Targeted therapies are made to find and attack specific areas or substances in cancer cells, or can detect and block certain kinds of messages sent inside a cancer cell that tell it to grow. Some of the substances in cancer cells that become the “targets” of targeted therapies are:
- Too much of a certain protein on a cancer cell
- A protein on a cancer cell that is not on normal cells
- A protein that is mutated (changed) in some way on a cancer cell
- Gene (DNA) changes that are not in a normal cell.

The action of targeted drugs can work to:
- Block or turn off chemical signals that tell the cancer cell to grow and divide
- Change proteins within the cancer cells so the cells die
- Stop making new blood vessels to feed the cancer cells
- Trigger your immune system to kill the cancer cells
- Carry toxins to the cancer cells to kill them, but not normal cells
The action of the drugs can affect where these drugs work and what side effects they cause.