Engineering the variable region of therapeutic IgG antibodies

Since the first generation of humanized IgG1 antibodies reached the market in the late 1990s, IgG antibody molecules have been extensively engineered. The success of antibody therapeutics has introduced severe competition in developing novel therapeutic monoclonal antibodies, especially for promising or clinically validated targets. Such competition has led researchers to generate so-called second or third generation antibodies with clinical differentiation utilizing various engineering and optimization technologies. Parent IgG antibodies can be engineered to have improved antigen binding properties, effector functions, pharmacokinetics, pharmaceutical properties and safety issues. Although the primary role of the antibody variable region is to bind to the antigen, it is also the main source of antibody diversity and its sequence affects various properties important for developing antibody therapeutics. Here we review recent research activity in variable region engineering to generate superior antibody therapeutics.Key words: antibody therapeutics, variable region, engineering, affinity, pharmacokinetics, stability, immunogenicity     

Engineering the variable region of therapeutic IgG antibodies

Since the first generation of humanized IgG1 antibodies reached the market in the late 1990s, IgG antibody molecules have been extensively engineered. The success of antibody therapeutics has introduced severe competition in developing novel therapeutic monoclonal antibodies, especially for promising or clinically validated targets. Such competition has led researchers to generate so-called second or third generation antibodies with clinical differentiation utilizing various engineering and optimization technologies. Parent IgG antibodies can be engineered to have improved antigen binding properties, effector functions, pharmacokinetics, pharmaceutical properties and safety issues. Although the primary role of the antibody variable region is to bind to the antigen, it is also the main source of antibody diversity and its sequence affects various properties important for developing antibody therapeutics. Here we review recent research activity in variable region engineering to generate superior antibody therapeutics.     

Engineering recombinant antibodies for immunotherapy

Recombinant antibody fragments binding with high affinity to their target can be obtained either from hybridomas or directly from antibody libraries on filamentous phage. These fragments are devoid of any activity other than antigen binding, and have to be processed and functionalized in order to be suitable for clinical applications. This article presents the authors’ view on the procedures and the features that are important for effective transformation of recombinant antibodies into useful immunotherapeutic agents. The topics presented include phage display methodologies, engineering of high-affinity binding, purification, and functionalization strategies of recombinant antibodies.     

Engineering antibodies for clinical applications

Molecular engineering has contributed immensely to the clinical success of antibodies in recent years. The modular structure of antibodies has permitted their modification in numerous ways, to meet various clinical requirements. With the help of antibody engineering, it has been possible to modify the molecular size, pharmacokinetics, immunogenicity, binding affinity, specificity and effector function of antibodies. In addition, fusion proteins of antibodies with various proteins and peptides have yielded targeted biological modifiers, toxins and imaging agents. This review focuses on the recent trends in antibody engineering for improving their clinical utility.     

Non-fucosylated therapeutic antibodies: the next generation of therapeutic antibodies

Therapeutic antibody IgG1 has two N-linked oligosaccharide chains bound to the Fc region. The oligosaccharides are of the complex biantennary type, composed of a trimannosyl core structure with the presence or absence of core fucose, bisecting N-acetylglucosamine (GlcNAc), galactose, and terminal sialic acid, which gives rise to structural heterogeneity. Both human serum IgG and therapeutic antibodies are well known to be heavily fucosylated. Recently, antibody-dependent cellular cytotoxicity (ADCC), a lytic attack on antibody-targeted cells, has been found to be one of the critical effector functions responsible for the clinical efficacy of therapeutic antibodies such as anti-CD20 IgG1 rituximab (Rituxan^®) and anti-Her2/neu IgG1 trastuzumab (Herceptin^®). ADCC is triggered upon the binding of lymphocyte receptors (FcγRs) to the antibody Fc region. The activity is dependent on the amount of fucose attached to the innermost GlcNAc of N-linked Fc oligosaccharide via an α-1,6-linkage, and is dramatically enhanced by a reduction in fucose. Non-fucosylated therapeutic antibodies show more potent efficacy than their fucosylated counterparts both in vitro and in vivo, and are not likely to be immunogenic because their carbohydrate structures are a normal component of natural human serum IgG. Thus, the application of non-fucosylated antibodies is expected to be a powerful and elegant approach to the design of the next generation therapeutic antibodies with improved efficacy. In this review, we discuss the importance of the oligosaccharides attached to the Fc region of therapeutic antibodies, especially regarding the inhibitory effect of fucosylated therapeutic antibodies on the efficacy of non-fucosylated counterparts in one medical agent. The impact of completely non-fucosylated therapeutic antibodies on therapeutic fields will be also discussed.     

Recombinant therapeutic antibodies

Recombinant antibody technology has revolutionized the development of antibody therapeutics. This minireview offers an overview of enabling technologies and future prospects of this rapidly progressing field. Remark: Trade names are copyright of distributing companies.     

