Enhanced anti-tumor activity of the glycoengineered type II CD20 antibody obinutuzumab (GA101) in combination with chemotherapy in xenograft models of human lymphoma

OBINUTUZUMAB DOES NOT IMPROVE COMPLETE METHABOLIC RESPONSE BUT DOES NOT COMPROMISE MOBILIZATION OR ENGRAFTMENT OF AUTOLOGOUS PERIPHERAL BLOOD STEM CELLS IN DIFFUSE LARGE B CELL LYMPHOMA: RESULTS FROM A FIL PROSPECTIVE PHASE II STUDY (THE GIOTTO STUDY)

Salvage immunochemotherapy and transplant consolidation is the standard treatment for relapsed or refractory (R/R) diffuse large B-cell lymphoma (DLBCL). We tested a combination of Obinutuzumab and DHAP for treating R/R DLBCL. The primary end point was the rate of complete metabolic response (CMR). Secondary end points were stem cell mobilization, stem cell engraftment, overall survival, and feasibility. In this prospective, phase-2, single-arm trial (EudraCT 2014-004014-17) patients received the standard three doses of Obinutuzumab for the first cycle, and then one dose. Patients with CMR were consolidated with an autologous stem cell transplantation (ASCT). An interim analysis was provided after the first 29 patients to confirm the initial null hypothesis that at least 10/29 patients would achieve CMR. Among the 29 patients evaluated for the first stage only 6 patients (6/29, 21%) achieved CMR, thus, study enrollment was stopped. Nine patients exhibited extra-hematologic toxicities ≥grade 3. Among the 19 patients that started stem cell mobilization, one failed (5%) and 18 achieved mobilization (95%). Of these 18 patients, 9 were reinfused. Mobilization was observed in 16 patients (89%) after 1 or 2 apheresis rounds. The mean number of CD34+ cells mobilized was 5.8 x 10⁶ /Kg (median: 5.5, IQR: 5 - 6.75). The mean number of reinfused CD34+ cells in the 9 patients was 4.1 x 10⁶ /Kg (median: 4.1, IQR: 3.5 - 5). Obinutuzumab combined with DHAP did not compromise stem cell mobilization or engraftment after ASCT in patients with DLBCL. However, Obinutuzumab+DHAP provided a lower CMR rate than expected. This article is protected by copyright. All rights reserved.

Does the Number of Bifunctional Chelators Conjugated to a mAb Affect the Biological Activity of Its Radio-Labeled Counterpart? Discussion Using the Example of mAb against CD-20 Labeled with 90Y or 177Lu

There has been considerable interest in developing a monoclonal antibody (mAb) against-CD-20 (for example, Rituximab) modified by bifunctional chelating agents (BCA) for non-Hodgkin's lymphoma radioimmunotherapy. Therefore, many researchers have modified this monoclonal antibody by attaching different BCA moieties and evaluated their biological activities in terms of in vitro study and in vivo study in healthy and tumor xenografted rodents. This mini-perspective reviews the in vitro studies, the immunoreactivity and physiological distribution studies: organ-to-blood and the tumor-to-organ ratio of conjugates with different numbers of chelators per mAb. We set up a null hypothesis that states there is no statistical significance between the biological activity of monoclonal antibody (Rituximab) and the number of conjugated bifunctional chelators. Overall, we have concluded that there is no strong evidence for this hypothesis. However, the literature data should be questioned due to the potential lack of uniform study methodology.

Coadministration with bendamustine restores the antitumor activity of obinutuzumab in obinutuzumab-resistant tumors

BACKGROUND

The glycoengineered, humanized anti-CD20 antibody obinutuzumab is indicated for previously untreated or relapsed/refractory CD20-positive follicular lymphoma (FL). However, the effectiveness of obinutuzumab retreatment in relapsed/refractory FL after prior obinutuzumab-containing therapy is unclear. To address this issue, we investigated the antitumor activity of obinutuzumab plus bendamustine in obinutuzumab-resistant tumors established from a human non-Hodgkin lymphoma xenograft model.

MATERIALS AND METHODS

Obinutuzumab-resistant tumors (SU-DHL-4-OR-18-8) were established from an SU-DHL-4 xenograft model by repeated administration of obinutuzumab. Antitumor activity was evaluated based on tumor volume after treatment with obinutuzumab on Day 1, 8, and 15 and/or bendamustine on Day 1 and 2. Intratumoral natural killer (NK) cells/macrophages were evaluated by immunohistochemistry and flow cytometry.

RESULTS

In SU-DHL-4-OR-18-8 xenografted tumors, intratumoral NK cells/macrophages after obinutuzumab treatment were significantly decreased compared with parent tumors on Day 4. The endoplasmic reticulum stress sensor phospho-IRE1 was also decreased. In SU-DHL-4-OR-18-8 tumors, bendamustine treatment increased phospho-IRE1 on Day 4 and intratumor NK cells/macrophages on Day 10. Obinutuzumab combined with bendamustine significantly increased antitumor activity compared with each single agent on Day 29, with an increase in chemoattractant CCL6 expression on Day 10.

