Annual report pursuant to Section 13 and 15(d)

Stock and Employee Benefit Plans (Tables)

v3.8.0.1
Stock and Employee Benefit Plans (Tables)
 12 Months Ended
Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]  
Fair Value Assumptions
The Company estimates the fair value of each employee stock award on the grant date using the Black-Scholes option-pricing model based on the following assumptions:
 
 
Years Ended December 31,
 
 
2017
 
2016
Risk free interest rate
 
1.77% - 2.22%
 
1.13% - 2.08%
Expected term
 
5.00 - 5.73 years
 
5.00 - 5.73 years
Dividend yield
 
—
 
—
Expected volatility
 
75.1% - 78.9%
 
74.9% - 76.0%
Stock Based Compensation Expense
Total stock-based compensation expense is recorded in operating expenses based upon the functional responsibilities of the individuals holding the respective options as follows (in thousands):
 
 
Years Ended
December 31,
 
 
2017
 
2016
Research and development
 
$
844

 
$
599

General and administrative
 
2,202

 
1,306

Total stock-based compensation
 
$
3,046

 
$
1,905

Summary of Stock Option Activity
The following table summarizes stock option activity for employees and nonemployees (shares in thousands):
 
Number of
Options
 
Weighted-
Average
Exercise
Price
 
Weighted-
Average
Remaining
Contractual
Life
 
Aggregate
Intrinsic
Value
(in thousands)
Outstanding, December 31, 2016
4,423

 
$
1.99

 
 
 
$
—

Granted
1,853

 
3.23

 
 
 
4

Exercised
(552
)
 
2.34

 
 
 
886

Canceled
(280
)
 
2.78

 
 
 
277

Outstanding, December 31, 2017
5,444

 
$
2.33

 
8.07 years
 
$
28,395

Vested or expected to vest, December 31, 2017
5,444

 
$
2.33

 
8.07 years
 
$
28,395

Exercisable, December 31, 2017
3,067

 
$
1.96

 
7.32 years
 
$
17,141


Periodically, the Company grants options outside of the 2014 and 2016 Plans as inducement options, which are material awards to the executive officers or other personnel entering senior leadership roles with the Company. These awards are excluded from the table above. The following table summarizes stock option activity for these inducement options (in thousands):
 
Number of
Options
 
Weighted-
Average
Exercise
Price
 
Weighted-
Average
Remaining
Contractual
Life
 
Aggregate
Intrinsic
Value
(in thousands)
Outstanding, December 31, 2016
1,000

 
$
2.41

 
 
 
$
—

Granted
625

 
$
5.24

 
 
 
$
—

Canceled
(94
)
 
$
1.45

 
 
 
$
572

Outstanding, December 31, 2017
1,531

 
$
3.62

 
8.79 years
 
$
6,015

Vested or expected to vest
1,531

 
$
3.62

 
8.79 years
 
$
6,015

Exercisable, December 31, 2017
688

 
$
2.23

 
8.39 years
 
$
3,657