pokazali su vjerojatnost preživljenja 67% nakon 30 mjeseci praćenja. Dobiveni rezultati pokazali su da je ibrutinib učinkovita i sigurna terapija u određenoj indikaciji., Chronic lymphocytic leukemia (CLL) is the most common leukemia in the developed world. It is the disease of the adults, which occurs more often in men. The discovery of new drugs that target tumor cells has greatly changed the approach in the treatment of patients with tumors, as well as those with chronic lymphocytic leukemia. One of these drugs is ibrutinib (Imbruvica), the first irreversible blocker of Bruton's tyrosine kinase (BTK) to be discovered. BTK is a molecule that plays a key role in the signaling pathway of B lymphocytes, the central cells of CLL. In addition to targeted action, which brings with it better endurance therapy with fewer side effects, this type of treatment has other benefits. The drug is taken orally once a day, which greatly facilitates treatment for the patient. All of the above has led to great advances in the treatment of CLL and has enabled the treatment of patients who are not candidates for chemotherapy or do not tolerate it. This thesis will present the experience of the Department of Hematology of the Clinical Hospital Merkur in the treatment of patients with CLL with ibrutinib. In retrospect, data from 58 patients form BIS were collected and further processed. Of these 58 patients, 41 continue therapy. Of the other 17, six died and 11 stopped receiving therapy. Of these, nine due to progression and two due to side effects. Our results showed a 67% probability of survival after 30 months of follow-up. The obtained results showed that ibrutinib is an effective and safe therapy in a certain indication.

Contains fulltext : 241347.pdf (Publisher’s version ) (Closed access) Asparaginase (ASNase) therapy has been a mainstay of acute lymphoblastic leukemia (ALL) protocols for decades and shows promise in the treatment of a variety of other cancers. To improve the efficacy of ASNase treatment, we used a CRISPR/Cas9-based screen to identify actionable signaling intermediates that improve the response to ASNase. Both genetic inactivation of Bruton's tyrosine kinase (BTK) and pharmacological inhibition by the BTK inhibitor ibrutinib strongly synergize with ASNase by inhibiting the amino acid response pathway, a mechanism involving c-Myc-mediated suppression of GCN2 activity. This synthetic lethal interaction was observed in 90% of patient-derived xenografts, regardless of the genomic subtype. Moreover, ibrutinib substantially improved ASNase treatment response in a murine PDX model. Hence, ibrutinib may be used to enhance the clinical efficacy of ASNase in ALL. This trial was registered at www.clinicaltrials.gov as # NCT02884453.

Background Acalabrutinib is a next-generation Bruton tyrosine kinase inhibitor (BTKi) that has moved to the forefront of treatment options for patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL). Patients with CLL/SLL can experience adverse events and toxicities unique to BTKi therapy. Objectives This article provides an overview of nursing considerations for the treatment of patients with CLL/SLL with acalabrutinib, focusing on safety, toxicity management, and adherence. Methods A review of information identified through structured searches of key publications and websites and data from pivotal clinical trials was performed. Findings Increased awareness of the unique disease characteristics of patients with CLL/SLL and of the efficacy and safety profile of acalabrutinib allows nurses to play a vital role in improving patient outcomes. With this knowledge, nurses can support patients through education on potential side effects, drug-drug interactions, and treatment adherence, as well as monitor for clinical symptoms and laboratory findings requiring intervention.

Immunoglobulin M (IgM) multiple myeloma (MM) is a rare disease subgroup. Its differentiation from other IgM-producing gammopathies such as Waldenström macroglobulinemia (WM) has not been well characterized but is essential for proper risk assessment and treatment. In this study, we investigated genomic and transcriptomic characteristics of IgM-MM samples using whole-genome and transcriptome sequencing to identify differentiating characteristics from non–IgM-MM and WM. Our results suggest that IgM-MM shares most of its defining structural variants and gene-expression profiling with MM, but has some key characteristics, including t(11;14) translocation, chromosome 6 and 13 deletion as well as distinct molecular and transcription-factor signatures. Furthermore, IgM-MM translocations were predominantly characterized by VHDHJH recombination-induced breakpoints, as opposed to the usual class-switching region breakpoints; coupled with its lack of class switching, these data favor a pre–germinal center origin. Finally, we found elevated expression of clinically relevant targets, including CD20 and Bruton tyrosine kinase, as well as high BCL2/BCL2L1 ratio in IgM-MM, providing potential for targeted therapeutics.

Activating mutations in MYD88 promote malignant cell growth and survival through hematopoietic cell kinase (HCK)–mediated activation of Bruton tyrosine kinase (BTK). Ibrutinib binds to BTKCys481 and is active in B-cell malignancies driven by mutated MYD88. Mutations in BTKCys481, particularly BTKCys481Ser, are common in patients with acquired ibrutinib resistance. We therefore performed an extensive medicinal chemistry campaign and identified KIN-8194 as a novel dual inhibitor of HCK and BTK. KIN-8194 showed potent and selective in vitro killing of MYD88-mutated lymphoma cells, including ibrutinib-resistant BTKCys481Ser-expressing cells. KIN-8194 demonstrated excellent bioavailability and pharmacokinetic parameters, with good tolerance in rodent models at pharmacologically achievable and active doses. Pharmacodynamic studies showed sustained inhibition of HCK and BTK for 24 hours after single oral administration of KIN-8194 in an MYD88-mutated TMD-8 activated B-cell diffuse large B-cell lymphoma (ABC DLBCL) and BCWM.1 Waldenström macroglobulinemia (WM) xenografted mice with wild-type BTK (BTKWT)– or BTKCys481Ser-expressing tumors. KIN-8194 showed superior survival benefit over ibrutinib in both BTKWT- and BTKCys481Ser-expressing TMD-8 DLBCL xenografted mice, including sustained complete responses of >12 weeks off treatment in mice with BTKWT-expressing TMD-8 tumors. The BCL_2 inhibitor venetoclax enhanced the antitumor activity of KIN-8194 in BTKWT- and BTKCys481Ser-expressing MYD88-mutated lymphoma cells and markedly reduced tumor growth and prolonged survival in mice with BTKCys481Ser-expressing TMD-8 tumors treated with both drugs. The findings highlight the feasibility of targeting HCK, a key driver of mutated MYD88 pro-survival signaling, and provide a framework for the advancement of KIN-8194 for human studies in B-cell malignancies driven by HCK and BTK.

