Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (57,892)	$ (29,214)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	87	15
Stock-based compensation	3,180	1,471
Foreign currency transactions	123	101
Changes in assets and liabilities:
Other current assets	2,262	(1,881)
Other assets	(131)	(188)
Accounts payable	1,031	1,700
Accrued liabilities and other	2,422	344
NET CASH USED IN OPERATING ACTIVITIES	(48,918)	(27,652)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(818)	(177)
NET CASH USED IN INVESTING ACTIVITIES	(818)	(177)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock, net of issuance costs		101,607
Payment of offering costs for private placement		(1,002)
NET CASH PROVIDED BY FINANCING ACTIVITIES		100,605
Effect of exchange rates on cash, cash equivalents and restricted cash	57	32
NET INCREASE/(DECREASE) IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(49,679)	72,808
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	98,192	163,323
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Property and equipment purchases in accounts payable	752
Right-of-use assets obtained in exchange for lease obligations	$ 901
Common stock issuance cost in accounts payable		517
Deferred offering costs included in other assets and accounts payable and accrued liabilities and other		$ 851