This week’s top gainers include Merrimack Pharmaceuticals Inc (NASDAQ:MACK), Anacor Pharmaceuticals Inc (NASDAQ:ANAC), Icahn Enterprises LP (NASDAQ:IEP) and weekly losers are Ingersoll-Rand PLC (NYSE:IR), Cobalt International Energy, Inc. (NYSE:CIE), Sears Holdings Corp (NASDAQ:SHLD).

Thanks to Icahn Enterprises, December Starts Out Strong for Icahn

Icahn gains with Icahn Enterprises LP

Merrimack Pharmaceuticals Inc (NASDAQ:MACK) is the top-gaining stock of the week. It increased +24.15%, even though today it dipped -0.42%. It is now valued at $4.71. Billionaire Thomas Stayer holds 805,000 shares, composing 0.06% of his fund. The investor paid an average price of $7.16 per share.

Anacor Pharmaceuticals Inc (NASDAQ:ANAC) had a nice week as well. This stock increased +19.31% and today rose +6.57% to $16.86. This is another hit for Stayer, who owns 450,000 shares (0.10% of his fund), acquired for $5.69.

Last but not least is Icahn Enterprises LP (NASDAQ:IEP). The stock rose +18.15%, climbing +3.12% today alone, to reach $144.10. IEP has the biggest allocation in Icahn’s fund at 100 million shares composing 33.95% of his portfolio. The investor paid an average price of $82.95 per asset.

Weekly Losers

This week, Ingersoll-Rand PLC (NYSE:IR) decreased -21.58%, despite rising +2.32% today. It is now priced at $57.06. Billionaire Thomas Stayer holds 675,000 shares, acquired at an average $52.22. This position comprises 0.90% of his fund.

Cobalt International Energy, Inc. (NYSE:CIE) dropped -21.56%, hitting $17.01. This movement affected billionaire John Paulson, who owns 11.6 million shares (1.86% of his portfolio), acquired for $27.05. Also taking a hit with this one is Ray Dalio, who owns 52,000 CIE shares (0.01% of his holdings).

It was a tough start to December for Sears Holdings Corp (NASDAQ:SHLD), too. The retailer suffered a drop of -21.51%, today trading at $48.92. The dip is largely the result of Edward Lampert’s decision to sell off seven million shares, even though he still holds 24.3 million assets in the company. Bruce Berkowitz holds 20.7 million shares (14.67% of his fund), acquired for $59.68.