Share-based compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based compensation

Schedule of share based compensation expense

The Company recorded share‑based compensation expense in the following expense categories of its condensed consolidated statements of operations and comprehensive loss (in thousands):

	Three				Nine
	Months				Months
	Ended				Ended
	September 30,				September 30,
	2019		2018		2019		2018
Research and development expenses	$	417	$	123	$	816	$	421
General and administrative expenses		402		107		1,184		395
	$	819	$	230	$	2,000	$	816

Schedule of share option activity

				Weighted
		Weighted		Average	Aggregate
	Number of	Average		Contractual	Intrinsic
	Shares	Exercise Price		Term	Value
				(in years)	(in thousands)
Outstanding as of December 31, 2018	863,712	$	1.01	8.75	$	3,292
Granted	2,068,095		11.92	—		—
Exercised	(16,442)		1.26	—		—
Forfeited	(278,090)		3.65	—		—
Outstanding as of September 30, 2019	2,637,275	$	9.29	9.27	$	9,088
Vested and expected to vest as of September 30, 2019	512,710	$	5.38	8.42	$	3,602
Options exercisable as of September 30, 2019	512,710	$	5.38	8.42	$	3,602

Schedule of assumptions used to determine the fair value of share options granted

	Three				Nine
	Months				Months
	Ended				Ended
	September 30,				September 30,
	2019		2018		2019		2018
Risk-free interest rate	1.7	%	3.0	%	2.2	%	2.5	%
Expected volatility	77.0	%	76.0	%	78.3	%	75.8	%
Expected dividend yield	—		—		—		—
Expected term (in years)	6.00		6.07		5.88		6.07

Schedule of restricted ordinary share award activity

		Weighted Average
		Grant-Date
	Shares	Fair Value
Unvested restricted ordinary shares as of December 31, 2018	83,947	$	1.93
Issued	—		—
Forfeited	—		—
Vested	(83,947)		1.93
Unvested restricted ordinary shares as of September 30, 2019	—	$	—