Influence of variable N-glycosylation on the cytolytic potential of chimeric CD19 antibodies

Prediction of neoadjuvant chemotherapeutic efficacy in patients with locally advanced gastric cancer by serum IgG glycomics profiling

Background

Neoadjuvant chemotherapy (NACT) could improve prognosis and survival quality of patients with local advanced gastric cancer (LAGC) by providing an opportunity of radical operation for them. However, no effective method could predict the efficacy of NACT before surgery to avoid the potential toxicity, time-consuming and economic burden of ineffective chemotherapy. Some research has been investigated about the correlation between serum IgG glycosylation and gastric cancer, but the question of whether IgG glycome can reflect the tumor response to NACT is still unanswered.

Method

Serum IgG glycome profiles were analyzed by Ultra Performance Liquid Chromatography in a cohort comprised of 49 LAGC patients of which 25 were categorized as belonging to the NACT response group and 24 patients were assigned to the non-response group. A logistic regression model was constructed to predict the response rate incorporating clinical features and differential N-glycans, while the precision of model was assessed by receiver operating characteristic (ROC) analysis.

Results

IgG N-glycome analysis in pretreatment serum of LAGC patients comprises 24 directly detected glycans and 17 summarized traits. Compared with IgG glycans of non-response group, agalactosylated N-glycans increased while monosialylated N-glycans and digalactosylated N-glycans decreased in the response group. We constructed a model combining patients' age, histology, chemotherapy regimen, GP4(H3N4F1), GP6(H3N5F1), and GP18(H5N4F1S1), and ROC analysis showed this model has an accurate prediction of NACT response (AUC = 0.840) with the sensitivity of 64.00% and the specificity of 100%.

Conclusion

We here firstly present the profiling of IgG N-glycans in pretreatment serum of LAGC. The alterations in IgG N-glycome may be personalized biomarkers to predict the response to NACT in LAGC and help to illustrate the relationship between immunity and effect of NACT.

Strategies to Augment Natural Killer (NK) Cell Activity against Solid Tumors

The immune system plays a crucial role to prevent local growth and dissemination of cancer. Therapies based on activating the immune system can result in beneficial responses in patients with metastatic disease. Treatment with antibodies targeting the immunological checkpoint axis PD-1 / PD-L1 can result in the induction of anti-tumor T cell activation leading to meaningful long-lasting clinical responses. Still, many patients acquire resistance or develop dose-limiting toxicities to these therapies. Analysis of tumors from patients who progress on anti-PD-1 treatment reveal defective interferon-signaling and antigen presentation, resulting in immune escape from T cell-mediated attack. Natural killer (NK) cells are innate lymphocytes that can kill tumor cells without prior sensitization to antigens and can be activated to kill tumor cells that have an impaired antigen processing and presentation machinery. Thus, NK cells may serve as useful effectors against tumor cells that have become resistant to classical immune checkpoint therapy. Various approaches to activate NK cells are being increasingly explored in clinical trials against cancer. While clinical benefit has been demonstrated in patients with acute myeloid leukemia receiving haploidentical NK cells, responses in patients with solid tumors are so far less encouraging. Several hurdles need to be overcome to provide meaningful clinical responses in patients with solid tumors. Here we review the recent developments to augment NK cell responses against solid tumors with regards to cytokine therapy, adoptive infusion of NK cells, NK cell engagers, and NK cell immune checkpoints.

