Condensed Statements of Operations and Comprehensive Loss (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
OPERATING EXPENSES:
Research and development	$ 17,287	$ 9,867
General and administrative	1,578	2,112
Loss from operations	(18,865)	(11,979)
OTHER (EXPENSE) INCOME:
Other income (expense), net	11,256	(467)
Interest income	2	17
Interest expense	(698)	(443)
NET LOSS	(8,305)	(12,872)
OTHER COMPREHENSIVE LOSS, NET OF TAX:
Unrealized loss from available-for-sale securities		(1)
COMPREHENSIVE LOSS	(8,305)	(12,873)
LOSS ATTRIBUTABLE TO COMMON STOCKHOLDERS - BASIC AND DILUTED (Note 10):	$ (11,887)	$ (16,226)
LOSS PER SHARE:
Basic (in dollars per share)	$ (13.71)	$ (20.92)
Diluted (in dollars per share)	$ (13.71)	$ (20.92)
WEIGHTED AVERAGE SHARES:
Basic (in shares)	867,204	775,590
Diluted (in shares)	867,204	775,590