Take a look at some of Monday's midday movers:
EBay - The online auctioneer rose after billionaire investor Carl Icahn issued an open letter to shareholders, saying his research uncovered multiple lapses in corporate governance. EBay responded by saying Icahn has cherry picked old news clip and anecdotes out of context.
Humana - The insurance company gained as proposed government reductions to the Medicare Advantage program were less than initially thought. United Health Group, Aetna, Health Net and Wellpoint also rose.
Pfizer - Shares of the drugmaker climbed after its pneumonia vaccine study met clinical objectives.
3D Systems - The maker of 3D printers fell after BofA/Merrill Lynch downgraded its shares to underperform from buy.
Trex - The deck maker gained after reporting better-than-expected fourth-quarter earnings.
Eli Lilly - Shares of the drug manufacturer rose after it said it would buy Germany's privately held Lohmann Animal Health for an undisclosed amount.
Hewlett-Packard - The technology company rose after Argus Research upgraded it to buy from hold.
Dillard's - The retailer fell after reporting weaker-than-expected fourth-quarter earnings.
Palo Alto Networks - The cybersecurity firm gained after posting better-than-expected second-quarter earnings.
Starz - Shares gained for a second session following the pay-network operator's fourth-quarter earnings report. Stifel Nicolaus upgrades the stock to hold from sell.
(Read More: See CNBC's Market Insider Blog)
—By CNBC's Rich Fisherman.
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