A new drug for late-stage breast cancer has been approved by the U.S. Food and Drug Administration.

Genentech's Kadcyla (ado-trastuzumab emtansine) is for use in patients with HER2-positive, late-stage breast cancer who were previously treated with another anti-HER2 drug called Herceptin (trastuzmab) and a class of chemotherapy drugs called taxanes, which are commonly used to treat breast cancer.

"Kadcyla is trastuzumab connected to a drug called DM1 that interferes with cancer cell growth," Dr. Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research, said in an FDA news relase.

"Kadcyla delivers the drug to the cancer site to shrink the tumor, slow disease progression and prolong survival. It is the fourth approved drug that targets the HER2 protein," he explained.

The FDA's approval of the drug was based on a study of 991 patients. Kadcyla carries a boxed warning that it can cause liver and heart problems and even death. It can also cause life-threatening birth defects, the agency said.