Abivertinib, a third-generation tyrosine kinase inhibitor, is originally designed to target epidermal growth factor receptor (EGFR)-activating mutations. Previous studies have shown that abivertinib has promising antitumor activity and a well-tolerated safety profile in patients with non-small-cell lung cancer. However, abivertinib also exhibited high inhibitory activity against Bruton’s tyrosine kinase and Janus kinase 3. Given that these kinases play some roles in the progression of megakaryopoiesis, we speculate that abivertinib can affect megakaryocyte (MK) differentiation and platelet biogenesis. We treated cord blood CD34+ hematopoietic stem cells, Meg-01 cells, and C57BL/6 mice with abivertinib and observed megakaryopoiesis to determine the biological effect of abivertinib on MK differentiation and platelet biogenesis. Our in vitro results showed that abivertinib impaired the CFU-MK formation, proliferation of CD34+ HSC-derived MK progenitor cells, and differentiation and functions of MKs and inhibited Meg-01-derived MK differentiation. These results suggested that megakaryopoiesis was inhibited by abivertinib. We also demonstrated in vivo that abivertinib decreased the number of MKs in bone marrow and platelet counts in mice, which suggested that thrombopoiesis was also inhibited. Thus, these preclinical data collectively suggested that abivertinib could inhibit MK differentiation and platelet biogenesis and might be an agent for thrombocythemia.

Key Points ctDNA technology is useful for noninvasive monitoring of lymphoma treated with targeted agents in the clinical trial setting.An early >2-log reduction of ctDNA levels after 2 treatment cycles was a confirmed threshold for molecular response., Visual Abstract, To advance the use of circulating tumor DNA (ctDNA) applications, their broad clinical validity must be tested in different treatment settings, including targeted therapies. Using the prespecified longitudinal systematic collection of plasma samples in the phase 1/2a LYM1002 trial (registered on www.clinicaltrials.gov as NCT02329847), we tested the clinical validity of ctDNA for baseline mutation profiling, residual tumor load quantification, and acquisition of resistance mutations in patients with lymphoma treated with ibrutinib+nivolumab. Inclusion criterion for this ancillary biological study was the availability of blood collected at baseline and cycle 3, day 1. Overall, 172 ctDNA samples from 67 patients were analyzed by the LyV4.0 ctDNA Cancer Personalized Profiling Deep Sequencing Assay. Among baseline variants in ctDNA, only TP53 mutations (detected in 25.4% of patients) were associated with shorter progression-free survival; clones harboring baseline TP53 mutations did not disappear during treatment. Molecular response, defined as a >2-log reduction in ctDNA levels after 2 cycles of therapy (28 days), was achieved in 28.6% of patients with relapsed diffuse large B-cell lymphoma who had ≥1 baseline variant and was associated with best response and improved progression-free survival. Clonal evolution occurred frequently during treatment, and 10.3% new mutations were identified after 2 treatment cycles in nonresponders. PLCG2 was the topmost among genes that acquired new mutations. No patients acquired the C481S BTK mutation implicated in resistance to ibrutinib in CLL. Collectively, our results provide the proof of concept that ctDNA is useful for noninvasive monitoring of lymphoma treated with targeted agents in the clinical trial setting.

With the advent of targeted therapies for chronic lymphocytic leukemia (CLL), treatment choice has expanded and patients are living longer. Careful consideration is needed regarding treatment duration and sequence, how best to meet patients' needs, balancing toxicities while improving long-term survival and maximizing depth of response. This review addresses these considerations and discusses current targeted treatment dilemmas. Targeted therapies have dramatically transformed the CLL treatment landscape. Two treatment paradigms have emerged using B-cell lymphoma 2 inhibitors (BCL2i) and Bruton's tyrosine kinase (BTK): (i) fixed duration and (ii) continuous treatment. The BCL2i venetoclax can attain deep remissions with a fixed-duration approach, resulting in high rates of undetectable minimal residual disease (uMRD) in treatment-naïve and relapsed/refractory (R/R) patients with CLL. BTKis such as ibrutinib and acalabrutinib achieve high objective response rates and long-term disease control, although they rarely attain complete response or uMRD status as monotherapy. Numerous studies are evaluating the clinical utility of BTKi and BCL2i as combination therapies, where deep remissions have been found to occur. MRD status may also be a useful marker for deciding when to stop continuous therapy, and randomized trials on MRD-guided treatment strategies are currently ongoing. The current treatment choice between continuous or fixed-duration therapy should be based on comorbidities, risks, preferences, and treatment goals, whilst areas of emerging clinical interest include the potential utility of BTKi-BCL2i combination therapies, as well as an MRD-guided treatment strategies in the future.

Bruton’s tyrosine kinase (BTK), expressed in B cells and cells of innate immunity, including microglia, is an essential signaling element downstream of the B‐cell receptor and Fc‐receptors. Tolebrutinib (PRN2246, SAR442168) is a potent BTK inhibitor that covalently binds the kinase, resulting in durable inhibition with the potential to target inflammation in the periphery and central nervous system (CNS). Tolebrutinib crosses the blood‐brain barrier and potently inhibits BTK in microglial cells isolated from the CNS. A first‐in‐human randomized, double‐blind, placebo‐controlled study of tolebrutinib was conducted. The trial design consisted of five single ascending dose arms with oral administration of a single dose of 5, 15, 30, 60, and 120 mg (n = 6 per arm, n = 2 placebo), five multiple ascending dose arms with oral administration of 7.5, 15, 30, 60, and 90 mg (n = 8 per arm, n = 2 placebo) over 10 days, and one arm (n = 4) in which cerebral spinal fluid (CSF) exposure was measured 2 h after a single 120 mg dose. Tolebrutinib was well‐tolerated in the study and all treatment‐related treatment emergent adverse events were mild. Tolebrutinib was rapidly absorbed following oral administration with a rapid half‐life of ~ 2 h. Peripheral BTK occupancy was assessed at various timepoints by an enzyme‐linked immunosorbent assay‐based readout using an irreversible probe. Assessments demonstrated extensive and prolonged peripheral BTK occupancy at steady‐state with once daily doses as low as 7.5 mg. Further, CSF exposure was demonstrated 2 h after administration at 120 mg.

