CD40 stimulation sensitizes CLL cells to lysosomal cell death induction by type II anti-CD20 mAb GA101

Recent Updates in Venetoclax Combination Therapies in Pediatric Hematological Malignancies

Venetoclax is a strongly effective B-cell lymphoma-2 inhibitor (BCL-2) with an ability to selectively restore the apoptotic potential of cancerous cells. It has been proven that in combination with immunotherapy, targeted therapies, and lower-intensity therapies such as hypomethylating agents (HMAs) or low-dose cytarabine (LDAC), the drug can improve overall outcomes for adult patients with acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and multiple myeloma (MM), amongst other hematological malignancies, but its benefit in pediatric hematology remains unclear. With a number of preclinical and clinical trials emerging, the newest findings suggest that in many cases of younger patients, venetoclax combination treatment can be well-tolerated, with a safety profile similar to that in adults, despite often leading to severe infections. Studies aim to determine the activity of BCL-2 inhibitor in the treatment of both primary and refractory acute leukemias in combination with standard and high-dose chemotherapy. Although more research is required to identify the optimal venetoclax-based regimen for the pediatric population and its long-term effects on patients' outcomes, it can become a potential therapeutic agent for pediatric oncology.

Surgical, Dermatological and Morphopathological Considerations in the Diagnosis and Treatment of Cutaneous Lymphoproliferative Tumors, Primary CD4+

Primary cutaneous lymphomas are a heterogeneous group of T-cell (CTCL) and B-cell lymphomas (CBCL) developing in the skin and without signs of extracutaneous disease at the time of diagnosis. The term “primary small/medium CD4+ T-cell lymphoma” was changed to “primary small/medium cutaneous CD4+ lymphoproliferative disorder” due to its indolent clinical behavior and uncertain malignant potential. This paper presents a rare case of primary cutaneous lymphoma with small to medium CD4+ T-cells. A 37-year-old patient presented with a tumor in the frontal region that had occurred approximately 8–9 months earlier. The tumor had a diameter of about 8–9 mm, well demarcated macroscopically, it was round in shape, about 6–7 mm high, pink in color, firm in consistency and painless during palpation. Surgical excision of the tumor was performed with a margin of safety of 8 mm and deep to the level of the frontal muscle fascia. The histopathological examination supported the diagnosis of cutaneous lymphoproliferation with a nodular disposition in the reticular dermis and extension around the follicular epithelia and sweat glands, composed mainly of dispersed medium-large lymphocytes. Additional immunohistochemical examination was requested. Immunohistochemical examination confirmed the diagnosis of “primary cutaneous CD4+ small/medium T-cell lymphoproliferative disorder.” Patient monitoring was carried out through clinical dermatological controls at 3, 6, and 12 months. After one year, a cranio-cerebral MRI was performed. For the following 5 years, an annual dermatological examination accompanied by cranio-cerebral MRI, blood count, and pulmonary X-ray were recommended. Similarly to all solitary skin lesions, the prognosis is excellent in this case, the only treatment being surgical excision.

In Vitro and In Vivo Models of CLL–T Cell Interactions: Implications for Drug Testing

Simple Summary

Chronic lymphocytic leukemia (CLL) cells in the peripheral blood and lymphoid microenvironment display substantially different gene expression profiles and proliferative capaci-ty. It has been suggested that CLL–T-cell interactions are key pro-proliferative stimuli in immune niches. We review in vitro and in vivo model systems that mimic CLL-T-cell interactions to trigger CLL proliferation and study therapy resistance. We focus on studies describing the co-culture of leukemic cells with T cells, or supportive cell lines expressing T-cell factors, and simplified models of CLL cells’ stimulation with recombinant factors. In the second part, we summarize mouse models revealing the role of T cells in CLL biology and implications for generating patient-derived xenografts by co-transplanting leukemic cells with T cells.

Abstract

T cells are key components in environments that support chronic lymphocytic leukemia (CLL), activating CLL-cell proliferation and survival. Here, we review in vitro and in vivo model systems that mimic CLL–T-cell interactions, since these are critical for CLL-cell division and resistance to some types of therapy (such as DNA-damaging drugs or BH3-mimetic venetoclax). We discuss approaches for direct CLL-cell co-culture with autologous T cells, models utilizing supportive cell lines engineered to express T-cell factors (such as CD40L) or stimulating CLL cells with combinations of recombinant factors (CD40L, interleukins IL4 or IL21, INFγ) and additional B-cell receptor (BCR) activation with anti-IgM antibody. We also summarize strategies for CLL co-transplantation with autologous T cells into immunodeficient mice (NOD/SCID, NSG, NOG) to generate patient-derived xenografts (PDX) and the role of T cells in transgenic CLL mouse models based on TCL1 overexpression (Eµ-TCL1). We further discuss how these in vitro and in vivo models could be used to test drugs to uncover the effects of targeted therapies (such as inhibitors of BTK, PI3K, SYK, AKT, MEK, CDKs, BCL2, and proteasome) or chemotherapy (fludarabine and bendamustine) on CLL–T-cell interactions and CLL proliferation.

