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Monoclonal Antibodies

Posted Aug 24 2008 1:49pm
ANNOUNCER: Non-Hogdkin's lymphoma, or NHL, is a white blood cell cancer of the lymphatic system. Over 50,000 new cases are expected to be diagnosed this year in the U.S. At a Gilda's club gathering in Chicago, lymphoma patients, and those who wanted to learn about the disease, found out about current treatment options.

LEO GORDON, MD: When we use the radioisotopes, we're giving it this way, and it goes out.

DONALD MECCIA, MD: I have three family members who have lymphoma, including my mother and as a doctor, my interest levels have been quite high, and I must suggest that this program tonight has been exemplary.

PAT BASHAW: There are people who are actively seeking out treatments that hopefully at some point will be curative. I feel certain, that eventually it will happen.

ANNOUNCER: One of the latest treatments discussed was Zevalin, a new type of treatment that contains a monoclonal antibody. But what are monoclonal antibodies? And how do they work?

RUSSEL SCHILDER, MD: Monoclonal antibodies are substances that our body normally makes to fight infections or in response to other foreign attack that our immune system makes. And normally our body makes a whole lot of different antibodies to different things, each cell making one type of antibody.

LEO GORDON, MD: Cancer investigators took advantage of that and attempted to make specific antibodies against certain targets on malignant cells. Most of those targets were proteins or antigens on the surface of the those cells. So the concept was if you could take an antibody, target it directly to the protein or antigen on the surface of the cancer cell, you could then cause that cell to stop growing, cause that cell to die and it's led to a host of new treatments for malignancies.

ANNOUNCER: Because they specifically fight one protein on a cancer cell, monoclonal antibodies are called targeted therapies. And the list of those available as treatment options in cancer, is growing.

RUSSEL SCHILDER, MD: The first one was rituximab in the treatment of lymphoma. That was followed quickly by a drug called Herceptin®, which is used in the treatment of breast cancer. Another one that's commonly referred to as Campath® in the treatment of chronic lymphocytic leukemia.

ANNOUNCER: All monoclonal antibodies used in medicine originate from mice. When used in humans, these mouse antibodies cause an immune response known as HAMA, human anti-mouse antibodies. This HAMA response can produce side effects in patients and reduce the effectiveness of the treatment.

LEO GORDON, MD: You're introducing a foreign protein, mostly a mouse protein, into a human system. So patients experience fevers, chills, sometimes a drop in blood pressure, sometimes wheezing, all the kinds of things that you might expect as a reaction to a foreign protein.

Another concern is that, again as a foreign mostly mouse protein, we know that the human body can elicit an immune response to the antibody. And so that if you have an injection of a mouse protein, within a month or two you might be making antibodies against that mouse protein, thereby limiting its effectiveness down the road.

ANNOUNCER: In an attempt to reduce the problems associated with HAMA, scientists have, in some cases, been able to replace large portions of the mouse antibody with human antibody.

LEO GORDON, MD: As we develop antibodies that are more of human origin, I think we'll see that those side effects become less.

ANNOUNCER: Despite some concerns, monoclonal antibodies are still seen as a more tolerable treatment than chemotherapy.

RUSSEL SCHILDER, MD: Most people think of chemotherapy as, whether people lose their hair, they have nausea and vomiting. Often times there could be a sore mouth, there could be reductions in the blood counts. The monoclonal antibodies because they are more targeted, tend to have fewer side effects.

ANNOUNCER: Monoclonal antibodies are also being combined with standard drugs in various treatment regimens to improve response rates.

LEO GORDON, MD: There are some laboratory studies that suggest that when you add chemotherapy agents and monoclonal antibodies to the test tube against cancer cells, you'll have more effective treatment when either one of the two are used alone. The combination of Rituxan and a standard chemotherapy for lymphoma called CHOP chemotherapy, in elderly patients is better than if you used just the CHOP chemotherapy alone.

ANNOUNCER: One of the latest advances involves the tagging of monoclonal antibodies with radioactive substances. This enables a new form of therapy called radioimmunotherapy.

RUSSEL SCHILDER, MD: We can put different things on monoclonal antibodies, such as radioactive, what we call nuclides that allow the antibody to target the radioactivity to the specific cells. For instance the drug recently approved, Zevalin, targets lymphoma cells because they express this antigen called CD20 and the antibody targets the CD20, but attached to the antibody is a radioactive atom of yttrium, thus bringing the radioactivity right to the target, and limiting the radiation exposure of normal tissues.

ANNOUNCER: Though some patients might have concerns about this new therapy, any risk from the radiation is very small. For those doctors and patients considering these new treatments, examining all the information available is important.

RUSSEL SCHILDER, MD: Most patients know somebody who may have already had chemotherapy and can draw from the experience of relatives or friends. But fewer patients have received some of these more recent developmental therapies, such as monoclonal antibodies or even the radioactive monoclonal antibodies.

ANNOUNCER: For cancer patients today, the ongoing research into targeted therapies like monoclonal antibodies and radioimmunotherapy means a whole new world of treatment possibilities is on the way--as many found out at this meeting.

LEO GORDON, MD: I think this is an extremely exciting time in cancer research and also I would say in medical research, in biology, because we're beginning to understand finally the mechanisms of disease, of DNA formation so I think we're going to see a lot more of this targeted, specific therapy against cancer and that's an exciting era.

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