A drug used to treat advanced kidney cancer and a type of liver cancer that cannot be removed by surgery. It is also used to treat a type of advanced thyroid cancer that did not get better with radioactive iodine treatment. It is being studied in the treatment of other types of cancer. Nexavar stops cancer cells from dividing and may prevent the growth of new blood vessels that tumors need to grow. It is a type of kinase inhibitor and a type of antiangiogenesis agent. Also called BAY 43-9006 and sorafenib tosylate.