BALANCE SHEETS (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 118,933	$ 60,392
Collaboration receivable	79
Prepaid expenses and other current assets	1,405	424
Total current assets	120,417	60,816
Property and equipment, net	886	253
Deposits	91	87
Other non-current assets	882	364
Total assets	122,276	61,520
Current liabilities:
Accounts payable	2,160	1,031
Accrued expenses	8,789	2,538
Deferred revenue - current portion	800
Deferred rent - current portion	21	43
Total current liabilities	11,770	3,612
Deferred revenue	3,733
Deferred rent	77	44
Warrant liabilities	22,584	27,311
Total liabilities	38,164	30,967
Commitments and contingencies (note 6)
Stockholders' equity:
Preferred stock, $0.001 par value; 30,000,000 shares authorized and no shares issued and outstanding
Common stock, $0.001 par value; 250,000,000 shares authorized; 68,451,324 and 48,466,562 shares issued and outstanding at September 30, 2011 and December 31, 2010, respectively	68	48
Additional paid-in capital - common stock	244,670	131,530
Additional paid-in capital - warrants issued	13,722	22,789
Deficit accumulated during the development stage	(174,348)	(123,814)
Total stockholders' equity	84,112	30,553
Total liabilities and stockholders' equity	$ 122,276	$ 61,520