Tumor-associated Carbohydrate Antigens Research Articles

Generation of glycan-specific nanobodies

The development of antibodies that target specific glycan structures on cancer cells or human pathogens poses a significant challenge due to the immense complexity of naturally occurring glycans. Automated glycan assembly enables the production of structurally homogeneous glycans in amounts that are difficult to derive from natural sources. Nanobodies (Nbs) are the smallest antigen-binding domains of heavy-chain-only antibodies (hcAbs) found in camelids. To date, the development of glycan-specific Nbs using synthetic glycans has not been reported. Here, we use defined synthetic glycans for alpaca immunization to elicit glycan-specific hcAbs, and describe the identification, isolation, and production of a Nb specific for the tumor-associated carbohydrate antigen Globo-H. The Nb binds the terminal fucose of Globo-H and recognizes synthetic Globo-H in solution and native Globo-H on breast cancer cells with high specificity. These results demonstrate the potential of our approach for generating glycan-targeting Nbs to be used in biomedical and biotechnological applications.

First-in-human study of OBI-999: A globo H-targeting antibody-drug conjugate in patients with advanced solid tumors.

3029 Background: OBI-999 is a novel antibody-drug conjugate, composed of a humanized monoclonal IgG1 antibody which targets the tumor-associated carbohydrate antigen Globo H, conjugated with monomethyl auristatin E (MMAE, vedotin). Upon binding to Globo H, OBI-999 is internalized into the tumor cell, and the linker (Thiobridge) connecting MMAE (an ultrapotent antimitotic agent) to the monoclonal antibody is cleaved by cathepsin B to release MMAE, thereby causing cell cycle arrest by inhibiting tubulin polymerization. We conducted a first-in-human, phase 1, dose-escalation study of OBI-999 monotherapy in patients with advanced cancer (NTC04084366). Methods: OBI-999 was administered intravenously at doses of 0.4, 0.8, 1.2, and 1.6 mg/kg on Day 1 of a 21-day cycle. Patients received study treatment until disease progression, unacceptable toxicity, or up to 2 years of treatment. Results: Overall, 15 adult patients were treated. OBI-999 administered on Day 1 of each 21-day cycle was well tolerated up to 1.2 mg/kg, the maximum tolerated dose (MTD). Treatment-related AEs (TRAEs) were noted in 40% (6/15) of patients. TRAEs ≥Grade 3 were noted in 27% (4/15) of patients; of whom 3 had neutropenia and 2 had anemia. OBI-999 exhibited non-linear pharmacokinetics from 0.4 mg/kg to 1.6 mg/kg, with lower clearance at higher doses. A retrospective validated automated immunohistochemistry assessment indicated 50% of patients with advanced solid tumors had high Globo H staining (H-score cutoff ≥100). Of 3 patients treated at the 1.6 mg/kg dose level; 2 developed Grade 4 neutropenia during Cycle 1 and the third developed Grade 4 neutropenia on Cycle 2 Day 15. One patient (1.6 mg/kg) with Grade 4 neutropenia also developed Grade 4 renal insufficiency and died from progressive disease (direct bilirubin, 3.5 mg/dL). Five (33.3%) patients had stable disease (SD), including 1 patient with adenoid cystic carcinoma of the oropharynx (SD for 13 cycles); 1 patient with gastroesophageal junction adenocarcinoma (SD for 8 cycles), and 3 patients with other tumor types (SD for 4, 2, and 2 cycles). Conclusions: We completed the dose-escalation portion of the study. OBI-999 was well tolerated. The recommended phase 2 dose was determined to be 1.2 mg/kg once every 3 weeks. Dose-dependent, non-cumulative neutropenia was dose limiting. We are currently enrolling patients with high Globo H expressing solid tumors (H-score ≥100) in the expansion phase of the study, which includes pancreatic, colorectal, and cancers of other histologic subtypes. Clinical trial information: NTC04084366.

Synthesis of MUC1 Peptide Backbone Bearing Sialyl‐Tn Antigen for Structural and Functional Studies With Endogenous Lectins

ObjectiveTo synthesize the tumor associated analogs of MUC1 for use in structural and functional studies between sialyl‐Tn (sTn) antigen with macrophage galactose‐specific lectin (MGL).AbstractMucin 1 (MUC1) is a heavily glycosylated transmembrane protein, altered in both expression and glycosylation pattern in human carcinomas of the epithelium. The presence of incomplete or truncated glycan structures, often capped by sialic acid, commonly known as tumor‐associated carbohydrate antigens (TACAs), on the cell surface is a well‐known cancer biomarker. Accumulating evidence suggests that TACAs expression is associated with tumor escape from immune defenses through interaction with endogenous carbohydrate binding proteins (lectins). These interactions often lead to creation of a protumor microenvironment, favoring tumor initiation, progression, metastasis, and immune evasion. Macrophage galactose binding lectin (MGL) is a C‐type lectin receptor found on antigen‐presenting cells (APCs) which facilitates the uptake of carbohydrate antigens for antigen presentation, modulating the immune response homeostasis, autoimmunity, and cancer. Considering the crucial role of tumor‐associated forms of MUC1 with MGL in tumor immunology, a thorough understanding of this interaction is essential for it to be exploited for cancer vaccine strategies. The specific aim of this research is to synthesize structurally well‐defined chemical probes, mono and multiple glycosylated MUC1 glycopeptide models carrying the Tn or sTn, that allow for the control of the complexity of the chemical space of the multivalent ligands. For this purpose, a concise scheme was developed for the large synthesis of the sTn antigen building block. Thiophenyl glycoside donors, in the presence TfOH/NIS or TMSOTf/NIS as promoter system, were used for the galactosylation and sialylation steps of the amino acid building block synthesis, respectively. We explored the effect of activator, temperature, solvent, and excess equivalent of sialic acid thioglycoside donor on sialylation reaction. The most favorable reaction conditions improved the desired α‐stereoselectivity, decreased the competing 2,3‐elimination reaction on the sialyl donor during activation, leading to overall increase in the reaction yield. This building block was used in the stepwise solid‐phase peptide synthesis of MUC1 glycopeptide models. The secondary structure of synthesized peptides was determined by circular dichroism (CD) spectroscopy.

Advances in the Immunomodulatory Properties of Glycoantigens in Cancer.

Simple SummaryThis work reviews the role of aberrant glycosylation in cancer cells during tumour growth and spreading, as well as in immune evasion. The interaction of tumour-associated glycans with the immune system through C-type lectin receptors can favour immune escape but can also provide opportunities to develop novel tumour immunotherapy strategies. This work highlights the main findings in this area and spotlights the challenges that remain to be investigated.Aberrant glycosylation in tumour progression is currently a topic of main interest. Tumour-associated carbohydrate antigens (TACAs) are expressed in a wide variety of epithelial cancers, being both a diagnostic tool and a potential treatment target, as they have impact on patient outcome and disease progression. Glycans affect both tumour-cell biology properties as well as the antitumor immune response. It has been ascertained that TACAs affect cell migration, invasion and metastatic properties both when expressed by cancer cells or by their extracellular vesicles. On the other hand, tumour-associated glycans recognized by C-type lectin receptors in immune cells possess immunomodulatory properties which enable tumour growth and immune response evasion. Yet, much remains unknown, concerning mechanisms involved in deregulation of glycan synthesis and how this affects cell biology on a major level. This review summarises the main findings to date concerning how aberrant glycans influence tumour growth and immunity, their application in cancer treatment and spotlights of unanswered challenges remaining to be solved.

Glycoconjugate Nanoparticle-Based Systems in Cancer Immunotherapy: Novel Designs and Recent Updates.

For many years, cell-surface glycans (in particular, Tumor-Associated Carbohydrate Antigens, TACAs) have been the target of both passive and active anticancer immunotherapeutic design. Recent advances in immunotherapy as a treatment for a variety of malignancies has revolutionized anti-tumor treatment regimens. Checkpoint inhibitors, Chimeric Antigen Receptor T-cells, Oncolytic virus therapy, monoclonal antibodies and vaccines have been developed and many approvals have led to remarkable outcomes in a subset of patients. However, many of these therapies are very selective for specific patient populations and hence the search for improved therapeutics and refinement of techniques for delivery are ongoing and fervent research areas. Most of these agents are directed at protein/peptide epitopes, but glycans–based targets are gaining in popularity, and a handful of approved immunotherapies owe their activity to oligosaccharide targets. In addition, nanotechnology and nanoparticle-derived systems can help improve the delivery of these agents to specific organs and cell types based on tumor-selective approaches. This review will first outline some of the historical beginnings of this research area and subsequently concentrate on the last 5 years of work. Based on the progress in therapeutic design, predictions can be made as to what the future holds for increasing the percentage of positive patient outcomes for optimized systems.