CONCLUSIONS

Coadministration of bendamustine in obinutuzumab retreatment may be effective against obinutuzumab-resistant tumors.

Genetic glycoengineering in mammalian cells

Advances in nuclease-based gene-editing technologies have enabled precise, stable, and systematic genetic engineering of glycosylation capacities in mammalian cells, opening up a plethora of opportunities for studying the glycome and exploiting glycans in biomedicine. Glycoengineering using chemical, enzymatic, and genetic approaches has a long history, and precise gene editing provides a nearly unlimited playground for stable engineering of glycosylation in mammalian cells to explore and dissect the glycome and its many biological functions. Genetic engineering of glycosylation in cells also brings studies of the glycome to the single cell level and opens up wider use and integration of data in traditional omics workflows in cell biology. The last few years have seen new applications of glycoengineering in mammalian cells with perspectives for wider use in basic and applied glycosciences, and these have already led to discoveries of functions of glycans and improved designs of glycoprotein therapeutics. Here, we review the current state of the art of genetic glycoengineering in mammalian cells and highlight emerging opportunities.

Anti-CD20 treatment for B-cell malignancies: current status and future directions

INTRODUCTION

The introduction of anti-CD20 monoclonal antibody therapy with rituximab in the 1990s greatly improved outcomes for patients with B-cell malignancies. Disease resistance or relapse after successful initial therapy and declining efficacy of subsequent rounds of treatment were the basis for the development of alternative anti-CD20-based antibody therapies.

AREAS COVERED

The novel anti-CD20 antibodies of atumumab, ublituximab, and obinutuzumab were developed to be differentiated via structural and mechanistic features over rituximab. We provide an overview of preclinical and clinical data, and demonstrate ways in which the pharmacodynamic properties of these novel agents translate into clinical benefit for patients.

EXPERT OPINION

Of the novel anti-CD20 antibodies, only obinutuzumab has shown consistently improved efficacy over rituximab in randomized pivotal trials in indolent non-Hodgkin lymphoma and chronic lymphocytic leukemia. The Phase 3 GALLIUM trial demonstrated significant improvements in progression-free survival with obinutuzumab-based immunochemotherapy over rituximab-based immunochemotherapy. Novel combinations of obinutuzumab, including with chemotherapy-free options are being explored, such as with the newly approved combinations of obinutuzumab with venetoclax, ibrutinib, or acalabrutinib. The biggest unmet need remains in the treatment of diffuse large B-cell lymphoma; emerging options in this field include the use of CAR-T cells and T-cell bispecific antibodies.

Analytical comparability study of anti-CD20 monoclonal antibodies rituximab and obinutuzumab using a stability-indicating orthogonal testing protocol: Effect of structural optimization and glycoengineering

Glycoengineering and biosimilarity are the key factors for growing, promising and progressive approaches in monoclonal antibodies development. In this study, the physicochemical stability of anti-CD20 rituximab (RTX); originator and biosimilar was compared to its glycoengineered humanized version; obinutuzumab (OBZ). An orthogonal stability-indicating protocol using a set of validated bioanalytical techniques; size exclusion high performance liquid chromatography (SE-HPLC), reversed phase liquid chromatography (RP-HPLC), quantitative gel electrophoresis by TapeStation, receptor binding assay and dynamic light scattering (DLS) was used to investigate the effect of different stress factors on the pattern and kinetics of degradation. SE-HPLC results supported with spectral purity showed similar degradation extent with a different pattern of degradation between RTX and OBZ. A lower tendency to form degraded fragments and a relatively higher favorability for degradation through aggregate formation has been revealed in case of OBZ. Results were in agreement with those of DLS and receptor binding assay which showed specificity to the intact antibodies in the presence of their degradation products. Furthermore, results were additionally confirmed through denaturing quantitative gel electrophoresis which suggested reducible covalent bonds as the mechanism for aggregates formation. RP-HPLC results showed two oxidized forms via excessive oxidation of RTX and OBZ with nearly the same degradation percent. Comparability data of RTX and OBZ using the applied methodologies showed that although glycoengineering; carried out to enhance the therapeutic and biological activity of OBZ altered the pattern of degradation but did not significantly affect the overall stability. Results showed also consistent stability profile between the biosimilar and its originator RTX products.

