Equity Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes stock option activity during the six months ended June 30, 2020:

	Shares Subject to Options Outstanding					Weighted- Average
				Weighted-		Remaining
				Average Exercise		Contractual Life		Aggregate
	Shares			Price		(Years)		Intrinsic Value
								(in thousands)
Outstanding as of December 31, 2019		8,538,060		$	13.67		9.0	$	35,385
Options granted		1,911,222		$	14.30
Option exercised		(44,007	)	$	3.49
Options forfeited/cancelled		(541,572	)	$	12.96
Outstanding as of June 30, 2020		9,863,703		$	13.88		8.6	$	22,225
Options vested and exercisable as of June 30, 2020		2,791,102		$	12.31		8.0	$	9,989

Summary of Restricted Stock Activity

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

	Number of			Weighted-
	Restricted			Average
	Stock Units			Grant Date
	Outstanding			Fair Value
Nonvested at December 31, 2019		4,648,526		$	3.98
Granted		1,176,340		$	11.94
Vested		(809,274	)	$	3.71
Forfeited		(51,048	)	$	14.21
Nonvested at June 30, 2020		4,964,544		$	5.80

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				Six months ended
	June 30,				June 30,
	2020		2019		2020		2019
Research and development	$	4,782	$	2,463	$	9,368	$	3,756
General and administrative		4,118		2,677		7,776		4,473
Total stock-based compensation	$	8,900	$	5,140	$	17,144	$	8,229