Selective Recognition of Carbohydrate Antigens by Germline Antibodies Isolated from AID Knockout Mice.

Germline antibodies, the initial set of antibodies produced by the immune system, are critical for host defense, and information about their binding properties can be useful for designing vaccines, understanding the origins of autoantibodies, and developing monoclonal antibodies. Numerous studies have found that germline antibodies are polyreactive with malleable, flexible binding pockets. While insightful, it remains unclear how broadly this model applies, as there are many families of antibodies that have not yet been studied. In addition, the methods used to obtain germline antibodies typically rely on assumptions and do not work well for many antibodies. Herein, we present a distinct approach for isolating germline antibodies that involves immunizing activation-induced cytidine deaminase (AID) knockout mice. This strategy amplifies antigen-specific B cells, but somatic hypermutation does not occur because AID is absent. Using synthetic haptens, glycoproteins, and whole cells, we obtained germline antibodies to an assortment of clinically important tumor-associated carbohydrate antigens, including Lewis Y, the Tn antigen, sialyl Lewis C, and Lewis X (CD15/SSEA-1). Through glycan microarray profiling and cell binding, we demonstrate that all but one of these germline antibodies had high selectivity for their glycan targets. Using molecular dynamics simulations, we provide insights into the structural basis of glycan recognition. The results have important implications for designing carbohydrate-based vaccines, developing anti-glycan monoclonal antibodies, and understanding antibody evolution within the immune system.

Role of GD3 Synthase ST8Sia I in Cancers.

Simple SummaryThe carbohydrate moiety of cell surface glycolipids is modified in cancers of neuro–ectoderm origin, leading to the expression of more complex structures with two or more sialic acid residues. These alterations result from the upregulation of the ST8SIA1 gene that encodes GD3 synthase, the enzyme controlling the biosynthesis of complex gangliosides, and are usually associated with a more aggressive phenotype and a poor outcome for patients, making GD3 synthase an interesting target for cancer therapy. This review reports our general knowledge of GD3 synthase gene expression and regulation, its role in both epithelial–mesenchymal transition (EMT) and cancer progression, and the different approaches targeting GD3S expression in cancers.GD3 synthase controls the biosynthesis of complex gangliosides, bearing two or more sialic acid residues. Disialylated gangliosides GD3 and GD2 are tumor-associated carbohydrate antigens (TACA) in neuro–ectoderm-derived cancers, and are directly involved in cell malignant properties, i.e., migration, invasion, stemness, and epithelial–mesenchymal transition. Since GD3 and GD2 levels are directly linked to GD3 synthase expression and activity, targeting GD3 synthase appears to be a promising strategy through which to interfere with ganglioside-associated malignant properties. We review here the current knowledge on GD3 synthase expression and regulation in cancers, and the consequences of complex ganglioside expression on cancer cell signaling and properties, highlighting the relationships between GD3 synthase expression and epithelial–mesenchymal transition and stemness. Different strategies were used to modulate GD3 synthase expression in cancer cells in vitro and in animal models, such as inhibitors or siRNA/lncRNA, which efficiently reduced cancer cell malignant properties and the proportion of GD2 positive cancer stem cells, which are associated with high metastatic properties, resistance to therapy, and cancer relapse. These data show the relevance of targeting GD3 synthase in association with conventional therapies, to decrease the number of cancer stem cells in tumors.

