Condensed Statements of Operations and Comprehensive Loss (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
OPERATING EXPENSES:
Research and development	$ 15,543	$ 14,173	$ 49,070	$ 38,539
General and administrative	1,621	1,918	4,643	6,209
Loss from operations	(17,164)	(16,091)	(53,713)	(44,748)
OTHER (EXPENSE) INCOME:
Other (expense) income, net	(2,607)	(604)	7,465	(1,788)
Interest income	11	18	27	53
Interest expense	(582)	(853)	(1,938)	(1,880)
NET LOSS	(20,342)	(17,530)	(48,159)	(48,363)
OTHER COMPREHENSIVE LOSS, NET OF TAX:
Unrealized gain from available-for-sale securities	(3)	(7)		(2)
COMPREHENSIVE LOSS	(20,345)	(17,537)	(48,159)	(48,365)
LOSS ATTRIBUTABLE TO COMMON STOCKHOLDERS - BASIC AND DILUTED (Note 10):	$ (25,090)	$ (21,090)	$ (60,857)	$ (58,733)
LOSS PER SHARE:
Basic (in dollars per share)	$ (28.53)	$ (24.53)	$ (69.77)	$ (70.76)
Diluted (in dollars per share)	$ (28.53)	$ (24.53)	$ (69.77)	$ (70.76)
WEIGHTED AVERAGE SHARES:
Basic (in shares)	879,370	859,769	872,195	830,068
Diluted (in shares)	879,370	859,769	872,195	830,068