Stock-Based Awards (Tables)

9 Months Ended

Sep. 30, 2019

Stock-Based Awards

Assumptions used to determine fair value of stock options granted

	Nine Months Ended
	September 30,
	2019		2018
Risk-free interest rate	2.27	%	2.65	%
Expected term (in years)	6.2		6.3
Expected volatility	101.70	%	96.56	%
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, 2018	4,282,081		$	20.53	7.91	$	2,404
Granted	44,500			5.75
Exercised	(66,376)			1.29
Forfeited and cancelled	(686,811)			23.35
Outstanding as of September 30, 2019	3,573,394		$	20.16	6.54	$	29
Options vested and expected to vest as of September 30, 2019	3,573,394		$	20.16	6.54	$	29
Options exercisable as of September 30, 2019	2,276,088	(1)	$	18.25	5.74	$	29

(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 options vest. This amount reflects the number of shares under options that were vested, as opposed to exercisable. 

Summary of restricted stock units activity

		Weighted
		Average
		Grant Date
	Number	Fair Value
	of Shares	Per Share
Outstanding as of December 31, 2018	626,407	$	20.30
Granted	1,520,942		6.26
Vested	(150,271)		20.50
Forfeited and cancelled	(361,440)		11.41
Outstanding as of September 30, 2019	1,635,638	$	9.19

Stock-based compensation expense

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2019		2018		2019		2018
Cost of revenue	$	25	$	194	$	454	$	560
Research and development		1,418		1,433		4,733		4,916
Sales and marketing		—		—		—		—
General and administrative		2,581		2,320		7,707		6,936
Total stock-based compensation expense	$	4,024	$	3,947	$	12,894	$	12,412