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IUPAC name N-((2S,3R,E)-1-(((2R,3R,4R,5S,6R)-5-(((2S,3R,4R,5R,6R)-5-(((2R,3R,4S,5S,6R)-4-(((2S,3R,4R,5R,6R)-3-acetamido-4-(((2R,3R,4S,5R,6R)-4,5-dihydroxy-6-(hydroxymethyl)-3-(((2S,3S,4R,5S,6S)-3,4,5-trihydroxy-6-methyltetrahydro-2H-pyran-2-yl)oxy)tetrahydro-2H-pyran-2-yl)oxy)-5-hydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)-3,5-dihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)-3,4-dihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)-3,4-dihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)-3-hydroxyoctadec-4-en-2-yl)palmitamide | |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Globo H (globohexaosylceramide) is a globo-series glycosphingolipid antigen that is present on the outer membrane of some cancer cells. [1] [2] Globo H is not expressed in normal tissue cells, but is expressed in a number of types of cancers, including cancers of the breast, prostate, and pancreas. [1] [3] Globo H's exclusivity for cancer cells makes it a target of interest for cancer therapies. [1] [2]
Defined by the monoclonal antibody MBr1, Globo H has been isolated from breast cancer cell line MCF-7, and its structure has been determined through several analyses, including NMR spectroscopy and methylation analysis. [5] Globo H consists of a hexasaccharide of the structure Fucα(1-2)Galβ(1-3)GalNAcβ(1-3)Galα(1-4)Galβ(1-4)Glcβ(1) with a ceramide attached to its terminal glucose ring at the 1 position in a beta linkage. [6]
Globo H's biosynthetic pathway is involved in the synthesis pathways of other globo-series glycosphingolipid antigens that are also specific to cancer cells, including stage-specific embryonic antigen-3 (SSEA3) and stage-specific embryonic antigen-4 (SSEA4). [1] The biosynthetic pathway of these antigens includes the enzyme β 1,3-galactosyltransferase V (β3GalT5). [1] β3GalT5 catalyzes the galactosylation of globoside-4 (Gb4) to SSEA3. [1] SSEA3 can then be converted to SSEA4 by sialyltransferase adding a sialic acid group to its end, or it can be converted to Globo H by fucosyltransferase adding a fucose ring to its end. [1] Playing a part in the formation of three different cancer-specific antigens, β3GalT5 is of particular interest in its relevance to cancer treatment, and it has been shown to be critical for cancer cell survival. [8]
In order to study its potential as a cancer therapy target, Globo H has been synthesized in the laboratory. [9] One synthesis is achieved by first building two trisaccharides from their component sugars, and then linking them. [9] The trisaccharides, with most of their functional groups protected to prevent side reactions, are linked by creating the GalNAcβ(1-3)Gal bond. [9] A thioethyl group is added to the 1 position on one of the protected galactose rings, and in the presence of methyl triflate, this reacts with the hydroxyl group on the 3 position of the other galactose to link the trisaccharides and form the hexasaccharide. [9] The ceramide is added to the 1 position of the terminal glucose ring after hexasaccharide formation. [9]
As a Tumor Associated Carbohydrate Antigen (TACA), Globo-H is a promising clinical target for immunotherapy. While absent in normal tissues, the glycosphingolipid is overexpressed in a variety of epithelial cancer cell types including human pancreatic, gastric, lung, colorectal, esophageal, and breast tumors. [10] [11]
Globo-H's TACA character allows for its utilization as an anticancer vaccine, inducing antibody response against the epitope. The resulting humoral immunity could enable the selective eradication of Globo H-presenting tumors. [12] The Taiwanese biopharma company OBI Pharma, Inc., was first to develop Adagloxad Simolenin (OBI-822), a Globo H hexasaccharide conjugated with the immunostimulatory carrier protein KLH. [12] The Phase III GLORIA study is underway evaluating the carbohydrate-based immunogen's effects in high risk triple-negative breast cancer (TNBC) patients with an estimated completion date in 2027. [13]
Alternative vaccine conjugates have been developed which avoid issues associated with the protein carrier KLH by substituting it with a lipid or carbohydrate-based carrier. Examples include the use of lipid A derivatives [14] or entirely carbohydrate vaccine conjugates such as Globo H-PS A1 [15]
