Production,characterization and pharmacokinetic properties of antibodies with N-linked Mannose-5 glycans

The effector functions of therapeutic antibodies are strongly affected by the specific glycans added to the Fc domain during post-translational processing. Antibodies bearing high levels of N-linked mannose-5 glycan (Man5) have been reported to exhibit enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) compared with antibodies with fucosylated complex or hybrid glycans. To better understand the relationship between antibodies with high levels of Man5 and their biological activity in vivo, we developed an approach to generate substantially homogeneous antibodies bearing the Man5 glycoform. A mannosidase inhibitor, kifunensine, was first incorporated in the cell culture process to generate antibodies with a distribution of high mannose glycoforms. Antibodies were then purified and treated with a mannosidase for trimming to Man5 in vitro. This 2-step approach can consistently generate antibodies with > 99% Man5 glycan. Antibodies bearing varying levels of Man5 were studied to compare ADCC and Fcγ receptor binding, and they showed enhanced ADCC activity and increased binding affinity to the FcγRIIIA. In addition, the clearance rate of antibodies bearing Man8/9 and Man5 glycans was determined in a pharmacokinetics study in mice. When compared with historical data, the antibodies bearing the high mannose glycoform exhibited faster clearance rate compared with antibodies bearing the fucosylated complex glycoform, while the pharmacokinetic properties of antibodies with Man8/9 and Man5 glycoforms appeared similar. In addition, we identified the presence of a mannosidase in mouse serum that converted most Man8/9 to Man6 after 24 h.     

Production,characterization and pharmacokinetic properties of antibodies with N-linked Mannose-5 glycans

The effector functions of therapeutic antibodies are strongly affected by the specific glycans added to the Fc domain during post-translational processing. Antibodies bearing high levels of N-linked mannose-5 glycan (Man5) have been reported to exhibit enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) compared with antibodies with fucosylated complex or hybrid glycans. To better understand the relationship between antibodies with high levels of Man5 and their biological activity in vivo, we developed an approach to generate substantially homogeneous antibodies bearing the Man5 glycoform. A mannosidase inhibitor, kifunensine, was first incorporated in the cell culture process to generate antibodies with a distribution of high mannose glycoforms. Antibodies were then purified and treated with a mannosidase for trimming to Man5 in vitro. This 2-step approach can consistently generate antibodies with > 99% Man5 glycan. Antibodies bearing varying levels of Man5 were studied to compare ADCC and Fcγ receptor binding, and they showed enhanced ADCC activity and increased binding affinity to the FcγRIIIA. In addition, the clearance rate of antibodies bearing Man8/9 and Man5 glycans was determined in a pharmacokinetics study in mice. When compared with historical data, the antibodies bearing the high mannose glycoform exhibited faster clearance rate compared with antibodies bearing the fucosylated complex glycoform, while the pharmacokinetic properties of antibodies with Man8/9 and Man5 glycoforms appeared similar. In addition, we identified the presence of a mannosidase in mouse serum that converted most Man8/9 to Man6 after 24 h.     

Modulation of therapeutic antibody effector functions by glycosylation engineering: influence of Golgi enzyme localization domain and co-expression of heterologous beta1, 4-N-acetylglucosaminyltransferase III and Golgi alpha-mannosidase II

The effector functions elicited by IgG antibodies strongly depend on the carbohydrate moiety linked to the Fc region of the protein. Therefore several approaches have been developed to rationally manipulate these glycans and improve the biological functions of the antibody. Overexpression of recombinant beta1,4-N-acetylglucosaminyltransferase III (GnT-III) in production cell lines leads to antibodies enriched in bisected oligosaccharides. Moreover, GnT-III overexpression leads to increases in non-fucosylated and hybrid oligosaccharides. Such antibody glycovariants have increased antibody-dependent cellular cytotoxicity (ADCC). To explore a further variable besides overexpression of GnT-III, we exchanged the localization domain of GnT-III with that of other Golgi-resident enzymes. Our results indicate that chimeric GnT-III can compete even more efficiently against the endogenous core alpha1,6-fucosyltransferase (alpha1,6-FucT) and Golgi alpha-mannosidase II (ManII) leading to higher proportions of bisected non-fucosylated hybrid glycans ("Glyco-1" antibody). The co-expression of GnT-III and ManII led to a similar degree of non-fucosylation as that obtained for Glyco-1, but the majority of the oligosaccharides linked to this antibody ("Glyco-2") are of the complex type. These glycovariants feature strongly increased ADCC activity compared to the unmodified antibody, while Glyco-1 (hybrid-rich) features reduced complement-dependent cytotoxicity (CDC) compared to Glyco-2 or unmodified antibody. We show that apart from GnT-III overexpression, engineering of GnT-III localization is a versatile tool to modulate the biological activities of antibodies relevant for their therapeutic application.     

