Statements of Operations and Comprehensive Loss (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		99 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013
Operating expenses
General and administrative	$ (3,287)	$ (1,416)	$ (6,693)	$ (3,701)	$ (26,590)
Research and development	(2,399)	(1,373)	(8,727)	(7,305)	(51,876)
Loss from operations	(5,686)	(2,789)	(15,420)	(11,006)	(78,466)
Other income (expense)-net	(5,062)	(803)	(5,446)	(427)	(6,188)
Net loss	(10,748)	(3,592)	(20,866)	(11,433)	(84,654)
Comprehensive loss	(10,748)	(3,592)	(20,866)	(11,433)	(84,654)
Net loss attributable to common stockholders-basic and diluted	$ (10,887)	$ (3,730)	$ (21,279)	$ (11,845)
Net loss per share attributable to common stockholders-basic and diluted	$ (10.81)	$ (3.87)	$ (21.61)	$ (12.38)
Weighted average number of common shares outstanding-basic and diluted	1,006,893	964,880	984,727	957,079