The Russell 2000 Index (RTY) rose for the first time in three days, adding 0.5 percent to 741.91 in New York. The Standard & Poor's 500 Index (SPX), whose companies have a median market value 22 times larger than the Russell 2000's, slipped 0.2 percent. The stock indexes have declined 3.2 percent and 13 percent, respectively, this year.
Ambac Financial Group Inc. (ABKFQ:US) jumped 22 percent to $8.65, the highest since March. The world's second-biggest bond insurer received approval from Wisconsin regulators to begin offering municipal bond insurance through a newly capitalized company.
Medivation Inc. (MDVN:US) surged 12 percent to $29.03, a record high. Pfizer Inc. (PFE US) said it would pay the biotechnology company as much as $725 million to develop the experimental drug Dimebon for Alzheimer's disease.
Newport Corp. (NEWP:US) added 6.6 percent, the most in four months, to $9.99. The maker of laser and optical equipment for aerospace companies predicted fourth-quarter profit that topped analysts' estimates and said it would fire as many as 10 percent of its workers.
Shanda Interactive Entertainment Ltd. American depositary receipts (SNDA US) added 9.4 percent, the most since April 23, to $28.91. China's biggest online games provider reported second- quarter profit of 58 cents a share, more than the 52-cent average estimate of analysts surveyed by Bloomberg.
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