Resistance to Ibrutinib in B Cell Malignancies: One Size Does Not Fit All

Targeting of human cancer stem cells predicts efficacy and toxicity of FDA-approved oncology drugs

Cancer remains the leading cause of death worldwide with approved oncology drugs continuing to have heterogenous patient responses and accompanied adverse effects (AEs) that limits effectiveness. Here, we examined >100 FDA-approved oncology drugs in the context of stemness using a surrogate model of transformed human pluripotent cancer stem cells (CSCs) vs. healthy stem cells (hSCs) capable of distinguishing abnormal self-renewal and differentiation. Although a proportion of these drugs had no effects (inactive), a larger portion affected CSCs (active), and a unique subset preferentially affected CSCs over hSCs (selective). Single cell gene expression and protein profiling of each drug's FDA recognized target provided a molecular correlation of responses in CSCs vs. hSCs. Uniquely, drugs selective for CSCs demonstrated clinical efficacy, measured by overall survival, and reduced AEs. Our findings reveal that while unintentional, half of anticancer drugs are active against CSCs and associated with improved clinical outcomes. Based on these findings, we suggest ability to target CSC targeting should be included as a property of early onco-therapeutic development.

Discovery of a novel BTK inhibitor S-016 and identification of a new strategy for the treatment of lymphomas including BTK inhibitor-resistant lymphomas

Bruton's tyrosine kinase (BTK) has emerged as a therapeutic target for B-cell malignancies, which is substantiated by the efficacy of various irreversible or reversible BTK inhibitors. However, on-target BTK mutations facilitating evasion from BTK inhibition lead to resistance that limits the therapeutic efficacy of BTK inhibitors. In this study we employed structure-based drug design strategies based on established BTK inhibitors and yielded a series of BTK targeting compounds. Among them, compound S-016 bearing a unique tricyclic structure exhibited potent BTK kinase inhibitory activity with an IC50 value of 0.5 nM, comparable to a commercially available BTK inhibitor ibrutinib (IC50 = 0.4 nM). S-016, as a novel irreversible BTK inhibitor, displayed superior kinase selectivity compared to ibrutinib and significant therapeutic effects against B-cell lymphoma both in vitro and in vivo. Furthermore, we generated BTK inhibitor-resistant lymphoma cells harboring BTK C481F or A428D to explore strategies for overcoming resistance. Co-culture of these DLBCL cells with M0 macrophages led to the polarization of M0 macrophages toward the M2 phenotype, a process known to support tumor progression. Intriguingly, we demonstrated that SYHA1813, a compound targeting both VEGFR and CSF1R, effectively reshaped the tumor microenvironment (TME) and significantly overcame the acquired resistance to BTK inhibitors in both BTK-mutated and wild-type BTK DLBCL models by inhibiting angiogenesis and modulating macrophage polarization. Overall, this study not only promotes the development of new BTK inhibitors but also offers innovative treatment strategies for B-cell lymphomas, including those with BTK mutations.

Pirtobrutinib in Covalent Bruton Tyrosine Kinase Inhibitor Pretreated Mantle-Cell Lymphoma

PURPOSE

Pirtobrutinib is a highly selective, noncovalent (reversible) Bruton tyrosine kinase inhibitor (BTKi). We report the safety and efficacy of pirtobrutinib in patients with covalent Bruton tyrosine kinase inhibitor (cBTKi) pretreated mantle-cell lymphoma (MCL), a population with poor prognosis.

METHODS

Patients with cBTKi pretreated relapsed/refractory (R/R) MCL received pirtobrutinib monotherapy in a multicenter phase I/II trial (BRUIN; ClinicalTrials.gov identifier: NCT03740529). Efficacy was assessed in the first 90 consecutively enrolled patients who met criteria for inclusion in the primary efficacy cohort. The primary end point was overall response rate (ORR). Secondary end points included duration of response (DOR) and safety.

