Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 29,442	$ 30,075
Marketable securities	25,697	9,650
Prepaid expenses and other current assets	803	561
Total current assets	55,942	40,286
Property and equipment, net	1,205	1,407
Other assets	466	631
Total assets	57,613	42,324
Current liabilities:
Accounts payable	3,690	3,467
Accrued contract research costs	3,719	2,841
Other accrued liabilities	3,643	4,594
Current portion of capital lease obligations	13	12
Current portion of term loans	7,900	4,234
Total current liabilities	18,965	15,148
Long-term liabilities:
Capital lease obligations, net of current portion	4	14
Term loans, net of current portion	6,454	12,388
Total long-term liabilities	6,458	12,402
Total liabilities	25,423	27,550
Stockholders' equity:
Preferred stock, par value $0.0001 per share Authorized: 5,000,000 shares at September 30, 2012 and December 31, 2011; no shares issued and outstanding at September 30, 2012 and December 31, 2011
Common stock, par value $0.0001 per share Authorized: 100,000,000 shares at September 30, 2012 and December 31, 2011; 61,881,097 and 49,539,808 shares issued and outstanding at September 30, 2012 and December 31, 2011, respectively	6	5
Additional paid-in-capital	475,273	413,196
Accumulated other comprehensive income	8	3
Accumulated deficit	(443,097)	(398,430)
Total stockholders' equity	32,190	14,774
Total liabilities and stockholders' equity	$ 57,613	$ 42,324