Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Stock-Based Compensation Expense by Award Type

The Company’s stock-based compensation expense by award type was as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Stock options	$	9,267	$	9,015
Restricted stock units		1,254		679
Employee stock purchase plan		279		226
	$	10,800	$	9,920

Stock-Based Compensation Expense

The Company recorded aggregate stock-based compensation expense in the consolidated statements of operations and comprehensive loss as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Research and development	$	5,670	$	5,031
General and administrative		5,130		4,889
	$	10,800	$	9,920

Summary of Unvested RSUs Activity Under 2015 Plan

The following table summarizes restricted stock unit activity under the 2015 Plan (in thousands, except per share data):

				Weighted-average
				Grant Date
	Shares			Fair Value
Unvested balance at December 31, 2021		277		$	43.62
Granted		265		$	33.92
Vested		(61	)	$	44.94
Forfeited		(10	)	$	38.80
Unvested balance at March 31, 2022		471		$	38.10

2014 and 2015 Equity Incentive Plan [Member]

Summary of Stock Option Activity

The following table summarizes stock option activity under the 2014 Plan and 2015 Plan (in thousands, except per share data):

						Weighted-
						average
				Weighted-		Remaining
				average		Contractual		Aggregate
				Exercise		Life		Intrinsic
	Shares			Price		(Years)		Value (a)
Outstanding at December 31, 2021		7,126		$	34.16		6.8	$	41,128
Granted		1,224		$	33.93
Exercised		(80	)	$	4.61
Cancelled or forfeited		(98	)	$	38.57
Outstanding at March 31, 2022		8,172		$	34.37		7.1	$	40,352
Exercisable at March 31, 2022		5,028		$	31.52		6.0	$	39,522
Vested and expected to vest at March 31, 2022		8,172		$	34.37		7.1	$	40,352

(a) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the fair value of the common stock for the options that were in the money at the dates reported.