DISEASE OVERVIEW Hairy cell leukemia (HCL) and HCL-like disorders, including HCL variant (HCL-V) and splenic diffuse red pulp lymphoma (SDRPL), are a very heterogeneous group of mature lymphoid B-cell disorders characterized by the identification of hairy cells, a specific genetic profile, a different clinical course, and the need for appropriate treatment. DIAGNOSIS Diagnosis of HCL is based on morphological evidence of hairy cells, an HCL immunologic score of 3 or 4 based on the CD11C, CD103, CD123, and CD25 expression, the trephine biopsy which makes it possible to specify the degree of tumoral medullary infiltration and the presence of BRAFV600E somatic mutation. RISK STRATIFICATION Progression of patients with HCL is based on a large splenomegaly, leukocytosis, a high number of hairy cells in the peripheral blood, and the immunoglobulin heavy chain variable region gene mutational status. VH4-34-positive HCL cases are associated with a poor prognosis. TREATMENT Patients should be treated only if HCL is symptomatic. Chemotherapy with risk adapted therapy purine analogs (PNAs) are indicated in first-line HCL patients. The use of chemo-immunotherapy combining PNAs and rituximab (R) represents an increasingly used therapeutic approach. Management of relapsed/refractory disease is based on the use of BRAF inhibitors (BRAFi) plus rituximab or MEK inhibitors (MEKi), recombinant immunoconjugates targeting CD22 or Bruton Tyrosine Kinase inhibitors (BTKi). However, the optimal sequence of the different treatments remains to be determined. The Bcl2-inhibitors (Bcl-2i) can play a major role in the future.

Most B-Raf proto-oncogene (BRAF)-mutant melanoma tumors respond initially to BRAF inhibitor (BRAFi)/mitogen-activated protein kinase kinase 1 inhibitor (MEKi) therapy, although few patients have durable long-term responses to these agents. The goal of this study was to use an unbiased computational approach to identify inhibitors that reverse an experimentally derived BRAFi resistance gene expression signature. Using this approach, we found that ibrutinib effectively reverses this signature, and we demonstrate experimentally that ibrutinib resensitizes a subset of BRAFi-resistant melanoma cells to vemurafenib. Ibrutinib is used clinically as an inhibitor of the Src family kinase Bruton tyrosine kinase (BTK); however, neither BTK deletion nor treatment with acalabrutinib, another BTK inhibitor with reduced off-target activity, resensitized cells to vemurafenib. These data suggest that ibrutinib acts through a BTK-independent mechanism in vemurafenib resensitization. To better understand this mechanism, we analyzed the transcriptional profile of ibrutinib-treated BRAFi-resistant melanoma cells and found that the transcriptional profile of ibrutinib was highly similar to that of multiple Src proto-oncogene kinase inhibitors. Since ibrutinib, but not acalabrutinib, has appreciable off-target activity against multiple Src family kinases, it suggests that ibrutinib may be acting through this mechanism. Furthermore, genes that are differentially expressed in ibrutinib-treated cells are enriched in Yes1-associated transcriptional regulator (YAP1) target genes, and we showed that ibrutinib, but not acalabrutinib, reduces YAP1 activity in BRAFi-resistant melanoma cells. Taken together, these data suggest that ibrutinib, or other Src family kinase inhibitors, may be useful for treating some BRAFi/MEKi-refractory melanoma tumors. SIGNIFICANCE STATEMENT: MAPK-targeted therapies provide dramatic initial responses, but resistance develops rapidly; a subset of these tumors may be rendered sensitive again by treatment with an approved Src family kinase inhibitor-ibrutinub-potentially providing improved clinical outcomes.

Bruton’s tyrosine kinase (BTK) is crucial for FceRI-mediated mast cell activation and essential for autoantibody production by B cells in chronic spontaneous urticaria (CSU). Fenebrutinib, an orally administered, potent, highly selective, reversible BTK inhibitor, may be effective in CSU. This double-blind, placebo-controlled, phase 2 trial (EudraCT ID 2016-004624-35 ) randomized 93 adults with antihistamine-refractory CSU to 50 mg daily, 150 mg daily and 200 mg twice daily of fenebrutinib or placebo for 8 weeks. The primary end point was change from baseline in urticaria activity score over 7 d (UAS7) at week 8. Secondary end points were the change from baseline in UAS7 at week 4 and the proportion of patients well-controlled (UAS7 ≤ 6) at week 8. Fenebrutinib efficacy in patients with type IIb autoimmunity and effects on IgG-anti-FceRI were exploratory end points. Safety was also evaluated. The primary end point was met, with dose-dependent improvements in UAS7 at week 8 occurring at 200 mg twice daily and 150 mg daily, but not at 50 mg daily of fenebrutinib versus placebo. Asymptomatic, reversible grade 2 and 3 liver transaminase elevations occurred in the fenebrutinib 150 mg daily and 200 mg twice daily groups (2 patients each). Fenebrutinib diminished disease activity in patients with antihistamine-refractory CSU, including more patients with refractory type IIb autoimmunity. These results support the potential use of BTK inhibition in antihistamine-refractory CSU. Fenebrutinib, an oral Bruton’s tyrosine kinase inhibitor, reduces disease activity in patients with chronic spontaneous urticaria refractory to antihistamines, suggesting that this treatment type could be an alternative to standard of care anti-IgE therapy.