Modulating Cytotoxic Effector Functions by Fc Engineering to Improve Cancer Therapy

In the last two decades, monoclonal antibodies have revolutionized the therapy of cancer patients. Although antibody therapy has continuously been improved, still a significant number of patients do not benefit from antibody therapy. Therefore, rational optimization of the antibody molecule by Fc engineering represents a major area of translational research to further improve this potent therapeutic option. Monoclonal antibodies are able to trigger a variety of effector mechanisms. Especially Fc-mediated effector functions such as antibody-dependent cell-mediated cytotoxicity (ADCC), antibody-dependent cellular phagocytosis (ADCP), and complement- dependent cytotoxicity (CDC) are considered important in antibody therapy of cancer. Novel mechanistic insights into the action of monoclonal antibodies allowed the development of various Fc engineering approaches to modulate antibodies' effector functions. Strategies in modifying the Fc glycosylation profile (Fc glyco-engineering) or approaches in engineering the protein backbone (Fc protein engineering) have been intensively evaluated. In the current review, Fc engineering strategies resulting in improved ADCC, ADCP and CDC activity are summarized and discussed.

Antibody-Based Cancer Therapy: Successful Agents and Novel Approaches

Since their discovery, antibodies have been viewed as ideal candidates or "magic bullets" for use in targeted therapy in the fields of cancer, autoimmunity, and chronic inflammatory disorders. A wave of antibody-dedicated research followed, which resulted in the clinical approval of a first generation of monoclonal antibodies for cancer therapy such as rituximab (1997) and cetuximab (2004), and infliximab (2002) for the treatment of autoimmune diseases. More recently, the development of antibodies that prevent checkpoint-mediated inhibition of T cell responses invigorated the field of cancer immunotherapy. Such antibodies induced unprecedented long-term remissions in patients with advanced stage malignancies, most notably melanoma and lung cancer, that do not respond to conventional therapies. In this review, we will recapitulate the development of antibody-based therapy, and detail recent advances and new functions, particularly in the field of cancer immunotherapy. With the advent of recombinant DNA engineering, a number of rationally designed molecular formats of antibodies and antibody-derived agents have become available, and we will discuss various molecular formats including antibodies with improved effector functions, bispecific antibodies, antibody-drug conjugates, antibody-cytokine fusion proteins, and T cells genetically modified with chimeric antigen receptors. With these exciting advances, new antibody-based treatment options will likely enter clinical practice and pave the way toward more successful control of malignant diseases.

Intracellular reprogramming of expression, glycosylation, and function of a plant-derived antiviral therapeutic monoclonal antibody

Plant genetic engineering, which has led to the production of plant-derived monoclonal antibodies (mAb(P)s), provides a safe and economically effective alternative to conventional antibody expression methods. In this study, the expression levels and biological properties of the anti-rabies virus mAb(P) SO57 with or without an endoplasmic reticulum (ER)-retention peptide signal (Lys-Asp-Glu-Leu; KDEL) in transgenic tobacco plants (Nicotiana tabacum) were analyzed. The expression levels of mAb(P) SO57 with KDEL (mAb(P)K) were significantly higher than those of mAb(P) SO57 without KDEL (mAb(P)) regardless of the transcription level. The Fc domains of both purified mAb(P) and mAb(P)K and hybridoma-derived mAb (mAb(H)) had similar levels of binding activity to the FcγRI receptor (CD64). The mAb(P)K had glycan profiles of both oligomannose (OM) type (91.7%) and Golgi type (8.3%), whereas the mAb(P) had mainly Golgi type glycans (96.8%) similar to those seen with mAb(H). Confocal analysis showed that the mAb(P)K was co-localized to ER-tracker signal and cellular areas surrounding the nucleus indicating accumulation of the mAb(P) with KDEL in the ER. Both mAb(P) and mAb(P)K disappeared with similar trends to mAb(H) in BALB/c mice. In addition, mAb(P)K was as effective as mAb(H) at neutralizing the activity of the rabies virus CVS-11. These results suggest that the ER localization of the recombinant mAb(P) by KDEL reprograms OM glycosylation and enhances the production of the functional antivirus therapeutic antibody in the plant.

