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Stock-Based Compensation (Tables)
 12 Months Ended
Dec. 31, 2017
Share-based Compensation [Abstract]  
Schedule of Weighted Average Grant-Date Fair Value of Stock Options
The weighted average grant-date fair value of stock options used in the calculation of stock-based compensation expense in the accompanying statement of operations for the years ended December 31, 2017 and 2016 is calculated using the following assumptions:

 
Years Ended December 31,
 
2017
 
2016
Risk-free interest rate
1.8- 2.1%
 
0.9- 1.8%
Expected dividend yield
—

 
—

Expected option term
5 years

 
5 years

Volatility
70.0
%
 
70.0
%
Summary of Option Activity
A summary of option activity for the year ended December 31, 2017 is presented below:

 
Number of
Options
 
Weighted
Average
Exercise Price
 
Weighted
Average
Remaining
Contractual
Life (in years)
 
Aggregate
Intrinsic Value
Outstanding at December 31, 2016
97,891

 
$
37.95

 
 
 
 

Granted
6,488

 
2.37

 
 
 
 

Exercised
—

 
—

 
 
 
 

Forfeited
(23,825
)
 
83.27

 
 
 
 

Expired
(17
)
 
11,187.28

 
 
 
 
Outstanding at December 31, 2017
80,537

 
19.32

 
8.6
 
$
—

Vested or expected to vest at December 31, 2017
80,537

 
19.32

 
8.6
 
—

Exercisable at December 31, 2017
25,388

 
37.26

 
8.3
 
—