CAT-8015: a second-generation pseudomonas exotoxin A-based immunotherapy targeting CD22-expressing hematologic malignancies

Cancer Drug Delivery Systems Using Bacterial Toxin Translocation Mechanisms

Recent advances in targeted cancer therapy hold great promise for both research and clinical applications and push the boundaries in finding new treatments for various currently incurable cancers. However, these therapies require specific cell-targeting mechanisms for the efficient delivery of drug cargo across the cell membrane to reach intracellular targets and avoid diffusion to unwanted tissues. Traditional drug delivery systems suffer from a limited ability to travel across the barriers posed by cell membranes and, therefore, there is a need for high doses, which are associated with adverse reactions and safety concerns. Bacterial toxins have evolved naturally to specifically target cell subtypes via their receptor binding module, penetrating the cell membrane efficiently through the membrane translocation process and then successfully delivering the toxic cargo into the host cytosol. They have, thus, been harnessed for the delivery of various drugs. In this review, we focus on bacterial toxin translocation mechanisms and recent progress in the targeted delivery systems of cancer therapy drugs that have been inspired by the receptor binding and membrane translocation processes of the anthrax toxin protective antigen, diphtheria toxin, and Pseudomonas exotoxin A. We also discuss the challenges and limitations of these studies that should be addressed before bacterial toxin-based drug delivery systems can become a viable new generation of drug delivery approaches in clinical translation.

Binding domain on CD22 molecules contributing to the biological activity of T cell-engaging bispecific antibodies

CD22, as the B-cell malignancies antigen, has been targeted for immunotherapies through CAR-T cells, antibody-drug conjugates (ADCs) and immunotoxins via interaction of antibodies with binding domains on the receptor. We hypothesized that avidity and binding domain of antibody to target cells may have significant impact on the biological function in tumor immunotherapy, and T cell-engaging bispecific antibody (TCB) targeting CD22 could be used in the therapy of hematologic malignancies. So, to address the question, we utilized the information of six previously reported CD22 mAbs to generate CD22-TCBs with different avidity to different domains on CD22 protein. We found that the avidity of CD22-TCBs to protein was not consistent with the avidity to target cells, indicating that TCBs had different binding mode to the protein and cells. In vitro results indicated that CD22-TCBs mediated cytotoxicity depended on the avidity of antibodies to target cells rather than to protein. Moreover, distal binding domain of the antigen contributed to the avidity and biological activity of IgG-[L]-scfv-like CD22-TCBs. The T cells' proliferation, activation, cytotoxicity as well as cytokine release were compared, and G5/44 BsAb was selected for further in vivo assessment in anti-tumor activity. In vivo results demonstrated that CD22-TCB (G5/44 BsAb) significantly inhibited the tumors growth in mice. All these data suggested that CD22-TCBs could be developed as a promising candidate for B-cell malignancies therapy through optimizing the design with avidity and binding domain to CD22 target in consideration.

The protective role of the microenvironment in hairy cell leukemia treatment: Facts and perspectives

Hairy cell leukemia (HCL) is an incurable, rare lymphoproliferative hematological malignancy of mature B cAlthough first line therapy with purine analogues leads to positive results, almost half of HCL patients relapse after 5-10 years, and standard treatment may not be an option due to intolerance or refractoriness. Proliferation and survival of HCL cells is regulated by surrounding accessory cells and soluble signals present in the tumor microenvironment, which actively contributes to disease progression. In vitro studies show that different therapeutic approaches tested in HCL impact the tumor microenvironment, and that this milieu offers a protection affecting treatment efficacy. Herein we explore the effects of the tumor microenvironment to different approved and experimental therapeutic options for HCL. Dissecting the complex interactions between leukemia cells and their milieu will be essential to develop new targeted therapies for HCL patients.

Synthesis of an Anti-CD7 Recombinant Immunotoxin Based on PE24 in CHO and E. coli Cell-Free Systems

Recombinant immunotoxins (RITs) are an effective class of agents for targeted therapy in cancer treatment. In this article, we demonstrate the straight-forward production and testing of an anti-CD7 RIT based on PE24 in a prokaryotic and a eukaryotic cell-free system. The prokaryotic cell-free system was derived from Escherichia coli BL21 StarTM (DE3) cells transformed with a plasmid encoding the chaperones groEL/groES. The eukaryotic cell-free system was prepared from Chinese hamster ovary (CHO) cells that leave intact endoplasmic reticulum-derived microsomes in the cell-free reaction mix from which the RIT was extracted. The investigated RIT was built by fusing an anti-CD7 single-chain variable fragment (scFv) with the toxin domain PE24, a shortened variant of Pseudomonas Exotoxin A. The RIT was produced in both cell-free systems and tested for antigen binding against CD7 and cell killing on CD7-positive Jurkat, HSB-2, and ALL-SIL cells. CD7-positive cells were effectively killed by the anti-CD7 scFv-PE24 RIT with an IC50 value of 15 pM to 40 pM for CHO and 42 pM to 156 pM for E. coli cell-free-produced RIT. CD7-negative Raji cells were unaffected by the RIT. Toxin and antibody domain alone did not show cytotoxic effects on either CD7-positive or CD7-negative cells. To our knowledge, this report describes the production of an active RIT in E. coli and CHO cell-free systems for the first time. We provide the proof-of-concept that cell-free protein synthesis allows for on-demand testing of antibody−toxin conjugate activity in a time-efficient workflow without cell lysis or purification required.

Recent advances in microbial toxin-related strategies to combat cancer

It is a major concern to treat cancer successfully, due to the distinctive pathophysiology of cancer cells and the gradual manifestation of resistance. Specific action, adverse effects and development of resistance has prompted the urgent requirement of exploring alternative anti-tumour treatment therapies. The naturally derived microbial toxins as a therapy against cancer cells are a promisingly new dimension. Various important microbial toxins such as Diphtheria toxin, Vibrio cholera toxin, Aflatoxin, Patulin, Cryptophycin-55, Chlorella are derived from several bacterial, fungal and algal species. These agents act on different biotargets such as inhibition of protein synthesis, reduction in cell growth, regulation of cell cycle and many cellular processes. Bacterial toxins produce actions primarily by targeting protein moieties and some immunomodulation and few acts through DNA. Fungal toxins appear to have more DNA damaging activity and affect the cell cycle. Algal toxins produce alteration in mitochondrial phosphorylation. In conclusion, microbial toxins and their metabolites appear to have a great potential to provide a promising option for the treatment and management to combat cancer.

