Multicenter phase II trial of immunotherapy with the humanized anti-CD22 antibody, epratuzumab, in combination with rituximab, in refractory or recurrent non-Hodgkin's lymphoma

A high-throughput lysosome trafficking assay guides ligand selection and elucidates differences in CD22-targeted nanodelivery

Targeted nanoparticles offer potential to selectively deliver therapeutics to cells; however, their subcellular fate following endocytosis must be understood to properly design mechanisms of drug release. Here we describe a nanoparticle platform and associated cell-based assay to observe lysosome trafficking of targeted nanoparticles in live cells. The nanoparticle platform utilizes two fluorescent dyes loaded onto PEG-poly(glutamic acid) and PEG-poly(Lysine) block co-polymers that also comprise azide reactive handles on PEG termini to attach antibody-based targeting ligands. Fluorophores were selected to be pH-sensitive (pHrodo Red) or pH-insensitive (Alexafluor 488) to report when nanoparticles enter low pH lysosomes. Dye-labelled block co-polymers were further assembled into polyion complex micelle nanoparticles and crosslinked through amide bond formation to form stable nano-scaffolds for ligand attachment. Cell binding and lysosome trafficking was determined in live cells by fluorescence imaging in 96-well plates and quantification of red- and green-fluorescence signals over time. The platform and assay was validated for selection of optimal antibody-derived targeting ligands directed towards CD22 for nanoparticle delivery. Kinetic analysis of uptake and lysosome trafficking indicated differences between ligand types and the ligand with the highest lysosome trafficking efficiency translated into effective DNA delivery with nanoparticles bearing the optimal ligand.

Identification of Immuno-Targeted Combination Therapies Using Explanatory Subgroup Discovery for Cancer Patients with EGFR Wild-Type Gene

(1) Background: Phenotypic and genotypic heterogeneity are characteristic features of cancer patients. To tackle patients’ heterogeneity, immune checkpoint inhibitors (ICIs) represent some the most promising therapeutic approaches. However, approximately 50% of cancer patients that are eligible for treatment with ICIs do not respond well, especially patients with no targetable mutations. Over the years, multiple patient stratification techniques have been developed to identify homogenous patient subgroups, although matching a patient subgroup to a treatment option that can improve patients’ health outcomes remains a challenging task. (2) Methods: We extended our Subgroup Discovery algorithm to identify patient subpopulations that could potentially benefit from immuno-targeted combination therapies in four cancer types: head and neck squamous carcinoma (HNSC), lung adenocarcinoma (LUAD), lung squamous carcinoma (LUSC), and skin cutaneous melanoma (SKCM). We employed the proportional odds model to identify significant drug targets and the corresponding compounds that increased the likelihood of stable disease versus progressive disease in cancer patients with the EGFR wild-type (WT) gene. (3) Results: Our pipeline identified six significant drug targets and thirteen specific compounds for cancer patients with the EGFR WT gene. Three out of six drug targets—FCGR2B, IGF1R, and KIT—substantially increased the odds of having stable disease versus progressive disease. Progression-free survival (PFS) of more than 6 months was a common feature among the investigated subgroups. (4) Conclusions: Our approach could help to better select responders for immuno-targeted combination therapies and improve health outcomes for cancer patients with no targetable mutations.

Immuno-PET Imaging and Radioimmunotherapy of Lymphomas

Monoclonal antibodies (Ab) have revolutionized the management of lymphomas, the most common hematologic malignancy in adults. Indeed, incorporation of rituximab into the regimen for indolent non-Hodgkin's lymphomas (NHLs) has dramatically improved treatment response and disease outcome. Yet, newer Ab therapeutics against promising antigen targets need to be developed to treat refractory or relapsed patients. Treatment efficacy can be further enhanced by conjugating toxic molecules to the Abs. Radioimmunotherapy (RIT) harnesses Abs as vehicles for targeted delivery of therapeutic radionuclide payloads for direct killing of targeted tumor cells. Positron emission tomography (PET) with radiolabeled Abs (called immuno-PET) can facilitate the development of new Ab therapeutics and RIT by providing pharmacokinetic and pharmacodynamic information and by quantifying tumor antigen level relevant for treatment decision. Immuno-PET has recently gravitated toward labeling Abs with ⁸⁹Zr, a radiometal with a 3.3 day half-life that is trapped following Ab internalization and thus provides high-resolution PET images with excellent contrast. Immuno-PET methods against major lymphoma antigens including CD20 and other promising targets are currently under development. With continued improvements, immuno-PET has the potential to be used in lymphoma management as an imaging biomarker for patient selection and assessment of treatment response.

Current and emerging monoclonal antibodies, antibody-drug conjugates, and bispecific antibodies in treatment of lymphoma

The improvement in outcomes seen with the introduction of rituximab, a CD20 monoclonal antibody in combination with chemotherapy or as a single agent in the treatment of indolent non-Hodgkin lymphomas has paved the way for development of various forms of monoclonal antibodies that act in different ways against non-Hodgkin lymphoma tumor cells. These could directly target a single surface antigen resulting in various ways of tumor cells toxicity and killing. Other forms of monoclonal antibodies include antibody-drug conjugates and bispecific antibodies. The role of therapeutic monoclonal antibodies in the treatment of lymphoma will be reviewed, highlighting their mode of action, clinical efficacy, and side effects.

Role of antibody-based therapy in indolent non-Hodgkin's lymphoma

Monoclonal antibodies (mAb) for indolent non-Hodgkin's lymphoma (iNHL) including follicular and marginal zone lymphomas was a key therapeutic development that changed the natural history of these diseases. Rituximab, a chimeric anti-CD20 mAb, was the first immunotherapy ever used in cancer, and a current cornerstone of lymphoma therapies. Since, we saw development of humanized antibodies, next generations anti-CD20, mAbs targeting other markers on tumor cells (CD19 and CD22), its microenvironment (PD-1, CD47), antibody drug conjugates and bispecific T cell engagers. Given their activity, safety and specificity, mAbs are well poised to remain an essential therapeutic tool for iNHL and other malignancies.