Quantitative evaluation of fucose reducing effects in a humanized antibody on Fcγ receptor binding and antibody-dependent cell-mediated cytotoxicity activities

The presence or absence of core fucose in the Fc region N-linked glycans of antibodies affects their binding affinity toward FcγRIIIa as well as their antibody-dependent cell-mediated cytotoxicity (ADCC) activity. However, the quantitative nature of this structure-function relationship remains unclear. In this study, the in vitro biological activity of an afucosylated anti-CD20 antibody was fully characterized. Further, the effect of fucose reduction on Fc effector functions was quantitatively evaluated using the afucosylated antibody, its “regular” fucosylated counterpart and a series of mixtures containing varying proportions of “regular” and afucosylated materials. Compared with the “regular” fucosylated antibody, the afucosylated antibody demonstrated similar binding interactions with the target antigen (CD20), C1q and FcγRIa, moderate increases in binding to FcγRIIa and IIb, and substantially increased binding to FcγRIIIa. The afucosylated antibodies also showed comparable complement-dependent cytotoxicity activity but markedly increased ADCC activity. Based on EC₅₀ values derived from dose-response curves, our results indicate that the amount of afucosylated glycan in antibody samples correlate with both FcγRIIIa binding activity and ADCC activity in a linear fashion. Furthermore, the extent of ADCC enhancement due to fucose depletion was not affected by the FcγRIIIa genotype of the effector cells.     

Quantitative evaluation of fucose reducing effects in a humanized antibody on Fcγ receptor binding and antibody-dependent cell-mediated cytotoxicity activities

The presence or absence of core fucose in the Fc region N-linked glycans of antibodies affects their binding affinity toward FcγRIIIa as well as their antibody-dependent cell-mediated cytotoxicity (ADCC) activity. However, the quantitative nature of this structure-function relationship remains unclear. In this study, the in vitro biological activity of an afucosylated anti-CD20 antibody was fully characterized. Further, the effect of fucose reduction on Fc effector functions was quantitatively evaluated using the afucosylated antibody, its “regular” fucosylated counterpart and a series of mixtures containing varying proportions of “regular” and afucosylated materials. Compared with the “regular” fucosylated antibody, the afucosylated antibody demonstrated similar binding interactions with the target antigen (CD20), C1q and FcγRIa, moderate increases in binding to FcγRIIa and IIb, and substantially increased binding to FcγRIIIa. The afucosylated antibodies also showed comparable complement-dependent cytotoxicity activity but markedly increased ADCC activity. Based on EC₅₀ values derived from dose-response curves, our results indicate that the amount of afucosylated glycan in antibody samples correlate with both FcγRIIIa binding activity and ADCC activity in a linear fashion. Furthermore, the extent of ADCC enhancement due to fucose depletion was not affected by the FcγRIIIa genotype of the effector cells.     

Antibody production using a ciliate generates unusual antibody glycoforms displaying enhanced cell-killing activity

Antibody glycosylation is a key parameter in the optimization of antibody therapeutics. Here, we describe the production of the anti-cancer monoclonal antibody rituximab in the unicellular ciliate, Tetrahymena thermophila. The resulting antibody demonstrated enhanced antibody-dependent cell-mediated cytotoxicity, which we attribute to unusual N-linked glycosylation. Detailed chromatographic and mass spectrometric analysis revealed afucosylated, oligomannose-type glycans, which, as a whole, displayed isomeric structures that deviate from the typical human counterparts, but whose branches were equivalent to fragments of metabolic intermediates observed in human glycoproteins. From the analysis of deposited crystal structures, we predict that the ciliate glycans adopt protein-carbohydrate interactions with the Fc domain that closely mimic those of native complex-type glycans. In addition, terminal glucose structures were identified that match biosynthetic precursors of human glycosylation. Our results suggest that ciliate-based expression systems offer a route to large-scale production of monoclonal antibodies exhibiting glycosylation that imparts enhanced cell killing activity.     

