Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (81,028,000)	$ (43,274,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	166,000	29,000
Stock-based compensation	4,657,000	1,966,000
Foreign currency transactions	43,000	97,000
Changes in assets and liabilities:
Other current assets	(1,158,000)	(2,821,000)
Other assets	(182,000)	(187,000)
Accounts payable	2,617,000	1,261,000
Accrued liabilities and other	1,388,000	1,700,000
NET CASH USED IN OPERATING ACTIVITIES	(73,497,000)	(41,229,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(1,965,000)	(234,000)
NET CASH USED IN INVESTING ACTIVITIES	(1,965,000)	(234,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock, net of issuance costs	134,704,000	99,765,000
Payment of offering costs for private placement		(1,002,000)
NET CASH PROVIDED BY FINANCING ACTIVITIES	134,704,000	98,763,000
Effect of exchange rates on cash, cash equivalents and restricted cash	23,000	56,000
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	59,265,000	57,356,000
Cash, cash equivalents and restricted cash at the beginning of period	147,871,000	90,515,000
Cash, cash equivalents and restricted cash at the end of period	207,136,000	$ 147,871,000
SUPPLEMENTAL DISCLOSURE OF NON-CASH ACTIVITIES
Property and equipment purchases in accounts payable	49,000
Right-of-use assets obtained in exchange for lease obligations	$ 901,000