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 (via CD3) and monocytes/macrophages, natural killer cells, dendritic cells or other Fc receptor expressing cells to the tumor cells, leading to their destruction. [1]
At an equivalent dose a trifunctional antibody is more potent (more than 1,000-fold) in eliminating tumor cells than conventional antibodies. [2] These drugs evoke the removal of tumor cells by means of (i) antibody-dependent cell-mediated cytoxicity, a process also described for conventional antibodies and more importantly by (ii) polyclonal cytotoxic T cell responses with emphasis on CD8 T cells. These trifunctional antibodies also elicit individual anti-tumor immune responses in cancer patients treated with e.g. catumaxomab; i.e. autologous antibodies as well as CD4 and CD8 T cells directed against the tumor were detected. [3] [4] Furthermore, putative cancer stem cells from malignant ascites fluid were eliminated due to catumaxomab treatment. [5]
Catumaxomab, was the first to be approved for clinical use (in 2009 for the treatment of malignant ascites in cancer patients).
Examples include catumaxomab (EpCAM / CD3), [6] [7] ertumaxomab (HER2/neu / CD3), [8] FBTA05 (CD20 / CD3, proposed trade name Lymphomun) [9] [10] and TRBS07 (GD2 / CD3, proposed trade name Ektomab), [11] drugs against various types of cancer.
Trifunctional antibodies were the first type of bispecific monoclonal antibodies to be produced. The first concepts date back to the mid-1980s. [12] [13] For over twenty years, no such antibody was approved for clinical use, mainly because of manufacturing difficulties. Immunogenicity results from the fact that appropriate parental antibodies are obtained from rat and mice. After application, the patient's immune system usually produces anti-drug antibodies, which represent early indicators for a beneficial clinical outcome. [14] Furthermore, despite the development of anti-drug antibody responses after the first catumaxomab application cycle a repeated cycle of catumaxomab also leads to a treatment success in recurrent malignant ascites. [15] Cross-linking leads to the release of cytokines, resulting in manageable adverse effects like fever, nausea and vomiting, that were generally reversible and mainly related to the immunological mode of action (e.g. catumaxomab). [16] Catumaxomab, which was approved in 2009 for the treatment of malignant ascites in cancer patients, satisfies these conditions. It was the first, and as of May 2011 the only approved one of these antibodies in clinical use.
Another way of immunotherapeutic intervention strategies is the exploration of bispecific antibodies with different structures, of which bi-specific T-cell engagers (BiTEs) have been produced since the mid-2000s. [17]
At first, mouse hybridoma cells whose monoclonal antibodies target one of the desired antigens are produced. Independently, rat hybridoma cells targeting the other antigen are produced. These two cell types are hybridised, yielding hybrid-hybridomas or quadromas, which produce hybrid (trifunctional) antibody as well as pure mouse and pure rat antibody. The trifunctional antibody is extracted chromatographically with protein A.
Using two different species (mouse and rat) has the advantage that less mismatched antibodies are produced because rat light chains preferably pair with rat heavy chains, and mouse light chains with mouse heavy chains. Single species (mouse/mouse or rat/rat) quadromas, by contrast, produce up to ten different kinds of antibody, most of which have mismatched heavy or light chains, or both. [18]
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.
Cancer immunotherapy is the stimulation of the immune system to treat cancer, improving on 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.
Monoclonal antibody therapy is a form of immunotherapy that uses monoclonal antibodies (mAbs) to bind monospecifically to certain cells or proteins. The objective is that this treatment will stimulate the patient's immune system to attack those cells. Alternatively, in radioimmunotherapy a radioactive dose localizes a target cell line, delivering lethal chemical doses. Antibodies have been used to bind to molecules involved in T-cell regulation to remove inhibitory pathways that block T-cell responses. This is known as immune checkpoint therapy.
Edrecolomab is a mouse-derived monoclonal antibody targeting the cell-surface glycoprotein EpCAM (17-1A), which is expressed on epithelial tissues and on various carcinomas.
Catumaxomab is a rat-mouse hybrid monoclonal antibody which is used to treat malignant ascites, a condition occurring in people with metastasizing cancer. It binds to antigens CD3 and EpCAM. It was developed by Fresenius Biotech and Trion Pharma (Germany).
Ertumaxomab is a rat-murine hybrid monoclonal antibody designed to treat some types of cancer.
Technetium (99mTc) arcitumomab is a drug used for the diagnostic imaging of colorectal cancers, marketed by Immunomedics. It consists of the Fab' fragment of a monoclonal antibody and a radionuclide, technetium-99m.
Ipilimumab, sold under the brand name Yervoy, is a monoclonal antibody medication that works to activate the immune system by targeting CTLA-4, a protein receptor that downregulates the immune system.
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 Alzeimer's disease.
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.
Siltuximab is a chimeric monoclonal antibody. It binds to interleukin-6. Siltuximab has been investigated for the treatment of neoplastic diseases: metastatic renal cell cancer, prostate cancer, other types of cancer, and for Castleman's disease.
Urelumab is a fully human, non‐ligand binding, CD137 agonist immunoglobulin‐γ 4 (IgG4) monoclonal antibody. It was developed utilizing Medarex's UltiMAb(R) technology by Bristol-Myers Squibb for the treatment of cancer and solid tumors. Urelumab promotes anti-tumor immunity, or an immune response against tumor cells, via CD137 activation. Clinical success of Urelumab has been limited due to the fact that it can cause severe liver toxicity, or hepatotoxicity, in human patients when administered beyond the maximum tolerated dose.
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.
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.
Immune checkpoints are regulators of the immune system. These pathways are crucial for self-tolerance, which prevents the immune system from attacking cells indiscriminately. However, some cancers can protect themselves from attack by stimulating immune checkpoint targets.
The immune-related response criteria (irRC) is a set of published rules that define when tumors in cancer patients improve ("respond"), stay the same ("stabilize"), or worsen ("progress") during treatment, where the compound being evaluated is an immuno-oncology drug. Immuno-oncology, part of the broader field of cancer immunotherapy, involves agents which harness the body's own immune system to fight cancer. Traditionally, patient responses to new cancer treatments have been evaluated using two sets of criteria, the WHO criteria and the response evaluation criteria in solid tumors (RECIST). The immune-related response criteria, first published in 2009, arose out of observations that immuno-oncology drugs would fail in clinical trials that measured responses using the WHO or RECIST Criteria, because these criteria could not account for the time gap in many patients between initial treatment and the apparent action of the immune system to reduce the tumor burden.
PD-1 inhibitors and PD-L1 inhibitors are a group of checkpoint inhibitor anticancer drugs that block the activity of PD-1 and PDL1 immune checkpoint proteins present on the surface of cells. Immune checkpoint inhibitors are emerging as a front-line treatment for several types of cancer.
V-domain Ig suppressor of T cell activation (VISTA) is a type I transmembrane protein that functions as an immune checkpoint and is encoded by the C10orf54 gene.
David G. Maloney is an oncologist and researcher at Fred Hutchinson Cancer Research Center and the University of Washington who specializes in developing targeted immunotherapies for the treatment of blood cancers.
Shimon Slavin, M.D., is an Israeli professor of medicine. Slavin pioneered the use of immunotherapy mediated by allogeneic donor lymphocytes and innovative methods for stem cell transplantation for the cure of hematological malignancies and solid tumors, and using hematopoietic stem cells for induction of transplantation tolerance to bone marrow and donor allografts.