Rapid production of recombinant human IgG With improved ADCC effector function in a transient expression system

Rapid production of recombinant human IgG with improved antibody dependent cell‐mediated cytotoxicity (ADCC) effector function is presented. The technique employs transient expression of IgG in suspension growing HEK‐293F cells in the presence of the glycosidase inhibitor kifunensine. The procedure takes ～7 days, provided that expression plasmids encoding the IgG of interest are available. Kifunensine inhibits the N‐linked glycosylation pathway of HEK‐293F cells in the endoplasmatic reticulum, resulting in IgG with oligomannose type glycans lacking core‐fucose. IgG1 transiently produced in kifunensine‐ treated HEK‐293F cells has improved affinity for the FcγRIIIA molecule as measured in an ELISA based assay, and almost eightfold enhanced ADCC using primary peripheral blood mononuclear effector cells. Biotechnol. Bioeng. 2010; 105: 350–357. © 2009 Wiley Periodicals, Inc.     

Comparison of biological activity among nonfucosylated therapeutic IgG1 antibodies with three different N-linked Fc oligosaccharides: the high-mannose, hybrid, and complex types

The structure of asparagine-linked oligosaccharides attached to the antibody constant region (Fc) of human immunoglobulin G1 (IgG1) has been shown to affect the pharmacokinetics and antibody effector functions of antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). However, it is still unclear how differences in the N-linked oligosaccharide structures impact the biological activities of antibodies, especially those lacking core fucose. Here, we succeeded in generating core fucose-lacking human IgG1 antibodies with three different N-linked Fc oligosaccharides, namely, a high-mannose, hybrid, and complex type, using the same producing clone, and compared their activities. Cultivation of an alpha-1,6-fucosyltransferase (FUT8) knockout Chinese hamster ovary cell line in the presence or absence of a glycosidase inhibitor (either swainsonine or kifunensine) yielded antibody production of each of the three types without contamination by the others. Two of three types of nonnaturally occurring atypical oligosaccharide IgG1, except the complex type, reduced the affinity for both human lymphocyte receptor IIIa (FcgammaRIIIa) and the C1q component of the complement, resulting in reduction of ADCC and CDC. The bulky structure of the nonreducing end of N-linked Fc oligosaccharides is considered to contribute the CDC change, whereas the structural change in the reducing end, i.e. the removal of core fucose, causes ADCC enhancement through improved FcgammaRIIIa binding. In the pharmacokinetic profile, although no significant difference of human neonatal Fc receptor (FcRn)-binding affinity was observed among the three types, the complex type showed longer serum half-lives than the other types irrespective of core fucosylation in mice, which also suggests the contribution of the nonreducing end structure. The present study provides basic information on the effects of core fucose-lacking N-linked Fc oligosaccharides on antibody biological activities.     

Carbohydrate and Domain Architecture of an Immature Antibody Glycoform Exhibiting Enhanced Effector Functions

Antibodies contain a conserved glycosylation site that has emerged as a target for the modulation of antibody effector functions. The crystal structure of a biosynthetic intermediate of human IgG1, bearing immature oligomannose-type glycans and reported to display increased antibody-dependent cellular cytotoxicity, demonstrates that glycan engineering can bias the Fc to an open conformation primed for receptor binding.     