Tyrosine kinase inhibitors (TKIs) have been widely used to treat various malignancies, dramatically improving survival. The use of these treatments has been limited by adverse effects. Ibrutinib, a Bruton’s tyrosine kinase (BTK) inhibitor, has been associated with increased prevalence of atrial fibrillation (AF) in approximately 5%–16% of patients, especially those with prior history of AF,1 and often leads to treatment discontinuation in a significant proportion of patients. Management of AF in this patient population also presents a unique challenge. Current guidelines recommend rate control as the primary strategy,2,3 which can be challenging, since pharmacological management is limited by significant drug interactions with cancer therapies as well as potential side effects. Additionally, the need for anticoagulation in this strategy is challenged by increased risk of bleeding owing to inhibition of collagen-induced platelet aggregation by ibrutinib.4 Recent studies document the long-term benefits of catheter ablation in maintaining sinus rhythm in the general population. We present a case of ibrutinib-associated symptomatic AF, which was successfully treated with ablation therapy, and allowed the patient to return to ibrutinib therapy for adequate management of his cancer (Figure 1). Open in a separate window Figure 1 Timeline showing cardiovascular and hematologic disease and treatment course. AF = atrial fibrillation; CLL = chronic lymphocytic leukemia; AAD = antiarrhythmic drug; OAC = oral anticoagulant. (Figure created with BioRender.com.)

Multiple sclerosis (MS) has long been considered a T-cell-mediated autoimmune disease of the central nervous system. However, newer evidence shows that B cells play a crucial role in the pathogenesis of MS via antibody production, antigen presentation, T cell stimulation and activation, and production of pro-inflammatory cytokines. Developing B cells express the CD20 molecule from the pre-B cell to the plasmablast stage, and the anti-CD20 monoclonal antibodies rituximab, ocrelizumab, ofatumumab and ublituximab are either in use or are being developed for treatment of MS as B cell-depleting therapies. They have shown profound efficacy in strongly suppressing relapse and radiological disease activity. Another promising approach is the inhibition of Bruton’s tyrosine kinase (BTK), a key enzyme that is intricately involved in signaling from the B cell antigen receptor and the Fc receptors in B cells and myeloid cells. BTK is considered to play an essential role for differentiation and survival of B-lineage cells, and BTK inhibition may dampen not only B cell activation but also innate immune activation in MS. Trials of BTK inhibitors are ongoing to establish their efficacy and safety in relapsing and progressive MS. The main safety issue with persistent B cell depletion is an increased risk of infection, possibly including an increased risk of severe COVID-19;unfortunately, vaccine responses against COVID-19 may also be blunted by anti-CD20 monoclonal antibodies.

A series of cases with rare thromboembolic incidents including cerebral sinus vein thrombosis (some of them fatal) and concomitant thrombocytopenia occurring shortly after vaccination with the coronavirus disease 2019 (COVID-19) vaccine AZD1222 (Vaxzevria) have caused significant concern and led to its temporary suspension in many countries. Immediate laboratory efforts in four of these patients have identified a tentative pathomechanism underlying this syndrome termed initially vaccine-induced prothrombotic immune thrombocytopenia (VIPIT) and renamed recently vaccine-induced immune thrombotic thrombocytopenia (VITT). It encompasses the presence of platelet-activating antibodies to platelet factor-4/heparin complexes, possibly emulated by polyanionic constituents of AZD1222, and thus resembles heparin-induced thrombocytopenia (HIT). Because these immune complexes bind and activate platelets via Fcγ receptor IIA (FcγRIIA), high-dose intravenous immunoglobulin G has been suggested for treatment of VITT in addition to non-heparin anticoagulants. Here we propose inhibitors of Bruton tyrosine kinase (Btk) approved for B cell malignancies (e.g., ibrutinib) as another therapeutic option in VITT, as they are expected to pleiotropically target multiple pathways downstream of FcγRIIA-mediated Btk activation, for example, as demonstrated for the effective inhibition of platelet aggregation, dense granule secretion, P-selectin expression and platelet-neutrophil aggregate formation stimulated by FcγRIIA cross-linking. Moreover, C-type lectin-like receptor CLEC-2- and GPIb-mediated platelet activation, the interactions and activation of monocytes and the release of neutrophil extracellular traps, as encountered in HIT, could be attenuated by Btk inhibitors. As a paradigm for emergency repurposing of approved drugs in COVID-19, off-label use of Btk inhibitors in a low-dose range not affecting haemostatic functions could thus be considered a sufficiently safe option to treat VITT.

Aberrant microRNA (miR) expression plays an important role in pathogenesis of different types of cancers, including B-cell lymphoid malignancies and in the development of chemo-sensitivity or -resistance in chronic lymphocytic leukemia (CLL) as well as diffuse large B-cell lymphoma (DLBCL). Ibrutinib is a first-in class, oral, covalent Bruton’s tyrosine kinase (BTK) inhibitor (BTKi) that has shown impressive clinical activity, yet many ibrutinib-treated patients relapse or develop resistance over time. We have reported that acquired resistance to ibrutinib is associated with downregulation of tumor suppressor protein PTEN and activation of the PI3K/AKT pathway. Yet how PTEN mediates chemoresistance in B-cell malignancies is not clear. We now show that the BTKi ibrutinib and a second-generation compound, acalabrutinib downregulate miRNAs located in the 14q32 miRNA cluster region, including miR-494, miR-495, and miR-543. BTKi-resistant CLL and DLBCL cells had striking overexpression of miR-494, miR-495, miR-543, and reduced PTEN expression, indicating further regulation of the PI3K/AKT/mTOR pathway in acquired BTKi resistance. Additionally, unlike ibrutinib-sensitive CLL patient samples, those with resistance to ibrutinib treatment, demonstrated upregulation of 14q32 cluster miRNAs, including miR-494, miR-495, and miR-543 and decreased pten mRNA expression. Luciferase reporter gene assay showed that miR-494 directly targeted and suppressed PTEN expression by recognizing two conserved binding sites in the PTEN 3′-UTR, and subsequently activated AKTSer473. Importantly, overexpression of a miR-494 mimic abrogated both PTEN mRNA and protein levels, further indicating regulation of apoptosis by PTEN/AKT/mTOR. Conversely, overexpression of a miR-494 inhibitor in BTKi-resistant cells restored PTEN mRNA and protein levels, thereby sensitizing cells to BTKi-induced apoptosis. Inhibition of miR-494 and miR-495 sensitized cells by cooperative targeting of pten, with additional miRNAs in the 14q32 cluster that target pten able to contribute to its regulation. Therefore, targeting 14q32 cluster miRNAs may have therapeutic value in acquired BTK-resistant patients via regulation of the PTEN/AKT/mTOR signaling axis.

