Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Share-based Payment Arrangement [Abstract]

Summary of stock option activity

The following table summarizes stock option activity during the six months ended June 30, 2020:

	Shares			Weighted average exercise price
Outstanding at January 1, 2020		1,461,987		$	64.67
Options granted		381,125			88.04
Options exercised		(8,970	)		12.19
Options cancelled		(14,000	)		80.99
Outstanding at June 30, 2020		1,820,142		$	69.70
Exercisable at June 30, 2020		1,123,761		$	51.06

Schedule of stock-based compensation expense

Stock-based compensation expense during the six months ended June 30, 2020 and 2019 was as follows (in thousands):

	Three Months Ended June 30,				Six MonthsEndedJune 30,
	2020		2019		2020		2019
Stock-based compensation expense by type of award:
Stock options	$	5,689	$	7,632	$	10,535	$	13,533
Restricted stock		—		123		—		244
Total stock-based compensation expense	$	5,689	$	7,755	$	10,535	$	13,777
Effect of stock-based compensation expense by line item:
Research and development	$	2,289	$	2,366	$	4,367	$	4,243
General and administrative		3,400		5,389		6,168		9,534
Total stock-based compensation expense included in net loss	$	5,689	$	7,755	$	10,535	$	13,777