Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Stock Incentive Plan Compensation [Abstract]

The Company estimates the fair value of stock options with performance and service conditions on the date of grant using the Black-Scholes valuation model. The assumptions used in the Black-Scholes model are presented below:



	Year ended December 31,
	2018		2017
Risk-free interest rate	2.74 to 2.99	%	1.27 to 2.36	%
Expected volatility	121 to 126	%	117 to 144	%
Expected term (in years)	6.02		2.0 to 9.1
Expected dividend yield	0	%	0	%

Allocation of Stock-Based Compensation Expenses

The table below summarizes the total stock-based compensation expense included in the Company’s consolidated statements of operations for the periods presented:



	Year Ended December 31,
	2018		2017

Research and development	$	326,000	$	171,000
General and administrative		152,000		529,000
Total stock-based compensation	$	478,000	$	700,000

Summary of Stock Option Activity

Stock option transactions during the years ended December 31, 2018 and 2017 are presented below:



	Options Outstanding
					Average
			Weighted		Remaining
			Average		Contractual			Aggregate
			Exercise		Term		Intrinsic
	Shares		Price		(Years)		Value
Outstanding at December 31, 2016		74,890	$	64.50		8.65
Granted		1,070,572		1.22
Forfeited/Cancelled		(29,597)		87.87
Outstanding at December 31, 2017		1,115,865		3.17		8.98
Granted		37,500		1.18
Forfeited/Cancelled		(3,300)		11.54
Outstanding at December 31, 2018		1,150,065	$	3.08		8.03	$	-
Vested and expected to vest at December 31, 2018		864,952	$	3.79		7.78	$	-
Exercisable at December 31, 2018		402,642	$	5.86		6.73	$	-

Shares Reserved for Future Issuance

As of December 31, 2018, the Company had reserved shares of its common stock for future issuance as follows:



	Shares Reserved
Stock options outstanding		1,150,065
Employee stock purchase plan		46,472
Available for future grants under the 2016 Plan		446,226
Warrants		26,961,187
Total shares reserved		28,603,950