Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2019

Stockholders' Equity Note [Abstract]

Summary of stock option activity

A summary of stock option activity for the six months ended June 30, 2019 under all of the Company’s options plans is as follows:

	Options			Weighted Average Exercise Price
Outstanding at January 1, 2019		15,409,357		$	0.95
Granted		728,610			1.10
Exercised		(488,625	)		0.67
Cancelled (forfeited)		(509,923	)		0.62
Cancelled (expired)		(45	)		9.68
Outstanding at June 30, 2019		15,139,374		$	0.97

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

The Company valued the options granted using the Black-Scholes options pricing model and the following weighted-average assumption terms for the six months ended June 30, 2019:

	Six months ended June 30, 2019
Exercise price	$0.84 - $1.30
Market value	$0.84 - $1.30
Risk-free rate	2.49% - 2.59%
Expected term	6 years
Expected volatility	99.1% - 99.3%
Dividend yield	-

Schedule of total stock-based compensation expense recognized

The Company recorded stock-based compensation expense in the Condensed Consolidated Statements of Operations and Comprehensive Loss as follows:

	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018
General and administrative	$	697	$	780	$	1,394	$	3,254
Research and development		32		-		32		201
Total stock-based compensation	$	729	$	780	$	1,426	$	3,455