Monoclonal antibody therapy includes some of the first agents that were used in the modern era of targeted therapies. Antibodies are glycoproteins produced in response to a specific antigen found in the body. Monoclonal antibodies are artificially produced proteins, from a single clone of cells sensitised to a specific antigenic protein present on the surface of a target tumour.10
There are four distinct types of monoclonal antibodies:
Hybridoma technology was first used to produce large quantities of specific antibodies using mouse models.14 Early challenges of this model were the immunogenic reactions involving murine antibodies. Further progress in this area with genetic engineering techniques produces monoclonal antibodies with components from both mouse and human which improves therapeutic applications.14, 15
In order for monoclonal antibodies to be successful in cancer therapy, a number of key characteristics must be met:14
- specificity - the target antigen must be present on malignant cells only
- density - the quantity of target antigen expression directly relates to tumour response
- function - the role of target antigen in cell survival and proliferation is instrumental in cell destruction
- modulation - modulating antigens internalise the antibody / antigen complex once binding has taken place. This is required for toxin conjugated monoclonal antibodies and is less desirable when it occurs rapidly for unconjugated monoclonal antibodies.
Both unconjugated and conjugated monoclonal antibodies are approved for clinical use in cancer therapy:9
Unconjugated monoclonal antibodies target a specific anti-tumour antigen initiating an immunologic response reliant on the host immune mechanisms to destroy the target cell. Unconjugated monoclonal antibodies include:
Conjugated monoclonal antibodies carry radioimmunoconjugates, chemoimmunoconjugates or immunotoxins to a specific target antigen. They are capable of killing cells and do not require any host immune mechanisms. Conjugated monoclonal antibodies include:
- gemtuzumab ozogamicin
- Y90 ibritumomab tiuxetan
- I131 tositimomab.
- Several other monoclonal antibodies have been developed that target specific molecular events and will be discussed later:
For the monoclonal antibody rituximab, identify the following:
- the antigen targeted
- its mechanism of action
- indications for its use in clinical practice
- nursing care considerations.
You are asked by a woman who has T-cell lymphoma why she is not receiving rituximab as part of her treatment. Outline your response and identify information resources you may provide her.