Maltotriose-modified poly(propylene imine) Glycodendrimers as a potential novel platform in the treatment of chronic lymphocytic Leukemia. A proof-of-concept pilot study in the animal model of CLL

Cancer nanotherapeutics have shown promise in resolving some of the limitations of conventional drug delivery systems such as nonspecific biodistribution and targeting, lack of water solubility, and low therapeutic indices, Among the various nanoparticles that are available, dendrimers, highly branched macromolecules with a specific size and shape, are one of the most promising ones. In this preliminary study, we tested the anti-tumor activity of maltotriose-modified fourth-generation poly(propylene imine) glycodendrimers (PPI-G4-M3) in vivo in the subcutaneous MEC-1 xenograft model of human chronic lymphocytic leukemia (CLL) in NOD scid gamma mice. Fludarabine was used for model validation and as a positive treatment control. The anti-tumor response was calculated as tumor volume, tumor control ratio, and tumor growth inhibition. The study showed that PPI-G4-M3 inhibited subcutaneous tumor growth more efficiently than fludarabine. The anti-tumor response was dose-dependent. Cationic PPI-G4-M3 showed the highest anti-tumor activity but also higher toxicity than the neutral dendrimers and fludarabine. These first promising results warrant further studies in the optimization of dendrimers charge, dose, route and schedule of administration to combat CLL.

Use of anti-CD20 therapy in follicular and marginal zone lymphoma: a review of the literature

The identification of the CD20 antigen in 1979 was the first step in what would become a therapeutic milestone opening the use of immunotherapy in hematological diseases. This protein is expressed on the surface of developing B cells, but not the early progenitors or mature plasma cells. In 1997, rituximab was approved by the Food and Drug Administration, and since then it has revolutionized the treatment of B-cell malignancies. It is used as a monotherapy and in combination, at induction, at relapsed, and also in maintenance. Indolent non-Hodgkin lymphomas are characterized by a long and non-aggressive course. In this group of lymphomas, rituximab represented a great therapeutic improvement, achieving lasting responses with few adverse effects. Nowadays, second-generation molecules are emerging that may have important advantages compared to rituximab, as well as biosimilars that represent an important cost-effective option.

Role of Calcium Signaling in GA101-Induced Cell Death in Malignant Human B Cells

GA101/obinutuzumab is a novel type II anti-CD20 monoclonal antibody (mAb), which is more effective than rituximab (RTX) in preclinical and clinical studies when used in combination with chemotherapy. Ca²⁺ signaling was shown to play a role in RTX-induced cell death. This report concerns the effect of GA101 on Ca²⁺ signaling and its involvement in the direct cell death induced by GA101. We reveal that GA101 triggered an intracellular Ca²⁺ increase by mobilizing intracellular Ca²⁺ stores and activating Orai1-dependent Ca²⁺ influx in non-Hodgkin lymphoma cell lines and primary B-Cell Chronic Lymphocytic Leukemia (B-CLL) cells. According to the cell type, Ca²⁺ was mobilized from two distinct intracellular compartments. In Raji, BL2, and B-CLL cells, GA101 induced a Ca²⁺ release from lysosomes, leading to the subsequent lysosomal membrane permeabilization and cell death. Inhibition of this calcium signaling reduced GA101-induced cell death in these cells. In SU-DHL-4 cells, GA101 mobilized Ca²⁺ from the endoplasmic reticulum (ER). Inhibition of ER replenishment, by blocking Orai1-dependent Ca²⁺ influx, led to an ER stress and unfolded protein response (UPR) which sensitized these cells to GA101-induced cell death. These results revealed the central role of Ca²⁺ signaling in GA101’s action mechanism, which may contribute to designing new rational drug combinations improving its clinical efficacy.

Anti-CD20 monoclonal antibodies: reviewing a revolution

Since the inception of rituximab in the 1990s, anti-CD20 monoclonal antibodies have revolutionised the treatment of B cell hematological malignancies and have become a cornerstone of modern gold-standard practice. Additionally, the potent efficacy of these agents in depleting the B cell compartment has been used in the management of a broad array of autoimmune diseases. Multiple iterations of these agents have been investigated and are routinely used in clinical practice. In this review, we will discuss the physiology of CD20 and its attractiveness as a therapeutic target, as well as the pharmacology, pre-clinical and clinical data for the major anti-CD20 monoclonal antibodies: rituximab, obinutuzumab and ofatumumab.

CD20-TCB with Obinutuzumab Pretreatment as Next-Generation Treatment of Hematologic Malignancies

Purpose: Despite promising clinical activity, T-cell-engaging therapies including T-cell bispecific antibodies (TCB) are associated with severe side effects requiring the use of step-up-dosing (SUD) regimens to mitigate safety. Here, we present a next-generation CD20-targeting TCB (CD20-TCB) with significantly higher potency and a novel approach enabling safer administration of such potent drug.Experimental Design: We developed CD20-TCB based on the 2:1 TCB molecular format and characterized its activity preclinically. We also applied a single administration of obinutuzumab (Gazyva pretreatment, Gpt; Genentech/Roche) prior to the first infusion of CD20-TCB as a way to safely administer such a potent drug.Results: CD20-TCB is associated with a long half-life and high potency enabled by high-avidity bivalent binding to CD20 and head-to-tail orientation of B- and T-cell-binding domains in a 2:1 molecular format. CD20-TCB displays considerably higher potency than other CD20-TCB antibodies in clinical development and is efficacious on tumor cells expressing low levels of CD20. CD20-TCB also displays potent activity in primary tumor samples with low effector:target ratios. In vivo, CD20-TCB regresses established tumors of aggressive lymphoma models. Gpt enables profound B-cell depletion in peripheral blood and secondary lymphoid organs and reduces T-cell activation and cytokine release in the peripheral blood, thus increasing the safety of CD20-TCB administration. Gpt is more efficacious and safer than SUD.Conclusions: CD20-TCB and Gpt represent a potent and safer approach for treatment of lymphoma patients and are currently being evaluated in phase I, multicenter study in patients with relapsed/refractory non-Hodgkin lymphoma (NCT03075696). Clin Cancer Res; 24(19); 4785-97. ©2018 AACR See related commentary by Prakash and Diefenbach, p. 4631.