RESULTS

The median patient age was 70 years (range, 46-87), the median prior lines of therapy was 3 (range, 1-8), 82.2% had discontinued a prior cBTKi because of disease progression, and 77.8% had intermediate- or high-risk simplified MCL International Prognostic Index score. The ORR was 57.8% (95% CI, 46.9 to 68.1), including 20.0% complete responses (n = 18). At a median follow-up of 12 months, the median DOR was 21.6 months (95% CI, 7.5 to not reached). The 6- and 12-month estimated DOR rates were 73.6% and 57.1%, respectively. In the MCL safety cohort (n = 164), the most common treatment-emergent adverse events (TEAEs) were fatigue (29.9%), diarrhea (21.3%), and dyspnea (16.5%). Grade ≥3 TEAEs of hemorrhage (3.7%) and atrial fibrillation/flutter (1.2%) were less common. Only 3% of patients discontinued pirtobrutinib because of a treatment-related adverse event.

CONCLUSION

Pirtobrutinib is a first-in-class novel noncovalent (reversible) BTKi and the first BTKi of any kind to demonstrate durable efficacy after prior cBTKi therapy in heavily pretreated R/R MCL. Pirtobrutinib was well tolerated with low rates of treatment discontinuation because of toxicity.

Pharmacological Modulation of the Crosstalk between Aberrant Janus Kinase Signaling and Epigenetic Modifiers of the Histone Deacetylase Family to Treat Cancer

Hyperactivated Janus kinase (JAK) signaling is an appreciated drug target in human cancers. Numerous mutant JAK molecules as well as inherent and acquired drug resistance mechanisms limit the efficacy of JAK inhibitors (JAKi). There is accumulating evidence that epigenetic mechanisms control JAK-dependent signaling cascades. Like JAKs, epigenetic modifiers of the histone deacetylase (HDAC) family regulate the growth and development of cells and are often dysregulated in cancer cells. The notion that inhibitors of histone deacetylases (HDACi) abrogate oncogenic JAK-dependent signaling cascades illustrates an intricate crosstalk between JAKs and HDACs. Here, we summarize how structurally divergent, broad-acting as well as isoenzyme-specific HDACi, hybrid fusion pharmacophores containing JAKi and HDACi, and proteolysis targeting chimeras for JAKs inactivate the four JAK proteins JAK1, JAK2, JAK3, and tyrosine kinase-2. These agents suppress aberrant JAK activity through specific transcription-dependent processes and mechanisms that alter the phosphorylation and stability of JAKs. Pharmacological inhibition of HDACs abrogates allosteric activation of JAKs, overcomes limitations of ATP-competitive type 1 and type 2 JAKi, and interacts favorably with JAKi. Since such findings were collected in cultured cells, experimental animals, and cancer patients, we condense preclinical and translational relevance. We also discuss how future research on acetylation-dependent mechanisms that regulate JAKs might allow the rational design of improved treatments for cancer patients. SIGNIFICANCE STATEMENT: Reversible lysine-ɛ-N acetylation and deacetylation cycles control phosphorylation-dependent Janus kinase-signal transducer and activator of transcription signaling. The intricate crosstalk between these fundamental molecular mechanisms provides opportunities for pharmacological intervention strategies with modern small molecule inhibitors. This could help patients suffering from cancer.

A novel IRAK4/PIM1 inhibitor ameliorates rheumatoid arthritis and lymphoid malignancy by blocking the TLR/MYD88-mediated NF-κB pathway

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a pivotal enzyme in the Toll-like receptor (TLR)/MYD88 dependent signaling pathway, which is highly activated in rheumatoid arthritis tissues and activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL). Inflammatory responses followed by IRAK4 activation promote B-cell proliferation and aggressiveness of lymphoma. Moreover, proviral integration site for Moloney murine leukemia virus 1 (PIM1) functions as an anti-apoptotic kinase in propagation of ABC-DLBCL with ibrutinib resistance. We developed a dual IRAK4/PIM1 inhibitor KIC-0101 that potently suppresses the NF-κB pathway and proinflammatory cytokine induction in vitro and in vivo. In rheumatoid arthritis mouse models, treatment with KIC-0101 significantly ameliorated cartilage damage and inflammation. KIC-0101 inhibited the nuclear translocation of NF-κB and activation of JAK/STAT pathway in ABC-DLBCLs. In addition, KIC-0101 exhibited an anti-tumor effect on ibrutinib-resistant cells by synergistic dual suppression of TLR/MYD88-mediated NF-κB pathway and PIM1 kinase. Our results suggest that KIC-0101 is a promising drug candidate for autoimmune diseases and ibrutinib-resistant B-cell lymphomas.