Bruton's tyrosine kinase (BTK) inhibitors suppressing the aberrant activation of BTK have led to a paradigm shift in the therapy of B-cell malignancies. However, there is an urgent need to discover more selective covalent BTK inhibitors owing to the off-target adverse effects of the approved inhibitor, ibrutinib. Herein, we disclose the discovery and preliminary activity studies of novel BTK inhibitors carrying 1-amino-1H-imidazole-5-carboxamide as a hinge binder. The most potent BTK inhibitor 26 demonstrates impressive selectivity, favorable pharmacokinetic properties, and robust antitumor efficacy in vivo, which indicates its potential as a novel therapeutic option for B-cell lymphomas. Importantly, to the best of our knowledge, this is the first example of a 1-amino-1H-imidazole-5-carboxamide scaffold used as the hinge binder of kinase inhibitors, which will largely expand the chemical diversity of kinase inhibitors.

Covalent Bruton tyrosine kinase inhibitors (BTKi’s) and the B-cell lymphoma 2 (BCL2) inhibitor venetoclax have significantly improved outcomes for patients with chronic lymphocytic leukemia (CLL), especially those with biologically adverse disease. Patients with CLL resistant to their first targeted agent (TA) can be effectively treated with the alternative class. However, relapses are expected with second-line TA therapy, and the clinical challenge of double class-resistant disease is now emerging with increasing frequency. To define the characteristics and outcomes of patients with double class-resistant disease, we retrospectively analyzed 17 patients who developed progressive disease (PD) on both TA classes for CLL (venetoclax, then BTKi, n=12; BTKi, then venetoclax, n = 5). The cohort was heavily pretreated (median lines of prior therapy, 4) and enriched for adverse disease genetics (complex karyotype, 12 of 12 tested [100%]; del(17p)/TP53 mutations, 15 of 17 [88%]). The median time to progression on prior venetoclax was 24 months (range, 6-94 months) and was 25 months (range, 1-55 months) on prior BTKi. Progression on second-line TA was manifest as progressive CLL in 11 patients and as Richter transformation in 6. The median overall survival after progression on second-line TA was 3.6 months (95% confidence interval, 2-11 months). Patients with double class-resistant CLL have a dismal prognosis, representing a group of high unmet need.

The chronic lymphocytic leukemia (CLL) armamentarium has evolved significantly, with novel therapies that inhibit Bruton Tyrosine Kinase, PI3K delta and/or the BCL2 protein improving outcomes. Still, the clinical course of CLL patients is highly variable and most previously recognized prognostic features lack the capacity to predict response to modern treatments indicating the need for new prognostic markers. In this study, we identified four epigenetically distinct proteomic signatures of a large cohort of CLL and related diseases derived samples (n = 871) using reverse phase protein array technology. These signatures are associated with clinical features including age, cytogenetic abnormalities [trisomy 12, del(13q) and del(17p)], immunoglobulin heavy-chain locus (IGHV) mutational load, ZAP-70 status, Binet and Rai staging as well as with the outcome measures of time to treatment and overall survival. Protein signature membership was identified as predictive marker for overall survival regardless of other clinical features. Among the analyzed epigenetic proteins, EZH2, HDAC6, and loss of H3K27me3 levels were the most independently associated with poor survival. These findings demonstrate that proteomic based epigenetic biomarkers can be used to better classify CLL patients and provide therapeutic guidance.

Mast cells have crucial roles in allergic and other inflammatory diseases. Preclinical approaches provide circumstantial evidence for mast cell involvement in many diseases, but these studies have major limitations — for example, there is still a lack of suitable mouse models for some mast cell-driven diseases such as urticaria. Some approaches for studying mast cells are invasive or can induce severe reactions, and very few mediators or receptors are specific for mast cells. Recently, several drugs that target human mast cells have been developed. These include monoclonal antibodies and small molecules that can specifically inhibit mast cell degranulation via key receptors (such as FceRI), that block specific signal transduction pathways involved in mast cell activation (for example, BTK), that silence mast cells via inhibitory receptors (such as Siglec-8) or that reduce mast cell numbers and prevent their differentiation by acting on the mast/stem cell growth factor receptor KIT. In this Review, we discuss the existing and emerging therapies that target mast cells, and we consider how these treatments can help us to understand mast cell functions in disease. Kolkhir and colleagues discuss how therapies targeting human mast cells in both allergic and non-allergic disease settings have provided crucial insights into the functions of these cells.

SummaryThe treatment landscape of chronic lymphocytic leukemia (CLL) has shifted from chemotherapy-based approaches to targeted agents in the last decade. However, evolving drug resistance and accumulating toxicity remain challenges that still limit patients’ clinical outcomes. Furthermore, currently licensed targeted agents such as inhibitors of Bruton’s tyrosine kinase (BTK) and anti-apoptotic protein B‑cell lymphoma 2 (BCL2) do not adequately compensate for the poor clinical outcomes associated with high-risk genetics such as TP53 alterations. New insights into disease biology facilitated design and investigation of several new targeted agents with encouraging results in early clinical trials. This short review focuses on novel actionable targets and investigational drugs aimed at circumventing acquired resistance and avoiding accumulating toxicity.