Boosting ADCC and CDC activity by Fc engineering and evaluation of antibody effector functions

In recent years, therapy with monoclonal antibodies has become standard of care in various clinical applications. Despite obvious clinical activity, not all patients respond and benefit from this generally well tolerated treatment option. Therefore, rational optimization of antibody therapy represents a major area of interest in translational research. Animal models and clinical data suggested important roles of Fc-mediated effector mechanisms such as antibody dependent cell-mediated cytotoxicity (ADCC) or complement dependent cytotoxicity (CDC) in antibody therapy. These novel insights into the mechanisms of action mediated by monoclonal antibodies inspired the development of different engineering approaches to enhance/optimize antibodies' effector functions. Fc-engineering approaches by altering the Fc-bound glycosylation profile or by exchanging amino acids in the protein backbone have been intensively studied. Here, advanced and emerging technologies in Fc-engineering resulting in altered ADCC and CDC activity are summarized and experimental strategies to evaluate antibodies' effector functions are discussed.

Protein production from the structural genomics perspective: achievements and future needs

Despite a multitude of recent technical breakthroughs speeding high-resolution structural analysis of biological macromolecules, production of sufficient quantities of well-behaved, active protein continues to represent the rate-limiting step in many structure determination efforts. These challenges are only amplified when considered in the context of ongoing structural genomics efforts, which are now contending with multi-domain eukaryotic proteins, secreted proteins, and ever-larger macromolecular assemblies. Exciting new developments in eukaryotic expression platforms, including insect and mammalian-based systems, promise enhanced opportunities for structural approaches to some of the most important biological problems. Development and implementation of automated eukaryotic expression techniques promises to significantly improve production of materials for structural, functional, and biomedical research applications.

Natural killer cell mediated antibody-dependent cellular cytotoxicity in tumor immunotherapy with therapeutic antibodies

In the last decade several therapeutic antibodies have been Federal Drug Administration (FDA) and European Medicines Agency (EMEA) approved. Although their mechanisms of action in vivo is not fully elucidated, antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells is presumed to be a key effector function. A substantial role of ADCC has been demonstrated in vitro and in mouse tumor models. However, a direct in vivo effect of ADCC in tumor reactivity in humans remains to be shown. Several studies revealed a predictive value of FcγRIIIa-V158F polymorphism in monoclonal antibody treatment, indicating a potential effect of ADCC on outcome for certain indications. Furthermore, the use of therapeutic antibodies after allogeneic hematopoietic stem cell transplantation is an interesting option. Studying the role of the FcγRIIIa-V158F polymorphism and the influence of Killer-cell Immunoglobuline-like Receptor (KIR) receptor ligand incompatibility on ADCC in this approach may contribute to future transplantation strategies. Despite the success of approved second-generation antibodies in the treatment of several malignancies, efforts are made to further augment ADCC in vivo by antibody engineering. Here, we review currently used therapeutic antibodies for which ADCC has been suggested as effector function.

IgG-Fc glycoengineering in non-mammalian expression hosts

The remarkable success of therapeutic applications of immunoglobulin G (IgG) in form of monoclonal antibodies and pooled immunoglobulin G preparations has directed attention to this class of glycoproteins. It is commonly appreciated that oligosaccharides attached to the Fc-region play a critical role in the biological activity of IgGs. Thus, glycosylation has been a focus of interest for many scientists and the biopharmaceutical industry and expression hosts have been engineered in order to optimize antibody products. In this review we focus on efforts towards a targeted manipulation of IgG-Fc N-glycans using non-mammalian expression hosts, i.e. yeast, insect cells and plants. Current achievements in generating human-like N-glycan structures will be presented and recent data on the molecular mechanisms that might explain how these potent drugs mediate in vivo activities will be discussed.

