UBS AG (Nyse: UBS) raised its price target on Facebook Inc (Nasdaq: FB) to $45.00 from $36.00 and maintained a Buy rating, adding the social networking giant's second-quarter operating momentum has continued into the third quarter.

Shares of Facebook edged down 0.67 percent to $38.28 in morning trade.

NRG Energy Inc (NYSE: NRG) reported earnings of 39 cents on sales of $2.93 billion, beating Wall Street estimates for 23 cents a share on revenue of $2.29 billion.

Shares of NRG Energy fell 0.52 percent to $26.76 in early trade.

Onyx Pharmaceuticals, Inc. (Nasdaq: ONXX) issued a smaller-than-expected loss as revenue more than doubled on sales of cancer drugs.

Shares of Onyx Pharmaceuticals were down 1.61 percent to $125.37.

The Dow Jones industrial average was down 47.46 points, or 0.31 percent, at 15,450.86. The S&P 500 fell 3.34 points, or 0.2 percent, at 1,694.09. The Nasdaq Composite Index was down 0.27 points, or 0.02 percent, at 3,668.47.