Effects of ibrutinib on T-cell immunity in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL), a highly heterogeneous B-cell malignancy, is characterized by tumor microenvironment disorder and T-cell immune dysfunction, which play a major role in the proliferation and survival of CLL cells. Ibrutinib is the first irreversible inhibitor of Bruton’s tyrosine kinase (BTK). In addition to targeting B-cell receptor (BCR) signaling to kill tumor cells, increasing evidence has suggested that ibrutinib regulates the tumor microenvironment and T-cell immunity in a direct and indirect manner. For example, ibrutinib not only reverses the tumor microenvironment by blocking cytokine networks and toll-like receptor signaling but also regulates T cells in number, subset distribution, T-cell receptor (TCR) repertoire and immune function by inhibiting interleukin-2 inducible T-cell kinase (ITK) and reducing the expression of inhibitory receptors, and so on. In this review, we summarize the current evidence for the effects of ibrutinib on the tumor microenvironment and cellular immunity of patients with CLL, particularly for the behavior and function of T cells, explore its potential mechanisms, and provide a basis for the clinical benefits of long-term ibrutinib treatment and combined therapy based on T-cell-based immunotherapies.

Mantle Cell Lymphoma: the Role of Risk-Adapted Therapy and Treatment of Relapsed Disease

PURPOSE OF REVIEW

In this review, the current treatment strategies are recapped, evolving agents are discussed, and we provide guidance in treating R/R MCL.

RECENT FINDINGS

There has been an advancement in treatment using targeted therapy, cellular therapies including chimeric antigen receptor (CAR) T cell therapy and hematopoietic stem cell transplantation (HSCT) and novel therapeutic agents including non-covalent BTKis, bispecific antibodies, and antibody-drug conjugates for treatment of refractory and relapsed mantle cell lymphoma. Mantle cell lymphoma (MCL) is a mature B-cell lymphoma that is associated with a poor prognosis. Current treatments include immunochemotherapy, chemotherapy and autologous stem cell transplantation (SCT) which place patients in remission but result in relapse. Chemoimmunotherapy uses chemotherapeutic agents paired with rituximab in patients who have chemo-sensitive disease with prolonged remission of at least > 2 years and/or have contraindications to chemotherapy that serve as bridges to more definitive treatment. Additional therapies including proteosome inhibitor-based therapies and immunomodulators, like bortezomib and lenalidomide, can be used as single agents or in combination with others. Bruton's tyrosine kinase (BTK) inhibitors including ibrutinib, acalaburtinib, and zanubrutinib have also been proven effective for the treatment of (R/R) disease. Another agent is Venetoclax, a robust drug that can be used in MCL after progression or intolerance to BTKi. Newer advances in the management of MCL have led to the utilization of cellular therapies including chimeric antigen receptor (CAR) T cell therapy and SCT that are options for healthy young (< 65 years old) who have progressed through several lines of therapies. With progression of disease, mutations are acquired that cause therapy resistance. Novel therapeutic agents such as non-covalent BTKis, bispecific antibodies, and antibody-drug conjugates are paving the way for advancements in treatment for R/R MCL. R/R MCL is a complex disease with many therapeutic options none of which has been proven superior in head-to-head comparison. In this review, the current treatment strategies are recapped, evolving agents are discussed, and we provide guidance in treating R/R MCL.

Outcomes for Recurrent Mantle Cell Lymphoma Post-Ibrutinib Therapy: A Retrospective Cohort Study from a Japanese Administrative Database

INTRODUCTION

Treatment options in patients with mantle cell lymphoma (MCL) failing ibrutinib are limited, with no standard therapies defined. This study aimed to investigate real-world treatment patterns and outcomes for patients with MCL following ibrutinib.

METHODS

This study utilized a de-identified hospital-based claims database (Medical Data Vision) in Japan. Eligible patients were adults who were diagnosed with MCL and had received antitumor drugs between December 2010 and July 2020. Patients were followed from the first antitumor drug treatment until the end of available data up to July 2021. Time-to-event analyses utilized the Kaplan-Meier method. Factors for receiving post-ibrutinib therapy were explored with logistic regression analysis.

