Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (51,010)	$ (30,608)	$ (21,846)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	6,514	3,083	1,023
Depreciation and amortization	1,277	960	712
Non-cash interest	78
Change in fair value of warrant liability		5,381	665
Changes in operating assets and liabilities:
Accounts receivable	(2,149)	4,909	(400)
Research and development incentives receivable	(1,786)	(383)	(3,586)
Prepaid expenses and other current assets	(49)	(2,723)	(1,329)
Operating lease right-of-use assets	771	712
Other assets	(122)	(397)	(301)
Accounts payable	(663)	220	(169)
Accrued expenses and other current liabilities	4,832	(852)	2,557
Operating lease liabilities	(621)	(709)
Deferred revenue	24,622	(9,295)	(3,947)
Other long-term liabilities	517	1,089	543
Net cash used in operating activities	(17,789)	(28,613)	(26,078)
Cash used in investing activities:
Purchases of property and equipment	(1,200)	(1,555)	(1,186)
Net cash used in investing activities	(1,200)	(1,555)	(1,186)
Cash flows from financing activities:
Proceeds from the issuance of ADSs, net of issuance costs	48,144	56,957	(576)
Proceeds from the exercise of share options and sale of ordinary shares	271	143	1
Proceeds from the exercise of warrants	1	6
Proceeds from issuance of debt	15,000
Payments of debt issuance costs	(573)
Net cash provided by financing activities	62,843	58,440	25,430
Effect of exchange rate changes on cash	19	465	(2,449)
Net increase (decrease) in cash	43,873	28,737	(4,283)
Cash at beginning of period	92,117	63,380	67,663
Cash at end of period	135,990	92,117	63,380
Supplemental disclosure of cash flow information
Cash paid for interest	378
Cash paid for income taxes	124	117	73
Cash paid for amounts included in the measurement of operating lease liabilities	961	891
Purchases of property and equipment included in accounts payable and accrued expenses	109	76
Advance billings on deferred revenue included in accounts receivable	$ 3,000		5,045
Series B2 convertible preferred financing costs accrued but not paid			249
Debt issuance costs accrued but not paid			1,076
Conversion of convertible preferred shares to ordinary shares upon closing of the initial public offering		123,780
Reclassification of warrant liability to additional paid-in capital		10,021
Series B2 Convertible Preferred Shares
Cash flows from financing activities:
Proceeds from issuance of convertible preferred shares, net of issuance costs		$ 1,334	$ 26,005