A Novel Anti-CD22 scFv.Bim Fusion Protein Effectively Induces Apoptosis in Malignant B cells and Promotes Cytotoxicity

CD22 is a B-cell surface antigen which is highly expressed in cancerous B-cell lineages. Anti-CD22 antibodies are currently under focus as promising biologics against hematologic B-cell malignancies. Herein, we introduce a novel active recombinant anti-CD22 scFv.Bim fusion protein for targeting this cancerous antigen. An expression cassette encoding anti-CD22 scFv.Bim fusion protein was expressed in Pichia pastoris. The binding ability, cytotoxicity, and apoptotic activity of the purified recombinant protein against CD22⁺ Raji cell line were assessed by flow cytometry, microscopy, and MTT assay. Using bioinformatics, the 3D structure of the fusion protein and its interaction with CD22 were assessed. The in vitro binding analysis by immunofluorescence microscopy and flow cytometry demonstrated the specific binding of scFv.Bim to CD22⁺ Raji cells but not to CD22^- Jurkat cells. MTT data and Annexin V/PI flow cytometry analysis confirmed the apoptotic activity of anti-CD22 scFv.Bim against Raji cells but not Jurkat cells. In silico analysis also revealed the satisfactory stereochemical quality of the 3D model and molecular interactions toward CD22. This novel recombinant anti-CD22 scFv.Bim fusion protein could successfully deliver the pro-apoptotic peptide, BIM, to the target cells and thus nominates it as a promising molecule in treating B-cell malignancies.

Advances on Delivery of Cytotoxic Enzymes as Anticancer Agents

Cancer is one of the most serious human diseases, causing millions of deaths worldwide annually, and, therefore, it is one of the most investigated research disciplines. Developing efficient anticancer tools includes studying the effects of different natural enzymes of plant and microbial origin on tumor cells. The development of various smart delivery systems based on enzyme drugs has been conducted for more than two decades. Some of these delivery systems have been developed to the point that they have reached clinical stages, and a few have even found application in selected cancer treatments. Various biological, chemical, and physical approaches have been utilized to enhance their efficiencies by improving their delivery and targeting. In this paper, we review advanced delivery systems for enzyme drugs for use in cancer therapy. Their structure-based functions, mechanisms of action, fused forms with other peptides in terms of targeting and penetration, and other main results from in vivo and clinical studies of these advanced delivery systems are highlighted.

An overview on display systems (phage, bacterial, and yeast display) for production of anticancer antibodies; advantages and disadvantages

Antibodies as ideal therapeutic and diagnostic molecules are among the top-selling drugs providing considerable efficacy in disease treatment, especially in cancer therapy. Limitations of the hybridoma technology as routine antibody generation method in conjunction with numerous developments in molecular biology led to the development of alternative approaches for the streamlined identification of most effective antibodies. In this regard, display selection technologies such as phage display, bacterial display, and yeast display have been widely promoted over the past three decades as ideal alternatives to traditional methods. The display of antibodies on phages is probably the most widespread of these methods, although surface display on bacteria or yeast have been employed successfully, as well. These methods using various sizes of combinatorial antibody libraries and different selection strategies possessing benefits in screening potency, generating, and isolation of high affinity antibodies with low risk of immunogenicity. Knowing the basics of each method assists in the design and retrieval process of antibodies suitable for different diseases, including cancer. In this review, we aim to outline the basics of each library construction and its display method, screening and selection steps. The advantages and disadvantages in comparison to alternative methods, and their applications in antibody engineering will be explained. Finally, we will review approved or non-approved therapeutic antibodies developed by employing these methods, which may serve as therapeutic antibodies in cancer therapy.

Treatment of Classic Hairy Cell Leukemia: Targeting Minimal Residual Disease beyond Cladribine

Simple Summary

Standard treatment with purine analogues facilitates a near normal life expectancy in the majority of patients with classic hairy cell leukemia (HCL), a rare chronic B-cell malignancy. However, nearly all patients ultimately relapse and require retreatment, while drug-induced myelotoxicity accumulates predisposing to infectious complications and, possibly, secondary malignancies. Persistence of minimal residual disease (MRD) in a substantial portion of treated patients has become a surrogate for this still limited treatment efficacy. New insights into disease biology initiated design and investigation of several new, chemotherapy-free, targeted drugs with encouraging efficacy in early clinical trials aimed at enhancing eradication of MRD and optimizing drug tolerability. This review provides an update on recent clinical trials investigating treatment strategies beyond purine analogues in HCL and discusses clinically relevant obstacles still to overcome.

Abstract

Classic hairy cell leukemia (HCL) is a rare indolent B-cell lymphoproliferative disorder characterized by profound pancytopenia and frequent infectious complications due to progressive infiltration of the bone marrow and spleen. Lacking effective treatment options, affected patients were confronted with a dismal survival prognosis of less than 5 years when the disease was first described in 1958. Tremendous therapeutic advances were accomplished with the introduction of purine analogues such as cladribine in the 1990s, facilitating a near-normal life expectancy in most HCL patients. Nevertheless, nearly all patients eventually relapse and require successive retreatments, while drug-associated myelotoxicity may accumulate and secondary malignancies may evolve. Detection of minimal residual disease (MRD) in a substantial portion of treated patients has become a surrogate for this still limited treatment efficacy. In the last decade, novel biologic insights such as identification of the driver mutation BRAF V600E have initiated the development and clinical investigation of new, chemotherapy-free, targeted drugs in HCL treatment, with encouraging efficacy in early clinical trials aimed at boosting eradication of MRD while optimizing drug tolerability. This review summarizes current clinical trials investigating treatment strategies beyond purine analogues in HCL and discusses clinically relevant obstacles still to overcome.

Insights into Modern Therapeutic Approaches in Pediatric Acute Leukemias

Pediatric cancers predominantly constitute lymphomas and leukemias. Recently, our knowledge and awareness about genetic diversities, and their consequences in these diseases, have greatly expanded. Modern solutions are focused on mobilizing and impacting a patient’s immune system. Strategies to stimulate the immune system, to prime an antitumor response, are of intense interest. Amid those types of therapies are chimeric antigen receptor T (CAR-T) cells, bispecific antibodies, and antibody–drug conjugates (ADC), which have already been approved in the treatment of acute lymphoblastic leukemia (ALL)/acute myeloid leukemia (AML). In addition, immune checkpoint inhibitors (ICIs), the pattern recognition receptors (PRRs), i.e., NOD-like receptors (NLRs), Toll-like receptors (TLRs), and several kinds of therapy antibodies are well on their way to showing significant benefits for patients with these diseases. This review summarizes the current knowledge of modern methods used in selected pediatric malignancies and presents therapies that may hold promise for the future.

Diagnosis and treatment of hairy cell leukemia as the COVID-19 pandemic continues

Hairy cell leukemia (HCL) is an indolent B-cell malignancy, usually driven by the BRAF V600E mutation. For 30 years, untreated and relapsed HCL was successfully treated with purine analogs, but minimal residual disease (MRD) remained in most patients, eventually causing relapse. Repeated purine analogs achieve decreasing efficacy and increasing toxicity, particularly to normal T-cells. MRD-free complete remissions (CRs) are more common using rituximab with purine analogs in both 1^st-line and relapsed settings. BRAF inhibitors and Ibrutinib can achieve remission, but due to persistence of MRD, must be used chronically to prevent relapse. BRAF inhibition combined with Rituximab can achieve high MRD-free CR rates. Anti-CD22 recombinant immunotoxin moxetumomab pasudotox is FDA-approved in the relapsed setting and is unique in achieving high MRD-free CR rates as a single-agent. Avoiding chemotherapy and rituximab may be important in ensuring both recovery from COVID-19 and successful COVID-19 vaccination, an area of continued investigation.

