Midday movers: CBS, Hanesbrands, Monsanto & more

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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."

Read MoreBristol immunotherapy prolongs survival in melanoma trial

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 beneath Wall Street's expectations.

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 raising its outlook for the year

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.

Read MoreRefiner shares fall after U.S. allows some light crude exports

(Read More: See CNBC's Market Insider Blog)

—By CNBC's Kate Gibson

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