Obinutuzumab: A Review in Rituximab-Refractory or -Relapsed Follicular Lymphoma

Obinutuzumab (Gazyva^®, Gazyvaro^®) is a recombinant, monoclonal, humanized and glycoengineered, type II, anti-CD20, IgG1 antibody. It has recently been granted an additional indication for the treatment of patients with follicular lymphoma who relapsed after, or are refractory to, a rituximab-containing regimen. In the primary analysis of the large, phase III GADOLIN study, induction therapy with obinutuzumab plus bendamustine followed by obinutuzumab maintenance prolonged progression-free survival (PFS) to a statistically significant extent relative to induction with bendamustine monotherapy in patients with indolent non-Hodgkin's lymphoma (iNHL). The improvement in PFS was largely driven by the subgroup of patients with follicular lymphoma, who also had prolonged overall survival (OS) in a planned updated analysis. Obinutuzumab had a generally manageable tolerability profile in these patients; mild to moderate infusion-related reactions (IRRs) were the most common treatment-emergent adverse events (AEs) and neutropenia the most common grade 3 or 4 treatment-related AEs. Although additional studies and longer-term data are needed to further assess treatment benefits with obinutuzumab, current evidence indicates that obinutuzumab is a useful treatment option for patients with rituximab-refractory or -relapsed follicular lymphoma.

Obinutuzumab for the treatment of chronic lymphocytic leukemia and other B-cell lymphoproliferative disorders

INTRODUCTION

Chemoimmunotherapeutic regimens using the anti-CD20 antibody rituximab improved significantly the survival rates in various B-cell lymphoproliferative disorders (LPDs), including chronic lymphocytic leukemia (CLL). The next-generation CD20 antibody obinutuzumab represents an addition to the drug armamentarium used for the therapeutic management of patients with LPDs. Areas covered: Herein, the authors discuss the biochemical and conformational engineering of obinutuzumab to increase antibody-dependent cell-mediated cytotoxicity and direct cell death. They also describe the available preclinical data on obinutuzumab's role in B-cell LPDs. Furthermore, the authors summarize the Phase I and II clinical trials of obinutuzumab, focusing on the main pharmacokinetic/pharmacodynamic characteristics, the most common clinically significant adverse events, dose optimization, and clinical outcomes of patients with CLL and other B-cell LPDs treated with obinutuzumab as monotherapy or in combination with other agents. To put these data in perspective, the use of obinutuzumab is compared with that of rituximab in CLL and other B-cell LPDs. Expert opinion: Clinical trials have demonstrated that obinutuzumab is well tolerated. The novel mechanism of action of obinutuzumab is associated with significant efficacy in CLL and other B-cell LPDs. Ongoing clinical trials are expected to determine the optimal use of obinutuzumab in these diseases.

Impact of obinutuzumab alone and in combination for follicular lymphoma

Although rituximab-based chemoimmunotherapy prolongs the survival of patients with follicular lymphoma (FL), this disease is considered incurable in most patients. Thus, new therapies are needed not only for those in the relapsed/refractory setting, but also for initial treatment. Obinutuzumab (G, GA101) is a third-generation, fully humanized type II glycoengineered, anti-CD20 monoclonal antibody that results in increased direct cell death and antibody-dependent, cell-mediated cytotoxicity/phagocytosis compared to rituximab. Obinutuzumab has significant antitumor activity when used alone or in combinations in untreated or relapsed refractory FL patients. Studies have demonstrated its ability to prolong progression-free survival and, in some cases, overall survival, and to eliminate minimal residual disease. Several ongoing trials are investigating combinations with chemotherapy, immunomodulators, targeted drugs, and immunotherapy agents. G is generally well tolerated, with associated adverse effects including infusion-related reactions, neutropenia, thrombocytopenia, and reactivation of hepatitis B virus. Future studies with this antibody should focus on identifying predictive markers and developing chemotherapy-free combinations that will improve the outcome of patients with FL.

