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Targeted Therapy

What are Targeted Therapies?

Targeted therapy is a term to describe drugs that bind to a specific “target” organ, gene or protein. They have the following functions:

  1. Prevent cancer cell division and proliferation
  2. Causing apoptosis, or programmed cell death of cancer cells by activating “death signals”

Targeted Therapy Drugs Used in Breast Cancer Treatment

There are three targeted therapy drugs that are currently being used in the treatment of breast cancer. They are all involved in critical cell signaling pathways associated with this cancer. Some of these are useful in other kinds of cancer and some have already been discussed, since they belong in more than one treatment class. The three drugs used in breast cancer are:

  • Herceptin (trastuzumab) – used only for women who have HER2-positive breast cancer, binding HER2 receptors on the breast cancer cell surface and preventing cell division
  • Tykerb (lapatinib) – also used in women with HER2-positive breast cancer, specifically affecting growth signal pathways, slowing or stopping tumor growth
  • Avastin (bevacizumab) – inactivates signals for the growth of new blood vessels that tumors are capable of producing, as they seek to receive nutrients and necessary factors from the blood to continue dividing

Other drugs are considered hormonal therapy drugs. These targeted therapy drugs include selective estrogen receptor modulators (SERMs) and aromatase inhibitors (AIs). These are:

  • SERMs – The drugs Tamoxifen and Toremifene bind to estrogen receptors (ER) to prevent estrogen from binding and enhancing cell growth. Another drug, Fulvestrant, binds estrogen receptors and downregulates their activity.
  • Aromatase inhibitors (AIs) – This category of hormone therapy drugs blocks the activity of the enzyme aromatase. Aromatase is responsible for converting hormones into estrogen, which is then used to encourage cancer growth. AIs are approved for ER-positive breast cancer in postmenopausal women. Anastrozole (Arimidex®), Exemestane (Aromasin®)and Letrozole (Femara®) have all been approved by the United States Food and Drug Administration (USFDA) to be used in the treatment of breast cancer.

Why Targeted Therapy?

More options for targeted therapy are being discovered as we learn about cancer at the microscopic level. The following are benefits of targeted therapy:

  • Targeted therapy is specific to a particular “target”. They inhibit the proteins used in activation, expression and regulation of several signaling pathways involved in the growth of breast cancer cells. As a result, they reduce the effects on normal, healthy cells causing fewer side effects.[1]
  • They function in a way that is similar to proteins in your own body, and some even boost your own body’s defenses to fight cancer.

Conclusion

New targeted therapy drugs are being discovered and actually represent a large percentage of the drugs that are currently being used in clinical trials. Clinical trials can be expensive and time-consuming, as they aim to determine appropriate dosing, timing of treatment and concern for safety.

References

1 Rojo, F; Albanell, J; Rovira, A; Corominas. JM; and Manzarbeitia, F (2008). Targeted Therapies in Breast Cancer. Seminars in Diagnostic Pathology, 25(4):245-261.

This article was originally published on July 27,2012 and last revision and update of it was 9/2/2015.