RESULTS

Of the 1386 patients who started antitumor drug therapy, 247 patients received and discontinued ibrutinib at any line of therapy. Among them, 137 patients (55.5%) received subsequent therapy. The median age at the end of ibrutinib therapy was 77 (range 42-95), and 44 patients had a dependent activity of daily living (ADL). Factors negatively associated with receiving post-ibrutinib therapy after discontinuation of ibrutinib were age ≥ 75 years (odds ratio [95% CI] 0.46 [0.26-0.80]) and emergency hospital admissions (0.37 [0.17-0.84]). Immediate post-ibrutinib therapy regimens were highly diverse, with BR (bendamustine, rituximab) only prescribed in more than 10% of patients. The median duration of post-ibrutinib therapy was 1.5 months (95% CI 1.07-2.07). The median overall survival from the end of ibrutinib therapy in patients regardless of the receipt of post-ibrutinib therapy (n = 247), in those who did not receive post-ibrutinib therapy (n = 110), and in those who received post-ibrutinib therapy (n = 137) was 5.6 months (95% CI 3.8-8.7), 2.3 months (95% CI 1.2-3.9), and 8.7 months (95% CI 5.6-13.8), respectively. The most common adverse event during post-ibrutinib therapy was infection, with the use of anti-infectives (17%).

CONCLUSIONS

Patients with MCL previously treated with ibrutinib have poor ability to carry out ADL and experience very poor outcomes. New safe, effective therapies are needed.

Genome Editing as a Vehicle to Drive Successful Chimeric Antigen Receptor T Cell Therapies to the Clinic

Chimeric antigen receptor (CAR) T cells have emerged as an effective therapy for patients with relapsed and refractory haematological malignancies. However, there are many challenges preventing clinical efficacy and thus broader translation of this approach. These hurdles include poor autologous T cell fitness, manufacturing issues and lack of conserved tumour-restricted antigens to target. Recent efforts have been directed toward incorporating genome editing technologies to address these challenges and develop potent CAR T cell therapies for a diverse array of haematopoietic cancers. In this review, the authors discuss gene editing strategies that have been employed to augment CAR T cell fitness, generate allogeneic ‘off-the-shelf’ CAR T cell products, and safely target elusive myeloid and T cell cancers that often lack appropriate tumour-specific antigens.

B-cell targeted therapies in pemphigus

Pemphigus is a rare autoimmune disease of the skin, characterized by autoantibodies targeting adhesion proteins of the epidermis, in particular desmoglein 3 and desmoglein 1, that cause the loss of cell-cell adhesion and the formation of intraepidermal blisters. Given that these autoantibodies are both necessary and sufficient for pemphigus to occur, the goal of pemphigus therapy is the elimination of autoreactive B-cells responsible for autoantibody production. Rituximab, an anti-CD20 monoclonal antibody, was the first targeted B-cell therapy approved for use in pemphigus and is now considered the frontline therapy for new onset disease. One limitation of this treatment is that it targets both autoreactive and non -autoreactive B-cells, which accounts for the increased risk of serious infections in treated patients. In addition, most rituximab-treated patients experience disease relapse, highlighting the need of new therapeutic options. This review provides a concise overview of rituximab use in pemphigus and discusses new B-cell and antibody-directed therapies undergoing investigation in clinical studies.

Neutralization of B-Cell Activating Factor (BAFF) by Belimumab Reinforces Small Molecule Inhibitor Treatment in Chronic Lymphocytic Leukemia

Simple Summary

Chronic lymphocytic leukemia (CLL) is the most common form of leukemia in Western countries. Despite the substantial progress achieved by the recent introduction of the novel small molecule inhibitors idelalisib, ibrutinib and venetoclax in CLL treatment, therapy resistance occurs frequently and the disease so far remains incurable. In the present study we report that BAFF, a member of the TNF protein family, protects CLL cells from treatment-induced cell death. In turn, the therapeutic effects of idelalisib, ibrutinib and venetoclax can be reinforced by neutralizing BAFF with belimumab, an antibody which presently is clinically approved for treatment of systemic lupus erythematosus. Based on the data presented in this study, a clinical study to evaluate whether drug repurposing of belimumab for BAFF neutralization can serve to improve response to small molecule inhibitor treatment in CLL is in preparation.