Abstract P5-08-01: Globo H: A Globo series glycosphingolipid target antigen in breast cancer

Abstract Cancer cells may be differentiated from normal cells by the surface expression of unusual glycosylation patterns: tumor-associated carbohydrate antigens (TACAs) may be expressed as membrane-bound glycoproteins or glycolipids. Differential expression of TACAs in multiple cancer types represents a potential therapeutic target for anticancer therapies. At least 16 different types of epithelial cancers have been found to be Globo H–positive, with 60% to 65% of patients with breast cancer having Globo H–positive tumors. It has been shown that tumor-infiltrating lymphocytes in breast cancer tissues could take up Globo H ceramide (GHCer) released by tumor cells masking cancer cells from immune surveillance through the suppression of Notch 1 signaling. Globo series antigens, including Globo H and stage-specific embryonic antigen 4 could associate with the FAK/CAV1/AKT/RIP complex to trigger the downstream β-catenin signaling pathway to promote tumor cell survival. Moreover, exogenous addition of GHCer promoted tumor cell migration. Thus, treatment-mediated depletion of GHCer may overcome the immunosuppressive mechanism of cancer cells, with resulting decreases in tumor cell survival and migration. OBI Pharma, Inc., in collaboration with NeoGenomics, has developed a validated immunohistochemistry assay to measure the expression of Globo H in clinical specimens. The intensity and extent of Globo H expression are determined microscopically using the histochemical scoring system (H-score), defined as the sum of the products of the staining intensity (score of 0-3) multiplied by the percentage of cells (0-100) stained at a given intensity. To date, 420 patients with triple-negative breast cancer (TNBC) have been screened across 4 separate clinical trials. Of those patients, 173 (41%) had an H-score of ≥15, with a median H-score of 70. Of the 173 patients with an H-score of ≥15, 69 (40%) had an H-score of ≥100. Adagloxad simolenin (AS/OBI-822) is a Globo H conjugate vaccine that when administered in combination with the adjuvant OBI-821 results in anti–Globo H IgM and IgG humoral immune responses. These responses have been assessed in all clinical trials of AS/OBI-821 to date. In the early trials that administered up to 9 doses, early and robust IgM responses were noted but with delayed and lower-titer IgG responses. When the number of doses was increased to 9-12 doses over an extended time (up to either 37 or 68 weeks), it became apparent that the peak IgG titers occurred at around the time of the last AS/OBI-821 dose. The time course for the development of anti–Globo H IgM and IgG humoral responses showed that following injection, anti–Globo H IgM and IgG antibody titers demonstrated a geometric mean ratio (GMR) increase of 10.26 and 12.47, respectively, from almost nondetectable levels at baseline. The GMR in the placebo group remained low in comparison. Mean time to peak titer was approximately 4 weeks for IgM and 40 weeks for IgG. These data were employed in the design of the phase 3, randomized, open-label study of the anti–Globo H vaccine AS/OBI-821 in the adjuvant treatment of patients with high-risk, early-stage Globo H–positive TNBC (The GLORIA Study). To enter the GLORIA study, patients must have a centrally confirmed Globo H IHC H-score of ≥15, and it is anticipated that approximately 40% of patients screened will have this level of expression. The GLORIA study is presently enrolling patients in 7 countries, with another 9 countries anticipated to begin recruiting in 2021. Citation Format: Darren S. Sigal, Apostolia Maria Tsimberidou, I-Ju Chen, Pei Hsu, Tillman Pearce. Globo H: A Globo series glycosphingolipid target antigen in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-08-01.

Structure Guided Design of Bacteriophage Qβ Mutants as Next Generation Carriers for Conjugate Vaccines.

Vaccines are critical tools to treat and prevent diseases. For an effective conjugate vaccine, the carrier is crucial, but few carriers are available for clinical applications. In addition, a drawback of current protein carriers is that high levels of antibodies against the carrier are induced by the conjugate vaccine, which are known to interfere with the immune responses against the target antigen. To overcome these challenges, we obtained the near atomic resolution crystal structure of an emerging protein carrier, i.e., the bacteriophage Qβ virus like particle. On the basis of the detailed structural information, novel mutants of bacteriophage Qβ (mQβ) have been designed, which upon conjugation with tumor associated carbohydrate antigens (TACAs), a class of important tumor antigens, elicited powerful anti-TACA IgG responses and yet produced lower levels of anticarrier antibodies as compared to those from the wild type Qβ-TACA conjugates. In a therapeutic model against an aggressive breast cancer in mice, 100% unimmunized mice succumbed to tumors in just 12 days even with chemotherapy. In contrast, 80% of mice immunized with the mQβ-TACA conjugate were completely free from tumors. Besides TACAs, to aid in the development of vaccines to protect against COVID-19, the mQβ based conjugate vaccine has been shown to induce high levels of IgG antibodies against peptide antigens from the SARS-CoV-2 virus, demonstrating its generality. Thus, mQβ is a promising next-generation carrier platform for conjugate vaccines, and structure-based rational design is a powerful strategy to develop new vaccine carriers.