Francesco Paolo Tambaro,1 Danilo De Novellis,1,2 William G Wierda3 1Unità Operativa di Trapianto di Midollo Osseo e Servizio Trasfusionale, Azienda Ospedaliera di Rilievo Nazionale Santobono-Pausilipon, Napoli, Italy; 2Department of Precision Medicine, University of Campania “L. Vanvitelli”, Napoli, Italy; 3Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX, USACorrespondence: William G Wierda Email wwierda@mdanderson.orgAbstract: The B cell receptor (BCR) signaling pathway is functional and has critical cell survival implications in B cell malignancies, such as chronic lymphocytic leukemia (CLL). Orally administered small molecule tyrosine kinase inhibitors of members of the BCR signaling pathway have proven to be transformational in treatment of CLL. The first-generation inhibitor, ibrutinib, covalently binds to the C481 amino acid of Bruton’s tyrosine kinase (BTK), thereby irreversibly inhibiting its kinase activity, and interferes with the biology of the cells, ultimately resulting in CLL cell death and therapeutic response. Remissions are not deep to the point of considering discontinuation for most patients, but BTK-inhibitor-based therapy provides exceptional long-term disease control with continuous treatment. There are in-class toxicities and more selective second- and subsequent-generation agents and reversible inhibitors have been developed with the intent of reducing toxicities. Also, strategies to subvert resistance have included tighter or alternative, non-covalent, inhibitor binding. Furthermore, other strategies to deplete BTK protein, such as degraders, are in development and being tested in the clinic. Ultimately, the development and approval of these agents targeting BTK have ushered in a new era of chemotherapy-free treatments with remarkably improved survival outcomes for patients with CLL.Keywords: chronic lymphocytic leukemia, CLL, Bruton’s tyrosine kinase, BTK, targeted therapy, ibrutinib, acalabrutinib, pirtobrutinib

The B cell receptor (BCR) signaling pathway is functional and has critical cell survival implications in B cell malignancies, such as chronic lymphocytic leukemia (CLL). Orally administered small molecule tyrosine kinase inhibitors of members of the BCR signaling pathway have proven to be transformational in treatment of CLL. The first-generation inhibitor, ibrutinib, covalently binds to the C481 amino acid of Bruton’s tyrosine kinase (BTK), thereby irreversibly inhibiting its kinase activity, and interferes with the biology of the cells, ultimately resulting in CLL cell death and therapeutic response. Remissions are not deep to the point of considering discontinuation for most patients, but BTK-inhibitor-based therapy provides exceptional long-term disease control with continuous treatment. There are in-class toxicities and more selective second- and subsequent-generation agents and reversible inhibitors have been developed with the intent of reducing toxicities. Also, strategies to subvert resistance have included tighter or alternative, non-covalent, inhibitor binding. Furthermore, other strategies to deplete BTK protein, such as degraders, are in development and being tested in the clinic. Ultimately, the development and approval of these agents targeting BTK have ushered in a new era of chemotherapy-free treatments with remarkably improved survival outcomes for patients with CLL.

Bruton tyrosine kinase inhibitors (BTKi) have significantly changed the treatment landscape for patients with B-cell malignancies, including chronic lymphocytic leukemia, Waldenstrom macroglobulinemia, mantle cell lymphoma, and marginal zone lymphoma. Unfortunately, patients with BTKi-resistant disease have shortened survival. Clinical and molecular risk factors, such as number of prior therapies and presence of TP53 mutations, can be used to predict patients at the highest risk of developing BTKi resistance. Many mechanisms of BTKi resistance have been reported with mutations in BTK and phospholipase C γ2 supported with the most data. The introduction of venetoclax has lengthened the survival of patients with BTKi-resistant disease. Ongoing clinical trials with promising treatment modalities, such as next-generation BTKi and chimeric antigen receptor T-cell therapy, have reported promising efficacy in patients with BTKi-resistant disease. Continued research focusing on resistance mechanisms and methods of how to circumvent resistance is needed to further prolong the survival of patients with BTKi-resistant B-cell malignancies.

Purpose of review \ud The clinical outcomes from COVID-19 in monogenic causes of predominant antibody deficiency have pivotal implications for our understanding of the antiviral contribution of humoral immunity. This review summarizes the lessons learned from COVID-19 infection in X-linked agammaglobulinemia (XLA) due to genetic defects in Bruton's tyrosine kinase (BTK).\ud \ud Recent findings \ud Key molecular pathways underlying the development of severe COVID-19 are emerging, highlighting the possible contribution of BTK to hyperinflammation. SARS-CoV-2 specific T-cell responses and complement activation appear insufficient to achieve viral clearance in some B-cell deficient individuals. Whilst appearing efficacious in this group, use of convalescent plasma has been recently associated with the evolution of viral escape variants. Early data suggests individuals with XLA can mount a viral-specific T-cell vaccine response, however, the clinical significance of this is still emerging.\ud \ud Summary \ud In contrast to reports made early in the pandemic, we show XLA patients remain susceptible to severe disease. Persistent infection was common and is likely to carry a significant symptom burden and risk of novel variant evolution. COVID-19 infection in this vulnerable, antibody deficient group due to genetic, therapeutic or disease causes may require prompt and specific intervention for both patient and societal benefit.

The streptavidin mass shift (SMaSh) assay is a robust and fast approach for quantifying target protein occupancy by a covalent inhibitor or ligand. It exploits the biotin-streptavidin bond using the Simple Western platform. One measurement on a single sample determines both total and occupied target protein simultaneously and is, therefore, self-normalizing. The approach works in diverse and complex biological matrices and, with no need for matched vehicle-treated controls, readily applies to tissues from animal pharmacology models. Assessing occupancy is critical in the development of targeted covalent drugs. We demonstrate its use by characterizing and validating a variety of chemical probes for Bruton's tyrosine kinase (BTK, UniprotKB Q10607) and mitogen-activated protein kinase (ERK1/2/MAPK1/2, UniprotKB P28482 and P27361) and determining target engagement of covalent inhibitors for both targets and off-target engagement for ERK. We demonstrated that it works in cell lysates, tissues, and human peripheral blood mononuclear cells. The SMaSh assay is superior to traditional methods and broadly useful as a tool in assessing covalent biological probes or targeted covalent inhibitors.

