Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Cash and cash equivalents	$ 88,668	$ 107,283
Investments in marketable securities - short term	87,890	87,721
Receivables from collaborations	319	218
Prepaid expenses	2,467	3,471
Total current assets	179,344	198,693
Investments in marketable securities - long term	47,179	54,266
Property and equipment, net	4,453	5,035
Intangible assets	128	132
Total assets	231,104	258,126
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	1,542	3,489
Accrued expenses	9,840	16,167
Current portion of long-term debt	896	1,241
Current portion of deferred revenue	35,917	57,714
Total current liabilities	48,195	78,611
Long-term debt, net of current portion	1,776	1,986
Deferred revenue, net of current portion	2,431	3,241
Total liabilities	52,402	83,838
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value, 100,000,000 shares authorized and 33,397,793 and 33,383,403 shares issued and outstanding at March 31, 2012 and December 31, 2011, respectively	33	33
Preferred stock, $0.001 par value, 5,000,000 shares authorized and 0 shares issued and outstanding at March 31, 2012 and December 31, 2011
Capital in excess of par value	403,113	401,149
Accumulated other comprehensive income	227	36
Accumulated deficit	(224,671)	(226,930)
Total stockholders' equity	178,702	174,288
Total liabilities and stockholders' equity	$ 231,104	$ 258,126