Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (33,970)	$ (17,788)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	39	6
Stock-based compensation	1,835	1,076
Foreign currency transactions	(11)	79
Changes in assets and liabilities:
Other current assets	635	(706)
Other assets	(57)	(188)
Accounts payable	3,015	(368)
Accrued liabilities and other	991	(575)
NET CASH USED IN OPERATING ACTIVITIES	(27,523)	(18,464)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(201)	(124)
NET CASH USED IN INVESTING ACTIVITIES	(201)	(124)
CASH FLOWS FROM FINANCING ACTIVITIES
Payment of offering costs		(1,768)
NET CASH USED IN FINANCING ACTIVITIES		(1,768)
Effect of exchange rates on cash, cash equivalents and restricted cash	16	24
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(27,708)	(20,332)
Cash, cash equivalents and restricted cash at the beginning of period	147,871	90,515
Cash, cash equivalents and restricted cash at the end of period	120,163	70,183
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Property and equipment purchases in accounts payable	23
Right-of-use assets obtained in exchange for lease obligations	$ 832
Deferred offering costs included in other assets and accounts payable and accrued liabilities and other		$ 239