NEW YORK -- Omega Advisors, a hedge fund run by CEO Leon Cooperman, sold its stake in Apple (AAPL) and took new stakes in SandRidge Energy and Facebook in the fourth quarter, a regulatory filing showed on Wednesday.

Cooperman, whose hedge fund had $7 billion in assets as of last November, sold his entire stake of 266,404 shares in tech giant Apple, the Securities and Exchange Commission filing showed.

Shares in Apple pared slight gains and were off 0.37 percent at $466.19 in afternoon trading Wednesday after the filing was released.

Apple has come under scrutiny from prominent hedge fund manager David Einhorn, who announced on Feb. 7 that he was suing the company to get it to deploy its $137 billion cash pile more effectively and halt a 35 percent drop in its share price from a record high in September. Einhorn's fund, Greenlight Capital, has a stake in the company worth about $600 million.

Cooperman's fund also took a new stake in U.S. oil and gas producer SandRidge Energy of 24.38 million shares, and a new stake of 3.16 million shares in Facebook in the fourth quarter. The fund also increased its stake in oil and gas company McMoRan Exploration Co by about 1.8 million shares to 9.11 million shares.

Shares in Facebook were trading up 2.2 percent at $27.97 in intraday trading.

SandRidge Energy is the target of activist hedge fund TPG-Axon Capital Management, which has launched an effort to replace the company's board. TPG-Axon and Mount Kellett Capital Management -- two of SandRidge's largest shareholders -- have also asked that CEO Tom Ward step down, citing poor management of the company and allegations of self-dealing by the executive.

SandRidge has given Ward wide latitude to profit from personal oil-and-gas deals in ways that pose potential conflicts of interest with the company, according to a Reuters review of employment contracts and recent transactions.

Shareholders can vote on whether to replace SandRidge's board until March 15.

Cooperman's new stake in SandRidge represents 4.97 percent of the company's outstanding shares, or just under the five percent threshold by which companies must file a separate 13D holding report indicating an "activist" stake.

The company's shares were trading up 3.37 percent to $5.82 a share on Wednesday.

Cooperman's main portfolio ended 2012 with a strong net return of 26 percent, a person invested with Omega said.

Most fund companies will file their holding reports for the fourth quarter of 2012 on Feb. 14.