Roche Holding unit Genentech and ImmunoGen obtained FDA approval to market Kadcyla, or ado-trastuzumab emtansine, as a treatment for patients who have HER2-positive, metastatic breast cancer who don't respond to other treatments. Because of associated mortality, liver and heart risks, the drug will carry a boxed warning. The approval means a $10.5 million milestone fee will be paid to ImmunoGen.