Closing Bell: Merck Falls, Gilead Jumps; Stocks End Mixed

Wall Street couldn't make up its mind with stocks veering wildly between heavy losses and mild gains for much of the session on Wednesday. The Dow and S&P 500 managed to end the day higher, though, after crude oil surged 8% to close above $32 a barrel. Merck (MRK) shares fell after the drugmaker issued a softer outlook for fiscal 2016 as some of its key treatments, including a drug for diabetes and another for arthritis, see weaker sales growth. The company is banking on its recently approved lung cancer treatment to boost earnings. Fellow drugmaker Gilead Sciences (GILD) spiked after breezing past analysts' estimates in its fourth quarter. The biotech company also announced a $12 billion stock buyback program. TheStreet's Keris Lahiff reports from Wall Street.