QUESTION AND ANSWER

Q. I've heard about some new drugs called Herceptin and Rituxan. What are they and how are they used?

 

A. Herceptin and Rituxan are two types of monoclonal antibodies, a form of biological therapy that uses the body's immune system to fight cancer. Rituxan was approved by the Food and Drug Administration (FDA) in November 1997 to treat non-Hodgkin's lymphoma. Herceptin is used to treat certain breast cancers that have spread to other parts of the body and which contain too much of a protein called HER2/neu. Herceptin is awaiting FDA approval.

 

To understand the function of monoclonal antibodies, it's helpful to know some basics of cancer biology. Certain cells and proteins present in the immune system are called antibodies. They fight cancer and other diseases by creating an immune response against foreign invaders called antigens.

 

"Antibodies respond by latching on to or binding with antigens and fitting together much like the way a key fits a lock," says Dr. Elihu H. Estey, professor of hematology at M. D. Anderson. "Once these cancer-associated antigens have been recognized, monoclonal antibodies carry out their role by summoning other immune system components to destroy the cancer cell."

 

Monoclonal antibodies may be used to treat cancer in several ways, including:

 

· To enhance a patient's immune response to cancer.

 

· To provide linkage and delivery of anticancer drugs, radioactive substances, biological

response modifiers or other toxins directly to the tumor, thus helping to destroy it.

 

· To attack residual tumor cells that remain after cancer treatments.

 

Since only cancerous cells are targeted with monoclonal antibodies, patients experience fewer serious side effects than with other treatments. For instance, most chemotherapeutic agents affect all fast-growing cells in the body, even healthy cells, therefore increasing the potential for adverse reactions.

 

Common side effects associated with Rituxan are related to the intravenous (I.V.) infusion itself and involve mild to moderate flu-like symptoms. In clinical trials, these symptoms most often occurred with the first treatment, were limited to the period of infusion and were less common and severe with subsequent infusions.

 

Side effects associated with Herceptin are similar and include mild to moderate cases of fever and chills, headache and sometimes, pain at the site of the tumor. Nausea, diarrhea and some serious cases of heart damage also have been reported. The cardiac toxicity may be related to prior or concurrent treatment with doxorubicin, a type of chemotherapy drug. In addition, it is not known if this adverse effect occurs in patients without any previous heart damage.

 

Although monoclonal antibodies are still undergoing investigation, they have proved promising in the treatment of certain tumors.

 

For more information on monoclonal antibodies, cancer biology and other promising new forms of treatment, or to find out how you can participate in clinical trials call the National Cancer Institute's Cancer Information Service at 1-800-4-CANCER.