XML 27 R12.htm IDEA: XBRL DOCUMENT v3.8.0.1
Note 8 - Stockholders' Equity
 3 Months Ended
Mar. 31, 2018
Notes to Financial Statements  
Stockholders' Equity Note Disclosure [Text Block]
8.
     Stockholders’ Equity
 
Common Stock Offering
s
 
In
January 2017,
we sold
14.1
million shares of our common stock at a public offering price of
$12.20
per share. We received total net proceeds of
$163.7
million (net of
$8.8
million in issuance costs) from the sale of the common stock.
 
In
December 2017,
we sold
9.7
million shares of our common stock at a public offering price of
$15.50
per share. We received total net proceeds of
$142.6
million (net of
$7.4
million in issuance costs) from the sale of the common stock.
 
In
April 2018,
we sold
6.9
million shares of our common stock at a public offering price of
$26.00
per share. We received total net cash proceeds of
$168.7
million (net of
$9.3
million in issuance costs) from the sale of the common stock (See Note
10
).
 
Stock Option
Activity
 
The following table summarizes the stock option activity for the
three
months ended
March 
31,
 
2018:
 
   
 
 
 
  
 
 
 
  
Weighted-
  
   
 
 
 
  
 
 
 
  
a
verage
  
   
 
 
 
  
Weighted-
    
Remaining
  
   
 
 
 
  
a
verage
    
Contractual
  
   
Shares
    
Exercise
    
Term
  
   
(in thousands)
    
Price
    
(Years)
  
Balance at December 31, 2017
    
13,463
     $
15.03
      
8.01
  
Granted
    
122
     $
23.06
      
 
  
Exercised
    
(435
)
   $
9.66
      
 
  
Expired and forfeited
    
(244
)
   $
19.02
      
 
  
Balance at March 31, 2018
    
12,906
     $
15.22
      
7.86
  
 
For the
three
months ended
March 31, 2018,
435,000
shares of common stock were issued pursuant to the exercise of stock options, resulting in net proceeds of
$4.2
million.
 
Stock-based Compensation
 
The following table summarizes stock-based compensation expense related to stock-based payment awards granted pursuant to all of our equity compensation arrangements for the
three
months ended
March 31, 2018
and
2017
(in thousands):
 
   
Three Months Ended
March 31,
  
   
2018
    
2017
  
                 
Research and development
   $
3,036
     $
3,208
  
General and administrative
    
2,276
      
2,374
  
Sales and marketing
    
2,389
      
2,439
  
Total stock-based compensation expense
   $
7,701
     $
8,021
  
 
As of
March 31, 2018,
there was
$79.7
million of total unrecognized compensation cost related to non-vested, stock-based payment awards granted under all of our equity compensation plans and all non-plan option grants. Total unrecognized compensation cost will be adjusted for future changes in estimated forfeitures. We expect to recognize this compensation cost over a weighted-average period of
2.8
 years.
 
We estimated the fair value of each option grant on the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions:
 
   
March 31
,
  
   
20
18
    
20
17
  
Risk-free interest rate
    
2.6
 %    
2.1
 %
Dividend yield
    
0.0
 %    
0.0
 %
Volatility
    
71.4
 %    
87.3
 %
Expected life (years)
    
6
      
6
  
 
We estimate the fair value of each purchase right granted under our
1997
Employee Stock Purchase Plan at the beginning of each new offering period using the Black-Scholes option pricing model. There were
no
new offering periods for the
three
months ended
March 31, 2018
and
2017.