Stockholders' Equity

3 Months Ended

Mar. 31, 2018

2. Stockholders’ Equity

The following is a summary of the Company’s outstanding common stock warrants:


			March 31, 2018		December 31, 2017
Expiration Date	Exercise Price		(in thousands)
04/16/18	$	3.40		1,460		1,460
09/23/18	$	2.80		147		147
02/11/19	$	2.56		293		293
02/18/19	$	2.75		1,872		1,872
08/28/19	$	2.90		2,700		2,700
03/20/20	$	2.13		234		234
03/25/20	$	1.71		2,920		2,920

Total Warrants Outstanding				9,626		9,626

The following is a summary of the Company’s stock option activity under its equity incentive plans:


	Options Available for Grant		Options Outstanding			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
	(in thousands)							(years)		(in thousands)
Balance at December 31, 2017		1,846		4,880		$	1.05		7.63	$	—
Options forfeited		175		(175	)	$	0.81

Balance at March 31, 2018		2,021		4,705		$	1.06		7.36	$	—

Vested and exercisable at March 31, 2018				2,252		$	1.09		7.15	$	—
Vested and expected to vest at March 31, 2018				4,077		$	0.87		7.27	$	—
Unvested at March 31, 2018				2,453		$	1.03

As of March 31, 2018, there was approximately $0.7 million of unrecognized compensation cost related to stock option awards that is expected to be recognized as expense over a weighted average period of approximately 1.9 years.

The fair value for stock options granted is estimated at the date of grant using the Black-Scholes option pricing model. No stock options were granted during the three months ended March 31, 2018. For the three months ended March 31, 2017, the Company used the following weighted average assumptions to estimate the fair value of the stock options:


Risk-free interest rate	2.0	%
Expected life (years)	6.3
Expected volatility	89	%
Dividend yield	0	%