Immunoglobulin G Fc N-glycan profiling in patients with gastric cancer by LC-ESI-MS: relation to tumor progression and survival

The IgG Fc glycans strongly influence the Fcγ receptor interactions and Fc-mediated effector mechanisms. Changes in the structure of IgG glycans are associated with various diseases, such as infections and autoimmunity. However, the possible role of Fc glycans in tumor immunity is not yet fully understood. The aim of this study was to profile the Fc N-glycans of IgG samples from patients with gastric cancer (n = 80) and controls (n = 51) using LC-ESI-MS method to correlate the findings with stage of cancer and patients survival. Analysis of 32 different IgG N-glycans revealed significant increase of agalactosylated (GnGnF, GnGn(bi)F), and decrease of galactosylated (AGn(bi), AGn(bi)F, AA(bi), AAF) and monosialylated IgG glycoforms (NaAF, NaA(bi)) in cancer patients. A statistically significant increase of Fc fucosylation was observed in tumor stage II and III whereas reverse changes were found for the presence of bisecting GlcNAc. Higher level of fully sialylated glycans and elevated expression of glycans with bisecting GlcNAc were associated with better survival rate. Our findings provide the first evidence that the changes in Fc glycan profile may predict the survival of patients with gastric cancer. Cancer stage-dependent changes in Fc fucosylation and the bisecting N-acteylglucosamine expression as well as an association of several IgG glycoforms with the survival suggest that IgG glycosylation is related to pathogenesis of cancer and progression of the disease.

A novel CD19-directed recombinant bispecific antibody derivative with enhanced immune effector functions for human leukemic cells

A novel bispecific antibody-derived recombinant protein targeting leukemias and lymphomas was designed, a single-chain Fv triple body (sctb) consisting of 1 polypeptide chain with 3 scFvs connected in tandem. The distal scFvs were specific for the tumor antigen CD19, and the central scFv for the trigger molecule CD16 (FcgammaRIII) on natural killer (NK) cells and macrophages. We had previously built a disulphide stabilized (ds) bsscFv [19 x 16] with monovalent binding for CD19 from ds components. The sctb ds[19 x 16 x 19] also used ds components and displayed 3-fold greater avidity for CD19 than the bsscFv (KD = 13 vs. 42 nM), whereas both had equal affinity for CD16 (KD = 58 nM). Plasma half-lives in mice were 4 and 2 hours for the sctb and the bsscFv, respectively. In antibody-dependent cellular cytotoxicity reactions with human mononuclear cells as effectors, the sctb promoted equal lysis of leukemic cell lines and primary cells from leukemia and lymphoma patients at 10-fold to 40-fold lower concentrations than the bsscFv. This new format may also be applicable to a variety of other tumor antigens and effector molecules. With half-maximum effective concentrations (EC50) in the low picomolar range, the sctb ds[19 x 16 x 19] is an attractive candidate for further preclinical evaluation.

Potent in vitro and in vivo activity of an Fc-engineered anti-CD19 monoclonal antibody against lymphoma and leukemia

CD19 is a pan B-cell surface receptor expressed from pro-B-cell development until its down-regulation during terminal differentiation into plasma cells. CD19 represents an attractive immunotherapy target for cancers of lymphoid origin due to its high expression levels on the vast majority of non-Hodgkin's lymphomas and some leukemias. A humanized anti-CD19 antibody with an engineered Fc domain (XmAb5574) was generated to increase binding to Fcgamma receptors on immune cells and thus increase Fc-mediated effector functions. In vitro, XmAb5574 enhanced antibody-dependent cell-mediated cytotoxicity 100-fold to 1,000-fold relative to an anti-CD19 IgG1 analogue against a broad range of B-lymphoma and leukemia cell lines. Furthermore, XmAb5574 conferred antibody-dependent cell-mediated cytotoxicity against patient-derived acute lymphoblastic leukemia and mantle cell lymphoma cells, whereas the IgG1 analogue was inactive. XmAb5574 also increased antibody-dependent cellular phagocytosis and apoptosis. In vivo, XmAb5574 significantly inhibited lymphoma growth in prophylactic and established mouse xenograft models, and showed more potent antitumor activity than its IgG1 analogue. Comparisons with a variant incapable of Fcgamma receptor binding showed that engagement of these receptors is critical for optimal antitumor efficacy. These results suggest that XmAb5574 exhibits potent tumor cytotoxicity via direct and indirect effector functions and thus warrants clinical evaluation as an immunotherapeutic for CD19(+) hematologic malignancies.

