SiliconBeat

AP Pharma decided to increase the amount of shares its biggest shareholder may accumulate before the company would need to swallow its poison pill, er, shareholder rights plan in order to deter him from gaining control, according to a regulatory filing Tuesday.

On Oct. 1, AP Pharma (ticker: APPA) amended its Preferred Shares Rights Agreement dated Dec. 18, 2006, to allow  Kevin Tang and his affiliated companies to acquire up to 30 percent of its outstanding shares before triggering the rights plan. Previously, the maximum was 20 percent.

Tang, who is the general manager of Tang Capital Partners and its associated funds, first disclosed owning a greater-than-10-percent stake in AP Pharma in June 2007. As of the end of the first quarter of 2008 Tang’s stake was equal to 15 percent of the company, a figure that was boosted by two subsequent acquisitions, most recently by the purchase of 650,000 shares on Sept. 30 for 97 cents each, which boosted his ownership to 18.5 percent.

Tang’s latest investment came the same day AP Pharma announced positive results from its pivotal Phase 3 study comparing the efficacy of its proprietary, sustained release formulation used to help prevent chemotherapy induced nausea and vomiting.

Tang is invested in a number of other biotechnology companies, including Threshold Pharmaceuticals of Redwood City, Questcor of Union City, and Aradigm of Hayward. AP Pharma may be glad to have Tang showing interest in its shares, the value of which have been slashed in half so far this year.

In August, another private investor in biotech companies, Baker Brothers, disclosed having acquired a 7.3 percent stake in AP Pharma. In July we wrote about a huge stock award granted to the company’s new chief executive.