Improving Biologics' Effectiveness in Clinical Oncology: From the Combination of Two Monoclonal Antibodies to Oligoclonal Antibody Mixtures

Simple Summary

The approval of the two antibody combinations trastuzumab/pertuzumab and ipilimumab/nivolumab in oncology has paved the way for novel antibody combinations or oligoclonal antibody mixtures to improve their efficacy in cancer. The underlying biological mechanisms and challenges of these strategies will be discussed using data from clinical trials listed in databases. These therapeutic combinations also lead to questions on how to optimize their formulation and delivery to induce a therapeutic polyclonal response in patients with cancer.

Abstract

Monoclonal antibodies have revolutionized the treatment of many diseases, but their clinical efficacy remains limited in some other cases. Pre-clinical and clinical trials have shown that combinations of antibodies that bind to the same target (homo-combinations) or to different targets (hetero-combinations) to mimic the polyclonal humoral immune response improve their therapeutic effects in cancer. The approval of the trastuzumab/pertuzumab combination for breast cancer and then of the ipilimumab/nivolumab combination for melanoma opened the way to novel antibody combinations or oligoclonal antibody mixtures as more effective biologics for cancer management. We found more than 300 phase II/III clinical trials on antibody combinations, with/without chemotherapy, radiotherapy, small molecules or vaccines, in the ClinicalTrials.gov database. Such combinations enhance the biological responses and bypass the resistance mechanisms observed with antibody monotherapy. Usually, such antibody combinations are administered sequentially as separate formulations. Combined formulations have also been developed in which separately produced antibodies are mixed before administration or are produced simultaneously in a single cell line or a single batch of different cell lines as a polyclonal master cell bank. The regulation, toxicity and injection sequence of these oligoclonal antibody mixtures still need to be addressed in order to optimize their delivery and their therapeutic effects.

Targeting CD22 for the Treatment of B-Cell Malignancies

Immunotherapeutic agents play an increasingly important role in the treatment of B-cell malignancies. CD19 and CD20 are common targets for lymphoid malignancies, though patients who relapse have few therapeutic options remaining. CD22 is a cell surface sialoglycoprotein uniquely present on B-cells and regulates B-cell function and proliferation. Thus, it is an appealing therapeutic target for autoimmune disorders and B-cell malignancies. A variety of therapies targeting CD22 have been developed, including monoclonal antibodies, antibody-drug conjugates, radioimmunoconjugates, chimeric antigen receptor T cells, and bispecific antibodies. Here, we review the biology of CD22 and key therapies targeting CD22 in lymphoid malignancies.

[Mimicking polyclonal immune response in therapy: from combination of two monoclonal antibodies to oligoclonal antibody-based mixtures]

Monoclonal antibodies have revolutionized the treatment of many diseases, but their clinical effectiveness remains limited in some cases. Associations of antibodies binding to the same target (homo-combination) or to several different targets (hetero-combination), thereby mimicking a polyclonal humoral immune response, have demonstrated a therapeutic improvement in pre-clinical and clinical trials, mainly in the field of oncology and infectious diseases. The combinations increase the efficacy of the biological responses and override resistance mechanisms observed with antibody monotherapy. The most common method of formulating and administering antibody combinations is a separate formulation, with sequential injection of each antibody as individual drug substance. Alternatively, combined formulations are developed where the separately-produced antibodies are mixed before administration or produced simultaneously by a single cell line, or a mixture of cell lines as a polyclonal master cell bank. The regulation, the toxicity and the injection sequence of these oligoclonal antibody-based mixtures remain points to be clarified and optimized for a better therapeutic effect.

Anti-CD22 epratuzumab for systemic lupus erythematosus: A systematic review and meta-analysis of randomized controlled trials

Systemic lupus erythematosus (SLE) is a remarkable and challenging autoimmune disorder that is characterized by a broad range of clinical manifestations, such as flares and remissions. Recently, the humanized anti-CD22 antibody epratuzumab for SLE has been extensively studied. The aim of the present study was to perform a meta-analysis on the findings of associated randomized controlled trials in order to evaluate the effects of epratuzumab on SLE. Data from publications in PubMed, EMBASE and the Cochrane Library were collected up to March 2017. To calculate the risk ratio or standardized mean differences (SMDs) with 95% confidence intervals (CIs), a random effect model was applied when heterogeneity was significant and a fixed effect model was used when heterogeneity was negligible. All statistical tests were performed using Review Manager 5.3 software. A total of 1,921 participants in 4 studies (5 trials) that met the selection criteria were analyzed in this meta-analysis. Analyses of the BILAG-based Combined Lupus Assessment (BICLA) response and SLE Disease Activity Index 2000 (SLEDA-2K) score revealed that epratuzumab (720-3,600 mg) significantly improved the BICLA response (RR=1.09; 95% CI, 1.04 to 1.14) and decreased the SLEDA-2K score (SMD=-0.31; 95% CI, -0.67 to 0.06; P=0.10). While the British Isles Lupus Assessment Group index score was not significantly altered between the epratuzumab and control groups. For safety analyses, no statistically significant differences were identified between the two groups, which were proved by the pooled results (all P-values >0.05). These findings suggested that epratuzumab may be relatively safe and may have better therapeutic effectiveness than placebo control conditions in patients with SLE.

Epratuzumab for the treatment of systemic lupus erythematosus

INTRODUCTION

Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease. There are three drugs licensed for the treatment of lupus: corticosteroids, hydroxychloroquine and belimumab. Immunosuppressants such as azathioprine, methotrexate and mycophenolate are also used. Despite these treatments there is still considerable morbidity. New treatments are needed for the management of active lupus. Epratuzumab a humanized IgG1 monoclonal antibody that targets CD22 resulting in selective B cell modulation that has been considered a potential treatment for SLE. Areas covered: Summary of the relevant pathogenesis and disease activity measurements used in SLE patients, current treatments and unmet needs in SLE, pharmacokinetics and pharmacodynamics of epratuzumab therapy, and a summary of the 7 clinical trials that have investigated the efficacy and safety of epratuzumab in SLE. Expert commentary: It is not clear why trials have failed to demonstrate efficacy but high placebo response rates from optimisation of standard of care and a sub-optimal dosing regimen may have played a role. Post-hoc analysis suggested that there may be subgroups that did respond, such as anti-SSA positive patients with features of Sjogren's syndrome. Further research is needed to explore this and other potential sub-groups that might respond.

