Targeted therapy is a type of medication that blocks the growth of cancer cells by interfering with specific targeted molecules required (i.e. specific markers which are present as cancer cells). That is why, they kill only the bad cells i.e. cancer cells and spare the Normal or food cells.

Types
The main categories of targeted therapy are small molecules and monoclonal antibodies.

Small molecules:- The main examples are:-

• Imatinib mesylate (Gleevec) is approved for chronic myelogenous leukemia (CML), gastrointestinal stromal tumor (GIST).
• Gefitinib (Iressa), targets the epidermal growth factor receptor (EGFR) which is present on may cancer cells it is approved in the U.S. for non small cell lung cancer. EGFR is also overexpressed in the cells of other solid tumors, such as lung and breast cancers.
• Erlotinib (marketed as Tarceva). Erlotinib also inhibits epidermal growth factor receptor, and works through a similar mechanism as gefitinib. Erlotinib has been shown to increase survival in metastatic non small cell lung cancer when used as second line therapy.
• Bortezomib (Velcade) is an apoptosis-inducing drug that causes cancer cells to undergo cell death by interfering with proteins. It is approved in the U.S. to treat multiple myeloma that has not responded to other treatments.
• The selective estrogen receptor modulator tamoxifen has been described as the foundation of targeted therapy.

Monoclonal antibodies

Several are in development and a few have been licenced by the FDA. Examples of licenced monoclonal antibodies include:

• Rituximab targets CD20 found on B cells. It is used in non Hodgkin lymphoma
• Trastuzumab (Herceptin) targets the Her2/neu (also known as ErbB2) receptor expressed in some types of breast cancer
• Cetuximab (marketed as Erbitux) targets the epidermal growth factor receptor. It is used in the treatment of colon cancer and non-small cell lung cancer.
• Bevacizumab (marketed as Avastin) targets circulating VEGF ligand. It is approved for use in the treatment of colon cancer, breast cancer, non-small cell lung cancer, and is investigational in the treatment of sarcoma. Its use for the treatment of brain tumors has been recommended .