Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Cash flows from operating activities
Net loss		$ (23,260)	$ (12,084)	$ (36,500)
Adjustment to reconcile net loss to net cash used in operating activities:
Stock-based compensation		507
Fair value adjustments on preferred stock tranche obligations and note tranche and derivative obligations			(1,364)
Amortization of right of use lease asset		136	81
Changes in operating assets and liabilities:
Prepaid expenses and other current assets		(220)	33
Tax credit receivable - noncurrent		(865)	(804)
Accounts payable		1,134	(762)
Accrued expenses and other current liabilities		(1,019)	908
Operating lease liabilities		(99)	(81)
Net cash used in operating activities		(23,686)	(14,073)
Cash flows from financing activities
Net cash provided by financing activities		95,599
Net increase (decrease) in cash and cash equivalents		71,913	(14,073)
Effect of exchange rate changes on cash and cash equivalents		2,136	(2,140)
Cash, cash equivalents and restricted cash, beginning of period		11,525	31,131	31,131
Cash, cash equivalents and restricted cash, end of period	$ 85,574	85,574	14,918	11,525
Components of cash, cash equivalents, and restricted cash
Cash and cash equivalents	85,333	85,333	14,695	11,294
Restricted cash	241	241	223	231
Cash, cash equivalents and restricted cash, end of period	85,574	85,574	14,918	$ 11,525
Supplemental disclosures of noncash activities
Operating lease liabilities arising from obtaining right-of-use assets	$ 420	672	391
Cumulative effect of change in accounting principle—adoption of ASC 842, Leases			$ 15
Series C Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuance of preferred stock		39,669
Series D Convertible Preferred Stock
Cash flows from financing activities
Proceeds from issuance of preferred stock		58,727
Series D preferred stock issuance costs		(2,797)
Supplemental disclosures of noncash activities
Receivable on issuance of Series D preferred stock		$ 5,473