Engineering host cell lines to reduce terminal sialylation of secreted antibodies

Covalently-linked glycans on proteins have many functional roles, some of which are still not completely understood. Antibodies have a very specific glycan modification in the Fc region that is required for mediating immune effector functions. These Fc glycans are typically highly heterogeneous in structure, and this heterogeneity is influenced by many factors, such as type of cellular host and rate of Ab secretion. Glycan heterogeneity can affect the Fc-dependent activities of antibodies. It has been shown recently that increased Fc sialylation can result in decreased binding to immobilized antigens and some Fcγ receptors, as well as decreased antibody-dependent cell-mediated cytotoxicity (ADCC) activity. In contrast, increased Fc sialylation enhances the anti-inflammatory activity of antibodies. To produce antibodies with increased effector functions, we developed host cell lines that would limit the degree of sialylation of recombinantly-expressed antibodies. Towards this end, the catalytic domain of the Arthrobacter ureafaciens sialidase (sialidase A) was engineered for secreted expression in mammalian cell lines. Expression of this sialidase A gene in mammalian cells resulted in secreted expression of soluble enzyme that was capable of removing sialic acid from antibodies secreted into the medium. Purified antibodies secreted from these cells were found to possess very low levels of sialylation compared with the same antibodies purified from unmodified host cells. The low sialylated antibodies exhibited similar binding affinity to soluble antigens, improved ADCC activity, and they possessed pharmacokinetic properties comparable to their more sialylated counterparts. Further, it was observed that the amount of sialidase A expressed was sufficient to thoroughly remove sialic acid from Abs made in high-producing cell lines. Thus, engineering host cells to express sialidase A enzyme can be used to produce recombinant antibodies with very low levels of sialylation.Key words: antibodies, IgGs, glycans, oligosaccharides, sialic acid, sialidase, ADCC, CDC, effector functions, cells, Fc receptors, proteases     

核心岩藻糖基化控制在治疗性抗体研究中的应用

对于人类许多疾病,抗体已成为了一种很重要的治疗制剂。如何进一步提高抗体的效能,是目前研究的主要热点之一。在抗体治疗过程中,抗体依赖性细胞介导的细胞毒作用(antibody dependent cellular cytotoxicity,ADCC)被认为是治疗性抗体临床疗效中一个重要的治疗功能。抗体恒定区Fc片段(crystalline fragment)的糖基化对ADCC起着至关重要的作用,尤其是抗体恒定区的核心岩藻糖基化。近些年来,很多研究报告表明,去除或降低岩藻糖基化的治疗性抗体不论在体内还是在体外都表现出更高的效能。这主要是由于去除或降低岩藻糖基化的治疗性抗体相对于岩藻糖基化的抗体,可以在更低浓度下通过与FcγRIIIa的高亲和力而表现出较强的ADCC作用。因此,去除或降低岩藻糖基化抗体的应用有望成为提高下一代治疗性抗体效能的有效手段。在此综述中,我们主要讨论了控制治疗性抗体恒定区岩藻糖基化的重要性及当前去除或降低岩藻糖基化治疗性抗体的生产控制方法。     

Yeast-elicited cross-reactive antibodies to HIV Env glycans efficiently neutralize virions expressing exclusively high-mannose N-linked glycans

The HIV envelope (Env) protein uses a dense coat of glycans to mask conserved domains and evade host humoral immune responses. The broadly neutralizing antibody 2G12, which binds a specific cluster of high-mannose glycans on HIV Env, shows that the glycan shield can also serve as a target for neutralizing antibodies. We have described a triple mutant Saccharomyces cerevisiae strain that expresses high-mannose glycoproteins that bind to 2G12. When used to immunize rabbits, this yeast elicits antibodies that bind to gp120-associated glycans but fail to neutralize virus. Here we sought to determine the reason for these discordant results. Affinity purification of sera over columns conjugated with three 2G12-reactive yeast glycoproteins showed that these proteins could adsorb 80% of the antibodies that bind to gp120 glycans. Despite binding to monomeric gp120, these mannose-specific antibodies failed to bind cell surface-expressed trimeric Env. However, when Env was expressed in the presence of the mannosidase inhibitor kifunensine to force retention of high-mannose glycans at all sites, the purified antibodies gained the abilities to bind trimeric Env and to strongly and broadly neutralize viruses produced under these conditions. Combined, these data show that the triple mutant yeast strain elicits antibodies that bind to high-mannose glycans presented on the HIV envelope, but only when they are displayed in a manner not found on native Env trimers. This implies that the underlying structure of the protein scaffold used to present the high-mannose glycans may be critical to allow elicitation of antibodies that recognize trimeric Env and neutralize virus.     

