Take a look at some of Wednesday's midday movers:
Bristol-Myers Squibb - The drug maker jumped after halting a late-stage trial of an experimental skin cancer drug after patients showed "superior overall survival."
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CBS - The broadcaster gained, as did CNBC parent Comcast and Walt Disney, after the U.S. Supreme Court ruled online-video provider Aereo had violated copyright law.
Read MoreKey Aereo investor Barry Diller: 'We did try but now it's over'
General Mills - The cereal maker declined after reporting a quarterly profit .
Hanesbrands - The underwear maker rose after saying it would buy former sister company DBApparel.
ImmunoGen - The biotechnology company fell after Morgan Stanley initiated coverage with an "underweight" rating.
Marathon Petroleum - The oil refiner and competitor Valero Energy declined on news the United States was ready to export oil for the first time in nearly four decades; traders speculated the earnings of both companies could come under pressure as U.S. exports narrow the prices between U.S. and foreign crude benchmarks.
Medical Action Industries - The maker of disposable medical and surgical products surged after Owens & Minor said it would purchase it for $13.80 a share, or about $226 million.
Monsanto - The world's biggest seed producer gained after
Pioneer Natural Resources - The energy company rose, as did Enterprise Products Partners, a day after The Wall Street Journal reported the government gave both companies permission to export very light oil with only minimal processing.
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—By CNBC's Kate Gibson
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