Introduction: Bruton's tyrosine kinase (BTK) inhibitors have revolutionized the treatment of B-cell lymphomas. Zanubrutinib was designed to achieve improved therapeutic concentrations and minimize off-target activities putatively accounting, in part, for the adverse effects seen with other BTK inhibitors.Areas covered: This drug profile covers zanubrutinib clinical pharmacology and the translation of pharmacokinetics (PK) and pharmacodynamics (PD) to clinical efficacy and safety profiles, by highlighting key differences between zanubrutinib and other BTK inhibitors. We discuss PK, sustained BTK occupancy, and potential factors affecting PK of zanubrutinib, including food effects, hepatic impairment, and drug-drug interactions. These data, along with exposure-response analyses, were used to support the recommended dose of 320 mg, either once daily or as 160 mg twice daily. Translation of PK/PD attributes into clinical effects was demonstrated in a randomized, phase 3 head-to-head study comparing it with ibrutinib in patients with Waldenstrom macroglobulinemia.Expert opinion: Among the approved BTK inhibitors, zanubrutinib is less prone to PK modulation by intrinsic and extrinsic factors, leading to more consistent, sustained therapeutic exposures and improved dosing convenience. Zanubrutinib PK/PD has translated into durable responses and improved safety, representing an important new treatment option for patients who benefit from BTK therapy.

Although Bruton's tyrosine kinase (BTK) has been recognized as a validated drug target for the treatment of B-cell malignances, the emergence of clinical resistance to the first-generation covalent BTK inhibitors is becoming a serious concern. As a part of our effort to develop noncovalent BTK inhibitors, a series of novel pyrrolopyrimidines was identified as noncovalent inhibitors of both the wild-type and C481S mutant BTKs. Subsequent lead optimization led to the identification of an orally available, potent, and selective BTK inhibitor 13f (AS-1763) as a next-generation noncovalent BTK inhibitor. With significant efficacies in vivo tumor xenograft models, AS-1763 has advanced to phase 1 clinical trials.

Purpose: Marginal zone lymphoma (MZL) is an uncommon non–Hodgkin lymphoma with malignant cells that exhibit a consistent dependency on B-cell receptor signaling. We evaluated the efficacy and safety of zanubrutinib, a next-generation selective Bruton tyrosine kinase inhibitor, in patients with relapsed/refractory (R/R) MZL. Patients and Methods: Patients with R/R MZL were enrolled in the phase II MAGNOLIA (BGB-3111–214) study. The primary endpoint was overall response rate (ORR) as determined by an independent review committee (IRC) based on the Lugano 2014 classification. Results: Sixty-eight patients were enrolled. After a median follow-up of 15.7 months (range, 1.6 to 21.9 months), the IRC-assessed ORR was 68.2% and complete response (CR) was 25.8%. The ORR by investigator assessment was 74.2%, and the CR rate was 25.8%. The median duration of response (DOR) and median progression-free survival (PFS) by independent review was not reached. The IRC-assessed DOR rate at 12 months was 93.0%, and IRC-assessed PFS rate was 82.5% at both 12 and 15 months. Treatment was well tolerated with the majority of adverse events (AE) being grade 1 or 2. The most common AEs were diarrhea (22.1%), contusion (20.6%), and constipation (14.7%). Atrial fibrillation/flutter was reported in 2 patients; 1 patient had grade 3 hypertension. No patient experienced major hemorrhage. In total, 4 patients discontinued treatment due to AEs, none of which were considered treatment-related by the investigators. Conclusions: Zanubrutinib demonstrated high ORR and CR rate with durable disease control and a favorable safety profile in patients with R/R MZL.

Primary CNS lymphoma (PCNSL) is a highly aggressive malignant disease with a high recurrence rate and a poor prognosis. We present the case of a 71-year-old woman diagnosed with PCNSL in June 2010. After 3 relapses and intensive treatment with multiple chemotherapy regimens and whole-brain radiotherapy, she received off-label treatment with the Bruton tyrosine kinase inhibitor ibrutinib, responded well, achieved a complete remission, and is progression-free for now >3 years.

BGB-3111, a novel Bruton's tyrosine kinase (BTK) inhibitor, shows promising anti-cancer effects in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), mantle cell lymphoma (MCL), and Waldenstrom macroglobulinemia (WM). This study aimed to investigate the anti-cancer effects of BGB-3111 combined with bortezomib (BTZ) against the BTK-expressing MCL. We found that BTK, which was overexpressed in 59.4% of patients with MCL, was mainly characterized by high Ki67 and elevated MIPI scores. BGB-3111 strongly inhibited cell proliferation, induced cell cycle arrest in the G1/G0-phase, and promoted cell apoptosis in the MCL cells expressing BTK. BGB-3111 provides better safety than another BTK inhibitor, ibrutinib as ibrutinib inhibits the inducible T-cell kinase (ITK) as an off-target effect but BGB-3111 does not inhibit ITK. Low doses of BTZ enhanced the anti-cancer effect induced by the low dose of BGB-3111 by downregulating the expression levels of PARP and Bcl-2 and increasing the expression levels of cleaved PARP and cleaved caspase-9. In addition, low doses of BGB-3111, but not of BTZ, inhibited BTK phosphorylation. However, low-doses of BTZ strengthened the anti-cancer effect induced by the low-doses of BGB-3111 via synergistically suppressing the IκBα and P65 phosphorylation. Taken together, our findings validate that BGB-3111 is a novel and effective BTK inhibitor for MCL-expressing BTK. Hence, it can be harnessed as a potential therapeutic strategy through a combinatorial treatment comprising low-dose BGB-3111 and low-dose BTZ to gain strong anti-cancer effects and better safety for MCL patients.

