Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities:
Net loss	$ (26,202)	$ (15,205)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	2,000	816
Depreciation and amortization	686	528
Change in fair value of warrant liability recorded as other expense	5,381	1,472
Changes in operating assets and liabilities:
Accounts receivable	5,064	(289)
Research and development incentives receivable	(4,813)	(821)
Prepaid expenses and other current assets	(1,638)	(1,902)
Operating lease right-of-use assets	528
Other assets	(216)	(315)
Accounts payable	516	(864)
Accrued expenses and other current liabilities	(611)	2,206
Lease liabilities	(526)
Deferred revenue	(4,502)	(3,258)
Other long-term liabilities	639	408
Net cash used in operating activities	(23,694)	(17,224)
Cash used in investing activities:
Purchases of property and equipment	(1,164)	(776)
Net cash used in investing activities	(1,164)	(776)
Cash flows from financing activities:
Gross proceeds from issues of shares	1,334
Proceeds from issuance of ADS in initial public offering, net of issuance costs	56,957
Proceeds from the exercise of share options	21
Proceeds from the exercise of warrants	6	1
Net cash provided by financing activities	58,318	1
Effect of exchange rate changes on cash	(886)	(1,742)
Net increase (decrease) in cash	32,574	(19,741)
Cash at beginning of period	63,380	67,663
Cash at end of period	95,954	47,922
Supplemental disclosure of cash flow information
Cash paid for income taxes	73
Cash paid for amounts included in the measurement of operating lease liabilities	447
Advance billings on deferred revenue included in accounts receivable		$ 5,353
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