Co-Stimulatory versus Cell Death Aspects of Agonistic CD40 Monoclonal Antibody Selicrelumab in Chronic Lymphocytic Leukemia

Simple Summary

Previous observations have shown that CD40 activation of CLL cells via coculture with CD40L-expressing fibroblasts increases sensitivity to cell death by CD20 mAbs rituximab and obinutuzumab. We studied the activity of the fully human-agonistic CD40 mAb selicrelumab in primary CLL cells in relation to cell activation, induced pro-survival profile and sensitization for cell death by aCD20 mAbs. We found that the pro-survival effect of selicrelumab is minimal, while cell death by combined selicrelumab plus anti-CD20 antibody treatment is maintained. Thus, further investigation of applying selicrelumab combined with anti-CD20 mAbs in a therapeutic setting might be considered.

Abstract

Objectives: Chronic lymphocytic leukemia (CLL) is a common form of leukemia with a heterogeneous clinical course that remains incurable due to the development of therapy resistance. In lymph node proliferation centers, signals from the microenvironment such as CD40 ligation through interaction with follicular T helper cells shield CLL cells from apoptosis. Previous observations have shown that, despite CD40-induced changes in apoptotic mediators resulting in cell survival, CD40 activation also increases sensitivity to cell death by CD20 mAbs rituximab and obinutuzumab. To further investigate these observations, we here studied the activity of the fully human agonistic CD40 mAb selicrelumab in primary CLL cells in relation to cell activation, induced pro-survival profile, and sensitization for cell death by aCD20 mAbs, in vitro. Methods: CLL cells from peripheral blood were isolated by the Ficoll density method. The expression of activation markers and cytokine production following CD40 stimulation was quantified by flow cytometry and ELISA. The anti-apoptotic profile of CLL induced by stimulation was evaluated by the expression of BCL-2 proteins with Western blot, and resistance to venetoclax with flow cytometry. Cell death induced by the combination of selicrelumab and aCD20 mAbs was quantified by flow cytometry. Results: CLL cells treated with selicrelumab upregulated co-stimulatory molecules such as CD86, TNF-α and death receptor CD95/Fas. In contrast to the CD40 ligand-transfected NIH3T3 cells, induction of resistance to venetoclax by selicrelumab was very moderate. Importantly, selicrelumab stimulation positively sensitized CLL cells to CD20-induced cell death, comparable to CD40 ligand-transfected NIH3T3 cells. Conclusions: Taken together, these novel insights into selicrelumab-stimulatory effects in CLL may be considered for developing new therapeutic strategies, particularly in combination with obinutuzumab.

AKT signaling restrains tumor suppressive functions of FOXO transcription factors and GSK3 kinase in multiple myeloma

The phosphatidylinositide-3 kinases and the downstream mediator AKT drive survival and proliferation of multiple myeloma (MM) cells. AKT signaling is active in MM and has pleiotropic effects; however, the key molecular aspects of AKT dependency in MM are not fully clear. Among the various downstream AKT targets are the Forkhead box O (FOXO) transcription factors (TFs) and glycogen synthase kinase 3 (GSK3), which are negatively regulated by AKT signaling. Here we show that abrogation of AKT signaling in MM cells provokes cell death and cell cycle arrest, which crucially depends on both FOXO TFs and GSK3. Based on gene expression profiling, we defined a FOXO-repressed gene set that has prognostic significance in a large cohort of patients with MM, indicating that AKT-mediated gene activation is associated with inferior overall survival. We further show that AKT signaling stabilizes the antiapoptotic myeloid cell leukemia 1 (MCL1) protein by inhibiting FOXO- and GSK3-mediated MCL1 turnover. In concordance, abrogation of AKT signaling greatly sensitized MM cells for an MCL1-targeting BH3-mimetic, which is currently in clinical development. Taken together, our results indicate that AKT activity is required to restrain the tumor-suppressive functions of FOXO and GSK3, thereby stabilizing the antiapoptotic protein MCL1 in MM. These novel insights into the role of AKT in MM pathogenesis and MCL1 regulation provide opportunities to improve targeted therapy for patients with MM.

