v3.8.0.1
Note 12 - Stock-based Compensation
 12 Months Ended
Dec. 31, 2017
Notes to Financial Statements  
Disclosure of Compensation Related Costs, Share-based Payments [Text Block]
12.
Stock-Based Compensation
 
The Company recorded total stock-based compensation expense for stock options, stock awards and the ESPP as follows
(in thousands):
 
   
December
31,
201
7
    
December
31,
201
6
    
December
31,
201
5
  
Cost of goods sold
   $
324
     $
302
     $
67
  
Research and development
    
1,901
      
2,308
      
2,587
  
General and administrative
    
2,069
      
1,869
      
2,356
  
Total
   $
4,294
     $
4,479
     $
5,010
  
 
The following table summarizes option activity under the
2011
Plan and
2006
Plan:
 
   
Number
of Stock Options
Outstanding
    
Weighted-
Average
Exercise
Price
    
Weighted-
Average
Remaining
Contractual
Life (Years)
    
Aggregate
Intrinsic
Value
  
   
 
 
 
  
 
 
 
  
 
 
 
  
(in
thousands)
  
December
31, 2016
    
6,307,756
     $
5.00
      
 
      
 
  
Granted
    
3,007,155
      
2.99
      
 
      
 
  
Forfeited
    
(438,519
 )    
4.28
      
 
      
 
  
Expired
    
(351,922
 )    
7.31
      
 
      
 
  
Exercised
    
(69,372
 )    
1.52
      
 
      
 
  
December
31, 2017
    
8,455,098
     $
4.25
      
7.1
     $
13
  
Vested and exercisable options
—December 31, 2017
    
4,529,174
     $
5.11
      
5.56
     $
13
  
Vested and expected to vest
—December 31, 2017
    
8,455,098
     $
4.25
      
7.1
     $
13
  
 
As of
December
 
31,
2017,
there were
2,368,992
shares available for future grant under the
2011
Plan. In
January 2018,
an additional
2,035,966
shares were authorized for issuance under the
2011
Incentive Plan.
 
Additional information regarding the Company
’s stock options outstanding and vested and exercisable as of
December 
31,
2017
is summarized below:
 
       
Options Outstanding
    
Options
Vested and Exercisable
  
Exercise Prices
  
Number of
Stock Options
Outstanding
    
Weighted-Average
Remaining
Contractual Life
(Years)
    
Weighted-Average
Exercise Price per
Share
    
Shares
Subject
to Stock
Options
    
Weighted-Average
Exercise Price per
Share
  
$1.20
-
$2.
30
    
105,900
      
8.4
     $
2.13
      
38,400
     $
1.84
  
$2.
40
-
$3.77
    
5,592,633
      
7.7
     $
3.10
      
1,948,300
     $
3.17
  
$
3.92
-
$6.60
    
2,060,565
      
5.7
     $
5.45
      
1,880,190
     $
5.36
  
$8.18
-
$10.55
    
696,000
      
6.2
     $
10.28
      
662,284
     $
10.28
  
 
 
 
    
8,455,098
      
7.1
     $
4.25
      
4,529,174
     $
5.11
  
 
The weighted average grant-date fair value of options granted during the years ended
December
 
31,
2017,
2016
and
2015
was
$1.91,
$2.24
and
$2.69
per share, respectively. As of
December 
31,
2017,
total stock-based compensation expense related to unvested options to be recognized in future periods was
$7.1
million which is expected to be recognized over a weighted-average period of
2.6
years. The grant date fair value of shares vested during the years ended
December 
31,
2017,
2016
and
2015
was
$3.5
million,
$3.9
million and
$5.4
million, respectively. The total intrinsic value of options exercised during the year ended
December 
31,
2017
was
$40
thousand. There were
no
option exercises during the year ended
December 31, 2016,
and the total intrinsic value of options exercised during the year ended
December 31, 2015
was
$1.3
million.
 
 
The Company used the following assumptions to calculate the fair value of each employee stock option:
 
   
Year
Ended December 31,
  
   
201
7
    
201
6
    
201
5
  
Expected term (in years)
  
5.70
    
5.25
-
6.25
    
5.25
-
6.25
  
Risk-free interest rate
  
 1.82%
-
2.09%
    
 1.24%
-
1.47%
    
 1.35%
-
1.82%
  
Expected volatility
  
73%
    
80%
    
72%
  
Expected dividend rate
  
0%
    
0%
    
0%