NEW YORK ( TheStreet) -- XenoPort ( XNPT) was the biggest gainer among small-caps Thursday after the biotech company won approval for its first drug Horizant used to treat moderate-to-severe restless leg syndrome. The stock was up 66% at $10.64 on volumes of more than 17 million shares.

Shares of Immunogen ( IMGN) jumped 21% to $11.28 after an experimental breast cancer drug that it is developing with Roche was found to be more successful than the standard treatment in a mid-stage study.

Retail stocks were buzzing after stronger-than-expected same-store sales data. Pier 1 Imports ( PIR) saw its shares climb 9% to $11.52 after it reported better-than-expected results. Sales rose 7.7% to $426.6 million, beating the analysts' average estimate of $425.6 million. Sales at stores open at least a year rose 8.9%.

Rite Aid ( RAD) was up 6.6% to $1.13 after it posted a narrower-than-expected loss and its sales stabilized. The company said it may narrow its losses significantly in fiscal 2012, and forecasted stronger revenue than analysts expected.

Express ( EXPR) shares were climbing 4.5% to $20.23. The company announced the pricing of the offering of 19,800,000 common shares by certain stockholders at $19 a share, reflecting an upsize from the previously announced offering of 16.5 million shares.

Shares of Intersil ( ISIL) rose rising 5.8% to $14.09. Stocks of semiconductor companies were climbing after Texas instruments (TXN) said earlier this week it will acquire National Semiconductor ( NSM) for $6.5 billion.

Shares of Rare Element Resources ( REE) and Avalon Rare Metals ( AVL) were soaring 10.7% and 4.9%, respectively. A bill was introduced Wednesday that would benefit U.S. rare earth miners, according to a release from the U.S. Magnetic Materials Association.

--Written by Shanthi Bharatwaj in New York

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Disclosure: TheStreet's editorial policy prohibits staff editors and reporters from holding positions in any individual stocks.

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