Despite their inherent level of reclusiveness activist investors , such as Warren Buffett and Carl Icahn , are required by the Securities and Exchange Commission to file for public record their public equity positions each quarter. If an investor takes a stake that is over the regulator requirements, additional filings are needed.

Here at we track many of the latest activist filings for investors interested in piggybacking these activist funds. We highlight a few of the latest activist situations here.

Kevin Tang of Tang Capital Management, an investment firm that specializes in the area of biotechnology and small-capitalized pharmaceutical firms, filed two interesting documents last week.

On Feb. 9, AP Pharma (APPA) appointed a representative from Tang Capital to the board of the company. AP Pharma is a small-cap biotechnology firm with a current market value of more than $20 million dollars, about $16.5 million in cash and zero debt.

It is currently in phase III clinical trial testing for its key drug candidate, APF530, which is being tested for prevention of acute and delayed onset chemotherapy-induced nausea and vomiting. The company expects final data for APF530 and potential approval from the Food and Drug Administration by the first quarter of 2010.

Tang Capital owns 28.4% of AP Pharma.
On Feb. 13, Tang Capital delivered a letter to Vanda Pharmaceuticals (VNDA) nominating two associates of Tang Capital for election to Vanda's board at the 2009 shareholders annual meeting.

Tang Capital also believes that in order to maximize value for all shareholders, Vanda Pharmaceuticals must cease all operations immediately, liquidate all assets and distribute all remaining capital to Vanda Pharmaceuticals shareholders.

Shares of Vanda Pharmaceuticals have been under substantial pressure ever since Vanda’s key drug for schizophrenia received a rejection letter from the Food and Drug Administration in July, flatling the stock from $4 to $1 in a single day.

Tang Capital also cites that Vanda’s current market capitalization of just $20.3 million, yet Vanda has about $46.5 million dollars of cash sitting in the bank, or $1.74 per share in cash, with zero debt.

Vanda is fighting back, saying: “The board is disappointed that Tang Capital has opted to conduct an election contest, particularly when the company is so close to receiving a response from the regulators regarding its lead compound, iloperidone," said Brian Halak, chairman of Vanda's corporate governance committee.

Tang Capital owns 14.9% of Vanda Pharmaceuticals.

Bill Ackman of Pershing Square Capital Management amended the terms of a purchase offer letter to extend until April 15, 2009, the purchase of Borders Group's (BGP) U.K.-based gifts and stationery business for $65 million.

Several months ago, Pershing Square lent Borders Group $42.5 million to shore up short-term liquidity concerns and to quiet investors' fears of a possible default on several of Borders debt offerings. Recently, however, Pershing Square also extended the deadline for repayment of the $42.5 million in senior secured notes until April 15, giving Borders Group several more weeks to pay back the short-term bridge loan.

Pershing Square Capital owns roughly 35% of Borders Group.

Earl Scheib (ESHB) has agreed to be acquired by private-equity firm Kelly Capital for $2 per share in cash. Earl Scheib operates auto paint and body repair locations for retail consumers and businesses in the U.S.

Before the announced buyout offer, Kelly Capital owned 25% of Earl Scheib.

Carl Icahn Carl Icahn bought 1.8 million shares of Lions Gate Entertainment (LGF) last week. Several analysts have suggested that Icahn intends to force Lions Gate to sell the company or to facilitate online distribution of its 12,000-title film and television library.

Icahn currently owns 14.28% of Lions Gate Entertainment, with an average price of $7.30 per share.

David Pomeroy sent a letter to the board of Pomeroy IT Solutions (PMRY) offering to buy the company for $55 million, or $4.50 per share.

This is David Pomeroy’s third and smallest purchase offer made to Pomeroy IT, which has revoked earlier offers to purchase the company at $7.05 per share last April and $6 per share in May.

For several other activist ideas, including the top holdings of Carl Icahn, Kevin Tang of Tang Capital Management and Bill Ackman of Pershing Square Capital, check out the Latest Activist Filings portfolio on Stockpickr.

P.S. Where is Jim Cramer putting his own money? Take a free peek at his personal portfolio to see all his buys and sells by clicking here. When you do, Jim will also send you exclusive email alerts telling you everything he's about to add to or shed from his Action Alerts PLUS portfolio -- before he makes his trade.