STIM1 knock-down decreases the affinity of obinutuzumab for CD20 by altering CD20 localization to Triton-soluble membrane

Obinutuzumab is thought to exert its effects through its high antibody-dependent cellular cytotoxicity (ADCC) via glyco-engineering of the Fc region. In addition, obinutuzumab causes direct binding-induced cell death (DCD) only by specifically binding to its target CD20, a Ca²⁺ channel. However, the specific features of CD20 related to obinutuzumab binding-induction of cell death are not clearly understood. In this study, we evaluated the relationship between the Ca²⁺ channel features of CD20 as a store-operated Ca²⁺ channel (SOC) and obinutuzumab binding-induced cell death. Ca²⁺ channel function and biochemical analysis revealed that CD20 is an Orai1- and stromal interaction molecule (STIM1)-dependent Ca²⁺ pore. However, binding of obinutuzumab on CD20 did not have any effect on Ca²⁺ influx activity of CD20; the direct cell death rate mediated by obinutuzumab binding was almost equivalent with or without the extracellular Ca²⁺ condition. Given the apparent interaction between STIM1 and CD20, we observed Triton-X solubilized obinutuzumab-bound CD20 accompanied by STIM1. Subsequently, obinutuzumab binding and cell death were decreased by STIM1 knock-down in Ramos B cells. Thus, STIM1 directly contributes to cell death by increasing the affinity of cells for obinutuzumab by transferring CD20 to the Triton-soluble membrane region.

Helping the Released Guardian: Drug Combinations for Supporting the Anticancer Activity of HDM2 (MDM2) Antagonists

The protein p53, known as the “Guardian of the Genome”, plays an important role in maintaining DNA integrity, providing protection against cancer-promoting mutations. Dysfunction of p53 is observed in almost every cancer, with 50% of cases bearing loss-of-function mutations/deletions in the TP53 gene. In the remaining 50% of cases the overexpression of HDM2 (mouse double minute 2, human homolog) protein, which is a natural inhibitor of p53, is the most common way of keeping p53 inactive. Disruption of HDM2-p53 interaction with the use of HDM2 antagonists leads to the release of p53 and expression of its target genes, engaged in the induction of cell cycle arrest, DNA repair, senescence, and apoptosis. The induction of apoptosis, however, is restricted to only a handful of p53^wt cells, and, generally, cancer cells treated with HDM2 antagonists are not efficiently eliminated. For this reason, HDM2 antagonists were tested in combinations with multiple other therapeutics in a search for synergy that would enhance the cancer eradication. This manuscript aims at reviewing the recent progress in developing strategies of combined cancer treatment with the use of HDM2 antagonists.

The B cell death function of obinutuzumab-HDEL produced in plant (Nicotiana benthamiana L.) is equivalent to obinutuzumab produced in CHO cells

Plants have attracted attention as bio-drug production platforms because of their economical and safety benefits. The preliminary efficacy of ZMapp, a cocktail of antibodies produced in N. benthamiana (Nicotiana benthamiana L.), suggested plants may serve as a platform for antibody production. However, because the amino acid sequences of the Fab fragment are diverse and differences in post-transcriptional processes between animals and plants remain to be elucidated, it is necessary to confirm functional equivalence of plant-produced antibodies to the original antibody. In this study, Obinutuzumab, a third generation anti-CD20 antibody, was produced in N. benthamiana leaves (plant-obinutuzumab) and compared to the original antibody produced in glyco-engineered Chinese hamster ovary (CHO) cells (CHO-obinutuzumab). Two forms (with or without an HDEL tag) were generated and antibody yields were compared. The HDEL-tagged form was more highly expressed than the non-HDEL-tagged form which was cleaved in the N-terminus. To determine the equivalence in functions of the Fab region between the two forms, we compared the CD20 binding affinities and direct binding induced cell death of a CD20-positive B cells. Both forms showed similar CD20 binding affinities and direct cell death of B cell. The results suggested that plant-obinutuzumab was equivalent to CHO-obinutuzumab in CD20 binding, cell aggregation, and direct cell death via binding. Therefore, our findings suggest that Obinutuzumab is a promising biosimilar candidate that can be produced efficiently in plants.

A Review of Obinutuzumab (GA101), a Novel Type II Anti-CD20 Monoclonal Antibody, for the Treatment of Patients with B-Cell Malignancies

Obinutuzumab (GA101) is a novel, type II, glycoengineered, humanized anti-CD20 monoclonal antibody that has been developed to address the need for new therapeutics with improved efficacy in patients with lymphocytic leukemia and lymphoma of B-cell origin. Obinutuzumab has a distinct mode of action relative to type I anti-CD20 antibodies, such as rituximab, working primarily by inducing direct cell death and antibody-dependent cell-mediated cytotoxicity. Obinutuzumab is under investigation in a wide-ranging program of clinical trials in patients with B-cell malignancies. Efficacy as monotherapy has been reported in patients with relapsed/refractory indolent and aggressive non-Hodgkin lymphoma (NHL) and in chronic lymphocytic leukemia (CLL) of B-cell origin. Improved outcomes have also been noted when obinutuzumab is added to chemotherapy in patients with B-cell NHL, and superiority over rituximab has been reported with combination therapy in patients with CLL. Ongoing research is focusing on developing options for chemotherapy-free treatment and on new combinations of obinutuzumab with novel targeted agents.

