Phase II study of enzastaurin, a protein kinase C beta inhibitor, in patients with relapsed or refractory diffuse large B-cell lymphoma

An Update on Protein Kinases as Therapeutic Targets-Part I: Protein Kinase C Activation and Its Role in Cancer and Cardiovascular Diseases

Protein kinases are one of the most significant drug targets in the human proteome, historically harnessed for the treatment of cancer, cardiovascular disease, and a growing number of other conditions, including autoimmune and inflammatory processes. Since the approval of the first kinase inhibitors in the late 1990s and early 2000s, the field has grown exponentially, comprising 98 approved therapeutics to date, 37 of which were approved between 2016 and 2021. While many of these small-molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP binding pocket have been massively successful for oncological indications, their poor selectively for protein kinase isozymes have limited them due to toxicities in their application to other disease spaces. Thus, recent attention has turned to the use of alternative allosteric binding mechanisms and improved drug platforms such as modified peptides to design protein kinase modulators with enhanced selectivity and other pharmacological properties. Herein we review the role of different protein kinase C (PKC) isoforms in cancer and cardiovascular disease, with particular attention to PKC-family inhibitors. We discuss translational examples and carefully consider the advantages and limitations of each compound (Part I). We also discuss the recent advances in the field of protein kinase modulators, leverage molecular docking to model inhibitor-kinase interactions, and propose mechanisms of action that will aid in the design of next-generation protein kinase modulators (Part II).

Molecular classification and therapeutics in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) encompasses a wide variety of disease states that have to date been subgrouped and characterized based on immunohistochemical methods, which provide limited prognostic value to clinicians and no alteration in treatment regimen. The addition of rituximab to CHOP therapy was the last leap forward in terms of treatment, but regimens currently follow a standardized course when disease becomes refractory with no individualization based on genotype. Research groups are tentatively proposing new strategies for categorizing DLBCL based on genetic abnormalities that are frequently found together to better predict disease course following dysregulation of specific pathways and to deliver targeted treatment. Novel algorithms in combination with next-generation sequencing techniques have identified between 4 and 7 subgroups of DLBCL, depending on the research team, with potentially significant and actionable genetic alterations. Various drugs aimed at pathways including BCR signaling, NF-κB dysfunction, and epigenetic regulation have shown promise in their respective groups and may show initial utility as second or third line therapies to patients with recurrent DLBCL. Implementation of subgroups will allow collection of necessary data to determine which groups are significant, which treatments may be indicated, and will provide better insight to clinicians and patients on specific disease course.

Altered pathways and targeted therapy in double hit lymphoma

High-grade B-cell lymphoma with translocations involving MYC and BCL2 or BCL6, usually referred to as double hit lymphoma (DHL), is an aggressive hematological malignance with distinct genetic features and poor clinical prognosis. Current standard chemoimmunotherapy fails to confer satisfying outcomes and few targeted therapeutics are available for the treatment against DHL. Recently, the delineating of the genetic landscape in tumors has provided insight into both biology and targeted therapies. Therefore, it is essential to understand the altered signaling pathways of DHL to develop treatment strategies with better clinical benefits. Herein, we summarized the genetic alterations in the two DHL subtypes (DHL-BCL2 and DHL-BCL6). We further elucidate their implications on cellular processes, including anti-apoptosis, epigenetic regulations, B-cell receptor signaling, and immune escape. Ongoing and potential therapeutic strategies and targeted drugs steered by these alterations were reviewed accordingly. Based on these findings, we also discuss the therapeutic vulnerabilities that coincide with these genetic changes. We believe that the understanding of the DHL studies will provide insight into this disease and capacitate the finding of more effective treatment strategies.

Equivocal, explicit and emergent actions of PKC isoforms in cancer

The maturing mutational landscape of cancer genomes, the development and application of clinical interventions and evolving insights into tumour-associated functions reveal unexpected features of the protein kinase C (PKC) family of serine/threonine protein kinases. These advances include recent work showing gain or loss-of-function mutations relating to driver or bystander roles, how conformational constraints and plasticity impact this class of proteins and how emergent cancer-associated properties may offer opportunities for intervention. The profound impact of the tumour microenvironment, reflected in the efficacy of immune checkpoint interventions, further prompts to incorporate PKC family actions and interventions in this ecosystem, informed by insights into the control of stromal and immune cell functions. Drugging PKC isoforms has offered much promise, but when and how is not obvious.

A Systematic Review of the Clinical Efficacy of Treatments in Relapsed or Refractory Diffuse Large B Cell Lymphoma

Introduction

Novel treatment options are needed to improve outcomes in transplant-ineligible relapsed/refractory (R/R) diffuse large B cell lymphoma (DLBCL). This systematic literature review evaluated clinical evidence on treatments for patients with R/R DLBCL ineligible for, or relapsed following, stem cell transplantation.

Methods

We assessed the feasibility of conducting an indirect treatment comparison (ITC) or network meta-analysis (NMA) to evaluate the relative efficacy and safety of polatuzumab vedotin in combination with bendamustine + rituximab versus other relevant treatments.

Results

Thirty-seven studies were identified, of which 20 were eligible [seven randomized, controlled trials (RCTs); 13 observational/single-arm trials]. Due to a lack of RCTs, an ITC/NMA summary of the relative efficacy and safety of the treatment options was not possible. Only two of the seven RCTs had positive outcomes.

Conclusions

These findings highlight the paucity of published RCTs to establish the comparative efficacy of treatments for transplant-ineligible R/R DLBCL and lack of standard of care in this setting.

Electronic Supplementary Material

The online version of this article (10.1007/s12325-020-01507-7) contains supplementary material, which is available to authorized users.

Biomarkers and novel therapeutic approaches for diffuse large B-cell lymphoma in the era of precision medicine

Despite the great efforts for better treatment options for diffuse large B-cell lymphoma (DLBCL) (most common form of non-Hodgkin lymphoma, NHL) to treat and prevent relapse, it continues to be a challenge. Here, we present an overview of DLBCL and address the diagnostic assays and molecular techniques used in its diagnosis, role of biomarkers in detection, treatment of early and advanced stage DLBCL, and novel drug regimens. We discuss the significant biomarkers that have emerged as essential tools for stratifying patients according to risk factors and for providing insights into the use of more targeted and individualized therapeutics. We discuss techniques such as gene expression studies, including next-generation sequencing, which have enabled a more understanding of the complex pathogenesis of DLBCL and have helped determine molecular targets for novel therapeutic agents. We examine current treatment approaches, outline the findings of completed clinical trials, and provide updates for ongoing clinical trials. We highlight clinical trials relevant to the significant fraction of DLBCL patients who present with complex cases marked by high relapse rates. Supported by an increased understanding of targetable pathways in DLBCL, clinical trials involving specialized combination therapies are bringing us within reach the promise of an effective cure to DLBCL using precision medicine. Optimization of therapy remains a crucial objective, with the end goal being a balance between high survival rates through targeted and personalized treatment while reducing adverse effects in DLBCL patients of all subsets.