Systemic autoimmune disorders are complex heterogeneous chronic diseases involving many different immune cells. A significant proportion of patients respond poorly to therapy. In addition, the high burden of adverse effects caused by “classical” anti-rheumatic or immune modulatory drugs provides a need to develop more specific therapies that are better tolerated. Bruton’s tyrosine kinase (BTK) is a crucial signaling protein that directly links B-cell receptor (BCR) signals to B-cell activation, proliferation, and survival. BTK is not only expressed in B cells but also in myeloid cells, and is involved in many different signaling pathways that drive autoimmunity. This makes BTK an interesting therapeutic target in the treatment of autoimmune diseases. The past decade has seen the emergence of first-line BTK small-molecule inhibitors with great efficacy in the treatment of B-cell malignancies, but with unfavorable safety profiles for use in autoimmunity due to off-target effects. The development of second-generation BTK inhibitors with superior BTK specificity has facilitated the investigation of their efficacy in clinical trials with autoimmune patients. In this review, we discuss the role of BTK in key signaling pathways involved in autoimmunity and provide an overview of the different inhibitors that are currently being investigated in clinical trials of systemic autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus, as well as available results from completed trials.

Primary central nervous system lymphoma (PCNSL) is a rare subtype of extranodal lymphoma which is associated with a relatively poor prognosis compared to other diffuse large B-cell lymphomas. Population-based cancer registry data demonstrates that there has been a significant improvement in the survival of patients with PCNSL over the past two decades. This improvement likely reflects the introduction of high-intensity chemotherapy based on an induction regimen with high-dose methotrexate, and consolidation strategy including autologous stem cell transplantation. As a result, the improvement has been mainly observed in younger patients. New approaches such as Bruton tyrosine kinase inhibitor, immunomodulatory agents, immune checkpoint inhibition, and chimeric antigen receptor T-cell therapy are under investigation for PCNSL. In addition, trials combining novel agents in front-line induction treatment are ongoing.

The management of older individuals (≥60 years) with primary central nervous system lymphoma remains a clinical challenge. Identification of optimal therapy and delivering adequate dose intensity are two of the major issues in treating elderly patients. Premorbid performance status and comorbidities influence individualised treatment approaches and geriatric assessment tools are increasingly utilised. Optimal induction treatment remains high-dose methotrexate-based immunochemotherapy, delivery is feasible in the majority of patients and the goal of treatment remains achieving complete remission. Consolidation strategies are also relevant in the elderly, aiming to maximise duration of response and quality of life (QoL). Potential options include high-dose therapy with haematopoietic stem cell consolidation, non-myeloablative chemotherapy and whole-brain radiotherapy. Efficacy of novel agents, such as Bruton tyrosine kinase inhibitors and lenalidomide, have been reported; these represent an alternative for elderly patients unfit for chemotherapy. Prognosis remains poor, improvement of outcomes in this age group is urgently needed.

Chronic lymphocytic leukemia (CLL) treatment landscape has changed dramatically with the recently developed drugs targeting the B-cell receptor (BCR) signalling pathway. Acalabrutinib, a second generation Bruton tyrosine kinase inhibitor, was approved in 2020 in Russia for the treatment of patients with CLL. Acalabrutinib was developed as a more selective Bruton tyrosine kinase inhibitor then ibrutinib. This drug is aimed at reducing the adverse events that limit the use of ibrutinib, such as atrial fibrillation and bleeding. Phase I/II multicenter studies have demonstrated the efficacy and safety of acalabrutinib monotherapy in untreated CLL patients and in patients with relapsed/refractory CLL and ibrutinib intolerance. Phase III trials, ASCEND and ELEVATE-TN, compared acalabrutinib monotherapy and a combination of acalabrutinib and obinutuzumab versus standard therapies and demonstrated improved efficacy and tolerability of acalabrutinib. A phase III trial comparing acalabrutinib and ibrutinib monotherapy (ELEVATE-RR) is ongoing. The results of this study along with real-life clinical data could determine the place of acalabrutinib in CLL treatment.

Laura C Arneson,1,* Kristen J Carroll,1,* Eric M Ruderman2 1Department of Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA; 2Department of Medicine, Division of Rheumatology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA*These authors contributed equally to this workCorrespondence: Eric M RudermanDepartment of Medicine, Division of Rheumatology, Northwestern University Feinberg School of Medicine, 675 N. St. Clair, Suite 14-100, Chicago, IL, 60611, USATel +1 312-503-3188Fax +1 312-695-0114Email e-ruderman@northwestern.eduAbstract: Bruton’s tyrosine kinase (BTK) inhibitors are an emerging class of drugs that inhibit B cell receptor activation, FC-γ receptor signaling, and osteoclast proliferation. Following on approval for treatment of hematologic malignancies, BTK inhibitors are now under investigation to treat a number of different autoimmune diseases, including rheumatoid arthritis (RA). While the results of BTK inhibitors in RA animal models have been promising, the ensuing human clinical trial outcomes have been rather equivocal. This review will outline the mechanisms of BTK inhibition and its potential impact on immune mediated disease, the types of BTK inhibitors being studied for RA, the findings from both preclinical and clinical trials of BTK inhibitors in RA, and directions for future research.Keywords: evobrutinib, spebrutinib, acalabrutinib, fenebrutinib, rheumatoid arthritis, Bruton’s tyrosine kinase

Targeting BCR and BCL-2 signaling is a widely used therapeutic strategy for chronic lymphocytic leukemia. C481S mutation decreases the covalent binding affinity of ibrutinib to BTK, resulting in reversible rather than irreversible inhibition. In addition to BTK, mutations in PLCG2 have been demonstrated to mediate acquired ibrutinib resistance. Venetoclax, a highly selective BCL2 inhibitor, has high affinity to the BH3-binding grove of BCL2. Mutation in BCL2 (Gly101Val) decreases the affinity of BCL2 for venetoclax and confers acquired resistance in cell lines and primary patient cells. This review discusses the common mechanisms of resistance to targeted therapies in chronic lymphocytic leukemia.