Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2021

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,
	2021		2020
Stock options	$	9,015	$	7,779
Restricted stock units		679		—
Employee stock purchase plan		226		238
	$	9,920	$	8,017

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,
	2021		2020
Research and development	$	5,031	$	4,047
General and administrative		4,889		3,970
	$	9,920	$	8,017

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, 2020		—		$	—
Granted		257		$	44.92
Vested		—		$	—
Forfeited		(3	)	$	44.97
Unvested balance at March 31, 2021		254		$	44.92

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, 2020		6,361		$	31.21		7.2	$	101,356
Granted		1,170		$	44.92
Exercised		(105	)	$	12.30
Cancelled or forfeited		(80	)	$	45.48
Outstanding at March 31, 2021		7,346		$	33.51		7.4	$	51,356
Exercisable at March 31, 2021		4,126		$	26.47		6.2	$	50,065
Vested and expected to vest at March 31, 2021		7,346		$	33.51		7.4	$	51,356

(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.