Protein kinases as targets for developing anticancer agents from marine organisms

Protein kinases play a fundamental role in the intracellular transduction because of their ability to phosphorylate plethora of proteins. Over the past three decades, numerous protein kinase inhibitors have been identified and are being used clinically successfully. The biodiversity of marine organisms provides a rich source for the discovery and development of novel anticancer agents in the treatment of human malignancies and a lot of bioactive ingredients from marine organisms display anticancer effects by affecting the protein kinases-mediated pathways. In the present mini-review, anticancer compounds from marine source were reviewed and discussed in context of their targeted pathways associated with protein kinases and the progress of these compounds as anticancer agents in recent five years were emphasized. The molecular entities and their modes of actions were presented. We focused on protein kinases-mediated signaling pathways including PI3K/Akt/mTOR, p38 MAPK, and EGFR. The marine compounds targeting special pathways of protein kinases were highlighted. We have also discussed the existing challenges and prospects related to design and development of novel protein kinase inhibitors from marine sources.

AEB-071 Ameliorates Muscle Weakness by Altering Helper T Lymphocytes in an Experimental Autoimmune Myasthenia Gravis Rat Model

Background

Myasthenia gravis (MG) is an autoimmune neurological disorder of neuromuscular junctions. In this study we established experimental autoimmune myasthenia gravis (EAMG) rat models to investigate the effects of AEB-071 (AEB), which is a specific inhibitor of protein kinase C that prevents T lymphocyte activation.

Material/Methods

We utilized animals divided into 4 groups: (1) control rats, (2) EAMG, (3) AEB-071+EAMG, and (4) AZP+EAMG. Drug treatment was continued for 10 days. Ten weeks after immunization we measured body weights, assessed mortality rates, and used Lennon scores to evaluate EAMG grades. We also assessed the proportions of T_reg, T_h1, T_h2, T_h17, and lymphocytes using flow cytometry.

Results

In the absence of drug treatment, we found a significant decline in body weights in the EAMG group in comparison to control rats, and EAMG group rats also had higher Lennon scores (P<0.05). Interestingly, we found that AEB-071 restored the body weight of EAMG rats and the decreased mortality rate compared to AZP treatment. Although a decrease in the number of T_reg cells was observed, the proportion of T_h lymphocytes was significantly increased in the EAMG group, and AEB-071 treatment decreased the proportion of T_h lymphocytes.

Conclusions

We concluded that AEB-071 treatment imparts beneficial effects in EAMG rat models by reducing mortality rate and restoring T_h lymphocyte balance, and thus may be an attractive candidate for use in MG treatment.

Tetraspanin CD53: an overlooked regulator of immune cell function

Tetraspanins are membrane organizing proteins that play a role in organizing the cell surface through the formation of subcellular domains consisting of tetraspanins and their partner proteins. These complexes are referred to as tetraspanin enriched microdomains (TEMs) or the tetraspanin web. The formation of TEMs allows for the regulation of a variety of cellular processes such as adhesion, migration, signaling, and cell fusion. Tetraspanin CD53 is a member of the tetraspanin superfamily expressed exclusively within the immune compartment. Amongst others, B cells, CD4+ T cells, CD8+ T cells, dendritic cells, macrophages, and natural killer cells have all been found to express high levels of this protein on their surface. Almost three decades ago it was reported that patients who lacked CD53 suffered from an increased susceptibility to pathogens resulting in the clinical manifestation of recurrent viral, bacterial, and fungal infections. This clearly suggests a vital and non-redundant role for CD53 in immune function. Yet, despite this striking finding, the specific functional roles of CD53 within the immune system have remained elusive. This review aims to provide a concise overview of the published literature concerning CD53 and reflect on the underappreciated role of this protein in immune cell regulation and function.

ENGINE: a Phase III randomized placebo controlled study of enzastaurin/R-CHOP as frontline therapy in high-risk diffuse large B-cell lymphoma patients with the genomic biomarker DGM1

While combination of rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP) cures most patients with diffuse large B-cell lymphoma (DLBCL), those with high-risk international prognostic index disease have inferior survival. Enzastaurin as a potent inhibitor of PKC-β and PI3K/AKT pathway suppressor has been tested in many clinical trials including two key studies in DLBCL: Phase III maintenance study (Preventing Relapse in Lymphoma Using Daily Enzastaurin [PRELUDE]) and a first-line Phase II study (S028). DNA extracted from PRELUDE patients' blood samples was retrospectively genotyped identifying a novel genetic biomarker, DGM1 that showed high correlation with response to enzastaurin. A similar finding observed in the S028 study suggested that addition of enzastaurin to R-CHOP may significantly improve outcomes as frontline therapy for high-risk DGM1 positive DLBCL patients. ENGINE is a global, multicenter, placebo-controlled and randomized study to compare the effect of R-CHOP/enzastaurin as frontline treatment in high-risk DLBCL patients. The primary end point for this study is overall survival in patients who are DGM1 positive. Clinical Trial Registration Identifier: NCT03263026.

Signal Pathways and Therapeutic Prospects of Diffuse Large B Cell Lymphoma

BACKGROUND

Diffuse Large B Cell Lymphoma (DLBCL) is the most common type of non-Hodgkin lymphoma which is heterogeneous both clinically and morphologically. Over the past decades, significant advances have been made in the understanding of the molecular genesis, leading to the identification of multiple pathways and molecules that can be targeted for clinical benefit.

OBJECTIVE

The current review aims to present a brief overview of signal pathways of DLBCL, which mainly focus on B-cell antigen Receptor (BCR), Nuclear Factor-κB (NF-κB), Phosphatidylinositol-3-Kinase (PI3K) - protein kinase B (Akt) - mammalian Target of Rapamycin (mTOR), Janus Kinase (JAK) - Signal Transducer and Activator (STAT), Wnt/β-catenin, and P53 pathways.

METHODS

Activation of signal pathways may contribute to the generation, development, chemotherapy sensitivity of DLBCL, and expression of pathway molecules is associated with the prognosis of DLBCL. Some agents targeting these pathways have been proved effective and relevant clinical trials are in progress. These agents used single or combined with chemotherapy/each other might raise the possibility of improving clinical outcomes in DLBCL.

CONCLUSION

This review presents several signal pathways of DLBCL and targeted agents had a tendency to improve the curative effect, especially in high-risk or relapsed/refractory DLBCL.