Pseudomonas Exotoxin-Based Immunotoxins: Over Three Decades of Efforts on Targeting Cancer Cells With the Toxin

Cancer is one of the prominent causes of death worldwide. Despite the existence of various modalities for cancer treatment, many types of cancer remain uncured or develop resistance to therapeutic strategies. Furthermore, almost all chemotherapeutics cause a range of side effects because they affect normal cells in addition to malignant cells. Therefore, the development of novel therapeutic agents that are targeted specifically toward cancer cells is indispensable. Immunotoxins (ITs) are a class of tumor cell-targeted fusion proteins consisting of both a targeting moiety and a toxic moiety. The targeting moiety is usually an antibody/antibody fragment or a ligand of the immune system that can bind an antigen or receptor that is only expressed or overexpressed by cancer cells but not normal cells. The toxic moiety is usually a protein toxin (or derivative) of animal, plant, insect, or bacterial origin. To date, three ITs have gained Food and Drug Administration (FDA) approval for human use, including denileukin diftitox (FDA approval: 1999), tagraxofusp (FDA approval: 2018), and moxetumomab pasudotox (FDA approval: 2018). All of these ITs take advantage of bacterial protein toxins. The toxic moiety of the first two ITs is a truncated form of diphtheria toxin, and the third is a derivative of Pseudomonas exotoxin (PE). There is a growing list of ITs using PE, or its derivatives, being evaluated preclinically or clinically. Here, we will review these ITs to highlight the advances in PE-based anticancer strategies, as well as review the targeting moieties that are used to reduce the non-specific destruction of non-cancerous cells. Although we tried to be as comprehensive as possible, we have limited our review to those ITs that have proceeded to clinical trials and are still under active clinical evaluation.

Moxetumomab Pasudotox in Hairy Cell Leukaemia: A Profile of Its Use

Moxetumomab pasudotox (Lumoxiti^®), an anti-CD22 recombinant immunotoxin, is an important treatment option that is approved in adults with relapsed or refractory hairy cell leukaemia (HCL) who have received at least two prior lines of treatment with systemic therapies including purine nucleoside analogues. In a pivotal phase III trial, treatment with moxetumomab pasudotox resulted in approximately one third of patients achieving durable complete response lasting more than 6 months, as well as improvements in other haematological parameters and disease-related symptoms. Moxetumomab pasudotox had a generally manageable tolerability profile; the most common treatment-related adverse events (AEs) included nausea, peripheral oedema, headache and pyrexia. AEs of special interest (including haemolytic uraemic syndrome and capillary leak syndrome) were generally manageable and reversible with monitoring and supportive care.

Uncialamycin-based antibody-drug conjugates: Unique enediyne ADCs exhibiting bystander killing effect

Antibody-drug conjugates (ADCs) have emerged as valuable targeted anticancer therapeutics with at least 11 approved therapies and over 80 advancing through clinical trials. Enediyne DNA-damaging payloads represented by the flagship of this family of antitumor agents, N-acetyl calicheamicin [Formula: see text], have a proven success track record. However, they pose a significant synthetic challenge in the development and optimization of linker drugs. We have recently reported a streamlined total synthesis of uncialamycin, another representative of the enediyne class of compounds, with compelling synthetic accessibility. Here we report the synthesis and evaluation of uncialamycin ADCs featuring a variety of cleavable and noncleavable linkers. We have discovered that uncialamycin ADCs display a strong bystander killing effect and are highly selective and cytotoxic in vitro and in vivo.

Pseudomonas Exotoxin A-Based Immunotherapy Targeting CCK2R-Expressing Colorectal Malignancies: An In Vitro and In Vivo Evaluation

Cholecystokinin-2 receptor (CCK2R) has been proven to be a specific biomarker for colorectal malignancies. Immunotoxins are a valuable class of immunotherapy agents consisting of a targeting element and a bacterial or plant toxin. Previous work demonstrated that targeting CCK2R is a good therapeutic strategy for the treatment of colorectal cancer (CRC). In the present study, we developed a new version of CCK2R-targeting immunotoxin GD9P using a targeted peptide, GD9, as the binding motif and a truncated Pseudomonas exotoxin A (PE38) as the cytokiller. BALB/c nude mice were treated with different doses of GD9P, and pharmacodynamics, pharmacokinetic, and toxicological data were obtained throughout this study. Compared to the parental immunotoxin rCCK8PE38, GD9P exhibited about 1.5-fold yield, higher fluorescence intensity, and increased antitumor activity against human CRC in vitro and in vivo. The IC50 values of GD9P in vitro ranged from 1.61 to 4.55 nM. Pharmacokinetic studies were conducted in mice with a T1/2 of 69.315 min. When tumor-bearing nude mice were treated with GD9P at doses ≥2 mg/kg for five doses, a rapid shrinkage in tumor volume and, in some cases, complete remission was observed. A preliminary safety evaluation demonstrated a good safety profile of GD9P as a Pseudomonas exotoxin A-based immunotherapy. The therapy in combination with oxaliplatin can increase the antitumor efficacy and reduce the toxic side effects caused by chemotherapy. In conclusion, the data support the use of GD9P as a promising immunotherapy targeting CCK2R-expressing colorectal malignancies.

Anti-cancer Immunotoxins, Challenges, and Approaches

The development of recombinant immunotoxins (RITs) as a novel therapeutic strategy has made a revolution in the treatment of cancer. RITs result from the fusion of antibodies to toxin proteins for targeting and eliminating cancerous cells by inhibiting protein synthesis. Despite indisputable outcomes of RITs regarding inhibition of multiple cancer types, high immunogenicity has been known as the main obstacle in the clinical use of RITs. Various strategies have been proposed to overcome these limitations, including immunosuppressive therapy, humanization of the antibody fragment moiety, generation of immunotoxins originated from endogenous human cytotoxic enzymes, and modification of the toxin moiety to escape the immune system. This paper is devoted to review recent advances in the design of immunotoxins with lower immunogenicity.

Antibody Libraries as Tools to Discover Functional Antibodies and Receptor Pleiotropism

Most antibodies currently in use have been selected based on their binding affinity. However, nowadays, antibodies that can not only bind but can also alter the function of cell surface signaling components are increasingly sought after as therapeutic drugs. Therefore, the identification of such functional antibodies from a large antibody library is the subject of intensive research. New methods applied to combinatorial antibody libraries now allow the isolation of functional antibodies in the cellular environment. These selected agonist antibodies have provided new insights into important issues of signal transduction. Notably, when certain antibodies bind to a given receptor, the cell fate induced by them may be the same or different from that induced by natural agonists. In addition, combined with phenotypic screening, this platform allows us to discover unexpected experimental results and explore various phenomena in cell biology, such as those associated with stem cells and cancer cells.