Antimicrobial peptide mimics for improved therapeutic properties

The relatively recent recognition of the major role played by antimicrobial peptides (AMPs) in sustaining an effective host response to immune challenges was greatly influenced by studies of amphibian peptides. AMPs are also widely regarded as a potential source of future antibiotics owing to a remarkable set of advantageous properties ranging from molecular simplicity to low-resistance swift-kill of a broad range of microbial cells. However, the peptide formula per se, represents less than ideal drug candidates, namely because of poor bioavailability issues, potential immunogenicity, optional toxicity and high production costs. To address these issues, synthetic peptides have been designed, reproducing the critical peptide biophysical characteristic in unnatural sequence-specific oligomers. Thus, the use of peptidomimetics to overcome the limitations inherent to peptides physical characteristics is becoming an important and promising approach for improving the therapeutic potential of AMPs. Here, we review most recent advances in the design strategies and the biophysical properties of the main classes of mimics to natural AMPs, emphasizing the importance of structure-activity relationship studies in fine-tuning of their physicochemical attributes for improved antimicrobial properties.     

International intellectual property strategies for therapeutic antibodies

Therapeutic antibodies need international patent protection as their markets expand to include industrialized and emerging countries. Because international intellectual property strategies are frequently complex and costly, applicants require sound information as a basis for decisions regarding the countries in which to pursue patents. While the most important factor is the size of a given market, other factors should also be considered.Key words: antibody, patent, international, PCT, filing strategy     

Engineering receptors and antibodies for biosensors

Biosensor sensitivity and selectivity depend essentially on the properties of the biorecognition elements to be used for analyte binding. Two principally different applications are considered, (1) effects monitoring with biological components as targets for bioeffective substances, among them endocrine disruptors; and (2) immunochemical analysis employing antibodies as binding proteins for a wide variety of analytes such as pesticides. Genetic engineering provides an elegant way not only for providing unlimited amounts of biorecognition molecules but also for the alteration of existing properties and the supplementation with additional functions. Instrumental applications were carried out with the optical sensor BIAcore. The first example deals with the characterization of receptors. For this purpose, the human estrogen receptor alpha was used. Binding studies were carried out with natural as well as xenoestrogens. An equilibrium dissociation constant K(d) of 2.3x10(-10) (M) was derived for 17beta-estradiol. A competition assay was performed with a bovine serum albumin (BSA)-17beta-estradiol conjugate, immobilized at the optical sensor surface, and the free estrogen. The signals obtained represent estradiol equivalents. This format was transferred to a microplate-based enzyme-linked receptor assay. It reached a detection limit of 0.02 microg l(-1) 17beta-estradiol and proved suitable for the detection of natural and synthetic estrogens as well as xenoestrogens in field studies. The second example is targeted at kinetic and affinity measurements of recombinant antibody fragments derived from antibody libraries with s-triazine selectivities. Different strategies for the synthesis of antibody fragment libraries, followed by the selection of specific antibody variants, were examined. An antibody library was derived from a set of B cells. Chain shuffling of the heavy and light chains provided the best binders. An enzyme linked immunosorbent assay (ELISA) was achieved for atrazine with an IC(50) of 0.9 microg l(-1) and a detection limit of 0.2 microg l(-1). The close relations between the optimization of recombinant antibodies by evolutionary strategies and genetic algorithms are considered.     

International intellectual property strategies for therapeutic antibodies

Therapeutic antibodies need international patent protection as their markets expand to include industrialized and emerging countries. Because international intellectual property strategies are frequently complex and costly, applicants require sound information as a basis for decisions regarding the countries in which to pursue patents. While the most important factor is the size of a given market, other factors should also be considered.     

Rethinking the INN system for therapeutic antibodies

In the context of a possible revision of the International Nonproprietary Names (INN) system of recombinant monoclonal antibodies, which is saturated, we propose several avenues of reflection driven by the primary goal of the INN, information of health-care professionals. Clinical considerations argue for an abandon of the substems A (target category) and B (origin category), which lengthen the INN without real added-value. On the contrary, new substems or suffixes are required to alert on the absence/presence of an Fc portion and/or multispecificity, which are essential from a pharmacological point of view. Moreover, we think it necessary to explicitly mention Fc variations since they could influence the pharmacology of these biopharmaceuticals, and hence their efficacy and side-effects. Besides indicating the subclass/isotype in the documents easily accessible to health care professionals, we propose to systematically describe both the natural variations (allotypes) by using the Gm (G marker) system, and the artificial variations by using a Ge (G engineering) system that is discussed here and could apply to all IgG constant domains (tentatively called the Fy portion).     

Engineering therapeutic proteins

Many early drug candidates derived from biotechnology failed in clinical trials because of their low affinity/specificity, short half-lives or immunogenicity. Protein engineering techniques have been applied to circumvent some of the problems that hindered these earlier trials, resulting in clinical benefits from a range of engineered antibodies and other proteins.     