Targeting Tumor Glycans for Cancer Therapy: Successes, Limitations, and Perspectives.

Simple SummaryAberrant glycosylation is a common feature of many cancers, and it plays crucial roles in tumor development and biology. Cancer progression can be regulated by several physiopathological processes controlled by glycosylation, such as cell–cell adhesion, cell–matrix interaction, epithelial-to-mesenchymal transition, tumor proliferation, invasion, and metastasis. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs), which are suitable for selective cancer targeting, as well as novel antitumor immunotherapy approaches. This review summarizes the strategies developed in cancer immunotherapy targeting TACAs, analyzing molecular and cellular mechanisms and state-of-the-art methods in clinical oncology.Aberrant glycosylation is a hallmark of cancer and can lead to changes that influence tumor behavior. Glycans can serve as a source of novel clinical biomarker developments, providing a set of specific targets for therapeutic intervention. Different mechanisms of aberrant glycosylation lead to the formation of tumor-associated carbohydrate antigens (TACAs) suitable for selective cancer-targeting therapy. The best characterized TACAs are truncated O-glycans (Tn, TF, and sialyl-Tn antigens), gangliosides (GD2, GD3, GM2, GM3, fucosyl-GM1), globo-serie glycans (Globo-H, SSEA-3, SSEA-4), Lewis antigens, and polysialic acid. In this review, we analyze strategies for cancer immunotherapy targeting TACAs, including different antibody developments, the production of vaccines, and the generation of CAR-T cells. Some approaches have been approved for clinical use, such as anti-GD2 antibodies. Moreover, in terms of the antitumor mechanisms against different TACAs, we show results of selected clinical trials, considering the horizons that have opened up as a result of recent developments in technologies used for cancer control.

Specific (sialyl-)Lewis core 2 O-glycans differentiate colorectal cancer from healthy colon epithelium.

Cells are covered with a dense layer of carbohydrates, some of which are solely present on neoplastic cells. The so-called tumor-associated carbohydrate antigens (TACAs) are increasingly recognized as promising targets for immunotherapy. These carbohydrates differ from those of the surrounding non-cancerous tissues and contribute to the malignant phenotype of the cancer cells by promoting proliferation, metastasis, and immunosuppression. However, due to tumor tissue heterogeneity and technological limitations, TACAs are insufficiently explored.Methods: A workflow was established to decode the colorectal cancer (CRC)-associated O-linked glycans from approximately 20,000 cell extracts. Extracts were obtained through laser capture microdissection of formalin fixed paraffin embedded tissues of both primary tumors and metastatic sites, and compared to healthy colon mucosa from the same patients. The released O-glycans were analyzed by porous graphitized carbon liquid chromatography-tandem mass spectrometry in negative ion mode.Results: Distinctive O-glycosylation features were found in cancerous, stromal and normal colon mucosal regions. Over 100 O-linked glycans were detected in cancerous regions with absence in normal mucosa. From those, six core 2 O-glycans were exclusively found in more than 33% of the cancers, carrying the terminal (sialyl-)LewisX/A antigen. Moreover, two O-glycans were present in 72% of the analyzed cancers and 94% of the investigated cancers expressed at least one of these two O-glycans. In contrast, normal colon mucosa predominantly expressed core 3 O-glycans, carrying α2-6-linked sialylation, (sulfo-)LewisX/A and Sda antigens.Conclusion: In this study, we present a novel panel of highly specific TACAs, based upon differences in the glycomic profiles between CRC and healthy colon mucosa. These TACAs are promising new targets for development of innovative cancer immune target therapies and lay the foundation for the targeted treatment of CRC.