Bacteriocins: New Potential Therapeutic Candidates in Cancer Therapy

Cancer is one of the most important disorders which is associated with high mortality and high costs of treatment for patients. Despite several efforts, finding, designing and developing, new therapeutic platforms in the treatment of cancer patients are still required. Utilization of microorganisms, particularly bacteria has emerged as new therapeutic approaches in the treatment of various cancers. Increasing data indicated that bacteria could be used in the production of a wide range of anti-cancer agents, including bacteriocins, antibiotics, peptides, enzymes, and toxins. Among these anti-cancer agents, bacteriocins have attractive properties, which make them powerful anti-cancer drugs. Multiple lines evidence indicated that several bacteriocins (i.e., colcins, nisins, pediocins, pyocins, and bovocins) via activation/inhibition different cellular and molecular signaling pathways are able to suppress tumor growth in various stages. Hence, identification and using various bacteriocins could lead to improve and introduce them to clinical practices. Here, we summarized various bacteriocins which could be employed as anti-cancer agents in the treatment of many cancers.

Advances in epidermal growth factor receptor specific immunotherapy: lessons to be learned from armed antibodies

The epidermal growth factor receptor (EGFR) has been recognized as an important therapeutic target in oncology. It is commonly overexpressed in a variety of solid tumors and is critically involved in cell survival, proliferation, metastasis, and angiogenesis. This multi-dimensional role of EGFR in the progression and aggressiveness of cancer, has evolved from conventional to more targeted therapeutic approaches. With the advent of hybridoma technology and phage display techniques, the first anti-EGFR monoclonal antibodies (mAbs) (Cetuximab and Panitumumab) were developed. Due to major limitations including host immune reactions and poor tumor penetration, these antibodies were modified and used as guiding mechanisms for the specific delivery of readily available chemotherapeutic agents or plants/bacterial toxins, giving rise to antibody-drug conjugates (ADCs) and immunotoxins (ITs), respectively. Continued refinement of ITs led to deimmunization strategies based on depletion of B and T-cell epitopes or substitution of non-human toxins leading to a growing repertoire of human enzymes capable of inducing cell death. Similarly, the modification of classical ADCs has resulted in the first, fully recombinant versions. In this review, we discuss significant advancements in EGFR-targeting immunoconjugates, including ITs and recombinant photoactivable ADCs, which serve as a blueprint for further developments in the evolving domain of cancer immunotherapy.

Moxetumomab pasudotox for hairy cell leukemia: preclinical development to FDA approval

Moxetumomab pasudotox (MP) is an immunotoxin that recently received US Food and Drug Administration (FDA) approval for the treatment of hairy cell leukemia (HCL) that has failed at least 2 prior lines of therapy, including a purine analog. MP is a recombinant immunotoxin that consists of an anti-CD22 immunoglobulin variable domain genetically joined to Pseudomonas exotoxin (PE38). Unlike most antibody-drug conjugates, which use a chemical linker, recombinant DNA techniques are used to produce MP. MP and its predecessor, BL22, were initially developed to treat non-Hodgkin lymphoma, acute lymphoblastic leukemia, and HCL. However, MP was found to be particularly effective in HCL due to the high level of CD22 cell-surface expression. The recent pivotal phase 3 trial of MP in relapsed/refractory HCL demonstrated a durable complete remission rate of 30%, and 85% of complete responders achieved minimal residual disease negativity, which is associated with improved disease-free survival outcomes in HCL. In addition to an exceptional depth of response, MP appears to be less immunosuppressive than purine analogs. MP is generally well tolerated but has unique toxicities, including capillary leak syndrome and hemolytic uremic syndrome, which are poorly understood. This review will encompass the preclinical and clinical development of MP, with particular attention to its current indication in HCL.

Treatment of hairy cell leukemia

INTRODUCTION

Purine analogs made dramatic improvements for patients with hairy cell leukemia (HCL), but patients often relapse, require multiple treatments, and may become refractory. Major developments in treatment of relapsed/refractory HCL occurred with discovery of disease biology. New agents increase the complexity of clinical decision-making.

AREAS COVERED

Anti-CD22 recombinant immunotoxin Moxetumomab Pasudotox (Moxe), CD20 Mabs rituximab and obinutuzumab, BRAF/MEK inhibitors vemurafenib and dabrafenib-trametinib, and Bruton's tyrosine kinase (BTK) inhibitor ibrutinib have been tested in HCL. All show efficacy but with different treatment durations and response rates, including for eradicating minimal residual disease (MRD). Side effects differ and must be considered when selecting treatment. Studies from PubMed indexed papers and abstracts presented at major international conferences are included.

EXPERT OPINION

Rituximab with either purine analog or BRAF-inhibitor achieves high rates of MRD-free complete remission (CR). Moxe achieves MRD-free CR without chemotherapy toxicities. Moxe should be considered prior to splenectomy or development of adenopathy. BRAF/MEK inhibition and ibrutinib are effective options but most patients remain MRD+, requiring indefinite treatment or rituximab to prevent relapse. Under investigation is MRD elimination with CD20 antibody combined with Moxe or BRAF inhibitor. High-risk diseases including HCL variant and IGHV4-34+ unmutated HCL require further investigation.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage–derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Development of Recombinant Immunotoxins for Hairy Cell Leukemia

Hairy cell leukemia (HCL) is an indolent B-cell malignancy with excellent initial response to purine analogs pentostatin or cladribine, but patients are rarely, if ever, cured. Younger patients will usually need repeat chemotherapy which has declining benefits and increasing toxicities with each course. Targeted therapies directed to the BRAF V600E mutation and Bruton's tyrosine kinase may be helpful, but rarely eradicate the minimal residual disease (MRD) which will eventually lead to relapse. Moxetumomab pasudotox (Moxe) is an anti-CD22 recombinant immunotoxin, which binds to CD22 on HCL cells and leads to apoptotic cell death after internalization and trafficking of the toxin to the cytosol. Phase I testing achieved a complete remission (CR) rate of 57% in relapsed/refractory HCL. Most CRs were without MRD and eradication of MRD correlated with prolonged CR duration. Patients were often MRD-free after five years. Important mild-moderate toxicities included capillary leak and hemolytic uremic syndromes which could be prevented and managed conservatively. A phase 3 trial met its endpoint of durable CR with acceptable toxicity, leading to FDA approval of Moxe for relapsed/refractory HCL, under the name Lumoxiti. Moxe combined with rituximab is currently being evaluated in relapsed/refractory HCL to improve the rate of MRD-free CR.