Improving therapeutic activity of anti-CD20 antibody therapy through immunomodulation in lymphoid malignancies

Nearly two decades ago rituximab heralded a new era in management of B cell malignancies significantly increasing response rates and survival. However, despite clear therapeutic advantage, significant numbers of patients become refractory to anti-CD20 mAb therapy, suggesting urgent improvements are required. It is now well recognized that the suppressive tumor microenvironment plays an important role in the outcome of anti-CD20 mAb therapy and that manipulation of this environment may improve the efficacy and produce long-term tumor control. The past few years have seen a surge of interest in immunomodulatory agents capable of overwriting immune suppressive networks into favorable clinical outcome. Currently, a number of such combinations with anti-CD20 mAb is under evaluation and some have produced encouraging outcomes in rituximab refractory disease. In this review, we give an outline of anti-CD20 mAbs and explore the combinations with immunomodulatory agents that enhance antitumor immunity through targeting stimulatory or inhibitory pathways and have proven potential to synergize with anti-CD20 mAb therapy. These agents, primarily mAbs, target CTLA-4, PD-1/PD-L1, and CD40.

Obinutuzumab for the treatment of patients with previously untreated chronic lymphocytic leukemia: overview and perspective

Chronic lymphocytic leukemia (CLL) is the most common lymphoproliferative disorder in the Western world and predominantly affects older people. Until recently, most studies in CLL focused on younger patients in whom intensive therapy with the addition of rituximab to fludarabine and cyclophosphamide was shown to improve survival. Obinutuzumab is a novel type II anti-CD20 monoclonal antibody (mAb) that recently demonstrated an overall survival advantage when combined with chemotherapy in previously untreated older patients with CLL and comorbidities. Obinutuzumab was superior to rituximab in this same study in terms of response rates and progression-free survival. Several preclinical and early phase clinical studies also support the efficacy of obinutuzumab. The most frequent adverse event noted with obinutuzumab is infusion-related reactions, which occur more frequently than with rituximab and are typically restricted to the first cycle of therapy. Based on these results, obinutuzumab should be considered the gold standard mAb for combination with chemotherapy in previously untreated patients with CLL and comorbidities. The marked efficacy of obinutuzumab with a weak chemotherapy backbone implies significant potency of this mAb, making it the ideal partner for combination studies with other agents in CLL.

Mechanism-based inhibitors of glycosidases: design and applications

This article covers recent developments in the design and application of activity-based probes (ABPs) for glycosidases, with emphasis on the different enzymes involved in metabolism of glucosylceramide in humans. Described are the various catalytic reaction mechanisms employed by inverting and retaining glycosidases. An understanding of catalysis at the molecular level has stimulated the design of different types of ABPs for glycosidases. Such compounds range from (1) transition-state mimics tagged with reactive moieties, which associate with the target active site—forming covalent bonds in a relatively nonspecific manner in or near the catalytic pocket—to (2) enzyme substrates that exploit the catalytic mechanism of retaining glycosidase targets to release a highly reactive species within the active site of the enzyme, to (3) probes based on mechanism-based, covalent, and irreversible glycosidase inhibitors. Some applications in biochemical and biological research of the activity-based glycosidase probes are discussed, including specific quantitative visualization of active enzyme molecules in vitro and in vivo, and as strategies for unambiguously identifying catalytic residues in glycosidases in vitro.

Obinutuzumab in hematologic malignancies: lessons learned to date

The routine use of anti-CD20 monoclonal antibodies (mAbs) has improved patient outcomes in CD20-positive non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL). Despite the clinical success achieved with rituximab, relapses are still common with further improvements in anti-CD20 mAb efficacy required. Many novel anti-CD20 antibodies are in development, but obinutuzumab is currently the only type II glycoengineered anti-CD20 mAb in clinical testing. Obinutuzumab has increased antibody-dependent cell-mediated cytotoxicity, reduced complement-dependent cytotoxicity and enhanced direct non-apoptotic cell death. In preclinical models, obinutuzumab induced superior tumor remission compared with rituximab at the equivalent dose levels, and was active in rituximab-refractory tumors. Obinutuzumab exhibits encouraging efficacy as monotherapy in NHL, and combined with chemotherapy in relapsed/refractory NHL and treatment-naïve symptomatic CLL. In a recent randomized, phase III trial in patients with untreated comorbid CLL, overall response rate was significantly greater (78% vs. 65%, P<0.0001) and median progression-free survival was significantly prolonged (26.7 vs. 15.2months, P<0.0001) for obinutuzumab plus chlorambucil vs. rituximab plus chlorambucil. Obinutuzumab is a type II anti-CD20 antibody that utilizes distinct mechanisms of action relative to type I antibodies like rituximab and has led to significant clinical improvement over rituximab in a phase III trial in CLL. Further trials are ongoing to determine whether such improvements in outcome will be seen in CD20-positive B-cell malignancies.

