Ligand Pharmaceuticals

(LGND) - Get Report

said Tuesday that David E. Robinson, its top executive, has resigned, effective immediately, to pursue other opportunities.

Robinson, 57, had been president, CEO and a director since 1991. He added the role of chairman in May 1996.

The San Diego-based drugmaker, which has been trying to emerge from a series of accounting and regulatory problems, said Henry F. Blissenbach, 63, a director since May 1995, would become interim CEO and chairman. Ligand didn't offer a timetable for choosing a new CEO.

"We are excited to work with Hank to continue the process of seeking to maximize value for all Ligand shareholders," said Daniel S. Loeb, a board member and chief executive of Third Point LLC, a hedge fund that is Ligand's largest shareholder.

Previously, Loeb had attacked Robinson for what he claimed was Ligand's subpar performance. Loeb threatened a proxy fight last year, and had enlisted the support of another hedge fund manager, David M. Knott. At the time, Loeb owned just more than 9.9% of Ligand's shares and Knott owned 9.7%.

But

the battle was called off in December when Ligand management agreed to add three Loeb nominees to the company's eight-member board of directors. According to the latest available information, Loeb owns about 9.4% of Ligand's shares and Knott owns around 8.4%.

The truce with Loeb was declared one month after Ligand had hired an investment banking firm to explore "strategic alternatives." Ligand's stock was delisted by

Nasdaq

in September after the company failed to promptly file its 2004 annual report with the

Securities and Exchange Commission.

The stock was relisted in mid-June.

Ligand remains under investigation by the SEC relating to the restatement of financial reports for 2002 and 2003, as well as for the first three quarters of 2004. In late June, Ligand agreed to pay $12.2 million to settle several lawsuits alleging breach of fiduciary duties. The settlements are subject to court approval. As part of the agreements, Ligand recently said it has "agreed to adopt certain corporate governance enhancements." The company didn't admit any violations or liabilities.

Shares of Ligand closed down 24 cents, or 2.6%, at $8.99.