LukS-PV Inhibits Hepatocellular Carcinoma Progression by Downregulating HDAC2 Expression

Hepatocellular carcinoma (HCC) is a common malignant tumor. LukS-PV is the S component of Panton-Valetine leukocidin (PVL), which is secreted by Staphylococcus aureus. This study investigated the effects of LukS-PV on the proliferation, apoptosis, and cell-cycle progression of HCC cells and the mechanisms of its activity. The HCC cells were treated with different LukS-PV concentrations in vitro. Cell Counting Kit-8 and 5-Ethynyl-2'-deoxyuridine (EdU) assays were used to study cell proliferation. Flow cytometry was used to measure apoptosis and cell-cycle progression. Quantitative reverse transcriptase PCR and western blot assays were used to determine mRNA and protein expression levels. Xenograft experiments were performed to determine the in vivo antitumor effect of LukS-PV. Immunostaining was performed to analyze Ki-67 and HDAC2 (histone deacetylase 2) expression. Our results showed that LukS-PV inhibited cell proliferation and induced apoptosis in a concentration-dependent manner in HCC cell lines. LukS-PV also can induce cell-cycle arrest. Moreover, we discovered that LukS-PV attenuated HDAC2 expression and upregulated PTEN; phosphorylated AKT was also reduced. Further studies demonstrated that LukS-PV treatment significantly reduced tumor growth in nude mice and suppressed Ki-67 and HDAC2 levels. Our data revealed a vital role of LukS-PV in suppressing HCC progression by downregulating HDAC2 and upregulating PTEN.

Bacterial expression and characterization of an anti-CD22 single-chain antibody fragment

Single-chain variable fragment (scFv) antibodies are fusion proteins of the variable regions of the heavy and light chains of immunoglobulins connected with a short linker peptide. They possess unique and superior features compared to whole antibodies for immunotherapy of various carcinomas, including hematologic B-cell malignancies. In the presented study we obtained efficient production of the recombinant anti-CD22 scFv in Escherichia coli expression system. The active recombinant protein was successfully recovered from inclusion bodies. Assays were performed to assess the in vitro targeting properties and specificity of the obtained anti-CD22 scFv antibody in the CD22 positive and negative lymphoma cell lines.

Bacteria and cancer: Different sides of the same coin

Conventional cancer therapies such as chemotherapy, radiation therapy, and immunotherapy due to the complexity of cancer have been unsuccessful in the complete eradication of tumor cells. Thus, there is a need for new therapeutic strategies toward cancer. Recently, the therapeutic role of bacteria in different fields of medicine and pharmaceutical research has attracted attention in recent decades. Although several bacteria are notorious as cancer-causing agents, recent research revealed intriguing results suggesting the bacterial potential in cancer therapy. Thus, bacterial cancer therapy is an alternative anticancer approach that has promising results on tumor cells in-vivo. Moreover, with the aid of genetic engineering, some natural or genetically modified bacterial strains can directly target hypoxic regions of tumors and secrete therapeutic molecules leading to cancer cell death. Additionally, stimulation of immune cells by bacteria, bacterial cancer DNA vaccine and antitumor bacterial metabolites are other therapeutic applications of bacteria in cancer therapy. The present study is a comprehensive review of different aspects of bacterial cancer therapy alone and in combination with conventional methods, for improving cancer therapy.

ADCs, as Novel Revolutionary Weapons for Providing a Step Forward in Targeted Therapy of Malignancies

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Antibody drug conjugates (ADCs), as potent pharmaceutical trojan horses for cancer treatment, provide superior efficacy and specific targeting along with low risk of adverse reactions compared to traditional chemotherapeutics. In fact, the development of these agents combines the selective targeting capability of monoclonal antibody (mAb) with high cytotoxicity of chemotherapeutics for controlling the neoplastic mass growth. Different ADCs (more than 60 ADCs) in preclinical and clinical trials were introduced in this novel pharmaceutical field. Various design-based factors must be taken into account for improving the functionality of ADC technology, including selection of appropriate target antigen and high binding affinity of fragment (miniaturized ADCs) or full mAbs (preferentially use of humanized or fully human antibodies compared to murine and chimeric ones), use of bispecific antibodies for dual targeting effect, linker engineering and conjugation method efficacy to obtain more controlled drug to antibody ratio (DAR). Challenging issues affecting therapeutic efficacy and safety of ADCs, including bystander effect, on- and off-target toxicities, multi drug resistance (MDR) are also addressed. 4 FDA-approved ADCs in the market, including ADCETRIS ®, MYLOTARG®, BESPONSA ®, KADCYLA®. The goal of the current review is to evaluate the key parameters affecting ADCs development.

Let's Talk About BiTEs and Other Drugs in the Real-Life Setting for B-Cell Acute Lymphoblastic Leukemia

Background: Therapy for acute lymphoblastic leukemia (ALL) are currently initially efficient, but even if a high percentage of patients have an initial complete remission (CR), most of them relapse. Recent data shows that immunotherapy with either bispecific T-cell engagers (BiTEs) of chimeric antigen receptor (CAR) T cells can eliminate residual chemotherapy-resistant B-ALL cells.

Objective: The objective of the manuscript is to present improvements in the clinical outcome for chemotherapy-resistant ALL in the real-life setting, by describing Romania's experience with bispecific antibodies for B-cell ALL.

Methods: We present the role of novel therapies for relapsed B-cell ALL, including the drugs under investigation in phase I-III clinical trials, as a potential bridge to transplant. Blinatumomab is presented in a critical review, presenting both the advantages of this drug, as well as its limitations.

Results: Bispecific antibodies are discussed, describing the clinical trials that resulted in its approval by the FDA and EMA. The real-life setting for relapsed B-cell ALL is described and we present the patients treated with blinatumomab in Romania.

Conclusion: In the current manuscript, we present blinatumomab as a therapeutic alternative in the bridge-to-transplant setting for refractory or relapsed ALL, to gain a better understanding of the available therapies and evidence-based data for these patients in 2019.

Phage Display Derived Monoclonal Antibodies: From Bench to Bedside

Monoclonal antibodies (mAbs) have become one of the most important classes of biopharmaceutical products, and they continue to dominate the universe of biopharmaceutical markets in terms of approval and sales. They are the most profitable single product class, where they represent six of the top ten selling drugs. At the beginning of the 1990s, an in vitro antibody selection technology known as antibody phage display was developed by John McCafferty and Sir. Gregory Winter that enabled the discovery of human antibodies for diverse applications, particularly antibody-based drugs. They created combinatorial antibody libraries on filamentous phage to be utilized for generating antigen specific antibodies in a matter of weeks. Since then, more than 70 phage-derived antibodies entered clinical studies and 14 of them have been approved. These antibodies are indicated for cancer, and non-cancer medical conditions, such as inflammatory, optical, infectious, or immunological diseases. This review will illustrate the utility of phage display as a powerful platform for therapeutic antibodies discovery and describe in detail all the approved mAbs derived from phage display.

