CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net loss	$ (46,127)	$ (33,311)
Non-cash adjustments reconciling net loss to operating cash flows:
Depreciation of property and equipment	153	154
Amortization of premium on investments	320	439
Share-based compensation expense	7,912	4,822
Change in fair value of warrant liability	0	4,544
Restructuring costs	0	13
Changes in operating assets and liabilities:
Other current assets	329	(493)
Other long-term assets	(1,675)	(440)
Accounts payable, accrued liabilities and other long-term liabilities	4,404	111
Cash flows used for operating activities	(34,684)	(24,161)
Investing activities:
Purchases of property and equipment	(296)	(320)
Purchases of short-term investments	(41,024)	(8,968)
Disposal and maturities of short-term investments	35,280	23,593
Cash flows (used for) provided by investing activities	(6,040)	14,305
Financing activities:
Proceeds from sale of common stock, net	143,289	0
Proceeds from exercise of common stock options	472	536
Proceeds from stock issuances under employee stock purchase plan	251	0
Cash flows provided by financing activities	144,012	536
Increase (decrease) in cash and cash equivalents	103,288	(9,320)
Cash and cash equivalents, beginning of period	6,593	14,235
Cash and cash equivalents, end of period	109,881	4,915
Fixed asset additions included within accounts payable	$ 0	$ 51