Bi-specific T-cell engagers (BiTEs) are a class of artificial bispecific monoclonal antibodies that are investigated for use as anti-cancer drugs. They direct a host's immune system, more specifically the T cells' cytotoxic activity, against cancer cells. BiTE is a registered trademark of Micromet AG (fully owned subsidiary of Amgen Inc). [1]
BiTEs are fusion proteins consisting of two single-chain variable fragments (scFvs) of different antibodies, or amino acid sequences from four different genes, on a single peptide chain of about 55 kilodaltons. One of the scFvs binds to T cells via the CD3 receptor, and the other to a tumor cell via a tumor specific molecule. [2] [3]
Like other bispecific antibodies, and unlike ordinary monoclonal antibodies, BiTEs form a link between T cells and tumor cells. This causes T cells to exert cytotoxic activity on tumor cells by producing proteins like perforin and granzymes, independently of the presence of MHC I or co-stimulatory molecules. These proteins enter tumor cells and initiate the cell's apoptosis. [2] [4]
This action mimics physiological processes observed during T cell attacks against tumor cells. [4]
Several BiTEs are currently in preclinical and clinical trials to assess their therapeutic efficacy and safety. [5]
Blinatumomab links T cells with CD19 receptors found on the surface of B cells. The Food and Drug Administration (US) and the European Medicines Agency approved this therapy for adults with Philadelphia chromosome-negative relapsed or refractory acute lymphoblastic leukemia. [6]
It is a bispecific CD20-directed CD3 T-cell engager. It was approved for medical use in Canada in March 2023, in the United States in June 2023, and in the European Union in July 2023.
Bispecifically binds CD20 and CD3 to engage T-cells. Mosunetuzumab was approved for medical use in the European Union in June 2022.
Solitomab links T cells with the EpCAM antigen which is expressed by colon, gastric, prostate, ovarian, lung, and pancreatic cancers. [7] [8]
Tarlatamab has shown promise for previously treated small cell lung cancer. [9]
After clinical trials, in January 2022, the US FDA approved tebentafusp (a BiTE targeting the gp100 peptide) for HLA-A*02:01-positive adult patients with unresectable or metastatic uveal melanoma. [10]
Utilizing the same technology, melanoma (with MCSP specific BiTEs) and acute myeloid leukemia (with CD33 specific BiTEs) can be targeted. [11] As of 2008 [update] , research in this area is active. [11]
Another avenue for novel anti-cancer therapies is re-engineering some of the currently used conventional antibodies like trastuzumab (targeting HER2/neu), cetuximab and panitumumab (both targeting the EGF receptor), using the BiTE approach. [12]
As of 2009 [update] , BiTEs against CD66e and EphA2 are being developed as well. [13]
Cetuximab, sold under the brand name Erbitux, is an epidermal growth factor receptor (EGFR) inhibitor medication used for the treatment of metastatic colorectal cancer and head and neck cancer. Cetuximab is a chimeric (mouse/human) monoclonal antibody given by intravenous infusion.
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.
A single-chain variable fragment (scFv) is not actually a fragment of an antibody, but instead is a fusion protein of the variable regions of the heavy (VH) and light chains (VL) of immunoglobulins, connected with a short linker peptide of ten to about 25 amino acids. The linker is usually rich in glycine for flexibility, as well as serine or threonine for solubility, and can either connect the N-terminus of the VH with the C-terminus of the VL, or vice versa. This protein retains the specificity of the original immunoglobulin, despite removal of the constant regions and the introduction of the linker. The image to the right shows how this modification usually leaves the specificity unaltered.
Cancer immunotherapy (immuno-oncotherapy) is the stimulation of the immune system to treat cancer, improving the immune system's natural ability to fight the disease. It is an application of the fundamental research of cancer immunology and a growing subspecialty of oncology.
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.
Panitumumab, sold under the brand name Vectibix, is a fully human monoclonal antibody specific to the epidermal growth factor receptor.
A bispecific monoclonal antibody is an artificial protein that can simultaneously bind to two different types of antigen or two different epitopes on the same antigen. Naturally occurring antibodies typically only target one antigen. BsAbs can be manufactured in several structural formats. BsAbs can be designed to recruit and activate immune cells, to interfere with receptor signaling and inactivate signaling ligands, and to force association of protein complexes. BsAbs have been explored for cancer immunotherapy, drug delivery, and Alzheimer's disease.
