Examples of the use of therapeutic antibodies
HER2-positive breast cancer
In about 25% of cases of breast cancer the presence of a certain receptor protein (HER2) on the surface of tumour cells is greatly increased. As a result, the cells are more receptive to growth signals and keep on dividing. A monoclonal antibody used to treat breast cancer blocks this HER2 receptor (the antigenic structure) and thereby prevents the cells from receiving growth signals. This slows tumour growth. In addition, when the antibody binds to the receptor it stimulates certain immune cells to kill the tumour cells.
Diagnostic tests can identify those breast cancer patients who are HER2-positive and therefore able to benefit from treatment.
HER2 receptors are present in small numbers on normal breast cells. These cells divide only when necessary.
If the concentration of the receptor is increased (as in about 20–30% of breast cancer patients), the cell is more receptive to growth signals and keeps on dividing, leading to uncontrolled growth of a malignant tumour.
The monoclonal antibody blocks the growth factor receptor HER2 and thereby prevents the cells from receiving growth signals. This slows tumour growth.
Lymphoma – non-Hodgkin’s lymphoma (NHL) – and rheumatoid arthritis (RA)
The target protein of a monoclonal antibody used to treat non-Hodgkin’s lymphoma is an antigen (CD20) present on the surface of the B lymphocytes (white blood cells) that undergo uncontrolled proliferation in lymphomas. Binding of the antibody marks the tumour cells for destruction by the patient’s immune system. The antibody also increases the susceptibility of the cells to certain chemotherapeutic agents. This improves the chances of cure in patients who have failed chemotherapy and have few treatment options left.
This therapeutic approach directed at B cells also opens up new possibilities in rheumatoid arthritis (RA), a progressive systemic autoimmune disease characterised by inflammation of the inner lining of the joints that causes pain, swelling and stiffness, and can ultimately lead to irreversible joint destruction and disability.
Thanks to its innovative mechanism of action, this antibody offers both doctors and patients decisive advantages in terms of symptomatic improvement, duration of action and safety.