Novel agents in follicular lymphoma: choosing the best target

Outcomes in patients with follicular lymphoma (FL) have improved dramatically over the last decade. However, novel agents are greatly needed for those who exhibit treatment resistance, in order to minimize lifelong toxicity and to enable combinations that may allow us to achieve the elusive goal of cure. Biological advances have led to the discovery of a large number of potential therapeutic targets and the development of a plethora of novel agents designed to exploit these processes. Possible targets include tumor cell surface markers, key components of intracellular pathways and epigenetic mechanisms, and reactive cells of the microenvironment. Given the large number of candidate drugs and potential combinations, it will be crucial to prioritize evaluation based on sound preclinical and early clinical studies. Combinations that exploit driver mechanisms within tumor cells and target parallel pathways to minimize the development of drug resistance, as well as harness the potential of the immune system would seem most logical. In order to expedite progress, future studies will need to use innovative trial designs and employ surrogate end points. The development of validated prognostic tools to identify higher risk patients and reliable predictive markers to select subgroups most likely to benefit from targeted agents will be paramount. The potential for unexpected toxicity with novel combinations must be recognized, necessitating both short- and long-term vigilance. Finally, as a greater number of treatment options become available, optimal sequencing must be determined in order to both prolong life and maintain its quality.

The use of combinations of monoclonal antibodies in clinical oncology

Treatment with monoclonal antibodies is becoming increasingly important in clinical oncology. These antibodies specifically inhibit signaling pathways in tumor growth and/or induce immunological responses against tumor cells. By combining monoclonal antibodies several pathways may be targeted simultaneously, potentially leading to additive or synergistic effects. Theoretically, antibodies are very suitable for use in combination therapy, because of limited overlapping toxicity and lack of pharmacokinetic interactions. In this article an overview is given of preclinical and clinical data on twenty-five different combinations of antibodies in oncology. Some of these combinations have proven clinical benefit, for example the combination of trastuzumab and pertuzumab in HER2-positive breast cancer, which exemplifies an additive or synergistic effect on antitumor activity in clinical studies and the combination of nivolumab and ipilimumab, which results in significant increases in progression-free and overall survival in patients with advanced melanoma. However, other combinations may lead to unfavorable results, such as bevacizumab with cetuximab or panitumumab in advanced colorectal cancer. These combinations result in shorter progression-free survival and increased toxicity compared to therapy with a single antibody. In summary, the different published studies showed widely varying results, depending on the combination of antibodies, indication and patient population. More preclinical and clinical studies are necessary to unravel the mechanisms behind synergistic or antagonistic effects of combining monoclonal antibodies. Most research on combination therapies is still in an early stage, but it is expected that for several tumor types the use of combination therapy of antibodies will become standard of care in the near future.

Novel Targeted Agents in Hodgkin and Non-Hodgkin Lymphoma Therapy

There has been a recent emergence of novel targeted agents for treatment of Hodgkin and non-Hodgkin lymphoma. In particular, antibodies and antibody-drug conjugates directed against surface antigens, agents that block immune checkpoint pathways, and small molecule inhibitors directed against cell signaling pathways have shown significant promise in patients with relapsed and refractory disease and in the frontline setting. With the development of these new therapies, cytotoxic chemotherapy may be avoided entirely in some clinical settings. This review will present the latest information on these novel treatments in Hodgkin and non-Hodgkin lymphoma and will discuss both recently approved agents as well as drugs currently being studied in clinical trials.

Development of a Trispecific Antibody Designed to Simultaneously and Efficiently Target Three Different Antigens on Tumor Cells

Targeting Eph (erythropoietin producing hepatoma) receptors with monoclonal antibodies is being explored as therapy for several types of cancer. To test whether simultaneous targeting of EphA2, EphA4, and EphB4 would be an effective approach to cancer therapy, we generated a recombinant trispecific antibody using the variable domain genes of anti-EphA2, anti-EphA4, and anti-EphB4 monoclonal antibodies. A multidisciplinary approach combining biochemical, biophysical, and cellular-based assays was used to characterize the trispecific antibody in vitro and in vivo. Here we demonstrate that the trispecific antibody is expressed at high levels by mammalian cells, monodispersed in solution, thermostable, capable of simultaneously binding the three receptors, and able to activate the three targets effectively as evidenced by receptor internalization and degradation both in vitro and in vivo. Furthermore, pharmacokinetic analysis using tumor-bearing nude mice showed that the trispecific antibody remains in the circulation similarly to its respective parental antibodies. These results indicate that simultaneous blockade of EphA2, EphA4, and EphB4 could be an attractive approach to cancer therapy.

Investigational therapies targeting lymphocyte antigens for the treatment of non-Hodgkin's lymphoma

INTRODUCTION

The advent of the anti-CD20 mAb rituximab has opened a new era in the treatment of non-Hodgkin's lymphomas (NHL), markedly altering standard treatment strategies. Moreover, the proof-of-concept that targeting a specific lymphocyte surface antigen may induce a highly effective and safe targeted killing of malignant cells has opened the door to the development of a plethora of novel mAbs directed towards different B- and T-cell-specific antigens.

AREAS COVERED

This review discusses the recent available clinical data about new-generation anti-CD20 mAbs characterized by increased antibody- (obinutuzumab) or complement-dependent cyotoxicity (ofatumumab) as well as novel investigational agents targeting other lymphocyte antigens (e.g., CD19, CD22, CD30, CD40, CD52, CCR4), which are currently under investigation for B- and T-cell NHL treatment. In addition, antibody-drug conjugates (inotuzumab ozogamicin, brentuximab vedotin, polatuzumab vedotin), bispecific T-cell engagers (blinatumomab) and a new class of antibodies targeting cytotoxic T-lymphocyte-associated antigen 4, programmed death 1 or programmed death ligand 1 (immune checkpoint inhibitors) are specifically considered.

