Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Stockholders' Equity Note [Abstract]

Schedule of shares of common stock reserved for issuance

The Company has reserved the following shares of common stock for issuance as of December 31, 2020:

Warrants to purchase common stock	51,238
Options:
Outstanding under the 2020 Equity Incentive Plan	637,286
Outstanding under the 2012 Equity Incentive Plan	3,090,821
Outstanding under the 2001 Equity Incentive Plan	42
Available for future grants under the 2020 Equity Incentive Plan	6,349,911
	10,129,298

Summary of stock option activity

The following table summarizes stock option activity for the years ended December 31, 2020 and 2019:

	Number of Shares			Weighted Average Exercise Price (per share)(1)		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value ($000's) (2)
Outstanding at January 1, 2019		3,081,863		$	4.75
Granted		294,191			3.90
Exercised		(97,725	)		3.35
Cancelled (forfeited)		(101,984	)		3.10
Cancelled (expired)		(9	)		48.40
Outstanding at December 31, 2019		3,176,336			4.75
Granted		981,164			7.35
Exercised		(429,330	)		3.55
Cancelled (expired)		(21	)		58.40
Outstanding at December 31, 2020		3,728,149		$	5.57		7.6	$	44,479
Options vested and expected to vest		3,715,473		$	5.57		7.6	$	44,328
Exercisable		2,999,502		$	5.07		7.2	$	10

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(1) The weighted average price per share is determined using exercise price per share for stock options.

(2) The aggregate intrinsic value is calculated as the difference between the exercise price of the option and the fair value of the Company’s common stock for in-the-money options at December 31, 2020.

Schedule of stock options outstanding and exercisable by exercise price

The stock options outstanding and exercisable by exercise price at December 31, 2020 are as follows:

	Stock Options Outstanding						Stock Options Exercisable
Range of Exercise Prices	Number of Shares		Weighted- Average Remaining Contractual Life In Years		Weighted- Average Exercise Price Per Share		Number of Shares		Weighted- Average Exercise Price Per Share
$1.65 - $3.33		2,534,965		7.30	$	3.14		2,372,837	$	3.18
$4.20 - $9.05		343,065		8.95	$	6.30		176,190	$	4.92
$9.65 - $16.50		587,286		9.31	$	10.57		187,642	$	12.53
$16.90 - $16.90		252,604		5.62	$	16.90		252,604	$	16.90
$17.00 - $18.00		10,125		5.72	$	17.01		10,125	$	17.01
$58.40 - $86.80		42		0.09	$	67.87		42	$	67.87
$216.40 - $240.00		62		0.12	$	225.92		62	$	225.92
		3,728,149		7.65	$	5.57		2,999,502	$	5.07

Schedule of fair value-based measurement of stock options granted under the entity's stock plans estimated using Black-Scholes model

The weighted-average fair value-based measurement of stock options granted under the Company’s stock plans in the years ended December 31, 2020 and 2019 was $7.35 and $3.95 per share, respectively. The fair value- based measurement of stock options granted under the Company’s stock plans was estimated at the date of grant using the Black-Scholes model with the following assumptions:

	Year Ended December 31,
	2020	2019
Expected term	5 - 6 years	5 - 6 years
Expected volatility	95% - 111%	96% - 99%
Risk-free interest rate	0.28% - 1.57%	1.74% - 2.59%
Expected dividend yield	0%	0%

Schedule of total stock-based compensation expense recognized

Total expense for stock option grants recognized was as follows:

	Year ended December 31,
	2020		2019
Selling,general and administrative	$	1,773	$	1,928
Reseach and development		337		97
Total stock-based compensation	$	2,110	$	2,025