Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activity

The following table summarizes stock option activity during the nine months ended September 30, 2021:

	Shares Subject to Options Outstanding			Weighted- Average
	Shares	Weighted- Average Exercise Price		Remaining Contractual Life (Years)	Aggregate Intrinsic Value
					(in thousands)
Outstanding as of December 31, 2020	9,401,082	$	13.42	8.1	$	10,182
Options granted	2,923,501	$	9.67
Options exercised	(280,895)	$	5.85
Options forfeited/cancelled	(2,503,356)	$	14.01
Outstanding as of September 30, 2021	9,540,332	$	12.33	7.5	$	22,958
Options vested and exercisable as of September 30, 2021	4,521,056	$	12.74	6.6	$	12,414

Summary of Restricted Stock Activity

The summary of the Company’s restricted stock activity is as follows:

	Number of Restricted Stock Units Outstanding	Weighted- Average Grant Date Fair Value
Nonvested at December 31, 2020	3,330,821	$	7.16
Granted	1,349,885	$	10.23
Vested	(983,485)	$	5.58
Forfeited	(676,712)	$	10.01
Nonvested at September 30, 2021	3,020,509	$	8.41

Stock-Based Compensation Expense Reported in Condensed Consolidated Statements of Operations

Stock-based compensation expense has been reported in the Company’s condensed consolidated statements of operations as follows (in thousands):

	Three months ended September 30,				Nine months ended September 30,
	2021		2020		2021		2020
Research and development	$	4,349	$	4,726	$	14,435	$	14,094
General and administrative	3,238		4,197		9,914		11,973
Total stock-based compensation	$	7,587	$	8,923	$	24,349	$	26,067