Genetic alterations and their clinical implications in DLBCL

Diffuse large B cell lymphoma (DLBCL) is a highly heterogeneous lymphoid neoplasm with variations in gene expression profiles and genetic alterations, which lead to substantial variations in clinical course and response to therapy. The advent of high-throughput genome sequencing platforms, and especially whole-exome sequencing, has helped to define the genetic landscape of DLBCL. In the past 10 years, these studies have identified many genetic alterations in DLBCL, some of which are specific to B cell lymphomas, whereas others can also be observed in other types of cancer. These aberrations result in altered activation of a wide range of signalling pathways and other cellular processes, including those involved in B cell differentiation, B cell receptor signalling, activation of the NF-κB pathway, apoptosis and epigenetic regulation. Further elaboration of the genetics of DLBCL will not only improve our understanding of disease pathogenesis but also provide further insight into disease classification, prognostication and therapeutic targets. In this Review, we describe the current understanding of the prevalence and causes of specific genetic alterations in DLBCL and their role in disease development and progression. We also summarize the available clinical data on therapies designed to target the aberrant pathways driven by these alterations.

Methodology of clinical trials evaluating the incorporation of new drugs in the first-line treatment of patients with diffuse large B-cell lymphoma (DLBCL): a critical review

Background

The first-line treatment of diffuse large B-cell lymphoma (DLBCL) is the combination of rituximab with CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone) chemotherapy, curing approximately 60% of patients. Many clinical trials have been carried out over the last 10 years trying to improve the results of this treatment, but the appropriateness of their planning strategies could be rediscussed.

Patients and methods

Reports of phase III trials evaluating the addition of molecularly targeted agents or new monoclonal antibodies to the classic R-CHOP backbone in first-line induction or maintenance treatment were reviewed. The trial design, primary end point, number of patients enrolled, patient selection criteria, treatment schedule and results were registered for each one. In addition, the phases I and II trials which preceded these phase III trials were also reviewed.

Results

Among six phase III trials with results, only one trial evaluating lenalidomide maintenance after response to R-CHOP induction was positive and reached its primary end point. The other five trials did not show an improved outcome with the addition of the new agent. The preceding phases I and II trials were very heterogeneous in their end points and design. Even though most of these trials were considered positive, thus encouraging further investigation, so far they failed to predict the results of the subsequent phase III trials.

Conclusion

The standard of care for DLBCL is still R-CHOP. Phase I/II trials failed to predict the results of subsequent phase III trials evaluating non-chemotherapeutic agents added to R-CHOP. The methodology of phase II trials evaluating new agents in DLBCL needs to be better defined in the future.

Are We Ready to Treat Diffuse Large B-cell and High-Grade Lymphoma According to Major Genetic Subtypes?

Diffuse Large B-Cell Lymphoma (DLBCL) is a clinically and biologically heterogeneous disease. The revised Classification of Lymphoproliferative diseases published in 2016 (WHO, 2016) refined the previous DLBLC subtypes and identified four categories: DLBCL not otherwise specified (NOS), other lymphomas of large B cells, high grade B-cell lymphoma, and B-cell lymphoma unclassifiable. High grade B-cell lymphomas include the entities carrying MYC, BCL2 and/or BCL6 translocations or cases with blastoid morphology without DH translocations. This classification also acknowledges the cell of origin (COO) classification, that has only a limited impact on the choice of frontline treatment for DLBCL, as most patients still receive R-CHOP chemoimmunotherapy. Attempts to improve the outcomes of specific subgroups, especially COO groups, have so far had limited success. Newer analyses have further subdivided DLBCL into genomically distinct subsets, not yet incorporated in the WHO classification, which may facilitate targeted approaches to therapy. In this review, we discuss the subgroups that are recognized by the WHO 2016 classification, review the newer genomic data, and speculate on how this could alter the treatment landscape of DLBCL in the future. We also discuss novel approaches to salvage therapy in the broad context of the heterogeneity of DLBCL.

Dysregulation of Cell Survival in Diffuse Large B Cell Lymphoma: Mechanisms and Therapeutic Targets

Diffuse large B cell lymphoma (DLBCL) is the most common type of lymphoma worldwide, representing 30-40% of non-Hodgkin lymphomas, and is clinically aggressive. Although more than half of patients with DLBCL are cured by using standard first-line immunochemotherapy, the remaining patients are refractory to the first-line therapy or relapse after complete remission and these patients require novel therapeutic approaches. Understanding the pathogenesis of DLBCL is essential for identifying therapeutic targets to tackle this disease. Cell survival dysregulation, a hallmark of cancer, is a characteristic feature of DLBCL. Intrinsic signaling aberrations, tumor microenvironment dysfunction, and viral factors can all contribute to the cell survival dysregulation in DLBCL. In recent years, several novel drugs that target abnormal cell survival pathways, have been developed and tested in clinical trials of patients with DLBCL. In this review, we discuss cell survival dysregulation, the underlying mechanisms, and how to target abnormal cell survival therapeutically in DLBCL patients.

Combination of Enzastaurin and Ibrutinib synergistically induces anti-tumor effects in diffuse large B cell lymphoma

Background

Diffuse large B cell lymphoma (DLBCL) is the most common form of lymphoma. Although durable remissions can be achieved in more than half of these patients, DLBCL remains a significant clinical challenge, with approximately 30% of patients not being cured. BCR-associated kinases (SYK, BTK, and PI3K) inhibitors have exhibited encouraging pre-clinical and clinical effects, as reported by many researchers. Early studies demonstrated that protein kinase C-β (PKCβ) inhibitors alter phosphorylation level the Bruton’s tyrosine kinase (BTK), which leads to enhanced BTK signaling. Here, for the first time, we investigate whether the combination of PKCβ inhibitor enzastaurin and BTK inhibitor ibrutinib has synergistic anti-tumor effects in DLBCL.

Methods

In vitro cell proliferation was analyzed using Cell Titer-Glo Luminescent Cell Viability Assay. Induction of apoptosis and cell cycle arrest were measured by flow cytometry. Western Blotting analysis was used to detect the essential regulatory enzymes in related signaling pathways. RNA-seq was conducted to evaluate the whole transcriptome changes brought by co-treatment with low doses of enzastaurin and ibrutinib. The synergistic anti-tumor effects of enzastaurin and ibrutinib were also evaluated in vivo.

Results

Combination of enzastaurin and ibrutinib produced a lasting synergistic effect on the survival and proliferation of DLBCL cells, including reduction of proliferation, promoting apoptosis, inducting G1 phase arrest, preventing cell invasion and migration, and down-regulating activation of downstream signaling. More importantly, whole-transcriptome changes results showed that combination therapy worked synergistically to regulate whole-transcriptome expression compared with enzastaurin and ibrutinib alone. Co-treatment with low doses of enzastaurin and ibrutinib could effectively downregulate BCR, NF-κB, JAK and MAPK related signaling pathway. Furthermore, the mRNA expression analysis further indicated that co-treatment significantly decreased the mRNA levels of NOTCH1. The combination effect in inhibiting proliferation of DLBCL cells probably was realized through suppression of NOTCH1 expression. Finally, the anti-tumor activity of co-treatment also was demonstrated in vivo.