Synthesis of Azido-Globo H Analogs for Immunogenicity Evaluation.

Globo H (GH) is a tumor-associated carbohydrate antigen (TACA), and GH conjugations have been evaluated as potential cancer vaccines. However, like all carbohydrate-based vaccines, low immunogenicity is a major issue. Modifications of the TACA increase its immunogenicity, but the systemic modification on GH is challenging and the synthesis is cumbersome. In this study, we synthesized several azido-GH analogs for evaluation, using galactose oxidase to selectively oxidize C6-OH of the terminal galactose or N-acetylgalactosamine on lactose, Gb3, Gb4, and SSEA3 into C6 aldehyde, which was then transformed chemically to the azido group. The azido-derivatives were further glycosylated to azido-GH analogs by glycosyltransferases coupled with sugar nucleotide regeneration. These azido-GH analogs and native GH were conjugated to diphtheria toxoid cross-reactive material CRM197 for vaccination with C34 adjuvant in mice. Glycan array analysis of antisera indicated that the azido-GH glycoconjugate with azide at Gal-C6 of Lac (1-CRM197) elicited the highest antibody response not only to GH, SSEA3, and SSEA4, which share the common SSEA3 epitope, but also to MCF-7 cancer cells, which express these Globo-series glycans.

Targeting Tn-Antigen-Positive Human Tumors with a Recombinant Human Macrophage Galactose C-Type Lectin.

Alterations in glycosylation cause the emergence of tumor-associated carbohydrate antigens (TACAs) during tumorigenesis. Truncation of O-glycans reveals the Thomsen nouveau (Tn) antigen, an N-acetylgalactosamine (GalNAc) frequently attached to serine or threonine amino acids, that is accessible on the surface of cancer cells but not on healthy cells. Interestingly, GalNac can be recognized by macrophage galactose lectin (MGL), a type C lectin receptor expressed in immune cells. In this study, recombinant MGL fragments were tested in vitro for their cancer cell-targeting efficiency by flow cytometry and confocal microscopy and in vivo after administration of fluorescent MGL to tumor-bearing mice. Our results demonstrate the ability of MGL to target Tn-positive human tumors without inducing toxicity. This outcome makes MGL, a fragment of a normal human protein, the first vector candidate for in vivo diagnosis and imaging of human tumors and, possibly, for therapeutic applications.

The Development of Vaccines from Synthetic Tumor-Associated Mucin Glycopeptides and their Glycosylation-Dependent Immune Response.

Tumor-associated carbohydrate antigens are overexpressed as altered-self in most common epithelial cancers. Their glycosylation patterns differ from those of healthy cells, functioning as an ID for cancer cells. Scientists have been developing anti-cancer vaccines based on mucin glycopeptides, yet the interplay of delivery system, adjuvant and tumor associated MUC epitopes in the induced immune response is not well understood. The current state of the art suggests that the identity, abundancy and location of the glycans on the MUC backbone are all key parameters in the cellular and humoral response. This review shares lessons learned by us in over two decades of research in glycopeptide vaccines. By bridging synthetic chemistry and immunology, we discuss efforts in designing synthetic MUC1/4/16 vaccines and focus on the role of glycosylation patterns. We provide a brief introduction into the mechanisms of the immune system and aim to promote the development of cancer subunit vaccines.

Chemoenzymatic Synthesis of 9NHAc-GD2 Antigen to Overcome the Hydrolytic Instability of O-Acetylated-GD2 for Anticancer Conjugate Vaccine Development.

Ganglioside GD2 is an attractive tumor-associated carbohydrate antigen for anti-cancer vaccine development. However, its low immunogenicity and the significant side effects observed with anti-GD2 antibodies present significant obstacles for vaccines. To overcome these, a new GD2 derivative bearing an N-acetamide (NHAc) at its non-reducing end neuraminic acid (9NHAc-GD2) has been designed to mimic the 9-O-acetylated-GD2 (9OAc-GD2), a GD2 based antigen with a restricted expression on tumor cells. 9NHAc-GD2 was synthesized efficiently via a chemoenzymatic method and subsequently conjugated with a powerful carrier bacteriophage Qβ. Mouse immunization with the Qβ-9NHAc-GD2 conjugate elicited strong and long-lasting IgG antibodies, which were highly selective toward 9NHAc-GD2 with little cross-recognition of GD2. Immunization of canines with Qβ-9NHAc-GD2 showed the construct was immunogenic in canines with little adverse effects, paving the way for future clinical translation to humans.

