Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of stock option activity

The following table summarizes stock option activity during the three months ended March 31, 2021:

	Shares			Weighted average exercise price
Outstanding at January 1, 2021		1,837,540		$	71.80
Options granted		360,625			117.46
Options exercised		(4,250	)		112.42
Outstanding at March 31, 2021		2,193,915		$	79.22
Exercisable at March 31, 2021		1,286,093		$	58.22

Schedule of stock-based compensation expense

Stock-based compensation expense during the three months ended March 31, 2021 and 2020 was as follows (in thousands):

	Three Months Ended March 31,
	2021		2020
Stock-based compensation expense by type of award:
Stock options	$	6,096	$	4,846
Total stock-based compensation expense	$	6,096	$	4,846
Effect of stock-based compensation expense by line item:
Research and development	$	2,637	$	2,078
General and administrative		3,459		2,768
Total stock-based compensation expense included in net loss	$	6,096	$	4,846