Podocalyxin promotes proliferation and survival in mature B-cell non-Hodgkin lymphoma cells

Podocalyxin (PCLP1) is a CD34-related sialomucin expressed by some normal cells and a variety of malignant tumors, including leukemia, and associated with the most aggressive cancers and poor clinical outcome. PCLP1 increases breast tumor growth, migration and invasion; however, its role in hematologic malignancies still remains undetermined. The purpose of this study was to investigate the expression and function of PCLP1 in mature B-cell lymphoma cells. We found that overexpression of PCLP1 significantly increases proliferation, cell-to-cell interaction, clonogenicity, and migration of B-cell lymphoma cells. Furthermore, PCLP1 overexpression results in higher resistance to death induced by dexamethasone, reactive oxygen species and type II anti-CD20 monoclonal antibody obinutuzumab. Strikingly, enforced expression of PCLP1 enhances lipid droplet formation as well as pentose phosphate pathway and glutamine dependence, indicative of metabolic reprogramming necessary to support the abnormal proliferation rate of tumor cells. Flow cytometry analysis revealed augmented levels of PCLP1 in malignant cells from some patients with mature B-cell lymphoma compared to their normal B-cell counterparts. In summary, our results demonstrate that PCLP1 contributes to proliferation and survival of mature B-cell lymphoma cells, suggesting that PCLP1 may promote lymphomagenesis and represents a therapeutic target for the treatment of B-cell lymphomas.

A TLR7 agonist enhances the antitumor efficacy of obinutuzumab in murine lymphoma models via NK cells and CD4 T cells

Anti-CD20 monoclonal antibodies (mAb) such as rituximab have been proven to be highly effective at improving outcome in B-cell malignancies. However, many patients ultimately relapse and become refractory to treatment. The glycoengineered anti-CD20 mAb obinutuzumab was developed to induce enhanced antibody-dependent cellular cytotoxicity, antibody-dependent phagocytosis and direct cell death and was shown to lead to improved outcomes in a randomized study in B-CLL. We hypothesized that immune stimulation through Toll-like receptor 7 (TLR7) agonism in combination with obinutuzumab would further enhance lymphoma clearance and the generation of long-term antitumor immune responses. Here we demonstrate, in syngeneic human CD20 (hCD20)-expressing models of lymphoma, that systemic administration of a TLR7 agonist (R848) increases responses when administered in combination with obinutuzumab and protects against disease recurrence. Depletion studies demonstrate that primary antitumor activity is dependent on both NK cells and CD4+ T cells but not on CD8+ T cells. However, both CD4+ and CD8+ T cells appear necessary for the generation of protective immunological memory. Importantly, increased tumor-free survival post obinutuzumab and R848 combination therapy was seen in hCD20 transgenic mice, which express hCD20 on normal B cells. These findings provide a rationale for clinical testing of obinutuzumab in combination with systemically administered TLR7 agonists to further improve outcome.

Obinutuzumab: what is there to learn from clinical trials?

Obinutuzumab (OBZ) is a recombinant type II anti-CD20 and immunoglobulin G1 Fc-optimized monoclonal antibody (mAb), recently approved in chronic lymphocytic leukemia (CLL; B-cell CLL) and follicular lymphoma (FL). Rituximab (RTX) is frequently considered as its "ancestor" and OBZ clinical development was justified by the importance of FcγRIIIA-mediated mechanisms in RTX clinical activity. However, RTX differs from OBZ in 2 critical independent properties: being a type I anti-CD20 mAb and not being Fc-optimized. Moreover, the use of a different dosing regimen for RTX and OBZ further complicates any interpretation of clinical results. The results obtained for OBZ in CLL provide new arguments for FcγRIIIA-mediated mechanisms when the target antigen is expressed at a low density. Results of OBZ in FL confirm the interest for FcγRIIIA-mediated mechanisms, with some limitations, some of them being possibly due to lack of OBZ-induced complement activation. The situation in diffuse large B-cell lymphoma is deceiving, as the possible gains of activity of OBZ appear to be annihilated by the lack of complement activation. Although RTX was by chance an anti-CD20 mAb with equilibrated pharmacodynamic properties, the reinforcement of some of these properties, which has been done at the expense of complement activation, has conferred an advantage in some B-cell disorders while restricting OBZ indications. The OBZ story nicely demonstrates that the future of naked mAbs is to design agents with optimized and tailored properties, and that this must be done step by step, with a full clinical validation.

The clinical development of obinutuzumab for the treatment of follicular lymphoma

Impressive progress has been made in recent decades for advanced-stage follicular lymphoma with the availability of anti-CD20 monoclonal antibodies, initially rituximab and more recently obinutuzumab. Obinutuzumab is a unique, third-generation, fully humanized glycoengineered IgG1 type II anti-CD20 monoclonal antibody. It has been shown to have increased antitumor activity compared to rituximab in preclinical studies, including whole-blood B-cell depletion assays, xenograft models, and primate models. This has spurred on the development of obinutuzumab through Phase I/II trials as monotherapy and in combination with chemotherapeutic agents and other targeted therapies. Its efficacy compared to rituximab and in rituximab-refractory disease has led to its continued development and eventual approval for the treatment of follicular lymphoma. Here in this review, we highlight the design and development of obinutuzumab in the treatment of advanced stage grade 1-3A follicular lymphoma and its future directions.

