Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [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 year ended December 31, 2018, were as follows:

	Employee	Non-Employee
Expected volatility	71.0%-79.8%	N/A
Expected dividend yield	—	N/A
Expected term (in years)	3.0-3.5	N/A
Risk-free interest rate	71.0%-79.8%	N/A

The weighted-average assumptions used in the Black-Scholes option-pricing model used to calculate the fair value of options granted during the year ended December 31, 2019, were as follows:

	Employee	Non-Employee
Expected volatility	76.4%-80.6%	N/A
Expected dividend yield	—	N/A
Expected term (in years)	3.0-6.0	N/A
Risk-free interest rate	1.63%-2.48%	N/A

Schedule of stock option activity

	Number of Options			Weighted Average Exercise Price Share		Weighted Average Remaining Contractual Per Term (years)		Aggregate Intrinsic Value (1)
Outstanding at December 31, 2017		82,590		$	33.40		3.7	$	—
Granted		8,974		$	30.60		4.4	$	—
Exercised		(2,450	)	$	10.00
Forfeited		(2,525	)	$	—
Expired		(530	)	$	—
Outstanding at December 31, 2018		86,059		$	31.40		4.0	$	—
Granted		58,396		$	25.80		4.9	$	—
Exercised		(3,450	)	$	13.00		—	$	—
Forfeited		(3,445	)	$	—		—	$	—
Expired		(1,071	)	$	—		—	$	—
Outstanding at December 31, 2019		136,489		$	27.84		3.9	$	—
Exercisable at December 31, 2019		88,029		$	30.77		2.8	$	—

(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 $11.00 and $11.70 per share for each of the years ended December 31, 2019 and 2018 respectively.

Schedule of summarizes restricted stock unit activity

	Number of			Weighted Average Grant Date Fair Value Per
	Units			Units
Outstanding as of December 31, 2017		14,395		$	37.20
Granted		3,787	(1)	$	32.40
Vested		(11,190	)	$	51.20
Forfeited		(179	)	$	139.80
Outstanding as of December 31, 2018		6,813		$	19.60
Granted		6,191	(2)	$	30.20
Vested		(7,127	)	$	22.00
Forfeited		—		$	—
Outstanding as of December 31, 2019		5,877		$	30.28

(1) 641 restricted stock units were granted on June 12, 2017 with a weighted average grant date fair value of $13.00 and 3,146 restricted stock units were granted on June 12, 2018 with a weighted average grant date fair value of $36.40

(2) 314 restricted stock units were granted on February 14, 2019 with a weighted average grant date fair value of $17.09. 3,877 restricted stock units were granted on June 18, 2019 with a weighted average grant date fair value of $28.40. 2,000 restricted stock units were granted on June 30, 2019 with a weighted average grant date fair value of $36.00.

Schedule of stock-based compensation expense

	Years Ended December 31,
	2019		2018
Research and development	$	14	$	106
General and administrative		859		3,306
Total stock-based compensation expense	$	873	$	3,412