Abstract

The introduction of idelalisib, ibrutinib and venetoclax for treatment of chronic lymphocytic leukemia (CLL) has greatly improved long term survival of patients. However, many patients do not achieve complete remission and suffer from development of resistance upon treatment with these small molecule inhibitors. Here we report that the TNF family member B-cell activating factor (BAFF) mediates resistance of CLL cells to idelalisib, ibrutinib and venetoclax by sustaining survival and preventing apoptosis of the malignant B cells as revealed by analysis of cellular ATP levels and mitochondrial membrane integrity as well as caspase activation, respectively. As BAFF also plays a prominent role in autoimmune diseases, the BAFF-neutralizing antibody belimumab was developed and approved for treatment of systemic lupus erythematosus (SLE). When we employed belimumab in the context of CLL treatment with idelalisib, ibrutinib and venetoclax, BAFF neutralization was found to significantly increase the sensitivity of the leukemic cells to all three small molecule inhibitors. Notably, BAFF neutralization proved to be beneficial independently of clinical stage according to Binet and Rai or IgVH mutational status. Our results identify drug repurposing of belimumab for neutralization of BAFF to complement small molecule inhibitor treatment as a promising therapeutic approach in CLL that is presently undergoing clinical evaluation.

Management of Mantle Cell Lymphoma in the Era of Novel Oral Agents

Objectives: To discuss (1) recent and emerging data for pharmacological management of untreated and relapsed/refractory (R/R) mantle cell lymphoma (MCL) with agents approved in the United States, (2) important considerations for toxicity monitoring and management, and (3) preliminary data and ongoing studies for agents in MCL-specific clinical trials. Data Sources: PubMed/MEDLINE, EMBASE, Google Scholar, product labeling, National Comprehensive Cancer Network, American Cancer Society, and ClinicalTrials.gov were searched for studies published between January 1, 2017, and January 31, 2020, and key historical trials. Study Selection and Data Extraction: Relevant studies conducted in humans and selected supporting preclinical data were reviewed. Data Synthesis: MCL is a rare but usually aggressive non-Hodgkin lymphoma that most commonly affects the older population. Traditionally, the treatment of MCL has been determined based on transplant eligibility. Newer data suggest that more tolerable frontline therapy may produce outcomes similar to intensive historical induction regimens, possibly precluding fewer patients from autologous stem cell transplant and producing better long-term outcomes in transplant-ineligible patients. In the R/R setting, novel regimens are improving outcomes and changing the landscape of treatment. Relevance to Patient Care and Clinical Practice: This review summarizes and discusses recent and emerging data for management of newly diagnosed and R/R MCL; key supportive care considerations for agents are also discussed. Conclusions: Recent study results are changing management of MCL. Although these data have complicated the picture of regimen selection, increasingly effective and tolerable therapy and additional anticipated data point to a brighter future for patients with MCL.

Ibrutinib Resistance Mechanisms and Treatment Strategies for B-Cell lymphomas

Chronic activation of B-cell receptor (BCR) signaling via Bruton tyrosine kinase (BTK) is largely considered to be one of the primary mechanisms driving disease progression in B-Cell lymphomas. Although the BTK-targeting agent ibrutinib has shown promising clinical responses, the presence of primary or acquired resistance is common and often leads to dismal clinical outcomes. Resistance to ibrutinib therapy can be mediated through genetic mutations, up-regulation of alternative survival pathways, or other unknown factors that are not targeted by ibrutinib therapy. Understanding the key determinants, including tumor heterogeneity and rewiring of the molecular networks during disease progression and therapy, will assist exploration of alternative therapeutic strategies. Towards the goal of overcoming ibrutinib resistance, multiple alternative therapeutic agents, including second- and third-generation BTK inhibitors and immunomodulatory drugs, have been discovered and tested in both pre-clinical and clinical settings. Although these agents have shown high response rates alone or in combination with ibrutinib in ibrutinib-treated relapsed/refractory(R/R) lymphoma patients, overall clinical outcomes have not been satisfactory due to drug-associated toxicities and incomplete remission. In this review, we discuss the mechanisms of ibrutinib resistance development in B-cell lymphoma including complexities associated with genomic alterations, non-genetic acquired resistance, cancer stem cells, and the tumor microenvironment. Furthermore, we focus our discussion on more comprehensive views of recent developments in therapeutic strategies to overcome ibrutinib resistance, including novel BTK inhibitors, clinical therapeutic agents, proteolysis-targeting chimeras and immunotherapy regimens.