Blinatumomab, sold under the brand name Blincyto, and known informally as blina, is a biopharmaceutical medication used as a second-line treatment for Philadelphia chromosome-negative relapsed or refractory acute lymphoblastic leukemia. It belongs to a class of constructed monoclonal antibodies, bi-specific T-cell engagers (BiTEs), that exert action selectively and direct the human immune system to act against tumor cells. Blinatumomab specifically targets the CD19 antigen present on B cells. In December 2014, it was approved by the US Food and Drug Administration under the accelerated approval program; marketing authorization depended on the outcome of clinical trials that were ongoing at the time of approval.
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.
Trastuzumab emtansine, sold under the brand name Kadcyla, is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the cytotoxic agent DM1. Trastuzumab alone stops growth of cancer cells by binding to the HER2 receptor, whereas trastuzumab emtansine undergoes receptor-mediated internalization into cells, is catabolized in lysosomes where DM1-containing catabolites are released and subsequently bind tubulin to cause mitotic arrest and cell death. Trastuzumab binding to HER2 prevents homodimerization or heterodimerization (HER2/HER3) of the receptor, ultimately inhibiting the activation of MAPK and PI3K/AKT cellular signalling pathways. Because the monoclonal antibody targets HER2, and HER2 is only over-expressed in cancer cells, the conjugate delivers the cytotoxic agent DM1 specifically to tumor cells. The conjugate is abbreviated T-DM1.
Patrick Baeuerle is a German-based molecular biologist, immunologist, professor and a biopharmaceutical entrepreneur. Baeuerle is known for his work on tyrosine sulfation of proteins, transcription factor NF-kappaB, and the development of bispecific T-cell engaging antibodies for therapy of cancer.
Nivolumab, sold under the brand name Opdivo, is an anti-cancer medication used to treat a number of types of cancer. This includes melanoma, lung cancer, malignant pleural mesothelioma, renal cell carcinoma, Hodgkin lymphoma, head and neck cancer, urothelial carcinoma, colon cancer, esophageal squamous cell carcinoma, liver cancer, gastric cancer, and esophageal or gastroesophageal junction cancer. It is administered intravenously.
Solitomab is an artificial bispecific monoclonal antibody that is being investigated as an anti-cancer drug. It is a fusion protein consisting of two single-chain variable fragments (scFvs) of different antibodies on a single peptide chain of about 55 kilodaltons. One of the scFvs binds to T cells via the CD3 receptor, and the other to EpCAM as a tumor antigen against gastrointestinal, lung, and other cancers.
Pembrolizumab, sold under the brand name Keytruda, is a humanized antibody used in cancer immunotherapy that treats melanoma, lung cancer, head and neck cancer, Hodgkin lymphoma, stomach cancer, cervical cancer, and certain types of breast cancer. It is administered by slow intravenous injection.
Immunocore is a global commercial-stage biotechnology company, based in Oxfordshire, which researches and develops biological drugs using soluble T-cell receptor technology.
Cytokine-induced killer cells (CIK) cells are a group of immune effector cells featuring a mixed T- and natural killer (NK) cell-like phenotype. They are generated by ex vivo incubation of human peripheral blood mononuclear cells (PBMC) or cord blood mononuclear cells with interferon-gamma (IFN-γ), anti-CD3 antibody, recombinant human interleukin (IL)-1 and recombinant human interleukin (IL)-2.
Trastuzumab deruxtecan, sold under the brand name Enhertu, is an antibody-drug conjugate consisting of the humanized monoclonal antibody trastuzumab (Herceptin) covalently linked to the topoisomerase I inhibitor deruxtecan. It is licensed for the treatment of breast cancer or gastric or gastroesophageal adenocarcinoma. Trastuzumab binds to and blocks signaling through epidermal growth factor receptor 2 (HER2/neu) on cancers that rely on it for growth. Additionally, once bound to HER2 receptors, the antibody is internalized by the cell, carrying the bound deruxtecan along with it, where it interferes with the cell's ability to make DNA structural changes and replicate its DNA during cell division, leading to DNA damage when the cell attempts to replicate itself, destroying the cell.
Tebentafusp, sold under the brand name Kimmtrak, is an anti-cancer medication used to treat uveal melanoma. Tebentafusp is a bispecific gp100 peptide-HLA-directed CD3 T cell engager. Tebentafusp is given by intravenous infusion.
Mosunetuzumab, sold under the brand name Lunsumio, is a monoclonal antibody used for the treatment of follicular lymphoma. It bispecifically binds CD20 and CD3 to engage T-cells. It was developed by Genentech.
Epcoritamab, sold under the brand name Epkinly, is a monoclonal antibody anticancer medication used for the treatment of diffuse large B-cell lymphoma. Epcoritamab is a bispecific CD20-directed CD3 T-cell engager. Epcoritamab was co-developed by AbbVie and Genmab.