Establishment of FUT8 knockout Chinese hamster ovary cells: an ideal host cell line for producing completely defucosylated antibodies with enhanced antibody-dependent cellular cytotoxicity

To generate industrially applicable new host cell lines for antibody production with optimizing antibody-dependent cellular cytotoxicity (ADCC) we disrupted both FUT8 alleles in a Chinese hamster ovary (CHO)/DG44 cell line by sequential homologous recombination. FUT8 encodes an alpha-1,6-fucosyltransferase that catalyzes the transfer of fucose from GDP-fucose to N-acetylglucosamine (GlcNAc) in an alpha-1,6 linkage. FUT8(-/-) cell lines have morphology and growth kinetics similar to those of the parent, and produce completely defucosylated recombinant antibodies. FUT8(-/-)-produced chimeric anti-CD20 IgG1 shows the same level of antigen-binding activity and complement-dependent cytotoxicity (CDC) as the FUT8(+/+)-produced, comparable antibody, Rituxan. In contrast, FUT8(-/-)-produced anti-CD20 IgG1 strongly binds to human Fcgamma-receptor IIIa (FcgammaRIIIa) and dramatically enhances ADCC to approximately 100-fold that of Rituxan. Our results demonstrate that FUT8(-/-) cells are ideal host cell lines to stably produce completely defucosylated high-ADCC antibodies with fixed quality and efficacy for therapeutic use.     

Sulfatide binding properties of murine and human antiganglioside antibodies

Antiganglioside antibodies form an important component of the innate and adaptive B cell repertoire, where they provide antimicrobial activity through binding encapsulated bacterial glycans. In an aberrant role, they target peripheral nerve gangliosides to induce autoimmune nerve injury. An important characteristic of antiganglioside antibodies is their ability to selectively recognize highly defined glycan structures. Since sialylated and sulfated glycans often share lectin recognition patterns, we here explored the possibility that certain antiganglioside antibodies might also bind 3-O-sulfo-beta-D-galactosylceramide (sulfatide), an abundant constituent of plasma and peripheral nerve myelin, that could thereby influence any immunoregulatory or autoimmune properties. Out of 25 antiganglioside antibodies screened in solid phase assays, 20 also bound sulfatide (10(-5) to 10(-6) M range) in addition to their favored ganglioside glycan epitope ( approximately 10(-7) M range). Solution inhibition studies demonstrated competition between ganglioside and sulfatide, indicating close proximity or sharing of the antigen binding variable region domain. Sulfatide and 3-O-sulfo-beta-D-galactose were unique in having this property amongst a wide range of sulfated glycans screened, including 4- and 6-O-sulfo-beta-D-galactose analogues. Antiganglioside antibody binding to 3-O-sulfo-beta-D-galactose was highly dependent upon the spatial presentation of the ligand, being completely inhibited by conjugation to protein or polyacrylamide (PAA) matrices. Binding was also absent when sulfatide was incorporated into plasma membranes, including myelin, under conditions in which antibody binding to ganglioside was retained. These data demonstrate that sulfatide binding is a common property of antiganglioside antibodies that may provide functional insights into, and consequences for this component of the innate immune repertoire.     

Development of a pre-glycoengineered CHO-K1 host cell line for the expression of antibodies with enhanced Fc mediated effector function

Novel biotherapeutic glycoproteins, like recombinant monoclonal antibodies (mAbs) are widely used for the treatment of numerous diseases. The N-glycans attached to the constant region of an antibody have been demonstrated to be crucial for the biological efficacy. Even minor modifications of the N-glycan structure can dictate the potency of IgG effector functions such as the antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC).

