10. Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Assumptions Used to Determine Fair Value of Option Grants

	December 31,
	2019	2018
Risk-free interest rate	1.85 – 2.58%	2.70 – 2.93%
Expected volatility	97.67 – 98.87%	91.28 – 161.45%
Expected lives (in years)	5.31	5.50 – 10.00
Expected dividend yield	0.00%	0.00%

Summary of Stock Option Activity

	Total Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Balance at December 31, 2018		2,576		$	3,645.95
Granted		273			22.00
Exercised		–			–
Cancelled		(200	)		3,296.15
Balance at December 31, 2019		2,649		$	3,298.90	7.39 years	$	–
Exercisable at December 31, 2019		1,344		$	6,389.90	6.26 years	$	–

Summary of RSU activity

	Number of Shares			Weighted- Average Grant Date Fair Value Per Share
Unvested units at December 31, 2018		2,500		$	98.45
Granted		18,467			17.05
Vested		(1,268	)		98.45
Forfeited		(4,754	)		27.30
Unvested units at December 31, 2019		14,945		$	20.50

Details of Stock-based Compensation Expense Recorded

	December 31,
	2019		2018
Research and development	$	21	$	40
General and administrative		279		242
Total stock-based compensation	$	300	$	282