Obinutuzumab treatment in the elderly patient with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults in Western countries. Fludarabine-based regimens demonstrate higher response rates in younger patients but have a significant risk of infection and are thus poorly tolerated by older, frail patients. Anti-CD20 monoclonal antibodies have added to the efficacy of chemotherapy in CLL. Obinutuzumab is a potent Type II anti-CD20 monoclonal antibody with enhanced antibody-dependent cellular toxicity and direct cell death compared with rituximab. In Phase I studies, infusion reactions and neutropenia were the predominant toxicities. Phase II studies demonstrated efficacy both as a single agent and in combination with chemotherapy in patients with CLL. The CLL11 trial was a Phase III randomized trial of chlorambucil alone or with either obinutuzumab or rituximab in elderly, unfit patients. Progression-free survival (the primary end point) was 26.7 months for patients receiving obinutuzumab plus chlorambucil versus 16.3 months for those receiving rituximab plus chlorambucil and 11.1 months for those receiving chlorambucil alone (P<0.001). Overall survival was improved for patients receiving obinutuzumab plus chlorambucil versus chlorambucil alone (P=0.002). This trial led to the US Food and Drug Administration (FDA) approval of obinutuzumab in this patient population.

Obinutuzumab (GA101) for the treatment of chronic lymphocytic leukemia and other B-cell non-hodgkin's lymphomas: a glycoengineered type II CD20 antibody

Obinutuzumab (GA101) is a humanized, monoclonal type II CD20 antibody modified by glycoengineering. The glycoengineered Fc portion enhances the binding affinity to the FcγRIII receptor on immune effector cells, resulting in increased antibody-dependent cellular cytotoxicity and phagocytosis. In addition, the type II antibody binding characteristics of obinutuzumab to CD20 lead to an efficient induction of direct non-apoptotic cell death. Preclinical data demonstrated more efficient B-cell depletion in whole blood and superior antitumor activity in xenograft models of obinutuzumab as compared to the type I CD20 antibody rituximab. In previously untreated patients with chronic lymphocytic leukemia (CLL) and comorbidities, obinutuzumab plus chlorambucil increased response rates and prolonged progression-free survival compared with rituximab plus chlorambucil. Obinutuzumab had an acceptable and manageable safety profile, with infusion-related reactions during the first infusion as the most common adverse event. Further phase I/II clinical trials have also shown promising activity in other CD20-positive B-cell non-Hodgkin's lymphomas (NHL). Therefore, several clinical studies are planned or ongoing to investigate obinutuzumab with different combination partners in both untreated and relapsed/refractory patients with different B-cell NHL entities, which in addition to CLL include diffuse large B-cell lymphoma and follicular lymphoma. © 2015 S. Karger GmbH, Freiburg.

Lysosomotropic agents selectively target chronic lymphocytic leukemia cells due to altered sphingolipid metabolism

Lysosome membrane permeabilization (LMP) mediates cell death in a variety of cancer cells. However, little is known about lysosomes and LMP in chronic lymphocytic leukemia (CLL). Owing to drug resistance and toxicity in CLL patients, better treatment strategies are required. Our results show that CLL cells were sensitive to the lysosomotropic agent siramesine. Furthermore, this drug was more effective in CLL cells, regardless of prognostic factors, compared with normal B cells. Siramesine caused LMP, lipid peroxidation and transcription factor EB nuclear translocation followed by mitochondrial membrane potential loss and reactive oxygen species release. Siramesine-induced cell death was blocked by lipid antioxidants, but not by soluble antioxidants or protease inhibitors. To determine whether CLL cells had altered lysosomes, we investigated sphingolipid metabolism as the lysosome is a hub for lipid metabolism. We found that CLL cells had more lysosomes, increased sphingosine-1-phosphate phosphatase 1 (SPP1) expression, and increased levels of sphingosine compared with normal B cells. Raising sphingosine levels increased LMP and cell death in CLL cells, but not in normal B cells. Together, these results show that excess sphingosine in CLL cells could contribute to their sensitivity toward LMP. Thus, targeting the lysosome could be a novel therapeutic strategy in CLL.

Clinical role of obinutuzumab in the treatment of naive patients with chronic lymphocytic leukemia

The introduction of targeted therapy against CD20⁺ with the monoclonal antibody rituximab has dramatically improved the survival of B-cell non-Hodgkin lymphoma including chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma. Unfortunately, CLL remains incurable with chemoimmunotherapy, with many patients having refractory or relapsing disease after rituximab-containing therapy. Obinutuzumab (GA101) is a novel humanized Type II anti-CD20 monoclonal antibody that has been investigated and compared to rituximab. Here, we provide an overview of obinutuzumab, including its mechanisms of action, preclinical data, and Phase I to III clinical studies. Preclinical data illustrate obinutuzumab’s higher potency compared to rituximab through antibody-dependent cellular cytotoxicity and direct cell death. Recently, the CLL11 study presented a significant benefit from obinutuzumab chemoimmunotherapy and supports its use for treatment-naive unfit CLL patients. Herein, we review that obinutuzumab is both a safe and effective alternative to rituximab.

