CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net loss	$ (11,940)	$ (13,656)
Non-cash adjustments reconciling net loss to operating cash flows:
Depreciation of property and equipment	44	78
Amortization of premium on investments	99	167
Share-based compensation expense	2,316	946
Change in fair value of warrant liability	0	5,475
Restructuring costs	0	13
Changes in operating assets and liabilities:
Other current assets	188	(517)
Other long-term assets	0	0
Accounts payable and accrued liabilities	(482)	(1,304)
Cash flows used for operating activities	(9,775)	(8,798)
Investing activities:
Purchases of property and equipment	(18)	(2)
Purchases of short-term investments	(35,979)	(4,423)
Disposal and maturities of short-term investments	4,880	7,043
Cash flows (used for) provided by investing activities	(31,117)	2,618
Financing activities:
Proceeds from sale of common stock, net	48,361	0
Proceeds from exercise of common stock options	245	262
Cash flows provided by financing activities	48,606	262
Increase (decrease) in cash and cash equivalents	7,714	(5,918)
Cash and cash equivalents, beginning of period	6,593	14,235
Cash and cash equivalents, end of period	14,307	8,317
Fixed asset additions included within accounts payable	$ 197	$ 42