Uses of Monoclonal Antibodies

Therapeutic uses of monoclonal antibodies

Therapeutics are perhaps one of the most relevant applications any new technology or tool can have, and monoclonal antibodies have shown that they can be used in effective drug therapies. As monoclonal antibodies are specific to an epitope, they are used to target a specific substance or cell of interest.

One therapeutic application that has shown success is cancer therapeutics. Many cancers are not easily treated. The ability to specifically target an antigen in many cancer cells using monoclonal antibodies allows for a more targeted approach than conventional radio and chemotherapy strategies.

The development of these strategies has already resulted in various effective drug therapies for cancer therapeutics, and others are continuously being explored through clinical trials. There are several ways monoclonal antibodies can be applied to cancer therapeutics, namely through direct or indirect monoclonal antibody therapies.

Direct monoclonal antibody therapy

Direct monoclonal antibody therapies have been the most successful cancer therapeutic strategy of monoclonal antibodies. Monoclonal antibodies can be made to target and bind to cancer cell antigens. The attachment of monoclonal antibodies to these epitopes on cancer cells blocks the chemical signals which stimulate their uncontrolled growth and help stop them from growing and dividing. The specific antigen-antibody binding also triggers the immune system to help recognise and destroy the cancer cells while avoiding other healthy cells.

mAbs have also had success as drug therapies for treatments that involve immune system response modification. This modification includes binding monoclonal antibodies to epitopes on immune system cells, like lymphocyte antigens. The binding interaction may enhance lymphocyte action against the desired target, like a cancer cell, or block its action when it is the own immune system that is causing the disease (autoimmune disease).

Fig. 1 - Monoclonal antibodies cancer therapeutics applications

Indirect monoclonal antibody therapy

In indirect monoclonal antibody therapeutics, monoclonal antibodies can be attached to radioactive or cytotoxic drugs and introduced into patients. The antibody then binds to the antigens on cancer cells and helps kill them through its interaction with its attached cargo. These therapies using antibody conjugates are usually referred to as antibody-drug conjugate therapies (ADC therapies). When mAbs are combined with cytotoxic drugs like toxins or small drug molecules, this is referred to as chemoimmunotherapy.

Radioactive monoclonal antibodies (radioimmunotherapy) and cancer

When monoclonal antibodies are used alongside radioactive particles, like radionuclides, this is referred to as radioimmunotherapy. These molecules include, for example, iodine-131 and yttrium-90. Radioimmunotherapy can treat cancers like non-Hodgkin lymphoma, which is cancer that affects B cells. Although they have had notable successes, radioimmunotherapeutics has overall been a disappointing strategy in cancer therapeutics.

Monoclonal antibody diagnostics

Considering that monoclonal antibodies bind to one specific antigen, they are an ideal diagnostic tool to identify the presence of the desired antigen. Monoclonal antibodies are used in hundreds of different diagnostic products in multiple applications, including:

• Diagnosis of disease - monoclonal antibodies can help diagnose certain cancers (e.g., prostate cancer), infectious diseases (e.g., hepatitis, chlamydia or influenza) and even blood clots by detecting and signalling the presence of the respective indicating antigen in a bodily fluid.

• Pregnancy tests – monoclonal antibodies can be made to bind the human chorionic gonadotropin (hCG) hormone, which is produced by the placenta during the early stages of pregnancy and can be found in a pregnant woman’s urine. Monoclonal antibodies in pregnancy tests are bound to coloured particles. In the event of hCG presence, a coloured line appears alongside a control line, resulting in a positive pregnancy test. This is perhaps one of the most widespread and important applications of monoclonal antibodies. Pregnancy tests are invaluable for informing and contributing to women’s reproductive health.

Fig. 2 - Pregnancy Test (Positive vs Negative)

Research – monoclonal antibodies are very relevant biomedical research tools used to identify or locate a specific molecule in a cell/tissue that may inform our understanding of how diseases work. These monoclonal antibodies are linked with a fluorescent dye which emits fluorescence upon binding the target antigen. In this way, it is possible to locate a specific protein simply by analysing the fluorescence intensity.

Benefits and drawbacks of monoclonal antibodies

Monoclonal antibody usage in therapeutics and diagnostics has shown clear benefits. Among them is the ability to target a wide array of diseases. Antigens can trigger an immune response so that hybridoma techniques can produce specific monoclonal antibodies against that antigen of interest. This enables scientists to generate monoclonal antibodies that target antigens associated with various conditions.

The specific binding between monoclonal antibodies and their corresponding antigen also allows us to have more control over treatment strategies. This means that common collateral damages that often arise from using conventional drug treatments can be avoided because healthy cells are not affected using monoclonal antibodies.

Despite the proven successes of monoclonal antibodies, their production has a high price tag, which continues to be a problem for its therapeutic applications. However, technological advancements may mean that someday, this tool will be cheaper than more conventional drug treatments.

Other problems, including connecting monoclonal antibodies to a therapeutic molecule, have largely been overcome with the development of new technologies. One very important limitation that has been surpassed concerning the use of these antibodies in therapeutics was excessive adverse effects caused by immune system rejection—initial strategies to produce mAbs used hybridomas consisting of animal cells artificially. The antibodies produced in animal cells consist of animal protein, which triggers an immune reaction in humans. The immune reaction makes the therapy ineffective and can cause life-threatening side effects. Side effects include bleeding, flu-like symptoms, and infusion reactions. Antibody humanisation allows modifying the animal protein to give rise to human-like protein, allowing antibodies to deceive the immune system and prevent the initiation of an immune response.