Jana Partners LLC, the hedge fund founded by Barry Rosenstein, added stakes in pharmaceutical companies and American International Group Inc. while exiting its position in Hertz Global Holdings Inc. last quarter.

The fund’s new U.S. equity positions included 9.2 million shares of Pfizer Inc., valued at $296 million as of Dec. 31, and 1.6 million shares of embattled drugmaker Valeant Pharmaceuticals International Inc., worth $159.2 million, according to a regulatory filing Tuesday. Jana also bought insurer AIG, purchasing 4.3 million shares with a market value of $263.6 million at the end of the quarter.

Jana’s top four new equity positions last quarter, which also included 5.9 million shares of cable giant Liberty Global Plc, declined this year through Feb. 12 more than the S&P 500, which fell 8.8 percent.

The fund shed stakes in 14 companies including Hertz and Mattel Inc., according to the filing. It boosted its position in Microsoft Corp. by 2.2 million shares to make it the fund’s third-largest holding as of Dec. 31.

The value of Jana’s U.S. equity positions dropped by $1.73 billion in the fourth quarter to $6.87 billion.

AIG has been facing pressure from activist investors Carl Icahn and John Paulson since October to split up, and last week nominated Paulson and an Icahn representative to serve on its board after posting two straight quarterly losses.

While most of Jana’s stakes aren’t tied to shareholder activism, which seeks to convince executives and directors to make changes, those campaigns often attract more attention.

The firm, which manages about $10 billion in investments and commitments, has targeted companies including ConAgra Foods Inc., Qualcomm Inc., Computer Sciences Corp., PetSmart Inc. and Hertz in recent active campaigns.

Money managers who oversee more than $100 million in U.S. equities must file a Form 13F within 45 days of the end of each quarter to list their holdings in stocks that trade on U.S. exchanges, as well as options and convertible debt. Hedge funds are lightly regulated pools of capital whose managers can invest in any asset and share in annual profits.