Molycorp, Pandora, Tiffany, TranS1: U.S. Equity Movers

Shares of the following companies had unusual moves in U.S. trading. Stock symbols are in parentheses and prices are as of 4 p.m. in New York.

American International Group Inc. (AIG US) rose 2 percent to $30.39, the highest price since May 20. The insurance company that received a $182.3 billion bailout after the collapse of Lehman Brothers Holdings Inc. is selling $6 billion of AIA Group Ltd. shares to pay back the U.S. government. Inc. (ACOM US) rose 2.6 percent to $23.65 for the biggest gain since Feb. 21. The family history provider’s “Who Do You Think You Are” episode with Reba McEntire drew 7.6 million viewers, a record for the program. The viewership reduced concern the show would be canceled, Morgan Stanley said in a note.

Archipelago Learning Inc. (ARCL US) rallied 23 percent, the most intraday since its initial public offering in November 2009, to $11.09. The subscription-based education company agreed to be bought by Plato Learning for $11.10 a share.

Big Lots Inc. (BIG US) rose the most in the Standard & Poor’s 500 Index, climbing 3.4 percent to $44.15. The discount retailer was lifted to buy from neutral at Northcoast Research Holdings LLC.

Harman International Industries Inc. (HAR US) fell 3.1 percent, the most since Dec. 14, to $47.27. The maker of audio equipment for cars and homes was rated underweight at Morgan Stanley, meaning the firm expects the stock to trail its peers over the next 12 to 18 months.

Keryx Biopharmaceuticals Inc. (KERX US) rallied 34 percent to $4.94 for the biggest gain in the Russell 2000 index. Investors speculated a new drug for treating colorectal cancer by Aeterna Zentaris Inc., a Quebec City-based cancer drug maker and partner of New York-based Keryx, may win approval from U.S. regulators.

MetroPCS Communications Inc. (PCS US) slipped 5.7 percent to $9.96, while Leap Wireless International Inc. (LEAP US) declined 7.5 percent to $9.76. The pay-as-you-go wireless providers were downgraded by Sanford C. Bernstein & Co., which cited “outsized business and financial risks.”

Molycorp Inc. (MCP US) increased 4.1 percent, the most since Feb. 16, to $25.56. The owner of the largest rare-earth deposit outside China may benefit from a recovery in prices as demand increases after a 25 percent decline this year, according to Morgan Stanley, which reiterated its overweight recommendation on the stock. The rating means the company is projected to perform better over the next 12 to 18 months than other stocks the analyst covers.

Nature’s Sunshine Products Inc. (NATR US) climbed 16 percent, the most since Aug. 3, to $16.97. The maker of nutritional and personal care products said that, excluding some items, it earned 48 cents a share in the fourth quarter.

Pandora Media Inc. (P US) rallied 5.5 percent to $14.66, the highest price since Nov. 10. The online music service provider was upgraded to buy from hold at Stifel Nicolaus & Co., which cited the expansion of the company’s advertising sales staff.

Polypore International Inc. (PPO US) declined the most in the Russell 1000 Index, falling 9.7 percent to $35.91. The maker of battery components is likely to be sensitive to events such as General Motors Co.’s five-week halt in production of its Volt plug-in hybrid until there’s clearer evidence of lithium sales increases, according to Robert W. Baird & Co.

TranS1 Inc. (TSON US) rallied 24 percent to $4.07, the highest price since Sept. 8. The maker of medical devices to treat spinal diseases said an American Medical Association panel approved its application for a category I CPT code for L5-S1 spinal fusion with its AxiaLIF implant.

Zynga Inc. (ZNGA US) slipped 4.9 percent, the most since Feb. 15, to $13.97. The biggest developer of games for social-networking sites was cut to neutral from overweight by JPMorgan Chase & Co., meaning the shares are expected to perform in line with the stocks the analyst covers over the next six-to-twelve months. JPMorgan cited Zynga’s rally since the end of January.

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