Conclusions

Combination of enzastaurin and ibrutinib had synergistic anti-tumor effects in DLBCL, independent of molecular subtype. These results provided a sound foundation for an attractive therapeutic treatment, and the simultaneous suppression of BTK and PKCβ might be a new treatment strategy for DLBCL.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1076-4) contains supplementary material, which is available to authorized users.

Treatment of aggressive B-cell non-Hodgkin lymphoma beyond frontline therapy in patients not eligible for stem cell transplantation: a structured review

Aggressive B-cell non-Hodgkin lymphoma (aNHL) accounts for ∼50% of all NHL cases. The only potentially curative, broadly available treatment for patients with relapse, failing frontline treatment, is high-dose therapy followed by autologous stem cell transplantation (ASCT); patients ineligible for/who have failed ASCT have limited standard-of-care options. We conducted a structured review of treatments for relapsed/refractory patients with aNHL based on literature published between 2006 and 2017. Of the 22 publications identified for inclusion, most described phase II, single-arm trials (N = 25-217), and only three were randomized studies (phase II [N = 96], phase II/III [N = 111] and phase III [N = 338]). The majority of treatments evaluated resulted in only modest efficacy (median progression-free survival, 2.1-20.0 months) and ultimately poor health outcomes (median overall survival, 25 weeks-15.5 months). In conclusion, there is an unmet need for novel, effective, and tolerable treatments for patients with relapsed/refractory aNHL who are ineligible for/have failed ASCT.

FHIT, a Novel Modifier Gene in Pulmonary Arterial Hypertension

RATIONALE

Pulmonary arterial hypertension (PAH) is characterized by progressive narrowing of pulmonary arteries, resulting in right heart failure and death. BMPR2 (bone morphogenetic protein receptor type 2) mutations account for most familial PAH forms whereas reduced BMPR2 is present in many idiopathic PAH forms, suggesting dysfunctional BMPR2 signaling to be a key feature of PAH. Modulating BMPR2 signaling is therapeutically promising, yet how BMPR2 is downregulated in PAH is unclear.

OBJECTIVES

We intended to identify and pharmaceutically target BMPR2 modifier genes to improve PAH.

METHODS

We combined siRNA high-throughput screening of >20,000 genes with a multicohort analysis of publicly available PAH RNA expression data to identify clinically relevant BMPR2 modifiers. After confirming gene dysregulation in tissue from patients with PAH, we determined the functional roles of BMPR2 modifiers in vitro and tested the repurposed drug enzastaurin for its propensity to improve experimental pulmonary hypertension (PH).

MEASUREMENTS AND MAIN RESULTS

We discovered FHIT (fragile histidine triad) as a novel BMPR2 modifier. BMPR2 and FHIT expression were reduced in patients with PAH. FHIT reductions were associated with endothelial and smooth muscle cell dysfunction, rescued by enzastaurin through a dual mechanism: upregulation of FHIT as well as miR17-5 repression. Fhit-/- mice had exaggerated hypoxic PH and failed to recover in normoxia. Enzastaurin reversed PH in the Sugen5416/hypoxia/normoxia rat model, by improving right ventricular systolic pressure, right ventricular hypertrophy, cardiac fibrosis, and vascular remodeling.

CONCLUSIONS

This study highlights the importance of the novel BMPR2 modifier FHIT in PH and the clinical value of the repurposed drug enzastaurin as a potential novel therapeutic strategy to improve PAH.

The roles of PKCs in regulating autophagy

PURPOSE

Autophagy, as a highly conserved cellular degradation and recycling process, plays an important part in maintaining cellular homeostasis. PKC signaling is involved in multiple pathways including cell cycle progression, tumorigenesis, migration and autophagy.

METHODS

Literatures about PKC and autophagy from PubMed databases were reviewed in this study.

RESULTS

Studies regarding the association of PKC and autophagy remain debatable. Different duration of the stimulation of autophagy and distinct cell contexts result in different function of PKC in regulating autophagy. The subcellular localization of PKCs and their downstream regulators may influence the autophagy regulation as well. As important intracellular components, the mitochondria play an important role in regulating autophagy, by metabolic modulation and structural derangement.

CONCLUSION

Phase II studies regarding PKC-β inhibitor, enzastaurin, showed promising results in MCL, DLBCL and recurrent high-grade gliomas. However, the detailed mechanism is still in need. The mechanism of PKC-β in mediating autophagy in lymphoma and high-grade gliomas remains elusive as well. Moreover, several studies were in agreement that rottlerin enhanced autophagy in breast cancer cells, which warrants further clinical studies to verify PKC-δ as a therapeutic target. Thus, identifying the function of PKC in modulating autophagy and conducting related clinical studies help find novel target for chemotherapy.

B-cell receptor-mediated NFATc1 activation induces IL-10/STAT3/PD-L1 signaling in diffuse large B-cell lymphoma

Knowledge of programmed death ligand 1 (PD-L1) expression and its regulation in B-cell lymphoma cells is limited. Investigating mechanisms that control PD-L1 expression in B-cell lymphoma cells might identify biomarkers that predict the efficacy of immunotherapy with anti-programmed death-1/PD-L1 antibodies. In addition, identification of mechanisms that regulate PD-L1 may identify molecules that can be targeted to improve the clinical efficacy of immune checkpoint inhibitors. In this study, we used proteomic approaches and patient-derived B-cell lymphoma cell lines to investigate mechanisms that regulate PD-L1 expression. We found that PD-L1 expression, particularly in nongerminal center B cell-derived diffuse large B-cell lymphoma (DLBCL), is controlled and regulated by several interactive signaling pathways, including the B-cell receptor (BCR) and JAK2/STAT3 signaling pathways. We found that that BCR-mediated NFATc1 activation upregulates IL-10 chemokine expression in PD-L1⁺ B-cell lymphoma cells. Released IL-10 activates the JAK2/STAT3 pathway, leading to STAT3-induced PD-L1 expression. IL-10 antagonist antibody abrogates IL-10/STAT3 signaling and PD-L1 protein expression. We also found that BCR pathway inhibition by BTK inhibitors (ibrutinib, acalabrutinib, and BGB-3111) blocks NFATc1 and STAT3 activation, thereby inhibiting IL-10 and PD-L1 expression. Finally, we validated the PD-L1 signaling network in 2 primary DLBCL cohorts consisting of 428 and 350 cases and showed significant correlations among IL-10, STAT3, and PD-L1. Thus, our findings reveal a complex signaling network regulating PD-L1 expression in B-cell lymphoma cells and suggest that PD-L1 expression can be modulated by small molecule inhibitors to potentiate immunotherapies.

