NEW YORK ( Stockpickr) -- Professional traders don't just look at a stock's price moves; they also look for big changes in volume.

Major moves in volume can signal unusual activity, such as insider buying or selling -- or buying or selling by "superinvestors."

Let's take a look at several stocks rising on unusual volume today. In today's trading, these stocks are all already recording volume that is 87% or more above their average trading volume for a full day.

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United Therapeutics ( UTHR) is a biotechnology company focused on the development and commercialization of products to address the unmet medical needs of patients with chronic and life-threatening cardiovascular and infectious diseases and cancer. The stock is trading up 1% at $40.14 in recent trading.

Volume: 5.2 million

Average Volume: 1.6 million

Volume % Change: 220.4%

On Tuesday, United Therapeutics announced plans to offer $210 million in senior notes and to buy back up to $212 million worth of stock.

The stock is one of the top holdings of Steven Cohen's SAC Capital as of the most recently reported period.

Liz Claiborne ( LIZ) and its subsidiaries are engaged mainly in the design and marketing of a global portfolio of retail-based premium brands, including Juicy Couture and Kate Spade. The stock is trading up 32.6% at $6.76 in recent trading.

Volume: 15.1 million

Average Volume: 3.5 million

Volume % Change: 320.8%

On Wednesday, Liz Claiborne announced plans to sell several brands for $328 million -- including its namesake brand, which will go to J.C. Penney ( JCP) -- to focus on higher-end brands such as Kate Spade and Juicy Couture. The company will also change its name.

Onyx Pharmaceuticals ( ONXX) is a biopharmaceutical company is engaged in the development of innovative therapies that target the molecular mechanisms that cause cancer. The stock is trading up 6% at $33.81 in recent trading.

Volume: 2.8 million

Average Volume: 901,600

Volume % Change: 214.8%

On Wednesday, Onyx and Bayer a settlement in the lawsuit over the development and marketing of the cancer drug regorafenib in which Onyx will receive 20% royalty from Bayer on worldwide sales of the drug.

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