Common Stock, Common Stock Warrants and Stock Option Plan (Tables)

12 Months Ended

Dec. 31, 2019

Equity [Abstract]

Schedule of Stock Reserved for Future Issuance

As of December 31, 2019 and 2018, we had reserved shares of common stock for future issuances as follows:

	December 31,
	2019	2018
Warrants to purchase common stock	1,165,282	1,239,423
Options outstanding	1,929,391	1,865,415
Restricted stock units outstanding	1,451,507	1,154,980
Shares available for future grants	288,813	96,515
Shares available for ESPP	373,428	362,938
Shares reserved for issuance upon conversion of the Notes	8,885,204	0
Total	14,093,625	4,719,271

Summary of Outstanding Common Stock Warrants

In connection with the conversion of preferred stock warrants upon the completion of our IPO on October 30, 2015, the following common stock warrants were outstanding:

As of December 31, 2019
Total amount of securities issuable
under the outstanding warrants	Exercise Price		Issuance Date	Expiration Date
315,282	$	2.38	2014-2015	2022-2024
850,000	$	8.62	2018	2024
1,165,282	$	6.93

As of December 31, 2018
Total amount of securities issuable
under the outstanding warrants	Exercise Price		Issuance Date	Expiration Date
74,141	$	30.35	2012-2013	2019
315,282	$	2.38	2014-2015	2022-2024
850,000	$	8.62	2018	2024
1,239,423	$	8.33

Summary of Stock Option Activity

	Stock Options
				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
		Exercise		Contractual	Intrinsic
	Shares	Price		Term (Years)	Value
	(aggregate intrinsic value in thousands)
Outstanding as of December 31, 2016	991,895	$	2.68	6.3	$	161
Granted	835,480		4.30
Exercised	(230,123)		1.92
Canceled	(36,799)		4.16
Outstanding as of December 31, 2017	1,560,453		3.63	7.6	$	4,632
Granted	479,375		7.25
Exercised	(112,965)		2.48
Canceled	(61,448)		3.65
Outstanding as of December 31, 2018	1,865,415		4.63	7.6	$	1,540
Granted	189,856		6.16
Exercised	(112,647)		3.36
Canceled	(13,233)		6.53
Outstanding as of  December 31, 2019	1,929,391	$	4.84	6.9	$	7,146
Options vested and expected to vest as of December 31, 2019	1,875,980	$	4.80	6.9	$	7,029
Options vested and exercisable as of December 31, 2019	1,248,054	$	4.23	6.3	$	5,408

Summary of Restricted Stock Units Activity

	Restricted Stock Units
				Weighted-
		Weighted-		Average
		Average		Remaining	Aggregate
		Grant Date		Contractual	Intrinsic
	Shares	Fair Value		Term (Years)	Value
	(aggregate intrinsic value in thousands)
Outstanding as of December 31, 2016	490,954	$	5.80	0.5	$	908
Granted	541,513		2.88
Released	(497,009)		5.64
Forfeited/expired	(25,564)		5.98
Outstanding as of December 31, 2017	509,984		2.84	1.4	$	3,288
Granted	925,578		6.55
Released	(264,568)		4.02
Forfeited/expired	(15,924)		8.34
Outstanding as of December 31, 2018	1,154,980		5.50	1.4	$	5,082
Granted	978,851		6.35
Released	(512,703)		5.31
Forfeited/expired	(169,621)		5.15
Outstanding as of December 31, 2019	1,451,507	$	6.18	1.3	$	12,314

Schedule of Additional Information Regarding Stock Options Outstanding and Vested

Additional information regarding stock options outstanding and vested as of December 31, 2019 is summarized below:

					Options Vested and
	Options Outstanding				Exercisable
		Weighted-	Weighted-			Weighted-
	Number of	Average	Average		Shares	Average
	Stock	Remaining	Exercise		subject	Exercise
	Options	Contractual	Price per		to Stock	Price per
Range of Exercise Prices	Outstanding	Life (Years)	Share		Options	Share
$1.60	4,417	6.8	$	1.60	3,416	$	1.60
$1.65	268,559	3.2		1.65	268,559		1.65
$3.30 - $3.48	212,307	5.9		3.40	208,584		3.40
$3.55	370,275	7.2		3.55	245,596		3.55
$3.60 - $4.58	155,365	7.4		3.76	109,460		3.66
$5.25	216,993	7.2		5.25	136,051		5.25
$5.30 - $5.87	205,018	9.1		5.76	42,531		5.56
$6.15 - $8.10	183,651	8.3		6.62	81,611		6.48
$8.45	239,413	8.3		8.45	89,777		8.45
$8.55 - $10.00	73,393	6.5		9.63	62,469		9.79
$1.60-$10.00	1,929,391	6.9	$	4.84	1,248,054	$	4.23