The Tn antigen promotes lung tumor growth by fostering immunosuppression and angiogenesis via interaction with Macrophage Galactose-type lectin 2 (MGL2).

Tn is a tumor-associated carbohydrate antigen that constitutes both a diagnostic tool and an immunotherapeutic target. It originates from interruption of the mucin O-glycosylation pathway through defects involving, at least in part, alterations in core-1 synthase activity, which is highly dependent on Cosmc, a folding chaperone. Tn antigen is recognized by the Macrophage Galactose-type Lectin (MGL), a C-type lectin receptor present on dendritic cells and macrophages. Specific interactions between Tn and MGL shape anti-tumoral immune responses by regulating several innate and adaptive immune cell programs. In this work, we generated and characterized a variant of the lung cancer murine cell line LL/2 that expresses Tn by mutation of the Cosmc chaperone gene (Tn+ LL/2). We confirmed Tn expression by lectin glycophenotyping and specific anti-Tn antibodies, verified abrogation of T-synthase activity in these cells, and confirmed its recognition by the murine MGL2 receptor. Interestingly, Tn+ LL/2cells were more aggressive in vivo, resulting in larger and highly vascularized tumors than those generated from wild type Tn- LL/2cells. In addition, Tn+ tumors exhibited an increase in CD11c+ F4/80+ cells with high expression of MGL2, together with an augmented expression of IL-10 in infiltrating CD4+ and CD8+ T cells. Importantly, this immunosuppressive microenvironment was dependent on the presence of MGL2+ cells, since depletion of these cells abrogated tumor growth, vascularization and recruitment of IL-10+ T cells. Altogether, our results suggest that expression of Tn in tumor cells and its interaction with MGL2-expressing CD11c+F4/80+ cells promote immunosuppression and angiogenesis, thus favoring tumor progression.

A Stable Gold Nanoparticle-Based Vaccine for the Targeted Delivery of Tumor-Associated Glycopeptide Antigens.

We have developed a novel antigen delivery system based on polysaccharide-coated gold nanoparticles (AuNPs) targeted to antigen-presenting cells (APCs) expressing Dectin-1. AuNPs were synthesized de novo using yeast-derived β-1,3-glucans (B13G) as the reductant and passivating agent in a microwave-catalyzed procedure, yielding highly uniform and serum-stable particles. These were further functionalized with both a peptide and a specific glycosylated form from the tandem repeat sequence of mucin 4 (MUC4), a glycoprotein overexpressed in pancreatic tumors. The glycosylated sequence contained the Thomsen–Friedenreich disaccharide, a pan-carcinoma, tumor-associated carbohydrate antigen (TACA), which has been a traditional target for antitumor vaccine design. These motifs were prepared with a cathepsin B protease cleavage site (Gly-Phe-Leu-Gly), loaded on the B13G-coated particles, and these constructs were examined for Dectin-1 binding, APC processing, and presentation in a model in vitro system and for immune responses in mice. We showed that these particles elicit strong in vivo immune responses through the production of both high-titer antibodies and priming of antigen-recognizing T-cells. Further examination showed that a favorable antitumor balance of expressed cytokines was generated, with limited expression of immunosuppressive Il-10. This system is modular in that any range of antigens can be conjugated to our particles and efficiently delivered to APCs expressing Dectin-1.

556TiP A phase I study of SGN-STNV, a novel antibody–drug conjugate targeting sialyl-thomsen-nouveau antigen (STn), in adults with advanced solid tumors (SGNSTNV-001)

STn is a tumor-associated carbohydrate antigen with high prevalence across various solid tumor types, including ovarian and non-small cell lung cancer (NSCLC). While its expression is restricted in normal tissues, it presents with several tumor-associated proteins, such as MUC1 and MUC16. STn is thought to influence cancer progression by affecting cell adhesion, migration and propagation of invasiveness, and has been linked to advanced disease, chemotherapy resistance, and decreased survival. SGN-STNV is an investigational antibody–drug conjugate which directs monomethyl auristatin E (MMAE) to STn-expressing cells.

