Cells are the most basic structure of the body. Cells make up tissues, and tissues make up organs, such as the lungs or liver. Each cell is surrounded by a membrane, a thin layer that separates the outside of the cell from the inside.
For a cell to perform necessary functions for the body and respond to its surroundings, it needs to communicate with other cells in the body. Communication occurs through chemical messages in a process called signal transduction. The purpose of these signals is to tell the cell what to do, such as when to grow, divide into two new cells, and die.
Targeted cancer therapies use drugs that block the growth and spread of cancer by interfering with specific molecules involved in the process by which normal cells become cancer cells (carcinogenesis) and tumor growth. By focusing on molecular and cellular changes that are specific to cancer, targeted cancer therapies may be more effective than current treatments and less harmful to normal cells.
However, monoclonal antibodies are "large" molecules. These very large molecules don't have a convenient way of getting access to the large majority of cells. Plus, there is multicellular resistance, the drugs affecting only the cells on the outside may not kill these cells if they are in contact with cells on the inside, which are protected from the drug. The cells may pass small molecules back and forth.
Exciting results have come from studies of multitargeted tyrosine kinase inhibitors, "small" molecules that act on "multiple" receptors in the cancerous cells, like Tykerb and Sutent. Drugs that inhibit/interfere with specific molecules. Basically inhibits various kinases, a type of enzyme that transfers phosphate groups from high-energy donor molecules to specific target molecules. Because they inhibit "multiple" kinases, it possesses activity against "multiple" types of tumors.