Share-based compensation (Tables)

3 Months Ended

Mar. 31, 2018

Share-based compensation

Schedule of share-based compensation expense by classification included in consolidated statements of operations and comprehensive loss

	Three months ended March 31,
	2018		2017
	in thousands
Research and development	$	806	$	687
Selling, general and administrative		1,721		918
Total	$	2,527	$	1,605

Schedule of share-based compensation expense

	Three months ended March 31,
	2018		2017
	in thousands
Award type
Share options	$	1,059	$	826
Restricted share units (“RSUs”)		746		516
Performance share units (“PSUs”)		722		263
Total	$	2,527	$	1,605

Schedule of unrecognized compensation cost related to unvested awards

			Weighted-average
	Unrecognized		remaining
	compensation		period for
	costs		recognition
Award type	in thousands		in years
Share options	$	12,641	3.20
Restricted share units		5,706	2.17
Performance share units		7,073	2.19
Total	$	25,420	2.68

Schedule of weighted-average assumptions for fair value of option issued

	Three months ended March 31,
	2018		2017
Expected volatility		75%		75%
Expected terms (in years)		10 years		10 years
Risk free interest rate		2.77% - 2.99%		2.53% - 2.70%
Expected dividends		0%		0%

Summary of RSUs activity

		RSU
			Weighted average
			grant-date fair
	Number of shares		value
Non-vested at December 31, 2017		683,663	$	6.38
Granted		207,599	$	19.39
Vested		(218,500)	$	6.11
Forfeited		(10,950)	$	9.26
Non-vested at March 31, 2018		661,812	$	10.51
Total fair value of RSUs awarded during the period (in million)			$	4.0
Granted to directors and officers during the period (shares, $ in million)		98,808	$	1.9

Summary of PSUs activity

		PSU
			Weighted average
			grant-date fair
	Number of shares		value
Non-vested at December 31, 2017		511,074	$	16.73
Granted		—
Vested		(68,115)	$	15.79
Forfeited		—	$
Non-vested at March 31, 2018		442,959	$	16.83
PSUs awarded but not yet earned		117,197	$	23.50
Total non-vested and discretionary PSUs		560,156	$	18.23
Total weighted average grant date fair value of PSUs awarded during the period (in million)			$	2.8

2014 Plan

Share-based compensation

Summary of option activity

		Weighted average
	Options	exercise price
Outstanding at December 31, 2017	2,456,433	$	10.06
Granted	614,637	$	20.11
Forfeited	(50,102)	$	10.13
Expired	(8,921)	$	14.00
Exercised	(135,572)	$	11.27
Outstanding at March 31, 2018	2,876,475	$	12.14
Fully vested and exercisable at March 31, 2018	937,773	$	11.58
Outstanding and expected to vest at March 31, 2018	1,938,702	$	12.41
Total weighted average grant date fair value of options issued during the period (in $ million)		$	7.3
Granted to directors and officers during the period (options, $ in million)	221,961	$	2.5
Proceeds from option sales (in $ million)		$	1.6