A Short History of the B-Cell-Associated Surface Molecule CD40

This perspective traces developments using monoclonal antibody technology that led to the discovery of CD40, a receptor that on B cells mediates “T cell help” and on dendritic cells helps to program CD8 T cell responses. I discuss some things that we got right during the path of discovery and some things we missed. Immunotherapies that block or stimulate the CD40 pathway hold great promise for treatment of autoimmune diseases and cancers.

Update on obinutuzumab in the treatment of B-cell malignancies

INTRODUCTION

The anti-CD20 mAb rituximab has revolutionized the treatment of B-cell malignancies, improving outcome for patients. Despite these improvements, the majority of patients still relapse and become refractory to rituximab. Further efforts to improve anti-CD20 mAb efficacy have recently focused on obinutuzumab /GA101, a novel anti-CD20 mAb glycoengineered to display enhanced Fc-mediated effector mechanisms and induce direct cell death.

AREAS COVERED

We provide an overview of the current insights into the mechanisms of action of obinutuzumab focusing on how structural modifications and differences to rituximab led to designation of obinutuzumab as a type II antibody. We summarize data from preclinical studies and recent clinical trials including the Phase III trial in chronic lymphocytic leukemia (CLL), which led to FDA approval in November 2013.

EXPERT OPINION

Clinical data are now emerging confirming the promise of the initial preclinical data that demonstrated superior efficacy of obinutuzumab over rituximab at similar dosing. The emerging randomized Phase III data from older comorbid patients with previously untreated CLL demonstrated significant improvements in molecular remission rates and median progression-free survival of obinutuzumab plus chlorambucil versus rituximab plus chlorambucil. This emerging data provide reasons to be optimistic that outcomes for patients with B-cell malignancies can be further improved with obinutuzumab.

Obinutuzumab for B-cell malignancies

INTRODUCTION

We analyse data for the use of obinutuzumab in the treatment of CD20(+) lymphoproliferative disorders with a focus on chronic lymphocytic leukaemia (CLL). Targeted therapy against CD20 with the mAb rituximab led to significant improvements in survival for patients with B-cell non-Hodgkin lymphoma (NHL) and is the current mainstay of treatment for CD20(+) malignancies. Despite this, many patients relapse or become refractory after rituximab-containing therapies, so efforts have been made to develop better anti-CD20 mAbs. Obinutuzumab recently demonstrated superiority over rituximab in the only published Phase III study comparing the two antibodies.

AREAS COVERED

Obinutuzumab is a humanised, anti-CD20 mAb being compared to rituximab in several Phase III studies. An overview of obinutuzumab, its mechanisms of action and results of Phase I-III studies are presented.

EXPERT OPINION

The demonstration of superiority of obinutuzumab over rituximab in the CLL11 Phase III study is potentially practice-changing. Obinutuzumab has also proven safe and efficacious in CD20(+) NHL in Phase I/II studies and results of Phase III studies in NHL are eagerly awaited. The potential implications of improved outcomes for CLL and NHL with the introduction of this more potent anti-CD20 antibody are tremendous given the impressive results obtained after the introduction of rituximab over a decade ago.

A novel anti-CD19 monoclonal antibody (GBR 401) with high killing activity against B cell malignancies

Background

CD19 is a B cell lineage specific surface receptor whose broad expression, from pro-B cells to early plasma cells, makes it an attractive target for the immunotherapy of B cell malignancies. In this study we present the generation of a novel humanized anti-CD19 monoclonal antibody (mAb), GBR 401, and investigate its therapeutic potential on human B cell malignancies.

Methods

GBR 401 was partially defucosylated in order to enhance its cytotoxic function. We analyzed the in vitro depleting effects of GBR 401 against B cell lines and primary malignant B cells from patients in the presence or in absence of purified NK cells isolated from healthy donors. In vivo, the antibody dependent cellular cytotoxicity (ADCC) efficacy of GBR 401 was assessed in a B cell depletion model consisting of SCID mice injected with healthy human donor PBMC, and a malignant B cell depletion model where SCID mice are xenografted with both primary human B-CLL tumors and heterologous human NK cells. Furthermore, the anti-tumor activity of GBR 401 was also evaluated in a xenochimeric mouse model of human Burkitt lymphoma using mice xenografted intravenously with Raji cells. Pharmacological inhibition tests were used to characterize the mechanism of the cell death induced by GBR 401.

Results

GBR 401 exerts a potent in vitro and in vivo cytotoxic activity against primary samples from patients representing various B-cell malignancies. GBR 401 elicits a markedly higher level of ADCC on primary malignant B cells when compared to fucosylated similar mAb and to Rituximab, the current anti-CD20 mAb standard immunotherapeutic treatment for B cell malignancies, showing killing at 500 times lower concentrations. Of interest, GBR 401 also exhibits a potent direct killing effect in different malignant B cell lines that involves homotypic aggregation mediated by actin relocalization.

