Stock-based Compensation (Tables)

6 Months Ended

Jun. 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 six months ended June 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		(20,000	)	$	15.00
Outstanding at June 30, 2017		1,603,800			2.00		5.3	$	5,934
Exercisable at June 30, 2017		1,055,581		$	2.18		5.0	$	3,716

Schedule of stock-based compensation expense

The stock-based compensation expense was recorded as follows: 

	Three Months Ended June 30				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development	$	90		87	$	184	$	174
General and administrative		721		255		1,688		1,299
Total stock-based compensation expense	$	811		342	$	1,872	$	1,473

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

The following table summarizes restricted stock unit activity for the six months ended June 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		(186,666	)	$	2.18
Forfeited		—		$	—
Outstanding as of June 30, 2017		386,649	(2)	$	1.70

(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 June 30, 2017, the total compensation cost related to non-vested restricted stock units not yet recognized was $1,229, which will be recognized over a weighted average period of 1.5 years, assuming the recipients complete their service period required for vesting.