Why Merck's Latest Success Means Trouble for Exelixis Inc.

Exelixis Inc. (NASDAQ: EXEL) was one of the best-performing biotech stocks of 2016, and it more than doubled in 2017 due to strong uptake of its kidney cancer therapy. Cabometyx sales are still on the rise, but recently released clinical trial results from Merck & Co. (NYSE: MRK) spell big trouble ahead.