Antibody fucosylation differentially impacts cytotoxicity mediated by NK and PMN effector cells

Glycosylation of the antibody Fc fragment is essential for Fc receptor–mediated activity. Carbohydrate heterogeneity is known to modulate the activity of effector cells in the blood, in which fucosylation particularly affects NK cell–mediated killing. Here, we investigated how the glycosylation profile of 2F8, a human IgG1 monoclonal antibody against epidermal growth factor receptor in clinical development, impacted effector function. Various 2F8 batches differing in fucosylation, galactosylation, and sialylation of the complex-type oligosaccharides in the Fc fragment were investigated. Our results confirmed that low fucose levels enhance mononuclear cell–mediated antibody-mediated cellular cytotoxicity (ADCC). In contrast, polymorphonuclear cells were found to preferentially kill via high-fucosylated antibody. Whole blood ADCC assays, containing both types of effector cells, revealed little differences in tumor cell killing between both batches. Significantly, however, high-fucose antibody induced superior ADCC in blood from granulocyte colony-stimulating factor–primed donors containing higher numbers of activated polymorphonuclear cells. In conclusion, our data demonstrated for the first time that lack of fucose does not generally increase the ADCC activity of therapeutic antibodies and that the impact of Fc glycosylation on ADCC is critically dependent on the recruited effector cell type.

The way forward, enhanced characterization of therapeutic antibody glycosylation: comparison of three level mass spectrometry-based strategies

Glycosylation which plays a crucial role in the pharmacological properties of therapeutic monoclonal antibodies (MAbs) is influenced by several factors like production systems, selected clonal population and manufacturing processes. Efficient analytical methods are therefore required in order to characterize glycosylation at different stages of MAbs discovery and production. Three mass spectrometry (MS)-based strategies were compared to analyze N-glycosylation of MAbs either expressed in murine myeloma (NS0) or Chinese Hamster Ovary (CHO) cell lines, the two current main production systems used for therapeutic MAbs. First a top-down approach was used on intact and reduced MAbs by liquid chromatography coupled to an electrospray ionization-time of flight mass spectrometer (LC-ESI-TOF), which provided fast and accurate profiles of MAbs glycosylation patterns for routine controls. Secondly, after digestion of the antibody with the peptide N-glycosidase F (PNGase F) enzyme, released N-linked glycans were directly analyzed by electrospray ionization-tandem mass spectrometry (ESI-MS/MS) without any prior derivatization, which gave precise details on the structure of the most abundant glycoforms. Finally, a bottom-up approach on tryptic glycopeptides using a nanoLC-Chip-MS/MS ion trap (IT) system equipped with a graphitized carbon column was investigated. Data were compared to those obtained with a more classical C18 reversed phase column showing that this last method is well suited to detect low abundant glycoforms and to provide in one shot information regarding both the oligosaccharide structure and the amino acid sequence of its peptide moiety.

Antithyroperoxidase antibody-dependent cytotoxicity in autoimmune thyroid disease

CONTEXT

Thyroid antibody-dependent cytotoxicity has been reported in autoimmune thyroid disease (AITD). Indeed, the role of thyroperoxidase (TPO) autoantibodies (aAbs) in complement-mediated damage by binding to TPO expressed on the surface of human thyroid cells was demonstrated, whereas their activity in antibody-dependent cell cytotoxicity (ADCC) is not well established.

OBJECTIVE

The aim of this study was to define the partners involved in antibody and complement-dependent cytotoxicity (CDC) in AITD and characterize which effector cells are involved in cytotoxicity mediated by anti-TPO aAbs using a chromium release assay.