Protein kinase C and cardiac dysfunction: a review

Heart failure (HF) is a physiological state in which cardiac output is insufficient to meet the needs of the body. It is a clinical syndrome characterized by impaired ability of the left ventricle to either fill or eject blood efficiently. HF is a disease of multiple aetiologies leading to progressive cardiac dysfunction and it is the leading cause of deaths in both developed and developing countries. HF is responsible for about 73,000 deaths in the UK each year. In the USA, HF affects 5.8 million people and 550,000 new cases are diagnosed annually. Cardiac remodelling (CD), which plays an important role in pathogenesis of HF, is viewed as stress response to an index event such as myocardial ischaemia or imposition of mechanical load leading to a series of structural and functional changes in the viable myocardium. Protein kinase C (PKC) isozymes are a family of serine/threonine kinases. PKC is a central enzyme in the regulation of growth, hypertrophy, and mediators of signal transduction pathways. In response to circulating hormones, activation of PKC triggers a multitude of intracellular events influencing multiple physiological processes in the heart, including heart rate, contraction, and relaxation. Recent research implicates PKC activation in the pathophysiology of a number of cardiovascular disease states. Few reports are available that examine PKC in normal and diseased human hearts. This review describes the structure, functions, and distribution of PKCs in the healthy and diseased heart with emphasis on the human heart and, also importantly, their regulation in heart failure.

Targeting the B-cell receptor pathway in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous diagnostic category with different molecular subtypes defined by distinct gene expression patterns and divergent mechanisms of oncogenic activation. Several studies have suggested an inferior survival for patients of the activated B-cell-like (ABC) versus the germinal center B-cell-like (GCB) DLBCL subtype which has led to increasing interest in investigating pharmacological inhibition of signaling pathways which contribute to lymphomagenesis and that are specifically utilized by ABC DLBCL cells. One of these signaling cascades is the B-cell receptor (BCR) pathway and several approaches in clinical trials to target this cascade have demonstrated promising therapeutic activity. This review discusses our current understanding of the role of BCR signaling in different DLBCL subtypes, including primary central nervous system lymphoma (PCNSL), a subgroup of DLBCL that is particularly dependent on BCR signaling. One specific aim of this review is to highlight novel approaches to therapeutically target BCR signaling in DLBCL.

Mantle cell lymphoma in the era of precision medicine-diagnosis, biomarkers and therapeutic agents

Despite advances in the development of clinical agents for treating Mantle Cell Lymphoma (MCL), treatment of MCL remains a challenge due to complexity and frequent relapse associated with MCL. The incorporation of conventional and novel diagnostic approaches such as genomic sequencing have helped improve understanding of the pathogenesis of MCL, and have led to development of specific agents targeting signaling pathways that have recently been shown to be involved in MCL. In this review, we first provide a general overview of MCL and then discuss about the role of biomarkers in the pathogenesis, diagnosis, prognosis, and treatment for MCL. We attempt to discuss major biomarkers for MCL and highlight published and ongoing clinical trials in an effort to evaluate the dominant signaling pathways as drugable targets for treating MCL so as to determine the potential combination of drugs for both untreated and relapse/refractory cases. Our analysis indicates that incorporation of biomarkers is crucial for patient stratification and improve diagnosis and predictability of disease outcome thus help us in designing future precision therapies. The evidence indicates that a combination of conventional chemotherapeutic agents and novel drugs designed to target specific dysregulated signaling pathways can provide the effective therapeutic options for both untreated and relapse/refractory MCL.

Diffuse large B-cell lymphoma: can genomics improve treatment options for a curable cancer?

Gene-expression profiling and next-generation sequencing have defined diffuse large B-cell lymphoma (DLBCL), the most common lymphoma diagnosis, as a heterogeneous group of subentities. Despite ongoing explosions of data illuminating disparate pathogenic mechanisms, however, the five-drug chemoimmunotherapy combination R-CHOP remains the frontline standard treatment. This has not changed in 15 years, since the anti-CD20 monoclonal antibody rituximab was added to the CHOP backbone, which first entered use in the 1970s. At least a third of patients are not cured by R-CHOP, and relapsed or refractory DLBCL is fatal in ∼90%. Targeted small-molecule inhibitors against distinct molecular pathways activated in different subgroups of DLBCL have so far translated poorly into the clinic, justifying the ongoing reliance on R-CHOP and other long-established chemotherapy-driven combinations. New drugs and improved identification of biomarkers in real time, however, show potential to change the situation eventually, despite some recent setbacks. Here, we review established and putative molecular drivers of DLBCL identified through large-scale genomics, highlighting among other things the care that must be taken when differentiating drivers from passengers, which is influenced by the promiscuity of activation-induced cytidine deaminase. Furthermore, we discuss why, despite having so much genomic data available, it has been difficult to move toward personalized medicine for this umbrella disorder and some steps that may be taken to hasten the process.

Targeting of B-cell receptor signalling in B-cell malignancies

Pharmacological agents that inhibit enzymes of the B-cell receptor (BCR) pathway are of increasing importance in the treatment of B-cell malignancies. These include inhibitors of Bruton tyrosine kinase (BTK), phosphatidylinositol 3-kinase (PI3K), splenic tyrosine kinase and protein kinase Cβ. Two agents are already approved in the USA and Europe: ibrutinib, a BTK inhibitor, for the treatment of chronic lymphatic leukaemia (CLL), mantle cell lymphoma (MCL) and Waldenström's macroglobulinemia; and idelalisib, a PI3Kδ inhibitor, for the treatment of CLL and follicular lymphoma. In addition, the role of these drugs in diffuse large B-cell lymphoma and marginal zone lymphoma is under investigation, as single agents and in combination with chemotherapy. In CLL, both ibrutinib and idelalisib have an established role as first-line therapy in patients with del(17p), and in MCL, ibrutinib is a standard option for patients relapsing after chemoimmunotherapy. Unexpected toxicities have been encountered when combining these potent new agents with other drugs, including chemotherapy and lenalidomide, and based on this experience the risks and benefits of novel combinations must be evaluated carefully. In this review, we summarize the efficacy and safety results with these inhibitors and discuss novel combinations that are under study and the future role of BCR inhibitors in these disorders.

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

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

A pharmacokinetic and safety study of a fixed oral dose of enzastaurin HCl in native Chinese patients with refractory solid tumors and lymphoma

Purpose

This study was conducted to assess the pharmacokinetics and safety of enzastaurin in native Chinese patients with refractory solid tumors and lymphoma.

Methods

Eligible patients received 500 mg of enzastaurin orally once daily. The pharmacokinetics of enzastaurin and its metabolites were assessed on days 14 to 18. Patients were allowed to continue receiving the agent in a safety extension phase until disease progression or presentation with unacceptable toxicity.

Results

Twenty-five patients received at least 1 dose of enzastaurin, and twenty-one patients completed the pharmacokinetic phase. Fifteen patients entered the safety extension phase. Except for transient, asymptomatic grade 3 QT interval prolongation in one patient who had baseline grade 2 QT prolongation, other adverse events were of grade 1 to 2. The t_1/2, C_{av, ss,} and AUC_{τ, ss} for enzastaurin and its primary active metabolite LSN326020 were 14 and 42 h, 1,210 and 907 nmol/L, and 29,100 and 21,800 nmol•h/L, respectively. One patient with relapsed diffuse large B-cell lymphoma achieved a partial response that lasted for 8.1 months.