Conclusion

These results contribute to consolidate clinical interest in developing GBR 401 for treatment of hematopoietic B cell malignancies, particularly for patients refractory to anti-CD20 mAb therapies.

Synergistic apoptotic response between valproic acid and fludarabine in chronic lymphocytic leukaemia (CLL) cells involves the lysosomal protease cathepsin B

Fludarabine, a nucleoside analogue, is commonly used in combination with other agents for the treatment of chronic lymphocytic leukaemia (CLL). In previous studies, valproic acid (VPA), an inhibitor of histone deacetylases, combined with fludarabine to synergistically increase apoptotic cell death in CLL cells. In the present study, we found that the combination of fludarabine and VPA decreases the level of the anti-apoptotic proteins Mcl-1 and XIAP in primary CLL cells. Treatment with fludarabine alone, or in combination with VPA, led to the loss of lysosome integrity, and chemical inhibition of the lysosomal protease cathepsin B, using CA074-Me, was sufficient to reduce apoptosis. VPA treatment increased cathepsin B levels and activities in primary CLL cells, thereby priming CLL cells for lysosome-mediated cell death. Six previously treated patients with relapsed CLL were treated with VPA, followed by VPA/fludarabine combination. The combined therapy resulted in reduced lymphocyte count in five out of six and reduced lymph node sizes in four out of six patients. In vivo VPA treatment increased histone-3 acetylation and cathepsin B expression levels. Thus, the synergistic apoptotic response with VPA and fludarabine in CLL is mediated by cathepsin B activation leading to a decrease in the anti-apoptotic proteins.

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

Reciprocal expression of the endocytic protein HIP1R and its repressor FOXP1 predicts outcome in R-CHOP-treated diffuse large B-cell lymphoma patients

We previously identified autoantibodies to the endocytic-associated protein Huntingtin-interacting protein 1-related (HIP1R) in diffuse large B-cell lymphoma (DLBCL) patients. HIP1R regulates internalization of cell surface receptors via endocytosis, a process relevant to many therapeutic strategies including CD20 targeting with rituximab. In this study, we characterized HIP1R expression patterns, investigated a mechanism of transcriptional regulation and its clinical relevance in DLBCL patients treated with immunochemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone, R-CHOP). HIP1R was preferentially expressed in germinal center B-cell-like DLBCL (P<0.0001) and inversely correlated with the activated B-cell-like DLBCL (ABC-DLBCL) associated transcription factor, Forkhead box P1 (FOXP1). HIP1R was confirmed as a direct FOXP1 target gene in ABC-DLBCL by FOXP1-targeted silencing and chromatin immunoprecipitation. Lower HIP1R protein expression (≤ 10% tumoral positivity) significantly correlated with inferior overall survival (OS, P=0.0003) and progression-free survival (PFS, P=0.0148) in R-CHOP-treated DLBCL patients (n=157). Reciprocal expression with ≥ 70% FOXP1 positivity defined FOXP1(hi)/HIP1R(lo) patients with particularly poor outcome (OS, P=0.0001; PFS, P=0.0016). In an independent R-CHOP-treated DLBCL (n=233) microarray data set, patients with transcript expression in lower quartile HIP1R and FOXP1(hi)/HIP1R(lo) subgroups exhibited worse OS, P=0.0044 and P=0.0004, respectively. HIP1R repression by FOXP1 is strongly associated with poor outcome, thus further understanding of FOXP1-HIP1R and/or endocytic signaling pathways might give rise to novel therapeutic options for DLBCL.

Blinatumomab induces autologous T-cell killing of chronic lymphocytic leukemia cells

Chronic lymphocytic leukemia is an incurable B-cell malignancy that is associated with tumor cell-mediated T-cell dysfunction. It therefore represents a challenging disease for T-cell immunotherapeutics. The CD19/CD3 bi-specific antibody construct blinatumomab (AMG103 or MT103) has been tested clinically in non-Hodgkin's lymphoma and acute lymphoblastic leukemia but has not been assessed in chronic lymphocytic leukemia. We investigated whether blinatumomab could overcome T-cell dysfunction in chronic lymphocytic leukemia in vitro. Blinatumomab was tested on peripheral blood mononuclear cells from 28 patients (treatment naïve and previously treated). T-cell activation and function, as well as cytotoxicity against leukemic tumor cells were measured. Blinatumomab induced T-cell activation, proliferation, cytokine secretion and granzyme B release in a manner similar to that occurring with stimulation with anti-CD3/anti-CD28 beads. However, only blinatumomab was able to induce tumor cell death and this was found to require blinatumomab-mediated conjugate formation between T cells and tumor cells. Cytotoxicity of tumor cells was observed at very low T-cell:tumor cell ratios. A three-dimensional model based on confocal microscopy suggested that up to 11 tumor cells could cluster round each T cell. Importantly, blinatumomab induced cytotoxicity against tumor cells in samples from both treatment-naïve and treated patients, and in the presence of co-culture pro-survival signals. The potent cytotoxic action of blinatumomab on tumor cells appears to involve conjugation of T cells with tumor cells at both the activation and effector stages. The efficacy of blinatumomab in vitro suggests that the bi-specific antibody approach may be a powerful immunotherapeutic strategy in chronic lymphocytic leukemia.