Abstract 50: Targeting Sialyl-Thomsen nouveau (STn) antigen with the SGN-STNV antibody-drug conjugate is effective in preclinical studies

Abstract Targeting glyco-epitopes with antibody-drug conjugates (ADCs) provides a unique advantage as multiple cell surface proteins expressing the same carbohydrate can be harnessed to deliver drug. Sialyl-Thomsen nouveau (STn) is a tumor associated carbohydrate antigen that has historically been difficult to target with specificity. Using glycan array screening, h2G12 was identified as a highly specific human IgG1 antibody, that exclusively binds the STn glyco-epitope independent of protein backbone. Here we introduce SGN-STNV, an investigational antibody-drug conjugate (ADC) targeting monomethyl auristatin E (MMAE) to STn expressing tumor cells with the clinically validated vedotin linker technology. STn has restricted normal tissue expression and is expressed on various solid tumors including ovarian, non-small cell lung, gastric, and endometrial carcinomas. Our work shows correlation of enzyme ST6GALNAC1 expression with STn expression on tumors. Given the frequent O-glycosylation of mucins, we also confirmed high STn expression in mucinous subtypes of ovarian, pancreatic, colorectal, and lung adenocarcinomas. Previous reports have confirmed STn is found on mucins MUC1, MUC5A, and MUC16 (CA-125), as well as cell surface receptors CD44 and integrin β1. These proteins are known to play functional roles in tumor progression and, importantly for ADC delivery, they internalize well to deliver cytotoxic payload. We sought to identify other proteins that may contribute to cytotoxic activity of SGN-STNV and determined that additional surface receptors are tagged with STn. These receptors are internalized and likely contribute to SGN-STNV activity. After binding to STn, SGN-STNV is internalized into cells and releases the microtubule inhibitor MMAE to drive mitotic arrest, apoptosis, and to induce immunogenic cell death. SGN-STNV further mediates anti-tumor response through Fc-mediated effector functions, including antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). In preclinical xenograft studies, SGN-STNV monotherapy treatment leveraged h2G12 specificity and ability to target STn on multiple tumor associated proteins to drive durable tumor regressions. SGN-STNV was well tolerated in non-human primates (NHP), with no concerning target-mediated toxicities and a maximum tolerated dose similar to other vedotin-platform ADCs. In summary, the antibody specificity, unique mechanism of targeting a carbohydrate, anti-tumor activity, and tolerability provide a strong rationale for initiation of a phase I study to investigate the therapeutic potential of SGN-STNV. Citation Format: Alyssa Schwartz, Hector Rincon, Nanna Hansen, Robert Lawrence, Sarah Anderson, Nicole Blesie, Kerry Klussman, Angela Epp, Shyra Gardai, William Arthur. Targeting Sialyl-Thomsen nouveau (STn) antigen with the SGN-STNV antibody-drug conjugate is effective in preclinical studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 50.

Biomolecular Recognition of the Glycan Neoantigen CA19-9 by Distinct Antibodies

Glycans decorate the cell surface, secreted glycoproteins and glycolipids, and altered glycans are often found in cancers. Despite their high diagnostic and therapeutic potential, however, glycans are polar and flexible molecules that are quite challenging for the development and design of high-affinity binding antibodies. To understand the mechanisms by which glycan neoantigens are specifically recognized by antibodies, we analyze the biomolecular recognition of the tumor-associated carbohydrate antigen CA19-9 by two distinct antibodies using X-ray crystallography. Despite the potential plasticity of glycans and the very different antigen-binding surfaces presented by the antibodies, both structures reveal an essentially identical extended CA19-9 conformer, suggesting that this conformer’s stability selects the antibodies. Starting from the bound structure of one of the antibodies, we use the AbLIFT computational algorithm to design a variant with seven core mutations in the variable domain’s light-heavy chain interface that exhibits tenfold improved affinity for CA19-9. The results reveal strategies used by antibodies to specifically recognize glycan antigens and show how automated antibody-optimization methods may be used to enhance the clinical potential of existing antibodies.