Conclusions

The pharmacokinetics of enzastaurin in Chinese cancer patients were consistent with those observed in previous studies abroad. Enzastaurin 500 mg daily was well tolerated by Chinese patients. We recommend 500 mg daily as the phase II dose in this population. Its efficacy in lymphoma deserves further investigation.

Trial Registration

ClinicalTrials.gov: NCT01432951

Enzastaurin: A lesson in drug development

Enzastaurin is an orally administered drug that was intended for the treatment of solid and haematological cancers. It was initially developed as an isozyme specific inhibitor of protein kinase Cβ (PKCβ), which is involved in both the AKT and MAPK signalling pathways that are active in many cancers. Enzastaurin had shown encouraging preclinical results for the prevention of angiogenesis, inhibition of proliferation and induction of apoptosis as well as showing limited cytotoxicity within phase I clinical trials. However, during its assessment in phase II and III clinical trials the efficacy of enzastaurin was poor both in combination with other drugs and as a single agent. In this review, we will discuss the development of enzastaurin from drug design to clinical testing, exploring target identification, validation and preclinical assessment. Finally, we will consider the clinical evaluation of enzastaurin as an example of the challenges associated with drug development. In particular, we discuss the poor translation of drug efficacy from preclinical animal models, inappropriate end point analysis, limited standards in phase I clinical trials, insufficient use of biomarker analysis and also patient stratification, all of which contributed to the failure to achieve approval of enzastaurin as an anticancer therapeutic.

Cerdulatinib, a novel dual SYK/JAK kinase inhibitor, has broad anti-tumor activity in both ABC and GCB types of diffuse large B cell lymphoma

B-cell receptor (BCR) and JAK/STAT pathways play critical roles in diffuse large B-cell lymphoma (DLBCL). Herein, we investigated the anti-lymphoma activity of cerdulatinib, a novel compound that dually targets SYK and JAK/STAT pathways. On a tissue microarray of 62 primary DLBCL tumors, 58% expressed either phosphorylated SYK or STAT3 or both. SYK and STAT3 are also phosphorylated in a panel of eleven DLBCL cell lines although ABC and GCB subtypes exhibited different JAK/STAT and BCR signaling profiles. In both ABC and GCB cell lines, cerdulatinib induced apoptosis that was associated with caspase-3 and PARP cleavage. The compound also blocked G1/S transition and caused cell cycle arrest, accompanied by inhibition of RB phosphorylation and down-regulation of cyclin E. Phosphorylation of BCR components and STAT3 was sensitive to cerdulatinib in both ABC and GCB cell lines under stimulated conditions. Importantly, JAK/STAT and BCR signaling can be blocked by cerdulatinib in primary GCB and non-GCB DLBCL tumor cells that were accompanied by cell death. Our work provides mechanistic insights into the actions of cerdulatinib, suggesting that the drug has a broad anti-tumor activity in both ABC and GCB DLBCL, at least in part by inhibiting SYK and JAK pathways.

Randomized, Double-Blind, Phase III Trial of Enzastaurin Versus Placebo in Patients Achieving Remission After First-Line Therapy for High-Risk Diffuse Large B-Cell Lymphoma

PURPOSE

To compare disease-free survival (DFS) after maintenance therapy with the selective protein kinase C β (PKCβ) inhibitor, enzastaurin, versus placebo in patients with diffuse large B-cell lymphoma (DLBCL) in complete remission and with a high risk of relapse after first-line therapy.

PATIENTS AND METHODS

This multicenter, phase III, randomized, double-blind, placebo-controlled trial enrolled patients who were at high risk of recurrence after rituximab-cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP). Patients (N = 758) with stage II bulky or stage III to IV DLBCL, three or more International Prognostic Index risk factors at diagnosis, and a complete response or unconfirmed complete response after 6 to 8 cycles of R-CHOP were assigned 2:1 to receive oral enzastaurin 500 mg daily or placebo for 3 years or until disease progression or unacceptable toxicity. Primary end point was DFS 3 years after the last patient entered treatment. Correlative analyses of biomarkers, including cell of origin by immunohistochemistry and PKCβ expression, with efficacy outcomes were exploratory objectives.

RESULTS

After a median follow-up of 48 months, DFS hazard ratio for enzastaurin versus placebo was 0.92 (95% CI, 0.689 to 1.216; two-sided log-rank P = .541; 4-year DFS, 70% v 71%, respectively). Independent of treatment, no significant associations were observed between PKCβ protein expression or cell of origin and DFS or overall survival.

CONCLUSION

Enzastaurin did not significantly improve DFS in patients with high-risk DLBCL after achieving complete response to R-CHOP. Achievement of a complete response may have abrogated the prognostic significance of cell of origin by immunohistochemistry.

Novel N-pyrimidin-4-yl-3-amino-pyrrolo [3, 4-C] pyrazole derivatives as PKC kinase inhibitors: a patent evaluation of US2015099743 (A1)

INTRODUCTION

Protein kinase Cβ (PKCβ) is a member of the PKC family of serine/threonine kinases that has been implicated in the pathophysiology of diabetic complications. Developing small molecule drugs targeting this PKC isozyme is a rational approach for treating these disease states. PKCβ belongs to the conventional class of PKC and contains both regulatory and kinase domain. Numerous compounds of different chemical classes were designed targeting the kinase domain, but achieved very limited success in clinical trials.

AREAS COVERED

This patent application reports the synthesis of about 100 new N-pyrimidin-4-yl-3-amino-pyrolo [3, 4-C] pyrazole derivatives and their competitive inhibition constant (Ki) for protein kinase C βII (PKCβII), one of the two splice variants of PKCβ. The compounds compete with ATP at the kinase domain of PKCβII, and inhibit with high potency having Ki values in the 0.1-181 nM range. The compounds are claimed to be selective towards PKCβI, PKCβII and PKCα over other protein kinases. Several routes of administration of these compounds are discussed for possible treatment of diabetes and related diseases.

EXPERT OPINION

This is an important effort toward developing PKC-based drugs for diabetic complications. Further biological evaluations of these compounds are required before proceeding toward clinical trails.