RESULTS

The relative capability of anti-TPO aAbs to mediate ADCC using human thyroid cells in culture varies from 11 to 74.5%, depending on the effectors cells used. The human monocyte cell line HL60 gives a better lysis than the THP-1 cell line as effector cells. It seems obvious that the mechanism of ADCC is mediated quite exclusively by FcgammaRI. Indeed, the two effector cell lines differ by the level of the FcgammaRI expression (91.83% for HL-60 cells and 22.55%t for the THP-1). In addition to ADCC, the anti-TPO aAbs mediate the destruction of thyrocytes by CDC (56%).

CONCLUSIONS

These results demonstrate that anti-TPO aAbs can damage cultured thyroid cells by ADCC and CDC mechanisms. The monocytes, via their FcgammaRI, are important effector cells in ADCC mediated by anti-TPO aAbs and may contribute with T cells to the destruction of thyroid gland in AITD.

Selective induction of apoptosis in leukemic B-lymphoid cells by a CD19-specific TRAIL fusion protein

Although the treatment outcome of lymphoid malignancies has improved in recent years by the introduction of transplantation and antibody-based therapeutics, relapse remains a major problem. Therefore, new therapeutic options are urgently needed. One promising approach is the selective activation of apoptosis in tumor cells by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). This study investigated the pro-apoptotic potential of a novel TRAIL fusion protein designated scFvCD19:sTRAIL, consisting of a CD19-specific single-chain Fv antibody fragment (scFv) fused to the soluble extracellular domain of TRAIL (sTRAIL). Potent apoptosis was induced by scFvCD19:sTRAIL in several CD19-positive tumor cell lines, whereas normal blood cells remained unaffected. In mixed culture experiments, selective binding of scFvCD19:sTRAIL to CD19-positive cells resulted in strong induction of apoptosis in CD19-negative bystander tumor cells. Simultaneous treatment of CD19-positive cell lines with scFvCD19:sTRAIL and valproic acid (VPA) or Cyclosporin A induced strongly synergistic apoptosis. Treatment of patient-derived acute B-lymphoblastic leukemia (B-ALL) and chronic B-lymphocytic leukemia (B-CLL) cells resulted in strong tumoricidal activity that was further enhanced by combination with VPA. In addition, scFvCD19:sTRAIL prevented engraftment of human Nalm-6 cells in xenotransplanted NOD/Scid mice. The pre-clinical data presented here warrant further investigation of scFvCD19:sTRAIL as a potential new therapeutic agent for CD19-positive B-lineage malignancies.

A CD19-specific single-chain immunotoxin mediates potent apoptosis of B-lineage leukemic cells

CD19 is a B-lineage-specific transmembrane signaling protein participating in the control of proliferation and differentiation. It is present at high surface density on chronic B-lymphocytic leukemia (B-CLL) cells and cells of other B-cell malignancies, and is a prime target for therapy with antibody-derived agents. Many attempts have been made to target malignant cells via CD19, but to date none of these agents have received drug approval. Here we report the design of a monovalent immunotoxin consisting of a CD19-specific single-chain Fv antibody fragment fused to a derivative of Pseudomonas Exotoxin A. This fusion protein induced efficient antigen-restricted apoptosis of several human leukemia- and lymphoma-derived cell lines including Nalm-6, which it eliminated at an effective concentration (EC(50)) of 2.5 nM. The agent displayed synergistic toxicity when used in combination with valproic acid and cyclosporin A in cell-culture assays. It induced apoptosis of primary malignant cells in 12/12 samples from B-CLL patients, including patients responding poorly to fludarabine, and of cells from one pediatric acute lymphoblastic leukemia patient. In NOD/SCID mice transplanted with Nalm-6 cells, the toxin prevented engraftment and significantly prolonged survival of treated mice. Owing to its efficient antigen-restricted antileukemic activity, the agent deserves further development towards clinical testing.