Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities
Net loss	$ (15,035,000)	$ (10,575,000)
Reconciliation of net loss to net cash used in operating activities:
Depreciation	33,000	21,000
Amortization of premium/discount on available-for-sale securities	$ 580,000	18,000
Accretion of discount and debt issuance cost of convertible notes payable		$ 742,000
Unrealized loss on forward foreign currency contracts included in net income	$ 426,000
Foreign currency remeasurement loss	29,000
Stock-based compensation	$ 1,494,000	$ 234,000
Change in fair value of investor rights/obligation		5,344,000
Change in fair value of derivative liability		81,000
Changes in:
Prepaid expenses and other assets	$ (181,000)	(2,234,000)
Interest receivable	(214,000)	(13,000)
Accounts payable and accrued expenses	$ 488,000	1,275,000
Accrued interest payable		115,000
Deferred revenue from sale of acquisition option to acquire company		(2,948,000)
Net cash used in operating activities	$ (12,380,000)	(7,940,000)
Investing activities
Purchases of available-for-sale investments	(66,136,000)	(19,697,000)
Proceeds from maturities of available-for-sale investments	43,752,000	$ 3,580,000
Proceeds from sale of available-for-sale investments	2,006,000
Purchase of property and equipment	(171,000)	$ (45,000)
Net cash used in investing activities	(20,549,000)	$ (16,162,000)
Financing activities
Proceeds from exercise of stock options	$ 49,000
Proceeds from issuance of Series D preferred stock		$ 25,000,000
Issuance costs for preferred stock		$ (452,000)
Proceeds from issuance of common stock under ESPP	$ 52,000
Net cash provided by financing activities	101,000	$ 24,548,000
Effect of exchange rate changes on cash	(29,000)
(Decrease) increase in cash and cash equivalents	(32,857,000)	$ 446,000
Cash and cash equivalents, beginning of period	68,840,000	2,793,000
Cash and cash equivalents, end of period	$ 35,983,000	3,239,000
Supplemental disclosure of non-cash investing and financing activities
Accretion of redeemable convertible preferred stock to redemption value		$ 5,686,000