The top after-market NASDAQ losers Thursday were: U.S. Auto Parts Network, SIGA Technologies, GTx, Amicus Therapeutics, SunPower Corp, Spectranetics Corp, Viacom, Orexigen Therapeutics, Zoltek Companies and Electronic Arts.

U.S. Auto Parts Network, Inc. (PRTS) stock slumped 15.35 in aftermarket trading session. Its fourth quarter net loss widened to $7.0 million or $0.23 per share from $2.9 million or $0.10 per share in the same period last year, while analysts' expected net loss of $0.04 per share.

SIGA Technologies Inc. (SIGA) stock plunged 11.29 percent to $2.75 in post market trading session. Its fourth quarter operating loss widened to $7.8 million from $4.2 million in the same period a year-ago.

GTx, Inc. (GTXI) stock declined 3.03 percent to $3.20 in post market trading session. The company stock plunged more than 4 percent in regular trading session.

Amicus Therapeutics, Inc. (FOLD) stock declined 2.68 percent to $5.80 in aftermarket trading session. The company announced the pricing of an underwritten offering of 10,000,000 shares of its common stock at a price of $5.70 per share.

SunPower Corp. (SPWR) stock declined 2.01 percent to $7.30 in post market trading session. The company stock was initiated with neutral rating at Brigantine.

Spectranetics Corp. (SPNC) stock declined 2.01 percent to $7.80 in aftermarket trading session.

Viacom Inc. (VIAB) stock fell 1.94 percent to $47.88 in post market trading session. The stock has a 52-week low of $35.12, a 52-week high of $52.67 and $26.40 billion in market capitalization.

Orexigen Therapeutics, Inc. (OREX) stock declined 1.77 percent to $3.88 in aftermarket trading session.

Zoltek Companies, Inc. (ZOLT) stock fell 1.75 percent to $11.78 in post market trading session.

Electronic Arts Inc. (EA) stock declined 1.65 percent to $16.41 in post market trading session. The stock has a 52-week low of $16.05, a 52-week high of $26.13 and $5.53 billion in market capitalization.

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