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.

Obinutuzumab in chronic lymphocytic leukemia: design, development and place in therapy

For decades, treatment of chronic lymphocytic leukemia (CLL) has been based on chemotherapy. This changed when the first CD20 antibody rituximab was introduced. Since 2008, the combination of chemotherapy and CD20 antibodies has become the standard of care for most patients, and a significant fraction of patients had very long-lasting remissions after chemoimmunotherapy. Despite the improvement of response rates and overall survival (OS) by the use of chemoimmunotherapy, most CLL patients will relapse eventually. One approach to achieve more durable responses was the development of obinutuzumab (GA101), a new type of CD20 antibody that has unique molecular and functional characteristics. Obinutuzumab is a type II fully humanized CD20 antibody that binds to a partly different epitope of the CD20 protein than rituximab and due to its glycoengineered design induces greater antibody-dependent cell-mediated cytotoxicity (ADCC). Initial preclinical observations of a more effective B-cell depletion have been successfully reproduced in clinical trials with CLL patients. This review summarizes results of preclinical as well as clinical studies with obinutuzumab and provides an outlook on its future role in the therapy of CLL.

Unexpected cross-reactivity of anti-cathepsin B antibodies leads to uncertainties regarding the mechanism of action of anti-CD20 monoclonal antibody GA101

GA101, also known as obinutuzumab or Gazyva (Gazyvaro), is a glycoengineered type II humanized antibody that targets the CD20 antigen expressed at the surface of B-cells. This novel anti-CD20 antibody is currently assessed in clinical trials with promising results as a single agent or as part of therapeutic combinations for the treatment of B-cell malignancies. Detailed understanding of the mechanisms of GA101-induced cell death is needed to get insight into possible resistance mechanisms occurring in patients. Although multiple in vitro and in vivo mechanisms have been suggested to describe the effects of GA101 on B-cells, currently available data are ambiguous. The aim of our study was to clarify the cellular mechanisms involved in GA101-induced cell death in vitro, and more particularly the respective roles played by lysosomal and mitochondrial membrane permeabilization. Our results confirm previous reports suggesting that GA101 triggers homotypic adhesion and caspase-independent cell death, two processes that are dependent on actin remodeling and involve the production of reactive oxygen species. With respect to lysosomal membrane permeabilization (LMP), our data suggest that lack of specificity of available antibodies directed against cathepsin B may have confounded previously published results, possibly challenging current LMP-driven model of GA101 action mode.

Safety and efficacy of obinutuzumab with CHOP or bendamustine in previously untreated follicular lymphoma

The GAUDI study assessed safety and preliminary efficacy of induction therapy with obinutuzumab plus chemotherapy, followed by maintenance therapy with obinutuzumab alone, in previously untreated patients with follicular lymphoma. Assignment to chemotherapy was decided on a per-center basis before the patients’ enrollment. Patients (n=81) received four to six cycles of obinutuzumab plus bendamustine every 4 weeks or six to eight cycles of obinutuzumab plus CHOP every 3 weeks. Patients with an end-of-treatment response were eligible for obinutuzumab maintenance therapy every 3 months for 2 years or until disease progression. Induction treatment was completed by 90% of patients in the obinutuzumab plus bendamustine group and 95% in the obinutuzumab plus CHOP group, while maintenance was completed by 81% and 72% of patients, respectively. All patients experienced at least one adverse event during induction, most commonly infusion-related reactions (58%), the majority of which were grade 1/2. The most common hematologic adverse event was grade 3/4 neutropenia (36% during induction and 7% during maintenance). One treatment-related death occurred during the maintenance phase. At the end of induction, 94% of patients had achieved an overall response, with complete response based on computed tomography in 36%. The progression-free survival rate at 36 months was 90% in the obinutuzumab plus bendamustine group and 84% in the obinutuzumab plus CHOP group. These results demonstrate that induction therapy with obinutuzumab plus bendamustine or obinutuzumab plus CHOP, followed by obinutuzumab maintenance, is associated with tolerable safety and promising efficacy. This study is registered at ClinicalTrials.gov as NCT00825149.

Anti-tumor efficacy study of the Bruton's tyrosine kinase (BTK) inhibitor, ONO/GS-4059, in combination with the glycoengineered type II anti-CD20 monoclonal antibody obinutuzumab (GA101) demonstrates superior in vivo efficacy compared to ONO/GS-4059 in combination with rituximab

The activated B-cell diffuse large B-cell-like lymphoma (ABC-DLBCL) correlates with poor prognosis. The B-cell receptor signaling pathway is known to be dysregulated in NHL/CLL and given BTK is a downstream mediator of BCR signaling, BTK constitutes an interesting and obvious therapeutic target. Given the high potency and selectivity of the BTK inhibitor, ONO/GS-4059, it was hypothesized that, the anti-tumor activity of ONO/GS-4059 could be further enhanced by combining it with the anti-CD20 Abs, rituximab (RTX) or obinutuzumab (GA101). ONO/GS-4059 combined with GA101 or RTX was significantly better than the respective monotherapy with tumor growth inhibition (TGI) of 90% for the GA101 combination and 86% for the RTX combination. In contrast, ibrutinib (PCI-32765) combined with RTX did not result in improved efficacy compared with respective monotherapy. Taken together these data indicate that the combination of ONO/GS-4059 with rituximab and particularly obinutuzumab may be an effective treatment for ABC-DLBCL.

