Condensed Consolidated Statement of Operations (Unaudited) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended		47 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011
Operating Expenses [Abstract]
Research and development expenses	$ (7,723)	$ (4,240)	$ (14,994)	$ (8,621)	$ (50,836)
General and administrative expenses	(7,161)	(2,122)	(11,350)	(3,348)	(24,564)
Depreciation and amortization expenses	(563)	(406)	(1,085)	(685)	(3,623)
Loss from operations	(15,447)	(6,768)	(27,429)	(12,654)	(79,023)
Other income (expense), net:
Interest income		2		2	170
Beneficial conversion feature expense related to convertible promissory note		(10,000)		(10,000)	(10,000)
Interest expense, net of amounts capitalized		(356)		(722)	(2,054)
Foreign currency gain (loss)		16		24	(435)
Loss from change in fair value of warrant liability	(5,504)	(2,290)	(6,914)	(2,290)	(9,278)
Other expense, net	(5,504)	(12,628)	(6,914)	(12,986)	(21,597)
Loss before income taxes	(20,951)	(19,396)	(34,343)	(25,640)	(100,620)
Income tax expenses - current					47
Net loss	(20,951)	(19,396)	(34,343)	(25,640)	(100,667)
Deemed dividend related to the beneficial conversion feature of Series C convertible preferred stock	19,669		19,669		19,669
Net loss attributable to stockholders	$ (40,620)	$ (19,396)	$ (54,012)	$ (25,640)	$ (120,336)
Net loss per share of Class A and B common stock, basic and diluted	$ (0.43)	$ (0.27)	$ (0.6)	$ (0.39)
Weighted-average Class A and B common share outstanding, basic and diluted	19,208	15,580	17,820	15,180