In the United States, researchers at three Harvard University-affiliated hospitals — Massachusetts General Hospital, Dana-Farber Cancer Institute, and Brigham and Women’s Hospital — have been testing a powerful drug on patients with breast, ovarian, and prostate cancer. “Tests show that the drug has been active enough to expand these trials,” says Bruce Chabner, a professor of medicine at Harvard Medical School. The drug comes from sea squirts, vase-shaped sacs of tough tissue that filter food particles from ocean water with the help of two siphonlike openings at the top. The drug derived from sea squirts is so incredibly powerful, only 0.05 ounce is enough to treat 100 patients. According to Elias J. Corey, Sheldon Emery Professor of Chemistry at Harvard, a mere 11 pounds of the drug would satisfy world demand for about a year. It’s good that it is so powerful, because a harvest of about 95,000 pounds of sea squirts yields a scant 3 ounces of the drug. Two years ago, Corey managed to make the drug synthetically. A Spanish company, PharmaMar, has established an underwater farm on which the tubelike creatures are being raised.