Novel drug targets for personalized precision medicine in relapsed/refractory diffuse large B-cell lymphoma: a comprehensive review

Diffuse large B-cell lymphoma (DLBCL) is a clinically heterogeneous lymphoid malignancy and the most common subtype of non-Hodgkin's lymphoma in adults, with one of the highest mortality rates in most developed areas of the world. More than half of DLBLC patients can be cured with standard R-CHOP regimens, however approximately 30 to 40 % of patients will develop relapsed/refractory disease that remains a major cause of morbidity and mortality due to the limited therapeutic options.Recent advances in gene expression profiling have led to the identification of at least three distinct molecular subtypes of DLBCL: a germinal center B cell-like subtype, an activated B cell-like subtype, and a primary mediastinal B-cell lymphoma subtype. Moreover, recent findings have not only increased our understanding of the molecular basis of chemotherapy resistance but have also helped identify molecular subsets of DLBCL and rational targets for drug interventions that may allow for subtype/subset-specific molecularly targeted precision medicine and personalized combinations to both prevent and treat relapsed/refractory DLBCL. Novel agents such as lenalidomide, ibrutinib, bortezomib, CC-122, epratuzumab or pidilizumab used as single-agent or in combination with (rituximab-based) chemotherapy have already demonstrated promising activity in patients with relapsed/refractory DLBCL. Several novel potential drug targets have been recently identified such as the BET bromodomain protein (BRD)-4, phosphoribosyl-pyrophosphate synthetase (PRPS)-2, macrodomain-containing mono-ADP-ribosyltransferase (ARTD)-9 (also known as PARP9), deltex-3-like E3 ubiquitin ligase (DTX3L) (also known as BBAP), NF-kappaB inducing kinase (NIK) and transforming growth factor beta receptor (TGFβR).This review highlights the new insights into the molecular basis of relapsed/refractory DLBCL and summarizes the most promising drug targets and experimental treatments for relapsed/refractory DLBCL, including the use of novel agents such as lenalidomide, ibrutinib, bortezomib, pidilizumab, epratuzumab, brentuximab-vedotin or CAR T cells, dual inhibitors, as well as mechanism-based combinatorial experimental therapies. We also provide a comprehensive and updated list of current drugs, drug targets and preclinical and clinical experimental studies in DLBCL. A special focus is given on STAT1, ARTD9, DTX3L and ARTD8 (also known as PARP14) as novel potential drug targets in distinct molecular subsets of DLBCL.

Molecular pathogenesis of lymphomas of mucosa-associated lymphoid tissue--from (auto)antigen driven selection to the activation of NF-κB signaling

Lymphomas of mucosa-associated lymphoid tissue (MALT) are typically present at sites such as the stomach, lung or urinary tract, where lymphoid tissues scatter in mucosa lamina propria, intra- or sub-epithelial cells. The infection of certain pathogens, such as Helicobacter pylori, Chlamydophila psittaci, Borrelia burgdorferi, hepatitis C virus, or certain autoantigens cause these sites to generate a germinal center called the "acquired lymphoid tissue". The molecular pathogenesis of MALT lymphoma is a multi-step process. Receptor signaling, such as the contact stimulation of B cell receptors and CD4 positive T cells mediated by CD40/CD40-ligand and T helper cell type 2 cytokines like interleukin-4, contributes to tumor cell proliferation. A number of genetic alterations have been identified in MALT lymphoma, and among them are important translocations, such as t(11;18)(q21;q21), t(1;14)(p22;q32), t(14;18)(q32;q21) and t(3;14)(p13;q32). Fusion proteins generated by these translocations share the same NF-κB signaling pathway, which is activated by the caspase activation and recruitment domain containing molecules of the membrane associated guanylate kinase family, B cell lymphoma-10 and MALT1 (CBM) protein complex. They act downstream of cell surface receptors, such as B cell receptors, T cell receptors, B cell activating factors and Toll-like receptors, and participate in the biological process of MALT lymphoma. The discovery of therapeutic drugs that exclusively inhibit the antigen receptor signaling pathway will be beneficial for the treatment of B cell lymphomas in the future.

PKC-Theta in Regulatory and Effector T-cell Functions

One of the major goals in immunology research is to understand the regulatory mechanisms that underpin the rapid switch on/off of robust and efficient effector (Teffs) or regulatory (Tregs) T-cell responses. Understanding the molecular mechanisms underlying the regulation of such responses is critical for the development of effective therapies. T-cell activation involves the engagement of T-cell receptor and co-stimulatory signals, but the subsequent recruitment of serine/threonine-specific protein Kinase C-theta (PKC-θ) to the immunological synapse (IS) is instrumental for the formation of signaling complexes, which ultimately lead to a transcriptional network in T cells. Recent studies demonstrated that major differences between Teffs and Tregs occurred at the IS where its formation induces altered signaling pathways in Tregs. These pathways are characterized by reduced recruitment of PKC-θ, suggesting that PKC-θ inhibits Tregs suppressive function in a negative feedback loop. As the balance of Teffs and Tregs has been shown to be central in several diseases, it was not surprising that some studies revealed that PKC-θ plays a major role in the regulation of this balance. This review will examine recent knowledge on the role of PKC-θ in T-cell transcriptional responses and how this protein can impact on the function of both Tregs and Teffs.

Emerging immunotherapy and strategies directly targeting B cells for the treatment of diffuse large B-cell lymphoma

During the last decade, significant prolonged survival in diffusive large B-cell lymphoma (DLBCL) has been observed. The efficacy of initial treatment improved mostly due to addition of a chimeric anti-CD20 monoclonal antibody (rituximab) to standard chemotherapeutic regimens. Moreover, accurate understanding of DLBCL pathogenesis and remarkable progress in gene expression profiling have led to the development of a variety of tumor-specific regimens. Novel agents target directly the pathways involved in signal transduction, lead to apoptosis and cancer cells differentiation. In this article, we mainly focus on new treatment options, such as monoclonal antibodies, tyrosine kinase inhibitors and immunomodulatory drugs, currently investigated in aggressive B-cell lymphoma with particular attention to DLBCL type.

Protein kinase C in cellular transformation: a valid target for therapy?

The protein kinase C (PKC) family of serine/threonine protein kinases share structural homology, while exhibiting substantial functional diversity. PKC isoforms are ubiquitously expressed in tissues which makes it difficult to define roles for individual isoforms, with complexity compounded by the finding that PKC isoforms can co-operate with or antagonize other PKC family members. A number of studies suggest the involvement of PKC family members in regulating leukaemic cell survival and proliferation. Chronic lymphocytic leukaemia (CLL), the most common leukaemia in the Western world, exhibits dysregulated expression of PKC isoforms, with recent reports indicating that PKCβ and δ play a critical role in B-cell development, due to their ability to link the B-cell receptor (BCR) with downstream signalling pathways. Given the prognostic significance of the BCR in CLL, inhibition of these BCR/PKC-mediated signalling pathways is of therapeutic relevance. The present review discusses the emerging role of PKC isoforms in the pathophysiology of CLL and assesses approaches that have been undertaken to modulate PKC activity.

QT Prolongation and Oncology Drug Development

Many pharmaceutical agents interact with cardiac ion channels resulting in abnormal ventricular repolarization and prolongation of the QT interval. In rare circumstances, this has resulted in the development of the potentially life-threatening arrhythmia, torsades de pointes. It is recognized, however, that accurate measurement of the QT interval is challenging, and it is a poor predictor for the development of this arrhythmia. Nevertheless, QT interval monitoring is an essential part of pharmaceutical development, and significant increases in the QT interval may prevent a drug from gaining approval.