EXPERT OPINION

Among the novel mAbs challenging rituximab, obinutuzumab seems to be in the most advanced phase, with the results of randomized trials awaited shortly. Brentuximab vedotin is increasing its role in T-cell NHL. Furthermore, immune checkpoint inhibitors have the potential to acquire a great relevance in NHL therapy.

The combination of milatuzumab, a humanized anti-CD74 antibody, and veltuzumab, a humanized anti-CD20 antibody, demonstrates activity in patients with relapsed and refractory B-cell non-Hodgkin lymphoma

As a result of the anti-tumour activity observed in vitro and in vivo with combined anti-CD20 and anti-CD74 antibodies, we initiated a phase I/II trial of veltuzumab and milatuzumab in patients with relapsed or refractory B-cell non-Hodgkin lymphoma (NHL). Patients received an induction of veltuzumab 200 mg/m(2) weekly combined with escalating doses of milatuzumab at 8, 16 and 20 mg/kg weekly for 4 weeks. Patients without disease progression could receive an extended induction with treatment on weeks 12, 20, 28 and 36. A total of 35 patients enrolled on the study. Median age was 63 years, median number of prior therapies was 3, and 63% of patients were rituximab refractory. No dose-limiting toxicities were observed in the phase I study. Related grade 3-4 toxicities included lymphopenia, leucopenia, neutropenia, anaemia, infusion reactions, hyperglycaemia, fatigue and atrial tachycardia. Median weeks of therapy was 12 and 29% of patients completed all 36 weeks of therapy. The overall response rate was 24%, median duration of response was 12 months, and responses were observed at all dose levels and in 50% of patients refractory to rituximab. Combination therapy with veltuzumab and milatuzumab demonstrated activity in a population of heavily pre-treated patients with relapsed or refractory indolent NHL.

Chemotherapy-free treatment in patients with follicular lymphoma

The outcome of patients with follicular lymphoma (FL) has improved over the last two decades through the introduction of anti-CD20 monoclonal antibodies, usually used in combination with chemotherapy. However, patients with FL still experience multiple relapses, requiring several lines of treatment. Early toxicity of chemotherapy is a significant concern and as the life expectancy of patients with FL is increasing, late toxicities become an increasingly important concern. Progress made in understanding the biology of FL, especially dysregulation of intracellular pathways and immunological antitumor responses, recently allowed for the development of innovative chemo-free therapeutic approaches. In this report, different options such as new anti-CD20 antibodies, antibodies targeting other cell surface antigens, bi-specific antibodies, immunomodulation, idiotype vaccine and other targeted therapies are presented. The article also highlights how, although promising in early phase studies, the cost-effectiveness of new agents will have to be justified in Phase III trials. Furthermore, chemo-free regimen might not mean toxicity-free treatment and monitoring of early and late toxicities is required.

Target Therapy in Hematological Malignances: New Monoclonal Antibodies

Apart from radio- and chemotherapy, monoclonal antibodies (MoAbs) represent a new, more selective tool in the treatment of hematological malignancies. MoAbs bind with the specific antigens of the tumors. This interaction is a basis for targeted therapies which exhibit few side effects and significant antitumor activity. This review provides an overview of the functional characteristics of MoAbs, with some examples of their clinical application. The promising results in the treatment of hematological malignancies have led to the more frequent usage of MoAbs in the therapy. Development of MoAbs is a subject of extensive research. They are a promising method of cancer treatment in the future.

New antibody approaches to lymphoma therapy

The CD20-directed monoclonal antibody rituximab established a new era in lymphoma therapy. Since then other epitopes on the lymphoma surface have been identified as potential targets for monoclonal antibodies (mAb). While most mAbs eliminate lymphoma cells mainly by antibody-dependent cellular cytotoxicity, complement-dependent cytotoxicity or direct cell death, others counter mechanisms utilized by malignant cells to evade immune surveillance. Expression of PD-L1 on malignant or stromal cells in the tumor environment for example leads to T-cell anergy. Targeting either PD-1 or PD-L1 via mAbs can indirectly eliminate cancer cells by unblocking the host intrinsic immune response. Yet another mechanism of targeted therapy with mAbs are bi-specific T-cell engagers (BiTE) such as blinatumomab, which directly engages the host immune cells. These examples highlight the broad spectrum of available therapies targeting the lymphoma surface with mAbs utilizing both passive and active immune pathways. Many of these agents have already demonstrated significant activity in clinical trials. In this review we will focus on novel CD20-directed antibodies as well as mAbs directed against newer targets like CD19, CD22, CD40, CD52 and CCR4. In addition we will review mAbs unblocking immune checkpoints and the BiTE blinatumomab. Given the success of mAbs and the expansion in active and passive immunotherapies, these agents will play an increasing role in the treatment of lymphomas.

Clinical and economic aspects of the use of rituximab in non-Hodgkin's lymphoma

Non-Hodgkin's lymphoma (NHL) consists of a group of neoplasias involving mainly B cells and represents 90% of all lymphomas. The current available therapy is based on chemotherapy associated with the monoclonal antibody rituximab (Mab Thera(r)), which targets the CD20 protein, present in over 80% of NHL mature B cells. Recent clinical reports show a preference for combining the benefits of immunotherapy and adjuvant chemotherapy, thus generating safe and effective alternative treatments. The current review aimed at evaluating various aspects related to the use of rituximab for NHL, highlighting the possible inhibitory mechanisms of cell proliferation, the achieved clinical results, and the expected clinical and economic outcomes of treatments. The results from clinical tests indicate the need for a better understanding of the critical mechanisms of action of this antibody, which may maximize its therapeutic efficacy. This therapy not only represents a viable option to treat most types of NHLs, especially when associated with conventional chemotherapy, but also offers cost-utility and cost-effectiveness advantages.

