Kadcyla is intended for the treatment of patients who have been previously treated with trastuzumab and taxanes. The safety and effectiveness of Kadcyla were evaluated in a clinical study of 991 patients. Patients treated with Kadcyla had a median progression-free survival of 9.6 months, compared to 6.4 months in patients treated with lapatinib plus capecitabine. The median overall survival was 30.9 and 25.1 months in the two groups, respectively.

Kadcyla carries a boxed warning alerting patients and health care professionals that the drug can cause liver toxicity, heart toxicity, and death. The drug can also cause severe life-threatening birth defects, and pregnancy status should be verified prior to starting Kadcyla, according to the FDA. The most common side effects reported were nausea, fatigue, muscle or joint pain, thrombocytopenia, increased levels of liver enzymes, headache, and constipation.

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

Kadcyla is marketed by San Francisco-based Genentech, a member of the Roche Group.

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