CONSOLIDATED BALANCE SHEETS (USD $)	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 45,533,443	$ 52,846,940
Short-term investments	79,536,211	70,434,148
Receivables	706,403	6,353,180
Prepaid expenses	609,771	3,200,924
Other assets	652,510	496,338
Total current assets	127,038,338	133,331,530
Long-term investments	81,761,177	25,571,659
Property and equipment, net	3,970,665	3,839,426
Other noncurrent assets	31,194	114,961
Total assets	212,801,374	162,857,576
Current liabilities:
Accounts payable	1,234,759	5,435,473
Accrued wages and benefits	2,567,924	3,065,905
Accrued clinical trial expenses	2,336,645	3,728,015
Accrued expenses	692,526	1,668,944
Deferred revenue	50,000	59,746,952
Current portion of other liabilities	3,142	18,168
Total current liabilities	6,884,996	73,663,457
Other liabilities, net of current portion	30,316	33,458
Deferred revenue, net of current portion	881,944	931,940
Total liabilities	7,797,256	74,628,855
Liabilities and Stockholders’ Equity
Common stock: $0.001 par value, 100,000,000 shares authorized; 36,155,509 and 41,784,692 shares issued and outstanding at December 31, 2013 and 2014	41,785	36,156
Additional paid-in capital	373,571,500	262,060,590
Accumulated other comprehensive income	(143,928)	56,691
Retained deficit	(168,465,239)	(173,924,716)
Total stockholders' equity	205,004,118	88,228,721
Total liabilities and stockholders' equity	$ 212,801,374	$ 162,857,576