Marketed therapeutic antibodies compendium

Therapeutic monoclonal antibodies (mAbs) are currently being approved for marketing in Europe and the United States, as well as other countries, on a regular basis. As more mAbs become available to physicians and patients, keeping track of the number, types, production cell lines, antigenic targets, and dates and locations of approvals has become challenging. Data are presented here for 34 mAbs that were approved in either Europe or the United States (US) as of March 2012, and nimotuzumab, which is marketed outside Europe and the US. Of the 34 mAbs, 28 (abciximab, rituximab, basiliximab, palivizumab, infliximab, trastuzumab, alemtuzumab, adalimumab, tositumomab-I131, cetuximab, ibrituximab tiuxetan, omalizumab, bevacizumab, natalizumab, ranibizumab, panitumumab, eculizumab, certolizumab pegol, golimumab, canakinumab, catumaxomab, ustekinumab, tocilizumab, ofatumumab, denosumab, belimumab, ipilimumab, brentuximab) are currently marketed in Europe or the US. Data for six therapeutic mAbs (muromonab-CD3, nebacumab, edrecolomab, daclizumab, gemtuzumab ozogamicin, efalizumab) that were approved but have been withdrawn or discontinued from marketing in Europe or the US are also included.     

Engineering bionanoparticles for improved biosensing and bioimaging

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抗体治疗的重生

近年来,治疗性单克隆抗体已成为基础和临床医学研究者及企业关注的热点。目前,针对免疫检查点的治疗性抗体用于肿瘤治疗已显示出较好疗效。在微生物耐药性日益增多、全球突发传染病威胁依然存在及持续性微生物感染难以治愈的当下,抗微生物领域中的抗体治疗正在积极研发中。本文综述了抗体治疗在抗微生物感染领域中的进展,并展望了其应用前景。     

Marketed therapeutic antibodies compendium

Therapeutic monoclonal antibodies (mAbs) are currently being approved for marketing in Europe and the United States, as well as other countries, on a regular basis. As more mAbs become available to physicians and patients, keeping track of the number, types, production cell lines, antigenic targets, and dates and locations of approvals has become challenging. Data are presented here for 34 mAbs that were approved in either Europe or the United States (US) as of March 2012, and nimotuzumab, which is marketed outside Europe and the US. Of the 34 mAbs, 28 (abciximab, rituximab, basiliximab, palivizumab, infliximab, trastuzumab, alemtuzumab, adalimumab, tositumomab-I131, cetuximab, ibrituximab tiuxetan, omalizumab, bevacizumab, natalizumab, ranibizumab, panitumumab, eculizumab, certolizumab pegol, golimumab, canakinumab, catumaxomab, ustekinumab, tocilizumab, ofatumumab, denosumab, belimumab, ipilimumab, brentuximab) are currently marketed in Europe or the US. Data for six therapeutic mAbs (muromonab-CD3, nebacumab, edrecolomab, daclizumab, gemtuzumab ozogamicin, efalizumab) that were approved but have been withdrawn or discontinued from marketing in Europe or the US are also included.Of the 28 mAbs currently marketed in the European Union or the US, 26 are marketed in Europe and 27 are marketed in the US, with 25 marketed in both regions (1 Of the 28 mAbs that are marketed in one or the other region, 43% (12/28) are produced in Chinese hamster ovary (CHO) cells, 25% (7/28) are produced in SP2/0 cells,² 18% (5/28) are produced in NS0 cells,³ and 7% (2/28) are produced in hybridomas. The remaining two products (ranibizumab, certolizumab pegol) are antigen-binding fragments (Fab) that are produced in E. coli. Humanized and human mAbs comprise 36% (10/28) and 32% (9/28) of the total, respectively, while 21% (6/28) are chimeric and 11% (3/28) are murine. Most (75%; 21/28) are canonical full-length mAbs. Of the 7 non-canonical mAbs, three (abciximab, ranibizumab, certolizumab pegol) are Fab, with one of these (certolizumab pegol) pegylated; two (tositumomab-I131, ibrituximab tiuxetan) are radiolabeled when administered to patients; one (brentuximab vedotin) is an antibody-drug conjugate (ADC); and one is bispecific (catumaxomab). Although 16 marketed mAbs target unique antigens, CD20 and tumor necrosis factor are each targeted by 4 mAbs, and epidermal growth factor receptor (EGFR) and vascular endothelial growth factor are each targeted by 2 mAbs. If approved, pertuzumab, which is undergoing regulatory review in Europe and the US as a treatment for breast cancer, would be one of 2 mAbs that target human epidermal growth factor receptor 2 on the market.Table 1. Therapeutic monoclonal antibodies marketed or in review in the European Union or United States

Engineering chromosomes for delivery of therapeutic genes

The ability to create fully functional human chromosome vectors represents a potentially exciting gene-delivery system for the correction of human genetic disorders with several advantages over viral delivery systems. However, for the full potential of chromosome-based gene-delivery vectors to be realized, several key obstacles must be overcome. Methods must be developed to insert therapeutic genes reliably and efficiently and to enable the stable transfer of the resulting chromosomal vectors to different therapeutic cell types. Research to achieve these outcomes continues to encounter major challenges; however recent developments have reiterated the potential of chromosome-based vectors for therapeutic gene delivery. Here we review the different strategies under development and discuss the advantages and problems associated with each.