Management of relapsed-refractory diffuse large B cell lymphoma

Relapsed-Refractory Diffuse Large B Cell Lymphoma (RR DLBCL), which accounts for approximately one-third of patients with DLBCL, remains a major cause of morbidity and mortality. Managing RR DLBCL continues to be a challenge to the treating hemato-oncologist. Salvage high-dose chemotherapy followed by autologous stem cell transplantation is the standard of care for chemosensitive relapses in DLBCL. Various salvage regimens are available, but the quest for an optimal regimen continues. The addition of rituximab to the salvage regimen has improved the outcome of RR DLBCL. Several pertinent issues regarding the management of RR DLBCL are discussed in this short review.

Clinical efficacy and safety in relapsed/refractory diffuse large B-cell lymphoma: a systematic literature review

This systematic literature review was designed to assess information on the clinical efficacy and safety of interventions used in the treatment of refractory or relapsed diffuse large B-cell lymphoma (R/R DLBCL) and to perform a meta-analysis if possible. We searched databases (PubMed, EMBASE, and Cochrane Library for articles from 1997 to August 2, 2012 reported in English), conference abstracts, bibliographic reference lists, and the ClinicalTrials.gov database for phase II to IV studies with results. Studies had to report on patients with R/R DLBCL who were not eligible to receive high-dose therapy (HDT) with stem cell transplantation (SCT) (autologous or allogeneic). Mixed-type non-Hodgkin lymphoma (NHL) studies were required to report R/R DLBCL outcomes separately. We identified 55 studies that presented outcomes data separately for patients with R/R DLBCL. Of 7 comparative studies, only 4 were randomized controlled trials (RCTs). In the 2 RCTs with a common regimen, the patient populations differed too greatly to perform a valid meta-analysis. The 48 single-arm studies identified were typically small (n < 50 in most), with 31% reporting median progression-free survival (PFS) or overall survival (OS) specifically for the R/R DLBCL population. In these studies, median OS ranged from 4 to 13 months. The small number of RCTs in R/R DLBCL precludes identifying optimal treatments. Small sample size, infrequent reporting of OS and PFS separated by histologic type, and limited information on patient characteristics also hinder comparison of results. Randomized studies are needed to demonstrate which current therapies have advantages for improving survival and other important clinical outcomes in patients with R/R DLBCL.

How we manage follicular lymphoma

Major changes have taken place within the last few years in the management of follicular lymphoma (FL) leading to substantial improvement in prognosis and overall survival. For some patients with limited disease stages I and II, radiotherapy may be associated with durable responses; however, it is unclear whether patients are cured and new approaches such as the combination of irradiation with rituximab or even single-agent rituximab need to be explored. Whereas watch and wait is the current standard for stage III and IV disease with low tumour burden, better indices are warranted to potentially select patients for whom early intervention is preferred. For advanced stages with a high tumour burden, immunochemotherapy followed by 2 years of rituximab maintenance is widely accepted as standard therapy, although re-treatment at recurrence may be an alternative option. Highly attractive new therapeutic options have recently arisen from new antibodies, and from new agents targeting oncogenic pathways such as B-cell receptor signalling pathways or inhibition of bcl 2. Furthermore, immunomodulatory drugs may add to the therapeutic armamentarium and may lead to 'chemotherapy-free' therapies in the near future. Hence, the management of FLs has become a moving target and the hope is justified that the long-term perspectives of patients suffering from the disease will be further improved in the near future.

Targeting CD22 in B-cell malignancies: current status and clinical outlook

CD22 is a B-cell-specific transmembrane glycoprotein found on the surface of most B cells; it modulates B-cell function, survival and apoptosis. CD22 has emerged as an ideal target for monoclonal antibody (mAb)-based therapy of B-cell malignancies including most lymphomas and many leukemias. Epratuzumab, an anti-CD22 mAb, has been developed in various forms, including as an unlabeled (naked) mAb, as a radioimmunotherapeutic, as an antibody drug conjugate (ADC), and as a vehicle for CD22-targeted nanoparticles. While clinical trials with unlabeled epratuzumab have demonstrated modest results, its combination with rituximab in phase II studies has been more encouraging. Based on the potential for CD22 to become internalized, CD22-targeted constructs carrying radioisotopes or toxins have generated promising results. Radioimmunotherapy, utilizing ⁹⁰Y-labeled epratuzumab, was shown to be highly effective in patients with follicular lymphoma, generating a complete response (CR) rate of 92 % and progression-free survival of more than 2 years. ADC therapy is a promising therapeutic approach to B-cell malignancies which includes the direct conjugation of mAbs with cytotoxic agents. Phase II studies of inotuzumab ozogamicin, an ADC which combines anti-CD22 mAb with calicheamicin, an enediyne antibiotic which mediates apoptosis, in patients with acute lymphoblastic leukemia have produced an overall response rate (ORR) of greater than 50 % in treatment-refractory patients. Phase I trials of moxetumomab pasudotox, an ADC which combines anti-CD22 with PE38, a fragment of Pseudomonas exotoxin A, have been completed in hairy cell leukemia with a ORR of 86 %. Finally, a review of CD22-targeted nanoparticles, that include a doxorubicin-containing lipid complex that uses synthetic high-affinity CD22 ligand mimetics as well as anti-CD22 mAb-coated pegylated liposomas doxorubin (PLD), has demonstrated promising results in pre-clinical models of human lymphoma. Moreover, novel anti-CD22 mAb that block CD22 ligand binding as well as second generation ADC that utilize biodegradable linkers and more potent toxins hold great hope for the future of CD22-targeted therapeutics that may translate into better outcomes for patients with CD22-positive malignancies.