Globo H-targeting antibodies are another strategy currently being evaluated in the cancer therapeutic space. OBI Pharma's OBI-888 is a humanized IgG1 antibody that selectively binds to the Globo H antigen among other Globo series glycosphingolipids such as SSEA-3 and SSEA-4. [16] Additionally, in vivo studies of OBI-888 in various Globo H-positive (GH+) xenografts models showed promising tumor growth inhibition results. [17] OBI-888's human Phase I/II study for the treatment of metastatic and locally advanced solid tumors is estimated to finish in December 2022. [18]
Based on OBI-888, the first-in-class antibody-drug conjugate (ADC) 0BI-999 was additionally developed, linking OBI-888 to monomethyl auristatin E, a synthetic antineoplastic agent. [19] The ADC is currently undergoing phase II trial in patients with advanced solid tumors, with an estimated completion date in Dec 2023. [20] In Dec 2019 & Jan 2020, OBI-999 was granted two Orphan Drug Designations by the FDA for the treatment of pancreatic and gastric cancer. [21]
Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells and tissue, by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Albert Hewett Coons, Ernest Berliner, Norman Jones and Hugh J Creech was the first to develop immunofluorescence in 1941. This led to the later development of immunohistochemistry.
Carcinoembryonic antigen (CEA) describes a set of highly-related glycoproteins involved in cell adhesion. CEA is normally produced in gastrointestinal tissue during fetal development, but the production stops before birth. Consequently, CEA is usually present at very low levels in the blood of healthy adults. However, the serum levels are raised in some types of cancer, which means that it can be used as a tumor marker in clinical tests. Serum levels can also be elevated in heavy smokers.
In biology, chimeric antigen receptors (CARs)—also known as chimeric immunoreceptors, chimeric T cell receptors or artificial T cell receptors—are receptor proteins that have been engineered to give T cells the new ability to target a specific antigen. The receptors are chimeric in that they combine both antigen-binding and T cell activating functions into a single receptor.
Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment (pharmacotherapy) for cancer, others being hormonal therapy and cytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumor growth, rather than by simply interfering with all rapidly dividing cells. Because most agents for targeted therapy are biopharmaceuticals, the term biologic therapy is sometimes synonymous with targeted therapy when used in the context of cancer therapy. However, the modalities can be combined; antibody-drug conjugates combine biologic and cytotoxic mechanisms into one targeted therapy.
Chi-Huey Wong is a Taiwanese-American biochemist. He is currently the Scripps Family Chair Professor at the Scripps Research Institute. He is a member of the United States National Academy of Sciences, as awarded the 2014 Wolf Prize in Chemistry and 2015 RSC Robert Robinson Award. Wong is also the holder of more than 100 patents and publisher of 700 more scholarly academic research papers under his name.
Antigenic escape, immune escape, immune evasion or escape mutation occurs when the immune system of a host, especially of a human being, is unable to respond to an infectious agent: the host's immune system is no longer able to recognize and eliminate a pathogen, such as a virus. This process can occur in a number of different ways of both a genetic and an environmental nature. Such mechanisms include homologous recombination, and manipulation and resistance of the host's immune responses.
Mucin short variant S1, also called polymorphic epithelial mucin (PEM) or epithelial membrane antigen (EMA), is a mucin encoded by the MUC1 gene in humans. Mucin short variant S1 is a glycoprotein with extensive O-linked glycosylation of its extracellular domain. Mucins line the apical surface of epithelial cells in the lungs, stomach, intestines, eyes and several other organs. Mucins protect the body from infection by pathogen binding to oligosaccharides in the extracellular domain, preventing the pathogen from reaching the cell surface. Overexpression of MUC1 is often associated with colon, breast, ovarian, lung and pancreatic cancers. Joyce Taylor-Papadimitriou identified and characterised the antigen during her work with breast and ovarian tumors.
