Sometimes, the biggest challenge to cancer treatment is getting medicine to where it’s needed most. That’s especially the case with one potent cancer fighter.
|The Chinese xi shu (“happy”) tree harbors a powerful anticancer drug. (Photo by Kazuo Yamasaki)|
Camptothecin, which is found in the bark of the Chinese xi shu or “happy” tree, delivers a strong punch to cancer cells, but it’s difficult to give to patients. It doesn’t dissolve well in water, and it breaks down quickly in blood and then sticks to blood proteins, effectively making it useless in the body.
Now researchers are trying to get around these snags by using what are called nanoparticles to carry the drug to a tumor. The combination of a synthetic nanoparticle connected to camptothecin is called IT-101. This combination drug is now in testing.
IT-101 dissolves well in water, and it keeps camptothecin protected in its active form until it reaches the tumor. Once there, natural processes release the camptothecin from the nanoparticle, allowing the drug to kill tumor cells.
City of Hope’s Yun Yen, M.D., Ph.D., Dr. & Mrs. Allen Y. Chao Chair in Developmental Cancer Therapeutics and professor and director of clinical and molecular pharmacology, conducted a phase I clinical trial testing IT-101 in patients in 2007 and 2008. The study showed the method is safe and tolerable to patients, and early results suggest it works against tumors, too.
The study involved 18 cancer patients who still had cancer despite going through courses of standard therapies. One group of these patients received IT-101 infusions for three weeks in a row with one week off; the other received IT-101 every other week.
The researchers found the doses they used were safe in both regimens, but patients tolerated the drug better when they received it every other week rather than for three straight weeks. The researchers recommended future trials use the every-other-week regimen.
Yen and his team hope IT-101 one day will let them provide patients with larger doses of chemotherapy delivered directly to tumor cells while limiting side effects common to treatment such as nausea and hair loss.
Yen noted that several patients showed promising responses to the nanoparticle, including one patient whose disease had not progressed in the nine months following the trial’s launch. He cautioned that more studies were necessary before the drug’s effectiveness could be measured for certain, though.
The “happy tree”
Known by scientists as Camptotheca acuminate, this tree is native to China and Tibet, where it is called the xi shu, or happy tree. Practitioners of traditional Chinese medicine have long used the bark, leaves and fruit of the tree to treat a variety of conditions.
The late scientists Monroe E. Wall, Ph.D., then of the U.S. Department of Agriculture, and Jonathon Hartwell, Ph.D., of the National Cancer Institute, first discovered and pursued the tree’s anticancer properties in 1958.
Since then, researchers have used the tree’s main cancer-fighting chemical, camptothecin, to create several anticancer drugs, including irinotecan and topotecan. So far, the U.S. Food and Drug Administration has approved topotecan for ovarian, cervical and small-cell lung cancers and irinotecan for metastatic colorectal cancer, although clinical trials are under way on their use in other cancers.