XML 33 R22.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock-Based Compensation (Tables)
 3 Months Ended
Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions
The fair market value of these stock options at the date of grant was estimated using the Black-Scholes option-pricing model with the following weighted average assumptions for the three months ended:
 
March 31, 2018
 
March 31, 2017
Expected term
6 years, 3 months

 
6 years, 3 months

Interest rate
2.47
%
 
2.17
%
Dividend rate
—

 
—

Volatility
87.7
%
 
89.3
%
Summary of Stock Option Activity
The following table summarizes stock option activity for the three months ended March 31, 2018:
 
Number of
shares
 
Weighted-
average
exercise
price
 
Weighted- average
remaining
contractual
term
 
Aggregate
intrinsic
value
Outstanding at December 31, 2017
1,089,513

 
$
12.06

 
7 years, 3 months
 
$
—

Granted
244,000

 
0.69

 
9 years, 10 months
 
—

Exercised
—

 
—

 
 
 
 

Forfeited
—

 
—

 
 
 
 

Expired
(822
)
 
6.24

 
 
 
 

Outstanding at March 31, 2018(1)
1,332,691

 
$
9.98

 
7 years, 6 months
 
$
—

Exercisable at March 31, 2018
707,687

 
$
16.74

 
6 years
 
$
—


(1)
Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition.