Targeted chemotherapy is a method, which focuses on the tumor rather than spreading the drug throughout the body. More concentration of drugs is accumulated near the tumor site to kill the tumor. This therapy identifies the difference between the normal cells and the cancer cells and hence the damage done to the normal cells is relatively less. This is unlike conventional chemotherapy that focuses on killing the rapidly proliferating cells.

Targeted therapy identifies some other features of the cancer cells and thus has fewer side effects. Each targeted therapy works in a different manner. However, all the drugs used interfere with the cell division and growth process and communicate with the other cells. Monoclonal antibodies and anti-angiogenesis drugs are commonly used in modern targeted therapy.

Targeted therapy is broadly classified in the following categories-

• Some drugs focus on inner components and functioning of the cancer cells.

• Some therapies use small molecules that penetrate the cell, disrupt the functioning and cause a programmed death of the cells.
• Some targeted therapies target receptors that focus on the outer part of the cell. These are called monoclonal antibodies.
• Anti-angiogenesis drugs target the blood vessels and block the supply of oxygen to the cells. The cells gradually starve and die.

Some Targeted Chemotherapies are-

• Signal Transduction inhibitors that are protein-tyrosine kinase inhibitors, and epidermal growth factor receptor

• Biological Response Modifiers
• Proteasome inhibitors

Monoclonal antibodies are relatively new. Antibodies are created by the body in response to an antigen entering the body. The antibodies attach themselves to the antigen to destroy the antigen. In clinical research, specific antigens are found out on the cancer cells. Then a protein from human or animal origin is used to create an antibody that matches and targets the specific cancer cell antigen. An antibody attaches to the antigen just like a lock and key model. Hence, the healthy cells are not affected. Monoclonal antibodies are used only wherein cancer cell antigen and specific antibodies are identified. Some of the monoclonal antibodies used are-

• Alemtuzumab

• Gemtuzumab ozogamicin
• Rituximab
• Trastuzumab
• Ibritumomab tioxetan

Anti-angiogenesis is a process wherein formation of new blood vessels is blocked. In normal case, blood vessels are formed during tissue growth and repair, for instance a healing wound or development of fetus. Blood vessels carry oxygen and nutrients to various body parts in normal case. However, in case of cancer, it spreads with the help of new blood vessels as the endothelial cells that line the blood vessels divide and grow to create new blood vessels. This is called angiogenesis. This occurs in healthy and cancer tissues.

Certain substances inhibit the process of angiogenesis. The logic here is the tumor would not spread if new blood vessels do not grow and the cancer cells would gradually starve to death. There are natural and synthetic substances used anti-angiogenesis agents or angiogenesis inhibitors. Angiogenesis inhibitors have been successfully used in animals to stop blood vessel formation.

It is still under clinical trial in treatment for humans. There are more than 20 compounds under research. However, some of them are approved and being used on humans.

Targeted chemotherapy is not a replacement for traditional therapies. Targeted therapies consist of components like monoclonal antibodies or anti-angiogenesis drugs that are used for a short duration or combined with other conventional treatments. Clinical research is going on to find out the types of cancers best treated with this therapy.