Here, we present the development of a glycoengineered CHO-K1 host cell line (HCL), stably expressing β1,4-N-Acetylglucoseaminyltransferase III (GnT-III) and α-mannosidase II (Man-II), for the expression of a-fucosylated antibodies with enhanced Fc-mediated effector function. Glycoengineered HCLs were generated in a two-step strategy, starting with generating parental HCLs by stable transfection of CHO-K1 cells with GnT-III and Man-II. In a second step, parental HCLs were stably transfected a second time with these two transgenes to increase their copy number in the genetic background. Generated glycoengineered CHO-K1 cell lines expressing two different mAbs deliver antibody products with a content of more than 60% a-fucosylated glycans. In-depth analysis of the N-glycan structure revealed that the majority of the Fc-attached glycans of the obtained mAbs were of complex bisected type. Furthermore, we showed the efficient use of FcγRIIIa affinity chromatography as a novel method for the fast assessment of the mAbs a-fucosylation level. By testing different cultivation conditions for the pre-glycoengineered recombinant CHO-K1 clones, we identified key components essential for the production of a-fucosylated mAbs. The prevalent effect could be attributed to the trace element manganese, which leads to a strong increase of a-fucosylated complex- and hybrid-type glycans. In conclusion, the novel pre-glycoengineered CHO-K1 HCL can be used for the production of antibodies with high ratios of a-fucosylated Fc-attached N-glycans. Application of our newly developed FcγRIIIa affinity chromatography method during cell line development and use of optimized cultivation conditions can ultimately support the efficient development of a-fucosylated mAbs.     

Expression-System-Dependent Modulation of HIV-1 Envelope Glycoprotein Antigenicity and Immunogenicity

Recombinant expression systems differ in the type of glycosylation they impart on expressed antigens such as the human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins, potentially affecting their biological properties. We performed head-to-head antigenic, immunogenic and molecular profiling of two distantly related Env surface (gp120) antigens produced in different systems: (a) mammalian (293 FreeStyle™ cells; 293F) cells in the presence of kifunensine, which impart only high-mannose glycans; (b) insect cells (Spodoptera frugiperda, Sf9), which confer mainly paucimannosidic glycans; (c) Sf9 cells recombinant for mammalian glycosylation enzymes (Sf9 Mimic™), which impart high-mannose, hybrid and complex glycans without sialic acid; and (d) 293F cells, which impart high-mannose, hybrid and complex glycans with sialic acid. Molecular models revealed a significant difference in gp120 glycan coverage between the Sf9-derived and wild-type mammalian-cell-derived material that is predicted to affect ligand binding sites proximal to glycans. Modeling of solvent-exposed surface electrostatic potentials showed that sialic acid imparts a significant negative surface charge that may influence gp120 antigenicity and immunogenicity. Gp120 expressed in systems that do not incorporate sialic acid displayed increased ligand binding to the CD4 binding and CD4-induced sites compared to those expressed in the system that do, and imparted other more subtle differences in antigenicity in a gp120 subtype-specific manner. Non-sialic-acid-containing gp120 was significantly more immunogenic than the sialylated version when administered in two different adjuvants, and induced higher titers of antibodies competing for CD4 binding site ligand-gp120 interaction. These findings suggest that non-sialic-acid-imparting systems yield gp120 immunogens with modified antigenic and immunogenic properties, considerations that should be considered when selecting expression systems for glycosylated antigens to be used for structure-function studies and for vaccine use.     

Engineering host cell lines to reduce terminal sialylation of secreted antibodies

Covalently-linked glycans on proteins have many functional roles, some of which are still not completely understood. Antibodies have a very specific glycan modification in the Fc region that is required for mediating immune effector functions. These Fc glycans are typically highly heterogeneous in structure, and this heterogeneity is influenced by many factors, such as type of cellular host and rate of Ab secretion. Glycan heterogeneity can affect the Fc-dependent activities of antibodies. It has been shown recently that increased Fc sialylation can result in decreased binding to immobilized antigens and some Fcγ receptors, as well as decreased antibody-dependent cell-mediated cytotoxicity (ADCC) activity. In contrast, increased Fc sialylation enhances the anti-inflammatory activity of antibodies. To produce antibodies with increased effector functions, we developed host cell lines that would limit the degree of sialylation of recombinantly-expressed antibodies. Towards this end, the catalytic domain of the Arthrobacter ureafaciens sialidase (sialidase A) was engineered for secreted expression in mammalian cell lines. Expression of this sialidase A gene in mammalian cells resulted in secreted expression of soluble enzyme that was capable of removing sialic acid from antibodies secreted into the medium. Purified antibodies secreted from these cells were found to possess very low levels of sialylation compared with the same antibodies purified from unmodified host cells. The low sialylated antibodies exhibited similar binding affinity to soluble antigens, improved ADCC activity, and they possessed pharmacokinetic properties comparable to their more sialylated counterparts. Further, it was observed that the amount of sialidase A expressed was sufficient to thoroughly remove sialic acid from Abs made in high-producing cell lines. Thus, engineering host cells to express sialidase A enzyme can be used to produce recombinant antibodies with very low levels of sialylation.     

