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Monoclonal antibodies (mABs) are a type of targeted drugs that work by recognizing and binding to specific proteins on cancer cells. Antibodies are found naturally in the blood stream to fight infections. A mAB is similar to a normal antibody but is created in the laboratory. The term ‘monoclonal’ refers to the fact that it concerns a lot of copies of the same, identical antibody. In the context of cancer, monoclonal antibodies are directed against specific proteins that are exclusively, or excessively present on the cell surface of cancer cells. In many cases these ‘target proteins’ are growth factor receptors that stimulate cancer cells to grow out of control. By blocking these receptors, cancer cells no longer receive the signals they need to grow and divide and the cancer cells are removed by immune effector cells.

Many different mABs, targeting a broad range of proteins, are used in the treatment of hematological and solid cancers. The names of all these drugs end with ‘mab’.

A first example of a mAB that is broadly used in the treatment of hematological malignancies consists of rituximab. This mAB is directed against CD20, a protein that is expressed on the cell surface of maturing B-lymphocytes. Rituximab, either alone or in combination with chemotherapy or other targeted agents, proved to be very effective in the treatment of patients with non-Hodgkin's lymphoma (NHL) and chronic lymphocytic leukemia (CLL). In addition to rituximab, researchers have developed several other mABs directed against CD20, including obinutuzumab.

In addition to CD20, also CD38 has been an extensively studied cell surface protein in hematological malignancies. This protein is highly expressed on the surface of multiple myeloma cells, with a minimal expression on healthy cells, making it an interesting therapeutic target. In line with this, mABs against CD38, such as daratumumab and isatuximab, were shown to be very effective in the treatment of patients with multiple myeloma.

All treatments have side effects, and this is not different for mABs. A common side effect of these agents is an allergic reaction to the drug. Such an allergic reaction can lead to breathlessness, fever, an itchy rash, and hot flushes. Other general side effects that can occur with mABs include changes in the skin (redness, sore skin, itch, etc.), diarrhea, fatigue, flu-like symptoms (e.g., chills, fever, dizziness) and nausea.

Monoclonal antibodies can also be used to carry chemotherapeutic agents to cancer cells (antibody-drug conjugates) or can simultaneously bind two different antigens (bispecific antibodies). A specific type of monoclonal antibodies consists of immune checkpoint inhibitors, which remove the break on the anti-immune response against cancer cells. These specific types of monoclonal antibodies are discussed in more detail on separate pages.

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