Liquidity	6 Months Ended
Jun. 30, 2011
Liquidity
Liquidity	Note 8. Liquidity Since its inception in 1980 through June 30, 2011 the Company has incurred losses of approximately $304.5 million, substantially all of which resulted from expenditures related to research and development, general and administrative charges and acquired in-process research and development resulting from two acquisitions. The Company has not generated any material revenue from product sales to date, and there can be no assurance that revenue from product sales will be achieved. The Company expects to incur operating losses over the next several years. At June 30, 2011, cash and cash equivalents were $54.2 million, compared to $33.6 million at December 31, 2010. The Company's principal sources of liquidity and cash have been equity financings and revenue from its U.S. government research contracts. The Company's principal uses of cash have been research and development expenses, general and administrative expenses and other working capital requirements. In the periods presented, substantially all of the revenue generated by the Company was derived from research contracts with the U.S. government. As of June 30, 2011, the Company had contracts with the U.S. government pursuant to which it is entitled to receive up to an aggregate of $152.3 million for development of its product candidates, of which $102.0 million had been recognized as revenue and $50.3 million of which relates to development that has not yet been completed and has not been billed. See Note 4 — "U.S. Government Contracts" for additional information. In January and August 2009, the Company sold shares of its common stock and also issued warrants to purchase shares of its common stock in offerings registered under the Securities Act of 1933 (the "Securities Act"). In April 2011, the Company sold 23.0 million shares of its common stock at the price of $1.50 per share in an offering registered under the Securities Act. The offering generated gross proceeds of $34.5 million. See Note 9 — "Equity Financings" for more information.

Liquidity

6 Months Ended

Jun. 30, 2011

Note 8. Liquidity

Since its inception in 1980 through June 30, 2011 the Company has incurred losses of approximately $304.5 million, substantially all of which resulted from expenditures related to research and development, general and administrative charges and acquired in-process research and development resulting from two acquisitions. The Company has not generated any material revenue from product sales to date, and there can be no assurance that revenue from product sales will be achieved. The Company expects to incur operating losses over the next several years.

At June 30, 2011, cash and cash equivalents were $54.2 million, compared to $33.6 million at December 31, 2010. The Company's principal sources of liquidity and cash have been equity financings and revenue from its U.S. government research contracts. The Company's principal uses of cash have been research and development expenses, general and administrative expenses and other working capital requirements.

In the periods presented, substantially all of the revenue generated by the Company was derived from research contracts with the U.S. government. As of June 30, 2011, the Company had contracts with the U.S. government pursuant to which it is entitled to receive up to an aggregate of $152.3 million for development of its product candidates, of which $102.0 million had been recognized as revenue and $50.3 million of which relates to development that has not yet been completed and has not been billed. See Note 4 — "U.S. Government Contracts" for additional information.

In January and August 2009, the Company sold shares of its common stock and also issued warrants to purchase shares of its common stock in offerings registered under the Securities Act of 1933 (the "Securities Act"). In April 2011, the Company sold 23.0 million shares of its common stock at the price of $1.50 per share in an offering registered under the Securities Act. The offering generated gross proceeds of $34.5 million. See Note 9 — "Equity Financings" for more information.