Experimental Drug Makes the Immune System Revolt Against Cancer

A biotech company, founded by researchers from the University of Munich, has developed a fascinating way to make the immune system fight cancer.

On Thursday, Micromet Inc. announced that its experimental drug, MT103, had impressive results in a test upon seven Non-Hodgkin's Lymphoma patients. All of them had failed at least three conventional treatments, but showed signs of recovery after receiving doses of a two-headed antibody.

BiTE antibodies, or bispecific T cell engagers, are highly-engineered biological molecules with sticky ends. One side can cling to CD19, a protein found on cancerous B cells, and the other half can grab onto CD3, which is found on cytotoxic T cells. By momentarily drawing those cells together, the drug can coax the cytotoxic T cells into fighting the disease.

Training the immune system to fight cancer may be one of the best ways to keep it from coming back after several rounds of standard treatment. In most cases, surgery and radiation cannot get rid of every last cancer cell. Traditional chemotherapy may halt the growth of tumors, but it will not finish them off. Even after the best treatments, clusters of cancerous or pre-cancerous cells, called micrometastases, often drift around in the body and lodge themselves into vital organs.

To eliminate those lingering killers, many researchers have turned to cancer vaccines, which can convince the body to hunt down stray cancer cells and destroy them when they flare up. BiTE antibodies are another way to harness the defensive power of our immune systems.

When I spoke to Christian Itlin, CEO of Micromet, he said that many blockbuster cancer drugs are made from antibodies, and there is some evidence that they work by stirring up the immune system -- even though that is not how they were meant to operate. His company does intentionally what others have done accidentally -- making drugs that train the body to viciously attack cancer. In theory, their strategy could be used to combat many varieties of the deadly disease, but their treatment for lymphoma happens to be furthest along in the pipeline.

Since this was a very early trial, which was meant meant to assess the safety rather than effectiveness of the new drug, the good news should be a source of cautious optimism. Three more clinical trials of the BiTE antibody are starting in Germany. Two are for lymphoma. The newest one is meant to attack colorectal, gastrointestinal, and lung cancer.

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