CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities:
Net loss	$ (63,396)	$ (46,127)
Non-cash adjustments reconciling net loss to operating cash flows:
Depreciation	139	153
Amortization of premium on investments	6	320
Share-based compensation expense	8,086	7,912
Changes in operating assets and liabilities:
Other current assets	571	329
Other long-term assets	1,134	1,675
Accounts payable, accrued liabilities and other long-term liability	3,834	4,404
Cash flows used for operating activities	(51,894)	(34,684)
Investing activities:
Purchases of short-term investments	(67,261)	(41,024)
Disposal and maturities of short-term investments	86,935	35,280
Purchases of property and equipment	(63)	(296)
Cash flows provided by (used in) investing activities	19,611	(6,040)
Financing activities:
Proceeds from sale of common stock, net	0	143,289
Proceeds from exercise of warrants and common stock options	2,355	472
Proceeds from stock issuances under employee stock purchase plan	237	251
Cash flows provided by financing activities	2,592	144,012
(Decrease) increase in cash and cash equivalents	(29,691)	103,288
Cash and cash equivalents, beginning of period	49,493	6,593
Cash and cash equivalents, end of period	$ 19,802	$ 109,881