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Advances in Targeted Therapies Tutorial

Introduction

In This Section:

How are Targeted Therapies Linked to Personalized Medicine?

Targeted therapies are transforming the way people treat cancer. With help from molecular biology and genomic sequencing technologies, it is now possible to discover good therapeutic targets within cancer cells and then to design treatments that selectively interfere with them.

Targeted therapies have already begun to make personalized medicine a reality and will continue to help doctors tailor cancer treatment based on the characteristics of an individual's cancer. As many new types of targeted therapies become available, patients will need help deciding among them. Health care professionals should become familiar with the concept of targeted therapies so they can communicate with their patients about these new approaches and help them make better informed treatment decisions.

This is a photograph of a doctor and other hospital staff talking to a cancer patient lying in a hospital bed.

This tutorial is for oncology health professionals who wish to learn more about targeted therapies. Some of the questions that will be answered include:

  • What are targeted therapies?
  • What do these new treatments target?
  • Which targeted cancer therapies are currently approved by the Food and Drug Administration (FDA)?
  • How can I find clinical trials that are evaluating targeted therapies?

What Is Standard Chemotherapy?

Over the years, oncologists have prescribed what we now call standard chemotherapy because they found by trial and error that these drugs worked. They reduced the cancer burden in many of their patients, largely by killing rapidly dividing cells.

This is an image of a human body connected to an intravenous (IV) fluid bag containing a chemotherapeutic agent. The chemotherapeutic agent from the IV fluid bag has entered the body and is running through the body's circulatory system.

Standard chemotherapy often results in collateral damage to healthy tissue, causing unwanted side effects that impair the circulatory system, the immune system, the digestive system, and others. Only later did oncologists discover which molecules and processes are disrupted by standard chemotherapy. Because these traditional drugs usually affect processes that occur in all rapidly dividing cells, many normal cells throughout the body that are undergoing active growth and cell division can also be damaged.

How Are Targeted Therapies Different?

Unlike standard chemotherapy, targeted therapies are designed to interact with specific molecules that are part of the pathways and processes used by cancer cells to grow, divide, and spread throughout the body. Targets are chosen very carefully. When researchers discover a potentially vulnerable molecule involved in a cancer process or pathway, they validate it by doing more research, and then, if all goes well, they design new therapies to disrupt its activity with great precision.

This is an image of cancer cells (colored green) over a layer of normal cells (pink). There is a close-up view of two cancer cells. In each close-up view a pair of receptor proteins embedded in the cell membrane is shown. Inside each cell is a series of proteins representing an intracellular signaling pathway that begins at the transmembrane receptors. The first close-up view illustrates a targeted therapy inside the cell that prevents the receptors at the membrane from activating the signaling pathway.

Many targeted therapies are associated with fewer and less toxic side effects than standard chemotherapy or radiation because they cause little or no collateral damage to normal cells. This can contribute to the quality of life for patients undergoing treatment.

In summary, targeted therapies are different because:

  • They act on specific molecular targets that have been identified through research, while most standard chemotherapies act on all rapidly dividing cells.
  • They are deliberately chosen or designed to interact with their target, while many standard chemotherapies were identified through trial and error.

Also, targeted therapies may be associated with fewer and less toxic side effects than standard chemotherapy, since they may cause less damage to normal cells.

What Makes a Good Target?

The best target for therapy is a molecule or pathway that is present in cancer cells and absent in normal cells. This ensures that the therapy will only attack cancer cells.

This image shows a layer of pink normal cells and a mass of green cancer cells. On the left, there is a close-up view of a cancer cell with six red circles representing targets. On the right, there is a close-up view of a normal cell with no red circles indicating no targets. The caption reads 'Best--targets in cancer cells, not in normal'.

Unfortunately, this is not usually the case. It is often difficult to find targets that are present only in cancer cells, in part, because cancer cells evolve from normal cells. The next best target for therapy is a molecule that is present more frequently in cancer cells compared to normal cells. In this case, it may be possible to adjust the dose of a drug so that cancer cells are killed more often than nearby normal cells.

This image shows a layer of normal cells (pink) and a cluster of cancer cells (green). There is a close-up view of the cancer cell on the left with six red circles representing targets. There is a close-up view of a normal cell on the right with three red circles indicating a smaller number of targets in the normal cell. The title reads 'Next best - more targets in cancer cells than in normal'.

Other possible targets for therapy include molecules that are present on both cancer cells and normal cells, but the patient's body can replace the normal cells that get destroyed.

This image shows a layer of normal cells (pink) and a mass of cancer cells (green). There is a close-up view of a cancer cell on the left with six red circles representing targets. There is a close-up view of a normal cell on the right with six red circles indicating the same number of targets in the normal cell. The title reads 'Also possible--targets in both cancer cells and normal, normal regenerates'.