A cell culture system that mimics chronic lymphocytic leukemia cells microenvironment for drug screening and characterization

Chronic Lymphocytic Leukaemia (CLL) is an incurable disease that warrants new therapeutic treatments. CLL cells accumulate in the peripheral blood, in the bone marrow and in secondary lymphoid organs. Unlike circulating CLL cells, CLL cells resident in these last two compartments display high chemoresistance and proliferative capacity. Given the importance of the microenvironment in this disease, strategies that aim to develop new therapeutic agents need to consider this critical factor. Various cell culture conditions have been described that attempt to emulate either the different types of microenvironments in which CLL cells are found or an individual component of a particular microenvironment. Here, a methodology that partially mimics the interaction between CLL cells and the CD3+ CD4+ CD154+ T cells is described. Moreover, within this method, two protocols are presented and compared that may partially recapitulate different physiological states. The methodology can be exploited for target validation and drug development in CLL.

Epitope interactions of monoclonal antibodies targeting CD20 and their relationship to functional properties

Several novel anti-CD20 monoclonal antibodies are currently in development with the aim of improving the treatment of B cell malignancies. Mutagenesis and epitope mapping studies have revealed differences between the CD20 epitopes recognized by these antibodies. Recently, X-ray crystallography studies confirmed that the Type I CD20 antibody rituximab and the Type II CD20 antibody obinutuzumab (GA101) differ fundamentally in their interaction with CD20 despite recognizing a partially overlapping epitope on CD20. The Type I CD20 antibodies rituximab and ofatumumab are known to bind to different epitopes. The differences suggest that the biological properties of these antibodies are not solely determined by their core epitope sequences, but also depend on other factors, such as the elbow hinge angle, the orientation of the bound antibody and differential effects mediated by the Fc region of the antibody. Taken together, these factors may explain differences in the preclinical properties and clinical efficacy of anti-CD20 antibodies.

7th cancer scientific forum of theCancéropôle Lyon Auvergne Rhône-Alpes: March 20-21, 2012, Lyon, France

The Innovative Approaches in Anti-Cancer Monoclonal Antibodies meeting, held on March 20, 2012 in Lyon, was organized by Cancéropôle Lyon Auvergne-Rhône-Alps in partnership with the French competitiveness cluster Lyonbiopôle. CLARA is one of the seven cancer research clusters within France in charge of facilitating Translational Oncology Research by taking into account the objectives of the French National Cancer Plans I and II and, in coordination with the French National Cancer Institute and local authorities (mainly Grand Lyon, Rhône County and Rhône-Alpes Region), to perform economic development of research findings. The contribution of lectures by outstanding speakers as described in this report, the organization of two-round tables: "Antibody treatment in cancer: Unmet needs in solid tumors and hematological malignancies," and "From chimeric to more than human antibodies," together with face-to-face meetings, was shared by over 230 participants. The lectures provided an overview of the commercial pipeline of monoclonal antibody (mAb) therapeutics for cancer; discussion of the distinction between biosimilar, biobetter and next generation therapeutic antibodies for cancer; updates on obinutuzumab and the use of mAbs in lymphoma; and discussion of antibody-drug conjugates.

Obinutuzumab for the treatment of lymphoproliferative disorders

INTRODUCTION

Targeted therapy against CD20 with the mAb rituximab has led to significant improvements in survival for patients with B-cell non-Hodgkin's lymphoma (NHL). Despite these improvements, many patients relapse and/or become refractory after rituximab-containing therapies and thus better therapies are required for NHL.

AREAS COVERED

Obinutuzumab is a novel, humanized, anti-CD20 mAb currently being investigated in Phase III studies in comparison to rituximab. An overview of obinutuzumab, its mechanisms of action and the results of pre-clinical and Phase I/II studies are presented.

EXPERT OPINION

Pre-clinical studies suggest that obinutuzumab is a more potent anti-CD20 mAb than Rituximab at inducing antibody-dependent cellular cytotoxicity (ADCC) and direct cell death (DCD). Obinutuzumab is safe and effective in CD20 + NHL and further study is warranted. Results of ongoing Phase III clinical trials comparing Obinutuzumab to Rituximab in different disease settings and with different chemotherapy regimens are eagerly awaited.