Hairy cell leukemia: present and future directions

Hairy cell leukemia (HCL) is an indolent B-cell malignancy, with long-term responses to purine analogs, but with decreasing efficacy and increasing toxicity with repeated courses. Leukemic cells express CD22, CD20, CD25, tartrate-resistant acid phosphatase (TRAP), annexin 1A (Anxa1), and BRAF V600E mutation. HCLv, lacking CD25, Anxa1, TRAP, and BRAF V600E, is more aggressive and less purine analog-sensitive. A molecularly defined IGHV4-34+ variant is also resistant whether HCL or HCLv immunophenotypically. Traces of HCL cells, termed minimal residual disease (MRD), accompany most with complete remission (CR) and may cause relapse. Rituximab has limited single-agent activity, but frequent CR without MRD when combined with purine analog, albeit with chemotherapy toxicities. The anti-CD22 recombinant immunotoxin Moxetumomab Pasudotox can achieve MRD-negative CR in multiply relapsed HCL without chemotherapy toxicities and was FDA approved in 2018 as Lumoxiti. Investigational oral non-chemotherapy options also include Vemurafenib or Dabrafenib/Trametinib targeting BRAF V600E ± MEK, and Ibrutinib targeting Bruton's tyrosine kinase.

Antibody-drug conjugates in clinical trials for lymphoid malignancies and multiple myeloma

Antibody-drug conjugates (ADC) represent a distinct family of chemoimmunotherapy agents. ADCs are composed of monoclonal antibodies conjugated to cytotoxic payloads via specialized chemical linkers. ADCs therefore combine the immune therapy with targeted chemotherapy. Due to the distinct biomarkers associated with lymphocytes and plasma cells, ADCs have emerged as a promising treatment option for lymphoid malignancies and multiple myeloma. Several ADCs have been approved for clinical applications: brentuximab vedotin, inotuzumab ozogamicin, moxetumomab pasudotox, and polatuzumab vedotin. More novel ADCs are under clinical development. In this article, we summarized the general principles for ADC design, and updated novel ADCs under various stages of clinical trials for lymphoid malignancies and multiple myeloma.

Moxetumomab pasudotox for the treatment of relapsed and/or refractory hairy cell leukemia

Introduction: Hairy cell leukemia is a rare indolent B-cell malignancy, characterized by pancytopenia, recurrent infections, and splenomegaly. After initial therapy with purine nucleoside analogs, up to 50% of patients relapse after several years of remission. The number of relapsed patients is increasing and, until recently, there was no approved therapy with durable responses for hairy cell leukemia patients in the relapsed setting, thus the need for new non-chemotherapy approach with significant efficacy and less myelosuppression. Areas covered: Moxetumomab pasudotox is a recombinant immunotoxin containing a Fv fragment of an anti-CD22 monoclonal antibody and truncated Pseudomonas exotoxin (PE38). The authors reviewed pre-clinical and clinical studies that led to the FDA approval of the drug in patients with relapsed and/or refractory hairy cell leukemia, who received at least two prior therapies, including at least one purine nucleoside analog. Expert opinion: Moxetumomab pasudotox demonstrated a durable complete remission rate of 30% in heavily pretreated patients with hairy cell leukemia, and MRD eradication in 85% of responding patients. Moxetumomab pasudotox got a global FDA approval in September 2018. The US prescribing information carries boxed warnings regarding the risk of capillary leak syndrome and hemolytic uremic syndrome. Long-term follow-up of the pivotal study is ongoing (NCT01829711).

Moxetumomab Pasudotox: First Global Approval

Moxetumomab pasudotox-tdfk (LUMOXITI™), an anti CD22 recombinant immunotoxin, has been developed by MedImmune and its parent company AstraZeneca for the treatment of hairy cell leukaemia. The product, discovered at the National Cancer Institute, is an optimised version of immunotoxin CAT-3888. Moxetumomab pasudotox is composed of the Fv fragment of an anti-CD22 monoclonal antibody fused to a 38 kDa fragment of Pseudomonas exotoxin A, PE38. The Fv portion of moxetumomab pasudotox binds to CD22, a cell surface receptor expressed on a variety of malignant B-cells, thereby delivering the toxin moiety PE38 directly to tumour cells. Once internalised, PE38 catalyses the ADP ribosylation of the diphthamide residue in elongation factor-2 (EF-2), resulting in the rapid fall in levels of the anti-apoptotic protein myeloid cell leukaemia 1 (Mcl-1), leading to apoptotic cell death. This article summarizes the milestones in the development of moxetumomab pasudotox leading to this first approval for the treatment of adults with relapsed or refractory hairy cell leukaemia who received at least two prior systemic therapies, including treatment with a purine nucleoside analogue. Development of moxetumomab pasudotox for non-Hodgkin's lymphoma, chronic lymphocytic leukaemia and precursor cell lymphoblastic leukaemia/lymphoma was discontinued.

Moxetumomab pasudotox-tdfk for relapsed/refractory hairy cell leukemia: a review of clinical considerations

PURPOSE

Hairy cell leukemia (HCL) is a rare mature B cell leukemia. Purine analogs are the mainstay of treatment of HCL, but relapse after purine analog therapy is common. Outcomes of treatment of relapsed/refractory HCL typically diminish with each successive line of therapy. Moxetumomab pasudotox-tdfk is a novel recombinant immunotoxin approved for the treatment of patients with relapsed/refractory HCL who have received at least two prior therapies, including a purine analog. This article reviews HCL treatment, focusing on moxetumomab pasudotox-tdfk, its place in therapy, considerations for preparation and administration, and strategies for prevention and management of toxicities.

METHODS

A literature search was conducted in the PubMed database from inception to January 2019, using the following terms: moxetumomab, hairy cell leukemia, relapsed/refractory hairy cell leukemia, immunotoxin, and CD22. The package insert and available posters and abstracts were also reviewed.

RESULTS

FDA approval of moxetumomab pasudotox-tdfk was based on a phase III single-arm, open-label trial in 80 patients. Treatment with moxetumomab pasudotox-tdfk yielded a durable complete response rate of 30% with a median duration of response that had not yet been reached at a median follow-up of 16.7 months. The objective response rate was 75% based on blinded independent central review. The most common adverse reactions were infusion-related reactions, edema, nausea, fatigue, headache, pyrexia and anemia. Serious adverse events include capillary leak syndrome and hemolytic uremic syndrome.

CONCLUSIONS

Clinicians providing care for patients receiving moxetumomab pasudotox-tdfk should be aware of the strategies required for safe administration, including the management of serious adverse events.

Hosts for Hostile Protein Production: The Challenge of Recombinant Immunotoxin Expression

For the recombinant expression of toxin-based drugs, a crucial step lies not only in the choice of the production host(s) but also in the accurate design of the protein chimera. These issues are particularly important since such products may be toxic to the expressing host itself. To avoid or limit the toxicity to productive cells while obtaining a consistent yield in chimeric protein, several systems from bacterial to mammalian host cells have been employed. In this review, we will discuss the development of immunotoxin (IT) expression, placing special emphasis on advantages and on potential drawbacks, as one single perfect host for every chimeric protein toxin or ligand does not exist.