The Novel PKCθ from Benchtop to Clinic

The protein kinases C (PKCs) are a family of serine/threonine kinases involved in regulating multiple essential cellular processes such as survival, proliferation, and differentiation. Of particular interest is the novel, calcium-independent PKCθ which plays a central role in immune responses. PKCθ shares structural similarities with other PKC family members, mainly consisting of an N-terminal regulatory domain and a C-terminal catalytic domain tethered by a hinge region. This isozyme, however, is unique in that it translocates to the immunological synapse between a T cell and an antigen-presenting cell (APC) upon T cell receptor-peptide MHC recognition. Thereafter, PKCθ interacts physically and functionally with downstream effectors to mediate T cell activation and differentiation, subsequently leading to inflammation. PKCθ-specific perturbations have been identified in several diseases, most notably autoimmune disorders, and hence the modulation of its activity presents an attractive therapeutic intervention. To that end, many inhibitors of PKCs and PKCθ have been developed and tested in preclinical and clinical studies. And although selectivity remains a challenge, results are promising for the future development of effective PKCθ inhibitors that would greatly advance the treatment of several T-cell mediated diseases.

Novel targeted therapies in diffuse large B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive non-Hodgkin's lymphoma. Next-generation sequencing techniques have improved our understanding of the molecular pathways that may drive oncogenesis. Many novel classes of drugs are in development that may improve the treatment of DLBCL, either as single agents or in combination, that exploit their synergy to overcome resistance. We review the key novel targets and therapeutics in the treatment of DLBCL, including immunomodulatory agents and immunotherapy.

Diffuse large B-cell lymphoma: optimizing outcome in the context of clinical and biologic heterogeneity

Although the majority of patients with diffuse large B-cell lymphoma (DLBCL) can be cured with standard rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP), patients who fail R-CHOP have a dismal outcome. Thus, optimization of front-line therapy, as well as the development of more effective salvage strategies, remains an important objective. Advances in molecular genetics have vastly improved our understanding of the biological diversity of DLBCL and have led to the discovery of key oncogenic pathways. In addition to the major molecular designations of germinal center B-cell and activated B-cell subtypes, next-generation sequencing technologies have unveiled the remarkable complexity of DLBCL and identified unique molecular targets that may be differentially exploited for therapeutic benefit. These findings have translated into a growing list of promising novel agents. Moving forward, it is of paramount importance to recognize the heterogeneity of DLBCL and to investigate these targeted agents within patient populations who are most likely to benefit. It will be necessary to prioritize drugs that affect key driver pathways and to combine them rationally to optimize their benefit. Improved prognostication and the availability of predictive biomarkers will be crucial to allow for the possibility of individualized risk-adapted therapy.

B-cell receptor pathway modulators in NHL

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

Targeting protein kinase C in sarcoma

Protein kinase C (PKC) is a family of serine/threonine tyrosine kinases that regulate many cellular processes including division, proliferation, survival, anoikis and polarity. PKC is abundant in many human cancers and aberrant PKC signalling has been demonstrated in cancer models. On this basis, PKC has become an attractive target for small molecule inhibition within oncology drug development programmes. Sarcoma is a heterogeneous group of mesenchymal malignancies. Due to their relative insensitivity to conventional chemotherapies and the increasing recognition of the driving molecular events of sarcomagenesis, sarcoma provides an excellent platform to test novel therapeutics. In this review we provide a structure-function overview of the PKC family, the rationale for targeting these kinases in sarcoma and the state of play with regard to PKC inhibition in the clinic.

A phase 1 and pharmacokinetic study of enzastaurin in pediatric patients with refractory primary central nervous system tumors: a pediatric brain tumor consortium study

BACKGROUND

We sought to estimate the maximum tolerated or recommended phase 2 dose and describe the pharmacokinetics and toxicities of enzastaurin, an oral inhibitor of protein kinase Cβ, in children with recurrent central nervous system malignancies.

METHODS

Enzastaurin was administered continuously once daily at 3 dose levels (260, 340, and 440 mg/m(2)) and twice daily at 440 mg/m(2)/day. Plasma pharmacokinetics were evaluated following a single dose and at steady state. Inhibition of protein kinase C and Akt cell signaling in peripheral blood mononuclear cells was evaluated. Akt pathway activity was measured in pretreatment tumor samples.

RESULTS

Thirty-three patients enrolled; 1 was ineligible, and 3 were nonevaluable secondary to early progressive disease. There were no dose-limiting toxicities during the dose-finding phase. Two participants receiving 440 mg/m(2) given twice daily experienced dose-limiting toxicities of grade 3 thrombocytopenia resulting in delayed start of course 2 and grade 3 alanine transaminase elevation that did not recover within 5 days. There were no grade 4 toxicities during treatment. The concentration of enzastaurin increased with increasing dose and with continuous dosing; however, there was not a significant difference at the 440 mg/m(2) dosing level when enzastaurin was administered once daily versus twice daily. There were no objective responses; however, 11 participants had stable disease >3 cycles, 7 with glioma, 2 with ependymoma, and 2 with brainstem glioma.

CONCLUSION

Enzastaurin was well tolerated in children with recurrent CNS malignancies, with chromaturia, fatigue, anemia, thrombocytopenia, and nausea being the most common toxicities. The recommended phase 2 dose is 440 mg/m(2)/day administered once daily.

The combination of bortezomib with enzastaurin or lenalidomide enhances cytotoxicity in follicular and mantle cell lymphoma cell lines

We analyzed the combination of a proteasome inhibitor (bortezomib) with enzastaurin (PKC/AKT-inhibitor) or lenalidomide (immunomodulatory agent) for the inhibition of proliferation and induction of apoptosis in B-cell lymphoma cell lines and primary malignant cells. The effects of bortezomib, enzastaurin or lenalidomide, alone or in combinations, on cell viability and apoptosis were evaluated using the Cell Proliferation Kit and flow cytometry analysis. The interaction between drugs was examined by the Chou-Talalay method. Cell cycle analysis was performed by flow cytometry. The PI3K/AKT, PKC and MAPK/ERK signaling pathways were analyzed using western blot. Bortezomib with either enzastaurin or lenalidomide synergistically induced anti-proliferative and pro-apoptotic effects in B-cell lymphoma cells, even in the presence of the bone marrow microenvironment. The direct cytotoxicity is mediated by signaling events involving the PI3K/AKT, PKC and MAPK/ERK pathways leading to cell death. The significant increase of apoptosis was mediated by an increased ratio of pro-apoptotic proteins (Bax, Bad and Bim) to anti-apoptotic proteins (Bcl-2, Bcl-xL and Mcl-1), triggering the cleavage of caspases -3, -9, -8 and PARP. Further evaluation of the combination of bortezomib with enzastaurin or lenalidomide for the treatment of B-cell lymphoma is warranted, with the goal to improve the quality of life and survival of patients.