Take a look at some of Tuesday's midday movers:
Achillion Pharmaceuticals - The drug developer surged after the Food and Drug Administration lifted its hold on trials of its hepatitis C drug.
Allergan - The drug developer edged lower after rejecting the latest takeover bid from Valeant Pharmaceuticals, saying the $53 billion isn't even worth talking about.
Blount International - The outdoor-equipment company rose after KeyBanc upgraded its shares to a buy from hold after meeting with management.
Colgate-Palmolive - The supplier of consumer products rose after BMO Capital Markets upgraded the stock to outperform from market perform.
Five Below - The discount-store chain rose after naming Walmart.com's chief executive, Joel Anderson, as its president.
Francesca's Holdings - The supplier of women's apparel fell after cutting its full-year forecast.
General Motors - The auto manufacturer edged higher after Chief Executive Mary Barra told a shareholdings meeting GM does not plan any more dismissals linked to a defective ignition switch tied to at least 13 deaths.
Netflix - The provider of online entertainment advanced after Evercore Partners hikes its price target on its shares to $500 from $400.
Receptos - The biotechnology company gained after releasing positive phase 2 trial results on its multiple sclerosis drug.
3D Systems - The printer gained ground after raised its 2014 revenue outlook.
Twitter - The social-media company rose after Wells Fargo upgraded its shares to market perform from underperform.
Tyson Foods - The poultry producer declined after Credit Suisse downgraded the stock to underperform from neutral.
United Continental Holdings - The airline rose after saying its frequent-flier rewards program would be based on ticket price instead of distance flown, starting in March.
Wynn Resorts - The casino operator and competitors including MGM Resorts International and Melco Crown Entertainment fell after UBS downgraded Las Vegas Sands to neutral from buy.
Zynga - The video-game publisher rose after UBS issued a positive note and reiterated its buy rating.
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—By CNBC's Rich Fisherman.
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