Obinutuzumab for relapsed or refractory indolent non-Hodgkin's lymphomas

The use of anti-CD20 monoclonal antibodies (mAbs), such as rituximab, in CD20-positive B-cell malignancies has dramatically improved the outcome of chronic lymphoid leukemia and non-Hodgkin's lymphomas (NHL). However, the occurrence of relapse and development of rituximab-refractory disease highlight the need to develop novel anti-CD20 mAbs, with improved mechanisms of action. Obinutuzumab is the first humanized type II glycoengineered anti-CD20 mAb. In vitro and in vivo data suggested several differences compared with rituximab, including a low level of complement-dependent cytotoxicity and an increased direct nonapoptotic cell death. Moreover, the glycoengineered Fc-linked nonfucosylated oligosaccharide enhanced the Fc-Fcγ receptor (FcγR) IIIa interaction, resulting in improved antibody-dependent cellular cytotoxicity and phagocytosis. Preclinical models suggested that these differences translate into superior survival in murine lymphoma models. Phase I/II trials in monotherapy in relapsed or refractory B-cell NHL demonstrated that obinutuzumab has an acceptable safety profile, infusion-related reactions being the most common adverse event. In rituximab-refractory indolent NHL, the recent randomized phase III GADOLIN study demonstrated an improved median progression-free survival for patients treated with obinutuzumab plus bendamustine rather than bendamustine alone. Further trials are ongoing to determine the role of obinutuzumab as a first-line agent in the treatment of follicular lymphoma.

Treating chronic lymphocytic leukemia with obinutuzumab: safety and efficacy considerations

INTRODUCTION

Obinutuzumab is a novel glycoengineered type II anti-CD20 monoclonal antibody (MoAb) with a higher affinity for CD20 epitope. It was approved by the United States Food and Drug Administration (FDA) in November 2013 for use in combination with chlorambucil for previously untreated chronic lymphocytic leukemia (CLL).

AREAS COVERED

This article evaluates the safety of obinutuzumab in CLL patients, also addressing pharmacokinetics/pharmacodynamics (PK/PD), clinical use and efficacy. Moreover, a comparison with other anti-CD20 MoAb is performed. The principal available studies on obinutuzumab are reviewed, focusing on CLL. A PubMed literature search (August 2002 to September 2015) was conducted using the terms obinutuzumab, GA101, anti-CD20 antibody, and CLL.

EXPERT OPINION

Obinutuzumab, a third-generation anti-CD20 MoAb, is a safe and effective treatment for elderly patients who are un-fit for fludarabine-based regimen. Its use, proven in the CLL11 study and the results of many ongoing trials evaluating other obinutuzumab-based regimen can lead obinutuzumab to be a candidate to replace rituximab as the first-line treatment option.

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.

Construction and characterization of an anti-CD20 mAb nanocomb with exceptionally excellent lymphoma-suppressing activity

The CD20-directed monoclonal antibody rituximab (RTX) established a new era in the treatment of non-Hodgkin lymphoma (NHL); however, suboptimal response and/or resistance to RTX still limit its clinical merits. Although four effector mechanisms are validated to participate in CD20-based immunotherapy, including complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, caspase-dependent apoptosis, and lysosome-mediated programmed cell death (PCD), they could hardly be synchronously activated by any anti-CD20 mAb or mAb derivative until now. Herein, a novel mAb nanocomb (polyethylenimine polymer–RTX–tositumomab [PPRT nanocomb]) was firstly constructed through mass arming two different anti-CD20 mAbs (RTX and tositumomab) to one polymer by nanotechnology. Comparing with free mAbs, PPRT nanocomb possesses a comparable binding ability and reduced “off-rate” to surface CD20 of NHL cells. When treated by PPRT nanocomb, the caspase-dependent apoptosis was remarkably enhanced except for concurrently eliciting complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity, and lysosome-mediated PCD. Besides, “cross-cell link”-assisted homotypic adhesion by PPRT nanocomb further enhanced the susceptibility to PCD of lymphoma cells. Pharmacokinetic assays revealed that PPRT nanocomb experienced a relatively reduced clearance from peripheral blood compared with free antibodies. With the cooperation of all the abovementioned superiorities, PPRT nanocomb exhibits exceptionally excellent in vivo antitumor activities in both disseminated and localized human NHL xenotransplant models.

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.