Comparison of cell lines for stable production of fucose-negative antibodies with enhanced ADCC

Several methods have been described to enhance antibody-dependent cellular cytotoxicity (ADCC) using different host cells that produce antibody with reduced levels of fucose on their carbohydrates. We compared the suitability of these methods for the serum-free fed-batch production of antibody for clinical trials and commercial uses. Recombinant anti-human CD20 chimeric IgG1-producing clones were established from host-cells that have been shown to produce more than 90% fucose-negative antibody. The cell lines were a FUT8 (alpha-1,6-fucosyltransferase) knockout Chinese hamster ovary (CHO) cell line, Ms704, and two Lens culinaris agglutinin (LCA)-resistant cell lines, one derived from a variant CHO line, Lec13 and the other from a rat hybridoma cell line, YB2/0. The amount of fucose-negative antibody produced by Lec13 and YB2/0 significantly decreased with the culture. The increase in fucosylation was due to remaining synthesis of GDP-fucose via de novo pathway for the CHO line and the elevation of FUT8 expression by the YB2/0 cells. In contrast, Ms704 cells stably produced fucose-negative antibody with a consistent carbohydrate structure until the end of the culture. The productivity of the Ms704 cells reached 1.76 g/L with a specific production rate (SPR) of 29 pg/cell/day for 17 days in serum-free fed-batch culture using a 1 L spinner bioreactor. Our results demonstrate that FUT8 knockout has the essential characteristics of host cells for robust manufacture of fucose-negative therapeutic antibodies with enhanced ADCC.     

Marketing approval of mogamulizumab

Therapeutic properties of antibodies strongly depend on the composition of their glycans. Most of the currently approved antibodies are produced in mammalian cell lines, which yield mixtures of different glycoforms that are close to those of humans, but not fully identical. Glyco-engineering is being developed as a method to control the composition of carbohydrates and to enhance the pharmacological properties of mAbs. The recent approval in Japan of mogamulizumab (POTELIGEO^®), the first glyco-engineered antibody to reach the market, is a landmark in the field of therapeutic antibodies. Mogamulizumab is a humanized mAb derived from Kyowa Hakko Kirin’s POTELLIGENT^® technology, which produces antibodies with enhanced antibody-dependent cell-mediated cytotoxicity (ADCC) activity. The approval was granted April 30, 2012 by the Japanese Ministry of Health, Labour and Welfare for patients with relapsed or refractory CCR4-positive adult T-cell leukemia-lymphoma.     

A novel monoclonal antibody associated with glucoside kills gastric adenocarcinoma AGS cells based on glycosylation target

Glycosylation results in the production of glycans which are required for certain proteins to function. These glycans are also present on cell surfaces where they help maintain cell membrane integrity and are a key component of immune recognition. As such, cancer has been shown to alter glycosylation to promote tumour proliferation, invasion, angiogenesis, and immune envasion. Currently, there are few therapeutic monoclonal antibodies (mAb) which target glycosylation alterations in cancer. Here, we report a novel mAb associated with a glucoside, mAb 201E4, which is able induce cancer cell death and apoptosis based on a specific glycosylation target. This mAb evokes cancer cell death in vitro via caspase, fas, and mitochondrial associated apoptotic pathways. The efficacy of this mAb was further confirmed in vivo as treatment of mice with mAb 201E4 resulted in potent tumour shrinkage. Finally, the antibody was proven to be specific to glycosylation alterations in cancer and have no binding to normal tissues. This data indicates that mAb 201E4 successfully targets glycosylation alterations in neoplasms to induce cancer cell death, which may provide a new strategy for therapy in cancer.