A Novel Antibody-Toxin Conjugate to Treat Mantle Cell Lymphoma

Matriptase is a transmembrane serine protease, synthesized as an inactive single-chain zymogen on the endoplasmic reticulum and transported to the plasma membrane. Matriptase is activated in different epithelial and some B-cell malignancies and changes its conformation and activity is inhibited mainly by its endogenous inhibitor HAI-1. Activated matriptase plays a key role in tumor initiation as well as tumor progression, including invasiveness, and metastasis. To target the anti-mitotic toxin (monomethyl auristatin-E) to activated matriptase, a novel antibody to activated matriptase was conjugated with this toxin via a valine-citrulline-PABA linker. In a previous study, this antibody-toxin conjugate was found to be effective against triple negative breast cancer cell lines and xenografts, alone, or in combination with cisplatin (1). In this study, we examined the anti-tumor effect of the antibody toxin conjugate (ADC) against activated matriptase positive mantle cell lymphoma cell lines (JeKo-1, Maver, Mino, and Z138). This ADC was cytotoxic to these cell lines with IC₅₀s between 5 and 14 μg/mL. The ADC also showed a dose dependent anti-tumor effect on the JeKo-1 xenograft in mice without toxicity.

Targeted human cytolytic fusion proteins at the cutting edge: harnessing the apoptosis-inducing properties of human enzymes for the selective elimination of tumor cells

Patient-specific targeted therapy represents the holy grail of anti-cancer therapeutics, allowing potent tumor depletion without detrimental off-target toxicities. Disease-specific monoclonal antibodies have been employed to bind to oncogenic cell-surface receptors, representing the earliest form of immunotherapy. Targeted drug delivery was first achieved by means of antibody-drug conjugates, which exploit the differential expression of tumor-associated antigens as a guiding mechanism for the specific delivery of chemically-conjugated chemotherapeutic agents to diseased target cells. Biotechnological advances have expanded the repertoire of immunology-based tumor-targeting strategies, also paving the way for the next intuitive step in targeted drug delivery: the construction of recombinant protein drugs consisting of an antibody-based targeting domain genetically fused with a cytotoxic peptide, known as an immunotoxin. However, the most potent protein toxins have typically been derived from bacterial or plant virulence factors and commonly feature both off-target toxicity and immunogenicity in human patients. Further refinement of immunotoxin technology thus led to the replacement of monoclonal antibodies with humanized antibody derivatives, including the substitution of non-human toxic peptides with human cytolytic proteins. Preclinically tested human cytolytic fusion proteins (hCFPs) have proven promising as non-immunogenic combinatory anti-cancer agents, however they still require further enhancement to achieve convincing candidacy as a single-mode therapeutic. To date, a portfolio of highly potent human toxins has been established; ranging from microtubule-associated protein tau (MAP tau), RNases, granzyme B (GrB) and death-associated protein kinase (DAPk). In this review, we discuss the most recent findings on the use of these apoptosis-inducing hCFPs for the treatment of various cancers.

Expression and Evaluation of HuscFv Antibody -PE40 Immunotoxin for Target Therapy of EGFR-Overexpressing Cancers

Background

Epidermal growth factor receptor (EGFR) plays an important role in the progression and tumorigenesis of the various cancers. In this regards, anti-EGFR antibodies are valuable approved therapeutics for the EGFR over-expressing cancers. However, the occurrence of mutations in the EGFR and/or KRAS genes; a common phenomenon which is seen in many cancers, lead to the resistance to the EGFR-directed antibodies. EGFR based immunotoxins are capable of overcoming this limitation by directing the toxin moieties to the cancer cells resulting in cell death.

Objectives

In the present study, a novel immunotoxin consisting of the truncated Pseudomonas exotoxin A (PE-40) and anti-EGFR huscFv was developed and evaluated for the induction of cell death in EGFR positive A431tumoral cells.

Materials and Methods

PE-40 fragment of the exotoxin A was amplified by using PCR and ligated to pET22b-huscFv. The reaction was confirmed by PCR and restriction digestion. The immunotoxin was expressed in E. coli BL21 (plysS) and then was purified by Ni-NTA affinity column. Subsequently, the toxicity of the purified immunotoxin was evaluated on EGFR over-expressing epidermoid carcinoma of skin, A431 cell line.

Results

PCR and restriction digestion experiments have verified the integrity of the immunotoxin construct. Purification by affinity column resulted in a highly purified recombinant immunotoxin. MTT assay revealed the growth inhibitory effect of the huscFv-PE40 immunotoxin on EGFR-over-expressing A431 cells with an IC50 value of 250 ng.mL^-1.

Conclusion

In conclusion, the results indicated that the immunotoxin developed in this study has a high toxicity on the EGFR-over-expressing tumor cells and could be considered as a promising candidate for the treatment of the EGFR positive cancers.

Interactions Between Pseudomonas Immunotoxins and the Plasma Membrane: Implications for CAT-8015 Immunotoxin Therapy

Acute Lymphoblastic Leukemia (ALL) remains the most frequent cause of cancer-related mortality in children and novel therapies are needed for the treatment of relapsed/refractory childhood ALL. One approach is the targeting of ALL blasts with the Pseudomonas immunotoxin CAT-8015. Although CAT-8015 has potent anti-leukemia activity, with a 32% objective response rate in a phase 1 study of childhood ALL, haemolytic-uremic syndrome (HUS) and vascular leak syndrome (VLS), major dose-limiting toxicities, have limited the use of this therapeutic approach in children. Investigations into the pathogenesis of CAT-8015-induced HUS/VLS are hindered by the lack of an adequate model system that replicates clinical manifestations, but damage to vascular endothelial cells (ECs) and blood cells are believed to be major initiating factors in both syndromes. Since there is little evidence that murine models replicate human HUS/VLS, and CAT-8015-induced HUS/VLS predominantly affects children, we developed human models and used novel methodologies to investigate CAT-8015 interactions with red blood cells (RBCs) from pediatric ALL patients and ECs of excised human mesenteric arteries. We provide evidence that CAT-8015 directly interacts with RBCs, mediated by Pseudomonas toxin. We also show correlation between the electrical properties of the RBC membrane and RBC susceptibility to CAT-8015-induced lysis, which may have clinical implication. Finally, we provide evidence that CAT-8015 is directly cytototoxic to ECs of excised human mesenteric arteries. In conclusion, the human models we developed constitutes the first, and very important, step in understanding the origins of HUS/VLS in immunotoxin therapy and will allow further investigations of HUS/VLS pathogenesis.