Novel targeted drug therapies for the treatment of childhood acute leukemia

The cure rates for childhood acute leukemia have dramatically improved to approximately 70% overal, with treatments that include intensive cytotoxic chemotherapy and, in some cases, hematopoietic stem cell transplantation. However, many children still die of their disease or of treatment-related toxicities. Even in patients that are cured, there can be significant and, not uncommonly debilitating, acute and late complications of treatment. Improved understanding of the molecular and cellular biology of leukemia and the increasing availability of high-throughput genomic techniques have facilitated the development of molecularly targeted therapies that have the potential to be more effective and less toxic than the standard approaches. In this article, we review the progress to date with agents that are showing promise in the treatment of childhood acute leukemia, including monoclonal antibodies, inhibitors of kinases and other signaling molecules (e.g., BCR-ABL, FLT3, farnesyltransferase, mTOR and γ-secretase), agents that target epigenetic regulation of gene expression (DNA methyltransferase inhibitors and histone deacetylase inhibitors) and proteasome inhibitors. For the specific agents in each of these classes, we summarize the published preclinical data and the clinical trials that have been completed, are in progress or are being planned for children with acute leukemia. Finally, we discuss potential challenges to the success of molecularly targeted therapy, including proper target identification, adequate targeting of leukemia stem cells, developing synergistic and tolerable combinations of agents and designing adequately powered clinical trials to test efficacy in molecularly defined subsets of patients.

A phase 2 trial of extended induction epratuzumab and rituximab for previously untreated follicular lymphoma: CALGB 50701

BACKGROUND

Rituximab combined with chemotherapy has improved the survival of previously untreated patients with follicular lymphoma (FL). Nevertheless, many patients neither want nor can tolerate chemotherapy, leading to interest in biological approaches. Epratuzumab is a humanized anti-CD22 monoclonal antibody with efficacy in relapsed FL. Because both rituximab and epratuzumab have single-agent activity in FL, the antibody combination was evaluated as initial treatment of patients with FL.

METHODS

Fifty-nine untreated patients with FL received epratuzumab 360 mg/m2 with rituximab 375 mg/m2 weekly for 4 induction doses. This combination was continued as extended induction in weeks 12, 20, 28, and 36. Response assessed by computed tomography was correlated with clinical risk factors, [18F]fluorodeoxyglucose positron emission tomography findings at week 3, Fcγ polymorphisms, immunohistochemical markers, and statin use.

RESULTS

Therapy was well-tolerated, with toxicities similar to expected with rituximab monotherapy. Fifty-two (88.2%) evaluable patients responded, including 25 complete responses (42.4%) and 27 partial responses (45.8%). At 3 years follow-up, 60% of patients remain in remission. Follicular Lymphoma International Prognostic Index (FLIPI) risk strongly predicted progression-free survival (P = .022).

CONCLUSIONS

The high response rate and prolonged time to progression observed with this antibody combination are comparable to those observed after standard chemoimmunotherapies and further support the development of biologic, nonchemotherapeutic approaches for these patients.

Treatment challenges in the management of relapsed or refractory non-Hodgkin's lymphoma - novel and emerging therapies

Over the last few decades, advances in immunochemotherapy have led to dramatic improvement in the prognosis of non-Hodgkin's lymphoma (NHL). Despite these advances, relapsed and refractory disease represents a major treatment challenge. For both aggressive and indolent subtypes of NHL, there is no standard of care for salvage regimens, with prognosis after relapse remaining relatively poor. Nevertheless, there are multiple emerging classes of targeted therapies for relapsed/refractory disease, including monoclonal antibodies, antibody- drug conjugates, radioimmunotherapy, small-molecule inhibitors of cell-growth pathways, and novel chemotherapy agents. This review will discuss treatment challenges of NHL, current available salvage regimens for relapsed/refractory NHL, and the safety and efficacy of novel emerging therapies.

Relapsed and refractory aggressive NHL: time for a change

Despite improvements in treatment for aggressive non-Hodgkin lymphoma (NHL), the outcomes for patients with relapsed or refractory B- or T-cell NHL after primary therapy remain poor. While some patients may be cured by the standard of care of salvage chemotherapy followed by high-dose chemotherapy and autologous stem cell transplantation (ASCT), this treatment is unsuitable for the majority. Advances in disease biology and novel therapies have created uncertainty as to the role of old standards and opportunities to develop new rationally developed treatment options. We will review the standard approaches in this disease area and highlight areas that merit further study.

An update on radioimmunotherapy for lymphoma

SUMMARY Radioimmunotherapy is a promising treatment for B-cell lymphoma. 90Y-ibritumomab tiuxetan (Zevalin®) and 131I-tositumomab (Bexxar®) combine the potent antilymphoma effect of radiation with the specificity of antibody targeting. They have shown efficacy in follicular lymphoma in the setting of relapsed or refractory disease as consolidation regimens after first-line therapy, and in the front-line setting as single agents. Given their tolerability, they are actively being investigated as therapies or adjuncts for elderly patients with relapsed or high-risk diffuse large B-cell lymphoma. They have been added to autologous and allogeneic stem cell transplant preparatory regimens in early clinical trials with acceptable safety and efficacy. Early concerns over excess rates of treatment-related myelodysplastic syndrome and acute myelogenous leukemia have not come to fruition, but these questions remain to be fully answered. Ultimately, these are promising treatments for a variety of B-cell lymphomas. They are also models for the development of new radioimmunotherapies.

Antibody–drug conjugates for the treatment of B-cell non-Hodgkin’s lymphoma and leukemia

Antibody–drug conjugates (ADCs) are a broad class of molecules comprising of a potent cytotoxic agent conjugated with a monoclonal antibody using a chemically stable linker. By selecting a monoclonal antibody directed against a tumor-specific or tumor-associated antigen, ADCs allow the targeted delivery of highly potent cytotoxic agents that result in unacceptable toxicity when administered as free agents. ADCs are currently being developed for the treatment of a wide variety of tumors. In this review, the current clinical and preclinical status of ADCs for the treatment of B-cell non-Hodgkin’s lymphoma and B-cell leukemia will be discussed. ADCs have the potential to alter treatment paradigms for these diseases by providing both increased efficacy and improved safety and tolerability over current chemotherapy-based regimens.

