On the Horizon: Cancer Drugs That Harness Your Immune System

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For years, researchers have longingly eyed the human immune system as a potentially powerful weapon against cancer. Yet while the prospect of getting the bodys antibodies and immune cells to seek and destroy cancer the same way they do bacteria and viruses seems like a home run in theory, it hasnt proven to be very reliable.

The reason has to do with the very nature of cancer itself: cancer cells arent invaders, but healthy cells gone rogue. So, targeting tumors often means having to target innocent, healthy tissue as well. Thats why cancer vaccines and immune-based treatments have had such mixed success.

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But last weekend, at the annual meeting of the American Society of Clinical Oncology (ASCO), researchers reported on a promising advance: Dr. Kimberly Blackwell, director of the breast cancer program at the Duke Cancer Institute, said that she and her colleagues had successfully treated 991 women with advanced and metastatic breast cancer with an innovative smart bomb of a therapy, an antibody designed to bind only to tumor cells and then deliver its killer payload, an uberpowerful toxin, to destroy them. The idea is eloquently simple, yet, says Blackwell, it was a dozen years in the making.

The key was finding a way to ferry the toxin straight to breast cancer cells while bypassing healthy tissues along the way. The answer was an antibody that recognizes a protein called HER2 on certain breast cancers. Once attached to the HER2 on the cancer, the antibody and its partner toxin enter the cell where the antibody is broken down, releasing the toxin to destroy the cell from the inside out.

In the study, this new drug, called T-DM1, delayed worsening of disease by three months in women who received it, compared with those taking two other commonly used drugs. For women who got T-DM1, their disease did not progress for 9.6 months, compared with 6.4 months for the other group. The data also hinted that T-DM1 could extend womens lives, but the study wasnt long enough to determine survival.

Because the drug was so targeted, it also spared patients many of the worst side effects of chemotherapy, including hair loss, nausea and vomiting.

This is important proof of principle that the time has come for this type of therapy, says Dr. Michael Link, president of ASCO and professor of pediatrics at Stanford University School of Medicine. Historically, people have talked about using antibodies as a way of targeting cancer cells specifically. We know peoples immune systems do this quite well. The question has been how to jury-rig the system for anti-tumor purposes.

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On the Horizon: Cancer Drugs That Harness Your Immune System