Special Conference on Tumor Immunology and Immunotherapy: A New Chapter

The overall objective of the fifth American Association for Cancer Research Special Conference, "Tumor Immunology and Immunotherapy: A New Chapter," organized by the Cancer Immunology Working Group, was to highlight multidisciplinary approaches of immunotherapy and mechanisms related to the ability of immunotherapy to fight established tumors. With the FDA approval of sipuleucel-T, ipilimumab (anti-CTLA-4; Bristol-Myers Squibb), and the two anti-PD-1 antibodies, pembrolizumab (formerly MK-3475 or lambrolizumab; Merck) and nivolumab (Bristol-Myers Squibb), immunotherapy has become a mainstream treatment option for some cancers. Many of the data presented at the conference and reviewed in this article showcase the progress made in determining the mechanistic reasons for the success of some treatments and the mechanisms associated with tolerance within the tumor microenvironment, both of which are potential targets for immunotherapy. In addition to combination and multimodal therapies, improvements in existing therapies will be needed to overcome the numerous ways that tumor-specific tolerance thwarts the immune system. This conference built upon the success of the 2012 conference and focused on seven progressing and/or emerging areas-new combination therapies, combination therapies and vaccine improvement, mechanisms of antibody therapy, factors in the tumor microenvironment affecting the immune response, the microbiomes effect on cancer and immunotherapy, metabolism in immunotherapy, and adoptive T-cell therapy. Cancer Immunol Res; 3(6); 1-8. ©2015 AACR.

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.

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.

Type II anti-CD20 mAb-induced lysosome mediated cell death is mediated through a ceramide-dependent pathway

In the past decade, monoclonal antibodies (mAbs) have revolutionized the treatment of non-Hodgkin lymphomas (NHLs). Although Fc-dependent mechanisms of mAb-mediated tumor clearance have been extensively studied, the ability of mAbs to directly evoke programmed cell death (PCD) and the underlying mechanisms involved remain unclear. It is well established that type II anti-CD20 mAb (Tositumomab) potently evoked PCD through a caspases-independent, lysosome-mediated process, which is related to homotypic adhesion (HA) in NHL cell lines. Herein, we reveal that the induction of ceramide generation by anti-CD20 mAbs directly correlates with their ability to induce PCD. The inhibition of ceramide abrogated Tositumomab-induced PCD indicating that ceramide is required for the execution of cell death. Further experimental results revealed that ceramide was generated downstream of mAb-induced HA and upstream of lysosome leakage. These findings provide further insights into a previously unrecognized role for ceramide generation in mediating PCD evoked by type II anti-CD20 mAbs in Burkitt's lymphoma cells. This newly characterized cell death pathway may potentially be exploited to eliminate malignant cells.

Targeted treatment for chronic lymphocytic leukemia: clinical potential of obinutuzumab

Introduction of targeted agents revolutionized the treatment of chronic lymphocytic leukemia (CLL) in the past decade. Addition of chimeric monoclonal anti-CD20 antibody rituximab to chemotherapy significantly improved efficacy including overall survival (OS) in untreated fit patients; humanized anti-CD52 antibody alemtuzumab and fully human anti-CD20 antibody ofatumumab lead to improvement in refractory disease. Novel small molecule inhibitors such as ibrutinib and idelalisib demonstrated excellent activity and were very recently licensed in relapsed/refractory CLL. Obinutuzumab (GA101) is the newest monoclonal antibody approved for the treatment of CLL. This novel, glycoengineered, type II humanized anti-CD20 antibody is characterized by enhanced antibody-dependent cellular cytotoxicity and direct induction of cell death compared to type I antibodies. Combination of obinutuzumab and chlorambucil yielded significantly better OS in comparison to chlorambucil monotherapy in untreated comorbid patients. These results led to approval of obinuzutumab for the treatment of CLL. Numerous clinical trials combining obinutuzumab with other cytotoxic drugs and novel small molecules are currently under way. This review focuses on the role of obinutuzumab in the treatment of CLL.

Ceramide participates in lysosome-mediated cell death induced by type II anti-CD20 monoclonal antibodies

Considering the variable and often modest therapeutic efficacy of rituximab for a substantial proportion of patients suffering from non-Hodgkin lymphomas (NHLs), various type II anti-CD20 monoclonal antibodies (mAbs) with excellent ability in inducing programmed cell death (PCD) are currently being developed for their enhanced therapeutic index. Although homotypic adhesion (HA) and lysosome leakage are proven to be of vital importance in type II mAb-induced PCD in NHL cells, the detailed relationship between them remains unclear. Herein, for the first time we discovered that improved intracellular ceramide level is an important mediator between HA and lysosome leakage in tositumomab-induced cell death. Further experimental results revealed that the generation of intracellular ceramide acts as the outcome of HA and major cause of lysosome leakage. The clarification of ceramide involvement in type II anti-CD20 mAb-induced PCD may provide new ideas on CD20-based immunotherapy against NHLs.