Compatibility and stability of pertuzumab and trastuzumab admixtures in i.v. infusion bags for coadministration

The physical/chemical stability and potential interactions after diluting two immunoglobulin G1 monoclonal antibodies (mAb), pertuzumab (Perjeta®) and trastuzumab (Herceptin®), in a single intravenous (i.v.) infusion bag containing 0.9% saline (NaCl) solution was evaluated. As commercial products, pertuzumab and trastuzumab are administered through i.v. infusion to patients sequentially, that is, one drug after the other. To increase convenience and minimize the in-clinic time for patients, the compatibility of coadministering pertuzumab (420 and 840 mg) mixed with either 420 or 720 mg trastuzumab, respectively, in a single 250 mL polyolefin or polyvinyl chloride i.v. bag stored for up to 24 h at 5°C or 30°C was determined. The controls (i.e., pertuzumab alone in an i.v. bag, trastuzumab alone in an i.v. bag) and the mAb mixture were assessed using color, appearance, and clarity, concentration and turbidity by ultraviolet spectroscopy, particulate analysis by light obscuration, size-exclusion chromatography, capillary electrophoresis-sodium dodecyl sulfate, analytical ultracentrifugation, and ion-exchange chromatography. Additionally, capillary zone electrophoresis, imaged capillary isoelectric focusing, and potency were utilized to measure the stability of the admixtures containing 1:1 mixtures of pertuzumab/trastuzumab and their respective controls (420 mg pertuzumab alone and 420 mg trastuzumab alone). No observable differences were detected by the above methods in the pertuzumab/trastuzumab mixtures stored up to 24 h at either 5°C or 30°C. The physicochemical methods as listed above were able to detect both molecules as well as the minor variants in the drug mixture, even though some overlap of mAb species were seen in the chromatograms and electropherograms. Furthermore, biophysical analysis also did not show any interactions between the two mAbs or any physical instability under these conditions. Additionally, the drug mixture tested by the pertuzumab-specific inhibition of cell proliferation bioassay showed comparable potency before and after storage. On the basis of these results, pertuzumab and trastuzumab admixture in a single i.v. bag is physically and chemically stable for up to 24 h at 5°C or 30°C and can be used for clinical administration.

Smarter drugs: a focus on pan-specific monoclonal antibodies

Antibodies capable of targeting more than one antigen are envisioned to expand therapeutic efficacy in complex disease settings. Several strategies have been developed to achieve multiple targeting, including antibody mixtures and bispecific formats. In recent years, several dual- and pan-specific antibodies have been described and represent an alternative approach. These antibodies bind to different targets using a single antigen-combining site while maintaining high affinity and specificity, thus challenging the 'one antibody, one antigen' dogma. Despite certain drawbacks, the simple IgG format of this drug class enables rapid progression into the clinic.

Dual-targeting immunotherapy of lymphoma: potent cytotoxicity of anti-CD20/CD74 bispecific antibodies in mantle cell and other lymphomas

We describe the use of novel bispecific hexavalent Abs (HexAbs) to enhance anticancer immunotherapy. Two bispecific HexAbs [IgG-(Fab)4 constructed from veltuzumab (anti-CD20 IgG) and milatuzumab (anti-CD74 IgG)] show enhanced cytotoxicity in mantle cell lymphoma (MCL) and other lymphoma/leukemia cell lines, as well as patient tumor samples, without a crosslinking Ab, compared with their parental mAb counterparts, alone or in combination. The bispecific HexAbs have different properties from and are more potent than their parental mAbs in vitro. The juxtaposition of CD20 and CD74 on MCL cells by the HexAbs resulted in homotypic adhesion and triggered intracellular changes that include loss of mitochondrial transmembrane potential, production of reactive oxygen species, rapid and sustained phosphorylation of ERKs and JNK, down-regulation of pAkt and Bcl-xL, actin reorganization, and lysosomal membrane permeabilization, culminating in cell death. They also displayed different potencies in depleting lymphoma cells and normal B cells from whole blood ex vivo and significantly extended the survival of nude mice bearing MCL xenografts in a dose-dependent manner, thus indicating stability and antitumor activity in vivo. Such bispecific HexAbs may constitute a new class of therapeutic agents for improved cancer immunotherapy, as shown here for MCL and other CD20+/CD74+ malignancies.

Novel therapies for aggressive B-cell lymphoma

Aggressive B-cell lymphoma (BCL) comprises a heterogeneous group of malignancies, including diffuse large B-cell lymphoma (DLBCL), Burkitt lymphoma, and mantle cell lymphoma (MCL). DLBCL, with its 3 subtypes, is the most common type of lymphoma. Advances in chemoimmunotherapy have substantially improved disease control. However, depending on the subtype, patients with DLBCL still exhibit substantially different survival rates. In MCL, a mature B-cell lymphoma, the addition of rituximab to conventional chemotherapy regimens has increased response rates, but not survival. Burkitt lymphoma, the most aggressive BCL, is characterized by a high proliferative index and requires more intensive chemotherapy regimens than DLBCL. Hence, there is a need for more effective therapies for all three diseases. Increased understanding of the molecular features of aggressive BCL has led to the development of a range of novel therapies, many of which target the tumor in a tailored manner and are summarized in this paper.

Novel targeted therapies for mantle cell lymphoma

Mantle cell lymphoma (MCL) is an aggressive B-cell malignancy characterized by short median survival despite intensive therapies. The clinical behavior of MCL may be due to the complex pathophysiology of the disease which includes its genetic hallmark, the chromosomal translocation t(11;14) resulting in aberrant expression of cyclin D1, alteration in the DNA damage response, and constitutive activation of key anti-apoptotic pathways such as phosphatidyl-inositol 3-kinase (PI3K)/Akt and nuclear factor-kB (NF-kB). Collectively, these changes result in cell cycle dysregulation and give rise to profound genetic instability. Given this complex pathophysiology, the limited number of options for patients with relapsed/refractory MCL, and the difficulty in achieving long-lasting remissions with conventional approaches, it is essential to explore new treatment options targeting the numerous dysregulated pathways that are operable in MCL. We have recently reported that milatuzumab, a fully humanized anti-CD74 monoclonal antibody (mAb), in combination with anti-CD20 mAbs has significant preclinical and clinical activity in MCL. Here we discuss these results, provide additional insights into milatuzumab-mediated MCL cell death, and report preliminary data on the activity of other targeted biologic agents including PCI-32765 and CAL-101 currently undergoing evaluation at our institution and others.

