Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Stock-based Compensation

Summary of performance share units activity

		Weighted-Average
	Shares	Grant Date Fair Value
Outstanding at December 31, 2019	99,400	$	15.90
Granted	187,978		28.49
Vested	—		—
Forfeited	—		—
Performance adjustment	(4,155)		15.90
Outstanding at March 31, 2020	283,223	$	24.26

Summary of restricted stock units activity

		Weighted-Average
	Shares	Grant Date Fair Value
Outstanding at December 31, 2019	849,679	$	17.10
Granted	725,422		21.34
Vested	(195,280)		17.83
Forfeited	(7,263)		17.63
Outstanding at March 31, 2020	1,372,558	$	19.23

Summary of stock option activity

				Weighted-
			Weighted-	Average
			Average	Remaining		Aggregate
			Exercise Price	Contractual		Intrinsic
	Shares		per Share	Term (in years)		Value
Outstanding at December 31, 2019	3,955,887	$	16.00	7.5	$	21,257
Granted	574,783		21.39
Exercised	(455,573)		9.78
Cancelled	(40,883)		19.36
Outstanding at March 31, 2020	4,034,214	$	17.44	7.8	$	5,904
Exercisable at March 31, 2020	1,916,510	$	16.55	6.7	$	3,550

Summary of stock-based compensation

	Three months ended March 31,
	2020		2019
Research and development expenses	$	770	$	567
Selling, general and administrative expenses		4,181		3,696
Total stock-based compensation expense	$	4,951	$	4,263

Schedule of fair value assumption using Black-Scholes option-pricing model

	Three months ended March 31,
	2020		2019
Risk-free interest rate	1.5	%	2.6	%
Volatility	65.5	%	63.3	%
Expected term (years)	6.1		6.1
Expected dividend yield	—	%	—	%