Treatment of pemphigus vulgaris: part 2 - emerging therapies

Introduction: Corticosteroids and immunosuppressive agents have been the mainstay for the treatment of pemphigus vulgaris (PV). While they have benefited patients, they have been associated with the risks of prolonged immune suppression and a high incidence of significant and catastrophic side effects. Relapses are common. Novel agents promising targeted therapies, that may provide better outcomes, are being studied. Areas covered: Recently rituximab with corticosteroids has been recommended as the first-line treatment for PV. A number of known and new therapeutic agents currently investigated are BAFF, P13K, BTK inhibitors along with the use of IVIg and CAR-T therapy. The possible role of these therapeutic targets in the pathophysiology appears to be the rationale for the treatment of this potentially fatal disease. Expert opinion: While there is significant enthusiasm for these therapies, certain concerns and consequences are being under-discussed. None of the current clinical trials in progress are specific for PV, except possibly CAR-T therapy. The major issue(s) that are unclear is whether these therapies would be successful in providing long-term clinical remissions. Will these therapies require additional agents to be effective? Will the benefits be limited in duration? The answers to many questions will determine their final place in the algorithm for the treatment of PV.

Human bone marrow-derived mesenchymal stem cells promote the growth and drug-resistance of diffuse large B-cell lymphoma by secreting IL-6 and elevating IL-17A levels

Background

The drug-resistance and relapse of diffuse large B-cell lymphoma (DLBCL), which are related to mesenchymal stem cells (MSCs), have become increasingly common. However, the underlying mechanisms remain elusive.

Methods

CCK 8 assay, colony formation assay, and xenograft mouse model were used to investigate the effects of hBMSCs on DLBCL growth. Immunohistochemistry, qRT-PCR, and ELISA were used to study the expressions of IL-6 and IL-17A. Flow cytometry was used to analyze Th17 cells and Treg cells expressions. Western blot analysis, microarray analysis, and bioinformatics analysis were used to analyze the pathways of IL-6 or IL-17A mediated DLBCL growth.

Results

HBMSCs promoted DLBCL growth by secreting IL-6 in vitro and in vivo and simultaneously upregulating IL-17A in vitro. IL-6 and IL-17A synergistically promoted the growth and drug-resistance of DLBCL cells by protecting them from spontaneous or drug-induced apoptosis in vitro. IL-6 or IL-17A activated the JAK2/STAT3 pathway or upregulated cyclin D2 via activation of PI3K/Akt signaling in vitro, respectively.

Conclusions

The present results indicated that hBMSCs might have a “dual effect” on promoting DLBCL progression and drug-resistance by secreting IL-6 and upregulating IL-17A. IL-6, IL-17A, p-STAT3, p-Akt or cyclin D2 may be potential molecular targets for overcoming drug-resistance in patients with relapsed or refractory DLBCL.

Recent advances and future directions in mantle cell lymphoma research: report of the 2018 mantle cell lymphoma consortium workshop

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma characterized by the t(11;14) chromosomal translocation. This translocation most often results in overexpression of cyclin D1. MCL is clinically heterogeneous, outcomes are generally poor, and no standard treatment has been established. The recent approvals of ibrutinib and acalabrutinib have provided an additional therapeutic option; however, resistance has emerged as a significant issue and presents the need for more detailed studies of resistance mechanisms. Recent clinical trials have provided new perspectives on the relative efficacy and safety of various approaches for both transplant-eligible and transplant-ineligible patients. Multiple novel strategies are being evaluated in the treatment of MCL, including both targeted agents and cellular immunotherapies. At the Lymphoma Research Foundation's 13th MCL Workshop, researchers gathered to discuss research findings, clinical trial results, and future directions related to MCL, its biology, and its treatment. This report, which includes a summary of each presentation, aims to review recent findings in MCL research and highlight potential areas for future study.