Idenix, SanDisk, St. Jude, Thoratec: 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. New York time.

Acuity Brands Inc. (AYI US) fell 9.7 percent, the most since June 2010, to $57.50. The maker of Gotham lighting fixtures posted second-quarter earnings excluding some items that fell short of the average analyst projection, data compiled by Bloomberg show.

American International Group Inc. (AIG US) rose 5.3 percent, the most in the Standard & Poor’s 500 Index, to $32.52. The bailed-out insurer was raised to outperform from market perform by Josh Stirling, an analyst at Sanford C. Bernstein & Co., meaning the company is expected to have better returns than its peers. Stirling said AIG may sell its $22 billion of non-core assets in coming months and may be able to help buy back the government’s stake before the November election.

Cleveland Biolabs Inc. (CBLI US) plunged 23 percent to $1.82 for the second-biggest retreat in the Russell 2000 Index. The Buffalo, New York-based pharmaceutical developer said the Biomedical Advanced Research and Development Authority won’t ask the company to submit a proposal for continued funding for the development of CBLB502 as a radiation countermeasure.

Ddi Corp. (DDIC US) advanced 5.5 percent, the most since Feb. 16, to $12.93. The maker of electronic components for computer and communications companies agreed to be bought by Viasystems Group Inc. (VIAS US) for $13 a share in cash. Viasystems rose 11 percent to $21.41.

G&K Services Inc. (GKSR US) increased 6.4 percent, the most since Nov. 30, to $36.93. The uniform clothing supplier declared a special cash dividend of $6 a share.

GMX Resources Inc. (GMXR US) surged 24 percent to $1.55 for the biggest gain in the Russell 2000 Index. The oil and natural-gas producer based in Oklahoma City said it drilled and completed its fourth operated horizontal Bakken well, in North Dakota.

Hovnanian Enterprises Inc. (HOV US) fell 8.5 percent, the most since Jan.17, to $2.15. The homebuilder will sell 25 million Class A shares in a secondary offering.

Idenix Pharmaceuticals Inc. (IDIX US) sank 12 percent, the most since Aug. 9, to $9. Investors speculated the drugmaker’s experimental hepatitis C treatment may face development hurdles. Roche Holding AG reported an “unacceptable relapse rate” for patients on a combination of medicines that Brian Skorney, a Brean Murray Carret & Co. analyst, called a “good surrogate for any oral combination that includes IDX184,” Idenix’s experimental medicine.

Magal Security Systems Ltd. (MAGS US) jumped 19 percent, the most since Dec. 1, to $5.43. The Israeli developer of computerized-security systems reported fourth-quarter earnings of 27 cents a share, compared with a loss of 14 cents a share a year earlier.

MDC Partners Inc. (MDCA US) increased 4.5 percent, the most since Feb. 3, to $10.93. The marketing communications firm raised its yearly forecasts for revenue and earnings before interest, depreciation, tax and amortization to more than analysts projected.

SanDisk Corp. (SNDK US) fell 11 percent to $44.51 for the biggest retreat in the S&P 500. The biggest maker of flash-memory cards cut its forecast for first-quarter sales, citing weaker-than-expected pricing and demand.

Micron Technology Inc. (MU US) slid 4.1 percent to $7.66.

Southwest Airlines Co. (LUV US) gained 2.2 percent, the most since March 15, to $8.38. The Dallas-based company was raised to overweight from equalweight at Barclays Plc, which means the stock is now expected to perform better than the unweighted expected total return of its industry group in the next 12 months.

St. Jude Medical Inc. (STJ US) declined 4.9 percent, the most since Dec. 2, to $41.67. The medical device maker said it will stop selling the QuickSite and QuickFlex left-ventricular leads, wires that help pace the heart in patients with heart failure after 39 reports of the wires protruding from their insulation.

Thoratec Corp. (THOR US) fell 4.4 percent, the most since Jan. 31, to $32.83. The maker of implantable heart devices is recalling the HeartMate ventricular assist devices over detachment risk, according to a statement from the U.S. Food and Drug Administration.

WebMD Health Corp. (WBMD US) fell 9.4 percent to $23.29, the lowest price since April 2009. The medical information company said it expects to buy 5.77 million shares at $26 each after a tender offer expired yesterday.

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