Immunotherapy for B-cell lymphoma: current status and prospective advances

Therapy for non-Hodgkin's lymphoma has progressed significantly over the last decades. However, the majority of patients remain incurable, and novel therapies are needed. Because immunotherapy ideally offers target selectivity, an ever increasing number of immunotherapies, both passive and active, are undergoing development. The champion of passive immunotherapy to date is the anti-CD20 monoclonal antibody rituximab that revolutionized the standard of care for lymphoma. The great success of rituximab catalyzed the development of new passive immunotherapy strategies that are currently undergoing clinical evaluation. These include improvement of rituximab efficacy, newer generation anti-CD20 antibodies, drug-conjugated and radio labeled anti-CD20 antibodies, monoclonal antibodies targeting non-CD20 lymphoma antigens, and bispecific antibodies. Active immunotherapy aims at inducing long-lasting antitumor immunity, thereby limiting the likelihood of relapse. Current clinical studies of active immunotherapy for lymphoma consist largely of vaccination and immune checkpoint blockade. A variety of protein- and cell-based vaccines are being tested in ongoing clinical studies. Recently completed phase III clinical trials of an idiotype protein vaccine suggest that the vaccine may have clinical activity in a subset of patients. Efforts to enhance the efficacy of active immunotherapy are ongoing with an emphasis on optimization of antigen delivery and presentation of vaccines and modulation of the immune system toward counteracting immunosuppression, using antibodies against immune regulatory checkpoints. This article discusses results of the various immunotherapy approaches applied to date for B-cell lymphoma and the ongoing trials to improve their effect.

The cytotoxicity of anti-CD22 immunotoxin is enhanced by bryostatin 1 in B-cell lymphomas through CD22 upregulation and PKC-βII depletion

BACKGROUND

In spite of potent first-line therapies for chronic lymphocytic leukemia, treatment remains palliative and all patients frequently relapse. Treatment options for these patients are more limited. BL22 is a recombinant protein composed of the variable region of a monoclonal antibody that binds to CD22 and of PE38, a truncated Pseudomonas exotoxin. BL22 is a very potent drug already used in patients with hairy cell leukemia, whereas in chronic lymphocytic leukemia its cytotoxicity is limited by a lower expression of CD22. Here we demonstrate that this limitation can be overcome by pre-activation of chronic lymphocytic leukemia cells with bryostatin 1.

DESIGN AND METHODS

Primary malignant B cells from chronic lymphocytic leukemia and mantle cell lymphoma patients were used in vitro to assess the therapeutic impact of drug combinations using BL22 and bryostatin 1.

RESULTS

We demonstrate that bryostatin 1 sensitizes chronic lymphocytic leukemia cells for the cytotoxic effects of BL22 through activation of protein kinase C and subsequently increased CD22 surface expression. Dose and time response analysis reveals that activation of protein kinase C further activates an autocrine feedback loop degrading protein kinase C-βII protein. Depletion of protein kinase C-βII and upregulation of CD22 persist for several days following pre-stimulation with bryostatin 1. Therefore, our data provide a rationale for the sequential administration of BL22 following bryostatin 1 treatment. In addition to primary chronic lymphocytic leukemia cells, bryostatin 1 also sensitizes diffuse large B-cell lymphoma and mantle cell lymphoma cells to BL22 induced apoptosis.

CONCLUSIONS

Our data suggest that the combination of bryostatin 1 with antibodies directed against CD22 is a potent drug combination for the treatment of low- and high-grade B-cell lymphoma.

Update on novel monoclonal antibodies and immunoconjugates for the treatment of lymphoproliferative disorders

The year 1997 was pivotal in lymphoma research, as it was the year that the US FDA approved rituximab. Rituximab significantly altered clinical management and outcomes of patients with B-cell malignancies. Despite a high initial response rate, the majority of patients subsequently develop variable degrees of therapeutic resistance to rituximab. Research attempting to understand the mechanisms of rituximab resistance and potential ways to overcome them has given rise to the development of novel targeted immunotherapeutics. This article will update the readers on advances in bioengineering of monoclonal antibodies and immunoconjugates that target CD20, as well as other surface antigens. Some additional novel immunotherapeutics, including small modular immunopharmaceuticals, bispecific monoclonal antibodies, T-cell engaging antibodies and immunoconjugates, will also be discussed.

A glycoengineered anti-CD19 antibody with potent antibody-dependent cellular cytotoxicity activity in vitro and lymphoma growth inhibition in vivo

Human cluster of differentiation (CD) antigen 19 is a B cell-specific surface antigen and an attractive target for therapeutic monoclonal antibody (mAb) approaches to treat malignancies of B cell origin. MEDI-551 is an affinity-optimized and afucosylated CD19 mAb with enhanced antibody-dependent cellular cytotoxicity (ADCC). The results from in vitro ADCC assays with Natural Killer cells as effector cells, demonstrate that MEDI-551 is effective at lower mAb doses than rituximab with multiple cell lines as well as primary chronic lymphocytic leukaemia and acute lymphoblastic leukaemia samples. Targeting CD19 with MEDI-551 was also effective in several severe combined immunodeficiency lymphoma models. Furthermore, the combination of MEDI-551 with rituximab resulted in prolonged suppression of tumour growth, demonstrating that therapeutic mAbs with overlapping effector function can be combined for greater tumour growth inhibition. Together, the data demonstrate that MEDI-551 has potent antitumour activity in preclinical models of B cell malignancies. The results also suggest that the combination of the ADCC-enhanced CD19 mAb with an anti-CD20 mAb could be a novel approach for the treatment of B cell lymphomas.