Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Activity

The following table summarizes stock option activity during the six months ended June 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	2,591,751	$	9.70
Options exercised	(109,643)	$	2.61
Options forfeited/cancelled	(1,447,260)	$	13.71
Outstanding as of June 30, 2021	10,435,930	$	12.56	7.6	$	6,887
Options vested and exercisable as of June 30, 2021	4,431,654	$	12.89	6.3	$	5,333

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	1,341,885	$	10.25
Vested	(755,401)	$	6.27
Forfeited	(531,484)	$	9.97
Nonvested at June 30, 2021	3,385,821	$	8.15

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 June 30,				Six months ended June 30,
	2021		2020		2021		2020
Research and development	$	4,644	$	4,782	$	10,086	$	9,368
General and administrative	3,410		4,118		6,676		7,776
Total stock-based compensation	$	8,054	$	8,900	$	16,762	$	17,144