Monoclonal Antibodies
What Are Monoclonal Antibodies (mAbs)?
Monoclonal antibodies (mAbs) are laboratory-engineered immune proteins designed to recognize and bind to a specific antigen. An antigen is a molecular structure such as a protein expressed on the surface of cancer cells, pathogens, or immune cells that can trigger an immune response.
Monoclonal antibodies are produced from a single clone of B lymphocytes, a specialized type of white blood cell responsible for antibody production. Because they originate from one identical immune cell, all monoclonal antibodies generated are structurally identical and bind to the same precise epitope on the target antigen.
This high specificity distinguishes monoclonal antibodies from polyclonal antibodies, which are derived from multiple B-cell clones and recognize multiple epitopes on the same or different antigens.
Due to their precision, monoclonal antibodies are widely used in oncology, autoimmune diseases, infectious diseases, and targeted immunotherapy.
How Are Monoclonal Antibodies Used?
Monoclonal antibodies are widely used in the treatment of various diseases, including multiple types of cancer, autoimmune disorders, and inflammatory conditions. In oncology, they are designed to specifically recognize and bind to molecular targets expressed on tumor cells or within the tumor microenvironment.
The development of a monoclonal antibody begins with the identification of an appropriate target antigen. This antigen must be sufficiently expressed on diseased cells while being limited or absent on healthy tissues to ensure therapeutic selectivity and minimize toxicity.
Identifying suitable cancer-specific antigens remains a major scientific challenge. Tumor cells can vary significantly in their molecular profiles, and not all cancers express ideal targetable markers. As a result, monoclonal antibodies have demonstrated strong clinical efficacy in certain malignancies such as those with well-defined surface antigens while showing more limited benefit in others.
Once developed, monoclonal antibodies may function through several mechanisms, including direct tumor cell targeting, immune system activation, or delivery of cytotoxic agents to malignant cells.
Are monoclonal antibodies immunotherapy or targeted therapy?
Different monoclonal antibodies can act as targeted therapy, immunotherapy, or both, depending on how they work.
- Some monoclonal antibodies are considered targeted therapy because they attach to a specific target on a cancer cell and stop it from functioning.
- Others act as immunotherapy because they help the immune system find and attack cancer cells more effectively.
Naked monoclonal antibodies
Naked mAbs are unconjugated antibodies, meaning they do not carry drugs or radioactive substances. They exert therapeutic effects on their own and represent the most commonly used type of mAbs in oncology.
These antibodies primarily target antigens on cancer cells, although some may bind to antigens on non-cancerous cells or soluble proteins. Their mechanisms of action include:
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Immune system activation:
Naked mAbs can mark cancer cells for destruction by the body’s immune system.- Example: Rituximab (Rituxan), used for certain types of non-Hodgkin lymphoma.
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Checkpoint modulation:
Some mAbs enhance immune response by targeting immune checkpoints, enabling the immune system to attack tumor cells more effectively.- Example: Pembrolizumab (Keytruda), used for some non-small cell lung cancers.
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Inhibition of cancer cell growth:
Naked mAbs may bind to proteins on cancer cells (or surrounding cells) that are critical for tumor growth or metastasis, effectively blocking these signals.- Example: Trastuzumab (Herceptin), used in HER2-positive breast cancer.
