SOUTH SAN FRANCISCO, Calif.
Shares of Exelixis lost a fifth of their value Monday after the cancer drug developer reported the deaths of six patients who took an experimental treatment in clinical trial.
The company was studying cabozantinib as a treatment for several types of solid tumors. It is the company's most advanced drug candidate and the study is intended to support a future marketing application. Exelixis said the causes of death included respiratory compromise, bleeding, gastrointestinal bleeding, and intestinal perforation.
Shares of Exelixis Inc. dropped $2.21, or 20 percent, to $8.68 in afternoon trading.
The company said two ovarian cancer patients died, along with one prostate cancer patient, one lung cancer patient, one breast cancer patient, and one pancreatic cancer patient. Exelixis did not say when the patients died, but the most recent data included in its report is from Feb. 11.
Exelixis said significant numbers of patients experienced at least some tumor shrinkage after 12 weeks of treatment for cabozantinib. The highest rates of disease control were observed in liver cancer, castration-resistant prostate cancer, and ovarian cancer.
The company said there were 490 patients in the mid-stage clinical trial, and about 40 percent of them reduced their dosage of cabozantinib at least once.
The most common side effects in the study were fatigue, diarrhea, high blood pressure, and hand-foot syndrome, a condition in which small amounts of the drug leak out of the blood vessels in the palms and the soles of the feet, causing reddened skin, tenderness, and peeling.