Stock-Based Awards (Tables)

3 Months Ended

Mar. 31, 2020

Stock-Based Awards

Assumptions used to determine fair value of stock options granted

	Three Months Ended
	March 31,
	2020		2019
Risk-free interest rate	0.97	%	2.53	%
Expected term (in years)	6.2		6.3
Expected volatility	85.28	%	101.70	%
Expected dividend yield	0	%	0	%

Summary of stock option activity

					Weighted
			Weighted		Average
			Average		Remaining	Aggregate
	Number		Exercise		Contractual	Intrinsic
	of Shares		Price		Term	Value
					(in years)
Outstanding as of December 31, 2019	3,102,221		$	20.33	6.55	$	148
Granted	602,800			1.28
Exercised	—			—
Forfeited and cancelled	(275,088)			21.36
Outstanding as of March 31, 2020	3,429,933		$	16.90	6.70	$	21
Options vested and expected to vest as of March 31, 2020	3,429,933		$	16.90	6.70	$	21
Options exercisable as of March 31, 2020	2,121,161	(1)	$	19.47	5.46	$	21

(1) All options granted under the 2012 Plan are exercisable immediately, subject to a repurchase right in the Company’s favor that lapses as the option vests. This amount reflects the number of shares under options that were vested, as opposed to exercisable, as of March 31, 2020. 

Summary of restricted stock units activity

		Weighted
		Average
		Grant Date
	Number	Fair Value
	of Shares	Per Share
Outstanding as of December 31, 2019	3,592,915	$	4.62
Granted	977,385		1.26
Vested	(430,896)		6.62
Forfeited and cancelled	(269,345)		4.96
Outstanding as of March 31, 2020	3,870,059	$	3.52

Stock-based compensation expense

	Three Months Ended
	March 31,
	2020		2019
Cost of revenue	$	260	$	206
Research and development		816		1,594
General and administrative		2,377		2,472
Total stock-based compensation expense	$	3,453	$	4,272