Stock-based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of fair value of options granted

The weighted-average assumptions used in the Black-Scholes option-pricing model used to calculate the fair value of options granted during the nine months ended September 30, 2017, were as follows:

	Employee			Non-Employee
Expected volatility		73.8% -83.7	%		N/A
Expected dividend yield		—			N/A
Expected term (in years)		3.0 to 3.5			N/A
Risk-free interest rate		1.45%-1.94	%		N/A

Schedule of stock option activity

The table summarizes the stock option activity, for both plans, for the periods indicated as follows:

	Number of Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (years)		Aggregate Intrinsic Value(1)
Outstanding at December 31, 2016		1,477,300			1.61		5.8	$	9,662
Granted		161,500		$	8.04		5.0	$	—
Exercised		(15,000	)	$	0.50		—		—
Forfeited		—		$	—		—		—
Expired		(65,000	)	$	10.22		—		—
Outstanding at September 30, 2017		1,558,800			1.73		5.1	$	183
Exercisable at September 30, 2017		1,263,599		$	1.08		4.8	$	968

⁽¹⁾ The aggregate intrinsic value on the table was calculated based on the difference between the estimated fair value of the Company’s stock and the exercise price of the underlying option. The estimated stock values used in the calculation was $1.85 and $8.15 per share at September 30, 2017 and December 31, 2016, respectively.

Schedule of stock-based compensation expense

The stock-based compensation expense was recorded as follows:

	Three Months Ended September 30				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	85		135	$	269	$	309
General and administrative		861		798		2,549		2,097
Total stock-based compensation expense	$	946		933	$	2,818	$	2,406

Schedule of summarizes restricted stock unit activity [Table Text Block]

The following table summarizes restricted stock unit activity for the nine months ended September 30, 2017: 

	Number of  Units			Weighted Average Grant-Date Fair Value Per Units
Outstanding as of December 31, 2016		455,430		$	0.76
Granted		117,885	(1)	$	6.95
Vested		(228,333	)	$	2.00
Forfeited		—		$	—
Outstanding as of September 30, 2017		344,982	(2)	$	2.05

(1) 40,000 restricted stock units were granted on March 27, 2017 with a weighted average grant date fair value of $8.35, 17,885 restricted stock units were granted on May 19, 2017 with a weighted average grant date fair value of $6.99 and 60,000 restricted stock units were granted on June 19, 2017 with a weighted average grant date fair value of $6.00.

⁽²⁾ At September 30, 2017, the total compensation cost related to non-vested restricted stock units not yet recognized was $1,075, which will be recognized over a weighted average period of 1.3 years, assuming the recipients complete their service period required for vesting.