Epithelial cell adhesion molecule (EpCAM), also known as CD326 among other names, is a transmembrane glycoprotein mediating Ca2+-independent homotypic cell–cell adhesion in epithelia. EpCAM is also involved in cell signaling, migration, proliferation, and differentiation. Additionally, EpCAM has oncogenic potential via its capacity to upregulate c-myc, e-fabp, and cyclins A & E. Since EpCAM is expressed exclusively in epithelia and epithelial-derived neoplasms, EpCAM can be used as diagnostic marker for various cancers. It appears to play a role in tumorigenesis and metastasis of carcinomas, so it can also act as a potential prognostic marker and as a potential target for immunotherapeutic strategies.
Glypican-3 is a protein that, in humans, is encoded by the GPC3 gene. The GPC3 gene is located on human X chromosome (Xq26) where the most common gene encodes a 70-kDa core protein with 580 amino acids. Three variants have been detected that encode alternatively spliced forms termed Isoforms 1 (NP_001158089), Isoform 3 (NP_001158090) and Isoform 4 (NP_001158091).
Glypican-1 (GPC1) is a protein that in humans is encoded by the GPC1 gene. GPC1 is encoded by human GPC1 gene located at 2q37.3. GPC1 contains 558 amino acids with three predicted heparan sulfate chains.
Transmembrane glycoprotein NMB is a protein that in humans is encoded by the GPNMB gene. Two transcript variants encoding 560 and 572 amino acid isoforms have been characterized for this gene in humans. The mouse and rat orthologues of GPNMB are known as DC-HIL and Osteoactivin (OA), respectively.
Transmembrane 4 L6 family member 1 is a protein that in humans is encoded by the TM4SF1 gene.
Zinc transporter SLC39A7 (ZIP7), also known as solute carrier family 39 member 7, is a transmembrane protein that in humans is encoded by the SLC39A7 gene. It belongs to the ZIP family, which consists of 14 proteins that transport zinc into the cytoplasm. Its primary role is to control the transport of zinc from the ER and Golgi apparatus to the cytoplasm. It also plays a role in glucose metabolism. Its structure consists of helices that bind to zinc in a binuclear metal center. Its fruit fly orthologue is Catsup.
A circulating tumor cell (CTC) is a cancer cell from a primary tumor that has shed into the blood of the circulatory system, or the lymph of the lymphatic system. CTCs are carried around the body to other organs where they may leave the circulation and become the seeds for the subsequent growth of secondary tumors. This is known as metastasis, responsible for most cancer-related deaths.
A trifunctional antibody is a monoclonal antibody with binding sites for two different antigens, typically CD3 and a tumor antigen, making it a type of bispecific monoclonal antibody. In addition, its intact Fc-part can bind to an Fc receptor on accessory cells like conventional monospecific antibodies. The net effect is that this type of drug links T cells and monocytes/macrophages, natural killer cells, dendritic cells or other Fc receptor expressing cells to the tumor cells, leading to their destruction.
Glembatumumab vedotin is an antibody-drug conjugate (ADC) that targets cancer cells expressing transmembrane glycoprotein NMB (GPNMB).
Antibody–drug conjugates or ADCs are a class of biopharmaceutical drugs designed as a targeted therapy for treating cancer. Unlike chemotherapy, ADCs are intended to target and kill tumor cells while sparing healthy cells. As of 2019, some 56 pharmaceutical companies were developing ADCs.
MK-2870 or SKB264 is an experimental antibody–drug conjugate. The antibody component is directed against "the trophoblast cell-surface antigen 2 (TROP2), which is overexpressed in many types of solid tumors, coupled to moderate cytotoxic belotecan-derivative through a novel linker which was designed to balance the extracellular stability and intracellular rupture". The drug is developed as a partnership between Merck and the Chinese company Kelun.
Patritumab deruxtecan is an experimental antibody–drug conjugate developed by Merck and Daiichi Sankyo to treat non-small-cell lung cancer.
Deruxtecan is a chemical compound and a derivative of exatecan that acts as topoisomerase I inhibitor.
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