Peptide-Directed Photo-Cross-Linking for Site-Specific Conjugation of IgG

Conjugation of antibody has expanded its applications in therapeutics and diagnostics, and various methods have been developed based on chemical or enzymatic reactions. However, the majority of them have focused on synthetic molecules such as small molecules, nucleic acids, or synthetic materials, but site-specific conjugation of antibody with protein cargo has rarely been demonstrated. In this Communication, we report a PEptide-DIrected Photo-cross-linking (PEDIP) reaction for site-specific conjugation of IgG with protein using an Fc-binding peptide and a photoreactive amino acid analogue, and demonstrate this method by developing an immunotoxin composed of a Her2-targeting IgG (trastuzumab) and an engineered Pseudomonas exotoxin A (PE24). The ADP-ribosylation of eukaryotic elongation factor-2 by the bacterial toxin inhibits the ribosomal translation of protein, and the trastuzumab-PE24 conjugate exhibited the cytotoxicity toward Her2-overexpressing cell lines. The PEDIP reaction can also be applied for many other types of cargo with slight modifications of the method.

Anticancer Activity of Bacterial Proteins and Peptides

Despite much progress in the diagnosis and treatment of cancer, tumour diseases constitute one of the main reasons of deaths worldwide. The side effects of chemotherapy and drug resistance of some cancer types belong to the significant current therapeutic problems. Hence, searching for new anticancer substances and medicines are very important. Among them, bacterial proteins and peptides are a promising group of bioactive compounds and potential anticancer drugs. Some of them, including anticancer antibiotics (actinomycin D, bleomycin, doxorubicin, mitomycin C) and diphtheria toxin, are already used in the cancer treatment, while other substances are in clinical trials (e.g., p28, arginine deiminase ADI) or tested in in vitro research. This review shows the current literature data regarding the anticancer activity of proteins and peptides originated from bacteria: antibiotics, bacteriocins, enzymes, nonribosomal peptides (NRPs), toxins and others such as azurin, p28, Entap and Pep27anal2. The special attention was paid to the still poorly understood active substances obtained from the marine sediment bacteria. In total, 37 chemical compounds or groups of compounds with antitumor properties have been described in the present article.

A novel anti-CD22 scFv-apoptin fusion protein induces apoptosis in malignant B-cells

CD22 marker is a highly internalizing antigen which is located on the surface of B-cells and is being used as a promising target for treatment of B cell malignancies. Monoclonal antibodies targeting CD22 have been introduced and some are currently under investigation in clinical trials. Building on the success of antibody drug conjugates, we developed a fusion protein consisting of a novel anti-CD22 scFv and apoptin and tested binding and therapeutic effects in lymphoma cells. The recombinant protein was expressed in E. coli and successfully purified and refolded. In vitro binding analysis by immunofluorescence and flow cytometry demonstrated that the recombinant protein specifically binds to CD22 positive Raji cells but not to CD22 negative Jurkat cells. The cytotoxic properties of scFv–apoptin were assessed by an MTT assay and Annexin V/PI flow cytometry analysis and showed that the recombinant protein induced apoptosis preferentially in Raji cells with no detectable effects in Jurkat cells. Our findings indicated that the recombinant anti-CD22 scFv–apoptin fusion protein could successfully cross the cell membrane and induce apoptosis with high specificity, make it as a promising molecule for immunotherapy of B-cell malignancies.

Characterization of the anti-CD22 targeted therapy, moxetumomab pasudotox, for B-cell precursor acute lymphoblastic leukemia

Moxetumomab pasudotox is a second-generation recombinant immunotoxin against CD22 on B-cell lineages. Antileukemic activity has been demonstrated in children with chemotherapy-refractory B-cell precursor acute lymphoblastic leukemia (BCP-ALL), with variable responses. Here, we report in vitro and in vivo evaluation of moxetumomab pasudotox treatment of human cell lines and patient-derived cells as a preliminary study to understand characteristics of sensitivity to treatment. Binding, internalization, and apoptosis were evaluated using fluorescently tagged moxetumomab pasudotox. Studies in NOD-scid IL2Rg^null mice showed a modest survival benefit in mice engrafted with 697 cells but not in NALM6 or the two patient-derived xenograft models.

Antibody Drug Conjugates (ADCs): Changing the Treatment Landscape of Lymphoma

OPINION STATEMENT

While strides advancing cancer treatment have made it possible to cure some malignancies, the effort to strike an intricate balance between attaining higher efficacy and lower toxicity has been difficult to accomplish, especially with conventional chemotherapy agents. Introduction of antibody drug conjugates (ADCs) has brought us a step closer to this goal and made it possible to target the cancer cells and to minimize effects on normal tissue. Continued efforts have led to approval of two ADCs for cancer therapy, while many others are in various stages of clinical development. The design of ADCs allows them to be internalized into the cancer cells where the drug payload is released and leads to cell death. The key is to identify targets that are exclusively expressed on malignant cells with minimal or no expression on normal cells, which allows for selective killing of tumor cells. Development and approval of more potent ADCs could change the landscape of cancer therapy and possibly eliminate traditional chemotherapy agents from treatment algorithms. In this review, we discuss the ADCs that are being investigated in early and late stage clinical trials for the treatment of B cell non-Hodgkin lymphoma (NHL).

[Thrombotic microangiopathy and cancer]

Thrombotic microangiopathy (TMA) is a group of disorders characterized by mechanical hemolytic anemia with thrombocytopenia and an ischemic organic lesion of variable and potentially fatal importance affecting mostly the kidneys and the brain with histologically a disseminated and occlusive microvasculopathy. The incidence of TMA represents 15% of acute kidney failure in oncological setting, largely due to the introduction of anti-angiogenic agents over the past decade. It may be more rarely related to cancer itself. The iatrogenic TMA can be classified into 2 types: The type I, secondary to chemotherapy (mitomycinC, gemcitabine), exposes to a chronic dose-dependent renal injury as well as an increase in morbidity and mortality; iatrogenic type II, secondary to anti-angiogenic agents', results in a dose-independent renal involvement and renal functional recovery is usual when the drug is discontinued. There is no randomized controlled trial to establish EBM-type management in TMA support. However, complement activation pathways and regulatory factors analyses allowed us to understand the mechanisms of endothelial lesions. As a result, the current trend includes the use of immunosuppressive agents in recurrent or plasmapheresis-refractory MAT.

Bacterial Toxins for Cancer Therapy

Several pathogenic bacteria secrete toxins to inhibit the immune system of the infected organism. Frequently, they catalyze a covalent modification of specific proteins. Thereby, they block production and/or secretion of antibodies or cytokines. Moreover, they disable migration of macrophages and disturb the barrier function of epithelia. In most cases, these toxins are extremely effective enzymes with high specificity towards their cellular substrates, which are often central signaling molecules. Moreover, they encompass the capacity to enter mammalian cells and to modify their substrates in the cytosol. A few molecules, at least of some toxins, are sufficient to change the cellular morphology and function of a cell or even kill a cell. Since many of those toxins are well studied concerning molecular mechanisms, cellular receptors, uptake routes, and structures, they are now widely used to analyze or to influence specific signaling pathways of mammalian cells. Here, we review the development of immunotoxins and targeted toxins for the treatment of a disease that is still hard to treat: cancer.